CA1150460A - Hydraulic controls for injection unit of injection molding machine - Google Patents
Hydraulic controls for injection unit of injection molding machineInfo
- Publication number
- CA1150460A CA1150460A CA000349428A CA349428A CA1150460A CA 1150460 A CA1150460 A CA 1150460A CA 000349428 A CA000349428 A CA 000349428A CA 349428 A CA349428 A CA 349428A CA 1150460 A CA1150460 A CA 1150460A
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- CA
- Canada
- Prior art keywords
- hydraulic
- cylinder
- pressure
- valve
- assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
- B29C45/47—Means for plasticising or homogenising the moulding material or forcing it into the mould using screws
- B29C45/50—Axially movable screw
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/82—Hydraulic or pneumatic circuits
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
A B S T R A C T
Hydraulic controls for the injection unit of an in-jection molding machine of the type which has tandem support-ing bridges rining on two guide rods and hydraulic cylinder assemblies surrounding the rods the cylinder assemblies in the rear supporting bridge which control the movements of the plastification screw being convertible from single-acting cylinders to double-acting cylinders with a differential pis-ton, for the selective connection to a first hydraulic con-trol system which has presettable proportional-response con-trol valves for the adjustment of the pressure and flow rate of the hydraulic fluid, or to a second hydraulic control sys-tem which provides a continuous electronic control input to a servo-valve, adjusted by an electronic feedback loop with pressure transducers. The conversion involves the exchange of a piston and a cylinder cover in the two cylinder assem-blies of the rear supporting bridge.
Hydraulic controls for the injection unit of an in-jection molding machine of the type which has tandem support-ing bridges rining on two guide rods and hydraulic cylinder assemblies surrounding the rods the cylinder assemblies in the rear supporting bridge which control the movements of the plastification screw being convertible from single-acting cylinders to double-acting cylinders with a differential pis-ton, for the selective connection to a first hydraulic con-trol system which has presettable proportional-response con-trol valves for the adjustment of the pressure and flow rate of the hydraulic fluid, or to a second hydraulic control sys-tem which provides a continuous electronic control input to a servo-valve, adjusted by an electronic feedback loop with pressure transducers. The conversion involves the exchange of a piston and a cylinder cover in the two cylinder assem-blies of the rear supporting bridge.
Description
The present invention relates to injeetion molcling machines ~hich process plastic materials, and, more parti-cularly, to the hydraulic controls for injection units of injection molding machines which serve to plastiEy plastic raw material and to inject it under pressure into an injec-tion molding die.
For the production of high quality injection-molded parts with minimal variations in size and weight, it is im-portant that -the operation of the injection unit be con-trolled with precision and consistency over -the entire pro-duc-tion run. The injection unit, on -the other hand, must be capable of accommodating a variety of operating condi-tions, in terms of plastic materials composition, injection rates and injec-tion volumes.
It is also important that the injection unit as a ~hole be of a cornpact and simple design which ofEers the necessary operational reliability and adjustability in corn-bination with a high longevity. Such an injection unit is known from my U.S. Patent No. 3,833,204, particularly as shown in FI~,. 2 th*reof. This prior ar-t injection unit fea--tures -two parallel guide rods which support -the injection unit and ~lhich, in turn, have olle extremity attached to a' stationary component part of the die closing unit ana the other extremity eit'ner supported on the machine base or ex-tending fro~ the die closing un;,t in a cantllever fashion.he two guide rods carry two ~uppor-ting bridyes in a tandem arrancJement, one behind the other. The front suppor~ing bridge ca-rries a cooperating p1astification cylincler in a 6~
parallel central relationship to the guide rods, and the rear supporting b~idge carries a cooperating plastification screw which is rotatable and axially movable inside the plas-tification cylinder. The rotation of the plastification screw is produced by a hydraulic rotary drive which is like-wise carried by the rear supporting bridge.
An operating cycle of the injection unit consists essentially of a plastiEication stroke and a subsequent in-jection s-troke. During the plastification stroke, the plas-tiEication screw rotates, as granular raw material is beingfed into the rear of the plastification cylinder, in the area where the latker is seated in the front supporting bri.dge. The forcible advance of the raw material by the plastification screw pushes the latter rearwardly, until -the required cluantity of raw material has accumula-ted in fron-t of the plastification screw. A-t that point, the unit is ready for the injection stroke which consists of a for-cible forward movement oE the plastification screw inside the plastification cy].inder, thereby injecting the plasti-fied raw material into the injection molding die, throughan ;njection nozzle at the forward extremity of -the plasti-Eication cylinder.
Both supporting bridges form hydraulic cylinder asseI~lbli.es where they surround the guide rods, for the con-trol oE the axial movements oE the supportinc) bridges onLhe guide rods. A movement oE the front supporting bridge produces a corre~pondin-J aY~ial mo~Iement of the entire i.njec-' tion uni-t, includincJ the plastiEication cylinder, therebi-giving access to the nozzle of the latter and the spruechannel of the injection molding die. The axial movements of the rear supporting bridye produce movements of the plas-tification screw relative to the plastification cylinder.
The movements are controlled by the cylinder assemblies of the rear supporting bridge, the pistons of these cylinder assemblies being hollow sleeve-like extensions of the front supporting bridge.
The hydraulic controls for such an injection unit are automated to the extent that they utilize control in-puts of prede-termined values in the form of electronic sig-nals which produce continuous adjustments of the pressure and Elow rate of the hydraulic fluid which is delivered to the cylinder assemblies, especially the cylinder assemblies lS of the rear supporting bridge of the above-described injec-tion unit.
In order to obtain the desired adjustments in fluid pressure and flow rate, the electronic input signals are fed to a suitab]e proportional-response valve which, depending on its connections in the hydraulic control circuit, serves as a throttle valve controlling the fluid flow ra-te or as a hypass valve controlling the fluid pressure. Both types of proportional-response valves are ~nown from the prior art.
A practical application of a proportional-response Elow control valve and a proportiona]-response press-lrc control valve in connection with an injection moldincJ mach;ne is disclosed in my U.S. Patent No. ~,020,633.
6~
It is also known from the prior art to equip an in-jeetion unit with hydraulic eontrols whieh inelude as their main eontrol eomponent a servo-valve whieh features pressure transdueers in the hydraulie supply lines as part of an elee-tronie feedbaek circuit and whieh reeeives its input signalsfrom an eleetronic computer, for example. Systems of this type are known as process control systems and they are nor-mally more complex and more expensive than control systems which utilize proportional-response valves with presettable input values. The eleetronic servo-valve eireuit, on the other hand, compensates automatieally for any pressure losses or leakages in the hydraulie controls, thanks to the feed-baek eonneetion between the supply lines of the hydraulie drive assembly and the input signal genera-tor. Its pre-ferred application is therefore found in connection with in-jeetion molding machines and injection units which have to meet very high procluc-t quality standards. Detailed perfor-manee clata of a machine with a servo-valve circuit are re-ported in the periodical "Plastverarbeiter", vol. 9, pp.
20 475-~79-) I-t is a primary objective of -the present invention to suggest improved hydraulic controls for an injection unit of the type described further above which, at minimal additional expense, rnake possible the interchancJeable use of two different hydraulic control systems, one having pre-settable proportional-response control valves for the ad-justment of the fluid pressure and flow ra-te, and the other ,. .
, .
having a process control circuit with an electronically controlled servo-valve and a feedback loop with pressure transducers.
