GB569410A - Improvements in or relating to power transmission device - Google Patents

Abstract

569,410. Variable, -speed gearing ; clutches. WOLFF, O. E. Sept. 19, 1942, No. 13251. Convention, date, April 15. [Class. 80 (ii)] A power transmission has a clutch adapted to transmit power from a driving shaft to a driven shaft only when the said shafts rotate at the same speed and a second power-transmitting means adapted to transmit power between said shafts only when they rotate at different speeds, the clutch being such that a change over from the clutch to the second power-transmitting means is automatically obtained at any speed whenever the driving torque exceeds a predetermined maximum for that speed. The clutch may be of the kind described in Specification 567,676. As shown, for a countershaft type gear-box, the inner members 65, 90 of two clutches are mounted on shafts 66, 88 and cooperate with the inner surface of a drum 62 fixed to a driving shaft 60. The drum 62 is fixed to a gear 77. Gears 86, 100 are fixed to the shafts 88, 66. Gears 77, 86, 100 mesh with gears 78, 85, 98, gear 78 being fixed to a countershaft 80 and gears 85, 98 being loose thereon and interconnected by freewheel clutches 84, 96. A final driven shaft 105 carries a dog clutch member 102. Fixed gears 106, 110 mesh with gears 108, 112 on the shaft 105, a reverse idler being arranged between the gears 110, 112. Each clutch comprises a spider 65 with centrifugal weights 70, Fig. 3, carrying pivoted pads 75. When the inner and outer parts of the clutch are revolving at the same speed oil is pressed out from between the pads 75 and the inner surface of the drum 62 and the clutch is engaged. If the torque transmitted becomes excessive the clutch slips and oil films are built up between the parts 75, 62, and the clutch is disengaged. With the parts positioned as shown in Fig. 2 and the driven shaft 105 stationary, rotation of the shaft 60 will drive the shaft 105 through the gears 77, 78, 85, 98, 100 and freewheel clutches 84, 96, and the drive will be in low gear. When the shaft 105 has increased in speed and a higher gear is required, the driving shaft 60 is retarded and when it reaches the speed of the clutch parts 90 the latter clutch engages and the drive is through the parts 60, 62, 90, 86, 85, 96, 98, 100, 105. When the parts have speeded up and high gear is required, the driving shaft is again retarded and the clutch 62, 65 engages and a one-to-one drive results through the parts 60, 62, 65, 66, 105. Gearing down is produced automatically in accordance with the torque on the driven shaft 105. When the clutch 102 is engaged with the gear 108 a fixed low gear results through the parts 60, 62, 77, 78, 106, 108, 102, 105. Instead of having, three automatic speeds as above one of the clutches and some of the gears may be omitted to give two automatic speeds. As applied to an epicyclic gear, gears 204, 212, Fig. 14, on driving and driven shafts 200, 202, mesh with parts 205, 206 of compound planet pinions carried by a cage 208. The latter has a clutch drum 220 and is prevented from rotating backwardly by a one-way brake 215. A spider 222 carrying centrifugal clutch members 224 is fixed to the shaft 202. When starting up the shaft 202 is driven at low gear through the gears 204. 205, 206, 212, the cage 208 being stationary. As the speed increases the weights 224 engage the drum 220. If the speed of the driving shaft is retarded inertia will cause the drum 220 to rotate forwardly and when its speed reaches that of the shaft 202 the parts 224, 220 engage in driving relationship and a direct drive results. Upon a predetermined maximum torque the gear goes automatically into low gear. In a modification, three epicyclic gears are arranged in series. A driving shaft 300, Fig. 16, has a clutch drum 312 and toothed annulus 315 meshing 'with planet pinions 316 on a carrier 322 fixed to a shaft 325. The carrier 322 has centrifugal weights 340 with pivoted pads 344 for engagement with the drum 312. The planets 316 mesh with a sun spur-wheel 326 connected to the fixed casing 334 by a one-way brake 330. A third shaft 364 is connected to the shaft 325 by a like epicyclic gear and the final driven shaft 302 is similarly geared to the shaft 364. The three sets of centrifugal weights are of differing weights, 340 being heavier than 365 and so on. The third epicyclic gear in the casing part 375 may be replaced by a reverse gear. At high loads all gears work epicyclically, giving a low gear. To increase the gear the driving shaft 300 is retarded to engage the clutch 312, 344 so that the first epicyclic gear becomes solid. When all the gears are solid the driven shaft 302 rotates at the same speed as the driving shaft 300. The clutches in any of the above constructions may be replaced by a clutch in which the outer member 122, Fig. 4, has a cam-like inner surface 128 and the inner clutch part comprises a spider 134 with links 136 carrying rollers 140 co-operating with the. surface 128. When the clutch is engaged the rollers engage in the corners 130 of the surface 128; at other times they roll round the surface 128.