Patent GB-371094-A (GB)
Title: Improvements in or relating to variable speed friction gearing
IPC: F16H61/664
Filed: 1931-02-21
Abstract: 371,094. Variable-speed friction gearing. ROBERTSON, J. H., ROBERTSON, J., GUTTERIDGE, L., and HOWARD, L. H., 1, Albemarle Street, Piccadilly, London. Feb. 21, 1931, No. 5519. [Classes 80 (i) and 80 (ii).] In variable-speed friction gearing suitable for motor vehicles of the type in which a driven member g, Fig. 1, making face contact with a coned driving-disc f is moved transversely from a coaxial clutch position to vary the speed, this controlling displacement of the member g is effected by a servomotor. The gearing is driven through an engine friction clutch B and drives through a torque-responsive helix i. Relatively to a driving-shaft f<2> of the steel cone f slides an element c of the engine clutch B which is preferably the centrifugal automatic clutch described in Specification 371,308. The friction member g comprises an aluminium spider g<3> with a friction rim g<1> of asbestos in combination with a synthetic resinous binder. The spider g<3> is bolted to a hub h which can slide axially and turn in a sleeve h<3> in turn supported in a socket h<4> forming part of the casing of an auxiliary gear box D which provides emergency lowspeed and reversed drives. A screw or helix i formed on the hub h engages a similar female helix i<1> on the sleeve h<3> so that the torque reaction of the sleeve thrusts the member g into frictional engagement with a force proportioned to the load. This helical coupling, by withdrawing frictional pressure, effects an automatic free-wheeling of the vehicle. Initial grip is produced by thrust due to a spring r supported by a thrust rod and ball r4 butting against the final shaft s of the transmission. An alternative form of helical coupling is shown in Fig. 5. The member g, socket h<4> and gear-box D are mounted so as to rise and fall under the action of the servomotor. The socket h4 is provided with lugs h<5>, Fig. 2, which slide on fixed guide rods k supported say parallel to the lowest radius of the cone f. Within the motor cylinder k<1> supported by a fixed beam k<3> is a double-acting piston k<2>, Fig. 1, connected by a rod k<0> directly to the socket h<4>. Oil from a plunger pump driven by the vehicle engine enters a pipe l<4>, Fig. 7, and is guided by a valve n to ducts n<6>, n<7> leading to the cylinder k<1> above and below the piston k<2>, so that the latter and the member g &c. follow up the displacement of a control lever p. A safety valve m<1> yields to allow excess oil to escape at m<4>. In the neutral position of the valve n shown, an annular port n<3> leading to the duct n<7> is closed whereby the movable gear members are prevented from descending under gravity. Pumped oil entering by port n<1> passes freely to an exhaust port n<4> by way of annular grooves n<8>, n<9> in the valve barrel. When the,lever p is moved between the positions shown in full and in chain lines, the valve n is first raised so that oil passes from the supply port n<1>, through the groove n<8> to the port n<3>, and by duct n<7> under the piston k<2>. As the piston k<2> rises, a lever o turns about a pivot o<3> so that the valve n is brought back to neutral with the gear members y &c. in a new position. A displacement of the lever p to the left lowers the valve n so that the oil passes from the port n<1> through the groove n<8> to a port n<2> leading through a duct n<6> to above the piston. A valve groove n<0> at the same time connects the port n<3> to an exhaust port n<5>. The piston might be rendered single-acting against gravity by omitting the duct n<6> and the valve parts corresponding. As described in Specification 355,977, the member g, Fig. 1, might be advanced into frictional engagement by oil pressure, and might be mounted to turn on a crank arm instead of to slide up and down on the guides k. Means for controlling an engine clutch of the plate type is described in which a single-acting oil-pressed piston acts on the clutch-disengaging pedal.