ERGONOMIC CHAIR

Abstract: Seating furniture including a substructure (4) having a pedestal arrangement (43, 44) which is arranged to rest securely on an underlying surface (5), a chair seat (2) which is supported by the substructure (4), and means (6; 422, 423, 424) for setting a desired distance between the pedestal arrangement (43, 44) and the seat (2). A driving means (7; 71-73, 75, 425, 9, 77, 78) is provided for the substantially continuous driving of the means (6; 422, 423, 424) for the purpose of slowly changing the distance (S) with a velocity of motion not exceeding 100 cm/minute.

Description: Ergonomic chair This invention is concerned with ergonomic seating furniture of the type described in the ingress to claim 1. The seating furniture of the invention is preferably in the form of a chair, especially a task chair such as an office chair, e.g. a desk chair. Seating furniture, e.g. office chairs, include a substructure having a pedestal arrangement which is usually arranged to rest securely on an underlying surface such as a floor and further include a seat which is supported by said substructure. In the context of task chairs/office chairs it is well-known to provide means for setting a desired distance between the pedestal arrangement/floor and the upper surface of the seat. It is well-known that workers who sit on a work chair during their working hours frequently suffer various kinds of health problems associated with sedentary work. Thus it is well-known that office workers who sit substantially still in an office chair whilst working often suffer pain in the back, arms and hands while carrying out conventional office work, study work, research work, computer work including use of a mouse etc. Stiffness and pain in various parts of the body are naturally more or less debilitating and also affect work capacity and staying power at work over longer periods. The purpose of the invention is to provide seating furniture which reduces the risk of negative effects of the type mentioned above. The purpose is achieved by seating furniture of the type described in the appended claim 1. Embodiments of the seating furniture according to the invention are described in the dependent claims. In a preferred embodiment of the invention, the seat of the seating furniture is automatically raised and lowered in a generally cyclical and substantially continuous fashion over a vertical range of approximately 7 cm at a vertical velocity of approximately 1 cm per minute. Inasmuch as the distance of the seat from the floor varies very slowly the movement will not interfere with the work being carried out by the operator using the seating furniture, while the pattern of motion of the seating furniture according to the invention gives rise to desirable mini-movements of the operator's body thereby counteracting stiffness, back pain, "mouse arm" and other problems suffered by office workers after sitting still for lengthy periods. The seating furniture according to the invention can also have a therapeutic effect on persons who are handicapped by back pain or other causes. For others, use of the seating furniture of the invention is restful and improves work capacity and staying power at work that is performed in the seating furniture, even during lengthy spells of work. The seating furniture of the invention produces the above-mentioned mini- movements of the body because the person using the seating furniture also has body parts in contact with vertically stationary surfaces. For example, the user has his or her feet in contact with the floor and/or his or her hands/arms resting on a desk or similar, so that the vertical displacements of the upper body also give rise to flexing movements of the arms and legs. In preferred embodiments of the invention the seat moves vertically with a velocity of approximately 1 cm/minute in a reciprocating motion over a vertical range of e.g. 5- 10 cm. Preferably the seat is propelled in one direction to one end point, after which it is driven in the other direction to its other end point, etc., in which case the motion can be described as cyclical. However, it should be evident that the motion is so slow that the user suffers no discomfort if the motion stops temporarily between the end points or if the direction of motion is reversed before the seat reaches one of its pre-set end points. Moreover, the motion may be temporarily interrupted at the end points. What is essential is that the seat is generally in vertical motion within the range defined by the end points, the velocity during operation being low. The seating furniture of the invention may have conventional means for adjusting the height of the seat above the floor, the tilt of the seat cushion in relation to the floor plane, the angle of the back in relation to the seat, the ability to tilt the seat and/or back in relation to the plane of the floor, etc. In conclusion it may be mentioned that it is well-known per se to impart a vibration to seating furniture for the purpose of relaxation, but such vibratory motion usually has an amplitude of no more than a centimetre or so and a frequency of several cycles per second; such vibratory motion is therefore of a quite different kind from the cyclical motion proposed according to the invention, and moreover said vibration does not produce the desirable patterns of movement obtained by means of the invention. The invention will hereafter be described in the form of examples with reference to the attached drawings. Fig. 1 shows schematically a chair according to the invention Fig. 2 shows an example of embodiment of the vertical displacement device of the chair according to the invention. Fig. 1 shows an office chair 1 standing on a floor 5. The chair 1 comprises a seat 2 and a back 3 which are supported by a substructure 4 which rests on the floor 5 via a base 43 with pedestals 44. The substructure 4 comprises a column 42 extending from the base 43 to a support plate 41 which in turn supports the seat 2 and the back 3. Adjustment means 21 may be provided to permit changing the tilt of the seat 2 in relation to the support plate 41. Conventional adjustment means 31 may be provided for setting the desired angular position of the back 3 in relation to the support plate 41. The column 42 further includes, in a manner conventional er se, an adjustment means 6 for setting the distance S between the floor 5 and the seat 2 (or rather the support plate 41). In an important feature of the invention, a driving means 7 is provided to allow the continuous cyclical adjustment of the means 6 within a selected vertical stroke length. The driving means 7 is designed to produce in conjunction with the adjustment means 6 a vertical motion of the seat 2 at a speed of preferably around 1 cm/minute through a vertical distance which is at least 2 cm and usually less than 20 cm. Cyclic motion means that the seat 2 moves e.g. in an upward direction to an upper end point and then immediately, or after a selected interval, moves in a downward direction to a lower end point, after which the seat 2 again moves in an upward direction, immediately or after a preselected interval, etc. The chair may be fitted with a load sensor 8 which keeps the driving means 7 activated only as long as the seat 2 is carrying a certain load corresponding to a user. The driving means 7 and the adjustment means 6 may be of various designs. For example, they may be pneumatic or hydraulic in action or may be of electromechanical design, in which case usually the driving motor of the driving means may be some form of electrical motor of which the power supply comes from the mains or from an battery supported by the chair. Other forms of driving motor are also possible. With reference to Fig. 2, a schematic example of embodiment may be seen in which the column 42 consists of a tubular lower section 421 having at its top end an internal thread 422 which receives the outer thread of a screw 423 of which the top end is securely fastened to the support plate 41 via a bearing 424, e.g. a deep groove ball bearing which permits the screw 423 to rotate freely relative to the support plate 41. The screw carries a gear wheel 425 which is in engagement with a drive gear 71 on the driving shaft 72 of an electric motor 73, the free end of the shaft 72 being journalled in a guide 75 attached to the cylindrical section 421 of the column. Additionally there are two vertically separated limit switches 77, 78 which sense the vertical end points of the gear wheel 425, which end points are adjustable in order to set a desired average height S of the seat 2 above the floor 5, and also a desired vertical range of motion of the seat 2. When the load sensor 8 senses that a person is sitting on the seat 2, it acts on a control 9 to cause the motor 73 to be energised from the mains 10. The control 9 is also acted upon by the limit switches 77, 78 in such a way that the screw 423 changes its direction of motion after having actuated the respective switch 77, 78. The chair may additionally be fitted with a switch 11 by which the vertical motion of the seat can be stopped, e.g. by interrupting the power supply to the driving means 7. The r.p.m. of the motor 73 and the gearing ratio of the transmission 71, 425, 422 are selected to produce a velocity of motion of approximately 1 cm per minute. It is within the capability of one skilled in the art to construct suitable adjustment means to permit the simple shifting of the switches 77, 78 to selected levels. It is likewise within the capability of one skilled in the art to replace the arrangement illustrated schematically in Fig. 2 with pneumatic or hydraulic or other electromechanical arrangements producing approximately the same effect, namely a slow vertical motion of the seat 2 at a speed in the order of 1 cm/minute over a vertical distance ranging from centimetres to tens of centimetres, the range of vertical motion being usually in the order of 10 cm. Since the vertical velocity is so low as to be essentially undetectable, it is of subsidiary importance whether the velocity of the vertical motion is constant or variable between the upper and lower end points. It should be clear that the means 6, 7 of the invention, which produce the slow motor- driven vertical motion of the seat, need not necessarily include an actual adjusting means for setting the "normal" or average height of the seat for the individual user. Thus the height adjusting means of the chair may be separate from the indicated means 6, 7. The invention has been described in relation to seating furniture in which the seat is supported from a floor by means of a seating furniture substructure. However, it should be clear that the invention is also applicable to other seating furniture designs, e.g. designs in which the "substructure" supports the seat from a wall or a ceiling of the space in which the seating furniture is set up. Thus in general the seating furniture has a seat which is supported from a fixed reference (such as a floor, a ceiling or a wall) by means of a supporting structure, means being provided for the setting of a desired vertical distance between the seat and the reference. By driving said means according to the invention, the distance between a work surface, a foot support (floor) or some other surface on which the user supports himself or herself is changed in a manner to secure the effects according to the invention.

