ARRANGEMENT IN AN ADJUSTABLE CHAIR

Abstract: The invention relates to a de­ vice in a chair, especially an adjus­ table chair (1aa) having an articula­ tion means (7) between a seat mem­ ber (3) a back rest member (8a), so as to allow an alteration of the an­ gular position therebetween, the al­ teration taking place by pivoting said back rest member (8a) around a pivoting point (8) whilst said seat member (3) is displaced along a predetermined sliding path. The in­ vention is characterized in that the device comprises one or more curved sliding means (1), the radius of curvature (R) of said sliding means (1) or of the center (4) thereof being arranged in accordance with given functional properties of said chair (1aa), which in turn means that for example an increase of the tangential angle (α) of the sliding means (1) may compensate for the increased weight from a person on the back rest member (8a) as the lat­ ter is taking a more reclined posi­ tion, for thereby providing a chair which is in balance in all positions and rendering smaller friction than compared with prior art models.

Description: Field of the invention The present invention relates to a device in an adjustable chair, comprising an articulation means between a seat member and a back rest member, so as to allow an alteration of the angular position therebetween. Prior art A chair of this type is for example known from NO-B-125 836. From SE-A-388 118 there is known such a chair having a back rest which is linked together with a seat member, the seat member on its lower side being equipped with straight metal hoops which can pass through a bearing cup provided fixedly on the chair frame, but pivotably in relation thereto. In order to maintain the chair in the sitting position having the back rest in an upright position there is provided on the metal hoop a wedge-shaped element wedging in the opening of the bearing cup. From FI-A-72865 there is known a device for regulating and locking the back member of a chair, there being provided on the seat member a straight guiding rod which at its one end is linked together with the front portion of the seat, and which at its other end freely protrudes through a recess in a lockable bearing cup. The locking means comprises a handle which with its one end can be pivoted into and out of the recess in the bearing cup for thereby catching or releasing the guiding bar in the recess. From DE-A-2 104 944 There is known a flip up device which can be used in connection with larger and heavier chairs, for example chairs in cosmetic treatment, dentist chairs, etc., in which for the various slanted positions of the chair the same centre of gravity is achieved for the chair and the user relative to the sub-frame of the chair. There is a curved guide rail which can move between rollers, and which resides in a box-shaped housing mounted on the seat member of the chair. In various positions of the back rest member and of an occupant, the chair will adjust itself to a position in which the centre of gravity is the same, since the seat member then will adjust itself such that the centre of gravity will be directly below the seat member. However, nothing is said in this Offenlegungsschrift about an articulation means between the seat member and the back rest member, let alone a pivot point on the back rest member around which the back rest member can be pivoted by the user in order to bring the back rest member to various angular positions, i.e. how various moments will be exerted by the body of the user depending on the inclination of the back rest member related to said pivot point, and how the seat member is to be displaced along a specific guiding path. From EP-0 096 273-A3 there is known a chair, wherein the back rest member can be pivoted about a fixed point on the chair frame, the bottom of the back rest member being linked to the seat which can slide along a guide bearing. In a given embodiment the guide bearing may take the form of curved guiding elements which are mounted on the seat, and which are guided in corresponding tracks provided stationary on the chair frame. From US-A-4 607 883 and US-A-4 660 884 there are also known chairs having an articulation means between a seat member and a back rest member. However, neither are there here given any instructions as to how it is possible with simple expedients to provide a double sliding path rendering larger options as regards versatility in the application facilities for such chairs. GB-A-470122 discloses a wooden-framed chair in which the underside of the seat base member co-operates cammingly with a portion of the frame in order to vary the inclination of the seat base member as the seat back member is pivoted about a fixed pivot intermediate its ends, for the purpose of varying the inclination of the seat back member. A pin and slot mechanism is disclosed in Figure 3 of GB-A-470122 and could loosely be referred to as a moving pivot. The pre-characterising portion of claim 1 is based on the disclosure of GB-A-470122. Brief discussion of the invention In view of this prior art an object of the present invention is to provide a device rendering larger possibilities for adjusting the force necessary for changing the relative position