Chair For Use In Dentistry

Abstract

An odontological chair has, in addition to the usual raisable seat and tiltable backrest longitudinally slidable seat and backrest frames. Movement of these two frames is effected in opposite directions and by different amounts automatically as the backrest is tilted, and proportionately to the angle of tilt, so that the frames approach each other as the backrest is lowered, avoiding movement of the patient's body on the seat and backrest, which would otherwise occur. In a modification the entire seat structure is moved horizontally as the backrest is raised or lowered, to prevent horizontal displacement of the patient's head.

Description

This invention relates to chairs for use in dentistry.

Known odontological chairs generally comprise a fixed base supporting a seat which is adjustable in height and a variable tilt backrest which is pivotally connected to the rear end of the seat. In known chairs of this type, herein referred to as the "type specified", the structures of the seat and of the backrest are interconnected by hinges, permitting angular movements about a horizontal axis.

A disadvantage of such a known arrangement is that the angular movements of the backrest relative to the seat, which take place about the axis of the hinges, are not followed by corresponding movements of the body of the patient, whose trunk rotates relative to the pelvis and other lower limbs which are resting on the seat, about an axis of rotation which does not coincide with that of the backrest of the chair. Consequently, during lowering movements of the backrest the trunk of the patient moves relative to the backrest, sliding upon the surface of the latter. In addition, the head of the patient moves relative to the head-rest which is usually integral with the backrest, so that, after the backrest has been lowered, a general adjustment of the head-rest and auxiliary apparatus, for example lighting apparatus, connected to the chair, is usually necessary.

An object of this invention is to avoid the above-mentioned disadvantages, by providing an odontological chair of the aforesaid type, which is of simple, sturdy and economical construction and easy to install, and in which there is automatic compensation for the relative movements between seat and backrest upon tilting of the backrest.

Another object of the invention is to provide a chair of the aforesaid type in which relative movement between the resting surfaces of the seat and of the backrest and those portions of the patient's body which rest upon these surfaces are eliminated or at least substantially reduced during relative angular movements between the seat and the backrest.

It is a further object of a preferred embodiment of the invention to provide an odontological chair as aforesaid which allows the position of the patient's head to remain substantially unchanged, in its vertical projection, upon rocking movement of the backrest, thereby rendering unnecessary any adjustment of the distance between the patient's head and the dentist's working seat and his working instruments.

A further object of the invention is to provide a chair of the aforesaid type which is easy and convenient in use and simple to adjust.

According therefore to the present invention there is provided an odontological chair of the type specified, wherein the seat has a support structure upon which a movable frame is mounted for longitudinal sliding movement, said frame carrying seat padding, and the backrest has a frame carrying backrest padding which is slidable along two parallel tubular supports articulated to the rear of the seat support structure, and including means for inducing, as a result of tilting of the backrest relative to the seat, longitudinal sliding movement of the backrest frame and of the seat frame in opposite directions and by different amounts, so as to move the said frames together proportionately with lowering of the tiltable backrest relative to the seat support structure and to move the frames apart proportionately with raising of the backrest relative to the seat support structure.

The invention will be more clearly understood from the following description, given by way of non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an odontological chair according to one embodiment of the invention;

FIG. 2 is a diagrammatic perspective view of the chair without its coverings;

FIG. 3 is a diagrammatic plan view of the lower portion of the chair;

FIG. 4 is a longitudinal section taken along the line IV--IV of FIG. 3;

FIG. 5 is a transverse section taken along the line V--V of FIG. 4;

FIGS. 6 and 7 are two diagrammatic side views, illustrating two different operative positions of the chair according to a variant of the embodiment of FIGS. 1 to 5;

FIG. 8 is a frontal perspective view of the central portion of an odontological chair according to the embodiment of FIGS. 6 and 7;

FIG. 9 is a lateral perspective view of the chair illustrated in FIG. 8, with its backrest in an upright position;

FIG. 10 is a similar view to that of FIG. 9, illustrating the backrest in a lowered position, and

Throughout the drawings the same reference numerals are used to designate the same or corresponding component parts. Reference will first be made to the chair shown in FIGS. 1 to 5.

