Chair with height-adjustable backrest

Abstract

Chair (1) comprising a first member (5) solidly constrained to a backrest (4), a second member (6) solidly constrained to a support (3) connected to a seat (2), a constraining element (8) received in a first guide (9) of the first member (5) and in a second guide (10) of the second member (6). The first member (5) and the second member (6) are slidably constrained to each other to move from an initial locking position to a transit position, by means of an initial sliding, and from the transit position to a final locking position by means of a final sliding. During the initial sliding and the final sliding, the first member (5) slides with respect to the second member (6) along respectively a second sliding direction (13) and a first sliding direction (12) and there are respectively an initial displacement and a final displacement of the constraining element (8) with respect to at least one of the first guide (9) and the second guide (10).

Description

[0001] DESCRIPTION

[0002] “CHAIR WITH HEIGHT-ADJUSTABLE BACKREST”

[0003] Technical field

[0004] The present invention relates to a chair with height-adjustable backrest.

[0005] As is known, a chair with a backrest that is height-adjustable with respect to the seat offers better ergonomics for the user compared to a chair with a fixed-height backrest.

[0006] Prior art

[0007] Chairs with a backrest that is adjustable through the use of various adjustment mechanisms have been present on the market for years. These mechanisms typically comprise a support that is essentially vertical and connected to the seat (also known as back bar), a first member connected to the support, and a second member connected to the backrest and mounted on the support.

[0008] These include some types of mechanisms that are extremely easy to produce, but that, despite their simple production, require manual adjustment by the user that is burdensome in terms of time.

[0009] A simple example is a chair on which the seat locking system uses a screw that, through friction or interference, prevents sliding of the first member with respect to the second member, and that the user unscrews and tightens, respectively, in order to unlock and lock the backrest. In addition to taking a considerable period of time for the unscrewingtightening operation, the user must also often support the backrest at the desired height while performing the tightening operation.

[0010] There are also alternative mechanisms to this type that allow a quicker and more immediate adjustment by the user, although they are more articulated and more complex to produce.

[0011] An example of these mechanisms comprises a first member solidly constrained to the support that is provided with a series of notched seats in which, in a position of use of the backrest, movable inserts solidly constrained to the second member solidly constrained to the seat mesh, which thus lock sliding downwards of the backrest with respect to the support. In order to raise the backrest, the user directly raises the backrest and then releases it in the new position: when the backrest is raised, the movable inserts return into a retracted position inside the first member, allowing raising of the backrest, whereas when the backrest is released, the inserts mesh in the notched seats of the new position. In order to lower the backrest, it must first be lifted up to a position of maximum height, in which the inserts are locked in the retracted position, and then lowered down to a position of minimum height, in which the inserts are freed from the retracted position, allowing them once again to mesh in the notched seats.

[0012] It can therefore be guessed from this example that these mechanisms, in order to be more simple to use by the user, require multiple components, of which various ones are movable components. The processing of several components, especially with tolerances that allow a fluid mechanism to be obtained and without excessive clearances, is more onerous in terms of costs and processing times than processing of a few, simple elements. Furthermore, the more numerous the movable components, the greater the wear and tear and the possibility of breakdowns of the adjustment mechanism during its use.

[0013] Object of the invention

[0014] In this context, the technical task underlying the present invention is to obtain a chair with height-adjustable backrest that remedies the aforesaid drawbacks.

[0015] A technical task of the present invention is, in particular, to obtain a chair with height-adjustable backrest with an adjustment mechanism that can be easily used by the user and, at the same time, relatively simple to produce compared with the current alternatives.

[0016] The technical task and the specified objects are substantially achieved by a chair with adjustable height, in accordance with what is defined in independent claim 1 . Particular embodiments of the present invention are defined in the corresponding dependent claims.

[0017] Brief description of the drawings

[0018] Further characteristics and the advantages of the present invention will appear more clearly from the detailed description of some preferred, but not exclusive, embodiments of a chair with adjustable backrest illustrated in the appended drawings, wherein:

[0019] - Figure 1 schematically illustrates a chair in accordance with the present invention, viewed from behind;

[0020] - Figure 2 illustrates, in a partial view, the chair of Figure 1 sectioned along the line ll-ll;

[0021] - Figures 3, 4 and 5 illustrate, respectively, a front view, a side view and a bottom view of a first member visible in Figure 2;

[0022] - Figures 6, 7 and 8 illustrate, respectively, a front view, a side view and a bottom view of a second member visible in Figure 2;

[0023] - Figure 9 illustrates, in a front view and in an initial locking position, the first member, the second member and a constraining element of Figure 2;

[0024] - Figure 10 illustrates the first member, the second member and the constraining element of Figure 9, in a transit position reached following an initial sliding from the initial locking position of Figure 9;

[0025] - Figures 11 and 12 illustrate the first member, the second member and the constraining element of Figure 10 in two successive positions assumed during a final sliding from the transit position of Figure 10;

[0026] - Figure 13 illustrates, in a front view, the first member, the second member and the constraining element in a final locking position reached following completion of the final sliding of Figures 11 and 12;

[0027] - Figure 14 illustrates, in a front view, the first member, the second member and the constraining element in another initial locking position;

[0028] - Figure 15 illustrates the first member, the second member and the constraining element of Figure 14 in a transit position reached following an initial sliding from the initial locking position of Figure 14;

[0029] - Figure 16 illustrates, in a front view, the first member, and, on the dashed line, a loop trajectory and some positions assumed by the constraining element with respect to the first member travelling along the loop trajectory;

[0030] - Figure 17 illustrates the second member, and, on the dashed line, a linear trajectory and some positions assumed by the constraining element with respect to the second member travelling along the linear trajectory.

