A STOOL SEAT

Abstract: A stool seat, particularly for a working stool, including a support means and a flexible sitting surface means attaches thereto. The suppport means comprises a frame (11) having a front frame part (12) bent to approximately inverted U-shape, and a back frame part (13) being straight or slightly curved. The sitting surface means comprises a netting (20), preferably of the type "plaiting", which is attached only to the front frame part (12) and to the back frame part (13). The individual threads of the netting have a main direction essentially parallel to these frame parts.

Description: A STOOL SEAT The present invention concerns a stool seat, particularly for a working stool, including a support means and a flexibl sitting surface means attached thereto. In standing position the spine of the body has an ideal S-shape. The intradiscal pressure is evenly distributed and low. The muscle activity in the extensor muscles of the spine is moderate. When on sits down the pelvis rotates backwards and the concave shape of the lumbar part of the spine is replaced by a straight or convex shape. The vertical line for the centre of gravity of the trunk and the arms is dislocated forwardly, which results in that the static load on the extensor muscles of the spine increases. This in turn makes the disc pressure increase. Since the natural S-shape is lost the pressure in the spinal discs further becomes un¬ evenly distributed, which increases the risk for back pains. If one, instead of sitting at a 45-50 cm sitting height (with a 90° angle in the hip-joints and the knee-joints) , one sits at a 65-80 cm sitting height (with a 120° angle in the hip-joints and knee-joints) , the backward rotation of the pelvis is prevented. Merely a high sitting position, however, is not sufficient for achieving an unloaded position of the back. In order to achieve the ideal position of the back, also the seat must be shaped such that one relaxedly can let the pelvis balance on the sitting 'tubers (ischiatic tubers; tubera ischiadica) or rotate somewhat forwards. The vertical line from the centre of gravity of the upper body then ends up above the sitting tubers while the pelvis is in the same po- sition as when standing up. The upper body balances on the OMPI tubers, and muscle activity and disc pressure become low. When sitting in the high sitting position the weight of the body is supported by the foremost parts of the sitting tubers, by the soft parts between them and in front of them and by a smaller part of the under-side of the thighs, Because of the greater angle in the hip-joint the area taking up the body weight becomes considerably less than when sitting at normal height. In order to enable a good sitting position with the spinal column in the ideal S-shape, the surface of the seat and the resilient properties thereof must be de¬ signed so that it is possible to sit with upright (not backwardly rotated) pelvis under sufficient comfort. The object of the invention is to provide a stool seat which is particularly suited for sitting at a great sitt¬ ing height and which satisfies the above demands. A considerable development work has been spent in solving the problems involved herein and has resulted in the stool seat according to the present invention, the special characteristics of which appear from the subsequent claims. By providing a sitting surface, that offers differentiated properties of resilience, the upright position of the pelvis is stimulated. A netting, preferably of metal and e.g. of the kind "plaiting", is mounted in a frame such * that the threads of the netting run from side to side. The front portion of the netting is bent to form an in¬ verted U-shaped surface, while the back part is maintained substantially plane. The netting is attached to the frame at its front and back part only. The consequence thereof is that the substantially flat back part of the netting is soft; the individual threads of the netting are tempo¬ rarily deflexed upon loading. OMPI The front part of the netting, forming a vault, is harder since the individual threads cannot be deflexed to the same extent because of the inverted U-shape, though the entire portion of the netting may very well deflex somewhat as the side portions are not attached to the side pieces of the frame. The result is that the portion underneath the sitting tubers deflex when one takes place on the seat. The portion in front of the sitting tubers is harder, while the portion behind them is softer. This has two effects: On one hand the front, somewhat harder portion prevents the backward rotation of the pelvis, since the front parts of the sitting tubers upon backward rotation meet a re- sistance in the flexible surface, on the other hand one can sit leaning forward with upright or forwardly leaning pelvis without sliding forward on the seat. Since the thighs* when sitting at a high sitting level have a steeper angle relative to the horizontal plane than at a low level, the seat has been given, as is known per se, a saddle-like triangular shape. In order to distribute the load of the body weight over. as great a surface as possible the front part of the seat is shaped like a ridge. An embodiment of the invention will be closer described in the following under reference to the accompanying draw- ing, wherein fig. 1 shows a perspective view of a saddle-shaped stool seat according to the invention fig. 2 similarly shows the same