Patent GB-1437585-A (GB)
Title: Drive for propelling automotive power machines especially  combine harvesters
IPC: B60K20/00
Filed: 1974-07-05
Abstract: 1437585 Change speed control GEBR CLAAS MASCHINENFABRIK GmbH 5 July 1974 [5 July 1973] 29952/74 Heading F2D A motor-propelled machine, such as a harvester thresher, is driven through stepped ratioshift gearing having forward and reverse clutches (79, 80), preceded in series by a steplessly variable mechanical gear (not described) the speed-ratio of which is controlled only by a manual lever 3 during travel, but is shifted to its lowest output-speed setting by depression of a pedal 5 which, during the first part of its travel, cuts off the supply of engaging fluid pressure to whichever of the forward or reverse clutches is engaged, the stepless gear reverting to its previously lever-selected ratio setting when the pedal is released to re-engage the forward or reverse clutch. The pedal 5 is used like a normal clutch pedal over a first part of its travel, and clutch engagement always commences with the stepless gear in its lowest (output-speed) ratio setting. Function summary.-The lever 3 controls the stepless gear through a follow-up electrohydraulic servo. Repeated depressions and releases of the pedal 5 beyond a first stage clutchrelease point, in a second stage of pedal travel produce alternate engagements of the forward and reverse clutches (79, 80) by fluid pressure, rendered gradual by accumulators (83) having a common loading spring. Movement of the ratio shift lever 3 to an idle (minimum speed) position shown, also disengages whichever clutch is engaged, thus producing a neutral condition. A neutral start switch 30 is closed in this position to complete an engine cranking circuit. The reverse gear comprises additional stepped forward ratios shifted in travel, when the clutchlike-pedal 5 is depressed. Forward reverse clutch control 11.-Downward travel of the pedal 5 has two stages, the first releasing the engaged clutch and re-engaging that same clutch on pedal release, the second stage, indicated by increased resistance, changing alternately between the forward and reverse clutches (79, 80), which are engaged by fluid pressure supplied by a pump 40 through a passage 42, 43, 44 and selector valve 45. Depression of the pedal 5 acts through a fluid line 9, connecting master and slave cylinders 8, 10, and a piston-rod 54, Fig. 3, to rock counterclockwise, about a fixed pivot 52, a lever 51 in opposition to a spring 53. During the first stage of pedal depression the lever 51 raises a spring- supporting abutment 50, permitting supply pressure 43, 44 to exhaust through a release valve 46, causing release of the engaged clutch (79 or 80), the same clutch being gradually reengaged as the pedal is released to allow a spring 53 to return the lever 51 and re-apply the spring- load to the release valve 46. Over this stage of pedal stroke therefore the pedal 5 acts as a normal clutch pedal. During the second stage of successive pedal travels, which is indicated to the driver by considerably increased resistance, a roller 58 on a rod 56, pivoted to the pedal-rocked lever 51, engages alternately on one or other side of an acute-angled projection 61 on an alternator 59, which is rocked thereby on a fixed pivot 60 to act, through a spring-loaded toggle 65, 68, 69, to snap the forward-reverse selector valve 45 between opposite settings to engage the forward or reverse clutch (79, 80) alternately. The clutch engaged at any time is indicated to the driver by a signal lamp. The angle of the rod 56 is retained in a normal setting by a spring link 55. A neutral valve 37 is lifted against spring load 36 through a cable 34, to exhaust the clutchpressure supply line 43 at 39, thus, in effect neutralizing the gear, when the control lever 3 of the stepless gear is placed in an idle setting. Stepless gear control 1.-The manual selector lever 3 controls the stepless ratio through a cam 12 and an electrical contact 19 on a spring- loaded bellcrank follower 16, the contact cooperating with upshift and downshift contact plates 23, 24 on an insulating slide 22, forming part of a follow-up electro-hydraulic servo (not described) operating the stepless ratio control. Clockwise (rearward) movement of the selector lever 3 about a fixed pivot 2, to the idle position shown, causes a pin 33 to act through a lever 32 on the cable 34, retracting the neutral valve 37, Fig. 3, for release of the forward or reverse clutch. A roller 14 on the cam follower 16 occupies a neutral notch in the cam, and a neutral switch 30 in the engine cranking circuit is closed. The electrical contact 19 lies on the downshift strip 24, which, through an electromagnetic valve, enforces the lowest (outputspeed) ratio of the stepless gear. Forward (counterclockwise) movement of the selector lever 3 to a second position, in which the roller follower rests in a second cam notch 21, moves the contact 19 on to the insulated bridge between the down and upshift strips 24, 23, without effect on the stepless gear, but the pin 33 retreats from the cable lever 32 and the spring 36, Fig. 3, then closes the neutral valve 37, permitting engagement of the forward or reverse clutch. Further lever movement in the same direction shifts the contact 19 on to the upshift strip 23, causing upshift of the stepless gear and thence, by mechanical feed back, (not described), and cable 27, allowing a spring 26 to advance the slide 22 until the insulated bridge underlies the contact 19, terminating the upshift in a setting corresponding to that of the selector lever 3. Interconnection control.-At each f-r clutch release depression of the pedal 5, pressure in the fluid line 9 forming the master and slave cylinders 8, 10, closes a normally open switch (not shown), which acts, by means not described, on the electrical control of the stepless gear to downshift the latter to its lowest (outputspeed) ratio, irrespective of the setting of the selector lever 3, the gear being returned to the ratio set by the lever 3 when the switch is reopened on release of the pedal 5 for re-engaging the forward or reverse clutch. A further, normally closed, switch, (not shown), is included in the pressure feed line 42 to the forward-reverse clutches (79, 80), and, when closed, prevents selection of any but the lowest (output-speed) ratio of the stepless gear, and is only opened, to permit such selection, after. engaging pressure has built up in the clutch line.