GB2133510A - Hydraulic flow control valve - Google Patents

Abstract

A directional hydraulic control valve has one or more helical grooves 7, 8 in its lands, communicating with a full-flow groove 6, so that in an intermediate spool position there is metered fluid flow between the inlet and outlet ports 2, 4 by way of the helical groove. <IMAGE>

Description

SPECIFICATION Hydraulic flow control valve This invention relates to hydraulic fluid control valves and in particular spool valves.

According to the invention a valve spool has at least one oblique, preferably helical groove whereby, over at least partofthe spool movement,thegroove provides metered fluid flow.

The flow metering can be controlled very finely by the degree of thread run-outatthe end of the thread.

The thread may be taper-cut, so thatthe varying depth of the thread will also affect the metered flow according to the spool position. The thread form will also qualifythe metering function; it can for example be square, triangular, or rounded.

The length and position ofthe groove will depend on the desired mode of use of the valve. Usuallythe groove will be open at one end into a circumferential groove or other recess of the spool, provided for controlling fluid flow in conventional manner, while theotherendofthegrooverunsoutinthesurfaceofa land of the spool. The run-out end of the groove will usually be placed so that it is closed off in at least one spool position whereby no flow is possible whereas on movement of the spool the run-out end moves into communication with a port of the valve to allow metered flow along the groove.In one useful arrangement, the valve has a first port associated with a flow recess in the spool, two further ports one on each side ofthefirst port for connection to the latter by the flow recess, and a respective helical groove in the lands of the spool on each side of the flow recess.

In the accompanying drawings, Figures 1 to 3 show a spool valve for directional control, in three different operating states.

The illustrated valve has a body 1 with an inlet channel or port2 and a pair of outlet channels or ports 3, 4, all interconnected buy a bore which contains a valve spool 5, in well known manner. The valve spool has a central circumferential groove 6 which on axial movement ofthe spool can interconnect the channels 2,3or2,4. Figure 1 shows the spool in its central or neutral position in which it prevents flow th rough the valve.

In each ofthe lands adjoining the central groove 6, the spool has a peripheral helical thread or groove 7,8 communicating with the central full-flow groove 6.

Figure 2 shows the spool after a limited movement to the right, sufficient to bring the end part of the helical groove 8 into the channel 4, but not enough to bring the groove 6 into communication with this channel. Consequently hydraulic fluid can flowfrom the channel 2 by way of the helical 9 roove 8 into the channel 4. Because the helical groove is shallow and narrow it has a throttling or metering effect and the rateofflowvariesinverselywiththe length of the groove traversed by the fluid, and therefore increases with increasing movement of the spool away from the neutral position. As the spool is moved further, the groove 6 comes into communication with the channel 4and the groove 8 no longer has any effect. The valve is now fully open and flow is substantially unrestricted.

Similarly, if spool were moved to the left, the groove 7 would provide a progressively increasing metered flow into the channel 3.

The drawings showgrooves 7, 8with a square or rectangularthread profile. Atriangularthread profile is a very practical form.

The illustrated metering grooves are of constant pitch, depth, and width. To provide a desired pattern of variation of metered flow with spool position, the thread may vary in width or depth e.g. being taper-cut towards its end, a nd/or its pitch may vary along its length; the degree of run-out can provide very fine control ofthe metering.

The valve described allowsvery fine flow control to be achieved by means of the helical grooves which can be produced economically using a screw-cutting lathe or other conventional screw-forming equipment.

1. A spool valve in which the valve spool has at least one oblique groove whereby, over at least part of the stroke ofthespool,thegroove provides metered fluid flow between ports ofthe valve.

2. Aspoolvalveasclaimedinclaim 1 inwhichthe spool has a full-flow recess and a said oblique groove informed in a land of the spool adjacentto this recess and communicateswiththe latter.

3. Aspool valve as claimed in claim 2 having a said oblique groove on each side ofthefull4low recess.

4. Aspool valve as claimed in claim 1,2 or3 constituting a directional valve.

5. Aspool valve as claimed in any preceding claim in which the oblique groove is helical.

6. A spool valve as claimed in any preceding claim in which the oblique groove is oftriangularform.

7. A spool valve as claimed in any preceding claim in which the oblique groove is tapered along its length.

8. A spool valve as claimed in any preceding claim in which the oblique groove has a run-out at its end selected to provide desired metering ofthe fluid flow.

