DEFLATION CONTROL VALVE

Abstract

A deflation control valve that automatically varies the rate of air flow through said control valve to provide a constant but adjustable rate of change of pressure during the deflation or exhaust of gas held in a closed pressurisable vessel to which said valve is connectable comprising a valve body having a passage communicatable with said pressurisable vessel, said valve body defining a valve chamber communicating with said passage in which a flexible diaphragm is provided partially or substantially closing said valve chamber, said diaphragm being in sealing abutment with a seat in said valve housing around the periphery of said diaphragm, and forming on the opposing side a part of an exhaust chamber, said diaphragm, in use, being, on the valve chamber side subject to the gas pressure in said pressurisable vessel and, on the opposing side, subject to the gas pressure in the exhaust chamber, which may be atmospheric pressure, and said diaphragm having an aperture or port extending therethrough, and said diaphragm on one side being in communication with said valve chamber and, on the opposite side, being in communication with said exhaust chamber or atmosphere and being closeable or partially closeable by a displaceable closure disc, plate or platen which is releasably held in the closing position against said diaphragm and covering said port by an operable, controllable or adjustable release means, which by adjusting said release means to open and closed positions or intermediate positions, controls the rate at which gas flows through the valve, gas passing from the valve chamber through the port in the diaphragm and between the face of the closure disc and diaphragm to exhaust or atmosphere to allow the pressure of the pressure chamber to drop in a controlled manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described further by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a side elevation of a first embodiment of a control valve of the present invention;

FIG. 1A is an end elevation of the valve of FIG. 1;

FIG. 1B is a perspective view from below of the control knob of FIGS. 1, 1A or 4;

FIG. 1C is a perspective view of a click spring;

FIG. 2 is an exploded perspective view of the components of the device of FIGS. 1, 1A and 4;

FIG. 3 is a perspective view of the underside of the preferred construction of the control disc or closure platen for use in the embodiments of FIGS. 1, 1A and 2 and 4 or FIGS. 5 to 15;

FIG. 4 is a cross section on the line A-A of FIG. 1A through the deflation control valve with rotary knob adjustment and shown partly connected downstream to a squeeze-bulb;

FIG. 5 is a perspective view of a second deflation control valve forming a preferred embodiment of the invention;

FIG. 6 is an exploded perspective view of the valve of FIG. 5;

FIG. 6A is a longitudinal cross section through the valve of FIGS. 5 and 6;

FIG. 6B is a transverse section through the valve of FIGS. 5 and 6;

FIG. 7 is a perspective view from the cuff attachment and of the valve of FIGS. 5 and 6 but without the inflation bulb and without the body halves and showing the cam in the maximum displacing and valve traveling position (the knob is in the fully closed position);

FIG. 8 is a view similar to FIG. 7 with the knob raised;

FIGS. 9 and 10 are reversed plan and perspective views from below of the part of the valve of FIGS. 7 and 8 but turned through 180° and without body halves (20a, 20b) still in the maximum lever displacement by the control of the rotary knob;

FIGS. 11 and 12 are similar views to FIGS. 9 and 10 but at an intermediate position of adjustment;

FIGS. 13 and 14 are opposite end views of the valve in the position as shown in FIGS. 11 and 12; and

