GB2453277A

GB2453277A - Gas pressure stabiliser having an automatic closing device

Info

Publication number: GB2453277A
Application number: GB0822376A
Authority: GB
Inventors: Neil Randall
Original assignee: R & D Ventilation Systems Ltd
Current assignee: R & D Ventilation Systems Ltd
Priority date: 2004-04-29
Filing date: 2004-04-29
Publication date: 2009-04-01
Anticipated expiration: 2024-04-29
Also published as: WO2005106345A1; GB2413627B; GB2453277B; GB0822376D0; GB0409508D0; GB2413627A

Abstract

A gas pressure stabiliser for regulating air pressure comprises a pivoting gas flow control member 5 mounted in an opening 3 about a pivot axis 'A'. A closure arm 13 is retracted into a housing 12 and can be released from the housing 12 in response to a stimulus (defined conditions) thereby causing the gas flow control member 5 to close the opening 3 cutting off gas flow. A counterbalance 8, 10 may be mounted on the pivot axis 'A', and the arm 13 may come into contact with the counterbalance 8, 10 in response to the stimulus. Control member 5 may be a plate having bent end portions and is mounted on a spindle 6. A cylindrical boss 7 may be secured to the spindle 6 and spigots 8, 9 with counterbalance weights 10, 11 attached may be screwed into the boss 7. Weights 10, 11 may be screwed onto the spigots 8, 9 at various distances so that the gas pressure stabiliser may be used in a vertical, horizontal or inclined mode. Arm 13 may comprise a forked arm 13 and may include a ratchet mechanism (14a, fig 2), may be released by a spring (fig 3), shape memory metal (fig 4), solenoid (fig 5) or cable (fig 6) operated release mechanism. Arm 13 may be ejected by a helical compression spring (fig 7), shape memory metal spring (fig 8), solenoid release (fig 9) or hydraulic release (fig 10) mechanism.

Description

I

Gas Pressure Stabilizer This invention relates to improvements to a gas pressure stabilizer and in particular but not exclusively to a gas pressure stabilizer for regulating air pressure.

In certain environments, such as surgical operating theatres or "clean" manufacturing rooms it is desirable to utilise an ambient air pressure slightly above atmospheric, to minimise ingress of contaminant materials, excess air flowing out of the room through gaps in (e.g.) the doors.

Such situations require the installation of an air pressure stabiliser which opens to vent the room should the pressure therein become excessive, and which returns to a closed position when the ambient pressures has been reached.

Pressure stabilisers for the regulation of differential air pressures are known. For example, a conventional air pressure stabiliser comprises a vent opening, and a control member mounted in the vent opening for movement between open and a closed positions. The control member is in the form of a flat plate mounted for pivotal movement about a longitudinal axis with the plate having an elongate tube secured to an outer surface, which can receive weights so providing a counterbalance to one side of the pivot axis of the plate.

As pressure increases, excess force on the plate above the pivot axis causes it to move from its closed position so allowing venting of excess pressure. However, as the plate opens, the effect of the counterbalance increases with the result that an increases in pressure has a reduced effect in opening the control member. This is disadvantageous because it produces a relatively high speed flow through a small aperture which can compromise controlled venting.

Attempts have been made to produce a control member where a reduced and more constant force acts on the control member to allow it to open. For example, suggestions have been made to provide an additional counterbalance close to the pivot axis in the form of a cantilever which acts to produce positive forces to urge the control member to its closed position. When pressure exceeds the desired maximum, the cantilevered counterbalance enables the control member to automatically move from its closed to its fully opened position allowing smooth venting of excessive pressure from a room. Nonetheless, an air pressure stabilizer of this kind cannot operate satisfactorily in both a vertical opening and in a horizontal opening.

The arrangement discussed in GB 2318865 overcomes the

problems of the prior art by providing a pressure

stabiliser having at least two counterbalancing weights, each acting on a spindle having a pivot axis. At least one of the weights is adjustable to alter the counterbalancing, so providing a more precise control of pressure regulation.