[0031] Detailed description of preferred embodiments of the invention

[0032] With reference to the cited figures, reference number 1 denotes in its entirety a chair with adjustable backrest according to the present invention. The chair 1 of the present invention comprises, first of all, a seat 2, a support 3 connected to the seat 2 and a backrest 4, slidably mounted on the support 3, adjustable in height with respect to the seat 2.

[0033] The chair 1 then comprises a first member 5 solidly constrained to the backrest 4 and a second member 6 solidly constrained to the support 3 that are part of an adjustment system 7 of the height of the backrest 4 with respect to the seat 2 and that are movable with respect to one another.

[0034] The first member 5 and the second member 6 are slidably constrained to each other, so as to be able to slide with respect to one another, to allow variation of the height of the backrest 4 with respect to the seat 2. It is emphasised that, within the scope of the present invention, reference will often be made to the relative movement of the first member 5 and of the second member 6 regardless of whether, referring to the chair 1 in its entirety, it is the first member 5 or the second member 6 that is moving. In further detail, in the more general embodiment, the first member 5 and the second member 6 are constrained so as to move with respect to one another from an initial locking position to a transit position by means of an initial sliding, and then, by means of a final sliding, from said transit position to a final locking position. The transit position is therefore a relative position of the first member 5 and of the second member 6 in which the initial sliding terminates and from which it is possible for them to start the final sliding to reach the final locking position. Advantageously, the transit position is a position in which there is a reversal of at least one component of the relative motion of the first member 5 and the second member 6.

[0035] In the initial locking position, the backrest 4 is at an initial height with respect to the seat 2, whereas in the final locking position the backrest 4 is at a final height, different from the initial height, with respect to the seat 2. By this it is meant that, by means of the initial sliding and the subsequent final sliding of the first member 5 and of the second member 6, the backrest 4 is adjusted in height with a lowering or a raising with respect to the seat 2.

[0036] The chair 1 subject-matter of the present invention further comprises a constraining element 8 that is placed between the first member 5 and the second member 6 and is movable with respect to them. A first portion of said constraining element 8 is received in a first guide 9 comprised in the first member 5, whereas a second portion of the same constraining element 8 is received in a second guide 10 comprised in the second member 6. Referring to a sliding interface 11 , along which the first member 5 and the second member 6 can slide with respect to one another, the constraining element 8 crosses said sliding interface 11. It is noted that said sliding interface 11 is not intended to be a physical component, but rather as the ideal surface interposed between the first member 5 and the second member 6, along which the first member 5 and the second member 6 can slide with respect to one another. Considering, for example, the embodiment illustrated, the sliding interface 11 along which the first member 5 and the second member 6 can slide with respect to one another is substantially a plane, which crosses the constraining element 8 interposed between the two members. The constraining element 8 is advantageously separate and detached from the first member 5 and from the second member 6, and is free to move by translating with respect to each member along the respective guide, which contains the respective portion of the constraining element 8.

[0037] The constraining element 8, thus received in the first guide 9 and in the second guide 10, prevents the first member 5 from sliding with respect to the second member 6 along a first sliding direction 12, both in the initial locking position and in the final locking position of the two members.

[0038] Advantageously, in these locking positions of the first member 5 and of the second member 6, the constraining element 8 is not able to translate with respect to the first guide 9 and to the second guide 10, due to the combination of constraints on the movement of the constraining element 8 introduced by the first guide 9 and by the second guide 10.

[0039] During the initial sliding between the first member 5 and the second member 6, the first member 5 slides with respect to the second member 6 along a second sliding direction 13 opposite to the first sliding direction 12 (the second sliding direction 13 is parallel to the first sliding direction 12 but with a travelling direction opposite to the one of the first sliding direction 12). Also during the initial sliding, the constraining element 8 performs an initial displacement with respect to at least one of the first guide 9 and the second guide 10.

[0040] When the first member 5 and the second member 6 then perform the final sliding from the transit position to the final locking position, the first member 5 slides, with respect to the second member 6, along the first sliding direction 12 until the first member 5 and the second member 6 have reached the final locking position. During this initial sliding, there is a further displacement of the constraining element 8: there is, in particular, a final displacement with respect to at least one of the first guide 9 and the second guide 10. In the embodiment illustrated, the first sliding direction 12 advantageously has a downward vertical component, and the second sliding direction 13 has an upward vertical component. In other words, when the first member 5 slides during the initial sliding, the backrest 4 connected to the first member 5 rises with respect to the seat 2, whereas when the first member 5 slides during the final sliding, the backrest 4 lowers with respect to the seat 2.