The present invention proposes to attain this ob-jective by suqgesting, in connection with an injection unitwhich has tandem supporting bridges riding on two guide rods, hydraulic cylinder assemblies in the rear supporting bridge which feature interchangeable pistons which are mounted on sleeve-like pis-ton rods attached to the front supporting bridge and matching rear cylinder covcrs, so that, in one assembly configuration, the pistons form the rearward extremities of the piston rods and the cylinder assemblies operate in the manner of single-acting cylinders, and in another assembly confiquration, the pistons have rearwardly oriented piston rod extensions of a diameter which is larger than the diameter of the piston rods, and the associated rear cylinder covers have matching bores which sealingly surround the pis-ton rod extensions, so that the cylinder assemblies operate in the manner of double-acting cylinders with differential pistons.
The first confiyuration of the cylinder assembliesis adapted for use with a hydraulic control circuit which ; features proportional-response control valves Eor the ad-justment of the fluid pressure and fluid flow rate by means of presettable inputs to the control valves. The second configuration of the hydraulic cylinder assemb]ies is adapted for -the connection of a hydraulic supply circuit which provides automatic process con-trol by mcans of an ' . .
electronieally controlled servo-valve receiving its input signals from a computer, for example, which also takes into aecount the results oE continuous pressure measurements in the pressure spaces of the hydraulic cylinder assemblies.
A preferred embodiment of this invention features two identical cylinder assemblies in the rear supporting bridge of the injection units, with hollow pis-ton rods ex-tending forwardly along the guide rods to the forward sup-porting bridge to whi.ch they are attached, the pistons being threaded onto the rear ex-tremities of the hollow pistonrods.
While the pistons for the first assembly configuration are simple internally threaded rings, and their rear cylinder covers ride on the guide rods, the pis-tons for the second assembly configurati.on include, integrally attached -thereto, the earli.er-mentioned rear piston ex-tensions which are slideable on the guide rods and which, in turn, serve as a sliding support Eor the rear cyli.nder covers which have cor-respondingly enlarc;ed bores.
In a preferLed embodiment, the invention further suggests that the connections oE the two -types of hydraulic supply circuits incLIlde flexible l:ine portions and stand-ardi.zed hollo~ connectors attaching the Latter either di-r-~ctly to the rear supporting bridge or to a distributor block ~"hich, in turn, is attached to the same connections on the rear supportincJ bridge. ~rhe distriblltor block would be used in the second assembly configuration, serv:incl as a housing and/or support fo.r the electronic servo-vall/e and its feedback pressure transducers, for example.
The proposed convertibility of the hydraulic cyl-inder assemblies for cooperation with two different hydrau-lic control systems makes it possible to meet different cus-tomer requirements, using a maximum of identical parts. The S invention thus also makes it possible to readily convert a given injection unit from one hydraulic control mode to the other.
Further special features and advantages of the in-vention will become apparent from the description following be].ow, when taken together with the accompanying drawings, which illustrate, by way of example, a preferred embodiment of the invention which is represented in the various fiyures as follows:
- FIG. l shows an injection unit, in a partially cross-sectioned plan view, including a circui-try diacJram of a hydraulic control system which utilizes presettable proportional-response control valves, in a first configura-tion of a preferred embodiment of the invention;
FIG. 2 shows the in~ection unit of FIG. 1 with a circuitry diayram of a hydraulic control system which uti-lizes an elec-tronically adjusted servo-valve, in a second confiyuration of the preferred embodiment of the invention;
FIG. 3 is a tcansverse elevational cross section throuyh the injection unit of FIG. 2, showiny -the rear sl~p-portlng hridge and an attached servo-valve assembly;
; FlG. ~ shows the rear supportiny bridge o~ FIG. 3 in a plan view (arrow U in k-IG. l);
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' .! ' FIG. 5 shows the rear supporting bridge of FIGS. 3 and 4 in a side view (arrow C in FIG. l); and FIG. 6 shows the hydraulic circuitry diagram for the servo-valve control system which is shown in FIGS. 2-5.
An embodiment of the present invention is shown in two different assembly configurations in FIG. 1 and FIG. 2 of the drawing, in connection with an injection unit of the type which rides on two parallel stationary guide rods 4.
The forward extremities of the two guide rods 4 are fixedly attached to the die closing unit of an injection molding ma-chine (not shown), and their rear extremities may be sup-ported on the machine base (not shown), if the injection unit is arranged for horizontal injection. The guide rods 4 support two supporting bridges 27 and 1 in a tandem ar-rangement, for axial movements along t.he longitudinal axisof the unit, which is also the injection axis. The front supporting bridge 27 carries a plastification cylinder 28 whose rear portion is engaged in a central bore of the bridge 27. It also carries a plastic raw material hopper (not shown) which feeds plastic granulate through a verti-cal chute into the rear portion of the plastification cyl-inder 28.
In the bore of the plastification cylinder 28 is arranged a plastification screw 23 which i.s rotatable and axially movable relative to the plas-tification cylinder 28, receiviny its rotational movements from a hydraulic rotary drive 3 which is ca.rried by the rear supporting bridge 1.
~ rl S~6~i A drive shaft 24 and a coupling 21 connect the rotary drive 3 to the plastification screw 23, so that the latter will execute the same axial movements as the supporting bridge 1.
Appropriate thrust bearings, held in place by a bearing cover 22, form a clearance-free axial connectlon between the drive shaft 24 and the rear supporting bridge 1.
The two supportlng bridges 27 and 1 are formed by similar castings, each having a central bore and two outer bores which concentrically surround the guide rods 4 so as to Eorm annular spaces, as part of hydraulic cylinder assem-blies. Thus, the front suppor-ting bridge 27 has two cyl-inder bores 27a which, in coopera-tion with two fixed pistons 29 on the guide rods 4, form a first set of double-acting hydraulic cylinder assemblies. Two pressure supply lines 30 and 31 lead to pressure spaces D and C on opposite sides of the stationary pis-tons 29. Accordinyly, i-t is possible to axially move the supporting bridge 27, and with it the en-tlre injec-tion unit, through pressurization of -the pressure spaces C or D of -the cylinder assemblies, -thereby approach-ing or retractinq the injection unit in relation to the in-jection molding die (not shown) of the injection molding machine.
The rear supporting bridge 1 features similar cyl-inder bores la which cooperate with matchiny pistons 25a.
The latter, however, arc not sea-ted on the guide rods 4, but on -the rear extremities of sleeve-like hollow piston rods 20 ~; which ex-tend forwardly and have their forward extremities at-tached to the front supporting bridge 27. For this purpose, .
' 4Ç~
the piston rods 20 have on their forward extremities en-larged attachment flanges 20a. These flanges conveniently serve as rear cylinder covers for the cylinder assemblies of the front supporting bridge 27.
The pistons 25a of the rear cylinder assemblies are thus solidary with the front supporting bridge 27. It follows that a pressurization of the cylinaer assemblies of the rear supporting bridge l produces a movement of this bridge away from, or towards, the front supporting bridge 27, thereby retracting the plastification screw 23 in a plasti-fication stroke, or advancing the plastification screw 23 in an injection s-troke, respectively. The cylinder bores la of the supporting bridge l Eorm front and rear pressure spaces ~ and B, respectively, on opposite sides of -the pis-lS tons 25a, the pressure spaces being delimited by front cyl-inder covers l9 and rear cylinder covers 34. These cylinder covers support and guide the rear supporting bridge l, as the front covers 19 slide on -the outer diameter of the pis-ton rods 20 and the rear covers 34 slide on the guide rods~.
