ES2409348T3 - Chair back - Google Patents

Abstract

A chair comprising a seat assembly (30) having a seat frame, a backrest assembly (24) supported backwardly adjacent to said seat assembly (30) and comprising a projected backrest frame (23) above the seat frame (30) and having an annular shape having an internal periphery and an external periphery and defining an open area (40) delimited by said internal periphery, the backrest assembly also including a suspension fabric (25 ) that covers the open area and is secured at its periphery to the outer periphery of the backrest frame, characterized in that the backrest frame (23) comprises front and rear backrest frame sections (57, 55) that have front and rear inner faces that fit one over the other in opposite facing relationship at their interface and are fixed to each other, and because a peripheral channel (42) is defined on the outer periphery between the frame sections front and rear in the interface between them, and open radially outward towards the side of said backrest frame to receive the periphery of the suspension fabric (25) in a tense condition that extends through an outer front face of the backrest frame.

Description

Chair back

5 Field of the invention

The invention relates to an office chair with an improved chair backrest and, more particularly, to a chair backrest with a peripheral frame and a suspension fabric fixed thereto.

Background of the invention

Preferably, conventional office chairs are designed to provide significant levels of comfort and adjustability. These chairs typically include a base that supports the tilt control assembly in which a seat assembly and a backrest assembly are mobile interconnected. He

The tilt control mechanism includes a vertical upright of the backrest that extends backward and upward, and supports the backrest assembly backward, adjacent to the seat assembly. The tilt control mechanism serves to interconnect the seat and backrest assembly so that they can lean back together in response to the movements of the chair occupant and, possibly, allow a limited forward tilt of the seat and the backrest . In addition, such chairs typically allow the backrest to also move relative to the seat during such a backward tilt.

The backrest assembly of such office chairs can have a variety of constructions where one type of construction includes an annular backrest frame that defines an open interior in which the back of the chair occupant is supported. This central open area is surrounded by a suspension mesh that extends along

25 of the opening and has the outer peripheral edge thereof fixed to the annular frame. An example is disclosed in WO 03/032780.

The backrest frame also has a section thereof rigidly connected to a vertical upright of the chair. The vertical upright is connected to a tilt control mechanism, a mechanism that supports the seat assembly and controls the backward tilt of the vertical upright. As such, the backrest assembly moves in combination with the vertical upright when the occupant reclines in the chair.

An object of the invention is to provide an office chair that has a chair backrest arrangement that is improved with respect to the previous chair backrest constructions.

Therefore, the invention relates to an office chair and, more particularly, to the construction of a chair backrest assembly and the assembly of this chair backrest assembly in a vertical upright.

The backrest assembly comprises an annular frame that has a suspension fabric that extends along the central opening of the backrest and has the periphery of the suspension fabric connected to the frame. Preferably, the suspension fabric comprises a single layer of suspension material that is connected to the frame by means of a plastic tongue that is snapped into an annular tongue channel formed around the periphery of the backrest frame.

The backrest frame is defined by side rails of the frame, which extend vertically and transverse rails that extend horizontally between the side rails at the top and bottom thereof. The backrest frame has a contoured shape, where the side rails of the frame are curved back and out in the side-to-side direction, while the transverse rails are also curved in the front-to-back direction to provide a contoured shape. for the backrest frame that fits comfortably to the chair back of the chair occupant.

To form the tongue channel, the backrest frame is constructed of molded front and rear annular sections that have grooves around their respective peripheries to define the front and rear channel portions. The front channel portion defines the front wall of the tongue channel while the portion of

55 rear channel defines the rear wall of the channel. The front and rear annular section overlap each other in opposite relation and are rigidly secured to each other by suitable fixing means, such as ultrasonic welding, adhesives or even threaded fasteners. When the two sections of the frame are rigidly joined together, the grooved portions align with each other and define the tongue channel. In this way, complex contours can be formed in a molded backrest frame while allowing the formation of a tongue channel around the periphery thereof.

Once the frame is mounted, the suspension fabric is fastened to the frame by a tab that is snapped into the tongue channel and catches the edge portions of the suspension fabric within this channel.

65 The backrest frame also has a column of the vertical upright frame that extends into the central opening of the chair and ends at its upper end in transverse support arms that extend outward and are rigidly fixed to the middle of the lateral frame members to provide greater support for the backrest frame. The lower end of the support column rigidly joins the vertical upright while the rest of the support column has an elongated vertical groove that separates the support column in the left and right halves. Since the backrest frame flexes during use as a result of

5 the loads applied to it when the occupant is supported on the backrest assembly, this separation slot is provided for greater independent movement of the upper corners of the chair backrest with respect to the other.

The lower end of the support column also includes an improved bayonet connection that rigidly joins the backrest frame to the vertical uprights.