FIG. 15 is a perspective view from below the components shown in the condition of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A rubber squeeze-bulb 1 (only shown in part but similar to bulb 12 in FIGS. 5 and 6) is provided for inflating a cuff (not shown) of a sphygmomanometer and is provided in known manner with an inlet aperture at one end for receiving a one-way inlet valve (not shown). At the opposite end outlet side of bulb 1 there is an outlet sleeve portion 1A sealed around a one way rubber valve or check valve 2 contained in an inlet of a valve body 3. The inlet of body 3 leads into the valve chamber formed by the valve body 3 having a tubular upper portion forming a seat for a flexible valve member or diaphragm 4. An outlet 3A leads to the cuff. Elastomeric disc-like diaphragm 4 (about 45 shore A material), is seated in the body 3 and sealed at its periphery against the seat by means of a sealing cap 6 including an externally threaded tubular portion which is threadingly engaged and secured in an upper portion of valve body 3 and urges the diaphragm 4 into sealing engagement with its seat. The cap 6 has a central aperture 6A for exhaust of air from the valve when opened and to enable a pin or boss to extend therethrough to act on the diaphragm 4 via a disc or platen. Diaphragm 4 has a central passage or hole or port 4A for flow of air which is controlled/stopped via a disc like platen 5. A rotary control knob 8 is provided threadingly mounted on valve body 3 which has a fine thread and axially displaceable by rotation to move towards and away from the platen 5. Knob 8 has a platen engagement pin or boss 8A on its lower inner side forming a control portion of the knob as it extends through aperture 6A in cap 6 and may bear against the upper surface of platen 5. A metal click spring 7 is mounted on the top of cap 6 on two retaining pins 6A, 6B extending through spring holes 7B and the knob 8 has a circle of serrations on its inner side engageable by a pawl portion 7C of spring 7. Click spring 7 and in particular pawl or dimple portion 7C operates against the ridges or serrations 8B on the underside of the knob 8. Spring 7 comprises two spaced apart flap-like portions 7D lying in the same plane and from which, in its position of use, two yoke-like springs arm portions 7E extend inclinedly downwardly to two spaced apart flat web-like mounting portions 7F both lying in the same plane and in which holes 7B are found. The small dimple 7D on one portion runs against the cap serrations 8B to create the click action. The other portion 7D also runs against the cap surface but on a smooth section inboard of the serrations. The spring 7 pivots against the clamp on the portion 7F of its surface with the two holes 7B and the cap 6 presses against both the bottom and top legs of the spring, ensuring the spring dimple clicks against the cap serrations. The platen/lever/cam assembly have the capability of closing the valve completely.

Air from the atmosphere is pumped into and through the valve body 3 by the rubber bulb 1, entering through the one way valve 2. The outlet of the body 3 has a rubber tube 3A running to the manometer and cuff. Diaphragm 4 is sealed to valve body 3 around its periphery by cap 6. There is a second outlet from valve body 3 via the port 4A in the centre of diaphragm 4 for exhausting/deflating the cuff. When the valve is closed, this exhaust hole or port 4A is sealed or substantially closed by platen 5, which is held down by the boss 8A on knob 8 which secured with a fine screw thread to valve body 3. When knob 8 is screwed closed (down), the pressure in the cuff and monitor can be raised by pumping bulb 1, typically to above systolic pressure. Unscrewing knob 8 slightly allows platen 5 to rise. Air can seep from valve body 3 (the high pressure area) through port 4A, along the passage formed by the groove in the platen, between the face of platen 5 and diaphragm 4 and through a hole in the knob 8, or otherwise to atmosphere, allowing the pressure in the cuff and monitor to drop. Opening and closing knob 8 controls the rate at which air flows through the valve.

A second effect provides pressure compensation. The underside of diaphragm 4 is subject to cuff pressure. The elastomeric diaphragm 4 will, if not constrained by the platen, lift (be deformed) by this pressure. If the cuff is pressurized and the platen 5 is raised, the diaphragm will tend to follow the platen, exposing the groove formed in the platen that connects port 4A to atmosphere by an amount proportional to the difference between the cuff pressure and atmosphere. As the pressure in the cuff drops, the diaphragm will deform less, increasing the size of the air passage leading from port 4A via the platen groove to atmosphere by exposing a section of the groove in the platen with a wider cross-sectional area. This effect, if correctly exploited, will compensate for the falling pressure in the cuff and mean that a clinician, once the correct flow rate has been achieved, will not have to continue to adjust the valve as the pressure drops.

It has been discovered that this effect is influenced by the surface finish of the platen and diaphragm, the shape of both parts and the softness of the diaphragm. Difficulties can be experienced achieving a precise control of the deflation rate and compensate for pressure effectively using a flat diaphragm and platen. The valve may tend either not to compensate enough for pressure (operate like a needle valve) or to overcompensate and increase flow rate dramatically as the pressure dropped. It has been discovered that adding a small groove to the face of the platen overcomes these difficulties and makes the compensation work well and the airflow control accurate and provides a preferred embodiment. The groove is at its deepest and widest over port 4A and tapers to nothing about 5 mm either side of port 4A.