As can further be seen in FIG. 1, the injection stroke of -the plas-tiEication screw 23 is obtained through pressuri~a-tion of the pressure spaces A of the cylinaer as-semblies in the rear supporting bridge l. For this purpose, -the pressure spa-es ~ have connected thereto a hydraulic control system ~hich is shown in the circuitry diagram of FIG. l. Tllere, it can be seen that the pressure for -the injection stroke is supplied through the main supply line 52 which leads from a variable delivery pump 37 to a mu]ti-~ ~ 5~
way valve 38 and, over supply branches 57 and flexible line portions 54, to the cylinder assemblies of the supporting bridge 1. The variable delivery pump 37 is driven by means of an electric motor 36.
The pressure and flow rate at which hydraulic fluid is supplied to the pressure spaces A can be adjusted by means of a proportional-response flow control valve 43which is arranged in the main supply line 52 and which, in accord-ance with a given setting of a potentiometer controlling the proportional-force electromagnet 43a of the valve 43, throt-tles the fluid flow in the main supply ].ine 52. The fluidvressure is adjusted by means of a proportional-response pressure control valve 42 which is arranged in a return branch 61 leading from the main supply line 52 to the fluid reservoir 55. The settir,g of the pressure control valve 42 is obtained by means of a proportional-force electromagnet 42a and a suitable potentiometer.
A leal.cage return line 51 links the flow control valve 43 to the return line 61, and a hydraulic feedback line G0 supplies an adjustment pressure to the vari.able de-livery pump 37 from a point on the return line 61 which is ; located bet~"een an adjustable con-trol diaphragm 49 and the pressure control valve 42. The potentiometers of the pro-portional-force electromagnets 42a and 43a, controlling the pressure control valve 42 and the flow control valve 43, are part of appropria~e electronic circui.ts which permit a readjustment of the valves 42 ancl 43, whenever the pres-,ure and flow rate vaLues deviate from the des.ired magniturles.
,,,; .
~S~6~
A pressure relief valve 41 in an overflow return branch 62, just upstream of the variable delivery pump 37, protects the latter in the cvent of a hydraulic blockage in the sys-tem. In the drawing, the proportional~response flow con-trol valve ~3 and the multiway valve 38 are shown in theirrest positions.
For the injection stroke oE the injection unit, the multiway valve 38 is in its left-hand position, so that pressuri~ed fluid will flow into the pressure space ~ of the cylinder bores la. During the subse~uent plastification stroke, the rotating plastification screw 23 creates a plas-tification pressure which causes the screw 23 to back up, pushing the supporting bridge 1 rearwardly and displacing fluid from -the pressure space A. This displaced fluid pass-es from the supply branch 57 to a reverse flow branch 63,where a predetermined resistance in the form of a counter pressure is created by means of a cartridge valve 39 which serves as a coun-terpressure throttle valve and is controlled by means of a proportional response counterpressure valve ~0. The setting of the latter is controlled by means of an electromagnet ~Oa. A resistance-free return flow is obtain-able in the right-hand position of the multiway valve 38, which allows the displaced fluid to pass freely from the supply branch 57 to the return line 53 which ]eads to the fluid reservoi~ 55. A bypass branch 67 with a check valve 66 bridges the muLtiway valve 38, linking one of the supply branches 57 to the return line 53.
.
A second configuration of the embodiment of the present invention is shown in FIG. 2, where it can be seen that the mechanical components of the injection unit remain unchanged, with the exception of the pistons and the rear cylinder covers of the hydraulic cylinder assemblies of the rear supporting bridge 1. The simple annular pistons 25a of the cylinder configuration of FIG. 1 have been replaced by pistons 125 which form rearwardly oriented piston rod extensions 125a. The latter reach axially -through the rear cylinder covers 35 which have correspondingly enlarged central guide bores.
The conversion from one assembly configuration to the other is made very simple through the arrangement of a threaded connection between the interchangeable piston 25a or 125 and the piston rod 20. An externally threaded end portion of the latter is engaged by a matching internal thread oE the interchangeable pis-ton. In order to exchange one piston for the o-ther, i-t is only necessary to remove the rear cover of the cylinder assembly and -to unscrew the piston from the piston rod 20, replacing it with the other piston, and replacing the previous rear cylinder cover with a matching new cover.
In -the hydraulic cylinder assembly confiyuration of FIG. 2, the piston rod extensions 125a of the pistons 125 have a diameter which is larger than the diameter of the piston rods 20. The result is a double-acting cylinder as-sembly which has a differential pis-ton, the forward pres-sure space ~ o~ the assembly having a larger effective cross-_] ~~
sectional area than the rearward pressure spaee B. The hy-draulie eylinder configuration of FIG. l, in contrast, oper-ates as a single-acting cylinder, as only the eylinder space A is pressuri2ed during the injection stroke.
The hydraulic cylinder configuration of FIG. 2 is adapted for conneetion to a hydraulie eontrol system which features an eleetronic servo-valve, as is shown in the cir-cuitry diagram of FIG. 2. The servo-valve and several asso-ciated components are integrated into, or attached to, a distributor bloek 6 which is shown in more detail in FIGS. 3-5.
The operative components of this so-called proeess control system are as follows: The power for the system is supplied by means of an electric motor 36 which drives a eonstant pressure pump 46 and a variable delivery pump 37a.
A pressure line g7 eonnects the constant pressure pump 46 to a fluid pressure boos-ter 8 of the servo-valve. An over-flow re-turn branch 64 with a pressure eontrol valve 50 limits the level of pressure which is produced by the con-stant pressure pump ~6. The variable delivery pump 37a de-livers hydraulic fluid to the servo-valve 7, via the pres-sure supply line l~l. The servo-valve 7, in -turn, is con-nected to the pressure spaces A and B of the cylinder bores la. TappincJ these connections are two pressure transducers 11 and 12 whicll thus eontinuously measure -the hydraulic pres-sure in the pressure spaces A and B, respectively, producing a correspondinc~ly changing outpu-t voltage.
The fluid pressure booster 8 receives an electronic input from an input signal generator 8a which, together with the pressure transducers 11 and 12, forms an electronic feed-back loop. The input signal generator 8a may be connected to a programmable computer, for example. The electronic feedback loop makes it possible to continuously compensate for any leakage or pressure losses in the fluid supply to the cylinder assemblies.
In the pressure line 47 is further arranged a micro-filter 9 which is controlled by a differential-pressure switch 10. The latter is arranged in a parallel branch 47a.
~; A return line 15 leads from the serve-valve 7 to the fluid reservoir 55. The variable delivery pump 37a is protected by a pressure relief valve 56 which is arranged in a return branch 65 oE the pressure line 14.
The servo-valve 7, its fluid pressure booster 8, and the pressure transducers l] and 12, as well as the micro-filter 9 and the associa-ted difEerential-pressure switch 10, are combined in a servo-valve assembly which, as shown in FIGS. 2-5, is conveniently accommoda-ted on the outside of the rear supporting bridge 1, in the form of a compact com-ponen-t cluster which is carried by a distributor block 6.
The la-tter is removably attached to a lateral face of the supporting hridge 1, using the same connec-ting bores as are used for the hydraulic control system of E~IG. 1.
