AIR MATTRESS AND METHOD FOR ADJUSTING IT

Abstract: The invention relates to an air mattress (1) comprising a number of successive, elongate and bag-like elements, which can be filled with gas such as air or with some other flowing medium. The elements are ar­ ranged transversally with respect to the lengthwise axis (D - D) of the mattress and/or the bed, and are connected to each other successively in a band-like fashion. The successive elements (2, 2′) are arranged so that the lenghtwise seam joints (6; 6b) of the ele­ mentes are located at given intervals in the bottom part (1b) of the mattress, and that the areas between these seam joints are arranged to form structures which are directed upwards from the bottom part (1b) of the mattress. The invention also relates to a method for adjusting an air mattress or the like. The elements (2, 2′; 9, 10) of the mattress are partly filled with for instance air, so that the mattress pressure cor­ responds to the pressure of the surroundings when the mattress elements are not subjected to a weight load, but the mattress pressure grows in a known fashion according to the weight load of the human body or part thereof, so that the mattress elements conform to the contours of the body or part thereof, and simultaneously the surface pressure against the body or part thereof is distributed evenly over the whole body or part there­ of.

Description: The invention relates to a mattress, particularly an air mattress or the like, comprising a plurality of elongate inflatable compartments arranged in side by side relationship and separated at least partly by parallelly extending seam joints, said compartments being partly connected to an underlay. Such a mattress is known from the nearest prior art document GB-A-1,498,661. The compartments of that prior mattress extend in the longitudinal direction thereof and communicate with one another. If a person is laid down on such a mattress, that person sinks down onto the bottom of the mattress, which is flattened out beneath that person or patient, whereas those parts of the mattress which remain outside the patient are bulged. A serious problem in modern nursing is to create a bed environment which causes as little trouble and inconvenience to the patient as possible, and where various tasks connected with the patient's care can be carried out, such as cleaning and washing. Particularly patients who are confined to bed for a long time or permanently, and cannot turn or move their limbs themselves, inevitably get bedsores when lying on ordinary beds and mattresses. The bedsores make the regular care of the patient even more difficult, and serve, among others, as entry routes for various infections. Bedsores are created in places where the surface pressure against the skin is continuously higher than 350-500 N/cm² (35-50 cm H₂O). These patients must therefore be turned, or their position changed, every two or three hours by nurses. However, the moving or turning of for instance multihandicapped patients may in practice be impossible. The object of the invention is the provision of a mattress that distributes the surface pressure directed against the patient's body or part thereof evenly over the whole body. This object is met, according to the present invention and as defined in independent Claim 1, by a mattress of the type as described above, in which said compartments are fully separated by the seam joints, extending in the transverse direction of the mattress, at least every second seam joint is connected to said underlay, the distance between two consecutive seam joints which are connected to said underlay being smaller than the combined width of two adjacent compartments, an elongate resilient element is disposed in every pocket thus defined by said underlay and said compartments. According to a preferred embodiment of this mattress every seam joint is connected to said underlay. The mattress according to the invention has a number of important features. The fully separated compartments extending in the transverse direction, in combination with the resilient elements enable the adjustment or adaptation of the inside pressure in the compartments depending on the local load exerted on the mattress. This local load is different for different parts of the human body. Under the load of a human body the rooflike or domed structure of the compartments undergoes a deformation such that adjoining compartments are pressed sideways into contact with one another. The surface pressure exerted on the human body lying on the mattress can be optimised and evenly distributed over different "slices" of that body. In GB-A-2,141,333 a mattress is described, comprising elongate inflatable compartments which extend in the transverse direction of the mattress. These compartments are divided into five groups, each of these groups being connected to an air supply device. The compartments belonging to each separate group are interconnected and are arranged inside a special bed frame structure. This mattress and bed structure form an inseparable entity which is particularly designed for hospital environments. The structure is complex, therefore expensive and not suitable as a regular mattress for use at home. The invention also relates to a method as defined in Claim 7 for adjusting the fluid pressure in a mattress of the type described above, said method comprising the steps of (a) partially filling the compartments of the mattress with fluid so that the fluid pressure corresponds to the pressure of the surroundings