The odontological chair in FIGS. 1 to 5 has a fixed base 1 adapted to be anchored to the floor. On one side of the base 1 there are articulated, by means of respective parallel horizontal pivot pins 2, 2', a lower pair of levers 3, 3', connected to an upper pair of levers 5, 5' by means of pivot pins 4, 4' to form a pantograph linkage in a vertical plane. An identical pantograph linkage is arranged symmetrically on the other side of the base 1, its respective levers 3, 3' and 5, 5' being parallel to the corresponding levers of the first pantograph.

The upper levers 5, 5' of both pantographs are articulated by means of pivot pins 6, 6' to a supporting cross member 7 which supports the seat part of the chair.

The adjacent ends of the pantograph levers 3, 3' and 5, 5' are furnished with toothed sectors 3a, 3a', and 5a, 5a' respectively, which mesh with each other to increase the stability of each pantograph linkage.

The pivot pins 4 of the two pantograph linkages support a first horizontal U-shaped yoke 8 which supports an electrically driven reduction gear 9. The opposite pivot pins 4' of the two pantograph linkages support a second horizontal U-shaped yoke 11, which in turn carries a nut co-operating with a worm screw 10 connected to and driven by the said reduction gear 9 (FIG. 4).

By rotating the screw 10 in one direction or the other the pivot pins 4, 4' and 5, 5' of the two pantograph linkages are drawn together or moved apart, respectively raising or lowering of the chair seat relative to the base 1. The use of U-shaped yokes 8 and 11 permits reduction of the overall length of the maneuvering screw 10.

To the supporting cross member 7 there are affixed two parallel longitudinal members 12 interconnected by two cross pieces 13, 14 and by a front plate 15. Respective bearings 16, 17 are secured to the undersides of the two cross pieces 13, 14. A worm screw 18 which is rotatable, in one direction or the other, by an electrically driven reduction gear 19 supported therefor by the front plate 15, is journaled in the bearings 16, 17.

Respective tubular guide sleeves 20 are attached to the outer sides of the longitudinal members 12. Respective horizontal parallel rods 21 run within the respective guide sleeves 20. Respective pairs of shaped blocks 22, 25 are attached to the opposite ends of the two rods 21 and are in turn affixed to a mobile seat frame 24 which supports the padding A of the seat (FIG. 1) and which is movable longitudinally.

To the two rear ends of the two longitudinal members 12 there are affixed two parallel brackets 12a which form, with the said longitudinal members, two forks in which respective horizontal hinge pins 26 are supported. Two flat lugs 27a formed at the ends of two parallel tubular supports 27 are pivotally attached to the longitudinal members 12 by means of the hinge pins 26. A pair of tubular elements 28 are arranged for sliding movement on the tubular supports 27, and a backrest frame 29 is carried by the tubular elements 28 (FIG. 2). The frame 29 supports the padding B of the backrest.

The entire backrest is therefore hinged to the seat frame 24 for rocking movement about the horizontal axis of the said pins 26; in addition the backrest frame 29 can run longitudinally upon the supports 27 so as to approach or move away from the hinge axis of the backrest.

Similarly, the movable seat frame 24 can move longitudinally relative to the fixed structure of the seat so as to approach or move away from the said hinge axis of the backrest.

Two crank arms 30 are formed integrally with the respective lugs 27a and project below the seat frame 24 (FIGS. 2 and 4). The crank arms 30 are pivotally attached at their free ends, by means of pins 31, to two links 32 which in turn are pivotally connected, by means of pins 33, to a cross member 34. The cross member 34 carries centrally a nut 35 which is threaded on to a screw 18.

The links 32 carry, near the cross member 34, respective pivot pins 36 by which respective stay rods 37, of curved profile, are pivotally attached to the said links 32. The stay rods 37 are articulated at their other ends to respective pins 38 on the movable frame 29 of the backrest.

Rotation of the screw 18 in either direction therefore controls the pivotal movement of the supports 27 of the backrest, while simultaneously controlling sliding movement of the movable frame 29 of the backrest so that the latter approaches the hinge axis of the hinge pins 26 as the backrest is lowered; conversely, if the backrest is raised, the movable backrest frame 29 moves away from the hinge axis of the said pivot pins 26.

