SEAT CUSHION

Abstract: The invention relates to a seat cushion comprising a number of elongate bag-like elements that can be filled with gas. According to the invention, the bag-like elements are arranged into element groups (12, 13, 14), so that the first element group (12) includes three elements, the first and second (12b, 12c) of which are arranged lengthwise at the sides (S) of the seat cushion, and the third (12a) is arranged transversally in the rear (T) of the seat cushion; the second element group (13) includes at least one element (13a, 13b), provided in the middle area of the seat cushion; and the third element group (14) includes at least one element (14), arranged transversally at the front (E) of the seat cushion, and the gas pressure of the elements in said element groups is adjustable from outside the seat cushion, so that the first element group supports, on an area as large as possible, the patient's buttocks from the sides and the region below the lumbar spine from the back, the second element group supports the tailbone region and essentially the back of the thighs, and the third element group is used for adjusting the seating angle of the patient.

Description: Seat cushion The invention relates to a seat cushion according to the introductory part of patent claim 1. The seat cushion is particularly designed as a wheelchair cushion for persons who are unable to walk. The seat cushion prevents the creation of pressure sores in the buttock area, helps the person sit in a straight posture in the wheelchair and prevents him from being inclined either sideways or forward. In the prior art there is known a seat cushion comprising a number of bag-like elements filled with gas. These elements are essentially quadratic in cross- section, and their height is larger than their width. Consequently they are upwardly oriented stud-like bags arranged on the seat area, for instance 8 x 8 numbers in all. A drawback with the described known seat cushion is that all elements are interconnected. The same air pressure prevails in all elements irrespective of the spot where the patient sits on the seat cushion. Air tends to flow from the bag-like elements from underneath the patient towards the elements located at the sides, where the weight pressure is weaker. Thus it is difficult for the patient to achieve a good balance on this type of seat cushion. Another drawback with said seat cushion is that if one of the bag-like elements is broken, the whole seat cushion immediately becomes unfit for use. In the prior art there is also known a seat cushion including both bag-like elements filled with liquid or gel, and shaped and padded support elements. A drawback with said known seat cushions is that they must generally be custom-shaped according to the measures of the patient, wherefore they are expensive. Another drawback is that the shaped and padded parts still can direct a high surface pressure towards certain body parts which rest against them, so that the conditions for developing pressure sores exist. The liquid element cannot smooth out the pressure directed to the critical tissue spots in order to prevent the development of pressure sores. The object of the present invention is to achieve a new seat cushion whereby the described drawbacks can for essential parts be eliminated. The invention is characterized by the features enlisted in the characterizing part of the patent claim 1. The seat cushion according to the invention comprises a number of elongate, bag-like elements which can be filled with gas. According to the invention, the bag-like elements are arranged into element groups, so that - the first element group includes three elements, the first and second of which are arranged lengthwise at the sides of the seat cushion, and the third is arranged transversally in the rear part of the seat cushion; - the second element group includes at least one element which is arranged in the middle area of the seat cushion; and - the third element group includes at least one element which is arranged transversally in the front part of the seat cushion, the gas pressure of the elements provided in the element groups being adjustable from outside the seat cushion, so that the first element group supports, on an area as large as possible, the buttocks of the patient at the sides and the region below the lumbar spine at the back, the second element group supports the tailbone region and essentially the back part of the thighs, and the third element group is used for adjusting the seating angle of the patient. An advantage of the seat cushion of the invention is that by using it, the buttocks and thighs of the patient can be shaped and supported, so that the patient sits straight and in a good position on the seat cushion, particularly in a wheelchair. Another advantage is that the gas pressure in the bag-like elements of the seat cushion is always adjustable to be individually suitable, in which case the pressure directed to the skin can be minimized in the whole seat region. Yet another advantage is that the location of the bony prominences of the patient, i.e. the tailbone and the ischial bones, is arranged on the seat cushion in an area where there is created a distinctive low-pressure zone as for the skin surface pressure. The reason for this is that the spots of the bony prominences constitute a