CN1906010B

CN1906010B - Injection compression moulding

Info

Publication number: CN1906010B
Application number: CN2004800404226A
Authority: CN
Inventors: P·R·克拉克
Original assignee: Im Pak Technologies Ltd
Current assignee: Im Pak Technologies Ltd
Priority date: 2004-01-16
Filing date: 2004-12-30
Publication date: 2010-06-09
Anticipated expiration: 2024-12-30
Also published as: GB0400936D0; CN1906010A; EP1704036A2; GB2410001A; CA2552893A1; US20060286916A1; WO2005068157A3; MXPA06008099A; WO2005068157A2; JP2007517690A

Abstract

A mould for injection compression moulding of an article includes a female mould part and a core for mounting in use on the platens of an injection moulding machine for movement towards and away from one another between an open and a closed position. A sealing ring surrounds the core for effecting a seal between the female mould part and the core. The core, the female mould part, and the sealing ring together define a closed mould cavity as the core approaches the closed position. The sealing ring has tapering sections, each tapering section having a tapering surface that seals against a tapering surface on the core only after the core has reached the closed position, leaving a venting clearance between the tapering surfaces of tapering sections of the sealing ring and the tapering surface of the core as the core approaches the closed position.

Description

Injection and compression molding

Technical field

The present invention relates to injection and compression molding, relate in particular to the improvement of the mould of narrating among the PCT publication number WO02/058909.

Background technology

In injection and compression molding technology involved in the present invention, accurately the plastic material of measured quantity was injected in it before die cavity is closed fully.With a plurality of component set of mould together the time, by be used for closing molding power rather than be used for the pressure of time of its injection in the mould with the plastic material compression of injection and be full of die cavity.Thereby, can obtain the slenderness ratio higher than traditional slenderness ratio that injection molding obtained, even when using full-bodied low-cost plastic material.This just can make this technology be used to make article as cup and margarine tub and so on, and wherein, described article as cup, margarine tub and so on must be used the additive method manufacturing so far, makes as vacuum mo(u)lding or mold pressing molding by the thermal softening sheet material.Another advantage is to have reduced cool time widely because of operating temperature is lower, and because by the faster filling rate (traditionally, leave die cavity wall owing to article produce to shrink, the heat loss of expectation 70% is scattered and disappeared by core) that improved of the heat loss of die cavity.

WO02/058909 has described the mould between a kind of platen that is installed in injection molding machine, and this injection molding machine is used for the injection and compression molding thin-walled articles, and wherein, this patent WO02/058909 is considered to immediate prior art of the present invention.Mould comprises former half mould (half) and pressing plate, and wherein, the former half mould is installed on the stationary platen of mould machine, and pressing plate is installed on the mobile platen and transports the core (if desired, these two parts must need reason ground to exchange) that is used for closing molding.Core passes the interior cylindrical hole of edge block ring and with respect to its sealing, wherein, this edge block ring is arranged between former half mould and the pressing plate.In use, when fixing die halves was advanced, the edge block ring was used for sealing die cavity before core arrives its terminal location at pressing plate.Therefore, when time of its injection was in die cavity, it was sealed fully, even thereby core does not also advance to fully and makes its volume be reduced to minimum in the mould.

Yet, it has been found in practice that to be difficult to form the edge block ring that has cylindrical hole that this edge block ring is sealed in around the core effectively and allows that also core freely passes.Allow core with respect to edge block ring freedom, move required gap reliably and do not allow and produce perfectly sealing and around the edge of moulded parts, produce not received witness line.

Summary of the invention

For alleviating aforesaid drawbacks, the invention provides a kind of mould with following feature, to be used for the injection and compression molding of article: this mould has die cavity, the injection of plastic material is with filling die cavity partly before mould is fully closed, subsequently, the compression plastic material is to be full of the whole volume of die cavity in the process of closing molding, this mould comprises can be at open position and the female part that be movable relative to each other between the closed position fully and core and around the sealing ring of core, the sealing ring is used for setting up sealing between female part and core, when core is in complete closed position, core, female part and sealing ring limit described die cavity together, wherein, before core arrives complete closed position, sealing ring operationally seals with female part and contacts, sealing ring has taper surface, only this taper surface just is sealed on the taper surface on the core after core has arrived complete closed position, advance towards complete closed position when injecting plastic material in the die cavity at core thus, between the taper surface of sealing ring and core, have ventilation gap with compression.

Material to be molded is molten thermoplastic material normally.Yet, it will be apparent to those skilled in the art that the present invention also can be applicable to molded melt metal, resin and thermosets.In fact, this material can be initial fully flowing and can by injection, subsequently will be by cooling, heating or chemical cure any material of hardening.

