Tension adjusting system of chair mechanism

Abstract

The invention provides a tension adjusting mechanism for an adjustable chair. The mechanism includes a spring supported at one end and a movable support device at the other end that interacts with a limiter surface inclined with respect to the longitudinal axis of the spring. The spring is rotatable at one end and longitudinally movable at the other end. The mechanism also includes a rotatable cam having a cam surface and a cam follower that adjusts the position of the support device relative to the limiter surface, thereby changing the effective length of the spring to adjust tension.

Description

Technical Field

[0001] The present invention relates to a chair, such as an office chair, equipped with a base mechanism for synchronous movement between a seat and a backrest. More particularly, the present invention relates to a tensioning mechanism and an adjustable seat mechanism. Background Art

[0002] Many chairs, particularly office chairs, are adjustable to some degree to accommodate users of different sizes and different sitting preferences. For example, the inclination of the seat and / or backrest, lumbar support, and neck support may be adjusted. Where office chairs are equipped with armrests, they may be foldable or adjustable.

[0003] It is known to use such mechanisms for tension adjustment in office chairs for synchronized movement between them, however, known solutions lack the scope to accommodate different users, either for comfort performance or for requirements arising from different weight groups. The most common type for adjusting the tension in office chairs is a screw-type knob located under the seat. This knob is difficult to reach and hard to turn. This is time consuming and cumbersome. In modern and flexible workplaces, a particular chair may be used by several different people during a day or week. Tedious adjustments may then need to be made very frequently.

[0004] Thus, there is a need to be able to easily and quickly adjust the tension of a back support over a wider range than has previously been possible.

[0005] Embodiments herein are directed to providing an adjustable tensioning mechanism for a chair that eliminates or at least reduces the problems and / or disadvantages associated with prior art solutions. Summary of the invention

[0006] The purpose of the present disclosure is to reduce, alleviate or eliminate one or more of the above-mentioned defects and shortcomings in the prior art, and at least solve the problems mentioned above. According to a first aspect, a tension adjustment mechanism for an adjustable chair is provided, the tension adjustment mechanism comprising: a spring, the spring being supported by a first spring support at one end, and comprising a support device at a second end, wherein the support device is movably supported against a limiter surface inclined relative to the longitudinal axis of the spring, and wherein the spring is rotatable about its first end and is translatable in the longitudinal direction at the second end, and wherein the tension adjustment mechanism also comprises: a rotatable cam, the rotatable cam comprising a cam surface, and a cam follower, the cam follower being adapted to follow the cam surface, wherein the cam follower is adapted to lift or lower the support device relative to the limiter surface to change the effective length of the spring.

[0007] According to some embodiments, the tension adjustment mechanism comprises a second spring support adapted to hold the second end of the spring.

[0008] According to some embodiments, the supporting device is a roller device, which is suitable for rotating and is supported against the limiter surface in a movably manner, wherein the tension adjustment mechanism also includes a connecting member, which connects the roller device and the cam follower so that the roller bearing moves the same distance when the cam follower is moved.

[0009] According to some embodiments, the tensioning mechanism comprises a handle connected to the rotatable cam via a cam shaft, the handle being adapted to be operable by a user and adapted to transmit rotation from the handle to the rotatable cam.

[0010] According to some embodiments, the limiter surface 8 comprises at least a plate member which is transverse and inclined with respect to the longitudinal axis of the spring 4 and wherein the limiter surface is also connected to a tie rod.

[0011] According to a second aspect, there is provided an adjustable seat mechanism for an office chair, the adjustable seat mechanism being used to adjust backrest tension, the seat mechanism comprising: a mechanism base which is adapted to be supported on an actuator column and is rotatable around a fixed vertical rotation axis, and a backrest support adapted to support at least one of a seat support and a back support, and wherein the first part and the second part are adjustable and relatively rotatable around a fixed horizontal axis, and wherein the tension between the relative rotation of the mechanism base and the backrest support is controlled by a tension adjustment mechanism according to any one of the first part and is adjustable.