critical area as for pressure sores. In the system according to the invention, particularly the tailbone and the ischial bones are located on the area in between the elements, and further, by adjusting the pressure in the first and second element groups, i.e. by adjusting the gas filling volumes, the seating comfort can be individually adjusted. Yet another advantage of the invention is that by means of the third element group provided at the front part of the seat cushion, the patient can be supported at his thighs, particularly at the front part thereof, and the patient's seating angle can be adjusted to be suitable. An advantage of the invention is the structure of its elements. The elements, which are realized as having the shape of an upturned letter U in cross- section, conform to the sideways movements of the sitting patient's body. This nώiimizes the shearing forces (tissue-stretching forces) directed to the skin, which affect the creation of bedsores. Yet another advantage of the invention is its dual element structure. In cross- section, the upper elements have the shape of an upturned letter U, so that inside them, there is created a lengthwise tunnel where the lower elements are fitted in. Most advantageously the gas filling volume of the lower element is optimized according to the use. The upper elements conform completely to the buttocks and thighs of the patient. This maximizes the contact surface between the seat and the patient. By means of the lower elements, there is realized a fine adjustment of the interphase pressure (pressure between the seat and the patient) and ensured that the interphase pressure is evenly distributed throughout the whole contact surface. Yet another advantage of the invention is that the elements of the seat cushion are most advantageously removable and replaceable elements. Thus the maintenance and care of the seat cushion takes place simply and quickly by replacing damaged elements. It is yet another advantage of the invention that the elements of the seat cushion are most advantageously prefilled in the factory, whereafter the patient can, when putting the seat cushion to use, by means of a hand pump and a pressure meter adjust the relative pressures of each element or element group to be individually suitable, as well as observe and readjust the gas filling volumes whenever necessary. The invention is described in more detail below with reference to the appended drawings, wherein figure 1 is a top-view illustration of a seat cushion according to the invention; figure 2 shows the seat cushion of figure 1 in cross-section A-A; figure 3 shows the seat cushion of figure 1 in cross-section A-A when a person is sitting on the cushion; figure 4 shows the seat cushion of figure 1 in cross-section B-B; figure 5 shows the seat cushion of figure 1 in cross-section B-B when a person is sitting on the cushion; figure 6 is a top-view illustration of another seat cushion according to the invention; figure 7 shows the seat cushion of figure 6 in cross-section F-F; figure 8 shows the seat cushion of figure 6 in cross-section G-G; and figure 9 is a top-view illustration of a third seat cushion according to the invention; figure 10 shows the seat cushion of figure 9 in cross-section H-H; figure 11 shows the seat cushion of figure 9 in cross-section I-I; figure 12 is a top-view illustration of a fourth seat cushion according to the invention; figure 13 is a schematic illustration of the fastening arrangement of one element, seen in cross-section; figure 14 is a top-view illustration of the fastening arrangement of figure 13; figure 15 is a cross-sectional illustration of the structure of the underlay structure; and figure 16 illustrates the equipment needed for filling the elements. The seat cushion of figure 1 includes a number of elongate bag-like elements which are made of a flexible material and can be filled with gas. The bag-like elements are arranged in element groups 1, 2, 3, so that the first element group 1 comprises the interconnected elements la, lb and lc, which are located lengthwise at the sides S of the seat cushion and transversally in a U- shape in the rear part T of the seat cushion; the second element group 2 comprises two likewise interconnected elements 2a, 2b arranged in the middle area of the seat cushion; and the third element group 3 comprises one element 3a, which is arranged transversally in the front part E of the seat cushion. The element groups and their elements are arranged symmetrically with respect to an illusory vertical central plane of the seat cushion, said central plane passing from the center of the seat cushion to the rear along the line C-C illustrated in figure 1. The elements la, lb, lc; 2a, 2b; 3a of the element groups are advantageously interconnected by means of joining seams 10, so that they together form a uniform padding of the size of a seating surface, for instance for a wheelchair, i.e. a seat cushion. Each element group 1, 2, 3 is connected, by means of an individual gas conduit 4, 5, 6, such as a thin hose, to outside the seat cushion. The gas conduits 4, 5, 6 are provided with valves 7, 8, 9, and further advantageously with coupling means at the free ends of the conduits for connecting the conduits to an air pump or a similar air or gas source (not illustrated in the drawings). In this embodiment, the elements