GB2263532A - Automatic shut-off valve - Google Patents

Abstract

A shut-off valve, particularly for use with abrasive blast cleaning equipment; comprises a movable valve member 11 located between an inlet 7 for connection to a supply line for compressed air and an outlet 8 for connection to a return line, a spring-loaded lever (4, not shown) which acts on a stem 12 of the valve member 11, and a bleed orifice 10 connecting the outlet 8 to atmosphere. The lever carries a rubber block which seals the outlet from the bleed orifice when the lever is moved to lift the valve member 11 from its associated seat. A spring-loaded latch (6, not shown) serves to return the valve to its closed condition on release of the lever (4). <IMAGE>

Description

AUTOMATIC SHUT-OFF VALVES This invention relates to automatic shut-off valves and particularly to the type of automatic shut-off valve ordinarily referred to as a "deadman handle".

In blast cleaning operations, particulate abrasive material is entrained in a high velocity air supply and issues from a nozzle at the end of a blast line for direction at the item to be cleaned. Given the nature of blast cleaning, it is most essential that compressed air/abrasive cannot issue accidentally from the nozzle in the absence of an operative, or should the operative accidentially drop the nozzle. It has long been the practice to provide at the nozzle a deadman handle e to ensure that compressed air/abrasive cannot issue from the nozzle either in the absence of an operative or should some accident or illness befall the operative causing the operative to drop the nozzle.

With conventional deadman handles, a spring-loaded lever is provided to act on a valve arrangement. During normal operation the operative holds the lever in a position to close a valve and cause compressed air supplied by a supply line to the deadman's handle to be diverted down a return line to the blast machine, and to activate valve means on the blast machine to supply compressed air/abrasive through a supply line to the nozzle. The instant that the handle is released, the said valve is opened and the return line is evacuated to atmosphere to deactivate the valve means at the blast machine to prevent the further supply of compressed air/abrasive to the blast line.

Whilst such deadman handles as are known are effective in closing down the supply of compressed air/abrasive to the nozzle, they are inefficient in the sense that in the normal course of events, there can be frequent and relatively prolonged periods where blast operations are temporarily suspended but where compressed air is continuously supplied through the supply line to the deadman's handle and bled to atmostphere, in readiness for the closing of the valve at the deadman handle to activate the supply of compressed air/abrasive to the blast line. This is particularly wasteful of the energy required at the source of production of compressed air (e.g. a compressor). Also, and in extremely cold conditions, the continuous expansion of cold compressed air as it bleeds to atmosphere can result in the production of ice at the bleed hole.Should this build-up to a degree to block the bleed hole, the effect would be the same as closing the valve on the deadman handle, the diversion of air down the return line and the activation of the blast machine.

It is the objective of the present invention to improve on known constructions of deadman handles.

According to the present invention, an automatic shutoff valve comprises a movable valve member located between an inlet for connection to a supply line for compressed air and an outlet for connection to a return line, a spring-loaded lever means to act on the valve means, and a bleed orifice connecting the outlet from the valve to atmosphere, and there being a means to seal the outlet from the bleed orifice with the lever means in its condition where it has acted on the valve member.

Thus the valve member may be a piston with a head to sealingly engage a seat within the valve and a rod to extend through and out of the inlet to the valve and the lever means may be a pivoted lever located in relation to the valve such that depression of the lever causes its end adjacent the piston rod to contact it and hence urge the piston head from its seat, and to open the communication of the valve inlet and outlet. Simultaneously a closure means, e.g. a sealing block, is brought by the pivotal movement of the lever against the orifice opening to close it.

