GB2347171A

GB2347171A - Pin locking assembly

Info

Publication number: GB2347171A
Application number: GB9927552A
Authority: GB
Inventors: Steven Mark Long
Original assignee: DOLPHIN PACKAGING MATERIALS
Current assignee: DOLPHIN PACKAGING MATERIALS
Priority date: 1998-12-01
Filing date: 1999-11-23
Publication date: 2000-08-30
Also published as: GB9826220D0; GB9927552D0

Abstract

A pin locking assembly 1, for a thermo-form mould tool part adapted to receive and lock a headed pin 6, of a tool part. The pin locking assembly comprising a plurality of spaced balls 7, which in the pin-locking condition (Figure 1) are urged by a spring 22, against the head 10, of the pin by means of engagement between the inclined clamping face 27 on cage 21. Compressed air is supplied to chamber 32 to overcome the force of the spring 22, and in so doing the balls 7, are urged upwards negotiating the bore restriction 29, and into the enlarged axially outer bore portion 28 (Figure 7), thus allowing the pin to be released from the pin locking assembly. The inventive assembly 1, advantageously allows mould tool parts to be changed quickly and easily so that there is only minimum disruption to the thermo-forming line.

Description

PIN LOCKING ASSEMBLY The present invention relates to a pin locking assembly particularly, but not exclusively, to a locking assembly for securing in position thermoforming tools, and for securing thermo-forming tool parts in position in a composite thermo-form mould.

Composite thermo-form moulds often comprise an array of individual tool parts, such as rectangular upstands, to produce a series of identical moulded items from a single sheet of thermo-formable material, the array of tool parts being clamped to a mould base by suitable clamping means.

Although the clamping means may comprise screws, it is desirable that the tool parts can be changed quickly to enable minimum disruption to the thermo-forming line.

It is known to provide a clamping assembly which is adapted to clamp the head of a headed pin which is secured to a tool part, thereby to clamp the tool part. The clamping assembly is provided with a bore to receive the head of the pin, spring-biassed jaws being provided to retain the head in the bore in a locking position. The jaws are releasable by air pressure to enable initial insertion of the head of the pin into the bore so as to reach the locking position, and subsequently to release the spring-biassing force to enable the pin and associated tool part to be removed.

With the known clamping assembly it is necessary to urge the tool part substantially to the locking position before the spring clamping force can lock the pin. Furthermore, it is often necessary to prise the tool part away from the mould base when removing the tool part, and this may cause damage to the tool part, or to any seals associated with the tool part.

We consider that it would be desirable if a headed pin could be drawn into a clamping assembly in order to reach a clamping position, and/or on subsequent unclamping of the pin to be urged outwardly of the clamping assembly, so as to facilitate withdrawal of the pin from the clamping assembly.

According to one aspect of the invention we provide a pin locking assembly adapted to receive and lock a headed pin, the pin locking assembly comprising a plurality of spaced rolling elements which in the locked condition of the pin are urged by spring means against the head of the pin, fluid-pressure-operable unseating means operative when actuated to overcome the spring means and unseat the rolling elements from the head and then to urge the rolling elements against a release shoulder on the pin thereby to urge the pin axially outwards of the pin locking assembly to a position in which the rolling elements are permitted to move radially outwards from the pin sufficient to allow the head of the pin to be withdrawn from between the rolling elements.

The rolling elements are preferably balls.

Preferably the pin comprises a shank with said head at one end thereof, a neck being defined between the head and the shank, and the pin comprising a frusto-conical clamping chin on the head which faces in a direction generally from the head and towards the shank, the rolling elements being urged against the clamping chin in the locked condition, and said release shoulder is a frusto-conical release shoulder on the shank and adjacent the neck, the release shoulder facing generally from the shank and towards the head.

Preferably the locking assembly comprises a body formed with a body bore in which a plunger is axially reciprocable between a retracted pin locking position, and a projected pin-releasing position, the plunger comprising a substantially tubular outer cage portion which defines an axial plunger bore to receive the pin and which provides a cage for holding captive the plurality of circumferentially-spaced rolling elements housed in respective circumferentially-spaced radial through ports in the cage portion.

The diameters of the rolling elements are preferably greater than the radial thickness of the cage portion, each port being bounded by an element clamping face and by an opposing element unseating face, the element clamping face facing generally inwardly of the body, and the element unseating face facing generally outwardly of the body.

