GB2043823A - Joint for Chair Legs - Google Patents

Abstract

A chair leg assembly comprises a hub (1) and legs (12), the seat of the chair (not shown) being supported by an upright (5, 7). The hub (1) comprises a monolithic plastics block with a bore (2) at its centre for receiving the upright and peripherally disposed dove-tail section slots (10) for engagement with legs (12) disposed radially of the hub. A retaining plate 14 is secured to the face of the hub. <IMAGE>

Description

SPECIFICATION Chair Construction This invention relates to chair construction.

A swivel-type chair generally consists of a seat asembly rotatably supported by an upright on a leg assembly. Usually means are included for adjusting the height of the seat, for example by the use of a screw arrangement.

Here we are particularly concerned with the leg assembly. Commonly this comprises a central hub with a central connection for the upright and three, four or even five legs radiating from it.

When made of metal the legs and hub may be cast as a single unit. When using wooden legs, as for example in reproduction furniture, the legs are each made separately and secured to a separate common hub. It is difficult, if not impossible, to make a wooden hub of reasonable size with sufficient strength, particularly with larger numbers of legs; a metal hub is therefore usually used, commonly of welded steel construction.

The conventional hub is costly to manufacture, requiring expensive tooling-up, and the necessary manufacturing equipment is difficult to modify for variations in design and for the production of hubs to accommodate differing numbers of legs.

Also, such conventional hubs are generally heavy, and also unslightly and thus unsuitable for many designs, particular reproduction types.

According to one aspect of the present invention there is provided a hub for supporting a chair on legs comprising a monolithic block of material with means at its centre for securing to an upright and peripherally disposed formations for engagement with legs disposed generally radially of the hub.

The hub may be generally cylindrical, of substantially circular or polygonal cross-section.

Preferably the formations take the form of axially extending slots. The slots can be of dovetail or other re-entrant cross-section to accommodate complementary formations on the legs to provide a good mechanical "key" for securing the legs, although in most cases it will be desirable to employ an adhesive or cement in addition.

The means for securing the upright may be of central bore in the hub in which the upright can be located.

Although it is possible to form the hub from cast metal, it is preferred to employ a plastics material, for example a glass-reinforced thermosetting material such as DMC (a Dough Mould Compound of heat-cured polyester and glass).

In another aspect the invention provides a chair leg assembly comprisng a hub as described above, with a leg secured in each slot. The invention also extends to a chair including such a leg assembly.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an exploded perspective view of the leg assembly and upright of a swivel chair; and Figures 2, 3 and 4 are respectively plan, elevation and underneath views of the hub shown in Figure 1.

In the arrangement shown in Figue 1, a hub 1 is formed as a single block of DMC, of generally cylindrical shape. It has a central bore 2 which is slightly tapered to receive the tapered end of a support and adjustment assembly 3.

The assembly 3 has an outer tube 4 with the tapered lower end 5, the upper end of the tube being fitted with an internally threaded insert 6 in which is received the threaded lower end of an upright 7. The upper end of the upright is secured to a seat assembly (not shown), and the height of the seat is adjustable by screwing the upright into and out of the insert. Its travel is limited by an adjustable ring 8 and a disc 9 (of low-friction plastics material) screwed to the lower end of the upright.

The hub 1 also has five axially extending slots 10 disposed at 720 intervals around its periphery (as more clearly seen in the plan, elevation and underneath views of Figures 2, 3 and 4). The slots are open at the lower end. Each slot 10 is of dovetail cross-section to receive the similarly formed end 11 of a respective leg 1 2. The slots 10 (and ends 11) are tapered towards their upper ends, to ensure that when assembled, the legs fit tightly into the slots, and to facilitate removal of the hub from its mould during manufacture. The hub also has flats 1 3 adjacent the slots so that the legs can fit snugly against it.

A circular retaining plate 14 is secured to the legs by screws 1 5 through tabs 1 6 extending from the plate, to provide additional rigidity and a neat finish for the underside of the assembly.

Claims

1. A hub for supporting a chair on legs comprising a monolithic block of material with means at its centre for securing to an upright and peripherally disposed formations for engagement with legs disposed generally radially of the hub.

2. A hub according to claim 1, in which the hub is generally cylindrical and of substantially circular or polygonal cross-section.

3. A hub according to claim 1 or 2, in which the formations are axially extending slots.

4. A hub according to claim 3, in which the slots are of dovetail cross-section.

5. A hub according to any one of the preceding claims, in which the means for securing the upright is a central bore in the hub in which the upright can be located.