The servo-valve assembly 26, shown in more detail in FIGS. 3-5, consis1s essentially of a rectangular distri-butor block 6 which is clamped to a planar lateral face of the rear supporting bridge 1, carrying on its bottom side the vertically oriented electronic servo-valve 7 and the micro-filter 9. The two pressure transducers 11 and 12 are arranged one above the other on a vertica] rear face of the distributor block 6, and the same face also carries the dif-ferential-pressure switch 10.
To the other lateral face of the distributor block 6 are connected the pressure supply line 14 and the return line 15, using the same line connectors 14a and lSa as are used for the supply branches 57 of -the hydraulic system of FIG. 1 which relies on proportional-response control valves.
Also connected to the outer lateral face of the distributor block 6 is the pressure line 47 which links the fluid pres-sure booster 8 to the constant-pressure pump 46. The en-tire servo-valve assembly 26 is readily removable from the suppor-ting hridge 1 and, in its place, the line connectors 14a and 15a of the supply branches 57 (FIG.]) can be at-tached directly to the lateral moun-ting face of the sup-porting bridge 1.
The front and rear pressure spaces ~ and B of the two cylinder bores la of the rear suppor-ting bridge 1 are transversely interconnected by means of connecting bores 38~ and 58B which are accommodated insicle two upwardly pro--truding transverse ribs 17 and 16, respectively. This places the connecting bores 58A and 58B avove the central bore which houses the bearinc;s for the drive shaft 24.
The injection unit further includes a displacement measurincJ device 48 which is arranged on the opposite late-.
ral side of the supporting bridges 27 and 1 and which meas-ures the relative displacements between the two supporting bridges. Adjustable displacement-triggered end switches are used to control the timing and length of the injectionstroke of the plastification screw 23.
It should be understood, oE course, that the fore-going disclosure describes only a preEerred embodiment of the invention and that it is intended to cover all changes and modifications of this example of the invention which fall within the scope of the appended claims.
., .
For the production of high quality injection-molded parts with minimal variations in size and weight, it is im-portant that -the operation of the injection unit be con-trolled with precision and consistency over -the entire pro-duc-tion run. The injection unit, on -the other hand, must be capable of accommodating a variety of operating condi-tions, in terms of plastic materials composition, injection rates and injec-tion volumes.
It is also important that the injection unit as a ~hole be of a cornpact and simple design which ofEers the necessary operational reliability and adjustability in corn-bination with a high longevity. Such an injection unit is known from my U.S. Patent No. 3,833,204, particularly as shown in FI~,. 2 th*reof. This prior ar-t injection unit fea--tures -two parallel guide rods which support -the injection unit and ~lhich, in turn, have olle extremity attached to a' stationary component part of the die closing unit ana the other extremity eit'ner supported on the machine base or ex-tending fro~ the die closing un;,t in a cantllever fashion.he two guide rods carry two ~uppor-ting bridyes in a tandem arrancJement, one behind the other. The front suppor~ing bridge ca-rries a cooperating p1astification cylincler in a 6~
parallel central relationship to the guide rods, and the rear supporting b~idge carries a cooperating plastification screw which is rotatable and axially movable inside the plas-tification cylinder. The rotation of the plastification screw is produced by a hydraulic rotary drive which is like-wise carried by the rear supporting bridge.
An operating cycle of the injection unit consists essentially of a plastiEication stroke and a subsequent in-jection s-troke. During the plastification stroke, the plas-tiEication screw rotates, as granular raw material is beingfed into the rear of the plastification cylinder, in the area where the latker is seated in the front supporting bri.dge. The forcible advance of the raw material by the plastification screw pushes the latter rearwardly, until -the required cluantity of raw material has accumula-ted in fron-t of the plastification screw. A-t that point, the unit is ready for the injection stroke which consists of a for-cible forward movement oE the plastification screw inside the plastification cy].inder, thereby injecting the plasti-fied raw material into the injection molding die, throughan ;njection nozzle at the forward extremity of -the plasti-Eication cylinder.
Both supporting bridges form hydraulic cylinder asseI~lbli.es where they surround the guide rods, for the con-trol oE the axial movements oE the supportinc) bridges onLhe guide rods. A movement oE the front supporting bridge produces a corre~pondin-J aY~ial mo~Iement of the entire i.njec-' tion uni-t, includincJ the plastiEication cylinder, therebi-giving access to the nozzle of the latter and the spruechannel of the injection molding die. The axial movements of the rear supporting bridye produce movements of the plas-tification screw relative to the plastification cylinder.
The movements are controlled by the cylinder assemblies of the rear supporting bridge, the pistons of these cylinder assemblies being hollow sleeve-like extensions of the front supporting bridge.
The hydraulic controls for such an injection unit are automated to the extent that they utilize control in-puts of prede-termined values in the form of electronic sig-nals which produce continuous adjustments of the pressure and Elow rate of the hydraulic fluid which is delivered to the cylinder assemblies, especially the cylinder assemblies lS of the rear supporting bridge of the above-described injec-tion unit.
In order to obtain the desired adjustments in fluid pressure and flow rate, the electronic input signals are fed to a suitab]e proportional-response valve which, depending on its connections in the hydraulic control circuit, serves as a throttle valve controlling the fluid flow ra-te or as a hypass valve controlling the fluid pressure. Both types of proportional-response valves are ~nown from the prior art.
A practical application of a proportional-response Elow control valve and a proportiona]-response press-lrc control valve in connection with an injection moldincJ mach;ne is disclosed in my U.S. Patent No. ~,020,633.
6~
It is also known from the prior art to equip an in-jeetion unit with hydraulic eontrols whieh inelude as their main eontrol eomponent a servo-valve whieh features pressure transdueers in the hydraulie supply lines as part of an elee-tronie feedbaek circuit and whieh reeeives its input signalsfrom an eleetronic computer, for example. Systems of this type are known as process control systems and they are nor-mally more complex and more expensive than control systems which utilize proportional-response valves with presettable input values. The eleetronic servo-valve eireuit, on the other hand, compensates automatieally for any pressure losses or leakages in the hydraulie controls, thanks to the feed-baek eonneetion between the supply lines of the hydraulie drive assembly and the input signal genera-tor. Its pre-ferred application is therefore found in connection with in-jeetion molding machines and injection units which have to meet very high procluc-t quality standards. Detailed perfor-manee clata of a machine with a servo-valve circuit are re-ported in the periodical "Plastverarbeiter", vol. 9, pp.
20 475-~79-) I-t is a primary objective of -the present invention to suggest improved hydraulic controls for an injection unit of the type described further above which, at minimal additional expense, rnake possible the interchancJeable use of two different hydraulic control systems, one having pre-settable proportional-response control valves for the ad-justment of the fluid pressure and flow ra-te, and the other ,. .
, .
having a process control circuit with an electronically controlled servo-valve and a feedback loop with pressure transducers.
The present invention proposes to attain this ob-jective by suqgesting, in connection with an injection unitwhich has tandem supporting bridges riding on two guide rods, hydraulic cylinder assemblies in the rear supporting bridge which feature interchangeable pistons which are mounted on sleeve-like pis-ton rods attached to the front supporting bridge and matching rear cylinder covcrs, so that, in one assembly configuration, the pistons form the rearward extremities of the piston rods and the cylinder assemblies operate in the manner of single-acting cylinders, and in another assembly confiquration, the pistons have rearwardly oriented piston rod extensions of a diameter which is larger than the diameter of the piston rods, and the associated rear cylinder covers have matching bores which sealingly surround the pis-ton rod extensions, so that the cylinder assemblies operate in the manner of double-acting cylinders with differential pistons.