However, such known devices do not provide a gas pressure stabilizer where there is automatic shut off of gas flow under certain conditions. For example, for an air pressure stabilizer, airflow between adjacent rooms may need to be restricted in the event of a fire, to comply with fire regulations.

Attempts have been made to produce an automatic closure of an air pressure stabilising device, for example in Wo 00/20803, a spring which is associated with a flow control member can be released to drag a closure member into a closed position on detection of a hazard. However, this device has the disadvantage that it is acting directly on the flow control member, which could distort it, and also there is the risk of an individual servicing the unit coming into contact with the spring closure member which is not desirable for Health & Safety or hygiene reasons.

Further this known device does not allow for the combination of having controlled air regulation as well as controlled and accurate shut of f of gas flow is needs be.

According to the present invention, there is provided a gas pressure stabiliser including: a frame defining an opening through which a gas can pass; a gas flow control member pivotally mounted in the opening about a pivot axis so that said gas flow control member can pivot between an open and a closed position; a counterbalancing means mounted on the pivot axis; and a closure arm which can be triggered in response to defined conditions to come into contact with the counterbalancing means so causing said gas flow control member to close the opening to substantially cut off gas flow through said opening.

It is envisaged that gas flow may be cut off completely with the assistance of seals around the gas flow control member which seal it in the frame. Alternatively, the seals)such as intumescent seals can be on the frame.

In a preferred arrangement the closure arm comprises an arm retracted into a housing, such that when defined conditions are met, the closure arm is released from the housing.

Preferably, the counterbalancing means is mounted on said pivot axis to one side of said flow closure member, such that when the closure arm is released, the closure arm comes into direct contact with the counterbalancing means causing movement thereof about said axis which movement indirectly causes the gas flow control member to close the opening.

It is preferred that the counterbalancing means comprises at least two counterbalancing members each mounted on said pivot axis.

It is envisaged that each counterbalancing member is mounted on an arm supported by the pivot axis, with a first portion of each arm extending from the pivot axis in a first direction forming a cantilever member and a second portion of each arm extending in a second direction and having a counterbalancing member thereon.

It is envisaged that the closure arm can be caused to abut against either a first or second portion of a counterbalancing member to cause movement thereof.

Advantageously, at least one of the counterbalancing members is adjustable by screw thread members by movement thereof in a radial plane passing through said pivot axis.

It is preferred that the gas pressure stabiliser is associated with a sensor which can detect one or more of a rise in temperate, the presence of smoke or changes in gaseous and if these meet defined conditions, the closure arm is caused to be released from the housing.

It is envisaged that the closure arm is released when the sensor detects a temperature of 74 degrees centigrade or above, although a range of between 70 and 78 degrees centigrade may be used. However, it is envisaged that the senser may be set to detect a range of temperatures and/or conditions, for example smoke density or the detection of particulates in air released as a result of the combustion of materials.

Preferably, the closure arm is held in the retracted position by a releasable connector between the housing and the closure arm, such that when defined conditions are met, the connection is broken and the closure arm is released.

In one embodiment, the releasable connector is a fusible alloy link.

In a further embodiment, the connector is a spring loaded pin between the closure arm and the housing, with the spring loaded pin being attached to the housing by a deformable material, which melts under the defined conditions thereby causing the pin to be retracted and so releasing the closure arm.

In a further arrangement, the connector is a shape memory alloy attached to the housing by a deformable material which melts under the defined conditions to release the connector from the closure arm so it can be activated.

In a further arrangement, the releasable connector can be a solenoid which can be activated to release a pin from the closure arm.

It is also envisaged that connector is a pin, one end of which is held in an aperture in the closure arm, with a second end of the pin being attached to a cable that can be operated remotely to retract the pin so releasing the closure arm.

