Beds – Bedclothing – And means to facilitate changing thereof
Patent
1991-08-26
1993-12-28
Grosz, Alexander
Beds
Bedclothing
And means to facilitate changing thereof
5914, 13761411, A47C 2710, A61G 7057
Patent
active
052727785
DESCRIPTION:
BRIEF SUMMARY
This invention relates to low air loss beds and in particular to means for controlling the air flow and pressure in the air sacs of such beds.
In a low air loss bed the user is supported on a series of inflated air sacs which are divided, for control purposes, into several groups. Each group is individually supplied with pressurised air so that each part of the body, viz:- the head, trunk, sacrum, thighs and feet can be supported at the most favourable contact pressure. Various features of commercial low air loss beds will be apparent from U.K. Patents Nos: 1,422,994; 1,474,018; 1,601,808 and 2,070,426 and U.S. Pat. Nos. 3,909,858 and 4,099,276.
One longstanding difficulty in operating low air loss beds (hereinafter referred to as L.A.L. beds), has been to adjust the pressures in individual groups of sacs rapidly to a desired pressure or series of pressures. Normally, L.A.L. beds have been fitted with air supply control valves for each section and sometimes also control valves on the exhaust side. Achievement of a desired pressure in a particular section has required a series of adjustments to the supply valves, because of the interaction of one set of sacs with the next. Also, the rate of flow of air through the sacs necessitates adjustment of exhaust valve setting in order to maintain a desired flow rate. Uniform flow rate is desirable since otherwise the bed will heat unevenly; heating normally being effected by passing air from the blower over heating elements and then feeding the heated air to the valve system. Although a compensator valve arranged at the exhaust side of the bed, as described in U.K. No: 1,601,808, does help to maintain desired air flow rates, some skill is still required by nursing staff to operate a L.A.L. bed in an optimum manner. Furthermore, current valve systems are not ideally suited to electronic process control since, as a result of the valve characteristics, it takes a long time for the system to settle to a new pressure.
According to the present invention there is provided a low air loss bed comprising a plurality of inflatable air sacs which are grouped in sections, the pressure of air in at least one section being controlled by a valve arrangement comprising an inlet valve and an exhaust valve, the inlet valve being linked to the exhaust valve so that opening of the inlet valve is automatically accompanied by a corresponding degree of closure of the exhaust valve and vice versa.
The linkage between the inlet and exhaust valves may be mechanical. However, as an alterative, the valves may be linked electrically or by a fluid connection or other means. For example, an electrical, magnetic or hydraulic clutch. Where a mechanical linkage is employed this may be achieved by mounting the valve heads on the same spindle. An alternative and currently preferred arrangement is to support the valves side-by-side in a housing and to link their spindles by gearing to a common drive shaft.
A most surprising finding of the valve arrangement according to this invention is that there is a virtually linear relationship between pressure in the bed section and valve angle or degree of opening. This makes the valve characteristics very predictable and facilitates the adaption of electronic microprocessor control in a bed fitted with valve assemblies in accordance with the invention. Microprocessor control may be achieved by driving the valves by a stepping motor through a common shaft, the motor being controlled by a computer. Since pressures established in the air sacs and air flows in the sacs will be determined by the valve openings and pressure of the air source applied to the valve assembly, individual pressure gauges can be eliminated. Once the system has been calibrated, the computer will be able to predict the pressures in the sacs from known valve angles.
Further features and advantages of the valve assembly according to the invention will become apparent from the following description and accompanying drawings in which:
FIG. 1 is a graph showing the operating characteristics of a con
REFERENCES:
patent: 3388701 (1968-06-01), Schreiber et al.
patent: 3646969 (1972-03-01), Stampfli
patent: 3909858 (1975-10-01), Ducker
patent: 4099276 (1978-07-01), Hunt et al.
patent: 4935968 (1990-06-01), Hunt et al.
patent: 4962552 (1990-10-01), Hasty
Grosz Alexander
The Mediscus Group Inc.
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