The first confiyuration of the cylinder assembliesis adapted for use with a hydraulic control circuit which ; features proportional-response control valves Eor the ad-justment of the fluid pressure and fluid flow rate by means of presettable inputs to the control valves. The second configuration of the hydraulic cylinder assemb]ies is adapted for -the connection of a hydraulic supply circuit which provides automatic process con-trol by mcans of an ' . .
electronieally controlled servo-valve receiving its input signals from a computer, for example, which also takes into aecount the results oE continuous pressure measurements in the pressure spaces of the hydraulic cylinder assemblies.
A preferred embodiment of this invention features two identical cylinder assemblies in the rear supporting bridge of the injection units, with hollow pis-ton rods ex-tending forwardly along the guide rods to the forward sup-porting bridge to whi.ch they are attached, the pistons being threaded onto the rear ex-tremities of the hollow pistonrods.
While the pistons for the first assembly configuration are simple internally threaded rings, and their rear cylinder covers ride on the guide rods, the pis-tons for the second assembly configurati.on include, integrally attached -thereto, the earli.er-mentioned rear piston ex-tensions which are slideable on the guide rods and which, in turn, serve as a sliding support Eor the rear cyli.nder covers which have cor-respondingly enlarc;ed bores.
In a preferLed embodiment, the invention further suggests that the connections oE the two -types of hydraulic supply circuits incLIlde flexible l:ine portions and stand-ardi.zed hollo~ connectors attaching the Latter either di-r-~ctly to the rear supporting bridge or to a distributor block ~"hich, in turn, is attached to the same connections on the rear supportincJ bridge. ~rhe distriblltor block would be used in the second assembly configuration, serv:incl as a housing and/or support fo.r the electronic servo-vall/e and its feedback pressure transducers, for example.
The proposed convertibility of the hydraulic cyl-inder assemblies for cooperation with two different hydrau-lic control systems makes it possible to meet different cus-tomer requirements, using a maximum of identical parts. The S invention thus also makes it possible to readily convert a given injection unit from one hydraulic control mode to the other.
Further special features and advantages of the in-vention will become apparent from the description following be].ow, when taken together with the accompanying drawings, which illustrate, by way of example, a preferred embodiment of the invention which is represented in the various fiyures as follows:
- FIG. l shows an injection unit, in a partially cross-sectioned plan view, including a circui-try diacJram of a hydraulic control system which utilizes presettable proportional-response control valves, in a first configura-tion of a preferred embodiment of the invention;
FIG. 2 shows the in~ection unit of FIG. 1 with a circuitry diayram of a hydraulic control system which uti-lizes an elec-tronically adjusted servo-valve, in a second confiyuration of the preferred embodiment of the invention;
FIG. 3 is a tcansverse elevational cross section throuyh the injection unit of FIG. 2, showiny -the rear sl~p-portlng hridge and an attached servo-valve assembly;
; FlG. ~ shows the rear supportiny bridge o~ FIG. 3 in a plan view (arrow U in k-IG. l);
.~ .
' .! ' FIG. 5 shows the rear supporting bridge of FIGS. 3 and 4 in a side view (arrow C in FIG. l); and FIG. 6 shows the hydraulic circuitry diagram for the servo-valve control system which is shown in FIGS. 2-5.
An embodiment of the present invention is shown in two different assembly configurations in FIG. 1 and FIG. 2 of the drawing, in connection with an injection unit of the type which rides on two parallel stationary guide rods 4.
The forward extremities of the two guide rods 4 are fixedly attached to the die closing unit of an injection molding ma-chine (not shown), and their rear extremities may be sup-ported on the machine base (not shown), if the injection unit is arranged for horizontal injection. The guide rods 4 support two supporting bridges 27 and 1 in a tandem ar-rangement, for axial movements along t.he longitudinal axisof the unit, which is also the injection axis. The front supporting bridge 27 carries a plastification cylinder 28 whose rear portion is engaged in a central bore of the bridge 27. It also carries a plastic raw material hopper (not shown) which feeds plastic granulate through a verti-cal chute into the rear portion of the plastification cyl-inder 28.
In the bore of the plastification cylinder 28 is arranged a plastification screw 23 which i.s rotatable and axially movable relative to the plas-tification cylinder 28, receiviny its rotational movements from a hydraulic rotary drive 3 which is ca.rried by the rear supporting bridge 1.
~ rl S~6~i A drive shaft 24 and a coupling 21 connect the rotary drive 3 to the plastification screw 23, so that the latter will execute the same axial movements as the supporting bridge 1.
Appropriate thrust bearings, held in place by a bearing cover 22, form a clearance-free axial connectlon between the drive shaft 24 and the rear supporting bridge 1.
The two supportlng bridges 27 and 1 are formed by similar castings, each having a central bore and two outer bores which concentrically surround the guide rods 4 so as to Eorm annular spaces, as part of hydraulic cylinder assem-blies. Thus, the front suppor-ting bridge 27 has two cyl-inder bores 27a which, in coopera-tion with two fixed pistons 29 on the guide rods 4, form a first set of double-acting hydraulic cylinder assemblies. Two pressure supply lines 30 and 31 lead to pressure spaces D and C on opposite sides of the stationary pis-tons 29. Accordinyly, i-t is possible to axially move the supporting bridge 27, and with it the en-tlre injec-tion unit, through pressurization of -the pressure spaces C or D of -the cylinder assemblies, -thereby approach-ing or retractinq the injection unit in relation to the in-jection molding die (not shown) of the injection molding machine.
The rear supporting bridge 1 features similar cyl-inder bores la which cooperate with matchiny pistons 25a.
The latter, however, arc not sea-ted on the guide rods 4, but on -the rear extremities of sleeve-like hollow piston rods 20 ~; which ex-tend forwardly and have their forward extremities at-tached to the front supporting bridge 27. For this purpose, .
' 4Ç~
the piston rods 20 have on their forward extremities en-larged attachment flanges 20a. These flanges conveniently serve as rear cylinder covers for the cylinder assemblies of the front supporting bridge 27.
The pistons 25a of the rear cylinder assemblies are thus solidary with the front supporting bridge 27. It follows that a pressurization of the cylinaer assemblies of the rear supporting bridge l produces a movement of this bridge away from, or towards, the front supporting bridge 27, thereby retracting the plastification screw 23 in a plasti-fication stroke, or advancing the plastification screw 23 in an injection s-troke, respectively. The cylinder bores la of the supporting bridge l Eorm front and rear pressure spaces ~ and B, respectively, on opposite sides of -the pis-lS tons 25a, the pressure spaces being delimited by front cyl-inder covers l9 and rear cylinder covers 34. These cylinder covers support and guide the rear supporting bridge l, as the front covers 19 slide on -the outer diameter of the pis-ton rods 20 and the rear covers 34 slide on the guide rods~.
As can further be seen in FIG. 1, the injection stroke of -the plas-tiEication screw 23 is obtained through pressuri~a-tion of the pressure spaces A of the cylinaer as-semblies in the rear supporting bridge l. For this purpose, -the pressure spa-es ~ have connected thereto a hydraulic control system ~hich is shown in the circuitry diagram of FIG. l. Tllere, it can be seen that the pressure for -the injection stroke is supplied through the main supply line 52 which leads from a variable delivery pump 37 to a mu]ti-~ ~ 5~
way valve 38 and, over supply branches 57 and flexible line portions 54, to the cylinder assemblies of the supporting bridge 1. The variable delivery pump 37 is driven by means of an electric motor 36.
