Abstract:
An armrest/backrest support bracket characterised by comprising: a support ( 4 ) provided in its lateral surface with a slot ( 14 ) and in its end surface with a hole which communicates with said slot, a blade ( 6 ) one end of which is insertable into said slot, locking means inserted into said hole and interacting with said support and with that blade part ( 6 ) housed in the slot.

Description:
The present invention relates to a armrest/backrest support bracket for chairs, in particular office chairs. 
     BACKGROUND OF THE INVENTION 
     Support brackets for chair armrests or backrests are known, consisting of an upper part or pad on which the arm or back of the chair user rests, a vertical support and a horizontal blade for its fixing to the chair frame. 
     These brackets however present the drawback of lack of flexibility and modularity. 
     In this respect, seeing the large variety of chairs and applications, it is important that these armrest and backrest brackets can be modified in terms of their main dimensions. 
     The known art often uses plastic or aluminium parts obtained by injection moulding, which by their very nature are very rigid in adapting to the individual person. 
     To obviate these drawbacks, brackets have been proposed consisting of separate vertical support elements and horizontal fixing elements welded together. 
     This arrangement only partly solves the problems as the parts produced in this manner are in any event bulky and rigid when the parts are combined. They also present considerable aesthetic problems which can be solved only by applying coverings on the weld region and by costly cleaning operations. 
     Another proposed arrangement consists of a single bent blade which performs both the bracket and support function. This arrangement however presents evident limits in terms of bulk, appearance and modularity. 
     Another proposed arrangement is to fix the blade to a tubular support element by screwing it onto a bush welded inside the tubular element. 
     This arrangement has the drawback of substantial cost due to welding and to the use of a relatively costly element such as the lathe-turned bush. 
     Moreover it does not enable the blade to be reliably orientated relative to the support, so that semi-permanent screwing operations have to be carried out in the factory (with the same drawbacks as the other arrangements) or further manufacturing costs have to be incurred by using insertion fitting between the parts. 
     Brackets are also known which enable the height of the arm/back support to be adjusted by the use of telescopic elements. 
     These known brackets present however certain drawbacks and in particular:
         slackness and jamming while sliding,   complicated construction,   a large number of components leading to high cost and possible reliability problems,   non-ergonomic adjustments.       

     With regard to the problem of sliding the telescopic elements within height-adjustable brackets, the known art has already proposed different solutions. 
     The most frequent solution, in which the sleeve is rigid with the arm/back support and slides directly on the surface of the vertical support element (tubular or blade) presents the drawback of unacceptable slackness as it is difficult to achieve a constructional precision which eliminates gaps within the guide regions. 
     Another drawback consists of the fact that the sliding between the constituent rigid material of the sleeve (typically polyamide filled with glass fibre) and the outer surface of the tubular element determines continuous rubbing leading to surface deterioration. 
     To solve this problem brackets have been proposed in which the tube slides internally via an additional guide while the outer sleeve has only an aesthetic function. Again in this case the addition of another important element leads to additional costs and does not fully solve the problem of sliding precision because of the aforesaid known problems. 
     In other cases use is made of bands of self-lubricating material rigid with one of the telescopic elements, which improve sliding without ruining the outer surface. However to apply these bands and maintain them in position, costly arrangements have to be used comprising seats obtained by rectifying machining or fixtures with movements to obtain undercuts, or open half-shells which once assembled enclose one of the telescopic elements. 
     The known art presents various solutions for locking the movement of the telescopic elements of the brackets. 
     In some cases controls are provided connected to a transmission which by means of a cam disengages a catch from the holes provided in the other telescopic element. 
     These solutions present the drawback of being complicated in terms of the large number of parts and of the difficulty and time of assembly. 
     Other simpler solutions exist comprising a control, usually a pushbutton, connected directly to the catch. However this penalizes the ergonomics of the bracket as the position of the control and the type of control movement are uncomfortable, not immediate and unnatural. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the invention all these drawbacks are eliminated by an armrest/backrest support bracket as claimed in claim  1 . 
    
    
     
       The present invention is described in detail hereinafter with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a chair provided with the bracket, 
         FIG. 2  is an exploded perspective view of a bracket, 
         FIG. 3  shows it in its assembled configuration, 
         FIGS. 4-6  show different connection systems for locking the blade to the tubular support, 
         FIG. 7  is an exploded perspective view of an adjustable bracket, 
         FIG. 8  is a cross-section therethrough, 
         FIG. 9  is a longitudinal section therethrough, and 
         FIG. 10  shows the connection of the sleeve shoes. 
     