Further, the closure arm can be released as a result of a helical compression spring, a shape memory metal spring or a solenoid held within the housing and which can be activated to eject the closure arm from said housing.

In a further arrangement, the housing or control arm includes a reservoir for receiving fluid from a feed reservoir, there being an actuator, which is response to conditions detected by the sensor, causes fluid to flow from the feed reservoir to the reservoir in the housing, thereby actuating the closure arm to be released from the housing.

It is further envisaged that once released from the housing, a latch operates to prevent return of the closure arm back into the housing.

Preferably, the latch is provided as a ratchet.

According to a further aspect of the invention, there is provided a gas pressure stabiliser including: a frame defining an opening through which a gas can pass; a gas flow control member pivotally mounted in the opening about a pivot axis so that said gas flow control member can pivot between an open and a closed position; and a closure arm which is retracted in a housing and which can be released from the housing in response to defined conditions so causing said gas flow control member to close the opening so cutting off gas flow.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying Figures in which: Figure 1 shows a schematic side elevational view of a gas flow stabiliser according to an embodiment of the invention; Figure 2 shows a schematic side elevational view of a gas flow stabiliser as shown in Figure 1, with a closure arm in the retracted position; Figure 3 shows a view from above of a pin and spring release mechanism; Figure 4 shows a view from above of a shape memory metal release mechanism; Figure 5 shows a view from above of a solenoid release pin; Figure 6 shows a view from above of a cable operated release pin; Figure 7 shows a view from above of a helical compression spring closure arm release mechanism; Figure 8 shows a shape memory metal spring closure arm release mechanism; Figure 9 shows a solenoid used to release a closure arm; and Figure 10 shows a hydraulic closure arm release mechanism.

As shown generally as 1 in Figure 1, the gas pressure stabiliser comprises a frame 2 having a generally rectangular opening 3 bounded on its front side by a flange 4. Although a rectangular opening is shown, the stabiliser of the invention could be dimensioned to fit other types of openings, e.g. square openings.

Mounted within the frame 4 for movement about a longitudinal pivot axis A extending parallel to the plane of the opening 3 is a control member 5, being generally in the form of a flat plate (shown as a dotted line) having forwardly and rearwardly bent end portions.

The pivot axis A is spaced from the centre line of the control member 5 so that a majority of the weight of the control member extends below the axis A, and the excess weight of the control member acts to urge the control member into its closed position. Stops (not shown may be positioned on inner faces of the side wall of the frame to limit movement of the control member 5.

Alternatively, the pivot axis A may be spaced from the centre line of the control member 5 so that a majority of the weight of the control member extends above the axis A, and the excess weight of the control member acts to urge the control member into its open position in engagement with stops on the frame.

A spindle 6 extends through bearings (not shown) and which support either end of the control member 5 in the frame, so allowing the control member to rotate about the pivot axis A between a closed position and an open position.

Secured to one of the stub shafts of the spindle conveniently externally of the frame 6, is a cylindrical boss 7 provided with threaded bores (not shown) extending there into mutually at right angles. However, the bores may be at different angles to one another. Screw threaded into the radial bores are threaded spigots 8, 9 said spigots being tightly screwed into the boss 7.

Mounted on each of the spigots 8, 9 is a counterbalance member afforded by a cylindrical weight 10, 11 respectively provided with threaded axial bores which are screw threaded Onto the spigots 8 and 9. By rotation of the member weights about their longitudinal axes, their respective distances from the pivot axis A may be varied.

Preferably each cantilevered weight member is mounted on a spigot extending in a radial direction from the spindle, and such weight member is conveniently screw threaded on the spigot, whereby the distance between the member and the axis may be varied, to vary the counterbalancing effect.

Conveniently each cantilevered weight member is circular in cross section, so that rotation about the spigot changes the position of the centre of gravity of the counterbalancing member only axially of the spigot.

However, a range of dimensioned weights could be used, e.g. hexagonal or square.