In the present invention, the purposes that is sealed to the sealing ring conical surface on the core is that the gap that is used for keeping between core and the sealing ring is fully closed until mould, moves freely with respect to core to allow sealing ring.This be located at sealing ring on to be used to the align conical surface of purpose different, as US6500376 exemplified, also there was not any gap therebetween in surface contact wherein before die cavity is closed fully.

Term " sealing ring " may not be interpreted as being confined to annulus in the context of the present invention certainly, and in all cases, its profile is limited by the profile of article to be molded.

Preferably, less with respect to the cone angle that the core moving direction is measured, usually less than 5 °, therefore, move in the last several millimeters process at core, between core and sealing ring, only there is little gap.Closely spaced width will not allow that injection material penetrates in it, but allow that air escapes from die cavity, wherein, still exist in this little gap during near the closed position at core.

Because air can be escaped from this die cavity at any time before die cavity is closed fully, can save ventilation gap fully like this, wherein, when injection or injection and compression molding goods, need this ventilation gap usually.Ventilation gap can be saved and many important advantages will be brought.At first, because gas must be escaped through steam vent, can not allow that injection material flows through to such an extent as to this steam vent is too little, this injection material is heated to high temperature, to such an extent as to the result causes a large amount of maintenance of ventilation gap needs and can arrive the burned plastic material of sufficiently high temperature.Secondly, will reduce the translational speed of injection material and the filling speed of mould by the back pressure that is produced by the ventilation gap suction air.

Sealing ring preferably is installed on the core by connecting portion, and allows that it does moving of limited extent with respect to core, and sealing ring is promoted on the direction that increases the gap length between the conical surface by in spring and the air pressure at least one.

Description of drawings

Narrate the present invention by way of example with reference to accompanying drawing, wherein:

Fig. 1 is the perspective view of the female part that observation post is seen in die cavity,

Fig. 2 is the perspective view of core, and this core will be coupled in the female part among Fig. 1,

Fig. 3 is the perspective view of two modules of Fig. 1 and 2, and wherein, mould is in the closed position,

Fig. 4 is the sectional view of the core among Fig. 2,

Fig. 5 illustrates a part of cross section of Fig. 4 with magnification ratio, and

Fig. 6 is the sectional view of this mould when mould is in the closed position.

The specific embodiment

Accompanying drawing shows a core/cavity set, and it is used for the article of injection and compression molding water glass form, and these article have the sidewall of flat usually base portion, frusto-conical and are looped around rim of a cup antelabium on every side, and this antelabium is the form of inverted " U ".Be appreciated that core/cavity set can be one of them in many groups in the multi-cavity mold, and different groups can be provided with abreast and/or back-to-back pile up.Yet, in the following description, only relate to the one-mode cavity mould for the sake of simplicity.

Mould comprises female part 10 and core part 12, and it cooperatively interacts in mode shown in Figure 3, thereby forms die cavity betwixt, and this die cavity has the required form of the water glass for the treatment of molding.

Traditional injection-molded in, at first come moulding article by complete closing molding.Next, with time of its injection in die cavity, thereby be full of this die cavity fully.After plastic material is sufficiently cooled, open mould, discharge molded article, and repeat this circulation.Yet there is restriction in above-mentioned technology to the slenderness ratio of moulding article.Obtainable minimum wall thickness (MINI W.) change along with the viscosity of plastic material, even in order to produce the article of the wall thickness bigger, need to use more expensive low viscosity plastic material than the needed wall thickness of the structural integrity that is used for moulding article.

On the contrary, in injection and compression molding, in the injection latter stage of plastic material, core is not in the complete closed position of die cavity.When advance in the closed position, force the plastic material of injection to be full of die cavity at core.Order about many advantages that plastic material flows and has in the prior art to be put down in writing by the compression stress of die cavity rather than by injection pressure.

Yet there is some problem that does not occur in traditional injection molding process really in injection and compression molding.First problem is relevant with aliging of mold component.Traditionally, the taper fit face is located on the different parts of mould, when mould is closed fully, and the mutual centering of taper fit face.Yet before mould was closed fully, mold component may not exclusively align, and it is not total to center or not coaxial in other words.Can not guarantee to be aligned to required accuracy by the guiding device of tie-rod acquisition or employed other guidance systems of machine producer of injection molding machine, especially, it should be noted that: the main purpose of using injection and compression molding is to obtain very large mobile slenderness ratio in article (as cup, margarine tub or dustbin).

In order to overcome these problems, in the illustrated embodiment of the present invention, three flat guide pins 14 are fixed firmly on the core part 12, with around accurately preposition is looped around the mold cores 16 at center.Each guide pins 14 has two parallel location divisions, side.A pair of location division 14a is located near the base portion of each guide pins 14, and another is located on its free end location division 14b.The width of location division 14a is greater than the width of location division 14b.The part of each guide pins between location division 14a and 14b is illustrated gradually shrinks, but it can be an Any shape, as long as its width never exceeds the width of location division 14a.The 18a of positioned parallel portion and the 18b that cooperate are a part of U-shaped groove that is formed by insert 18, and this insert 18 similarly is fixed on the female part 10.

