GB173734A - Improvements in and relating to means for converting rotary into reciprocating motion - Google Patents

Abstract

173,734. Rooney, P. J. Jan. 7, 1921, [Convention date]. Screw-and-nut mechanism.-Comprises screw- and-nut mechanism for converting a high-speed rotary motion as of an electric motor or gas engine into a slow reciprocating motion suitable for pumps, compressors, &c., and is of the type in which a nut or follower pivotally secured on the reciprocated shaft is in alternate engagement with a pair of opposite screw threads of uniform pitch of a rotated internal or external cylindrical surface, the ends of the two screw threads being merged together to cause the follower to pass from one to the other at the ends of its stroke. According to the invention, the screw threads terminate at each end abruptly in a parallel sided groove normal to the axis of rotation. As shown in Fig. 1, the screw and nut device comprises a cylinder 1 rotating on bosses 6 projecting from end frames 5<a>, 5b and formed internally with a pair of intersecting right and left-handed screw threads 2, 3 shown developed in Fig. 7. Passing through the cylinder and through squared holes in the end frames is a non-rotary rod or shaft 11 carrying a follower comprising a collar 12 with a thread-engaging rib 16 and an enlarged rectangular hole 13 allowing the follower to rock on the shaft about the transverse fixing pin 14 to suit the inclination of either screw-thread. The rod 11 may be directly connected to a pump piston working in a cylinder 23. At each end of the stroke the rib 16 is rocked to engage the return thread by engagement with the parts 18a, 18<b>, the end faces of the parts 4 left between the threads being abruptly flattened as shown at 17a, 17b, to form a parallel sided groove normal to the axis of rotation. Springs 19 are compressed at each end of the stroke to eliminate jar and assist reversal. The frames 5<a>, 5b are connected by tierods 7 adjusting-nuts 8 and serve to take the thrust of the cylinder 1, ball or roller bearings being interposed between the faces 9 if required. In the arrangement shown, the drive is transmitted from a motor through a belt 21. Alternatively, the cylinder 1 is connected to a concentric hollow driving shaft passing through one of the end frames. In a modification, the screwthreads are formed externally on a solid cylinder or shaft, the follower being carried by a parallel rod and having a rib with a concave instead of a convex periphery. This arrangement preferably works in an oil bath.