GB2246537A

GB2246537A - Removing injection moulded articles from between opened moulds

Info

Publication number: GB2246537A
Application number: GB9116741A
Authority: GB
Inventors: Lawrence John Thorpe
Original assignee: WREN ROBOTIC ENGINEERING LIMIT
Current assignee: WREN ROBOTIC ENGINEERING LIMIT
Priority date: 1990-08-02
Filing date: 1991-08-02
Publication date: 1992-02-05
Also published as: GB9016960D0; GB9116741D0

Abstract

An arm (14) which is cranked to avoid platen guide rails (24), is pivotally moveable to advance into an open mould between the platens (16, 18) to engage a moulded article (46), and to retract to withdraw it from the mould. The arm (14) advances and retracts under control of a closed hydraulic circuit including rotatable or linear double acting control actuating, and drive piston/cylinders (22, 20). The control piston cylinder (22) e.g. incorporating a double-acting rotatable fin, is displaced by a lever connection (40) operated by the movable platen (16), so that the movement of arm (14) is coordinated with that of the platen (16). The moulded articles (46) are engaged by suction pads (50) on the arm (14), which is linearly axially reciprocated into and out of engagement with arm (14), by a double acting pneumatic cylinder (34). A microprocessor (80, Fig 4) controls the pneumatic cylinder and the suction to the pads (50), in conjunction with proximity sensors which detect the location of the movable platen (16). <IMAGE>

Description

Injection Moulding The present invention relates to injection moulding, and in particular to emptying moulds of injection moulding machines.

Injection moulding machines commonly comprise two platens movable relative to each other and carrying respective mould portions which together form a mould when the platens are brought together. After moulding material has been injected into the mould, the platens are separated. When an article fails to be released from the mould, an operator may reach in between the platens to release the article, thereby risking injury if the platens were to close to re-form the mould. This danger is particularly serious when platen movement is automatically controlled and therefore likely to begin regardless of the presence of an operator's limb.

The present invention seeks to overcome these or other disadvantages of the prior art.

According to the present invention there is provided apparatus for use with an injection moulding machine for ejecting articles from moulds, comprising a release member movable to advance into an open mould to engage a moulded article, and movable to withdraw the article from the mould, drive means for moving the release member, and hydraulic control means operable to control the drive means to advance the release member when opening of the mould is detected and to withdraw the release member when closing of the mould is detected.

The drive means may comprise a piston connected to the release member and movable in a cylinder under the control of the control means which provide hydraulic fluid for moving the piston. The control means may comprise a second piston and cylinder arrangement, the arrangement being coupled to the moving platen of the machine to create hydraulic pressure in accordance with the platen position. Preferably the second piston and cylinder arrangement is connected to the cylinder of the drive means to form a closed hydraulic circuit, whereby motion of the release member is directly coupled to the motion of the platen.

The second piston and cylinder arrangement may comprise a double-acting piston member. The piston member is preferably rotatably mounted in a cylinder between two cylinder outlets, whereby the piston member may rotate in either sense to drive hydraulic fluid out of either outlet. The control means may comprise a mechanical linkage which moves the piston member relative to the cylinder in accordance with movement of the moving platen of the machine. The control means are preferably mounted on the moving platen, the linkage providing a link with a fixed point relative to which the control means moves with the platen.

Preferably, the control means, the drive means and the release member are mounted on the movable platen.

The release member may be mounted for rotary movement when advancing and withdrawing. The position of the release member is preferably controlled by a rotary actuator.

Preferably the drive means cause the release member to effect a preliminary releasing operation before withdrawing. The preliminary releasing operation may include moving the moulded article from the mould into the space between the platens. The release member may be arranged to advance and withdraw in directions generally perpendicular to the platen stroke, the preliminary releasing operation being a movement generally parallel to the platen stroke.

The control means are preferably operable to prevent the preliminary releasing operation until the release member has been fully advanced. Preferably separate circuits are provided to control the position of the release member and the preliminary releasing operation.

The release member may comprise an arm driven by the drive means and carrying a head which, in use, engages a moulded article to cause the article to be withdrawn with the release member.

