GB2578925A

GB2578925A - A dynamic mattress assembly

Info

Publication number: GB2578925A
Application number: GB1818589.2A
Authority: GB
Inventors: John Baker Richard; John Baker Gary
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-11-14
Filing date: 2018-11-14
Publication date: 2020-06-03
Also published as: GB201818589D0; WO2020099835A1

Abstract

A dynamic mattress comprising a mattress 4 formed from a plurality of cells 8 and a compressor 20 with an outlet conduit 30 extending from the compressor to the cells and a return conduit 40 extending from the cells to the compressor to return gas from the cells. There may be a second layer of cells and the cells may be independently inflated in groups. The compressor may have a second inlet 24 to take in air from the surrounding environment and there may be an expanded polyurethane foam base. Also disclosed are mattresses wherein the outlet conduit or an exhaust conduit have a baffle 60 to dampen noise and vibrations and an arrangement with a heater 56 to warm the compressed gas before it enters the cells. The baffles may be a plurality of tubes with smaller diameters. Recirculating gas is designed to keep the temperature in the mattress in equilibrium with a patient so they retain heat.

Description

A DYNAMIC MATTRESS ASSEMBLY

The present invention relates to a mattress assembly, in particular to a dynamic mattress assembly having therapeutic applications and/or health benefits.

A wide variety of mattresses are known in the art and are commercially available. In many cases, mattresses are generally static and comprise a foam structure which conforms to the body of the user and the pressure applied to the capillaries and skin tissue of the user causes the capillaries to partially or wholly occlude. The occlusion of the capillaries reduces the flow of blood through the tissue and therefore reduces the rate of oxygenation, nutrition delivery and toxin removal from the affected area. This causes a negative effect on the health of the localised area of skin. In order to counter this the brain instructs the body of the user to rotate through various sleep positions, moving between lying on their back, their left side, their back again, their right side and occasionally sleeping on their front. This action can disrupt the sleep of the user and any partner present leading to potential restlessness, tiredness and sometimes pain upon awakening. Any user incapable of repositioning themselves naturally due to mobility issues or medication requires manual repositioning by another person at regular intervals and would therefore benefit from a mattress comprising inflatable cells that relieves pressure.

Dynamic mattresses are known in the art and are commercially available. Dynamic mattresses comprise a plurality of inflatable cells. In many known designs, the inflatable cells are elongate or tubular and extend laterally across the mattress, perpendicular to the lengthwise position of the person lying on the mattress. The dynamic mattress may comprise a single layer of cells. The dynamic mattress may also comprise one or more layers of foam material. In this case, the cells are typically located in the uppermost region of the mattress, as the mattress is oriented in use. Alternatively, the mattress may comprise a plurality of layers of cells. Again, these may be accompanied by one or more layers of foam material. The cells of the mattress may be provided with gas permeable portions, for example perforations, allowing gas to bleed or leak from the cell at a predetermined rate.

Dynamic mattresses of this type typically have found considerable use in hospitals, clinics and the like. In particular, such mattresses are commonly used to relieve pressure and provide comfort for patients that are confined to a bed for extended periods due to long term illnesses and/or difficulties. It is known to use pumps and a control system to selectively inflate and deflate the cells with gas, typically air, according to various regimes. These inflation/deflation regimes can be used to alter the static form of the mattress for comfort. Alternatively the pump and control system can be used to wholly or partially inflate and deflate cells in an assigned pattern to create movement of mattress beneath the user and to relieve pressure on areas of the body of the user. Generally, these techniques can be used to avoid the occurrence of pressure sores, which are caused by constant localised pressure restricting blood flow in the capillaries of the skin of a bed ridden patient.

An early design of dynamic mattress is described and shown in GB 1,595,417 and comprises two layers of laterally extending chambers or 25 tubes, separated by a shaped layer of foam.

GB 2,197,192 discloses an alternating pressure pad having two or more layers of cells. The cells of each layer are inflatable independently of the cells in the other layer. The cells in one layer of the pad overlie the cells in another layer of the pad.

GB 2,327,874 discloses an inflatable support, in particular a low air loss mattress having an upper layer of inflatable cells and a lower layer of cells. In use, the lower layer of cells is maintained at a constant pressure, higher than the pressure in the upper layer of cells. In this way, the person lying on the mattress is prevented from contacting the underlying supporting surface, in particular when sitting on the mattress or when being moved. The cells in the upper layer may be inflated to different pressures, to provide differential support to different parts of the person. As above, operation and control of the inflatable support in practice is typically by a person other than the user of the support, such as a clinician or nurse.

A mattress having a plurality of transverse air-filled chambers or cells is also disclosed in each of US 2008/0095322 and EP 2 465 480.

A mattress is described and shown in GB 2,458,892 and comprises a plurality of laterally extending air-filled tubes or chambers. A compressor for providing air to the tubes is provided and is operated to inflate and deflate the tubes independently in a predetermined pattern over time. Again, in use, the compressor of a mattress of this kind is generally operated by a person other than the user of the mattress. The compressor is typically located at the foot of the bed, out of reach of the person lying on the mattress.

One design of a therapeutic bed assembly is disclosed in US 2010/0306924. There is described and shown an inflatable mattress for a bed, the mattress being operable to provide a range of therapies. The mattress is of a complex construction, formed from many different components, necessary to provide the range of therapies. In particular, the mattress comprises one or more inflatable bladders, on which lies a plurality of laterally extending, inflatable tubes. The tubes are typically inflated under the control of a person other than the user of the mattress. One or more layers of foam are provided on the upper surface of the inflatable tubes.

