Tensioning mechanism for a drawstring for an upholstery cover

Abstract

A tensioning mechanism (200) for a drawstring (304) for an upholstery cover (106, 110) of an upholstery comprises a support means (306) attached to a support structure (308, 1102, 1902) of the upholstery and an elongated lever (310) having a first end (312) and a second end (314). The first end (312) is pivotally attached to the support means (306) about a pivot axis (502). The second end (314) is opposite to the first end (312) in a longitudinal direction (504) of the elongated lever (310) and has a handle (316). The pivot axis (502) is perpendicular to the longitudinal direction (504). The elongated lever (310) includes at least one fastening arrangement (318) for fastening the drawstring (304) and a locking means (320) engageable with one of a plurality of mating locking means (322) provided on the support means (306).

Description

[0001] TENSIONING MECHANISM FOR A DRAWSTRING FOR AN UPHOLSTERY

[0002] COVER

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a tensioning mechanism for a drawstring for an upholstery cover of a chair. In particular, the present invention relates to a tensioning mechanism for a drawstring that can be easily operated by an end user and that can be applied to an upholstery cover of a chair seat and a chair backrest. The present invention relates furthermore to a chair comprising the tensioning mechanism.

[0005] BACKGROUND OF THE INVENTION

[0006] A chair, for example an office chair or a non-office chair, for example a chair at home or in a restaurant or concert hall or theater, can have an upholstered seat and / or an upholstered backrest. An upholstered seat typically comprises a seat base plate, for example made of metal, wood or plastics, a padding attached to the seat base plate, for example made of foam, and an upholstery cover which is stretched over the padding and attached to the seat base plate. Similarly, an upholstered backrest typically comprises a backrest base plate made of plastics, wood or metal, a padding attached to the backrest base plate, and an upholstery cover which is stretched over the padding and attached to the backrest base plate. For example, the upholstery cover may be stapled or nailed to the base plate or a base plate frame.

[0007] Due to soiling or wear, it may be desirable to remove the upholstery cover of the seat or backrest for cleaning or replacement. Attaching and removing the upholstery cover using nails or staples may be time consuming and may require special tools. In addition, some legislation, such as European legislation, is evolving and forcing product manufacturers to offer not only a warranty for chair repair, but also the possibility of chair repair by the end user.

[0008] Sometimes the upholstery cover has a circumferential guide channel (hem) through which a drawstring passes. By pulling the drawstring, the upholstery cover can be tightened around the seat or backrest. Special tensioning tools may be used to control the tension of the drawstring. Once tensioned, the drawstring may be held in place by a clamping device clamping the drawstring to the seat or backrest.

[0009] BRIEF SUMMARY OF THE INVENTION

[0010] There is a need in the art for a chair seat or chair backrest upholstery cover that can be quickly assembled and disassembled at the factory or by the end user.

[0011] This need is met by a tensioning mechanism for a drawstring for an upholstery cover of an upholstery as defined in the independent claim. The dependent claims define embodiments.

[0012] A tensioning mechanism for a drawstring for an upholstery cover of an upholstery comprises a support means attached to a support structure of the upholstery and an elongated lever. The support structure may comprise for example a seat base plate or a backrest base plate of a chair. The elongated lever has a first end and a second end. The first end is pivotally attached to the support means about a pivot axis. The second end is opposite to the first end in a longitudinal direction of the elongated lever and has a handle. The pivot axis is perpendicular to the longitudinal direction. The elongated lever includes at least one fastening arrangement for fastening the drawstring. The elongated lever includes a locking means engageable with one of a plurality of mating locking means provided on the support means.

[0013] For example, the locking means may be provided at the second end of the elongated lever. The mating locking means may be arranged at the support means along a circular path about the pivot axis in a sector having an angular range of, for example, 90°, preferably 45°. For example, the number of mating locking means may be in a range of four to ten, for example six. A distance from each of the locking means to the pivot axis may be substantially the length of the elongated lever, for example 5 to 20 cm, for example 10 or 12 cm.

[0014] By pivoting the elongated lever about the pivot axis, the drawstring attached thereto can be tensioned to a desired amount. At this position of the elongated lever, the locking means of the elongated lever can be engaged with one of the mating locking means on the support means, thereby securing the elongated lever and the drawstring in place.

[0015] This allows a fast assembly in the factory and then the possibility to remove and clean or replace the upholstery cover by the end user. Furthermore, from an environmental point of view, it facilitates the separation of the different materials at the end of the life of the product.

[0016] According to various examples, the at least one fastening arrangement for the drawstring is provided between the first end and the second end. Thus, a leverage effect can be achieved and the tension on the drawstring can also be adjusted accurately and without excessive effort by the end user. A plurality of fastening arrangements may be provided to balance the effort and the string length. For example, three fastening arrangements may be provided along the length of the elongated lever, a first fastening arrangement substantially at a central position, a second fastening arrangement closer to the pivot axis and a third fastening arrangement closer to the lever.

