Patent GB-783630-A (GB)
IPC: A01B63/14
Filed: 1955-02-11
Abstract: 783,630. Tractor power-lift linkage mechanisms. BROWN TRACTORS (ENGINEERING), Ltd., D. May 11, 1956 [Feb. 11, 1955], No. 4079/55. Addition to 747,674. Class 79(1) In an improvement or modification of the invention claimed in the parent Specification the hydraulic cylinder e, Fig. 1 is of double-acting type and the construction and arrangement of the means controlling the supply of pressure liquid to the cylinder e are of such that the pressure of liquid can, in addition to being utilized to lift, hold raised, or lower the implement, be caused to effect transfer of a pre-determined downward force either from the implement to the tractor or vice versa. The upper end of the cylinder e is pivotally mounted on the end of a rock shaft b to which are secured arms h and which is carried by the tractor in brackets a. The lower end of the rod f<SP>1</SP> of the piston f is pivoted at f<SP>2</SP> to one of the two lower links d in turn pivoted in brackets c to the tractor. A lift rod g<SP>1</SP> has its lower end pivoted to the one link d at f<SP>2</SP>, and its upper end selectively pivoted to one arm h. A screw adjustable two-part lift rod g<SP>2</SP> is pivoted at its lower end to the other link d and pivoted at its upper end to the other arm h. The usual central upper draft link is provided but not shown. The hydraulic system shown in Fig. 2 (Provisional Specification) includes a pump k connected by a pipe system with a master control valve i, a traction control valve j and a valve p which can selectively control an auxiliary circuit through pipes p<SP>4</SP> and p<SP>3</SP>. Also provided in the circuit arc an unloading valve m having reduced portions m<SP>1</SP>, m<SP>3</SP> and a restricted port m<SP>2</SP> the valve m being urged upwardly on to a seat m<SP>4</SP> by a spring m<SP>5</SP>; a maximum pressure relief valve v; a check valve n under the urge of a spring n'; a traction and penetration valve o having reduced portions (e.g. O<SP>3</SP>) and a restricted port o' and urged on to a seat O<SP>2</SP> by a light spring O<SP>4</SP>; a manually controllable spring-urged relief valve u; and a relief valve t. The outlets of the valves v, u and t and a pipe q all connect with a region of low pressure. In the positions of the valves i, and p shown, the valve m is closed since it is hydraulically balanced via the port m<SP>2</SP> and the'lower side of the valve m through a reduced portion j<SP>1</SP> of the valve is blocked from a region of low pressure by the valve i. Liquid from the pump passes round the portion m<SP>1</SP> and opens the check valve n against its spring n<SP>1</SP> and passes the portion O<SP>3</SP> of the valve o, a reduced portion j<SP>2</SP> of the valve j and a reduced portion p<SP>1</SP> of the valve p into the lower end of the cylinder e to lift the piston f. Liquid is removed from the upper end of the cylinder e and passes a reduced portion p<SP>2</SP> of the valve p, a reduced portion j<SP>3</SP> of the valve j and a reduced portion i<SP>1</SP> of the valve i, to the pipe q. When the piston reaches its upper limit the valve v operates. During this operation the valve o is closed on its seat O<SP>2</SP> since it is hydraulically balanced through its port O<SP>1</SP> and the outer end thereof is cut-off from the valve u by the valve j. In order to hold the piston f raised the valve i is moved to the left so that its portion i<SP>2</SP> unblocks connection to a region of low pressure s. The lower end of the valve m is now at reduced pressure and the valve no longer balanced and so opens against its spring m<SP>5</SP> to allow the pump output to be returned via the pipe q to a region of low pressure. The check valve n closes by its spring n<SP>1</SP> and the valve o remains seated. Liquid on both sides of the piston f is locked by the valves i and n. To lower the piston the valve i is moved further to the left. The valve m remains unbalanced and the valves o and n remain closed and both ends of the cylinder e are open to low pressure since reduced portions i<SP>1</SP>, i<SP>3</SP> of the valve i are each aligned with a pipe. The lowering of the piston is assisted slightly by a downward force on the piston f since its upper face is of greater area than its lower face, but liquid below the piston is expelled through a restriction r to control the speed of lowering. When it is desired to transfer part of the weight of the implement to the tractor, the valve i is retained in the last mentioned position but the valve j is lowered to connect the outer end of the valve o to the valve u whereby the vale O is unbalanced when u opens and opens the seat O<SP>2</SP>, and to block the lower end of the valve m, whereby the latter is balanced and closes on its seat m<SP>4</SP>. In these circumstances the pressure applied to the lower end of the piston f is reduced according to the opening of the valve o as controlled by the adjusted valve