GB2382639A

GB2382639A - An integrated pressure relief and flow control valve

Info

Publication number: GB2382639A
Application number: GB0128764A
Authority: GB
Inventors: Andrew Jenkins; Louise Murphy
Original assignee: Flexicare Medical Ltd
Current assignee: Flexicare Medical Ltd
Priority date: 2001-11-30
Filing date: 2001-11-30
Publication date: 2003-06-04
Anticipated expiration: 2021-11-30
Also published as: GB0128764D0; GB2382639B

Abstract

A pressure-limiting valve, particularly suitable for venting excess pressure from a conduit used for administering anaesthetic gas or oxygen in medical procedures, has an intake (21) and an exhaust (22). An annular valve seat (6) defines a central opening (61) subject to a valve plate (7), which can be lifted from the opening (61), allowing venting of gas when there is an excess pressure at the intake (21), against the restoring force of a spring (9). The valve seat (6) has a slot (8) and the valve plate (7) has a radial enlargement (76) with a varying radius. By rotating the top control knob (1, Fig. 1) the varying radius of the valve plate (7) can progressively unblock the slot 8 in the valve seat (6), allowing a controllable degree of bleeding of gas even when the plate (7) is not lifted from its seat.

Description

VALVES This invention has to do with valves useable to regulate or limit fluid pressure, especially gas pressure, in a vessel or conduit. In particular but not exclusively the invention is applicable to controlling the pressure of gases administered to a patient for medical procedures, especially anaesthetic gases or oxygen.

In a gas line along which anaesthetic gas is fed, it is a conventional requirement to include a pressure limiting valve between the flow and an exhaust conduit.

Should the flow pressure for any reason rise to a level which might present a danger to the patient, its pressure on the undersurface of a sprung valve member covering an opening leading to an exhaust conduit pushes the valve member off its seat against the spring to vent the excess gas. Conventionally this limiting valve is used to control the flow on an ongoing basis by adjusting the spring compression using a threaded control knob behind the spring. According to the spring force, gas will start to bleed away through the valve at different pressures and this provides a control adjustment.

The flow control is difficult, however, because tolerances in spring manufacture lead to different behaviours in different valves at the same apparent setting, and the relation between the controlled flow pressure and control knob setting is far from linear. Of course, more sophisticated valves exist which are capable of giving a more linear relationship but these are firstly expensive and secondly more complicated than would be desirable in such a situation, leading to concerns about maintenance and failure.

What we propose is a pressure limiting valve in which there is an excess pressure vent opening between

the intake and exhaust of the valve, bordered by a valve seat and subject to the action of a valve member which is movable between a closed position lying over the vent opening in contact with the valve seat and an open position lifted away from the valve seat to allow venting of excess pressure. The valve seat and valve member are resiliently urged together, e. g. by a compression spring, to the closed position. Thus far, this is similar to the existing arrangement. However, we propose to provide in the valve additionally a bleed opening providing communication between the intake and exhaust, and whose size can be controllably adjusted over a range of available values by a control accessible from outside the valve.

By this means one can achieve an adjustable bleed flow which is useful for controlling the pressure in the vessel or conduit and which does not depend on the precision available for adjusting the spring pressure acting on the valve member.

The bleed orifice adjustment may include a fullyclosed position. It may proceed either stepwise or substantially continuously from a minimum to a maximum bleed orifice flow area.

The bleed orifice-and it should be understood that this term unless the context requires otherwise comprehends that there may be more than one opening, and the term"bleed orifice"may refer to the combination of these-is preferably defined between or through first and second elements of the valve which are relatively movable over an operational range. A clearance, recess or window which provides the bleed orifice communication between the intake and exhaust, and which is defined partly or entirely by the two elements, is progressively increased in size with said relative movement e. g. from one end of the operational range to the other. For

example, one of the elements may have a clearance, recess or window which is progressively occluded by a portion of the other as the relative movement proceeds. Preferably the occluding part has an edge which is non perpendicular (and preferably at an acute angle) to the direction of relative movement so that a fine adjustment is easily available with large movements of the control. This enables a control member to be directly connected to one or the other of the elements rather than via some reducing drive.

Preferably the relative movement of the first and second elements is rotational. It is also preferred that the first and second elements are in sliding face-to-face contact over the movement, with the bleed flow being generally perpendicular to that face.

Drawing together these preferences, a particularly preferred bleed flow control has a fixed seat element and a rotatable valve element contacting it slidably. One of these elements has a window or recess and the other element has an edge with a progressively-varying radius so that as the rotatable member is turned the edge progressively changes the degree of occlusion of the window as the two move circumferentially relative to one another. Another possibility is a discontinuous adjustment in which one element has a window or recess and the other element has a circumferential series of windows or recesses of progressively increasing size.