Preferably the plunger comprises an inner, actuating portion, the spring means being operative normally to urge the actuating portion of the plunger inwardly of the body towards the pin-locking position, and said unseating means comprising a fluid-pressure-operable movable wall operative to overcome the force of the spring means and to urge the plunger outwardly towards the pin-releasing position.

Preferably said body bore comprises an enlarged axially outer portion of a diameter sufficient to accommodate the radially outer projecting portions of the rolling elements when the plunger is in the pin-releasing position, thereby to enable the head of the pin to pass axially outwards of the plunger bore between the rolling elements, said body bore comprising a restriction and an enlarged axially inner portion of lesser diameter than said enlarged axially outer portion, said restriction being positioned between and adjacent to said enlarged axially inner and axially outer portions.

Preferably the arrangement is such that the pin can be clamped to the body and when the plunger is held by the spring means in said pinlocking position, the elements are wedged between the element clamping faces of said ports and the clamping chin on the head of the pin, the elements then being engaged in said enlarged axially inner portion of the body bore; and such that on supply of fluid pressure to said movable wall, the plunger is urged outwardly of the bore, and said element unseating faces urge the elements against the neck of the pin so as to release the elements from the enlarged axially inner portion, and then to urge the plunger and the pin axially outwards of the body bore, to cause the elements to pass said restriction and then enter said enlarged axially outer enlarged portion of the body bore, thereby permitting the head of the pin to be released from the plunger bore by passing between the rolling elements.

A thermo-forming tool pin locking assembly, and two modifications thereof, each in accordance with the invention, will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an enlarged vertical cross-section of the locking assembly and shown in the pin-locking position, Figures 2 to 7 are a series of sections similar to Figure 1 and showing in sequence the various stages of unlocking, ejection and withdrawal of the pin, Figures 8 to 12 are a similar series of sections showing in sequence the various stages in the insertion, drawing down and locking of the pin, and Figures 13 and 14 are modifications of the locking assembly of Figure 1.

With reference to Figure 1, a pin locking assembly 1 comprises a body 2 formed with a waisted and multi-stepped through bore 3 which is closed at the lower end by a closure plate 4 provided with a compressed air port 5. The assembly 1 comprises a headed locking pin 6, the movement of which is adapted to be controlled by four rolling elements in the form of ball bearings 7.

The pin 6 comprises a shank 8, a threaded free end 9 for attachment to a tool part of a composite thermo-form mould, and a head 10, the head 10 being connected to the shank by a neck 11 of substantially diabolo shape which is continuous in a downward direction with a substantially frustoconical clamping chin 12 which faces in an upward direction, that is generally from the head 10 and towards the shank 8, the neck being continuous in an upward direction with a substantially frusto-conical release shoulder 13, the release shoulder 13 facing downwards, that is generally from the shank 8 and towards the head 10.

A pneumatic piston 14 slidably works in an enlarged lower bore portion 15 of bore 3 and is fast with a cylindrical plunger 16 which extends upwards through a reduced diameter bore portion 17. Piston 14 is sealed in bore portion 15 by annular piston seal 18, and the plunger 16 is sealed in bore portion 17 by annular seal 19.

The upper, axially outer, portion of plunger 16 constitutes a tubular cage 21 which holds captive the four balls 7.

A blind axial bore 20 in the upper part of the plunger 16 is dimensioned to receive the locking pin 8, and defines the radially inner wall of the cage 21.

Piston 14 is resiliently biased downwards by a coiled compression spring 22 which abuts at its upper end with an annular step 23 in the bore 3 defined between reduced diameter portion 17 and an intermediate diameter bore portion 24, and at its lower end with the piston 14.

The cage 21 is formed with four circumferentially equally-spaced through-ports 25, each port extending generally in a radial direction and being bounded on the lower side by a concave element unseating face 26, and on the upper side by an opposing, inclined element clamping face 27.

Thus, the element clamping face 27 faces generally inwardly of the body 2, and the element unseating face faces generally outwardly of the body.

The plunger 16 is axially movable between a retracted pin-locking position, shown in Figure 1, and a projected pin-releasing position, shown in Figures 6 and 7.

Body bore 3 further comprises an enlarged axially outer portion 28, a bore restriction 29, a frusto-conical bore portion 30 connecting the outer portion 28 to the bore restriction 29, and an enlarged axially inner portion 31 which, as shown in Figure 1, in radial cross-section is of complementary shape to that of an arc of the surface of balls 7. Bore restriction 29 is thus positioned axially between and adjacent to the axially outer portion 28 and the enlarged axially inner portion 31.