The amount of the groove revealed by the diaphragm defines the size of the gap through which air can flow, the more the diaphragm bulges, the more of the platen face it covers and the smaller the passage for air to flow through. This additional feature is easily mouldable and makes the pressure compensation and flow control much more reliable and precise. Good compensation can be achieved by choosing the correct groove profile, diaphragm material, thickness and texture and overall geometry.

One of the characteristics of a face valve is that very small movements of the platen can have a large effect on airflow. The elasticity of the diaphragm and the application of pressure to most of its under surface (causing it to bulge under pressure) increase the amount of movement needed to change the air flow rate. The provision of a groove or slot helps further. It is desirable that the screw thread should have some tolerance, and gripping the knob in different ways can also significantly affect the flow rate through the valve. A screw thread gives a linear relationship between the rotation of the knob and its axial movement. This is not helpful when designing one valve to cope with different cuff and patient sizes—much more air needs to flow from a large cuff on a large patient than a small cuff on a child to deliver the same deflation rate. Nor does the clinician want to turn the knob 8 far to shut off or fully open the valve (both actions are needed during a blood pressure test).

A second and preferred embodiment of deflection control valve 10 is illustrated in FIGS. 3 and 5 to 15 wherein a known rubber squeeze inflation bulb 12 is provided with inlet check valve 12A at its inlet end and connected at its outlet end via check valve 11 to the inlet portion of the valve body 13 which has knob—mounting spindle 13A extending from the top thereof and, like in FIG. 4, defines a seat in a chamber on one side of its air through-flow passage and on which seat a diaphragm 24 is clamped by means of a clamp 16 which snap-fits onto the body 13 sealing the diaphragm 14 against the seat.

Diaphragm 14 has a central aperture or port 14A similar to that described previously and communicates the through-flow passage with the upper side of the diaphragm from whence air under pressure may escape to atmosphere. A disc or platen 15 is provided identical or similar to platen 5 described previously with a double tapered groove 15A part way along its diameter as described previously. Platen 15 is releasably urgeable against diaphragm 14 to close or partially close aperture 14A by means of a lever 19 which has an annular or ring-like portion 19A on which a cam 18A of raising knob 18 may slidingly act, and has a plate-like portion 19B which is displaceable in aperture 16A of clamp 16 to act on platen 15. Lever 19 is a pivotally mounted at 19B on clamp 16. Clamp 16 has diametrically opposite recesses 16B, 16C in which flanges 13A, 13B of the valve body 13 locate to prevent relative rotation. Two clam shells on upper and lower cases 20A, 20B, clamp together and hold knob 18 rotatable on spindle 13A.

The disk or platen 15 (identical or similar to platen 5 described previously) is controlled by the action of the cam 18A on the face of the knob 18 which is rotatable on spindle 13A. This cam 18A is preferably shaped so that the valve behaves to the user in an apparently linear way in the adjustment zone, does not have to be turned much more for large cuffs than for small, or to reach closed and fully open states. Placing the knob on the opposite side of the valve the platen 15 and the diaphragm 14 brings a number of advantages. Mechanical advantage can be built into the lever 19 that transmits the cam 18A movement to the face of the platen 15, so that there is more travel at the knob cam 18A than at the platen 15—this helps reduce the effect of knob bearing tolerance and any sideways movements of the knob caused by the clinicians holding the valve in unexpected ways.

Any axial movement of the knob which is more difficult to control does not affect the position of the lever or platen. The knob bearing shaft or spindle 13A is mounted directly to the back of top face of the valve body and is provided with rotation stops 13E, and knob 8 is located axially between abutment surfaces on the valve body and on the inside of case 20B so that the knob can be handled reasonably roughly without applying forces to the valve mechanism. A click action (click 17A and metal click spring 17B operating on knob ridges 8B) can also be assembled easily in such a way that the forces generated by the spring 17B and click 17A do not affect the position of the lever 19 or platen 15. The diaphragm 14 is sealed to the body with snap-fit clamp 16. Clamp 16 also provides a pivot 19B & C for lever 19 and pivot 17AA for click 17A. The two body halves 20A and 20B, protect the mechanics of the valve.

