Patent GB-631665-A (GB)
Title: Automatic device for changing the gear ratio in machines comprising a change-speed gear and facilitating the control of several coupled machines from a single control lever
IPC: B61C17/12
Filed: 1946-06-28
Abstract: 631,665. Controlling change-speed gearing. REGIE NATIONALE DES USINES RENAULT. June 28, 1946, Nos. 19442 and 19443. Convention dates, April 1, 1943 and April 30, 1943. [Class 80 (ii)] In a change-speed gear control system for two or more gearboxes controlled from a single station by interconnected wires, and where the change of gear is made by the engagement of dogs or clutches, the gear changing operations are initiated by a servopilot which only allows changing after previous synchronisation of the gears. Fig. 1 shows the invention applied to one unit of a series of vehicles each driven by an engine through a sliding wheel variable-speed gear and a main clutch, the gears and the clutch being operated by electropneumatic servo-motors. A servo-pilot drum 1 is rotated in either direction by an electric motor 3, energisation of which is provided from the main supply wires 6, 10 on the drum, and thence appropriately to the contact makers 7 or 8 which control the forward and reverse rotations of the motor 3. The drum 1 is positively located in each postion corresponding to 0, neutral, I<1> starting from rest, I, first gear II, second gear ... &c., by a solenoid controlled arm 17 having a detent which locks into the recesses 15 of a disc 14 attached to the drum. Movement of the switch 4 from O to I<1> positions energises the contact maker 7 and the drum 1 rotates to the I<1> position, thereby allowing current to flow through the wire 37, brush 36 and the plate 35 to brush 38 for the electro-valve 42 which operates the engagement of the first gear. The other side of this valve is connected to one segment 50 of a synchronisation indicating device, such as is described in Specification number 612,230, which has a moving arm 54 which occupies the positions 50, 51, 52, 53 when the primary and secondary shafts of the gearbox are synchronised relative to the respective gear ratios, the arm 54 being connected with the main supply 26. The alternate segments 66, 67, 68, 69 are connected through . the plates 56, 57 on the drum 1 with the members 58, 59 which control the speed of the engine independently of the manual engine speed control. The main clutch is actuated by compressed air supplied to the cylinder 70 through either the electrovalve 72 for slow engagement or the valves 72, 73 combined for fast engagement, these valves being energised respectively by the contact makers 74, 75. When the contact maker 7 is excited the contact 34 is broken, causing de-energisation, and therefore closing, of the contact maker 74 and consequent de-clutching, the circuit being completed by the wires 77, 81 which are connected by the contact 79 actuated, as are similar contacts 80a, 80b, 80c, by the controls of the sliding wheels of the variable speed gear. When the servo-pilot drum stops, the contact 34 closes and the clutch is engaged slowly. Movement of the control 4 to initiate an upward or downward change in ratio, once the I<1> position has been passed, results in the respective contact maker 7 or 8 being energised to rotate the drum to the corresponding gear position and to break the contact 33 or 34 to de-clutch. While the drum is rotating, the circuit of the plate 35 and the energised electro-valve 42, 43, 44, or 45 is broken, thus the sliding gears return to the neutral position and the circuit 82, which is broken when an electro-valve is engaged, is again completed. Stoppage of the drum and consequent de-energisation of the appropriate contact maker 7 or 8 results in completion of the circuit of the contact maker 75 through contacts 33 or 34, the wire 82, the plate 85 and the return wire 123, and rapid clutch engagement by the opening of the contacts 83, 84 which de-energise the electro-valves 72, 73. At this instant the synchronising operation takes place by the arm 54 being clockwise or anticlockwise of the respective segment 50, 51, 52, or 53 in which case the engine is accelerated or retarded by the members 58 or 59 respectively. The control of the engine by member 58 is described below. When synchronism is obtained, the circuit of the appropriate electro-valve 42, 43, 44 or 45 is energised to shift the gear and at the same time breaks the circuit 82 thus causing a second disengagement of the clutch by the de-energisation of the circuit maker 75. The sliding wheel of the selected gear moves into engagement and thereby re-establishes the circuit of the contact maker 75 through one of the contacts 80a, 80b, 80c, causing a rapid clutch engagement. Thus a cycle of clutch withdrawal, gear disengagement, clutch engagement speed synchronisation, clutch withdrawal, gear engagement, and clutch engagement takes place, the speed control of the engine having been controlled independently of the manual control during the cycle. The engine speed control is operated by a compressed air servo motor 86 fed from a main 92 which supplies air, at a pressure determined by the driver, through an electro-valve 91. For overriding the driver's control to decelerate the engine, the valve 91 is energised to open the servo motor cylinder 86 to a pressure limiting device 93, the valve being connected so that automatic speed reduction is obtained when either the gear or the position of the servo-pilot is changed, for all positions of the latter except when in the O and I<1> positions. For accelerating the engine independently of the driver's control, the member 58 comprising an electro-valve 90 and a servo-motor 89 is connected in parallel with the servo-motor 86 to the speed control of the engine. When it is desired to synchronise several engines with one another, a synchronising relay 102 is connected in parallel with the electro-valve 90 so that synchronisation takes place at each declutching and also when the gears are in neutral. Testing of the control may be carried out after manual energisation of the contact maker 160 which short circuits the synchronisation indicating device. In a modification as shown in Fig. 2, which represents a part of the arrangement shown in Fig. 1, the electro-valves 42, 43, 44, 45 are replaced by double contact makers 104, 105, 106, 107, which first break the return circuit 75<1> and then, after a pre-determined period, the contact 108, 109, 110, or 111 controlling the gear engaging servo-motor. A contact maker 112 is provided to override the slow engagement of the clutch to produce rapid engagement over the last part of the slow-engagement period and to provide rapid engagement when changing down into first gear. To enable clutch engagement to be controlled manually when desired, a contact maker 117 may be added to the circuit. The modification shown in Fig. 2 also provides means whereby the first servopilot of the several machines to reach the P position energises the contact maker 104 of each machine to ensure simultaneous first gear and slow clutch engagement when starting from rest. The manual control, or its equivalent, may be of the drum or sliding contact type or may comprise a lever, oscillatably mounted on a shaft which it can turn, working in a gate which has a catch to prevent changing down to first gear without the use of the synchronising device and to prevent rapid engagement of the clutch when starting. Other modifications are shown in which a six-speed machine, having a two ratio planetary gear followed by a variable speed gear in which the gear engagement is effected by individual clutches, is similarly controlled from an external control means linked thereto electrically. This type of variable speed gear may also be connected to operate in parallel with the sliding gear arrangement described with reference to Figs. 1 and 2. Specification 620,047 also is referred to.