GB1601808A

GB1601808A - Automatic compensator valve

Info

Publication number: GB1601808A
Application number: GB5304576A
Authority: GB
Original assignee: Watkins and Watson Ltd
Current assignee: Watkins and Watson Ltd
Priority date: 1978-03-17
Filing date: 1978-03-17
Publication date: 1981-11-04

Description

(54) AUTOMATIC COMPENSATOR VALVE (71) We, WATKINS & WATSON LIM ITED, a British company of Westminster Road, Wareham, Dorset, BH20 4SP, 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:- This invention relates to an automatic compensator valve for controlling gas flow in a container, especially a support appliance such as a bed, having inflatable sacs for supporting the weight of an occupant.

In our British Patent Specification No.

1,422,994 there is described a bed comprising a plurality of inflatable elongated sacs arranged transversely of the bed on support members extending parallel to and beneath the sacs, means being provided for admission of air to the sacs through the support members while maintaining an airtight seal between the sacs and the support members.

The specific embodiments illustrated in our above prior specification provide generally satisfactory support appliances which have proved to be very effective for use in nursing patients afflicted with bed sores, burns or other lesions.

Continuing experience with this type of support appliance has highlighted two problems which sometimes arise during use. The first of these problems arises from the large number of mutually angled surfaces and crevices in the embodiments described in our prior specification in which dirt, waste matter and food can lodge and which is difficult to clean thoroughly unless the bed is substantially dismantled. Another problem is caused by the variation in the porosity of the material used for manufacturing the air sacs over a period of time, for example, because of laundering, or the development of small leaks in the air supply to the sacs.As a result of these factors, there is a need to adjust the rate of air supply to individual sacs or groups of sacs in order to maintain the desired differential air pressures in the sacs, and at the same time to adjust the rate at which air is exhausted at the exit side of the sacs in order to maintain the desired rate of air flow through the sacs. In an effort to make the necessary adjustment by the manual control valves previously provided, nursing staff have tended to over compensate for the change in leakage characteristics, and there is accordingly a need to provide an automatic system of compensating for such changes in leakage characteristics.

The present invention provides an automatic compensator valve in combination with a container through which a gas flow passes, via a pressure-reducing device, from a supply of pressurised gas, the valve being located at the exit from the container and comprising a valve plate and a diaphragm in operative connection therewith, the valve being such that the pressure of gas within the container acts upon the valve plate tending to open the valve to allow the gas to escape from the container, and the diaphragm is acted upon by the pressure of gas from said supply and tends to close the valve, the pressure-reducing device being such, and the relative effective areas of the valve plate and the diaphragm, acted upon by the pressure of gas within the chamber and of said supply respectively, being such that gas flow in the container is maintained at a constant rate.

Preferably, the valve plate and diaphragm are mounted on a spindle for conjoint axial movement.

Advantageously, the valve has a housing which, in use, is fixed to the container at its exit so that the valve plate can close said exit.

In this case, the valve plate may be provided with a sealing ring for sealing the interior of the housing from the container. Prefearably, the housing interior is divided into two chambers by the diaphragm, the chamber remote from the valve plate being provided within an inlet connectible to the supply of pressurised gas.

The pressure-reducing device may be constituted by a sharp-edged metering orifice provided in an input line leading from said supply to the container. Preferably, the metering orifice is such as to create a small, fixed pressure differential between gas from said supply and gas flowing through the container.

The invention also provides a bed (as herein before defined) which comprises a plurality of containers arranged transversely of the bed and mounted on support members extending beneath the containers, each container being constituted by an inflatable elongated sac, and means for admitting air to the sacs through the support members from a supply of pressurised air, via a pressure reducing device, each support member comprising a plenum chamber through which air is exhausted from a group of two or more mutually parallel sacs mounted thereon, each plenum chamber being provided with an automatic compensator valve for controlling the escape of gas from the sacs associated with that plenum chamber, wherein each valve comprises a valve plate and a diaphragm in operative connection therewith, the valve being such that the pressure of air within the sacs acts upon the valve plate and tends to open the valve to allow gas to escape from the sacs and the diaphragm is acted upon by the pressure of air from said supply tending to close the valve, the pressure reducing device being such, and the relative effective areas of the valve plate and the diaphragm, acted upon by the pressure of air within the sacs and of said supply respectively, being such that air flow in the sacs is maintained at a constant rate.

Throughout this specification, the term "bed" is used to describe beds, mattresses, chairs or similar support appliances.

Preferably, each automatic compensator valve is positioned at the exit of a subchamber into which each of the sacs controlled by that valve exhausts.