In use, be not connected to the mold component of injecting systems, normally core part 12 is installed the lost motion of allowing that promptly there is little degree in it with respect to the machine platen in the following manner.Powerful spring pressure is used for mold component is remained on the appropriate position, and still, if enough big power is applied to this mold component, this mold component will move laterally.

The very first time closes mould fully, and pin and insert may fully not cooperate mutually, and this will apply active force to core part, aligns with female part thereby promote this core part.When mould is fully closed then, the mutual in a conventional manner complete matching of the parts of mould.In operation cycle subsequently, before mould is closed fully, location division 14a and 14b will be in contact with one another with surface element 18a and 18b, and will make mold component in two different and planes axial separation, carry out any small relative displacement, concerning the aspect of the capable aligning of near peace, the relative displacement of mold component is for guaranteeing before closing fully at mould that the correct aligning of mold component is necessary from proper alignment.

Though guide pins 14 and insert 18 are guaranteed the concentricity of mold component at the two ends of die cavity,, under the situation of the location division that the length that does not need to use its axial length and die cavity is complementary, it can guarantee concentricity really.As an alternative, there is not active force to be used to aim at mold component, till mould is when closing fully.Because it can avoid the excessive wear of location division, so this point is extremely important.

People can consider to use tapered rod to come the guide pins 14 of instead of flat, but the latter is preferred, and this is because only need each guide pins to revise in a plane, to have simplified the location of location division on mold component thus.

In a multimode cavate mould, preferably around each independent core/cavity set, provide guide pins, so that a plurality of core/cavity set is relative to each other carried out possible moving.About more small-sized product, can around two or four die cavitys, provide guide pins, if described die cavity is closely condensed together.

Although adopt three guide pins 14 to aim at each mould in the illustrative embodiment of the present invention,, also can adopt a plurality of guide pins, preferably adopt four.

Another problem that needs in the injection and compression molding to overcome is included in the reducing of volume of the plastic material in the die cavity.In the prior art, this problem is by using the edge block ring to isolate the die cavity in the female part and be resolved by the cylindrical hole that core is passed in the edge block ring.This is not gratifying solution, and this is to be very difficult because form the edge block ring with cylindrical hole.Described cylindrical hole freely passes therethrough around core sealing and permission core effectively.Allow core can not produce good sealing, and cause around the edge of moulding article, producing unacceptable witness line with respect to the gap that edge block ring freedom moves reliably.

(referring to Fig. 4 to 6) in a preferred embodiment of the invention, sealing ring 20 is looped around around the core 16.Sealing ring is held on the core part 12, and can carry out moving of less degree with respect to 12 of core part on the axis of movement direction of core part 12.The hard spring (or air pressure) that can bear the pressure in the mould is used for sealing ring 20 is remained on the top surface of female part 10, therefore, does not have plastic material to overflow from the top cross ground of die cavity.

Sealing surfaces between sealing ring 20 and the core 16 is not as of the prior art cylindrical, but is formed by two tapered portion of adjoining 22,24, and wherein, the cone angle of tapered portion 24 is very little, less than 5 °, preferably approximately is 1 °, and the cone angle of tapered portion 22 is bigger.In two tapered portion, before die cavity is closed fully, between sealing ring 20 and core 16, can not produce the sealing contact.

In common operation cycle, core 16 advances in the die cavity in the female part 10 at first fully, thereby the most of air in the die cavity is discharged.Next, the time of its injection of accurately measured quantity in die cavity, is formed material base (biscuit) with the base portion at die cavity.During this period of time, the effect by injection pressure or by core die cavity mobile core is returned in the female part slightly to remove.

Begin back to remove move before, according to the range of sealing ring be expelled to the thickness of the blank in the mould, sealing ring can contact or not contact with the front portion of female part.If sealing ring does not contact with the front portion of female part, then according to sealing ring with respect to the stroke of core with return the mobile amplitude of removing, move or only returning in the process of removing mobile beginning part removing for whole time, the sealing ring can still keep contacting with the female part sealing.

Remove in the moving process returning, to be used for the aiming at of maintenance core 16 and female part by guide pins 14.Core 16 has formed the gap with respect to moving axially at this of sealing ring 20 between the two, this is because the sealing 22 of taper and 24 cause.Yet, because the steepness of the cone angle of sealing 24 former thereby to make the width in the gap that is produced be wide to being used as the ventilating opening that permission gas is escaped in the die cavity.