The rotary knob 18 turns freely on the spindle 13A (through approximately 310° as controlled by stop 13E (FIG. 8). The cam is radially tapered and moves lever 19 which acts on the platen 15 and therefore on diaphragm 14. Lever 19 pivots in bearing holes 19B & C in clamp 16. The platen 15 is not sealingly mounted to the valve body. The diaphragm 14 is sealed to the body by a periphery at edge of clamp 16, which snaps onto the body 13. Air cannot escape from the valve body through hole 14A in the diaphragm to atmosphere when the diaphragm is pressed flat against the valve body by the platen (the platen is forced against the diaphragm by the lever 19 and knob cam 18A). The diaphragm 14 seals against the platen 15 around the periphery of the platen (not a particularly good seal) and also against the spigot 13F formed in the centre of the valve body (which contacts the raised annular wall 14B on the diaphragm 14—this thin wall 14B reduces the force needed to seal the diaphragm and reduces the likelihood of parts creeping over time if the valve is left tight shut for long periods).

When the knob 18 is turned and the platen 15 allowed to lift away from the valve body, the pressure in the valve flexes the diaphragm 14 and lifts the platen 15. The diaphragm 14 flexes at its centre (it is held around its periphery), and an escape path is created for the pressurized air in the valve body past the thin sealing rib on the diaphragm and the valve spigot, through the hole in the centre of the diaphragm, down the two passages formed between the platen groove and the diaphragm and, if the curvature of the diaphragm is sufficient, to atmosphere. The more the diaphragm is curved (flexed), the more of the ends of the platen groove are revealed and the larger the air escape path cross section becomes. The diaphragm curvature depends on the position of the platen (controlled by the cam and lever) and on the pressure drop across the diaphragm (as mentioned previously, the higher the pressure in the valve, the greater the diaphragm deflection, the more the platen groove is covered, the smaller the air escape orifice—hence pressure compensation).

Whilst there is axial movement of the knob in the first embodiment there is no movement along the axis of rotation in this second embodiment merely about said axis. Thus it is possible to have whatever desired relationship between the knob rotation and platen movement thereof, (if need not be linear, and can be adjusted so that the relationship between the knob rotation and deflation rate (rather than platen movement) appears linear to the user). The knob bearing is easy to form, the knob can be robust, the delicate mechanics of the valve protected and a tactile ‘click’ is provided.

The click action of the tactile means is created here by a flat spring, trapped at its centre on the valve body (the post-like moulding 13D locates the click spring) driving the plastic pawl 17C (called the click) against serrations or ridges 188. The pawl 17C is pivoted on the clamp 16 to prevent any sideways movement. The reason for using a plastic pawl 17C (rather than simply having a detail on the spring that engages on the ridges 18B on the underside of the knob 18) is to control the feel of the click with greater accuracy—these clicks happen every 6° of knob rotation, which is a small movement to identify with the click. The shape of the ridges on the underside of the knob and the co-operating boss on the face of the plastic pawl or ‘click’ component create the feel. The ridges do not cover all the rotation of the knob—they define the ‘working zone’.

Taking the knob zero point (cam point 18C against 19A) as being when the valve is fully shut off, the first click is felt after 48° of rotation. With the smallest cuff size used on a child, the correct deflation rate for reading systolic or diastolic blood pressure will be reached after about 6 clicks, or a further 36° rotation (at normal room temperature). The knob is turned a further 15 or so clicks (approximately 90°) to deflate the cuff reasonably fast between measuring points. The correct deflation rate for measuring the blood pressure of an obese adult is reached about 15-20 clicks in (rather than 6 for a child). A total of 38 clicks (or 228° of rotation) has been provided, so that a clinician should in most cases be working within the ‘click’ zone while taking pressure readings and moving between measuring points. Once the blood pressure has been measured, the valve is opened fully to give the quickest deflation. The valve is fully open (18D adjacent 19A) when the knob is rotated 310° from the zero (or closed) position and the last 34° of valve movement have no clicks. One stop for knob rotation is provided—it can be seen on the valve body on the bulb side of the knob spindle 13A and there is a corresponding rib 18E on the underside of the knob.