[0041] Advantageously, in the embodiment illustrated, the constraining element 8 prevents, in the transit position, a sliding of the first member 5 along the second sliding direction 13 with respect to the second member 6. In other words, the constraining element 8 prevents a further sliding in the second sliding direction 13 by the first member 5, when the transit position has already been reached; at this point, the direction along which the first member 5 slides with respect to the second member 6 may be reversed to perform the final sliding.

[0042] In the preferred embodiments, at least one of the initial displacement and the final displacement that the constraining element 8 performs with respect to both the first guide 9 and the second guide 10 comprises at least one displacement component perpendicular to the first sliding direction 12. In the embodiment illustrated, both the initial displacement and the final displacement provide for a displacement of the constraining element 8 with respect to each of the first guide 9 and the second guide 10, and comprise said perpendicular displacement component. The perpendicular component is, advantageously, substantially tangential to the sliding interface 11 (a plane in the embodiment illustrated) along which the first member 5 and the second member 6 can slide.

[0043] In the preferred embodiments, the constraining element 8 is advantageously a sphere, and is therefore capable of rolling and roto- translating with respect to the first guide 9 and to the second guide 10.

[0044] In the preferred embodiments, the initial locking position, the transit position and the final locking position constitute advantageously a sequence of positions, which forms part of a plurality of sequences of positions. The final locking position of any sequence of positions that is part of said plurality of sequences coincides with the initial locking position of a different sequence of positions that is also part of the plurality of sequences. The first member 5 and the second member 6 are constrained by means of the constraining element 8 so as to slide with respect to one another, in succession, through each sequence of positions of the plurality of sequences of positions. The first member 5 and the second member 6 can slide through each sequence of positions of the plurality of sequences of positions in succession: this means that one and only one different sequence of positions of the plurality of sequences is successively concatenated to each sequence of positions of the plurality of sequences, so that the plurality of sequences forms a closed chain of sequences of positions. In other words, once final sliding from the transit position to the final locking position of any one sequence of positions of the closed chain has terminated, the first member 5 and the second member 6 are in the initial locking position of a successive sequence of positions of the closed chain.

[0045] Advantageously, the plurality of sequences comprises at least one lowering sequence, in which the final height is lower than the initial height, and at least one raising sequence, in which the final height is higher than the initial height. Since any final locking position of a first sequence of the plurality of sequences coincides with the initial locking position of a second sequence of the plurality of sequences, the final height of the first sequence coincides with the initial height of the second sequence. In referring, therefore, to the height assumable by the backrest 4 in any one locking position comprised in the plurality of sequences, for the sake of simplicity of exposition no distinction will be made below between the initial height and the final height, but reference will simply be made to a height. In each embodiment of the present invention, the plurality of sequences of positions can advantageously comprise various combinations of lowering and raising sequences.

[0046] A first case is the one of the embodiment illustrated, in which a plurality of consecutive lowering sequences and a single raising sequence are present.

[0047] In a second case, a single lowering sequence and a plurality of consecutive raising sequences are present.

[0048] In a third case, there are a first plurality of consecutive lowering sequences and a second plurality of consecutive raising sequences. In this case, the number of consecutive lowering sequences and the number of consecutive raising sequences are advantageously equal. The user is thus provided with a number of raising adjustments of the backrest 4 equal to the number of lowering adjustments.

[0049] If, in these three cases, all the heights assumable by the backrest 4 are considered, determined by all the locking positions comprised in the plurality of sequences, it is possible to identify: a minimum height, lower than all the other heights; a maximum height, higher than all the other heights; one or more intermediate heights, i.e. all the remaining heights that are neither the minimum height nor the maximum height.

[0050] In the first case already cited, therefore, the backrest 4, through the single raising sequence, can be raised from the minimum height up to the maximum height, from which it can be lowered in succession through the intermediate heights until it once again assumes the minimum height, from which the cycle can be repeated.

[0051] In the second case, the backrest 4, through the single lowering sequence, can be lowered from the maximum height down to the minimum height, from which it can be raised in succession through the intermediate heights until it once again assumes the maximum height, from which the cycle can be repeated.

[0052] In the third case, the backrest 4 can be raised from the minimum height through a first group of intermediate heights up to the maximum height, from which it can be lowered through a second group of intermediate heights down to the minimum height. Since the number of lowering sequences is equal to the number of raising sequences, the number of intermediate heights of the first group of intermediate heights is equal to the number of intermediate heights of the second group of intermediate heights. Advantageously, each intermediate height of the first group of intermediate heights coincides with only one intermediate height of the second group of intermediate heights, so that the intermediate heights reachable through the consecutive raising sequences coincide with the intermediate heights reachable through the consecutive lowering sequences.

[0053] Advantageously, in the preferred embodiments at least one of the first guide 9 and the second guide 10 is a loop guide, which defines a loop trajectory 14 for the displacement of the constraining element 8 (Figure 16). The constraining element 8 travels, according to a single travelling direction, along the loop trajectory 14 during the sliding of the first member 5 and of the second member 6 through the plurality of sequences of positions. This means that the loop trajectory 14 is a loop circuit that the constraining element 8 travels in its entirety and with a single travelling direction when the first member 5 and the second member 6 slide in succession through each sequence of positions of the plurality of sequences of positions (at least in normal functioning conditions with the chair straight). If the first member 5 and the second member 6 slide once again in succession through each sequence of positions of the plurality of sequences of positions, the constraining element 8 once again travels along the loop trajectory 14 with the same travelling direction.