la, lb, lc of the first element group 1 form a uniform element group arranged in a U-shape when seen from the top. Said elements are directly connected to each other and in fact constitute one uniform element. The gas pressure in said element group 1 can be adjusted to be suitable by means of air or gas to be fed in via the gas conduit 4. When the desired gas filling volume and pressure is achieved, the valve 7 is closed. In this embodiment, the elements of the second element group include two parallel elements 2a, 2b. Said elements are arranged in between the elements lb, lc of the first element group 1 arranged lengthwise along the sides S of the seat cushion and parallel to said elements lb, lc. These elements 2a, 2b are interconnected by means of a connecting conduit 11, so that the elements form a uniform gas-filled element group. The elements 2a, 2b of this element group 2 are connected, by means of a gas conduit 5, to a suitable gas source such as an air pump. From the gas source, the elements are filled to a suitable gas pressure, whereafter the valve 8 provided in the conduit 5 can be closed. The elements la, lb of the first element group are relatively wide and spacious elements, and particularly the width 1 of the element la arranged transversally in the rear of the seat cushion is advantageously of the order 10- 15 cm. All elements la, lb, lc of the first element group 1 may have the same width, but the width may also differ to some extent. Further, the elements la, lb, lc of the first element group 1 are designed so that their pressurized height hi is such that they rise higher than the height h of the elements 2a, 2b of the second element group 2 in pressurized state (cf. figure 2). It will be appreciated that pressurizing here means a slight excess pressure of the filling gas (in relation to air pressure) or most advantageously a pressure corresponding to the surroundings, so that the gas spaces of the elements are partially filled with gas, but they are not inflated to their maximum dimensions and/or that the element shells are not remarkably stretched. When a person H sits on this pressurized seat cushion, the elements la, lb, lc of the first element group 1 form around the buttocks and the thighs an essentially U-shaped circular support open on one side, as is illustrated in figure 3. Now the top surface of the elements 2a, 2b of the second element group 2 remains on a lower level than the top surface of the elements la, lb, lc of the first element group 1, but they still support the tailbone region and the inner surface of the thighs, so that the buttock region of person H does not get a bottom contact with the top surface of the seat P proper. Thus the patient is supported in straight posture in his position on the seat, particularly in a wheelchair or the like, where specially the side supports and arm rests provided at the sides of the chair support the patient and the seat cushion and help maintain a good position and posture. The element 3 a of the third element group 3 is designed so that the height h 3 of said element in pressurized state is such that its height, depending on the pressure, can most advantageously be fitted in between the heights hi, h 2 of the second element group 2 particularly when using the seat. Again the pressurized element 3a means an element where the pressure of the filling gas is of the order of the pressure of the surroundings, so that the gas space is not inflated to maximum and its shell is not tightly stretched. Consequently, by means of the element 3 a of the third element group 3, the height h 3 (arrow D) of the front edge of the seat cushion can be adjusted, and thereby the seating angle (arrow E) of person H sitting on the seat P, as is illustrated in figure 5. It will be appreciated that the first and second element groups 1, 2 are matched so that the first element group 1 supports, on an area as large as possible, the buttocks region and the region below the lumbar spine at the side and at the back, and the second element group 2 supports the tailbone region and essentially the inner and rear part of the thighs. This is illustrated in figures 3 and 5. It is also pointed out that the first and second element groups 1, 2 are fitted most advantageously so that the tailbone region of the patient essentially falls on the area of the seam joints 10a of the element groups (for example figure 1). The transversal element la of the rear part in element group 1 prevents the patient, among other things, from sliding backwardly in the wheelchair and from pushing out of the aperture in between the back rest and the seat. Another seat cushion according to the invention is illustrated in figures 6, 7 and 8. Also here the seat cushion comprises elongate bag-like elements which are arranged into a first 12, second 13 and third element group 14. The first element group 12 includes three separate elements 12a, 12b, 12c interconnected by conduits 15; 15a, 15b. The first element 12a is arranged transversally in the rear part T of the seat cushion, and the second and third element 12b, 12c are arranged lengthwise at the sides S of the seat cushion. Also in this embodiment, the second element group 13 comprises two elements 13a, 13b, which are fitted, parallel to the elements 12a, 12b of the first element group 12 arranged at the sides S of the seat cushion, in