Patent GB-528561-A (GB)
Title: Improvements in or relating to power transmissions for motor vehicles
IPC: F16H37/00
Filed: 1939-01-31
Abstract: 528,561. Variable-speed gearing: servo-motors. CHRYSLER CORPORATION. Jan. 31, 1939, No. 28063. Convention date, May 13, 1938. Divided out of 528,508. [Class 80 (ii)] [Also in Group XXIX] A double planetary gear C' comprising two trains in series is utilized in combination with a gear D' giving a direct drive and a reverse, whilst a hydraulic coupling B<1> is employed instead of a normal friction clutch. In the first planetary train, the annulus 129 is secured to the driving shaft 124, the sun gear 135 being adapted to be held by an over-running clutch device F' and the planet carrier 132 serving as the driven member. The carrier 132 forms the annulus 221 of the second planetary train which includes stepped planet pinions 222 mounted on a carrier 226 secured to the driven shaft 134, the sun gear 227 being prevented from backward rotation by an over-running clutch device L. The first train gives two speeds, the direct drive being obtained by engagement of a friction clutch H arranged between the sun gear 135 and the driving shaft 124 and actuated by fluid pressure on a piston 172. A reduced drive through the second train is obtained by holding the sun gear 227 from backward rotation whilst direct drive, giving a step-up in the reduction drive, is obtained by the arrangement of a centrifugal clutch M between the carrier 226 and the annulus 221 which is automatically brought into action on the vehicle attaining a predetermined speed, for example, 10-15 miles per hour, and the engine being momentarily slowed down by release of the accelerator pedal. The first speed is obtained with both trains in reduced drive, second speed of the vehicle by the centrifugal clutch M locking the second train and a third speed by operation of the clutch H of the first train which may also be automatic and is controlled by a valve means K. Oil is supplied under pressure to operate this clutch from a pump N driven at a speed proportional to that of the vehicle so that at a predetermined speed, for example, 25 miles per hour, the clutch is automatically engaged for direct drive. The vehicle speed at which this operation takes place can be varied by means of a byepass valve at the valve means K which can be actuated from a knob 297 situated on the dash. This direct drive clutch operation can also be over-ridden by a main control valve at K which is operated from a selector control lever 212 on the steering column to maintain the first planetary train in reduced drive. A second lever serves for selecting forward, reverse, or neutral, and operates on a gear mechanism D' to clutch the shaft 134 direct to the tail-shaft 125 by a clutch member 261, to bring in a reversing train, or to leave the clutch member in a neutral position. The outer ring 148 of the overrunning clutch service F' for preventing backward rotation of the sun gear 135 is itself normally held by a brake J. This brake is however adapted to be released by fluid pressure derived from a piston 162 actuated by a footpedal 168, which pressure acts on pistons to release the brake, so that the drive from shaft 124 to the driven member 132 of the first planetary train can be completely interrupted despite the unavoidable drag through the fluid coupling so as to facilitate the engagement of the forward or reverse gears when the vehicle is at a standstill and to accelerate the vehicle. The direct drive obtained by the engagement of clutch H is arranged to be equivalent to an overdrive ratio which can be entirely excluded by operation of selector control 212 but when in service is subject to automatic control. The arrangement may be modified by the substitution of a fluid coupling in place of the normal friction clutch and the outer member of the over-running clutch device F<1> may be held by a releasable brake so that the drag effect of the coupling can be negatived as previously described.