TECHNICAL FIELD

This invention relates to a portable chair for use in medical treatment or examination, obstetrics, minor surgery, chiropody, or dentistry, for example.

DISCLOSURE OF INVENTION

In one aspect the invention provides a portable collapsible chair comprising a base structure, a superstructure which comprises a seat and a back rest, the superstructure being mounted on the base structure so as to be pivotable about a horizontal axis and a jack which acts between the superstructure and the base structure and is actuable to tilt the superstructure, the jack being releasable so as to allow free pivoting of the superstructure.

In another aspect the invention provides a portable collapsible chair having a superstructure which is supported by a base structure so as to be pivotable about a horizontal axis and which is releasably connected to the base structure by connection means including a bar carried by the superstructure and a latching mechanism carried by the base structure. Preferably, the base structure comprising a front part and a rear part which are pivotable relative to each other about a horizontal axis and between which the bar is jammed by the latching mechanism so as to prevent mutual pivoting.

In a further aspect the invention provides a portable collapsible chair comprising a superstructure pivoted to a base structure and carrying a bar which is releasably connectable to the base structure by a latching mechanism, the latching mechanism comprising a hook-shaped latch pivotably mounted on an eccentric which is rotatable to trap the bar securely between the latch and the base structure.

The invention also provides a chair having at least one leg rest mounted on a rotatable shaft having a socket at one end, a shaft having a polygonal cross-section being axially movable, rotationally fixed, and coaxial with the socket, the polygonal shaft being movable to and from a position in which it engages in the socket so as to locate the rotatable shaft in a selected angular position corresponding to a desired angle of the leg rest.

Further preferred and optional features of the invention will be apparent from the following description.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described further, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a portable medical chair;

Figure 2 is a side view of the chair;

Figure 3 is a perspective view of the chair in the folded condition;

Figures 4 and 5 are diagrammatic side views of the chair, illustrating means for locking the seat of the chair in position;

Figures 6 and 7 diagrammatically illustrate a: detail of the locking means;

Figure 8 is a diagrammatic perspective view of the chair, with certain parts omitted for clarity, illustrating means for tilting the upper part of the chair; and

Figure 9 is an exploded perspective view of a catch mechanism allowing adjustment of the angle of a leg rest on the chair.

BEST MODE FOR CARRYING OUT THE INVENTION

The chair illustrated has a base structure 1 comprising a rear part 2 and a front part 3 which are mutually pivotable about a horizontal axis. The rear part 2 comprises a rear frame 4, having two legs 6 connected by a cross-piece 7, and side pieces 8 fixed to the upper ends of the respective legs. The front part 3 has two legs 9 connected by a cross-piece 11 and pivoted to the respective side pieces 8 at 12.

The front part 3 is pivotable between an operative position (Figures 1 and 2), in which the upper end portion of each of its legs 9 bears against an abutment surface 13 on the associated side piece 8, and an inoperative position (Figure 3) for storage or transport, in which the upper end portion of each leg 9 bears against an abutment surface 14 on the associated side piece 8, with the legs 6 and 9 being approximately

parallel. The front part 3 can be locked in the operative position by means of a tie bar, as described below.

The chair also comprises a superstructure 16 which is pivotable relative to the base structure 1 about a horizontal axis. The superstructure includes a seat 17 having a frame 18 with side members 19 which are pivoted to the respective side piece 8 of the base structure at 21. Behind the pivot point 21, each side member 19 is cranked upwards to form a back rest support portion 22. The seat frame 18 is additionally connected to the base structure 1 by a tilting mechanism, described in detail below.

The superstructure 16 also includes a back rest 23 having a frame 24 with side members 26 pivoted to the portions 22 of the seat frame at 27. In the operative position shown in Figures 1 and 2, each side member 26 bears on a rear flange (not visible) on the associated portion 22. The back rest 23 is pivotable to an inoperative position (Figure 3) in which it is approximately parallel to the seat 17.

A head rest 28 is carried by a pillar 29 which fits iii a bracket 31 on the rear surface of the back rest 23. When the chair is folded up, the head rest 28 is removed from the bracket 31 and its pillar 29 is inserted into a carrying bracket 32 on the back rest frame 24 (or on some other convenient part of the chair).

The chair has two arm rests 33. To facilitate entering and leaving the chair each arm rest (or at least one of them) is pivotally connected to the chair. For this purpose the rear of the arm rest is cranked downwards and is pivoted at 34 to the associated support portion

22, which carries a flange 36 against which the arm rest is to bear.

The superstructure 16 is additionally connected to the base structure 1 by a jack 37 connected between the seat 17 and a tie bar 38 which is releasably locked to the base structure in a manner to be described below. In the illustrated embodiment the jack 37 is a double screw jack having oblique struts 39 whose lower ends are pivoted to the tie bar 38 and whose upper ends are pivoted to respective nuts 41 running on respective right hand and left hand screw threads 42 on an actuating rod 43 rotatably mounted in brackets 44 on the seat frame. The actuating rod 43 is turned by a handle 46 in order to vary the tilt of the superstructure 16 about the axis 47 of the pivots 21. The handle 46 is hinged to the rod 43 so as to be foldable to a position (Figures 2 and 3) in which it lies alongside the seat 17 and can be located there by a clip 48 on the seat frame.

The tie bar 38 is releasably connected to the base structure 1 by a pair of latching mechanism 49, one at each end of the bar 38. When latched, the tie bar 38 is jammed between the legs 9 of the front part 3 and the side pieces 8 of the rear part 2, thereby rendering the base structure 1 rigid. Each latching mechanism 49 comprises a hook-shaped latch 51 freely pivotable on an eccentric 52 pivoted at 53 (coaxial with pivot 12) to the associated leg 9. When unfolding the chair from the inoperative position shown in Figure 3 to the operative position shown in Figures 1, 2, and 5, an intermediate ^* stage (Figure 4) is reached in which the jack 37 hangs freely beneath the seat. As the seat is raised further, the tie bar 38 can be brought up to lie between the side pieces 8 and the legs 9 and hooked there by the latches 51 (Figures 5 and 6). The latches 51 are then raised by

turning each eccentric 52 by means of an associated lever 54 to the over-centre position shown in Figure 7 so that the tie bar 38 is forced between the side piece 8 and the leg 9.

Two leg rests 56 are mounted on the front of the seat

17. Each leg rest 56 is hinged to an arm 57 fixed on a square shaft 58 which is rotatably mounted on the front of the seat frame 18. At its outer end the shaft 58 is fixed to a socket 59 having internal axial fluting (Figure 9). An axially movable, rotationally fixed polygonal (hexagonal) shaft 61 is mounted on the seat frame coaxially with the socket 59 and is urged towards the socket by a helical compression spring 62 acting between an abutment 66 on the seat frame and a circlip 63 in a groove 64 in the shaft 61. The shaft 61 extends through the abutment 66 and is connected to a lever 67 by a pivot pin 68. When the lever 67 is vertical, as shown in Figures 1, 2, and 9, its one side rests against the abutment 66 and the hexagonal shaft 61 engages in the socket 59, thereby locking the arm 57 of the leg rest 56 in a selected angular position. If the leg rest is to be moved to a different angle, the lever 67 is pivoted until it extends horizontally and its end surface 69 rests against the abutment 66. Consequently, the pivot pin 68 pulls the shaft 61 until its hexagonal cross-section is no longer engage with the fluting of the socket 59, whereupon the leg rest 56 can be moved, since the shaft 58 is rotatable. By restoring the lever 67 to the vertical position the leg rest can be again locked in the selected position.