[0012] According to some embodiments, the spring is supported at one end, i.e. the first end, in a rotatable manner to the first spring support or retainer, wherein the first spring retainer includes a seating surface suitable for seating an end of a spring, the spring being, for example, a coil spring, and the first spring retainer includes an additional pivot support member suitable for pivotally attaching the spring retainer to the mechanism base, the pivot support member being a protruding member suitable for being supported by respective parts of a bracket or a corresponding member of the mechanism base, and / or a corresponding female connector and a male connector of the first spring retainer and the mechanism base.

[0013] According to some embodiments, the spring is arranged at the other end, i.e., the second end, in a second spring holder, which comprises a seating surface suitable for seating the second end of the spring, such as a helical spring. The second spring holder also comprises a holding device for rotatably holding the roller device, bearing, wheel or rotating member.

[0014] According to some embodiments, the spring is capable of translating in its longitudinal direction so that the distance between the first end and the second end increases or decreases, and the spring tension, or resistance to movement, or elasticity is adjusted by the length of the spring, and wherein the spring is capable of rotating around the pivot support member.

[0015] According to some embodiments, the limiter surface includes an inclined surface member having a portion located at a first distance from the pivot support member and a second portion below the first portion and located at a second distance from the pivot support member, wherein the first distance is closer than the second distance, and the inclined surface member is suitable for allowing the spring to rotate around the pivot support member in a first direction, the limiter surface compresses the spring by providing the inclined surface member, and if the spring rotates around the pivot support member in a direction opposite to the first direction, the spring will expand due to the increased distance provided by the inclined limiter surface.

[0016] According to some embodiments, the tensioning mechanism is located within a housing defined by the mechanism base, wherein the tensioning mechanism is connected to the back support via a tie rod.

[0017] According to a third aspect, there is provided a chair comprising the tension adjustment mechanism according to the first aspect, the tension adjustment mechanism being used for tension adjustment of a reclining function.

[0018] According to a fourth aspect, there is provided a chair comprising an adjustable seat mechanism according to the second aspect.

[0019] The effects and features of the second to fourth aspects are largely similar to those described above in conjunction with the first aspect. The embodiments mentioned with respect to the first aspect are largely compatible with the second to fourth aspects.

[0020] The present disclosure will become apparent from the detailed description given below. The detailed description and specific embodiments disclose preferred embodiments of the present disclosure only by way of illustration. It will be appreciated by those skilled in the art that changes and modifications may be made within the scope of the present disclosure based on the guidance in the detailed description.

[0021] Therefore, it should be understood that the disclosure disclosed herein is not limited to the specific components of the described device or the steps of the described method, because such devices and methods can change. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments, and are not intended to be restrictive. It should be noted that, as used in the specification and the appended claims, the articles "one", "an", "the" and "said" are intended to indicate the presence of one or more elements, unless the context clearly stipulates otherwise. Thus, for example, reference to "a unit" or "the unit" can include several devices, etc. In addition, the words "comprise", "comprises", "contains" and similar words do not exclude other elements or steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above objects as well as additional objects, features and advantages of the present disclosure will be more fully understood by referring to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure when taken in conjunction with the accompanying drawings.

[0023] Figure 1 The diagram illustrates a chair movement mechanism according to some embodiments.

[0024] Figure 2 The diagram illustrates a chair movement mechanism in a state of maximum tension, according to some embodiments.

[0025] Figure 3 A portion of a tensioning mechanism is shown according to some embodiments.

[0026] Figure 4 The figure shows that the tension adjustment mechanism is adjusted to a low tension state.

[0027] Figure 5 The figure shows that the tension adjustment mechanism is adjusted to a low tension state.

[0028] Figure 6 The figure shows that the tension adjustment mechanism is adjusted to a low tension state.

[0029] Figure 7 The diagram shows portions of the tension adjustment mechanism being brought into a low tension state.

[0030] Figure 8 The figure shows the parts of the tension adjustment mechanism that are in a low tension state when the backrest is reclined.

[0031] Fig. 9 The figure shows that the tension adjustment mechanism is adjusted to the maximum tension state.

