EP0552388A1 - Backrest for an office chair - Google Patents

Abstract

A backrest consists of a lumbar part (1) and a shoulder part (2), which parts are connected to one another via elastic bands (3, 4). The guiding of the relative movement of the shoulder part (2) relative to the lumbar part (1) is effected by convex bars (4, 5) which are mounted movably on the lumbar part (1) and on the shoulder part (2) at their nose-like ends by means of prestressed spring elements (7, 8). The lumbar part (1) and the shoulder part (2) move on the concave rear side of the bars between two well-defined stop positions. <IMAGE>

Description

The invention relates to the field of office seating.

It relates in particular to a backrest for an office chair, which is designed as a shell consisting of a lower lumbar part and an upper shoulder part, these two parts being connected to one another in an articulated manner, and the shoulder part being held in the front position in the unused state by means of spring elements provided in the articulated connection becomes.

STATE OF THE ART

Such a backrest is known for example from DE-A 3743013. This document describes a horizontally divided backrest for an office chair, the two parts in the lumbar region being connected to one another by means of an articulated bracket via two articulated axes lying one above the other. The aim of this is to ensure that the upper part of the backrest does not move sharply over an axis when leaning back, but rather moves softly and largely without kinks to the rear in the region of the user's lumbar spine. Together with a suitably designed upholstery, the backrest should bend according to a bend line that corresponds to the natural curvature of the spine and provide a constant back support.

From DE-A 3630503 a seat-back construction for an office chair is known, in which the backrest shell is divided into a lower pelvic or lumbar and an upper shoulder part, and these two parts are connected to one another on the outer sides via joints. The two back shell parts can be pivoted relative to one another from a stop position against a spring support. This is to avoid an otherwise common back support protruding from the back and to achieve a narrow side silhouette.

An office chair with a split backrest is known from EP-B 0277912, the segments of which are arranged one above the other are connected to one another by two spring joints arranged at a distance from one another. The spring joints consist of resilient round rods. This is to avoid hinges with separate springs, which - attached to the outside of the backrest - result in constructional problems due to the curvature of the backrest, and - attached in the middle of the backrest - cause difficulties with regard to the stability of the backrest.

From WO-A 90/02503 a chair is known with two supports for the backrest which are directed upwards on the outer sides of the seat and which are connected to one another in the lower part via a spring joint. The backrest has no lumbar part supporting the user in the lumbar region, and the spring joints essentially only affect the mobility of the shoulder support.

All these known backrests have the disadvantage that the curvature of the backrest adapts only very imperfectly to the shape of the spine of the user that has been reclined, and on top of that they still have quite complex mechanical constructions, which are complex to produce and thus expensive to sell are.

PRESENTATION OF THE INVENTION

It is therefore the object of the invention to design a backrest for an office chair in such a way that, on the one hand, it adapts as optimally as possible to the changing shape of the spine of a reclining user, in particular in the lubam area, but on the other hand it is structurally simple and thus possible in production is inexpensive.

The object is achieved by the features specified in claim 1.

The essence of the invention is that the lumbar and shoulder parts of the backrest are not connected to one another via a point-like hinge joint, but instead via the bending zone of the connecting elastic bands. The bending line of these ligaments corresponds optimally to the deformation of the user's spine when leaning back in the lumbar region. In combination with these straps, the aluminum brackets mean that the lumbar and shoulder parts can only move between two well-defined stop positions. The prestressed spring elements mean that the shoulder part only begins to move when the pressure is high. The construction resulting from the invention is extremely simple and comprises only a few parts. It is therefore very inexpensive to produce.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

schematisch die Seitenansicht eines Bürostuhls, bei welchem Sitz und Lehne über eine Synchronmechanik an der Standsäule gehaltert sind, und die Lehne gemäss der Erfindung zweigeteilt ist,

Fig. 2

die Ansicht einer Lehnenschale nach der Erfindung von hinten, und

Fig. 3

im Detail Ausbildung und Lagerung des Bügels am Lumbal- und Schulterteil der Lehne.

The invention is explained in more detail below with reference to an embodiment shown in the drawings. It shows

Fig. 1

schematically the side view of an office chair, in which the seat and backrest are held by a synchronous mechanism on the pillar, and the backrest is divided in two according to the invention,

Fig. 2

the view of a backrest shell according to the invention from behind, and

Fig. 3

detailed design and storage of the temple on the lumbar and shoulder part of the backrest.

WAY OF CARRYING OUT THE INVENTION

1 schematically shows a backrest consisting of a lower lumbar part 1 and an upper shoulder part 2, which is connected to the seat 10 and the pedestal 12 of an office chair via a synchronous mechanism 11. The synchronous mechanism 11 is preferably designed as in EP-A 86102522.9.

As can also be seen from FIG. 2, the lumbar part 1 is fastened to the backrest support 9 and moves back / down when the seat 10 is lowered.

