Patent GB-471797-A (GB)
Title: Improvements in change speed gearing
IPC: F16H61/00
Filed: 1935-12-10
Abstract: 471,797. Change speed gearing. MONOPOWER CORPORATION. Dec. 10, 1935, No. 34146. Convention date, Dec. 10, 1934. [Class 80 (ii)] [Also in Group XXVI] A main centrifugal friction - clutch 67, 68 drives change-speed countershaft gearing, controlled by plate-clutches 5, 6, which are fluidoperated under the automatic control of a centrifugal governor 17, driven by the final driven sleeve 49. The governor-action may be modified by engine - suction, and may also be subjected to an escapement control such that ratio-change is prevented until the operator releases a vehicle accelerator-pedal, as described in Specification 455,083. A manual control is also provided for holding the gear in low or second speeds. The main centrifugal clutch 67, 68, described below, provides a drive from an engine flywheel 2 to a drum 4, which is arranged inside or outside the flywheel-casing and is in permanent driving connection with a first driving pinion 8. The drum 4 encloses the plate-clutches 5, 6, the common driven member 155 of which is in permanent driving connection through cushioning springs 184, with an intermediate driven shaft 56 of the gear. The driving member 325 of the plateclutch 6 is riveted to the drum 4 and provides a direct drive therefrom to the driven shaft 56. The driving member 178 of the plateclutch 5 is drivingly connected to a secondspeed pinion 10, and provides second-speed by way of drum 4, pinion 8, countershaft pair 9, 11, pinion 10, a one-way roller clutch 180, referred to below, and the plate-clutch 5, to the driven shaft 56. Low-speed, neutral and reverse are obtained by a sliding wheel 13, mounted on an overrunning roller clutch 44, splined on a final driven sleeve 49, rotatably mounted on the intermediate driven shaft' 56, the roller clutch being automatically locked out at 248 when reverse is engaged. A modification, Fig. 16, (not shown), provides also bidirectional locking in forward lowspeed, when required. When the wheel 13 is moved to low-speed position into engagement with the countershaft pinion 12, clutch teeth 52 on its driven hub drive a centrifugal governor 17, operating through a mechanical relay, a slide valve 89, which hydraulically controls the second- and high-speed clutches 5, 6. Pressure-oil for the clutches is supplied by a sliding-vane type rotary pump 90 (described below), in driving connection with the governor 17. The pump and valve assembly 90, 89 are freely mounted on the driven shaft 56 and are restrained from rotation by engagement with the gear-casing. The governor 17 comprises segmental centrifugal masses 131, which are guided radially and engage inclines 135, 136, 137 on side walls 83, 138, one, 83, of which, moves axially in response to radial movement of the masses. The parts 135, 136 of the movable-side wall 83 are differently inclined, and the wall is loaded axially by springs 134, 188 of different strengths so as to provide two differently controlled ranges of operation corresponding to second- and high-speeds of the gear. Additional laterally extending blade-springs 133 act directly on the governor-masses 131, and engine-suction, acting through a rock-shaft 261, may provide additional variable loading. In view of the fact that the thrust faces of the governormasses are more steeply inclined to the axial than to the radial plane, downward changes occur at lower speeds the corresponding upward changes. The movable side-wall 83 operates the speed-changing valve 89 through a mechanical relay comprising a cam 82, integral with the movable wall 83, which rotates with the driven shaft 56. Speedresponsive axial movement of the wall 83 selectively positions the cam 82 in front of axially-spaced tappets 84, 239, 139, 189, Fig. 9, projecting to different extents from the arms of a lever 85, an arm 87 on which operates the speed-changing valve 89. This valve has three positions in each of which it is retained by a spring detent engaging one of three holes 142, Fig. 10. In the position shown, a pressurechamber 111, fed by the pump 90, is vented to exhaust through the interior of the valve 89. With increase in speed of the