ADJUSTABLE CHAIR

Abstract: A chair having an adjustable seat and an ergonomically cooperating foot support to be used at high tables, wherein foot support for passive (closed) and active (open) sitting position automatically is adjusted to correct level below the seat and to correct horizontal distance from the seat front edge whenever the seat is adjusted to correct level below a tabletop in relation to the body of the user. Through a lifting strut (14), the seat (10) influences the rear foot support (15) which, through a sliding/pushing strut (20), influences the front foot support (24).

Description: ADJUSTABLE CHAIR The invention relates to a chair having an adjustable seat and an ergonomically cooperating foot support to be used at high tables, especially in schools. Within the school, tall pupil tables are tried out in order to avoid load damages affecting teachers bending forwardly during guidance, together with tall chairs to prevent back problems affecting pupils, giving them the possibility of changing between usual "passive" sitting position (90° between calf (lower leg) and thigh on the one hand and between thigh and body on the other hand) and a more open "active" sitting position (120° between calf and thigh respectively between thigh and body) . Such a work-place has been developed by dr. A. C. Mandal, Denmark, and is produced i.a. by MK Stalmøbler a.s., DK-5500 Middelfart. Disadvantages consist in that many chair variants are required; the foot support of the chair for "passive" sitting position must be adjusted separately; the table must be adjusted vertically separately; the various levels of the tables differ, and the foot support of the table for "active" sitting position must be adjusted separately. The same favourable working position is achieved by teacher and pupil if all adjustments are gathered on the chair, using tables positioned at one fixed level. Tables without adjustments are labour-saving and prevent risks for errors. Equal table level is necessary upon grouping. Such a chair is disclosed in Norwegian patent speci ications Nos. 135,118 and 150,743, now cancelled. The disadvantage of this chair is that the vertical distance from seat to tabletop as well as the vertical distance from foot support to seat must be adjusted separately; the chair does not offer any possibility of sitting in an open "active" position, and it is only intended for usual dining table levels. The invention is based on the above-mentioned, . known solutions, but it has the advantage that when the seat is set at a correct level beneath the tabletop, it is automatically positioned at a correct distance from the back of the chair as well as at a correct level above foot supports for active and passive working positions, gathered in one and the same hand grip. A simple adjustment saves work and prevents risks for errors; the chair offers possibilities for varied sitting positions; the same chair may be used for persons having a difference of 70 cm in body length, simplifying both purchase and storage. According to the invention, synchronous adjustment is achieved in that, when the seat, as known, is displaced along the guidance portion extending obliquely upwardly and rearwardly, to a desired level below the tabletop at a correct level and distance from the back of the chair, a strut attached to the seat lifts with it the foot support for passive sitting position to a correct distance from the seat. Simultaneously, a strut from foot support for passive sitting position carries another foot support for active sitting position to correct height level in relation to the seat. Seat level and, thus, all other adjustments, are locked in a desired position, the part carrying the seat in a correct angle relative to the underframe (the guidance portion) being attached thereto as known: A Through friction coating which, by means of the weight of the seat and of the user, locks the seat infinitely variable in correct position on the guidance portion; B Through friction coating which, by means of the weight of the seat and of the user, locks the seat infinitely variable in correct position on the guidance portion, with the addition of a clamp device of known structure, preventing the seat from being displaced due to a mishap; C Through a locking pin on the guidance portion, or on the underframe of the seat, said pin engaging a hole in an opposing part and, thus, locking the two parts together in fixed steps at a desired level; D Through a screw adapted to pull and lock the seat on the guidance portion of the chair, in an infinitely variably chosen position. The alternatives B, C and D are adapted to be controlled by the user without tools, but the chair should also be available in an embodiment which must be controlled and adjusted by means of special tools, e.g. by a caretaker. A method for the use of ergonomically cooperating adjustment of a seat-carrying device according to the invention is shown in the drawings, in which: Figure A shows the chair in section/side elevational view; Figure B shows the same in a front view; Figure C shows the same as seen from above; Figure D shows a detail of a lifting strut below the seat; Figure E shows a detail of the lifting strut in lifting axis and pushing strut in rear annular fastener; and Figure F shows the pushing strut in the front annular fastener. The fixed structure of the chair consists of rear bars 1 having a fixed lateral connection 2 at the upper edge thereof. The back 3 is attached to the lateral connection. From the lower ends thereof, the front legs 4 of the chair are bent to transit into inclined guidance rails 5, each of which has an upper fixed connection 6 to the rear bars 1. Additionally, the front legs 4 and the rear bars 1 have a fixed connection through longitudinal struts 7 in the form av horizontal pipes adjacent the floor. The longitudinal struts 7 are connected to rear and front lateral struts 8 and 9, respectively, bracing the chair and forming an axis for the foot supports. The adjustable structure of the chair consists of the seat 10 which, at the rear edge, is piovotally attached through a horizontal, lateral seat shaft 11 fastened to sleeves such as 12 sliding along the guidance rails 5. The seat 10 is rigidly connected to a carrier 13, maintaining it in the correct angle above the guidance rails 5. The carrier 13 is attached to the guidance rails in a known manner, i.e. through friction coating or friction coating plus clamp or pin engaging hole or screw; this previously known attaching method is not further described herein. To the seat shaft 11, a lifting strut 14 is rotatably attached. The lower end of the lifting strut 14 is rotatably attached (16) to a foot support 15. The rear foot support shaft 17 rotates around the rear lateral strut and is equipped with a rear ring fastener 18 for an eccentric fastener 19 transferring forces through a sliding or pushing strut 20 to an eccentric fastener 21 on a front ring fastener 22 on a front foot support shaft 23 and, thus, positions the front foot support 24 in a desired position. The inclined position of the guidance rails 5, carrying the seat towards the back 3 with a larger horizontal than vertical motion component, the positioning of the lifting strut's 14 fastener to the seat, the distance from the lifting strut's 14 shaft 16 to the rear foot support shaft 17, the distance from the centre of the foot support shaft 17 and 23 to the fasteners 18 and 22 for the sliding or pushing strut, bring the chair's cooperating functional measures - distance between seat, back, rear and front foot supports - into ergonomic position in relation to each other according to average measures of a human body. Adjustment of lifting and sliding/pushing struts adjusts the level of the foot support for people having a leg length which is out of proportion with the rest of the body. With simple hand grips, one may adjust the chair to correct sitting position for users having differing body sizes and proportions.

