GB2033522A - Locking screw-threaded members - Google Patents

Abstract

A locking device which locks a screw member 5 in a selected location comprises a second screw member 6 which is adapted to screw up behind the first member 5. In order that the second member 6 does not of itself disturb the setting of the first member 5, a rigid ball 7 is interposed between the two members on their common screwing axis. Ball 7 may be received in a hexagonal recess 8 in member 5, which recess can receive a driving tool to rotate member 5 in the threaded sleeve 3 to adjust the compression of a spring 4. <IMAGE>

Description

SPECIFICATION Locking devices The present invention relates to locking devices. A particular application of the present invention is to locking a preset adjustment on an apparatus of small dimensions.

It is common practice to adjust, for example, the position of a screw-threaded shaft, and to use two nuts to lock it in position. The nuts bear against one another and any rotational force applied to one is transmitted to the other. Thus, tightening one nut is likely to move the other and possibly alter the position of the shaft.

British Patent Specification 94401 7 discloses a lock nut assembly having a thrust bearing in a recess in one end face of the nut assembly. The bearing spaces the end face from a member (e.g. another nut) to be locked, and reduces the transmission of rotational forces from the member to the locking nut or vice versa.

It is an object of the present invention to provide an alternative locking device which is simpler than the lock nut assembly mentioned above, and which is more suitable for apparatus of small dimensions.

According to the invention, there is provided a locking device wherein a pair of screw-threaded members are supported for screw-wise movement along a common axis, and are spaced apart by a rigid ball held on the axis between the members.

The ball provides a single point of contact with each member at the centres of the faces of the members so rotational force is not transmitted from one member to the other.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example to the accompanying drawing, the single figure of which shows a locking device in accordance with the invention.

Referring to the figure, reference numeral 1 denotes the shaft of, for example, an adjustable potentiometer which is accurately preset.

Reference numeral 2 generally indicates the locking device which locks the shaft 1 in its preset position.

The locking device 2 comprises an internally threaded tube 3 containing a spring 4 set to a critical tension between the shaft 1 and a screw-threaded adjuster member 5 by rotating the adjuster member 5 in the tube. A screw-threaded locking member 6, having a screw-driver slot 61, is screwed down in the tube 3 to lock the adjuster member 5 in position. If the locking member 6 came into contact with the adjuster member 5, the member 5 would rotate altering the tension in the spring 5 and upsetting the preset position of the shaft 1. Therefore, in this example, in accordance with the present invention, a ball 7 is inserted in a recess 8 in the adjuster member to space the members 5 and 6 apart.

The ball contacts the centres of the facing faces of the members 5 and 6 at single points of contact. This avoids any rotational force being transmitted between the adjuster and locking members, and prevents subsequent movement due to vibration.

In the example shown, the recess 8 is of hexagonal cross-section to allow the adjuster member 5 to be screwed down using an Allen key. After screwing down the member 5, the ball is put into the recess before the locking member 6 'is screwed down.

Various modifications may be made to the locking device described hereinbefore.

For instance, instead of using the recess 8 to screw down the adjuster member 5 and to contain the ball 7, the ball 7 could be held in the recess by a spot of grease or by a cage over the top of the recess and some other provision made for screwing down the member 5. This other provision could be a pair of recesses spaced apart along a diameter of the member 5 to be engaged by a forked member to screw down the member 5.

1. A locking device wherein a pair of screw-threaded members are supported for screw-wise movement along a common axis, and are spaced apart by a rigid ball held on the axis between the members.

2. A device according to Claim 1 wherein the members are supported within an internally screw-threaded tube for said screw-wise movement.

3. A device according to Claim 1 or 2, wherein the ball is in a recess in one of the members.

4. A device according to Claim 3 wherein the recess is hexagonal to engage with an Allen key.

5. A device according to Claim 3, wherein the ball is retained in the recess by a cage.

6. A device according to any preceding claim, further including a spring, the screwthreaded members being arranged to maintain a preset tension on the spring.

7. A locking device substantially as hereinbefore described with reference to the drawings.

CLAIMS (15 Mar 1979) 1. A locking device comprising an internally threaded tube within which are first and second threaded members, each in screwthread engagement with the tube for screwwise movement along the axis of the tube, and rigid ball held on the axis between the members and maintaining them in axially spaced relationship.

