GB2163519A

GB2163519A - A bore gripping tool

Info

Publication number: GB2163519A
Application number: GB08421422A
Authority: GB
Inventors: George Ronald Robinson
Original assignee: Automotive Products PLC
Current assignee: Automotive Products PLC
Priority date: 1984-08-23
Filing date: 1984-08-23
Publication date: 1986-02-26
Also published as: GB8421422D0; GB2163519B

Abstract

The tool to grip the wall of a bore has a body 11 of circular section with a diametral groove 12 receiving a lever 16 pivoted at 15, the groove being wide enough to allow manual pivoting of the lever through some distance in either direction. The body also has two chordal passages which cross the groove 12. One passage is formed by passage portions 17 and 18 each respectively containing sliding sprags formed by pins 21 and 22. The other passage is formed by passage portions 19 and 20 containing sprag pins 23 and 24. Pivoting the lever 16 in one sense pushes the pins 21 and 23 outwardly of the body 11 to grip the bore, pivoting in the other sense pushes out the pins 22 and 24 for gripping. <IMAGE>

Description

SPECIFICATION A bore gripping tool This invention relates to hand tools and in particular to a tool for gripping or holding a circular bore of an object.

In certain situations such as the rotation or extraction of a disc brake piston the outer surface must be prevented from damage if the operating efficiency of the disc brake is not to be reduced. Although it is possible to use internal pliers or similar devices these have the disadvantage that they are difficult to use in a confined space and may distort the bore if excessive force is used.

According to the invention there is provided a tool for gripping an object having a circular bore and comprising a body supporting an actuator member and at leat one sprag member, the actuator member being moveable relative to the body to displace the or each sprag member outwardly for engagement with the bore.

The tool may have two sprag members arranged such that movement of the actuator member relative to the body in one direction displaces one sprag member outwardly for engagement with the bore and movement of the actuator member relative to the body in the other direction displaces the other sprag member outwardly for engagement with the bore.

Althernatively, the tool may have a pair of sprag members both of which are displaced outwardly for engagement with the bore by movement of the actuator member relative to the body in one direction in which case the positions of reaction of the pair of sprag members against the bore are in diagonal opposition.

Preferably the tool has two pairs of sprag members arranged such that movement of the actuator member relative to the body in one direction displaces one pair of sprag members outwardly for engagement with the bore and movement of the actuator member relative to the body in the other direction displaces the other pair of sprag members outwardly for engagement with the bore.

A tool according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a plan view of a tool for gripping a circular bore; Figure 2 is a side view of the tool shown in Fig. 4; Figure 3 is a cross-sectional view of part of a disc brake assembly showing the tool shown in Figs. 1 and 2 positioned in the bore of a disc brake piston ready for use; Figure 4 is an end view of the piston shown in Fig. 3 and showing the tool shown in Figs.

1 and 2 positioned redy for use; and Figure 5 is an enlarged view of the area A on Fig. 4 showing the engagement of one pin of the tool with the bore of the disc brake piston.

The tool shown in the figures comprising a disc shaped body 11 having a diametral groove 12 in one face 13 and a central threaded hole for a threaded pivot pin 15. An actuating member in the form of a lever 16 is pivotally mounted by the pivot pin 15 for rotational movement relative to the body 11.

One end of the lever 16 is located in the groove 12 so that the amount of movement of the lever relative to the body is limited by the clearance between the lever and the groove 12.

The body 11 has four passageways 17, 18, 19 and 20 arranged as two parallel incline pairs 17 and 18, 19 and 20, one pair on each side of a diametral plane x-x passing through the pivot axis of the lever 16. Each of the passageways 17, 18, 19 and 20 slidingly supports a respective sprag member in the form of a pin 21, 22, 23 or 24. One end of each of the pins 21, 22, 23 and 24 is conical in shape.

In use the tool is inserted into the bore of the object to be gripped such as the disc brake piston 14 and is tilted at a slight angle relative-to the longitudinal axis of the bore,-as theidiameter of the body 11 is only slightly less than the diameter of the bore interference occurs causing the body 11 to loosely grip the bore. This allows the lever 16 be rotated relative to the body 11 and into contact with a pair of pins 21 and 23 or 22 and 24 depending on the direction of the applied force.

