GB2285112A - Lockable valve in an hydraulic circuit - Google Patents

Abstract

An hydraulic circuit of an item of plant machinery comprises: at least one hydraulically-operated device (not shown); a fluid tank (50); pump (55) for supplying fluid, at high pressure, from the tank (50) to the at least one hydraulically-operated device; a lockable valve (10), the circuit providing, when the valve is in its locked condition, a low pressure return passage (R) to the tank, through the valve (10) for the high pressure fluid supplied from the pump, whereby insufficient fluid pressure is supplied to the least one hydraulically-operated device for it to operate, the valve (10) blocking the return passage when in its unlocked condition. Also disclosed is a tamperproof collar (102) which surrounds the connection between the valve (10) and the pipe providing the section passage, the collar being secured in position by a spanner (130) having a sleeve portion (134) of C-shaped section (Fig. 5, not shown). <IMAGE>

Description

SECURITY OF PLANT MACHINERY The present invention relates to the security of plant machinery, especially plant machinery including hydraulically-operated devices.

Items of plant machinery such as diggers, earth movers, dumper trucks and forklift trucks, which commonly include hydraulically-operated digging and lifting devices, are often left at night on site in an area which can be quite easily accessed by the public.

As a result, the theft and misuse of unattended plant machinery is a widespread occurrence.

It is an object of the present invention to provide enhanced security for plant machinery.

With this in mind, in a first aspect of the invention there is provided an hydraulic circuit of an item of plant machinery comprising: at least one hydraulically-operated device; a fluid tank; a pump for supplying fluid, at high pressure, from the tank to the at least one hydraulically-operated device; a lockable valve, the circuit providing, when the valve is in its locked condition, a low pressure return passage to the tank, through the valve, for the high pressure fluid supplied from the pump, whereby insufficient fluid pressure is supplied to the least one hydraulically-operated device for it to operate, the valve blocking the return passage when in its unlocked condition.

In a second aspect of the invention, there is provided: a valve comprising: a housing having an inlet and outlet port; a lock; a valve member coupled to the lock; and a valve seat, the valve member being moveable from a first position at which it rests upon the valve seat and thereby blocks the path from the inlet to the outlet port, when the lock is in its unlocked condition, to a second position at which the valve member is displaced from the valve seat in a direction generally towards the inlet port and thereby provides a passage from the inlet port to the outlet port, when the lock is in its locked condition.

Preferably, the valve member includes a spring which is operable to bias the valve member into its first position.

Preferably, the lock is movably mounted in the housing and moves in unison with the valve member. The movement of the valve member and lock may be linear and can be co-linear.

The valve in accordance with this second aspect of the invention is the preferred valve for use in the first aspect of the invention.

Using the valve, as previously described, a determined criminal with a good knowledge of hydraulics could overcome and defeat the system by disconnecting the valve from the circuit and fitting a blanking plug.

For this reason, the present invention, in a third aspect of the invention, provides a device for protecting the coupling between a fluid conduit and an element of an hydraulic circuit, the element including a body, a port and a first adapter mountable to the port, the fluid conduit having a second adapter, which is disposed at one end thereof, and can be screwed to the first adapter to form the coupling, the device comprising a collar having an internal flange at one end thereof, the collar being adapted to be arranged, in use, such that it surrounds the coupling and the internal flange is retained between the body of the element and the first adapter, the dimensions of the collar being such that there exists a small gap between the inside surface of the collar and the outside surface of the first adapter.

In order to attach and detach the first and second adapters a spanner in accordance with the invention, in a fourth aspect, is provided. The spanner comprises a operating portion and a sleeve of generally C-shaped cross-section projecting from the operating portion, the sleeve being adapted to fit in the small gap between the inside surface of the collar and the outside surface of the second adapter, and engage the outside surface of the second adapter.

Exemplary embodiments of the invention are hereinafter described with reference to the accompanying drawings, in which: Figure 1 shows a cross-sectional view of a valve in accordance with the present invention: Figure 2 shows a cross-sectional view of an hydraulic circuit in accordance with the present invention incorporating the valve of Figure 1 in its unlocked or drive condition; Figure 3 shows the hydraulic circuit of Figure 2 when the valve is in its locked or disabling condition; Figure 4 shows a view in cross-section of one embodiment of a coupling protection device in accordance with the present invention; Figure 5 shows a perspective view of the spanner forming part of Figure 4; and Figure 6 shows a view in cross-section of another embodiment of a coupling protection device in accordance with the present invention.

Referring to Figure 1, a valve in accordance with the present invention is generally designated by the reference numeral 10.

The valve 10 includes a housing comprising a generally cylindrical body portion 12 having its longitudinal axis indicated by the dotted line A-A'; an end cap 13 disposed at a first end of the body portion 12; and a mouth portion 21 at the second end of the body portion 12. The end cap 13 is secured to the body portion 12 and defines a first port 14. An O-ring 23 provides a seal between the body portion 12 and the end cap 13. An outlet port 16 is formed in the side wall of the body portion 12.

