The present invention relates to a height adjustment device for an armrest of a chair or other seating furniture, preferably an office chair. More specifically, the invention relates to a height adjustment device as specified in the preamble of claim 1.

There exist several previously known height adjustment devices for seating furniture, and especially office chairs. Such a height adjustment device as used by the applicant comprises a pivotable rod with teeth arranged on a side of the rod along the length of this, and where the teeth are pivoted in and out of intervention with corresponding shaped portions on a circumferential part such as to lock the armrest at different heights where each tooth constitutes a freely selectable height.

Another solution is proposed in US 7 556 316 B1.

Even though the abovementioned solutions are said to operate well, it is an object of the invention to provide a height adjustment device which is easily adapted to several different types of chairs and armrests. Further, it is an object of the invention to provide a height adjustment device which produces audible clicks during adjustment, in order to give the solution a more technical user experience and also give the user indication regarding the adjustment position, which easily secures even adjustment of both armrests. A further object of the invention is to provide a simple and robust solution, with a minimum of components, for reduced production cost.

The abovementioned and/or other objects are sought solved with the height adjustment device according to the present invention.

The height adjustment device according to the invention is characterized by the indicated features in the characteristic of claim 1.

Preferential embodiments of the invention are disclosed in the dependent claims.

A preferred, not limiting embodiment of the invention is further described in the following, with reference to the attached drawings, where

• fig. 1 is a cross-sectional view of the height adjustment device according to the invention normal on the longitudinal direction of an armrest indicated with stippled lines,
• fig. 2 is a perspective view of the height adjustment device shown in fig. 1, with just a small part of the armrest shown,
• fig. 3 is a cross-sectional view of the height adjustment device shown in fig. 2, in a locked adjustment position,
• fig. 4 is a detailed view of the portion within the circle B in fig. 3,
• fig. 5 is a cross-sectional view of the height adjustment device shown in fig. 3, but in an open adjustment position,
• fig. 6 is a detailed view of the portion within the circle B in figure 5,
• fig. 7 is a perspective view of an assembly of an inner and an outer locking pin slidably spring loaded in relation to each other, and which forms a substantial part of the height adjustment device according to the invention, and
• fig. 8 is a split view of the assembly shown in fig. 5.

In the following description, direction indications such as "upwards", "downwards" and similar are related to an office chair or other seating furniture provided with the invention and in normal use position, standing on a floor or other base.

With reference to the attached figures, and introductorily especially to fig. 1 and 2, it is according to the invention provided a height adjustment device for an armrest 1 indicated with stippled lines in fig. 1 and where a portion of the armrest 1 for pivotably fastening of a locking pin assembly 2 is indicated with 1', as the locking pin assembly 2 is pivotably supported in relation to the armrest 1 via two opposite directed pivots 3 arranged in an upper end of the locking pin assembly 2 and which grips correspondingly shaped holes in the armrest 1.

For raising and lowering of the armrest 1 the locking pin assembly 2 is slidably arranged in an internal groove 4 in an upper part of the stem 5 of the armrest, and where the stem 5 typically is attached to a not shown fitting or undercarriage of an office chair and projecting out and up on each side of a not shown chair seat, as will easily be evident for the person skilled in the art. As is evident from fig. 1, a lower part of the armrest 1 preferably encloses the upper part of the stem 5, and thus conceals and protects that part of the locking pin assembly 2 which at any given time projects up and out from the stem 5, and also forms a guiding between the armrest 1 and stem 5. Because the armrest 1 is pivotably supported in relation to the locking pin assembly 2, the adjustment device can also be easily adapted stems 5 which are arranged at an angle in relation to the shown vertical orientation of the stem 5. The locking pin assembly 2, and so the armrest 1, is locked in the desired adjustment position/height by a locking pin 6 which is brought in intervention with a chosen number of locking grooves 7 in the locking pin assembly 2. As is especially evident from fig. 4 and 6, the locking pin 6 is in its two ends slidably supported in two respective horizontal grooves 8 arranged in an upper end piece 9 of the stem 5, and with a free middle portion for intervention with a chosen one of the locking grooves 7. As is especially evident from fig. 4, the locking pin 6 in a locked position is spring loaded to intervention with a locking groove 7 of a spring 10, here a plate spring, which is also located in the upper end part 9. In this position of the locking pin 6 the arm rest 1 will thus be locked in a particular adjustment position/height. For adjustment of the arm rest 1 it is thus required that the locking pin is brought out of intervention with the locking groove 7, as is shown in fig. 5 and 6, and this happens by pressing an adjustment lever 11 connected to the armrest 1 in, an inner part 12 of the locking pin assembly 2 is displaced upwards in relation to an outer part 13 of this, and with that presses the locking pin 6 out of the locking groove 7 from the effect of the spring 10, as will be further described below.