A mattress assembly comprising two layers of inflatable cells on a foam base is described and shown in GB 2,473,661. The mattress assembly comprises a base of expanded foam, a first layer of cells orientated transverse to the longitudinal axis of the bed and an upper second layer of cells orientated transverse to the longitudinal axis of the bed. The first layer of cells are static and remain at a constant pressure. The cells in the second layer are of two forms, the first being a perforated variety in which the air pressure is maintained by a means provided to supply gas at a constant rate and pressure. The second layer has cells of the second form that are selectively inflated and deflated according to a predetermined regime. The mattress of this type has proven to be successful in relieving pressure in bed-ridden patients. Mattresses of the general type disclosed in GB 2,473,661 are available commercially.

A number of problems can arise with the known designs of dynamic mattresses. In general, patients or users can experience discomfort and restlessness, leading to a significant number of instances where the dynamic mattress is rejected in favour of mattresses of a more conventional design.

One reason that dynamic mattresses are rejected is due to the noise created by the components of the control and gas delivery system. The system can be very loud and can disturb the sleep of the user and those in close proximity.

A further disadvantage of such mattresses results from the movement caused by operation which can result in the user experiencing symptoms of motion sickness.

Further, the use of dynamic mattresses can lead to cooling of the body of the patient or user. In the case of the elderly or infirm, this can lead to hypothermia.

It would therefore be an advantage if a mattress having all the benefits of the aforementioned known dynamic mattresses could be provided, while at the same time reducing the effects leading to the use of dynamic mattresses being rejected. In particular it would be advantageous if such a mattress could be provided that could be used for both immobile patients or as an alternative to a traditional mattress that provides more comfort and reduced restlessness compared to other inflated cell mattresses.

Accordingly, in a first aspect, the present invention provides a dynamic mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a first pressure; a compressor comprising: a first inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the inflatable cells for providing compressed gas from the compressor to the cells; and a return conduit extending from the inflatable cells to the first inlet of the compressor for returning gas from the cells to the compressor.

In a further aspect, there is provided a method of operating an active mattress assembly, the active mattress assembly comprising; a first layer comprising a first plurality of cells inflatable with gas to a first pressure; and a compressor; the method comprising; operating the compressor to produce a compressed gas at an outlet of 30 the compressor; supplying the compressed gas to the cells to inflate the cells and returning gas from the cells to a first inlet of the compressor.

It has been found that providing a user or a patient with a dynamic mattress assembly according to the present invention and/or a mattress assembly operating according to the method of the present invention gives rise to a significant improvement in the sleep patterns of the user or patient, in turn leading to a significantly reduced rate of rejection of the mattresses.

As noted above, a disadvantage of known dynamic mattresses results from the effect the dynamic mattress has on cooling the body of the user and/or patient. One of the most important functions of the human body is the maintenance of a core body temperature of about 36.5 to 37.5 °C. This temperature is normally achieved and maintained by the body despite considerable fluctuations in external air temperatures and provides an inner body climate in which the various chemical and biological processes can function. Thermoregulation of the body is facilitated by the skin, which forms a barrier between the external and internal environments. The skin can absorb heat that is radiated towards it, convected via air past it or conducted through a warm surface. The elderly, due to age related vascular deterioration, and those with cardio vascular disease are often subject to impaired thermoregulation and hence a reduction in the ability to maintained the core body temperature at the appropriate level. This can manifest itself in the person feeling cold. Such persons can be at risk of hypothermia, in particular while in an environment with temperatures that would normally be considered healthy.

During the operation of known dynamic mattresses, a large volume of fresh air is drawn in from outside of the pump housing and circulated through a network of conduits or lines to the inflatable cells, before exhausting this air back into the external environment. The material separating the inflatable cells from the skin tissue of the user is often less than 2mm thick and covered in cotton sheets of 2mm thick. The substantial flow of air below the patient, causes heat to be conducted and convected away from the body therefore causing an unnatural and accelerated artificial cooling effect. This causes some patients to feel cold, and impairs their ability to create a heat reserve necessary to allow bodily processes to occur. This can manifest itself as a range of symptoms, including neurological pain, cold, discomfort and shivering, through to fatal hypothermia in the case of particularly elderly and/or infirm patients.

The dynamic mattress assembly and method of the current invention employ the continuous re-use of air from within part or the entire mattress assembly. This allows the air to commence its use at room temperature. The patient may initially transfer some heat to the circulating air and the air will progressively warm until equilibrium is achieved between the patient and the mattress. At this point the patient should start to retain heat rather than lose it through the circulation of air within the dynamic mattress assembly.

The dynamic mattress assembly employs a compressor to create a flow of gas to and from the inflatable cells of the mattress. Compressors are prone to overheating and if a compressor overheats it can cause it to break down. If the compressor breaks down then the mattress deflates placing the patient at a high risk of serious injury. Overheating reduces the life span of the compressor. The cost of replacing a compressor is generally not high. However, the disruption and the possible risk to life are high. In the mattress assembly of the present invention, gas within the cells is returned to the inlet of the compressor. As the gas being recirculated will be at close to the operating pressure of the cells, the load on the compressor is reduced. Further, the flow of recirculated gas can be directed over the compressor motor, creating a cooling effect by forced convection. Both of these factors contribute to the cooling of the compressor and reduction of the potential for overheating. A further advantage of the present invention, therefore, is an improvement in the compressor life and reduce the likelihood of compressor failure. The risk to patient health is therefore reduced and a more reliable system is provided.

The mattress of the assembly of the present invention comprises a first layer of inflatable cells. The cells may have any suitable shape and form.

Preferably, the cells are elongate, that is have a length that is greater than the width. The cells may have any suitable cross-sectional shape. In one preferred embodiment, the cells are generally cylindrical. In another preferred embodiment, the cells are generally rectangular in cross-section.

The inflatable cells are formed with a cell wall of flexible, gas-impermeable material. Suitable materials are known in the art and are commercially available. Preferred materials for forming the cell wall include known polymers, in particular polyurethane.

