GB2146285A - Injection moulding apparatus - Google Patents

Abstract

An injection moulding apparatus, suitable for moulding motor vehicle bumper units (11) having end parts (12) for extending around the vehicle sides and terminating in inwardly extending end flanges (13), has an inner core body (17) and an outer impression block (15) between which the bumper moulding is formed in a cavity (16). The core (17) has laterally extending slide blocks (30) (only one shown) movable by hydraulic rams (38) for moulding the inturned flanges (13) by means of a recess (31) in the upper faces of each slide blocks. After forming of the moulding in cavity (16), the slide blocks are moved outwardly to draw the bumper ends outwardly of the core surface to enable the moulding to be stripped from the core by ejectors (20) extending through the core and driven upwardly through the core by an ejector plate. A modified arrangement of the slide blocks (30) is described, Fig. 4 (not shown). <IMAGE>

Description

SPECIFICATION Injection moulding apparatus This invention relates to injection moulding apparatus and is particularly although not exclusively applicable to apparatus for injection moulding of motor vehicle bumpers in plastics.

The invention provides an injection moulding apparatus comprising separable core and cavity blocks defining between them the shape of the article to be produced including a main body and transversely extending through the core to engage the main body part of the moulding formed thereon to detach the moulding from the core, the end parts of the mould core having undercut mould cavities to form undercut projections or elements on said end parts of the moulded article and means being provided on the core to engage the ends of the moulded article to press said ends outwardly of the core and thereby detach the undercut projections or elements on the moulded article from the mould cavities to enable the moulded article to be stripped from the core.

The core block may have slide elements defining the ends of the moulded article and each having a shoulder facing outwardly of the core to define and engage behind the inner sides of the ends of the article to be moulded and means are provided for displacing the slide elements outwardly of the core to release undercut portions at or adjacent the ends of the moulded article from the core to enable the moulded article to be stripped therefrom.

Each slide element and the adjacent part of the core form between them a cavity extending into the core may and ending in said shoulder on the core to define an end flange on the article to be moulded.

Further each slide may be mounted on the slideway on the core block and means are provided for moving the slide along the slideway between a moulding position and a mould releasing position.

In any of the preceding arrangements the means for moving the slide along the slideway may comprise a double acting ram.

Retractable abutment means may be provided on the slide elements adjacent said shoulders means are provided for causing said abutment means to extend automatically as the slide elements are moved outwardly of the core to release said undercut portions of the moulded article to prevent the undercut portions springing back into engagement with the core.

Said abutments may comprise one or more spring loaded retainer pins mounted on each of the slide elements to project from the elements when the latter are moved outwardly of the core.

The upper ends of the pins may be shaped to engage with the core when the slide elements are moved inwardly to retract the pins automatically into the slide elements.

In any of the preceding arrangements one or more recesses may be formed in the face of the core adjacent the ends thereof to create bosses on the inner side of the end parts of the moulded article.

Also in any of the preceding arrangements the means to strip the moulded article from the core may comprise one or more ejectors extending through the core to the surface of the core adjacent the centre of the mould surface and means to cause the ejectors to project from the core to detach the moued article from the core.

The ejectors may project from the opposite side of the core body to the mould surface thereof and are connected to a platen having ram means for moving the platens towards and away from the core body to project and retract the ejectors with respect to the core body.

Guide pillars may be provided between the core body and platens for guiding the platen towards and away from the core body under the action of said ram means.

In any of the preceding arrangements the core of the mould may be formed with recesses in said end parts of the mould core to form projections on the inside of the moulding and ejector means are provided in the mould core for ejecting a moulded projection formed in the recess for removal of the moulded article from the mould.

The ejector means may comprise an ejector member movably mounted in the mould core to move into and out of said recess and means for projecting and retracting the member into and out of the recess respectively.

The means for moving the ejector member into and out of the recess and the means for pressing the ends of the moulded article outwardly of the core may have a common drive means e.g., a double acting ram.

