DE2218294A1 - Method and apparatus for embedding rigid reinforcement reinforcement in plastic in a mold - Google Patents

Description

GKN Sänke, y. Limited in Bilston, Staffordshire

(Great Britain)

and

Aro Plastic Building Supplies Limited in (London W.l. (Great Britain)

Method and apparatus for embedding rigid reinforcement reinforcement in plastic in a mold.

The invention relates to methods and devices for the manufacture of articles that have a Include stiffening reinforcement that is embedded in synthetic resin, i.e. in plastic, with which the reinforcement is wrapped in a form.

In the manufacture of such objects, the reinforcement with the in a flowable state is Plastic overmolded under high pressure, and it is necessary to insert the reinforcement in the molding process To hold the mold cavity in place so that it is not displaced by the flowing plastic.

It has already been proposed to hold the reinforcement in position in the mold cavity by means of projections, which proceed from the walls of the mold cavity. The projections are retracted during the molding process, so that the cavities remaining due to the retraction of the projections can still be filled with plastic. The reinforcement is held in place by the projections during the initial phase of the molding process. But if the Plastic almost fills the mold cavity is the hydrostatic pressure exerted on the reinforcement by the plastic sufficient to maintain the reinforcement during the final stages of the forming process hold in position.

20 98 45/0806

It has been found that in some cases one after these; Process manufactured item markings or has depressions on the surface where the plastic leaves those left by the projections as they are retracted Has not completely filled the cavities. It is believed that these markings or depressions caused by the hardening of the material in contact with those normally made of steel Projections stands or is located in their vicinity.

If the plastic is a thermoplastic, the mold is cooled to harden the material and it hardens from the outside, i.e. from the mold walls inwards, and from the inside, i.e. from the reinforcement reinforcement to the outside, if the reinforcement has not been preheated, in which case the hardening is delayed from the inside out. If the Plastic may solidify around the free end of a protrusion and pull the protrusion back on in this way the entire cavity left by the projection is prevented from filling with plastic, so that a mark or depression remains in the manner described.

If it is a thermosetting plastic and the one supplied to the molded parts for curing the material Heat also passes through the projections, the material is at their free ends when they are withdrawn hardens and prevents the flowable, not yet hardened material that flows inside the mold cavity, began to fill the voids left by the retraction of the projections.

It is an object of the invention to overcome this problem, or at least to reduce its effects.

According to one aspect of the invention, there is a method for overmolding a rigid reinforcement reinforcement with plastic provided in a form in which the reinforcement in one. Mold cavity is held by projections from the

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Walls of the mold cavity protrude and grab the reinforcement ^ -.; the plastic is introduced into the mold under pressure; while the plastic around the reinforcement and the projections is still flowable, heat is transferred through the V / andungen of the mold cavity transferred through to the plastic in contact with it to harden, so that it surrounds a flowable mass of plastic Skin forms; The heat transfer through the projections is controlled in order to harden the contact therewith to delay standing plastic until after skin formation; The protrusions are made while the plastic is still under Pressure is withdrawn into the walls of the mold cavity, the part located in the interior of the mold cavity of the plastic is still sufficiently flowable to take under the pressure to flow and to fill the voids left by the retraction of the projections.

By controlling the heat generated by the protrusions flow is a premature hardening of the one located in their vicinity Plastic avoided and ensured that when the projections are withdrawn, the cavities left thereby can be filled with flowable plastic.

The heat transfer through the protrusions and the heat transfer through the walls of the mold cavity can run in the same direction, but with the heat transfer is slower through the projections than through the walls. The protrusions can be as follows is described, comprise a material or is attached therein be, which has a lower thermal conductivity than the material of the molded parts.

In an alternative embodiment, the heat is transferred through the walls of the mold cavity and the heat transfer through the projections at least up to Withdrawal of the projections into the walls of the mold cavity in different directions.

2096 ^ 5/0806

In the case of thermoplastic plastic, the projections can be heated and in the case of thermosetting plastic the protrusions are cooled.

In the case of thermoplastic material, the molding is preferably carried out by injection, while in the case of thermosetting Material the molding is done by compression molding. In accordance with another aspect of the invention is an apparatus for molding plastic around a rigid reinforcement reinforcement around, the mold parts movable against each other arranged to form a mold cavity; it includes projections that are movable on one or more of the mold parts are attached and drive means that move the projections between a working position in which they can protrude into the mold cavity and fix the reinforcement therein, and move back and forth to a rest position, in which they are withdrawn from the mold cavity; it comprises first means in the molded parts for controlling the heat transfer through the walls of the mold cavity; it comprises second means associated with the projections and control the heat transfer through the protrusions so that that heat transfer occurs at a slower rate or in the reverse direction of the aforesaid heat transfer going on.