During normal operation, the operative activates the lever to open the piston valve and close the bleed orifice connected to the valve outlet, and when pressure air in the supply line is diverted down the return line to valve means on the blast machine, to cause the supply of compressed air/abrasive to the blast line, and hence to the nozzle. If the handle is deliberately or accidentally released, it swings under its spring-loading to allow the piston under its springloading to close the inlet to the valve, and simultaneously open the bleed orifice communicating with the outlet from the valve. This results in instantaneous depressurising of the return line to the blast machine, the deactivation of its valve means, and the prevention of the further supply of compressed air/abrasive to the blast line.Alternatively, a valve block is provided with a through-passage in which a valve stem is located, and which extends out of the passage for contact by the lever, there being an inlet for connection to the supply line for pressure air communicating with the passage to one side of a valve seat and an outlet connected to the return line communicating with the passage to the other side of the valve seat, a through-bore in the valve seat with a bleed passage communicating with the outlet, at least one bleed passageway connecting the through-passage to atmosphere to the outlet side of the valve seat, and a valve stem extending along the through-passage and having an end section to pass through the valve seat to contact a valve head located to the other side of the valve seat, there being sealing means provided between the stem and the valve seat.

During normal operations and with the lever of the deadman's handle depressed, the stem is urged along the through-passage, its end section passing through the valve seat to push the valve head away from the seat. With the stem sealed in relation to the valve seat, pressure air from the inlet passes into the valve seat and is directed to the outlet, to activate the main valve of the equipment. Should the lever of the deadman's handle be accidentally or deliberately released, the valve head is urged against the seat either by pressure air behind it or by providing an appropriate spring closing the inlet, and the stem is pushed through the seat, clearing the seal and when the return line is connected to the bleed passageway to atmosphere, to exhaust the return line and close the main valve on the equipment.

With the invention, and in its OFF condition, the valve inlet at the deadman handle is closed and there is no continuous bleeding of compressed air to atmosphere, with the two-fold advantage that there is no waste of energy at the source of supply of compressed air, and no possibility of ice build up at the bleed orifice.

As a further precaution, it is preferred to provide a spring-loaded latch that acts on the lever to prevent accidental depression of the lever and opening of the piston valve. Thus, an operative must deliberately depress the latch before the lever can be pivoted to act on the piston and close the bleed orifice, to enable blasting operations to commence.

One embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a deadman's handle in accordance with the invention; Figure 2 is a view in the direction of arrow A of Figure 1; Figure 3 is a view in the direction of arrow B of Figure 1; Figure 4 is a section of part of Figure 1 on the line 4-4 of Figure 1; and Figure 5 corresponds to Figure 4 but shows an alternative construction.

In the drawings, a deadman's handle has a body 1 provided with connections 2 to a compressed air supply line 3 to a return line. Pivotally secured to the body 1 is a handle 4 having a rubber block 5 on its inner surface. Also mounted on the body is a spring-loaded lever 6 the free end of which acts below the handle.

The connections 2 and 3 extend to respective passageways 7, 8 within the body, the passageway 7 communicating with a chamber 9 in the body to one side of a valve seat, and the passageway 8 communicating with an outlet orifice 10 from the chamber. A valve member 11 lies in the chamber 9 and has a stem 12 extending through the orifice to emerge from the body.

Thus, at the onset of operations, the lever 6 is swung by hand away from the handle, and the handle pressed to urge the block 5 against the exposed end of the stem 12, to urge the valve member 11 from the seat in the chamber, the block closing on to the top face of the body to seal the outlet from the orifice 10. In this condition, the pressure line connected to the connection 2 and the return line connected to the connection 3 are put into communication.

In the event of the handle being accidentally or deliberately released, the spring-loaded lever 6 acts on the handle to swing it to an inoperative position until the lever locks below the handle to prevent it from being depressed without the lever being deliberately removed.

The valve 11 is then urged by pressure air to close on the valve seat, and when the pressure line is sealed at the deadman's handle and held under pressure, and the return line is opened to atmostphere by allowing air to bleed from the return line through the now open orifice 10.

When the deadman's handle is connected to abrasive blast cleaning equipment, normal operation is caused by an operative activating the deadman's handle to put the pressure line to the handle in communication with the return line, whereby to put pressure air to the blast line of the equipment, and hence to the nozzle of the equipment. When the handle is accidentally or deliberately released the pressure line is closed at the handle and the return line opened to atmosphere, with its instant depressurisation and deactivation of the main valve and hence prevention of further supply of pressure air to the blast line to the nozzle.However, as the pressure line to the handle is closed, there is prevented the continuous bleeding of pressure air at the handle to atmosphere, with the twin advantages of no waste of energy at the source of supply of compressed air and no build-up of ice at the outlet bleed orifice on the handle that could, if present, cause accidental switch-on of the equipment when the deadman's handle has been released, along with the avoidance of irritating noise caused by air bleeding through an orifice.