the middle area of the seat cushion. Likewise, the third element group 14 comprises only one element 14a, and it is arranged transversally in the front part E of the seat cushion. The elements 12a, 12b, 12c; 13a, 13b; 14a are formed as arched structures directed upwardly from an underlay 16 and have the shape of an upturned letter U, as is seen in the cross-sections F-F, G-G of figures 7 and 8. In this embodiment, the seat cushion is provided with a plate¬ like flexible underlay 16, whereto the elements of the element groups 12, 13 and 14 are attached either permanently or suitably removably, in which case the elements of the element groups 12, 13 and 14 are replaceable. The first element group 12 and respectively the second and third element group 13, 14 are connectable, via conduits 17, 18, 19, such as thin hoses, and valves 20, 21, 22 to a suitable gas source, such as an air pump or a gas tank in order to adjust the gas filling volume and gas pressure of the element groups in similar fashion as was explained in the description of the embodiment of figure 1. An advantage of the arched U-shaped structure of the elements 12a, 12b, 12c; 13a, 13b; 14a of the element groups 12, 13, 14 is that their flexibility is easily adjustable by means of the gas filling volume and hence the gas pressure, and that they are easily attached to the underlay 16 either permanently or replaceably. Another advantage of the elements 12a, 12b, 12c; 13a, 13b; 14a is their flexibility and movability in the transversal sideways direction. They thus prevent the creation of shearing forces towards the skin surface and the development of bed sores. The elements 12a, 12b, 12c; 13a, 13b; 14a of the element groups 12, 13, 14 are advantageously removably attached by suitable fastening means to the underlay 16, in which case a damaged single element/element group can be easily replaced. The heights hi, h 2 , h 3 (h 3 ') of the elements 12a, 12b, 12c; 13a, 13b; 14a of the element groups 12, 13, 14 are advantageously arranged in similar fashion as above, in the embodiment of figures 1-5. The elements 12a, 12b, 12c; 13a, 13b; 14a of the element groups 12, 13, 14 can be partly or completely replaced by dual elements. In the middle of the elements 12a, 12b, 12c; 13a, 13b; 14a, in the lengthwise direction thereof, there is formed an elongate tunnel-like cavity, over which the element itself arches in the shape of an upturned letter U, particularly when gas is supplied in the seat cushion when it is being inflated. In the cavity of each element 12a, 12b, 12c; 13a, 13b; 14a, or at least in part of the cavities, there can be provided an additional element 12d, 12e, 12f; 13c, 13d; 14b, which can be filled with for instance gas, in similar fashion as the element proper. As an alternative, the additional element 12d, 12e, 12f; 13c, 13d; 14b is made of some flexible material, such as suitable foam plastic or foam rubber. The proper element 12a, 12b, 12c; 13a, 13b; 14a, having the shape of an upturned letter U in cross-section, is henceforth called the top element, and the additional element 12d, 12e, 12f; 13c, 13d; 14b is called the bottom element. Among the advantages of the dual element structure, let us point out that the gas filling to suitable pressure of the top elements 12a, 12b, 12c; 13a, 13b; 14a, in connection whereof the bottom elements 12d, 12e, 12f; 13 c, 13 d; 14b are fitted, takes place more rapidly than without the bottom elements. Moreover, either of the elements of the dual structure, either the top or bottom element, can be a closed element with a standard pressure, so that only the other is adjustable as for gas filling volume and pressure. Yet another advantage is that the bottom elements also serve as effective preventives of bottom contact, for instance when crossing over thresholds and other bumpy areas in a wheelchair. A third seat cushion according to the invention is illustrated in figures 9, 10 and 11. Also here the seat cushion comprises elongate bag-like elements arranged in a first 23, second 24 and third 25 element group. The first element group 23 includes three separate elements 23a, 23b and 23c. The first element 23 a is arranged transversally in the rear part T of the seat cushion, and the second and third element 23b, 23 c are arranged lengthwise at the sides S of the seat cushion. Likewise, in this embodiment the second element group 24 includes two elements 24a, 24b, which are located in the middle area of the seat cushion, in parallel to the elements 23 a, 23b of the first element group 23 arranged at the sides S of the seat cushion. Also in this embodiment, the third element group 25 includes only one element 25a, and it is arranged transversally in the front part E of the seat cushion. The elements 23a, 23b, 23c; 24a, 24b; 25a of the element groups 23, 24, 25 are formed as arched structures directed upwardly from bottom to top and have the shape of an upturned letter U in cross-section, as is seen in the cross-sections H-H, I-I of figures 10 and 11. The seat cushion is provided with a plate-like flexible underlay 26, whereto the elements of the element groups 23, 24, 25 are attached, either permanently or most advantageously removably, in which case the elements of the element groups are replaceable. The elements 23a, 23b, 23c of the first element group 23 are all independent, separate elements, each