In particular, the vertical uprights are formed as independent arms that each independently connect to the tilt control mechanism and move in unison. The rearmost ends of the vertical uprights are arranged adjacent to each other and define a connector center with a receptacle of

15 opening up in which the bayonet connector is slidably inserted. Each vertical upright defines a half of the receptacle and includes ribs that project into the receptacle that are then slidably received within a corresponding conical slot of the bayonet connector, where this slot of the bayonet connector connector serves to hold the rear ends of the vertical upright laterally to each other and to avoid their separation An additional clamping element is also provided vertically between the center of the vertical upright and the backrest frame to drag these components vertically together, such that the separate vertical uprights are held rigidly joined by the bayonet connector and as such move to the unison.

The above features provide an improved backup framework layout, where other objectives

25 and purposes of the invention, and variations thereof, will be apparent after reading the following specification and inspecting the attached drawings.

Brief description of the drawings

Figure 1 is a front elevation view of an office chair that has an arrangement of the inventive backrest assembly.

Figure 2 is a side elevation view of the office chair.

35 Figure 3 is a rear isometric view thereof.

Figure 4 is a front isometric view thereof.

Figure 5 is a side view of a backrest assembly.

Figure 6 is a front view of it.

Figure 7 is an exploded isometric view of the backrest assembly with a fastener for mounting the backrest frame on the chair tilt control mechanism.

45 Figure 8 is an exploded exploded view of the mounting section of the backrest frame.

Figure 9 is an exploded isometric view of the backrest components that form the backrest assembly.

Figure 10 is a side cross-sectional view of the backrest assembly taken along the centerline of the backrest assembly.

Figure 11 is a rear view of the backrest frame.

55 Figure 12 is a front view of the backrest frame.

Figure 13 is a schematic view illustrating the manufacture of suspension tissue sheets from a raw material.

Figure 14 is a cross-sectional top view of a side frame member taken along line 14-14 of Figure 6.

Figure 15 is a side cross-sectional view of the upper frame member taken along line 65 15-15 of Figure 6.

Figure 16 is a side cross-sectional view of the lower frame member taken along line 16-16 of Figure 6. Figure 17 is a front view of a cushion adapted for mounting on the backrest assembly on The tissue 5 suspension.

Figure 18 is an exploded isometric view of the cushion components. Figure 19 is an enlarged cross-sectional side view of the lower frame member with a connection of bayonet together with a pelvic support member mounted on the lower frame member.

Figure 20 is a partial, enlarged front view of the backrest frame. Figure 21 is a rear view of the pelvic support.

15 Figure 22 is a side view of the pelvic support. Figure 23 is a side cross-sectional view of the pelvic support. Figure 24 is an enlarged partial isometric view of the backrest assembly, seat assembly and mechanism

tilt control. Figure 25 is an enlarged rear view of the bayonet connector. 25 Figure 26 is an enlarged side view of the bayonet connector.

Figure 27 is a top cross-sectional view of the bayonet connector, taken along line 2727 of Figure 26. Figure 28 is a cross-sectional top view of the bayonet connector, taken along the line 28

28 of Figure 26. Figure 29 is an inner side view of a vertical support post. 35 Figure 30 is a front view of the vertical upright.

Figure 31 is a cross-sectional top view of a center section of the vertical upright, taken at along line 31-31 of Figure 29. Figure 32 is a top cross-sectional view of the center section taken along line 32-32

of Figure 29. Figure 33 is a cross-sectional top view of the bayonet connector seated within a receptacle defined by a center of the vertical uprights.

Figure 34 is an exploded isometric view of the second embodiment of a backrest assembly. Figure 35 is a top cross-sectional view of the backrest frame of the second embodiment of the

Figure 34 Figure 36 is an isometric view of the suspension fabric assembly to cover the backrest frame. Figure 37 is a front view of a tongue adapted for attachment to a suspension fabric of Figure

36.

55 Figure 38 is a top view of a first tongue section.

Figure 39 is a top view of a second tongue section.

Certain terminology will be used in the following description only for convenience and reference, and will not be limited. For example, the expressions "up", "down", right "and" left "will refer to directions in the drawings referred to. The expressions" in "and" out " they will refer to the senses to and out of, respectively, the geometric center of the arrangement and its designated parts.This terminology will include the specifically mentioned expressions, their derivatives and expressions

65 of similar meaning.

Detailed description

Referring to Figures 1-4, the invention generally relates to an office chair 10 that includes various features of the invention that accommodate the different physical characteristics and comfort preferences of a chair occupant and also improve the assembly. from chair 10.

In general, this chair 10 includes sets of improved height-adjustable arms 12 that are easily adjustable. The structure of each arm assembly 12 is disclosed in US Provisional Patent Application Serial No. 60/657 632, filed on March 1, 2005, entitled ARM ASSEMBLY FOR A CHAIR, which is owned by Haworth, Inc., the common assignee of the present invention. The disclosure of this patent application is incorporated herein in its entirety by reference.

