FIELD OF INVENTION

This invention lies in the field of fast opening valves, that is, valves that hold a gas, powder or other substance supply under pressure and must open upon actuation to release the gas or powder, or both. Valves of this kind find application in fire and explosion suppression devices, for example used in mines, factories and other areas subject to risk of explosion, electrical sub stations and switching rooms, etc. Such valves are also used in military applications. Valves used in these applications are known and for example include the "Deugra" (Deutsch Graviner) and "Explospot" valves.

BACKGROUND

A vital function of such valves is that they retain pressure over long periods, which is a challenging requirement contradictory to the requirement to open fast when actuated. By the same token it must be possible to check the pressure retained by the valve and to check all moving parts for free movement without friction. This type of inspection must be done at regular intervals, often prescribed by strict operation manuals or regulation. It must be possible to certify the condition of the valve with absolute confidence and reliability. The reason for this is that a loss of pressure or defective moving parts could render the protection intended by the device less effectual or even nugatory.

The very requirement to be able to check pressure regularly raises challenges as this is done by opening a bleed valve to a pressure gauge and thereafter closing the bleed valve. This entails a loss of the gas, powder or other substance under pressure, albeit small, nevertheless repetitively over a period of time, which can be years in the cases of many installed devices. Where gas and powder are involved the passage of gas past the bleed valve commonly causes leaks as perfect closure is inhibited by the powder, a risk of an operative imperfectly closing the bleed valve is also there. These problems are serious in the context of the very rigorous requirements of fire and

explosion protective devices since in many cases human life is at risk, not to mention expensive equipment.

THE INVENTION

The present invention provides a valve assembly, which includes a body having a passage in the body, the passage adapted to provide communication from a container of a substance under pressure to discharge means for the substance, a piston which can move as a valve from a sealing position to an opening position, a trigger mechanism which retains the piston in the sealing position by means of a sear that engages the piston and when triggered disengages the piston to release to piston to move to the opening position, characterised in the addition to the body of a pressure tester assembly consisting of a cylinder, a plunger movable in the cylinder, a rod that passes through the plunger and may be moved in the plunger to contact and lift the piston off the sear.

The rod is conveniently a screw that may be moved in the plunger by screwing the rod in a screw thread in the plunger.

The cylinder is filled with a fluid, conveniently an incompressible fluid such as an oil and a pressure gauge is attached to the cylinder. When in use the piston is lifted off the sear the full force on the piston generated by the pressure of the gas or powder is transmitted by the rod to the plunger and is carried by the plunger, which converts the force to pressure in the oil and this pressure is measured by the pressure gauge. The oil pressure will be an indirect but accurate measure of the gas or powder pressure. By choice of the cylinder size and effective plunger area the oil pressure can be made an easy whole number ratio to the gas or powder pressure or even equal to it.

The pressure tester assembly is made to be attached to the valve body for use in testing the gas or powder pressure, and an assembly which distributes the gas or powder upon discharge and catches the piston is normally attached to the body.

Thus a pressure tester assembly consisting of a cylinder, a plunger movable in the cylinder, a rod, optionally a screw that passes through the plunger and may be moved, optionally screwed in a screw thread, in the plunger, is included in the scope of this invention.

The cylinder preferably has a means for connection of an oil filler, to fill the space between the cylinder and plunger before use of the pressure tester.

THE DRAWINGS

The invention will be more fully described by way of an example, with reference to the drawings, in which : -

Figure 1 is an exploded isometric view of the components of a valve assembly body and a pressure tester assembly,

Figure 2 is an exploded isometric view of the components of the pressure tester assembly,

Figure 3 is an axial cross section of the pressure tester assembly,

Figure 4 is and end view of the pressure tester assembly,

Figure 5 is an isometric view of the plunger of the pressure tester assembly,

Figure 6 is an isometric view of the cylinder of the pressure tester assembly,

Figure 7 is an isometric view of the end wall and connection flange of the pressure tester assembly,

Figure 8 is an axial section of the whole valve assembly, and

Figure 9 is an axial section of the valve assembly body to which the pressure tester assembly has been fitted.