The pressure and flow rate at which hydraulic fluid is supplied to the pressure spaces A can be adjusted by means of a proportional-response flow control valve 43which is arranged in the main supply line 52 and which, in accord-ance with a given setting of a potentiometer controlling the proportional-force electromagnet 43a of the valve 43, throt-tles the fluid flow in the main supply ].ine 52. The fluidvressure is adjusted by means of a proportional-response pressure control valve 42 which is arranged in a return branch 61 leading from the main supply line 52 to the fluid reservoir 55. The settir,g of the pressure control valve 42 is obtained by means of a proportional-force electromagnet 42a and a suitable potentiometer.
A leal.cage return line 51 links the flow control valve 43 to the return line 61, and a hydraulic feedback line G0 supplies an adjustment pressure to the vari.able de-livery pump 37 from a point on the return line 61 which is ; located bet~"een an adjustable con-trol diaphragm 49 and the pressure control valve 42. The potentiometers of the pro-portional-force electromagnets 42a and 43a, controlling the pressure control valve 42 and the flow control valve 43, are part of appropria~e electronic circui.ts which permit a readjustment of the valves 42 ancl 43, whenever the pres-,ure and flow rate vaLues deviate from the des.ired magniturles.
,,,; .
~S~6~
A pressure relief valve 41 in an overflow return branch 62, just upstream of the variable delivery pump 37, protects the latter in the cvent of a hydraulic blockage in the sys-tem. In the drawing, the proportional~response flow con-trol valve ~3 and the multiway valve 38 are shown in theirrest positions.
For the injection stroke oE the injection unit, the multiway valve 38 is in its left-hand position, so that pressuri~ed fluid will flow into the pressure space ~ of the cylinder bores la. During the subse~uent plastification stroke, the rotating plastification screw 23 creates a plas-tification pressure which causes the screw 23 to back up, pushing the supporting bridge 1 rearwardly and displacing fluid from -the pressure space A. This displaced fluid pass-es from the supply branch 57 to a reverse flow branch 63,where a predetermined resistance in the form of a counter pressure is created by means of a cartridge valve 39 which serves as a coun-terpressure throttle valve and is controlled by means of a proportional response counterpressure valve ~0. The setting of the latter is controlled by means of an electromagnet ~Oa. A resistance-free return flow is obtain-able in the right-hand position of the multiway valve 38, which allows the displaced fluid to pass freely from the supply branch 57 to the return line 53 which ]eads to the fluid reservoi~ 55. A bypass branch 67 with a check valve 66 bridges the muLtiway valve 38, linking one of the supply branches 57 to the return line 53.
.
A second configuration of the embodiment of the present invention is shown in FIG. 2, where it can be seen that the mechanical components of the injection unit remain unchanged, with the exception of the pistons and the rear cylinder covers of the hydraulic cylinder assemblies of the rear supporting bridge 1. The simple annular pistons 25a of the cylinder configuration of FIG. 1 have been replaced by pistons 125 which form rearwardly oriented piston rod extensions 125a. The latter reach axially -through the rear cylinder covers 35 which have correspondingly enlarged central guide bores.
The conversion from one assembly configuration to the other is made very simple through the arrangement of a threaded connection between the interchangeable piston 25a or 125 and the piston rod 20. An externally threaded end portion of the latter is engaged by a matching internal thread oE the interchangeable pis-ton. In order to exchange one piston for the o-ther, i-t is only necessary to remove the rear cover of the cylinder assembly and -to unscrew the piston from the piston rod 20, replacing it with the other piston, and replacing the previous rear cylinder cover with a matching new cover.
In -the hydraulic cylinder assembly confiyuration of FIG. 2, the piston rod extensions 125a of the pistons 125 have a diameter which is larger than the diameter of the piston rods 20. The result is a double-acting cylinder as-sembly which has a differential pis-ton, the forward pres-sure space ~ o~ the assembly having a larger effective cross-_] ~~
sectional area than the rearward pressure spaee B. The hy-draulie eylinder configuration of FIG. l, in contrast, oper-ates as a single-acting cylinder, as only the eylinder space A is pressuri2ed during the injection stroke.
The hydraulic cylinder configuration of FIG. 2 is adapted for conneetion to a hydraulie eontrol system which features an eleetronic servo-valve, as is shown in the cir-cuitry diagram of FIG. 2. The servo-valve and several asso-ciated components are integrated into, or attached to, a distributor bloek 6 which is shown in more detail in FIGS. 3-5.
The operative components of this so-called proeess control system are as follows: The power for the system is supplied by means of an electric motor 36 which drives a eonstant pressure pump 46 and a variable delivery pump 37a.
A pressure line g7 eonnects the constant pressure pump 46 to a fluid pressure boos-ter 8 of the servo-valve. An over-flow re-turn branch 64 with a pressure eontrol valve 50 limits the level of pressure which is produced by the con-stant pressure pump ~6. The variable delivery pump 37a de-livers hydraulic fluid to the servo-valve 7, via the pres-sure supply line l~l. The servo-valve 7, in -turn, is con-nected to the pressure spaces A and B of the cylinder bores la. TappincJ these connections are two pressure transducers 11 and 12 whicll thus eontinuously measure -the hydraulic pres-sure in the pressure spaces A and B, respectively, producing a correspondinc~ly changing outpu-t voltage.
The fluid pressure booster 8 receives an electronic input from an input signal generator 8a which, together with the pressure transducers 11 and 12, forms an electronic feed-back loop. The input signal generator 8a may be connected to a programmable computer, for example. The electronic feedback loop makes it possible to continuously compensate for any leakage or pressure losses in the fluid supply to the cylinder assemblies.
In the pressure line 47 is further arranged a micro-filter 9 which is controlled by a differential-pressure switch 10. The latter is arranged in a parallel branch 47a.
~; A return line 15 leads from the serve-valve 7 to the fluid reservoir 55. The variable delivery pump 37a is protected by a pressure relief valve 56 which is arranged in a return branch 65 oE the pressure line 14.
The servo-valve 7, its fluid pressure booster 8, and the pressure transducers l] and 12, as well as the micro-filter 9 and the associa-ted difEerential-pressure switch 10, are combined in a servo-valve assembly which, as shown in FIGS. 2-5, is conveniently accommoda-ted on the outside of the rear supporting bridge 1, in the form of a compact com-ponen-t cluster which is carried by a distributor block 6.
The la-tter is removably attached to a lateral face of the supporting hridge 1, using the same connec-ting bores as are used for the hydraulic control system of E~IG. 1.
The servo-valve assembly 26, shown in more detail in FIGS. 3-5, consis1s essentially of a rectangular distri-butor block 6 which is clamped to a planar lateral face of the rear supporting bridge 1, carrying on its bottom side the vertically oriented electronic servo-valve 7 and the micro-filter 9. The two pressure transducers 11 and 12 are arranged one above the other on a vertica] rear face of the distributor block 6, and the same face also carries the dif-ferential-pressure switch 10.
To the other lateral face of the distributor block 6 are connected the pressure supply line 14 and the return line 15, using the same line connectors 14a and lSa as are used for the supply branches 57 of -the hydraulic system of FIG. 1 which relies on proportional-response control valves.