[0054] In one embodiment of the present invention, not illustrated, both the first guide 9 and the second guide 10 are loop guides.

[0055] In some embodiments, the first guide 9 is a loop guide and the second guide 10 is not a loop guide (as in the embodiment illustrated), or the first guide 9 is not a loop guide and the second guide 10 is a loop guide. In these embodiments, the one of the first guide 9 and the second guide 10 that is not a loop guide advantageously defines a linear trajectory 15 for the displacement of the constraining element 8 with respect to the second guide 10 (Figure 17). Said linear trajectory 15 essentially extends along a line that extends between two separate ends, between which the line can comprise rectilinear and / or curved sections. During the sliding of the first member 5 and the second member 6 through the plurality of sequences of positions, the constraining element 8 travels along the linear trajectory 15 both according to a first travelling direction and according to a second travelling direction opposite to the first, i.e. passing several times through positions placed along the linear trajectory 15. In the embodiment illustrated, the first guide 9 is a loop guide and the second guide 10 defines a linear trajectory 15. In one embodiment of the present invention, not illustrated, the second guide 10 is a loop guide and the first guide 9 defines a linear trajectory 15.

[0056] In the embodiments having at least one loop guide, during the initial sliding of the first member 5 and of the second member 6, the initial displacement of the constraining element 8 along the loop trajectory 14 advantageously has a component along an initial direction 16. If the first guide 9 is a loop guide, this initial direction 16 is that direction along which, during the initial sliding, the second member 6 slides with respect to the first member 5. If the second guide 10 is a loop guide, the initial direction 16 is that direction along which, again during the initial sliding, the first member 5 slides with respect to the second member 6. In the same embodiments having at least one loop guide, during the final sliding of the first member 5 and of the second member 6, the initial displacement of the constraining element 8 along the loop trajectory 14 also has a component along a final direction 17 opposite (in direction) to the initial direction 16. The result is that if the first guide 9 is a loop guide, the final direction 17 is that direction along which, during the final sliding, the second member 6 slides with respect to the first member 5. The result is therefore also that if the second guide 10 is a loop guide, the final direction 17 is that direction along which, again during the final sliding, the first member 5 slides with respect to the second member 6.

[0057] In embodiments in which a loop guide is present, this is shaped so that, during the sliding of the first member 5 and of the second member 6 through any one sequence of positions of the plurality of sequences, the loop trajectory 14, along which the constraining element 8 moves, comprises at least one substantially U-shaped section. This means that, when the first member 5 and the second member 6 slide through any one sequence of positions of the plurality of sequences, the constraining element 8 performs at least one reversal of the travelling direction.

[0058] In embodiments of the present invention, respectively the first member 5 or the second member 6 advantageously comprises a magnet 18 associated respectively with the first guide 9 or with the second guide 10, and the constraining element 8 comprises a ferromagnetic material. The magnet 18 is arranged so that, at least in the transit position, the magnet 18 holds the constraining element 8 still with respect, respectively, to the first guide 9 or to the second guide 10 (the one with which the magnet is associated). In the embodiments in which at least one loop guide is present, the magnet 18 is advantageously comprised in the one of the first member 5 and the second member 6 that does not comprise the loop guide. This means that, if the first guide 9 is a loop guide, the magnet 18 is comprised in the second member 6, and if the second guide 10 is a loop guide, the magnet 18 is comprised in the first member 5. In the embodiment illustrated, since only the first guide 9 is a loop guide, the magnet 18 is comprised in the second member 6.

[0059] In preferred embodiments of the present invention, at least one of the first guide 9 and the second guide 10 advantageously defines a housing 19, into which the constraining element 8 is inserted when the first member 5 and the second member 6 are in the initial locking position and in the final locking position. This means that when the first member 5 and the second member 6 are in each of the initial locking position and the final locking position (of any one sequence of positions), at least one of the first guide 9 and the second guide 10 defines a housing 19, into which the constraining element 8 is inserted.

[0060] Advantageously, the elements of the adjustment system 7 (the first and the second member 5, 6, and the constraining element 8) determine a locking condition in stable equilibrium. When the first member 5 and the second member 6 are in the initial locking position and in the final locking position, the constraining element 8 is in a position of stable equilibrium. If, for example, it is subjected to a stress that shifts the constraining element 8 away from its position of stable equilibrium, the constraining element 8 returns, advantageously under the effect of the force of gravity of the constraining element and / or the first member 6 connected to the backrest, to its position of stable equilibrium (advantageously inserted into the housing 19). The first member 5 and the second member 6, possibly shifted away from the initial locking position or from the final locking position following said stress, return, respectively, to the initial locking position or to the final locking position.

[0061] In the embodiment illustrated, in which the first guide 9 is a loop guide and the constraining element 8 is a sphere, the first guide 9 is advantageously defined by a channel made inside the first member 5, shaped so that the first portion of the sphere, received in the first guide 9, is a spherical segment at a base (with height equal to the depth of the channel), the volume of which remains constant while the constraining element 8 travels along the loop trajectory 14 (advantageously substantially equal to a halfsphere).

