SYNCHRONOUS LOCKING MECHANISM OF BACK-REST AND SEAT ANGULAR POSITION WITH RESPECT TO FOOT COLUMN, PARTICULARLY FOR CHAIRS

Abstract: A synchronous locking mechanism of back-rest and seat angular position with respect to footing column, particularly for chairs, consists of a toothed rack (7) secured integrally to a seat carrier (1) in a trough (5) formed in the seat carrier (1), and of a detent mechanism (8) having at least two detent plates (9) and installed in a beam body (2) in which body a foot column (4) of the chair is mounted. Displacement of the detent plates (9) is actuated by means of a spring system (19) mounted in a basket (15) fastened to the gas pressure spring thrust lever (17). The lever (17) is movable along the beam body (2) axis upon change of position of lever (31). The mechanism features a multiplied number of meshing positions and in consequence, a multiplied locking position with relation to the quantity of tooth spaces of the rack (7). Owing to use of the spring system (19), actuating the displacement of the detent plates (9), the mechanism features anti-shock operation.

Description: Synchronous locking mechanism of back-rest and seat angular position with respect to foot column, particularly for chairs. The object of the invention is a locking mechanism for synchronous locking back-rest and seat position with respect to foot column, particularly for chairs. The mechanism according to the present invention may be applied for locking angular position of back-rest, seat or back-rest and seat together, in synchronous or asynchronous mechanisms for chairs, easy chairs, armchairs etc. of various types. There are many locking mechanisms, known and described in patent documents, and then applied in production practice, serving for locking the angular position of back-rest and/or seat in relation to chair footing. The invention disclosed in US patent No 4.372.611, concerns locking mechanism of back-rest inclination angle with respect to chair seat. In this realisation, a rack is fastened to the chair seat in such a way that the rack can pivot about a fulcrum point, situated on the seat, and the detent element is firmly fastened to the seat frame. This mechanism, as well as other known realisations on the subject, utilise locking systems in which a single toothed element engages one of the teeth of the rack. The drawback of known realisations consists of limited number of rack teeth , and in consequence, limited number of possible meshing positions, which limits the number of possible positions of back-rest. The synchronous locking mechanism of back-rest and seat angular position with respect to the foot column according to this invention consists of a toothed rack, secured to the seat carrier and a detent mechanism, operatively connected with a beam body into which a footing column is placed, The detent mechanism has at least two detent plates . According to one of advantageous embodiment of the invention, the displacement of the detent plates is forced by a spring system, where position change of this system occurs in stepwise manner, after changing the position of lever actuating the locking system. According to yet another advantageous embodiment of the invention, the change of position of spring system forcing the displacement of detent plates occurs upon displacement of the spring end onto the other side of protrusion limiting the spring position. The object of this invention was shown in the preferred embodiment on the accompanying drawing of which fig. 1 is a top plan view of seat carrier; fig. 2 is an elevation view of seat carrier; fig. 3 is a fragmentary vertical sectional view of the seat carrier; fig. 4 is an enlarged fragmentary vertical sectional view of the detent mechanism ; fig. 5 is a vertical sectional view of the gas pressure spring thrust lever; fig. 6 is a vertical sectional view of beam body; fig. 7 is a vertical sectional view taken along line A - A on fig. 3; fig. 8 is a vertical sectional view taken along line B - B on fig. 3; fig. 9 is a fragmentary horizontal sectional view of the dented mechanism in the course of locking operation, where fig. I shows the mechanism unlocked; fig. II shows the detent plates ready for actuating the locking operation; fig. Ill shows meshing the upper detent plate; and fig. 10 is the top plan view of a single detent plate. The locking mechanism according to the present invention determines the relative position of seat carrier 1 with respect to beam body 2 , within whose bush 3 a chair foot column 4 is mounted. In seat carrier 1 a trough 5 is formed, in which, by means of fastening plate 6 , a toothed rack 7 is secured in an integral manner, by means of a bracket 6 .In the beam body 2, in front of teeth of the rack 7 a detent mechanism 8 is situated, comprising two detent plates 9 formed in the shape of rectangle, provided with three rectangular indentations 10 ,lj_and 12 identical in both plates. The detent plates 9 are placed in guide-way 13 , formed in beam body 2. The detent plates 9 are arranged one upon another in such a manner that longer indentation J . of the upper plate is superimposed upon shorter indentation 12 of the lower plate. The plates 9 are mounted to slide along the beam body axis but their upward movement is prevented by a blocking element \_. Two springs 19 , formed in the shape of not closed, isosceles triangles, are mounted over the detent plates 9 , in a basket 15 , attached by means of fasteners 16 to the gas pressure spring lever 17 . The ends 