Patent GB-658212-A (GB)
Title: Improvements relating to overload control of the clutch of an agricultural tractor
Inventor: MERRITT HENRY EDWARD
IPC: A01B67/00
Filed: 1949-03-24
Abstract: 658,212. Controlling tractors. WOLSLEY MOTORS, Ltd. March 24, 1949, No. 8010. [Class 79 (v)] [Also in Group XXXII] In an agricultural tractor the clutch is controlled by overload by the provision of a draw bar frame coupled at its front end to the belly of the tractor by a single point hitch constituted by a yoke which is journalled in a pair of supports on the tractor, one of which is constituted by a pivoted lever which is normally restrained by movement in the fore and aft direction by a device which, when the draw pull is excessive, yields with a snap action to cause the tripping of a preset mechanism which releases the clutch and holds it disengaged. As shown in Fig 2 the draw bar frame comprises a longitudinal member 1 and rearwardly branching members 2, which members 2 are interconnected by a transverse beam 8, a cross bar 6 and a quadrant 3. The beam 8 carries pins 9 for the attachment of an implement and abutments 10 which bear against plates 11 secured to the rear axle casing 13 of the tractor and prevent lateral swaying of the frame. The cross bar 6 pivotally carries the draw bar 4 proper which can be locked in the desired position by pins in the quadrant 3. The members 2 carry pins 15 which either are connected by links to the hydraulic power lift if fitted on the tractor or, as shown, are connected by links 14 to pins 16 on the tractor to facilitate height adjustment of the draw bar frame. At its front end the member 1 carries a bolt 19 which is pivotally attached to a yoke 20. One end 21 of the yoke is pivotally carried in a bracket 22 secured to the belly of the tractor, whilst the other end of the yoke is carried in a horizontal slot in a bracket 24 and is pivotally connected to one arm of a lever 25 pivoted at 26 on the bracket 24. The other arm of the lever 25 is connected by a clevis 28 to a rod 27, downward movement of which rod due to the draft load is resisted by a detent mechanism of the wedging ball type. The rod 27 has a bobbin 29 which is formed by a bevelled shoulder 31 engaged by a ring of balls 32. The balls are retained between a fixed abutment 33 and a spring loaded abutment 35. Immediately the draft load exceeds the predetermined amount, the yoke 20 rocks about the end 21, the other end moving in the slot in the bracket 24, thus causing anticlockwise movement of the lever 25, downward movement of the rod 27 and outward movement of the balls 32. Such rotation of the lever 25 also causes rotation of a lever 38, pivoted at 26, through the pin in the clevis 28 passing through a slot in the lever 38. The lever 38 carries a cam 41 which during the rotation of the lever engages a roller 42 carried on a lever 43 which when deflected by the cam 41, trips a preset clutch controlling mechanism shown as being in accordance with that in Specification 658,201. When the overload release mechanism has operated, reverse gear has to be engaged and the clutch re-engaged by a hand lever (not shown) to back the tractor in order to free the implement.