Claims: Claims 1. Seating furniture including a seat (2), a supporting structure (4) which supports the seat from a fixed reference (5), and means (6; 422, 423, 424) for setting a desired vertical distance (S) between the seat (2) and the reference (5), characterised by a driving means (7; 9, 71-73, 75, 77, 78, 425) for automatically driving the means (6; 422, 423, 424) for the purpose of slowly increasing and decreasing the distance (S) with a velocity of motion not exceeding 100 cm/minute. 2. Seating furniture according to claim 1 , characterised in that the driving means is arranged to produce a velocity of motion of the seat (2) not exceeding 50 cm/minute. 3. Seating furniture according to claim 1 , characterised in that the velocity of motion is not more than 10 cm/minute. 4. Seating furniture according to claim 1 , characterised in that the driving means is arranged to produce a velocity of vertical motion of the seat (2) of the order of 1 cm/minute. 5. Seating furniture according to any of claims 1-4, characterised in that the driving means includes means (77, 78) for setting a vertical distance between the end points of the slow vertical motion of not less than 1 cm and not more than 30 cm. 6. Seating furniture according to claim 5, characterised in that the vertical distance between the end points is not more than approximately 10 cm. 7. Seating furniture according to claim 5 or 6, characterised in that the distance between the end points is at least 4 cm. 8. Seating furniture according to any of claims 1-7, characterised by a sensing device (8) arranged to keep the driving means (7) activated when the sensor senses that the seating furniture is under load from a user thereof. 9. Seating furniture according to any of claims 1-8, characterised in that said seating furniture is a task chair. 10. Seating furniture according to any of claims 1-9, characterised by a switch (11) for setting a velocity of motion of 0 cm/minute.

Inventors: SIMON BELA, SIMON, BELA
Applicants: SIMON BELA, SIMON, BELA
Application year: 1998
Main classification: A47C9
IPC codes: A47C9