Elastic support device for inclinable portions of office chairs and the like

Abstract: It is provided for a mechanism of elastic prop for reclining portions of office chairs and the like, comprising an elastic element with linear strain (8) having a first end (8a) abutting against the primary body (2) of a chair, and a half-shell element (12) adapted to house at least a portion of the elastic element (8) starting from a second end (8b) of the latter, said half-shell element (12) having two abutment portions (12b) for a pair of pushing extensions (13) integral with the support element (4) of the reclining back.

Description: The present invention relates to a mechanism of elastic prop for reclining portions of office chairs and the like (see document EP-A-0 901 763). As is known, office chairs generally have portions with adjustable height and/or inclination. In particular, they can be adjusted in the inclination of the back, and sometimes of the seat as well. In the latter case the seat can be wholly integral with the back, so that both can incline together of the same angle, or the seat can be only partially connected with the back so as to incline less than the latter. Chairs of the above-mentioned kind should normally be provided with mechanisms of elastic prop for reclining portions, which can exert on said portions reaction forces opposed to those developed against said portions by the user's body. Moreover, said chairs usually consist of a primary body, for instance box-shaped, adapted to be engaged with an upper end of an upright defining a vertical stand for an office chair. A support element of the back is turnably engaged with the primary body around an oscillation axis, so as to enable the adjustment of the inclination of said back. At least a support element of the seat of the chair is located above the primary body. The mechanism of elastic prop is generally placed between said primary body and said support element and comprises at least an elastic element with linear strain, such as for instance a cylindrical helical compression spring, having a main direction of development which is perpendicular to the oscillation axis of said support element and a first end which abuts against the primary body. Moreover, the mechanism of elastic prop comprises means to transfer to the elastic element the pressing force pushing the back backwards, said means being placed between the support element and a second end of said elastic element. In practice, in the known technique said transfer means normally consist of a part of the above-mentioned support element arranged outside said second end of the elastic element, so as to abut against said second end. The known technique, briefly disclosed above, is disadvantageous because it makes it necessary to place the elastic element in a given position, for instance in a position close to the front edge of the chair, since the above-mentioned second end of said elastic element should not be placed in such an inner position to be in contact with the pushing portion of the support element. In practice, the primary body of the chair does not often have a suitable front space which can house the group for the adjustment of the elastic force of the elastic element with linear strain and which can be easily handled from outside. In some technical applications the length of the elastic element and the need to compress it on its ends makes it necessary to place it in an inclined, almost vertical position, thus giving rise to quite bulky and high primary bodies of the chair. In this situation the technical task of the present invention is to provide for a mechanism of elastic prop which can substantially obviate said disadvantages. Within said technical task an important purpose of the present invention is to provide for a mechanism of elastic prop for reclining portions of office chairs which enables the maximum freedom in the design of a wide range of technical solutions, allowing for instance to place the elastic element horizontally and/or in a withdrawn position with respect to the front edge of the seat or anyway in the position which is deemed as most suitable from a functional point of view, also considering the chair comfort and the easy handling of its adjustments. A final technical purpose of the present invention is to provide for a mechanism of elastic prop for reclining portions of office chairs which ca be easily carried out with limited costs. The technical task and the purposes indicated above are substantially reached by means of a mechanism of elastic prop characterized in that it comprises one or more of the technical solutions claimed later. The description of a preferred though not exclusive embodiment of a mechanism according to the invention is now disclosed as a mere non-limiting example, as shown in the enclosed drawings, in which: Fig. 1 shows a view in longitudinal section, according to line I-I of Figure 3, of a mechanism according to the invention applied to an office chair having a reclining back and a seat partially connected to the latter, in a first operating position; Fig. 2 shows the mechanism of Figure 1 in a second operating position corresponding to the backward inclination of both back and seat; Fig. 3 shows a top view of the mechanism of Figure 1; Fig. 4 is a front view of a half-shell element comprised in the mechanism of Figure 1; Fig. 5 shows a longitudinal section of the half-shell element of Figure 4. With reference to the mentioned figures, the mechanism of elastic prop according to the invention is generally indicated with the numeral 1. Said mechanism is applied to an office chair comprising a primary body 2 adapted to be engaged with an upper end of an upright (not shown in the enclosed figures) defining the vertical stand of the chair. The primary body 2 is turnably engaged with a support element 4 of the back of the chair along an oscillation axis 3. At least a support element 5 of the seat of the chair is located above the primary body 2. In the embodiment shown