US3330595A - Chair, especially dentist's chair - Google Patents

Description

July 11. 19 A. G. svARD 3,330,595

CHAiR. ESPECIALLY DENTIST'S CHAIR Filed Jan, 20, 1966 2 Sheets-Sheet 1 INVENTOR. /4L F Gfales 514420 Y r JM July 11, 1967 A. G. svARD 3,330,595

CHAIR. ESPECIALLY DENTISTS CHAIR Filed Jan. 20, 1966 2 Sheets-Sheet 2 I N V EN TOR. 44 F Gib/e6 5 law By r iii 1) United States Patent 3,330,595 CHAIR, ESPECIALLY DENTISTS CHAIR Alf Georg Svtird, Matrosvagen 6, Saltsjobaden, Sweden Filed Jan. 20, 1966, Ser. No. 521,939 Claims priority, applicatiorzssweden, Jan. 25, 1965,

7 Claims. (Cl. 297--71) Existing dentists chairs suffer from a plurality of inconveniences. Chairs in which the patient assumes a sitting posture compel the dentist to work standing and usually in an uncomfortable and fatiguing posture. In a type of chairs, the so called relaxation chairs, the conventional foot-rest is replaced by a projection which makes a relatively small angle with the horizontal. During the treatment the patient places his legs on this projection. The chair is uncomfortable for the patient to sit down because the seat has to be taken from the side of the chair which for many patients requires help from the dentist or nurse. Certain stages of dental treatment require inspection of the oral cavity directly from the front in which case the oral cavity is located too far from the dentist. In order to provide for a better working posture for the dentist, the so called contour chair has been constructed which comprises a horizontal front portion and an even and continuous back portion and in which the position of the head of the patient is varied by means of cushions. This chair has the same drawback as the previously mentioned chair and involves additional problems. For instance, the backrest on being turned downwards draws the clothes of the patient, and the chair does not suit patients of different heights.

The object of this invention is to eliminate the above inconveniences and in addition to provide a construction of a dentists or other chair which in each position allows the patient to assume an anatomically correct posture. Such posture can be maintained during continuous change from sitting to lying position and vice versa.

In its broadest aspect the invention is characterized in that a leg support appertaining to the chair comprises a thigh support and a shank support making an angle with each other and articulated to each other and to a seat in such a manner that the angle between the thigh support and the shank support is increased when the shank support is moved from sitting to lying position. The term sitting position refers to a position in which the upper body of the patient is substantially upright or slightly rearwardly inclined, whereas the term lying position refers to a position in which the upper body of the patient is substantially horizontal.

Due to the fact that the angle between the thigh support and the shank support is increased when the patient is about to assume a lying posture the patient is compelled during this movement to straighten his legs and thereby to compensate for the displacement of the centre of gravity occurring during this movement. Consequently, in this respect the chair adapts itself to the natural move ment which the legs of the human body tend to make on changing from sitting'to lying posture.

To obtain a comfortable sitting position it is suitable that the thigh support in this position is parallel to or on a level with the seat and in lying position makes an angle with the seat so that the thighs of the lying patient, with the backrest turned downwards, make an angle with the upper body of the patient. Such posture is felt comfortable and calming.

In order to ensure that the leg support automatically assumes a proper position on changing of the chair from sitting to lying position, the high support and the shank Ice support may be substantially in the form of a linkage comprising two links having a common pivot, one end of the linkage being articulated to the seat at a place comparatively close to the backrest and the other end being articulated, by means of an additional link, to the seat at or near the front edge thereof, To the same end, said additional link which in the sitting position connects the lower end of the shank support with the seat may in said position make an acute angle with the shank support which angle is increased when the shank support is swung upwards from sitting to lying position.

In order to have the backrest, too, anatomically adaptable to the back of the patient it may comprise an upper section forming a support for the shoulders of the patient and a lower section serving as a support for the small of the back of the patient, said sections being displaceable relative to each other for adaptation to patients having different lengths of the back.

Further, the lower portion of the shank support may be narrower than the upper position so as to make it easier for the patient to sit down on the chair and to allow the dentist to assume a comfortable posture when treating the patient directly from the front.

A further improvement consists in that the backrest is provided with armrests preventing the arms of the patient from falling when the backrest is turned backward.

The invention is described more closely hereinbelow with reference to an embodiment thereof illustrated in the annexed drawing. FIG. 1 is a diagrammatic view of the linkage considered to be formed by the parts of a chair according to the invention. FIG. 2 is a more detailed lateral elevation and FIG. 3 a front elevation of the chair.

