Patent GB-531171-A (GB)
Title: Improvements in or relating to power transmission gear
IPC: F16H3/089
Filed: 1939-03-28
Abstract: 531,171. Variable-speed gearing. ARMSTRONG, J. J. V. (Szekely, O. E.). March 28, 1939, No. 9590. [Class 80 (ii)] An automatically operating power transmission system for vehicles comprises a centrifugally actuated friction clutch 19, 20 between the engine flywheel 12 and a clutch shaft 23 which latter drives the tail-shaft 76 either through a fixed reducing train for a low speed and high torque drive or through a hydraulicallycontrolled epicyclic train for a variable high speed and low torque drive. Secured to the shaft 23 is a casing 30, 32 of a gear pump which has a cage-like extension 33, 34 attached to a sleeve 35 which carries a gear 36 of a low speed train 36, 70, 71 and 82, see also Fig. 7, for driving a slidable gear and clutch member 74 on the driven tail-shaft 76. Also secured to the shaft 23 is a sun gear 52 of an epicyclic train, the annulus 55 of which is connected to a driven shaft 62 and the planet pinions of which are mounted upon a carrier__48 which is connected to the driving gear 46 of the pump 30, 32. The opposite end of the shaft 62 is provided with clutch teeth 64 adapted to be engaged by teeth 75 of the clutch member 74 on the tail-shaft 76. A one-way clutch 81 is provided between the gear 82 and the clutch member 74 on which it is rotatably mounted and a similar one-way clutch 59 is provided between the driving sun 52 and the driven annulus 55 of the planetary train. The clutch member 74 with the gear 82 and also a reverse gear 86 is adapted to be positioned for " forward driving, as in Fig. 1, " neutral," as in Fig. 7, and " reverse " when the gear 86 engages with a gear on a reverse idler shaft. For " forward driving the clutch member 74 engages the clutch teeth 64 on the shaft 62 so that the tail-shaft is directly connected to the annulus 55 of the planetary train. The pump 30, 32 comprises a number of pinion gears 40 mounted in the casing which are adapted to be rotated by the gear 46 on a difference of speed between this gear and the casing, the delivery from the pump passing through restrictions 43, which enable a fluid resistance to be built up, to the outer casing and sump. The inlet to the pump from the sump S is obtained through a passage 45 and is further controlled by a valve 111, Fig. 5, which is actuated by engine induction pressure on a piston 114 through a conduit 117. When this valve is open the pump suction is wholly or partly broken which reduces the resistance to rotation of the pump gears. Operation. With the gear clutch member 74 in the " forward position the vehicle is started by increasing the speed of the engine which brings in the centrifugally-actuated clutch 19, 20 and the shaft 23 drives the tail-shaft 76 through the pump casing 30, 32 and gears 36, 70, 71, 82 for a low speed drive. The planetary sun 52 is driven at engine speed whilst the annulus being directly connected to the tail-shaft is driven at a reduced speed so that the planets are rotated to drive the pump gears. With a small throttle opening, however, the pump suction valve 111 is open and there is no resistance to the pump action, but as the throttle is opened to speed the engine up, the valve 111 is closed and oil is drawn into the pump to provide a resistance to the pump action. This resistance provides a reaction for the planetary train and hence a driving torque on the annulus 55 which is clutched to the tail-shaft. Thus a part of the torque is delivered through the low speed train whilst a part is delivered through the planetary gear. As the pump resistance increases the torque through the planetary train increases and if the load resistance is not too high the tailshaft is speeded up to the speed of the engine, i.e. to a direct drive, the one-way clutch 81 allowing the low speed train to be over-run. Between the low speed and direct drive the slip in the pump allows for the torque conditions of the tail-shaft and the speed is adjusted accordingly. Should the torque at the tail-shaft increase to a value greater than that which can be supplied by the engine the slip in the pump allows the tail-shaft to slow down for the slow speed train to take up the drive at an increased torque.