From Figure 2 it can also be seen that the backrest consists of a one-piece self-supporting shell made of a material with a certain intrinsic elasticity, preferably made of polypropylene plastic, which has a horizontally extending slot 13 in the lower region, the outside through vertical short slots is completed. This results in a very simple manner in the lower lumbar part 1 and the upper shoulder part 2, which are connected to one another in an articulated manner via bending zones 3, 4 produced by the elastic bands.

The guidance of the relative movement of the shoulder part 2 with respect to the lumbar part 1 is brought about by the bracket construction which is shown in FIG. 1 and in more detail in FIG. 3:

The convex brackets 5 and 6 made of die-cast aluminum are fastened to the lumbar part 1 by means of a hinge 14 and 15, respectively. They have noses at their ends. In these noses pressure acting springs, preferably cylindrical PUR plastic springs 7,8 are used, which are set and held under tension by covers 16 screwed onto the lumbar part 1 or shoulder part 2. The bracket 5, 6 can advantageously also consist of magnesium or correspondingly stiff glass fiber reinforced plastic. In principle, steel springs could also be used instead of the plastic springs.

Lumbar part 1 and shoulder part 2 lie on the concave back of the brackets 5, 6 such that the shoulder part 2 is pressed into the front stop positions by the spring elements 7, 8 when not in use. However, if the user exerts a force on the shoulder part 2, the corresponding surfaces of the lumbar part 1 and the shoulder part 2 move into the other stop positions against the spring forces.

The articulated connection consisting of the elastic bands 3, 4 together with the brackets 5, 6 responds softly but in a defined manner, and not only works sagittally, but also torsionally. The latter is an effect which is not readily predictable and which is very favorable for the user. The sequence of movements is determined by defined initial and final forces. The twisting possibility of movement is deliberately restricted by the prestressed spring elements in order to exclude feelings of insecurity which can arise for the user due to the overall more elastic backrest. The freedom of movement of the shoulder part 2 of the backrest is deliberately ended when the two brackets 5, 6 lie against the adjacent lumbar and shoulder parts of the backrest, which creates a continuously rigid backrest.

In addition to the two brackets 5, 6, the entire construction only includes the spring cover 16 and bolts (not shown) for fastening the brackets 5, 6 in the hinges 14, 15 as individual parts. Production and assembly are therefore extremely simple and therefore inexpensive.

REFERENCE SIGN LIST

1

Lumbar part

2nd

Shoulder part

3rd

Left band

4th

Right band

5

Left bracket

6

Right bracket

7

Spring element on the lumbar part

8th

Spring element on the shoulder part

9

Backrest support

10th

Seat

11

Synchronous mechanism

12

Pedestal

13

slot

14

Left hinge

15

Right hinge

16

Spring cover

Claims (8)

Backrest for an office chair with a shell consisting of a lower lumbar part (1) and an upper shoulder part (2), which are articulated to one another, the articulated connections being arranged on the two outer sides of the backrest, and the shoulder part (2) by means of spring elements provided in the articulated connection are held in the front position when not in use, characterized in that the shoulder part (2) and the lumbar part (1) are connected to one another via elastic bands (3, 4) lying on the two outer sides of the backrest shell, and For guiding the movement of the shoulder part (2) with respect to the lumbar part (1), a strap (5, 6) which is convex in shape when viewed from the front and which is connected to the lumbar part (1 ) and the shoulder part (2) is movably connected, and its concave rear side is formed in such a way and on the corresponding surfaces of the rear side of the lumbar part (1) or shoulder Rush (2) is arranged and held in such a way that these surfaces on the back of the bracket can only move between two stop positions, and the bracket (5, 6) in each case on its holders on the lumbar part (1) or shoulder part (2) in this way is under the force of spring elements (7,8) that the shoulder part (2) is in the unused state in the front position. Backrest according to claim 1, characterized in that the lumbar part (1) is fastened to a backrest support (9) which, together with the seat (10), is part of a synchronous mechanism. Backrest according to claim 1, characterized in that the spring elements (7, 8), by means of which the brackets (5, 6) are held on the lumbar part (1) or shoulder part (2), are also pretensioned when the backrest is not in use. Backrest according to claim 3, characterized in that the spring elements (7, 8) are bodies with resilient properties, preferably cylindrical bodies made of elastic plastic. Backrest according to claim 4, characterized in that the spring elements (7,8) consist of poly urethane (PUR). Backrest according to Claim 1, characterized in that it is a one-piece plastic shell which is cut out in the region of the articulated connection in such a way that a horizontally extending slot (13) extends over the central part and extends outside of the elastic bands (3 , 4) is limited. Backrest according to claim 6, characterized in that it is a shell made of pure polypropylene (PP). Backrest according to claim 1, characterized in that the brackets (5, 6) consist of aluminum, magnesium or correspondingly stiff glass fiber reinforced plastic.

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