[0017] In some examples, the mating locking means are holes in the support means. The locking means at the elongated lever may be a protrusion configured to be inserted at least partially into one of the plurality of holes in the support means. The locking means may have a hook shape configured to engage with an edge of one of the plurality of holes in the support means. Such configuration of the locking means and the mating locking means may be implemented at low cost, requires very little installation space and may be intuitively and reliably used by the end user. In various examples, the tensioning mechanism further comprises a guide element configured to cross two parts or portions of the drawstring to the fastening arrangement of the elongated lever. The guide element may be provided at the support means. For example, the guide element may be integrally formed with the support means. The guide element may be a protrusion formed at the support means. Crossing the portions of the drawstring prior to attachment to the fastening arrangement may reduce loads on a hem of the upholstery cover in which the drawstring is guided.

[0018] According to various examples, the support means may be integrally formed with the support structure of the upholstery. This may reduce cost and may require little installation space only.

[0019] A chair seat with an upholstery comprises a support structure, an upholstery cover and a drawstring. The chair seat may comprise further components, for example a padding between the support structure and the upholstery cover, and a mounting structure for mounting the chair seat to a chair base or a tilt mechanism of the chair. The drawstring is at least partially arranged in a circumferential hem of the upholstery cover. The chair seat is provided with the above tensioning mechanism. In particular, the tensioning mechanism may be arranged at a lower side of the support structure of the chair seat.

[0020] A chair backrest with an upholstery comprises a support structure, an upholstery cover and a drawstring. The chair backrest may comprise further components, for example a padding between the support structure and the upholstery cover, and a mounting structure for mounting the chair backrest to a chair seat or a tilt mechanism of the chair. The drawstring is at least partially arranged in a circumferential hem of the upholstery cover. The chair backrest is provided with the above-described tensioning mechanism. For example, the tensioning mechanism may be arranged at a rear side of the support structure of the backrest, i.e. at the side of the support structure opposite to the side of the upholstery. A chair comprises a chair base assembly and the above-described chair seat and / or the above described chair backrest coupled to the chair base assembly.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the invention will be described with reference to the accompanying drawings.

[0023] Fig. 1 is a schematic view of a chair comprising a chair seat with an upholstery and a chair backrest with an upholstery according to one or more embodiments.

[0024] Fig. 2 is a schematic view from below of a chair comprising a chair seat with a tensioning mechanism according to one or more embodiments.

[0025] Fig. 3 shows a schematic perspective exploded view from below of a chair seat with a tensioning mechanism in a seat panel according to one or more embodiments.

[0026] Fig. 4 shows a schematic perspective partially exploded view from below of a chair seat with a tensioning mechanism in a seat panel according to one or more embodiments.

[0027] Fig. 5 shows a schematic perspective view from below of a chair seat with a tensioning mechanism in a seat panel according to one or more embodiments.

[0028] Fig. 6 shows a schematic perspective view from above of a seat panel of a chair seat with a tensioning mechanism according to one or more embodiments.

[0029] Fig. 7 shows a schematic plan view from below of a seat panel of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring not fastened.

[0030] Fig. 8 shows a schematic plan view from below of a seat panel of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring fastened and not tensioned. Fig. 9 shows a schematic plan view from below of a seat panel of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring fastened and tensioned.

[0031] Fig. 10 shows a schematic sectional side view of a seat panel of a chair seat with a tensioning mechanism according to one or more embodiments.

[0032] Fig. 11 shows a schematic perspective exploded view from below of a chair seat with a tensioning mechanism in a seat carrier according to one or more embodiments.

[0033] Fig. 12 shows a schematic perspective partially exploded view from below of a chair seat with a tensioning mechanism in a seat carrier according to one or more embodiments.

[0034] Fig. 13 shows a schematic perspective view from below of a chair seat with a tensioning mechanism in a seat carrier according to one or more embodiments.

[0035] Fig. 14 shows a schematic perspective view from above of a seat carrier of a chair seat with a tensioning mechanism according to one or more embodiments.

[0036] Fig. 15 shows a schematic plan view from below of a seat carrier of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring not fastened.

[0037] Fig. 16 shows a schematic plan view from below of a seat carrier of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring fastened and not tensioned.

[0038] Fig. 17 shows a schematic plan view from below of a seat carrier of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring fastened and tensioned.

[0039] Fig. 18 shows a schematic sectional side view of a seat carrier of a chair seat with a tensioning mechanism according to one or more embodiments. Fig. 19 shows a schematic perspective exploded view from the rear of a chair backrest with a tensioning mechanism in a backrest panel according to one or more embodiments.

[0040] Fig. 20 shows a schematic perspective partially exploded view from the rear of a part of a chair backrest with a tensioning mechanism in a backrest panel according to one or more embodiments.

[0041] Fig. 21 shows a schematic perspective view from the rear of a part of a chair backrest with a tensioning mechanism in a backrest panel according to one or more embodiments.