In this manner, the counterbalancing required for the control member may readily be achieved irrespective of the location of the air pressure stabiliser. In particular, such adjustment may be utilised to counter-balance the air pressure stabiliser for use in a vertical mode or for use in a horizontal mode, or at any appropriate inclination there-between.

In this way not only can the control member 5 be counterbalanced in a convenient manner, but also counterbalancing may be achieved which is effective generally throughout the range of movement of the control member, irrespective of the orientation of the control member, so that in the event that the pressure within the room being served by the air pressure stabilizer rising above the pre-determjned maximum, the control member will move generally fully from its closed to its open position.

Access may be obtained to the counterbalance members depending on the orientation of the control member 5 by bringing them into alignment with an aperture in the frame, thus permitting the aligned counterbalance member to be rotated by use of a suitable tool inserted through the aperture.

Accordingly, there may be provided engagement formations or recesses on the outwardly facing surfaces of counterbalance members 10 and ii, for engagement with corresponding formations provided on one end of a suitable tool.

Associated with the frame is a housing 12, which houses a control arm 13, which in Figure 1 is shown as a blade member. The control arm 13 has guide arms 14 at one end so forming a fork. When the control arm is released from the housing, the forked arm extend either side of the counterbalancing means that it abuts against, so that the counterbalancing means can be pushed in the direction of travel of the control attn. When the control arm is retracted into the housing the counterbalancing means is able to move away from the vertical so that the control member 5 can open if required to allow venting of gas.

As shown in Figure 2, when the control arm 13 is released from the casing 12 the arms 14 abut against a cantilever 8 of the counterbalancing means. The whole balancing assembly is pivoted around axis A into the vertical. Movement of the counterbalancing means forming the balance assembly in turn results in the closure member closing the opening 3. Also, the control arm 13 includes a ratchet mechanism 14a along its length which can interact with the housing, thereby maintaining the closure arm in an extended position until released, reset or recalibrated by an operator. A further control feature is that the cantilever are 9 includes a stop 15, which assists in defining the angular motion of the counterbalancing means to within defined limits.

Movement of the control arm is triggered by an actuator. The position of the actuator can be varied, for example in the side walls of the aperture 3, in flange faces at the front or back of the unit, or even, there may be remote operation of the system.

Various types of actuators are shown in Figures 3 to 6 but these are not to be taken as limitations as to the types of actuators that. can be used with the present invention.

A typical actuator is a thermal actuator is used but other types of actuators, possibly those that are sensitive to particular compounds in a gas or air may be used.

As shown in Figure 3, a pin 17 extends into an aperture in the housing 12 and the closure arm 12. The pin supports a spring 16, which is held in compression between a shoulder on the pin and the housing 12 at one end and the other end of the pin rests against an area of fusible material 18 forming a bridge across an aperture in a casing for the actuator. When the fusible material, which is preferably an alloy reaches its melting point, the spring loaded pin is released from the housing 12 and the closure arm 12, so that the closure arm can be released from the housing and move towards the counterbalancing means. The counterbalancing means is caused to rotate about the pivot axis A with the result that the associated closure member closes the vent.

As shown in Figure 4, instead of a spring and pin, the thermal "fuse" could be combined as one component, allowing for ease of manufacture. The component is formed of a shape memory alloy 20, having a pin at one end which passes through the housing and locates in the closure are 13. The shape memory alloy is in a stressed and extended configuration and secured at the other end to a casing 18.

On heating, the shape memory alloy retracts into its original configuration and withdraws the pin from the closure arm 13, which is turn is released from the housing 12. The arrangement can be configured to operate with the shape memory metal alloy contracting or extending. When the arrangement is configured to extend a thermal plug 18 can be caused to melt so that the alloy spring can be withdrawn from the arm 13.