In the linkage illustrated in FIG, 1 reference numeral 10 corresponds to the seat of the chair, numeral 12 to a thigh support and numeral 14 to a shank support which via a hinge 16 is connected to the thigh support. The thigh support 12 is articulated to the seat at a pivot 18, and the lower end of the shank support is by means of an additional link 20 articulated to the front edge of the seat. The common pivot of the links 14 and 20 is indicated at 22 in FIG. 1, whereas the pivot at the front edge of the seat is indicated at 24. The pivot 18 is located near the rear edge of the seat to which a pivoted backrest 26 is also articulated.

In the sitting position shown by full lines in FIG. 1 the links 12, 14 make an angle v with each other corresponding to a comfortable sitting posture of the patient with his thighs resting on the thigh support and his shanks resting on the shank support. If now the lower end of the shank support is swung upwards for changing the sitting posture of the patient to a lying position the angle v will be increased and in the lying position amounts to v The links are illustrated in lying positions by chaindotted lines. At the same time the thigh support 12 is swung upwards from a substantially horizontal position to a position in which it makes an angle u with the seat 10. Consequently, if the patient is lying down as the backrest 26 is turned backward about its pivot 28 he will straighten his legs as compared with the sitting posture and corresponding to the increase of the angle v to v thereby compensating for the rearward displacement of the centre of gravity which otherwise would occur due to the backward movement of the patients back. In the lying posture the thighs of the patient are slightly raised corresponding to the angle u, resulting in a comfortable lying posture.

The backrest comprises an upper section 30 forming a support for the shoulders of the patient and a lower section 32 serving as a support for the small of the back of the patient. The sections are displaceable relative to each other for adaptation to patients having different lengths of the back. The upper section 30 is interconnected with the lower section 32 by having one of the sections, for instance, the lower one, provided at its lateral edges with a guide rail 34 which is slidably engaged by a guide bar 36 at either edge of the upper section 30. In order to provide for an improved support for the small of the back of the patient along a greater area, the lower section 32 has an upwardly projecting central portion 38, which fits a central recess 40 in the upper section 30 when the sections 30 and 32 are together.

As shown in FIG. 3 the lower portion of the shank support is narrower than the upper portion so as to provide room for the feet of the patient about to sit down on the chair and for the dentist treating the patient from the front. Consequently, the patient can place himself in front of the chair with one foot on either side of the lower narrow portion of the shank support and then conveniently sit down on the chair.

Provided on either side of the backrest are forearm supports 42 preventing the arms of the patient from falling when the backrest is turned backward. Provided at the upper part of the backrest is a support 44 for the nape of the neck of the patient and an armrest 46 for the dentist. The nape support can be turned about a pivot 48 which may comprise means for locking the nape support in adjusted position. 1

The various adjusting movements for the various parts of the chair may be performed manually, but are considerably facilitated by the use of hydraulic jacks. FIG. 3 illustrates a hydraulic cylinder 50 secured to the lower section 32 of the backrest, and an associated piston 52 which is connected to the upper section 30. This construction allows automatic adjustment of the upper section of the backrest relative to the lower section. For turning the backrest there is provided a hydraulic cylinder 54, FIG. 2, the piston 56 which is articulated to a crank arm 58 which is rigidly connected to the lower end of the backrest and consequently upon movement of the piston in the cylinder is turned about the pivot 28 of the backrest. A further hydraulic cylinder 60 having a piston 62 is provided for turning the shank support upwards and downwards. The downwards movement of the backrest and the swinging movements of the leg supports may be coordinated such that the leg rests are turned up to the position shown by chain-dotted lines at the same time the backrest is turned backward to lying position. These movements are preferably controlled in such a manner that the legs of the patient will be successively straightened to the position v in FIG. 1 while the upper body of the patient is being lowered. This is an anatomically correct manner that prevents material changes in the position of the centre of gravity of the patient during this movement. Corresponding conditions apply when the backrest is to be turned upwards and the patient is to assume a sitting posture.

The chair may be constructed, in a manner known per se, to be lifted and lowered on a foot 64 and may also comprise arm rests 66 to be used in the sitting position.

The chair may be constructed in a manner to permit variation of the angle v by varying the length of the link 20, such as by making this link of two parts, one of which has secured to it a hydraulic cylinder 68 while the other part is connected with a piston 70 displaceable in the cylinder, as indicated in FIG. 1. The arrangement may be such that the links 12, 14 can be adjusted in line with each other or at any desired suitable angle.