6. A hub according to any one of the preceding claims, formed of plastics material.

7. A hub according to claim 6, in which the plastics material is a glass-reinforced thermosetting material.

8. A hub for supporting a chair on legs substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Chair Construction This invention relates to chair construction. A swivel-type chair generally consists of a seat asembly rotatably supported by an upright on a leg assembly. Usually means are included for adjusting the height of the seat, for example by the use of a screw arrangement. Here we are particularly concerned with the leg assembly. Commonly this comprises a central hub with a central connection for the upright and three, four or even five legs radiating from it. When made of metal the legs and hub may be cast as a single unit. When using wooden legs, as for example in reproduction furniture, the legs are each made separately and secured to a separate common hub. It is difficult, if not impossible, to make a wooden hub of reasonable size with sufficient strength, particularly with larger numbers of legs; a metal hub is therefore usually used, commonly of welded steel construction. The conventional hub is costly to manufacture, requiring expensive tooling-up, and the necessary manufacturing equipment is difficult to modify for variations in design and for the production of hubs to accommodate differing numbers of legs. Also, such conventional hubs are generally heavy, and also unslightly and thus unsuitable for many designs, particular reproduction types. According to one aspect of the present invention there is provided a hub for supporting a chair on legs comprising a monolithic block of material with means at its centre for securing to an upright and peripherally disposed formations for engagement with legs disposed generally radially of the hub. The hub may be generally cylindrical, of substantially circular or polygonal cross-section. Preferably the formations take the form of axially extending slots. The slots can be of dovetail or other re-entrant cross-section to accommodate complementary formations on the legs to provide a good mechanical "key" for securing the legs, although in most cases it will be desirable to employ an adhesive or cement in addition. The means for securing the upright may be of central bore in the hub in which the upright can be located. Although it is possible to form the hub from cast metal, it is preferred to employ a plastics material, for example a glass-reinforced thermosetting material such as DMC (a Dough Mould Compound of heat-cured polyester and glass). In another aspect the invention provides a chair leg assembly comprisng a hub as described above, with a leg secured in each slot. The invention also extends to a chair including such a leg assembly. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an exploded perspective view of the leg assembly and upright of a swivel chair; and Figures 2, 3 and 4 are respectively plan, elevation and underneath views of the hub shown in Figure 1. In the arrangement shown in Figue 1, a hub 1 is formed as a single block of DMC, of generally cylindrical shape. It has a central bore 2 which is slightly tapered to receive the tapered end of a support and adjustment assembly 3. The assembly 3 has an outer tube 4 with the tapered lower end 5, the upper end of the tube being fitted with an internally threaded insert 6 in which is received the threaded lower end of an upright 7. The upper end of the upright is secured to a seat assembly (not shown), and the height of the seat is adjustable by screwing the upright into and out of the insert. Its travel is limited by an adjustable ring 8 and a disc 9 (of low-friction plastics material) screwed to the lower end of the upright. The hub 1 also has five axially extending slots 10 disposed at 720 intervals around its periphery (as more clearly seen in the plan, elevation and underneath views of Figures 2, 3 and 4). The slots are open at the lower end. Each slot 10 is of dovetail cross-section to receive the similarly formed end 11 of a respective leg 1 2. The slots 10 (and ends 11) are tapered towards their upper ends, to ensure that when assembled, the legs fit tightly into the slots, and to facilitate removal of the hub from its mould during manufacture. The hub also has flats 1 3 adjacent the slots so that the legs can fit snugly against it. A circular retaining plate 14 is secured to the legs by screws 1 5 through tabs 1 6 extending from the plate, to provide additional rigidity and a neat finish for the underside of the assembly. Claims

1. A hub for supporting a chair on legs comprising a monolithic block of material with means at its centre for securing to an upright and peripherally disposed formations for engagement with legs disposed generally radially of the hub.

2. A hub according to claim 1, in which the hub is generally cylindrical and of substantially circular or polygonal cross-section.

3. A hub according to claim 1 or 2, in which the formations are axially extending slots.

4. A hub according to claim 3, in which the slots are of dovetail cross-section.

5. A hub according to any one of the preceding claims, in which the means for securing the upright is a central bore in the hub in which the upright can be located.

6. A hub according to any one of the preceding claims, formed of plastics material.

7. A hub according to claim 6, in which the plastics material is a glass-reinforced thermosetting material.

8. A hub for supporting a chair on legs substantially as herein described with reference to the accompanying drawings.

9. A chair leg assembly comprising a hub according to any one of the preceding claims, with a leg secured in each of said formations.

10. A chair including a leg assembly according to claim 9.