Conveniently, the sacs are retained in place by restraining webs extending between the ends of the sacs and the support member or a member attached thereto.

In the application of the compensator valve to a bed of the kind referred to above, the compensator valve may be housed within the or each support member and be arranged to control the air pressure within a single inflatable sac or group of sacs.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic elevation of the kind of bed to which the invention may be applied; Figure 2 is a plan view of one support member, with inflatable sacs removed; Figure 3 is a side elevation of the support member shown in Figure 2, sectioned to show the interior; Figure 4 is an end elevation of the support member shown in Figure 3, and Figure 5 is a collection of scrap views showing details of the manner of anchoring the inflatable sacs.

Referring to Figure 1 of the drawings, the bed comprises a head section 1 which is hingedly connected to the main section of the bed 2 by means of a pivot 3 which is free to move along a track 4 in the direction shown by the arrow Z when the part 1 is hinged upwardly. In the bed illustrated in Figure 1, the air cells or sacs 40 which form the patient support surface are mounted in groups on support members (not shown), the support members being mounted on and extending between frame members (not shown, but extending longitudinally of the bed at each edge thereof). Such cells or sacs are connected, via the support members, to a source of thermo-statically controlled pressurised air.

Upward movement of the head section 1 is effected by supplying air under pressure to a bellows 5 disposed underneath the head section 1.

An automatic control valve 9 and a wire and pulley arrangement 10, 11, 12, 13, 14 and 15 is provided to maintain the pressure of air within the bellows 5.

A further feature of the bed shown in Figure 1 is that the entire appliance can be pivoted to any desired angle. The arrangement for achieving this is indicated in Figure 1, from which it can be seen that the main section 2 is pivotally mounted on an axle 51 supported in bearings on a post 52 at each side of the main section. The posts 52 are mounted on a trolley 50 and braced by struts 53. Mounted on a transverse bar of the frame of the trolley 50 is a screw jack 54 which is arranged to extend and retract approximately along the centre line of the trolley frame. The main body of the screw jack 54 and its associated driving electric motor 55, are secured to the transverse bar, while the screw thread of the jack is coupled to one end of a lever 56 which is connected at its other end to the main section 2 of the bed.

It will be appreciated that extension of the screw thread will cause the main section 2 to tilt upwardly, while retraction will have the opposite effect. The trolley 50 includes castor wheels 57 of which at least one is fitted with a foot-operated brake (not shown).

Referring to Figures 2 to 5, each support member comprises a relatively flat hollow box section 20 which is adapted to extend between the longitudinally extending, edge frame members and support a plurality of air sacs (three in number in the arrangement illustrated). The interior of the box section 20 is divided by a wall 21 into a supply chamber 22 and an exhaust chamber 23. Thermostatically controlled heated air is supplied under pressure through a pipe 24, through a fixed sharp edge metering orifice 25, and into inlets 26, 27 and 28 for, respectively, air sacs 29, 30 and 31. For ease of cleaning and anchorage of the sacs 29, 30 and 31, the inlets 26, 27 and 28 (as well as the corresponding outlets 32, 33 and 34 from the sacs) are located adjacent to the ends of the box section 20.

Each air sac 29, 30 and 31 has an inlet nozzle 35 and an outlet nozzle 36 which are fixed, for example, by adhesive, to the fabric of that sac. The nozzles 35 and 36 are each a sliding fit within a corresponding bush 37 or 38 fitted into the box section 20. In order to allow for longitudinal shrinkage of the sacs 29, 30 and 31, during laundering, the nozzles 35. and 36 are spaced apart by a slightly greater distance than the spacing between the corresponding bushes 37 and 38. As can be seen from Figures 3 and 5, the bushes 37 and 38 stand proud of the box section 20 and each has a relatively sharp lip 39 on which an air seal is obtained by virtue of the downward force extended on the flange of the nozzle 35 or 36 by the air pressure within the corresponding sac.

Anchoring of the air sacs to the box section 20 is achieved by forming loops in the ends ofthe webs 60, 61 and 62 attached to the ends of each sac, passing the loops through a spaced bar 63 and trapping the loops with plastic dollies 64.

A compensator valve 65 is fitted in each box section 20 in order automatically to maintain the rate of escape of air from the air sac system at a desired level. Referring to Figures 2 and 3, the compensator valve 65 is located in the exhaust chamber 23 of the box section 20, and is arranged to maintain the air flow in all three sacs 29, 30 and 31 mounted on that box section at the same level. The exhaust outlets 32, 33 and 34 all discharge into a sub-chamber 66 located within the chamber 23 and the compensator valve 65 is positioned to control the flow of air from the chamber 66 to the chamber 23 and thence to atmosphere. The compensator valve 65 comprises a housing 67 attached to a lower wall 68 of the chamber 66, the wall 68 being apertured at 69 to allow air to pass from the chamber 66 to the chamber 23.A valve plate 70 is mounted on a spindle 71, and is provided with a sealing ring 72 so that movement of the valve plate 70 and the spindle 71 upwardly reduces, or closes off completely, the escape of air from the air sacs 29, 30 and 31.

