Self-balancing ergonomic armchair

Abstract: Self-balanced ergonomic armchair, composed of a seat body (1), a sustaining support (2) and a mechanism (3) for adjusting the angular position of the body (1). The adjustment mechanism is composed of a structure which, in vertical cross-section, defines a jointed triangle, whose vertices (8, 9 and 10) are constituted by freely rotating shafts. Side (11) of this triangle has fixed length and position, side (12) has fixed length and swivelling position, and side (13) has variable length and swivelling position. The seat body (1) rests on and is fixed to the second and third sides, while via the first side (11) is mounted the mechanism on the support (2). The shaft (8) is constituted by a torsion bar that is mounted with freedom of complete rotation on the side (11) and carries secured to one end the side (13) and on the opposite end a lever with an adjustment control (33).

Description: This invention concerns a self-balancing ergonomic armchair, with adjustable angular position, and which is conceived in such a way that it allows stable equilibrium to be maintained in any selected angular position. The name "ergonomic armchair" applies to all those items of furniture for sitting that offer excellent support anatomy and also allow easy adjustment of that anatomy and of its position, in accordance with the users's movements or wishes. More specifically, the armchair of the invention is of the type that consists of a seat body, a sustaining support on which the seat body is mounted, and a mechanism that links the seat body and the sustaining support and allows the angular position of that seat body to be adjusted with respect to the support, the seat body being composed of a forward padded element and a rear casing which can flex backward elastically, which is moulded in a single piece and secured to the adjustment mechanism via the seat zone. The adjustments of position and anatomy of the seat and back surfaces are generally achieved by combining the capacity for partial deformation of the body defining the seat and back of the armchair with the action of an adjustment mechanism, linking the seat body to the lower support element. From the swiss patent n° 679 269 a mechanism is known, where the foremost part of a seat plate is installed rotably at the support. A spring between the support and the seat plate serves as compensation for the weight of the chair user and as return spring. A slide is disposed on both sides of the seat plate. In the slits of the slide run pins of bars. Laminas are fixed at one pin, which are gripped by a blocking device and therefore prevent against movement of the bar. A relatively small friction force is sufficient to block the laminas because the force, which is applied to the bar against the spring force by means of the weight of the chair user thru the seat plate, the slide, and the pin, only originates a relatively small force component, which tends to move the laminas. In that manner the seat plate is continuously variable by means of a simple mechanism when operating a key. A slight swinging of the chair is also possible. An armchair of the type described is already known from patent ES-309368, in which the casing of the seat body is a single piece and has capacity flexing backward. In that patent, the mechanism adjusting the angular position of the seat body is composed of a pivoting plate mounted on a transverse shaft of the seat zone, and of a spring mounted between a fixed point of the rigid support and the pivoting plate, in such a way that when the seat swivels to the rear, the plate pivots, compressing the spring. With the adjustment mechanism described, good stability for the seat body in the different selectable angular positions is not achieved if the degree of compression of the spring has not been suitably adjusted beforehand in accordance with the weight of the user. Moreover, the casing of the seat body also requires a special design so that the upper portion of the back can flex backwards elastically. On the one hand, this upper zone of flexion of the back of the casing is composed of a structure formed on the basis of rigid transverse ribs alternating with flexible transverse slots that act as intermediate hinges. On the other hand, associated with the seat casing is a structure formed from tubular profiles running in the seat zone below that zone and in the back zone along the interior of it. The shaping of the upper zone of flexion of the back, with the structure described, considerably increases the manufacturing costs and does not allow a back to be obtained of sufficient height for acting as a support for the shoulders, with which it does not offer maximum comfort, particularly for complete