Patent GB-446397-A (GB)
Title: Improvements in gear shifting mechanism
Filed: 1935-08-30
Abstract: 446,397. Controlling change speed gearing. BENDIX - WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO., 5001, Centre Avenue, Pittsburg, U.S.A.-(Assignees of Eaton, W. A. ; 5001, Centre Avenue, Pittsburg, and Sanford, R. S. ; 33, West 55th Street, New York, both in U.S.A.) Aug. 30, 1935; No. 24280. Convention date, Sept. 10, 1934. [Classes 80 (ii) and 80 (iii)] Pre-selective gear-changing mechanism comprises a plurality of shift bars 11, 12, 13, Fig. 1, and a pre-selecting valve device. 24 adapted to be operated step by step so as to supply pressure fluid in instalments under stepped increments of pressure to an integrating control device 17 which is held against movement until an executive control such as a main clutch releasing pedal 36 is operated, whereupon the said control device carries the pre-selected speed-change into effect. At each stepped displacement of a hand lever 25, an instalment of air is admitted from a reservoir 38 to the valve device 24 whence, when its pressure has risen by a definite increment, it is allowed to pass by a duct 26 to a chamber behind a piston 27. The rod 89, Fig. 3, of the piston 27 is held by a detent 30 so that the definite increment of pressure, say 15 lbs. per sq. in., builds up behind the piston 27 and remains so. The sum of these built-up pressures can never exceed the pressure in the reservoir 38. The integrating rod 89, which carries multiple cams 63-70, is held by the detent 30 until the detent is released by the act of depressing the clutch pedal 36, whereupon the rod 89 moves a step to operate the integrating device 17. The device 17 comprises four similar valves 18, 19, 20, and 21, Fig. 1, arranged in opposing pairs. The pair 20, 21 operate a double-acting selector servomotor 14 and they do so directly. This motor turns a main selector bar 9 so that a selector finger 129, Fig. 5, engages the shift bars 11, 12, 13, selectively. The pair 18, 19, Fig. 1, operate an executive servomotor 15 and they do it indirectly through a relay motor 22 and a follow-up valve 23. The pressure air for these motors 14, 15, and 22 is derived from a second reservoir 16. The executive servomotor 15 slides the bar 9 one way or the other so as to carry with it the shift bar 11 &c. engaged by the finger 129. The bar 11 is for reverse, the bar 12 for third and fourth speeds, the bar 13 for first and second. The integrating control 17 operates both the selector motor 14 and the executive motor 15 because of the arrangement of the cams 63-70 on the integrating bar 89. Each step of the preselector lever 25, Fig. 2, turns a hollow shaft 55 which by a helical cam 61 and a slip joint 62 causes the abutment 54 of a spring 53 to move down one step corresponding to a definite increment in spring tension. The spring 53 through a cone 57 thrusts down a beam 58. A spring 51 yields first to close an exhaust valve 45 and then series springs 48, 49 yield to open a valve 47 which admits air from the reservoir 38 through a pipe 39 and into a chamber 41 under a diaphragm 52. Air keeps entering the chamber 41 and passing along the pipe 26 to behind the piston 27 until its pressure builds up to about 15 Ibs. when the thrust on the diaphragm 52 compresses the spring 53 to its initial length, and the beam 58 rises to shut the valve 47. The parts remain so until the pedal 36, Fig. 1, is depressed, whereupon air passes from the reservoir 38 past an opened valve 37, then on through a pipe 33 to a clutch disengaging motor 34 and also on through a pipe 331 to under the piston of the detent 30, so freeing the integrating cam bar 89. The cams are set so as first to open one of the valve pair 20, 21 of the selector motor 14, and afterwards to open one of the valve pair 18, 19 controlling the executive motor 15. The construction of distributing valve is shown at 19, Fig. 3. When a cam 63 thrusts down a ball 88 and a hollow stem 75, an exhaust valve 86 is closed and an intake valve 84 is opened thereby connecting an intake manifold 80 to an outlet pipe which is either of the pipes 124a or 124b, Fig. 1, leading to one end or other of the selector motor 14. Another cam on the bar 89, Fig. 3, opens either valve 18 or valve 19 so that pressure air passes by pipe 22a or pipe 22b to one end or other of the relay 22, Fig. 1. This relay operates the follow-up valve 23 by which pressure air fresh from the reservoir 16 is passed through the pipe 134 or the pipe 135 to one end or the other of the executive motor 15 to carry the selected gear change into effect. Means are provided to prevent pressure air reaching the manifold 80 from the reservoir 16 unless the main selector bar 9 is in neutral. When this is the case, a swell 105, Fig. 5, on the bar 9 opens a valve 106 which allows air from the reservoir 16 to pass by pipes 107, 108 to above a piston 104 which is thrust down of Fig. 3 and by an end cam 110 centres a ring 90 fitting frictionally on the bar 89. By a pin 92, a slide valve 91 is thus centred in the position shown whereby a pipe 95 leading from the reservoir 16 communicates through passages 94, 96, and 97 with the manifold 80. If the main bar 9 is not in neutral, the slide valve 91 is displaced so that the manifold pipe 97 is exhausted at 98. In making a gear change, the handle 25 is turned and the pedal 36 depressed. The pairs of valves 18, 19 and 20, 21 of the integrating device 17 make exhaustions which allow the selector and relay motors 14, 22 to be spring-centred in mid position, the executive motor 15 following to neutral, so that the neutralizing cam 105 can act to admit pressure air to the manifold 80 to effect the next change. The follow-up valve 23 is intended to get an accurate control of the executive motor 15. A pair of similar valves 139, 140, Fig. 6, are housed in a casing 141 rigid with the main selector bar 9, as shown in Fig. 5. The rod 138 of the piston 137 of the relay 22 is jointed to a lever 161 rigid with a rocking pin 160 which carries a cross arm 158 with two screws 157 engaging the two valves 139, 140, respectively. Thus a slight displacement of the rod 138 depresses one or other of these valves. When by a rightward displacement the valve 139 is depressed, an exhaust valve 155 is closed and an inlet valve 151 opened so that pressure air from the reservoir 16 entering by a pipe 144 to a passage 150 passes up into a chamber 145 below the piston 139 and through a pipe 135 at the back of the arrangement of Fig. 6 and shown in Fig. 5 to the left end of the motor 15, as shown in Fig. 1. The main selector bar 9 is therefore displaced to the right, following the rod 138, and this displacement rocks back the pin 160 and cross arm 158 so as to lap the valves shutting off the chamber 150. During this movement, the right end of the motor 15 is exhausted through a pipe 134, a chamber 145<1> below the valve 140, past an exhaust valve 155<1> and through vents 1471, 149<1>. Thus the main selector bar 9 follows the relay rod 138 accurately in both directions, centring springs 139a, Fig. 1, of the relay 22 serving always to bring the bar 9 to neutral.