GB1355269A - Self adjusting wrenches - Google Patents

1355269 Gripping tools N R WILSON 13 Jan 1973 1875/73 Heading B4W A wrench which is adapted automatically to apply a predetermined gripping pressure to items gripped between its jaws irrespective of size comprises fixed and movable jaws 64, 68, a handle 66 extending from the fixed jaw, a cam bar 82 slidably mounted in the handle 66 and having at its forward end a cam surface 84 which is adapted lockingly to engage a part of the movable jaw and at its rear end carries an abutment 90 for a link 96 of a toggle lever arrangement which includes also a handle member 92 pivoted to the movable jaw. Closing movement of the handle member 92 initially pivots the jaw 68 into contact with the object to be gripped, then slides the cam bar rearwardly until cam surface 84 becomes wedged against a portion of the movable jaw (i.e. against pin 76 as shown); the abutment 90 thus becomes fixed and the final over centre closing movement of the toggle linkage applies gripping pressure to the article between the jaws. The extent of movement of the cam bar depends upon the size of the article to be gripped and this ensures that for any given setting of the screw 88 (which provides the abutment 90) the gripping pressure will be constant. In an alternative embodiment (Fig. 1, not shown) the movable jaw is pivotally mounted on the fixed handle and has a cam surface corresponding to the cam surface of the slidable cam bar, engagement of the two cam surfaces locking the cam bar against further movement. In a further alternative (Fig. 12, not shown) the movable jaw has a floating pin passing therethrough and projecting on either side thereof and the cam bar has two shaped cam fingers, one on either side of the movable jaw and adapted to engage the pin, the cam surface facing in the reverse direction relative to the handle as compared with the embodiment of Fig. 7.