US2993509A - Arrangement in control valves for controlling the hydraulic lift cylinder of tractors - Google Patents

Description

July 25, 1961 E. ANDERSEN 2 993,509

ARRANGEMENT IN CONTROL VALVES FOR CONTROLLING THE HYDRAULIC LIFT CYLINDER OF TRACTORS Filed Oct. 6, 1959 ATTORNEYS United States Patent O ARRANGEMENT 1N CONTRL VALVES FOR CON- TRULLING THE HYDRAULIC LIFT CYLINDER F TRACT ORS Eilif Andersen, 30 Strandstien, Kalundborg, Denmark Filed Oct. 6, 1959, Ser. No. 844,781 Claims priority, application Denmark Oct. 11, 1958 6 Claims. (Cl. 137-621) This invention relates to an arrangement in control valves for controlling the hydraulic lift cylinder of tractors with a view to raising and lowering of a mounted implement, and to transfer of part of the Weight of the implement in the operative position thereof to the tractor for increasing its rear-wheel pressure, the control valve comprising a bore which through slide-valve controlled ports is in communication with a pump for supplying pressure liquid, and with the hydraulic lift cylinder and a liquid reservoir connected to the inlet of the pump, the iiow connection from the lift cylinder through the bore to the reservoir comprising an opening controlled by a springloaded valve, which by throttling the liquid flow affords the possibility of maintaining a cylinder pressure which is lower than the pressure required for lifting the implement.

In a known control valve of this type the said bore is provided with a first port which is connected to the liquid pump and is continuously open, and a second, a third and a fourth port leading from the bore to the lift cylinder via a non-return valve, from the lift cylinder to the bore bypassing said nonreturn valve, and from the bore to the liquid reservoir, respectively. In a certain position of the slide-valve within the bore, the last-mentioned port is controlled by the said spring-loaded valve. For practical reasons, the liquid pump must work continuously and care should, therefore, be taken that the pressure liquid supplied by the pump can flow to the liquid reservoir except for such periods when, with a view to raising the implement, a certain maximum pressure is to be built up in the lift cylinder. In the known control valve this problem is solved by providing a slide-valve portion which controls the second, the third, and the fourth port, with one or more axial passages which provide communication between the first port and the fourth port except in one particular position of the slide-valve, namely when said slide-valve is to cause pressure liquid to be supplied to the lift cylinder with a view to raising the implement. The passage or passages through the slide-valve portion require that said portion has a comparatively great diameter, which must be considered a not inessential drawback as the risk of unwanted leakage of liquid within the control valve is hereby increased.

This drawback is remedied by the arrangement according to the invention which further involves a certain simplification of the control valve, for one thing because the said non-return valve may be dispensed with, and for another because the spring-loaded valve may continuously be in an operative position and shall not, as is the case with the said known construction, be brought into an inoperative position.

The characteristic of the arrangement according to the invention is that the bore has a first port in connection with the liquid reservoir, a second port in connection with the pump, a third port in connection with the lift cylinder, and a fourth port n connection with the pump ICC and the opening controlled by the spring-loaded valve, the slide-valve being so designed that in a rst position it keeps the first and the fourth ports shut off and affords admission from the second to the third bores in order to allow the supply of pressure liquid to the lift cylinder, in another position keeps the third port shut olf and aiords admission from the second to the first port so that the pressure provided in the lift cylinder is maintained While the liquid coming from the pump is transferred direct to the reservoir, in a third position leaves all of the ports open whereby a relief of the pressure in the lift cylinder may take place, and in a fourth position shuts off the second port and ailords communication between the third and the fourth ports so that in the lift cylinder a pressure is built up, the height of which is controlled by the spring-loaded valve, while excess liquid from the pump is transferred to the reservoir via this spring-loaded valve.

A particular advantage, in addition to those already mentioned, attached to this arrangement according to the invention is that the spring-loaded valve may be kept stationary in its closing position in the three first positions of the slide valve and shall only be moved in the fourth position of said valve whereby the wear on the spring-loaded valve which in a way is the most sensitive element of the control valve is reduced to a minimum.

The invention will be more fully explained in the following description with reference to the accompanying drawing wherein FIGURES l-4 are diagrammatical axial sectional views of an embodiment of the invention and show the above four positions of the slide valve.

