RECLINING CHAIR FRAME WITH ADJUSTABLE SEAT AND BACK-REST, IN PARTICULAR FOR USE IN DENTISTRY

Abstract: The reclining chair frame disclosed is principally for use in dentistry, and has an adjustable seat (2) and back-rest (3), the seat (2) connecting with the base (1) at one side, or both, by way of two struts (4, 5) that converge slightly toward the top ends and form an articulated quadrilateral with the seat (2) and the base (1). One of the struts (4) extends upwards and is hinged to a connecting link (6), this hinged in turn to the back-rest (3) at a point (7) lower than the point (8) at which the back-rest (3) is hinged to the seat (2). An actuator (14) impinges on the remaining strut (5), rotating it about the pivot (12) by which it is anchored to the base (1) in such a way that the chair is taken through an infinitely variable range of adjustments from a normal sitting position, with the back-rest (3) upright, to a fully reclined position in which the back-rest (3) is disposed substantially horizontal and the seat (2) ultimately positioned above the level of the back-rest (3).

Description: The invention relates to a reclining chair according to the first part of claim 1. Such a reclining chair is disclosed by the FR-A-2 339 390. Conventional chair frames with adjustable seat and back-rest, especially those installed in dentists' surgeries, consist fundamentally of a base, seat, and back-rest; the seat is carried by the base, and the back-rest hinged to the seat. Such chairs provide three basic adjustments, namely, raising and lowering of the seat (height), back-rest angle (rake), and simultaneous rotation or tilt of seat and back-rest (posture). Separate controls are provided for the three types of movement. A chair of this kind is singularly useful for the purposes of dental treatment, since it enables the dentist to manoeuvre the patient from a sitting to a reclining position as and when necessary, according to the type of treatment being carried out. Nonetheless, the conventional design of chair frame presents the drawback that increased rake causes the patient's head to move away through, in effect, a circular arc, thus becoming distanced from the point occupied by the dentist. This is illustrated, for example, in the French publication N. 2.339.390 in which the patient's chair is provided by a reclining motor which acts on the back, seat aid leg rests in order to realize a combined did coordinated movement; the motor acts on two struts which are rotated in a counterclockwise direction, when the chair is seen from the side whereby the back is positioned to the left of its pivot and the leg rests to the right thereof, this producing a moving back of the extremity of the back rest with respect to the dentist operating point. This problem is heightened by the fact that a modern surgery contains numerous items of equipment, laid out generally in a circumferential array having its centre at the spot normally occupied by the dentist (central operating point), in the interests of ergonomic efficiency. It follows therefore, that if the position of the patient's head is altered, the dentist must necessarily stray from his/her preferred station, i.e. the point from which all of the various items of equipment can be reached without difficulty. In practice, certain operations are carried out with the patient in a sitting position, whereas others require a reclining position; it becomes impossible, therefore, to establish an exact station for the dentist to adopt with the end in view of laying out equipment to best advantage. Another requirement that may be encountered during a session of treatment is that of having to arrange the patient in haste with his/her head positioned on a level below that of the legs. This posture, known in medical circles as the Trendelenburg, is provided for in certain conventional chairs, but obtainable only by way of additional movements and controls that complicate the construction of the chair, and besides the disadvantage of a complicated structure, one has the drawback that a dentist will in practice use such a facility but rarely, and thus not always achieve its operation with the requisite speed. The object of the invention is that of embodying a reclining chair frame with adjustable beat and back-rest, in particular for use in dentistry, that is free from the drawbacks thus described. The solution to the problem is disclosed in the second part of claim 1. One of the advantages of the invention consists in having succeeded in embodying a simple, functional structure in which rotational movement of the back-rest is accompanied by forward movement of the seat, thereby confining the movement of the patient's head to a vertical path, for all practical intents and purposes. Another advantage of the chair disclosed is that the facility exists of obtaining Trendelenburg position utilizing a single, universal control that reclines the back-rest and moves the seat forward in one and the same manoeuvre. The dimensions of the struts are such, that the back-rest is taken through infinitely variable rake from a first, essentially vertical position to a second, essentially horizontal, while the seat is angled progressively in relation to the back-rest to