366,081. Power transmission system for motor vehicles &c. SINCLAIR, H., 6, The Crest, Surbiton Hill, Surrey. Sept. 25, 1930, No. 28682. [Classes 79 (ii) and 79 (v).] A power transmission system comprises an hydraulic coupling, change-speed gearing, and a control member which, while the driving engine is running, while a gear of said gearing is engaged, and while power is not being trans-. mitted owing to the driven member of the coupling having been arrested either by separate braking means or by the load, can be operated to engage one of the rotatable elements of said gearing, or a member connected for rotation therewith, and to impart to said element a rotation sufficient to release torque loading on the engaged gear so as to facilitate disengagement thereof, together with the addition of a device whereby the driven shaft of said gearing can be disconnected from the driven shaft (e.g. the road wheel axle) of the system. The control member referred to above is that described in Specification 365,998, [Group XXIV]. In the construction shown in Fig. 1, an engine 2 drives the road wheels of a vehicle through an hydraulic coupling 3, a changespeed gear 4 and a free-wheel clutch 69 which is normally locked by a friction clutch 9 so as to transmit drive in both directions. A'pedal 18 is depressed prior to changing gear and this pedal, acting through a link 17, disengages the friction clutch 9, so that the drive is now through the free-wheel clutch only and the propeller shaft 13 can overrun the gear-box shaft 10 thus facilitating gear-changing. At the same time the pedal 18 closes the throttle 24 through a link 23 and afterwards applies a brake 21 to the driving-shaft 20 of the gear-box by means of a link 22 ; further depression of the pedal after the shaft 20 has been stopped gives the shaft a partial rotation in the reverse direction, as described in Specification 365,998, [Group XXIV]. The hydraulic coupling is preferably of the Vulcan or Fottinger type and means may be provided for increasing the slip at low speeds, as, e.g. by reducing the degree of filling or by obstructing the hydraulic circuit. Instead of the combined friction and free-wheel clutch any of the following devices may be used :- (1) a simple free-wheel clutch, (2) a combined dog-clutch and free-wheel clutch, (3) a freewheel clutch which may have a locked position, and may have, in addition, a totally free position, and (4) a friction clutch. The pedal 18 is so connected to the throttle that, when depressed, it closes the throttle independently of the position of the normal throttle-operating means. Thus, in the construction shown in Fig. 6, the usual accelerator pedal 33 is connected by an extensible spring link 35, lever arms 34<1>, 34, and a link 23 to the throttle 24. The pedal 18 is pivoted at 25 and actuates an arm 30 having a pin 31 working in a slot 321 in a stronger spring link 32 connected to another arm of the lever 34. The pedals are normally raised by springs 36, 37 to the position shown in Fig. 6, the throttle being closed. When the accelerator pedal is depressed the arm 34 rotates and opens the throttle, while the link 32 is raised until the pin 31 is at the bottom of the slot 32<1>. If now the pedal 18 is depressed the pin 31 acts on the link 32 and this link, being stiffer than the link 35, rotates the lever 34 to close the throttle while the link 35 is extended. Further depression of the pedal 18 after the throttle is closed extends the link 32. The pedal 18 may act on the clutch behind the gear box through the device shown in Fig. 5, in which, while the pedal moves from a to b an arm 29, connected through a spring link 17 to the clutch, moves from a<1> to b<1> while further movement of the pedal from b to e merely moves the arm slightly from b<1> to el. For this purpose the pedal is pivoted at 25 and carries a pin 26 acting on a cam arm 27 fixed to the arm 29. The following modifications of the disconnectible clutch are described-(1) A roller free-wheel clutch, Fig. 2 (not shown.), of the kind described in Specification 261,486, [Class 79 (ii), Motor vehicles, Driving &c.], locked and unlocked by a separate hand-lever so as to act as either a two-condition or threecondition clutch. (2) A