The projections can comprise a material that has a lower thermal conductivity than the material of the mold parts having, the material forming said second means. The free ends of the projections can be made of the material lower thermal conductivity exist or be coated with it. However, each projection can also consist of a sleeve this material include, which is placed in the vicinity, but at a distance from the free end of the projection and is within the mold cavity when the projection is in its operative position.

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In another embodiment, each can protrude comprise a core of the material of lower thermal conductivity.

Alternatively, the second means can also comprise bushings in the molded parts, which are made of a smaller material Thermal conductivity exist as the material of the molded parts, the projections in the sleeves are movable, which in turn are arranged in the vicinity of the mold cavity.

In another embodiment, that for molding thermoplastic material is usable, the second means may comprise heating devices within the protrusions, for example electric heaters.

In yet another embodiment, the second Means causing a flow of liquid through the projections. The flow of liquid can occur during thermosetting Material cool the projections or, in the case of thermoplastic material, heat the projections.

The invention will now be described in detail with the aid of an exemplary embodiment which is shown in the drawing.

Fig. 1 is a cross-section through an apparatus embodying the invention for practicing the invention Procedure in which the projections are shown in their working position are;

Figure 2 is a view corresponding to Figure 1 but showing the projections in their rest position;

Fig. 3 * 4 \ ind 5 are sections through the cavity of the The apparatus of Figure 1 showing three successive stages of formation;

6 to 10 are individual views of sections through the mold cavity of the device according to FIGS. 1 and 2, in which however, different embodiments of the means for controlling the heat flow along the protrusions are shown «

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According to FIGS. 1 and 2, the device comprises a base plate 10 on which spacer blocks provided with an opening 11 are mounted, which have openings 12 for receiving hydraulic cylinders 13. On the top the spacer blocks 11 is attached to a plate 14- has the openings 15 as a passage for the hydraulic cylinder.

The mold is formed by a lower mold part 16, which is designated as a whole with 17 on its upper surface Slot with a lower narrower part 18 and an upper further part 19 contains. This slot forms part of the mold cavity and cooperates with an upper mold part 20 of the upper slot part 19 when closed Form is recorded. The upper mold part 20 is supported by a top plate 21. The mold cavity is with as a whole 22 designated. The lower molded part has a bore 23 provided in which an ejector pin 2 & is attached, the is moved by an ejector plate 25, which in turn with is connected to a hydraulic cylinder, not shown. The ejector plate 25 is guided by pins 26, which are attached to the plate 14. The molded parts 16 and 20 have passages 16 a and 20 a, passed through the cooling water can be used to harden thermoplastic material injected into the mold cavity. In the lower molded part 16, two groups of projections are attached, two of which are shown at 27. The protrusions are the bores 28 in the lower mold part 16 from the working position shown in Fig. 1 in which they are in the Project cavity 22 into the rest position shown in Fig. 2, in which the free ends of the projections lie flush with the walls of the lower, narrower part 18 of the slot 17.

The outer ends of the projections 27 are on sliding pieces »29 attached, which are movable horizontally to the movement of the projections between their working position and to effect their rest position.

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Each sliding piece has an inclined bore 30 in which a Pin 31 is slidable. The pins 31 are again fixed in sliders 32 which are connected to the piston rods of the hydraulic cylinders 13, the The cylinder itself is attached to the lower mold part 16 at 34 are.

When the parts are in the positions of FIG the projections 27 being in their working position and the sliders 32 being actuated by the cylinders are moved down, the sliding pieces move apart and pull the projections 27 into their in Fig. shown rest position back.

The device shown in Figs. 1 and 2 is used to produce a window frame in which a rectangular Reinforcement reinforcement is provided, which is to be embedded in thermoplastic material. The invention however, it can also be used in the manufacture of other items. In this case, the mold cavity and the Reinforcement designed accordingly.

In Fig. 3 is a reinforcement 35 I-shaped cross-section ^ housed in a mold cavity 22. The reinforcement accordingly comprises two oppositely directed recesses 36, in which the free ends of the projections 27 sit. The reinforcement 35 is in this way against vertical Movement set. It is in a horizontal movement due to the arrangement of the projections 27 around the mold cavity prevented around. The reinforcement 35 comprises a central part and flanges 38 and 39

Each projection 27 consists essentially of metal, for example steel, and has a stepped part 40 at its free end. This stepped part 40 is surrounded by a cover kl made of a material which is a poor conductor of heat, for example sintered aluminum oxide. The cover is shaped to fit into the recess to define the reinforcement.