the point where it assumes an elevated position with respect thereto. A further advantage of the invention is that one has the facility of using the same single control to produce rotation of the foot-rest into a horizontal position, simultaneously with the reclining movement of the seat and back-rest. The invention will now be described in detail by way of example with the aid of the accompanying drawings in which: fig 1 is a side elevation of the reclining chair frame disclosed, viewed in the configuration assumed with the patient in a sitting position; fig 2 is the same side elevation, showing the chair in the configuration assumed with the patient in a reclining posture. With reference to the accompanying drawings, a chair with adjustable seat and back-rest of the type, in particular, used in dentistry, consists essentially in a base 1, and two supports denoted 2 and 3 which are hinged together and carry the seat and back-rest proper. For the sake of simplicity, these supports will be directly referred to as the seat 2 and back-rest 3, respectively. The seat 2 is supported by the base 1 in such a way as to permit of its being raised and lowered; since, however, the type of base which produces this up and down movement of the seat 2 constitutes prior art, no description is included. According to the invention, the seat 2 is carried by the base 1 on a pair of struts 4 and 5 that converge slightly toward the top and are hinged to the base 1 via pivots denoted 10 and 12, and to the seat 2 via pivots denoted 11 and 13, respectively. The struts 4 and 5, the section 1a of the base 1 to which they are pivotably attached, and the seat 2, combine to create an articulated quadrilateral. Depending on the individual type of chair, one may have two struts 4 and 5 at either side of the seat, or at one side only. The seat 2 consists in a horizontal part 2a to which the top pivots 11 and 13 of the struts 4 and 5 are anchored, and two upright side pieces 2b (or one) each one of which provides the anchor for the pivot 8 of the back-rest 3 (one such side piece 2b only is visible in the drawings). In the example illustrated, each strut denoted 4 extends upward through a stretch 4a the projecting end 4b of which is hinged via a pivot 6a to one end of a connecting link 6. The remaining end of the connecting link 6 is hinged to the back-rest via a pivot 7 positioned at a lower level than the main bearer pivot 8 between seat and back-rest. The struts denoted 5 in the example illustrated are interconnected at respective points intermediate of their hinge pivots 12 and 13 by a horizontal bar 9 to which one end of an actuator 14 is hinged, its other end 15 pivoted to the section 1a of the base 1 that provides the anchor for the bottom pivots 10 and 12 of the struts 4 and 5. The actuator 14 appears in the drawings as a fluid power cylinder, though its ultimate embodiment is a matter of choice, the requirement being simply that the two relative pivots 9 and 15 can draw together and spread apart. The dimensions of the struts 4 and 5 and of the connecting link 6, and the distance separating the hinge pivots 7 and 8 associated with the back-rest 3 will be proportioned according to the dimensions of the chair as a whole. At all events, the dimensions and the clearance in question are established such that a given point on the moving back-rest 3, which coincides, in effect, with the position of the head of a patient of average height (denoted A in the drawing, by way of example), will be displaced, for all practical intents and purposes, through a given vertical plane. Marginal deviation from the vertical can be considered acceptable, however. The same dimensions and clearance must also be such that a single stroke of the one actuator 14 produces rotation of the adjustable back-rest 3 from a first, substantially vertical limit position, in which the patient will be settled in a sitting posture (see fig 1) and the angle of the seat is that nearest to the horizontal, through an infinitely variable range of positions in which the angle of rake increases and the seat traverses forward so as to offset the vertical position of the patient's head, remaining at substantially the same angle nonetheless, to a second limit position, in which the back-rest 3 is almost horizontal, the patient assumes a reclining posture (see fig 2), and the seat 2 is discernably angled and raised above the level of the back-rest. Thus, rotational movement of the back-rest 3 occurs simultaneously with the traversing movement of the seat 2; however, given the difference in length of the struts 4 and 5, the angle of the seat is more accentuated and more swiftly assumed as the back-rest approaches its limit position. This same position is known as the Trendelenburg, and is gained only during the closing stages of the extending stroke of the fluid power cylinder 14. In effect, the Trendelenburg position will be used only rarely in the general course of events, but if required, it suffices simply to take the fluid power cylinder 14 to full extension, without operating any special or auxiliary controls. In the example illustrated, the strut denoted 5 is rigidly associated with a respective connecting link 21, the remaining end of which is