As is especially evident from fig. 7 and 8, the locking pin assembly 2 includes the inner part 12, the outer part 13 in which the inner part is slidably arranged, and also a spring 14, here a helical spring, which spring loads the two parts 12, 13 to a mutual position where the locking grooves 7 are open, as open portions or notches 15 on the outer part 13 are then aligned with open portions or notches 16 on the inner part 12, as is shown in fig. 7. The open portions 15 on the outer part 13 are adapted to the cross section of the locking pin 6, and the same also goes for an upper part of the open portions 16 on the inner part 12. However, a lower part of the open portions 16 is shaped like an inclined plane 17, which forces the locking pin 6 out of the locking groove 7 from the effect of the spring 10. Further, the open portions 16 are divided by closed portions 18 which completely close the locking grooves 7 when the locking pin 6 is forced out by means of the inclined plane 17 because of upwards displacement of the inner part 12 in the outer part 13 by pressing in the adjustment lever 11. Because closed portions between each respective open portion 15 on the outer part 13 are provided with respective convex curved outer edges 19, preferential, and as introductory mentioned, audible clicks are formed when adjusting the armrest 1, as the spring loaded locking pin 6 upon adjusting will slide against a curved surface with peaks and bottoms, as is especially shown in fig. 6, and where a click will sound each time the locking pin 6 reaches a bottom, and where each bottom coincides with an entrance point for the locking pin 6 to each respective locking groove 7, as is shown in fig. 6. A user will thus be able to use the number of clicks from an outer position of the armrest 1 for deciding the desired adjustment position, and to ensure equal adjustment of both the armrests 1 of the chair or seating furniture. An upper respectively a lower outer position of the armrest 1 is secured in that in a lower part of the outer part 13 of the locking pin assembly 2, a stopping hook 20 is shaped for contact with an inner surface of the end piece 9 and that in an upper end of the locking assembly 2, a horizontally projecting plane 21 is shaped for contact with an outer surface of the end piece 9.

By again especially referring to fig. 1 and 2, a pin 22 is provided in an end of the adjustment lever 11 far from the longitudinal axis of the stem 5, and thus also from an upper end of the inner part 12 of the locking pin assembly 2, pivotably supported in a correspondingly shaped hole 25 in the armrest 1. The latter constitutes thus a fixed pivot point in the armrest 1. An opposite end of the adjustment lever 11 is provided with a rectangle shaped pocket groove 23 for pivotable support to a hook shaped upper portion 24 of the inner part 12. As the outer part 13 of the locking pin assembly 2 is pivotably attached to the portion 1' of the armrest 1 via the projecting pins 3, while the inner part 12 of the locking pin assembly 2 is pivotably attached to an end of the adjustment lever 11 via the hook shaped portion 24 will, upon pressing in the adjustment lever 11 (ref. double arrow A in fig. 1), the inner part 12 is raised in relation to the outer part 13 and thus force the locking pin 6 out of the locking groove 7 it is currently in and thus make possible raising and lowering of the locking pin assembly 2 (ref. double arrow B in fig. 1) and thereby the armrest 1 for adjusting the latter. As previously mentioned, fig. 1 shows the locking pin 6 in intervention with one of the locking grooves 7, and thus in a locked position without possibility of raising or lowering the locking pin assembly 2 and thus the armrest 1. As the spring 14 keeps the adjustment lever 11 out (i.e. not pushed in, as shown in fig. 1) and the spring 10 keeps the locking pin 6 in intervention with the locking groove 7 when the adjustment lever 11 is not activated by a user, the adjustment device according to the invention automatically return to the locked position shown in fig. 1 as soon as a user has finished adjusting.

The present invention is not limited by the above description, but can vary within the scope of the attached claims. Among others, the activation can happen in a lot of other ways than with the shown and described lever 11, as the central object of the activation is to provide the desired displacement between the inner 12 and the outer part 13 of the locking pin assembly 2.