Patent GB-946922-A (GB)
Title: Improvements in and relating to control means for infinitely variable conical pulleyfriction gears
IPC: F16H61/662
Filed: 1960-03-04
Abstract: 946,922. Change-speed control; expanding- wheel gear. W. REIMERS. March 4, 1960 [March 6, 1959], No. 7681/60. Heading F2D. Change-speed control for a continuouslyvariable-ratio expanding-pulley gear comprises means producing a reaction force applied to the movable flange of one of the expanding pulleys to maintain or at will vary the gear ratio, operation of the reaction force means being effected through a control device which is operated either automatically in dependence upon, and in opposition to, a variation tending to occur in the gear ratio due to a change in load, or arbitrarily at will to vary the gear ratio, at least one device being provided to limit the reaction force to a desired value. In one form, expanding pulley gearing between driving and driven shafts 1, 2, Fig. 1, having fixed pulley flanges 3, 6 and axially movable pulley flanges 4, 5 connected by a chain 11, has its ratio determined by a lever 20 pivoting at 22 and moved by a follow-up servomotor 26 controlled from a valve 33. Load-responsive cam-and-ball thrust devices 16, 17 act through thrust bearings 18 upon the movable pulley flanges 4, 5, and are effective, respectively, to vary the gear ratio and to tension the chain 11 in dependence upon load. The ratio control lever 20 is pivoted to the control slider 42 of the valve 33 and to a control lever 21 coacting with the movable flange 5 of the driven pulley, a hand-operated ratio selection lever 44 also coacting with the valve control slider 42 and the ratio control lever 20. The valve 33 comprises two pistons 34, 35 upon the slider 42, effective to control ingress of oil under pressure from an engine driven pump 30 through a pipe 31 to an inlet port 32 and its passage through ports leading to servo pipes 39, 40 and to a vent pipe 38. With the pulley flanges in the position shown, an increase in load applied to the driven shaft 2 causes a reaction upon the pulley flange 4, tending to draw the belt 11 between the driving pulley flanges 3, 4 and slide the flange 4 rightwards, thus turning the lever 20 and pulling the valve slider 42 leftwards. Accordingly the valve piston 34 moves relatively to the valve casing, opens the port leading to the servo pipe 39 to pressure oil from the pipe 31, &c. and simultaneously moves the valve piston 35 to open the pipe 40 to the vent pipe 38. Pressure oil is supplied to the left-hand side of a movable cylinder 26 containing a fixed piston 27, and the cylinder reacts back through a connecting rod 25 on the link 20 in such a direction as to oppose the movement of the pulley flange 4, thus increasing the frictional grip between the chain 11 and the driving pulley. The return movement of the ratio selection lever 20 thus effected moves the valve slider 42 back towards the position of equilibrium shown, when the servo pipe 39 is again at least in part connected to the vent pipe 38, and the servo pipe 40 is again connected at least in part connected to the pressure pipe 31. Manual selection of a desired ratio can be effected by movement of the hand lever 44 to slide the valve 42, which accordingly causes a follow-up movement of the servo 26 until a new position of equilibrium is reached. A pressure release valve 50 is provided, operative either to limit the pressure in the high pressure pipe 31, or alternatively to limit the pressure in the servo pipes 39, 40. In the position shown, two reversible valves 60, 61 connect the pressure release valve 50 in parallel with the high pressure pipe 31. The pressure release valve 50 can be controlled to give a desired limiting pressure by means of a handle 55 and a cam 54. In the position shown, the spring 51 of the pressure release valve 50 is compressed to its maximum extent, and the pressure release valve is closed for all pressures in the pipe 31. Accordingly, however great the load applied to the driven shaft 2 of the gear, the follow-up servomotor 26 is effective to maintain the ratio preset by the handle 44, within normal limits of operation. If, however, the handle 55 is moved to a position which allows the pressure release valve 50 to become operative, then ultimately with increasing load applied to the driven gear shaft 2, oil passes from the high pressure pipe through the valve 50, and further increase in load upon the driven gear shaft merely causes a reduction in ratio as the chain 11 digs-in between the pulley flanges 3, 4. If the reversing valves 60, 61 are moved to their second position, then the pressure release valve 50 is instead connected between the servo pipe 39 and the vent pipe 38, and a second pressure release valve 62 is connected between the servo pipe 40 and the vent pipe 38. In a modification, movable pulley flanges 4<SP>1</SP>, 5<SP>1</SP>, Fig. 2, are formed as parts of expansible servo cylinders 70, 71 fed with oil under pressure through pipes 75, 76 controlled by a valve 81, the two servo cylinders corresponding functionally to the servomotor 26 and the valve 81 corresponding to the valve 33 of Fig. 1 above. In this form, the valve 81 is operated by movement of the pulley flange 4<SP>1</SP> acting through a tracing link 77 the far end of which is connected through a normally unstressed spring link 87 to a hand operated ratio selecting lever 86. A pressure release valve 90 is controlled by two cams 100, 101, the first being set by a hand lever 95 and the second by linkwork 102 connected to the tracing link 77. With the hand lever 95 in the position shown, the cam 100 maintains the pressure release valve 90 permanently closed. If the hand lever 95 is set to an alternative position, however, the pressure release valve 90 becomes operative when a sufficient load is applied to the driven shaft of the gear to allow oil to pass therethrough, with a corresponding decrease in ratio when a sufficiently large load is applied to the driven shaft of the gearing. The cam 101 varies the compression of the pressure release valve spring, e.g., to obtain constant input torque requirements of the gear even if, for any reason, the shapes of the tracks of the load responsive cam- and-ball devices are not such as to maintain a constant torque. A lost-motion connection 105 between a bell-crank 104 and the ratio selecting hand lever 86 enables the latter to be moved to extreme positions beyond its normal ratio selecting positions, so that lobes 109, 110 on the cam 101 act on the balance lever 94 to so actuate the pressure release valve 90 that the gear is rapidly adjusted to one or other of its ratio limits. As a modification, Fig. 3 (not shown), instead of adjusting the degree of compression of the pressure release valve spring to obtain a reduction in ratio when a sufficiently great torque is applied to the driven gear shaft, two pressure release valves having closure springs of different characteristics are alternatively connected in circuit with the servo control valve by actuation of a separate hand lever. In another modification, control of a pressure release valve 140, Fig. 4, and of the servo control valve 81 is effected by movement of a single hand lever 130 in two different planes at right angles. Movement of the hand lever 130 in- and-out of the plane of the paper rotates a cam 134 engaging a follower plate 136 acting through a balance lever 137 on the pressure release valve 130 without effecting movement of a lever 133 connected to the servo control valve. Movement of the hand lever 130 in the plane of the paper turns the lever 133 to effect movement of the servo control valve and adjust the ratio in the gearing, without effecting the setting of the pressure release valve 140 by movement of the cam 134. Movement of the servo control valve is, however, effective through links 141 to turn a cam 138 also acting upon the balanced lever 137 for adjustment of the pressure release valve 140.