US2598233A - Sequence valve for hydraulic power systems - Google Patents

Description

c. DEARDORFF 2,598,233

SEQUENCE VALVE FOR HYDRAULIC POWER SYSTEMS May 27, 1952 Filed Nov. 29, 1948 20 Z4 Z4 6 f .6

B I ii' 4 INVENTOR c; E. DEARDORFF ATTORNEY Patented May 27, 1952 UNITED STATES I Fl SEQUENCE VALVE FOR HYDRAULIC POWER SYSTEMS Application November 29, 1948 Serial No. 62,471

(Cl. c 52) Claims. 1

Thi invention relates to hydraulic systems containing a plurality of fluid motors or jacks to be operated sequentially from a single source of pressure fluid, and the general object is to provide a simple and practicable hydraulic circuit and valve for causing the desired sequential operation to automatically take place.

A more specific object is to provide a sequence valve that is mechanically separate from the motors or jacks that it controls and is connected thereto only by fluid lines.

Other more specific objects and features of the invention will appear from the description to follow:

Briefly, in a system in accordance with the present invention, a pair of hydraulic jacks to be operated sequentially have their input ports connected simultaneously directly to the actuating source of fluid pressure but have their output ports connected to exhaust through a special sequence valve. Thev construction of this valve is such that, in response to flow from one of the jacks to exhaust, it blocks flow from the other jack to exhaust, thereby preventing the second jack from being actuated simultaneously with the first. However, when the first jack has completed its movement, and the flow of exhaust fluid therefrom ceases, the sequence valve is springactuated into another position in which it connects the exhaust port of the second jack to the exhaust line, thereby permitting the second jack to be actuated. Since the sequence valve is controlled entirely by the flow of fluid from the jacks to the exhaust line it need not be directly mechanically associated with the jacks but can be located at any convenient point in the hydraulic system.

The single figure of the drawin is a schematic diagram of a simple hydraulic system incorporating the invention.

In the drawing there are shown two hydraulic motors in the form of jacks l and 2 respectively, a fluid reservoir 3, a pump a 4-way valve 5, a check valve 6, and a sequence valve 1 in accordance with the invention. The jack l comprises a cylinder la and a piston lb, and the jack 2 comprises a cylinder 2a having a piston 2b. The cylinder la has two ports 8 and 9' respectively, and the cylinder 2a has two ports Iii and ll respectively. The port 8 functions as the inlet port of cylinder la, and the port 9 functions as the outlet thereof when the piston lb is being moved downwardly, and vice versa when movement is in the opposite direction. Similarly, the port It is the inlet port and port II is the outlet port of cylinder 2a when the piston 21) is moving to the right, and vice versa when the movement of the piston is to the left.

In the position of the e-way valve 5 shown in the drawing, the output of the pump 4 is connected through lines l 3 and M directly to the ports 8 and lil respectively of the cylinders Ia and 2a. The port 9 of cylinder la is permanently connected by a line l5 to a first port l6 of the sequence valve 7, and the port ll of the cylinder 2a is permanently connected by a line I! to a third port l9 of the sequence valve l. A second port I 8 of the valve 7 is shown connected through a line 28, the 4-way valve 5, and a line 2| to the reservoir 3.

The valve 7 comprises a casing 22 containing the ports l5, l3 and I9 and defining a cylindrical bore 23 with which these ports communicate. Thus the first port it communicates with the left end of the :bore 23, the second port It communicates with the side of the bore 23 at a point displaced from the left end of the bore, and the third port I9 communicates with the bore at a point spaced still further from the left end. The bore 23 contains a freely slideable piston 24 which is urged into the left end of the bore 23 by a light (weak) helical compression spring 25. To enable the use of a spring having a low loading rate, the piston 24 is formed with a passage 24a therein extending from the right end of the piston almost to the left end, and the spring 25 is partially contained within the bore 24a and is compressed between the inner (left) end of the bore and a closure assembly 28 that seals the right end of the cylinder bore 23. This closure assembly 28 is shown as consisting of a plate 23a, a disc 28b, and a sealin ring 280, which are retained by a split ring 28d in a groove 28c provided therefor in a counterbore so at the right end of the cylinder bore 23.

