Patent GB-702406-A (GB)
Title: Semi-automatic change speed gear control device
Filed: 1951-06-11
Abstract: 702,406. Controlling change-speed gearing. FIAT SOC. PER AZIONI. June 11, 1951 [June 30,1950], No. 13829/51. Class 80 (2). A semi-automatic change-speed gear control device comprises a set of selectively energized electromagnets 20, 20', Fig. 4, 34, Fig. 9 &c. and a pneumatic cylinder 22, Fig. 8, having a movable piston 35 actuating two gear shift rods 3, 4, Figs. 1, 2, and is characterized in that the electromagnets act on rockers 10, 11, 12 carried by the hubs of the change-speed gear forks 7, 8 9, so as solidly to connect the said forks with either of the two rods which are adapted to shift the forks for establishing a selected gear. As shown the two rods 3, 4 are connected by a pivoted lever 5 and urged to the inoperative position of Fig. 2 by a spring 6. The rocker members 10, 11, 12 are pivoted on the forks 7, 8, 9 and have arms such as 10<SP>1</SP>, 10", Fig. 4, which can be engaged in notches in the rods 3, 4. In the idle position of Fig. 4, the rockers 10, 11, 12 engage in notches in horizontal members 13, 14 and are thereby held from being moved axially by frictional contact of the rods 3, 4 sliding in the gear change forks 7, 8, 9. The notches in members 13, 14 prevent engagement of arms 10<SP>1</SP>, 10" &c. with rod 3 or 4 except when the gear change forks are in the idle position. Pivoted interlocking members 16, 17, Figs. 1, 5 and 6, prevent simultaneous engagement of two gears. The interlocking members 16, 17 are connected by a telescopic strut 18, whose minimum length is such that if, for example, rocker 10 has been tilted to engage arm 10<SP>1</SP> with rod 3, and interlocking member 16 accordingly turned clockwise, rocker 12 cannot be tilted without first returning rocker 10 to the horizontal position. A compression spring 19 surrounds the telescopic strut 18 and tends to return rockers 10, 12 to the horizontal neutral position. The rocker 11, which controls the engagement of reverse, can only move to engage one of its arms with a notch in selector rod 4, in which position the other arm rises beneath the adjacent ends of the interlocking members 16, 17 and thereby prevents either of interlocking members 16, 17 and rockers 10, 12 being tilted to engage the forward speeds. The rockers are tilted by the electromagnets, e.g. 20, 20<SP>1</SP>, Fig. 4, and 34, Fig. 9. When a rocker arm such as 10', 10", has been engaged with one of the notches in the rods 3, 4 and moved thereby to cause engagement of a gear, it is held in its tilted position by the arms becoming engaged above and below the horizontal members 13, 14. The rods 3, 4 are moved by compressed air from the vehicle braking system, admitted through an electromagnetic valve 23, Fig. 8, urging the piston 35 in the cylinder 22 against the action of a spring 41 to move a lever 24, Fig. 9, fast on a spindle to which is secured a threearmed cam lever 25, Fig. 2. One arm of the lever 25 engages a cam lever 26 to actuate a pneumatic valve 28. which controls the throttle of the vehicle engine in such a way that as soon as the piston 35 begins to move, the engine is throttled down to idling speed. The cam lever 26 is fast on a spindle connected to a lever 27, Fig. 9, which actuates the main clutch. Another arm of the three-armed lever 25 engages with a spring tappet 29 to move the rods 3, 4 from the inoperative position shown in Fig. 2 to the operative position, when rod 3 abuts against a stop 30. In the operative position the notches of gear-shift rods 3, 4 are in register with arms 10<SP>1</SP>, 10" &c. and any of the gear forks 7, 8, 9 can be coupled to the rods for engagement of a particular speed by exciting the corresponding electromagnet 20 &c. Further slight movement of the three-armed lever 25 compresses the spring tappet 29 and serves to break the circuit controlling the electromagnet valve 23, as described below, which thereupon cuts off the supply of compressed air and opens the cylinder 22 to the atmosphere. The piston 35 therein accordingly moves back to its original position and rods 3, 4 are similarly returned by spring 6 to the Fig. 2 position, the main clutch being re-engaged. A hydraulic