The chair 10 is supported on a base 13 having radiant legs 14 that are supported on the ground by wheels 15. The base 12 also includes a vertical upright pedestal 16 that projects vertically and supports a

15 tilt control mechanism 18 at the upper end thereof. The pedestal 16 has a pneumatic cylinder inside which allows the height or elevation adjustment of the tilt control mechanism 18 with respect to a floor.

The tilt control mechanism 18 includes a control body 19 in which a pair of generally upright L-shaped uprights 20 are pivotally supported by their front ends. The vertical uprights 19 converge back together to define a center of the connector 22 on which the backrest frame 23 of a backrest assembly 24 is supported. The structure of this tilt control mechanism is disclosed in the Provisional Patent Applications of United States with Serial No. 60/657 541, filed on March 1, 2005 and 60/689 723, filed on June 10, 2005, both titled MECHANISM OF CONTROL OF

25 ELEVATION FOR A CHAIR, and the US Provisional Patent Application with serial number 60/657 524, filed on March 1, 2005, entitled TENSION ADJUSTMENT MECHANISM FOR A CHAIR, applications that are owned by Haworth, Inc.

In addition, the chair 10 includes a seat assembly 30 that defines an upwardly oriented support surface 31 on which the occupant seat is supported.

More particularly as regards the backrest assembly 24, the backrest assembly 24 is generally illustrated in Figures 5-7. The backrest frame 23 comprises a pair of vertical side frame rails 35, a rail of the upper frame 36, and a rail of the lower frame 37 that join together in the upper corners 38 of the assembly

35 of the backrest 24, as well as the lower corners 39 to define an annular or endless frame having a central opening 40.

As can be seen in Figures 5-7, the backrest frame 23 has a contoured shape that ergonomically supports the user's back. In particular, the side rails 35 are curved backwards as seen in Figures 5 and 7, as well as outwards (Figure 6) in relation to the lower portions of the side rails 35. In addition, the upper rail 36 and the rail Lower 37 each have a corresponding curvature to closely fit the curvature of a typical chair occupant.

To support the occupant, the backrest assembly 24 includes the suspension fabric 25 which is secured in the form

45 taught in the frame. In particular, the backrest frame 23 includes a peripheral tongue channel 42, in which the peripheral edge of the suspension fabric 25 is fixed as will be described in more detail herein.

The backrest frame 23 generally includes a support structure 43 to which the side rails 35 and the bottom rail 37 are rigidly interconnected. This support structure 43 comprises a vertical upright support column 44 that extends along the center line of the chair 41 (Figure 7) to an elevation located just below the middle of the side rails 35. The upper end of The support column 44 includes a pair of support arms 45 that extend laterally and have each of their respective outer ends rigidly connected to one of the side rails 35.

55 The lower end of the support column 43 includes a flange of the generally L-shaped connector 46 (Figures 5 and 7) that projects forward and then downward in fixed engagement with the lower cross rail 37. Moreover, this Bottom end of the column includes a bayonet connector 49 that projects downwardly for rigid connection to the vertical uprights 20 by the clamping bolt 50 and the nut 51, as will be described in more detail hereafter.

Referring more particularly to the components of the backrest assembly 24, Figure 9 illustrates these components in an exploded view thereof. In particular, the frame 23 comprises a molded rear frame unit 55 that includes the support structure 44 described above, as well as a rear frame ring 56 that is supported on the support arms 45 of the support structure 44. The frame of the backrest 24 65 further includes a molded front frame ring 57 that is adapted to be mounted on the rear frame ring 56 in overlapping relationship to define the tongue channel 42 around the periphery thereof.

In addition, the backrest assembly 24 includes the suspension fabric 25 described above and an elastomer tongue 58.

Referring to Figures 11 and 12, the rear frame unit 55 comprises the support structure 43 and the

5 rear frame ring 56. Both the support structure 43 and the rear frame ring 56 are simultaneously molded together in a monolithic single-piece construction having the contoured shape described above. To facilitate molding in this contoured manner while still having the tongue channel 42 mentioned above, the rear frame ring 56 and the front frame ring 57 are molded separately from each other and then fixed together.

As for the support structure 43, the support column 44 thereof is centrally located within the lower half of the opening of the central frame 40. The support column 44 has a base end 59 and a pair of halves of columns 60 and 61 that are separated from each other by a vertically elongated column groove

62. Thus, column 44 is formed as a column divided by slot 62 that extends along a

Substantial portion of the length of the column 44, with the column halves 60 and 61 being joined together by the solid base section 59. As such, the column halves 60 and 61 are supported in cantilever by the base section 59. The rear frame unit 55 and the front frame ring 57 are formed of glass-loaded nylon material that is molded into the desired shapes, where this material has limited bending to allow flexion of the various areas of the frame when It is placed under load by an occupant of the chair. Since column halves 60 and 61 are separated from each other by slot 62, these column halves 60 and 61 can be articulated independently of each other to facilitate flexion and movement of the various corners of the frame. 38 and 39.