Also connected to the outer lateral face of the distributor block 6 is the pressure line 47 which links the fluid pres-sure booster 8 to the constant-pressure pump 46. The en-tire servo-valve assembly 26 is readily removable from the suppor-ting hridge 1 and, in its place, the line connectors 14a and 15a of the supply branches 57 (FIG.]) can be at-tached directly to the lateral moun-ting face of the sup-porting bridge 1.
The front and rear pressure spaces ~ and B of the two cylinder bores la of the rear suppor-ting bridge 1 are transversely interconnected by means of connecting bores 38~ and 58B which are accommodated insicle two upwardly pro--truding transverse ribs 17 and 16, respectively. This places the connecting bores 58A and 58B avove the central bore which houses the bearinc;s for the drive shaft 24.
The injection unit further includes a displacement measurincJ device 48 which is arranged on the opposite late-.
ral side of the supporting bridges 27 and 1 and which meas-ures the relative displacements between the two supporting bridges. Adjustable displacement-triggered end switches are used to control the timing and length of the injectionstroke of the plastification screw 23.
It should be understood, oE course, that the fore-going disclosure describes only a preEerred embodiment of the invention and that it is intended to cover all changes and modifications of this example of the invention which fall within the scope of the appended claims.
., .
Claims (7)
1. Hydraulic controls for the injection unit of an injection molding machine processing plastic raw mate-rials, which injection unit has a plastification cylinder defining an injection axis and a cooperating plastification screw reaching into the plastification cylinder from behind, including means for rotating the plastification screw in a plastification stroke and means for axially advancing it in an injection stroke, the hydraulic controls for said injec-tion unit being associated with the means for advancing the plastification screw and comprising:
a hydraulic cylinder assembly of which the cylinder cavity is formed by a bore in a movable member which is con-nected to the plastification screw for axial movements there-with, and of which the piston is connected to the plastifica-tion cylinder by means of a piston rod extending forwardly from the cylinder assembly, so that pressurization of the cylinder space forward of the piston produces an injection stroke of the plastification screw; and wherein the cylinder assembly is convertible so that, in a first assembly configuration, the piston forms the rearward extremity of the piston rod and the cylinder assembly oper-ates in the manner of a single-acting cylincler, suitable for the connection thereto of a hydraulic supply circuit which has presettable proportional-response control valves for the adjustment of the fluid pressure and flow rate which deter-mine the injection stroke and return movement of the plasti-fication screw, and so that, in a second assembly configura-tion, the piston is adjoined by a rearwardly oriented piston rod extension of a diameter larger than the diameter of the piston rod, and the associated rear cylinder cover has a matching bore forming a seal with the piston rod extension, whereby the cylinder assembly operates in the manner of a double-acting cylinder of the differential-piston type, suit-able for the connection thereto of a hydraulic supply cir-cuit which includes an electronically controlled servo-valve receiving electronic input signals from pressure transducers measuring the fluid pressure of both sides of the piston.
a hydraulic cylinder assembly of which the cylinder cavity is formed by a bore in a movable member which is con-nected to the plastification screw for axial movements there-with, and of which the piston is connected to the plastifica-tion cylinder by means of a piston rod extending forwardly from the cylinder assembly, so that pressurization of the cylinder space forward of the piston produces an injection stroke of the plastification screw; and wherein the cylinder assembly is convertible so that, in a first assembly configuration, the piston forms the rearward extremity of the piston rod and the cylinder assembly oper-ates in the manner of a single-acting cylincler, suitable for the connection thereto of a hydraulic supply circuit which has presettable proportional-response control valves for the adjustment of the fluid pressure and flow rate which deter-mine the injection stroke and return movement of the plasti-fication screw, and so that, in a second assembly configura-tion, the piston is adjoined by a rearwardly oriented piston rod extension of a diameter larger than the diameter of the piston rod, and the associated rear cylinder cover has a matching bore forming a seal with the piston rod extension, whereby the cylinder assembly operates in the manner of a double-acting cylinder of the differential-piston type, suit-able for the connection thereto of a hydraulic supply cir-cuit which includes an electronically controlled servo-valve receiving electronic input signals from pressure transducers measuring the fluid pressure of both sides of the piston.
2. Hydraulic injection unit controls as defined in Claim 1, wherein the piston of the cylinder assembly is removably attached to the rear extremity of the piston rod by means of a threaded connection;
the piston rod extension of the second cylinder as-sembly configuration is attached to the adjoining piston;
and the rear cylinder cover of the second cylinder as-sembly configuration cooperates with the piston rod exten-sion in such a way that the cylinder assembly and the mova-ble member of which the assembly is a part are guidingly supported on the piston rod extension.
the piston rod extension of the second cylinder as-sembly configuration is attached to the adjoining piston;
and the rear cylinder cover of the second cylinder as-sembly configuration cooperates with the piston rod exten-sion in such a way that the cylinder assembly and the mova-ble member of which the assembly is a part are guidingly supported on the piston rod extension.
3. Hydraulic injection unit controls as defined in Claim 1 or Claim 2, wherein the hydraulic cylinder assembly is arranged in said first assembly configuration, and, to the cylinder assembly is connected a hydraulic control circuit which includes:
a variable delivery hydraulic pump driven by an electric motor and adjustable in output by means of a pump control member, the pump having an inlet connected to a fluid reservoir;
a main supply line connecting the outlet of the pump to the cylinder assembly;
a proportional-response flow control valve in the main supply line, the setting of the valve being adjustable by means of a proportional-force electromagnet which moves in response to an electronic control signal imposed on it by a presettable signal source;
a return branch leading from a point on the main supply line downstream of said flow control valve to the fluid reservoir, the return branch including an adjustable control diaphragm;
a proportional-response pressure control valve in the return branch, the setting of the valve being adjustable by means of a proportional-force electromagnet which moves in response to an electronic control signal imposed on it by a presettable sunnily source;
a hydraulic feedback line leading from a point on the return branch between the diaphragm and the pressure con-trol valve to the control member of the pump;
a return line connecting the cylinder assembly to the fluid reservoir;
a multiway valve simultaneously controlling the main supply line and the return line so as to selectively block both lines and to alternatively connect one of the two lines to a supply branch leading to the front side of the hydraulic cylinder and the other line to a supply branch leading to the rear side thereof; and a reverse flow branch leading from said front side supply branch to the fluid reservoir and having in it a counterpressure throttle valve controlled by means of a proportional-response counterpressure valve which is pre-settable like said other proportional-response valves.
a variable delivery hydraulic pump driven by an electric motor and adjustable in output by means of a pump control member, the pump having an inlet connected to a fluid reservoir;
a main supply line connecting the outlet of the pump to the cylinder assembly;
a proportional-response flow control valve in the main supply line, the setting of the valve being adjustable by means of a proportional-force electromagnet which moves in response to an electronic control signal imposed on it by a presettable signal source;
a return branch leading from a point on the main supply line downstream of said flow control valve to the fluid reservoir, the return branch including an adjustable control diaphragm;
a proportional-response pressure control valve in the return branch, the setting of the valve being adjustable by means of a proportional-force electromagnet which moves in response to an electronic control signal imposed on it by a presettable sunnily source;
a hydraulic feedback line leading from a point on the return branch between the diaphragm and the pressure con-trol valve to the control member of the pump;
a return line connecting the cylinder assembly to the fluid reservoir;
a multiway valve simultaneously controlling the main supply line and the return line so as to selectively block both lines and to alternatively connect one of the two lines to a supply branch leading to the front side of the hydraulic cylinder and the other line to a supply branch leading to the rear side thereof; and a reverse flow branch leading from said front side supply branch to the fluid reservoir and having in it a counterpressure throttle valve controlled by means of a proportional-response counterpressure valve which is pre-settable like said other proportional-response valves.