When next core 16 advances in the die cavity of female part, the material base of compression plastic material, and force its edge to flow upward to the sidewall of die cavity towards container.During this period of time, the gas of discharging from die cavity at first passes the gap between sealing ring and the die cavity, passes the gap between sealing ring 20 and the core 16 then.When core arrived its end position, the gap between itself and the sealing ring 20 was fully closed, and produced any outflow to prevent plastic material in mould.

Because by using cone pin 14 and U-shaped portion 18 to obtain to axially align accurately, plastic material is at the uniform velocity mobile at the whole peripheral of die cavity, and arrives the end of die cavity in the essentially identical time.This has just reduced the distance that sealing ring 20 must move with respect to core 16.

It should be noted that the sealing ring parts are not only closed die cavity effectively, discharge to avoid any moment, and under the situation of the core that do not rub, also can avoid moment to discharge.In addition, sealing ring provides ventilating opening, and when core arrived the closed position, this ventilating opening had reduced cross-sectional area.Therefore, in the beginning that air need be discharged the compression travel of die cavity, air can freely at first pass through between sealing ring 20 and the die cavity 10, freely passes through then between sealing ring 20 and the core 16.This has just been avoided arriving high temperature in the ventilating opening and having reduced the air damping that core moves.When finally being closed in the gap, all air are discharged from mould cavity fully, and sealing will prevent any discharge of plastic material.

Female part and core have been narrated in further detail than being used for understanding content required for the present invention, but, the parts that herein are not described in detail normally use traditionally, and those skilled in the art just are appreciated that its function under the situation that does not need explanation in detail.Especially, the parts relevant have been narrated with this function, described function for example be with time of its injection in die cavity, the cooling of mould, with discharge and parts the installation mold tool in of moulding article from mould, this mold tool is installed on the platen of injection molding machine.

Be appreciated that also described mould need be installed in the mould machine, this mould machine orders about core with suitable speed and female part moves relative to each other, and applies suitable pressure simultaneously.Pressure/the range distribution (profile) that has been found that the mould machine of axostylus axostyle (toggle) operation is ideally suited for injection and compression molding technology, but other machines can be programmed to obtain similar pressure/range distribution.Can not be when the big displacement model of low pressure to be changed into high pressure small displacement mode smooth-goingly at machine, another possibility will be between mould and machine platen module to be set, this module can produce required distance/pressure profile.

Claims

1. mould that is used for the injection and compression molding goods, this mould has die cavity, the injection of plastic material is with filling die cavity partly before mould is fully closed, subsequently, the compression plastic material is to be full of the whole volume of die cavity in the process of closing molding, this mould comprises can be at open position and the female part (10) that be movable relative to each other between the closed position fully and core (16) and the sealing ring (20) that centers on core (16), sealing ring (20) is used for setting up sealing between female part (10) and core (16), at core (16) when being in complete closed position, core (16), female part (10) and sealing ring (20) limit described die cavity together, it is characterized in that, before core arrives complete closed position, sealing ring (20) operationally seals with female part and contacts, sealing ring (20) has taper surface (24), only this taper surface (24) just is sealed on the taper surface on the core (16) after core (16) has arrived complete closed position, advance towards complete closed position when injecting plastic material in the die cavity at core (16) thus, between the taper surface (24) of sealing ring (20) and core (16), have ventilation gap with compression.

2. mould as claimed in claim 1 is characterized in that, the cone angle of measuring with respect to the moving direction of core is less than 5 °.

3. mould as claimed in claim 2 is characterized in that, the cone angle of measuring with respect to the moving direction of core is 1 °.

4. the described mould of arbitrary as described above claim is characterized in that, it is the taper surface (24) of sealing ring (20) and the gap between the core (16) that the unique ventilation gap be used for gas is discharged in the mould cavity is set.

5. mould as claimed in claim 1, it is characterized in that, sealing ring (20) is installed on the core (16), so that can carry out moving of limited extent with respect to core (16), sealing ring (20) is promoted by at least one direction along the gap between increase taper surface (24) and the core (16) in spring and the gas pressure.

6. mould as claimed in claim 1, it is characterized in that, at least one adjustable ground in core and the female part is installed on the platen of injection molding machine, so that core and female part axially align mutually, wherein, a plurality of guide pins are located on one of them mold component, and around the distribution of core axis, and at mold component during near complete closed position, described guide pins is received in the groove as the compensation shape in another mold component of mold component, each guide pins has two parallel location divisions, side, described location division is spaced from each other along the length of guide pins, and the free-ended location division of more close guide pins is narrower than the location division on the other end, and the length of each location division equals the last part of the stroke of platen at least, in the trip, the compression of the plastic material of injecting.

7. mould as claimed in claim 6 is characterized in that, the part of each guide pins between two parallel location divisions, side is continuous convergent.

8. as claim 6 or 7 described moulds, it is characterized in that each guide pins is flat, and be fixed on the core that groove is formed in the flat insert, this insert is fixed on the female part releasedly.