Patent GB-524711-A (GB)
Title: Improvements in and relating to control means for variable speed transmission systems
IPC: B60K31/00
Filed: 1939-02-03
Abstract: 524,711. Variable-speed gearing. PESCARA, R. P. Feb. 3, 1939, No. 3718. Convention date, Feb. 3, 1938. [Class 80 (ii)] The control of a variable speed transmission system by a servo-motor-operated change-speed gear and clutch wherein the gear ratios are automatically pre-selective and introduced by personal intervention, e.g., a pedal, is characterized by the provision of a single controlling member whereby such intervention regulates an engine fuel supply and also the operation of the clutch. As applied to a three-speed gear having parallel selector bars 1, 2 for reverse and first gears and second and third gears respectively, a shaft 11 both rotatable and movable axially is disposed perpendicular to the bars 1, 2 and provided with a pair of notched levers 15, 15<1> and an arm 12 coupled through a lost motion device with a control pedal 10. When the vehicle is at rest, a bar 17 pivoted about an axis opposite the space between the levers 15, 15<1> lies parallel to the snaft 11, a slider 19 movable along a slot 18 in the bar is drawn by a spring 24 into engagement with a housing 22 on the shaft 1, and the lever 15 is opposite an abutment 16 on the bar 17. To engage first gear, the pedal 10 is depressed first disengaging the clutch through a lever 37 and then rocking the arm 12 to rotate the shaft 11 whereupon the lever 15 engages the abutment 16 turning the bar 17 anticlockwise to move the shaft 1 to engage the gear. As the bar 17 moves an incline 29 on one end thereof engages a rocker arm 30 to compress a spring 32 engaging the end of the shaft 11. On release of the pedal 10, a spring 27 returns the shaft 11 to its former position and as soon as the lever 15 leaves the abutment 16, the spring 32 displaces the shaft 11 axially bringing the lever 15 opposite a second abutment 16<1> on the bar 17. If now the speed of the vehicle justifies a change to second gear, a centrifugally closed switch 26 closes and permits a battery A to energize an electro-magnet 23 mounted on the bar 17 with its armature connected to the slider 19. The next depression of the pedal 10 engages the lever 15<1> with the abutment 16<1>, swinging the bar 17 clockwise and displacing the selector bar 1 to the neutral position whereupon the slider, under the influence of the magnet 23, traverses the slot 18 to engage a housing 22<1> on the other selector bar 2 and, as the bar 17 continues to swing round, the slider 19 moves the selector bar 2 into the " second gear position. During this movement of the bar 17, the incline 29 does not contact with the rocker arm 30 and the spring 32 is inactive, permitting another spring 28 to pull the shaft 11 to its first position as soon as the lever 15<1> clears the abutment 16<1> on release of the pedal 10. Provided the speed is sufficient to keep the switch 26 closed, the slider 19 remains in engagement with the housing 22<1> on the selector bar 2 and the next depression of the pedal 10 swings the bar 17 anticlockwise to engage the third gear, the spring 32 being compressed on this movement to operate as previously described. Successive operations of the pedal 10 will alternatively engage second and third gears as long as the speed is sufficient to keep the switch 26 closed, but if the speed falls below this value, the slider 19 will be drawn by its spring 24 to engage the other selector bar 1 and first gear will be engaged. While the speed remains below this value, successive depressions of the pedal 10 would alternately engage first and reverse gears but a spring-pressed detent 33 prevents engagement of the latter until a separate additional operation has been performed to free the detent. The pedal 10 is actuated by a servo motor system controlled by movement of the acceleration pedal which comprises a plate 36 adapted to be rocked about a pivot 41, depression of the upper part of the plate opening the carburetter throttle and movement in the opposite direction opening a valve D connected to it by a rod 39. The valve D exposes to engine suction a servomotor S operating the clutch lever 37 to release the clutch and let the vehicle " freewheel." This releasing movement of the clutch lever 37 closes a master switch 45 and permits further movement of the accelerator by closing a pair of contacts 43, to complete the circuit of a solenoid 40 which actuates a valve D<1> controlling a second servo-motor S' operating the gear-change lever 12. The circuit of the electro-magnet 23 branches from this circuit. To give the slider time to move from one selector bar to the other, rotation of the shaft 11 is checked intermediately by interrupting the circuit to the solenoid 40. The solenoid 40 attracts a valve 46, Fig. 2, normally exposing the servo-motor S<1> to the atmosphere, to expose that motor to engine suction and is energized through parallel circuits 47, 47<1> including respectively switches 48, 48<1>. Normally, the switch 48 is closed and the switch 48<1> open. When the selector bars 1, 2 are both in the neutral position and the slider is, in consequence, free to move across them, a projection 49 on the piston rod of the servo-motor S' opens the switch 48 de-energizing the solenoid 40 and exposing the servo-motor S<1> to the atmosphere. Opening the switch 48 depresses a tappet 54 engaging a spring 53 seated at its opposite end on a piston rod 52 forming part of a dash-pot 50 and the piston ; after a predetermined delay closes the switch 48<1> to re-energize the solenoid and continue the action of the servo-motor, whereupon the switch 48 closes as soon as the projection 49 clears it. To permit engagement of the second speed if, while the third speed is engaged the vehicle speed drops below that at which the electromagnet 23 is energized, a centrifugal switch is shunted by a circuit 60 including a switch 61 normally held closed as long as third gear is engaged but opened by a dashpot, similar to the dashpot 50, actuated by the bar 2 when the bar has been moved to its neutral position, the opening being delayed to give the bar time to pass from the neutral position before it occurs. The device is then ready for engagement of the first gear in the ordinary way. The reverse gear catch 33 may be held open to permit successive operations of the control alternately to engage first and reverse gears.