The following is a description of a specific embodiment of the invention, reference being made to the accompanying drawings in which: Figure 1 is a perspective view of a moulded plastics motor vehicle bumper to be produced by the apparatus in accordance with the invention; Figure 2 is a sectional view through part of the apparatus for moulding the plastics bumper of Fig. 1; Figure 3 is a cut-away perspective view of one part of the apparatus shown in Fig. 2, and Figures 4 to 9 show modifications to the mould apparatus of Figs. 2 and 3.

Referring firstly to Fig. 1 of the drawings there is shown a moulded plastics motor vehicle bumper 10 of channel section and having a main part 11 and wrap-round end parts 12. the end parts 12 terminate in inwardly extending end flanges 13 bridging the side walls of the channel. Adjacent the ends of the bumper, bosses 14 are formed on the inner side thereof for attachment of the end parts to the vehicle body in conventional manner. The bumper is moulded in an injection moulding apparatus which will now be described with reference to Figs. 2 and 3 of the drawings.

The injection moulding apparatus comprises a cavity impression block 15 formed with a cavity 16 corresponding to the outer profile of the bumper and a core impression block 17 having a mould surface 18 a profile of which corresponds to the inner profile of the required bumper.

At the centre of the core body 1 7 there are one or more bores 19 extending vertically through the core body in which ejectors 20 are mounted which project from the underside of the core body and are attached to and ejector plate 21 which has upstanding parallel pillars 22 slidably mounted in bores 23 in the underside of the core body to guide the plate vertically with respect to the core body. The ejector plate 21 is supported at the lower limits of its travel by a back plate 24. The ejector plate is raised and lowered by a double acting hydraulic ram 25 mounted on one side of the core body 17 and having a piston rod 26 having a head 27 engaged in a slot 28 in one side of the ejector plate. Fig. 2 shows only one half of the core body and ejector plate and its mechanism for raising and lowering the ejector plate and the latter is repeated on the other side of the core body.

When the ejector plate is raised by the hydraulic cylinder 25, the ejectors 20 are lifted in the bores 19 to project through the upper ends thereof to raise a moulded article on the die core from the core.

At the ends of the mould surface 18 of the die core, the core is formed with inwardly extending cavities 29 to create the flanges 13. The lower sides of the cavities 29 are formed by insert slide blocks 30. The upper surface of each slide block 30 has a curved recess 31 defining the outer side of the bumper flange 13 and ending in a step 32 defining the inner edge of the flange.

Each slide block 30 is formed with an elongate T-section slot 33 in its underside and is engaged on a T-section slideway 34 extending laterally away from the core block 17 and mounted on a carrier 35. The ends of the carrier remote from the core block 17 are swept up into lugs 36 connected together by a mounting plate 37 on which a laterally acting double acting hydraulic ram 38 is mounted. The ram has a plunger extending through the plate 37 between the lugs 36 and connected to the slide block 30 to move the slide block into and out of engagement with the core block.

The slide carrier 35 is secured in position on the die block by means of the ends of the pillars 23 and is further located by an end plate 38 secured to the end of the die core 17 and overlapping the carrier 35 below the mounting plate 37.

The ram 38 is extended to move the slide block 30 into engagement with the die core 17 for the moulding operation and the cavity block 15 has wedge blocks 39 to engage behind chamfers 40 on the upper side of the slide blocks to lock the blocks in position during the #moulding operation. Plastics material is injected into the cavity between the cavity impression block and core impression block to create the bumper moulding. After the injection operation, the cavity impression block 15 is raised clear of the core leaving the newly formed moulding in place on the core.

