Patent GB-910162-A (GB)
Title: Fluid actuated friction clutch
Inventor: BLOCH PETER
IPC: F16D25/10
Filed: 1959-05-04
Abstract: 910,162. Friction clutches; controlling clutches; reverse gearing. TWIN DISC CLUTCH CO. May 4, 1959, No. 15223/59. Class 80 (2). A multiple-disc clutch is engaged and disengaged by supplying fluid pressure to engage and release spaces on opposite sides of a fixed piston surrounded by a movable cylinder, the release space being continuously filled at low pressure and engagement being produced by supplying fluid at high pressure to the engage space, the cylinder then acting through elastic means to engage the clutch discs, a throttle controlling egress of fluid from the release space and providing cushioned clutch engagement. The clutch may be engaged either pneumatically or hydraulically. In one form, multiple discs 13, Fig. 1, between a driving shaft 10 and a driven disc carrier 14 are engaged when oil is drawn through a filter 32 from a sump 31 by a pump 30 and passed through a pipe 33, a two-position clutch control valve 34 and pipes 37, 35 to a space 22 between a flange 19 fast upon the driving shaft and a two-part piston 52, which is thereby slidden rightwards so that a Belleville spring 24 engages the clutch discs. As the volume of the space 22 increases during clutch engagement, a space 29 on the opposite side of the flange 19 decreases in volume, so that oil contained therein is forced out through a pipe 50 and through a throttling restriction 48 to pipes 44, 41 and a low pressure relief valve 42 communicating through a further pipe 43 with the sump 31. Accordingly the speed of engagement of the clutch is reduced by the restriction 48. The pressure of the oil supplied through the pipe 33 for clutch engagement is controlled by a pressure relief valve 40 having the pressure on its downstream side controlled by the pressure relief valve 42, the pressure in the pipe 44, &c. being substantially less than that in the pipe 33, &c. To disengage the clutch, the clutch control valve 34 is adjusted to connect the pipe 37, &c. and the space 22 through a pipe 38 to the sump 31. Accordingly, the pressure in the space 22 falls, but the pressure in the space 29 on the opposite side of the flange 19, which is the same as the reduced pressure in the pipe 44, is maintained, so that the two-part piston 52 is slidden leftwards towards the clutch disengaged position. A one-way valve 47 in parallel with the throttling restriction 48 now opens to allow rapid admission of oil under low pressure to the space 29 for quick disengagement of the clutch. The Belleville spring 24 cushions engagement of the clutch with gradual build-up of the clutchengaging force until maximum torque transmitting capacity is reached. As a modification, the Belleville spring 24 may be replaced by a number of helical springs 55, Fig. 2, carried in recesses 56 in the back of a piston 54. In another form, multiple disc clutches 79, 80, Fig. 3, comprising the forward and reverse drive clutches of a reverse gear having an input shaft 57, 59 and an output shaft 69, are engaged when oil under relatively high pressure is admitted through one or other of two shaft ducts 110, 124 to spaces 94, 95 in a two-part piston 93 on opposite sides of a radial flange 84 fast upon the input shaft. Oil pressure is maintained at all times in the shaft ducts 110, 124, engagement of the desired clutch being effected by increasing this oil pressure in one duct at a time to a relatively high value. To engage the forward drive clutch 79, the pressure in the duct 110 is increased and oil passes through a port 112 to open one-way valves 114 admitting the increased pressure to the space 94, so that the twopart piston 93 commences to move to the left. A number of pins 115 sliding in apertures 116 in the fixed flange 84 are formed with recesses 120 coacting with oil passages 121 to form valves. When the two-part piston 93 commences its leftwards movement from the neutral position shown, the pins 115 are slidden by the two-part piston to open large ports so that oil under pressure is admitted directly from the ports 112 to the space 94. At the same time, similar pins 129 arranged reversely to the pins 115 are slidden so that small ports 133 afford restricted passages through which oil in the space 95 can escape to ducts 134 in the radial flange 84 and thence through ports 126 to the shaft duct 124. The restricted passages opened by the pins 129 reduce the speed of the engagement of the clutch 79. Leftwards movement of the two-part piston 93 acts through a Belleville spring 88 to engage the multiple disc clutch 79, so that drive passes through a gear 67 journalled upon the input shaft 57 to a gear 68 fast upon the output shaft 69. To disengage the clutch 79, the pressure in the shaft duct 110 is reduced to the normal low pressure, and springs 96, 97 restore the two-part piston 93 to the position shown. To engage the reverse drive clutch 80, the pressure in the shaft duct 124 is increased to a higher level, opening a one-way valve 128, similar to the one-way valve 114, which admits oil to the space 95, thus commencing rightwards sliding movement of the two-part piston 93. The pins 129 are now slidden within the fixed flange 84 to open relatively large apertures 132, so that direct communication is established between the shaft duct 124 and the space 95, while the pins 115 are also slidden to open restricted passages through which the oil in the space 94 can be slowly vented to the duct 110, for gradual engagement of the clutch. When the clutch 80 has been engaged, the drive is transmitted through a gear 76 journalled upon the input shaft 59 through an idler gear 77 to a gear 78 fast upon the output shaft 69. The control circuit for the reverse gearing comprises a pump 98, Fig. 4, supplying oil to a pressure release valve 101 and a control valve 102 connected through pipes 103, 104 to the shaft ducts 110, 124. Pipes 105, 106 lead back to the sump. As a modification, the single Belleville spring may be replaced by two concentric Belleville springs 139, 140, Fig. 10, lying between a piston 141 and a stack of discs 142 engaged against a reaction ring 143. The Belleville spring may alternatively be located between the reaction ring and the stack of clutch discs, instead of between the piston and the clutch discs.