The invention further provides an injection moulding machine incorporating ejecting apparatus as defined in any of the preceding six paragraphs.

One embodiment of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings in which: Fig. 1 is a schematic side elevation of an injection moulding machine incorporating apparatus according to the invention, shown with the platens together and the mould closed; Fig. 2 is a similar but partial view with the platens apart and the release member advanced; Figs. 1A and 2A are elevations of the moving platen and corresponding to rigs. 1 and 2; Fig. 3 is a schematic diagram of the hydraulic circuit employed; and Fig. 4 is a schematic diagram of the pneumatic circuit employed.

The drawings show apparatus 10 for use with an injection moulding machine 12 for ejecting articles from the moulds. The apparatus 10 comprises a release member in the form of an arm 14 movable to advance into an open mould (between the platens 16,18 of the machine 12) to engage a moulded article, and movable to withdraw from the mould with the article. Drive means 20 in the form of a hydraulic rotary cylinder move the arm 14.

Hydraulic control means including a rotary cylinder 22 are operable to detect the opening of the mould and to control the drive means 20 to advance the arm 14, and are operable to detect closing of the mould and to withdraw the arm 14.

In more detail, the injection moulding machine comprises a fixed platen 18 and a movable platen 16 which move together or apart along guide rails 24. The platens 16,18 support respective mould portions 26. In Fig. 1 the mould portions 26 abut to form moulds 28 which can be filled with mould material by means of a filling piston 30 and communicating channels shown partially at 31.

The operating cycle of the moulding machine comprises moving the platens 16,18 together to close the moulds 28; injecting moulding material into the moulds 28; moving the platens 16,18 apart to open the moulds 28 and allow the moulds to be emptied. During this process, the platen 18 is fixed, while the platen 16 moves.

The ejecting apparatus includes a hydraulic cylinder at 20 which causes the arm 14 to swing about the axis 32, along the arc 33 (Fig. 1A). At its extreme withdrawn position, the arm 14 adopts the position shown in Figs. 1 and 1A, while at its fully advanced position, the arm 14 is in the position shown in Figs. 2 and 2A.

It can be seen that the arm 14 is shaped to avoid fouling the platen guide rails 24 as it moves.

A pneumatic cylinder 34 is provided between the cylinder 20 and the arm 14, to move the arm 14 back and forth along the axis 32, that is, parallel to the stroke of the moving platen 16. The purpose of this movement will be explained below.

The control means 22 comprise a hydraulic rotary actuator, shown schematically in Figs 1, 1A, 2 and 2A, and in more detail in Fig 3. The actuator consists of a fin 37 rotatably mounted in a cylinder 38, and connected to a fixed point 39 on the machine by articulated rods 40, so that as the platen 16 moves relative to the point 39, the rods 40 swing the fin 37 in a corresponding direction. The interior of the cylinder 38 on either side of the fin 37 is connected through hydraulic lines 44 (shown only in Fig. 3) to respective sides of a double-acting piston at 20. It can thus be seen that the actuator 36 and cylinder 20 form a closed hydraulic circuit, so that rotation of the fin in either direction within the cylinder 38 causes the cylinder 20 to swing the arm 14 in a corresponding sense.Since the actuator 22 is driven by the platen 16, the arm 14 will advance into the space between the platens 16,18 as the platen 16 moves away from the platen 18 to open the moulds 28, and as the platen 16 moves back towards the platen 18, the arm 14 will be withdrawn from the space.

Check valves 45 in the form of one-way ball valves are provided in each line 45 to allow the working pressure in the circuit to be maintained.

It may be desirable to allow the rods 40 to be disconnected, so that the arm 14 will remain withdrawn even if the platens separate. This allows the moulds to be opened for cleaning, maintenance, or replacement with new mould portions 26. The mould portions illustrated combine to form four moulded articles at once, indicated by numerals 46.

In an alternative arrangement, the rotary actuator may be replaced by a linear, double-acting piston and cylinder mounted at a fixed position on the machine, the pistons being connected to the platen 16 by rods, so that the piston moves with the platen.

It may also be desirable to provide one of the rods with a threaded connection by means of which it can be lengthened, so that the relative positions of the arm 14 and the platen 16 can be precisely controlled.