comprising a conduit 27a, 27b, 27c, such as a thin hose, to outside the seat cushion. The elements 24a, 24b of the second element group 24 are separate elements, but they are interconnected by means of a conduit 28. Further, the element 24b (or alternatively element 24a) of the second element group is provided with a conduit 27d, such as a thin hose, leading to outside the seat cushion. Respectively, the element 25a of the third element group 25 includes a conduit 27e, also leading to outside the seat cushion. Each conduit 27a, 27b, 27c, 27d, 27e leading out of the seat cushion is provided with a valve 29a, 29b, 29c, 29d, 29e, through which the elements are connected to a suitable gas source, such as an air pump or a gas tank, in order to adjust the gas filling volumes and hence gas pressure of the elements/element groups, in similar fashion as was explained above, in the description of the embodiments of figures 1 and 6, for example. The elements 23a, 23b, 23c; 24a, 24b; 25a are advantageously attached removably with suitable fastening means to the underlay 26, in which case a damaged single element or element group is easily replaced. The heights h 2 , h 3 (h 3 ') of the elements 23a, 23b, 23c; 24a, 24b; 25a of the element groups 23, 24, 25 are advantageously arranged in similar fashion as in the embodiments of figures 1-8 above. The elements 23a, 23b, 23c; 24a, 24b; 25a of the element groups 23, 24, 25 can be partly or completely replaced by dual elements. In this embodiment, only the elements of the second element group 24 are provided with a dual element structure. Inside the elements 24a, 24b of the second element group 24, in the lengthwise direction thereof, there is formed an elongate cavity. In this embodiment, in the cavity of each element 24a, 24b, which are henceforth called top elements, there is arranged an additional element, i.e. a bottom element 24c, 24d that can be filled with gas like the top element. Moreover, one of the elements of the dual structure, either the top or the bottom element, can be a closed element with standard pressure, so that only one of the two elements is adjustable in gas filling volume and pressure. As an alternative, the bottom element 24c, 24d is made of some flexible material, such as suitable foam plastic or rubber. The advantages of the dual element structure were explained above, for instance in the description of the embodiments of figures 6-8. An advantage of the third embodiment of the seat cushion according to the invention is that it includes five separately and flexibly adjustable seat cushion sections; thus the seat cushion can be effectively shaped by the user according to his personal needs. Owing to the separate border elements, i.e. the elements 23a, 23b, 23c of the first element group, the sitting position can be well adjusted. In principle the adjusting takes place in similar fashion as was explained above, in connection with figures 1-5, but this embodiment has a wider range of adjusting possibilities, because the elements 23a, 23b, 23c of the first element group 23 can be adjusted separately. The elements 24a, 24b of the second element group 24 are realized as dual structures, and consequently bottom contact is prevented even in a case where the other part of the element, either the top or bottom element, is damaged. The elements are advantageously removable, so that the seat cushion is easily maintained when one of the elements starts to leak. A fourth seat cushion according to the invention is illustrated in figure 12 as seen from the top. The seat cushion comprises three element groups 30, 31, 32. Again the first element group 30 includes elements 30a, 30b, 30c arranged lengthwise at the sides S of the seat cushion and transversally in the rear part T in U-shape, said elements being most advantageously independent, separate elements, as in the embodiment of figures 9-11. The second element group 31 includes three elements 3 la, 3 lb, 3 lc, which are arranged in the middle area of the seat cushion, in parallel to the sides S thereof. The gas spaces of the elements 3 la, 3 lb, 3 lc are interconnected by conduits 33a, 33b. In this case the third element group 32 includes two elements 32a, 32b, the gas spaces being interconnected by a conduit 34. The elements 32a, 32b of the third element group are arranged transversally in the front part E of the seat cushion. Each separate element 30a, 30b, 30c and each element group 31, 32 interconnected by conduits is provided with a respective conduit 35a, 35b, 35c; 35d, 35e, such as a thin hose, to outside the seat cushion. Each conduit 35a, 35b, 35c, 35d, 35e leading out of the seat cushion is provided with a valve 36a, 36b, 36c, 36d, 36e, through which the elements/element groups are connected to a suitable gas source, such as an air pump or a gas tank, in order to adjust the gas filling volumes and hence gas pressures of the elements/element groups, in principle in the same fashion as was already explained in the description of the embodiments of figures 1, 6 and 9, among others. The elements 30a, 30b, 30c; 31a, 31b; 32a of the element groups 30, 31, 32 are advantageously removably attached by suitable fastening means to an underlay 37, in which case a damaged single element or element group is easily replaced. The heights h,, h 2 , h 3 (h 3 ') of the elements 30a, 30b, 30c; 31a, 31b; 32a of the