DEVICE FOR ADJUSTING THE INCLINATION OF THE SEATING PORTION IN CHAIRS IN GENERAL

Abstract: A device for adjusting the inclination of the seating portion in chairs in general, to be applied to a support for the seating portion formed in at least two parts (2, 12) hinged together about a transverse axis (14) and associated with a spring (20) interposed between them to elastically maintain the back rest of the chair in its most forwardly inclined position, and also associated with a locking member (24) to maintain them in other predetermined positions corresponding to different inclinations of said back rest, characterised by comprising: a locking bolt (26) forming part of the locking member (24) and fixed to one (2) of the two parts (2, 12) of the support for the seating portion, a plurality of holes (22) provided in the other part (12) of the support for the seating portion in positions engageable by the bolt (26) and corresponding to different relative inclinations between the two parts (2, 12) of said support, a rod (30) for axially operating said bolt (26), an axially bistable device (34) for controlling said rod (30), a pair of preloaded springs (50, 52) interposed between said rod (30) and said bistable device (34), and an operating pusher (46) for said bistable device (34).

Description: DEVICE FOR ADJUSTING THE INCLINATION OF THE SEATING PORTION IN CHAIRS IN GENERAL This invention relates to a device for adjusting the inclination of the seating portion in chairs in general. Chairs are known, particularly for office use, provided with a back rest the inclination of which can be adjusted either alone, or together with the seating portion if it forms a single body therewith, or synchronously with the seating portion but with a different angle of inclination. The purpose of this is to achieve the correct positioning for the particular work which the operator seated thereon has to perform. This adjustability of the back rest inclination is generally obtained, in the case for example of inclination of the back rest alone, by hinging the rest support member about a transverse axis to the seating portion support member, le to the member which is mounted on the column of the chair oase and which supports the seating portion. The desired inclination of the back rest is achieved by locking the two members together in predetermined angularly different positions. However in the case of inclination of the back rest together with or in synchronism with the seating portion, the adjustment is obtained by hinging together two separate parts forming the member for supporting the seating portion on the column and, in the case of synchronized inclination between the seating portion and back rest, by also hinging the back rest support member to one of the two parts forming the support member for the seating portion. Considering the need to lock two hinged-together parts in different positions corresponding to different operator requirements, the system for locking these two parts together is generally of multiple type, ie with a locking bolt rigid with one of them and engaging a chosen one of several holes provided in the other part; or alternatively with a comb structure rigid with one of them and engaging with a chosen one of the spaces between its teeth an edge present on the other part. The most forwardly inclined position of the back rest is achieved by a spring interposed between the back rest support member and the seating portion support member, the other rearwardly inclined positions being achieved by stressing by the operator seated on it, and who by a rearward thrust loads the spring until the desired inclination is achieved, this being then permanently maintained by activating the locking system. This system for elastically returning the back rest into its most forwardly inclined configuration involves the risk of sudden return into that configuration if the locking device is deactivated voluntarily or accidentally when the operator is not seated on the chair, this not only being the cause of possible danger but also conflicting with current accident prevention regulations. To eliminate this drawback it has already been proposed to make operation of the locking system (for activation or deactivation) possible only when the operator is seated on the chair and can in this manner oppose the elastic reaction on the return spring by his own presence. For example, Italian utility model application BS91U000068 describes a chair adjustment device comprising a comb-type locking member which can be activated and deactivated by a lever via a control rod provided with springs which are loaded by the operator seated on the chair, but which can move the comb member only after the operator has set the chair into the correct position for allowing this movement and has mechanically locked rigidly together the two parts of the support for the seating portion. A drawback of this known arrangement is that if it is also required to adjust the height of the seating portion a second lever must be provided which not only complicates the chair construction but can also cause operating difficulty and uncertainty because of the inevitable risk of confusing the two levers. A further