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The cover 4l is long enough in the axial direction to extend into the lower molded part Ιό, when the projection 27 is in its working position shown in Fig. 3, i.e. in the position in which it the reinforcement 35 specifies. The covers 4l have a considerable thickness in the illustration; but they could also consist of a thin coating of sintered aluminum oxide or another ceramic material on the free ends of the projections 27 exist.

The procedure is carried out in the following manner. The base plate 10 and the top plate 21 are attached to the lower or upper pressure plates of a molding press attached. The mold is opened by moving the top plate 21 upward. Thereon

the reinforcement 35 is placed in the mold cavity. Preferred
wisely, the mold cavity consists of an endless channel which is rectangular in plan so that a frame member, in particular a window frame, can be produced therein by the method.

When the reinforcement 35 is inserted into the mold cavity, the projections 27 are in the positions shown in FIG retracted by suitable actuation of the hydraulic cylinder 13 been. The ejector pin 24 is with its free End substantially level with the reinforcement under surface to support it at a desired height. The cylinders 13 are then actuated to drive the projections inward so that they engage the reinforcement and fix them on all sides according to their shape. The longitudinal axes of all projections lie in one plane. The reinforcement is held against movement in the plane of the drawing by the projections on the reinforcement. It is also against movement in planes perpendicular to the plane of the drawing by the arrangement of the projections around the reinforcement set around.

When the core is fixed by the projections 27, the ejector pin 24 is in the position shown in FIG withdrawn, in which the upper end of the ejector pin is flush with the bottom of the slot 17.

209846/0 806

The mold cavity is then closed by inserting the upper mold part 20 into the slot, whereupon the Tool assumes the state shown in Fig. 1.

It is now thermoplastic by not. The cuts shown are pressed into the mold cavity 22. Since the molded parts 16 and 20 are cooled by circulating cold water through the passages 16 a and 20 a, hardened the thermoplastic material and forms a skin where it comes into contact with the molded parts is located. This skin is designated by 42 in FIG. 3. Ever according to the temperature of the reinforcement 35 can also be around the Reinforcement 35 form a skin around which is indicated at 43. When the reinforcement before placing in the mold cavity has been preheated, the formation of the skin 43 will be delayed. There is one between the skins 42 and 43 Mass of still flowable plastic. Since the covers 41 of the projections 27 made of a material of lower thermal conductivity as the material of the moldings 16 and 20 exist, the formation of a skin similar to the skin 42 around the covers 41 around, i.e. in areas 44 in Fig. 3 "delayed because the heat from the inner mass of flowable material through the covers 4l is not as fast can escape as it flows through the molded parts l6 and 20 abs.

The projections 27 are now withdrawn as in FIG. 4. Since the covers 4l are made of a material that is not a good conductor of heat, the forms across the ends of the Protrusions after their retraction no skin, so that immediately after retraction the situation will be like this, as shown in FIG. 4, the skin 42 being interrupted across the ends of the projections 27. The mass the still flowable material can now be inserted into the projections 27 abandoned rooms 46 flow, which are indicated in Fig. By cross hatches.

209845/0306

- ίο -

The cooling now continues and, as in FIG. 5, the skin 42 expands over the ends of the projections at 47 the end. Gradually, all of the bulk of the plastic in the mold cavity will harden. The mold cavity is about to retract the projections 27 filled with plastic. After the withdrawal, therefore, more plastic is in the mold cavity pushed through the gates in order to fill the spaces 46 left by the retraction of the projections 27. The projections 27 define the reinforcement 35 during the initial filling of the mold. During and after as the projections 27 are withdrawn, the reinforcement is held in place by the hydrostatic pressure of the material held.

It has been found that by forming a skin 42 around protrusions 27 that formed at 47 in FIG Skin has its outer surface in a plane with the adjacent parts of the outer surface of the skin 42 and accordingly essentially no marks or pits are formed.

Various provisions can now be made to control the flow of heat through the projections will. In Fig. 6 projections 48 are shown, each of which comprises a metal shaft 49, which at its free End equipped with an internally threaded bore 50 is. The bore 50 receives the threaded shank 51 ″, a bolt 52 which ends on the head. The shaft has a smaller diameter than the shaft 49 and carries a ceramic sleeve 53 between his head and the End of shaft 49.