element groups 30, 31, 32 are advantageously arranged in similar fashion as above, in the embodiments of figures 1-11. The elements 30a, 30b, 30c; 31a, 31b; 32a of the element groups 30, 31, 32 can be partly or completely replaced by dual elements. Most advantageously only the elements 3 la, 3 lb, 3 lc of the second element group 31 are provided with dual element structure, in similar fashion as in the embodiments of figures 9-11. The conduits 4, 5, 6; 27a, 27b, 27c, 27d, 27e; 35a, 35b, 35c, 35d, 35e (figures 1-5, 9-11 and 12) of the elements or element groups of the seat cushion are most advantageously arranged to lead out of the seat cushion through its side S. Alternatively, the conduits 17, 18, 19 can be arranged to lead out of the seat cushion at its front E, particularly at the right edge of the front, as is illustrated in the embodiments of figures 6-8. Thus the free ends of the conduits can easily be brought out when it is necessary to adjust the gas filling volume and pressure of the elements (or element groups). Figures 13 and 14 illustrate an arrangement for fastening the elements 38 (12a, 12b, 12c, 13a, 13b, 14a; 23a, 23b, 23c, 24a, 24b, 25a; 30a, 30b, 30c, 3 la, 3 lb, 3 lc, 32a, 32b) of the second, third and fourth embodiment removably to the underlay 39 (16; 26; 37). On both long sides of the elongate, bag-like element 38, there are provided fastening straps 40; 40a, 40b, extending in this embodiment along the whole length of the element 38, but they can also be short fastening lugs or the like, spaced apart at short intervals at the sides of the element. In the underlay 39, there are provided grooves 41, 41, 41, wherein the fastening straps 40, 40a, 40b of the elements are fitted. Each element 38 is attached, by the fastening straps 40, to the grooves 41 of the underlay 39. The grooves 41; 41a, 41b are arranged in the underlay 39 at such distances that the element forms a tunnel-like structure having the shape of an upturned letter U in cross-section, said structure being directed upwardly from the underlay 39, when it is inflated to suitable pressure with gas. For fastening the elements 38 in place in the underlay 39, there are used special fastening means 42. The fastening means 42 include fastening bits 43 and fastening members 44. The element 38 is attached at the fastening straps 40 to the underlay 39, particularly to its grooves 41, so that in the grooves 41 and the fastening straps 40, and respectively in the fastening bits, there are arranged perforations 45 spaced apart, most advantageously at regular distances, said distances being most advantageously regular, and the fastening means 44 are fitted in the perforations in order to bind the different parts together. The fastening bits 43 are narrow, advantageously rectangular plates always provided with two holes 45 located at the same distance from each other as in the underlay 39 and in the fastening straps 40 of the elements 38. The fastening means 44 are pins, tapes or the like to be inserted in the perforations 45, and in the fastening process, they are arranged to proceed through the perforations 45 of the underlay 39, through the fastemng straps 40 and the fastening bits 43 and to bind these together. In the embodiments of figures 6-12, 13, the seat cushion comprises a plate¬ like flexible underlay 16; 26; 37; 39, including at least two overlapping and at least partly detachable underlay parts 26a, 26b; 39a, 39b, as is illustrated in figures 10 and 13. The underlay parts 26a, 26b; 39a, 39b are most advantageously connected in a hinge-like fashion at the side of the seat cushion, so that they can be turned apart along the side, as is illustrated by the dotted lines in figure 10. In between the underlay parts 26a, 26b; 39a, 39b there are provided grooves 46 or recesses for the conduits 47, such as hoses, of the elements or element groups, as is seen for instance in the cross- sectional illustration of figure 15. In this embodiment, in the first underlay part 39a, there is provided a perforation 48, and in the second part 39b a groove 46, which extends to the sides of the underlay 39 of the seat cushion. The conduit 47 passes at the junction 49 of the element 38 through the perforation 48 to the groove 46 and further to the side of the seat cushion. At least part of the elements 12a, 12b, 12c, 13a, 13b, 14a; 23a, 23b, 23c, 24a, 24b, 25a; 30a, 30b, 30c, 31a, 31b, 31c, 32a, 32b of the element groups 12, 13, 14; 23, 24, 25; 30, 31, 32 are formed as upwardly directed arch-like structures having the shape of an upturned letter U in cross-section. Particularly the elements 12a, 12b, 12c; 23a, 23b, 23c; 30a, 30b, 30c of the first element group have this kind of structure. The advantage is that the elements are effectively flexible both in the vertical and sideways direction, and thus reduce the shearing forces directed to the skin surface of the seated person. At least part of the elements 12a, 12b, 12c, 13a, 13b, 14a; 23a, 23b, 23c, 24a, 24b, 25a; 30a, 30b, 30c, 31a, 31b, 31c, 32a, 32b of the element groups 12, 13, 14; 23, 24, 25; 30, 31, 32 are provided with additional elements and thus formed to be dual elements. Particularly the elements 13a, 13b; 24a, 24b; 31a, 3 lb, 31c of the second element group 13; 24; 31 are such dual elements. This ensures the supportive capacity of the seat cushion's middle area, where the main