Figure 5 shows a solenoid release pin 21 which is used to maintain the closure arm in the retracted position. When coils of the solenoid are powered to produce a magnetic field, this holds the pin in position. When the power is turned off by for example, a sensor detecting smoke, the magnetic filed keeping the pin in place is removed and the pin is retracted by a spring attached to casing 19, so allowing the closure arm to be released from the housing.

As shown in Figure 6, a pin 22 may be used to lock the closure arm 13 in the retracted position. Cable 23 passes through an aperture in casing 19 and the cable is linked to a remote control unit which can be activated to remove the pin and release the control arm on detection of for example fire. This arrangement can be used as an additional back up to automatic control systems as previously mentioned because as it. is remotely activated it can be operated by a person should they see a fire.

Figure 7 to 10 show means to eject the closure arm 13 from the housing 12.

In Figure 7, a spring 24 is held in compression when the actuator assembly is loaded. When the release connector is activated, the closure arm moves under the force of the spring in the direction of the arrow shown. The spring may be located inside the housing 12 or is may be located externally of the closure member but in communication therewith.

The helical spring shown in Figure 7 may be replaced by a shape memory material such as an alloy as shown in Figure 8. This arrangement has advantages in that unlike an ordinary spring, the shape memory spring is in a compressed condition during normal use. This has the advantage that there is no need to maintain a force on the spring during assembly of the actuator. When exposed to an increase in temperate, the spring will expand with sufficient force to eject the closure arm from the housing. The shape memory alloy and the configuration and length of the spring can be selected in accordance parameters for the housing 12 and closure arm 13, such as length of the housing and distance of the closure arm form the counterbalancing means.

Figure 9 shows a solenoid 27 which in normal operation is activated to maintain the closure arm in a predetermined location against the force of a compression spring. This is when the assembly is in the "loaded position". When current to the solenoid is disrupted, the magnetic field is no longer generated to maintain the spring in compression and this will allow the spring to push the closure arm 13 from the housing in the direction of the arrow shown. When a solenoid arrangement is used, the power switch off to the ejection mechanism and the release connector can be substantially simultaneous or staggered so the release mechanism is operated to prime the control arm, which is then ejecced by the release of the spring as shown in S Figure 9.

Figure 10 shown a hydraulic system used to power the closure arm. Under normal conditions, the hydraulic fluid is maintained in a supply reservoir 29. When exposed to certain conditions an actuator 28 causes fluid to be forced from the supply reservoir to a reservoir 30 in the housing and/or the closure arm 13. The pressure of the fluid 10, results in the movement of the closure arm 13 from the housing. As the volume of fluid 30 is relatively large compared with the volume of the housing/closure arm, a relatively small amount of fluid can be use to effect displacement of the closure arm in the direction as shown.

A typical actuator in such an arrangement would be a thermal actuator.

The present invention has advantages in that the control arm acts on the counterbalancing means, which is associated with the spindle of the control member rather than on the control member itself. This, unlike the prior art has the benefit that there is no distortion of the control member during rotation thereof from the closed to the open position.

Furthermore, the counterbalancing means used in the air pressure stabilizer according to the present invention can be positioned at any desired angular position relative to the pivot axis A. This allows for optimum positioning of the counterbalancing member relative to the control arm which can cause optimum operation of the device to close flow of gas through the opening.

Although the invention has particular uses in the closing of a flow control member in the event of fire, the invention may be utilised to ensure closure of the flow control member in the event of other hazards, for example, should there be a build up of toxic fumes in a laboratory.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings expressed in their specific form or in terms of performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate may, separately or in any combination of features, be utilised in realising the scope of the invention.