The piston 24 has a pair of land portions 2% and 250 which are closely fitted to the cylinder bore 23. A small bleed passage 3 3 is provided in the end of the piston 24, and the right end of the cylinder 23 is permanently connected to the second (exhaust) port It by a passage 35.

Let it be assumed that the jack pistons lb and 2b and the valve piston 24 are in the position shown in the drawing, and that the 4-way valve 5 has just been rotated into the position shown, thereby applying pressure fluid from the pump 4 through the lines l3 and M to the ports 8 and ll] of the jacks l and 2. Pressure is therefore developed against the upper side of the piston lb tending to move it downward, and against the left end of the piston 2b, tending to move it to the right. Both pistons begin to move, discharging fluid from the other ports 9 and H respectively of the two jacks. Fluid from the port 9 of jack l flows through the line l5 and into the first port [6 of the sequence valve 1 and overcomes the force of the spring 25 and moves the piston 24 to the right until the left edge of the land 24b clears the second port l8 and permits fluid to flow from the first port It to the second port l8 and thence through the line 29, valve 5, and line 2| back to the reservoir 3. A path is therefore provided for the discharge of the fluid from jack 1 through the port 9, and the piston lb moves downward.

However, the piston 21) cannot continue to move because when the valve piston 24 moved to the right sufficiently to display the land 24b from. its blocking position between the first and second ports l6 and I8 respectively it moved into blocking relation in the bore between the second port It and the third port l9, thereby blocking discharge of fluid from the port ll of cylinder 2, so that, after a slight initial movement, piston 2b remains stationary while piston lb is moving to the end of its stroke, at which time it is necessarily stopped, and discharge of fluid out of the port 9 and into the first port ll; of the sequence valve ceases.

Thereupon, the piston 25 is restored into its leftmost position by the spring 25, the residual fluid in the left end of the cylinder bore 23 leaking through the bleed hole 34 to permit such movement. Restoration of the piston 24 into its normal leftmost position moves the land 24b out of the path between the second port l8 and the third port [8, so that a path is provided for fluid flow from the cylinder port ll through the line H, the third port l9, bore 23, and second port l8 of the sequence valve l to the exhaust line 22!, whereby the piston 2b of the jack 2 can now complete its movement to the right.

The time lag between completion of movement of piston lb and beginning of movement of the piston 2b can be varied by varying the size of the bleed hole 34, and also by varying the strength of the spring 25. It is to be understood, however, that the force of the spring 25 is ordinarily small compared to the resistance to movement of the jack pistons lb and 2b caused by the loads connected to those pistons.

To restore the jack piston lb into uppermost position, and the jack piston 2b into leftmost position, the 4-way valve 5 is actuated to connect the port Hi to the line 25, and connect the line 2| to the line Id. The cylinder ports 8 and ll) of the jacks l and 2 respectively are thereby directly connected to the exhaust line 2l so that there is no resistance to the discharge of exhaust fluid from either of the jacks during reverse movement. Pressure fluid is also supplied without restriction simultaneously to the other ports 9 and I9 respectively of the two jacks so that the pistons lb and 2b can move simultaneously in reverse direction. The path of pressure fluid flow from the line 26 to the port 9 of jack l is through the check valve e which permits flow in this direction, while blocking reverse flow. The path of pressure fluid flow to port ll of jack 2 is from the line 2% through the second port l8 of the sequence valve 1 into the cylinder bore 23 between the two piston lands 24b and 2&0, and out through the third port I 9 and through the line ii.

The piston 24 remains in its leftmost position during reverse movement because high pressure fluid is applied to both ends thereof; thus the 4 high pressure fluid is applied through the line l5 and the port Hi to the left end of the piston, and through the second port l8 and the passage 35 to the right end of the piston.

It will be observed therefore that the system described provides for sequential movement of the pistons lb and 2b in one direction in response to actuation of the 4-way valve 5 into the position shown in the drawing, and simultaneous movement of the pistons lb and 2b in the reverse direction when the 4-way valve 5 is reversed.