[0032] Fig.10 The figure shows that the tension adjustment mechanism is adjusted to the maximum tension state.

[0033] Fig.11The figure shows that the tension adjustment mechanism is adjusted to the maximum tension state.

[0034] Fig.12 The figure shows the parts of the tension adjustment mechanism in a state of maximum tension.

[0035] Fig.13 The figure shows the parts of the tension adjustment mechanism that are in a state of maximum tension when the backrest is reclined. DETAILED DESCRIPTION

[0036] The embodiments herein will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown. However, the present application should not be construed as being limited to the embodiments set forth herein. As will be readily appreciated by those of ordinary skill in the art to which the present application pertains, the disclosed features of the example embodiments may be combined. Like numbers always refer to like elements.

[0037] Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity.

[0038] Typically, for an adjustable seat and backrest mechanism for an office chair, a spring 4 is used to provide resistance and tension when a user leans back on the backrest. The stiffer the spring, the greater the tension that the backrest can withstand, so that the user must push the backrest harder to find a comfortable position. There are situations where a user desires a soft tension in the backrest to easily change between a reclined or upright position. In other cases, a user may desire a harder tension between the backrest and the seat to resist involuntary seat back tilting with greater support. Thus, the present invention proposes a mechanism for adjusting seat and backrest movement, and more specifically, a mechanism for adjusting backrest tension, i.e., backrest resistance. An adjustable chair should be understood as a chair that includes at least a recline and / or tilt function.

[0039] Figure 1 The figure shows the underside of a mechanism for controlling seat movement and backrest movement, and / or adjusting and controlling the tension of the mechanism. The figure does not show the seat and backrest, however, the mechanism is typically located and attached to the seat portion, backrest portion and support actuator column, wherein the support actuator column is connected via a plurality of actuators such as Figure 2 12 is attached to the mechanism or part thereof by means of the attachment means 15 in the mechanism base 12 as seen in FIG. However, it will be appreciated that other parts, such as armrests, may also be fitted. Figure 1In the illustration of , the mechanism is illustrated with a mechanism base 12, which may be a frame or housing adapted to be supported on a support, actuator or leg (not shown) and to support a seat and / or back support and rotatable about a fixed vertical axis of rotation. The mechanism is also illustrated with a backrest support 13, which may be a frame or housing adapted to support the other of the seat support and the back support. The backrest support 13 is the primary carrier of the load applied to the assembled backrest frame. The first and second parts are adjustable and relatively rotatable about a fixed horizontal axis, and the tension between the relative rotation of the first and backrest supports is controlled by a tension adjustment mechanism.

[0040] When the backrest (not shown) of the chair is reclined, the spring 4 is compressed between the first spring retainer 2 and the second spring retainer 3. A load is applied from the backrest via the backrest support 13, which then pulls a tie rod 10 connected to the limiter surface 8. This limiter surface acts on the end of the spring 4. The spring 4 is housed in a box or housing formed by a mechanism base 12 and the backrest support 13 as well as the first spring retainer 2 and the second spring retainer 3. The stiffer or more rigid the spring 4, the greater the tension required to compress the spring. The load or tension is applied to the spring 4 by a tie rod 10, one end of which is connected to the backrest support 13 or parts thereof and the other end is connected to the second spring retainer 3 via the limiter surface 8 and the roller device 5. The tension adjustment mechanism can be operated and adjusted by the user via at least one handle 1, 1'.

[0041] As from Figure 2 As can be seen in the illustrated embodiment, Figure 1 The handle 1 seen above interacts in a rotatable manner with a rotatable cam 6 comprising a cam surface. As illustrated, the cam 6 comprises a surface having a variable distance from the center of the cam 6.