support of the back. Nor does the said structure allow certain torsion movements to be impressed on the seat and, also, it does not withstand high backward deformation stresses of the back. In terms of the seat zone, the casing works under traction and flexion, thereby reducing its life. The object of the present invention is an armchair that avoids the drawbacks stated above and allows perfect synchronization to be achieved among the movements of the different zones of the seat body when its angular position is varied, as well as stable equilibrium in any chosen angular position of that seat body. The invention also has the object of achieving an armchair that offers a correct support surface for the body, with the maximum comfort and security. A further advantage of the invention is that it allows the angular position of the seat body to be varied by means of smooth, easily controllable movements. These and other advantages are achieved by means of the combination of a new mechanism for adjusting the angular position of the seat body with a new design and structure for that body. In accordance with the present invention, the mechanism is of the type that links the seat body to the sustaining support, and which serves for adjusting the angular position of that body, is composed of a structure which, in its vertical cross-section, defines a jointed triangle, whose vertices are made up of as many more horizonal and parallel rotation shafts, and whose sides include one side with fixed length and position, one side with fixed length and swivelling position, and one side with variable length and swivelling position, the second and third sides mentioned being provided with means for supporting and fixing the seat body, while by means of the first side the mechanism is mounted on the rigid support. In the mechanism of the invention with the described design, the linkage shaft between the first and third sides mentioned is constituted by a torsion bar, which is mounted with freedom of complete rotation about the side with fixed length and position. Secured to one of the ends of this torsion bar, without possibility of relative rotation, is the side with variable length and position, while secured to the opposite end, also without possibility of relative rotation, is an adjustable angular position lever, this lever resting at its free end on an operating control fitted to the side with fixed length and position. The side with variable length and swivelling position forming part of the adjustment mechanism is composed of two parallel telescopic piston, each of them formed from two sections telescopically inserted into each other. One of these sections is integral in the two pistons with an upper rigid plate, while the other section is linked in both pistons by their free end to the torsion bar. Resting on and fixed to the said rigid plate, in front of the linkage shaft between the side with variable length and position and the side with fixed length and swivelling position, is the seat zone of the seat body. The telescopic pistons mentioned above are linked with the torsion bar via the tubular profiles of that bar. One of the pistons is fixed to the corresponding tubular profile without freedom of rotation with respect to it, while the other piston is connected to the other tubular profile with the possibility of free rotation with respect to it. This second piston include an adjustable tension spring that acts against elongation of the piston and which will serve for increasing the response or recovery capacity of the seat body starting from its position furthest back or most reclined. Moreover, between the inserted sections, the two pistons are provided with a contact bush that prevents adherence or seizing between each section and ensures a constant degree of friction, a high compression being achieved between the sections of the pistons, without adherence which could cause undesired seizing or locking in the relative movement of their components. The adjustable position lever mentioned above is fixed to the torsion bar via the same tubular profile, to which is connected with freedom of complete rotation one of the pistons of the side with variable length and position. Starting from the linkage vertex with the side with variable length and position, the side with fixed length and adjustable position, forming part of the adjustment mechanism, is extended in a portion on which rests the rear part of the seat zone of the seat body secured to it. According to another aspect of the invention, the casing for the seat body is subdivided into three zones, a lower seat zone, an upper back zone and an intermediate transition zone, offering structural continuity along the three zones. The capacity