Fig. 6 shows the projections 48 in their working position, in which they have a reinforcement 5 ^ I-shaped cross-section in one Define mold cavity 55. The ceramic sleeves 53 are sufficient into the mold cavity and isolate the plastic 56 from direct contact with the metal parts of the protrusions. Of course there will be some heat flow through the reinforcement and the heads of the bolts 51 take place therethrough, yet will

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the total heat flow through the projections 48 through the sleeves 5] 5 controlled in such a way that the formation of a skin in the vicinity of the projections is prevented, as has already been done with reference to FIGS has been described. When the projections are withdrawn to their rest position, the heads of the bolts lie with the Bandings of the mold cavity 55 flush.

Fig. 7 shows another embodiment in which the Mold cavity 57 a reinforcement 58 I-shaped cross-section as in the previous example. In this case, the projections 59 are made of metal and sit in ceramic Bushings 60 mounted in the walls of the mold cavity in the vicinity thereof. It can heat up the plastic 61 pass into the mold cavity in the projections. However, it is through the sleeves 60 on a certain The axial length of the projections is prevented from crossing over directly from the projections into the adjacent molded part 62. In this way, the heat flow along the protrusions and the skin formation in the with respect to the Fig. 3 to 5 described manner controlled. When the projections are withdrawn from their rest position, lie the ends 63 of the projections are flush with the walls of the mold cavity. .

8 shows yet another embodiment in which a mold cavity 64, as described above, has reinforcement 65 of I-shaped cross section. In this case, the projections 66 are made as hollow metal cylinders with fixed ends 68 and contain a core 69 made of ceramic material, which is a poor conductor of heat. In this case, heat from the plastic 70 can pass into the projections, but the cross section available for the heat flow is small because of the cores 69. The formation of a skin in the vicinity of the projections 66 is prevented in the manner described with reference to FIGS. 3 to 5.

• 209845/0806

In Fig. 9 an arrangement is shown in the heat from the projections on the plastic in the Mold cavity is transferred. The mold cavity in FIG. 1 is denoted by 71 and contains a reinforcement 72 I-shaped cross-section. In the molding 72 there are two Projections 7 ^ provided, both in a sleeve 75 heat insulating material are displaceable, each in the molded part in the vicinity of the mold cavity are arranged. In each protrusion 74, which is in the shape of a hollow closed-ended cylinder, is an electrical heating element designated 76 housed. During the first molding phase, when the projections are in their working position, as shown in Fig. 9, are located, electricity is supplied to the heating elements 76 and heat is supplied through the protrusions transferring forming hollow cylinder. The hollow cylinders are made of metal, around the plastic with the projections is in contact, in a flowable state, to allow the formation of a skin such as skin 42 in the mold cavity to prevent near the protrusions. When the projections are withdrawn in their rest position, so that the closed ends are aligned with the walls of the mold cavity, one of the sliders 32 actuates a Microswitch 77 by an arm 78 and a roller 79 and interrupts the supply of electricity to the heating elements in the projections so that the plastic in contact with the end portions of the projections harden can.

Fig. 10 shows a, mold cavity 80 with a reinforcement 81 I-shaped cross-section therein which is held in place by projections 82 in the prescribed manner. Each protrusion is in the shape of a hollow metal ring with a closed end 84.

209 8AS / 0806

In the hollow metal cylinder is a feed pipe 85 for a liquid, which is just before the closed end of the cylinder ends. The projections are shown in their working position in which they hold the reinforcement in place by attacking it in its recesses. Hot oil or other oil is passed through the pipes 85 Liquid passed back through the annulus between the tubes and the inner surfaces of the metal cylinders flows. The heat applied to the protrusions by the oil or other liquid holds the plastic material in place flowable near the projections, with the advantages described with reference to FIGS. 3 to 5. When the projections are withdrawn to their rest position in which the closed ends 84 are flush with the walls of the mold cavity, the oil is supplied through the projections by a microswitch prevented, which works in the manner already described in connection with FIG.

The invention is above in connection with the manufacture of an article from a stiffening Reinforcement, usually made of metal, and a thermoplastic material have been described. When using of such a material, heat must be removed from the mold in order to cause the material to harden. The heat is dissipated by water that flows through water passages 16 a and 20 a. From the foregoing it can be seen that the heat transfer from the plastic to the mold walls is greater than the heat transfer through the protrusions so that curing of the plastic in the vicinity of the protrusions is delayed. However, the invention is equally applicable to thermosetting material where it is necessary to shape apply heat to harden the plastic.