[0042] The cam follower 7 is located above the cam surface and in contact with the cam 6, and when manipulated by the user through the handle 1, the cam follower is adapted to follow the cam surface as the cam rotates. Figure 2 In FIG. 1 , the cam follower 7 is seen to contact the cam at the point on its surface farthest from the centre of the cam. Figure 6 In FIG. 6 , it is seen that the cam follower 7 contacts the cam at the point where the surface is closest to the center of the cam. Since the cam follower 7 can only move in a translational manner, as will be disclosed later, as the cam 6 rotates clockwise, the cam follower 7 will gradually move upward and away from the center of the cam 6 until it reaches Figure 2 to the point shown in the figure, at which point it will drop to Figure 6 The point on the cam surface shown in the figure that is closest to the center of the cam 6. The cam follower 7 can be a protrusion protruding from a bracket, and the bracket is suitable for translational movement relative to the rotation of the handle 1. In one embodiment, the support device 5 is a roller device 5, such as a wheel, which is suitable for rotation and is supported against the limiter surface 8 in a movable manner, wherein the mechanism also includes a connecting member 14 connecting the roller device 5 and the cam follower 7, so that the roller device 5 moves the same distance when the cam follower 7 moves. The connecting member 14 can be a frame part or the like having at least an attachment section or attachment point for the roller device 5 and the cam follower 7, and it can also include a guide groove 18, such as Figure 5 , Figure 6 and Fig.10 As can be seen in FIG. 1 , a portion of the main shaft 9 can pass through or be located in the guide groove 18 .

[0043] Figure 3 The figure shows the interior of the tension adjustment mechanism without any housing. The spring 4 is rotatably supported at one end (i.e. the first end) to a first spring support or retainer 2. The first spring retainer 2 includes a seating surface, i.e. a placement surface, suitable for seating, i.e. placing an end of a spring (such as a coil spring in the figure). The first spring retainer 2 also includes a pivot support member 11, 11' suitable for pivotally attaching the spring retainer 2 to the mechanism base 12. The pivot support member 11 can be a protruding member, as shown in the figure, which is suitable for being supported by a bracket of the mechanism base 12 or a corresponding member not shown in the figure, and / or multiple parts of corresponding female connectors and male connectors of the first spring retainer 2 and the mechanism base 12, respectively. As shown in Figure 3 As can be seen in the figure, the limiter surface 8 is attached to and between the first and second side panels 17, 17'. The side panels 17, 17' are hinged at one end about the axis 2 and are connected to the tie rods 10, 10' at the other end, so that the movement of the tie rods 10 is transmitted to the limiter surface 8 via the side panels 17, 17'. The tie rods 10 will in turn be connectable to the backrest of the chair or parts thereof, so that when the backrest is reclined or tilted, the tie rods 10 will move and thereby push / pull will act on the limiter surface 8 of the spring 4.

[0044] Figure 3The figures further show two handles 1, 1', each protruding from a separate side of the mechanism, the two handles being connected by a main shaft 9. The shaft 9 passes through a frame portion and is supported in a frame portion, which is connected to the limiter surface 8 and at least one rotatable cam 6, or to two rotatable cams 6, 6', as shown. In these figures, the shaft 9 is faceted for transmitting the rotation from the handles 1, 1' to the rotatable cams 6, 6' via corresponding shaft receiving surfaces of the cams 6, 6'. Thus, the shaft 9 acts as a camshaft. The limiter surface 8 is transverse and inclined relative to the longitudinal axis L of the spring 4 (see Figure 5 ), and is further connected to a tie rod 10, or two or more tie rods 10, 10', as illustrated.

[0045] Figure 4 , Figure 5 and Figure 6 The figure shows how the tension of the tension adjustment mechanism can be adjusted by adjusting the handle 1 to a position that can be considered as a low tension position. Figure 4 As can be seen in FIG. 1 , the handle 1 is rotated counterclockwise to adjust the tension system to the "low" setting.

[0046] like Figure 5 As can be seen in FIG. 1 , this lowers the cam follower 7 and thereby the roller means 5 so that they are moved to the lowest position relative to the limiter surface 8. Since the lower part of the limiter surface 8 is further away from the first spring retainer 2 than the upper part of the limiter surface 8, the spring 4 will be able to extend and therefore require less force to be compressed than if the spring were more compressed, for example if it were located Figure 2 The roller means 5 may be a ball bearing, wheel, slide or the like, supported to the spring 4 by a retainer via a spring retainer 3 .

