GB2156951A - Directional control spool valve - Google Patents

Abstract

A directional control spool valve has service ports A, B, a supply port 5 and a bifurcated exhaust port 6 permitting direct through flow in a central position of the spool 2. For each service port, the spool has an internal passage 9, 10 with lateral openings 13, 14. When the spool is displaced from the central position, the internal passages and lateral openings define paths within the spool from the supply port to one service port, and from the other services port to the exhaust. Load check valves 15 are provided in the supply flow paths. <IMAGE>

Description

SPECIFICATION Directional Control Spool Valve This invention relates to fluid directional control spool valves, in particular for hydraulic systems.

Directional control valves are used to control the flow of fluid to and from one or more load devices, for example double-acting cylinders. Commonly, such a valve has three positions namely a central position for neutral or locked-load operation, and respective deflected positions each connecting one service port to the fluid supply and the other service port to the fluid exhaust, for example for reversible operation of a double-acting cylinder, or selective operation of different cylinders. Existing directional control spool valves are of relatively complicated design and therefore expensive.

An object of the present invention is to provide a directional control spool valve of simplified design.

According to the present invention, a directional control spool valve has two spaced service ports, and mutually opposite supply and exhaust ports, the spool is designed to permit direct flow between the supply and exhaust ports when in a central position, and the spool has for each service port a respective internal passage provided with lateral openings such as to define, when the spool is displaced from the central position, a first path within the spool from the supply to a first service port, and a second path within the spool from the other service port to the exhaust.

Preferably, the spool also incorporates within it, load check valves in the flow paths from the supply to the respective service ports.

Avalve embodying the invention is shown in the accompanying drawings, in which: Figure 1 shows the valve with its spool in the central neutral position.

Figure 2 shows the spool displaced in one direction, and Figure 3 shows the spool displaced in the opposite direction.

The illustrated valve has a body 1 in which slides a spool 2 with a projecting stub 3 for connection to an operating lever or handle, and a centering spring assembly 4 which defines a central neutral position of the spool.

The valve body has a central supply port 5 for connection to a pump or other fluid source, and directly opposite this an exhaust port 6 for connection to a hydraulic fluid tank. The exhaust port is bifurcated with internal branches 7, 8 spaced axially. The supply port 5 and exhaust branches 7,8 communicate with respective ring grooves inside the body.

Spaced axially on opposite sides of the supply and exhaust ports are respective service ports A, B with respective ring grooves in the body.

The valve spool has internal axial bores 9, 10 separated by a narrow central partition 11 and each closed at its outer end. Each such bore is provided with three lateral passages or sets of passages.

A first passage or set of passages 12 is adjacent to the partition 11 and communicates with a respective ring groove in the spool, which in the central position of Figure 1 provides direct communication between the supply port and both exhaust port branches 7, 8. In this position there is no flow through the bores 9, 10. Both service ports are blocked by lands of the spool and therefore the load is or loads are held in position.

Each bore also has a lateral opening or set of openings 13 which in the neutral position lies between the respective service port and the exhaust port, and a lateral opening or set of openings 14 which in the neutral position lie outside the associated service port. The ports 14 are provided with load check valves 15 mounted inside the spool, and shown as ball and spring valve assemblies.

If the spool is moved to the left (Figure 2) the bore 10 communicates through its openings 12 with the supply port and through its opening 14 with the service port B by way of the load check valve 15. The land corresponding to the partition 11 blocks communication from the supply port to the exhaust branch 7, and a land between the openings 12 and 13 of the bore 10 blocks communication with the exhaust branch 8. Fluid therefore flows from the source to the service port B to operate the corresponding load.

On the other side of the partition 11, the openings 13 of bore 9 communicate with the service port A and the openings 12 communicate with the exhaust branch 7, so that the service portA communicates through the spool with the exhaust port 6.

Correspondingly, when the spool is moved to the right (Figure 3) fluid flows from the pump through the path 5-12-9-14 to the service port A, and fluid is exhausted through the path B-13-10-12-8 to the exhaust port 6.

In the illustrated valve design, no additional ports or galleries are required to feed fluid flowto orfrom the spool when it is in any of the three positions.

This valve is therefore much simpler than known directional control spool valves.

1. A directional control spool valve which has two spaced service ports, and mutually opposite supply and exhaust ports, and in which the spool is designed to permit direct flow between the supply and exhaust ports when in a central position, and the spool has for each service port a respective internal passage provided with lateral openings such as to define, when the spool is displaced from the central position, a first path within the spool from the supply to a first service port, and a second path within the spool from the other service port to the exhaust.

