GB2087732A - Valves - Google Patents

Abstract

A valve, notably for use as a demand valve in breathing apparatus, has a pressure-responsive diaphragm (28) coupled to one arm (18) of a two-armed spring member (19), which lies in the path of a jet of gas which vents from a control chamber (14) through an orifice (17), gas being continuously supplied to the control chamber via another orifice (15). Deflection of the diaphragm in response to pressure changes in the outlet chamber (3) caused by inhalation and exhalation pivots the arm (18) towards or away from the orifice (17) to control the rate of venting from the control chamber and thereby vary the pressure within the control chamber. The setting of the arm (18) in relation to the orifice (17) is adjustable by means of a spindle (21) which applies a variable clamping force to the other arm (20) of the spring member (19); flexure of this arm (20) shifts the spring member in the corner (22) into which it is pressed at the junction between its two arms (18, 20). Modifications of the variable clamping means are described with respect to Figs. 3 and 4, (not shown). Spec. No., 2,054,207 A and 2,076,661 A are referred to. <IMAGE>

Description

SPECIFICATION Valves This invention relates to gas flow control valves and is concerned especially, though not exclusively, with demand valves for breathing apparatus.

The invention relates more particularly to valves of the kind in which main gas flow is regulated in accordance with pressure within a control chamber, gas being supplied substantially continuously to the control chamber and venting substantially continuously therefrom through a jet orifice at a rate dependent upon deflection of a pressure-responsive member whereby the pressure within the control chamber, and accordingly flow of gas through the valve, is dependent upon such deflection. A valve of this kind (referred to hereafter as "of the kind specified") is described in our published United Kingdom Patent Application No. 2054207A, as used in breathing apparatus for regulating the flow of gas to a user in accordance with breathing demands.In the valve described in said Application a pressure responsive diaghragm is coupled to one arm of an essentially two-armed spring member located in the outlet chamber of the valve, said one arm lying in the path of the jet of gas vented from the control chamber via the aforesaid orifice, so that deflection of the diaphragm moves that arm about a flexural pivot towards or away from the orifice so as to change the control chamber pressure, (and thereby vary the main gas flow through the valve), by its variable interaction with the gas jet. The other arm of the spring member is clamped to a side wall of the outlet chamber with its free end held against a resilient seating interposed between the arm and the wall.The set spacing of the first-mentioned arm from the jet orifice in the "neutral" condition of the valve (ie in which there is zero, or other specified, pressure differential across the diaphragm), is controlled by adjusting the clamping pressure of the other arm, which is intended to be rigid in use, against its seating to thereby vary its angular lie with respect to a shoulder against which the spring member abuts at the junction between its two arms.

Such adjustment, which would be performed during the assembly and testing of the valve, is necessary to ensure that a desired relationship is established in use between the pressure differential across the diaphragm and the degree of opening of the valve, and in particular determines whether the valve will operate in a so-called "negative pressure" mode (ie normally closed and opening only when a predetermined sub-ambient pressure is generated on one side of the diaghragm by inspiration of the user) or a "positive pressure" mode (ie normally open and closing only when a predetermined super-ambient pressure is generated on one side of the diaphragm eg by expiration of the user).As described in the said Application, the other arm of the spring member is clamped against its resilient seating by means of a nut on the end of a screw which passes from the adjacent wall of the outlet chamber th rough an aperture in the arm, tightening the screw and nut thereby increasing the clamping pressure. In practice, however, it has been found that this form of mounting and adjustment of the spring member is not entirely satisfactory and the present invention seeks to provide a valve with a spring member generally as described above and having improved means for the mounting and adjustment thereof.

The present invention accordingly resides in a valve of the kind specified in which the pressureresponsive member is coupled to one arm of an essentially two-armed spring member, said one arm of the spring member lying in the path of the jet of gas vented from the control chamber via said orifice such that deflection of the pressure-responsive member moves that arm about a flexural pivot towards or away from said orifice so as to change the main gas flow through the valve, the other arm of the spring member being flexible and bowed in its length and held to a fixed structure with the spring member being pressed against an abutment in the vicinity of the junction between its two arms; and comprising an adjustment member arranged to bear against said other arm of the spring member and being operable to alter the force with which it so bears thus to flex said other arm and shift the position of the spring member in relation to said abutmentto alter the set spacing of said one arm from the jet orifice.