drawback, again related to the presence of the two levers, is that as for obvious reasons of practicality they have to be located on opposite sides of the chair, their operation requires the use of both hands. A further drawback is that the lever for adjusting the inclination of the seating portion requires accurate construction and likewise accurate positioning on the chair. As generally the lever for adjusting the height of the seating portion is positioned on the right, the lever for adjusting the inclination of the seating portion is constructed to be always and only positioned on the left and could not be positioned on the right even if the lever for adjusting the height of the seating portion is not provided. A further drawback is that generally the manoeuvre to be carried out on the lever to lock and release the seating portion are opposing, ie are different from each other. This results in a possible operational uncertainty by the operator, who cannot always immediately remember which of the two operations has to be carried out to lock or release the seating portion. A futher drawback is that the system for operating the manual locking member of a rigid rod involves the need to apply the control lever in a precise position, which is generally in proximity to the inclination mechanism of the seating portion. A further drawback is a certain complexity of construction and assembly, both of the locking member and of its operating device. According to the invention all these drawbacks are eliminate through a device for adjusting the inclination of the seating portion in chairs in general as described in claim 1. A preferred embodiment of the present invention is further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is a vertical section through the device of the invention to be applied to a chair for a video terminal operator with its back rest adjustable relative to its seating portion; Figure 2 is a partly sectional plan view thereof taken in the direction II-II of Figure 1; Figure 3 to 7 are five longitudinal sections showing different operating conditions of the control member of the adjustment device. As can be seen from the figures, the adjustment device according to the invention comprises a box structure 2 applicable to the lower surface of the seating portion (not shown) of a chair for a video terminal operator, and provided with a frusto-conical bush 4 for insertion of the upper end of the rod of a traditional gas spring 6, the purpose of which is to support the box structure 2 on a support base while at the same time adjusting the height of the seating portion. The box structure 2 is provided with two spaced-apart longitudinal shoulders 8 between which there are interposed the flanges 10 of a member 12 for supporting the back rest (not shown) and for hinging it to the seating portion. The support member 12, which is hinged to the box structure 2 on a transverse pin 14 which passes through the shoulders 8 and the flanges 10, comprises, in addition to said flanges 10, a bracket 16 to which the back rest is applied, and an upper plate 18 for connecting the flanges together, against this plate there acting a spring 20 which lowerly rests on the base of the box structure 2, in order to elastically maintain the back-rest in its most forwardly inclined position, as will be clear hereinafter. In a curved wall 21 connecting together the two flanges 10 of the member 12, to this wall there being fixed the bracket 16, there are provided a plurality of aligned holes 22 such that, when the support member 12 rotates relative to the box structure 2 about the pin 14, they all face a locking member 24 comprising a locking bolt 26 slidable axially within a cylindrical housing 28 fixed to said box structure 2. The bolt 26 is movable axially between two end positions in which it respectively engages and disengages one of the holes 22, and is controlled in these movements by a flexible rod 30 housed in a flexible sheath 32 which connects said locking member 24 to an operating device of push type, indicated overall by 34. The operating device 34, which can generally be fixed to any part of the chair, is incorporated in the illustrated example into the lever 36 which when rotated controls the valve 38 of the gas spring 6 in traditional manner to enable the height of the chair seating portion to be adjusted. In detail the operating device 34 comprises a cylindrical casing 40 closed at one end by a base 42 which is traversed by the flexible rod 30 and against which the end of the relative sheath 32 rests. Within the cylindrical casing 40 there is slidable a piston 44 the axial movements of which can be controlled by a pusher 46 emerging from that end of the casing distant from that closed by the base 42. That end of the flexible rod 30 within the operating device 34 is provided with an enlargement 48 freely slidable within an axial cavity in the piston 44 and against which there rest two preloaded springs 50, 52 of which the spring 50 is interposed between said enlargement 48 and the base 42, and the other spring 52, opposite the preceding, is interposed between the said enlargement 48 and the closed end of the piston 44. — o — The operating device 34, ie the unit comprising