INVENTION DESCRIPTION

1. FIELD OF APPLICATION The invention relates to an ergonomic back support, placed between the chair- back and the back when seated, keeping the spine in its natural position. In the International Patent Classification it is classified as A - Human necessities; A 47 - Furniture; A 47 C - Chairs, sofas and beds; or as A 61 F 5/00 - Orthopaedic methods or devices for non-surgical treatment of bones or joints. It can also be classified as A 47 C 7/46 - Parts, details, or accessories of chairs or stools with special, e.g. adjustable, profile.

2. TECHNICAL PROBLEM The human spine is naturally S curved. In its upper part it is bent backward, and in its lower, sacral, part it is bent forward. In the sitting position, without proper support to the lower back, the natural curvature of the spine is disturbed. The spine tends to further bend, which results in increase of the pressure of the vertebrae to the cartilaginous discs and damages to the discs. Such damages in the lumbar spine pressure the nerves, this producing intensive pains. We know from our daily life how hard sitting may be. This is particularly experienced by persons who do their work seated, such as drivers, office workers, students, etc. The above mentioned problems can be prevented or decreased by building of a back support, designed to be adjustable by each person to fit their personal constitution and posture.

3. STATE OF THE ART Today, there are various solutions to this problem. There are special chairs designed to be used by persons doing particular professions, such as typists, whose chair-backs are protruded in the lumbar region in order to protect the spine from damages. Car seat producers, too, adjust seat shape to the drivers' correct posture. When sitting in armchairs, people use various portable back supports and pillows of various shapes, filled with various materials, as well as various other supports that may help in easing lower-back pain caused by incorrect seating.

4. DISCLOSURE OF THE INVENTION The essence of the invention is the back support consisting of the carrying plate and, vertically fitted, one or more parallel elastic bands. Below the elastic bands, perpendicularly to them, there is a mobile roller with a stopper. The roller enables positioning of the band curve by height. The roller may be of various diameters, this adjusting the depth of the curve. The elastic bands enable adjusting of the ergonomic back support to the user's needs or to the form of his spine which the back support will keep in its natural shape, preventing thus its damaging and decreasing the lower-back pains. The ergonomic back support can also be used without the roller.

5. ILLUSTRATION DESCRIPTIONS Figure 1. shows the basic construction of the ergonomic back support - front view. Figure 2. shows the support shown in Figure 1 viewed from above. Figure 3. shows the support shown in Figure 1 viewed from below. Figure 4. shows the support shown in Figure 1 viewed from aside. Figure 5. shows connecting of elastic bands to the carrying plate - detail A in Figure 4. Figure 6. shows the roller shown in Figure 1, covered with a soft, spongy, material over the elastic bands - front view. Figure 7. shows the support shown in Figure 6. - viewed from above. Figure 8. shows the support shown in Figure 6. - viewed from below. Figure 9. shows the support shown in Figure 6. - viewed from aside. Figure 10. shows the support with cover reaching half the width - front view. Figure 11. shows the support shown in Figure 10. - viewed from above. Figure 12. shows the support shown in Figure 10. - viewed from aside. Figure 13. shows the ergonomic back support with cover - front view. Figure 14. shows the support shown in Figure 13. - viewed from above. Figure 15. shows the support shown in Figure 13. - viewed from below. Figure 16. shows the support shown in Figure 13. - viewed from aside.

