Patent GB-868217-A (GB)
Title: Control mechanism for variable speed transmissions and the like
IPC: A21C3/02
Filed: 1958-10-17
Abstract: 868,217. Rolling machines. SEEWER, G. A. Oct. 17, 1958 [Oct. 31, 1957], No. 33175/58. Class 87(2). [Also in Group XXIV] A control mechanism for a variable speed mechanical or hydraulic gear or variable speed electric drive of the Ward-Leonard type (mechanical gear only described) which drives the input conveyer of a roller mill at a speed depending on the rolling gap setting, the reduction ratio being equal to the ratio between the input and output thickness of the workpiece, has a single control 13 for setting the rolling gap and operating the gear as described below. A single shift regulating member 44 which when displaced angularly or linearly (as shown) by a cam selector 56 one, two, three .... n units from its zero position changes the gear ratio by the first, second, third, .... nth power of. a predetermined transmission constant a, the cam having such shape that to displace the shift member 44 by successive units the cam is turned through successive increments each of which is the product of the preceding increment and the transmission constant a (i.e. in geometric progression). A reversible electric motor 16 drives two rollers 2, 3 and through fixed ratio chain gearing 26-29, and oppositely acting one way clutches 30, 31 the driving roller of one of two conveyers 20, 21 the other being driven at a reduced ratio fromthe lower roller shaft 17 through a disc and roller friction gear 32, 33, bevels 35, fixed ratio chain gearing 37 . . 40 and one of two electromagnetic clutches 41, 42. Clockwise rotation of an automatic or, as shown, manual control 13 rotates clockwise the cam 56 and a sprocket 11, which former through a cam follower 52 clamped at 55 to the regulating member 4 moves the member 44 right against the action of a return spring 57 and a cam follower 46 rides up a cam 45 on the regulating member thereby raising the roller 33 of the friction gear to reduce the ratio, and which latter (11) through chain gearing 9, 10 and cranks 6, 7 lowers the upper roller 3 to reduce the roll gap. The shape of the cams 56, 45 (a method of obtaining the required shape is described in the Specification) and the configuration of the cranks 6, 7 are such that when the regulating member 44 is moved through equal unit distances, the cam 56 and control 13 are rotated through angles equal to the product of the previous angular rotation multiplied by the transmission constant a, the gap between the rollers 2, 3 is reduced by an amount equal to the previous gap reduction multiplied by the transmission constant a and the gear ratio is reduced to a ratio equal to the previous ratio multiplied by the transmission constant a. If the thickness of the workpiece is to be reduced in two or more stages after each operation the clamp 55 is released, permitting the regulating member 44 to return to its zero position, whereupon the clamp 55 is again tightened before the control 13 is moved to further reduce the gap between the rollers, thereby compensating for the reduced thickness of the workpiece on the input conveyer. A lock may be provided for the control 13 to prevent accidental change of ratio &c. and the clamp 55 may be a manually operated tightening screw or an electromagnetic clamp in which case it may be in circuit with the lock which when released breaks the circuit to the clamp 55 for a short period allowing the regulating member 44 to be returned to its zero position. The gear 32, 33 may be replaced by a stepped ratio gear.