The operation of the clamping pin assembly will now be described.

In the condition shown in Figure 1, the pin 6 is clamped in position by the action of balls 7 engaging with chin 12 on the pin 6, each ball 7 being urged in the direction of arrow A by the engagement between the respective inclined clamping face 27 on cage 21 and the ball 7 which is held against outwards radial movement by being engaged fully in the enlarged bore portion 31, to provide a radially inward reaction on each ball 7 indicated by arrow B in Figure 1. The engagement between each ball 7 and inclined chin 12 provides a clamping force on the pin 10 indicated by the reaction arrow C in Figure 1, the clamping force on chin 12 having an axially downward component which thereby holds the pin 10 against axially outward movement, and thereby holds the associated mould part, not shown, in an operative position for use in a thermoforming operation.

In Figure 2 compressed air has begun to be supplied to compressed air port 5 to commence pressurisation of chamber 32 beneath piston 14 thereby to begin to overcome the force of spring 24, to commence upward movement of the plunger 16 from its pin-locking position. The axial clearance in Figure 1 between the concave element unseating face 26 and the balls 7 has been taken up in Figure 2, where it is seen that the concave unseating face 26 is so shaped that the radially outer edge 33 thereof first contacts the respective ball 7 to initiate unpicking of the balls 7 from the walls of enlarged bore portion 31.

In Figure 3 it is seen that as the plunger 16 rises further as pressure in chamber 32 is increased, the balls are urged upwards by the intimate engagement of the concave unseating faces 26 with the respective balls, and radially inwardly of the cage by the engagement of the balls with the corner 34 defined at the junction between the enlarged bore portion 31 and the bore restriction 29, the balls sliding across the sloping face of chin 12 towards the annular recess 35 extending around neck 11.

In Figure 4 the balls 7 have fully entered the annular recess 35 which is made sufficiently deep that the balls 7 are now able to pass axially through the bore restriction 29 as increasing pressure in chamber 32 urges the plunger 16 further upward. During the upward movement of balls 7 past the bore restriction 29, from the position shown in Figure 4, the balls 7 carry with them the pin 6 which is thereby lifted to lift the associated mould part from the operative clamped position of the mould part. The ejection force exerted on the associated mould part, which is generated by pressure in chamber 32, is sufficient to overcome any friction forces exerted on the mould part by any seals associated with the mould part.

In Figure 5 the balls 7 have just negotiated the bore restriction 29 and have entered frusto-conical bore portion 30, and as the plunger 16 is urged further upwards, to the position of Figure 6, the piston 14 reaches its uppermost position as determined by the step 36 between bore portions 24 and 15.

Figure 7 shows that the pin 6, in the condition of Figure 6, can now be manually withdrawn upwards, as shown in Figure 7, because the balls 7 are able to be urged radially outwards by the chin 12 and the head 10 of the pin 6, the balls 7 being accommodated in the enlarged axially outer bore portion 28 whilst engaging with the element clamping faces 27.

Figures 8 to 12 show substantially the reverse of the foregoing sequence of steps.

In Figure 8 the pin 6 has been inserted into the bore 20 of the cage 21, the head 10 of the pin passing downwards between the balls. The pressure in chamber 32 is then progressively released, and the force of spring 22 causes the piston 14 and the plunger 16 to be moved downwards. As shown in Figure 9 downward movement of the cage 21 causes each ball to be urged downwards and radially inwards by virtue of the action of the respective element clamping face 27 and the respective wall of frusto-conical bore portion 30, said wall extending at a steeper angle than face 37 thereby to permit said movements without the balls becoming trapped.

Figures 10 and 11 are largely self-explanatory and show how the balls 7 negotiate the bore restriction 29, the radially inner portions of the balls being accommodated within the annular recess 25 surrounding neck 11.

Finally, Figure 12 shows the condition just before the piston 32 is arrested by closure plate 4.

The action of element clamping face 27 is to urge the balls 7 downwards, but also radially outwards relative to the axis of the assembly, and so the balls 7 will move radially outwards when permitted. As the balls 7 reach the enlarged bore portion 31 they are able to move radially outwards into bore portion 31, and finally the condition of Figure 1 is re-established.