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

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

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Hydraulic flow control valve This invention relates to hydraulic fluid control valves and in particular spool valves. According to the invention a valve spool has at least one oblique, preferably helical groove whereby, over at least partofthe spool movement,thegroove provides metered fluid flow. The flow metering can be controlled very finely by the degree of thread run-outatthe end of the thread. The thread may be taper-cut, so thatthe varying depth of the thread will also affect the metered flow according to the spool position. The thread form will also qualifythe metering function; it can for example be square, triangular, or rounded. The length and position ofthe groove will depend on the desired mode of use of the valve. Usuallythe groove will be open at one end into a circumferential groove or other recess of the spool, provided for controlling fluid flow in conventional manner, while theotherendofthegrooverunsoutinthesurfaceofa land of the spool. The run-out end of the groove will usually be placed so that it is closed off in at least one spool position whereby no flow is possible whereas on movement of the spool the run-out end moves into communication with a port of the valve to allow metered flow along the groove.In one useful arrangement, the valve has a first port associated with a flow recess in the spool, two further ports one on each side ofthefirst port for connection to the latter by the flow recess, and a respective helical groove in the lands of the spool on each side of the flow recess. In the accompanying drawings, Figures 1 to 3 show a spool valve for directional control, in three different operating states. The illustrated valve has a body 1 with an inlet channel or port2 and a pair of outlet channels or ports 3, 4, all interconnected buy a bore which contains a valve spool 5, in well known manner. The valve spool has a central circumferential groove 6 which on axial movement ofthe spool can interconnect the channels 2,3or2,4. Figure 1 shows the spool in its central or neutral position in which it prevents flow th rough the valve. In each ofthe lands adjoining the central groove 6, the spool has a peripheral helical thread or groove 7,8 communicating with the central full-flow groove 6. Figure 2 shows the spool after a limited movement to the right, sufficient to bring the end part of the helical groove 8 into the channel 4, but not enough to bring the groove 6 into communication with this channel. Consequently hydraulic fluid can flowfrom the channel 2 by way of the helical 9 roove 8 into the channel 4. Because the helical groove is shallow and narrow it has a throttling or metering effect and the rateofflowvariesinverselywiththe length of the groove traversed by the fluid, and therefore increases with increasing movement of the spool away from the neutral position. As the spool is moved further, the groove 6 comes into communication with the channel 4and the groove 8 no longer has any effect. The valve is now fully open and flow is substantially unrestricted. Similarly, if spool were moved to the left, the groove 7 would provide a progressively increasing metered flow into the channel 3. The drawings showgrooves 7, 8with a square or rectangularthread profile. Atriangularthread profile is a very practical form. The illustrated metering grooves are of constant pitch, depth, and width. To provide a desired pattern of variation of metered flow with spool position, the thread may vary in width or depth e.g. being taper-cut towards its end, a nd/or its pitch may vary along its length; the degree of run-out can provide very fine control ofthe metering. The valve described allowsvery fine flow control to be achieved by means of the helical grooves which can be produced economically using a screw-cutting lathe or other conventional screw-forming equipment. CLAIMS

1. A spool valve in which the valve spool has at least one oblique groove whereby, over at least part of the stroke ofthespool,thegroove provides metered fluid flow between ports ofthe valve.

2. Aspoolvalveasclaimedinclaim 1 inwhichthe spool has a full-flow recess and a said oblique groove informed in a land of the spool adjacentto this recess and communicateswiththe latter.

3. Aspool valve as claimed in claim 2 having a said oblique groove on each side ofthefull4low recess.

4. Aspool valve as claimed in claim 1,2 or3 constituting a directional valve.

5. Aspool valve as claimed in any preceding claim in which the oblique groove is helical.

6. A spool valve as claimed in any preceding claim in which the oblique groove is oftriangularform.

7. A spool valve as claimed in any preceding claim in which the oblique groove is tapered along its length.

8. A spool valve as claimed in any preceding claim in which the oblique groove has a run-out at its end selected to provide desired metering ofthe fluid flow.

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