One or more of the inflatable cells may be provided with one or more openings or perforations in the wall of the cell to allow gas to escape from within the cells. The size of the openings or perforations may be selected to control the rate at which During operation of the mattress assembly, the pressure of gas within the cells of the first layer is selected to provide the required level of support to the patient, when the mattress is in use. Preferably, the pressure of gas within the cells of the first layer is in the range of 2700 to 11000 Pa (20 to 80 mmHg), more preferably from 3300 to 9300 Pa (25 to 70 mmHg), still more preferably from 4000 to 8000 Pa (30 to 60 mmHg). A minimum gas pressure of 3300 Pa (25 mmHg), more preferably 4000 Pa (30 mmHg), has been found to be suitable for providing the required level of support to a patient lying on the mattress for a prolonged period of time.

The pressure of gas within the cells of the first layer may be varied, according to the size and weight of the patient using the mattress. In one embodiment, it is preferred that all cells are maintained at substantially the same gas pressure. In an alternative embodiment, the first layer is divided into two or more portions, each portion comprising one or more cells, the gas pressure within the cells varying from portion to portion.

In one preferred embodiment, the pressure of gas in some or all of the inflatable cells of the first layer is varied over time. In particular, it is preferred that the cells are repeatedly inflated and deflated over time. Any suitable pattern of inflation and deflation may be employed, while ensuring that the person lying on the mattress has sufficient support. One arrangement is to divide the cells of the first layer into two groups, X and Y, with the cells from group X alternating with cells from group Y in the first layer. One example of an alternating pattern of cells in groups X and Y is XYXYXY. The cells in group X are inflated and deflated over time, according to a predetermined regime, with the cells in group Y being inflated and deflated over time using the equal but opposite regime. Preferably, all the cells in group X are inflated and deflated at the same time according to the same regime. In one regime, the cells in group X are deflated and held in the deflated state for a period of time, in particular from 1 to 5 minutes, more preferably from 2 to 4 minutes, especially about 3 minutes. During this inflation/deflation of cells in group X, the cells in group Y are held at constant pressure. Thereafter the cells in group X are inflated and all cells in the second layer held inflated for a period of time, in particular from 0.5 to 5 minutes, more preferably from 0.5 to 3 minutes, especially about 1 minute. The inflation and deflation of the cells depends upon the volume of the cell and the pressure of the gas supply. Typically, inflation and deflation times are from 15 to 60 seconds, more preferably from 20 to 40 seconds, especially about 30 seconds. While keeping the cells in group X at a constant pressure, the cells in group Y are then inflated and deflated according to the same regime as those for group X. The regime is then repeated. This alternating pattern of inflation and deflation has been found to assist patients, in particular avoiding the occurrence of conditions, such as sores and the like, that arise from prolonged periods of time in bed. All the inflatable cells in the first layer may be subjected to the inflation/deflation regime described above, that is the groups of cells X and Y may extend the entire length of the mattress. In one preferred embodiment, the cells at each end of the mattress, for example from 2 to 7, more preferably 5 cells at each end, are kept constantly inflated and are not subjected to the inflation/deflation regime.

Preferably, the cells of the first layer have the relevant dimension (for example a diameter in the case of cylindrical cells) to provide the first layer of cells when inflated to operating pressure with a thickness of up to 20 cm, more preferably up to 15 cm, still more preferably up to 13 cm, more preferably still up to 10 cm. In many embodiments the cells have a relevant dimension to provide the first layer of cells with a thickness of greater than 10 cm. However, the thickness of the first layer of cells may be from 3 cm, preferably from 5 cm, more preferably from 7 cm, still more preferably from 8 cm. The cells may have a relevant dimension to provide the first layer with a thickness of from 3 to 15 cm, preferably from 4 to 12 cm, more preferably from 5 to 10 cm.

In one embodiment, in which cells are only present in a first layer, the layer of cells has a thickness of from 8 to 12 cm, more preferably from 9 to 11 25 cm, more preferably about 10 cm. A thickness of less than 10 cm may also advantageously be employed.

In a preferred embodiment, in which the mattress comprises a first layer of cells and a second layer of cells, as described in more detail below, the first layer of cells has a thickness of from 3 to 8 cm, preferably from 4 to 7 cm, more preferably about 5 cm or less. A thickness of about 6.5 cm may also be employed.

As noted above, the cells are prepared from a suitable gas-impermeable material. The thickness of the cell wall is selected according to the material of construction to provide sufficient strength to the cell wall to resist the internal gas pressure and retain the shape and form of the cell when the mattress is in use. A typical thickness of the cell wall is from 0.2 to 1.0 mm, more preferably from 0.25 to 0.6 mm, still more preferably from 0.3 to 0.5 mm. A wall thickness of about 0.35 mm has been found particularly suitable for cylindrical or oblong cells formed from polyurethane.

The inflatable cells of the first layer are preferably of a uniform shape and size. However, if desired, the first layer may be provided with cells of different shapes and sizes, so as to accommodate the needs of the patient. Preferably, each cell of the first layer extends laterally across the entire width of the mattress.

The inflatable cells of the first layer preferably extend transversely across the mattress, that is perpendicular to the lengthwise axis of the mattress. In this way, the inflatable cells extend generally perpendicular or across a person lying on the mattress.

Preferably, the cells in the first layer are arranged so as to provide a continuous layer, that is adjacent cells in the layer are touching or abut each other.

The number of cells in the first layer will be determined by the overall length of the mattress and the dimensions of the cells in the layer. Preferably, the individual cells and the mattress are sized to provide the first layer with from 20 to 40 cells, more preferably from 25 to 35 cells. It has been found that providing the first layer with from 28 to 32 cells is a particularly effective arrangement.

The first layer of cells may be divided into two regions: a first region comprising one or more cells underlying the head of the subject when the mattress is in use; and a second region comprising one or more cells, preferably a plurality of cells, underlying the remainder of the body of the subject, when the mattress is in use. It is preferred that the cell or cells in the first region are static cells and are not subjected to an inflation/deflation regime. It is preferred that the cells in the second region are dynamic cells and are inflated and deflated as described above.