The upper ends of the halves of the frame 60 and 61 are integrally joined to the transverse arms 45. The

25 outer ends of the arms 45 extend outwardly and are integrally molded with the vertical sides of the rear frame ring 56. As seen in Figure 12, the inner faces of the column halves 60 and 61 and the support arms 45 has an appropriate pattern of ribs 64 to selectively stiffen the support structure 43 while allowing flexion thereof.

In column base 59, this column base 59 ends in a lower wall 65 (Figures 9, 10 and 12), which is formed with a perforation 66 that extends vertically therethrough. The lower wall 65 is further formed integral with the bayonet connector 49 where the perforation 66 extends vertically through this lower wall 65 and the bayonet 49, as seen in Figure 10. By joining the backrest frame 23 to the vertical uprights of the chair 20, the clamping element 50 extends upwards from the uprights

35 vertical 20, as will be described in more detail in this document and extends through the perforation of the clamping element 66, so that it projects vertically above the wall of the lower column 65. The upper end of the element of fastener 50 is coupled by threaded nut 51 as seen in Figure 10 to thereby secure the backrest frame 23 to vertical uprights 20. This interconnection between these components will be described in more detail hereafter.

In addition to the bottom wall 65, this wall extends forward to define a horizontal leg 68 of the L-shaped flange 46, flange 46 which is then turned down to define a vertical leg 69 (Figures 5, 7 and 10). The lower column section 59 serves to rigidly support the lower transverse rail 37 of the backrest frame 23. As such, the lower frame rail 37 is supported more rigidly and has less movement

45 relative under the loads of the occupants than the areas of the central frame supported by the support arms 45 or even the corners of the upper frame 38 which have the greatest amount of displacement capacity. In this way, the rear frame unit 55 is provided for controlled bending of the entire backrest frame 23.

Referring to Figures 11 and 12, the rear frame ring 56 comprises upper and lower annular sections 71 and 72 and left and right annular sections 73 extending vertically. As seen in Figure 14, each side annular section 73 includes raised connector ribs 74 and 75, as well as an additional rib 76 that defines the inner end of the tongue channel 42 and is also located directly adjacent to a tongue groove 77 which is adapted to accommodate the thickness of the tongue 58. The outer edge of the annular side section 73 includes a thinner portion 78 and essentially defines the portion of the rear side of the carcass channel.

55 tab 42.

As for the horizontal rail section 71, this rail section 71 includes an inner rib 80, a channel rib 81 and an intermediate connector face 82. Adjacent to the channel rib 81, a tongue groove 83 is provided for accommodate the thickness of the tongue 58, while the outer edge portion 73 continues through the upper annular section 71.

Referring to Figures 16 and 20, the lower rail section 72 includes a tongue channel 85 along its entire lateral width to accommodate the tongue 58. Here again, the outer edge portion 78 continues through this region to define the rear portion of the tongue channel 42. In the middle of the annular section

65 lower 72, a recessed pocket 87 is defined which opens upwards and is positioned vertically adjacent to a locking post 88, whose function will be described in more detail hereafter.

The pocket 87 is defined by side walls 89, side walls 89 that include notches 90 at the lower end thereof directly adjacent to the tongue groove 85. It is noted that all tongue grooves 77, 83 and 85 are arranged in relation to end to end to define a continuous groove to continuously accommodate the tongue 58 inside. In addition, channel ribs arranged directly adjacent to these grooves

5 of tabs 77, 83 and 85 are continuously formed in end to end relationship.

Turning next to the front frame ring 57, this frame ring 57 has a front face 92 that is facing forward and a rear face 93 that is facing back toward the rear frame ring 56 and is adapted to abut against the same and fixedly attached to it. This frame ring 57 is defined by vertical annular sections 94 and an upper annular section 95 and a lower annular section 96.

As for the lateral annular sections 94 (Figure 14), these annular sections 94 include a connector rib that protrudes backward 98 and an inner edge portion 99 that are adapted to butt and securely secure the ribs of connector 75 on the rear frame ring 56. Preferably, the

15 rings of the front and rear frame 57 and 56, respectively, are joined together by ultrasonically welding these components with the faces arranged in contact by welding together. The front annular sections 94 are molded with a channel rib 99 arranged directly adjacent to a tongue groove 100, tongue groove 100 that is arranged in oppositional relationship with the other tongue groove 77 to define an enlarged inner portion in which the tongue 58 can be received. The outer edge portion 101 of the front ring 57 is disposed adjacent to, but separated from the other edge portion 78 to thereby define the inlet portion of the tongue channel 42.

As for the upper annular section 95 (Figure 15), this is similarly formed, since it includes a channel rib 102 and a tongue groove 103 that is disposed directly adjacent to the outer edge portion 101 so as to

25 forming the tongue channel 42 in cooperation with the tongue groove 83 and the outer edge portion 78 of the rear frame ring 56. The outer edge portion 101 of the front frame ring 57 further extends downwardly along the other vertical annular section 93 and then through the lower annular section 96.