when the mattress compartments are free of a weight load; (b) laying a human body or part thereof on said compartments of the mattress in a resting position; (c) adjusting the fluid pressure of the compartments to within the range of about 150-200 N/cm² (15-20 cm H₂O) (d) maintaining the fluid pressure of the compartments within a predetermined range. Embodiments of the mattress according to the invention and the method for adjusting the fluid pressure therein are defined in dependent claims 2 to 6, and 8 and 9 respectively, and are explained in detail with reference to the drawings, wherein: Fig. 1 is a top-view illustration of the basic structure of the mattress of the present invention in flat condition; Fig. 2 is a cross-sectional illustration of a first embodiment of a mattress according to the present invention; Fig. 3 is a cross-sectional illustration of a second embodiment of a mattress according to the invention; Fig. 4 is a cross-sectional illustration of a third embodiment; Fig. 5 is a schematical illustration of a mattress according to the invention with the compartments thereof being divided into groups, and wherein the adjusting device and the gas supply source thereof are also shown; Fig. 6 is a top-view illustration of a section of a mattress according to the invention; and Fig. 7 is an illustration of a valve to be used in connection with the mattress according to the invention. The mattress 1 of Figure 1 comprises a number of adjacent, elongate and bag-like compartments or elements 2, 2', which can be inflated with air or with some other gas. The elements 2, 2' are arranged transversally with respect to the longitudinal axis D-D of the mattress and/or the bed or some other supporting structure. The elements 2, 2' are interconnected successively in a band-like fashion. Thus the mattress can advantageously be manufactured as a uniform band of two overlapping material webs 3, 4, which are connected together in a ladder-like fashion at the seam joints 5, 6. The intervals of the transversal seam joints 6, including one or several seams, form the elements 2, 2' of the mattress. The band thus obtained is cut into basic sections of suitable lengths, which are for instance 4 - 6 meters each. The length of the basic section depends, except for the length of the bed, also on how many elements are desired to be included in the bed. The successive elements 2, 2' are arranged so that the seam joints 6; 6b of the elements are located at given intervals in the bottom part 1b of the mattress, and that the areas between these seam joints are arranged to form domed structures which are directed upwards from the bottom part 1b of the mattress. In fact the structure between the seam joints 6; 6b of the elements are bent upward loop-like in cross-section as shown in Figures 2 and 3 of the first and second embodiments. The successive elements 2, for example in the basic section mentioned above, are in Figure 2 folded against each other in pairs so that every second longitudinal seam joint 6a is located in the top part 1a of the mattress, and every second seam joint 6b is located in the bottom part 1b of the mattress 1. Alternatively the successive elements 2' are in Figure 3 bent to an upside-down U-form so that the longitudinal seam joints 6 of the elements are always located in the bottom part 1b of the mattress. In that case the elements 2' rise like loops up from the bottom. In the first embodiment of the invention, the basic section of the mattress 1 received from production is folded in the lengthwise direction to form a bed-long mattress with an accordion-like structure (figure 2), which is then placed for instance in a bed frame. At the seam joints 6b the elements 2 are connected to the underlay 7, or they are mechanically attached to each other at the sides only. The basic section of the mattress produced in the manufacturing process can also be compiled to form the mattress proper, so that in the lengthwise direction D - D of the mattress, the elements 2' form loop-like parts protruding upwards from the underlay 7, i.e. successive elements are bent to an upside-down U-form, as was described above (figure 3). Now the seam joints 6, which are advantageously relatively broad, are attached adjacently to the underlay 7 so that the elements 2 rise loop-like from the underlay 7. Beneath the elements 2, 2' of the mattress, there is advantageously arranged some additional padding in order to prevent bottom contact. This padding can be for instance a uniform padding carpet. It can also be realized so that beneath the successive elements 2, 2', and in between the seam joints 6b; 6 located in the bottom part 1b of the mattress 1, there is placed one or several elongate paddings 8 (figure 3), which can be successively interconnected in order to facilitate their production. They can be bag-like elements 9 (figure 2), which are also inflatable with air or with some other gas. On the other hand, these elongate elements can as such be made of some solid but resilient material or filled with the same. The air mattress of the invention can also be realized so that underneath the first successive elements 2 there is arranged a second set of corresponding successive elements 10, which first and second elements are advantageously connected to each other as is apparent from figure 4. This kind of air mattress can be manufactured according to the same principle as the one illustrated in figure 1. In the manufacturing process, there is needed only a third material web to be placed