The first region may comprise from 1 to 10 cells, preferably from 2 to 8, more preferably from 3 to 7, still more preferably from 4 to 6 cells, with 5 cells being preferred for many embodiments. The second region may comprise from 15 to 35 cells, preferably from 18 to 30 cells, more preferably from 20 to 28 cells, still more preferably from 22 to 26 cells, with 24 cells being preferred for many embodiments.

In one preferred embodiment, the first layer of cells comprises 29 cells.

In one arrangement of this embodiment, 5 cells underlying the head of the subject, when the mattress is in use, are static cells, that is are not subjected to an inflation/deflation regime, such as described above. The remaining 24 cells underlying the body of the subject are dynamic cells as are subject to an inflation/deflation regime, preferably according to the embodiments described above.

The mattress of the present invention may further comprise a base. The base may be formed from an expanded foam material. Suitable foam materials are well known in the art and are commercially available. Preferred foam materials are polyurethane foams, in particular open-cell polyurethane foams. The density of the foam material of the base layer is selected, together with the pressure of gas within the cells of the first layer and the dimensions of the cells of the first layer, to provide the requisite level of support for the patient, when the mattress is in use. Preferably, the density of the foam material of the base is in the range of from 20 to 50 kg/m3, more preferably from 25 to 40 kg/m3, with a foam density in the range of from 30 to 35 kg/m3 being especially preferred.

The thickness of the base is selected according to the density of the foam material. The thickness of the foam base is preferably in the range of from 2 to 6 cm, more preferably from 2.5 to 5 cm, still more preferably from 2.5 to 4 cm. A base thickness of about 3 cm is particularly suitable for the mattress of the present invention.

A particularly preferred base layer comprises a polyurethane foam having a density of between 32 and 32.5 kg/m3 and a thickness of 3 cm.

The mattress may further comprise a second layer of inflatable cells. The cells of the second layer may have any suitable shape and form.

Preferably, the inflatable cells are elongate, that is have a length that is greater than the width. The cells may have any suitable cross-sectional shape. In one preferred embodiment, the cells are generally cylindrical. In another preferred embodiment, the cells are generally rectangular in cross-section.

The inflatable cells of the second layer are formed with a cell wall of flexible, gas-impermeable material. Suitable materials are known in the art and are commercially available. Preferred materials for forming the cell wall include known polymers, in particular polyurethane.

One or more of the inflatable cells of the second layer may be provided with one or more openings or perforations in the wall of the cell to allow gas to escape from within the cells. The size of the openings or perforations may be selected to control the rate at which The second layer of cells extends across the lower surface of the first layer, with the mattress assembly in use.

In operation of the mattress assembly, the cells of the second layer are inflated to a second pressure with gas. The cells are preferably maintained at a substantially constant gas pressure during use. Accordingly, the cells in the second layer may be referred to as 'static cells'. Preferably, the gas within the cells of the second layer is kept at a constant, predetermined pressure. It is preferred that all the cells of the second layer are filled with gas to substantially the same pressure.

The pressure of gas within the cells of the second layer is selected, together with the density of the foam material of the base layer and the gas pressure within the cells of the second layer, to provide the required level of support to the patient, when the mattress assembly is in use. Preferably, the pressure of gas within the cells of the second layer is in the range of from 2700 to 11000 Pa (20 to 80 mmHg), more preferably from 3300 to 9300 Pa (25 to 70 mmHg), still more preferably from 4000 to 8000 Pa (30 to 60 mmHg). A minimum gas pressure of 3300 Pa (25 mmHg), more preferably 4000 Pa (30 mmHg), has been found to be suitable for providing the required level of support to a patient lying on the mattress for a prolonged period of time.

The pressure of gas within the cells of the second layer may be varied, according to the size and weight of the patient using the mattress. It is preferred that all cells in the second layer are maintained at substantially the same gas pressure. However, should it be required, the second layer may be divided into two or more regions, each region comprising one or more cells, the gas pressure within the cells varying from region to region. It is particularly preferred that the gas pressure within the cells of the second layer is constant.

Preferably, the inflatable cells of the second layer have the relevant dimension (for example a diameter in the case of cylindrical cells) to provide the second layer of cells when inflated to operating pressure with a thickness of up to 20 cm, more preferably up to 15 cm, still more preferably up to 13 cm, more preferably still up to 10 cm. In many embodiments the cells have a relevant dimension to provide the second layer of cells with a thickness of greater than 10 cm. However, the thickness of the second layer of cells may be from 3 cm, preferably from 5 cm, more preferably from 7 cm, still more preferably from 8 cm. The cells may have a relevant dimension to provide the second layer with a thickness of from 3 to 15 cm, preferably from 4 to 12 cm, more preferably from 5 to 10 cm.

In a preferred embodiment, in which the mattress comprises a first layer of cells and a second layer of cells, the second layer of cells has a thickness of from 3 to 8 cm, preferably 4 to 7 cm, more preferably about 5 cm. A thickness of about 6.5 cm may also be employed.

The total combined thickness of the first and second layers of cells is preferably in the range of from 7 to 20 cm, more preferably from 8 to 15 cm, still more preferably from 9 to 13 cm. A total combined thickness of about 10 cm is preferred for many embodiments. A total combined thickness of less than 10 cm may also be employed.

As noted above, the cells of the second layer are prepared from a suitable gas-impermeable material. The thickness of the cell wall is selected according to the material of construction to provide sufficient strength to the cell wall to resist the internal gas pressure and retain the shape and form of the cell when the mattress is in use. A typical thickness of the cell wall is from 0.2 to 1.0 mm, more preferably from 0.25 to 0.6 mm, still more preferably from 0.3 to 0.5 mm. A wall thickness of about 0.35 mm has been found particularly suitable for cylindrical or oblong cells formed from polyurethane.