2. A spool valve as claimed in claim 1, in which the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Directional Control Spool Valve This invention relates to fluid directional control spool valves, in particular for hydraulic systems. Directional control valves are used to control the flow of fluid to and from one or more load devices, for example double-acting cylinders. Commonly, such a valve has three positions namely a central position for neutral or locked-load operation, and respective deflected positions each connecting one service port to the fluid supply and the other service port to the fluid exhaust, for example for reversible operation of a double-acting cylinder, or selective operation of different cylinders. Existing directional control spool valves are of relatively complicated design and therefore expensive. An object of the present invention is to provide a directional control spool valve of simplified design. According to the present invention, a directional control spool valve has two spaced service ports, and mutually opposite supply and exhaust ports, the spool is designed to permit direct flow between the supply and exhaust ports when in a central position, and the spool has for each service port a respective internal passage provided with lateral openings such as to define, when the spool is displaced from the central position, a first path within the spool from the supply to a first service port, and a second path within the spool from the other service port to the exhaust. Preferably, the spool also incorporates within it, load check valves in the flow paths from the supply to the respective service ports. Avalve embodying the invention is shown in the accompanying drawings, in which: Figure 1 shows the valve with its spool in the central neutral position. Figure 2 shows the spool displaced in one direction, and Figure 3 shows the spool displaced in the opposite direction. The illustrated valve has a body 1 in which slides a spool 2 with a projecting stub 3 for connection to an operating lever or handle, and a centering spring assembly 4 which defines a central neutral position of the spool. The valve body has a central supply port 5 for connection to a pump or other fluid source, and directly opposite this an exhaust port 6 for connection to a hydraulic fluid tank. The exhaust port is bifurcated with internal branches 7, 8 spaced axially. The supply port 5 and exhaust branches 7,8 communicate with respective ring grooves inside the body. Spaced axially on opposite sides of the supply and exhaust ports are respective service ports A, B with respective ring grooves in the body. The valve spool has internal axial bores 9, 10 separated by a narrow central partition 11 and each closed at its outer end. Each such bore is provided with three lateral passages or sets of passages. A first passage or set of passages 12 is adjacent to the partition 11 and communicates with a respective ring groove in the spool, which in the central position of Figure 1 provides direct communication between the supply port and both exhaust port branches 7, 8. In this position there is no flow through the bores 9, 10. Both service ports are blocked by lands of the spool and therefore the load is or loads are held in position. Each bore also has a lateral opening or set of openings 13 which in the neutral position lies between the respective service port and the exhaust port, and a lateral opening or set of openings 14 which in the neutral position lie outside the associated service port. The ports 14 are provided with load check valves 15 mounted inside the spool, and shown as ball and spring valve assemblies. If the spool is moved to the left (Figure 2) the bore 10 communicates through its openings 12 with the supply port and through its opening 14 with the service port B by way of the load check valve 15. The land corresponding to the partition 11 blocks communication from the supply port to the exhaust branch 7, and a land between the openings 12 and 13 of the bore 10 blocks communication with the exhaust branch 8. Fluid therefore flows from the source to the service port B to operate the corresponding load. On the other side of the partition 11, the openings 13 of bore 9 communicate with the service port A and the openings 12 communicate with the exhaust branch 7, so that the service portA communicates through the spool with the exhaust port 6. Correspondingly, when the spool is moved to the right (Figure 3) fluid flows from the pump through the path 5-12-9-14 to the service port A, and fluid is exhausted through the path B-13-10-12-8 to the exhaust port 6. In the illustrated valve design, no additional ports or galleries are required to feed fluid flowto orfrom the spool when it is in any of the three positions. This valve is therefore much simpler than known directional control spool valves. CLAIMS

1. A directional control spool valve which has two spaced service ports, and mutually opposite supply and exhaust ports, and in which the spool is designed to permit direct flow between the supply and exhaust ports when in a central position, and the spool has for each service port a respective internal passage provided with lateral openings such as to define, when the spool is displaced from the central position, a first path within the spool from the supply to a first service port, and a second path within the spool from the other service port to the exhaust.

2. A spool valve as claimed in claim 1, in which the spool incorporates load checkvalves in the flow paths from the supply to the respective service ports.

3. A spool valve substantially as herein described with reference to the accompanying drawings.