Crane Electronics, Inc.

John Edward Burton

Peter William Everitt

Andrew Chapman

Neil Andrew McDonald

Adrian James Duffin

Andrew Wilkins

Ben William Tyers

The invention provides a variable torque-rate test joint for the performance testing of rotary tools for threaded fasteners. In a typical test routine a nut is repeatedly tightened by the tool and after each tightening the nut must be released and run back to its start position. The invention provides a means for rapidly releasing the pressure on the tightened nut so that it can be run back quickly and easily. The variable joint is supported by a reaction surface that is the operative face of a piston and cylinder assembly seated on a shoulder fast to a shank of the threaded fastener. A hydraulic control is provided for the piston and cylinder assembly including means for hydraulically extending the piston from the cylinder to a fixed maximum extension which defines a test position of the reaction surface, and means for hydraulically retracting the piston back into the cylinder to remove the pressure from the nut at the end of the test. During tightening the piston is extended and preferably hydraulically locked.

Variable torque-rate test joint

In a variable torque rate test joint, screw-threaded first and second elements are rotated relative to one another by a tool under test. At least one spring beam is cantilevered over a pivot point to exert an axial force between the first and second elements and the torque rate of the test joint can be varied by moving the pivot point to change the axial force. The first element may be a shaft that is fixed during testing and the second element is a nut rotatably mounted on the shaft, whereby the element rotated by the tool has a minimal moment of inertia. Whichever of the first and second elements is held stationary during the test may be mounted in a hub that is locked during the test but can be rotated at the end of the test to reset the test joint. Measurements may be made of the torque and the rotation angle to derive an actual torque rate of the joint, which allows correction of errors by moving the pivot point.

Variable torque rate test joint

A variable torque-rate test point for the performance testing of rotary tools for threaded fasteners comprises a screw-threaded bolt () having a moment of inertia comparable to that of a bolt to be tightened using the rotary tool. The bolt () is tightened in the test joint against a torque-rate adjustment device () which can be adjusted to simulate a hard or a soft joint. The adjustment device () comprises a washer portion () beneath the bolt head (), at least one spring beam () extending from a reaction point () radially outwardly of the bolt (), and a pivotal bearing member () or other pivot at a mid portion of the beam (). The beam () flexes as it extends in cantilever over the pivot point, and that flexure can be adjusted to vary the torque-rate of the test joint by varying the distance between the pivot point and the rotary axis of the bolt ().

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Birmingham, United Kingdom

John Edward Burton