A CHAIR WITH AN ADJUSTABLE LEG SUPPORT

Abstract: A chair with an underframe (10, 11, 12) in which a back is rotatably mounted, said back being in turn hinged to a seat (14), has additionally a foot support (15), which is hinged to the seat at the front end of the seat. The foot support is firmly connected with a control rod (20), which is slidable in a slide sleeve (21) rotatably secured to the underframe so that the foot support can pivot outwards and inwards by displacememt of the seat. The geometrical arrangement is such that a pressure at right angles to the foot support cannot cause displacement of the seat when the foot support is in its fully outwardly pivoted position. The seat has additionally rotatably secured to it another slide sleeve (24) which grips around an inclined slide rod (26) secured to the underframe so that the seat is lifted by forward and lowered by rearward displacement. This provides, in all positions, a good balance between oppositely directed forces which influence the relative positions of the various members.

Description: - 1 - A chair with an adjustable leg support The invention concerns a chair with an underframe, which is rotatably connected with a back, which is in turn rota¬ tably connected with a seat, which is additionally rota¬ tably connected at its front end with a foot support, which is so connected with the underframe by control means that the angle formed by the foot support with the seat varies by displacement of the seat- Chairs of this type are known where the control means are formed by a rod parallelogram which connects the back with the foot support and which may be incorporated as one rod in the seat. Such a parallelogram does not enable balancing of the forces which influence the mutual position of the back, the seat and the foot support such that these members can be retained with reasonable stability in any desired position, and it is therefore necessary to use special lock¬ ing means to provide such stability. The object of the invention is to provide a chair of the present type which, by simple and inexpensive means, enab¬ les the provision of such balancing of the forces that the various chair members can be retained with good stability in any desired position without using special locking means, This object is achieved in that the chair is so shaped that the control means are formed by a control rod secured to the foot support and slidable in a slide sleeve rotatably secured to the underframe. This structure makes it possible to vary the influence which a pressure against the foot support exerts on the mutual position of the chair members, from virtually zero in the fuuly outwardly pivoted position to an ever increasing influence as the foot support approach- es its inwardly pivoted, substantially vertical position in which it is no longer affected by the weight of a seated person's legs. - 2 - Claim 2 specifies measures to obtain the intended effect. The embodiment of the chair as defined in claim 3 provides the advantage that the weight of a seated person and the pressure against the back affect the seat for displace¬ ment in opposite directions so that the oppositely acting forces are balanced in all relative seat and back positions. The invention will be explained more fully below with refe- rence to the drawing in which fig. 1 is a side view of an embodiment of the chair frame, and fig. 2 shows a detail, illustrating on an enlarged scale control means instrumental in controlling the relative po¬ sitions of the chair members in different positions there¬ of. In fig. 1, an underframe is shown in broken lines, compris- ing a ring-shaped foot 10, two wide, plate-shaped legs 11 forming together a V, and two side members 12 forming arm rests and serving to attach the movable members of the chair. These members comprise a back frame 13, a seat frame 14 and a foot support frame 15. The back frame 13 has at each side a forwardly extending arm 16 which is rotatably connected with the side members of the underframe by a pi¬ vot 17. The back frame and the seat frame 14 are rotatably interconnected by a hinge 18, and the seat frame and the foot support frame 15 are rotatably interconnected by a hinge 19. The foot support frame 15 is firmly connected with two con¬ trol rods 20 which are disposed at each side of the frame and form an obtuse angle with the frame and extend oblique- ly upwards and backwards in the position shown in fig. 1. Each control rod extends through and is slidable in a slide sleeve 21 which is rotatably secured to the side member 12 - 3 - by a pivot 22 and consists of a low friction material such as e.g. polyamide. A fitting 23 is attached to the underside of the seat frame 14 at each side of it and adjacent