Claims: C l a i m s 1. An adjustable chair, where the seat (10) of the chair is vertically adjustable for adaptation to a working table or the like, and where the chair also is provided with a vertically adjustable foot support having a foot resting portion, c h a r a c t e r i z e d i n that the foot support is rotatably attached to the chair at a substantially horizontal and lateral foot support axis (17) disposed below the seat (10) , and that the foot support is connected to the seat (10) by means of a lifting strut (14) adapted to rotate the foot support around the foot support axis (17), whereby the distance between the foot resting portion of the foot support and the seat (10) is changed when the seat is vertically adjusted, the lifting strut (14) is attached to the foot support, spaced from the foot support axis (17) . 2. An adjustable chair as set forth in claim 1, c h a r a c t e r i z e d i n that the foot support comprises a rear foot support (15) and a front foot support (24), each having a foot resting portion positioned at a distance from the seat (10) differing from corresponding spacing of the other, the rear foot support's (15) preferably being positioned closest to the seat (10) . 3. An adjustable chair as set forth in claim 1 and 2, c h a r a c t e r i z e d i n that the distance between the lifting strut's (14) attachment in the foot support (15) and the foot support axis (17) is such adapted that the distance between the seat (10) and the foot support's (15, 24) foot resting portion descreaseε with increasing seat level. 4. An adjustable chair as set forth in claim 3, c h a r a c t e r i z e d i n that the distance between the lifting strut's (14) attachment in the foot support (15) and the foot support axis (17) is such adapted that the distance reduction taking place between the seat (10) and the foot resting portion of the foot support (15, 24) when the seat (10) is raised, fit average human body proportions, a person with a low body height having to raise the seat (10) more than a bigger person, in order to achieve a correct sitting position at a working table or the like. 5. An adjustable chair as set forth in one or more of the preceding claims, c h a r a c t e r i z e d i n that the lifting strut (14) is longitudinally adjustable, so that the distance between the seat (10) and the foot support (15, 24) can be adjusted in order to adjust the spacing between the seat (10) and the foot support's (15, 24) foot resting portion for persons having various body proportions. 6. An adjustable chair as set forth in one or more of the preceding claims, c h a r a c t e r i z e d i n that the front foot support (24) is rotatably attached to the chair at a substantially horizontal and lateral axis (23) in front of the foot support axis (17) and connected to the rear foot support (15) by means of a parallel strut connector, so that the front foot support (24) rotates about the axis (23) when the rear foot support (15) rotates about the foot support axis (17) .

Inventors: SLETTEBOE TRYGGVE, SLETTEBOE, TRYGGVE
Applicants: SLETTEBOE TRYGGVE, SLETTEBOE, TRYGGVE
Application year: 1996
Main classification: A47C3
IPC codes: A47C1