GB2272428A

GB2272428A - Chuck assembly.

Info

Publication number: GB2272428A
Application number: GB9223922A
Authority: GB
Inventors: Anthony John Hart
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1992-11-14
Filing date: 1992-11-14
Publication date: 1994-05-18
Anticipated expiration: 2012-11-14
Also published as: GB2272428B; GB9223922D0

Abstract

A self-centring chuck assembly for drivably connecting a cardboard tube 13 on which strip material is stored is locatable at a required position on a driven shaft 6 which locates in the open centre of the tube. The chuck comprises a housing 2, three gripper arms 3 and an actuating ring 4. Rotation of the ring 4 on threads 11 causes it to move towards or away from cam surfaces 17, thus causing arms 3 to pivot and an axial blade 16 on each arm to move towards or away from the internal surface of the tube 13. <IMAGE>

Description

CHUCK ASSEMBLY This invention relates to a chuck assembly.

Long length sheet or strip material such as paper or polythene film is conventially stored on cylindrical tubes of cardboard or similar substance.

When the material is required to be fed to or from the tube, the tube is placed on a rotatably driven bar, which passes through the central aperture of the tube, and a chuck assembly is provided to driveably connect the tube to the bar. Such a device needs to be actuated quickly, to provide adequate connection between the bar and the tube so that torque is effectively transmitted therebetween, and to ensure that the tube is accurately centred about the rotational axis of the bar and it is an object of the present invention to provide a chuck assembly which substantially meets these requirements.

In accordance with the invention a chuck assembly for locating a cylindrical tube relative to a bar comprises a main body having a central aperture in which a rotatably driven bar may be positioned, three gripper arms pivotally attached to and equally spaced part around the periphery of the body, the gripper arms each having indentation means for indenting the interior surface of the tube, and actuating means capable of co-operating with the gripper arms to cause each to pivot between a parked position out of engagement with the tube and an indenting position where each is in indenting contact therewith.

Preferably the actuation means comprises an internally screw-threaded collar rotatably engaged on a correspondingly screw-headed part of the outer periphery of the main body and formed with a ramp surface which is engageable with a cam surface on each of the gripper arms whereby rotation of the collar causes pivotting of each gripper arm.

Preferably the indentation means comprises a knife edge formed on each gripper arm and arranged to extend substantially axially with respect to the tube axis.

Preferably also locking means is provided to ensure that the main body may be located in a required position on the bar.

One embodiment of the invention will now be described by way of example only with reference to the accompanying drawing showing a longitudinal cross-section through the chuck assembly of the invention in use.

As shown the assembly 1 comprises a main body 2, three gripper arms 3 (only one shown) pivotally attached to and equally spaced apart around the periphery of the main body, and an actuating collar 4.

The main body 2 having a generally circular outer cross-section comprises a central aperture 5 corresponding to and of slightly larger dimensions than the outer shape of the bar on which it is slideably located. For example the bar may be of square cross-section and the central aperture 5 may be correspondingly square, the sides of the square of the aperture being each slightly longer than the sides of the square of the outer surface of the bar. A screw 8 is located in an aperture 7 formed in the body so as to extend perpendicularly to the axis 0-0 of the bar 6. One end 10 of the screw 8 contacts the outer surface of the bar 6 and the other end is formed with a knob 9 by means of which the screw 8 may be hand tightened or released. The aperture 7 for the screw 8 is located adjacent one end of the main body 2.

Axially spaced apart from the aperture 7 is a screw-threaded portion 11 on the outer periphery of the main body 2. At the end of the screw-threaded portion further from the aperture the main body is formed with a shoulder 12. At the end of the body further from the aperture 7 the wall thickness is substantially increased to form a thickened portion 20 so that the outer diameter is slightly less than that of the cylindrical tube 13 with which the chuck assembly 1 is to engage. A peripheral flange 14 is formed substantially mid way along the length of the main body having an outer diameter greater than the internal diameter of the tube 13. This abuts the end of the tube in use.

Three gripper arms 3 are pivotally mounted adjacent the end of the main body 2 further from the aperture 7. The pivot 24 for each gripper arm is arranged to be located in one of three axially extending channels 30 formed with the thickened portion 20 so that the pivot axis extends generally tangentially to the main body. Each gripper arm is constructed to extend beyond the end of the main body and the outer surface of each gripper arm is formed with a knife blade 16 having a convex configuration as shown in the drawing. The end of each gripper arm further from the knife blade is formed with a convex radially outwardly facing cam surface 17 as shown on the drawing.

Adjacent this end and on the radially-inward side of the gripper arm opposite to the cam surface is an aperture 18 housing a small helical spring 19, the other end of which is housed in one of three correspondingly-shaped apertures 21 formed in the base of the channel 30 within which the gripper arm is located.

The actuating collar 4 is located on the screw-threaded portion 11 of the main body 2. This has an outer knurled surface 2 which enables it to be gripped and turned readily by an operator. At the side of the collar opposite to the screw 8 the collar is formed with a frusto-conical ramp surface 22 which engages the cam surface 17 formed on each of the three gripper arms 3. The three spiral springs 19 are arranged to be in compression and to press the cam surface 17 of each of the three gripper arms 3 against the frusto-conical ramp surface 22 on the collar 4.