Although particularly applicable to use as demand valves, valves according to the invention may find more general application as pressure-reducing or regulating valves.

Three preferred embodiments of demand valve in accordance with the invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a sectional side elevation of the first valve; Figure 2 is a section on the line Il-Il of Figure 1; and Figures 3 and 4 are sectional side elevations of the second and third valves respectively.

Referring to Figure 1,the illustrated demand valve has a casing 1 of plastics or metal that includes a cup-shaped body part 2 defining the outlet chamber 3 of the valve. In use the part 2 is coupled into the mask of a breathing apparatus eg as described in our published UK Patent Application No 2074278A, and a source of gas of virtually constant pressure for supplying the breathing needs of the mask wearer is connected to the valve via a union 4. The union 4 is formed at the outer end of a cylindrical insert 5 that is retained, with a gas-tight seal provided by an O-ring 6, within a tubuiar portion 7 of the casing 1.

Gas supplied to the union 4 enters a central bore 8 of the insert 5, and admission of this gas to the chamber 3 via two ports 9 in the wall of the portion 7, and thence into the mask, is regulated by an elastomeric disc 10.

The disc 10 is located against the flat inner endface 11 of the insert 5 within the tubular portion 7 of the casing 1. Eight equally-spaced apertures 12 formed in the face 11 encircle the bore 8 at that end, and open into an external annular groove 13 ofthe insert 5. Deflection of the disc 10 to lift it off its seating on the face 11 allows gas to pass from the bore 8 into the groove 13 via the apertures 12, and thence via the ports 9 into the chamber 3 to the mask. Such deflection of the disc 10 to admit gas to the mask, and its return to its seating flat against the face 11 to block admission of gas again, is dependent on variation of a control pressure established in a small chamber 14 located behind the disc 10 within the portion 7.More particularly the disc 10 responds to the balance of difference of th rust between the pressure of the gas within the bore 8 acting on a central, limited region of one side of the disc 10, and the control pressure within the chamber 14 acting over the full area of the other side of the disc.

The control pressure is established by continuous leakage of gas from the bore 8 into the chamber 14 through a small aperture 15 in a central spool 16 in the disc 10, and is varied by regulating the continuous venting of this gas from the chamber 14 via a small jet orifice 17. In the latter respect, an arm 18 of a generally L-shaped, single-piece spring-metal strip 19 of eg beryllium copper, lies in the path of the jet of gas escaping from the orifice 17 such that ofthe jet of gas escaping from the orifice 17 such that pressure build up in the chamber 14 varies in dependence upon movement of the arm 18 towards or away from the orifice 17.When the spacing of the arm 18 from the orifice 17 is decreased, the rate of venting of gas from the chamber 14 is decreased by the interaction of the arm with the gas jet and the back pressure acting in the chamber 14 on the disc 10 increases and so reduces, or blocks entirely, the main flow of gas under the disc 10 and into the chamber 3. Increase of the spacing, on the other hand, relieves the pressure in the chamber 14 by increasing the rate of venting via the orifice 17, so enabling or increasing flow of gas under the disc 10 and into the chamber 3. At no time does the arm 18 come into mechanical contact with the orifice 17.

7The arm 18 of the spring member 19 is arranged for resilient pivotal movement about the junction between the two arms of the member, the other arm 20 being clamped to the sidewall of the chamber 3 by means of an adjustment spindle 21. The arm 20 is bowed in its length and has a scroll formation at its free end, the member 19 being held with the concave side of the arm 20 facing the adjacent chamber wall and with the junction between the two arms pressed into abutment with the corner 22 defined between the side wall of the chamber 3 and an adjacent internal shoulder 23 of the body part 2. The adjustment spindle 21 extends diametrically across the chamber 3 and is supported at each end in bores 24 and 25 in the body part 2.It is of stepped diameter to define a nose portion 26 and a shoulder 27, the shoulder 27 bearing laterally against the convex side of the spring arm 20 while the nose portion 26 extends through an aperture in that arm (see Figure 2) and into the bore 24. The opposite end ofthe spindle is screw-threaded and meshes with a corresponding thread formed in the bore 25. Rotation of the spindle 21 thereby shifts it axially to adjust the clamping force of the shoulder 27 on the bowed spring arm 20.