20 of springs 19 are bent at the angle of 90° with respect to the plane of the triangles, and these ends are mounted into indentations H and 12 Respectively, of detent plates 9. The detent plates 9 are restricted in their movement along the beam body 2 axis by a V-shaped spring 21 , installed transversally to the beam body 2 axis in the trough 5 near foot column 4 . The bending of the spring 21 is placed in a hole 22 , made in the vertical wall of the beam body 2 , and the endings of the spring 21 are placed, respectively : lower ending 23 locked in an aperture 24 made in the bottom part of the beam body 2 , and upper ending 25 is blocked in an indentation 26 of plate J_ connected integrally to gas pressure spring thrust lever 17 , and the extension of this ending 25 further passes through a hole 28 in the wall of beam body 2 , admitting positions A or B in relation to protrusion 29 limiting the positions of the spring 2 In a wall of the trough 5 of the seat carrier 1 there is a hole 30 in which a lever 31 in the shape of a rod, is mounted, passing through port 32 in plate 27 of gas pressure spring thrust lever 17 and further passing through port 36 in the wall of beam body 2 in which port 36 the lever 31 is locked. At the end part of beam body 2 , behind the bush 3 , opposite to blocking element 14 , a compression spring is installed , for fixing the position of beam body 2 with respect to seat carrier 1. The beam body 2 other end 34, opposite to spring 33, is rested upon end of the chair back-rest carrier 35 . In unlocked state the detent mechanism 8 is situated in position I. Shifting the lever 31 toward the forward portion of the seat causes, through pressure of the lever 31 exerted upon the plate 22 , shifting the gas pressure spring thrust lever 17 and through the pressure of springs 19 exerted upon the detent plates 9 , their shift toward rack 7 .The upper end 2 of the spring 21 , located in the aperture 28 changes its position, from position A into position B . The detent mechanism 9 takes position II. In this position, any pressure exerted upon the chair back-rest , for instance by the back of a sitting person, causes a slight pivot movement of the back-rest-carrier 35 about pivot 38, and a slight lifting of its lower end, and as a consequence, a slight lifting of the end 34 of the beam body 2 with the detent mechanism 8 ,in relation to seat carrier 1 and toothed rack 7 . One of the detent plates 9 meets the nearest tooth space of the toothed rack 7 and engages it. The detent mechanism is in position III or IV, depending on which detent plate 9_is meshed with the teeth of the rack 7 .Shifting the lever 31 in opposite direction , i.e. toward the backward portion of the seat, causes, through pressure exerted upon the plate 22 , shifting the thrust lever 17 toward the foot column 4 . The upper end 25 of the spring 21 changes its position from position B into position A. The ends 2Φ_of springs 19 exert pressure upon the detent plates 9 , but do not disengage them out of mesh with the toothed rack 2 , because of frictional engagement between a tooth flank of the rack 7 and the locked detent plate 9. A pressure exerted upon the chair back-rest by a sitting person, causes a slight lifting of the back-rest carrier end 35 as well as end 34 of the beam body 2 and in consequence, reduction of frictional force created between detent plate 9 and tooth flank of the rack 7 and thus sliding the detent plate 9 out of the engagement with the rack 7 and return the detent mechanism 8 to its initial position I. The locking mechanism according to the invention displays features of step-less regulation, because of the increased number of possible meshing engagements, and in consequence, the increased number of possible positions of the chair seat in respect to foot column as those positions are function not only of quantity of tooth spaces in the rack, but also of quantity of detent plates. A further advantageous feature of the mechanism according to the invention consists of obtaining of so called "anti-shock effect" , where a change of position of chair seat and back-rest does not occur directly after shifting the respective lever but after subsequent pressure upon the chair back-rest , for instance, by the back of the sitting person. This avoids any sudden back -rest inclination change which could provoke the unpleasant effect on a sitting person.

Claims: Claims 1. A synchronous locking mechanism of back-rest and seat angular position with respect to foot column, particularly for chairs, consisting of a toothed rack secured to the seat carrier and a detent mechanism connected to a beam body in which the foot column is mounted, characterised by fact, that the detent mechanism (8)_comprises at least two detent plates (9). 2. A mechanism according to claim 1, characterised by fact, that the displacement of the detent plates (9) is actuated by means of a spring system (19), where the change of position of the spring system (19 occurs in step-wise manner, after changing the position of lever (31) actuating the locking system. 3. A mechanism according to claim 1, characterised by fact, that the position change of the spring system (19) ,actuating the displacement of detent plates (9) occurs upon the displacement of end (25) of spring (21) into opposite side of protrusion (29) limiting the spring (21) position.

Inventors: WRONSKI SLAWOMIR, WRO&NACUTE
Applicants: WRONSKI SLAWOMIR, WRO&NACUTE
Application year: 1998
Main classification: A47C1
IPC codes: A47C1