part of the weight of the seated person rests. Moreover, the breaking of one element of a dual element structure does not yet lead to a catastrophe, because the other element still supports the patient. The additional element, such as 24c, 24d, belonging to the dual element, i.e. the bottom element, is most advantageously also a gas-filled element, like the element proper located above it and at its sides and being U-shaped in cross- section, i.e. the top element, such as element 24a, 24b (cf. figures 10 and 11). The top elements proper 24a, 24b of the dual element 24a, 24c; 24b, 24d are advantageously standard-pressure elements, whereas the bottom elements 24c, 24d are gas-filled elements with adjustable gas pressure. The top elements 24a, 24b are adjusted to optimum pressure and closed. The supportive capacity of the dual element is adjusted by adjusting the gas pressure of the bottom element 24c, 24d from outside the seat element. Most advantageously the supportive capacity is adjusted by the person seated on the cushion. In the conduits 4, 5, 6; 17, 18, 19; 27a-27e; 35a-35c; 47, such as hoses, of the elements or element groups of the seat cushion, there are fitted valves, advantageously back pressure valves 53. Thus gas can be fed to each element or element group interconnected by conduits, so that gas cannot be uncontrollably discharged back the way it came. Each conduit, such as hose, is similar in cross-section, or the conduits are at least provided with identical end pieces, so that they can be connected to a gas source with a similar joining piece. The employed gas is most advantageously air, and the gas source is a manually operated air pump, i.e. a hand pump 50, as is illustrated in figure 16. In connection with the hand pump 50, there is also provided a pressure meter 51, whereby the gas pressure in an element or element group is observed. In connection with coupling, the joining piece 52 eliminates the influence of the back pressure valve 53 in order to measure the pressure of an element or element group. The gas pressure of each element or element group is adjusted separately by connecting the hand pump 50 and the pressure meter 51 to said conduit 54, i.e. hose. When one element or element group is adjusted to suitable pressure, the hand pump 50 and the pressure meter 51 are connected to the conduit 54 or hose of the next element or element group, and this procedure is continued until all elements or element groups are adjusted. The element groups of the seat cushion are advantageously covered with cloth or the like. Thus the seat cushion includes for instance a cloth bag 55 (figure 11) in which the element groups and a possible underlay are arranged. The gas pressure of the element groups 1, 2, 3; 12, 13, 14; 23, 24, 25; 30, 31, 32 and/or of separate elements of the seat cushion according to the invention is advantageously adjusted to a low basic pressure in connection with manufacturing the seat cushion. When the seat cushion is put to use, it is first set on the seat P of a wheelchair or the like, whereafter the user sits on the seat cushion. Then the gas pressures of the elements in the separate element groups are adjusted by utilizing a gas source, such as a hand pump 50, and a pressure meter 51 as follows. The gas pressures of the first and second element group 1, 2; 12, 13; 23, 24 are adjusted with respect to each other, so that in the region of the buttocks and thighs of person H, the skin surface that rests against the elements is maximized (cf. figure 3). Thus the skin surface pressure is minimized. At the same time, the gas pressure in the elements of the second element group 2; 13; 24 is adjusted to be such that the tailbone and/or buttocks of the patient H do not get bottom contact with the seat P. By adjusting the gas pressure of the elements la, lb, lc; 12a, 12b, 12c; 23a, 23b, 23c of the first element group 1; 12; 23, there is set a U-shaped supportive frame at the sides and at the back, so that it forms a support around the lumbar spine, buttock region and thighs of person H. The gas pressure of the elements of the third element group 3; 14; 25 is adjusted so that the seating angle and posture of person H are arranged to be suitable (cf. figure 5). The above described measures can be repeated when necessary, so that the patient is always seated in a position as comfortable and appropriate as possible, particularly in a wheelchair or any other seat in use. In the above specification, the invention is described with reference to a few preferred embodiments only, but it is obvious that the invention can be modified in many ways within the scope of the inventional idea defined in the appended patent claims.

