as shown in fig1 the support for the chair comprises a fork 1 , equipped with base 2 of attachment to the back ( not shown ). the fork oscillates on the transversal pivot 3 by means of the rotation supports 4 with which the body 5 of the support is provided . an arm 6 oscillating within the body 5 is rigidly connected to pivot 3 , and carries a reaction pivot 7 , shown in fig2 and 3 , for spring 8 that regulates the effort necessary for the inclination of the chair . there is also provided a stop pivot 9 on arm 6 , located on the part most distant from the axis of rotation of arm 6 . pivot 9 has the function of engaging rack 28 ( fig1 ), commanded from the outside by means of lever 29 and rod 30 to stop the chair in the desired inclined position . [ 0023 ] fig2 also shows a bush 35 joined to reaction pivot 7 and acting as a housing for the mobile extremity 36 of spring 8 . the spring 8 is joined at the other extremity to the regulation device by means of the spring adjuster according to the present invention . such device has a fixed part 13 rigidly connected with body 5 and a mobile part 10 on which an extremity of spring 8 is coupled . according to the invention the fixed part or the mobile , or both parts , has a surface 14 inclined with respect to the axis of spring 8 ( which coincides with the right portion of the ii - ii section line outlined in fig1 ). between the fixed part 13 and mobile part 10 is arranged at least one wedge 12 also having an inclined complementary surface matching the surface of the fixed and / or mobile part . the wedge or wedges are mobile along an axis that is substantially perpendicular to the axis of spring 8 . due to the surface 14 the movement of wedges 12 is converted to the movement of mobile part 10 along the axis of spring 8 . in the preferred embodiment shown , there are two flat inclined surfaces 14 both on fixed part 13 and on mobile part 10 and there are two wedges 12 , each with two flat inclined surfaces 14 . wedges 12 are slidable on inclined and converging surfaces 14 of fixed part 13 and mobile part 10 under the action of screw 15 , which is operated from the outside via the knob 16 and rotating rod 17 . preferably , the inclined surfaces provide a mirror - image angle of inclination with respect to a common reference line . the angle a of inclination of the surfaces ( fig1 ) is between 85 and 65 degrees and is preferably around 80 degrees . the device according to the invention comprises means also to regulate the so - called “ zero position ,” or starting position , of the inclination . to such end the oscillating arm 6 is engaged by means of the slot 18 with the nose 19 of a spacer 20 . the nose 19 has a side prominence 25 and is transversely mobile on pivot 21 , operated from the outside by means of lever 22 . at its rear , the spacer is in contact with shelf 26 of the boss 27 attached to the chair support column 24 . when nose 19 is inserted into slot 18 , the spacer 20 is in contact with arm 6 by means of side prominence 25 that abuts the arm beside the said slot . when the nose is not lodged in the slot the nose abuts arm 6 . by means of pivot 21 , lever 22 also commands the finger lever 23 driving the damper , adjustable in height , located in the chair support column 24 . the support mechanism for chair presents , finally , l - shaped irons 31 for fixing the seat ( not shown ). irons 31 are coupled in an oscillating way via pivots 32 and 33 to fork 1 and to body 5 ; pivot 33 is controlled from the outside via knob m . the l - shaped irons have slots 34 to allow the horizontal shift of the seat with respect to the back . the support according to the invention operates as follows : the user , acting on knob 16 and , therefore , on screw 15 brings together or separates wedges 12 of the mechanism ; the position of reaction of spring 8 is thus consequently modified , changing the elastic characteristics and therefore the setting . more particularly , in the configuration shown in fig1 and 2 the wedges 12 are at their maximum distance and spring 8 is in its widest configuration ( i . e . set for the least effort of oscillation ). rotating knob 16 and screw 17 two wedges 12 are drawn together and simultaneously mobile part 10 is moved away from fixed part 13 , compressing spring 8 as shown in fig3 . in this configuration spring 8 is set for a greater oscillation force . the rotation action of the user is mediated by the inclined surfaces 14 of the wedges and of the fixed part 10 and mobile part 13 of the mechanism : this action is smoother , both in terms of the direct effort on the part of the user and in the search for a position more suited to his requirements . the angle α of the inclination of the surfaces can reach 85 degrees giving a strong amplification effect of the fineness of regulation and smootness of actuation . the regulation of the starting position of the oscillation is achieved by shifting spacer 20 transversely to the support for the oscillating chair upon pressure on pivot 21 through the lever 22 . the spacer has two positions : the first , corresponding to fig1 and 2 , where the nose 19 is housed in the slot 18 in oscillating arm 6 , and a second position , visible in fig3 where nose 19 leans externally against said arm 6 , after a translation of pivot 21 toward lever 22 . the second position is attainable after the user has inclined the chair so as to allow the disengagement of nose 19 from slot 18 and permit the translation of pivot 21 . the forces exerted by the oscillating arm to the body are not transmitted via pivot 21 , but are transferred directly by spacer 20 to shelf 26 and onto rib 11 . the horizontal regulation of the seat position is achieved by operating knob m which controls the spring loaded disengagement pivot 33 and the l - shaped irons can then run with their slots 34 on the pivots 32 and 33 of fork 1 and body 5 . when the desired position is reached the user releases the knob that blocks , under the action of the spring wound on pivot 33 , the sliding of said l - shaped irons and therefore of the seat with respect to the back . the inclined surfaces 14 , other than flat as shown in the figures , could be achieved by constant curvature , cylindrical , or varying , elliptical or with other types of curve , for determine a variation in behavior on the basis of the position of the interposed wedges , with the object of compensating the increase of the elastic reaction of the spring during compression .
an inclinable support for chairs , oscillating or synchronized armchairs and similar furniture has a device of regulation of the suspension and of the seat inclination , by means of setting an inclination spring , that comprises : at least one inclined surface between a fixed part and a mobile part in contact with the extremity of the said spring ; at least one wedge interposed between the fixed part and the mobile part with at least one inclined surface complementary to and matching the inclined surface ; and means for moving said wedge to cause said fixed and mobile parts to separate or come together .