GB2237767A - Moulding machine ejector devices - Google Patents

Abstract

A coupling device, for use in a plastics injection moulding machine, to connect a workpiece ejector device to an ejector actuator for translational motion of the ejector comprises: 1) a housing (30) having a bore (35) flanked by opposed jaws (41, 42) movable towards and away from each other between a coupling disposition and an open disposition respectively; 2) an ejector link rod (24) with a first end to be mounted to the ejector device and a second end (38) to be received in the bore of the housing; 3) an annular recess (37) on the second end of the link rod, to be engaged when in a coupling disposition by the jaws in their coupling disposition to retain the link rod against longitudinal movement in the bore in the housing; 4) at least one jaw actuator (45) to drive the jaws apart from each other to their open disposition for admission between them of the link rod into the bore to take up its coupling disposition relative to the housing, and release of the link rod from the jaws; and 5) means (43) to bias the jaws towards their coupling disposition.

Description

COUPLING DEVICE This invention relates to a coupling device, for use in a plastics injection moulding machine, to connect a workpiece ejector device to an ejector actuator for translational motion of the ejector device.

When installing a mould (otherwise called "die halves" or "tooling") in an injection moulding machine there are difficulties in manually connecting the ejector device of the mould to the ejector actuator of the machine. The connection is on the axis of the machine so access is difficult, particularly on a big machine. Establishing the connection is difficult because the space is confined, dangerous because the site is deep inside the machine, and dirty because the machines are coated with lubricant.

Conventionally, the connection is made using threaded elements. These are prone to unscrew in use unless they are carefully secured from the outset, which cannot be relied upon because of the unpleasant aspects of the installation operation as explained above.

An object of the present invention is to provide a device for coupling the ejector device and its actuator, which can be remotely actuated so as to avoid the need for manual connection at the site of the coupling. Space for the coupling is confined, so one constraint on the coupling device design is that it must be economical in its use of space transverse to is working longitudinal axis.

According to the present invention, there is provided a coupling device as hereinbefore defined, and comprising: 1) a housing having a bore flanked by opposed jaws movable towards and away from each other between a coupling disposition and an open disposition respectively; 2) an ejector link rod with a first end to be mounted to the ejector device and a second end to be received in the bore of the housing; 3) an annular recess on the second end of the link rod, to be engaged when in a coupling disposition by the jaws in their coupling disposition to retain the link rod against longitudinal movement in the bore in the housing;; 4) at least one jaw actuator to drive the jaws apart from each other to their open disposition for admission between them of the link rod into the bore to take up its coupling disposition relative to the housing, and for release of the link rod from the jaws, and 5) means to bias the jaws towards their coupling disposition; Whereby actuation of the jaw actuator moves the jaws apart to permit the link rod to be received in the bore, whereupon termination of the actuation allows the biasing means to move the jaws to their coupling disposition engaged in the recess of the link rod and, with the link rod and housing interengaged, translational movement of the housing with the ejector actuator results in corresponding translational movement of the link rod (and hence ejector device).

The jaws may be biased to the coupling dispositon by compression springs. In the case of two opposed jaws, each jaw may have a spring between it and the housing, one at each end of each jaw.

The jaw actuators can be pistons and cylinders (preferably pneumatic). In one preferred embodiment these lie along the axis of the housing, one each side of a diameter, and each driving a mushroom-shaped piston head into the space between inclined shear faces on the facing ends of two opposed jaws held in place by a retaining plate on one axial end of the housing, each piston head being driven towards the retaining plate to squeeze the jaws apart to admit the ejector link rod into the bore of the housing.

Machined bores in the housing create a manifold for supply, from a single input line, of compressed air to the two jaw actuators.

For a better understanding of the invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a longitudinal diametral section of an.

injection moulding machine with which the coupling device of the invention is used; and Figure 2 is an isometric view of an embodiment of the coupling device in accordance with the invention.

Referring to Figure 1, components 10 of plastics material are moulded in a cavity 11 formed between a fixed die half 12 and a moving die half 13. Not shown in the figure is the equipment for injecting into the cavity 11 the fluid plastics material which is moulded to form the component 10.