for backward flexing of the back zone is regulated, at the same time as the transition zone is rigidized, by means of a structure attached to the internal surface of the casing. This arrangement also reinforces the flexion of the back zone, in such a way that it can withstand the maximum stresses to which the armchair can be subjected during its use, without risk of breaking or of flexion to an undesired degree. Moreover, the back can adopt any reclining angle, sufficient for offering complete support for the user's back and shoulders, at the same time as allowing a certain degree of torsion, with which the maximum security and comfort have indeed been achieved. The padded element of the seat body includes an intermediate portion of lenticular transverse cross-section, coincident with the transition zone of the casing, and offering efficient support for the user's pelvic zone. With the arrangement commented upon of the casing of the seat body and its securing to the adjustment mechanism, two zones of flexion are achieved in that casing, one of which is located between the seat zone and the transition zone and the other in the lumbar zone of the back. By means of the arrangement commented upon of the adjustment mechanism and seat body, synchronization of the relative movement between the transition and seat zones of the casing is achieved, with which excessive elevation of the forward part of the seat zone is avoided, all this thanks to the combination of the swivelling and displacement movement of the seat body, and moreover, relative flexion is achieved in the neutral line of the casing, located between the transition and seat zones, thereby avoiding traction stresses that occur in traditional armchairs of the same type. This synchronization is boosted by means of the possibility of flexion in the lumbar zone of the seat body of the armchair, along with the possibility of a certain torsion movement in the upper part of the back. Also obtained with the adjustment mechanism included in the armchair of the invention is a stable equilibrium in any selected angular position of the seat body, this body moreover having a high capacity for recovery from its backward position, ensuring permanent contact with the user's body regarding any rapid action of incorporation of his body. The inclusion in the casing of the seat body of the frame coupled to the internal surface of it allows safety measures to be provided against sudden high supporting forces, which could produces excessive flexion in the back. As has been stated above, the regulation mechanism includes two elastic control elements, one of which is constituted by the torsion bar, which forms the control element in the strict sense for the movement of the seat body, while the other is defined by the spring of one of the pistons, which is used for increasing the response capacity from the furthermost back position of the seat body. The tension of these two elastic elements can be adjusted by means of the corresponding controls. All the stated characteristics and advantages will be able to be understood more easily with the following description, made with reference to the attached diagrams, in which in shown one possible form of design, given by way of an example rather than being restrictive. In the diagrams: Figure 1 is a vertical cross-section of an armchair designed in accordance with the invention, occupying its most upright position. Figure 2 is a cross-section similar to figure 1, in which the armchair appears in its position of maximum inclination or leaning backwards. Figure 3 is an upper plan view of the adjustment mechanism linking the seat body to the sustaining support. Figure 4 is a vertical cross-section of the adjustment mechanism, taken along the line of cut IV-IV of figure 3, showing the position corresponding to the situation of maximum elevation of the armchair shown in figure 1. Figure 5 is a cross-section similar to figure 4, in which the adjustment mechanism occupies the position corresponding to maximum inclination or leaning backwards, shown in figure 2. Figure 6 is a vertical cross-section of the adjustment mechanism, taken along the line of cut VI-VI of figure 3. Figure 7 is a vertical cross-section of the adjustment mechanism, taken along the line of cut VII-VII of figure 3. Figures 8 and 9 are vertical cross-sections of the adjustment mechanism, respectively taken along the lines of cut VIII-VIII and IX-IX of figure 3. Figure 10 is an interior perspective view of the casing of the seat body. Figure 11 is a profile view of the seat body, including the rear casing and the forward filling element. The armchair represented in figures 1 and 2 includes a seat body, referenced in general with number 1, a sustaining