The inlet and outlet ports communicate with one another via a passage which comprises two chambers, an outlet chamber 17 adjacent the outlet port 16 and a wider inlet chamber 15 adjacent the inlet port 14. The wall of the outlet chamber 17 which boarders on the inlet chamber 15 forms a valve seat 24. Each port 14, 16 includes threaded walls 19 for receiving a threaded male portion of a coupling.

The mouth portion 21 receives and provides for the axial movement of a barrel lock 25 along the axis A-A'. When the lock 25 is in its locked condition as is shown in Figure 1, a bar 27 projects from the barrel of the lock 25 and engages a recess 22 of the mouth portion 21. The end of the lock is coupled to a valve member 30 by means of a guide pin 29. The inlet chamber 17 is sealed from the mouth portion 21 by an O-ring 34.

The valve member 30 includes a spigot portion 31 which is attached to a spring 32. The spring 32 is operable to bias the valve member 30 towards the mouth portion 21 in the direction indicated by the arrow B.

It will be appreciated that when the valve 10 is in its locked condition as illustrated in Figure 1, fluid entering the inlet port 14 is free to pass through the inlet and outlet chambers 15,17, past the valve member 30 and then to the outlet port 16.

When the valve 10 is put into its unlocked condition, the bar 27 of the lock 25 is retracted and the biasing action of the spring 32 comes into play, whereby the valve member 30 and the lock 25 move in unison along the axis A-A' until the spigot portion 31 engages the valve seat 24. The valve 10 is shown in this condition in Figure 3. It will be appreciated that the flow from the inlet portion 14 to the outlet port 16 is prevented by the engagement of O-rings 36 in the spigot portion 31 with the valve seat 24.

Figure 2 and 3 show the valve of Figure 1, in use, in an hydraulic circuit of an item of plant machinery, for example, a digger.

Referring to Figure 2 and 3, the hydraulic circuit comprises an oil tank 50 form which a pump 55 can draw oil and supply it at high pressure to hydraulically operated devices 100 in the circuit. For the sake of diagrammatic simplicity, these devices have not been illustrated, but might include, for example, the front and back buckets and the stabilizing legs of the digger.

In accordance with the invention, the hydraulic circuit also comprises a Tjunction 60 at the outlet of the pump 55. The T-junction 60 provides a flow path from the pump 55 to the hydraulically-operated devices 100 (and then back to the tank 50) and also a flow path from the pump 55 straight back to the tank 50 via the valve 10 of Figure 1.

In use, when the valve 10 is in its unlocked or drive condition as shown in Figure 2 the valve 10 presents a closed circuit to the fluid flowing to the valve 10 (see the arrow R), whereby the hydraulically-operated devices 100 are able to function normally. It will be noted that the higher the pressure in the circuit the more tightly the valve member 30 is urged against the valve seat 24.

When the valve 10 is put into its locked or disabling condition as shown in Figure 3, the valve 10 offers a low pressure return passage to the output of the pump (see the arrow R), whereby insufficient fluid pressure (see arrow C) is supplied to the hydraulically-operated devices 100 for them to operate so the hydraulic circuit is effectively disabled.

If, for example, prior to leaving a digger the operator dropped the front and back buckets, digging them into the earth, jacked the stabilizing legs down hard and then locked the plant lock into the disabled position as in Figure 3, thereby making it impossible to raise the hydraulic operated buckets and legs, it would be difficult for an unauthorised person to move the digger.

Using the lockable valve 10 as previously described a determined criminal with a good knowledge of hydraulics could overcome and defeat the system by disconnecting one of the couplings marked 'x' in Figure 2 and fitting a blanking plug. For this reason, the present invention also provides devices for securing those couplings; the device, designated 101, is featured in Figures 4 to 6. In Figure 4 the device 101 is shown protecting the coupling to the inlet portion 14 of the valve 10.

It will be appreciated that the device 101 can be secured to the ports of any element of an hydraulic circuit, for example the T-junction 60.

In this example, the coupling comprises a first adapter 110 having a nut 1 10a and two threaded male portions, one of which can engage the threaded walls 19 of the inlet port 16 and the other of which can engage the internal threads (not shown) of a second adapter 120, the second adapter also including a nut 120a and being connected to the end of a hose 95.

The device 101 itself comprises a cylindrical collar 102 having an internal flange 103 at one end thereof. The collar 102 is preferably made from case-hardened steel.

As will become apparent, hereinafter, a special spanner 130 is required to attach and detach the device 101. It comprises a operating portion 132 and a sleeve 134 of generally C-shaped cross-section projecting from the handle portion 132. The internal cross-section of the sleeve 134 is selected to match the external cross-section of the nuts 110a, 120a of the coupling. The operating portion 132 can include a handle portion.

In order to attached the hose 95 to the inlet port 14, the first adapter 110 is positioned inside the collar 102 such that one of its threaded male portions projects through the aperture defined by the internal flange 103.