2. A device according to claim 1, wherein the ball is in a recess in one of the members.

3. A device according to claim 2, wherein the ball is retained in the recess by a cage.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Locking devices The present invention relates to locking devices. A particular application of the present invention is to locking a preset adjustment on an apparatus of small dimensions. It is common practice to adjust, for example, the position of a screw-threaded shaft, and to use two nuts to lock it in position. The nuts bear against one another and any rotational force applied to one is transmitted to the other. Thus, tightening one nut is likely to move the other and possibly alter the position of the shaft. British Patent Specification 94401 7 discloses a lock nut assembly having a thrust bearing in a recess in one end face of the nut assembly. The bearing spaces the end face from a member (e.g. another nut) to be locked, and reduces the transmission of rotational forces from the member to the locking nut or vice versa. It is an object of the present invention to provide an alternative locking device which is simpler than the lock nut assembly mentioned above, and which is more suitable for apparatus of small dimensions. According to the invention, there is provided a locking device wherein a pair of screw-threaded members are supported for screw-wise movement along a common axis, and are spaced apart by a rigid ball held on the axis between the members. The ball provides a single point of contact with each member at the centres of the faces of the members so rotational force is not transmitted from one member to the other. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example to the accompanying drawing, the single figure of which shows a locking device in accordance with the invention. Referring to the figure, reference numeral 1 denotes the shaft of, for example, an adjustable potentiometer which is accurately preset. Reference numeral 2 generally indicates the locking device which locks the shaft 1 in its preset position. The locking device 2 comprises an internally threaded tube 3 containing a spring 4 set to a critical tension between the shaft 1 and a screw-threaded adjuster member 5 by rotating the adjuster member 5 in the tube. A screw-threaded locking member 6, having a screw-driver slot 61, is screwed down in the tube 3 to lock the adjuster member 5 in position. If the locking member 6 came into contact with the adjuster member 5, the member 5 would rotate altering the tension in the spring 5 and upsetting the preset position of the shaft 1. Therefore, in this example, in accordance with the present invention, a ball 7 is inserted in a recess 8 in the adjuster member to space the members 5 and 6 apart. The ball contacts the centres of the facing faces of the members 5 and 6 at single points of contact. This avoids any rotational force being transmitted between the adjuster and locking members, and prevents subsequent movement due to vibration. In the example shown, the recess 8 is of hexagonal cross-section to allow the adjuster member 5 to be screwed down using an Allen key. After screwing down the member 5, the ball is put into the recess before the locking member 6 'is screwed down. Various modifications may be made to the locking device described hereinbefore. For instance, instead of using the recess 8 to screw down the adjuster member 5 and to contain the ball 7, the ball 7 could be held in the recess by a spot of grease or by a cage over the top of the recess and some other provision made for screwing down the member 5. This other provision could be a pair of recesses spaced apart along a diameter of the member 5 to be engaged by a forked member to screw down the member 5. CLAIMS

1. A locking device wherein a pair of screw-threaded members are supported for screw-wise movement along a common axis, and are spaced apart by a rigid ball held on the axis between the members.

2. A device according to Claim 1 wherein the members are supported within an internally screw-threaded tube for said screw-wise movement.

3. A device according to Claim 1 or 2, wherein the ball is in a recess in one of the members.

4. A device according to Claim 3 wherein the recess is hexagonal to engage with an Allen key.

5. A device according to Claim 3, wherein the ball is retained in the recess by a cage.

6. A locking device substantially as hereinbefore described with reference to the drawings.

6. A device according to any preceding claim, further including a spring, the screwthreaded members being arranged to maintain a preset tension on the spring.

7. A locking device substantially as hereinbefore described with reference to the drawings.

CLAIMS (15 Mar 1979)

1. A locking device comprising an internally threaded tube within which are first and second threaded members, each in screwthread engagement with the tube for screwwise movement along the axis of the tube, and rigid ball held on the axis between the members and maintaining them in axially spaced relationship.

2. A device according to claim 1, wherein the ball is in a recess in one of the members.

3. A device according to claim 2, wherein the ball is retained in the recess by a cage.

4. A device according to claim 2, wherein the recess is hexagonal to engage with an Allen key.

5. A device according to any preceding claim, further including a spring, the screwthreaded members being arranged to maintain a preset tension on the spring.