The present invention relates to a self-orienting caster for pieces of furniture and the like.
Self-orienting casters are known, particularly of the so-called twin type, which are constituted by two wheels that are mounted so they can rotate about a horizontal shaft. The shaft is supported in a seat formed in a supporting structure that is arranged between the wheels.
In the supporting structure there is a vertical cylindrical recess, which is open upward, is axially offset with respect to the shaft, and acts as a rotation seat for a vertical pivot for the spontaneous orientation (pivoting) of the wheel, which is intended to be inserted and retained in a receptacle of the piece of furniture on which the caster is to be fitted.
Self-orienting casters are also known in which the wheels can rotate about a tubular shaft that protrudes on opposite sides of the central supporting structure. Casters of this type, also known as hubless casters, are disclosed in U.S. Pat. No. 978,161, in US publication 2002/01758539, in British patent 967,915, and in German publication 101 28 099. Swiss patent 477,999, British patent 967,915 and US publication 2002/1178539 describe solutions in which the wheels and the tubular shaft are provided with mutually opposite tracks for the rolling of balls or rollers for rotatably supporting the wheels. Known casters have drawbacks as regards the structure composed of the central support and the tubular shaft, which is unable to combine satisfactorily mechanical strength characteristics, in order to be able to withstand the loads, with the need to obtain a product which, as it is intended for pieces of furniture (chairs, tables, etc.), must meet appreciable aesthetic requirements.
The aim of the present invention is to provide a contribution in this regard, by providing a caster that is capable of meeting these requirements, is easy and cheap to manufacture and assemble, and offers new aesthetic standards.
Within this aim, an object of the present invention is to provide a caster having a structure suitable to ensure very smooth rolling on surfaces of any kind.
Another object of the present invention is to provide a caster that can be provided with a braking device that can be neutralized when necessary.
This aim and these and other objects that will become better apparent hereinafter are achieved with a self-orienting caster for pieces of furniture and the like, the characteristics of which are defined in the appended claims.
Further characteristics and advantages will become better apparent from the following detailed description of some preferred but not exclusive embodiments of the caster according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:
With reference to
The body 2 is provided with a through seat 5 that has a circular cross-section and through which a tubular element or sleeve 6 is arranged; such element comprises two cylindrical portions 7, 8, which protrude coaxially in a cantilever fashion from opposite sides of the body 2. The portions 7, 8 are aligned along a horizontal axis A, which is axially offset and perpendicular with respect to the vertical axis B of the recess 4, and enclose a cylindrical cavity 9, which passes through the body 2.
The sleeve 6 is provided with a collar 10 (
The forcing action can be facilitated by acting on the configuration of the annular ridges 11, 12 and by resorting to a suitable choice of the materials for the sleeve 6 and the body 2. Advantageously, the sleeve 6 is made of plastic material, whereas for the body 2 it is possible to use plastic material and metal, for example a metallic alloy of zinc, aluminum and magnesium, known by the tradename ZAMA, depending on the load stresses to which the caster is subjected.
Respective annular slots 19, 20 are formed in the tubular portions 7, 8, proximate to their free ends, and form respective annular lips 21, 22, which are folded outward.
Two wheels 25, 26 are fitted rotatably on the tubular portions 7,8 (
The wheels 25, 26 have, on the side that faces the body 2, respective grooves 34, 35 and, on the opposite side, respective internal collars 36, 37. The internal collars 36, 37 are sized so as to engage by elastic forcing in the slots 19, 20 of the sleeve 6 and therefore retain axially thereon the wheels 25, 26 with minimal friction. At the same time, two annular ridges 38, 39 engage in the grooves 34, 35, protrude frontally from the lateral faces of the body 2 and surround the seat 5, forming a sort of labyrinth-like coupling that prevents foreign particles and dirt from penetrating toward the bearings 23, 24 and compromising their correct operation.
The caster is fitted to the piece of furniture by means of a pivot 40, which can rotate in a bush 41 (
In order to retain the bush 41 in the recess 4, the inlet of the recess is formed by a protruding rim, which has a groove 45 that divides it into two mutually concentric lips 46, 47. The inner annular lip 46 is suitable to be folded onto the rim of the bush 41, so as to lock it axially in the recess. Advantageously, the outer rim of the bush 41 is rounded in order to allow the internal lip 46 to be folded over onto it and ensure more effective axial retention of the bush. Likewise, the outer annular lip 47 is folded outward so as to lock any optional ring-like element 48 that is applied so as to cover the expansion 3 and is shaped so as to mate with the contour of the body 2.
During use, the described caster 1 behaves like a known twin caster, but with the considerable advantage that the sleeve 6, by way of its radial dimensions, provides the caster with the rigidity required to withstand effectively load imbalances on the two wheels and facilitate their smooth rotation. Further, the hollow structure of the sleeve 6 does not encumber, also from an aesthetic standpoint, the caster, whose appearance maintains the requirements of lightness even in the case of large casters.
It should be noted that the bush 41 may be omitted. In this embodiment, shown in
In the caster of
A through hole 5 is provided centrally through the lower semicylindrical portion 53 and is aligned vertically with a blind seat 56 formed in the upper semicylindrical portion 54. A spring 57 is inserted in the blind seat 56, before the sleeve 6 is positioned in the seat 5, and acts on said sleeve, when said sleeve is inserted, so as to push it towards the lower portion 53.
The spring 57, once the caster 1 has been fitted to the chair, allows the body 2 to move with respect to the sleeve 42. In particular, the spring 57 is sized as so as to lift the body 2 with respect to the sleeve 6 when the caster is not loaded and instead allow its lowering when the caster 1 is loaded. In the first manner of use (for example, when the caster 1 is mounted on an office chair on which no one is sitting), locking of the caster is provided by way of the friction effect obtained by means of the contact of sliding blocks 58, 59, which are constituted by protrusions formed above the top of the ridges 38, 39, against the walls of the grooves 34, 35 of the wheels 25, 26 in which the ridges 38, 39 are engaged. In the second manner of use, i.e., when the caster is loaded (for example when a person is sitting on the chair), the ridges 38, 39 are perfectly free in the grooves 34, 35, allowing the free gliding of the chair.
The spring 57 may also act as a shock absorber. In this case, the sliding blocks 58, 59 are omitted in order to avoid a braking effect.
The caster of
In the embodiment shown in
In the embodiment shown in
In another embodiment, a metal strip is applied, is connected to the metal body 2 and is in sliding contact with the rolling surface of the casters in order to discharge any electrostatic charges to the ground.
The disclosures in Italian Patent Application No. BO2004A000352 from which this application claims priority are incorporated herein by reference.
Number | Date | Country | Kind |
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BO2004A000353 | Jun 2004 | IT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/00870 | 1/28/2005 | WO | 8/30/2006 |