Increasing that force tends to flatten the curvature of the arm 20 with the result that the arm 20 is pressed harder into the corner 22 and the portion of the member 19 at the junction between the arms 18 and 20 which is constrained there rolls in that corner to pivot the arm 18 away from the jet orifice 17. The spindle 21 may in practice be set - and such setting will be assumed, for ease of explanation, initially in the following description -to position the arm 18, in the condition of the valve in which there is no pressure difference across the diaphragm, just close enough to the orifice 17 against the force ofthe jet vented therefrom to ensure that gas flow under the disc 10 is blocked. Pivotal movement of the arm 18 away from this position is regulated by an elastomeric diaphragm 28.

The diaphragm 28 is clamped to the casing 1 around its periphery under an external collar 29, to respond to the difference between the pressure in the chamber 3 and the ambient pressure to which the diaphragm is exposed on its side remote from the chamber 3. A coupling member 30 is secured centrally to the diaphragm and extends into the chamber 3 where it has a bifurcated end 31 which clips to the free end of the arm 18 so that deflection of the diaphragm 28 is communicated to the arm 18 for regulating admission of the breathing gas to the mask. Inhalation by the mask wearer reduces pressure within the chamber 3, and the consequent inward deflection of the diaphragm 28 pivots the arm 18 away from the orifice 17.This reduces the control pressure within the chamber 14 and so enables gas flow under the disc 10 into the chamber 3 via the ports 9 to meet the breathing needs of the mask wearer. When inhalation stops and the pressures either side of the diaphragm 28 equalisethe diaphragm moves back to its undeflected position and the arm 18 moves back towards the orifice 17, under the resilient bias of the spring member, so shutting off gas flow under the disc 10. The mask will include provision for venting exhaled gas so that there is appropriate reduction in pressure, to draw the diaphragm 28 inwardly and supply fresh breathing gas through the demand valve, upon each inhalation.

Although the demand valve may be set to operate as described above in a so-called "negativepressure" mode, it is more desirably set to operate in a "positive-pressure" mode in which it is arranged that the pressure within the mask and chamber 3 does not fall below the ambient pressure at anytime during the respiratory cycle. This ensures that any leakage from the mask (eg from an imperfectface seal) can only be in the outward direction and that there is no risk of contaminated or noxious gas being breathed in from the environment during use. For the "positive-pressure" mode, the spindle 21 is set to bias the arm 18 further away from the orifice 17 so that the valve normally admits gas to the mask and closes only in response to outward deflection of the diaphragm 28 upon pressure build-up from the admitted gas or from exhalation.

A consequence of "positive-pressure" operation of the valve is that when the associated mask is not actually being worn, ie so that the chamber 3 of the valve is effectively open to atmosphere, the valve will respond by opening fully under the biasing of the arm 18 and if the gas supply to the valve is turned on it will vent continuously through the valve and be wasted. The valve therefore incorporates a manually-operable switch device generally indicated at 32 which can be actuated to selectively shut off the main gas flow under the disc 10 irrespective of the pressure within the chamber 3.The construction of switch devices suitable for this purpose is described in detail in our published United Kingdom Patent Application Nos 2054207A and 2076661 A, but briefly the switch comprises a manually-operable slide 33 which in a selected OFF condition releases a leaf spring 34 to engage the coupling member 30 and thereby lift the arm 18 to a position close to the orifice 17 in which gas flow under the disc 10 is prevented.

Preferably, the arm 18 of the spring member 19 is curved transversely of its width so as to increase its rigidity and more precisely isolate pivoting to the junction between the two arms. Such curvature of the arm 18, being convex in relation to the orifice 17, is also believed to have advantage in requiring less thrust for movement of the arm 18 against the force of the jet of gas from the chamber 14. The arm 20, being required to flex in order to achieve adjustment of the arm 18 as described above, does not have such transverse curvature.

