Patent GB-815373-A (GB)
Title: Improvements in or relating to shift devices for change-speed gears for motor vehicles
IPC: F16H1/30
Filed: 1955-11-25
Abstract: 815,373. Change-speed control. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. Nov. 25, 1955 [Nov. 27, 1954], No. 33929/55. Class 80 (2). [Also in Group XXIX] Change-speed gearing shift mechanism comprises a control tube 1, rotated by hand operation of a lever 3 to select a two-ratio channel and slidden axially, to establish either of the two selected ratios,. by a compressed-air follow-up servo mechanism. A striker fork 2 is fast with the control tube 1, and a hand-operated lever 3 co-operates with an arm 4 fast on a control rod 5. The control rod passes through the control tube 1 and is connected to rotate therewith by a flanged coupling member 6, fast on its end, having axially projecting claws interdigating with corresponding claws on the tube 1, a snap ring 7 on the flanged member 6 co-operating with a circumferential groove 40 in the tube to allow limited axial lost motion between the tube 1 and rod- 5. Plungers 19, 20, 191, 201 pass through holes in the tube 1 to engage at their inner ends in recesses 23, 24, 231, 241 in the rod 1, the recesses 23, 24 being axially offset along the rod 5, relative to the recesses 231, 241, by an amount equal to half the lost motion permitted by the coupling 6 &c. between the tube 1 and rod 5. At the outside of the tube 1, the plungers 19 &c. abut two semicylindrical plates 18, 18<SP>1</SP> in turn abutted by flat plates 16 formed as parts of valves 14 spring biased to the open positions shown. A piston 8 fast with the rod 1 lies in a cylinder formed in a stationary casing 9, the spaces 27, 28 on the opposite sides of the piston communicating with the valves 14 through conduits 33, 26 and thence with the atmosphere. To change from the position shown, when the striker fork 2 &c. is at the left-hand end of its travel and a ratio has been established, the hand-operated lever 3 is moved slightly to slide the control rod 5 to the right and take up the lost motion between it and the tube 1. This movement serves to force the plungers 19, 20 out of their recesses and thereby close the upper valve 14. Closure of this valve 14 simultaneously opens a valve 13, so that compressed air is admitted through an orifice 12 and the conduits 33 to the space 27 at the left of the piston 8, which is thus moved to the right and with the control tube 1 &c. follows the movement of the rod 1. The plungers 19<SP>1</SP>, 20<SP>1</SP>are not forced outwardly by the sliding of the control rod 5, the width of their cooperating recesses 23<SP>1</SP>, 24<SP>1</SP> allowing the described relative axial motion between the tube and rod to occur without closing the lower valve 14 &c. so that the space 28 to the right of the piston 8 remains in communication with the atmosphere through the conduit 26. Continued movement of the control rod 1 towards its central, or neutral, position keeps the valve 13 open, so that the control tube 1, fork 2, &c., follow its motion. The handle 3 ultimately reaches its neutral position and its movement is stopped. The control rod 5 correspondingly stops, and the tube 1 &c. continues momentarily to slide rightwards relatively thereto until the plungers 19, 20 re-enter their recesses 23, 24, the valve 13 closes and the upper valve 14 opens to reconnect the cylinder space 27 with the atmosphere. A spring-biased ball detent, Fig. 8 (not shown), in the stem of the striker fork 2 and in a radial hole in the tube 1 co-operates with a recess in the control rod 5 to. maintain the striker fork 2 in the neutral position. If the control rod 5 is slidden further to the right to engage another ratio, the same sequence of events as above described is performed to obtain compressed air actuation of the piston 8 &c. If the control rod 5 is slidden to the left relatively to the tube 1 when in the neutral position, to restore the position shown in Fig. 1, the plungers 19<SP>1</SP>, 20<SP>1</SP> are forced out of their recesses to close the lower valve 14 and supply compressed air to the space 28 on the right of the piston 8, the plungers 19, 20 this time not being moved radially and the upper valve 14 thus remaining open. In the neutral position, the control tube 1 &c. can readily be rotated on its own axis by operation of the hand lever 3 to select a new ratio channel, e.g. from the Fig. 2 to the Fig. 3 position. If the supply of compressed air fails or the like, direct mechanical connection between the flange member 6 and control tube 1, after the lost motion has been taken up, allows the tube 1 to be slidden axial to establish the selected gear ratio by hand operation of the lever 3.