GB803627A - Improvements in variable speed transmission - Google Patents

Abstract

803,627. Variable-speed ratchet gear. SOUDURE ELECTRIQUE AUTOGENE S.A. Sept. 5, 1956 [Sept. 6, 1955], No. 27197/56. Classes 80 (2) and 80 (3). A variable-ratio transmitter, more particularly of the oscillating ratchet type, is based on a linkage for obtaining constant angular or linear velocity throughout an effective oscillation of an output crank 34 or cam, whilst an input crank 31 or cam rotates through an arc of 120 degrees. The input and output cranks are connected by a slidable lever 36 carried on a pivot 37, the crank axes and lever pivot being fixed in any one adjustment setting. To obtain negligible departure from uniformity of motion of the output crank throughout its stroke for a 120 degree input crank stroke, the following dimensional relation must be satisfied:- where n and m are respectively the ratios between the crank radii and the adjacent distance 33-37 ; 30-37, m being the greater; and b and c are the crank angles shown and given by the following rotations :- With three phased crank-lever systems, Fig. 5, and ratchets between the output cranks 34A &c., and the output shaft 33, successive 120 degree arcs of the input cranks 31A &c. produce successive uniform rotations of the output shaft 33, which is thus driven continuously. Ratio variation is effected by either (a) varying the stroke of the cranks, or (b) varying the centre distances 33-37; 30-37, in which case the axis of one shaft is stationary, but that of the other must be moved with the axis 37 to satisfy the above relations, or (c) both shaft axes remain fixed, the axis 37 is moved, and the stroke of the output crank is varied. Condition (b) is fulfilled in Fig. 5 by swinging the axis 30 of the input cranks 31A about meshing gear-wheels 46A on a parallel non-movable input shaft 45, and moving the lever-pivot shaft 37; or in Fig. 3, not shown, by connecting the output crank 34 through a parallelogram link to a crank, ratchet-mounted on a parallel output shaft, which permits movement of the crank axis 33. In Fig. 6, not shown, the output axis 33 is stationary, and the axes 33, 37 are carried on radius arms swinging about fixed pivots and also connected by links to a third radius arm which also swings on a fixed pivot. Cam guides may replace the radius arms. In Fig. 7, not shown, the lever 36 is a bell-crank, there being a fixed angle between the links 34, 37 and 31, 37, whilst in Fig. 8, not shown, this angle is reduced to zero, the input and output axes being coincident. In Figs. 13a, 14a, not shown, the lever slots 50, Fig. 5, are eliminated by the use of a lever built up of several articulated links providing an identical degree of freedom. The lever may, Fig. 17, not shown, be a simple non- slotted bar loaded radially against the crankpins by a single tension spring acting on the output crank. In Fig. 16, not shown, the three-phased output cranks are permanently loaded in one direction through balance-beams by a single spring capable of overcoming inertia forces and serving to avoid the ill-effects of play in the pin-and-slot joints of the preceding constructions. Condition (c) above, variablethrow output crank and shiftable axis 37, is satisfied in Fig. 11a, not shown, wherein the output crankpin 34 slides in a slot in the output crank and is carried rigidly in an intermediate crank-arm having its axis between the axes 33, 37 and shiftable with 37. In one limit position the crank-pin 34 is coincident with the axis 37, resulting in zero output speed. A reversible ratchet for use at the output cranks, comprises balls 83, Fig. 15, between an output polygon 81 and an input, cylindrical shell 82, the balls being loaded in the appropriate direction by inclined compression springs 84, which are turned over centre (dotted position.) for reversal by relatively turning an outer ring 86 rotating with the inner polygon 81. Reversal may be effected manually or automatically by torque reaction.