to its front end, and a slide sleeve 24 of the same type as the sleeve 21 is rotatably secured to the fitting 23 by a pivot 25. The slide sleeve 24 surrounds and is slidable on a slide rod 26 which is secured to the side member 12 at both ends and forms an acute angle with the seat frame 14. When a person seated in the chair urges the back backwards so that it is pivoted about the pivot 17, the seat is pushed forwards and also lifted a little in that the slide sleeve 24 moves obliquely upwards on the slide rod 26. The axis of the hinge 19 will thus move along an oblique for¬ wardly and upwardly directed line which is virtually straight and parallel with the slide rod 26 and which is shown in dash-and-dot lines at 27 in fig. 2, the limit positions be- ing marked from 0 to 8 and intermediate positions from 1 to 7. The corresponding positions of the front end of the slide sleeve 24 on the slide rod 26 are marked with the corresponding numerals 0 to 8 on this rod, and the sleeve is shown in broken lines in position 7. During this move- ment of the hinge 19 the control rod 20 is displaced in the slide sleeve 21, which rotates at the same time about the pivot 22. The various positions of the centre lines of the control rod and the foot support frame corresponding to the marked positions of the hinge axis are shown by lines 28 and 29, respectively, and also the corresponding positions marked 0 to 8 of the free end of the control rod are shown. Additionally, the slide sleeve 21 is shown in broken lines in position 7. When the hinge 19 is in one of the lower intermediate po¬ sitions, e.g. position 2, it can, as will readily be seen, - 4 - be pushed backwards together with the seat, and the foot support can simultaneously be pivoted downwards and inwards by application of an inwardly directed pressure on the foot support. When the hinge 19 is in its extreme position or adjacent to this, such a pressure, however, will just pro¬ duce a very small component of force against the hinge in the direction of the seat and just a downwardly directed pressure against the seat, e.g. from the weight of a per¬ son seated in the chair, said pressure acting on the slide sleeve 26 to move it downwardly and rearwardly on the slide sleeve 26, in combination with relief of the pressure on the foot support can make the seat move rearwardly and make the foot support pivot down. As the hinge 19 moves downwards and rearwards, the effect of the pressure on the foot support increases, but this is accompanied by a de¬ crease in the pressure which is solely caused by the weight of a seated person's legs. If the transmission ratio is defined as the ratio of a gi- ven foot support pivot angle to the corresponding displace¬ ment of the hinge, it will be seen that this transmission ratio decreases as the members move from position 0 to po¬ sition 8. Thus, in all positions, there will be a good ba¬ lance of the forces influencing the mutual position of the various members so that there is no need for locking means to retain the members in any desired position. The func¬ tional relation between angular rotation and displacement can be changed by changing the relative location of pivot axes, control rod and slide rod and of the angles formed by these rods with the other chair members. The details of the shown and described chair can be varied in many ways within the scope of the invention.

Claims: 49 P a t e n t C l a i s 1. A chair with an underframe, which is rotatably f connected with a back, which is in turn rotatably connected with a seat, which is additionally rotatably connected at its front end with a foot support, which 5 is so connected with the underframe by control means that the angle formed by the foot support with the seat varies by displacement of the seat, c h a r a c t e r i z e d in thatthe control means are formed by a control rod secured to the foot support and slidable in a slide 10 sleeve rotatably secured to the underframe. 2. A chair according to claim 1, c h a r a c t e r ¬ i z e d in that the control rod and its slide sleeve are so positioned that the component of force in the 15 direction of the seat, produced by a pressure substan¬ tially at right angles to the foot support, is small in the fully outwardly pivoted position of the foot support and great in the inwardly pivoted position of the foot support. 20 3. A chair according to claim 1 or 2, c h a r a c t e r ¬ i z e d in that the underframe has additionally secured to it an inclined slide rod which is slidable in a slide sleeve rotatably secured to the seat adjacent to the front

Inventors: OESTERGAARD STEEN, OESTERGAARD, STEEN
Applicants: BRAMIN MOEBLER AS, BRAMIN MOEBLER A/S
Application year: 1986
Main classification: A47C1
IPC codes: A47C1