[0042] Fig. 22 shows a schematic perspective view from the front of a backrest panel of a chair seat with a tensioning mechanism according to one or more embodiments.

[0043] Fig. 23 shows a schematic perspective partially exploded view from the rear of a chair backrest with a tensioning mechanism in a backrest panel according to one or more embodiments.

[0044] Fig. 24 shows a schematic plan view from the rear of a backrest panel of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring not fastened.

[0045] Fig. 25 shows a schematic plan view from the rear of a backrest panel of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring fastened and not tensioned.

[0046] Fig. 26 shows a schematic plan view from the rear of a backrest panel of a chair seat with a tensioning mechanism according to one or more embodiments with the drawstring fastened and tensioned.

[0047] Fig. 27 shows a schematic sectional side view of a backrest panel of a chair seat with a tensioning mechanism according to one or more embodiments.

[0048] DETAILED DESCRIPTION OF EMBODIMENTS Exemplary embodiments of the invention will be described with reference to the drawings. While some embodiments will be described in the context of specific fields of application, such as in the context of an office type chair, the embodiments are not limited to this field of application. The features of the various embodiments may be combined with each other unless specifically noted otherwise. Same reference signs in the various drawings refer to similar or identical components.

[0049] Fig. 1 shows schematically a chair 100, for example an office chair. The chair 100 has a chair base assembly 102 and a superstructure. The superstructure includes a chair seat 104, a chair backrest 108 and components to interconnect the chair seat 104, the chair backrest 108 and the chair base assembly 102, e.g. a tilt and height adjustment mechanism 202 shown in Fig. 2. The chair base assembly 102 includes a pedestal column, a number of support legs extending radially from the pedestal column and a corresponding number of casters supported on the outer ends of the support legs. A gas cylinder or any other lifting mechanism may be supported by the pedestal column to enable the height of the chair seat, and thus of the chair superstructure, to be adjusted by a user. The chair seat 104 as well as the chair backrest 108 are upholstered. For example, the chair seat 104 may comprise a support structure and a padding attached to the support structure and an upholstery cover 106 which is stretched over the padding. The padding may be made of foam, for example. Similarly, the chair backrest 108 may comprise a support structure and a padding attached to the support structure and an upholstery cover 110 which is stretched over the padding.

[0050] It is to be understood that the terms "forward", "rearward", and "lateral", as used herein, each have a particular meaning that is defined with respect to a flat support surface beneath the chair 100 (for example parallel to a floor on which the casters rest) and with respect to an occupant of the chair. For example, the term "forward" refers to a direction moving away from the chair backrest 108 and in front of a chair occupant along an axis which extends parallel to such a flat support surface, while the term "rearward" refers to a direction opposite to the forward direction. The term "lateral" refers to generally horizontal directions perpendicular to both the forward and rearward direction and extending parallel to the aforementioned flat support surface. "From below" means a direction from the floor upwards, and "from above" means a direction from above the chair downwards. "From the rear" means a direction from behind the chair backrest 108 in the forward direction, and "from the front" means a direction from in front of the chair backrest 108 in the rearward direction. Accordingly, a front side and a rear side of the chair backrest 108 are defined.

[0051] Fig. 2 is a schematic view of the chair 100 from below. As illustrated, a tilt mechanism 202 couples the chair base assembly 102 to the chair seat 104. At a mounting 204, the chair backrest 108 may be coupled to the tilt mechanism 202. However, the illustrated chair 100 is only an example, and in other examples, the chair base assembly 102 may be coupled to the chair seat 104 and the chair backrest 108 by a different component or mechanism, such as a component that does not provide a tilt functionality for the chair seat 104 and the chair backrest 108.

[0052] As further illustrated in Fig. 2, the upholstery cover 106 of the chair seat 104 extends circumferentially around an edge of a support structure 206 of the chair seat 104. A padding may be provided between the support structure 206 and the upholstery cover 106. The upholstery cover 106 may have a circumferential hem at its outer edge, i.e. a circumferential guide channel in which a drawstring is provided. When the drawstring is tensioned, the hem of the upholstery cover 106 is pulled together, whereby the upholstery cover is secured to the support structure 206, for example in a circumferential groove or channel provided in the support structure 206, or by stretching the upholstery cover over an edge of the support structure 206.

[0053] In order to tension the drawstring and secure the tensioned drawstring, a tensioning mechanism 200 is provided at the support structure 206. The support structure 206 may comprise a seat panel and a seat carrier. The seat panel may refer to an essentially flat surface where a person sits on a chair. Typically, the seat panel is designed for comfort and may carry upholstery. The seat panel may be made of various materials like wood, fabric, plastic, or metal. The seat carrier may encompass the entire structure supporting the seat panel and provides the coupling to the chair base assembly, e.g. via a tilt mechanism. The seat carrier may be made of plastic or metal, e.g. sheet steel, or other materials. The seat panel and the seat carrier may be separate parts connected to each other or maybe integrally formed as one piece. If the seat panel and the seat carrier are integrally formed as one piece, this piece may be regarded as the seat carrier.