[0047] This can be done by Figure 6 6 is adapted to rotate counterclockwise so that the cam follower 7 is guided to a point or section of the cam surface that is closest to the center of the cam 6. It should be understood that clockwise and counterclockwise directions are associated with the various figures. If the cam surface is opposite to the cam surface illustrated, the direction of rotation will be reversed to achieve the same effect.

[0048] Figure 7The present invention is shown with the tensioning system set to a "low" setting. This produces less compression on the spring 4 than the "maximum" setting. The slanted relationship between the limiter surface 8 and the roller arrangement 5 produces a lower leverage by shortening the momentum arm.

[0049] Figure 8 The figure shows a position of the invention in which the back support (not shown) is tilted. As can be seen, Figure 7 Compared to the position of the back support 13 in the backrest relative to the mechanism base 12, the back support 13 has been moved downward by rotation. When the back support reclines, the spring 4 is compressed between the first spring retainer 2 and the second spring retainer 3, and when the pull rod 10 connected to the back support 13 is pulled as the backrest is tilted, it pushes the limiter surface 8 toward the spring 4 to compress the spring 4. The harder the spring 4 is, or the shorter the spring is before the backrest reclines, the greater the tension required to further compress the spring.

[0050] In order to reduce the risk of the cam 6 moving unintentionally, for example due to the force of a pin of a cam follower 7 on the cam surface, the cam surface may include recesses or indentations 16 spaced apart along its surface, such as Figure 6 and Fig.11 This allows the tensioning system to rest in different locking positions due to the support of the cam follower 7 pins which are housed, ie reside in recesses in the surface of the rotatable cam 6. The recesses 16 may be located along the entire periphery of the cam 6.

[0051] Fig. 9 and Fig.10 The figure shows how the tension of the tension adjustment mechanism can be adjusted by adjusting the handle 1 to a position which can be considered as a high tension position which is higher than the low tension position. Fig. 9 As can be seen in FIG. 1 , turning the handle 1 clockwise adjusts the tension system to the "HIGH" setting by forcing the roller device 5 upwards (in the figure), so the length of the spring 4 decreases, making it stiffer. In order to adjust the tension system to the "HIGH" setting, the handle 1 needs to be turned nearly 360° clockwise, as shown in FIG. Fig. 9 By turning the handle 1, the roller device 5 and the cam follower 7 are lifted. Fig.10 The cam follower 7 and thus the roller arrangement 5 are shown in their highest setting.

[0052] As in Fig.10As can be seen in FIG. 1 , this lifts the cam follower 7 and thus the roller means 5 so that they are moved to the upper portion positioned relative to the limiter surface 8. Since the upper portion of the limiter surface 8 is closer to the first spring retainer 2 than the lower portion of the limiter surface 8, the spring 4 is forced to compress and is therefore less compressed than if it were located at Figure 6 A greater force is required to be further compressed, compared to the case of the "low" bottom of the restrictor surface 8 shown in the figure.

[0053] This can be done by Fig.11 , wherein the rotatable cam 6 is adapted to rotate clockwise so that the cam follower 7 is guided on the cam surface to a point or section of the cam surface that is farthest from the center of the cam 6. The cam 6 may include different types of cam surface shapes, such as eccentric circular, eccentric, oval, elliptical, heart-shaped or snail-shaped.

[0054] Fig.12 The figure shows the relationship with the back support when the tension system is set to the "MAX" setting. This produces a compression on the spring 4 compared to the "LOW" setting. In this position, the position of the roller device 5 on the limiter surface 8 results in a higher leverage through a longer momentum arm between the cam and the roller device.

[0055] When the back support of a chair including the invention as disclosed is reclined, the spring 4 is compressed. Fig.13 , which shows that the spring is compressed on the inside.

