Patent GB-1064688-A (GB)
Title: Improvements in or relating to control mechanisms for hydraulic regulating devices
IPC: A01B63/111
Filed: 1964-09-24
Abstract: 1,064,688. Tractor power lift mechanisms. ZKL ZAVODY NA VALIVA LOZISKA A TRAKTORY, NARODNI PODNIK. Sept. 24, 1964 [Nov. 25, 1963], No. 38954/64. Heading A1P. A hydraulic control mechanism for an agricultural implement, such as a plough P, can be set to be responsive to positional control, draft force or a combination of the two. The plough is connected to the normal three point hitch linkage and is raised or lowered by a piston and cylinder device 23, 24 connected by linkage 25, 26 to a shaft 27 carrying arms 28 connected to rods 29. A valve 33 controls the supply and exhaust of fluid to the cylinder 23, the valve being connected to a bell-crank lever 48 whose opposite end carries a cam follower 51, the lever being loaded by a spring 53. The lever 48 is pivoted at 49 to a lever 44 whose opposite end is connected to a pivot 45 on a fixed member 62. The pivot 45 also acts as a pivot for a selector lever 68 which moves a hub 64 to one of three positions, shown in the figure as being in position 67a in which positions the hub is held by a lock. Movement of the hub 64 adjusts a lever 72 and linkage 70 to move a cam 31, rotatable on the shaft 27 and a lever 81 and linkage 82, 21 to move a slider 55 on a spring loaded rod having an abutment 56. A positional control lever 75 is pivoted at 76 and carries a roller 77 and abutment 78 engageable with a lever 58 connected to the hub 64.  Positional control. With the lever 68 in the position shown, the system is set for positional control. Movement of the lever 75 acts through roller 77, lever 58 and a roller 47 to move lever 44. This causes movement of pivot 49 to adjust lever 48 to move the valve 32. Subsequent movement of the shaft 27 to move the plough rotates a cam 30 fixed to the shaft to recentre the valve 32. Draft control. The lever 68 is moved in an anti-clockwise direction about pivot 45 to move the hub 64. This movement causes anti-clockwise rotation of cam 31 to move the roller 51 of lever 48 out of engagement with cam 30. The lever 58 is moved out of engagement with roller 77 and abutment 78 and lever 81 acts through linkage 82, 21 to move slider 55 into engagement with abutment 56 and a rod 19 into abutment with an adjustable stop 18. The adjustable stop is connected through a torsion rod 16 to a push rod 4 which acts in response to the draft force. Variations in draft force thus act through torsion rod 16, stop 18, rod 19, lever 21 and slider 55 to move pivot 49 to adjust valve 33 to control the piston-cylinder device as above. In this control, the lever 44 is moved to allow opening of a valve 43 which allows the hydraulic supply 34 to be by-passed through a manually adjustable valve 41 thus controlling the speed of movement of the piston-cylinder device when the valve 33 is actuated. In the event of the plough encountering sudden resistance, e.g. if it strikes an obstacle, the valve 43 is closed by movement of lever 44 to provide a rapid response of the piston-cylinder device. Combined regulation. With the lever 68 moved to a mid-position in between draft and positional control, the rod 19 still engages the abutment 18 to move the valve 33 in response to draft force as above, but the roller 51 still engages the cam 30 thus movement of the shaft 27 in response to changes in draft force provides a feed back as in positional control. This control provides a smaller movement of the plough in response to draft force variations.