The lower annular section 96 (Figure 16) is formed with a tongue groove 105 that extends therethrough in alignment with the opposite rear tongue groove 85. In this way, the rear frame ring 56 defines a rear portion of the tongue groove 42 while the front frame ring 57 defines a front portion thereof that said frame rings 56 and 57 when arranged in opposite relation define the channel 42 so that it opens radially outward and has an inner groove expanded in which the tongue 58 and associated tissue material can be received in non-detachable coupling. As best seen in the Figure

35 14, the fabric 25 is wound around the tongue 58 to essentially define a folded hem, folded hem which is then pressed into the tongue channel 42 by an appropriate tool or tools.

In this way, the suspension fabric 25 fits firmly into the frame of the backrest 23 so that the fabric material 25 is tensioned as generally illustrated in Figure 10 and placed at angles then away from the frame of the backrest 23 and at length of the central frame opening 40.

The suspension fabric 25 is formed of any suitable suspension material that is preferably elastomeric and preferably has an open fabric that is provided for breathability. Figure 13 generally illustrates the formation of the pieces of the suspension fabric 25, where Figure 13 illustrates a subject

Initial cousin 110 from which multiple pieces of the suspension fabric 25 are cut. The suspension fabric 25 is preferably formed as a single layer, but may have multiple overlapping layers and may also include padding inside.

In the office chair 10 of the invention, the chair 10 may be provided with a separate padding pad 111 (Figures 17 and 18) covering the suspension fabric 25. The pad 111 has an upper pocket 112 and a lower pocket 113 which are adapted to be removed and mounted on the backrest frame 23. The pad 111 is formed as a composite pad having a rear fabric layer 114, an intermediate cushion 115 and a front fabric layer 116, layers 114, 115 and 116 that are all sewn together about their peripheral edges.

55 To define the upper pocket 112, upper and lower pocket walls 117 and 118 are provided which are formed of a flexible fabric material and are sewn on three sides to the adjacent peripheral edges of the composite pad 111. The pad 111 it is installed by first placing one of the pockets 112 or 113 on the associated horizontal edge of the backrest frame 23 and then pulling the other pocket vertically and adjusting this on the edge of the opposite horizontal frame.

More particularly, as for the frame mounting pocket 87 formed in the rear frame ring 56, the front side of the pocket 87 is enclosed by the front frame ring 57. This pocket 87 is provided to support the lower end of a unit or pelvic support pusher 120 that is facing forward and adapts 65 to press against the rear pelvic region of a seat occupant. Referring to Figures 21-23, the pelvic support 120 has an elongated pad or panel 121 that is supported on a cantilever support arm

122. The lower end of the support arm 122 has a cap portion 123 that forks to define a pair of locking legs 124. The distal ends of the legs 124 include protrusions 125 that project laterally or outwardly for engagement with the notches 90 formed in the pocket 87. Also the cap portion 123 includes a locking recess 126 that opens backwards and is essentially defined by a

5 blind drilling.

When the rings of the front and rear frame 56 and 57 are fixed together, such as by welding, the support pocket 87 still opens upwardly between the interface between these two annular sections. This allows the plug portion 123 of the pelvic support 120 to be connected downwardly in the pocket 87. During this downward insertion, the connector legs 124 are turned inward toward each other until the protuberances 125 align with the notches corresponding pocket and then return to their condition not diverted with the protuberances 125 seated in the notches 90.

Since the pelvic support 120 is formed of an elastically deformable material, such as plastic, the arm of

15 support 122 is capable of bending forward during insertion or even for removal, to allow pocket post 88 to slide along the face of pelvic support 120 until it aligns with the corresponding locking recess 126, thereafter, the support arm 122 returns to its non-deflected condition with the post 88 seated within the recess 126. These cooperating components prevent unintended vertical displacement of the pelvic support 120. Since the elastically deviable suspension fabric 25 is supported against the front face 127 of the support panel 121, the fabric 25 tends to press the pelvic support 120 back so that the stop post 88 is more effective in preventing the removal of the pelvic post 120. However, since the tissue of Suspension 25 can also be stretched, the pelvic support 120 can still be folded forward to allow it to be removed from the support pocket 87.

25 As for the connection of the backrest assembly 24 with the tilt control mechanism 19, this is achieved through the bayonet connector 49 mentioned above. The tilt control mechanism 19 has two separate vertical uprights 20 that project backwards from opposite sides of the chair and have their upper ends aligned side by side to define the center of the aforementioned connector 22. The central column described above of the backrest assembly 24 fits in this center 22 and rigidly supports the vertical uprights 20 on the side aligned by the lateral relationship through the use of the aforementioned bolt 50.