[0056] Fig.13 The figure shows a position of the invention in which the backrest (not shown) is tilted. As can be seen, Fig.12 Compared to the position of the backrest support 13 in FIG. 1 relative to the mechanism base 12, the backrest support 13 has been moved downward by rotation. When the backrest is reclined, the spring 4 is compressed between the first spring retainer 2 and the second spring retainer 3, and when the pull rod 10 connected to the backrest support 13 is pulled as the backrest is tilted, it pushes / pulls the limiter surface 8 toward the spring 4 to compress the spring 4 (illustrated by the arrow). In this figure, the cam 6 is in a rotated position so that the cam follower 7 is in its farthest position away from the shaft 9 and the center of the cam 6, so that the roller device 5 is positioned on top of the limiter surface 8, thereby initially compressing the spring 4. Fig.13 The figure shows that the spring 4 is further compressed by the downward tilt of the backrest, and therefore the initial compression increases the tension of the spring 4. The stiffer the tension of the spring 4, or the shorter the spring 4 is before the backrest reclines, the greater the tension required to further compress the spring.

[0057] In order to hold the spring 4 in a supporting manner, the spring 4 is supported at one end (i.e., the first end) to the first spring support or holder 2. The spring can be rotatably supported by a pivot support member 11. Wherein, the first spring holder 2 includes a seating surface or a placement surface suitable for seating or placing the end of a spring (such as a coil spring). The first spring holder 2 also includes a pivot support member 11 suitable for pivotally attaching the spring holder 2 to the mechanism base 12. The pivot support member 11 can be a protruding member, which is suitable for being supported by a bracket or corresponding member of the mechanism base 12, and / or multiple parts of corresponding female connectors and male connectors of the first spring holder 2 and the mechanism base 12.

[0058] The other end (second end) of the spring 4 is seated or placed in the second spring holder 3, which comprises a seating surface or a placement surface suitable for placing the second end of the spring (such as a coil spring). The second spring holder 3 also comprises a retaining device 19, such as a retaining shoe or a bracket, such as Figure 2 and Figure 6 As seen in FIG. 1 , it is used to hold the roller device 5 in a rotatable manner.

[0059] The spring is translatable in its longitudinal direction, and it should be understood that the spring can extend and contract in the length direction so that the distance between the first end and the second end increases or decreases. The tension or resistance to movement, or elasticity of the spring is adjusted by the length of the spring. In addition, the spring can rotate around the pivot support member 11.

[0060] The limiter surface 8 includes an inclined surface member having a portion located at a first distance from the pivot support member 11, and a second portion located below the first portion and at a second distance from the pivot support member 11, wherein the first distance is closer than the second distance. Thus, when the spring 4 rotates about the pivot support member 11 in a first direction, the limiter surface 8 compresses the spring 4 by providing the inclined surface member, and if the spring 4 rotates about the pivot support member 11 in a direction opposite to the first direction, the spring 4 will expand due to the increased distance provided by the inclined limiter surface 8.

[0061] Since the tension or resistance of the spring 4 depends on the length of the spring, the spring 4 will provide a higher tension or greater resistance when it is shortened by compression, and will provide a lower tension when it is extended. Thus, the present invention achieves this by rotating the spring 4 about the pivot support member 11, so that the roller bearing 5 at the second end moves against the tilt of the limiter surface 8, thereby forcing the spring 4 to shorten and thus compress.

[0062] Those skilled in the art recognize that the present disclosure is not limited to the preferred embodiments described above. Those skilled in the art also recognize that modifications and variations are possible within the scope of the claims. In addition, by studying the drawings, the present disclosure, and the claims, those skilled in the art can understand and implement variations of the disclosed embodiments when practicing the disclosure claimed for protection.

Claims

1. A tension adjustment mechanism for an adjustable chair, the tension adjustment mechanism comprising: A spring (4) supported at one end by a first spring support (2) and comprising a support device (5) at a second end, wherein the support device (5) is movably supported against a limiter surface (8) inclined relative to a longitudinal axis (L) of the spring, and The spring (4) is capable of rotating about its first end and translating in the longitudinal direction at the second end, and the tension adjustment mechanism further comprises: a rotatable cam (6), the rotatable cam comprising a cam surface, and A cam follower (7) is adapted to follow the cam surface, wherein the cam follower (7) is adapted to raise or lower the support device (5) relative to the limiter surface (8) to change the effective length of the spring (4).

