Patent GB-518265-A (GB)
Title: Improvements in and relating to power transmission systems
IPC: F16H15/48
Filed: 1938-07-18
Abstract: 518,265. Brakes. MULDER, C. A. H. July 18; 1938, No. 21289. Convention date, July 19, 1937. [Class 103 (i)] [Also in Group XXIV] In continuously-variable friction-gearing of the kind described in Specification 352,778, [Class 80 (ii)], comprising loose planetary balls 10 contacting driving, driven and reaction members 8, 11, 25 respectively, the reaction member 25 is so mounted that it can rotate forwards with the driving and driven members in the one-to-one solid drive position. In the torque-controlled automatic form shown, the contact-elements on the driven body 11 comprise a number of spring-pressed cones 12, forming with the driving and reaction races 8, 25 wedged-shaped spaces into which the planetary balls 10 are urged by springs 13, Fig. 5, and by the driving torque, the tractionpressure being thereby proportioned to the load. During indirect drive, the planetary balls 10 always turn about an axis a a passing through that of the cones 12 and the transmission ratio is varied by axial movement of the driving race 8 under the automatic influence of the driving torque acting through the cones 12 and resisted by a spring 19, acting at 17 on the driving shaft 1 on which the race 8 is fast. Initial adjustment of the axial position of the reaction-race 25 is effected by turning the hexagon head 24b of a thrust-sleeve 24, screwthreaded in a fixed sleeve 23, which latter is also externally threaded to receive a screwed thrust-cup 22, by which the initial compression of the torque-opposing spring 19 is adjusted. For reversed drive and engine-braking in reduced ratios, the driven member 11 may also carry an oppositely-arranged set of friction cones 12a, Fig. 5. The planetary members may be mounted on pivots. In Figs. 1 and 3 the reaction race 25 is always prevented from backward movement by a pair of one-way roller detents 30 in a ring 29, which is prevented from rotation by fixed tongues 33 allowing freedom of movement along. the diameter including the detents, to prevent the latter from loading the reaction race in a lateral direction. In Fig. 7, 7A, and 7B the one-way detent for the reactionrace 25 is replaced by a band-brake 44 which is controllable by an independent pedal 64 and the engine accelerator-pedal 65, to give enginebraking and automatic engagement as the throttle is opened, the latter resulting in the equivalent of accelerator-controlled clutching of the transmission. The drag on the brake-band 44 in the negative direction (clockwise) causes' self-energizing automatic engagement to be effected by means of a lever 61, the free end of which is held down by a spring 62, whilst its other end fulcrums'between and spreads the overlapped operative ends 46, 60 of the brakeband 44, contracting the latter on the reactionrace 25. The degree to which the clockwise drag is allowed to energize the brake is limited by the abutment of a part 70 of the lever 61 against a sector 68 pivoting with the acceleratorpedal 65, whereafter any further increase in torque results in slipping. The sector 68 is so shaped that the torque-sustaining capacity of the brake is proportioned to the throttleopening and is zero when the accelerator-pedal 65 is fully released, corresponding to 'a declutched transmission. Upon starting, depression of the aceelerator-pedal 65 causes' the brake to be gradually applied with increasing force, corresponding to automatie clutching. The accelerator-pedal 65 acts on the sector 68 through a stop 67 and spring 68b so that the pedal can rise without the sector if the latter is temporarily detained. To initiate the drag on the band 44, inclined springs 131, Fig. 7A, press the band axially against a flange 133 on the reaction-race 25. A stop 72 prevents the brake from energizing in the positive (anticlockwise) direction, so that the reaction-race 25 is free to rotate solidly with the driving and driven members in direct drive, whereupon centrifugal force bows the springs 131 and removes the axial drag on the brake-band. To brake the positive rotation, of the reactionrace 25 for transmitting engine-braking torque and thus preventing free-wheeling which would otherwise occur, the free end of the .lever 61 is raised against the spring 62 by depression of the pedal 64, until, Fig. 7B, the lever presses upwardly on pin 49a carried by an arm 49 connected to the operative end 60 of the brakeband 44, which is thereby contracted on the reaction-race 25. To provide an automatic adjustment for wear of the brake-band the operative end 60 of the band and the arm 49 are each connected to the band 44 by an oppositely-acting one-way gripping roller 56, 52 respectively. When due to wear depression of the pedal 64 brings'the hooked end 70 of the lever 61 into contact with the operative end 60, the roller 56 allows the part 60 to slide downwards over the band 44, and an interposed spring 51 moves the arm 50 correspondingly downwards. The effective length of the band is thereby shortened. The operator can also use the pedal 64 merely to release the brake 44 to allow the engine to be warmed up before starting. Fig. 8 shows a modified brake which does not produce any lateral loading on the reaction-race 25, is self-energized in.both directions and is automatically released in the direct drive position by an external hydraulic control. The brake-band is in two halves 74, 76, the operative ends of which are controlled by levers 87, .88, and struts 94, 93 connected by levers 101, 103 having a common link 102<1> carrying a piston 119. In geared drive positions pressure-oil acts on the piston 119 thrusting ,both struts 93, 94 downwards. The clockwise drag on the hands, due to the negative torquereaction Rk, thereupon causes the hooked end 84 of the lower band 76 to engage a projection 96 on the strut 94 at the point P. The latter point, together with fulcrum points Q, R on the lever 87 then form a rigid triangle and no tightening takes place at this side. On the other side, the lever 88 fulcrums on the end of the downwardly-pressed strut 93 and spreads the overlapped ends 78, 81 of the bands to contract them onto the reaction-race 25 in the same manner as the lever 61 in Fig. 7. A similar action occurs in the positive direction at the other side. The degree of self-energization of the brake is limited by fixed stops 120 or 122 which are contacted by the corresponding levers 87 or 88 whereafter any torque-increase results in slip. The degree of brake-application in the negative direction is proportioned to the position-of the accelerator-pedal, depression of which acts through a spring 116 on a pistonvalve 112 supplying pressure-oil to a'piston 107 which supports the lever 103. The selfenergizing clockwise movement of the brakebands 75, 76 thus drag down the strut 94 in opposition to the accelerator-responsive oilpressure on the piston 107. If this pressure is low or zero as at relaxed throttle, the lever 87 contacts with the limit stop 120 at a lower torque than at the higher pressure obtaining at under throttle openings. The braking capacity can thus be increased gradually by depression of the accelerator pedal. When braking positive reaction Mk, the force on the piston 107 due to the struts 93, 94 is reversed and the piston goes to the top of the cylinder. The limit braking-torque is now determined by springs 97, 108 resisting the downward movement of the lever 88 towards the limit stop 122. The axial ratio-changing movement of the driving friction race 8 in the change-speed gear itself, controls a valve (not shown) which, when the direct-drive position is reached, vents the cylinder 118 of the common piston 119, so that the latter is moved downwards by the struts 93, 94, thereby releasing the brake and permitting the reaction-race to rotate freely forward with the driving and driven members. Figs. 10, 11 and 12 show a self-energizing disc brake, the reaction-race 25 carrying a flange 140 which is gripped axially between a pair of brake-discs 143, 144 whenever the drag thereon in either direction tilts spring-supported levers 149 causing radially-adjustable cams 148 thereon to spread apart overlapped lugs 146, 147 on the discs. The drag is permitted to act selectively in. either direction by withdrawing one or other of two stops 153, 154 from the path of a projection 160 on the disc 144.