The inflatable cells of the second layer preferably extend transversely across the mattress, that is perpendicular to the lengthwise axis of the mattress. In this way, the inflatable cells extend generally perpendicular or across a person lying on the mattress.

Preferably, the cells in the second layer are arranged so as to provide a continuous layer, that is adjacent cells in the layer are touching or abut each 15 other.

The number of cells in the second layer will be determined by the overall length of the mattress and the dimensions of the cells in the layer. Preferably, the individual cells and the mattress are sized to provide the second layer with from 20 to 40 cells, more preferably from 25 to 35 cells. It has been found that providing the second layer with from 28 to 32 cells is a particularly effective arrangement. In one preferred embodiment, the second layer comprises 29 cells.

Any suitable gas may be used to inflate the cells of the mattress. Air is a most suitable and convenient gas.

The dynamic mattress assembly is provided with a system to provide gas to the cells of the first layer, and the second layer if present, in order to provide the required pressure of gas and/or to change the gas pressure within the cells, as required. In particular, the mattress assembly comprises a compressor. Suitable compressors are known in the art and are available commercially.

The compressor comprises a first inlet for receiving gas to be compressed. The inlet is arranged to receive gas being returned to the compressor from the inflatable cells. The compressor further comprises an outlet for the compressed gas.

The mattress assembly further comprises an outlet conduit that extends from the outlet of the compressor to the cells for providing compressed gas from the compressor to the cells. The gas flows through the outlet conduit to the cells in order to inflate the cells or maintain the internal pressure of the cells. The outlet conduit may comprise one or more lines or pipes to supply compressed gas to each inflatable cell.

The outlet conduit is arranged to provide a supply of compressed gas to each inflatable cell. In embodiments in which different cells are operated at different pressures, the outlet conduit comprises one or more valves, to control the flow of gas to the cells.

Further, the mattress assembly also comprises a return conduit extending from the inflatable cells to the first inlet of the compressor for returning gas from the cells to the compressor. The return conduit may comprise one or more lines or pipes, as required, to return gas from the inflatable cells to the compressor. The recirculation of gas provides the aforementioned benefits of reducing the cooling effect on the patient and extending the compressor life.

In one embodiment, gas may be returned from some but not all of the inflatable cells of the or each layer to the compressor. More preferably, gas is returned to the compressor through the return conduit from all of the inflatable cells of the or each layer of cells.

Gas is returned to the compressor from inflatable cells in the first layer.

Preferably, gas is also returned to the compressor from inflatable cells in the second layer of cells.

The compressor may also comprise a second inlet for gas to be compressed. The second inlet is preferably open to the external environment and operates to provide additional gas, most preferably air, to be compressed should the amount of gas being recirculated not allow for the internal pressure to be maintained at the required level. The second inlet may also be employed to draw gas, in particular air, into the compressor to inflate the cells of the mattress when the mattress assembly is first operated, for example after being stored in a deflated condition.

The second inlet may be passive and allow gas, such as air from the environment, to be drawn in by the compressor when required, in addition to the gas being recirculated. Alternatively, the second inlet may comprise a valve, which is opened when the pressure of gas within the mattress falls below a required minimum level and further gas is required within the system.

The operation of the compressor and any valves present in the mattress assembly is preferably controlled by a controller.

As noted above, one advantage of the mattress assembly of the present invention is a reduction in the heat lost by a person lying on the mattress. If needed, the mattress assembly may further comprise a heater to heat gas provided to the inflatable cells. If provided, the heater is used to heat gas supplied to the first layer of inflatable cells. In embodiments comprising a second layer of cells, the gas supplied to the cells of the second layer may also be heated by the heater.

If a heater is provided, the heater is preferably arranged to heat the gas after it has left the compressor and before it is fed to the inflatable cells.

A method of operating an active mattress assembly according to the present invention is also provided. First, the compressor is operated to produce compressed gas at the outlet of the compressor. The compressed gas is supplied to the cells in order to inflate the cells to the required pressure. The gas from the cells is the then returned to the first inlet of the compressor. As noted above, additional gas may be supplied to the compressor through a second inlet, for example to replenish gas lost from the cells or to inflate the mattress when first being used.

The method of operation may also comprise sensing the pressure in the system and deactivating the compressor once an upper threshold pressure is reached. In this way, over-pressurizing the cells is avoided and the duty applied to the compressor reduced. The pressure in the cells may be sensed and the compressor reactivated when the pressure falls below the threshold.

In order to release pressure from cells during an inflation and deflation cycle, the gas removed from the cells may be recirculated through the inlet of the compressor, before being vented from the mattress assembly, for example to the atmosphere in the case of air. Alternatively, the recirculated gas can be used to inflate other cells of the mattress.

The mattress assembly may also comprise a sensor for measuring the temperature of the gas within the inflatable cells of the mattress. The temperature of the gas may range from 18 to 30°C during operation. Temperatures outside of this range may also be used. The temperature of the gas may be varied according to the needs of the person using the mattress, for example being kept higher in the case of an elderly or infirm person. As noted above, the mattress assembly may comprise a heater. The heater may be operated when the temperature of the gas is required to be increased.

As noted above, dynamic mattresses are often refused by users due to their excessive noise. Some people believe this to be due to vibrating compressors. This has been resolved by some parties. However, there is still a need for an improved dynamic mattress assembly that is more acceptable to users.

A further aspect of the present invention provides a dynamic mattress assembly that is more acceptable for users and which is less likely to be rejected.

Accordingly, in a further aspect, the present invention provides a mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a pressure; a compressor comprising: a first inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the cells for providing compressed gas from the compressor to the cells; and one or more baffles disposed within a conduit between the plurality of cells and the compressor.

The gas flushing through the inflated cells and conduits within the mattress assembly causes a vibration or oscillation effect. When the mattress assembly is in use, the ear of the person lying on the mattress is typically about 2 mm from the gas within the cells of the mattress, without a pillow being used. As a result, this vibration can sound very loud to the user. The noise can still be apparent to the user with a pillow, as the pillow fibres or feathers act as a conduit for the vibrations.