2. The tension adjustment mechanism according to claim 1, wherein: The tension adjustment mechanism comprises a second spring support (3) adapted to hold the second end of the spring (4).

3. The tension adjustment mechanism according to claim 1 or 2, wherein: The supporting device (5) is a roller device (5) which is suitable for rotation and is supported against a limiter surface (8) in a movably manner, wherein the tension adjustment mechanism further comprises a connecting member (14) which connects the roller device (5) and the cam follower (7) so that the roller bearing (5) moves the same distance when the cam follower (7) is moved.

4. A tensioning mechanism according to any one of the preceding claims, wherein: The tension adjustment mechanism comprises a handle (1) connected to the rotatable cam (6) via a cam shaft (9), the handle being adapted to be operable by a user and adapted to transmit rotation from the handle (1) to the rotatable cam (6).

5. A tensioning mechanism according to any one of the preceding claims, wherein: The limiter surface (8) comprises at least a plate member which is transverse and inclined relative to the longitudinal axis of the spring (4), and wherein the limiter surface (8) is also connected to a tie rod (10).

6. An adjustable seat mechanism for an office chair, the adjustable seat mechanism being used to adjust the tension of a backrest, the seat mechanism comprising: a mechanism base (12) which can be adapted to be supported on the actuator column and can rotate about a fixed vertical axis of rotation, and a backrest support (13) adapted to support at least one of a seat support and a back support, and The first part and the second part are capable of adjustment and relative rotation about a fixed horizontal axis, and the tension between the relative rotation of the mechanism base (12) and the backrest support (13) is controlled by a tension adjustment mechanism according to any one of claims 1 to 5 and is adjustable.

7. The adjustable seat mechanism according to claim 6, wherein: The spring (4) is rotatably supported at one end, i.e. the first end, to the first spring support or holder (2), wherein the first spring holder (2) comprises a seating surface suitable for seating an end of a spring, the spring being, for example, a helical spring, the first spring holder (2) comprising a further pivot support member (11) suitable for pivotally attaching the spring holder (2) to the mechanism base (12), the pivot support member (11) being a protruding member suitable for being supported by a bracket or corresponding member of the mechanism base (12), and / or respective parts of corresponding female and male connectors of the first spring holder (2) and the mechanism base (12).

8. An adjustable seat mechanism according to claim 6 or 7, wherein: The spring (4) is arranged at the other end, i.e. the second end, in a second spring holder (3), the second spring holder comprising a seating surface suitable for seating the second end of the spring, for example a helical spring. The second spring holder (3) further comprises a retaining device for rotatably retaining the roller device (5), the bearing, the wheel or the rotating member (5).

9. An adjustable seat mechanism according to any one of claims 6 to 8, wherein: The spring is capable of translating in its longitudinal direction so that the distance between the first end and the second end increases or decreases, and the spring tension, or resistance to movement, or elasticity is adjusted by the length of the spring, and wherein the spring is capable of rotating around the pivot support member (11).

10. An adjustable seat mechanism according to any one of claims 6 to 9, wherein: The limiter surface (8) includes an inclined surface member having a portion located at a first distance from the pivot support member (11) and a second portion below the first portion and located at a second distance from the pivot support member (11), wherein the first distance is closer than the second distance, and the inclined surface member is adapted to allow the spring (4) to rotate around the pivot support member (11) in a first direction, the limiter surface (8) compresses the spring (4) by providing the inclined surface member, and if the spring (4) rotates around the pivot support member (11) in a direction opposite to the first direction, the spring (4) will expand due to the increased distance provided by the inclined limiter surface (8).

11. An adjustable seat mechanism according to any one of claims 6 to 10, wherein: The tensioning mechanism is located within a housing defined by the mechanism base (12), wherein the tensioning mechanism is connected to the backrest support (13) via a tie rod (10, 10').

12. A chair, comprising the tension adjustment mechanism according to any one of claims 1 to 5, wherein the tension adjustment mechanism is used for adjusting the tension of a reclining function.

13. A chair comprising an adjustable seat mechanism according to any one of claims 6 to 11.

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