seat with only two threads entirely drawn, and O PI fig. 3 schematically shows the stool seat from the side together with portions of a sitting human skeleton. The embodiment of the stool seat according to the in- vention shown in the drawing includes a closed frame 11 of e.g. round steel. Seen from above the frame has substantially trapezoidal shape, the two parallel sides forming the front part 12 and the back part 13 of the frame and the two non-parallel sides forming the side parts 14 a d-j5 of the frame. The front part 12 of the frame is bent into substantially inverted U-shape, in the example shown trapezoidal shape with a central, horizontal middle portion 16 and two down- wardly inclined side portions 17 and 18. The front part 12 can also be shaped as an inverted V or a circular arc. The side portions 17 and 18 extend diverging backward to the back part 13 of the frame which is straight or slight¬ ly curved. As a sitting surface the seat according to the invention has a netting 20 of metal or other resilient material. The netting 20 preferably is of the kind denominated "plaiting",i.e. , a net the individual threads of which in approximately continuous Z-shape extend in a fixed main direction and are loosely linked to adjacent threads. Such a net has an elasticity at bending about an axis perpendicul¬ ar to the main direction of the threads and located in the plane of the net that is defined by the threads constitut¬ ing the net, whereas it - due to the loose linkage of adjacent threads to each other - at bending about an axis perpendicular to the axis mentioned, i.e. an axis running in the main direction of the threads, has practically no elasticity, but at such bending in principle is to be compared with a chain. According to the invention the individual threads of the netting 20 extend between the side parts 14, 15 of the frame and have a ma.tn direction parallel to the front part 12 of the frame. Two individual threads 21 and 22 are shown in fig. 2. According to the invention the netting 20 is further attach ed to the frame 11 only in the front part 12 and back part 13 thereof, whereas it is completely freely movable relativ to the side, parts 14 and 15, preferably under those parts (fig. 1) . The attachment of the net can be practised in any suitable manner, such as for instance by tying with thread around the respective frame part, or by welding. Depending on the desired conditions of elasticity in the netting 20 this may - at least in the portion intended for attachment to the front part 12 of the frame - be pre-bent into the trapezoidal or vault shape shown, or, flat. In the latter case the bending is achieved during the attach- ment of the netting to the frame. In order to more or less stretch the netting 20 between the front part 12 of the frame and the back part 13 thereof the back part may be slightly curved in the horizontal plane In order to give also the back part of the netting some vault shape the back part 13 of the frame may be slightly curved in the vertical plane. As appears particularly from fig. 2 the netting has closest * x to the front frame part 12 a pronounced vault shape (thread 21) , which successively declines (thread 22) towards the back frame part 13. The vault shape of the net in the front part of the seat provides greater resistance to deflexion than the more flat shape further backwards (fig. 3) , i.e. successively harder resilience in the direction of arrow A and successively softer resilience in the direction of arrow B. CMPI The advantages of the stool seat according to the inven¬ tion are: A stool seat comprising a preferably pre-bent netting 5 attached to a frame, the front part of the netting form¬ ing a vault and,therefore, resisting a higher load before it deflects, and the back part of the netting being rela¬ tively flat and, herefore, resisting less load before it deflects, allows sitting on it with upright, balanced pel- 3_0 vis, which in turn contributes to a position of the spine as favourable as when standing up. The differentiated properties of resilience completely counteract forward sliding, since the front surfaces of τ_5 the seat have a harder characteristic of resilience than its back surfaces. This is a pre-requisite for the favour¬ able sitting position just mentioned. Further, these properties allow sitting on seats having different degree of forward inclination as well as comfortable sitting when 20 one leans forward. When sitting at a high level the seat must in certain situations be somewhat inclined forward to give room for the thighs which then point steeply down to¬ wards the floor. The fact that the front portion of the seat according to the invention has a harder resilience 25 then effectively prevents forward sliding on the seat. In certain cases it is a great advantage if a stool seat can be tilted forward in relation to the extent of forward lean¬ ing of the sitting person. On conventional seats forward sliding is prevented only by the friction of the surface 3Q material against the clothes; one slips off a surface having ■ a low coefficient of friction, whereas, on a surface having a high coefficient of friction, the clothes stand still relative to the surface of the seat, while the body slides relative to the clothes, the clothes then pulling uncom- 35 fortably.Contrarily hereto, the differentiated resilience in the seat according to the invention enables that one can remain seated on the inclined seat. When