The skilled person will realise that there are numerous ways in which relatively moveable elements can provide a variable-size opening, occluded to progressively greater degrees covering according to the degree of movement.

Preferably the sliding interface of the elements is flat.

A specially preferred proposal now made, and enabling the operational advantages referred to above without increasing complexity and expense, is that one of the relatively movable valve elements which co-operate to provide the adjustable bleed orifice is or is integral with the valve member moveable to close or open the vent opening. For example, the valve member which is movable under the influence of the spring force up and down from the valve seat (to provide venting of large excess pressures) may be movable in sliding contact with the valve seat-preferably rotationally-with the contacting parts of the valve member and valve seat providing shape features for the adjustable bleed orifice function as described above. In our preferred construction the vent opening is a central hole surrounded by an annular valve seat. The centre part of the valve member is closed, to enable closure of the vent opening. The valve seat and the periphery of the valve member are provided with openings, profiles, windows, recesses etc-preferably the progressively-varying radius described above-to give the adjustable bleed orifice function.

Since the bleed orifice is adjustable independently of the spring pressure, the latter need not be adjusted at all and if it is adjustable, tolerances do not adversely affect the use of the device for fine pressure/flow adjustment.

Conveniently the valve is formed in an elbow conduit, with an intake arm and an exhaust arm, the valve seat terminating the intake arm and facing the outside of the elbow, a control spindle being mounted through that outside part with a control member e. g. a knob or lever on its outer end and the valve member mounted on its inner end, with a spring acting between the valve member and elbow conduit to urge the valve member against the valve seat. Preferably provision is made for axial

sliding between the valve member and control member so that the valve member movement on venting does not move the control member. In this case the rotational coupling between valve member and control member can be maintained, e. g. by an axially slotted or splined or other non-circular connection between these elements.

Depending on the technical context and the nature of the gas or other fluid being regulated, the exhaust of the valve may either be open to the exterior or lead to some containment. It may in some contexts be desirable to provide a non-return valve, e. g. a flexible flap valve, in the exhaust of the valve to prevent reverse flows.

A further aspect of the invention is gas flow apparatus including a gas supply conduit and a pressure limiting valve as described above connected in communication with the conduit. A preferred embodiment is anaesthetic or oxygen gas supply apparatus incorporating such a pressure limiting valve.

Corresponding methods of gas supply, including regulation of the pressure by operation of the valve, are further aspects of the invention.

An embodiment of the invention is now described by way of example, with reference to the accompanying drawings in which Fig 1 is an end view of a valve embodying the invention ; Fig 2 is an axial cross-section at II-II of Fig 1; Fig 3 is a top view of a valve member, to a larger scale; Fig 4 is a top view of the valve body with the valve member and control components removed ; Fig 5 is a side view of the complete valve and Fig 6 is a top view.

With reference firstly to Figs 1,5, 6 which show the general appearance of the valve, it has a one-piece moulded plastics body 2 providing a vertical cylindrical part with a lower intake 21 and a branch conduit forming an exhaust 22. A flat annular valve seat 6 is provided as an integral inward flange projection from the wall of the tube 2, defining a central circular vent opening 61.

The exhaust conduit 22 opens into the main vertical conduit through a window 13 above the valve seat 6.

A moveable valve arrangement is provided above the valve seat, to govern the flow of gas from the intake conduit 21 to the exhaust conduit 22. The movable valve components include a valve plate or disc 7 formed integrally with an upright central stem 72, seen in plan view in Fig. 3. Fig. 3 shows how the valve disc 7 is eccentrically formed, the radius of its periphery increasing progressively and smoothly from a minimum radius region 78 to a maximum radius region 76, with an abrupt step 77 between. A resilient gasket layer 75 (see Fig. 2) e. g. of closed-cell rubber, covers the underside of the valve disc 7 and has the same peripheral shape.

The radius of the valve disc 7 is everywhere larger than that of the central vent opening 61 so that it rests stably on top of the valve seat 6 in the position shown, covering the opening 61.

As seen in Fig. 4 the valve seat flange 6 includes a circumferentially-localised window 8, which in this embodiment is formed separately from the central opening 61.

The radial variation of the valve plate 7 corresponds to the radial extent of the window 8. Thus, in the closed position shown in Fig. 2, the central region of the disc 7 completely covers and seals the

central vent 61. Also, according to the rotational orientation of the valve disc 7 relative to the seat 6, a bleed opening of corresponding variable size is provided through the valve construction according to the unoccluded extent of the window 8, the vent opening 61 remaining closed. By bringing the disc's large radius region 76 over the window 8 it can be completely closed.

This rotational alignment is by turning the disc 7, to which end an exterior control knob 1 is snapped over suitable edge formations 3 at the top of the body tube.