In the embodiment shown on the drawing the control valve comprises a housing 1 with a bore 2 which forms a slide Way for a ldisplaceable slide-valve 3 which in a conventional manner is connected with a handle 4 serving for adjusting the slide-valve in the bore 1. The housing 1 comprises an inlet 5 which is connected to a liquid pump, not shown, and an outlet 6 leading to a liquid reservoir, not shown either, and further the housing 1 is provided with a passage 7 connected With the lift cylinder of the tractor. For the sake of clearness this cylinder is also left out of the drawing.

The bore 2 has a rst port 8, FIGS. 2, 3 and 4, leading to the outlet 6 and controlled by a slide-valve portion 9. A second port 10 communicates the bore 2 with the inlet 5, a third port 11 communicates the bore 2 with the passage 7, and a fourth port 12 forms a further connection between the bore 2 and the inlet 5, namely through a bore 13 parallel with the bore 2. The three ports 10, 11 and 12 are controlled by a common slide-valve portion 14.

At the left-hand end of the bore 13 provision is made of a conventional safety valve 15, which in its open position. FIG. l, through a cross-bore 19 and a space 29 surrounding the slide-valve portion 9 affords liquid discharge to the reservoir. The right-hand end of the bore 13 constitutes a seat for a Valve 16 which is loaded by a spring 17, the tension of which can be adjusted by means of an adjustment screw 18. In its open position, the valve 16 gives communication from the bore 13 to a cross-bore 21 leading to the first mentioned bore 2. Through a channel 22 in a cover 23 there is from the right-hand end of said bore 2 a permanent communication to a third bore 24 leading to the outlet 6. A slidevalve portion 25 at the right-hand end of the slide-valve 3 serves in the position shown n FIG. 4 for separating the right-hand end of the bore 2 from the other portion thereof.

In the position shown in FIG. 1 of the slide-valve 3 its portion 9 shuts ofi the port 8 from the bore 2 to the outlet 6, and at the same time the slide-valve portion 14 shuts off the port 12. Between these two slide-valve portions there is an open connection from the port 10 to the port 11, and the pressure liquid coming from the pump is, therefore, transferring through the inlet 5, the bore 2 and the passage 7 to the lift cylinder, whereby an implement operated thereby can be raised. When the implement has reached its top position, the safety valve 15 gives way as shown in FIG. l, whereupon the pressure liquid supplied fiows directly to the reservoir.

In the position shown in FIG. 2, the slide-valve portion 14 shuts off the port 11, so that liquid discharge from the lift cylinder is prevented. This is tantamount to the fact that the implement is retained in its raised position. In the same position of the slide-valve 3, its portion 9 has released the port 8 so that pressure liquid from the pump flows directly through the inlet 5, the bore 2 and the outlet 6 to the liquid reservoir.

In FIG. 3, the slidevalve 3 has been displaced a further step towards the left, so .that the slide-valve portion 14 is situated between the ports 1t) and 11 but leaves both of said ports free. The port 8 is still open, and the liquid supplied through the inlet will, therefore, continuously flow directly to the liquid reservoir, but at the same time liquid previously pumped into the lift cylinder can through the passage 7, the port 11, the bore 2, the port 12, the bore 13, the port 10, the bore 2 and the port S flow away into the liquid reservoir whereby the implement is lowered into its working position owing to its own weight.

Now, if it is desired to have the rear-wheel pressure of the tractor amplified by transferring part of the weight of the implement to the tractor, the slide-valve 3 is displaced a further step towards the left into the position shown in FIG. 4. In this position the slide-valve portion 14 shuts off the port 10 between the inlet 5 and :the bore 2, but via the bore 13, the port 12, the bore 2, the port 11 and the passage 7 there is communication from the inlet 5 to the lift cylinder; When in this path of ow a certain pressure has built up which, by way of example, may amount to a little below the half of the pressure required for raising the implement, the valve 16 gives way against the infiuence of the spring 17, and hereby a communication from the port 11 via the cross bore 21, the right-hand end of the bore 2, the channel 22, and the bore 24 is created to the outlet 6; The slidevalve portions 14 and 25 prevent any discharge of liquid along other channels than past theV spring-loaded valve 16 and the pressure provided in the lift cylinder will, therefore, clearly be defined by the tension of the spring 17 which can be adjusted by turning of the adjustment screw 18, if desired.

The pressure which is in this way provided in the lift cylinder will by means not illustrated on the drawing, because they form no part of the invention, tend to raise the implement drawn by the tractor. Accordingly, the implement is subjected to an upwardly directed pull, and the rear end of the tractor is subjected to a corresponding downwardly directed pressure.

