GB339239A - Improvements in or relating to chain driving gear - Google Patents

Abstract

339,239. Link-Belt Co., (Assignees of Brandt, W. F.). March 30, 1929, [Convention date]. Driving and like chains with separate joint pins. - To ensure constant angular velocity and tangential entry and departure in silent chain gearing, the opposed working surfaces of the teeth of chain and sprocket are conjugate and are so formed by generating the teeth of one element with .respect to the arbitrarily chosen other element. " Chordal action," i.e. transverse wave motion of the chain, is thereby overcome and correct tooth relation is independent of increase in pitch due to stretching the. chain. The links may be of the outside as shown, of the inside contact type and in the preferred form shown the inside contacting teeth A<7> are generated with respect to existing sprocket teeth A<1>. Clearance is provided by increasing the distance between the working surfaces of a link and by deepening the pockets. This may be done by generating each working surface independently with reference to centre lines spaced apart by the required amount of clearance. The outer link surfaces A<6> are cut away, and the arrangement is such that there is never simultaneous contact between a sprocket tooth and the working surface of two teeth on the same link. The clearance B between a following tooth on the entry side of the chain, Fig. 2, and a tooth A<1> on the driving sprocket decreases as at B<1> &c. progressively around the periphery of the sprocket until a transition point is reached whereafter there is a gradually increasing clearance B<4> &c. on the departure side Fig. 4, between the leading teeth of the chain and the sprocket teeth until at the part 6, the chain is free to move in its tangential path. The reverse occurs on the driven sprocket. The position of the transition point, at which there may or may not be a floating chain link may vary within the total angle of contact. A method of obtaining the required link-tooth form by drawing in the trace of the profiles of an arbitrarily chosen sprocket tooth on transparent paper is also shown and described. The pivot pins A<8>, which are upset against holding washers, may be solid, hollow or built-up.