on top of the first two, which third web is connected to the rest at the seam joints 5, 6 in a ladder-like fashion. The elements 2 of the mattress 1 are advantageously divided at least into three different groups A, B and C in the direction D - D of the lengthwise axis of the mattress, as is illustrated in figure 5. The elements of the air mattress are divided into groups for instance so that one of the said groups, for example A, is located under the head of the person lying on the bed, the second, for example B, is located under the middle part of the body, and the third group, for example C, is located under the legs. The elements 2a, 2b, 2c of each group are connected to each other and/or to a connecting duct 12a, 12b, 12c by means of inlet conduits 11a, 11b, 11c such as flexible tubes, and further, via controllable valves 14a, 14b, 14c and a suitable adjusting device 15, whereto the said valves are connected, to the gas supply 16 or the like, such as an air pump, which also is advantageously under the control of the adjusting device 15. By means of the auxiliary conduits 17a, 17b, 17c, the gas pressures prevailing in the various groups are registered in the pressure sensors 13a, 13b, 13c, which are connected to the adjusting unit 15. The pressure sensors 13a, 13b, 13c can also be installed in the connecting ducts 12a, 12b, 12c. The gas pressure of the elements 2a, 2b, 2c of each group A, B, C can thus be measured, adjusted to be suitable and maintained on the desired level particularly when the mattress 1 is being used. In principle either set of elements 2, 2'; 9, 10, which are air-inflatable and located either in the top or bottom part of the air mattress, can be divided into the said groups. In that case the air pressure in either set of elements is set to be constant, whereas the air pressure in the other set is adjustable. Moreover, the gas pressure in the separate elements can be adjusted to be suitable and maintained on this level when the mattress is in use. In the border areas between the groups A, B and C, the elements of separate groups, such as 2b and 2c in figure 6, can be alternately placed in different groups, for instance into both of the said groups B and C. Thus the groups are interlaced near the boundary surface R to be partly overlapping, so that for instance every second element 2c belongs to the group C under the legs, and every second element 2b belongs to the group B under the body. This procedure is advantageously followed only as regards one or two elements placed in the vicinity of the illusory boundary surface R. The advantage of this arrangement is that the person lying on the bed does not feel any clear division of the elements into different groups. The elements 2a, 2b, 2c of the mattress 1 are connected, via the inlet conduits 11a, 11b, 11c, in groups A, B, C to the connecting ducts 12a, 12b, 12c and to each other, and further to the gas supply 16 such as an air pump or tank or the like, as is illustrated in figure 5. The conduits 11 or 12 can be provided with cut-off valves 18, as is apparent from figure 6. Each valve functions so that it closes the conduit, such as the inlet conduit 11, when the gas flow surpasses the predetermined limit. An advantages of this arrangement is that when the body weight is suddenly shifted, for instance when sitting up in the bed, on top of only a couple of the elements 2 of the mattress, these are not completely flattened out but maintain their supporting effect because the valves 18 prevent the elements from being suddenly exhausted. It is not absolutely necessary to provide the said cut-off valves 18 in connection with all elements 2 of the mattress. They can be installed for instance in the elements located in the middle area B of the mattress, or in connection with at least one or two such elements that are likely to be placed under the buttocks of the person lying on the bed. The group B can also be divided into two sub-groups of elements, in between which the cut-off valve 18 is installed. The said cut-off valve 18 is advantageously of the type illustrated in figure 7, but some other type of suitable valve can also be employed. The cut-off valve 18 comprises a housing 19, a chamber 20, which is located inside the housing 19, and a bobber 21 placed in the chamber 20. The cross-sectional surface of the bobber 21 is smaller than the corresponding dimension of the chamber. A gas inlet channel 22 is connected to the first end of the chamber, and a gas outlet channel 24 is connected to the second end of the chamber. The bobber 21 is placed in the chamber in between the said inlet and outlet channels 22, 23. The bobber 21 remains at least roughly in place in the chamber 20 when the gas flow is smaller than a predetermined flow rate but when the gas flow surpasses the predetermined flow rate the bobber is shifted, along with the flow, and closes the outlet channel 23. The cut-off valve 18 advantageously allows the gas to flow in the opposite direction, from the outlet channel into the inlet channel, irrespective of the flow rate. If necessary, the valve can be adjusted, for instance by changing the weight of the bobber or said surface areas, or by means of suitable spring arrangements. The heights of the elements 2, 2' of the mattress 1 according to the invention, i.e. the thickness of the mattress, is advantageously within the range 10 - 20 cm,which corresponds to a normal mattress thickness. The width of the mattress 1, and accordingly the width of the elements 2, 2', is chosen according to the