Patent GB-677715-A (GB)
Title: Improvements in or relating to power transmissions and controls therefor
IPC: F16H61/02
Filed: 1948-02-18
Abstract: 677,715. Change-speed control. BARNES, W. B., and BARNES, F. A., (trading as BARNES MOTOR DEVELOPMENTS CO.). Feb. 18, 1948 [July 22, 1940No. 4751/48. Class 80 (ii). A motor vehicle change-speed gear has one speed ratio which is established by the engagement under fluid pressure means of relatively movable positively interengaging elements and another speed ratio which is automatically established, upon disengagement of the elements by separate means rendered effective through momentary, engine torque interruption controlled by vehicle accelerator operation, at least one ot the element moving means being under speed-responsive control. As applied to an auxiliary kickdown overdrive 1, Fig. 1, behind a normal three-speed and reverse main transmission 2, a planetary step-up gear has a driving planet carrier 18 connected to the output shaft 5 of the transmission 2, a driven annulus 16 connected to a shaft 11 powering the vehicle propeller shaft, and a reaction sun 19 on a sleeve 20 which is axially movable to bring teeth 21 thereon into mesh either with fixed teeth 22 to establish an overdrive or with teeth 24 on the carrier 18 for a two-way direct drive. When the teeth 21 are free of both the teeth 22 and 24, an overrunning direct drive is automatically brought in by a one-way roller clutch 15 between the carrier 18 and annulus 16. The sleeve 20 is slidden to the left to engage the teeth 21, 22 by engine suction acting in a fluid pressure motor cylinder 48 on a piston 49 connected by a crank linkage 51, 52 with a disc 46 on the sleeve 20, and to the right to disengage the teeth 21 from the teeth 22 by a spring 55 in the cylinder 48 and by a spring 88 acting directly on the disc 46. The sleeve 20 is normally prevented from moving far enough to the right to cause the teeth 21, 24 to interengage, by a linkage 43, Fig. 3, connected by a rod 45 to the disc 46 and detained by an arm 42 on one end of a cross shaft 41 before the teeth 21, 24 interengage. To allow the spring 88 to establish the two-way direct drive, the shaft 41 is rotated by a linkage comprising an arm 33, Fig. 2, on the other end of the shaft and having a pin 35 engaging a slotted link 32 pivoted to the low speed and reverse shift lever 30 of the transmission 2. The shaft 41 may be so rotated, against the pressure of a spring 36 normally retaining it by re-acting between a collar 40 on a rod 37 and the arm 33, either by the anticlockwise rotation of the lever 30 to engage reverse gear in the transmission 2, or by pulling a preferably dash-mounted handle 38<SP>111</SP> to rotate a bell-crank 38 pivotally connected to the rod 37, which has a lost motion connection with the arm 33. The slotting of the link 32 allows engagement of low speed in the transmission 2 without affecting the shaft 41. To enable the sleeve 20 to move to the right to engage the teeth 21 with the teeth 24, the piston 49 has a limited lest motion connection to its rod. Admission of engine suction from a conduit 66 to the cylinder 48 is controlled by a valve 67, working in a chamber connected to the cylinder by suitable ports, and which, in its left hand position, blocks off the conduit 66 from the chamber and also vents the cylinder 48 via passages illustrated in detail in Fig. 5 (not shown), and in its right hand position opens the conduit 66 to the cylinder and prevents venting thereof. The valve 67 is controlled by a solenoid 58 which, when energized, draws a core 61 rigid with the valve 67 to the right. The consequent movement under suction of the piston 49 to the left inserts a second core 59 on the rod 50 into the solenoid 58 and renders it effective enough to hold the valve 67 to the right despite a reduction in engine suction. With the solenoid 58 de-energized, the valve 67 is held to the left by engine suction. To prevent clashing of the teeth 21, 22, a frictionally operated blocking ring 200 is provided having axial tails passing through the disc 46 and shouldered to co-act therewith, and prevent advance thereof to engage the teeth 21 with the teeth 22, until the sun 19 changes its direction of rotation. Operation-Positioned in the cylinder 48 is an insulated disc 69 on which are mounted normally spring-closed switch contacts 73, Fig. 9, opened by an insulated push-piece on the rod 50 when the latter is moved to the left, and normally spring-opened switch contacts 70 similarly closed by the piston 49. The solenoid 58 is connected to earth by simultaneous closing of switches 79, 80 and, when the vehicle ignition switch 82 is closed, may be connected in parallel with the engine ignition circuit 84, 85 to an earthed battery 83 either through a switch 81 or through one or other of the switches 70, 73. The switch 79 is operated by the second and third speed shift lever 27, Fig. 2, of the transmission 2, the arrangement being such that the switch is closed