[0054] The tensioning mechanism may be provided at the seat panel or at the seat carrier. In the example illustrated in connection with Figs. 3 to 10, the tensioning mechanism 200 is provided at the seat panel. In the example illustrated in Figs. 11 to 18, the tensioning mechanism 200 is provided at the seat carrier.

[0055] Fig. 3 shows a schematic perspective exploded view from below of the chair seat 104 with the tensioning mechanism 200 in the seat panel 308. The chair seat 104 comprises the upholstery cover 106, the seat panel 308, and a padding 340 between the upholstery cover 106 and the seat panel 308. The upholstery cover 106 is provided with a circumferential hem 302 in which a drawstring 304 is arranged as a closed loop. The length of the drawstring 304 is at least such that the circumferential hem 302 can be stretched over an outer edge of the seat panel 308. As illustrated in Fig. 3, the drawstring 304 provides some additional length for passing through the tensioning mechanism 200 as will be described in more detail in connection with Figs. 7 to 9.

[0056] The tensioning mechanism 200 comprises a support means 306 attached to the seat panel 308. The support means 306 may be a plate-like component attached to the seat panel 308. The support means 306 may be a separate component attached to the seat panel 308 by bonding, welding or clipping. In other examples, the support means 306 may be integrally formed with the seat panel 308. The support means 306 may be made of plastic or metal. The tensioning mechanism 200 comprises an elongated lever 310 having a first end 312 and a second end 314.

[0057] The first end 312 is pivotally attached to the support means 306 about a pivot axis extending perpendicular to the plate-like support means 306. For example, a hole may be provided in the support means 306 and the elongated lever 310 may provide a corresponding protrusion at the first end 312 that may be inserted into the hole. The hole may be configured such that the protrusion can be inserted into the whole along the pivot axis only in a particular orientation such that the first end 312 is fixed in the direction along the pivot axis when rotated about the pivot axis. The pivot axis is perpendicular to a longitudinal direction of the elongated lever 310. The protrusion may extend along the pivot axis, i.e. , perpendicular to the longitudinal direction of the elongated lever 310.

[0058] The second end 314 is opposite to the first end 312 in the longitudinal direction of the elongated lever 310 and has a handle 316. The handle 316 may be integrally formed with the elongated lever 310. The elongated lever 310 may be made of plastic or metal. The elongated lever 310 includes at least one fastening arrangement 318 for fastening the drawstring 304. In the example illustrated in Fig. 3, the elongated lever 310 is provided with three fastening arrangements 318 at different locations along the longitudinal direction of the elongated lever 310. In this example, a first fastening arrangement 318 is positioned between the center of the elongated lever 310 and the handle 316, a second fasting arrangement 318 is positioned essentially at the center, and the third fastening arrangement 318 is positioned between the center and the first end 312. Each fastening arrangement 318 may be configured as a protrusion having a hook-shaped head such that the drawstring can be wrapped around the body of the fastening arrangement 318 and prevented from disengaging from the fastening arrangement 318 by the hook-shaped head. The fastening arrangements 318 may be positioned on the same side of the elongated lever 310 as the handle 316. The fastening arrangements 318 may be integrally formed with the elongated lever 310 or may be separate components attached at the elongated lever 310. For example, the fastening arrangements 318 may include bolts that are bonded or screwed to the elongated lever 310.

[0059] The elongated lever 310 includes a locking means 320 engageable with one of a plurality of mating locking means 322 provided on the support means 306. The locking means may be provided at the second end 314 of the elongated lever 310. The locking means 320 may be a protrusion at a side of the elongated lever 310 opposite the side on which the fastening arrangements 318 and the handle 316 are positioned. The mating locking means 322 may comprise holes in the support means 306 arranged in an arc around the pivot axis. In the example of Fig. 3, six mating locking means 322 are provided at equidistant positions in an arc around the pivot axis.

[0060] The tensioning mechanism 200 further comprises a guide element 324 configured to cross two portions of the drawstring 304 to the fastening arrangement 318 of the elongated lever 310. Details regarding the guide element 324 will be described in connection with Figs. 8 and 9.

[0061] Fig. 4 to 6 describe the attachment of the elongated lever 310 to the support means 306.

[0062] Fig. 4 shows a schematic perspective partially exploded view from below of the chair seat 104 with the tensioning mechanism 200 in the seat panel 308. The support means 306 may be provided with a hole 402. The hole 402 may have a central round hole with two opposing recesses. The protrusion at the first end 312 of the elongated lever 310 may have a round body and a head that mates to the hole 402 in the support means 306. When the head of the protrusion at the first end 312 of the elongated lever 310 is aligned with the hole 402, the protrusion may be inserted into the hole 402.