With the mutual location of the ports 10, 11 and 12 shown in the drawing, the advantage is obtained that said three ports can be controlled by a single slide-valve portion, namely the portion 14, and it clearly appears from the drawing that this slide-valve portion as well as the two other slide-valve portions 9 and 25 only need to have a small diameter so that the extensions of the sealing surfaces will be correspondingly small.

The passages formed by the bores 13 and 24 might also be established outside the housing 1 proper, but the arrangement shown in the drawing with the bores 1 3 and 24 must be considered advantageous, for one thing because it makes possible a particularly compact construction and for another because the number of connections to the housing 1 may be reduced to a minimum.

It is also owing to the desire for a particularly simple and reliable construction that the discharge from the opening controlled by the spring-loaded valve 16, i.e. the cross bore 21, is connected to the bore 24 through a portion of the bore 2, as the said connection might also have been provided in another manner. Further should be mentioned that the safety valve 15 need not necessarily be built into the housing 1 of the control valve, as it may be in communication with the path of flow from the pump to the lift cylinder at any place.

What I claim is:

1. A hydraulic control valve comprising a housing, said housing having a bore, said bore having a first port communicating with a low pressure iiuid outlet, a second port communicating with a high pressure huid inlet, a third port communicating with a high pressure fiuid outlet, and a fourth port communicating with said high pressure fluid inlet and with a discharge passage controlled by a throttle valve determining a discharge pressure intermediate said low and said high pressure, a slide-valve shiftably accommodated in said bore and having a plurality of lands c0- operating with said ports, and means for shifting said slide-valve axially in said bore between a first position in which said first andy said fourth ports are obstructed by two of said lands whereas said third port is in flow connection through said bore with said second port, a second position in which one of said lands obstructs said third port while at least said first and said second ports are unobstructed and are in ow connection with one another through said bore, a third position in which all of said portsV are unobstructed, and a fourth position in which the land which in said second position obstructs said third port, obstructs said second port and prevents fluid ow to said first port, whereas said third port is through said bore in flow connection with said fourth port and, accordingly, with said high pressure iuid inlet and said intermediate pressure iiuid discharge passage via said throttle valve.

2. A hydraulic control valve as claimedV in claim l, wherein said ports Aare located in said sequence in the aXial direction of said bore, said slide-valvecomprising a single land for obstructing successively said fourth, third and second ports.

3. A hydraulic control valve comprising a housing, said housing having a first bore, said bore having a first port communicating with a low pressure uid outlet, a second port communicating with a high pressure uid inlet, a third port communicating with a high pressure iiuidV outlet, and a fourth port communicating with said high pressure fluid inlet and with a discharge passage Vcontrolled by a throttle valve determining a discharge pressure intermediate said `low and said high pressures, a slide-valve shiftably accommodated in said first bore and having a plurality of lands cooperating with said ports, said housing having a second bore communicating with said high pressure fiuid inlet and with said second and fourth ports and said discharge passage via said throttle valve, and means for shifting said slide-valve axially in said first bore between a' first position in which said first and said fourth ports are obstructed byV two ofV saidv lands whereask said third port is in iiow connection through said'rst bore with said second port, a second position in which one of said lands obstructs said third port while atleast said first and Vsaid second ports are unobstructed and are in iiow connection with one another through said first bore, a third position in which all of said ports are unobstructed, and a fourth position in which the land which in Said second position obstructsV said third port, obstructs saidV second port and preventsuid flow to said first port, whereas said third port is through said first` bore in ow Connection with said fourth port and, accordingly',

through said second bore communicates with said high wherein said throttle valve is a spring-loaded valve, the

pressure uid inlet and said intermediate pressure uid load of which is adjustable at will. discharge passage via said throttle valve. 6. A hydraulic control valve as claimed in claim 3, 4. A hydraulic control valve as claimed in claim 3, wherein said throttle Valve is a spring-loaded valve, the

wherein said intermediate pressure uid discharge pas- 5 load of which is adjustable at Will. sage connects the discharge side of said throttle valve with said first bore at a portion thereof which in said References Cited in the flle 0f this patent fourth position of said slide-valve by one of said lands UNITED STATES PATENTS is shut oi from the remaining portion of said rst bore and is in open communication with a third bore provided 10 gwdg En 213g in said housing. anuc ug 5. A hydraulic control Valve as claimed in claim 1, 2698632 Mal-grave et al Jan 4 1955

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