Referring to Figures 25-28, the bayonet connector 49 projects downwardly from a lower surface 130 of the column base 59. As seen in Figure 25, the bayonet connector 49 which is

35 projects downwards has the perforation of fastener 66 which extends through the vertical length thereof. The lateral sides 131 of the bayonet connector 49 have a shallow conical shape where the sides 131 converge inwardly and downwardly. In the middle of the rear bayonet face 132, a vertically elongated groove 133 is provided along the entire length of the bayonet connector 49. This groove 133 has a bottom opening 134 and converging groove edges 135 that narrow toward the inside and up.

Referring to Figure 26, the bayonet front face 136 is also tapered relative to the rear face 132, although the taper of the rear face 132 is less deep than the taper of the front face

136. Therefore, bayonet 49 is conical in both the front-to-back plane and the side-to-side plane. The lower corners of the front face 136 are provided with reliefs or cuts 137.

Figures 27 and 28 are cross-sectional views, taken through bayonet connector 49. As can be seen, the central bore 66 extends vertically therethrough. The front face 136 is oriented forward and has facets that generally bend laterally until they end in the reliefs 137 in the lower area thereof.

In the central portion of the front face 136, a front groove 138 is provided between a pair of protuberances

139. When comparing Figures 27 and 28, the groove 138 is deeper near the top of the bayonet connector 49, as seen in Figure 27 and is less deep at the lower end (Figure 28). The

55 protrusions 139 also decrease in height when comparing the upper end (Figure 27) and the lower end (Figure 28).

As for slot 133, slot 133 is less deep at the lower end (Figure 28) compared to the upper end (Figure 27). This groove 133, as well as the groove 138 tends to attract the upper ends of the vertical uprights 20 laterally together and keep these ends in a side-to-side relationship. At the same time, the conical side faces 131 and the conical front and rear faces 132 and 136 facilitate a perfect fit when these components are removed together by the bolt 50.

More particularly, as regards the vertical upright 20, Figures 29 and 30 illustrate a vertical upright side

65 left 20. The vertical right side post 20 is formed substantially as a mirror image with respect to the vertical amount of Figures 29 and 30 and, therefore, no description is required.

Detailed of it.

More particularly, the front end of the vertical upright 20 includes a hexagonal hole 141 that fits at the end of a pivot shaft disposed within the tilt control housing 19. The opposite vertical upright 5 is also mounted at the opposite end of it. pivot shaft so that both of the vertical uprights 20 pivot down in unison during the rotation of the shaft.

The intermediate section of each vertical upright 20 includes a seat support 142 in which the rear end of the seat assembly 30 is supported.

More importantly, at the rear end of the vertical upright 20, a center section 143 is provided that defines half of the center 22 mentioned above. The center section 143 includes a chamber 144 having an open upper end 145 and an open inner side 146. On the left-side vertical post 20 illustrated in Figures 29 and 30, a locator knob 145 projects laterally from the inner face 146 of the

15 center section 143. With respect to the right-hand vertical upright 20, this locator knob 145 is, instead, replaced with a shallow locator bore in which knob 145 is received in tightly fitting coupling. The illustration of the inner face of this right-side vertical post 20 is identical to Figure 29, except that it is a mirror image thereof where the illustrated handle 145 of Figure 29 would in fact be a circular recess.

Referring to Figures 31 and 32, the shape of the receptacle section 144 has an inner profile as illustrated in Figures 31 and 32, which is substantially a negative image of the outer profile of the bayonet connector 49 illustrated in the Figures 27 and 28.

More particularly, the section of the receptacle 144 has a bottom wall 150 that has half of a perforation 151 formed therein adjacent to the inner face of the center 147. When two sections of the center 143 are joined side by side, the sections of perforation 151 is aligned laterally adjacent to each other to define a circular perforation through which the bolt 50 is passed. These perforation sections 151 open downwardly adjacent to a bottom wall face 152 against which the head 153 of the bolt 50 abuts , as illustrated in Figure 19.

The receptacle sections 144 also each include a receptacle side face 155 that narrows upwardly, outwardly, and a rear face 156 that also narrows upwardly outwardly. The front receptacle face 157 has a curved profile and narrows upwards, outwards, with one more taper

35 pronounced compared to the rear face 156. This front face is then curved to define a projection 158 that is progressively thicker in the upward direction as seen in Figures 32 and 31. In addition, the rear face 156 ends in a central rib section 160.

With reference to Figure 33, when the two center sections 143 are joined side by side to each other, the two receptacle sections 144 are aligned laterally in the register to define an upward opening receptacle 162 of the center 22, and the sections of rib 160 essentially defines a vertically elongated rib 161. This rib 161 slides into the corresponding groove 133 of bayonet connector 49. Since groove 133 is conical, it attracts rib sections 160 laterally together and prevents any lateral displacement of center sections 143 away from each other once the

45 backrest assembly 24 is installed within center 22. Similarly, projections 158 define a surface rib 164 that fits into groove 138 to further aid in the attraction of these sections of center 143 laterally to each other.