Thus in summary, the present invention provides an adjustable face valve connectable to a pressurisable cuff or other vessel to control air flow from the cuff, preferably with pressure compensation such that valve automatically maintains a constant rate of pressure change in the cuff for a given setting of the valve regardless of the pressure in the cuff, the main reason for pressure compensation being to provide the clinician with a valve that does not need to be adjusted as the pressure in the cuff falls. The advantages of driving the platen with a cam, other than the mechanical and structural advantages of the cam arrangement we have arrived at (mechanical advantage, minimal disturbance of the platen position if the user applies pressure to the knob while holding it, disconnection of the more delicate parts of the valve from the user so that they cannot be abused easily), include making the relationship between knob rotation and deflation rate more intuitive to the user—more proportional, which means that the cam profile has to be slightly unusual such that it has a shut off ramp operating to close the valve, which reduces to a very gradual spiral angle at the beginning of the deflation zone (for controlling small cuffs). The spiral angle then increases as the valve is opened further for controlling larger cuffs or quick exhaust.

It is intended the technique of and valve for controlling small air flow with pressure compensation, has applications other than for sphygmomanometers.

Claims

1. A deflation control valve that automatically varies the rate of air flow through said control valve to provide a constant but adjustable rate of change of pressure during the deflation or exhaust of gas held in a closed pressurisable vessel to which said valve is connectable comprising a valve body having a passage communicatable with said pressurisable vessel, said valve body defining a valve chamber communicating with said passage in which a flexible diaphragm is provided partially or substantially closing said valve chamber, said diaphragm being in sealing abutment with a seat in said valve housing around the periphery of said diaphragm, and forming on the opposing side a part of an exhaust chamber, said diaphragm, in use, being, on the valve chamber side subject to the gas pressure in said pressurisable vessel and, on the opposing side, subject to the gas pressure in the exhaust chamber, which may be atmospheric pressure, and said diaphragm having an aperture or port extending therethrough, and said diaphragm on one side being in communication with said valve chamber and, on the opposite side, being in communication with said exhaust chamber or atmosphere and being closeable or partially closeable by a displaceable closure disc, plate or platen which is releasably held in the closing position against said diaphragm and covering said port by an operable, controllable or adjustable release means, which by adjusting said release means to open and closed positions or intermediate positions, controls the rate at which gas flows through the valve, gas passing from the valve chamber through the port in the diaphragm and between the face of the closure disc and diaphragm to exhaust or atmosphere to allow the pressure of the pressure chamber to drop in a controlled manner.

2. A valve as claimed in claim 1, where the resistance to the passage of gas from the higher pressure in said valve chamber to the lower pressure in said exhaust chamber is determined by the surface area of said diaphragm in contact with said closure disc, the local contact pressure between said diaphragm and said closure disc and the material, geometry and surface finish of said diaphragm and said closure disc.

3. A valve as claimed in claims 1 and 2, such that, on releasing the release means slightly, the closure disc moves away from the diaphragm, the pressure difference between the higher pressure in the valve chamber and the lower pressure in the exhaust chamber urges said flexible diaphragm towards said closure disc, creating a curvature in said diaphragm such that the surface area of said diaphragm in contact with said closure disc and the local contact pressure between said diaphragm and said closure disc controls the rate at which gas can seep from the higher pressure area in the valve chamber through the port in the diaphragm to the lower pressure area in the exhaust chamber in a manner that is dependent on the position of the closure disc in relation to the diaphragm, the pressure difference between the higher and lower pressure areas and the nature of the materials, surface finishes and form of the diaphragm and closure disc, such that the valve automatically maintains a constant rate of pressure change in the pressurisable vessel as the pressure difference between the valve chamber and the exhaust chamber changes due to loss of gas from the pressurisable vessel.