Also mounted on the spindle 71 is a diaphragm 73 which, together with the housing 67, defines a compartment 74. The compartment 74 is pressurised with air at the air supply pressure by a connecting tube 75.

The metering orifice 25 is so arranged as to provide a small, fixed pressure drop which leads to a difference between the pressure of air from the supply and that flowing through the sacs 29, 30 and 31 and into the subchamber 66. If there should be an excessive air leak (for example, owing to development of greater porosity of the fabric forming the sacs after washing) this differential will increase. As a result the compensator valve 64 will move towards the closed positioned, since the upward force exerted on the diaphragm 73 by air at the supply pressure will exceed the downward force exerted on the valve plate 70 by air at the exhuast pressure.

At other times, the rate of air leakage from the system may be reduced (for example by collection of dust in pores in the air sacs) in which case the pressure differential will be reduced so that the compensator valve 65 will operate in the opposite direction to increase the rate of exhaust of air.

It will be appreciated that the desired balance between the inlet and outlet pressures is maintained by selection of the ratio of the effective areas of the valve plate 70 and the diaphragm 73.

Thus, it is no longer necessary to juggle with both a pressure supply valve and an exhaust valve on the exit side of the support members when the leakage characteristics of the air sacs change since the compensator valve automatically takes account of such variations.

Instead of providing a single wall 21 for dividing the interior of each box section 20 transversely, a pair of transverse wall divisions may be provided and the space thus formed used as trunking for leading flexible air supply pipes from a common supply manifold to the individual box sections.

WHAT WE CLAIM IS: 1. An automatic compensator valve in combination with a container which a gas flow passes, via a pressure-reducing device, from a supply of pressurised gas, the valve being located at the exit from the container and comprising a valve plate and a diaphragm in operative connection therewith, the valve being such that the pressure of gas within the container acts upon the valve plate and tends to open the valve to allow gas to escape from the container, and the diaphragm is acted upon by the pressure of gas from said supply tending to close the valve, the pressure-reducing device being such, and the relative effective areas of the valve plate and the diaphram, acted upon by the pressure of gas within the container and of said supply respectively, being such that gas flow in the container is maintained at a constant rate.

2. An automatic compensator valve as claimed in Claim 1, wherein the valve plate and diaphragm are mounted on a spindle for conjoint axial movement.

3. An automatic compensator valve as claimed in Claim 1 or Claim 2, wherein the valve has a housing which, in use, is fixed to the container at its exit so that the valve plate closes said exit.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of the sacs 29, 30 and 31, the inlets 26, 27 and 28 (as well as the corresponding outlets 32, 33 and 34 from the sacs) are located adjacent to the ends of the box section 20. Each air sac 29, 30 and 31 has an inlet nozzle 35 and an outlet nozzle 36 which are fixed, for example, by adhesive, to the fabric of that sac. The nozzles 35 and 36 are each a sliding fit within a corresponding bush 37 or 38 fitted into the box section 20. In order to allow for longitudinal shrinkage of the sacs 29, 30 and 31, during laundering, the nozzles 35. and 36 are spaced apart by a slightly greater distance than the spacing between the corresponding bushes 37 and 38. As can be seen from Figures 3 and 5, the bushes 37 and 38 stand proud of the box section 20 and each has a relatively sharp lip 39 on which an air seal is obtained by virtue of the downward force extended on the flange of the nozzle 35 or 36 by the air pressure within the corresponding sac. Anchoring of the air sacs to the box section 20 is achieved by forming loops in the ends ofthe webs 60, 61 and 62 attached to the ends of each sac, passing the loops through a spaced bar 63 and trapping the loops with plastic dollies 64. A compensator valve 65 is fitted in each box section 20 in order automatically to maintain the rate of escape of air from the air sac system at a desired level. Referring to Figures 2 and 3, the compensator valve 65 is located in the exhaust chamber 23 of the box section 20, and is arranged to maintain the air flow in all three sacs 29, 30 and 31 mounted on that box section at the same level. The exhaust outlets 32, 33 and 34 all discharge into a sub-chamber 66 located within the chamber 23 and the compensator valve 65 is positioned to control the flow of air from the chamber 66 to the chamber 23 and thence to atmosphere. The compensator valve 65 comprises a housing 67 attached to a lower wall 68 of the chamber 66, the wall 68 being apertured at 69 to allow air to pass from the chamber 66 to the chamber 23.A valve plate 70 is mounted on a spindle 71, and is provided with a sealing ring 72 so that movement of the valve plate 70 and the spindle 71 upwardly reduces, or closes off completely, the escape of air from the air sacs 29, 30 and 31. Also mounted on the spindle 71 is a diaphragm 73 which, together with the housing 67, defines a compartment 74. The compartment 74 is pressurised with air at the air supply pressure by a connecting tube 75. The metering orifice 25 is so arranged as to provide a small, fixed pressure drop which leads to a difference between the pressure of air from the supply and that flowing through the sacs 29, 30 and 31 and into the subchamber 66. If there should be an excessive air leak (for example, owing to development of greater porosity of the fabric forming the sacs after washing) this differential will increase. As a result the compensator valve 64 will move towards the closed positioned, since the upward force exerted on the diaphragm 73 by air at the supply pressure will exceed the downward force exerted on the valve plate 70 by air at the exhuast pressure. At other times, the rate of air leakage from the system may be reduced (for example by collection of dust in pores in the air sacs) in which case the pressure differential will be reduced so that the compensator valve 65 will operate in the opposite direction to increase the rate of exhaust of air. It will be appreciated that the desired balance between the inlet and outlet pressures is maintained by selection of the ratio of the effective areas of the valve plate 70 and the diaphragm 73. Thus, it is no longer necessary to juggle with both a pressure supply valve and an exhaust valve on the exit side of the support members when the leakage characteristics of the air sacs change since the compensator valve automatically takes account of such variations. Instead of providing a single wall 21 for dividing the interior of each box section 20 transversely, a pair of transverse wall divisions may be provided and the space thus formed used as trunking for leading flexible air supply pipes from a common supply manifold to the individual box sections. WHAT WE CLAIM IS:

