GB417806A - Improvements in or relating to power transmission mechanism and variable speed gearing - Google Patents

Abstract

417,806. Controlling change-speed gearing. LAGO, A. F., 1a, High Road, Kilburn, London. May 31, 1933, No. 15717. [Class 80 (ii).] Relates to means for controlling changespeed gearing of the " Wilson " type and an engine clutch in such a way that the greater part of the slip in starting up, say, a vehicle, or in changing speed is taken by the clutch, the brake bands in the change-speed gearing being completely applied prior to the full engagement of the clutch, which is of known type. The gearing, which is described in Specifications 328,660, [Class 80 (ii)], and 370,442, comprises a selector cam shaft 28 which thrusts out struts one at a time into the path of a bus-bar shown at 32, Fig. 7, which as it is raised by a spring 33 after having been depressed by a pedal 3 picks up the selected strut and applies the corresponding brake 34. In a simple embodiment shown in Fig. 1, the bus-bar is operated through an executive control crank 9 connected through a lostmotion link 6 to the pedal 3, which also disengages the engine clutch 1 and is operated by the driver at his own volition only. Movement of the pedal 3 from A to B is free. Movement from B to C initiates the disengagement of the clutch 1, the lost motion at 11 being taken up. Continued depression from C to D disengages the clutch 1 fully and releases the last - applied brake 34. Further depression to E leaves the clutch disengaged and the gearing in neutral irrespective of preselection by a lever 28b and cam shaft 28. As the pedal is allowed to rise under the action of clutch and gear springs, the selected brake 34 is fully engaged at C and the clutch also at B. Starting shocks on gear teeth are thus mitigated by slip both in the brake and in the clutch. Forms shown in Figs. 2 and 7 ensure that the drive is disconnected when the gearing is set to neutral. As the pedal 3, Fig. 2, rises, a stop bar 12 moves to the right, and a stop trigger 18 is provided which prevents this rightward motion of the bar 12 when the gearing is set to neutral, so preventing the clutch 1 from engaging. The preselector cam shaft 28 has an extra lobe 27, Fig. 5, for the purpose. The trigger 18 is a lever pivoted at 19 on a swing link 20, the lower end of the trigger lever being constantly acted on by a spring plunger 23. When the shaft 28 is set to neutral, the cam 27 turns to the position of Fig. 4, thrusting back the link 20. The clutch being still engaged, the bar 12 is in the path of and stops the trigger 18 so that the spring of the plunger 23 is compressed. On depressing the pedal 3 to disengage the clutch, the bar 12 is withdrawn from contact with the trigger 18, which then swings to the left so as to obstruct the bar 12 when it tries to return on release of the pedal. In the form shown in Fig. 7, the neutral setting effects that two brakeengaging struts are thrust out simultaneously by the selector cams 28<a> into the path of the rising bus-bar 32. The interlocking tongues shown at m in Fig. 4 of Specification 370,442 then prevent the rise of the bus-bar, since one strut d alone can pass between the tongues m. The link 31 which connects the bus-bar 32 to the executive control lever 9 has hitherto been made so as to transmit thrust but not pull. It has been made with telescoping parts 31<a>, 31<b>, Fig. 8, with a collar 31<c> on the latter to transmit thrust only. To produce the required stop action, the telescoping parts 31<a>, 31b are locked together by a through pin 35. When the bus-bar 32 is prevented from rising under the action of its spring 33, a connecting lever 30 is also prevented from rising by tension in the link 31 acting against the tension of the engaging-spring, not shown, of the engine clutch 1, which is thus prevented from engaging as long as the gearing is set in neutral. According to the Provisional Specification, when the combined load of the clutch and brake band springs is unduly heavy, a servomotor may be used for depressing the control pedal.