The arm 14 carries a plate 48 at its free end and the plate in turn carries devices 50 for engaging corresponding ones of the articles 46 when the arm 14 is fully advanced. At this stage, the cylinder 34 is activated to move the arm 14 away from the platen 16 by a distance corresponding to the depth of the mould in the mould portion 26. This movement moves the articles 46 into the space between the mould portions 26 so that they are free to swing out when the arm 14 withdraws as the moulds close. When the arm is fully withdrawn, and before it swings back between the platens, the cylinder 34 is again activated to move the arm 14 back towards the platen 16, so that the devices 50 can engage the next articles 46 immediately the arm 14 swings down.

The operation of the pneumatic cylinder 34 which provides axial movement of the arm 14 is controlled by a pneumatic circuit such as that shown schematically in Fig. 4. The circuit shown in Fig. 4 also controls the operation of the devices 50 which engage articles 46 and withdraw them from the mould.

The double acting piston of the cylinder 34 is supplied with compressed air from a supply at 70, through valves 72, 74. The valves 72, 74 are three-port, two way valves. In the position shown, the valve 72 connects the corresponding side of the cylinder 34 to a vent 76 and closes the supply from 70. The valve 74 connects the supply 70 to the corresponding side of the cylinder 34 and closes a vent 78. When the valves 72, 74 move together to their other position, the valves 72 connects the corresponding side of the cylinder 34 to the supply at 70, and closes the vent 76, while the supply 70 is closed by the valve 74 and the corresponding side of the cylinder 74 is connected to the vent at 78. Thus, the piston can be reciprocated in the cylinder 34 by moving the valves 72 together, to their two positions alternately.

The positions of the valves 72, 74 are controlled by a microprocessor 80. The microprocessor 80 also controls the state of a valve 82 located between the devices 50 and a pump at 84. In the position shown, the devices 50 are connected to the pump 84 so that a suction force is generated at 50 which causes the articles in the mould to be gripped by the device 50. When the valve 82 moves to its other position, the devices 50 are connected to a vent 86 so that the articles are released.

The microprocessor 80 instructs the valves 72, 74, 82 in response to signals from proximity switches 86 which are located on the machine to detect respective extreme positions of the moving platen 1. The sequence of operations is as follows, commencing with the mould closed and the arm withdrawn. When moulding is complete, the platen 16 begins to move and the microprocessor 80 detects this through the proximity switches 86. As the platen 16 moves, the arm swings in between the platens 16, 18. When the platen 16 reaches its fully withdrawn position, the microprocessor 80 detects this through the proximity switches 86 and moves the valve 82 to the position shown, so that the devices engage articles in the moulds by suction.After an appropriate time determined by the microprocessor, and sufficient to have securely engaged the articles, the microprocessor sets the valves 72, 74 to move the arm 14 away from the platen 16, thereby withdrawing the articles from the mould. The mould can then begin to close, by moving the platen 16.

The movement of the platen 16 causes the arm 14 to swing out, carrying the articles from the mould. When the mould is fully closed the microprocessor detects this through the proximity switches 86 and moves the valve 82 to its other state to release the articles. They may drop on to a conveyor belt, for instance. The valves 72, 74 are moved to their other positions so that the arm 14 moves back towards the platen 16, to complete the cycle.

It will be apparent that the microprocessor 80 could be used only to control the circuit shown in Fig.

4, or could be connected to control the operation of the complete machine. Additional proximity switches could be included to allow the microprocessor to monitor the position of the arm 14, to ensure that it is moving correctly in relation to the platen 16.

The use of a closed hydraulic circuit to drive the arm 14 provides the advantage that the movement of the arm 14 and of the platens 16 is automatically coordinated. Consequently, the arm movement does not require adjustment even if the platen speed is changed, or the frequencies of moulding operations is changed, because the arm remains coordinated with the platens.

Although the automatic coordination between the arm 14 and the platens allows the machine to be operated arbitrarily quickly without waiting for the arm 14, where fast operation is envisaged it is advisable to construct the arm 14 of low density material to reduce inertia within the system. Honeycombed aluminium or carbon fibre materials are envisaged.