The moulding cannot be ejected immediately from the core because the inturned flanges 13 at the ends of the moulding formed in the cavities 29 prevent the moulding from being lifted off the core by the plunger 20. In order to release the moulding, the slide blocks 30 are moved outwardly from the core block by the ram 38. Since the outwardly facing shoulders 32 on the upper sides of the slide block 30 are in engagement with the inner ends of the flanges 13, the ends of the moulding are drawn outwardly from the core-form 29 by the slide blocks thus springing the ends of the moulding apart. In the outer positions of the slide blocks 30 as shown in Fig. 3, the flanges 13 are clear of the core-form 29 and the rams 25 can then be operated to lift the ejector plate 21 and, with it, the ejectors 20 to push the moulding upwardly off the die core.

Reference is now made to Fig. 4 of the drawings in which a modified form of the moulding apparatus illustrated in Figs. 2 and 3 is shown. Like parts have been allotted the same reference numerals as used hereinbefore in relation to Figs. 2 and 3. In the bumper moulding of Fig. 1 the end flanges 13 are not angled at 90 to the end part 12 of the moulding but are angled outwardly by about 10 from a right angle. In the mould apparatus for creating the bumper moulding, the side wall 12 are moulded vertically and the end flanges 13 are moulded to extend downwardly at about 10 from the horizontal towards the centre of the mould by angling of the recesses 31 in the slide block 30 and the opposing faces on the core block 17. Thus when the slide block 30 are moved horizontally outwardly prior to stripping of a moulding from the core, the downwardly angled flanges automatically have a release angle from the underside of the cavities 29 of the core to prevent binding of the flanges to the core. Some bumper designs however are required to have divergent side walls 12 termi nating in inwardly extending flanges 13 for which a modified form of the apparatus of Figs. 2 and 3 as illustrated in Fig. 4 of this patent is required. It will be noted that the side faces of the core 17 which form the side walls 12 of the bumper moulding do not extend vertically as in the Fig. 2 apparatus but are inclined outwardly towards their lower ends to form the divergent side walls 12 of the bumper moulding.The cavity 29 in which the flange 13 is to be moulded at the lower end of the side wall 12 formed between the recess 31 in the slide block 30 and face 29a of the core block extends horizontally to the step 32 defining the extremity of the flange.

To assist in the release of the flange 13 from the face 29a of the core, the slideway 34 is inclined downwardly at an angle of about 10 below the horizontal in a direction extending away from the centre of the core and the slide 33 formed on the underside of the block 30 is correspondingly downwardly inclined. Thus as the slide block 30 is moved outwardly to release the flange 31 from the face 29a of the cavity 29, the slide block moves both downwardly and outwardly from the "shut off" face of the mould part of which is indicated at 40. The flange 13 is thus drawn downwardly away from the face 29a of the core at 17 as it is urged outwardly of the core by the slide block 30.

In order to prevent the side wall of the moulding from slipping back on to the core of the mould after being detached from the core by the slide block 30, two inclined bores 41 extend side by side one another into the block from the upper surface thereof adjacent the abutment 32 against which the extremity of the flange 13 is formed and retainer pins 42 are mounted in the bores and are spring loaded upwardly by compression springs 43 to urge the pins outwardly of the bore. The outward movement of each pin 42 is limited by a stop 44 secured in the slide block on the opposite side of the pin to the abutment 32 and engaging in a groove 45 extending down the pin and terminating in a shoulder 46.

Engagement of the shoulder 46 with the underside of the stop 44 limits the upward movement of the pin. The block also stops the pin rotating in its bore.

Thus when a moulding has been formed and the slide blocks 30 are moved outwardly of the sides of the core to release the flanges 13 of the moulding from the undersides 29 of the core 17, the spring loaded retainer pins 42 will gradually emerge from their respective bores 41 as the slide block move downwardly and outwardly away from the core. Should the flanges 13 spring out of their recesses 31, they will lodge against the retainer pins 42 on the slide block so that they are prevented from relocating under the faces 29a of the core. The heads of the retainer pins are chamfered as indicated at 47 on the sides remote from the abutment 32 so that when the slide blocks 30 are returned to their inner positions for a further moulding operation, the chamfered faces 47 will engage to the underside of the core block 17 and cause the retainer pins to be deflected back into their bores 41.

