IL22765A - Process and apparatus for forming tubular plastic members - Google Patents

Description

FOE BABBITT PIPS FORGES The invention disclosed herein the tion of tubular members of fibrous material and ting and more particularly to the apparatus and process for their fabrication either as a lining or for a metal tubular member or as a tubular member usable as a pipe conduit or other similar numerous processes and means have been used for the making of tubular plastic Herein the invention is directed to the type wherein a fibrous material is ted with a resin advanced to the and thereafter either spirally or convolutely wound into a form by any of the processes well known in the the preform has usually been placed within a rigid mold and subjected to heat and radial the pressure being either exerted radially outward compressing form outwardly against the mold or radially inward sing it against a rigid In accordance with the invention disclosed herein posed radial pressures are employed which permits the zation of relatively thin metal tubes within which the form is fabricated to its finished state although the sures employed are of such degree that creeping or other mage to the metal would result unless compensated for by the utilization of an opposed The foregoing is accomplished by utilizing an tus wherein the metal tubular member in which the preform is fabricated constitutes the inner wall or shell of a double wall tubular the spacing therebetween defining a pressure An advantage of the invention disclosed herein is that the apparatus and process may be used for fabricating tubular members having different outside diameters inasmuch as the inner wall is a removable When metal tubes are being lined or that the plastic tubular member is being formed integrally metal tubes having a bow or ovality which would prevent their fitting within a mold having true internal can be processed and the bow and for all cal be The foregoing and other advantages and uses will come apparent the description of the invention when read in view of the wherein figure 1 is a side view of the apparatus disclosed figures 2 and 2a show a horizontal sectional view of figure with the device under pressure during a curing figure 3 is a vertical sectional view showing the position of the parts during a curing and figure 4 is a view of the yoke for the forward thrust Referring to t drawings the mold comprises an outer tubular shell 1 of any suitable rigid metal having a wall thickness sufficient to withstand the maximum pressure to be established within the Mounted in each end of shell 1 are closure members secured in position by bolts any suitable sealer being used therebetween to make a pressure and leak proof Each closure member 2 is of ring form having a central opening and the inner circumferential face of each of the receive an 0 ring 6 to provide a the closures providing supports for concentrically positioning an inner casing as hereinafter The outer shell has a top fluid inlet at one end thereof which is provided with a suitable control valve and at its opposite end with a bottom fluid outlet provided with a control valve for draining or connecting it to a vacuum producing The shell 1 pivotally mounted thereon front rear thrust means 11 and The front thrust means 11 clude diametrically opposed welded to shell and pivotally mounted on each trunion is a yoke supporting arm having a threaded outer Carried by the arms is a yoke having spaced openings 16 through which arms extend and a central opening 1 for ling the extending end of a mandrel 18 hereinafter The yoke is positioned and secured on arms opposed holding nuts The rear thrust means 12 also includes the on which are pivotally mounted the arms threaded at their outer ends and supporting a thrust screw carrier plate 20 having spaced openings through which arms extend and on which they are positioned by nuts The screw carrier 20 has a central threaded opening 22 for receiving a threaded thrust screw The inner end of thrust screw has a duced end threadedly projecting through a central opening in the base of a cup shaped end support the forward cumferential face or rim of the cup engaging the end of an inner mold casing as subsequently The casing is pivotally mounted on a support having a base 26 provided with an arm ding upwardly and rearwardly and having an ning 28 at its upper end for receiving a pivot Pivot 29 is integral with and laterally extends from a pivot block welded to the casing Pivotally mounted at on the upper edge of block is a latch which engages a keeper holding the casing in a horizontal The casing pivot is positioned forward of the center of gravity of shell 1 and when latch is released the casing will pivot into engagement with stop extending rearwardly from base whereupon the casing will assume an angular incline of approximately reasons after As best seen in figures 2 and the inner casing of the mold is a flexible or metal tubular member 35 herein being a rocket casing having a relatively heavy forward throat portion alight elongated body portion an end portion having a central opening The throat portion and bottom portion have a substantially heavier wall thickness than the body and a tubular collar portion extending beyond the end The end portion central opening is closed by a stop 1 mounted on the end of a threaded bolt which projects rearwardly through the opening to receive nut for holding the stop in Projecting inwardly from stop and integral with is a mushroom seal holder carrying a flash seal of or other suitable material which is with and overlies the casing end portion The inner casing the outer casing and of such diameter that it is engaged by the 0 rings mounted in the end The inner and outer casings thus define a pressure chamber In fining the inner casing as flexible and the terms are used to indicate a thin walled tube wherein the metal may be slightly flexed without damaging Positioned the inner casing is a mandrel 18 having a threaded neck portion a throat portion and a hollow core portion all integrally The tour of the core is similar to an elongated flask or bag having a cylindrical wall portion and end or bottom Overlying the entire core and closely fitting when not in the expanded position is a diaphragm of expansible material such as The diaphragm has the same shape as core in order to overly and enclose with the open end extending beyond a radially tial flange on the inner end of the neck portion where the diaphragm is secured by the gasket sealing means sealirgcup and nut The neck portion of the mandrel is hollow and tending centrally therethrough is an inlet tube which tinues through and closes the throat and projects into the hollow core The outer end of passage connects to a hydraulic fluid line which connects through valve to a suitable source of heated hydraulic fluid under pressure As indicated by the arrows when fluid under pressure is it will flow into the mandrel core then through openings end thereof against the diaphragm upon the flow of the fluid is reversed and it flows ly and out through openings in the throat into the hollow neck passage of the neck The passage nects to an outlet line 60 controlled by two way valve 61 which may direct the fluid hack to its source or connect it to a vacuum pump Obviously by proper control of the outlet valve the pressure within the mandrel may be The plastic tubular member or preform 62 is asbestos sheet material which has been treated with setting resin and cured to the In this instance phenolic resin is being used and the material has been either convolu tely or spirally wound into a preform onto a steel mandrel with a sufficient number of plies to assure proper wall thic of the finished which herein will become a lining for the rocket As the inner mold casing in this embodiment a throat portion of lesser inside diameter than its body portion 22 preform must have an outside diameter slightl smaller than the throat With the preform placed within the an air mandre is placed within the The air mandrel is of similar construction to mandrel but is connected to a source of air instead of Air is then injected to expand the man drel diaphragm until the preform fits tightly against the wall of casing whereupon the air is released and the man drel is Following the withdrawal of the air mandrel a teflon spacer ring is plaoed in position at the forward end of the lining and the mandrel 18 is thereafter A cup shaped spacer member is then positioned with its inner end or rim abutting teflon ring The forward end of ber has a reduced outside end diameter to fit inside the inner casing 62 with shoulder abutting the end of the A nut 66 screw threadedly mounted on the mandrel neck may then be taken up to position the member in Thereafter the front and rear thrust members are pivoted into position and are secured as shown with the 15 at the forward end abutting nut 66 and cup member at the rear end abutting the end portion of the rocket Obviously the inner casing is open at its rear the cup member would be similar to the forward cup member 64 to engage the end of the casing With the thrust members in position the inner casing is fixed relative to the outer and thus the mold has an outer rigid wall and an inner flexible The thrust means further serve to hold the mandrel in proper With the type of mandrel used a sudden surge of pressure acting against the bottom could cause the mandre to become dislodged were it not It thus becomes apparent that the thrust means position and hold the outer inner casing and mandrel in positive position throughout the molding The fluid control valve in now opened and hydraulic heated to a temperature below the curing temperature of the is admitted to the the outlet valve 61 being kept open until all air has been eliminated from the Valve is then partially closed to cause pres sure to build within the mandrel and expand the The temperature of the fluid is kept below the curing perature of the resin until the resin has softened and the entire preform becomes extremely In order to obtain the desired adhesion it has been found that high pressures are that pressures approximating 1000 although the inner casing is it has in this instance a wall thickness of of an the high pressure used would cause the metal to creep and surges of pressure could rupture the tube To pretfent the foregoing an opposed pressure is blished between the inner and outer mold casings 1 and Because of this as outlet valve is gradually closed to build up the internal outwardly acting pressure in the inlet valve 8 on casing 1 is opened and outlet valve 10 closed to build up an external inwardly acting pressure in the The pressure in the mold that is acting internally on the casing may be relatively low in that i needs only be to prevent the inner shell from creeping or otherwise be Assuming that the pressure at which the metal would yield or creep is 900 psi an external sure of 125 psi is established so that the internal pressure is acting outwardly against 1025 which vents creeping and acts as a safety factor against sudden pressure In effect the inner casing is reinforced by surrounding it with a pressure restraining With the pressures the temperatures of the fluids are raised to the curing temperature of the resin and held for the required curing time of approximately two tes per During the curing period the device is set at an angle by releasing latch permitting gas to rise and escape from the upper Upon the completion of the curing cycle temperatures ar reduced to the pressures are released and the inlet valves To assure emptying of the mandrel and withdrawal of the diaphragm from the tubular valve 61 can he set to connect outlet passage to a vacuum ce assuring withdrawal of all The thrust means are then mandrel is from the rocket whereupon the latter is As determined from the foregoing description heat and pressure are simultaneously applied both internally and By the application of external pressure it is possible to line metal tubings which would otherwise creep or burst under high internal pressures By simultaneous appli cation of in both rapid transfer is plished resulting in excellent adhesion of the lining to the Another result accomplished by the simultaneous cation of external and internal heat and pressure is that the casing to almost true cylindrical shape and axial As previously stated the metal casings ofte have a wall thickness as low as of an inch and during initial heat in the making of the metal they become oval assume a that true axial The distortion is such that the tubes will not fit into molds having a fixed inside When to the high pressure where the tube is the and so held throughout the curing cycle the ovality and are for all practical purposes brought within acceptable Although the inner casing has here been shown as a rocket tube and the process of lining the tube th removability of the inner casing is indicative of the tility of the The present apparatus may be utilized for rent sizes of Herein the outer casing must the highest external pressure required and for purposes of explanation may be said to have a four inch inside diameter whereas the external diameter of casing illustrated is By changing end closures 2 the inner casing may be of varying sizes with an upper limit of outside diameter only sufficiently less than four inches to provide space for the outer pressure Because of various sizes of tubing be made by interchanging the end res to accept inner casings of different outside Moreover as the inner casing is pressure relatively light casings may be permitting the use of an aluminium mold which will not require a special internal This interchangeability is highly desirable from a production At present a specific mold is quired for each size of With this apparatus a single mold with interchangeable end closures and inner may be used for numerous thus reducing the number of installations required together with all the auxiliary ment necessary for each Summarizin it becomes evident that the utilization of compensating forces or degrees of pressures result in the utilization of the apparatus described for the fabrication of various types of tubular When pressure of such a degree that damage to the casing may it is readily compensated for by the opposed pressure and circumferential or longitudinal rupturing by sudden surges is It is apparent that if it is desired to cover the inner a be formed directly thereon or it may be inserted in a Because of the increased diameter the end closures g may be slipped over the oasing ends and then secured in The process pressures would be reversed with mandrel acting as a compensating Obviously lining and covering can be accomplished insufficientOCRQuality

Claims (1)

1. 22765/2 - 13 - - τ ■ ♦ . 1 · A method of forming a thermoplastic tubular member within a metal tubular member comprising the steps of inserting in the metal tubular member a preformed member formed of thermoplastic ma erial, applying an internal fluid pressure to the ormed member which is greater than that which the metal tubular member oan withstand, simultaneously applying an external pressure to the metal tubular member to compensate for the internal fluid pressure and heating the internal pressure fluid to cure the thermoplastic materials 2· The method as claimed in Claim 1 in which the thermoplastic tubulaiJmeiBber forms a lining within the metal tubular member* 3, She method as claimed in Claim 1 or Claim 2 in which the thermoplastic tubular member is formed of resin treated fibrous material. 4· The method as claimed in any preceding claim in which the external pressure applied to the metal tubular member when added to the pressure at which the metal tubular member will become damaged equals the internally applied pressure* 5· The method as claimed in any one of Claims 1 to 4 further comprising the initial steps of positioning the metal tubular member within a larger diameter tubular casing capable of withstanding a maximum external fluid pressure* sealing off the spacing formed between the metal tubular member and the larger diameter tubular casing at each end of the casing, inserting the preformed thermoplastic tubular member within the metal tabular member, inserting in the preformed thermoplastic tubular member a fluid tight expendible diaphragm* 22765/2 - 14 applying said internal pressure to expand the di agm 7· and compress the preformed thermoplastic tabular member against the metal tubular member and simultaneously applying the external pressure into said spacing and heating the internal pressure fluid to cure the thermoplastic material. 6· Apparatus for carrying out the method claimed in any of the preceding claims comprising a metal tubular member which is flexible, a fluid tight expendible diaphragm insertable in the metal tubular member, a larger diameter tubular casing which is rigid and which has a fluid inlet, said metal tubular member being disposed within said larger diameter casing so as to be radially spaced, closure means for closing the ends of the tubular casing, said closure aean having central openings, in which the metal tubular member is supported and means to supply pressure fluid to the fluid. inlet* 7* Apparatus as claimed in Claim 6 in which the closure members are detaehably mounted on the tubular casing, 8* Apparatus as claimed in Claim 6 or Claim 7 in whioh closure means mounted on the tubular easing releasably engage the end of the metal tubular member for positioning it relative to the tubular casing* 9* Apparatus as claimed in Claim 8 wherein said olosure means comprises a pair of oppositely disposed trunnions secured to said metal casing, an arm plvotally mounted at one end on each of said trunnions, a yoke carried on the free ends of said arms and abutting olosure means intermediate of the yoke and the en of the metal tubular member* 10* Apparatus as claimed in Claim β or 81alm 9 ia whioh 11· Apparatus as claimed in any one of Claims 6 to 10 in which the expansible diaphragm can expand against the interior of said metal tubular member and against the closed end, a first closure means mounted on said tubular casing and engaging the open end of the metal tubular member and the diaphragmβ and the second closure means being mounted on the tubular casing and engaging the closed end of the metal tubular member* 12· Apparatus as claimed in any one of Claims 6 to 11 in which the closure means are formed as rings removably mounted in the ends of said tubular casing* said metal tubular member being removably mounted in said rings* and sealing means being provided between said rings and said inner casing. 13· Apparatus as claimed in/one of Claims 6 to 12 In which the tubular mold is pivotable so as to be positioned in an inclined position, latch means being provided to maintain the tubular casing in a substantially horizontal position* 14· A method of forming a thermoplastic tubular member within a metal tubular member substantially as hereinbefore described with reference to the accompanying drawings* 15* Apparatus for forming a thermoplastic tubular member within a metal tubular member substantially as hereinbefore desoribed with reference to and as illustrated in the accompanying drawings* For the Applicants KJ/DIi