The invention is not limited to the illustrated embodiment which is only an example. The upper section of the backrest may be detachable and exchangable so that backrest sections of different lengths may be inserted according to the length of the back of the patient. Instead of hydraulic operation, pneumatic cylinders may be employed or even manually operable cranks acting on screw and nut devices. Various combinations of such operating devices are conceivable.

What I claim is:

1. A chair comprising a seat, a backrest pivoted to the seat, a thigh support articulated at a first point to the seat, a shank support articulated to the thigh support, said supports forming an angle between one another, and connecting means to actuate the lower end of the shank support for swinging it from a sitting position to a lying position, said means comprising a link having one end pivoted at a second point to the lower end of the shank support and its other end pivoted at a third point to the seat, the length of said link plus the straight line distance between said first and third points being greater than the straight line distance between said first and second points when the shank support is in said sitting position so as to augment said angle as the shank support is moved from a position for sitting in the chair to a position for lying therein.

2. A chair as claimed in claim 1, characterized in that the thigh support in sitting position is parallel to or on a level with the seat and in lying position makes an angle with the seat so that the thighs of the lying patient, while the backrest is turned downwards, make an angle with the upper body of the patient.

3. A chair as claimed in claim 1, characterized in that the thigh support and the shank support are substantially in the form of a linkage comprising two links having a common pivot, one end of the linkage being articulated to the seat at a place comparatively close to the backrest and the other end being articulated, by means of an additional link, to the seat at or near the front edge thereof.

4. A chair comprising a seat, a backrest pivoted to the seat, a thigh support articulated to the seat, a shank support articulated to the thigh support, said supports forming an angle between one another, and connecting means between the shank support and the thigh support providing mutual guidance therebetween, the backrest comprising an upper section forming a support for the shoulders of the patient and a lower section serving as a support for the small of the back of the patient, said sections being displaceable relative to each other for adaptation to patients having different lengths of the back.

5. A chair as claimed in claim 4, characterized in that the lower section of the backrest has an upwardly projecting central portion and that the upper section has a corresponding recess.

6. A chair comprising a seat, a backrest pivoted to the seat, a thigh support articulated to the seat, a shank support articulated to the thigh support, said supports forming an angle between one another, and connecting means between the shank support and the thigh support providing mutual guidance therebetween, said shank support comprising a lower portion and an upper portion, the lower portion of the shank support being narrower than the upper portion so as to provide room for the feet of the patient about to sit down on the chair and for the dentist treating the patient from the front.

7. A chair as claimed in claim 1, characterized in that the length of said link is variable.

References Cited UNITED STATES PATENTS 2,617,118 11/1952 Lorenz 29783 X 2,714,922 8/ 1955 McKibbon et al. 297--83 2,753,920 7/1956 Ranger 29783 3,147,038 9/1964 Barabas 297316 X 3,191,990 6/1965 Rugg et al. 29783 3,222,105 12/1965 Cross 29783 X 3,235,307 2/1966 Knabusch et al. 297-69 X FOREIGN PATENTS 97,308 11/1963 Denmark.

DAVID J. WILLIAMOWSKY, Primary Examiner.

JAMES T. MCCALL, Examiner.

Claims (1)

1. A CHAIR COMPRISING A SEAT, A BACKREST PIVOTED TO THE SEAT, A THIGH SUPPORT ARTICULATED AT A FIRST POINT TO THE SEAT, A SHANK SUPPORT ARTICULATED TO THE THIGH SUPPORT, SAID SUPPORTS FORMING AN ANGLE BETWEEN ONE ANOTHER, AND CONNECTING MEANS TO ACTUATE THE LOWER END OF THE SHANK SUPPORT FOR SWINGING IT FROM A SITTING POSITION TO A LYING POSITION, SAID MEANS COMPRISING A LINK HAVING ONE END PIVOTED AT A SECOND POINT TO THE LOWER END OF THE SHANK SUPPORT AND ITS OTHER END PIVOTED AT A THIRD POINT TO THE SEAT, THE LENGTH OF SAID LINK PLUS THE STRAIGHT LINE DISTANCE BETWEEN SAID FIRST AND THIRD POINTS BEING GREATER THAN THE STRAIGHT LINE DISTANCE BETWEEN SAID FIRST AND SECOND POINTS WHEN THE SHANK SUPPORT IS IN SAID SITTING POSITION SO AS TO AUGMENT SAID ANGLE AS THE SHANK SUPPORT IS MOVED FROM A POSITION FOR SITTING IN THE CHAIR TO A POSITION FOR LYING THEREIN.

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