the cylindrical casing 40, the piston 44, the pusher 46 and the springs 50,52, can be defined as a pusher-operated axially bistable device, ie a device with a part, namely the piston 44, able to assume two axially different stable positions, each of which can be attained by axially pressing the pusher 46 in the direction of the base 42 of the casing 40, in a like manner to that which occurs with the pusher of a traditional ballpoint pen. As this type of operation is known, a detailed description of its operation will be omitted for simplicity, as will any reference to other already known details. The operation of the locking device according to the invention will now be described with reference, for simplicity of description, to the condition illustrated in Figure 3, in which the locking member 24 is deactivated, ie the bolt 26 is in its retracted position within its housing 28, and does not engage any of the holes 22 provided in the curved wall 21 of the support member 12. In this condition, which is made stable by the balancing effect of the two springs 50 and 52 on the enlargement 48 of the rod 30, the back rest can be freely inclined rearward by the effect of the thrust of the operator seated on the chair, and forward by reducing this thrust to a sufficient extent to enable the spring 20 interposed between the box structure 2 and the support member 12 to react elastically. If under these conditions the operator, after attaining approximately the desired degree of inclination of the back rest, instantaneously operates the pusher 46, the interaction between this, the piston 44 and the cylindrical casing 40 moves the piston into the other end position, hence loading the spring 52 to a greater extent than the spring 50 (see Figure 4) . This non-uniform stressing of the two springs 50 and 52 does not result m activation of the locking member 24 because generally the locking bolt 26 does not face a hole 22 into which it can enter. If however following a small inclination movement in one or other direction a hole 22 exactly faces the locking bolt 26, the elastic reaction of the loaded spring 52 urges said bolt to engage said hole and to mechanically lock the box structure 2 and the support member 12 together (see Figure 5), even if the operator leaves the chair. To release the back rest in order to vary its inclination, the operator must firstly again operate the pusher 46 which, as a result of this operation, is subjected to the elastic action of the preloaded spring 52, which extends and returns the piston 44 into its other end position (see Figure 6) . However this movement does not result in any extension of the spring 50, because the locking bolt remains in its locking position by friction due to the tangential force induced between the box structure 2 and the support member 12 by the spring 20 interposed between them. However when the operator sits on the chair so that his weight causes a slight mutual movement between the two parts 2 and 12, sufficient to cause exact alignment between the bolt 26 and the hole engaged thereby, the elastic reaction of the spring 50 prevails, to withdraw the bolt 26 from the hole 22 (see Figure 7) and enable the operator to move the back rest into the new chosen configuration, in which he can lock it by again operating the pusher 46 in the aforedescribed manner. The adjustment device of the invention is extremely advantageous compared with traditional devices, and in particular: - it enables the operator to lock and release the back rest by the same operation, without any uncertainty or confusion, - it can be controlled by a pusher which can be positioned either to the right or left of the chair at will, - It is practically positionable in any position within the box structure supporting the seating portion, and in particular can be incorporated into the lever which adjusts the height of the seating portion. - it requires no force for the locking or release operation, but simple instantaneous pressure on the presser, - if the control rod of the locking member is of flexible type, ie in the form of a cable housed in a sheath, the position of the pusher, ie the control member, can be chosen at any point of the chair, for example even on the arm rest, - it is of extremely simple construction, using only a few components. The drawings show a device applicable to a chair with its back rest inclinable to the seating portion rigid with the chair support base. The invention is however also applicable to chairs with a onepiece body supported by a support structure hinged to a structural part rigid with the support base, and is also applicable to chairs of so-called synchronized inclination of the seating portion and back rest. In this case the support structure for the seating portion comprises a first part rigid with the support base, a second part rigid with the seating portion and hinged to the first about a first transverse axis, and a third part rigid with the back rest and hinged to the second about a second transverse axis and also connected to it by means for synchronizing the inclination movements of said seating portion and said back rest . In an embodiment (not shown on the drawings ) the rod 30 is substantially rigid.