The screw 18 has a front portion 18a, having an opposite hand of rotation and a smaller pitch than the hand and pitch of the rear portion 18b (FIG. 3). This front part 18a co-operates with a nut 39 carried by a transverse member 40 which is attached to the movable seat frame 24. In consequence, the rotation of the screw 18 also causes the movable seat frame 24 to move towards the hinge pins 26 when the backrest is lowered, in order to compensate for the movement of the patient's body, and similarly causes the movable seat frame 24 to move away from the hinge pins 26 when the backrest is raised. The extent of movement of the backrest frame 29 on the supports 27, 27 is such that the patient's head remains in substantially the same position on the padding B for all positions of the backrest.

The seat frame 24 and the backrest frame 29 therefore make contrary movements, by different amounts, such as to avoid relative sliding movement of the patient's body on the seat and backrest as the backrest is raised and lowered.

IN FIGS. 8 to 10 there is shown a chair according to a variant of the embodiment shown in FIGS. 1 to 5, in which the whole structure is movable in relation to the fixed base 1. The base 1 and the means which control vertical movement of the chair structure are the same as those previously described with reference to FIGS. 1 to 5.

The supporting cross member 7 is provided with two parallel longitudinally extending members 44 along its two sides. The ends of the two members 44 project beyond the member 7 and carry four cross rollers 45 with horizontal axes (one of which is indicated in broken outline in FIG. 8) which engage in respective parallel longitudinal channels 46 (FIG. 9) formed in two movable longitudinal members 12' placed on the outside of the two sides of the fixed chair structure.

The two movable longitudinal members 12' are connected together either by means of three upper cross pieces 13', 13, and 14 and/or by means of a front plate 15 which carries a reduction gear 19. The reduction gear 19 controls the rotation of a worm screw 18, as previously described, the worm screw 18 being journaled in bearings. 16', 16 and 17 carried beneath the respective cross pieces 13', 13 and 14.

The two movable longitudinal members 12' support two laterally outwardly projecting pairs of shaped transverse rollers 20a having transverse axes and acting as guides for two longitudinal guide rods 21 supporting two pairs of shaped longitudinally spaced support blocks 25 and 25' upon which the movable padded frame (not shown) of the seat is supported for longitudinal movement.

To the front ends of the guide rods 21 two further small blocks 22' are secured, the blocks 22' being connected to each other by a lower cross piece 40 which supports a nut 39 engaged with a front portion 18a of the screw 18, having a short pitch.

A cross piece 47 is located between the two longitudinal members 44 and is secured to the cross member 7. The cross piece 47 carries a fixed nut 48 which engages a center portion 18b of the screw 18, having a long pitch of the same direction as the pitch of the front portion 18a.

The screw 18 has in addition a rear portion 18c having a medium pitch, intermediate that of the portions 18a and 18b, with a direction contrary to that of the other two portions 18a and 18b. The rear portion 18c engages a nut 34 supported by a movable cross piece 35 to which two links 32 are pivotally connected, the other ends of the links 32 being pivotally connected to respective crank arms 30 attached to respective tubular supports 27 for the backrest. The tubular supports 27 are attached to the rear ends 12'a of the movable longitudinal member 12' by way of respective hinge pins 26 defining a horizontal hinge axis.

Respective curved stay rods 37 are pivotally connected to the movable cross piece 35, the rods 37 being connected at their upper ends (not shown) to the movable backrest frame 29, upon which backrest padding (not shown) is carried.

The chair shown in FIGS. 8 to 10 operates as follows.

Supposing the backrest to be initially in an upright position, as illustrated in FIG. 6, the screw 18 is rotated in such direction as to induce lowering of the backrest. As a result of such rotation of the screw 18 and the engagement of the center portion 18b of the latter in the fixed nut 48, the screw 18 and the two movable longitudinal members 12' move axially forwards causing the whole chair to travel longitudinally forwards relative to the base (FIG. 10). At the same time the front nut 39 is displaced along the front screw portion 18a of short pitch and causes rearward movement of the rods 21, so that the seat frame is moved longitudinally relative to the movable longitudinal members 12' towards the hinge pins 26 of the backrest. Also at the same time the rear nut 35 is displaced along the rear screw portion 18c of medium pitch, causing lowering of the backrest with consequent sliding displacement of the movable backrest frame 29 towards the axis of the hinge pins 26 by the action of the stay rods 37, as previously described.