between seat member and back rest member. It is also an object of the invention also being to provide a regulating mechanism which further improves the operational facilities of the chair. In other words, the invention aims at providing a chair which, independently of the geometry of the chair, produces a predetermined resistance when the chair is adjusted, i.e. a resistance which is most favourable for the user when changing the sitting position from an upright position to a backwardly inclined or lowered position. According to the invention there is provided a device in a chair with the features laid out in independent Claim 1 In other words, the invention is based on the fact that the centre of curvature of the curved sliding means can be adjusted up from or down towards the chair, a lowering including a reduction of the radius of curvature of the sliding means and therefore a large difference in the slanting angle of the sliding means when the back rest member is moved from a raised to a lowered position. Appropriately, the present chair may be an adjustable chair, such that a displacement of the notional center of the sliding means rearwardly towards the back rest member, involves an increase in the total angle, i.e. an overall steeper angle of the sliding means in all positions of the back rest member. Brief discussion of the drawings Fig. 1 is a diagrammatic sideview of an embodiment of a chair of the present type, wherein a first embodiment of the device according to the invention has been implemented. Fig. 2 and 2a are views similar to Fig. 1, but illustrate the chair in a reclined position. Fig. 3 and 3a illustrate on a larger scale details of the friction and height adjustment means. Fig. 4 is a view as seen from the front of the chair illustrated in Fig. 1, 2 and 2a. Description of preferred embodiments With reference to Fig. 1, 2 and 2a which illustrate an embodiment of a chair of the present adjustable type, it should be noted that Fig. 1 illustrates an embodiment of the present chair, which here is generally designated by reference numeral 1aa, and which is shown in an upright position, i.e. in which position a back rest member 8a takes a substantially upright position and a seat member 3 takes a substantially horizontal position, whereas Fig. 2 and 2a illustrate a reclined or stretched-out position of the seat member and the back rest member, the seat member 3 still having a substantially horizontal position but the back rest member 8a having been displaced from its previous erect position to an approximately horizontal slightly slanted position. The embodiment of the adjustable chair 1aa according to the invention, comprises a back rest member 8a and a seat support member 3, which are interconnected to each other by means of an articulation means 7 for enabling alternative angular positions between said back rest member 8a and seat support member 3. Said members 8a, 3 are provided on a sub-frame 109a which in turn is supported on an adjustable gas column 109 provided on a base plate 108. On the sub-frame 109a there are provided slide bearings 2a through which can be displaced one or more sliding means 1, taking the form of at least one curved arc, preferably a circular arc, which at its front end is provided with an arm element 2 extending from the sliding means 1 towards the seat support member 3, the sliding means 1 and its arm 2 preferably comprising an integral unit, but being connected to the seat support member 3 through a second articulation means 6. As further indicated, especially in Fig. 4, the sliding means 1 here comprise two substantially parallel sliding elements, but it is to be understood that fewer or more sliding elements can of course be used. The centre of curvature 4 of the curved sliding means 1 is indicated as a notional point 4 in Fig. 1, 2 and 2a, it being understood that if the sliding means 1 are provided with a constant radius of curvature, this centre 4 will be a fixed point. The function of the chair 1aa is such that when the top of the back rest member 8a is pressed backwards or forwards, or the seat member 3 is pushed forwards or rearwards, then the back rest member 8a will turn around a first pivot point 8 which is stationary in relation to the sub-frame 109a. The articulation means 7 between the seat member 3 and the back rest member 8a will then move along a substantially circular path having its centre of curvature at the pivot point 8, and a first radius designated R3. Due to its connection with the arm 2 integral with the sliding means 1, the second articulation means 6 on the seat member 3 will move along a circular path having its notional centre of curvature at the previous discussed point 4, but having a second radius of curvature designated R2. In this case when the sliding means 1 represent circular arcs, the sliding means 1 which controls the movement of the seat member 3, will also have the centre of curvature located at the same point 4, but the distance therefrom to the sliding means 1 will be a third radius designated R1. It is to be understood that the sliding means 1 are guided in said sliding bearings 2a which are substantially stationarily arranged in relation to the sub-frame 109a, but have associated therewith