[0062] The first guide 9 further defines four first housings 191 for the constraining element 8, with which an equal number of initial and final locking positions of the first member 5 and the second member 6 correspond, between which the first member 5 and the second member 6 can slide through a plurality of sequences, comprising three consecutive lowering sequences and one raising sequence. Considering a first member 5 that defines a loop trajectory 14 in which the final displacement of the constraining element 8 has a component along a final direction 17 aligned vertically upwards (Fig. 3), the four first housings 191 are placed each at a different height along said final direction 17. It is thus possible to identify: a first lower housing 1911 , placed lower down than all the other first housings 191 , into which the constraining element 8 is inserted when the first member 5 and the second member 6 are in the locking position in which the backrest 4 is placed at a maximum height; a first intermediate lower housing 1912, placed higher up than the first lower housing 1911 , into which the constraining element 8 is inserted when the first member 5 and the second member 6 are in the locking position in which the backrest 4 is placed at a first intermediate height; a first intermediate upper housing 1913, placed higher up than the first intermediate lower housing 1912, into which the constraining element 8 is inserted when the first member 5 and the second member 6 are in the locking position in which the backrest 4 is placed at a second intermediate height lower than the first intermediate height; a first upper housing 1914, placed higher up than the first intermediate upper housing 1913, into which the constraining element 8 is inserted when the first member 5 and the second member 6 are in the locking position in which the backrest 4 is placed at a minimum height.

[0063] The first lower housing 1911 , the first intermediate lower housing 1912 and the first intermediate upper housing 1913 are advantageously distributed equally along an imaginary line 20 parallel to the final direction 17, whereas the first upper housing 1914 lies misaligned from said imaginary line 20 by a first distance.

[0064] Taking as a reference an inner edge 21 and an outer edge 22 of the loop guide, each first housing 191 of the first guide 9 is defined in an enlargement of the channel on the side of whichever of the inner edge 21 and the outer edge 22 is placed higher up along the final direction 17 with respect to the other of the inner edge 21 and the outer edge 22. In particular, each first housing 191 is advantageously counter-shaped to a portion of the surface of the constraining element 8, so that the constraining element 8, inserted into the first housing 191 , can only perform displacements with a component along the initial direction 16 (in the opposite direction to the final direction 17, i.e. downwards in the appended figures) with respect to the first housing 191. In the embodiment illustrated, in which the constraining element 8 is a sphere, each first housing 191 is counter-shaped to a circumferential arc of the constraining element 8.

[0065] From the first lower housing 1911 as far as the first upper housing 1914 there extends a lowering portion 23 of the loop guide that also comprises the first intermediate lower housing 1912 and the first intermediate upper housing 1913, and that is travelled by the constraining element 8, passing in succession through those first housings 191 when the first member 5 and the second member 6 slide in succession through the three consecutive lowering sequences.

[0066] In detail, the first lower housing 1911 and the first intermediate lower housing 1912 are connected through a first segment of the lowering portion 23 comprising various sections connected in succession. Firstly, a rectilinear section descending along an oblique direction that is tangential to the sliding interface 11 . Secondly, a first U-shaped coupling with direction exiting from the coupling parallel to the oblique direction. Thirdly, a rectilinear section ascending parallel to the oblique direction, overlying the descending rectilinear section, of a greater length than the descending rectilinear section and intersecting the imaginary line 20 (along which the first lower housing 1911 and the first intermediate lower housing 1912 are arranged). Lastly, a second U-shaped coupling, similar to the first U- shaped coupling with direction exiting from the coupling parallel to the oblique direction.

[0067] The first intermediate lower housing 1912 and the first intermediate upper housing 1913 are connected by means of a second segment of the lowering portion 23 identical in extension to the first segment.

[0068] The first intermediate upper housing 1913 is connected to the first upper housing 1914 by means of a third segment of the lowering portion 23 comprising various sections connected in succession. Firstly, an ascending rectilinear section similar to the ascending rectilinear section of the first segment. Secondly, a first U-shaped coupling similar to the first U- shaped coupling of the first segment. Thirdly, an ascending rectilinear section parallel to the oblique direction, overlying the descending rectilinear section of the third segment, of a greater length than the ascending rectilinear section of the first segment and intersecting the imaginary line 20.

[0069] From the first upper housing 1914 as far as the first lower housing 1911 there then extends a lowering portion 24 of the loop guide, which is travelled by the constraining element 8 when the first member 5 and the second member 6 slide along the raising sequence of the plurality of sequences. Said raising portion 24 comprises a fourth segment and a successive fifth segment connected to the fourth segment. The fourth segment comprises: a coupling between the first upper housing 1914 and a descending vertical section; the descending vertical section, parallel to the initial direction 16, which is tangential to the sliding interface 11 and which is displaced from the imaginary line 20 by a second distance, greater than the first distance by which the first upper housing 1914 is displaced; a coupling between the descending vertical section and a descending rectilinear section parallel to the oblique direction and terminating at the intersection with the imaginary line 20. The fifth segment extends from said intersection and is identical to the first segment of the lowering portion 23: it therefore comprises a descending rectilinear section, a first U-shaped coupling, an ascending rectilinear section and a second U-shaped coupling.