The first adapter is then screwed into the first portion 14 using the spanner 130, the sleeve 134 of which, it will be noted, fits in a small gap between the inside surface of the collar 102 and the outside surface of the first adapter 110.

The sleeve 134 need not snugly fit into the gap between the collar 102 and the first adapter 110, although this arrangement is preferred. However, it is preferred that the gap is relatively small as this prevents the use of other more conventional spanners.

Next the second adapter 120 is screwed onto the first adapter 110 again using the spanner 130. It will be appreciated that as the second adapter 120 is screwed onto the first adapter 110, the sleeve 134 of the spanner 130 will extend only partially into the collar 102 in order that the nut 120a can be rotated relative to the nut 110a.

Once the adaptors are connected as shown in Figure 4, the spanner 130 is removed.

The use of a case-hardened steel makes the collar 102 very difficult to cut away from the coupling 110, 120.

Once the spanner 130 is removed, the would-be thief is presented with a coupling which is completely inaccessible to any conventional spanner.

Preferably, the adapter 110 is not screwed tight against the valve 10, but is slightly spaced therefrom, so that collar 102 can rotate relative to the coupling 110, 120. This makes tampering with the collar 102 even more difficult.

In another embodiment featured in Figure 6, the security device 101 also includes an insert 140 which is interposed between the first adapter 110 and the internal flange 103. The insert 140 comprises an annular ring 142 having an annular flange 144 upstanding therefrom. The insert 140 and particularly the flange 144 is dimensioned such that when the insert 140 contacts the flange 103 and the adaptor 110 as shown in Figure 6, the flange 144 projects through the aperture defined by the flange 103, and can contact the valve 10. Thus, it may seem that as the adaptor 110 is screwed into the inlet port 14, it is only the insert 140 which is held tightly between the nut 110a and the valve 10, the collar 102 being free to rotate in a gap 146 created by the flange 144.

An advantage of the Figure 6 arrangement over that shown in Figure 4 is that the operator is not required to create intentionally the gap between the collar 102 and the valve 10 (ie. by deciding not to screw the adapter 110 tight against the valve 10), but is merely required to fit the security device 101 to the coupling 110, 120, an appropriate size gap arising from the structure of the security device 101 itself.

In other embodiments, the first adapter 110 need not be screwable to the circuit element, but may be attached thereto in another way. In such an instance, it will be appreciated that the sleeve 134 would not need to be substantially as long as the collar 102 and there would not necessarily be a small gap between the first adapter 110 and the collar 102.

An item of plant, such as a digger, fitted with both the valve 10 and the collar 102 would be very difficult to steal.

Claims (10)

1. A hydraulic circuit of an item of plant machinery comprising: at least one hydraulically-operated device; a fluid tank; a pump for supplying fluid, at high pressure, from the tank to the at least one hydraulically-operated device; a lockable valve, the circuit providing, when the valve is in its locked condition, a low pressure return passage to the tank, through the valve, for the high pressure fluid supplied from the pump, whereby insufficient fluid pressure is supplied to the least one hydraulically-operated device for it to operate, the valve blocking the return passage when in its unlocked condition.

2. A valve comprising: a housing having an inlet and outlet port; a lock; a valve member coupled to the lock; and a valve seat, the valve member being moveable from a first position at which it rests upon the valve seat and thereby blocks the path from the inlet to the outlet port, when the lock is in its unlocked condition, to a second position at which the valve member is displaced from the valve seat in a direction generally towards the inlet port and thereby provides a passage from the inlet port to the outlet port, when the lock is in its locked condition.

3. A valve as in Claim 2, wherein the valve member includes a spring which is operable to bias the valve member into its first position.

4. A valve as in Claim 3, wherein the lock is mounted for linear movement in the housing and moves in unison with the valve member.

5. An hydraulic circuit as in Claim 1 incorporating the valve of any of Claims 2 to 4.

6. A device for protecting the coupling between a fluid conduit and an element of an hydraulic circuit, the element including a body, a port and a first adapter mountable to the port, the fluid conduit having a second adapter, which is disposed at one end thereof, and can be screwed to the first adapter to form the coupling, the device comprising a collar having an internal flange at one end thereof, the collar being adapted to be arranged, in use, such that it surrounds the coupling and the internal flange is retained between the body of the element and the first adapter, the dimensions of the collar being such that there exists a small gap between the inside surface of the collar and the outside surface of the first adapter.

7. A spanner for use with the device of Claim 6 comprising an operating portion and a sleeve of generally C-shaped cross-section projecting from the handle portion, the sleeve being adapted to fit in the small gap between the inside surface of the collar and the outside surface of the second adapter, and engage the outside surface of the second adapter.

8. An hydraulic circuit as in Claim 1 or 5 including the device of Claim 6 being used in protecting the inlet and outlet ports of the valve.

9. An hydraulic circuit constructed, arranged, and adapted to operate substantially as herein described with reference to the accompanying drawings.

10. A valve constructed, arranged and adapted to operate substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.