Patent GB-599075-A (GB)
Title: Improvements in or relating to power transmissions
IPC: F16H47/06
Filed: 1944-05-22
Abstract: 599,075. Variable-speed gearing. CHILTON, R. May 22, 1944, No. 9855. Convention date, March 22, 1943. [Class 80 (ii)] In variable-speed gearing a normally unloaded slip coupling between the driving and driven shafts is loaded, when changing the gear ratio, to relieve the speed ratio shift means of driving torque, the slip coupling being combined with gearing, so that only a portion of the relieving torque is transmitted through the slip coupling. As shown, a two-speed gearing for driving two propeller shafts 74, 80, in opposite directions, comprises a planet carrier having planets 108 meshing a sun gear 106 and annulus 100. The sun 106 is fixed to a driving member 104 of a fluid coupling 96, 104, and the annulus 100 to the driven coupling member 96 fixed to shaft 80. A gear 78 fixed to the annulus 100 meshes gears 76 on countershafts 64 having gears 70 meshing a gear 72 on the shaft 74 and gears 66, 68, meshing gears 54, 56, freely mounted on sleeves 50, 52, fixed to a drum 22 on the planet carrier. Either gear 54, 56, may be clutched to the drum 22 to give two speeds to the shafts 74, 80. A shift member 30 splined helically to the drum 22 has clutch teeth 62 engageable with teeth 58, 60, on the gears 54, 56, and jaws 30a engageable with jaws 32a on a locking ring 32 splined axially at 26 to the drum 22. Oppositely acting pawls 158, 160, are mounted on opposite sides of the member 30. One face of the jaws 30a, 32a, is axial and the other face is helical of the same pitch as the helical splines on the drum 22. The ring 32 by pins 36 is connected to a shift collar 40 having slotted rods 42 engaged by a control lever 46 fixed to a shaft 48. The latter has a seating for a valve 114, Figs. 9 and 13, and flanges 128, 130, on the valve and shaft have normally aligned conical holes each having a ball 132. A flange 138 splined to the valve, and a flange 144 on a control shaft 146 have interengaging cam teeth 140, 142, Fig. 11, and lugs 154, 156, engaging with clearance a slot 152 in a cylinder 150 adjustably secured to the housing 149. A compression spring 134 acts between the flanges 128, 138. During normal operation the valve 114 is seated and the fluid coupling 96, 104, which has drain holes 110 is empty. To change from the high gear position shown to low gear the control shaft 146 is partially turned so that the cam teeth 140 ratchet over the teeth 142 to move the flange 128 angularly relatively to the flange 130 which remains stationary due to the driving load on the jaws 30a, 32a. The balls 132 cause axial movement of the valve 114. Thus pressure oil, supplied to a passage 117 from a pump, passes through the valve 114 and ducts 116, 112, to the fluid coupling. As the coupling fills, the locking collar 32 and gears 54, 66, are relieved of torque. The locking collar 32 then snaps to the right, Fig. 1, due to the torque imposed on the lever 46 by the spring 134 and balls 132 whereupon the valve 114 closes and the coupling 96, 104 drains through the holes 110. The driving engine now being relieved from load accelerates and screws the driving ring 30 into a neutral position between the teeth 58, 60, so that both pawls 158, 160 ratchet over the respective teeth. When the engine speed synchronises with the speed of the gear 56 the pawls 160 engage the teeth 60 and the driving ring 30 is moved further to the right to engage teeth 62, 60, and the jaws 30a, 32a. The drive now proceeds in low gear. To change back into high gear the same procedure is followed with this difference. When the coupling 96, 104, fills to relieve the load on jaws 30a, 32a, the engine is decelerated so that the driving ring 30 is screwed to the left, Fig. 1, into neutral, the pawls 158, 160 ratchetting. Upon synchronisation, the ring 30 moves further to engage the teeth 62, 58, whereupon the locking member 32 snaps to the left and the coupling 96, 104, is drained.