I-t may be desirable to incorporate a brake in the system, for instance between the arm 14 and the cylinder 20, so that the arm can be stopped and held at any position, in the event of an emergency or failure in the hydraulic system. A brake is shown highly schematically at 90 in Fig. 3.

The axial movement provided by the cylinder 34 may not be necessary when moulds are shallow.

It can be seen from Fig. 3 that the cylinder arrangements at 20 and 22 may both be rotary arrangements of the type described in detail in relation to the arrangement 22. Alternatively, one or both of the arrangements could be replaced by linear arrangements appropriately coupled to the arm 14 or the rods 40.

It can be seen that the arm 14 and apparatus for controlling it are all mounted on the moving platen, with no mechanical link to the fixed platen being required.

In some circumstances it may be more desirable to mount the ejection apparatus 10 on the fixed platen 18, rather than the moving platen 16.

Variations and modifications may be made to the apparatus described above without departing from the scope of the present invention and in particular, the choice and location of the various components and the design of the closed hydraulic circuit and the pneumatic circuit can be varied according to the operational needs encountered.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. Apparatus for use with an injection moulding machine for ejecting articles from moulds, comprising a release member movable to advance into an open mould to engage a moulded article, and movable to withdraw the article from the mould, drive means for moving the release member, and hydraulic control means operable to control the drive means to advance the release member when opening of the mould is detected and to withdraw the release member when closing of the mould is detected.

2. Apparatus according to claim 1, wherein the drive means comprise a piston connected to the release member and movable in a cylinder under the control of the control means which provide hydraulic fluid for moving the piston.

3. Apparatus according to claim 1 or 2, wherein the control means comprise a second piston and cylinder arrangement, the arrangement being coupled to the moving platen of the machine to create hydraulic pressure in accordance with the platen position.

4. Apparatus according to claim 3, wherein the second piston and cylinder arrangement is connected to the cylinder of the drive means to form a closed hydraulic circuit, whereby motion of the release member is directly coupled to the motion of the platen.

5. Apparatus according to claim 3 or 4, wherein the second piston and cylinder arrangement comprises a double-acting piston member.

6. Apparatus according to claim 5, wherein the piston member is rotatably mounted in a cylinder between two cylinder outlets, whereby the piston member may rotate in either sense to drive hydraulic fluid out of either outlet.

7. Apparatus according to claim 5 or 6, wherein the control means comprises a mechanical linkage which moves the piston member relative to the cylinder in accordance with movement of the moving platen of the machine.

8. Apparatus according to claim 7, wherein the control means are mounted on the moving platen, the linkage providing a link with a fixed point relative to which the control means moves with the platen.

9. Apparatus according to any preceding claim, wherein the control means, the drive means and the release member are mounted on the movable platen.

10. Apparatus according to any preceding claim, wherein the release member is mounted for rotary movement when advancing and withdrawing.

11. Apparatus according to claim 10, wherein the position of the release member is controlled by a rotary actuator.

12. Apparatus according to any preceding claim, wherein the drive means cause the release member to effect a preliminary releasing operation before withdrawing.

13. Apparatus according to claim 12, wherein the preliminary releasing operation includes moving the moulded article from the mould into the space between the platens.

14. Apparatus according to claim 12 or 13, wherein the release member is arranged to advance and withdraw in directions generally perpendicular to the platen stroke, the preliminary releasing operation being a movement generally parallel to the platen stroke.

15. Apparatus according to any of claims 12 to 14, wherein the control means are operable to prevent the preliminary releasing operation until the release member has been fully advanced.

16. Apparatus according to any of claims 12 to 15, wherein separate circuits are provided to control the position of the release member and the preliminary releasing operation.

17. Apparatus according to any preceding claim, wherein the release member comprises an arm driven by the drive means and carrying a head which, in use, engages a moulded article to cause the article to be withdrawn with the release member.

18. Apparatus for use with an injection moulding machine, substantially as described above, with reference to the accompanying drawings.

19. An injection moulding machine incorporating ejecting apparatus according to any preceding claim.

20. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.