The solution offered by the present invention is for the compressed gas leaving the compressor to flow past, through or around a baffle within one or more of the conduits extending between the compressor and the inflatable cells. The baffle reduces the vibration of gas within the conduit and the other parts of the mattress assembly, in particular within the inflatable cells. This in turn makes the flow of gas through the mattress less noisy and improves the uptake of such dynamic mattresses.

In a preferred embodiment, one or more baffles are located in the outlet conduit extending between the outlet of the compressor and the inflatable cells of the mattress. A single baffle may be employed in this location.

Alternatively, two or more baffles may be employed of the same or different configurations.

It is preferred to have at least one baffle located in the outlet conduit in the region of the outlet of the compressor, more preferably within 20 cm of the outlet of the compressor, still more preferably within 15 cm, more preferably still within 10 cm, especially within 5 cm. The baffle may be located closer to the outlet of the compressor, for example, within 4 cm, preferably within 3 cm, more preferably within 2 cm, such as within 1 cm.

In some embodiments, as described above, the mattress assembly may comprise a return conduit for returning gas from the inflatable cells to an inlet of the compressor. One or more baffles may additionally be located in the return conduit in such embodiments.

The baffle may have any suitable form that dampens or reduces the vibrations within the gas flowing out of the outlet of the compressor. One preferred form for the baffle is one having one or more passages therethrough for the flow of gas, the passage having a diameter that is smaller than the diameter of the outlet conduit. The or each passage may have any suitable cross-section. In one embodiment, the passage is generally circular in cross-section. The or each passage may extend along the conduit substantially parallel to the longitudinal axis of the conduit. Alternatively, the or each passage may extend in one or more directions at a non-zero angle to the longitudinal axis of the conduit, that is the or each passage provides a more labyrinthine path for the gas to flow along.

In one preferred embodiment, the baffle comprises a baffle member having a plurality of passages formed therethrough and/or defining a plurality of passages between the baffle member and the inner surface of the outlet conduit.

In another preferred embodiment the baffle consists of a tube disposed within the outlet conduit. The tube is preferably sized such that it is retained in place by contact friction with the inner surface of the outlet conduit, more preferably in an annular arrangement.

In an alternative embodiment, the baffle comprises a plurality of tubes disposed within the outlet conduit, each tube providing a passage therealong. The plurality of tubes are preferably arranged with their passages parallel to one another.

The mattress assembly may comprise a single baffle. Alternatively, two or more baffles may be present in the conduits of the mattress assembly. If two or more baffles are employed, they may be of the same configuration or have different configurations.

In addition to compressed gas passing from the outlet of the compressor to the inflatable cells, during operation of the mattress assembly compressed gas is caused to leave the inflatable cells during an inflation/deflation regime. To reduce the occurrence of noise due to this flow of compressed gas leaving the inflatable cells, one or more baffles may be provided in the conduit through which the gas from the cells is exhausted.

Accordingly, in a further aspect, the present invention provides a mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a pressure; a compressor comprising: a first inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the cells for providing compressed gas from the compressor to the cells; an exhaust conduit for receiving compressed gas leaving the cells; and one or more baffles disposed within the exhaust conduit.

As noted above, in some preferred embodiments, the exhaust conduit is connected to an inlet of the compressor and forms a return conduit, allowing the compressed gas leaving the cells to be returned to the compressor, recompressed and recirculated.

Baffles for use in the exhaust conduit are as described above.

In one preferred embodiment, one or more baffles are disposed in each conduit of the mattress assembly for transporting compressed gas.

Baffles, as described above, may be used together with one or more of the other aspects of the present invention described herein or independently thereof.

As described above, one particular problem with dynamic mattresses can be the loss of heat from a subject using the mattress. This can be a particular problem for the elderly or the infirm. As described above, one solution to this problem is to heat the gas entering the cells of the mattress from the compressor.

Accordingly, in a further aspect, the present invention provides a dynamic mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a first pressure; a compressor comprising: an inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the inflatable cells for providing compressed gas from the compressor to the cells; and a heater for heating the gas leaving the compressor before the gas enters the inflatable cells.

In a further aspect, there is provided a method of operating an active mattress assembly, the active mattress assembly comprising; a first layer comprising a first plurality of cells inflatable with gas to a first pressure; and a compressor; the method comprising; operating the compressor to produce a compressed gas at an outlet of the compressor; heating the compressed gas; and supplying the compressed gas to the cells to inflate the cells.

Details of preferred embodiments of the dynamic mattress are as described above.

Heating of the compressed gas being fed to the cells of the dynamic mattress can be employed together with one or more of the other aspects of the present invention described herein, or can be employed independently thereof.

Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of a mattress assembly according to one embodiment of the present invention; Figure 2 is a diagrammatic representation of a mattress assembly according to a second embodiment of the present invention; Figure 3 is a diagrammatic representation of the compressor of the mattress assemblies of Figures 1 and 2; Figures 4 and 4a are a diagrammatic representation of a conduit comprising a baffle according to one embodiment of the present invention; Figure 5 and 5a are a diagrammatic representation of a conduit comprising a baffle according to a further embodiment of the present invention; Figure 6 and 6a are a diagrammatic representation of a conduit comprising a baffle according to a still further embodiment of the present invention; and Figure 7 and 7a a diagrammatic representation of a conduit comprising a baffle according to a yet further embodiment of the present invention.

Turning to Figure 1, there is shown a mattress assembly of one embodiment of the present invention. The mattress assembly, generally indicated as 2 comprises a mattress 4. The mattress 4 of this embodiment comprises a single layer 6 of inflatable cells 8 enclosed in a removable cover 10. Each inflatable cell 8 is generally tubular in configuration and extends laterally across the width of the mattress 4.