[0070] The first guide 9 also has an insertion channel 25 for inserting the constraining element 8 to facilitate the assembly of the height adjustment system 7 of the backrest 4, which is not used in normal functioning. Said insertion channel 25 is an extension of the descending rectilinear section in the upper part of the first guide 9, and is advantageously made inaccessible to the constraining element 8, when the chair 1 is in use, by means of the insertion of a removable cap 26.

[0071] In the embodiment illustrated, the first member 5, in which the first guide 9 is obtained, is a plate in which a seat is obtained to guide both the relative sliding between the first member 5 and the second member 6, and the relative sliding between the first member 5 and the support 3, to which the second member 6 is solidly constrained (Figs. 3, 4 and 5).

[0072] Once again in the embodiment illustrated, the second member 6 (Figs. 6, 7, 8) is a shaped plate that has a C shape, which forms internally a cavity 28 delimited in one of its parts by an opening between the two ends of the C shape. An inner side of the C shape defines the second guide 10 in which the constraining element 8, in use, can move. In particular, a lower inner side 27 of the C shape has a second housing 192 placed in a median horizontal position with respect to the cavity 28, into which the constraining element 8 is inserted in some locking positions of the first member 5 and of the second member 6. Similarly to the first housings 191 of the first guide 9, the second housing 192 of the second guide 10 is advantageously counter-shaped to a portion of the surface of the constraining element 8, so that the constraining element 8, inserted into the second housing 192, can only perform displacements with a component directed upwards with respect to the second housing 192. In the embodiment illustrated, in which the constraining element 8 is a sphere, the second housing 192 is counter-shaped to a circumferential arc of the constraining element 8. In particular, the constraining element 8 is inserted into the second housing 192 of the second guide 10 when the first member 5 and the second member 6 are in the locking positions in which the backrest 4 is placed at the maximum height, or at the first intermediate height, or at the second intermediate height. This means that the constraining element 8 is inserted into said second housing 192 of the second guide 10 when, in the first guide 9, the constraining element 8 is inserted into the first lower housing 1911 , or into the first intermediate lower housing 1912, or into the first intermediate upper housing 1913.

[0073] Referring to a horizontal direction, the lower inner side 27 of the second guide 10 defines: a horizontal section of the linear trajectory 15, to the right of the second housing 192 (between the second housing 192 and the opening of the cavity 28); an inclined section (with respect to the horizontal direction) of the linear trajectory 15, to the left of the second housing. Moving away from the second housing 192 along the inclined section, the lower inner side 27 approaches the upper inner side 29 of the second guide 10 (which is parallel to the horizontal section in the figures). At the portion of the upper inner side 29 closest to the lower inner side 27, the magnet 18 is advantageously positioned. Lastly, the second member 6 has pivots 30, perpendicular to the shaped plate, insertable into corresponding holes obtained in the support 3, thanks to which the second member 6 can be fixed to the support 3.

[0074] Whereas the first guide 9, obtained in the first member 5, prevents movement of the constraining element 8 in a first direction of a direction perpendicular to the sliding interface 11 between the first member 5 and the second member 6, the support 3 prevents movement of the constraining element 8 in the opposite direction to said perpendicular direction.

[0075] In order to better illustrate functioning of the invention, reference will be made to the embodiment illustrated in the appended figures from 9 to 15, in which the first member 5 and the second member 6 have an orientation such that the first sliding direction 12 of the first member 5 with respect to the second member 6 is vertically oriented downwards and the second sliding direction 13 of the first member 5 with respect to the second member 6 is vertically oriented upwards. Starting from any position, the user, in order to adjust the height of the backrest 4, must first raise the backrest 4 (by sliding the first member 5 along the second sliding direction 13 according to the initial sliding) until the first member 5 and the second member 6 have reached a transit position (getting locked), and then allow the backrest 4 to descend, thus sliding the first member 5 with respect to the second member 6 along the first sliding direction 12 by means of the final sliding. During each initial sliding and final sliding of the first member 5 and of the second member 6, the sphere (which is the constraining element 8) roto-translates along each guide as a result of its own weight and of the respective edges of the first guide 9 and of the second guide 10.

[0076] Referring, in particular, to Figure 9, the first member 5 and the second member 6 are shown in an initial locking position corresponding with the maximum height of the backrest 4 (not shown); said initial locking position is part of the first lowering sequence of the three consecutive lowering sequences. In the same figure, the constraining element 8 is inserted into the first lower housing 1911 of the first guide 9 and into the second housing 192 of the second guide 10, preventing sliding of the first member 5 along the first sliding direction 12 with respect to the second member 6 (downwards).

[0077] In Figure 10, the first member 5 and the second member 6 are in a transit position reached following an initial sliding from the initial locking position of Figure 9, with the constraining element 8 that prevents a further sliding of the first member 5 with respect to the second member 6 along the second sliding direction 13 (upwards, in the opposite direction to the first sliding direction 12): as can be deduced from a comparison with Figure 9, in order to reach the position shown in Figure 10, the constraining element 8 has performed an initial displacement, with respect to the first guide 9, moving away from the first lower housing 1911 along the descending rectilinear section of the first segment of the loop guide, and, with respect to the second guide 10, moving away from the second housing 192 along the inclined section of the second guide 10 until it comes into contact with the magnet 18 comprised in the second guide 10.