4. A valve as claimed in claim 1, 2 and 3, in which a manually operable release means is a reversibly rotatable and axially displaceable control knob bearable on the platen.

5. A valve as claimed in 1, 2 and 3, in which a manually operable release means is a non-axially displaceable rotary knob with cam and lever means for reversibly urging the platen into a closing position, the cam so formed that there appears to the user to be a linearly (or any other) proportional relationship between the angular position of the knob and the rate of change of pressure difference between the valve chamber and the exhaust chamber.

6. A valve as claimed in claim 5, in which the displacement means associated with the knob and is such that the movement is amplified and thus greater movement of the knob enables a smaller movement of the disc or platen.

7. A valve as claimed in any of claims 1 to 6, in which the closure disc and/or diaphragm has an air escape passage or means which varies in cross-section as the deformation of the diaphragm due to the pressure difference across it and the position (lifting and lowering) of the closure disc varies.

8. A valve as claimed in claim 7, wherein alternate air escape control means is provided on or in the diaphragm to compensate for falling pressure in the pressurisable vessel.

9. A valve as claimed in claim 7 or 8, in which the air escape means is an escape passage in the form of a recess to compensate, in use, for falling pressure in the pressure chamber and enable the rate of change of pressure in the valve chamber to be controlled.

10. A valve as claimed in claim 7, wherein alternate air escape control means is provided on or in the closure disc to compensate for falling pressure in the pressurisable vessel.

11. A valve as claimed in claim 8, in which the alternate air escape means is a small groove or channel or other airflow control enhancing feature on or in the surface of said diaphragm facing said closure disc.

12. A valve as claimed in claim 10, in which the alternate air escape means is a small groove or channel, or a projection (such as a ridge or bump) or other airflow control enhancing feature on or in the surface of said closure disc facing said diaphragm.

13. A valve as claimed in claim 11, in which the groove is elongate and diametrical and central and positioned over or through the port perforating the diaphragm and of a varying/differing cross-sectional area, largest in the centre of either the closure disc or the diaphragm and reducing to zero nearer to the edge of the closure disc or diaphragm, such that amount of surface area of the diaphragm in contact with the closure disc determines the minimum cross-sectional area of the groove through which gas escaping from the higher pressure chamber to the exhaust chamber has to flow.

14. A valve as claimed in any of claims 1 to 13, in which the airflow control enhancing features are provided additionally or alternatively including the surface finish of the closure disc and/or the diaphragm and/or the shape of both parts and/or the softness and/or thickness of the diaphragm.

15. A valve as claimed in any of claims 1 to 14, in which, in use, when the valve is closed, the diaphragm port is sealed or substantially closed by the closure disc or platen, which is held down by means extending from the release means.

16. A valve is claimed in claim 15, in which the release means is an axially displaceable rotary knob secured with a fine screw thread to the valve body or a non-axially displaceable rotary knob having a cam which acts on lever means to achieve the same effect.

17. A valve as claimed in any of claims 1 to 16, in which click or pawl and ratchet means are associated with the release means and regulate the movement of the control knob and provide audible and/or physical feedback to the clinician.

18. A deflation control valve substantially as herein described with reference to the accompanying drawings.

19. A deflation control valve as claimed in any of claims 1 to 18 in combination with a sphygmomanometer.

20. A deflation control valve in the form of a face valve for a sphygmomanometer comprising a valve body having a first outlet passage connectable to be communicatable with a pressurisable tube connected to a cuff of a sphygmomanometer, and an inlet passage connectable to a rubber bulb pump or like inflation means, said valve body defining a valve chamber in which a flexible diaphragm is provided partially or substantially closing the chamber and said diaphragm having a deflation, air-flow passage which on one side of the diaphragm is in communication with said inlet and outlet passage and, on the opposite side of the diaphragm, is in communication with an exhaust outlet or atmosphere and is closeable or partially closeable during inflation by a displaceable closure disc, plate or platen which is releasably held in the closing position against said passage by a manually operable, controllable or adjustable release means.