In use, the chuck assembly is slid onto the bar 6 and when in the required position the knob 9 rotated by hand to tighten the screw against the outer surface of the bar 6. The collar is rotated so that it travels towards the screw 8 so as to allow each of the three springs 19 to push the ends of the gripper arms engaging the collar radially outwards causing each arm to pivot about its pivot axis 25 and thus move each knife edge 16 radially inwards to a parked position A cardboard tube is then positioned on the bar so that the end thereof abuts the collar 14 on the main body 2. The collar 14 is then rotated about the screw-threaded portion 11 on the main body so that it moves towards the flange 14.The frusto-conical surface 22 reacts against the cam surface 17 on each of the three gripper arms 3 causing each of the three spiral springs 19 to be compressed and the gripper arms 3 to be pivotted about their pivot axis 25. The end of each gripper arm having the knife edge is moved radially outwards so that each knife edge indents the interior surface of the tube 13. The cardboard tube is then in engagement with the chuck assembly 1 so that it is unable to rotate relative thereto. Thus when a torque is applied to either rotatably accelerate or decelerate the bar 6 the torque is efficiently transmitted via the chuck assembly to the cardboard tube or vice verso Sheet or strip material positioned on the outer peripheral surface may be batched up or fed off accurately as required.

The provision of three equally-spaced gripper arms ensures that the cardboard tube is accurately centred with respect to the rotational axis of the chuck 1 and the bar 6 on which the chuck is mounted.

When the tube needs to be removed from the bar the collar 4 is rotated a small number of turns to move it away from the flange 14. The spiral springs expand and cause the gripper arms to pivot taking the knife blades 16 out of indenting relationship with the internal surface of the tube. The tube 6 may then be removed from the bar.

If the position of the chuck on the bar needs to be changed this may be achieved quickly by releasing the screw 8 by turning the knob 9, sliding the chuck assembly to its new position and then re-tightening the screw.

Claims

CLAIMS:

1. A chuck assembly for locating a cylindrical tube relative to a bar comprising a main body having a central aperture in which the bar may be positioned, three gripper arms pivotally attached to and equally spaced part around the periphery of the body, the gripper arms each having indentation means for indenting the interior surface of the tube, and actuating means capable of co-operating with the gripper arms to cause each to pivot between a parked position out of engagement with the tube and an indenting position where each is in indenting contact therewith.

2. A chuck assembly according to Claim 1 wherein the actuation means comprises an internally screw-threaded collar rotatably engaged on a correspondingly screw-threaded part of the outer periphery of the main body and formed with a ramp surface which is engageable with a cam surface on each of the gripper arms whereby rotation of the collar causes pivotting of each gripper arm.

3. A chuck assembly according to Claim 2 wherein the ramp surface is a frusto-conical surface.

4. A chuck assembly according to Claim 2 or Claim 3 wherein the cam surface on each of the gripper arms is convex.

5. A chuck assembly according to any one of the preceding claims wherein the indentation means comprises a knife edge formed on each gripper arm.

6. A chuck assembly according to Claim 5 wherein the knife edge is convex.

7. A chuck assembly according to Claim 5 or Claim 6 wherein the knife edge formed on each gripper arm is arranged to extend substantially axially with respect to the tube axis.

8. A chuck assembly according to any one of the preceding claims wherein each gripper arm is provided with biassing means to bias the indentation means away from the tube surface.

9. A chuck assembly according to any one of the preceding claims wherein each gripper arm is located in a channel formed on the outer periphery of the main body.

10. A chuck assembly substantially as described herein with reference to and as shown in the accompanying drawing.

10. A chuck assembly according to any one of the preceding claims comprising locking means to ensure that the main body is locatable in a required position on the bar.

11. A chuck assembly substantially as described herein with reference to and as shown in the accompanying drawing.

Amendments to the claims have been filed as follows 1. A chuck assembly for locating a cylindrical tube relative to a bar comprising a main body having a central aperture in which the bar may be positioned, three gripper arms pivotally attached to and equally spaced part around the periphery of the body, the gripper arms each having indentation means for indenting the interior surface of the tube, and actuating means comprising an internally screwthreaded collar rotatably engaged on a correspondingly screw-threaded part of the outer periphery of the main body and formed with a ramp surface which is engageable with a cam surface on each of the gripper arms whereby rotation of the collar causes each gripper arm to pivot between a parked position out of engagement with the tube and an indenting position in indenting contact therewith.

2. A chuck assembly according to Claim 1 wherein the ramp surface is a frusto-conical surface.

3. A chuck assembly according to Claim 1 or Claim 2 wherein the cam surface on each of the gripper arms is convex.

4. A chuck assembly according to any one of the preceding claims wherein the indentation means comprises a knife edge formed on each gripper arm.

5. A chuck assembly according to Claim 4 wherein the knife edge is convex.

6. A chuck assembly according to Claim 4 or Claim 5 wherein the knife edge formed on each gripper arm is arranged to extend substantially axially with respect to the tube axis.

7, A chuck assembly according to any one of the preceding claims wherein each gripper arm is provided with biassing means to bias the indentation means away from the surface.

8. A chuck assembly according to any one of the preceding claims wherein each gripper arm is located in a channel formed on the outer periphery of the main body.

9. A chuck assembly according to any one of the preceding claims comprising locking means to ensure that the main body is locatable on a required position on the bar.