Chairs and seats – Movable back
Patent
1997-11-25
1999-03-16
Brown, Peter R.
Chairs and seats
Movable back
248412, A47C 740
Patent
active
058820779
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a height adjustment for back rests.
Such a height adjustment for back rests of chairs, in particular office chairs, consisting of a housing in which a flat back rest carrier is held by a detent ball clamping arrangement, whereby the back rest carrier is provided in axial direction with successively arranged indentations or openings for detent balls which are held in the indentations or openings by a spring-loaded clamping bevel, and whereby a push button that extends laterally from the housing can be used to move the clamping bevel against the elastic force to disengage it, is known, for example, from EP-A-O 264 555.
The objective of the present invention is to create a height adjustment of the type mentioned above which is easy and comfortable to operate and which functions reliably.
Further developments and advantageous embodiments of the invention are described hereinafter.
According to the invention, spring-loaded means are arranged in the housing to prevent lateral play of the back rest carrier. Thanks to this measure, the back rest cannot tilt and rock. According to a preferred embodiment of the invention, the means to prevent the lateral play of the back rest carrier consist of two wedges whose bevelled surfaces lie apart, whose parallel outside surfaces adjoin the housing wall on one side and on a side of the back rest carrier on the other side, and whereby the wedge adjoining the housing wall is spring-loaded on its wider end. The spring-loaded wedge presses its bevel against the bevel of the wedge that adjoins the back rest carrier, so that a force is applied laterally to the back rest carrier and brings it to adjoin the housing or a part connected to same. Thus, the back rest carrier can slide without play.
According to a preferred embodiment of the invention, inside the housing, a base plate is fastened in which the other side of the back rest carrier is guided and which supports the spring for the wedge adjoining the housing wall. The base plate contains guidance means, such as grooves, for guidance components such as journals, of the wedge adjoining the back rest carrier.
To prevent that the back rest is unintentionally pulled out of the housing, another indentation or opening is arranged, in addition to the row of indentations or openings, laterally at the bottom end of same, and above this indentation or opening a spring-loaded locking means is arranged for engaging in the further indentation or opening. Preferably, the locking means is a detent arm which locks when the back rest carrier is pulled upward and releases the back rest carrier again when it is pushed in. For example, this detent arm can be pivotably mounted in the base plate.
The invention is described below by way of example and with reference to the drawings, in which:
FIGS. 1 to 3 show three views of a height adjustment including a top view in FIG. 1 with the upper housing part cut away, in FIG. 2 a section along the line A--A, and in FIG. 3 a section along the line B--B of FIG. 1;
FIGS. 4a to 6c show separate components from FIG. 1.
The height adjustment according to FIGS. 1 to 6c consists of a flat housing 1, with a substantially rectangular cross section, in which a flat back rest carrier 2 is slidably guided and can be clamped. The housing can be extended at the bottom and connected to a seat carrier. It can also have different dimensions than those shown, and it can have a curved shape.
Along its center axis, back rest carrier 2 is provided with a number of holes 3 which define the insertion depth. In one of these holes 3 is a detent ball 4 which is pressed into the hole by a clamping bevel 5' of a shuttle 5. The pressure results from a spring 6 which is supported in a base plate 7 fastened in housing 1, for example by means of screws 17 or catches. Base plate 7 is provided with a groove 16 in which the shuttle 5 can slide and on which the side opposite spring 6 comes to a stop. On this side, shuttle 5 is adjoined by a push-button 8 with which it can be pushed back against the force
REFERENCES:
patent: 1075323 (1913-10-01), Benjamins
patent: 1101552 (1914-06-01), Hume
patent: 3467352 (1969-09-01), Bohler
Brown Peter R.
Sifa Sitzfabrik GmbH
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