GB650387A - Improvements in or relating to controlling agricultural tractors - Google Patents

Abstract

650,387. Operating clutches. ZBROJOVKA BRNO, NARODNI PODNIK, April 19, 1948, No. 10804. Convention date, June 27, 1947. [Class 80(ii)] [Also in Groups XXIX and XXXI] In an agricultural tractor hauling an implement which is raised out of and lowered into its operative position by a hydraulic device any resistance to the operative movement of the implement is transmitted to the main cylinder of the hydraulic device and any increase in the resistance due for example to an obstruction causes an increase of pressure in the cylinder which sets into operation a mechanism to disengage the clutch of the tractor engine and re-engagement of the clutch is dependent upon the engagement of the reverse drive of the tractor. In the embodiment shown, when the implement meets an obstruction the pressure of liquid in the main cylinder 1 is increased as the implement is connected by a rod 4 to the piston 3 within the cylinder. The excess pressure forces a piston 6 in a cylinder 5 to the left against a spring 7 thus allowing liquid to flow through ports 8, 9 into a subsidiary cylinder 10, the port 8 being closed by the piston 6 through the action of the spring 7 on the pressure being equalized. The liquid in the cylinder 10 forces a piston 11 to the left against the action of a spring .12 and a rod 17 connected to the piston 11 rotates a twoarmed lever 18 about its pivot 19 in an anticlockwise direction. This rotation causes disengagement of the clutch through a rod 20, a pedal 21 and rod 22. The piston 11 stays in this position with the clutch disengaged since escape of the liquid from the cylinder 10 through ports 13, 16 is prevented by the position of a piston 15. Movement of the piston 15 can either be effected directly by engaging the reverse drive on the tractor or can be preceded by engagement of the reverse drive and effected by a hand lever 28 which controls the hydraulic device for raising or lowering the implement. The piston 15 which is urged to the left by a spring 24 is connected directly by a rod 42 to a member 40 slidable on a fork 37 of the change-speed gear so that movement of the fork 37 in the direction of the arrow by the change-speed gear lever 35 moves the member 40 and the piston 15 to the right, thus opening the cylinder 10 to the exhaust port 16. The piston 15 is alternatively connected by rods 25, 41 pivoted at 25 to the member 40 so that after the reverse drive has been engaged, the fork 37 preventing any movement of the member 40 to the left, the lever 28 pivoted at 29 is moved in the direction of the arrow causing the rods 41, 25 to act as a toggle linkage and move the piston 15 to the right thus opening the ports 13, 16 to exhaust and subsequent re-engagement of the clutch. In the former construction movement of the member 40 to the right is necessary whilst with the latter construction it is only necessary for the fork 37 to prevent tne member 40 moving to the left. Specification 632,884, [Group I], is referred to.