support, which can adopt any shape and of which only the upper part of the column 2 is represented, and a mechanism 3 linking the seat body 1 to the sustaining body 2 and which serves for adjusting the angular position of the seat body 1 with respect to that support. As can be appreciated from figure 11, the seat body 1 is formed from a single-piece rear casing 4 and a forward padded element 4a. The rear casing 4 defines a seat zone 5, a back zone 6 and an intermediate transition zone 7. The three zones form a backward flexing, continuous, single-piece shell or casing. The adjustment mechanism 3 is formed from a structure that, in vertical cross-section, defines a jointed triangle whose vertices, which are referenced with the numbers 8, 9 and 10, are made up of as many more horizontal and parallel rotation shafts. This triangle is composed of one side with fixed length and position 11, one side with fixed length and swivelling position 12, and one side with variable length and swivelling position 13. The side 11 forms part of the base piece 14 of the structure, via which the mechanism 3 is connected to the column 2 of the sustaining support. The side 13, with variable length and swivelling position, is composed of two telescopic pistons 15 and 16, parallel to each other, as can be better seen in figure 3. The piston 15 is shown in partial cross-section in figures 1 and 2 and in longitudinal cross-section in figure 9, while the piston 16 appears represented in longitudinal cross-section in figures 4 and 5. The two pistons are composed of two sections 17 and 18 telescopically inserted into each other. Section 17 of both pistons is integral with an upper plate 19, whose shape is represented by means of dashed lines in figure 3, while section 18 of the two pistons reaches the vertex or linkage shaft 8, constituted by a torsion bar 20. Side 12 of the triangle is composed of a rigid piece, which projects to the back with respect to the base piece 14. Resting on and secured to the plate 19 and over the backward extension of side 12 is the seat zone 5 of the seat body, as can be appreciated in figures 1 and 2. As can be better seen in figure 7, the torsion bar 20 consists of a longitudinal central core 20a of polygonal cross-section, on which are mounted from its ends individual and independent tubular profiles 21 and 22, of different lengths, which are terminated by their internal sections 23. The profiles 21 and 22 are secured by their end portions to the core 20a, for example by means of section reductions 24 and 25 which offer an axially grooved or ribbed internal profile that can be adjusted over the polygonal cross-section of that core 20a, thereby preventing relative rotation between those profiles and the core. The profiles 21 and 22 then run as far as the internal section 23 with the possibility of rotation with respect to the core 20a. The base piece 14 of the structure, in the section defining the side 11 with fixed position and length, shapes two parallel arms 26, figure 3, provided at their free ends with aligned passage housings 28, via which is mounted with freedom of complete rotation the torsion bar 20, by means of the interposition of intermediate bushes 29, as can be appreciated in figures 7 and 8, freedom of relative rotation thus existing between the torsion bar 20 and the side 11 of the adjustment mechanism triangle. As can be appreciated in figures 4 and 7, the piston 16 is linked to the torsion bar 20 via the section 18 of that piston, which is crossed by the profile 21 of the torsion bar, with the interposition of the bush 29 that ensures free rotation between the said profile and piston. As can be better appreciated from figure 4, the piston 16 includes a compression spring 30 whose tension can be adjusted by means of a threaded plug 31. The piston 15 is, as can be appreciated from figures 7 and 9, linked to the torsion bar 20 via the tubular profile 22, which have coincident polygonal cross-sections, thereby preventing relative rotation between the piston 16 and the torsion bar. Both the piston 15 and the piston 16 include between their telescopic sections 17 and 18 a contact bush 31 of a self-lubricating nature that prevents adherence or seizing between both sections and ensures a constant degree of friction between them. Finally, secured on the profile 21 of the torsion bar is a central lever 32, figures 3, 6 and 7, which has a passage of cross-section coincident with the profile 21 for its assembly on it, preventing relative rotation between both components. The lever 32 rests by its free end on an operating control 33' mounted in the base 14 defining the side 11 with fixed length and position. With the arrangement commented upon, the piston 15 is secured to one of