hinged to one end of an elongated member 22 via a relative pivot 22a. The elongated member 22 is supported and guided by two round horizontal and parallel bars 24 carried by two vertical lugs 23 attached to the bottom of the flat part 2a of the seat 2. The projecting end 22a of the elongated member 22 provides the slidable support for a foot-rest 20 hinged about a pivot 20a at the front edge of the flat part 2a of the seat 2. The connecting link 21 is located above the relative strut 5 and is of length such as to produce gradual rotation of the foot-rest 20 from an angled position (fig 1) to an almost horizontal position (fig 2) as the actuator 14 progressively extends. Such a change in position occurs in harmony with that of the chair as a whole, the movement of the foot-rest enhancing effectiveness of the position gained by the back-rest 3 and the seat 2, as the patient reclines fully with his/her legs in a horizontal position above the level of the head A. Accordingly, the chair is adjustable, by operation of the actuator 14, through an infinitely variable range of positions, those described above being the most worthy of note. The succession of movements and positions of the seat 2 thus illustrated is obtained by virtue of the special linkage of the struts 4 and 5, and of their dimensions, within the framework of the articulated quadrilateral. As the drawings illustrate, the hinge pivot 10 of the one strut 4 is located at a lower level than the corresponding pivot 12 of the other strut 5, whilst the length of the self-same strut 4 between its two pivots 10 and 11 is less than that of the second strut 5 between its pivots 12 and 13; the two struts 4 and 5 also exhibit a slight upward convergence, as aforementioned. Accordingly, during the greater part of the struts' rotation, the hinge pivots 11 and 13 anchored to the seat 2 will remain substantially at the same relative height, whilst in the final stages of rotation, the pivot 13 nearest the foot-rest will be raised to a greater height than that of the pivot 11 nearest the back-rest.

Claims: Reclining chair with a height adjustable seat rest (2) and a back rest (3), in particular for use in dentistry, comprising: a base (1) constructed to support and operate the height adjustable seat to which the back rest is pivotally attached; at least one pair of struts (4, 5), lying in a vertical plane, hinged to said base (1) and to said seat rest (2) to form an articulated quadrilater with the base and seat rotating at least between a first limit position, an intermediate position and a second limit position, in said first limit position the back rest being substantially vertical and the seat rest substantially horizontal, in said intermediate position the back rest being substantially horizontal and the seat likewise substantially horizontal, and in said second limit position the seat being angled and raised above the level of the back rest, which remains substantially horizontal; an extendable and retractable actuator (14) hinged at one end to the base and at the other end to one of said struts; characterized by the fact that said struts (4, 5) are hinged at their opposite side to the base and to the seat, converging slightly in the upwards direction; a connecting link (6), one end of which is pivotably attached to a top most part of one of said struts, the other end of the connecting link (6) being attached rotatably to a pivot (7) anchored to the back rest (3), in such a way that the two pivoted ends (6a, 7) of the connecting link (6) are located one on each side of a transverse vertical plane passing through the pivot (8) connecting the back rest and the seat, when the back rest is in an upright position; said struts (4, 5), connecting link (6) and actuator (14) being attached and positioned in such a way that a point near to the top end of the back rest moves substantially in a vertical line when the struts are rotated in a clockwise direction when the chair is seen from the side, whereby the head rest is to the left of the pivot and the foot rest to the right thereof. Reclining chair frame as in claim 1, characterized by the fact that said connecting link (6) is pivotably attached to the strut (4) located nearest to the back rest (3). Reclining chair frame as in claim 1, characterized by the fact that said actuator (14) is hinged at one end to the base (1a) and at the other end to the strut (5) not connected to the back rest and in a point between the pivots (12, 13) by which this strut is associated to the base and to the back rest respectively, in order to realize said clockwise rotation. Reclining chair frame as in claim 1, characterized by the fact that said one of said struts is the strut (4) nearest to the back rest (3) and the distance measured between its base and seat pivots (10, 11) is less than the distance measured likewise between the corresponding pivots (12, 13) of the other strut (5), and by the fact that the pivot (10) that connects the said one strut (4) with the base (1) is located at a level lower than that of the pivot (12) that connects the other strut (5) with the base.

Inventors: CASTELLINI, FRANCO
Applicants: CASTELLINI S.P.A.
Application year: 1986
Main classification: A61G15
IPC codes: A61G15, A61G9