The effect of these combined movements, illustrated diagrammatically in FIGS. 6 and 7, is to ensure that the patient's head C remains in substantially the same vertical transverse plane as the backrest tilts. In FIG. 6 the vertical projection of the patient's head C on to the horizontal chair supporting surface is initially at the position C' and would be displaced to C" if the backrest B tilted alone, as indicated by broken lines. By the means just described, however, lowering of the backrest B is accompanied by longitudinal compensating horizontal displacement of the entire chair structure, including the seat A, in this case forwards, by an amount D such as to compensate for the movement backwards of the vertical projection of the head C, so that the patient's head C remains in the same vertical plane (FIG. 7).

It is not therefore necessary for the dentist to move his working position or his working seat ro to move his fixed working instruments to bring them near the patient's head after tilting of the backrest, since the distance between the said instruments and the head of the patient has remained virtually unchanged.

It will be appreciated that details of specific embodiments of the invention may be varied widely from those described and illustrated without departing from the scope of the invention, as defined in the following claims.

Claims

I claim:

1. An odontological chair having a fixed base, raisable seat supported on the base, means varying the height of the seat relative to the base, a variable tilt backrest pivotally connect the rear end of the seat, and means varying the tilt of the backrest to the seat, wherein:

the raisable seat comprises a support structure, a seat frame carried by the support structure and movable longitudinally thereon, and seat padding carried by said seat frame;

ii. the backrest comprises a backrest frame; backrest padding carried by the frame; backrest supports on which the backrest frame is longitudinally slidable, and means pivotally connecting the support members to the rear of the seat support structure, and including

iii. means controling the movement of the seat frame, the backrest supports and the backrest frame and inducing, upon pivotal movement of the backrest supports relative to the seat, longitudinal sliding movement of the backrest frame on the backrest supports and of the seat frame in opposite directions and by different amounts, whereby the said frames are moved together upon lowering of the backrest relative to the seat, and are moved apart upon raising of the backrest relatively to the seat.

2. The chair defined in claim 1, wherein the means controlling the movement of the seat and backrest frame comprise a screw having a rear portion and a front portion of shorter pitch than, and opposite hand to, the rear portion, first and second nuts co-operating with said two screw portions, hinged backrest supports, a linkage connecting the first nut to the hinged backrest support to control the angle of tilt of the backrest, means connecting the second nut to the seat frame to control the longitudinal movement of the latter, and stays connecting the first nut to the movable backrest frame to control longitudinal movements of the backrest frame along said backrest supports in opposition to the longitudinal movements of the seat frame.

3. The chair defined in claim 1, wherein the means varying the height of the seat include two pairs of levers arranged in a pantograph linkage, nuts carried by said linkage, a central control screw co-operating with said nuts, and electric drive means connected to the screw to rotate the latter.

4. The chair defined in claim 3, wherein adjoining pairs of levers of the pantograph linkage are provided with toothed sectors meshing with each other to assist stabilization of the linkage. 5. The chair defined in claim 1, and further comprising:

i. a raisable fixed part of the seat;

ii. a fixed cross piece supported by the raisable part;

iii. a fixed nut and two parallel longitudinally extending support members carried by the cross piece;

iv. two longitudinal members forming part of the seat support structure and mounted on the said longitudinally extending support members for movement longitudinally relative thereto;

v. a longitudinal screw supported by the longitudinal members and having a center portion of relatively long pitch with which the fixed nut is engaged, a front portion of relatively short pitch, of the same screw direction as the center portion, and a rear portion, of intermediate pitch, of the opposite screw direction to the front and central portions;

vi. two longitudinal guide rods guiding relative movement of the longitudinal members and supporting the seat frame;

vii. a lower transverse member interconnecting said guide rods;

viii. a second nut carried by said transverse member, and engaging the front screw portion;

ix. a movable cross member carrying a third nut co-operating with the rear screw portion;

x. two links articulated to the movable cross member and controlling the slope of the backrest frame and

xi. two curved stays articulated to the movable cross-member and controlling the longitudinal sliding movement of the backrest frame,

whereby rotation of the screw causes the backrest, variation of the distance between the movable seat and backrest frames, and horizontal movement of the whole seat support structure such as effectively to annul any horizontal displacement of the vertical projection of a patient's head when rested on the backrest.