Claims: C L A I M S 1. A device for adjusting the inclination of the seating portion in chairs in general, to be applied to a support for the seating portion formed in at least two parts (2,12) hinged together about a transverse axis (14) and associated with a spring (20) interposed between them to elastically maintain the back rest of the chair in its most forwardly inclined position, and also associated with a locking member (24) to maintain them in other predetermined positions corresponding to different inclinations of said back rest, characterised by comprising: - a locking bolt (26) forming part of the locking member (24) and fixed to one (2) of the two parts (2,12) of the support for the seating portion, - a plurality of holes (22) provided in the other part (12) of the support for the seating portion in positions engageable by the bolt (26) and corresponding to different relative inclinations between the two parts (2,12) of said support, - a rod (30) for axially operating said bolt (26) , - an axially bistable device (34) for controlling said rod (30), - a pair of preloaded springs (50,52) interposed between said rod (30) and said bistable device (34), and - an operating pusher (46) for said bistable device (34) . 2. A device as claimed in claim 1, characterised in that the support for the seating portion is formed in two parts (2,12), of which one (12) is rigid with the support base and supports the chair seating portion and the other (12) is rigid with a bracket (16) supporting the back rest. 3. A device as claimed in claim 1, characterised in that the support for the seating portion is formed in two parts, one of which is rigid with the chair support base and the other is rigid with the chair body. 4. A device as claimed in claim 1, characterised in that the support for the seating portion is formed in three parts, of which the first is rigid with the chair support base, the second is rigid with the seating portion and is hinged to the first about a first transverse axis, and the third is rigid with the back rest and hinged to the second about a second transverse axis and is also connected to it by means for synchronizing the inclination movements of said seating portion and said back rest. 5. A device as claimed in claim 1, characterised in that the support member (12) for the seating portion comprises a curved portion (21) provided with holes (22) . 6. A device as claimed in claim 1, characterised in that the locking member (24) comprises a cylindrical housing (28) within which the locking bolt (26) is axially slidable. 7. A device as claimed in claim 1, characterised in that the operating rod (30) for the bolt (26) is flexible and is housed in a flexible sheath (32) . 8. A device as claimed in claim 1 characterised in that the operating rod (30) is of rigid type. 9. A device as claimed in claim 1, characterised in that the axially bistable device (34) comprises a cylindrical casing (40) provided at one end with a pusher (46) and within which a piston (44) is axially slidable between two end positions, within said piston there being positioned the end of said rod (30) , which is provided with an enlargement (48) cooperating with a pair of opposing preloaded springs (50,52) . 10. A device as claimed in claim 9, characterised in the that one (52) of the two springs is interposed between the enlargement (48) on the rod (30) and a closed end of said piston (44), the other spring (50) being interposed between said enlargement (48) and the closed base (42) of said cylindrical casing (40) . 11. A device as claimed in claims 7 and 10, characterised in that the base (42) of the cylindrical casing (40) is traversed by the flexible rod (30) and supports the end of its sheath (32) . 12. A device as claimed in claim 11 to be applied to chairs with arm rests, characterised in that the axially bistable device (34 ) and its operating pusher (46 ) are housed in one of the arm rests . 13. A device as claimed in claim 11 to be applied to a chair with a height-adjustable seating portion, characterised in that the axially bistable device . (34 ) and its operating pusher (46) are housed in the body of the lever (36 ) which adjusts the height of said seating portion.

Inventors: GORGI CLAUDIO, ZANETTI DANIELA, GORGI, CLAUDIO, ZANETTI, DANIELA
Applicants: GORGI CLAUDIO, IMARC SRL, ZANETTI DANIELA, GORGI, CLAUDIO, IMARC S.R.L., ZANETTI, DANIELA
Application year: 1996
Main classification: A47C1
IPC codes: A47C1