THE PREFERRED EMBODIMENTS

Figure 1 shows the components of the valve body 1, including in particular the valve piston 2, which moves in passage, which passes through the body. The view also shows the two levers 3, which are joumalled on the sear 4, which is in the form of a shaft with a flattened edge. Reference is hare made to South African patent 96/0718 where a full description of the valve body and associated components is given. Cover plates 5 cover the recesses in which the levers are located, with seal rings 9. A pressure switch assembly 14 is fitted to the body, but not accepted as a sufficiently reliable indicator to trust alone. A filler assembly 23 is fitted to the body of the valve.

Figure 1 also shows the components of the pressure tester, including the pressure tester piston 27, which works in the cylinder 30, sealed with O-rings 28 and 29. The end of the cylinder is closed by a wall 26, which is bolted to the cylinder. A screw 31-33 is shown here as if separated merely for convenience in the exploded view, in fact it is a single rod (see figure 3). For convenience the threads are not shown in this view but are present in fact, (see figure 2).

Figure 2 to 4 show the pressure tested components and again the screw rod is shown as if separated into two parts but is in fact one (see figure 3). The

screw rod screws in a thread in the pressure tester piston, passing right through this piston to project out the other side. The part 31 of the rod is threaded and the part 33 is unthreaded. The cylinder has a hole 34 for fitting a pressure gauge and a hole 35 for attaching a fluid filling means. More detailed illustrations are given of the pressure tester piston 27 in figure 5, the cylinder in figure 6 and the end wall for the cylinder in figure 7.

Figure 8 shows a complete assembly of a valve body 90, a tank 107 for a gas or powder or water under pressure for fire or explosion extinguishing purposes and a diffuser section 91 with valve piston receiver 92. Again a full description of this unit is provided in patent 96/0719.

Figure 9 shows the valve body 90, which has had the distributor section 91 and valve piston receiver 92 removed and replaced by the pressure tester, which has been described above. The valve body and the pressure tester are held together by clamps of the kind indicated by reference numeral 95 in this figure. As can be seen, the pressure is not released at all by this process, as the valve piston, designated 98 in this drawings, remains undisturbed in the sealing position retained by the sear, designated 1 11 in this drawing. The screw 31 - 33 is the screwed in until it just lifts the valve piston off the sear. The full force on the valve piston caused by the pressure of the gas in the tank 107 is then is carried by the screw-rod 31 - 33 and hence by the pressure testing piston, which is transferred to the pressure of the oil in the cylinder 30. This pressure can be measured by an accurate gauge as a reliable measure of pressure in the tank, without releasing any gas or otherwise disturbing the system. The pressure tester is then removed and the diffuser and receiver replaced to render the system operational.

Clearly other mechanically equivalent arrangements can be adopted to achieve the purpose of this invention, namely the transfer of the force on the valve piston from the sear to a pressure tester.

Another arrangement according to the invention would be to measure the force on the screw 31 -33, by means of a force gauge. For example, the pressure tester piston and cylinder would be replaced by a spring gauge with an accurately calibrated spring and graduated scale.

Friction efforts at the valve piston, between its O-rings and the passage walls is negligible at the high pressures commonly used, but if it is a factor to consider, the measure could be made both after screwing the screw in and then after screwing the screw out, if there is a measurable difference, the average value is the true one.

The valve described above is provided with specific attachments that enable the following to be done without loss of pressure : - test the inside pressure of the cylinders check all moving parts for free movement without friction physically activate the valve under pressure without losing pressure or any other extinguishing material test forces necessary to operate the valve.

REFERENCES

1 valve body

2 valve piston

3 lever

4 shaft

5 cover

6 lock washer

7 washer

8 indicator

9 indicator

10 shim

nut O-ring O-ring pressure switch O-ring O-ring

O-ring bolt bolt bolt O-ring filler body O-ring O-ring cylinder wall pressure tester piston O-ring O-ring cylinder screw socket set screw screw/rod pressure gauge connection oil filler connection

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