In the alternative construction illustrated in Figure 5, a valve has a through-passage 13 and inlet 14 for connection to a supply line and an outlet 15 for connection to a return line, the inlet and the outlet communicating with the through-passage 13 to opposite sides of a valve seat 16. A valve head 17 is provided spring loaded towards the valve seat, and to the opposite side of the valve seat to the valve head, bleed passageways 18 are provided communicating the through-passage to atmosphere. Lying in the through-passage is a valve stem 19 passing through a guide bush 20 and emerging from the valve through the bush. To its opposite end, the valve stem has a section of reduced diameter 21 to extend through a bore through the valve seat, the bore having a bleed passage 22 communicating with the outlet from the valve.Sealing means 23 are provided on the valve seat to engage the stem.

Thus with the lever of the deadman's handle depressed the valve stem 19 is urged along the through-passage 13, its section of reduced diameter 21 passing through the valve seat to contact the valve head and urge the valve head away from the valve seat against the action of a spring 24. In this condition the valve stem engages the seal 23 to close the valve seat at that side.

In this condition, pressure air from the supply line passes through the inlet 14 into the valve seat and through the passage 22 to the outlet 15, to provide pressure air in the return line to activate such as a main valve on abrasive cleaning equipment. In the event that the lever on the deadman's handle is deliberately or accidentally released the spring 24 urges the valve head 17 against the valve seat 16 to close the bore. The stem 19 is urged through the stem to release it from the seal 23 and when the outlet 15 communicates with the through-passage 13 through the passage 22 in the seat and when pressure air in the return line exhausts through the through-bore 13 and the bleed passageways 18 to atmosphere. Exhausting of the return line causes the instant closing of the main valve of the equipment. As with the construction of Figures 1 to 4, there is again the closure of the supply line at the valve and the prevention of continuous bleeding at the deadman's handle with those benefits that have been hitherto mentioned.

Claims (8)

1. An automatic shut-off valve comprising a movable valve member located between an inlet for connection to a supply line for compressed air and an outlet for connection to a return line, a spring-loaded lever means to act on the valve means, and a bleed orifice connecting the outlet from the valve to atmosphere, and there being a means to seal the outlet from the bleed orifice with the lever means in its condition where it has acted on the valve member.

2. An automatic shut-off valve as in Claim 1, wherein said means to seal said outlet from the bleed orifice is on the lever.

3. An automatic shut-off valve as in Claim 2, wherein the valve member is a piston with a head to sealingly engage a seat within the valve and a rod to extend through and out of a bleed orifice of the valve and the lever means is a pivoted lever located in relation to the valve such that depression of the lever causes its end adjacent the piston rod to contact it and hence urge the piston head from its seat, and to open the communication of the valve inlet and outlet.

4. An automatic shut-off valve as in Claim 3, wherein pivoting of the lever to open the valve causes the means on the lever to close the bleed orifice.

5. An automatic shut-off valve as in any of Claim 1 to 4, wherein the means on the lever to close the orifice is a sealing block.

6. An automatic shut-off valve as in Claim 1, wherein a valve block has a through-passage in which a valve stem is located and which extends out of the passage for contact by the lever, there being an inlet for connection to the supply line for pressure air communicating with the passage to one side of a valve seat and an outlet connected to the return line communicating with the passage to the other side of the valve seat, a through-bore in the valve seat with a bleed passage communicating with the outlet, at least one bleed passageway connecting the through-passage to atmosphere to the outlet side of the valve seat, and a valve stem extending along the through-passage and having an end section to pass through the valve seat to contact a valve head located to the other side of the valve seat, there being sealing means provided between the stem and the---valve seat.

7. An automatic shut-off valve as in any of Claims 1 to 6, wherein a spring-loaded latch acts on the lever to hold it in inoperative position and prevent accidental depression of the lever.

8. An automatic shut-off valve substantially as hereinbefore described with reference to the accompanying drawings.