Patent GB-556625-A (GB)
Title: Improvements in or relating to controlling means for variable speed gears
Filed: 1942-04-14
Abstract: 556,625. Fluid-pressure servomotor-control systems. HOBBS, H. F. April 14, 1942, No. 4888. [Class 135] [Also in Group XXIV] Control means for variablespeed gears for automobiles and other purposes comprises in combination a device actuated according to gear input shaft speed and adapted to control variation of gear ratio automatically so as to maintain input speed within a predetermined range, manually-operated means acting on the device to vary this range, means which move according to throttle opening and operate to render the said device capable of causing transmission ratio change to lower gear ratios only when operating above a predetermined throttle opening (preferably at or near full throttle) and means actuated by gear output speeds and serving to effect change to low gear ratios when the output speed falls below a predetermined minimum. As shown, applied to gearing described in Specification 549,988, in which gear changing is effected by actuating rotary valves 1, 2, the latter have gears 3, 4, meshing with a rack 5 fixed to a piston 6 in a cylinder 7. Fluid pressure is supplied to the valves 1, 2, and cylinder 7 from a pump 8 through pipes 63, 81, 83 respectively. The cylinder 7 has fluid pressure inlet and exhaust valves 11, 12, actuated by solenoids 15, 16. Solenoid 15 is energized only when contacts 25, 26 are closed, contact 25 being carried by a rod 23 controlled by a spring 24 and centrifugal weights 20 rotated through gearing 21 driven by the gear-box input shaft. Thus, when the engine speed reaches a predetermined maximum, the contacts 23, 26, close, the solenoid 15 is energized to open inlet valve 11 and fluid pressure acts on the piston 6 to move it downwardly and introduce a higher gear ratio. The electric circuit of solenoid 16 includes wires 52, 54, and contacts 47, 50. The latter are rotated by the driven shaft 45 of the gear-box. When the shaft 45 slows down, e.g. when stopping the vehicle, the contacts 47, 50 close, the solenoid 16 is energized, outlet valve 12 opens, and the piston 6 rises to introduce low gear. Thus every time the vehicle stops the speed gear will be in its low gear setting. The cylinder 7 may have a hand-controlled stop to prevent the piston 6 from rising completely so that, when the vehicle is stationary, the gear-box is set in an intermediate gear ratio, instead of the lowest. In parallel with the contacts 47, 50, are three contacts 25, 27, 29. Contact 29 is carried by a pivoted member 30 connected by link 31 to.a link 32 pivoted at 35 to the engine casing. Link 32 has a pin-and-slot connection with a rod 33 connected to a lever 34 pivoted at 48 and connected to the accelerator pedal 36. Lever 34 is connected by lost motion devices 37, 41 to the throttle lever 38. The arrangement is such that the contacts 27, 29 close only when the accelerator pedal is depressed beyond that necessary for full throttle opening. When this occurs, and if contact 25 engages contact 27, then solenoid 16 is energized and a lower gear results. The spring 24 is connected at one end to the link 32 so that the action of the centrifugal weights is modified by the position of the accelerator pedal. The link 32 can also be moved, independently of the pedal 36, by a hand control 40 through a wire 39, to permit automatic introduction of lower gears. To provide a neutral condition of the gear-box, a valve 60 in the pipe line 63 is connected by elements 35, 61, and spring 62 to the lever 34. The valve is closed when the pedal 36 is released, but opens during initial movement of the pedal 36 while the lost motion 41 is being taken up.