[0078] Figure 11 shows the first member 5 and the second member 6 during a final sliding starting from the transit position of Figure 10: it can be noted, in particular, that the constraining element 8 retained by the magnet 18, in starting the final displacement with respect to the first guide 9, crosses the first U-shaped coupling of the first segment of the first guide 9 and starts to travel backwards along the inclined section of the second guide 10.

[0079] Figure 12 shows the first member 5 and the second member 6 during the final sliding, but in a subsequent moment to the one of Figure 11 , with the constraining element 8 that, with respect to the first guide 9, has travelled along the ascending rectilinear section and that, with respect to the second guide 10, has travelled backwards along the oblique section, has passed beyond the second housing 192 and has travelled along a first part of the horizontal section (of a length lower than half the length of the horizontal section).

[0080] Figure 13 shows the first member 5 and the second member 6 in the final locking position reached at the end of the final sliding of Figures 11 and 12, with the constraining element 8 inserted into the first intermediate lower housing 1912 of the first guide 9 and into the second housing 192 of the second guide 10. In said locking position, the backrest 4 is placed at the first intermediate height with respect to the seat 2, lower than the maximum height. The first member 5 and the second member 6 have thus performed an initial sliding and a final sliding through the first lowering sequence. From comparison with Figure 12, completion of the final displacement of the constraining element 8 can be deduced, which, with respect to the first guide 9, has travelled along the second U-shaped coupling of the first segment and which, with respect to the second guide 10, has travelled backwards along the first part of the horizontal section.

[0081] Subsequently, the first member 5 and the second member 6 can slide through the second lowering sequence, consecutive to the first lowering sequence, in a similar manner to what has occurred in the first lowering sequence. The constraining element 8, in a sliding of the first member 5 and of the second member 6 through the second lowering sequence, moves along the second segment of the lowering portion 23 of the loop guide to insert itself into the first intermediate upper housing 1913. In the final locking position of the second lowering sequence, the backrest 4 is placed at the second intermediate height with respect to the seat 2, lower than the first intermediate height.

[0082] Subsequently, the first member 5 and the second member 6 can slide through the third lowering sequence, consecutive to the second lowering sequence. When the first member 5 and the second member 6 slide through the third lowering sequence, the constraining element 8 moves with respect to the second guide 10 by travelling along the oblique section as far as the magnet 18, then travelling backwards along the oblique section, passing beyond the housing 19 and moving along the horizontal section up to around half the length of the horizontal section. With respect to the first guide 9, on the other hand, the constraining element 8 moves by travelling along the third segment of the lowering portion 23 to insert itself into the first upper housing 1914. In the final locking position of the third lowering sequence (Fig. 14), the backrest 4 is placed at the minimum height with respect to the seat 2, lower than the second intermediate height.

[0083] Subsequently, the first member 5 and the second member 6 can slide through the single raising sequence in order to return to the locking position corresponding with the maximum height of the backrest 4 with respect to the seat 2. During the initial sliding through said raising sequence, the constraining element 8 moves, with respect to the first guide 9, travelling along the fourth segment of the raising portion 24 and the descending rectilinear section of the fifth segment of the raising portion 24. With respect to the second guide 10, on the other hand, the constraining element 8 completes the travel of the horizontal section towards the opening of the cavity 28 and then travels backwards along the horizontal section, passes beyond the housing 19 and travels along the oblique section. The first member 5 and the second member 6 are shown in the transit position at the end of said initial sliding in Figure 15. In the final sliding of the first member 5 and of the second member 6 starting from said transit position, the constraining element 8 moves with respect to the second guide 10 in a similar manner to what has occurred during the final sliding of the first member 5 and of the second member 6 through the first lowering sequence. With respect to the first guide 9, on the other hand, the constraining element 8 completes the travel of the fifth segment of the raising portion 24 of the loop guide to insert itself into the first lower housing 1911. The final locking position of the raising sequence therefore coincides with the initial locking position of the first raising sequence, shown in Figure 9.

[0084] In order to summarise the displacements of the constraining element 8 with respect to the first guide 9, the first guide 9 is illustrated in Figure 16 with the loop trajectory 14 as a dashed line, with an arrow indicating the direction of travel and the positions assumed by the constraining element 8, on the dashed line, when inserted into the housings of the first guide 9.

[0085] In order to summarise, on the other hand, the displacements of the constraining element 8 with respect to the second guide 10, Figure 17 illustrates the second guide 10 with the linear trajectory 15 of the constraining element 8 on the dashed line, together with some positions assumed by the constraining element 8, on the dashed line, when travelling along the linear trajectory 15.

[0086] The present invention achieves important advantages.

[0087] The components required by the invention are limited in number and relatively simple to manufacture, which can be performed with standard equipment for the sector. Given the number of components, the chair is relatively easy to assemble, as well as being simple to use by the user. The number of movable components and the wear and tear caused by the relative motion between the components during adjustment are also reduced.

[0088] The invention thus conceived is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept that characterises it.

