Patent GB-857480-A (GB)
Title: Variable speed transmission
IPC: F16H47/04
Filed: 1958-08-20
Abstract: 857,480. Change-speed control. BULLARD, E. P. Aug. 20, 1958 [Aug. 30, 1957], No. 26760/58. Class 80 (2). A transmission for obtaining a variable output speed from a constant input speed comprises two alternative power paths provided by two epicyclic gear trains, the reaction elements of which are so driven by a variable speed device that the driven element of one train increases in speed whilst the driven element of the other train decreases in speed when the speed of the variable speed device is changed. A constant speed electric motor 13 drives sun gears 14, 19 of epicyclic trains D, C, the planet carriers 30, 34 of which rotate gears 40, 38 meshing gears 41, 39 clutchable to an output shaft 37, and the ring gears 27<SP>1</SP>, 28<SP>1</SP> of which are rotated by a constant displacement hydraulic motor 22 driven by a variable displacement pump 20 driven by the shaft of the sun 19. Motor 13 is started by closing a switch 99<SP>1</SP>, and in the position shown the output shaft is rotated at minimum speed through train C and gears 38, 39. To increase the output speed a switch 101 is closed, which energizes a relay MF thereby closing switches F, which starts a motor 102, opening contacts MF-1 which prevents energization of a relay MR, and closing contacts MF-2 which energizes a solenoid 99 moving a pivot 75 of a displacement varying lever 74 to the position shown which slightly shortens the arc of movement of a pump adjustment lever 21. Motor 102 rotates a shaft 84 having a cam grooved cylinder 83 actuating a follower 81 on a saddle 78 which is thereby moved downwardly, and which in turn through a pin-and-slot connection moves the lever 74 downwardly and thus moves the lever 21 towards the zero displacement position 2, and thereafter moves it towards its maximum - displacement - in - the opposite-sense position 3. When lever 21 is close to position 3, gear 39 is rotated by train C at a speed slightly less than that at which gear 41 is rotated by train D, and at this point a cam 92 on a cam-shaft 87 rotated by the motor 102 closes a switch 95, thereby energizing a solenoid 68 and moving a valve spool 63 to the right so that liquid passes through a line 60, moving a piston 52 to the left to engage clutch 43 with gear 41. Since gear 41 is rotating slightly faster than gear 39, clutch 42 is relieved of load, and when cam-shaft 87 is rotated a little further a land 106 of a cam 91 closes a switch 94 which energizes a solenoid 67 moving a valve spool 58 to the right whereupon liquid is supplied through a line 55 to move a piston 47 to the left to disengage clutch 42. During the period in which both clutches are engaged a land 107 on a cam 93 closes a holding contact 98 which prevents the transmission being left in a locked condition by opening switch 101. The drive now occurs through train D, and further rotation of shaft 84 moves the lever 21 towards its maximum displacement position 1, the output shaft speed increasing accordingly. Close to position 1 a land 104 of a cam 90 opens a switch 96 which de-energizes relay MF so that motor 102 is stopped. To reduce the output speed a switch 100 is closed and motor 102 is driven in reverse. The operation is substantially as before, except that a solenoid 100<SP>1</SP> is energized to move pivot 75 to a position 75<SP>1</SP> to increase the throw of lever 21, this ensures that lever 21 reaches position 3, in which position gear 39 is rotated slightly faster than gear 41 in order to allow clutch 42 to be engaged. When the lowest output speed position 1 is reached, the land 104 opens a switch 97 to de-energize the relay MR. The hydraulic transmission 20, 22 may be replaced by some other form of variable speed device, which may be driven by an external source of power.