4. Hydraulic injection unit controls as defined in Claim 1, wherein the hydraulic cylinder assembly is arranged in said second assembly configuration, and, to the cylinder as-sembly is connected a hydraulic control circuit which in-cludes:
a variable delivery hydraulic pump and a constant-pressure pump, both being driven by an electric motor and having their inlets connected to a fluid reservoir;
a pressure supply line leading from the outlet side of the variable delivery pump to the hydraulic cylinder;
a return line leading from the hydraulic cylinder to the fluid reservoir;
an electronic servo-valve simultaneously control-ling the pressure supply line and the return line so as to selectively block both lines and to alternatively connect one of the two lines to a supply branch leading to the front side of the hydraulic cylinder and the other line to a sup-ply branch leading to the rear side thereof, the servo-valve including a fluid pressure booster which is connected to the outlet side of the constant-pressure pump and an electronic signal generator controlling the pressure booster, so as to adjust the hydraulic pressure and flow rate in at least one of the two supply branches in response to a predetermined electronic signal program, the servo-valve further including pressure transducers in the two supply branches, as part of an electronic feedback loop which continuously supplies pres-sure information to the electronic signal generator.
a variable delivery hydraulic pump and a constant-pressure pump, both being driven by an electric motor and having their inlets connected to a fluid reservoir;
a pressure supply line leading from the outlet side of the variable delivery pump to the hydraulic cylinder;
a return line leading from the hydraulic cylinder to the fluid reservoir;
an electronic servo-valve simultaneously control-ling the pressure supply line and the return line so as to selectively block both lines and to alternatively connect one of the two lines to a supply branch leading to the front side of the hydraulic cylinder and the other line to a sup-ply branch leading to the rear side thereof, the servo-valve including a fluid pressure booster which is connected to the outlet side of the constant-pressure pump and an electronic signal generator controlling the pressure booster, so as to adjust the hydraulic pressure and flow rate in at least one of the two supply branches in response to a predetermined electronic signal program, the servo-valve further including pressure transducers in the two supply branches, as part of an electronic feedback loop which continuously supplies pres-sure information to the electronic signal generator.
5. Hydraulic injection unit controls as defined in Claim 4, wherein the hydraulic control system further includes a distributor block which is removably attached to the hydrau-lic cylinder assembly and which incorporates the two supply branches leading to the front and rear sides of the hydrau-lic cylinder;
the electronic servo-valve is mounted on the out-side of, and supported by, the distributor block, forming a rigid assembly therewith; and the pressure transducers in the two supply branches are likewise arranged on the outside of the distributor block, reaching the supply branches through connecting bores in the distributor block.
the electronic servo-valve is mounted on the out-side of, and supported by, the distributor block, forming a rigid assembly therewith; and the pressure transducers in the two supply branches are likewise arranged on the outside of the distributor block, reaching the supply branches through connecting bores in the distributor block.
6. Hydraulic injection unit controls as defined in Claim 5, wherein the hydraulic control circuit further includes a line connecting the constant-pressure pump to the pressure booster and, in said line, a filter and a parallel-connected differential-pressure switch, both being incorporated in the distributor block.
7. Hydraulic injection unit controls as defined in Claim 5, wherein the hydraulic cylinder assembly comprises two par-allel-aligned cylinders, as part of a transversely oriented supporting bridge which is guided for axial movements on two parallel stationary guide rods extending in the two cylinder axes;
the two cylinders are hydraulically interconnected by means of two internal transverse channels; and the distributor block carrying the electronic servo-valve is attached to a lateral mounting face of the support-ing bridge.
the two cylinders are hydraulically interconnected by means of two internal transverse channels; and the distributor block carrying the electronic servo-valve is attached to a lateral mounting face of the support-ing bridge.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2914472A DE2914472C2 (en) | 1979-04-10 | 1979-04-10 | Injection unit of a plastic injection molding machine |
| DEP2914472.7-16 | 1979-04-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1150460A true CA1150460A (en) | 1983-07-26 |
Family
ID=6067976
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000349428A Expired CA1150460A (en) | 1979-04-10 | 1980-04-09 | Hydraulic controls for injection unit of injection molding machine |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS55140538A (en) |
| AT (1) | AT370678B (en) |
| CA (1) | CA1150460A (en) |
| DE (1) | DE2914472C2 (en) |
| FR (1) | FR2453722A1 (en) |
| GB (1) | GB2048156B (en) |
| IT (1) | IT1141562B (en) |
| NL (1) | NL8002059A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3447605C1 (en) * | 1984-12-28 | 1986-05-07 | Karl 7298 Loßburg Hehl | Hydraulic device for the injection molding unit of a plastic injection molding machine |
| DE4446412A1 (en) * | 1994-12-23 | 1996-06-27 | Strunz Heinrich Gmbh & Co Kg | Roof window for angled or flat roof |
| CN107008875B (en) * | 2017-04-12 | 2022-07-05 | 宣化钢铁集团有限责任公司 | Device for realizing double operation modes of billet continuous casting machine |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE7143319U (en) * | 1970-04-25 | 1972-03-16 | Hehl K | Injection unit for an injection molding machine for processing plastics |
| DE2227133C3 (en) * | 1972-06-03 | 1981-04-30 | Hehl, Karl, 7298 Loßburg | Injection unit for a plastic injection molding machine |
| DE7046626U (en) * | 1970-12-17 | 1971-03-25 | Stuebbe Maschinenfab Gmbh | Injection unit for injection molding machines |
| DE2528963C2 (en) * | 1975-06-28 | 1983-11-03 | Karl 7298 Loßburg Hehl | Control device for the hydraulic circuit of an injection molding machine |
-
1979
- 1979-04-10 DE DE2914472A patent/DE2914472C2/en not_active Expired
-
1980
- 1980-04-01 FR FR8007343A patent/FR2453722A1/en active Granted
- 1980-04-03 GB GB8011248A patent/GB2048156B/en not_active Expired
- 1980-04-08 JP JP4530280A patent/JPS55140538A/en active Pending
- 1980-04-08 NL NL8002059A patent/NL8002059A/en not_active Application Discontinuation
- 1980-04-09 CA CA000349428A patent/CA1150460A/en not_active Expired
- 1980-04-10 IT IT21295/80A patent/IT1141562B/en active
- 1980-04-10 AT AT0193980A patent/AT370678B/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| IT8021295A0 (en) | 1980-04-10 |
| ATA193980A (en) | 1982-09-15 |
| DE2914472A1 (en) | 1980-10-16 |
| FR2453722B1 (en) | 1984-03-23 |
| NL8002059A (en) | 1980-10-14 |
| DE2914472C2 (en) | 1982-09-16 |
| GB2048156B (en) | 1983-02-16 |
| FR2453722A1 (en) | 1980-11-07 |
| AT370678B (en) | 1983-04-25 |
| JPS55140538A (en) | 1980-11-04 |
| IT1141562B (en) | 1986-10-01 |
| GB2048156A (en) | 1980-12-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |