Back-to-back valve gate system

Abstract: A manifold is disposed within a pair of abutting pre-load mold plates in a pre-load relationship. Fluid flowing through the manifold is heated by a first heater. The fluid is then divided into a plurality of passages in the manifold. Pairs of passages have a back-to-back in-line relationship. A cylinder between each pair of the in-line passages holds a pair of pistons in the in-line relationship. Each piston in the pair has piston units in an interdigitated relationship with piston units on the other piston in the pair. Each pair of pistons is movable by pressurized fluid (e.g. air) between first and second positions. In the first position, each piston provides for the fluid (e.g. resin melt) flow through one of the passages to a pair of runners in the manifold. In the second position, each piston prevents the resin melt flow through the passages. A first heater heats the resin melt flowing through the passages. A second heater heats the resin melt flowing through the runners. Resin melt is prevented from leaking between the manifold and the mold plates even with temperature changes in the manifold as a result of the heating of the resin melt. This is accomplished by a pair of tongues, one rigid and the other resilient, extending from the manifold to the mold plate. In this way, fluid flowing into the manifold through one inlet exits through a plurality (e.g. 8) of gates without leakage after being heated at the passages and at the runners.

Description: This invention relates to an injection molding apparatus according to the preamble of clam 1. US-A-4 682 945 discloses a thermal insulating and expansion assembly for injection molding which includes a telescoping assembly of sleeves for supporting and sealing a floating manifold. An inner sleeve is integrally formed with a nozzle body that abuts the manifold, the sleeve projecting oppositely in spaced relation both to a main portion of the nozzle and to a passage formed in a mold plate through which the nozzle projects. An outer sleeve extends an annular space between the inner sleeve and the passage, having an outwardly projecting flange and a short centering enlargement that engages the mold plate and the passage, and an inwardly projecting flange that engages a free end of an inner sleeve. Fluids such as plastic material are molded into different configurations. The fluid is passed through apparatus for heating the fluid and for injecting the fluid into the molds. When the fluid solidifies, it forms an article with a shape corresponding to the shape of the molds. It is important that the fluid is heated before it is injected into the molds to insure that the fluid will flow easily into the molds and completely fill the molds before it solidifies. The injection apparatuses now in use produce articles of like configuration by the thousands. Because of this, it is important to mold the articles as quickly as possible. It would accordingly be desirable to inject fluid into a plurality of cavities simultaneously from a single heating and injecting apparatus. It would additionally be desirable to provide pairs of gates, and the pistons for controlling the fluid to the gates, in a back-to-back in-line relationship in such apparatus to double the number of cavities while maintaining the cavities compact. In such an arrangement, fluid (e.g. resin melt) would flow through one of the passages in one direction in the in-line relationship and fluid would flow through the other passage in the opposite direction in the in-line relationship. The fluid flowing through the passages would then flow through gates in the apparatus to individual cavities within a mold. To minimize the size of the fluid-injecting apparatus and to increase the number of cavities simultaneously receiving fluid (e.g. resin melt) in a mold from a single injecting apparatus, it would even be desirable to provide for the introduction of fluid through a single inlet and to provide for the flow of fluid simultaneously through a multiple number of passage and then to a multiple number of gates. In such apparatus, it would be desirable to pair the passages, and the pistons for controlling the flow of fluid through the passages to the gates, in a back-to-back in-line relationship. The desirability of having a multiple number of passages and the associated pistons in a paired back-to-back in-line relationship has been known for some time. However, no one has been able to provide apparatus which provides such a relationship of the passages and the associated pistons satisfactorily in an in-line relationship. The problem of providing such apparatus has been further compounded as a result of the difficulty of providing such apparatus without having fluid leak from the apparatus when the apparatus becomes heated by heaters in the apparatus for heating the fluid. The object of the present invention is achieved by an injection molding apparatus according to claim 1. Fluid (e.g. resin melt) is prevented from leaking between the manifold and the mold plates even with temperature changes in the manifold as a result of the heating of the fluid. This is accomplished by a pair of tongues, one rigid and the other resilient, extending from the manifold to the mold plate. In this way, fluid flowing into the manifold through one inlet exits through a plurality (e.g. 8) of gates without leaking after being heated at the passages and at the gates. In the drawings: Figure 1 is a top view of apparatus constituting one embodiment of the invention; Figure 2 is a front elevational view, partially in section, of the apparatus shown in Figure 1; Figure 3 is a fragmentary side elevational view, partially in section, of the apparatus shown in Figures 1 and 2; Figure 4 is an enlarged fragmentary sectional view similar to that shown in Figure 2 and shows a pair of back-to-back in-line pistons in an open relationship for passing fluid to associated gates and additionally shows channels for receiving fluid such as air under pressure for moving the pistons to close the gates; Figure 5 is an enlarged fragmentary view similar to that shown in Figure 4 and shows the pair of back-to-back in-line pistons in a closed relationship for preventing fluid from passing to the associated gates and also shows the channels for receiving the fluid such as the air under pressure for moving the pistons to close the gates; Figure 6 is a side elevational view and shows the back-to-back in-line pistons and channels for receiving the fluid such as air under pressure to open the gates; Figure 7 is an enlarged fragmentary elevational view of one of the pistons in the apparatus; Figure 8 is an enlarged fragmentary side elevational view similar to that shown in Figure 3 and illustrates in additional detail the passage of the fluid through the apparatus constituting this invention; Figure 9 illustrates an arrangement for providing a sealing between a nozzle and manifolds in the apparatus against the leakage of fluid when the manifolds are cold; and Figure 10 is a view similar to that shown in Figure 9 and illustrates the arrangement shown in Figure 9 for providing the seal between the nozzle and the manifold against the leakage of fluid when the manifold has been heated by the heat from the heaters. An embodiment of an apparatus constituting one embodiment of this invention is generally shown at 10. The embodiment includes mold plates 12 (Figure 2) joined as by bolts 14. A main manifold 15 (Figure 2) and sub manifolds 16 are disposed within the mold plates 12. The main manifold 15 and sub manifolds 16 are pre-loaded within the mold plates 12 to abut the mold plates and one another in a tightly pressed relationship. The mold plates 12, the main manifold 15 and the sub manifolds 16 may be considered as a housing. An inlet 18 is disposed within a sprue bar 19 in one of the sub manifolds 16 and the main manifold 15 to receive fluid from a source (not shown). The fluid is then transferred from the inlet 18 to a plurality of passages 20a, 20b, 20c and 20d. The fluid is then transferred from each of the passages 20a, 20b, 20c and 20d to another pair of passages. For example, the fluid in the passage 20b is transferred to another pair of passages 22a and 22b (Figure 3). Each of the passages such as the passages 22a and 22b is disposed in an injection nozzle such as an injection nozzle 23. In this way, the fluid passing through the single inlet 18 is transferred into a plurality (e.g. 8) of passages such as the passages 22a and 22b. The number of passages in the plurality may be any desired number and may be considerably greater than eight (8). The fluid flowing from the passages such as the passages 22a and 22b may be injected into hollow cavities in the mold (not shown). Each of the cavities has an individual shape to produce articles of that shape. Heaters 24 (Figures 1 and 2) are disposed to heat the fluid (e.g. resin melt) in the passages 20a, 20b, 20c and 20d. Heaters 26 are disposed to heat the fluid in the passages such as the passages 22a and 22b. The heaters 26 may be disposed in an assembly to facilitate removal of the heaters from the assembly when the heaters become worn or defective. Such a heater assembly is disclosed and claimed in application Serial No. 08/186,281 filed by Alan McGrevey on January 24, 1994, and entitled "Heater for Injection Molding" and assigned of record to the assignee of record of this application. The heaters 24 may produce a temperature the same as, or different from, the heaters 26. A number of members may be included to position the main manifold 15 and the sub manifold 16 properly relative to each other and to the mold plate 12. For example, a ring 28 (Figure 2) made from a suitable material such as steel may be provided as a center locator and pressure ring between the mold plate 12 and the main manifold 15. Dowel pins 30 (Figure 1) may be provided for locating the main manifold 15 relative to the mold plates 12 and for preventing swivelling of the main manifold relative to the mold plates. Dowels 32 may be provided to locate the sub manifold 16 relative to the main manifold 15. The dowels 32 prevent the sub manifold 16 from swivelling with respect to the main manifold 15 and assure that the passages 20a, 20b, 20c and 20d in the main manifold and the sub manifolds will be properly aligned. Dowels 34 (Figure 2) locate the outlets such as the outlets 22a and 22b properly. Cylinder bodies 38 (Figure 2) are disposed in the main manifold 15. The cylinder bodies 38 are hollow to define a chamber for receiving pistons 40 for movement in such chamber. For example, pistons 40a and 40b are movable in the chamber in the cylinder body 38 shown in Figure 1. A pair of piston units are attached as by screws 44 to each of the pistons 40 and 40b. For example, piston units 42a and 42b (Figures 1 and 2) are attached to the piston 40a and a pair of piston units 42c and 42d (Figure 1) are attached to the piston 40b. The piston units 42a and 42b are diametrically opposite each other as are the piston units 42c and 42d. However, the piston units 42a and 42b are angularly displaced by 90° from the piston units 42c and 42d. In this way, the piston units 42a and 42b are disposed in an interdigitated or nesting relationship with the piston units 42c and 42d. This causes a compact relationship to be established between the piston units 40a and 40b and the piston units 42c and 42d. Furthermore, this nested or interdigitated relationship prevents the pistons 40a and 40b from rotating relative to each other. This provides for the movement of the pistons 40a and 40b only in a back-to-back in-line relationship. The pistons such as the pistons 40a and 40b are provided with captive nuts such as a captive nut 46 (Figure 2) which screws on the piston. The captive nuts such as the captive nut 46 have a first portion (e.g. 46a for the piston 40a) of large diameter and have a second portion (e.g. 46b for the piston 40a) of reduced diameter. Valve pins such as a valve pin 48 (Figures 2 and 8) extend through centrally disposed holes in the captive nuts such as the captive nut 46. The valve pins such as the valve pin 48 are movable with the associated piston such as the piston 40b. The pistons such as the piston 40 and the valve pins such as the valve pin 48 have two positions. In one position, the pistons such as the piston 40 close the gates at the end of the passages 22a and 22b against the passage of fluid (e.g. resin melt) to the mold cavities. This occurs when the portion 46a of the enlarged diameter in the cap 46 closes the associated one of the passages 20a, 20b, 20c and 20d. The closed position is shown in Figure 5. In a second position, the pistons open the passages such as the passages 22a and 22b to the passage of fluid. This occurs when the portion 46b of reduced diameter in the cup 46 opens the associated passage. The open position is shown in Figure 4. Bushings such as a bushing 50 (Figure 2) envelope the valve pins such as the valve pin 48. The bushings such as the bushing 50 limit the movement of pairs of valve pins such as the valve pin 48 to an in-line relationship. The bushings such as the bushing 50 may be made from a suitable material such as a carbide. Shims such as a shim 53 (Figures 2 and 8) are disposed on the heads of the valve pins such as the pin 48. The thickness of the shims such as the shim 53 may be varied so that the positions of the valve pins such as the valve pin 48 do not have to be adjusted. Instead of, or in addition to, the shims 53, springs such as Belleville springs 51 (Figure 7) may be provided to adjust for the spacing between the valve pins such as the valve pin 48 and the associated pistons. Cylinder cover plates such as cylinder cover plates 54 (Figures 4 and 5) are attached to the cylinder 38 as by screws 55. The cover plates such as the cover plates 54 are provided with openings to receive the pistons such as the pistons 40a and 40b. Dowels 57 are disposed between the cover plates such as the cover plate 54 and the sub manifolds 16 to prevent rotation of the cover plate relative to the sub manifold. As will be seen, the pistons such as the pistons 40a and 40b are disposed in a back-to-back in-line relationship. The pistons such as the pistons 40a and 40b are simultaneously moved by a pneumatic fluid such as air under pressure to either the open or closed relationships. The flow of the fluid (e.g. pressurized air) under pressure to move the pistons such as the pistons 40a and 40b is provided through channels for passing the air under pressure. For example, air channels such as an air channel 56 (Figure 6) are provided to move the pistons such as the pistons 40a and 40b to the open relationship for the passage of the pressurized through the passages such as the passages 22a and 22b. The movements of the pistons 40a and 40b to the open relationships are indicated by arrows 57 in Figure 6. Air channels such as an air channel 58 are provided to provide for the disposition of air under pressure against the piston units such as the piston units 42a to move the pistons such as the piston 40a to the closed relationship (Figure 4). Similarly, air under pressure flows through channels such as a channel 60 to apply a pressure against the piston units such as the piston units 42b for moving the pistons such as the piston 40b to the closed relationship. Seals such as a seal 62 (Figures 2 and 7) are provided between the pistons such as the pistons 40a and 40b and the cylinder bodies such as the cylinder bodies 38. The seals such as the seals 62 may be made from a suitable material such as a reinforced high temperature plastic designated as Meldin by the Furon Corporation of Worcester, Massachusetts. A fluorosilicone material may also be used for the seals such as the seals 62. O-rings such as O-rings 64 are disposed between the cylinder body 38 and the main manifold 15. The O-rings such as the O-rings 64 may be made from the same material as the seals 62. An air gap 65 (Figure 2) is provided between the mold plates 12 and each of the main manifold 15 and between the mold plates 12 and the sub manifolds 16 to insulate the main manifold and the sub manifolds from the mold plates. Plugs 66 extend into the sub manifolds 16 to close the sub manifolds so that the fluid will flow only through the passages such as the passages 20a and 20b in the sub manifolds. The plugs 66 are adjustably positioned in the sub manifolds 16 and are fixedly disposed as by screws 67 after such adjustment. In like manner, plugs 68 are adjustably disposed in the main manifold 15 to close the main manifold so that the fluid will flow only through the passages such as the passages 20a and 20b in the main manifold. After such adjustment in the position of the plugs 68, screws 69 are disposed in the maintain manifold 15 to main the plugs in fixed position. The provision of the openings filled by the plugs 66 and 68 respectively in the sub manifolds 16 and the main manifold 15 facilitates the formation of the passages such as the passages 20a and 20b in the sub manifolds and the main manifold. Arrangements are provided for preventing the fluid from leaking between the mold plates 12 and the injection nozzles such as the injection nozzle 23 when the temperature of the sub manifolds 16 changes as a result of the heat imparted to the fluid in the passages such as the passages 20a, 20b, 20c and 20d and the passages such as the passages 22a and 22b. Each of the arrangements includes a pair of tongues 70 and 72 (Figures 9 and 10). The tongue 70 extends into a cavity 74 in one of the mold plates 12 and has a displacement of a few thousandths of an inch from the mold plate 12 when the injection nozzle 23 and the mold plate 12 are cold. When the fluid in the gates such as the gates 22a and 22b become heated, the tongue 70 expands against the mold plate 12 and provides a seal with the mold plate. The tongue 72 is disposed in the cavity 74 against a ledge 76 in the cavity whether the mold plate 12 and the injection nozzle 23 are hot or cold. In this way, the tongue 72 provides a seal between the mold plate 12 and the injection nozzle 23 whether the mold plate 12 and the injection nozzle 23 are hot or cold. When the fluid in the outlets such as the outlets 22a and 22b heats the injection nozzles such as the injection nozzle 23, the resultant resilient expansion in the tongues such as the tongue 72 causes the tongue to move along the ledge 76 while maintaining the tongue against the ledge. In this way, the tongues such as the tongue 76 maintain a seal between the mold plate 12 and the injection nozzles such as the nozzle 23 when the injection nozzles expand with heat. The apparatus constituting this invention has certain important advantages. It provides for the introduction of fluid into the inlet 18, the heating of the fluid during the movement of the fluid through the passages 20a, 20b, 20c and 20d in the apparatus and the flow of the fluid simultaneously through a plurality of passages such as the passages 22a and 22b. It provides for the disposition of pairs of the passages in a back-to-back in-line relationship. It also provides for the disposition in a single cylinder body 38 of a pair of the pistons 40a and 40b controlling the movement of the fluid through the pair of passages in the back-to-back in-line relationship. The apparatus constituting this invention further provides for the disposition and movement of the pair of pistons 40a and 40b in opposite directions in the back-to-back in-line relationship to obtain the simultaneous closure of the passages such as the passages 20a and 20b against the flow of fluid (e.g. resin melt) or the simultaneous opening of the passages to the flow of fluid. The apparatus constituting this invention further provides for the disposition of the pistons such as the pistons 40a and 40b in a compact relationship in the in-line relationship and prevents the pistons from rotating in the cylinder. This is accomplished by disposing the piston units such as the piston units 42a and 42b on the piston 40a in a diametrically disposed relationship and in a quadrature relationship to the diametrically disposed piston units 42c and 42d on the piston 40b. The apparatus of this invention is also constructed to prevent fluid (e.g. resin melt) from leaking from the apparatus at different temperatures. This is accomplished by disposing the tongues 70 and 72 on the injection nozzle 23 and extending the tongues to the mold plate 12. The tongue 70 expands against the adjacent mold plate 12 with heat to seal the injection nozzle against the mold plate and manifold. The tongue 72 resiliently expands along the mold plate 12 with increases in temperature to maintain the seal between the injection nozzle 23 and the mold plate 12. Although this invention has been disclosed and illustrated with reference to particular embodiments, the principles involved are susceptible for use in numerous other embodiments which will be apparent to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

Claims: An injection molding apparatus for injecting a heated resin into a mold from a distribution manifold (15, 16) for formation of articles having a configuration corresponding to that of the mold and including at least one mold plate (12) equipped with passages through which flows the heated resin under pressure from the manifold through the at least one mold plate to at least one mold, the at least one mold plate (12) is adapted to include an injection nozzle (23) adjacent that at least one mold, with heaters (26) which are provided for heating the resin to a flowable molten characterised In that first and second tongue elements (70, 72) disposed relative to the passages and the mold plates (12), the tongue elements (70, 72) being responsive to changes in the temperature of the fluid flowing through the passages and the manifold (15, 16) such that: (i) the first tongue element (70) expands rigidly against the mold PLATE and provides a seal between the mold plate (12) and an injection nozzle (23); and (ii) the second other tongue element (72) resiliently provides a seal between the mold plate (12) and an injection nozzle (23) for maintaining a pre-loaded abutting relationship between the mold plate (12) and the manifold (15, 16), the seals and the pre-loaded abutting relationship preventing leakage of fluid from the mold plate (12) with changes in temperature of the fluid flowing through the passages in the manifold means (15). Apparatus as set forth in claim 1, comprising an injection nozzle (23), the injection nozzle (23) comprising the first and second tongue elements (70, 72). Apparatus as set forth in claim 2, the first and second tongue elements (70, 72) being integrally formed with a portion of the injection nozzle (23). Apparatus as set forth in claim 2 or 3, the at least one mold plate (12) having a first socket, the injection nozzle (23) and the first tongue element (70) rigidly extending into the first socket, the second tongue element (72) resiliently maintaining a pre-loaded abutting relationship between the mold plate (12) and the manifold (15) with changes in temperature in the fluid flowing through the mold plate (12) and the manifold (15, 16). Apparatus as set forth in claim 4, the at least one mold plate (12) also having a second socket, the second tongue element (72) extending into and engaging the second socket to provide the resilient pre-loaded abutting relationship. Apparatus as set forth in claim 5, the first socket constituting an extension of the second socket. Apparatus as set forth in claim 1, the at least one mold plate (12) comprising a pair of mold plates.

Inventors: MCGREVY ALAN N, MCGREVY, ALAN N.
Applicants: CACO PACIFIC CORP, CACO PACIFIC CORPORATION
Application year: 1995
Main classification: B29C45
IPC codes: B29C45