It will be understood that the arrangement of retainer pins on the slide blocks 30 may be provided whether the slide blocks move both downwardly and outwardly from the core as shown in Fig. 4 or horizontally as shown in Fig. 2 or any other direction to release the inwardly projecting flange at the ends of the side wall moulding from the underside of the core.

In the arrangement o Fig. 4 the directing acting hydraulic ram 38 for moving the slide block 30 is replaced by T-shaped guide 48 attached to the inner side of the block nearest the centre of the core 17 and is inclined in a horizontal plane to the side of the block. The guide engages in a correspondingly angled Tshaped slideway in a horizontally moveable slide member 44 located in a throughway in the core. The member 49 is moved to and fro by a hydraulic ram mechanism which will be described in reference to Fig. 9 below. That movement of the slide member effects a corresponding in-and-out movement of the slide block 30 on its slideway 34.

Reference is now made to Figs. 5 to 8 of the drawings which illustrate a further modification to the core block 17. As indicated earlier, bosses 14 may be formed on the inner sides of the wrap round end parts 12 of the bumper moulding for securing those parts to the vehicle body work. Fig. 5 is a detailed view of the part of the core block 17 showing the location at which a boss 14 is formed on the side wall 12. The boss 14 is formed in an insert 50 let into the core having a cavity indicated generally at 15 corresponding to the external shape of the required boss with its central cylindrical part 14a and spaced supporting webs 14b. A core pin 52 extends through the core to form the central cylindrical bore in the boss.The core pin 52 is encircled by an ejector sleeve 53 extending through the insert 50 around the pin 52.In the moulding position, the end of the ejector sleeve defines the end of the cylinder 14a of the boss as shown in Fig. 5. The other end of the ejector sleeve 53 has an angled/flanged end 54 which projects into a bore 55 extending transversely to the access of the sleeve.

The bore 55 contains hardened steel drive shaft 56 having a recess 57 cut in one side thereof in which a slide member 58 is mounted. the pin 56 is reciprocated along the wall 55 by a hydraulic cylinder (described below) in the direction of the arrow 59 indicated on Fig. 8. The slide member 58 is formed with oppositely facing recesses 60 forming slideways in which the flange 54 on the ejector sleeve engages and the slideways 60 are angled to the direction of movement of the shaft 56 and the bore 55 as best seen in Fig. 8. Thus movement of the shaft 56 in either direction along the bore 55 extends and retracts the ejector sleeve 52 along the insert 50. In the moulding position shown in Fig. 5 the sleeve 53 is fully retracted.When the sleeve is extending by movement of the shaft 56, the ejector sleeve moves to the end of the bore 53 in the insert 50 and thus ejects the boss 14 from the insert.

Referring now to Fig. 9 of the drawings there is shown a common drive mechanism for the shaft 56 and the slide block 30 consisting of a double acting hydraulic ram 61 the cylinder of which is mounted on a vertical base plate 62 secured to the core body 17. The ram has a piston rod 63 extending through the plate 62 and attached to a coupling plate 64 the upper end of which has a spigot 65 engaged with one end of the shaft 56 and the lower end of which carries a spigot 56 coupled to the slide member 49 A similar arrangement is provided at the other end of the core block. Thus a common hydraulic cylinder for moving the ejector sleeve 53 to eject a newly formed boss 14 from the inset 50 is the core body 17 and also for displacing a newly formed flange 12 on the side wall of the new moulding on the underside 29a of the core body to permit stripping of the new moulding from the core body.

It will be understood that other "under-cut" elements can be provided on the inner side of the moulding such as the bosses 14 are as shown in Fig. 1 in which case appropriate recesses are provided on the mould surface of the core to create the bosses. Since the ends of the bumper are sprung outwardly from the die core before it is ejected from the core, the bosses 14 will be withdrawn from their moulding cavities and will not therefore inhibit ejection of the moulding on the core.