two-condition freewheel clutch of the kind described in Specification 239,894, [Class 80 (ii), Gearing, Variablespeed &c.], and shown in Fig. 3, in which diagonally disposed wedging rollers 87, 93 lie between conoidal roller paths. The gear-box shaft 10 carries a disc 81 to which the forward drive outer roller path 82 and the reverse drive outer roller path 83 are secured. The forward and reverse inner roller paths 84, 88 are slidably splined on the driven or propeller shaft 79 and are respectively pressed rearwardly and forwardly by springs 85, 89. Normally both springs are active and the shaft 10 can drive the shaft 79 through the rollers 87 while the shaft 79 can drive the shaft 10 through the rollers 93. When the pedal 18 is depressed a ring 96 is moved rearwardly (i.e. to the right in Fig. 3) and its bevelled rear end forces balls 95 into a wedge-shaped space between a sleeve 94 having an abutment on the roller path 83 and lock-nuts 92 fixed on the inner roller path 88, the result being that the inner roller path is forced rearwardly and the gap between the reverse drive roller paths is so widened that the rollers 93 cannot become wedged therein. The clutch therefore becomes a free-wheel clutch, the rollers 87 driving in one direction only. (3) A dog-clutch 100, 103, Fig. 4, is combined with a free-wheel clutch 104, the dog-clutch being normally engaged, but being disengaged by the pedal 18 preparatory to gear-changing. In order to ensure that the dog-clutch is engaged when the reverse gear is engaged the link 17 of the pedal 18 acts on the clutch lever 15<11> through a sliding rod 107 carrying a bell-crank lever 109 having a hook 110 passing through a slot in the lever and normally engaging the back of the lever, so that a pull on the rod 107 disengages the clutch. When reverse gear is engaged a reverse selector rod 113 projects from the gear box into the path of an arm 112 of the lever 109, so that when the pedal 18 is depressed the arm 112 is rotated and the hook 110 is raised clear of the slot in the lever 15<11> and the dog-clutch is not disengaged. When a forward drive is next selected and the reverse selector rod has been withdrawn the pedal 18 is depressed and released and the hook 110 rides over a slope 114 on the lever and engages behind the lever again. (4) A combined dogclutch and free-wheel clutch are arranged in the gear box 4, Fig. 8. The left-hand side of the gear box provides for four forward speeds of the shaft 123 in the usual way, and this shaft 123 is connected to the final gear-box shaft 134 through a dog-clutch 137 and a freewheel clutch 146. Normally the dog-clutch is engaged, but when the pedal 18 is depressed this clutch is disengaged and the drive is through the free-wheel clutch only. The reverse drive is positive in both directions and is obtained by means of a gear wheel 151 on an extension of the lay shaft 122, a reverse pinion (not shown) being moved into simultaneous engagement with this gear wheel and with a wheel 139 fixed on the shaft 134 and forming one of the clutch members. (5) A dogclutch 136, 139, Figs. 10 and 11, associated with a free-wheel clutch 146, is provided with an elastic " baulking " device which gives the clutch jaws a certain amount of backlash with the object of avoiding jamming. Two teeth 137<1> on the clutch part 136 are partly cut away on the trailing edges to receive spring members 181 fastened to the clutch part, these members acting as parts of the teeth 137<1> and making these teeth wider than the others under no-load conditions. Thus the clutch teeth cannot engage until they are in such relative positions that when engaged the leading edges of the teeth 138 of the clutch part 139 are free to move through the distance by which the members 181 are.normally clear of the cut-away faces 180 of the teeth 137<1>. A certain amount of backlash is thus assured and the teeth cannot jam even if the members of the free-wheel clutch are elastically strained. Instead of spring control of the " baulking " device centrifugal, fluid pressure, or magnetic means may be employed. Specifications 282,097, [Class 80 (ii), Gearing, Variable-speed &c.], and 285,970, [Class 79 (ii), Motor vehicles, Driving &c.], also are referred to.