Patent GB-1479486-A (GB)
Title: Drive system for a self-propelled combine-harvester
IPC: F16H3/00
Filed: 1974-06-21
Abstract: 1479486 Controlling change-speed gear CLAAS MASCHINENFABRIK GmbH Gebr 21 June 1974 [25 June 1973] 27721/74 Heading F2D In a drive system for a self-propelled machine such as a combine-harvester and comprising hydraulically operated forward and reverse clutches and a stepless variable V-belt drive gear, control of the clutches and of the variable speed gear is effected by a common selector 40 arranged that engagement and disengagement of the clutches can be effected only when the stepless gear is adjusted to its lowest drive speed setting and admission of pressure fluid to the clutches can be effected only gradually. In the described embodiment the common selector lever 40, movable in a gate 42, turns a cam disc 36 controlling the stepless gear and a valve member 5 controlling the clutches. Fig. 3 shows cross-sectional views of the valve member in its housing in three spaced planes normal to the rotational axis of the member which is shown in its neutral position in which an inlet 7 from a pump 29 is closed, ports 13, 16 leading to forward and reverse clutches 15, 18 respectively, have restricted communication with an exhaust port 10 connected by a conduit 35 with a tank 34, a port 8 connected to the pump delivery conduit 28 through a pressurizing valve 51 is connected by a passage 27 with an exhaust port 11, and ports 19, 20 connecting with pressure reservoirs 23, 24 have restricted communication with both the pump delivery conduit 28, through a conduit 30, and an exhaust port 12. To engage, say, the forward clutch 15 the lever 40 is moved to a position I determined by the gate to move the valve member slightly anticlockwise from the position shown in Fig. 3 so that restricted communication is effected between ports 7, 13, restricted communication is maintained between ports 8, 11, and ports 9, 19 and 12, 20 are interconnected. The clutch 15 and also the pressure reservoir 23 are thereby energized at a relatively low pressure determined by the valve 51 for slow forward motion. To increase speed, the lever 40 is rocked about a pivot 39 to move laterally in the gate to position II, such movement increasing the pressure determined by the valve 51 by depressing an adjusting member 50 of the valve through a link 43 and lever 44. Rapid movement of the lever to this position does not result in rapid build up of pressure in the clutch because of the capacity of the pressure reservoir 23. The lever 44 now being disengaged from a recess 47 in the disc 36, the lever 40 can be moved to position III, in which a roller 55 rests in a detent portion 54 of the disc 36, the valve passage 27 is out of register with the ports 8, 11, and the pressure supplied to the clutch is fixed at a value set by a valve 33. Should the lever 40 be released at any position just before the roller enters the detent 54 it is returned to the neutral position 0 by spring means. Movement of the lever 40 in the III-IV range causes a cam portion 53 to displace a plunger 56 and lever 60 to actuate a lever 62 with a contact pin 64 coacting with conductive plates 70, 71 in a slidable plate 69, the electric circuit so controlled governing an electromagnetic valve (not shown) which controls the hydraulic operation of the movable member 76 of the steplessly gear. Displacement of the member 76 is made proportional to that of the contact pin 64 by a feedback connection 75, 74 to the plate 69. The lever 40 is held in the III-IV range by a brake 82, 79. Selection of movement of the reverse clutch 18 and subsequent control of the mechanical gear is effected in similar manner by movement of the lever 40 in the opposite direction.