The conical shape of the bayonet connector 49 and the corresponding receptacle 162 provides a perfect fit between the opposite faces of these components. It will be understood that Figure 33 includes some clearance between these spaces for schematic purposes to aid in the illustration thereof, but that the separation between such surfaces is much closer in practice to avoid any unwanted loosening in the backrest assembly 24. Referring to Figure 19, the center 22 is generally represented by the bottom wall 150 thereof. During assembly, the bayonet connector 49 is inserted into the receptacle 162 of the center 22 and a

Then, these components are firmly attracted together by the insertion of the bolt 50 through perforation 66 and then the nut 51 is screwed onto them to place these components in compression. A Bellville 165 washer or other elastic or mechanical locking means can be provided to prevent any loosening of bolt 50 and nut 51.

As an additional feature of this connector arrangement, this arrangement can also be used to secure the lumbar assembly 28 in position. Referring to Figure 10, this lumbar assembly 28 may include a vertical support bracket 170 having a bottom bracket wall 171. As seen in Figure 19, this bottom bracket wall 171 includes a rear opening slot 172 to allow the square 170 to slide around or astride the bolt 50 where the nut 51 then presses 65 directly down on this square wall 171 to secure the lumbar assembly 128 in position. As an alternative, as shown in general in Figure 7, this lumbar assembly 28 will also not have to

provided when the nut 51 is positioned directly on the upper face of the column wall 65.

Therefore, the bayonet connection 49 not only serves to connect the bayonet connector 49 to the center 22, but also serves as the connector arrangement for the lumbar assembly 28, which optionally can be installed in this chair 10.

With respect to the chair 10 described above, the backrest frame 24 is mounted by first attaching the rear frame ring 56 to the front frame ring 57 by ultrasonic welding. Thereafter, the suspension fabric 25 stretches elastically on the backrest frame 23 with the peripheral edges of the fabric 25 fixed in the tongue groove 42 by the tongue 58. If desired, the pelvic support 120 can be connected in the appropriate pocket 87 formed in the lower frame rail 37.

Thereafter, to mount the backrest assembly 24 on the tilt control mechanism 19, the bayonet connector of the frame 49 is connected with the connector 162 of the center 22. The clamping element 50

15 appropriate with its associated Bellville 165 washer is inserted upwardly through the perforation of the clamping element 60 and then the nut 51 is screwed into the upper end of the bolt 50. If the lumbar assembly 28 is provided, it is then positioned by sliding its bracket 170 on bolt 50 after which nut 51 is then tightened to secure all of these components together. In this way, the backrest assembly 24 is rigidly connected to the vertical uprights 20 and tilts back with them.

As an alternative to the frame construction described above, Figures 34 and 35 illustrate a multi-component backrest frame 180 comprising a rear frame unit 181 and a front frame ring 182. The rear frame unit 181 and the ring Front frame 182 are substantially similar to the components described above and, therefore, a detailed description of these components is not believed

25 necessary in the following description mainly related to additional modifications to this construction of the frame.

In this regard, these frame components 181 and 182 would include perforations of appropriate fasteners 183 such that the rear frame unit 181 and the front frame ring 182 could be fixed together by screws 184. Once these two Frame sections 181 and 182 are joined together, essentially defining a tongue groove 185 in a manner substantially similar to that described above. Thereafter, the backrest frame 180 also includes an elastomeric pad ring 190 that generally conforms to the shape of the front frame ring 182, but is formed of a compressible material such as a spongy foam. Figure 35 shows in dotted lines the outline of the initial cross section profile

35 of this pad ring 190 when secured to the front frame ring 182.

The backrest frame 180 also includes a suspension fabric 191 having a tongue 192 sewn on its periphery by threads 193 or other suitable fastening means. This tab 192 fits into the tongue channel 185 to secure the suspension fabric 191 in position.

The suspension fabric 191 is preferably an elastomeric material that is tensioned when installed. To facilitate tensioning of this suspension fabric 191, the pad ring 190 is preferably compressed as illustrated in a solid line in Figure 35 where the compression of the pad 190 adds an additional outward pushing force to the suspension fabric. 191 to increase the tension inside. As a function

In addition, the pad ring 190 also superimposes the screws 184 and conceals these components from view.

Referring to Figure 35, as well as additional Figures 36-39, tongue 192 also has an improved inventive construction. More particularly, the suspension fabric 191 comprises an initial pattern of sheet material 195 formed from an elastomeric fabric cut to an appropriate shape as seen in Figure 36. The tongue itself comprises two U-shaped tongue sections 196 and 197. Initially, as seen in Figures 38 and 39, these tongue sections 196 and 197 are formed in a straight configuration with V-shaped cuts provided therein. In particular, these V-shaped cuts facilitate bending of the tongue sections 196 and 197.