u. When it is desired to transfer part of the weight of the tractor to the implement, the valve i remains in its last mentioned position and the valve j is raised whereby oil at a pressure determined by the adjustment of the valve u is delivered to the upper end of the cylinder e. During this operation the valve u is connected to the valve o through a reduced portion of the valve j. The valves i and j are preferably controlled by a single hand lever (not shown) movable in two planes (at right angles), movement in one plane controlling one valve and movement in the other plane controlling the other valve. In another embodiment shown in Fig. 5, (Complete Specification), a valve 3 is axially slidable in a bore 4 in a valve housing 1, and has six positions " LIFT" "TRACTION," " HOLD"; "FLOAT" which corresponds with the usual lowering position, "PENETRATION' and "LOWER" in which the implement is "crowded" by pressure into the ground. The valve 3 in its extreme left hand position effects "LIFT" and in its extreme right hand position effects "LOWER" or " crowding." In either of these two positions a spring 13 is compressed through the agency of rod 8 slidable in the valve 3 and caps 11 and 12. When a handle (not shown) operating the valve 3 is released from the "LIFT" position the valve is returned to the "HOLD" position by the spring 13 which position is determined by a dimple 14 on the valve engaging a spring-pressed plunger in the housing. When the handle is released from the "LOWER" position the spring 13 urges the valve 3 to the "FLOAT" position where it is retained by another dimple 14 on the valve engaging the spring-pressed plunger, this latter position being depicted in Fig. 5. The action of the spring is negligible when the valve is in either the "HOLD" or "FLOAT" positions. A depressible latch member on the valve operating handle is engageable when depressed with either one of two detents described with reference to Fig. 4, of the Complete Specification (not shown) as the handle is urged by the spring 13 from either the "LIFT" position, before it can move to the "HOLD" position, or from the "LOWER" position, before it can move to the "FLOAT" position. The two positions in question are "TRACTION" in which weight is transferred from the implement to the tractor and "PENETRATION" in which the weight is transferred from the tractor to the implement and the handle latch is maintained against its associated detent by the action of the spring 13. Passageways 24 and 40 in the b o r e 4 are connected respectively by a manually controlled selector valve and flexible pipes with the bottom and top respectively of the hydraulic cylinder. The selector valve has two positions, one in which the hydraulic mechanism is connected to the lift cylinder for the implement and the other in which the lift cylinder is cut-off and the liquid pressure is directed to auxiliary equipment e.g. a front-end loader. When the valve 3 is in the "LIFT" position liquid enters the housing 1 from the pump (not shown) at 20, passes through ports 21 into an internal bore 10 in the valve 3 and thence through further ports 23 to the passage 24 which is under the control of a manually adjustable valve used for controlling the rate of lowering of the implement as described with reference to Fig. 7 (not shown). Liquid from the top of the cylinder passes from the passage 40 to a passage 41 and thus to a region of low pressure e.g. sump. The liquid from the pump also passes directly to a passage 28 and a bore 29 and can pass through a bore 32 in a spring-loaded valve 31 and a hole 33 into a chamber 34 having a maximum pressure relief valve 35. The chamber 34 communicates through a ball valve 36 with a passage 42 which communicates with a region of low pressure through a manually adjustable pressure relief ball valve for operating the mechanism in the "TRACTION and "PENETRATION" positions, as described with reference to Fig. 9 (not shown). The ball 36 is normally held off of its seat by a plunger 37 engaged by the valve 3. In the "LIFT" and "LOWER" positions the plunger can drop into a recess 38 or 50 respectively so that the ball 36 can be seated to seal the chamber 34 from the passage 42. The valve 31 in the "LIFT" position is therefore hydraulically balanced and does not therefore open the bore 29 to a passageway 30 connected to a region of low pressure. In the "TRACTION" position of the valve 3 the ball valve 36 is opened by the plunger 37 and whilst liquid can enter the bottom of the hydraulic cylinder the valve 31 becomes unbalanced and can open when the pressure of liquid is slightly below the normal lifting pressure as determined by the setting of the valve in the passage 42. When the valve 31 opens liquid is by-passed to the passage 30 and thus to the region of low pressure. Liquid in the top of the cylinder can still flow to the passage 40 and thus passage 41. In the "HOLD" position the valve 3 is positioned so that the port 20 communicates wi