friction means 5 which are also arranged relative to the sub-frame 109a and can be operated by the user through an operating means 12 connected through a transmission 5a from an appropriate place, for example on an arm rest 15. When the back rest member 8a is displaced backwards as illustrated in Fig. 2 and 2a the tilting angle β, i.e. the angle between a vertical plane 11 and a radius R1 or R2 running from the notional centre of curvature 4 to the articulation point 6 on the seat member 3 will increase from β1 to β2. At the same time the tangential inclination angle α, i.e. the angle, between a horizontal plane H and a tangent to the curved sliding means 1 substantially in the region of the second articulation point 6 between the arm 2 of the sliding means 1 and the seat member 3, will increase from α1 to a larger angle α2. The advantage of introducing such a sliding means 1 which will have its tangential inclination angle α changed depending on the angular position between the seat member and the back rest member, is the fact that the force required by the user to effect this change in angular position can be regulated depending on whether the user is to carry out an inclining or reclining movement. When the user is sitting in a substantially erect position, i.e. with an approximately 90° inclined position between back and seat, the embodiment according to Fig. 1, 2 and 2a will render a small tangential inclination angle α for the sliding means 1 in the area of the articulation means 6 or in the area of the slide bearings 2a, which is due to the fact that the user will have to exert a relatively small force in order to change the angular position between seat member and back rest member. This is favourable since, with prior art adjustable chairs, it is usually difficult to move the chair when sitting in an upright position. In the reclined position of the chair 1aa, i.e. when the back rest member 8a is fully lowered, it is with prior art adjustable chairs, usually, too easy to perform a backwards tilting movement, but in accordance with the present invention and the present arrangement, the tangential inclination angle α of the sliding means 1 will become larger the larger the angle of inclination of the back rest member 8a becomes. This in turn requires the seat member 3 to be lifted more and more steeply as the back rest member 8a is lowered, and this raising of the seat member for example from a level H1 to a level H2, including the lower part of the body of the user, will compensate for the weight of the back of the user resting on the back rest member 8a. In other words, the change in tangential inclination angle α of the sliding means 1 will compensate for the increased effect of the lever arm represented by the back rest member 8a and the upper part of the body of the user, the weight of which will create a moment by pressing against the upper part of the back rest member 8a with an increased moment arm proportional to the increasing tilting angle of the back rest member (8a). As an overall concept this variation in tangential inclination angle α and inclination angle β will provide a chair which will in all positions function in a balanced state, provided the friction means are appropriately adjusted, this balanced position rendering a relatively lower friction than compared with prior art adjustable chairs of any model. An important feature of the present invention is the fact that if it is desired to change the individual functional properties of the chair, this can be done by reducing or increasing the length of the radius R2, i.e. reducing or increasing the radius of curvature of the sliding means 1. In accordance therewith a small or a larger difference is then achieved in the tangential inclination angle of the sliding means in the vertical and the reclined position of the back rest member 8a. Likewise, by increasing or reducing the distance L between the centre of curvature 4 of the sliding means 1 and the vertical line 11 extending through the central line of the support column 109 of the chair 1aa, it is possible to increase or reduce the average tangential inclination angle of the sliding means 1. Experience has indicated that in such an adjustable chair including a friction means 5 it is more easy to achieve an appropriate adjustment of the friction and a smooth sliding during adjustment of the chair, and also to achieve a smooth sliding velocity along the slide bearings as the chair's angular position is altered, if the chair is provided with a sliding means having a relatively long extent. A disadvantage which may be experienced in this connection is a large movement of the seat member and a large difference in level of the seat in the various positions. In the present design the length and the curvature of the sliding means can be regulated without involving an increase in the length of movement of the seat member. This is mainly achieved by giving the sliding means 1 a relatively large radius of curvature and by mounting said sliding means below the seat member 3. By this arrangement there is also achieved a difference between the adjusting velocity of the seat member 8a and the sliding means 1 by keeping the angular velocity of the tilting angle β constant, but