Claims

Claims 1. A gas pressure stabiliser including: a frame defining an opening through which a gas can pass; a gas flow control member pivotally mounted in the opening about a pivot axis so that said gas flow control member can pivot between an open and a closed position; and a closure arm which is retracted in a housing and which can be released from the housing in response to defined conditions so causing said gas flow control member to close the opening so cutting of f gas flow.
2. A gas pressure stabiliser according to claim 1, wherein the closure arm comprises an arm retracted into a housing, such that when the defined conditions are met, the closure arm is released from the housing.
3. A gas pressure stabiliser according to claim 1 or claim 2, wherein counterbalancing means is mounted on said pivot axis to one side of said flow closure member, such that when the closure arm is released, the closure arm comes into direct contact with the counterbalancing means causing movement thereof about said axis, said movement indirectly causing the gas flow control member to close the opening.
4. A gas pressure stabiliser according to claim 3, wherein the counterbalancing means comprises at least two counterbalancing members each mounted on said pivot axis.
5. A gas pressure stabiliser according to claim 3 or claim 4, wherein each counterbalancing member is mounted on an arm supported by the pivot axis, with a first portion of each arm forming a cantilever member extending from the pivot axis in a first direction and a second portion of each arm extending in a second direction and having a counterbalancing member thereon.
6. A gas pressure stabiliser according to any of claims 3 to 5, wherein the closure arm can be caused to abut against either a first or second portion of a counterbalancing member to cause movement thereof.
7. A gas pressure stabiliser according to any of claims 3 to 6, wherein at least one of the counterbalancing members is adjustable by screw thread members by movement thereof in a radial plane passing through said pivot axis.
8. A gas pressure stabiliser according to any preceding claim, wherein said gas pressure stabiliser is associated with a sensor to detect defined conditions these being one or more of: rise in temperate, the presence of smoke in air or changes in composition of a gas.
9. A gas pressure stabiliser according to any preceding claim, wherein the closure arm is caused to be released when the sensor detects a temperature of 74 degrees centigrade or above.
10. A gas pressure stabiliser according to any preceding claim, wherein the closure arm is held in the retracted position by a releasable connector between the housing and the closure arm, such that when defined conditions are met, the connection is broken and the closure arm is released.
11. A gas pressure stabiliser according to claim 10, wherein the releasable connector is a fusible alloy link.
12. A gas pressure stabiliser according to any of claims 1 to 10, wherein the releasable connector is a spring loaded pin between the closure arm and the housing, with the spring loaded pin being attached to the housing by a deformable material, which melts under the defined conditions thereby causing the pin to be retracted and so releasing the closure arm.
13. A gas pressure stabiliser according to any of claims 1 to 10, wherein the releasable connector is a shape memory alloy attached to the housing by a deforrnable material which melts under the defined conditions to release the connector from the closure arm so it can be activated.
14. A gas pressure stabiliser according to any of claims 1 to 10 wherein the releasable connector is a solenoid which can be activated to release a pin from the closure arm.
15. A gas pressure stabiliser according to any of claims 1 to 10 wherein the releasable connector is a pin, one end of which is held in an aperture in the closure arm, with a second end of the pin being attached to a cable that can be operated remotely to retract the pin so releasing the closure arm.
16. A gas pressure stabiliser according to any of claims 1 to 10, a helical compression spring, a shape memory metal spring is used to eject the closure arm from said housing when the releasable connector is activated.
17. A gas pressure stabiliser according to any of claims 1 to 10, wherein the housing includes a reservoir for receiving fluid from a feed reservoir, there being an actuator, which is response to conditions detected by the sensor, causes fluid to flow from the feed reservoir to the reservoir in the housing, thereby causing the closure arm to be released from the housing.
18. A gas pressure stabiliser according to any preceding claim wherein the housing includes a latch such that once the closure arm is released from the housing, prevents return of the closure arm back into the housing.
19. A gas pressure stabiliser according to claim 18, wherein the latch is provided as a ratchet mechanism along the housing.
20. A gas pressure stabiliser according to any preceding claim arranged to operate in the event of a hazardous material being released, smoke being detected or fire being detected.
21. A gas pressure stabiliser as substantially described herein, with reference to and as illustrated in the accompanying figures.