GB1558414A

GB1558414A - Pressure indicator

Info

Publication number: GB1558414A
Application number: GB87277A
Authority: GB
Original assignee: FIREMASTER EXTINGUISHER Ltd
Current assignee: FIREMASTER EXTINGUISHER Ltd
Priority date: 1978-01-11
Filing date: 1978-01-11
Publication date: 1980-01-03

Description

(54) PRESSURE INDICATOR (71) We, FIREMASTER EXTINGUISHER LIMITED, a British Company, of Firex Works, Friendly Place, Lewisham Road, London SE13., England, do hereby declare this invention to be described in the following statement: This invention relates to pressure indicators for incorporation in fluid pressure containing assemblies, typically pressure containers, whereby a check can be made as to whether pressure within the assembly is below or above a predetermined level.

The invention has particular but not exclusive application to fire extinguishers of the stored pressure type, in which an extinguisher body holds a charge of extinguishant under fluid pressure, for example a charge of dry powder extinguishant under gas pressure. Fire extinguishing apparatus is subjected to lengthy periods of non-use, often under adverse conditions as in vehicles or boats, and not always under periodic inspection by specialists, and undue reliance may easily be placed on apparatus which is no longer reliable or even operable due, for example, to undetected leakage. Thus it is particularly desirable that a ready means of checking the condition of an extinguisher is available as a built-in feature and can easily be operated by a person having no special skills and without the use of test equipment or the need to unseal and re-charge the extinguisher.

The object of the invention is to provide a pressure indicator which is of particularly simple construction yet which is reliable and efficient in use.

According to the invention a fluid pressure indicator comprises a body member adapted to be mounted cn a fluid pressure containing assembly in communication with its interior, a plunger member moveable relative to the body member between respective inner and outer positions and adapted to be urged toward the latter position by fluid pressure within the assembly in use, sealing means maintaining a fluid tight seal between said members throughout the range of movement of the plunger member, and a dished spring element having an outer margin engaged with one member and a central region engaged with the other member, movement of the plunger member from one to the other of said positions causing deflection of said element springing it from outwardly convex to outwardly concave conditions and vice versa, the spring element providing a predetermined resistance to movement of the plunger from the inner to the outer position which will be overcome by fluid pressure loading from within the assembly in use which is above a predetermined minimum level.

The spring element is conveniently a metal Bellville washer whose outer peripheral margin and margin of its central aperture are located by formations of the respective members, the sealing means preferably acting between relatively moveable surfaces of the members inwardly of the spring element so that the latter is not exposed to the contents of the body.

A tail portion of the plunger member may be formed as a piston in sliding engagement with a cylinder defined by part of the body member and within which said fluid pressure loading acts in use.

Alternatively part of the body member might form a piston co-acting with a cylinder formation of the plunger member, or a flexible diaphragm could be used to transmit the fluid pressure to the plunger member.

Preferred embodiments of the invention are now more particularly described with reference to the accompanying drawings wherein: Figure 1 is a longitudinal section of one form of pressure indicator for a stored pressure fire extinguisher; Figure 2 is a like view of a modification of said indicator,. and Figure 3 is a like view of another form of pressure indicator for the like purpose.

Referring now to Figure 1 the indicator comprises a body member which is built up of two main parts, a cylinder block 11 and a nut 12 enabling it to be mounted in an aperture of a body 10 of the extinguisher, a gasket 13 being provided to prevent leakage. The cylinder 9 defined by block 11 opens axially outwardly into a larger diameter chamber 14 defined by the outer end of nut 12 and a threaded retainer 15 having a central aperture. All three components of the body member are plastics mouldings and the inner end of cylinder 9 is closed except for a vent 16 which contains a filter 17 to prevent the powder charge entering the cylinder when used in a dry powder fire extinguisher.

A plunger member is built up of two main moulded plastics components, a piston 18 forming a tail of the plunger member axially moveable within cylinder 9 and having an outer flanged head 19, and a push-button 20 located in the aperture in retainer 15 and having an inner flange 21.

A spring element in the form of a spring steel Bellville washer 22 has the margin of its central aperture located in a groove defined between flanges 19 and 21 within chamber 14, its outer peripheral margin being located in another groove defined between nut 12 and retainer 15, thus the plunger member can be moved inwardly and outwardly of the body by springing washer 22 from an outwardly concave condition to an outwardly convex condition as shown in the drawing and vice versa, inward movement being effected from the exterior of the extinguisher by pressing push-button 20. The said grooves are wide enough to allow clearance for the angular displacement of said margins as the conical profile of washer 22 is reversed during said plunger movement.

An 0 ring 23 is located in an annular groove of piston 18 to provide a fluid tight sliding seal with the wall of cylinder 9.

