Patent GB-524311-A (GB)
Title: Improvements in and relating to differential gearing
IPC: F16H48/20
Filed: 1939-01-26
Abstract: 524,311. Differential gearing. PORSCHE, F. Jan. 26, 1939, Nos. 2776 and 2777. Convention dates, Jan 26, 1939, and Nov. 17, 1938. [Class 80 (ii)] In self-locking differential gearing, for motor vehicles, machine-tools or calculating-machines, .elastic members, such as springs 3, Fig. 1, transmit the driving torque to the driven sideshafts 10, 10', which are provided with torqueresponsive friction clutches, e.g., 13, 13<1>, so arranged that, in the absence of load or either side-shaft, the elastic members cause engagement .of the corresponding clutch, locking it to the driving casing 11 until the load is restored, whereupon the clutch is released and differential action is unimpeded. The locking, being torque-responsive, takes place as soon as one side-wheel, e.g, on a motor vehicle, ceases to adhere to the ground, and is not delayed until spinning takes place, whereby jerks are avoided. In Fig. 1, the driven member of each clutch 13, 13<1> is a disc 4, splined on a sleeve 9, fixed to the respective side-shaft 10 or 10<1>, whilst its driving member is a bell-shaped extension of the main driving carrier 11 of the spur or bevel planets. Leaf or helical springs 8 press each disc 4 in the inward direction to engage its clutch in opposition to the normal driving torque acting on inclined teeth 5, Fig. 4, between the discs 4 and discs 2 integral with the loosely mounted differential side-wheels 1, so that in the absence of such torque on either side-shaft 10, 10<1>, the spring 8 engages the corresponding clutch 13 or 13<1> and locks the differential. The spring 8 may, as shown, be assisted by circumferentially arranged helical springs 3 engaging alternating axial lugs on the discs 2 and 4 so as to form a spring coupling therebetween, and the circumferential yield of such coupling may be limited by positive stops. The inclined-tooth coupling 5 may be replaced by a cam and ball arrangement, and the sides of the teeth 5 may be alternately axial so as to give torqueresponse in one direction only, whereby the clutches 13, 13<1> are always both engaged in one direction of drive. In the modification shown in Figs. 7-9 the planet-carrier 6 is mounted for free relative rotation in relation to the driving casing 2 and frictional locking is effected by springs 13, 13<1> which, in the absence of driving torque, turn levers 10 in the direction of the arrow R, Fig. 8, in relation to abutment arms 14 fast to the planet-carrier 6, the levers 10 being fast to radial shafts 11, the consequent turning of which acts on wedging balls or rollers 17, which force the driven side-gears 7 axially outwards into frictional engagement with the sidewalls of the driving casing 2, thereby locking the differential. The normal driving torque passes from the casing 2 to the carrier 6 by way of stops 12 or 12<1>, according to direction, acting through the levers 10, upon the springs 13, 13<1>, which latter yield causing the levers 10 and radial shafts 11 to be turned in a direction against the arrow R so that the wedging rollers 17 cease to act on the side-wheels 7, whereby the frictional lock is removed. The side-shafts 10, 10<1>, Fig. 1, may be swinging half-axles and the clutches may be arranged for engagement in the radial instead of axial direction. The Specification as open to inspection under Sect. 91 states that the two clutches may be replaced by a single clutch. This subject-matter does not appear in the Specification as accepted.