The assembly 2 further comprises a compressor 20. The compressor has a first inlet 22 and a second inlet 24. Both the inlets 22, 24 are for receiving a gas, in this case air, to be compressed. The first inlet 22 is for receiving air recycled from the cells 8. The second inlet 24 is for receiving air from the surroundings, to compensate for air lost from within the system. The compressor 20 further comprises an outlet 26.

An outlet conduit 30 extends between the outlet 26 of the compressor 20 and the mattress 4 and provides compressed air from the compressor 20 to the inflatable cells 8. The outlet conduit 30 may comprise a suitable arrangement of headers and pipes (not shown for clarity) within the mattress 4 for feeding compressed air to each cell 8 as required.

A return conduit 40 extends from the mattress 4 to the first inlet 22 of the compressor 10. The return conduit 40 returns air from each of the inflatable cells 8 to the first inlet of the compressor 10. The return conduit 40 may comprise a suitable arrangement of headers and pipes (not shown for clarity) within the mattress 4 for receiving compressed air from each cell 8 as required.

The assembly 2 further comprises a controller 50. The controller 50 controls the operation of the compressor 10, in particular turning the compressor on and off as required to regulate the pressure within the cells 8 of the mattress 4. The controller receives an indication of the pressure within the cells from a pressure sensor 52. In addition, the controller 50 receives an indication of temperature of the air being circulated from a temperature sensor 54. A heater 56, operated by the controller 50, is provided and can be operated to provide additional heat to the air flowing in the outlet conduit 30 to the cells 8.

Finally, the outlet conduit 30 is provided with a baffle assembly 60. In the embodiment shown, the baffle assembly 60 is located in the outlet conduit in the region adjacent the outlet 26 of the compressor 10.

Turning to Figure 2, there is shown a second embodiment of the mattress assembly of the present invention. The assembly of this embodiment, generally indicated as 102, has a similar configuration to the assembly 2 shown in Figure 1. Components common to the assemblies of Figures 1 and 2 are indicated using the same reference numerals and are as described above. The differences between the embodiments of Figures 1 and 2 are as follows: In the embodiment of Figure 2, the mattress 104 comprises a first layer 106 of inflatable cells 108 overlying a second layer 110 of inflatable cells 112. A base layer 114 of foam is provided beneath the second layer 108. A removable cover 116 is provided over the first and second layers 106, 110 and the base layer 114.

Turning to Figure 3, there is shown a diagrammatic representation of a compressor for use in the mattress assemblies of Figures 1 and 2. The compressor, generally indicated as 202, comprises a compressor housing 204. A motor 206 is disposed within the housing and has a drive coupling 208 connected to a compressor unit 210. The motor 206 may be any suitable motor for driving the compressor unit. For example, the electric motor may be a simple electromagnet connected to a moveable diaphragm within the compressor unit. Suitable compressor units and compatible motors are known in the art.

The compressor housing 204 comprises a first inlet 212 for receiving air returned from the inflatable cells of the mattress. A second inlet 214 is provided in the housing 204 to allow air to enter the housing. The air within the housing 204 is drawn into the compressor unit 210 through an inlet 216. As can be seen in Figure 3, the inlets 212 and 214 are arranged in the housing 204 to allow the air to pass over and around the motor 206 before entering the compressor unit 210.

The compressor unit 210 has an outlet 218 connected to an outlet 220 in the housing 204, through which compressed air is provided to the outlet conduit and to the cells of the mattress.

Turning to Figures 4 and 4a, there is shown a first embodiment of a baffle assembly for use in the assemblies of Figures 1 and 2. The baffle assembly 302 is shown in position in an outlet conduit 304. Figure 4 shows a cross-sectional view through the baffle assembly 302 and the outlet conduit 304, while Figure 4a shows a longitudinal-sectional view through the baffle assembly and the outlet conduit.

In the embodiment of Figures 4 and 4a, the baffle comprises a single tube 306 disposed within the tubular outlet conduit 304. The tube 306 has a single bore 308. The tube 306 has an outer diameter substantially the same as the inner diameter of the outlet conduit 304, such that the tube 306 is retained within the outlet conduit by friction. In operation, gas flows through the bore 308, as indicated by the arrow in Figure 4a, and acts to reduce vibrations being transmitted through the flowing gas.

Turning to Figures 5 and 5a, there is shown a further embodiment of a baffle assembly for use in the assemblies of Figures 1 and 2. The baffle assembly 402 is shown in position in an outlet conduit 404. Figure 5 shows a cross-sectional view through the baffle assembly 402 and the outlet conduit 404, while Figure 5a shows a longitudinal-sectional view through the baffle assembly and the outlet conduit.

In the embodiment of Figures 5 and 5a, the baffle comprises a baffle member 406 disposed within the tubular outlet conduit 404. The baffle member 406 has a cross-section in the form of a cross, defining four passages 408 with the inner surface of the outlet conduit 404, as shown in Figure 5. The baffle member 406 has a diameter substantially the same as the inner diameter of the outlet conduit 404, such that the baffle member 406 is retained within the outlet conduit by friction. In operation, gas flows through the passages 408, as indicated by the arrows in Figure 5a, and acts to reduce vibrations being transmitted through the flowing gas.

Turning to Figures 6 and 6a, there is shown a further embodiment of a baffle assembly for use in the assemblies of Figures 1 and 2. The baffle assembly 502 is shown in position in an outlet conduit 504. Figure 6 shows a cross-sectional view through the baffle assembly 502 and the outlet conduit 504, while Figure 6a shows a longitudinal-sectional view through the baffle assembly and the outlet conduit.

In the embodiment of Figures 6 and 6a, the baffle comprises a baffle member 506 disposed within the tubular outlet conduit 504. The baffle member 506 has a plurality of bores 508 extending longitudinally therethrough. The baffle member 506 has an outer diameter substantially the same as the inner diameter of the outlet conduit 504, such that the baffle member 506 is retained within the outlet conduit by friction. In operation, gas flows through the bores 508, as indicated by the arrows in Figure 6a, and acts to reduce vibrations being transmitted through the flowing gas.