[0063] Fig. 5 shows a schematic perspective view from below of the chair seat 104 with the protrusion at the first end 312 of the elongated lever 310 inserted into the hole 402. In this state, the first end 312 of the elongated lever 310 can be rotated in the hole 402 about a pivot axis 502. A longitudinal direction 504 of the elongated lever 310 is perpendicular to the pivot axis 502. Depending on the angle of rotation, the locking means 320 at the second end 314 of the elongated lever 310 (see Fig. 4) may be inserted into one of the mating locking means 322.

[0064] Fig. 6 shows a schematic perspective view from above of the seat panel 308. As illustrated, the head 602 of the protrusion at the first end 312 of the elongated lever 310 is passed through the hole 402, thereby engaging the first end 312 with the support means 306 for rotation about the pivot axis 502. A head 604 of the locking means 320 is passed through one of the mating locking means 322 thereby securing the elongated lever 310 at a given angle of rotation.

[0065] The configuration of the protrusion and head 602 at the first end 312 of the elongated lever 310 and the configuration of the hole 402 in the support means 306 is merely an example. In other examples, the first end 312 may be rotatably coupled to the support means 306 by a pin provided on the support means 306 passing through a corresponding hole in the first end 312 of the elongated lever 310 and / or by a snap-fit connection pivotally attaching the first end 312 at the support means 306.

[0066] Fig. 7 shows a schematic partial plan view from below of the seat panel 308, focusing on the tensioning mechanism 200. In this state, the drawstring 304 is not attached to the tensioning mechanism 200. The elongated lever 310 is arranged along a direction 702 such that the fastening arrangements 318 are close to the outer edge of the seat panel 308, i.e. , close to the hem 302. The hem 302 has at least one opening for access to the drawstring 304. For example, the hem 302 may have two openings, one for each portion 304A and 304B of a loop of the drawstring 304. In other examples the hem 302 may have only one opening for passage of both portions 304A and 304B. The upholstery cover 106 is arranged such that the at least one opening is located near the guide element 324. The guide element 324 may comprise a block protruding from the surface of the support means 306 such that the portions 304A and 304B of the drawstring 304 can be guided by side surfaces of the guide element 324. Grooves for receiving the drawstring 304 may be provided in the side surfaces of the guide element 324.

[0067] As illustrated in Fig. 8, the portions 304A and 304B of the drawstring 304 are crossed between the hem 302 and the guide element 324, then passed along the side surfaces of the guide element 324 and wrapped around one of the fastening arrangements 318. Already in this position, the drawstring 304 may be tensioned slightly, thereby tensioning the upholstery cover 106 around the padding 340 and the edge of the seat panel 308.

[0068] A user may now use the handle 316 to rotate the elongated lever 310 about the pivot axis 502 at the first end 312 of the elongated lever 310 such that the fastening arrangement 318 is moved away from the guide element 324 and the drawstring 304 is further tensioned as illustrated in Fig. 9. For example, the elongated lever 310 may be moved until it is positioned along a direction 902. As a result, the upholstery cover 106 is tensioned around the padding 340 and the edge of the seat panel 308. In this position of the elongated lever 310, the locking means 320 at the second end 314 of the elongated lever 310 may engage with one of the mating locking means 322.

[0069] As shown in Fig. 10, the locking means 320 may be provided with a hookshaped head 1002 configured to engage with an edge 1004 of the mating locking means 322 to securely fix the elongated lever 310 at the support means 306 in the position illustrated in Fig. 9.

[0070] To remove the upholstery cover 106, the above steps shown in Figs. 7 to 9 may be performed in reverse order. The user may use the handle 316 to disengage the locking means 320 from the mating locking means 322 and may release / move the elongated lever 310 until it is positioned along the direction 702. In this state, the drawstring 304 can be detached from the fastening arrangement 318 and the guide element 324. The hem 302 can be widened and the upholstery cover 106 can be removed from the edge of the seat panel 308 and the padding 340, for example for cleaning or replacement. Figures 11 to 18 show a further exemplary chair seat 104 in which a tensioning mechanism 200 is provided at a seat carrier 1102.

[0071] Fig. 11 shows a schematic perspective exploded view from below of the chair seat 104 with the tensioning mechanism 200 in the seat carrier 1102. The seat carrier 1102 has a receptacle 1104 for coupling with the chair base assembly 102, e.g. with the tilt and height adjustment mechanism 202 shown in Fig. 2.

[0072] The chair seat 104 comprises the upholstery cover 106, the seat carrier 1102, and a padding 340 between the upholstery cover 106 and the seat carrier 1102. The upholstery cover 106 is provided with a circumferential hem 302 in which a drawstring 304 is arranged as a closed loop. The length of the drawstring 304 is at least such that the circumferential hem 302 can be stretched over an outer edge of the seat carrier 1102. As shown in Fig. 11 , the drawstring 304 provides some additional length for passing through the tensioning mechanism 200 as will be described in more detail in connection with Figs. 15 to 17.