making the radius R1 of the sliding means larger than the radius R2 of the seat member 3. By increasing the difference L2 between R1 and R2 the difference in adjusting velocity and sliding length at a point on the sliding means 1 and the seat member 3, for example at point 6a and point 6, respectively, will increase. By systematically changing said distances and numeric values, as well as by changing the radius R3 and the distance between the first articulation means 7 and the second articulation means 6, it is possible to manufacture a chair having very favourable sliding properties and functioning in a balanced mode with very low friction. It also been possible to produce all desired relations between the operating force which has to be exerted in the vertical and reclined position of the chair, respectively. In the present case there have been used two sliding means 1x and 1y as illustrated in Fig. 3, 3a and 4, the center of each sliding means having its own notional center as discussed previously. Whether two or more or even one sliding means are used, the chair will function so as to allow varying operating characteristics by moving said centers up from or down towards the seat member, a reduction of the radius of the sliding means meaning that there is achieved a large difference in the tangential angle of the sliding means in the erected position an the reclined position of the back rest member, respectively. It is to be understood that the friction means can be made as a hidden arrangement, it being observed that no jamming should be risked at any place between moving parts. In Fig. 3 and 3a there is illustrated a suggested braking mechanism in which a cable 5a in a sheath , as indicated in the drawings, is contemplated used for compressing the friction means 5 in the direction of the arrow A. By pressing said friction means 5 a pressure is transferred against the two curved sliding means 1x, 1y, and this preasure is to be regulated through the operating means 12 on the arm rest 15. It is also possible to use other forms for locking mechanisms. It is also to be understood that the chair can operate satisfactorily by using only one sliding means and a friction means pressing on the outside of said single sliding means. The friction means 5 thus comprises an elastic element 107 which through a force in the direction of the arrow A is subjected to a structural change so as to expand substantially in a direction perpendicular to the direction of the arrow A, for thereby pressing a braking block 107a, 107b against a braking surface 4c of the sliding means 1x, 1y, respectively. The embodiment of chair illustrated in the drawings is also equipped with an adjustable supporting column 109, and the operation thereof is indicated by reference numeral 10, said means preferably being arranged on the arm rest 15, and operating through a wire 6a. In Fig. 4, which is a view as seen from the front of the chair of Fig. 1, 2 and 2a it appears that the seat supporting member 3 is comprised by a transverse member 3a, which is provided at its center portion with two of the previously discussed second articulation means 6x, 6y, each of which is connected to a respective arm element 2x and 2y. These merge into a curved sliding means 1x and 1y, respectively, which in turn are supported in a slide bearing 2a and 2b, respectively, substantially stationarily fixed to the sub-frame 109a of the chair 1aa. In such a structure the seat member 3 will consequently move along a first circular path having said second radius R2, whereas the sliding means 1x, 1y which are provided at a distance L2 from the seat member 3 will move along the third radius R1 which is larger than said second radius R2. It is to be understood that the shape of any of the sliding means can have a varying curvature along its extent, for example including a steeper curvature at its rear end, i.e. at the end closest to the back rest member of the chair. In connection with such an embodiment including a variable curvature of the sliding means, it is to be understood that the slide bearings carrying and guiding said variable curvature sliding means must be arranged pivotably around an axis substantially perpendicular to the sliding means. It is to be understood that in any embodiment, whether one, two or more parallel sliding means are used, each sliding means could be supported by two shorter guiding means or bearing means arranged at an appropriate mutual spacing. Depending on whether the sliding means is or are given a varying curvature, said single guiding means or multiple guiding means may be arranged to be either stationary or pivotable relative to a fixed structure of the chair. Further, it is to be understood that the size of the radius of curvature R2 of the third pivot 6 may be in the range of 0.5-1.5 m, whereas the length of the second radius R1, could be 0.3-0.5 m larger. In other words it is possible within the scope of the present invention, to arrange a curved sliding means 1 below the path followed by the seat member 3 during the adjustment thereof, and to regulate the length and the curvature of said sliding means in a simple and practical way in accordance with the various operating properties of the different chairs.