1. An automatic compensator valve in combination with a container which a gas flow passes, via a pressure-reducing device, from a supply of pressurised gas, the valve being located at the exit from the container and comprising a valve plate and a diaphragm in operative connection therewith, the valve being such that the pressure of gas within the container acts upon the valve plate and tends to open the valve to allow gas to escape from the container, and the diaphragm is acted upon by the pressure of gas from said supply tending to close the valve, the pressure-reducing device being such, and the relative effective areas of the valve plate and the diaphram, acted upon by the pressure of gas within the container and of said supply respectively, being such that gas flow in the container is maintained at a constant rate.

4. An automatic compensator valve as

claimed in Claim 3, wherein the vale plate is provided with a sealing ring for sealing the interior of the housing from the container.

5. An automatic compensator valve as claimed in Claim 3 or Claim 4, wherein the housing interior is divided into two chambers by the diaphragm, the chamber remote from the valve plate being provided with an inlet connected to the supply of pressurised gas.

6. An automatic compensator valve as claimed in any one of Claims l to 5, wherein the pressure-reducing device is constituted by a sharp-edged metering orifice provided in an input line leading from said supply to the container.

7. An automatic compensator valve as claimed in Claim 6, wherein the metering orifice is such as to create a small, fixed pressure differential between gas from said supply and gas flowing through the container.

8. A bed (as hereinbefore defined) which comprises a plurality of containers arranged transversely of the bed and mounted on support members extending beneath the containers, each container being constituted by an inflatable elongated sac, and means for admitting air to the sacs through the support members, from a supply of pressurised air, via a pressure reducing device, each support member comprising a plenum chamber through which air is exhausted from a group of two or more mutually parallel sacs mounted thereon, each plenum chamber being provided with an automatic compensator valve for controlling the escape of gas from the sacs associated with that plenum chamber, wherein each valve comprises a valve plate and a diaphragm in operative connection therewith, the valve being such that the pressure of air within the sacs acts upon the valve plate and tends to open the valve to allow gas to escape from the sacs and the diaphragm is acted upon by the pressure of air from said supply tending to close the valve, the pressure reducing device being such, and the relative effective areas of the valve plate and the diaphragm, acted upon by the pressure of air within the sacs and of said supply respectively, being such that air flow in the sacs is maintained at a constant rate.

9. A bed as claimed in Claim 8 wherein each automatic compensator valve is positioned at the exit of a sub-chamber into which each of the sacs controlled by that valve exhausts.

10. A bed as claimed in Claim 8 and Claim 9 wherein the sacs are retained in place by restraining webs extending between the ends of the sacs and the support member or a member attached thereto.

11. A bed substantially as hereinbefore described with reference to, and as illustrated by the accompanying drawings.