only when third speed is engaged and may even at such times be opened by all extension 38' of the bell-crank 38 when the handle 38<SP>111</SP> is pulled. The switch 80 is operated by a governor responsive to the speed of the vehicle or of the shafts 5 or 11, so that it respectively closes and opens above and below a predetermined speed thereof when, with the transmission 2 in third speed, overdrive and. direct drive respectively are normally established by consequent energization and de-energization of the solenoid 58. Kickdown into direct drive in the auxiliary transmission at overdrive speeds is effected by depression of the vehicle accelerator pedal 86 beyond its normal full throttle position to open the switch 81 when, provided the engine suction is sufficiently reduced to have allowed the piston 49 to move to the right relative 'to its rod 50 sufficiently to open the contacts 70, the solenoid 58 will be deenergized and the ignition circuit 84, 85 will be cut off in order to release the torque load on the teeth 21, 22 to allow them to disengage. Im-. mediately the piston rod 50 moves to the right sufficiently to allow the contacts 73 to close, the ignition circuit is again completed. The solenoid 58 having been re-energized independently of the switch 81. by the closing of the contacts 73, overdrive may be re-established when required by releasing the pedal 86 until the suction on the piston 49 supplements the solenoid pull sufficiently to move the' sleeve 20. In a modification, Fig. 11 (not shown), the fluid pressure motor is replaced by a solenoid having mul-. tiple windings, the electrical control circuit being appropriately modified and including also a holding coil circuit having both a mechanically operated cut-out switch replacing the fully mechanical interlock with the main transmission, and an engine-suction operated cut-out switch to ensure synchronous engagement of the teeth 21, 24. Momentary ignition interruption for torque release is here effected by temporary completion of a distributor shorting circuit. In a further modification, a simple engine-suction operated fluid pressure motor 123, Fig. 18, acts, to engage overdrive, directly through a bell crank 129 on a helically toothed coupling sleeve (not shown) slidable on the sun gear and having a blocking ring in frictional engagement with the transmission housing and co-acting with the helical teeth, the conduit 131 from the engine inlet manifold to the motor having interposed therein a speed-responsive valve comprising a casing 132, Fig. 17, mounted on the vehicle engine block and receiving a shaft 136 rotatable, against the bias of a torsion spring 138 and under the pressure of the engine cooling fan slipstream (acting as a function of vehicle speed) on a paddle 137, to cause the establishment of overdrive above a predetermined vehicle speed by the rotation of a valve member 140 so that a groove 140<SP>1</SP> therein interconnects two parallel passages such as 133 respectively communicating with the two parts of the conduit 131. The member 140 is rotatably mounted on the shaft 136 and is actuated therefrom through a device consisting of a hub 144 loose on the shaft 136 and having a pin 143 located between two spaced arms (not shown) on the member 140 and acted on by a spring 147 via a hooked link 146 so that the hub 144 has a snap-over action when sufficiently rotated in either direction by one or other of two spaced arms (not shown) on a collar 150 fast on the shaft 136. With the overdrive engaged the bell crank 129 closes switch contacts 154 so that on overtravel of the accelerator pedal 86 past full throttle position to close a switch 165 the engine circuit breaker 162 is shorted by earthing of the primary coil 163, the consequent torque release allowing direct drive re-engagement as the suction in the motor 123 is too low under open throttle conditions to be effective. Overdrive engagement is, however, prevented at undesirably high speeds by the opening of normally closed switch contacts 155, the bridging lever 158 of which is at such times forced away by one of the arms of the collar 150 pressing thereon. In Fig. 21 (not shown) the control arrangement of Figs. 17 and 18 is employed in conjunction with a positive dog sliding radially in the transmission housing to co-act with teeth on a sleeve secured to the sun gear to bring in the overdrive, the sleeve being provided with a frictionally operated blocking ring to prevent dog engagement until the sun gear changes its direction of rotation, and there being a spring lostmotion device between the dog and the fluidpressure motor to store the movement of the motor until the dog can follow it. A dog of this nature can be used with the electromagnetic control system of Fig. 11. In Figs. 24, 25 (not shown), a further control system for use with the mechanical actuating mechanisms of Figs. 1, 18 or 21 comprises a fluid pressure motor in the form of a piston slidable in a cylinder connectible to the engine inlet ma