[0089] All the details may be replaced by other technically equivalent ones and the materials used, as well as the shapes and sizes of the various components, may be any whatsoever according to needs.

Claims

CLAIMS1. A chair provided with a seat (2), a support (3) connected to the seat (2) and a backrest (4) mounted on the support (3) and adjustable in height with respect to the seat (2), comprising: a first member (5) solidly constrained to the backrest (4); a second member (6) solidly constrained to the support (3); a constraining element (8) placed between the first member (5) and the second member (6); wherein: the first member (5) and the second member (6) are slidably constrained so as to move with respect to one another from an initial locking position to a transit position, by means of an initial sliding, and then from said transit position to a final locking position by means of a final sliding; in the initial locking position the backrest (4) is, with respect to the seat (2), at an initial height; in the final locking position the backrest (4) is, with respect to the seat (2), at a final height different from the initial height; the first member (5) comprises a first guide (9) that receives a first portion of the constraining element (8); the second member (6) comprises a second guide (10) that receives a second portion of the constraining element (8); in both the initial locking position and in the final locking position, the constraining element (8) prevents a sliding of the first member (5) with respect to the second member (6) along a first sliding direction (12); during the initial sliding, the first member (5) slides with respect to the second member (6) along a second sliding direction (13) opposite to the first sliding direction (12); during the initial sliding, there is an initial displacement of theconstraining element (8) with respect to at least one of the first guide (9) and the second guide (10); during the final sliding, the first member (5) slides with respect to the second member (6) along the first sliding direction (12); and during the final sliding, there is a final displacement of the constraining element (8) with respect to at least one of the first guide (9) and the second guide (10); and further wherein the constraining element (8) is a sphere.

2. The chair according to claim 1 , wherein in the transit position the constraining element (8) prevents a sliding of the first member (5) along the second sliding direction (13) with respect to the second member (6).

3. The chair according to any one of claims 1 or 2, wherein: the initial locking position, the transit position and the final locking position constitute a sequence of positions forming part of a plurality of sequences of positions; the final locking position of any one sequence of positions that is part of the plurality of sequences coincides with the initial locking position of a different sequence of positions that is part of the plurality of sequences; the first member (5) and the second member (6) are constrained so as to slide one with respect to the other in succession through each sequence of positions of the plurality of sequences of positions; and the plurality of sequences of positions comprises at least one lowering sequence, in which the final height is lower than the initial height, and at least one raising sequence, in which the final height is higher than the initial height; wherein the plurality of sequences of positions further comprises: a plurality of consecutive lowering sequences and a single raising sequence; ora single lowering sequence and a plurality of consecutive raising sequences; or a first plurality of consecutive lowering sequences and a second plurality of consecutive raising sequences; wherein, furthermore, one of the first guide (9) and the second guide (10) is a loop guide that defines a loop trajectory (14) for the displacement of the constraining element (8), and wherein the constraining element (8), during the sliding of the first member (5) and of the second member (6) through the plurality of sequences of positions, travels along the loop trajectory (14) with a single travelling direction; and wherein: during the initial sliding, the initial displacement of the constraining element (8) along the loop trajectory (14) has a component along an initial direction (16) along which the one of the first member (5) and the second member (6) that does not comprise the loop guide slides with respect to the one of the first member (5) and the second that comprises the loop guide; and during the final sliding, the final displacement of the constraining element (8) along the loop trajectory (14) has a component along a final direction (17) opposite to the initial direction (16).

4. The chair according to claim 3, wherein the loop guide is shaped so that, during the sliding of the first member (5) and of the second member (6) through any one sequence of positions of the plurality of sequences of positions, the loop trajectory (14) along which the constraining element (8) moves comprises at least one substantially U-shaped section.

5. The chair according to any one of claims 3 or 4, wherein: the first guide (9) is a loop guide and the second guide (10) is not a loop guide; or the first guide (9) is not a loop guide and the second guide (10) is aloop guide.

6. The chair according to claim 5, wherein the one of the first guide (9) and the second guide (10) that is not a loop guide defines a linear trajectory (15) for the displacement of the constraining element (8), and wherein the constraining element (8), during the sliding of the first member (5) and of the second member (6) through the plurality of sequences of positions, travels along the linear trajectory (15) both according to a first travelling direction and according to a second travelling direction opposite to the first.

7. The chair according to any one of claims 1 to 6, wherein: respectively the first member (5) or the second member (6) comprises a magnet (18) associated, respectively, with the first guide (9) or with the second guide (10); and the constraining element (8) comprises a ferromagnetic material and, at least in the transit position, the magnet (18) holds the constraining element (8) still with respect, respectively, to the first guide (9) or to the second guide (10).

8. The chair according to claim 7 when it depends on claim 3, wherein the magnet (18) is comprised in the one of the first member (5) and the second member (6) that does not comprise the loop guide.

9. The chair according to any one of claims 1 to 8, wherein at least one of the first guide (9) and the second guide (10) defines a housing (19), into which the constraining element (8) is inserted when the first member (5) and the second member (6) are in the initial locking position and in the final locking position.

10. The chair according to any one of claims 1 to 9, wherein the elementsdetermine a condition of locking in stable equilibrium.

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