The pair of pins 21 and 23 or 22 and 24 thereby contacted are moved outwardly in the direction for engagement with the bore under the action of the lever 16 until they react against the bore at two positions which are in diagonal opposition. The conical ends of the pins 21, 22, 23, 24 increases the grip of each pin when it engages the bore. If the force applied to the lever 16 is now increased the force applied to each pin will increase until all of the clearance between the lever 16 and the body 11 is exhausted. Increasing the force further will then result only in an increase in the torque applied to the bore. In most cases the piston 14 will begin to rotate relative to the caliper 28 before the clearance is exhausted, in which case the radially applied grinding force is substantially proportional to the applied torque and so only the minimum radial force required to allow rotation of the piston 14 is applied.

Although the invention has been described with reference to a tool having four outwardly moveably pins a tool having two or only one moveable sprag members acting against the bore is envisaged. In the case of there only being one sprag member the body provides the reaction against the bore.

The tool may also be provided with resiliently biased members to grip the bore upon insertion or a second lever connected to the body both of which would eliminate the need to tilt the body during the initial operation of the tool.

Claims

1. A tool for gripping an object having a circular bore and comprising a body supporting an actuator member and at least one sprag member, the actuator member being moveable relative to the body to displace the or each sprag member outwardly for engagement with the bore.

2. A tool as claimed in Claim 1 in which there are two sprag members arranged such that movement of the actuator member relative to the body in one direction displaces one sprag member outwardly for engagement with the bore and movement of the actuator member relative to the body in the other direction displaces the other sprag member outwardly for engagement with the bore.

3. A tool as claimed in Claim 1 in which there is a pair of sprag members both sprag members being displaced outwardly for engagement with the bore by movement of the actuator member relative to the body in one direction.

4. A tool as claimed in Claim 3 in which in use the postions of reaction of the pair of sprag members against the bore are in diagnonal opposition.

5. A tool as claimed in Claim 3 or Claim 4 in which there are two pairs of sprag members arranged such that movement of the actuator member relative to the body in one direction displaces one pair of sprag members outwardly for engagement with the bore and movement of the actuator member relative to the body in the other direction displaces the other pair of sprag members outwardly for engagement with the bore.

6. A tool as claimed in any one preceding Claim, in which the body has a diametral groove in which the lever is located with clearance to allow pivoting of the lever.

6. A tool as claimed in any preceding claim in which the actuator member is a lever pivotally mounted on the body.

7. A tool as claimed in Claim 6 in which the body has a diametral groove in which the lever is located with clearance.

8. A tool as claimed in any preceding claim in which the or each sprag member is slideably supported by a passageway in the body.

9. A tool as claimed in Claim 3 in which the or each sprag member is a pin.

10. A tool for gripping an object having a circular bore substantially as herein described with reference to the accompanying drawings.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1, 2, 3, 5, 6, 7 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:- Claims 8, 9, 10 above have been re-numbered as 7, 8, 9 and their appendancies corrected.

1. A tool for gripping an object having a circular bore, said tool comprising a body supporting a lever and at least one sprag member, and the lever being pivotable relative to the body to displace the sprag member outwardly of the body for engagement with the bore when the tool is in use.

2. A tool as claimed in Claim 1, in which there are two said sprag members arranged such that pivoting of the lever relative to the body in one direction displaces one sprag member outwardly for engagement with the bore and pivoting of the lever member relative to the body in the other direction displaces the other sprag member outwardly for engagement with the bore.

3. A tool as claimed in Claim 1, in which there is a pair of said sprag members both sprag members being displaced outwardly for engagement with the bore by pivoting of the lever relative to the body in one direction.

5. A tool as claimed in Claim 3 or Claim 4, in which there are two pairs of said sprag members arranged such that pivoting of the lever relative to the body in one direction displaces one pair of the sprag members outwardly for engagement with the bore and pivoting of the lever relative to the body in the other direction displaces the other pair of the sprag members outwardly for engagement with the bore.