GB1598689A - Control valve assembly for low pressure air beds - Google Patents

Description

(54) CONTROL VALVE ASSEMBLY FOR LOW PRESSURE AIR BEDS (71) We, ROBERT KELLIE & SON LIM ITED, a Company registered in Scotland, of Rutherford Road, Dryburgh Industrial Estate, Dundee, Scotland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a valve assembly which may be used to control the pressure in air filled mattress for the care of immobilised or partially immobilised patients in hospitals or in the home.

Patients who are immobilised are prone to develop pressure sores. One approach to preventing or curing pressure sores is to nurse the patient on a bed which takes the form of a hollow mattress or of two or more hollow mattresses, one upon the other, which are filled with air at a low positive pressure such that the top surface of the mattress wraps or moulds itself to the contours of the patient's body and provides even support without excessive pressure build-up at any one point. Hitherto the pressure of the air in the bed has been regulated by means of a tube depending into a cylinder or tank filled with water, but this method of pressure regulation is both inconvenient and noisy.

It is an object of the invention to provide means whereby the pressure in the bed can be easily, quietly, and safely controlled. It is a further object of the invention to enable the bed to operate at a wider range of pressures than before, particularly to facilitate nursing handling of the patient.

In one aspect the invention provides a pressure relief valve for control of a low volume air flow comprising: a body having a chamber, an inlet port for admission of air into the chamber and an outlet port in an upper portion thereof; a valve disc resting on the outlet port and liftable to allow air to escape from the valve chamber; a lever carrying a movable weight and pivoted to the valve body, the lever applying a downward load to the valve disc whose magnitude is variable within a range of 2 to 12 inches water gauge in accordance with the position of the weight along the lever; a control shaft and knob operatively connected through a radius arm and a rod to the weight and rotatable to adjust the weight to an intended pressure setting; and means frictionally restraining the control shaft so that it remains at the intended pressure setting.

In another aspect of the invention there is provided an air-supported mattress for the care of an immobilised or partially immobilised patient comprising one or more hollow mattresses filled with air through a supply pipe and a pressure relief valve as aforesaid connected so as to vent air when the prevailing air pressure rises above a preset operational pressure.

The invention has the advantages that it is more easily set than the previous water column control method, that it dispenses with the requirement for water altogether and the consequent filling, refilling, spillage and corrosion problems associated with water, and that it contributes to the electrical safety of the control unit as a whole, due to the absence of water.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is an oblique perspective view of a low pressure air-bed and control valve, a surround for the bed being partly cut-away to show the mattresses; Figure 2 is a rear view of the valve partly in section; and Figure 3 is a plan view of the valve body.

In Figure 1, a bed base 1 houses two hollow mattresses 2 one on top of the other.

The mattresses are connected by an air supply tube 3 to a control box 4 which houses an electrically driven air pump and associated controls including a valve assembly according to the invention. The control box further houses a T-piece (not shown). A first arm of the T-piece is connected to the air pump. The second arm of the T-piece is connected to the air supply tube 3. The third arm of the T-piece is connected to the inlet side of the valve assembly which is arranged to act as a pressure relief valve, the outlet side thereof venting to atmosphere.

Figure 2 shows a chamber 5 within the valve body, above which chamber is an 'O' ring seal 6 seated on a circular ledge. A circular valve plate 7 rests on the '0' ring and in operation is urged upwardly by the pressure of the air within the chamber 5.

Upward movement of the valve plate 7 allows air to escape between the plate and the seal 6. The wire arm 9 extends centrally over the valve plate 7 and is supported by it.

It continues through a positioning slot in the valve body for some distance and then turns through 90 degrees and again through 90 degrees to reflect back along its original path and terminate beyond the pivot point. The wire arm 9 is pivoted to the valve body and carries a movable weight 8 on the top runner thereof. Its lower runner rests on the conical crown of the valve plate 7 to apply thereto a load whose magnitude depends upon the position of the weight 8 along the arm. The maximum position as shown corresponds to a positive pressure of about 10 to 12 inches of water gauge and the minimum position corresponds to about 2 inches of water gauge.

Adjustment of air pressure in chamber 5, and hence in the hollow mattresses 2, is effected by varying the position of the weight 8 along the wire arm 9. The weight 8 is movable by means of connecting rod 10 which is pivoted to radius arm 11 which in turn is affixed to and rotated by control shaft 12.