the ends of the torsion bar via the tubular profile 22, while the lever 32 is secured to the opposite end of the torsion bar via the tubular profile 21, the torsion bar being freely rotating with respect to the support 14, which defines the side 11 with fixed length and position and with respect to the piston 16. By means of operating the control 33' the inclination of the lever 32 can be varied and with it the tension of the torsion bar 20. As can be appreciated in figures 1, 2 and 10, the casing of the seat body is composed of a continuous wall to which is fixed on its internal surface a reinforcing element that includes a rigid frame 33 and certain straps 34 that are elastically flexible in the transverse direction. The rigid frame 33 runs over the transition zone 7 and is slightly extended over the seat zone 5, on one side, and over the back zone 6 on the opposite side. The straps 34 run longitudinally over the middle part of the back zone 6, to which they are connected by their upper end by means of the plates 35, with partial freedom of displacement, while via the lower ends they are secured to the rigid frame 33. The resistance to flexion of the straps 34 will be greater than that of the back zone 6 of the casing. The securing of the rigid frame 33 is carried out on the one side by means of plates 36 and on the opposite side by means of a central piece 37, which also acts as a securing element for the rear part of the seat zone 5 to the piece 12 defining the side with fixed length and swivelling position of the adjustment mechanism triangle. Fitted on the internal surface of the casing represented in figure 10 is the padded element 4a, figure 11, which includes an intermediate body 38, with a lenticular shape, located coincident with the intermediate transition zone 7 of the casing. This lenticular body 38 acts as a support for the pelvic zone of the chair user. Figure 1 represents the armchair in its most upright position, in which the back zone 6 can be flexed backwards as far as occupying the position represented by means of a dashed line and referenced with number 6a. The maximum degree of flexion is defined by the capacity of the straps 34. By means of the adjustment mechanism 3, the user can recline or swivel the seat body between the positions represented in figures 1 and 2, in the second of which the back zone 6 can also be flexed as far as occupying position 6a. When passing from the position of figure 1 to the position of figure 2, the pistons 15 and 16 become elongated, increasing the length of side 13 of the adjustment mechanism triangle. At the same time, swivelling of this side occurs against the force of the torsion bar. Swivelling of side 12 of the adjustment mechanism triangle also occurs in synchronization with respect to side 13. All these movements, which are controlled by the torsion bar 20, the setting of the pistons 15 and 16 and the characteristics of the bushes 31 included in those pistons, causes swivelling of the seat zone 5, as well as a slight displacement of that zone 5, and a minimal elevation takes place of the forward edge of that seat zone 5, all of which correctly simulates the absolute and relative movements of the skeletal structure of the human body (pelvis, femur, etc.). Figures 1 and 2 show the contracted and elongated positions of the piston 15. Figures 4 and 5 show the positions of maximum and minimum length, in the second of which the spring 30 is compressed in order to act as an element that will increase the response or recovery capacity of the armchair from the position of figure 2 to the position of figure 1. The casing of the seat body has two zones of flexion, one located between the seat zone 5 and the transition zone 7 and the other in the lower half of the back zone 6. The piston 15 acts as an element for transmitting torque and guarantees the maintenance of the selected position of the seat body. The piston 16 serves for balancing the deformable triangle and for facilitating the recovery of the mechanism, as has already been commented upon. The inclusion of the straps 34 in the back zone 6 controls the backward flexing of that zone and allows a back to be achieved that can withstand certain torsion movements and which can reach a sufficient height for providing adequate support for the user's back, as far as the height of the shoulders. Indeed, the seat of the invention ensures perfect support for the body, providing great comfort, allowing the different movements of swivelling and flexion to be synchronized, and allowing a stable equilibrium to be obtained in any selected angular position of the seat body. The armchair is completed with support arms 40 that can take any shape, as well as with locking controls, not represented.

