GB574346A - Improvements in or relating to spanners - Google Patents

Abstract

574,346. Spanners. FAIREY AVIATION CO., Ltd., and PEEL, A. C. April 27, 1944, No. 7935. [Class 61 (iii)] A torque-limiting spanner of the type having a box spanner rotatably mounted in a handle, has a spring-controlled driving means which consists of a roller seated partly in a recess in the periphery of the spanner and partly in a recess in the inner peripheral wall of an aperture in the head of the handle. As shown in Fig. 5, the box spanner or rotor a, having a recess b extending partially through it, has a central surface c bearing against the head e and outer surfaces d bearing against two side plates g. These plates are joined together by a pin j, Fig. 2, and are joined by links k to a pin m which moves in a slot o located in a plunger n. A cap p, having an abutment bearing against one end of the spring q, is screwed on to the handle f at r, allowing the initial stress of the spring to be adjusted. At the position of minimum stress the roller w, the ends of which project into radial slots in the plates g, is in the position shown in Fig. 2. When the spanner is turned to tighten a bolt, the rotor a is carried round in the handle until sufficient resistance is offered by the bolt to cause slight relative angular movement 'between the rotor and the head e. This causes the obtuse angle between the plates g and links k'to be increased and the plunger n to be forced back against the spring q. This continues until a predetermined value of spring pressure is reached, when the plates g and links k are in alignment, the roller w then moving into the enlarged part v of the recess in the head e, freeing the rotor a from motion with the handle. More than one roller and a corresponding number of recesses may be employed. A modification for both right- and left-hand threaded bolts has the recess b extending completely through the rotor, which is marked to indicate which end should be outmost in each case. Alternatively, the plunger n may work between two coiled springs, there being two enlargements such as v in the recess in the head.