[0073] Similar to the tensioning mechanism 200 shown in Fig. 3, the tensioning mechanism 200 comprises a support means 306 attached to the seat carrier 1102 and an elongated lever 310 having a first end 312 and a second end 314. The first end 312 is pivotally attached to the support means 306 about a pivot axis 502 (see Fig. 13) extending perpendicular to the plate-like surface of the support means 306 and perpendicular to a longitudinal direction of the elongated lever 310. The second end 314 is opposite to the first end 312 in the longitudinal direction of the elongated lever 310 and has a handle 316. The elongated lever 310 includes at least one fastening arrangement 318 for fastening the drawstring 304. In the example illustrated in Fig. 11 , the elongated lever 310 is provided with three fastening arrangements 318 at different locations along the longitudinal direction of the elongated lever 310. The elongated lever 310 includes a locking means 320 (e.g. at the second end 314) engageable with one of a plurality of mating locking means 322 provided on the support means 306. In the example of Fig. 11 , six mating locking means 322 are provided at equidistant positions in an arc around the pivot axis (only four of them are visible in Fig. 11 ).

[0074] The tensioning mechanism 200 further comprises a guide element 324 configured to cross two portions of the drawstring 304 before the two portions are passed to the fastening arrangement 318 of the elongated lever 310.

[0075] Fig. 12 to 14 describe the attachment of the elongated lever 310 to the support means 306.

[0076] Fig. 12 shows a schematic perspective partially exploded view from below of the chair seat 104 with the tensioning mechanism 200 in the seat carrier 1102. The support means 306 may be provided with a hole 402. The hole 402 may have a central round hole with two opposing recesses. A protrusion at the first end 312 of the elongated lever 310 may have a round body and a head that mates to the central round hole with the two opposing recesses in the support means 306. When the head of the protrusion at the first end 312 of the elongated lever 310 is aligned with the hole 402, the protrusion may be inserted into the hole 402.

[0077] Fig. 13 shows a schematic perspective view from below of the chair seat 104 with the protrusion at the first end 312 of the elongated lever 310 inserted into the hole 402. In this state, the first end 312 of the elongated lever 310 can be rotated in the hole 402 about the pivot axis 502. A longitudinal direction 504 of the elongated lever 310 is perpendicular to the pivot axis 502. Depending on the angle of rotation, the locking means 320 at the second end 314 of the elongated lever 310 may be inserted into one of the mating locking means 322.

[0078] Fig. 14 shows a schematic perspective view from above of the seat carrier 1102. As illustrated, a head 602 of the protrusion at the first end 312 of the elongated lever 310 is passed through the hole 402, thereby engaging the first end 312 with the support means 306 for rotation about the pivot axis 502. A head 604 of the locking means 320 is passed through one of the mating locking means 322 thereby securing the elongated lever 310 at a given angle of rotation.

[0079] Fig. 15 shows a schematic partial plan view from below of the seat carrier 1102, with details of the tensioning mechanism 200. In Fig. 15, the drawstring 304 is not attached to the tensioning mechanism 200. The elongated lever 310 is arranged along a direction 702 such that the fastening arrangements 318 are close to the outer edge of the seat carrier 1102, i.e. , close to the hem 302. The hem 302 has at least one opening for access to the drawstring 304. For example, the hem 302 may have openings for two portions 304A and 304B of a loop of the drawstring 304. The upholstery cover 106 is arranged such that the at least one opening is located near the guide element 324. The guide element 324 may comprise a block protruding from the surface of the support means 306 such that the portions 304A and 304B of the drawstring 304 can be guided by side surfaces of the guide element 324.

[0080] As illustrated in Fig. 16, the portions 304A and 304B of the drawstring 304 are crossed between the hem 302 and the guide element 324, then passed along the side surfaces of the guide element 324 and wrapped around one of the fastening arrangements 318. Already in this position, the drawstring 304 may be tensioned slightly, thereby tensioning the upholstery cover 106 around the padding 340 and the edge of the seat carrier 1102.

[0081] A user may now use the handle 316 to rotate the elongated lever 310 about the pivot axis 502 such that the fastening arrangement 318 is moved away from the guide element 324. The drawstring 304 is further tensioned as illustrated in Fig. 17. For example, the elongated lever 310 may be moved until it is positioned along the direction 902. As a result, the upholstery cover 106 is tensioned around the padding 340 and the edge of the seat carrier 1102. In this position of the elongated lever 310, the locking means 320 at the second end 314 of the elongated lever 310 may engage with one of the mating locking means 322.

[0082] As shown in Fig. 18, the locking means 320 may be provided with a hookshaped head 1002 configured to engage with an edge 1004 of the mating locking means 322 to securely fix the elongated lever 310 in the position illustrated in Fig. 17.

[0083] To remove the upholstery cover 106, the above steps shown in Figs. 15 to 17 may be performed in reverse order. The user may use the handle 316 to disengage the locking means 320 from the mating locking means 322 and may release / move the elongated lever 310 until it is positioned along the direction 702. Then, the drawstring 304 can be detached from the fastening arrangement 318 and the guide element 324. The hem 302 can be widened and the upholstery cover 106 can be removed from the edge of the seat carrier 1102 and the padding 340, for example for cleaning or replacement.