specific needs and the measures of the bed. The bed in itself can be any type of normal bed or for instance a hospital bed, whereto an ordinary spring mattress can be placed. The material of which the mattresses are made is plastic or some other flexible and inextensible material which is impermeable to gas or to air. The method according to the invention for adjusting the fluid pressure in the air mattress is based on the idea that underneath the human body or part thereof, there is arranged a supporting gas or air cushion, the pressure p of which is minimized, and the contact surface A with the body or part thereof is maximized. In order to make the air support the weight m of the body, the pressure p should apparently be p = m/A . Let us suppose that the surface area of the human body, from the neck down to the gluteal skinfold, is A = 50 x 70 cm = 3 500 cm² , and the weight m of the upper part of the body = 50 kg, then the pressure p required in the mattress for supporting the body is about 150 N/cm² , i.e. 15 cm H₂O ≈ 15 mbar. If a person is laid down on a normal, conventional air mattress, the pressure of which is the sum of the air pressure and said load supporting pressure, the person sinks down onto the bottom of the mattress, i.e. the mattress is flattened out beneath the patient, and the parts of the mattress which remain outside the person are bulged. The patient is not lifted on top of the bedding before the mattress pressure is considerably higher than the one calculated above. In the air mattress according to the invention, its standard-volume elements reach the calculated pressure, whereafter they are pressed together and shaped so that the contact surface between the human body or parts thereof and the mattress is as large as possible. Each element 2, 2' of the mattress 1, or each group A, B, C of the mattress is, when using the method according to the invention, only partly filled with gas, advantageously with air, in such a way that the air pressure in each element corresponds to the pressure of the surroundings, i.e. p ≈ 1 bar when the weight load directed thereon is nonexistent. In that case each element is partly compressed. When the human body or part thereof is laid to rest on top of the mattress elements, the pressure p' in each elements grows, according to the weight load of the body or part thereof, in a known fashion p' = p + m/A, where p is the earlier pressure, m is the mass of the body or part thereof, and A is the contact surface between the body and the mattress element. Thus the supporting, resilient surface of each element conforms to all protruding parts and recesses of the body or part thereof, and simultaneously distributes the surface pressure against the body etc. evenly over the whole body or part thereof. The gas pressure in the mattress elements 2, 2' is most suitably set within the range of about 150 - 250 N/cm² (15 - 25 cm H₂O) when the mattress is being used, i.e. somebody is lying on it. The gas pressure in an element is dependent, among other things, on the location of said element with respect to the body: under the back and the buttocks, the pressure is naturally higher than under the head and the legs. If the air mattress is formed of the compartments 2, 2' and the resilient elements 9; 10, which are placed on top of each other in the mattress (figures 2, 3 and 4), and which elements are both inflatable with gas or air, the gas pressure can be brought in either set of the compartments or elements, for instance in the first set 2, 2', to a suitable constant value. The gas pressure of the second set of elements 9; 10 is adjusted according to the above described method. Alternatively the pressures of the elements 2, 2' and 9; 10 can be set in the opposite fashion. The method of the invention is advantageously provided with a method for controlling critical low and high pressures in cases where the mattress is used as a high-class nursing mattress in a hospital or other such institution. Then the mattress is formed to be relatively thick, for instance 15 - 20 cm, and it allows the use of particularly low gas pressures. The control system is operated so that when the pressure falls below the critical limit either in the mattress 1, in the elements 2, 2' thereof of in one of the groups A, B or C, more gas or air is let or inflated into it. The gas supply is cut off at the critical top limit, for instace when the gas pressure in the elements of group B has reached the critical limit 150 - 250 N/cm² (15 - 25 cm H₂O.) The mattress is also advantageously provided with zero-pressure control: when the gas pressure falls for instance below 100 N/cm² (10 cm H₂O,) the air supply is stopped, because it is probable that the mattress is not in normal use. Otherwise the mattress would bulge to excessive pressure when the patient leaves the bed. In the above described situations the patient "floats" deep in the mattress. For various tasks required in the care of the patient, such as washing, bed-making and cleaning, the mattress can be over-filled and the patient thus be lifted up on top. In the above description the invention has been described particularly as an air mattress, but the invention can obviously be applied to other corresponding supports, such as seat cushions, which are provided with padding. In the above specification it was also mentioned that the elements of the mattress or the like can be inflated with air or with some other gas. Instead of air or gas, the use of some other flowing medium, such as water, can be applied.