Figure 3 is a top view of the valve body, control shaft, and radius arm assembly with parts 6 to 10 omitted for clarity. Air inlet 13 is shown leading from the third arm of the Tpiece into chamber 5. A slot 14 is formed in the top of the valve body and is arranged to locate and steady the wire arm 9. A control shaft 12 extends forwards and protrudes through the wall of control box 4, its protruding end carrying a control knob. A spring washer 15 or similar device is fitted to the control shaft to provide sufficient friction to retain any given rotational setting thereof.

It will be appreciated that various modifications may be made to the embodiment described above without departing from the invention.

WHAT WE CLAIM IS: 1. A pressure relief valve for control of a low volume air flow comprising: a body having a chamber, an inlet port for admission of air into the chamber and an outlet port in an upper portion thereof; a valve disc resting on the outlet port and liftable to allow air to escape from the valve chamber; a lever carrying a movable weight and pivoted to the valve body, the lever applying a downward load to the valve disc whose magnitude is variable within a range of 2 to 12 inches water gauge in accordance with the position of the weight along the lever; a control shaft and knob operatively connected through a radius arm and a rod to the weight and rotatable to adjust the weight to an intended pressure setting; and means frictionally restraining the control shaft so that it remains at the intended pressure settling.

2. An air supported mattress assembly for care of an immobilised or partially immobilised patient comprising one or more hollow mattresses filled with air through a supply pipe and a pressure relief valve as claimed in Claim 1, connected so as to vent air to atmosphere when the prevailing air pressure rises above a preset operational pressure.

3. A bed for nursing an immobilised or partially immobilised patient, said bed comprising a hollow air-inflated mattress, the internal pressure of which is regulated by means of a control valve substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

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

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. side of the valve assembly which is arranged to act as a pressure relief valve, the outlet side thereof venting to atmosphere. Figure 2 shows a chamber 5 within the valve body, above which chamber is an 'O' ring seal 6 seated on a circular ledge. A circular valve plate 7 rests on the '0' ring and in operation is urged upwardly by the pressure of the air within the chamber 5. Upward movement of the valve plate 7 allows air to escape between the plate and the seal 6. The wire arm 9 extends centrally over the valve plate 7 and is supported by it. It continues through a positioning slot in the valve body for some distance and then turns through 90 degrees and again through 90 degrees to reflect back along its original path and terminate beyond the pivot point. The wire arm 9 is pivoted to the valve body and carries a movable weight 8 on the top runner thereof. Its lower runner rests on the conical crown of the valve plate 7 to apply thereto a load whose magnitude depends upon the position of the weight 8 along the arm. The maximum position as shown corresponds to a positive pressure of about 10 to 12 inches of water gauge and the minimum position corresponds to about 2 inches of water gauge. Adjustment of air pressure in chamber 5, and hence in the hollow mattresses 2, is effected by varying the position of the weight 8 along the wire arm 9. The weight 8 is movable by means of connecting rod 10 which is pivoted to radius arm 11 which in turn is affixed to and rotated by control shaft 12. Figure 3 is a top view of the valve body, control shaft, and radius arm assembly with parts 6 to 10 omitted for clarity. Air inlet 13 is shown leading from the third arm of the Tpiece into chamber 5. A slot 14 is formed in the top of the valve body and is arranged to locate and steady the wire arm 9. A control shaft 12 extends forwards and protrudes through the wall of control box 4, its protruding end carrying a control knob. A spring washer 15 or similar device is fitted to the control shaft to provide sufficient friction to retain any given rotational setting thereof. It will be appreciated that various modifications may be made to the embodiment described above without departing from the invention. WHAT WE CLAIM IS:

1. A pressure relief valve for control of a low volume air flow comprising: a body having a chamber, an inlet port for admission of air into the chamber and an outlet port in an upper portion thereof; a valve disc resting on the outlet port and liftable to allow air to escape from the valve chamber; a lever carrying a movable weight and pivoted to the valve body, the lever applying a downward load to the valve disc whose magnitude is variable within a range of 2 to 12 inches water gauge in accordance with the position of the weight along the lever; a control shaft and knob operatively connected through a radius arm and a rod to the weight and rotatable to adjust the weight to an intended pressure setting; and means frictionally restraining the control shaft so that it remains at the intended pressure settling.

2. An air supported mattress assembly for care of an immobilised or partially immobilised patient comprising one or more hollow mattresses filled with air through a supply pipe and a pressure relief valve as claimed in Claim 1, connected so as to vent air to atmosphere when the prevailing air pressure rises above a preset operational pressure.

3. A bed for nursing an immobilised or partially immobilised patient, said bed comprising a hollow air-inflated mattress, the internal pressure of which is regulated by means of a control valve substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.