With reference to Figure 35, it is noted that the tongue section has a relatively wide cross-sectional shape defined by a bulbous end portion 200 and an inner edge 201. One side of the tongue section 196 includes sliding ribs 202, while the opposite side includes a locking rib 203 thereon. This locking rib 203 projects outwardly and inwardly into the groove to firmly press the material of the suspension fabric against the inner side wall of the tongue groove 185.

Due to this wide form, it is necessary to provide the patterns of the cuts to facilitate the flexion of this wide piece of plastic tongue. More particularly, each of the tongue sections 196 and 197 as illustrated in Figures 38 and 39 include the first and second groups of V-shaped cuts 205, 206, 207 and 208 corresponding to the corners of the backrest frame , as well as additional 209 individual cuts. The

65 patterns of the cuts in the corners 205, 206, 207 and 208 provide a large amount of flexion, while additional individual cuts 209 are only necessary to provide a smooth curvature.

As seen in Figures 36 and 37, the tabs 196 and 197 initially have the cutouts that are oriented outward, after which the tongue sections 196 and 197 are sewn directly onto the fabric material 195 with the threads 193. These threads 193 directly pierce the fabric material, as well as the plastic of the tongue sections 196 and 197.

5 To insert the tongue 192 into the tongue groove 185, the tongue sections 196 and 197 are then turned, or folded inwards where the edge 201 initially begins on the outside of the fabric 195 as seen in Figure 36 and then folds inwardly so that it sits inside the inner end of the tongue groove 185. Therefore, the various serve first to allow flexion in the

10 form illustrated in Figures 36 and 37 where the cutouts are located along the outer edge and then turned inwards and allows reverse bending in the tongue sections 196 and 197 with the cuts being now located at the inner end of the tongue groove 185. In this manner, tongue 192 is installed by folding the tongue inwardly and inserting it into the peripheral tongue groove 185 formed in the backrest frame

180

Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the re-arrangement of parts, are within the scope of the present invention, as defined by the claims.

Claims (6)

1. A chair comprising a seat assembly (30) having a seat frame, a backrest assembly (24) supported backward adjacent to said seat assembly (30) and comprising a backrest frame 5 peripheral (23) projecting above the seat frame (30) and having an annular shape having an internal periphery and an external periphery and defining an open area (40) delimited by said internal periphery, also including the backrest assembly a suspension fabric (25) that covers the open area and is secured at its periphery to the outer periphery of the backrest frame, characterized in that the backrest frame (23) comprises front and rear backrest frame sections (57, 55) that have front and front inner faces 10 that fit one over the other in opposite facing relationship at its interface and are fixed to each other, and by which a peripheral channel (42) is defined at the outer periphery between the front and rear frame sections at the interface between them , and opens radially outward towards the side of said backrest frame to receive the periphery of the suspension fabric (25) in a tense condition that extends through a front outer face of the backrest frame. 2. A chair according to claim 1, characterized in that said front and rear frame sections are contoured molded frames having an outline such that said opposite inner faces of said front and rear frame sections (57, 55) they have a three-dimensional shape such that each of said inner faces is curved. 3. A chair according to claim 1 or 2, characterized in that said inner faces collide in continuous contact with each other around the periphery of said backrest frame (23). 4. A chair according to any one of the preceding claims, wherein said fabric (25) is continuously fixed around the periphery thereof to the corresponding peripheral edge of said backrest frame. A chair according to any of the preceding claims, wherein said suspension fabric (25) is stretched to a tense condition when said periphery of said fabric is attached to said backrest frame. A chair according to any of the preceding claims, characterized in that said backrest frame (23) is supported in said seat assembly (30) by a column structure (43) comprising a vertical upright support column (44) having a lower end attached to said seat assembly by a base connector, such that said support column is supported in a cantilever relation with respect to said seat assembly (30), including an end portion upper of said support column 35 transverse column arms (45) extending sideways from said support column (44) and have external lateral ends that are attached to said intermediate backrest frame (23) between the upper and lower edges of said backrest frame , said support column (44) having separate left and right column halves (60, 61) each supporting a respective one of said transverse arms (45) thereon, such that said column halves and said arms are movable separately the one of Another in the upper end portion of said support column (44), while said column halves (60, 61) are joined together at the lower end of said support column close to said base connector, allowing said column halves the separate movement of said backrest frame on the left and right sides thereof. A chair according to any of the preceding claims, characterized in that said backrest frame is connected to said seat assembly by a base connector, wherein said base connector is a bayonet connector (49) that projects down and has a conical shape that narrows inward in the downward direction; and said seat assembly comprises an upright that has a front end attached to said seat assembly and a rear end that extends backward and is attached joins said connector of 50 bayonet of said backrest frame, said vertical upright comprising separate frame sections on opposite sides of said chair that have respective front ends attached to said seat assembly and respective rear ends that converge towards each other and that collide against each other to define a connector center, said connector center comprising an upward opening receptacle in which said bayonet connector is received slidably and fixedly attached thereto. A chair according to claim 1, characterized in that said periphery of said suspension fabric is in non-removable coupling with said peripheral channel.