dashpot, Fig. 10, (not shown), may be provided to give smooth engagement, or other similar pneumatic or electric means. The stroke of rods 3, 4 produced by the compressed air is the pre-selecting stroke, and the stroke following is the actuating stroke, when whichever gear fork 7, 8, 9 has been coupled to selector rod 3 or 4 is moved to throw in the selected gear. Disengagement of a gear can take place by repeating the cycle described above but without exciting the corresponding electromagnet 20, 20<SP>1</SP> &c. To prevent re-engagement of the main clutch before the selected gear has been fully thrown into mesh, an arm 42, Fig. 2, is provided on the three-armed lever 25, which engages with the extruding end of rod 4 until the latter has fully returned to the inoperative Fig. 2 position. The arm 42 also prevents accidental disengagement of the gears, since it locks the rods 3, 4 in the inoperative position. The gear is controlled by a lever L, Fig. 9, in a gate, this lever being the moving part of a controlling switch. The current for the electric circuit of the gear control mechanism is provided by the vehicle battery 100, Fig. 8. To engage, for example, third speed, the lever L is moved from the neutral position shown into the corresponding slot III. This connects contacts a-b and c-d. The contacts a-b close a circuit from battery 100 through the coil 33 of the electromagnetic valve 23 to earth, so that the valve is opened and compressed air is admitted to the cylinder 22. Contacts a-b extend over a short length of the switch slot, so that this circuit is only closed during the initial movement of lever L. A secondary shunt circuit is accordingly provided to keep coil 33 excited until the piston 35 has reached the end of its stroke. This circuit is comprised by a lead 105 in parallel with lead 101 and contacts e-f, closed by a lever 36 under the influence of a spring 43 when the core 37 of the electromagnetic valve is lowered on excitation of the coil 33. As the stroke of the piston 35 begins, a switch 38, Fig. 9, is closed so that contact d is connected to the battery. The switch 38 prevents any of the electromagnets 20 &c. from being excited except when the piston 35 has begun to move the selector rods 3, 4 to the operative position. On further movement of piston 35, the main clutch is put out by lever 27, the engine is throttled down to idling speed by pneumatic valve 28, and gear-shift rods 3, 4 move to the operative position. Slight further movement of the threearmed lever 25 to compress the spring tappet 29 breaks the circuit through lead 105, contacts e-f being disconnected by means of a lever 39 connected by a link 40 to the lever 24 and piston 35. Energization of the coil 33 now ceases, so that the valve 23 cuts off the supply of compressed, air to the cylinder 22 and simultaneously throws it open to the atmosphere. The piston 35 can then perform its return stroke under the action of the spring 41. During the return stroke, the selected third speed is thrown in, the corresponding arm of rocker 12 having been engaged with its notch in selector rod 3 by electromagnet 34, so that gear fork 9 is carried along by the selector rod. The main clutch is re-engaged and the valve 28 allows 'the throttle to return to manual control so that the engine speeds up, and electromagnet 34 is de-energized by the opening of switch 38. To return the gear box from third speed to neutral, the lever L is moved back to the central position and the cycle of operations is repeated, with the exception that the initial .movement of rods 3, 4 throws the third speed out of mesh, and, none of electromagnets 20, 20', 34 &c. being energized, the return movement of the selector rods does not engage a further gear ratio. The main clutch can be thrown out by holding the control lever L to the left and engaging contacts t-s-r. A safety lock is provided for the reverse gear position RM of the lever L, consisting of a bolt which must be operated prior to movement of the lever into this position and which automatically resumes its original position when the lever is brought back to neutral. Alternative remote control circuits can be provided in place of the lever L &c. if the current used is large.