Turning now to Figure 3, this shows a second example of a demand valve in accordance with the invention. The construction and operation of this valve is generally the same as for the valve of Figures 1 and 2, and like reference numerals are used to denote like parts in the two embodiments. The difference lies in the form and mounting of the spring member 19' which in this case has a first arm 18' coupled to the diaphragm 28 to control the venting of gas through the orifice 17 as previously described, and a second arm 20' extending away at an acute angle from the arm 18', into a slot 35 of a mounting block 36. The block 36 extends diametrically across the chamber 3 (so that gas can flow past either side of the block to the mask) and is there secured bytwo screws 37.The arm 20' is bowed in its length, with its concavity facing towards the arm 18', and is secured to the block at its free end by a fixing screw 38. In addition, an adjustment screw 39 is threaded into the block 36 and bears laterally against the opposite side of the spring arm 20'. Increasing the force with which the adjustment screw bears on the arm 20' flexes that arm to roll the spring member 19' in the corner 22 and thereby pivot the arm 18' away from the jet orifice 17, and slackening that force has the converse effect.

A third example of a demand valve in accordance with the invention is shown in Figure 4, wherein again like reference numerals denote like parts.

There is a spring member 19" having a first arm 18" coupled to the diaphragm 28 to control the venting of gas through the orifice 17 as previously described, and a second arm 20" of bowed form generally similay to the arm 20 in the embodiment of Figures 1 and 2. In this case, however, the lower end of the arm 20" is received in a mount 40 which is secured to the side wall of the chamber 3 by a screw41. An adjustment screw 42 is threaded into the base of the mount 40 to bear upwards, generally axially of the arm 20", against the scroll formation at the end of the arm 20", while a projection 43 of the mount bears against the convex side of the bowed arm at an intermediate position. Increasing the force with which the adjustment screw 42 bears on the arm 20" deflects that arm to shift the spring member 19" in the corner 22 and pivot the arm 18" away from the jet orifice 17, and slackening that force has the converse effect.

Claims (10)

1. A valve of the kind specified in which the pressure-responsive member is coupled to one arm of an essentially two-armed spring member, said one arm of the spring member lying in the path of the jet of gas vented from the control chamber via said orifice such that deflection of the pressureresponsive member moves that arm about a flexural pivot towards or away from said orifice so as to change the main gas flow through the valve, the other arm of the spring member being flexible and bowed in its length and held to a fixed structure with the spring member being pressed against an abutment in the vicinity of the junction between its two arms; and comprising an adjustment member arranged to bear against said other arm of the spring member and being operable to alter the force with which it so bears thus to flex said other arm and shift the position of the spring member in relation to said abutment to alter the set spacing of said one arm from the jet orifice.

2. A valve according to claim 1 wherein the spring member and the adjustment member are located within an outlet chamber of the valve through which the main gas flow is lead away from the valve and into which the jet of gas from the control chamber also vents.

3. A valve according to claim 1 or claim 2 wherein the spring member is generally L-shaped and said other arm is clamped against a surface by means of the adjustment member, with the concave side of said other arm facing said surface.

4. A valve according to claims 2 and 3 wherein said surface is a wall of said outlet chamber and the adjustment member is in the form of a screwed spindle which extends across the outlet chamber from that wall to the opposite wall thereof.

5. A valve according to claim 1 or claim 2 wherein said other arm of the spring member extends at an acute angle to said one arm with its concave side facing that one arm, said other arm is held to a fixed structure at a location remote from the said junction and the adjustment member bears against the opposite side of said other arm at a location between the first mentioned location and said junction.

6. A valve according to claims 2 and 5 wherein said other arm is held to a mounting block which extends across the outlet chamber and the adjustment member is in the form of a screw threaded in said block.

7. A valve according to claim 1 or claim 2 wherein the spring member is generally L-shaped and said adjustment member bears against the distal end of said other arm generally axially thereof.

8. A valve according to claim 7 wherein said other arm has a scroll-like formation at its distal end against which the adjustment member bears, and a fixed abutment bears against the convex side of said other arm at a position intermediate the said junction and the distal end of said other arm.

9. A valve according to any preceding claim wherein the said abutment is a corner and the said flexure of said other arm causes the spring member to roll in that corner to alter the set spacing of said one arm from the jet orifice.

10. A gas flow control valve substantially as hereinbefore described with reference to Figures 1 and 2, Figure 3 or Figure 4 of the accompanying drawings.