sitting on a high sitting level the body weight can be taken up by a considerably smaller area than when sittin on a normal level. The vault shape of the netting in combi¬ nation with the properties of resilience of the seat accord ing to the invention advantageously distributes the pressur over the limited area available. This results in great sitting comfort. The vault shape of the net in combination with the resilien properties also results in a high degree of generality, i.e the deflexion of the netting is varied and automatically adapted to the body shape, size and weight of different persons. The resilient surface also allows those small variations in sitting position that are necessary at all sitting. The fact that the seat comprises a netting results in good ventilation between the seat surface and the body clothing. Discomfort in the form of heat and moisture accumulation, which is a frequent problem when tight seat surfaces are concerned, is entirely eliminated. When sitting in cold environment when the seat surface is cooled, extremely little heat is conducted from the body to the seat surface due to the point-wise contact with the body surface. In those cases where the netting is made of metal a stool seat is obtained which is insusceptible to glowing particles is greatly resistent to mechanical wear, sharp objects, corroding acids etc. Dirt in the form of particles or in liquid form, e.g. oils and the like, is neither absorbed nor accumulated on the seat surface. The resistance of the seat to glowing particles, mechanic¬ al wear, oils etc. makes it suitable as a sitting surface '- in hard environments within different industrial sectors. The small tendency of the netting to accumulate dirt and pollution, and the easiness to clean it by e.g. flushing with water makes the stool seat according to the inven- tion suitable also in such environments as, e.g. , food production industry, catering etc. Other fields of app¬ lication can be such where the hygienic requirements are high, e.g., within the nursing sector, dentists etc. As mentioned above the front part 12 of the frame can have another shape than that shown, e.g..inverted V-shape or circular arc shape, which both alternative shapes can be considered having a substantially horizontal portion, be it very small, and two side portions extending there- from. The essential feature of the invention is that the netting is attached only to the front part and the back part of the frame - in the front part to the horizontal portion as well as to the two side portions thereof - whereas the sides of the netting are completely free. Thus, the frame may comprise merely a front frame part forming a vault, and a substantially horizontal back part which two parts may be otherwise interconnected than shown, e.g. by means of a bar underneath the netting, the sides of the netting thereby being completely uninfluenced by the frame structure. OMPI

Claims: CLAIMS - " 1. A stool seat, particularly for a working stool, in¬ cluding a flexible sitting surface means (20) and a support means (11) carrying said surface means, said support means including a front part (12) having substantially inverted U-shape with a substantially horizontal portion (16) and downwardly directed side portions (17,18) extending there¬ from, and a back portion (13) having at least a substantial¬ ly horizontal portion, c h a r a c t e r i z e d in that the sitting surface means comprises a netting (20) of metal or other elastic material, said netting being attached to the substantially horizontal portion (16) as well as to the side portions (17,18) of the front part (12) of the support means, whereas the netting is attached only to the substan¬ tially horizontal portion of the back part (13) of the support means, so that the netting exhibits a vault shape decreasing from the front part towards the back part of the support means. 2. A stool seat according to claim 1, c h a r a c t e r ¬ i z e d in that it has approximately saddle shape, and, when seen from above, a substantially trapezoidal shape having the substantially horizontal portions of the front (12) and back (13) parts substantially parallel. 3. A stool seat according to claim l or 2, c h a r a c ¬ t e r i z e d in that the netting (20) exhibits relative¬ ly great resistance to bending about an axis perpendicular ' Λ to the substantially horizontal portion (16) of the front part of the support means and located in the plane of the net ing, and insignificant resistance to bending about an axis perpendicular to the axis mentioned and likewise being located in the plane of the netting. 4. A stool seat according to claim 3, c h a r a c t e r ¬ i z e d in that the threads of the netting extend in OMPI approximately Z-shape in a main direction being parallel to the substantially horizontal portion (16) of the front part (12) of the support means, and that adjacent threads are loosely linked to each other. 5. A stool seat according to claim 1, c h a r a c t e r ¬ z e d in that the support means is a closed frame (11) having two side parts (14,15) connecting the front part (12) with the back part (13) . 6. A stool seat according to claim 5, c h a r a c t e r ¬ i z e d in that the loose side portions of the netting extend underneath the side parts (14,15) of the frame. OMPI

Inventors: PALMGREN BENGT, PALMGREN, BENGT
Applicants: ERGONOMI DESIGN GRUPPEN AB
Application year: 1982
Main classification: A47C7
IPC codes: A47C7