[0084] Fig. 19 shows a schematic perspective exploded view from the rear of a chair backrest 108 with a tensioning mechanism 200 in a backrest panel 1902.

[0085] The backrest panel 1902 has an attachment means 1904 for coupling to the chair base assembly 102, e.g. threaded holes for attaching a support 1908 that can be attached to the tilt and height adjustment mechanism 202 shown in Fig. 2.

[0086] The chair backrest 108 comprises the upholstery cover 110, the backrest panel 1902, a padding 1906 between the upholstery cover 110 and the backrest panel 1902, and a backrest cover 1910 at the rear side of the backrest panel 1902 for covering the attachment means 1904 and the tensioning mechanism 200. The upholstery cover 110 is provided with a circumferential hem 302 in which a drawstring 304 (see Fig. 24) is arranged as a closed loop. The length of the drawstring 304 is at least such that the circumferential hem 302 can be stretched over an outer edge of the backrest panel 1902. As shown in Fig. 24, the drawstring 304 provides some additional length for passing through the tensioning mechanism 200 as will be described in more detail in connection with Figs. 24 to 26.

[0087] The tensioning mechanism 200 comprises a support means 306 integrally formed with the backrest panel 1902 and an elongated lever 310 having a first end 312 and a second end 314. The first end 312 is pivotally attached to the support means 306 about a pivot axis 502 extending perpendicular to the platelike surface of the support means 306 and perpendicular to a longitudinal direction of the elongated lever 310. The second end 314 is opposite to the first end 312 in the longitudinal direction of the elongated lever 310 and has a handle 316. The elongated lever 310 includes at least one fastening arrangement 318 for fastening the drawstring 304. In the example illustrated in Fig. 19, the elongated lever 310 is provided with three fastening arrangements 318 at different locations along the longitudinal direction of the elongated lever 310. The elongated lever 310 includes a locking means 320 engageable with one of a plurality of mating locking means 322 provided on the support means 306. In the example of Fig. 19, six mating locking means 322 are provided at equidistant positions in an arc around the pivot axis 502.

[0088] The tensioning mechanism 200 further comprises a guide element 324 configured to cross two portions of the drawstring 304 before the two portions are guided to the fastening arrangement 318 of the elongated lever 310.

[0089] Fig. 20 to 22 describe the attachment of the elongated lever 310 to the support means 306.

[0090] Fig. 20 shows a schematic perspective partially exploded view from the rear of the backrest panel 1902 with the tensioning mechanism 200. The support means 306 may be provided with a hole 402. The hole 402 may have a central round hole with two opposing recesses. A protrusion at the first end 312 of the elongated lever 310 may have a round body and a head that mates to the hole 402 including the two opposing recesses in the support means 306. When the head of the protrusion at the first end 312 of the elongated lever 310 is aligned with the hole 402, the protrusion may be inserted into the hole 402.

[0091] Fig. 21 shows a schematic perspective view from the rear of the backrest panel 1902 with the protrusion at the first end 312 of the elongated lever 310 inserted into the hole 402. In this state, the first end 312 of the elongated lever 310 can be rotated in the hole 402 about the pivot axis 502. A longitudinal direction 504 of the elongated lever 310 is perpendicular to the pivot axis 502. Depending on the angle of rotation, the locking means 320 at the second end 314 of the elongated lever 310 may be inserted into one of the mating locking means 322.

[0092] Fig. 22 shows a schematic perspective view from the front of the backrest panel 1902. As illustrated, a head 602 of the protrusion at the first end 312 of the elongated lever 310 is passed through the hole 402, thereby engaging the first end 312 with the support means 306 for rotation about the pivot axis 502. A head 604 of the locking means 320 is passed through one of the mating locking means 322 thereby securing the elongated lever 310 at a given angle of rotation.

[0093] Fig. 23 shows the backrest panel 1902, the upholstery cover 110 and the tensioning mechanism 200 in an assembled state. After tensioning the drawstring 304, the support 1908 and the backrest cover 1910 may be attached to the backrest panel 1902.

[0094] Fig. 24 shows a schematic partial plan view from the rear of the backrest panel 1902, with details of the tensioning mechanism 200. In Fig. 24, the drawstring 304 is not attached to the tensioning mechanism 200. The elongated lever 310 is arranged along a direction 702 such that the fastening arrangements 318 are close to the outer edge of the backrest panel 1902, i.e. , close to the hem 302. The hem 302 has at least one opening for access to the drawstring 304. For example, the hem 302 may have openings for two portions 304A and 304B of a loop of the drawstring 304. The upholstery cover 110 is arranged such that the at least one opening is located near the guide element 324. The guide element 324 may comprise a block protruding from the surface of the support means 306 such that the portions 304A and 304B of the drawstring 304 can be guided by side surfaces of the guide element 324.