in the enclosed figures said support element 5 is hinged to the primary body 2 according to a first hinging axis 6 located before the oscillation axis 3 and parallel to it, and it is turnably engaged with the support element of the back 4 on a second hinging axis 7 located behind the oscillation axis 3 and parallel to it. Moreover, said hinging axes 6 and 7, and the oscillation axis 3 are substantially lined up, so as to enable the inclination, with respect to the primary body, both the support element 4 and, to a smaller extent, the seat engaged with the support element 5. In order to avoid a three-hinge arch which would not enable the reciprocal inclination of said portions, it is necessary to carry out a slot 7a within which one of the hinging points defining the above-mentioned rotation axes can slide. It is also possible to provide to carry out, instead of the kind of chair disclosed above with synchronous inclination both of the back and of the seat, other kinds of chairs in which for instance also the second hinging axis 7 is integral with the primary body 2 and therefore with the fixed seat, i.e. in "permanent contact" with the latter, or in which the support element of the seat is integral with the support element of the back and the seat can therefore oscillate integrally with the back. The mechanism of elastic prop 1 is placed between the support element 4, which is integral with the back, and the primary body 2, and it comprises an elastic element with linear strain 8, preferably a cylindrical helical compression spring. The latter has a main direction of development, i.e. its longitudinal axis 9, lying on a plane which is perpendicular to the oscillation axis 3 and a first end 8a which abuts against the primary body 2, though not directly, but advantageously with the interposition of an adjustment group 10 increasing or reducing the reaction force exerted by the elastic element 8, as will be better described below. Furthermore, the mechanism 1 comprises means 11 to transfer to the elastic element 8 the pressing force pushing the back backwards, said means being located between the support element 4 and a second end 8b of said elastic element 8. Said transfer means 11 comprise in their turn a half-shell element 12 having a hollow 12a housing at least the portion of the elastic element 8 starting from its second end 8b and at least a pushing extension 13 integral with the support element 4. Originally, said half-shell element 12 shows at least an abutment portion 12b for the pushing extension 13, which can place the application point of the pressing force exerted by the support element through said pushing extension, directly on the second end 8b of the elastic element 8, instead of placing it in an area far from the said end. In further detail, it is provided for two abutment portions 12b located in diametrically opposite positions on the half-shell element 12 for the same number of pushing extensions 13. Advantageously, the abutment portions 12b are placed outside near the entry of the hollow 12a, so as to exploit the whole length of the half-shell element 12 in order to move the action point of the force coming from the pushing extension 13 towards the first end 8a as much as possible. The adjustment group 10 comprises a reference element 14 abutting against the first end 8a of the elastic element 8 and moving along a direction of translation corresponding to the direction of the elastic strain of said elastic element 8, i.e. the longitudinal axis 9. The reference element 14 is operated by control means 15 which can vary its position in order to change the compression on the elastic element 8 and thus its reaction force. The control means 15 consist of a shaft 16 which is turnably engaged with the primary body 2 parallel to the oscillation axis 3, and which can be operated by means of a handling knob 17 laterally projecting from the seat. A handling screw 18 is coupled with the reference element 14 by means of a nut 14a integral with said element, and it develops along said direction of translation. The rotatory motion is transmitted from the shaft 16 to the handling screw 18 by means of an oblique gear 19 consisting of a worm 20 integral with the shaft 16 and of a helical toothed wheel 21 connected to said handling screw 18. Furthermore, the handling screw 18 reaches on one side beyond the helical toothed wheel 21 so as to support a bearing 22 which is placed between said wheel and the primary body to enable its low-friction rotation, and has on the other side an unthreaded stem portion 18a going through the elastic element 8. Said stem portion 18a is slidingly coupled with the half-shell element 12 and has an end head 18b constituting a stroke end for said half-shell element when the elastic element 8 is stretched and is not pressed by the pushing extension 13. In practice, the stem portion 18a defines a guide for the translation of the half-shell element 12 along the longitudinal direction 9 of the elastic element 8 during the axial deformations of the latter. The invention shows important advantages. As a matter of fact, the mechanism according to the invention allows to place the elastic element it comprises in the most suitable position, for instance in order to leave suitable spaces to house the group for the adjustment of the reaction force of said elastic element, so as to simplify the operation of the handling knob it is provided with, since said knob can be arranged laterally with respect to the chair, in a comfortable position with an easy access. Moreover, it should be pointed out that by suitably choosing the length of the half-shell element into which the elastic element is partially inserted, it is possible to locate the latter also horizontally if this is deemed as necessary to optimize the overall dimensions and the functional features of the mechanism as a whole. Finally, it should be observed that the present invention can be easily carried out and that also the costs related to its implementation are not very high.