The control knob has an internal skirt, which fits closely inside the body tube to form an effective seal, and an outer skirt 11 with a lower flange 12 marked with a suitable series of indicia to indicate variable degrees of gas flow bleed. These are read against a pointer 25 (see Fig 2) on the body. A radially-enlarged part 121 of the control knob flange forms a limit stop for the movement, corresponding at one end to zero bleed orifice and at the other end to maximum bleed orifice.

The central downwardly-projecting boss of the control knob forms a cylindrical socket 14 with vertical wall slots 141 in which corresponding ribs 73 of the valve central stem 72 are slidably received. A spring 9 which may be of conventional type is trapped in compression between the boss of the control knob and the top of the valve disc 7. Thus, the spring 9 urges the valve disc 7 into its sealing contact against the valve seat 6. In the event of substantial excess pressure arising in the intake conduit 21, the action of this pressure on the valve disc 7 through the opening 61 forces the disc 7 upwardly against the force of the spring 9 to vent the excess pressure. This movement is accommodated by the valve disc stem 72 sliding up inside the socket 14 of the control knob 1. At the same time the engagement of the ribs 73 in the control knob socket slots 141 couples the knob 1 and disc 7 rotationally so

that, with the disc down as in Fig 2, turning the control knob 1 assures a positive and gradual adjustment of the bleed orifice size independently of the spring pressure.

It will be appreciated that by routine trials the rate of progressive radius increase of the disc periphery 71 around the circumference can be determined so as to give an effectively linear bleed adjustment with knob rotation angle.

Claims

Claims 1. A pressure limiting valve having a vent opening for venting excess pressure, from an intake of the valve, to an exhaust of the valve, the vent opening having a valve seat and being subject to the action of a valve member which is movable between a closed position, in which it lies over the vent opening under the influence of a resilient closing force, and an open position in which it is lifted away from the valve seat against that force by excess fluid pressure at the intake in order to vent such excess pressure, characterized in that the valve additionally has a bleed orifice which communicates between the intake and exhaust in the closed position of the valve member, and whose size can be controllably adjusted over a range of available values by a control accessible from outside the valve.
2. A pressure limiting valve according to claim 1 in which the bleed orifice can be fully closed.
3. A pressure limiting valve according to claim 1 or 2 in which the bleed orifice is defined between or through first and second elements of the valve which are relatively movable over an operational range, one of the elements having a clearance, recess or window which is progressively occluded by a portion of the other as the relative movement proceeds.
4. A pressure limiting valve according to claim 3 in which the occluding part has an edge at an acute angle to the direction of the relative movement.
5. A pressure limiting valve according to claim 3 or 4 in which the relative movement is rotational.

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6. A pressure limiting valve according to claim 3,4 or 5 in which the first and second elements are in sliding face to face contact over the operational range of said relative movement, to allow a bleed flow generally perpendicular to the sliding faces.
7. A pressure limiting valve according to claims 3 to 6 in which one of said first and second relatively moveable elements of the valve is or is integral with said valve member movable between said closed and open positions.
8. A pressure limiting valve according to claim 7 in which the valve seat constitutes the other of said first and second relatively moveable elements.
9. A pressure limiting valve according to claim 1 or 2 in which the vent opening is a central hole surrounded by the valve seat which is annular, the valve member has a closed central part to enable blocking of the vent opening, and the valve seat and the periphery of the valve member constitute first and second elements rotationally slidable against each other in the closed conditions of the valve, the adjustable bleed orifice being provided by a clearance, recess or window defined at least partly by said elements and which can be increased progressively in size by said relative sliding rotation.
10. A pressure limiting valve according to claim 9 in which one of the valve member and valve seat has a window or recess and the other has an edge with a progressively varying radius, so that said edge can progressively occlude the recess or window as the member and seat move circumferentially in relation to one another.
11. A pressure limiting valve according to any one of the preceding claims in which the valve is formed in an

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elbow conduit with an intake arm and an exhaust arm, the valve seat terminating the intake arm and facing an outside part of the elbow, a control spindle being mounted through that outside part and having a control member on its outer end and the valve member on its inner end, and a spring acting between the valve member and conduit to provide said closing force.
12. A pressure limiting valve according to claim 11 in which the valve member and control member are relatively axially slidable so that valve member movement between the open and closed positions does not move the control member.
13. A pressure limiting valve according to claim 12 in which rotational coupling between the valve member and control member is via a slotted, splined or other noncircular axially slidable connection.
14. Gas flow apparatus including a gas supply conduit or vessel and a pressure limiting valve in accordance with any one of claims 1 to 13 connected to said conduit or vessel as a means of venting excess pressure therein.
15. Gas flow apparatus according to claim 14 which is anaesthetic or oxygen gas supply apparatus.
16. A pressure limiting valve, or gas supply apparatus comprising such a valve, substantially as described herein with reference to the accompanying drawings.