Claims (18)

1. An injection moulding apparatus comprising separable core and cavity blocks defining between them the shape of the article to be produced including a main body and transversely extending end parts, the core having stripper means extending through the core to engage the maon body part of the moulding formed thereon to detach the mouding from the core, the end parts of the mould core having undercut mould portions to form undercut projections or elements on said end parts of the moulded article and means being provided on the core to engage the ends of the moulded article to press said ends outwardly of the core and thereby detach the undercut projections or elements on the moulded article from the mould portions to enable the moulded article to be stripped from the core.

2. An apparatus as claimed in claim 1 wherein the core block has slide elements defining the ends of the moulded article and each having a shoulder facing outwardly of the core to define and engage behind the inner sides of the ends of the article to be moulded and means are provided for displacing the slide elements outwardly of the core to release undercut portions at or adjacent the ends of the moulded article from the core to enable the moulded article to be stripped therefrom.

3. An apparatus as claimed in claim 2 wherein each slide element and the adjacent part of the core form between them a cavity extending into the core and ending in said shoulder on the core to define an end flange on the article to be moulded.

4. An apparatus as claimed in claim 2 or claim 3 wherein each slide is mounted on the slideway on the core block and means are provided for moving the slide along the slideway between a moulding position and a mould releasing position.

5. An apparatus as claimed in any of the preceding claims wherein the means for moving the slide along the slideway comprise a double acting ram.

6. An apparatus as claimed in any of claims 2 to 5 wherein retractable abutment means are provided on the slide elements adjacent said shoulders means are provided for causing said abutment means to extend automatically as the slide elements are moved outwardly of the core to release said undercut portions of the moulded article to prevent the undercut portions springing back into engagement with the core.

7. An apparatus as claimed in claim 6 wherein said abutments comprise one or more spring loaded retainer pins mounted on each of the slide elements to project from the elements when the latter are moved outwardly of the core.

8. An apparatus as claimed in claim 7 wherein the upper ends of the pins are shaped to engage with the core when the slide elements are moved inwardly to retract the pins automatically into the slide elements.

9. An apparatus as claimed in any of the preceding claims wherein one or more recesses are formed in the face of the core adjacent the ends thereof to create bosses on the inner side of the end parts of the moulded article.

10. An apparatus as climed in any of the preceding claims wherein the means to strip the moulded article from the core comprise one or more ejectors extending through the core to the surface of the core adjacent the centre of the mould surface and means to cause the ejectors to project from the core to detach the moued article from the core.

11. An apparatus as claimed in claim 10 wherein the ejectors project from the opposite side of the core body to the mould surface thereof and are connected to a platen having ram means for moving the platens towards and away from the core body to project and retract the ejectors with respect to the core body.

12. An apparatus as claimed in claim 11 wherein guide pillars are provided between the core body and platens for guiding the platen towards and away from the core body under the action of said ram means.

13. An apparatus as claimed in any of the preceding claims wherein the core of the mould is formed with recesses in said end parts of the mould core to form projections on the inside of the moulding and ejector means are provided in the mould core for ejecting a moulded projection formed in the recess for removal of the moulded article from the mould.

14. An apparatus as claimed in claim 13 wherein the ejector means comprise an ejector member movably mounted in the mould core to move into and out of said recess and means for projecting and retracting the member into and out of the recess respectively.

15. An apparatus as claimed in claim 14 wherein the means for moving the ejector member into and out of the recess and the means for pressing the ends of the moulded article outwardly of the core have a common drive means.

16. An apparatus as claimed in claim 15 wherein the common drive means comprises a double acting ram.

17. An injection moulding apparatus substantially as described with reference to and as illustrated in Figs. 2 and 3 of the accompanying drawings.

18. An ejection moulding apparatus substantially as desribed with reference to and as illustrated in Figs. 2 and 3 as modified by Fig.

4, Figs. 5 to 8 or Fig. 9 of the accompanying drawings.