The fixed die half 12 is supported on a fixed platen 14 and the moving die half 13 on a moving platen 15. In the figure, the die halves 12 and 13 (otherwise called the "tooling") is shown in an open disposition for removal of the workpiece 10 from the cavity 11. For the moulding step, the platen 15 is moved in the direction of arrow f, towards the fixed platen 14, until the die halves 12 and 13 abut one another along the mating faces 16 and 17 in fluid-tight manner.

For extraction of the moulded workpiece 10 from the cavity 11, an ejection device 18 is employed, which operates on the longitudinal axis of the moulding machine and, in the embodiment of figure 1, it is shown within the envelope of the fixed platen 14. The ejection device 18 comprises an ejector plate 19 which carries a plurality of ejector pins 20 which extend through the fixed die half 21 and are movable with the ejector plate 19 along the axis of the machine in the direction shown by arrow g to urge the workpiece 10 away from the mould surface 21 of the fixed die half 12.

This axial movement of the ejector plate 19 is achieved by actuation of a piston and cylinder actuator 22, the piston 23 of this actuator being connected to the ejector plate 19 by a link rod 24 which extends on the axis of the machine from the back of the ejector plate 19 towards the actuator 22.

These injection moulding machines are employed to make all sorts of different plastics components 10. Each time a different component is to be made, the tooling 12, 13 has to be exchanged. Apart from the attachment of the tooling to the associated platens 14 and 15, another connection has to be made between the ejector plate 19 of the new tooling, and the actuator 22 of the ejection device of the machine itself. This coupling is made within the area enclosed by the dashed line 25 shown in the drawing.

Turning now to Figure 2 of the drawings, there is shown a first embodiment of connector for making the connection within the area 25. The connector has a hollow housing 30 which is generally of cylindrical shape and so has a longitudinal axis. On that axis, and extending from the rear face 31 of the housing 30 is a threaded rod 32 by which the coupling may be attached to the piston 23 of the ejector actuator 22.

The front face 33 of the housing 30 carries a retaining plate 34 which has a through bore 35 on its axis and the link rod 24 of the ejector plate 19 is received, in use, through this bore 35. The retainer plate 34 is held to the housing 30 by a set of four retaining bolts in bores 36.

The link rod 24 is provided with an annular recess 37 close to its distal end 38. The recess has a base surface 39 which is parallel to the axis of the rod 24, and is flanked by wall surfaces 40 each of which is perpendicular to the axis of the rod 24. The recess has a width (in the axial direction of the rod 24) of P.

The housing 30 includes a cavity 48 which contains a first jaw 41 and a second jaw 42 and each of these jaws are urged towards the axis of the housing 30 by a pair of compression springs 43. Each jaw has an arcuate engagement surface 44, the two surfaces 44 facing each other across the longitudinal axis of the housing 30.

The thickness of the jaws 41 and 42 is just slightly less than the width P of the recess 37 on the rod 24, and the engagement surfaces 44 are shaped for accommodation within the recess 39 on the rod 24. With the rod 24 fully home in the housing 30, it can be retained in this position by engagement of the jaws 41 and 42 in the recess 37.

The jaw cavity 48 is spacious enough to permit the jaws 41 and 42 to withdraw away from each other and from the axis of the housing 30, with consequent compression of the springs 43, far enough to permit the distal end 38 of the rod 24 to extend into the hollow housing 30 between the jaws, so that the jaws can then move back towards the axis to engage with the recess 37. In the figure, the retaining plate 34 is shown spaced away from the end surface 33 of the housing 30 but it will be appreciated that the plate 34 is normally tight against the end surface 33 so that the jaws 41 and 42 in fact slide on the inside facing surface of the retaining plate 34.

To urge the jaws 41 and 42 away from one another, there is employed a pair of pneumatic piston and cylinder actuators, of which only one, 45, is visible in the figure. The piston of the actuator 45 carries a mushroom shaped head 46 which co-operates with a correspondingly inclined shear face 47 on each one of the jaws 41 and 42. In effect, each actuator 45 drives its associated piston head 46 in a wedging action between the jaws 41 and 42, in order to drive them apart from one another.

Upon release of fluid pressure to the actuator 45, the springs 43 are effective to drive the jaws 41 and 42 back towards to each other, for engagement between them and the recess 37 on the rod 24.