6. DETAILED DESCRIPTION OF INVENTION EMBODIMENT The basic structure of the ergonomic back support, as shown in Figures 1. to 13., consists of the carrying plate 1 , to which there are fitted with bolts 5 one or more elastic bands 4. Below the elastic bands there is inserted the movable roller 6, that enables adjusting of the back support by height and depth. The roller is fixed at both sides into the wanted position under the elastic bands by the pegs 7. The elastic-band and carrying-plate ends are covered at their top and bottom ends with soft sponge 9. The above described support structure is inserted into the cover 10 and 12, and closed by the zippers 13 at sides. Here follows a detailed description of the ergonomic back support according to this invention. The carrying plate 1 , as shown in Figures I1 2., 3. and 4., is made of a hard material, normally plastics. The carrying-plate edges 2 are bent inward, towards the person's back. Edges are bent at both vertical lateral sides and at the bottom side, which enables the carrying plate to mildly bend under pressure. At one of the bent lateral sides there is the semicircular opening 3 to embed the roller 6. At the carrying plate top and bottom sides, there are openings for fixing the elastic bands. The elastic bands 4, as shown in Figures 1., 2., 3. and 4., are made of an elastic material, normally spring steel or a synthetic material such as polycarbonate. The bands are connected by their upper and lower ends to the front side of the carrying plate 1 , parallel to the bent lateral edges 2. The bands are fixed to the plate with bolts 5, with their heads at the back side of the carrying plate, and bolts 5b, with elastic washers 5a, at the bands. The holes in the carrying plate, through which pass the bolts, have diameter somewhat larger than the bolts 5, to enable adjustment of the band tension. At the elastic plate there can be one or more elastic bands. The elastic bands may be of the same or different widths, variously distributed at the carrying plate and at various distances between the bands, as well as at various distances between the band edges and the bent vertical lateral sides of the carrying plate. The roller 6, Figure 1., is made of a hard material, normally plastics, as a hollow, partly hollow or solid roller. The roller is inserted between the elastic bands 4 and the carrying plate 1 , perpendicularly to the elastic bands. The band lifts the elastic bands, creating thus a, larger or lesser, hump towards the back. The roller may be of various diameters, the experience proving the best ones being between 25 and 32 mm. Rollers of lesser diameters are harder and those of larger diameters softer. The roller enables adjustment of the back support by height. Moving of the roller up and down the carrying plate cause the hump to change its position, so that, thanks to the elastic bands, the back support is adjusted to the user's needs, that is, the form of their spine that the back support will keep in natural position. At both sides of the roller there can be placed pegs 7, made of a hard spongy material, functioning as stops when the roller is to be fixed in a given position. Moving of the roller below the elastic bands, or insertion of thinner or thicker rollers, adjusts the ergonomic back support by height and depth. This way, it is adjusted to the needs of various users who, due to long and often irregular sitting suffer spine pains, which may result in permanent spine damages. If the movable roller 6 is taken out of the ergonomic back support, tension of the elastic bands can be used for a mild massage of the back. Over the top and the bottom edges of the carrying plate 1 and the elastic bands 4, there is pulled the protective cover 9, Figures 9. to 12., normally made of rubbered canvas that covers the bolts 5 and the nuts 5b, thus preventing damaging of the outer cover 10 and 11 , in which there is placed the basic structure of the support, and of the seat on which the support is used. The elastic bands 4 are, for the purpose of comfort, covered by their entire area, with the soft spongy material 9, Figures 6. to 9. Thus furnished, the ergonomic support isO inserted into the outer cover, Figures 11. to 15., consisting of the front part 10 and the back part 12, mutually connected at the upper and the lower ends. The outer side of the cover, that is in touch with the seat, is additionally strengthened with rubbered canvas 11 and 12. The vertical lateral openings in the outer cover, between the front and the back parts 10 and 12, are connected with the zipper 13, closed downward. Through the lateral openings, the roller 6 is manually moved up and down, whereby the hump curve of the elastic bands is adjusted to the user's needs. The front part of the outer cover is recommended to be made of plush. The outer cover colours may vary to fit the colour of the seat at which the portable ergonomic back support is to be used. The support may be added an elastic band embracing the back of the seat, holding thus the support in position. The front surface of the cover can be used for displaying various promotional messages. Using the above described structure, the back support can be produced as portable or built in the back of the seat.

7. INVENTION APPLICATION The ergonomic back support, by this invention, makes a very useful device, serving the human health, that can be produced in an economic way, portable or to be built in the back of the seat, of various embodiments and purposes. It contains significant improvements relative to the previously known devices of this kind. Experts will find evident possibilities of modifications of the ergonomic back support by this invention, still maintaining the invention essence.