driven shaft the governor 17 moves the valve 89 one step to the right, Fig. 10, thereby communicating the pressure-chamber 111 with the fluidspace 153 behind the diaphragm 154 of the second-speed clutch 5. Second-speed is thereby engaged and the low-speed wheel 13 overruns. Further speed increase moves the valve 89 another step to the right, venting the fluid-space 153 of the clutch 5 and energizing that 200 of the direct-drive clutch 6. Communication between the valve 89 and the clutches 5, 6 is effected through radial borings 147, 195, leading to axial ducts 148, 196 in the shaft 56. In addition to the ports 152 communicating the fluid-spaces, e.g. 153 of each clutch 5 or 6 with their ducts 148 or 196, there are ports 156, closed in the entry direction by one-way check valves 158, such ports permitting rapid exhausting. Manual control for locking in low- or second-speeds comprises a button 19, Fig. 10, which, when depressed one step 235, against a weak spring 230, moves a valve 118 one step to the right, thereby permanently communicating the pressurechamber 111 with the inlet 145 leading to the second-speed clutch 5, irrespective of the position of the automatic valve 89. Depression of the button 19 a further step 237, against a stronger spring 229, vents the pressure-chamber 111 directly into the gear-casing, thereby rendering both clutches 5, 6 inoperative, so that the lowest speed is retained. There is a further valve 36, operated by a cam-groove 40 in the selector-rod 31 of the low-speed and reverse wheel 13, the valve being allowed to move to the right and open a relief port 37, to render the fluid-pressure ineffective, when the selector rod 31 is in neutral or reverse positions. The centrifugal main-clutch comprises friction facings 67, 68, on the drum 4, engaging the flywheel 2 and a presser-plate 66, moved axially inwards to engage the clutch by radially-moving wedge-shaped centrifugal masses 60, carrying rollers 63, engaging wedges 65 fixed to flywheel-cover 69. Springs 61, 62 oppose the masses, and the engaging thrust is taken by further springs 71, which secure the cover 69 to the flywheel, and ensure uniform engagement in spite of wear. In low-speed, centrifugal force alone supplies the engaging-pressure, but in second- and highspeeds. it is augmented by fluid-pressure acting behind a diaphragm 173, which backs the friction element 68. This fluid-pressure is taken from the pressure-space 153 or 200 of whichever plate-clutch 5 or 6 happens to be engaged, the supply being effected through a port 169, controlled by an automatic valve 167, opposite sides of which communicate with the pressure-spaces 153, 200 respectively. In a modification, Fig. 15 (not shown), the main clutch is separate from the drum 4, which latter, with its clutches 5, 6, is outside the flywheel-casing, whilst the main-clutch surfaces 67, 68, are both backed by diaphragms. The hub 178 of the second-speed plate-clutch 5, may or may not include an overrunning clutch in which former case, the control-valve 89 may be suitably modified to ensure that the clutch 5 does not disengage when the directdrive clutch 6 engages. As shown in Fig. 2, the hub 178 includes such an overrunning clutch 180, but the roller-cage 179 thereof is permanently connected to one, 162, of the driving clutch-discs. With this arrangement, when the plate-clutch 5 is disengaged and the plate-clutch 6 engaged, the rollerclutch 180 overruns and permits all the plates of the clutch 5, with the exception of the plate 162, to rotate together and thus eliminates relative rubbing of all except the plate 162. This plate 162 also has sufficient capacity to hold a vehicle against free coasting on a downgrade. The individual plates of the clutches 5, 6 have integral peripheral spring tongues tending to separate them and their presser-plates are curved. The sliding-vane rotary pump 90, shown in Fig. 11, comprises radially-sliding vanes 95 on a driving member 93 rotating in a fixed eccentric casing 100 provided with inlet and outlet ports 109, 110 respectively. Pressure fluid from the chamber 111 has access to channels 242 under the vanes, and constitutes the sole means for pressing them radially outwards into contact with the casing.