GB543356A - Improvements in or relating to mechanisms for hoists, windlasses, tensioning machines, torsion machines, lifting appliances and the like - Google Patents

Abstract

543,356. Winches. THORPE, B. J., and NIXON, J. May 19, 1939, No. 14910; [Class 78 (v)] [Also in. Group XXIV] Consists in ratchet mechanism applicable to hoists, windlasses, tensioning and like machines, in which a positive drive in forward and reverse direction is obtained. The ratchet wheels A, A<SP>1</SP> are secured together or made in one piece with their teeth staggered by half the pitch relatively to one another. The driving shaft B carries eccentrics on which are mounted the pawls C, C<SP>1</SP> and lifters D, D<SP>1</SP> therefor. The pawls are kept in engagement with the teeth by gravity or springs. The lifters so regulate the action of the pawls that they engage the teeth without snap. On rotating the shaft B in the reverse direction, the wheels A, A' still being subjected to the load, the unloaded driver, e.g. C<SP>1</SP>, is raised clear of the teeth by lifter D' to allow the forward movement imparted to it by its eccentric while pawl C holds the load and allows it to move backward. When pawl C has reached its extreme position, the pawl C<SP>1</SP> is moved forward to engage the wheel A<SP>1</SP> and receive the load. Continued rotation of shaft B brings lifter D in contact with driver C which being freed of the load is now lifted clear of the tooth on wheel A while pawl C<SP>1</SP> continues to carry the load backwards until relieved by the pawl C. To prevent jamming of the pawls in the teeth, a small negative movement is imparted to each pawl during its stroke to ensure that the lifting movement of either driving pawl does not commence until the other pawl has taken over the load entirely.