Finally, turning to Figures 7 and 7a, there is shown a further embodiment of a baffle assembly for use in the assemblies of Figures 1 and 2.

The baffle assembly 702 is shown in position in an outlet conduit 704. Figure 7 shows a cross-sectional view through the baffle assembly 702 and the outlet conduit 704, while Figure 7a shows a longitudinal-sectional view through the baffle assembly and the outlet conduit.

In the embodiment of Figures 7 and 7a, the baffle comprises a baffle member 706 disposed within the tubular outlet conduit 504. The baffle member 706 is in the form of a honeycomb structure having a plurality of elongate passages 708 extending longitudinally therethrough. The baffle member 706 has an outer diameter substantially the same as the inner diameter of the outlet conduit 704, such that the baffle member 706 is retained within the outlet conduit by friction. In operation, gas flows through the passages 708, as indicated by the arrows in Figure 7a, and acts to reduce vibrations being transmitted through the flowing gas.

EXAMPLE

A study was conducted to determine the rejection rate of a dynamic mattress assembly according to the present invention.

12 subjects were provided with a dynamic mattress assembly of the general configuration shown in Figure 2 and described above. Each mattress assembly was fitted with a baffle in the outlet conduit in the region of the outlet of the compressor. The baffle was in the form of a tube disposed within the outlet conduit and having a bore therethrough with a diameter smaller than the bore of the outlet conduit.

Each subject was requested to test the dynamic mattress assembly.

The test was conducted for a period of 8 weeks, at the end of which the 20 subjects were informed the test had ended.

All 12 subjects continued to use the dynamic mattress for the entire test period of 8 weeks. None of the 12 subjects rejected the dynamic mattress.

Claims

CLAIMS1. A dynamic mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a first pressure; a compressor comprising: a first inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the inflatable cells for providing compressed gas from the compressor to the cells; and a return conduit extending from the inflatable cells to the first inlet of the compressor for returning gas from the cells to the compressor.
2. The mattress assembly according to claim 1, wherein the mattress comprises a second layer comprising a second plurality of cells inflatable with gas to a second pressure.
3. The mattress assembly according to claim 2, wherein the second layer underlies the first layer with the mattress assembly in use.
4. The mattress assembly according to any preceding claim, wherein the mattress further comprises a base.
5. The mattress assembly according to any preceding claim, wherein the compressor comprises a second inlet for receiving gas.
6. The mattress assembly according to any preceding claim, wherein the return conduit is arranged to return compressed gas from all the cells of the mattress to the first inlet of the compressor.
7. The mattress assembly according to any preceding claim, further comprising a heater, in use the heater receiving compressed gas from the outlet of the compressor and providing heated gas for supplying to the cells of the mattress.
8. The mattress assembly according to any preceding claim, further comprising one or more baffles in the outlet conduit and/or one or more baffles in the return conduit.
9. A method of operating an active mattress assembly, the active mattress assembly comprising; a first layer comprising a first plurality of cells inflatable with gas to a pressure; and a compressor; the method comprising; operating the compressor to produce a compressed gas at an outlet of the compressor; supplying the compressed gas to the cells to inflate the cells; and returning gas from the cells to a first inlet of the compressor.
10. The method according to claim 9, wherein the compressor further comprises a second inlet, the method further comprising supplying gas to the compressor through the second inlet.
11. The method according to either of claims 9 or 10, wherein the compressed gas supplied to the cells is heated.
12. A mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a pressure; a compressor comprising: a first inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the cells for providing compressed gas from the compressor to the cells; and one or more baffles disposed within a conduit between the plurality of cells and the compressor.
13. The mattress assembly according to claim 12, wherein one or more baffles are disposed in the outlet conduit.
14. The mattress assembly according to claim 13, wherein one or more baffles are disposed in the outlet conduit in the region of the outlet of the compressor.
15. The mattress assembly according to any of claims 12 to 14, further comprising a return conduit for returning compressed gas leaving the cells to the first inlet of the compressor.
16. The mattress assembly according to claim 15, wherein one or more baffles are disposed in the return conduit.
17. A mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a pressure; a compressor comprising: a first inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the cells for providing compressed gas from the compressor to the cells; an exhaust conduit for receiving compressed gas leaving the cells; and one or more baffles disposed within the exhaust conduit.
18. The mattress assembly according to any of claims 12 to 17, wherein one or more baffles comprises a passage therethrough for the passage of gas, the passage having a diameter smaller than the diameter of the conduit in which the baffle is disposed.
19. The mattress assembly according to claim 18, wherein one or more baffles comprises a baffle member having a plurality of passages therethrough and/or defining a plurality of passages between the baffle member and the inner surface of the conduit.
20. The mattress assembly according to claim 18, wherein the baffle consists of a tube disposed within the conduit.
21. The mattress assembly according to claim 18, wherein the baffle comprises a plurality of tubes.
22. The mattress assembly according to any of claims 18 to 21, wherein the or each passage extends substantially parallel to the longitudinal axis of the conduit.
23. A dynamic mattress assembly comprising: a mattress having a first layer comprising a first plurality of cells inflatable with gas to a first pressure; a compressor comprising: an inlet for receiving a gas to be compressed; and an outlet for the compressed gas; an outlet conduit that extends from the outlet of the compressor to the inflatable cells for providing compressed gas from the compressor to the cells; and a heater for heating the gas leaving the compressor before the gas enters the inflatable cells.
24. A method of operating an active mattress assembly, the active mattress assembly comprising; a first layer comprising a first plurality of cells inflatable with gas to a first pressure; and a compressor; the method comprising; operating the compressor to produce a compressed gas at an outlet of the compressor; heating the compressed gas; and supplying the compressed gas to the cells to inflate the cells.