Patent GB-888286-A (GB)
Title: Improvements in or relating to the control of implements by mechanically propelled vehicle
IPC: A01B63/111
Filed: 1960-02-19
Abstract: 888,286. Tractor power lift linkages. BOSCH G.m.b.H., ROBERT. Feb. 19, 1960 [Feb. 20, 1959], No. 5923/60. Class 79(1). A depth control arrangement for a tractor hydraulic power lift mechanism comprises a manually operated device for controlling the implement depth and means responsive to both the drag and depth of the implement acting upon the control device. The implement 24 is carried by lower arms 25 pivoted at 26 to the tractor and supported by a draw bar 28 suspended from' a crank 30 which is acted upon by a hydraulic ram 4 supplied with pressure fluid by a pump 2 from a reservoir 1 through a control member 3. The control member 3 has a valve spool 5 operated by a lever 10 through links 9 and 11. Passages 20 and 21 return to the reservoir and 18 and 19 lead to the ram. In the left hand position of the lever 10 in which spool 5 is in the right hand position, liquid from the pump 2 is short circuited back to the reservoir 1 through 13, 14, and 23. In its right hand position, the lever 10 has moved the spool to the left and liquid is fed to the ram through 13, 12, 22 and 19. Intermediate positions of the spool are possible giving a slow feed of liquid to the ram or throttled return from the ram (for lowering the implement) through 18, 16, 15 and 21. An "equalising" piston 6 is provided preventing surges of liquid, the piston moving to either the left or right according to whether the chamber 22 or 23 is under pressure, or remaining in the centre when both are under pressure during the slow lift. A non-return valve 7 is provided which comes into play during the lowering operation. The upper arm 36 of the lift linkage comprises telescoping members 35 and 36 and spring 34, the member 36 being connected to the lower arms 25 through a link 38. A link 44 is pivoted to the crank 30 at 43 and is connected to link 10 by a rod 45 and also by a flexible cable 41 and bracket 40 to member 36. Drag upon the implement tends to turn the lower arms about pivots 26 causing movement of 36 relative to 35 in one direction or the other, the movement being transmitted through 40, 41, 44, 45, 11 and 9 to the valve spool 5. Rise and fall of the implement also transmits a movement to the valve spool 5 through 28, 30, 44, 45, 11 and 9. The lift and drag-responsive control mechanism tends to keep the implement at a given working depth. A plurality of implements may be controlled through a number of control devices in series or parallel. Fig. 2 shows an embodiment in which two pressure cylinders 4, 4<SP>1</SP> are controlled through a series arrangement of control devices 3, 3<SP>1</SP>, the passage 20 from device 3 providing the supply to control device 3<SP>1</SP>. The control device may be replaced by a rotary control valve, Fig. 3, having connections 111 to 115 corresponding to the connections 17, 21, 18, 20 and 19 respectively of Fig. 1, two end chambers 107 and 108 corresponding to chambers 22 and 23 formed within the rotary control member 103 by a pressure balancing piston 106. A crank may be attached to the protruding end 104 of the member 103. This device may be used to put the implement in a fully trailed position wherein the lift and depth control devices are inoperative. The upper link 35 is shown in Fig. 4, the portion 139 being movable to the left relatively to the portion 128 to extend the link against the force of a helical spring 146 or to the right to shorten the link against the compressive force exerted by a series of spring washers 149. The bracket 150 corresponds to the bracket 40. A length adjusting sleeve 155 comprising left and right hand threaded portions is provided. An alternative device with two helical springs of unequal strengths is also described. An alternative depth control may include a feeler wheel or skid runner. A link system as shown in Fig. 1 with a control device as shown in Fig. 3 is shown in Fig. 7, the control member 103 being rotated through a crank 166, and links 165, 167 from a hand lever 127 or through links 165, 167, arm 175 and link 170 in response to movement of a cable 151. The cable 151 corresponds to cable 41, link 170 to link 44 arm 175 (which comprises telescopic portions connected by a spring 180) to arm 45, and a lifting shaft 159, to a retaining collar 169 of which the link 170 is pivoted at 171, corresponds to the crank 30.