Hub construction for a rotatable chair

Abstract

The invention relates to a hub construction for a rotatable chair, whereby an uncomplicated and robust plain bearing design is provided. The plain bearing parts are manufactured of metal in such a way that the bearing surface on the underlying pin is softer than that of the overlying sleeve. A plain bearing according to the invention may be provided with an adjustable device for obtaining higher friction and thus an increased rotational resistance. In the upper part of the pin is arranged a horizontal bore, into which is fitted a plug shaped body, the ends of which extend outside the mouths of the bore in the bearing surface as an adjusting screw in the upper end of the pin is tightened against the middle section of the plug-shaped body.

Claims

1. A hub construction for a rotatable chair comprising: a metal pin having an upper section and a corresponding sleeve enclosing the upper section of the pin, the pin and sleeve forming a plain bearing, wherein the sleeve is made of metal so that at least the inner surface of the sleeve has a hardness that is greater than that of the pin, wherein the upper section of the pin comprises a horizontal bore into which has been inserted a plug-shaped body consisting of one or several parts.

2. The hub construction according to claim 1, wherein the pin and sleeve are movable in relation to each other.

3. The hub construction according to claim 1, wherein the upper section of the pin comprises a vertical, central and threaded hole opening into the horizontal bore, the hole being adapted for receiving an adjustment screw, the end of which abuts the plug-shaped body.

4. The hub construction according to claim 3, wherein the plug-shaped body consists of a single piece of a flexible material.

5. The hub construction according to claim 3, wherein the plug-shaped body consists of several parts of a non-elastic material.

6. The hub construction according to claim 3, wherein the adjustment screw is provided with a locking nut or a screw head.

7. The hub construction according to claim 1, further comprising, below the upper section of the pin, a cylindrical section, whose upper surface the lower surface of the sleeve abuts.

8. The hub construction according to claim 7, wherein the length of the hollow in the sleeve is larger than the length of the upper section of the pin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in further detail in the following with reference to the appended drawings, in which FIG. 1 shows an example of a rotatable chair having a hub construction according to the invention,

(2) FIG. 2 shows the hub construction as indicated by A in FIG. 1,

(3) FIG. 3 shows a section in plane B-B of the hub construction in FIG. 2,

(4) FIG. 4 shows the central parts C in the hub construction according to FIG. 3,

(5) FIG. 5 shows the parts of FIG. 4 separated and rotated 90 degrees around their vertical axis.

EMBODIMENTS

(6) A chair according to FIG. 1 is provided with a hub construction A according to certain embodiments of the present invention. The hub construction A is further shown in FIG. 2 and as a section in FIG. 3. At the center of the hub is the swivel, the lower part of which is attached to the steel pedestal structure 7.

(7) The swivel C is shown in greater detail in FIGS. 4 and 5. It comprises a pin 1, the cylindrical upper part of which is surrounded by a sleeve 2. The sleeve preferably has a conical external shape for fitting into the chair seat structure. Below the cylindrical upper part 1a is a collar section 1b having a diameter greater than that of the upper part. Below the collar section 1b is, in this embodiment, provided an additional cylindrical pin 1c for fastening the swivel in a base pedestal structure of the chair.

(8) At least the inner surface of sleeve 2 is made from a material harder than the pin part 1. For example, the sleeve can be made of the same base material as the pin part but has been subjected to a hardening treatment. The sleeve may also be made of bearing bronze while the pin is of steel. The inner surface of the sleeve and the outer surface of the pin upper part 1a constitute bearing surfaces 9, on which conventional lubricants may be used.

(9) The length of the hollow in the sleeve 2 is greater than the length of the upper part 1a of the pin. The lower edge of the sleeve, which preferably is flanged, thus abuts the upper surface of the collar section 1b and constitutes a bearing surface. Between the upper surface of the pin upper section 1a and the sleeve 2, there thus appears a space or distance 8. The vertical, axial load caused by the chair seat and someone seated there is thus carried by the lower edge of the sleeve and the collar section 1b of the pin part.

(10) The pin 1 is made of metal, preferably solid metal. The sleeve 2 is also made of metal. The surface on the sleeve abutting the pin part can consist of a material different from that of the rest of the sleeve, whereby it is essential that this countersurface is of a greater hardness than the pin.

(11) The difference in hardness between the materials of the pin vs. the sleeve can be illustrated by both being made from Fe 52 steel according to the SFS standard, and the sleeve being given a Rockwell hardness (HRC) of 50-55 by means of nitration. Depending on the material, hardening may be used to achieve the desired result. The difference in hardness prevents galling. The sleeve can also me manufactured from e.g. bearing bronze.

(12) The pin 1 in the figures is made as a single piece, but it may also be assembled from multiple parts, possibly having different hardnesses.

(13) For controlling the friction between the movable parts and thus the rotational resistance in the chair hub, the hub according to the invention may be provided with an adjustable friction brake, most clearly shown in FIGS. 4 and 5. In the upper part 1a of the pin 1 is a horizontal bore, filled by a plug-shaped body 6, at least the central part of which can have a certain elasticity. The body 6 may consist of e.g. polyurethane.

(14) From the top of the pin 1, along its vertical central axis, extends a threaded bore opening into the horizontal bore. Into this threaded bore is screwed an adjustment screw 5, the head of which is provided with a socket for receiving a tool, e.g. a hex key, a torx key or a similar screwdriver or the like.

(15) The sleeve is provided with a corresponding hole through which the upper end of the adjustment screw extends.

(16) As the adjustment screw is tightened against an elastic, plug shaped body 6, the latter is deformed and its ends are to some extent forced out of the mouths of the horizontal bore in the cylindrical surface of the upper section of the pin part. This causes increased friction between the plain bearing surface of the sleeve and the ends of the plug shaped body, and increased resistance to rotation.

(17) The body 6 can consist of a non-elastic material and multiple parts, for example two parts of bearing bronze, whereby the lower end of the adjustment screw is conical and the parts are shifted radially outwards as the screw is tightened, whereby the ends of the parts are forced outwards through the openings in the bearing surface.

(18) The adjustment screw may be provided with a locking nut 4 facing a washer 3. In the alternative, the adjustment screw can have a head.

(19) The possible cone shape of the sleeve 2 may be in accordance with an industry standard, e.g. Morse. The seat structure may be fastened to the outside of the bearing sleeve 2 according to known methods, e.g. using a corresponding female part, i.e. a conical recess as shown in FIG. 3.