It is to be understood that in order to clearly show the construction of the sequence valve 1, the latter is shown disproportionately large in comparison with the motor or jack cylinders l and 2. In actual practice, the bore 23 in the sequence valve 1 will be very small compared to the bores of the jacks l and 2 so that only a very slight movement of the jack piston lb is sufficient to shift the sequence valve piston 24 from left to right position and thereby lock the piston 2b of the jack 2 against movement. Tests have indicated that both pistons lb and 2b start to move in response to application of the full flow of pressure fluid from the pump 4 to line it, even though the static load on piston lb is substantially heavier than that on piston 2b. The reason for this appears to be that the rapid acceleration of either piston and its load develops a dynamic reactive force therein which is a function of the inertia of the piston and its load and the rate at which it is being accelerated. In other words, much greater pressure in line I4 is required to rapidly accelerate the piston 2b from rest to its normal speed than is required to maintain it in motion at that speed. Hence the initial pressure in line [4 while piston 2b is accelerating can be greater than that necessary to start the piston lb even though its static load is greater than that of piston 2b. Of course the rate of acceleration of piston lb is less than that of piston 2b if the latter has a lighter load, but unless the load on piston lb is very much greater than that on piston 2b, piston lb will move the short distance necessary to shift the sequence valve piston, before piston 2b reaches full speed and the pressure drops to the lower value sufficient to maintain piston 2b in motion.

Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and described, obvious modifications will occur to a person skilled in the art, and I do not desire to be limited to the exact details shown and described.

I claim:

1. A valve of the type described comprising, a cylinder having first, second and third longitudinally spaced ports; a piston in said cylinder and spring means urging it in one direction from said third port toward said first port, said piston having a land portion sealing with and blocking said cylinder between said first and second ports when said piston is at the limit of its travel in said one direction, said piston being movable in the other direction in response to fluid flow into said first port into position in which said land clears said cylinder between said first and second ports and blocks said cylinder between said second and third ports, and passage means permanently connecting said second port with the end of said cylinder remote from said first port.

2. A hydraulic system comprising first and second motors, each having a pair of ports; means for supplying pressure fluid simultaneously to one of the ports of both motors; avalve casing having first, second and third ports, the first port being connected to the other port oi said first motor, said second port being connected to exhaust, and thethird port being connected to the other port of said second motor, valve means within said casing responsive to fluid flow into said first port for communicating said first port with said second port and blocking communication between said third and second ports, said valve means including a spring responsive to cessation of fluid flow into said first port for shifting said valve to communicate said third port with said second port. v

3. A system according to claim 2 in which said motors are reversible, and said means for sup plying pressure fluid includes a pump, a 4-way valve for selectively connecting the pump output to said one port of said motors and the pump inlet to said second port of said valve casing in one position, and connecting the pump outlet to said second port and the pump inlet to said one port of the motors in the other position; and a line including a check valve interconnecting said first and second ports for bypassing fluid direct from said pump to the other port of said first motor when said 4-wa valve is in its said other position.

4. A system according to claim 3 including passage means permanently connecting said sec-- and port with the said other end of said cylinder.

5. A hydraulic system comprising first and second hydraulic motors each having a pair of 6 ports; means ior supplying pressure fluid simultaneously to one of the ports of both motors; a sequence valve having a first port connected to the other port of said first motor, a second, exhaust, port, and a third port connected to the other port of said second motor, said sequence valve comprising a cylinder with which said first. second and third ports communicateat longitudinally spaced points; a piston in said cylinder, and spring means urging it in one direction away from said third port and toward said first port, said piston having a land portion sealing with and blocking said cylinder between said first and second ports when said piston is movedby said spring means to its limit of travel, said piston being movable against said springforce in re-' sponse to fluid flow into said first port into position clearing said cylinder between said first and second ports and blocking said cylinder between said second and third ports;

CLINTON E. DEARDORFF.

REFERENCES CITED The following references are of record in the

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