GB614428A - Improvements in change speed gear transmission controls - Google Patents

Abstract

614,428. Change-speed control. TRIGGS, W. W. (Carter Carburetor Corporation). March 7, 1946, No. 7096. [Class 80 (ii)] [Also in Group XXXVII] In a change-speed gear in which an automatic shift is made in response to engine speed and a further shift in response to movements of the engine throttle to a predetermined position, a control device responsive to a predetermined suction in the fluid intake of the engine renders the further shift means ineffective. As applied to the transmission of a motor vehicle in which an engine 11 drives a propeller shaft 16 through a gear-box 14 and a solenoidoperated overdrive 15, the latter being arranged to be thrown out on full depression of the throttle pedal 25, the carburetter 12 has attached thereto a switch 20 which prevents the completion of the battery circuit to the solenoid 17 when the engine suction and hence vehicle speed exceeds a predetermined figure. The switch 20 has two hollow legs 31, 32, the leg 31 receiving a cup-shaped piston 33 normally urged downwards by a spring 34 and acted upon by engine suction through a port 36 connecting with the venturi 37. Secured to the base of the piston is a spring contact 38 normally slightly spaced from the contact 23 which is insulated from the body 30 and connected to the solenoid 17. The other leg 32 has a slidable plunger 40 and collared pin 42 acted upon by the spring 45 to normally retract the plunger 40, and by the spring 44 to extend the plunger when the pin 42 is contacted by an arm 57 attached to the throttle spindle 51. The differential action of the springs 44, 45 limits the contact pressure when the pin 42 is depressed by the arm 57 and the depression above the piston 31 is insufficient to raise the piston and its contact 38. If the vehicle speed is above the predetermined figure the contact 38 will be withdrawn from the position suitable for contacting the contact 23 and the shift to a lower gear will not then take place automatically until the depression is insufficient to move the piston and the throttle has again been operated under such conditions. Several modifications to the shape of the contacts, such as a spring-loaded disc and a free ball, are also described.