It will be appreciated that in proceeding from the condition of Figure 9 through Figures 10,11,12 and returning to the condition of Figure 1, the downward movement of the balls 7 results in a drawing down of the pin 6 by virtue of the engagements between the balls 7 and the chin 12 on the pin 6. In Figures 13 and 14 parts corresponding to those of the embodiment of Figure 1 have been given corresponding reference numbers.

Figure 13 shows a modification of the assembly of Figure 1, and shown in the condition of Figure 1, in which an additional port 5'is provided connecting with the chamber 32'above piston 32, to enable air pressure to be applied above piston 14 to assist the force of spring 22.

Figure 14 shows a modification in which the housing 1 is provided as an integral part of a large mould support plate 1'. The movement of piston 14 is controlled in this case by vacuum in chamber 32'.

A series of circumferentially spaced coil springs 22'are utilised, the upper ends of springs 22'being housed in respective bores in the underside of a plug member 40.

Claims

CLAIMS 1. A pin locking assembly adapted to receive and lock a headed pin, the pin locking assembly comprising a plurality of spaced rolling elements which in the locked condition of the pin are urged by spring means against the head of the pin, fluid-pressure-operable unseating means operative when actuated to overcome the spring means and unseat the rolling elements from the head and then to urge the rolling elements against a release shoulder on the pin thereby to urge the pin axially outwards of the pin locking assembly to a position in which the rolling elements are permitted to move radially outwards from the pin sufficient to allow the head of the pin to be withdrawn from between the rolling elements.
2. A pin locking assembly as claimed in claim 1 in which the rolling elements are balls.
3. A pin locking assembly as claimed in claim 1 or claim 2 in which the pin comprises a shank with said head at one end thereof, a neck being defined between the head and the shank, and the pin comprising a frusto-conical clamping chin on the head which faces in a direction generally from the head and towards the shank, the rolling elements being urged against the clamping chin in the locked condition, and said release shoulder is a frusto-conical release shoulder on the shank and adjacent the neck, the release shoulder facing generally from the shank and towards the head.
4. An pin locking assembly as claimed in any preceding claim in which the locking assembly comprises a body formed with a body bore in which a plunger is axially reciprocable between a retracted pin-locking position, and a projected pin-releasing position, the plunger comprising a substantially tubular outer cage portion which defines an axial plunger bore to receive the pin and which provides a cage for holding captive the plurality of circumferentially-spaced rolling elements housed in respective circumferentially-spaced radial through ports in the cage portion.
5. A pin locking assembly as claimed in claim 4 in which the diameters of the rolling elements are greater than the radial thickness of the cage portion, each port being bounded by an element clamping face and by an opposing element unseating face, the element clamping face facing generally inwardly of the body, and the element unseating face facing generally outwardly of the body.
6. A pin locking assembly as claimed in claim 4 or claim 5 in which the plunger comprises an inner, actuating portion, the spring means being operative normally to urge the actuating portion of the plunger inwardly of the body towards the pin-locking position, and said unseating means comprising a fluid-pressure-operable movable wall operative to overcome the force of the spring means and to urge the plunger outwardly towards the pin-releasing position.
7. A pin locking assembly as claimed in any of claims 4,5 or 6 in which the body bore comprises an enlarged axially outer portion of a diameter sufficient to accommodate the radially outer projecting portions of the rolling elements when the plunger is in the pin-releasing position, thereby to enable the head of the pin to pass axially outwards of the plunger bore between the rolling elements, said body bore comprising a restriction and an enlarged axially inner portion of lesser diameter than said enlarged axially outer portion, said restriction being positioned between and adjacent to said enlarged axially inner and axially outer portions.
8. A pin locking assembly as claimed in claim 7 in which the arrangement is such that the pin can be clamped to the body and when the plunger is held by the spring means in said pin-locking position, the elements are wedged between the element clamping faces of said ports and the clamping chin on the head of the pin, the elements then being engaged in said enlarged axially inner portion of the body bore; and such that on supply of fluid pressure to said movable wall, the plunger is urged outwardly of the bore, and said element unseating faces urge the elements against the neck of the pin so as to release the elements from the enlarged axially inner portion, and then to urge the plunger and the pin axially outwards of the body bore, to cause the elements to pass said restriction and then enter said enlarged axially outer enlarged portion of the body bore, thereby permitting the head of the pin to be released from the plunger bore by passing between the rolling elements.
9. A pin locking assembly substantially as described with reference to the accompanying drawings.