209845/0 8 06

In this Pall is through the passages 16 a and 20 a hot liquid passed through. The passages can also have electrical heating elements for warming up the Moldings included.

The preceding description of FIGS. J5 and 8 applies also allow for the use of thermosetting material, with the exception that the material is near the protrusions is kept liquid, insofar as the plastic through the projections does not heat at the speed is supplied, as happens with the mold walls.

The embodiment of Fig. 9 is for manufacture of an object made of reinforcement and thermosetting material not applicable. The embodiment of FIG. 10 however, it is applicable to thermosetting material when the liquid flowing through the projections is a cooling liquid instead of a heating liquid.

The invention provides an effective means of delaying the hardening of the plastic in the vicinity of the Holding projections before they are withdrawn, and ensures a good surface quality of the molded Subject.

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Claims (14)

GKN Sankey Limited in Bilston, Staffordshire (Great Britain) and Aro Plastic Building Supplies Limited in (London W.l. (Great Britain) Claims. (1 .J Procedure for embedding rigid reinforcement reinforcement in plastic in a form in which the reinforcement is held in a mold cavity by projections protruding from the wall of the mold cavity and attack the reinforcement, and in which the plastic under pressure and in the flowable state around the Reinforcement and the projections around is pressed in, characterized in that the heat through the walls of the mold cavity is transferred therethrough so that the plastic in contact therewith is formed a skin surrounding a still flowable mass of the plastic hardens that the heat transfer through the projections through it is controlled in order to harden the plastic in contact therewith until after to delay the formation of the skin and that the projections are retracted into the wall of the mold cavity as long as the plastic is still under pressure and the plastic is in the interior of the mold cavity is still sufficiently flowable to be left under the pressure in the by the retraction of the projections To flow in cavities and to fill them. 2. The method according to claim 1, characterized in that the heat transfer through the walls of the mold cavity and the heat transfer through the protrusions is in the same direction, but the heat transfer goes through the projections at a slower speed than through the walls. '209845/0806 3. The method according to claim 1, characterized in that that the heat transfer through the walls of the mold cavity and heat transfer through the projections at least until the projections are retracted into the Walls of the mold cavity proceed in different directions. 4, method according to any one of claims 1 to jj / characterized characterized in that the plastic is a thermoplastic and that the reinforcement is embedded in the injection molding process he follows. 5 · Method according to one of Claims 1 to 3>, characterized characterized in that the plastic is a thermosetting plastic and that the embedding of the Reinforcement is done by compression molding. o. Device for embedding a rigid reinforcement reinforcement in plastic in a forin, with mutually moving mold parts that form a mold cavity, with projections movably arranged on one or more of the mold parts - i with actuating devices that move the projections out of a working position in which they are in the . The mold cavity can protrude and the reinforcement can thus be brought into its rest position, in which oils are withdrawn from the Jermhohi space, thereby ge-Ivennzaio'.ir.ts ",; .a5 them in the form of a first means um-TiSS-T ". ; i ~; e ^ Varrr.e transition auroü aie walls of: ~ ^ rrr.r ..: ".-" .. raurr.c. ^ s ^ ern,; na Is. ζ rie z ^ n ".e , cen protrusions. ^ gec: - :::. i: i. ■ .: ~; e. zi-issei :. *! ■? .; - :. r. heat- ^ eübergan ;? along Lir '-: ■ _ ;;: ·· .. ::;. · £ Λ -: ^;:, .- ■ i-idi:. :: ss-: r ■ • ärT.eübergan.-ί; long- ? 218,294 4% S. Device according to claim "J, characterized in that the free ends of the projections are formed from the material with the lower thermal conductivity or are coated therewith. 9. Apparatus according to claim 7> characterized in that that each projection comprises a sleeve made of the material with the lower thermal conductivity, which is in the vicinity, but is provided at a distance from the free end of the projection and is located in the mold cavity, when the projection is in its working position. 10. Apparatus according to claim "J, characterized in that each projection contains a core made of the material of low thermal conductivity. 11. The device according to claim 6, characterized in that the second means arranged in the molded parts cans comprises of the material of lower thermal conductivity than the material of the molded parts and the projections in the arranged in the vicinity of the mold cavity cans are displaceable. 12. The device according to claim 6, characterized in that the second means comprise heating elements in the projections. 13 · Device according to claim 6, characterized in that in that the second means comprise means for inducing a flow of liquid through the projections. 14. Object with a reinforcement reinforcement embedded in plastic, characterized in that it is after the method of claims 1 to 5 is produced. ' 209845 / 080B Λ *. Blank page