Claims: chair comprising a mechanism of elastic prop (1) for a reclining portion, said chair comprising: a primary body (2) adapted to be engaged with an upper end of an upright defining the vertical stand of the chair, a support element (4) of the back of the chair, which is turnably engaged with said primary body (2) on an oscillation axis (3), and at least a support element (5) of the seat of the chair, which is placed above said primary body (2), the mechanism of elastic prop (1) being located between said support element (4) of the back and said primary body (2) and comprising: at least an elastic element (8) with linear strain having a main direction of development perpendicular to said oscillation axis (3) and a first end (8a) abutting against said primary body (2), and transfer means (11) to transfer to the elastic element (8) the pressing force pushing the back backwards, said transfer means (11) being placed between said support element (4) of the back and a second end (8b) of said elastic element (8), characterized in that said transfer means (11) comprise: a half-shell element (12) having a hollow (12a) adapted to house at least a portion of said elastic element (8) starting from said second end (8b), and at least a pushing extension (13) integral with said support element (4) of the back, and in that said half-shell element (12) comprises at least one abutment portion (12b) for said pushing extension (13), placing the point of application of said pressing force exerted by the support element (4) of the back through said pushing extension (13) in an area located far from said second end (8b) of said elastic element (8). Chair according to claim 1, characterized in that said at least one abutment portion (12b) of said half-shell element (12) is defined by an extension placed near the entry of said hollow (12a) and outside the latter. Chair according to claim 1, characterized in that it comprises two of said abutment portions (12b) for the same number of pushing extensions (13), which are placed in diametrically opposite positions on said half-shell element (12). Chair according to claim 1, characterized in that it comprises an adjustment group (10) connected with said primary body (2) to increase or reduce the elastic reaction force exerted by said elastic element (8). Chair according to claim 4, characterized in that said adjustment group (10) comprises a reference element (14) moving along a direction of translation corresponding to the direction of the linear strain (9) of said elastic element (8), and abutting against the first end (8a) of said elastic element (8), and control means (15) acting on said reference element (14) and changing its stop position. Chair according to claim 5, characterized in that said control means (15) comprise: a shaft (16) turnably engaged with the primary body (2) parallel to the oscillation axis (3) and operated by means of a handling knob (17) laterally projecting from the seat, a handling screw (18) coupled with said reference element (14) and developing along said direction of translation (9), and an oblique gear (19) for transmitting the motion from said control shaft (16) to said handling screw (18). Chair according to claim 6, characterized in that said handling screw (18) has an unthreaded stem portion (18a) developing through said elastic element (8) and slidingly coupled with said half-shell element (12), so as to define for the latter a guide for the translation along the direction of the linear strain (9) of said elastic element (8). Chair according to claim 6, characterized in that said oblique gear (19) consists of a worm (20) integral with said shaft (16) and of a helical toothed wheel (21) integral with said handling screw (18). Chair according to any of the claims 1 to 8, characterized in that said support element (5) of the seat is hinged to said primary body (2) along a first hinging axis (6) arranged before said oscillation axis (3) and parallel to it, and also to said support element (4) of the back on a second hinging axis (7) arranged behind said oscillation axis (3) and parallel to it, and in that said oscillation axis (3) and said hinging axes (6 and 7) are substantially lined up. chair according to any of the claims 1 to 8, characterized in that said support element (5) of the seat is integral with said primary body (2). chair according to any of the claims 1 to 8, characterized in that said at least one support element (5) of the seat is integral with said support element (4) of the back.

Inventors: MORESCHI SERGIO, MORESCHI, SERGIO
Applicants: COFEMO SPA, CO.FE.MO S.P.A.
Application year: 2001
Main classification: A47C1
IPC codes: A47C1, F16F1