[0095] As illustrated in Fig. 25, the portions 304A and 304B of the drawstring 304 are crossed between the hem 302 and the guide element 324, then passed along the side surfaces of the guide element 324 and wrapped around one of the fastening arrangements 318. Already in this position, the drawstring 304 may be tensioned slightly, thereby tensioning the upholstery cover 110 around the padding 1906 and the edge of the backrest panel 1902.

[0096] A user may now use the handle 316 to rotate the elongated lever 310 about the pivot axis 502 such that the fastening arrangement 318 is moved away from the guide element 324. The drawstring 304 is further tensioned as illustrated in Fig. 26. For example, the elongated lever 310 may be moved until it is positioned along the direction 902. As a result, the upholstery cover 110 is tensioned around the padding 1906 and the edge of the backrest panel 1902. In this position of the elongated lever 310, the locking means 320 at the second end 314 of the elongated lever 310 may engage with one of the mating locking means 322.

[0097] As shown in Fig. 27, the locking means 320 may be provided with a hookshaped head 1002 configured to engage with an edge 1004 of the mating locking means 322 to securely fix the elongated lever 310 in the position illustrated in Fig. 26.

[0098] To remove the upholstery cover 110, the above steps shown in Figs. 24 to 26 may be performed in reverse order. The user may use the handle 316 to disengage the locking means 320 from the mating locking means 322 and may release / move the elongated lever 310 until it is positioned along the direction 702. Then, the drawstring 304 can be detached from the fastening arrangement 318 and the guide element 324. The hem 302 can be widened and the upholstery cover 110 can be removed from the edge of the backrest panel 1902 and the padding 1906, for example for cleaning or replacement.

[0099] In summary, the above techniques facilitate the quick assembly or disassembly of the upholstery of the chair seat or backrest cover fabric of office and nonoffice chairs. The peculiarity is that the assembly or disassembly of the cover fabric can be performed by the end user without the need for tools or special skills. This system allows an easier maintenance of the chairs after sale, keeping them cleaner over the years, having the possibility to remove the cover fabric and then reassemble it. The techniques can be applied to both the seat and the back of the chair.

[0100] The techniques can also avoid the use of steel staples in the plastic parts, which can be beneficial from a sustainability perspective.

Claims

1 . A tensioning mechanism (200) for a drawstring (304) for an upholstery cover (106, 110) of an upholstery, the tensioning mechanism (200) comprising: a support means (306) attached to a support structure (308, 1102, 1902) of the upholstery, an elongated lever (310) having a first end (312) and a second end (314), the first end (312) being pivotally attached to the support means (306) about a pivot axis (502), the second end (314) being opposite to the first end (312) in a longitudinal direction (504) of the elongated lever (310) and having a handle (316), wherein the pivot axis (502) is perpendicular to the longitudinal direction (504), wherein the elongated lever (310) includes at least one fastening arrangement (318) for fastening the drawstring (304), wherein the elongated lever (310) includes a locking means (320) engageable with one of a plurality of mating locking means (322) provided on the support means (306).

2. The tensioning mechanism of claim 1 , wherein the at least one fastening arrangement (318) is provided between the first end (312) and the second end (314).

3. The tensioning mechanism of claim 1 or claim 2, wherein the locking means (320) is provided at the second end (316) of the elongated lever (310).

4. The tensioning mechanism of any one of the preceding claims, wherein the mating locking means (322) are holes in the support means (306).

5. The tensioning mechanism of claim 4, wherein the locking means (320) is a protrusion configured to be inserted at least partially into one of the plurality of holes in the support means (306).

6. The tensioning mechanism of claim 4 or claim 5, wherein the locking means (320) has a hook-shaped head (1002) configured to engage with an edge (1004) of one of the plurality of holes in the support means (306).

7. The tensioning mechanism of any one of the preceding claims, further comprising a guide element (324) configured to cross two portions (304A, 304B) of the drawstring (304) to the fastening arrangement (318) of the elongated lever (310).

8. The tensioning mechanism of any one of the preceding claims, wherein the support means (306) is integrally formed with the support structure (308, 1102, 1902) of the upholstery.

9. A chair seat (104) with an upholstery comprising a support structure (308, 1102), an upholstery cover (106) and a drawstring (304), wherein the drawstring (304) is at least partially arranged in a circumferential hem (302) of the upholstery cover (106, 110), wherein the chair seat (104) is provided with the tensioning mechanism (200) of any one of the preceding claims for tensioning the drawstring (304).

10. A chair backrest (108) with an upholstery (110) comprising a support structure (1902), an upholstery cover (110) and a drawstring (304), wherein the drawstring (304) is at least partially arranged in a circumferential hem (302) of the upholstery cover (110), wherein the chair backrest (108) is provided with the tensioning mechanism (200) of any one of claims 1 -8 for tensioning the drawstring.

11. A chair comprising: a chair base assembly (102), and at least one of the chair seat (104) of claim 9 and the chair backrest (108) of claim 10 coupled to the chair base assembly (102).

Images