Claims: Claims 1. A seat cushion comprising a number of elongate, bag-like elements which can be filled with gas, characterized in that the bag-like elements are arranged in element groups (1, 2, 3; 12, 13, 14; 23, 24, 25; 30, 31, 32), so that - the first element group (1; 12; 23; 30) includes three elements, the first and second (lb, lc; 12b, 12c; 23b, 23c; 30b, 30c) of which is arranged lengthwise along the sides (S) of the seat cushion, and the third (la; 12a; 23a; 30a) is arranged transversally in the rear part (T) of the seat cushion; - the second element group (23; 13; 24; 31) includes at least one element (2a, 2b; 13a, 13b; 24a, 24b; 3 la, 3 lb, 3 lc) provided in the middle area of the seat cushion; and - the third element group (3; 14; 25; 32) includes at least one element (3a; 14a; 25a; 32a; 32b) arranged transversally at the front (E) of the seat cushion, and that the gas pressure of the elements of said element groups is adjustable from outside the seat cushion, so that the first element group supports, on an area as large as possible, the patient's buttocks from the sides and the region below the lumbar spine from the back, the second element group supports the tailbone region and essentially the back part of the thighs, and the third element group is used for adjusting the seating angle of the patient. 2. A seat cushion according to claim 1, characterized in that at least part of the elements (23a, 23b, 23c, 24a, 24b, 25a; 30a, 30b, 30c, 31a, 31b, 31c, 32a, 32b) of the element groups (23, 24, 25; 30, 31, 32), particularly the elements (23a, 23b, 23c; 30a, 30b, 30c) of the first element group are separate independent elements which are connected by conduits (27a, 27b, 27c, 27d, 27e; 35a, 35b, 35c, 35d, 35e) to outside the seat cushion, the gas pressure of said elements being separately adjustable from outside the seat cushion. 3. A seat cushion according to claim 1, characterized in that the elements (la, lb, lc, 2a, 2b, 3a; 12a, 12b, 12c, 13a, 13b, 14a) of each element group ( 1, 2, 3; 12, 13, 14) are connected to each other and further by conduits (4, 5, 6; 17, 18, 19) to outside the seat cushion, and that the gas pressure of said element groups is separately adjustable from outside the seat cushion. 4. A seat cushion according to any of the preceding claims, characterized in that at least part of the elements ( 12a, 12b, 12c, 13a, 13b, 14a; 23a, 23b, 23c, 24a, 24b. 25a; 30a, 30b. 30c, 31a, 31b, 31c, 32a, 32b) of the element groups ( 12, 13, 14; 23, 24, 25; 30. 31, 32) are formed as arch-like structures protruding upwardly from the base and having the shape of an upturned letter U in cross-section. 5. A seat cushion according to claim 4, characterized in that at least part of the elements (12a, 12b, 12c, 13a, 13b, 14a; 24a, 24b) of the element groups (12, 13, 14; 23, 24, 25) are provided with additional elements (12d, 12e, 12f; 13c, 13d, 14b; 24c, 24d) and are thus formed as dual element structures. 6. A seat cushion according to claim 5, characterized in that the additional elements (12d, 12e, 12f; 13c, 13d, 14b; 24c, 24d) are gas-filled elements. 7. A seat cushion according to claim 5 or 6, characterized in that the elements proper (24a, 24b) are standard-pressure elements, whereas the additional elements (24c, 24d) have an adjustable gas pressure. 8. A seat cushion according to any of the preceding claims, characterized in that the elements of the second element group (2; 13; 24) include two adjacent elements (2a, 2b; 13a, 13b; 24a, 24b). 9. A seat cushion according to any of the preceding claims, characterized in that the first and second element groups (1, 2) are matched so that the patient's tailbone region rests essentially on the area of the seam joints (10a) of the element groups. 10. A seat cushion according to any of the preceding claims, characterized in that the elements (la, lb, lc; 12a, 12b, 12c; 23a, 23b, 23c) of the first element group (1; 12; 23) are designed so that the height (hi) of the elements in pressurized state is larger than the height (h 2 ) of the elements (2a, 2b; 13a, 13b; 24a, 24b) of the second element group (2; 13; 24) in pressurized state. 11. A seat cushion according to claim 10. characterized in that the elements (3a; 14a, 25a) of the third element group (3; 14; 25) are designed so that the height (h 3 ) of the elements in pressurized state is adjustable, by means of the gas filling volume and thus the gas pressure, advantageously in the region between the heights (hi, h 2 ) of the first ( 1; 12; 23) and second (2; 13; 24) element group. 12. A seat cushion according to any of the preceding claims, characterized in that the seat cushion comprises a plate-like flexible underlay (16; 26; 37) to which the elements (12a, 12b, 12c, 13a, 13b, 14a; 23a, 23b, 23c, 24a, 24b, 25a; 30a, 30b, 30c, 31a, 31b, 31c, 32a, 32b) of the element groups (12, 13, 14; 23, 24, 25; 30, 31, 32) are attached. 13. A seat cushion according to claim 12, characterized in that the elements (38) are removably fastened to the underlay (39) by means of fastening members (42). 14. A seat cushion according to any of the preceding claims, characterized in that the seat cushion comprises a plate-like flexible underlay (26; 39) including two overlapping and at least partly detachable underlay elements (26a, 26b; 39a, 39b), and that in between said elements there are provided grooves (46) or recesses for the conduits (47) of the elements or element groups. 15. A seat cushion according to any of the preceding claims, characterized in that the conduits (47) of the elements or element groups of the seat cushion include a back pressure valve (53), and that the conduits (47) can most advantageously be provided with a pressure meter (51) and a hand pump (50) for pumping air into the elements in order to adjust the pressure therein.

Inventors: OLKKONEN KARI, SAARINEN HANNU, OLKKONEN, KARI, SAARINEN, HANNU
Applicants: CARITAL OY, OLKKONEN KARI, SAARINEN HANNU, OLKKONEN, KARI, SAARINEN, HANNU
Application year: 1996
Main classification: A47C27
IPC codes: A47C27