Thus, in use of the coupling device, it is fitted by its threaded rod 32 to the ejector actuator 22, while the link rod 24 is secured to the back of the ejector plate 19, on the same axis as that of the ejector actuator 22. for coupling, it is necessary simply to provide a fluid supply to the actuators 45, to hold apart the jaws 41 and 42 long enough to permit entry of the distal end 38 of the link rod 24 into the volume of the housing 30, whereupon release of actuation pressure allows the jaws 41 and 42 to engage the recess 37. For de-coupling the reverse process is followed.

In practice, it is desirable to allow some play between the rod 24 and the housing 30, both axially and radially with respect to the housing 30, so the thickness of the jaws is made slightly less than the width P of the recess 37, and the bore in the housing which receives the rod 24 is of slightly greater diameter than the diameter of the rod 24.

It is also desirable that there should be the minimum of connections between the coupler and the exterior of the machine, so it will generally be convenient to provide (suitably on the rear face 31 of the housing 30) a manifold arrangement whereby fluid to each of the actuators 45 can be delivered from a single supply line.

A major advantage of the illustrated device is that its diameter is relatively small, making it highly suitable for installation in confined spaces. Another advantage is that the housing 30 is inherently very strong, because only a relatively small proportion of its volume need be machined away to accommodate the actuators, jaws, and distal end 38 of the link rod 24.

Claims (10)

1. A coupling device, for use in a plastics injection moulding machine, to connect a workpiece ejector device to an ejector actuator for translational motion of the ejector device, the coupling device comprising: 1) a housing having a bore flanked by opposed jaws movable towards and away from each other between a coupling disposition and an open disposition respectively; 2) an ejector link rod with a first end to be mounted to the ejector device and a second end to be received in the bore of the housing; 3) an annular recess on the second end of the link rod, to be engaged when in a coupling disposition by the jaws in their coupling disposition to retain the link rod against longitudinal movement in the bore in the housing;; 4) at least one jaw actuator to drive the jaws apart from each other to their open disposition for admission between them of the link rod into the bore to take up its coupling disposition relative to the housing, and for release of the link rod from the jaws; and 5) means to bias the jaws towards their coupling disposition; Whereby actuation of the jaw actuator moves the jaws apart to permit the link rod to be received in the bore, whereupon termination of the actuation allows the biasing means to move the jaws to their coupling disposition engaged in the recess of the link rod and, with the link rod and housing interengaged, translational movement of the housing with the ejector actuator results in corresponding translational movement of the link rod (and hence ejector device).

2. A coupling device as claimed in claim 1 wherein the biasing means are compression springs mounted between each jaw and the housing.

3. A coupling device as claimed in claim 1 or 2 wherein the or each jaw actuator comprises a piston and cylinder actuator which acts along a line parallel with the axis of the bore in the housing, the piston head having at least one inclined shear face which co-operates with a correspondingly inclined shear face on one of the jaws.

4. A coupling device as claimed in claim 3 comprising a pair of the jaw actuators one on each side of the bore axis, and each having a piston head with two opposed said shear faces, each of which co-operates with a different one of the jaws.

5. A coupling device as claimed in any one of the preceding claims wherein the jaws are captivated in the housing by a retaining plate on that end of the housing at which the said bore emerges, the plate having an axial aperture through which the link rod may pass.

6. A coupling device as claimed in claim 5, when dependent on either one of claims 3 and 4, wherein the jaws are slidable on the retaining plate, with the movement of the piston head which drives the jaws apart being in a direction perpendicularly towards the plane of the retaining plate.

7. A coupling device as claimed in any one of claims 3 to 6 wherein the angle subtended between the inclined face of the piston head and the axis of the associated piston and cylinder actuator is in a range of from 300 to 350.

8. A coupling device as claimed in claim 7 wherein the said subtended angle is 320.

9. A coupling device as claimed in any one of the preceding claims wherein there is more than one jaw actuator, and each of the actuators is a fluid-powered actuator powered by a supply of fluid from a manifold on the housing.

10. A coupling device as claimed in any one of the preceding claims wherein the or each jaw actuator is a pneumatic actuator.