Claims: Self-balanced ergonomic armchair, consisting of a seat body (1), a rigid sustaining support (2) on which the seat body (1) is mounted, and a mechanism (3) that adjusts the angular position of the seat body (1) with respect to the support (2); the seat body (1) including a backward flexing casing that defines a seat zone (5), which is secured to the adjustment mechanism (3), and a back zone (6), said mechanism (3) comprising a structure which, in vertical cross-section, defines a jointed triangle, whose vertices are made up of as many more freely rotating horizonal shafts (8, 9, 10), and whose sides include one side (11) with fixed length and position, one side (12) with fixed length and swivelling position, and one side (13) with variable length and swivelling position, the second and third sides (12, 13) mentioned being provided with means for supporting and fixing the seat body (1), while by means of the first side (11) the mechanism is mounted on the rigid support (2); characterized in that the linkage shaft (8) between the first and third sides (11, 13) mentioned being constituted by a torsion bar (20) mounted with freedom of complete rotation on the side (11) with fixed length and position and which carries secured to one of its ends, without possibility of relative rotation, the side (13) with variable length and position and on the opposite end an adjustable angular position lever (32), which lever (32) rests at its free end on an operating control (33') fitted to the arm (11) with fixed length and position; and by the fact that the said casing carries fixed on its internal surface a reinforcing element (33, 34) that provides rigidity for the rear part of the seat zone (6), controls the capacity for backward flexing of the back zone and allows a certain degree of capacity for torsion of that back. Armchair according to patent claim 1, characterized by the fact that the side (13) with variable length and swivelling position runs on top of the other two sides (11, 12) of the mechanism and includes two parallel telescopic pistons (15, 16), both composed of two sections (17, 18) telescopically inserted into each other, one of which sections (17) is integral in the two pistons (15, 16) with an upper rigid plate (19), while the other section (18) is linked by its free end to the torsion bar (20); the seat zone of the seat body (1) resting on and fixed to the said rigid plate (19), in front of the linkage shaft (9) between the side with variable length and position (13) and the side with fixed length and swivelling position (12). Armchair according to patent claim 1, characterized by the fact that the torsion bar (20) includes a longitudinal central core (20a) on which are mounted from its ends individual and independent tubular profiles, (21, 22) which profiles are secured by their external end (24, 25) to the adjacent end of the core (20a), without possibility of rotation with respect to it, and running as far as their internal end with the possibility of free rotation with respect to the said core (20a). Armchair according to patent claims 2 and 3, characterized by the fact that each one of the said telescopic pistons (15, 16) is linked to the torsion bar (20) by means of one of the tubular profiles (21, 22) of that bar, one of the pistons (15) being fixed to the corresponding tubular profile (22) without freedom of rotation with respect to it, while the other piston (16) is connected to the other tubular profile (21) with the possibility of free rotation with respect to that profile; this second piston (16) including an adjustable tension spring (30) that acts against elongation of that piston (16) and both pistons (15, 16) being provided with a contact bush (29) between the inserted sections that prevents adherence or seizing of both sections and ensures a constant degree of friction between them. Armchair according to patent claims 1, 3 and 4, characterized by the fact that adjustable position lever (32) is fixed to the torsion bar (20) via the same tubular profile to which is connected one of the said pistons with freedom of rotation. Armchair according to patent claim 1, characterized by the fact that the side (11) with fixed length and position is defined by a piece in the approximate shape of a U, which is coupled on the sustaining support via the central section and whose lateral arms are linked by an intermediate point to the side (12) with fixed length and swivelling position and are provided at their free ends with aligned passage housings via which is mounted with freedom of complete rotation the torsion bar (20); the adjustable position lever (32) being located between those arms. Armchair according to patent claim 1, characterized by the fact that the side (12) with fixed length and adjustable position is extended from the linkage vertex with the side (13) with variable length and position in a portion on which rests and is secured the rear part of the seat zone of the seat body (5). Armchair according to patent claim 1, characterized by the fact that the casing (4) of the seat body (1) is composed of a continuous wall to which is fixed on its internal surface a reinforcing element (33, 34) that is subdivided into three zones, a lower seat zone (5), an upper back zone (6) and an intermediate transition zone (7), the upper back zone (6) being elastically flexible backward and under torsion; the reinforcing element (33, 34) being composed of a rigid frame (33) and certain straps (34) that are elastically flexible backward; which frame (33) runs over the transition zone (7) of the seat body (1) and is slightly extended over the seat (5) and back (6) zones, and which straps (34) run longitudinally over the middle part of the back zone (6), to which they are connected by their upper end with partial freedom of longitudinal displacement, while via their lower end they are secured to the rigid frame (33), the resistance of the straps (34) to backward flexing being greater than that of the upper back zone (6).

Inventors: TROYAS BERMEJO VICTOR, TROYAS BERMEJO, VICTOR
Applicants: JEVIT MANUFACT METALICAS SA, MANUFACTURAS METALICAS JEVIT, S.A.
Application year: 1995
Main classification: A47C3
IPC codes: A47C3, A47C1, A47C7