Claims: A device in a chair having a back member (8a); a seat member (3); a frame (109a) for supporting said back and seat members; a first pivot (8) between said back member and said frame fixed relative to said frame for mounting said back member for pivotal movement thereabout; curved sliding means (1) supporting said seat member on said frame and located below said seat member, for mounting said seat member for sliding forward and rearward relative to said frame along a predetermined guiding path and in substantially horizontal positions; a second pivot (7) movable relative to said frame for pivotally interconnecting said back and seat members for altering the relative angular positions therebetween from and to erected and reclining positions of said back member during pivoting thereof about said first pivot, said second pivot being movable along a first upwardly concave arcuate path of first radius (R₃) fixed by said first pivot and said slide means; characterised by a third pivot (6) movable relative to said frame for interconnecting said curved sliding means and said seat member for altering the relative angular positions between said seat member and back member, and for pivoting said seat member between said substantially horizontal positions with said curved sliding means moving along a second upwardly concave arcuate path of second radius (R₁) larger than the radius of curvature (R₂) of the locus of said third pivot during said alteration of the relative angular positions of said seat member and back member; and by the fact that the centres of curvature (4) of said second arcuate path and of the locus of said third pivot are coincident so that the difference (L2) between said second radius (R₁) and the radius of curvature (R₂) of the third pivot locus remains constant during sliding of the curved sliding means. A device as claimed in claim 1, in which an arm rest (15) at the side of said seat member forms a part of said frame and extends above said seat member, and in which the curved sliding means have a radius of curvature (R₁) which is larger than the distance from the level of the seat member to the level of said arm rest. A device as claimed in claim 1 or 2, in which the curved sliding means have a centre of curvature (4) so high above the seat member that the angle of inclination (α) of a tangent to said second path at said third pivot (6) relative to the horizontal is changed within relatively small limits when the seat member is displaced from and erected to a more reclined position. A device as claimed in claim 1, 2 or 3, in which the curved sliding means have a centre of curvature (4) which is so close to the back rest member that the angle of inclination of a tangent to said second path at said third pivot (6) relative to the horizontal changes rapidly towards a higher value when the seat member is displaced by pivoting the back rest member from an erected to a more reclined position. A device as claimed in claim 3 or 4, in which the centre of curvature (4) of the sliding means is located a distance behind a vertical plane through a central column (109) of the chair, and wherein further displacement of said centre of curvature rearwardly from said vertical plane results in an overall increase of the tangential angle (α) of said curved sliding means in all positions of said chair. A device as claimed in any one of the preceding claims, in which the curved sliding means comprises one or more curved sliding rails (1) which at their front end are each pivoted with a connection arm (2), which arms (2) are joined to said seat member by means of said second articulation means. A device as claimed in claim 1 or 2, in which the shape of the sliding means has a varying curvature along its extent. A device as claimed in any one of the preceding claims, in which the radius of curvature (R₂) of the third pivot is is in the range 0.5 to 1.5 meters, whereas the second radius (R₁) exceeds it by approximately 0.3 to 0.5 meters. A device as claimed in any one of the preceding claims, in which the device also comprises a first operating mechanism (5) for operating a friction element (107a, 107b) influencing said curved sliding means. A device as claimed in claim 9, wherein said first operating mechanism comprises a cable (5a) extending from an operating control (12). A device as claimed in claim 10, in which the friction element comprises an elastic element (107) which, under the influence of a force, is subjected to a structural change for expanding in a direction towards a braking surface of the curved sliding means. A device as claimed in claim 11, in which the elastic friction element (107a, 107b) is arranged between two said curved sliding means and by the influence of a pressure initiated by said operating control (10) will have its centre zone compressed for thereby pressing the side zones towards a respective braking surface of the curved sliding means. A device as claimed in claim 12, further comprising a gas column (109) carrying said curved sliding means and an operating mechanism (10) for operating said gas column.

Inventors: EKORNES JOSTEIN, EKORNES, JOSTEIN
Applicants: EKORNES FABRIKKER AS J E, J.E. EKORNES A/S
Application year: 1988
Main classification: A47C1
IPC codes: A47C1