Figure 2 shows a modification of the above construction in which the body 10 is provided with an internally threaded bush 10a in its wall, the indicator in this case having a unitary body member 1 la (instead of the separate cylinder block 11 and nut 12 of Figure 1) which is screwed directly into bush lOr and sealed by a gasket 13a engaging the outer face of the body wall.

Cylinder 9a defined by member 1 la is somewhat longer than that shown in Figure 1 and accommodates a longer piston 18a having two axially spaced 0 rings 23a.

The vent filter 17a is mounted in the inner end of the cylinder bore itself. In all other respects the construction and operation is the same as the embodiment of Figure 1.

The size and spring characteristics of washer 22 are selected in combination with the effective diameter of piston 18 or 18a and its frictional resistance to movement so that the plunger member will only be displaced outwardly to the position shown in the drawing by fluid pressure within body 10 and communicated to cylinder 9 or 9a which is above a predetermined minimum level being a level necessary for effective operation of the extinguisher.

The condition of the extinguisher can be readily and speedily tested at any time by pressing the button 20 inwards until a click is heard and felt as washer 22 snaps to its outwardly concave condition, the button is then released and if the pressure level is adequate the plunger member will be returned to its initial outward position, again causing a click, thus the check is both visual and can be heard giving particularly reliable and positive response. If the pressure is insufficient the plunger member will remain at its inward position showing that further checks and possible servicing or recharging of the extinguisher is necessary.

In some applications the indicator may be applied to indicate the presence of excessive pressure within an assembly, safe working pressure being indicated by the plunger member remaining at its inward position when depressed, and a danger level being indicated by the return of the plunger to its outward position.

The operation of the indicator and response to indications obtained therefrom may be effected and/or sensed from a remote station e.g. by electrical means if desired, or may be employed to actuate a visual and! our audible alarm signal, or safety device.

The indicator can be extremely neat and compact, for example the embodiments shown in Figures 1 and 2 need only have cylinder 9 or 9a with a bore of 6.5mm, plunger stroke 1.5mm, and overall length 23-32mm, for use with a portable dry powder extinguisher of the kind commonly carried in cars and small boats.

An important feature of the above constructions is that, except when a test is actually being carried out, spring washer 22 is not subjected to any loading or stress, it is in a substantially free condition engaged only loosely by the grooves in which its margins locate. Thus, as there is no pre-loading on the spring, there will be no substantial variation in its spring rate even over an extreme period of time and a constant response will be given throughout the life of the extinguisher or other pressure assembly.

The embodiment of Figure 3 operates generally as described above but uses a different body structure and plunger sealing arrangement. Its body member is again an assembly of plastics mouldings; an outer shell 12b, a cylinder block llb, and a retainer 15b, the two latter being screwed into a cup like outer end portion of shell 12b to define therebetween chamber 14b and locate push-button 20b which is acted on by Bellville washer 22 in the manner previously described.

The inner end portion of shell 12b is smaller in diameter and is externally threaded for engagement with either an integral threaded bush of a pressure container wall (as shown in Figure 2) or in a container wall aperture by means of a nut.

In each case an appropriate sealing washer or gasket (not shown) could be used. Said portion is axially shorter than the equivalent structures shown in Figures 1 and 2 and does not serve as the cylinder for the plunger. Its inner end mounts a vent filter 17b and the part of its internal bore between the filter and block llb is widened to accomodate a mushroom head 30 on the inner end of plastics piston 18b. Piston 18b is a sliding fit in a central aperture of block ll',b and is actuated by push-button 20b. A flat elastomeric sealing washer 31 locates in a recess between the inner face of block llb and shell 1 2b around piston 1 8b and serves not only to provide a fluid seal at the joint between the shell and block llb but also a fluid tight sliding seal around the piston, and additional sealing when the latter is urged fully outwards under the container fluid pressure as the inner face of washer 31 is then engaged by a radial sealing face of head 30. The sealing effect is enhanced by an annular ridge 32 on said face, and by a lip 33 on shell 12b. Washer 31 is shaped to provide a lip seal against the cylindrical periphery of piston 18b which slides therethrough during plunger actuation. The additional sealing provided by head 30 acting on the flat washer means that this sliding seal is not the sole defence against leakage in the normal static condition shown in Figure 3 in which piston 18b is urged outward to its maximum extent.

WHAT WE CLAIM IS: 1. Fluid pressure indicator comprising a body member adapted to be mounted on a fluid pressure containing assembly in communication with its interior, a plunger member moveable relative to the body member between respective inner and outer positions and adapted to be urged toward the latter position by fluid pressure within the assembly in use, sealing means maintaining a fluid tight seal between said members throughout the range of movement of the plunger member, and a dished spring element having an outer margin engaged with one member and a central region engaged with the other member, movement of the plunger member from one to the other of said positions causing deflection of said element springing it from outwardly convex to outwardly concave conditions and vice versa, the spring element providing a predetermined resistance to movement of the plunger from the inner to the outer position which will be overcome by fluid pressure loading from within the assembly in use which is above a predetermined minimum level.