Claims: Mattress, particularly an air mattress or the like, comprising a plurality of elongate inflatable compartments (2, 2') arranged in side by side relationship and separated at least partly by parallelly extending seam joints (6, 6a, 6b), said compartments being partly connected to an underlay (7), characterized in that said compartments (2, 2') are fully separated by the seam joints (6, 6a, 6b), extending in the transverse direction of the mattress (1) at least every second seam joint (6b) is connected to said underlay (7), the distance between two consecutive seam joints (6b) which are connected to said underlay (7) being smaller than the combined width of the two adjacent compartments (2, 2'), an elongate resilient element (8, 9, 10) is disposed in every pocket thus defined by said underlay (7) and said compartments (2, 2'). Mattress as claimed in claim 1, characterized in that every seam joint (6, 6a, 6b) is connected to said underlay (7). Mattress as claimed in claim 1 or 2, characterized in that the compartments (2, 2') of the mattress in the longitudinal direction (D-D) thereof are divided into at least three groups (A, B, C), the compartments (2a, 2b, 2c) of each group being mutually connected by means of inlet ducts (11a, 11b, 11c) and a connecting duct (12a, 12b, 12c) said connecting ducts (12a, 12b, 12c) being connected to a fluid supply source (16) by means of pressure sensors (13a, 13b, 13c), control valves (14a, 14b, 14c) and a pressure control device (15) such that the fluid pressure in the compartments of each group (A, B, C) can be measured and adjusted to a desired level as well as maintained at such level when the mattress is being used. Mattress according to claim 3, characterized in that in the boundary area between separate groups (A, B, C), the compartments of two adjacent groups are alternately placed in said groups. Mattress according to any of the preceding claims 1-4, characterized in that at least one of the compartments (2, 2') of the mattress (1) is connected to at least one of the adjacent compartments or to the connectingduct by means of a conduit (11, 12) and a cut-off valve (18), so that the cut-off valve (18) closes the conduit when the fluid-flow surpasses a predetermined critical value. Mattress according to claim 5, characterized in that the cut-off valve (18) comprises a housing (19), a chamber (20) located inside said housing, and a bobber (21) with a smaller cross-sectional area than the corresponding dimension of the chamber (20), and that a fluid inlet channel (22) is connected to a first end of the chamber, and a fluid outlet channel (23) is connected to the second end of said chamber, said bobber (21) being located in said chamber (20) between said inlet and outlet channels (22, 23), so that with a fluid flow smaller than a predetermined flow rate the bobber (21) stays at least roughly in place in the chamber (20), but with a fluid flow larger than the predetermined rate the bobber (21) shifts along with the flow and closes the fluid outlet channel (23), and that said valve (18) allows the fluid to flow in the opposite direction from the outlet channel (23) to the inlet channel (22) irrespective of the flow rate. A method for adjusting the fluid pressure in a mattress according to one or more of the claims 1-6, characterized by the following steps: (a) partially filling the compartments (2, 2') of the mattress (1) with fluid so that the fluid pressure corresponds to the pressure of the surroundings when the mattress compartments are free of a weight load; (b) laying a human body or part thereof on said compartments of the mattress in a resting position; (c) adjusting the fluid pressure of the compartments to within the range of about 15-20 cm H₂O; (d) maintaining the fluid pressure of the compartments within a predetermined range. The method of claim 7, characterized in that the fluid pressure of the resilient elements (9, 10) is set at a standard value, and that the fluid pressure of the compartments (2, 2') (9, 10) is set within the range of roughly 150 - 200 N/cm² (15-20 cm H₂O), when the mattress is in use. The method of claim 7 or 8, characterized in that the fluid pressure in the compartments (2, 2') is continuously maintained at the set values when the mattress is in use, whereas the fluid supply into the compartments is cut off when the pressure drops below a minimum level for instance 100 N/cm²(10 cm H₂O.)

Inventors: TOIVIO, ILKKA, TOIVIO, TERTTU
Applicants: AHLSTROM CONSUMER PRODUCTS LTD.
Application year: 1988
Main classification: A47C27
IPC codes: A47C31, A47C27, A61G7