    
    
     DETAILED DESCRIPTION 
     As can be seen from the figures, the support bracket according to the invention comprises substantially a horizontal support  2  rigid with a tubular support  4 , a blade  6  with threaded hole  8  and a knob  10  provided with a threaded pin  12  and a pressing surface  13 . 
     A through slot  14  is provided in the tubular support  4 . 
     To assemble the bracket of the invention, the blade  6  is inserted into the slot  14 , after which the threaded pin is inserted from the support base to engage in the hole  8 . When the knob has been screwed in, its surface  13  presses against the end of the support. 
     In the different embodiment of the bracket shown in  FIG. 4 , a screw  18  and cap  21  are used to achieve pressing against the tubular support and tightening of the bracket, in contrast to the embodiment of  FIGS. 3 and 3  in which these functions are performed by the knob  10 . 
     In the embodiment shown in  FIG. 5  the cap  20  is provided internally with a threaded nut  16  in which a screw  18  engages after passing through the (no longer threaded) hole  8  of the blade  6 . 
     In the embodiment shown in  FIG. 6  the fixing element consists of a lever  22  with an eccentric head  24  to which there is pivoted a tie bar  26  which passes through an elongate hole  9  provided in the blade  6  and is provided at its other end with a counteracting plate  28 . 
     In this embodiment, rotation of the lever  22  locks the blade within the slot and enables the position of the support element to be modified relative to the bracket. 
       FIGS. 7-9  show a height-adjustable armrest. Said armrest comprises a metal tubular element  30 , a wall of which comprises a plurality of overlying holes  32  and two inwardly facing lugs  31 . This tubular element is inserted into a plastic sleeve  34  rigidly fixed to the arm support  36  by screws  38 . 
     The lower end of the tubular element  30  is inserted into a cap  40  into which the end of the blade  6  is also inserted by the already described systems, between the tubular element  30  and the sleeve  34  there being interposed two shoes  42  of self-lubricating material. 
     The shoes  42  perform various functions. They firstly prevent the hard plastic of the sleeve from directly contacting the tube surface, so ruining it during movement. They also enable very controlled sliding free from jamming by virtue of the self-lubricating properties of the material. At the points of contact with the internal tube they also present arch-shaped raised portions which by flexing, enable any slackness to be deadened, so compensating the connection inaccuracies of the telescopic elements. 
     Said shoes are provided with annular recesses  44  in which there engage corresponding ribs  46  provided in each sleeve, so making them rigid with it. Once the inner tube has been inserted into the outer sleeve, the shoes are compelled to remain in position. To facilitate assembly, vertical edges  43  are provided within the sleeve to retain the shoes before insertion of the tube ( FIG. 10 ). 
     The armrest also comprises a substantially T-shaped locking element  48 . The vertical portion  50  presents channels  51  in which the two lugs  31  engage to limit the stroke of the telescopic elements. The lower end of the vertical portion  50  is provided with a tooth  52  selectively engagable in one of the holes  32  of the tubular support  30 . This locking element  48  also has an end  54  of a horizontal portion housed in a seat  56  provided on the top of the sleeve and retained by the arm support element  36 . This end  54  acts as a hinge for the lever formed by the locking element, which also comprises a spring urging the tooth  52  into engagement with the holes. 
     The tooth  52  can be disengaged from the hole  32  by operating the other portion  58  of the element  48 , to enable the sleeve to slide relative to the support. 
     For ergonomic reasons the pushbutton is positioned immediately below and to the side of the arm support element  36  and moves vertically, i.e. the same adjustment direction as the telescopic elements of the armrest. 
     From the aforegoing it is apparent that the bracket of the invention presents numerous advantages, and in particular:
         it is of completely modular construction adaptable to the individual person in that by modifying the height of the tubular element and changing the shape and dimensions of the blade, the depth, height and inclination of the bracket can be modified, including at the moment of final assembly,   it enables very controlled sliding without slackness,   it presents extreme constructional simplicity, resulting in product economy and reliability,   it is highly ergonomic as adjustment is particularly simple and intuitive for the chair user, because of the position and movement of the release control,   it presents substantial robustness to resist stresses during use and during the regulatory tests on the chair, by virtue of the fixing of the bracket element on the vertical tubular support element, which occurs directly by iron/iron contact within the appropriate slot of the tubular element.