2. An indicator as claimed in Claim 1 wherein the spring element is a metal Belville washer whose outer peripheral margin and margin of its central aperture are located by formations of the respective members.

3. An indicator as claimed in Claim 1 or 2 wherein the fluid sealing means acts between relatively moveable surface of the members inwardly of the spring element so that the latter is not exposed to the contents of the body in use.

4. In indicator as claimed in any one of the preceding claims wherein the plunger member includes a piston in sliding engagement with a cylinder defined by part of the body member, the sealing means acting between said piston and cylinder.

5. An indicator as claimed in any one of Claims 1 to 3 wherein part of the body member forms a piston co-acting with a cylinder formation of the plunger member, the sealing means acting between said piston and cylinder means.

6. An indicator as claimed in any one of the preceding claims wherein the sealing means includes one or more 0 rings.

7. An indicator as claimed in any one of claims 1 to 5 wherein the sealing means includes a flat elastomeric washer which is engaged by a radial sealing face on the plunger when the latter is at the outer position.

8. An indicator as claimed in any one of claims 1 to 3 including a flexible diaphragm which transmits said fluid pressure to the plunger in use.

9. An indicator as claimed in any one of the preceding claims including a filter in a vent connecting the assembly with the interior of the indicator in use to prevent a powder charge in the assembly entering the indicator.

10. An indicator as claimed in any one of the preceding claims wherein the plunger member includes a push button accessible from the exterior of the assembly in use to

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. and a constant response will be given throughout the life of the extinguisher or other pressure assembly. The embodiment of Figure 3 operates generally as described above but uses a different body structure and plunger sealing arrangement. Its body member is again an assembly of plastics mouldings; an outer shell 12b, a cylinder block llb, and a retainer 15b, the two latter being screwed into a cup like outer end portion of shell 12b to define therebetween chamber 14b and locate push-button 20b which is acted on by Bellville washer 22 in the manner previously described. The inner end portion of shell 12b is smaller in diameter and is externally threaded for engagement with either an integral threaded bush of a pressure container wall (as shown in Figure 2) or in a container wall aperture by means of a nut. In each case an appropriate sealing washer or gasket (not shown) could be used. Said portion is axially shorter than the equivalent structures shown in Figures 1 and 2 and does not serve as the cylinder for the plunger. Its inner end mounts a vent filter 17b and the part of its internal bore between the filter and block llb is widened to accomodate a mushroom head 30 on the inner end of plastics piston 18b. Piston 18b is a sliding fit in a central aperture of block ll',b and is actuated by push-button 20b. A flat elastomeric sealing washer 31 locates in a recess between the inner face of block llb and shell 1 2b around piston 1 8b and serves not only to provide a fluid seal at the joint between the shell and block llb but also a fluid tight sliding seal around the piston, and additional sealing when the latter is urged fully outwards under the container fluid pressure as the inner face of washer 31 is then engaged by a radial sealing face of head 30. The sealing effect is enhanced by an annular ridge 32 on said face, and by a lip 33 on shell 12b. Washer 31 is shaped to provide a lip seal against the cylindrical periphery of piston 18b which slides therethrough during plunger actuation. The additional sealing provided by head 30 acting on the flat washer means that this sliding seal is not the sole defence against leakage in the normal static condition shown in Figure 3 in which piston 18b is urged outward to its maximum extent. WHAT WE CLAIM IS:

1. Fluid pressure indicator comprising a body member adapted to be mounted on a fluid pressure containing assembly in communication with its interior, a plunger member moveable relative to the body member between respective inner and outer positions and adapted to be urged toward the latter position by fluid pressure within the assembly in use, sealing means maintaining a fluid tight seal between said members throughout the range of movement of the plunger member, and a dished spring element having an outer margin engaged with one member and a central region engaged with the other member, movement of the plunger member from one to the other of said positions causing deflection of said element springing it from outwardly convex to outwardly concave conditions and vice versa, the spring element providing a predetermined resistance to movement of the plunger from the inner to the outer position which will be overcome by fluid pressure loading from within the assembly in use which is above a predetermined minimum level.

move said member inwardly.

11. An indicator as claimed in Claim 10 wherein said push button is located in an aperture of a retainer of the body member for axial movement therein, the spring element being located within a chamber defined within the body member.

12. An indicator as claimed in any one of the preceding claims wherein the body and plunger members are formed from plastics materials.

13. An indicator as claimed in any one of the preceding claims wherein the spring element is engaged only loosely by said respective members so that it is not subjected to any substantial loading or stress when in the outwardly convex condition while the plunger member is at rest.

14. A pressure indicator substantially as hereinbefore described with reference to and as shown in Figure 1, 2 or 3 of the accompanying drawings.

15. A fire extinguisher including a pressure inaicator according to any one of the preceding claims.