Abstract:
A seat arrangement includes a backrest frame and a base frame with the backrest frame connectable, adjacent the lower extent of each of opposite sides thereof, to respective mounting that facilitate pivotable mounting of the backrest frame to the base frame. Each mounting includes a respective load dispersing member and the backrest frame is connected to the mounting by fasteners inserted laterally of the frame, through the frame and the load dispersing member of the mounting. The fasteners draw each load dispersing member into a respective recess defined by the backrest frame, with each recess having a form complementary to the load dispersing member to define respective base surfaces through which the fasteners extend, and opposing side surfaces. The fasteners, in fastening the backrest frame to the mounting, cause each load dispersing member to be clamped in the respective recess whereby respective adjacent side surfaces of the recess and the load dispersing member are urged into surface to surface contact.

Description:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/AU98/00686 which has an International filing date of Aug. 26, 1998, which designated the United States of America. 
     FIELD OF THE INVENTION 
     This invention relates to an improved arrangement for seats, such as motor vehicle seats, which have a backrest frame that is adjustable relative to a seat base via a seat recliner system. 
     BACKGROUND OF THE INVENTION 
     In seats of the above-indicated types, especially with those for automotive use, there has been a considerable effort in recent years to introduce weight-reducing improvements. One such improvement has seen the introduction of seat backrest frames cast from light alloys or molded from engineering plastics. These backrest frames are connected to the seat base via the seat recliner system. Accordingly, in order to achieve a connection which does not adversely impair the overall strength of the seat, it has been necessary to adopt a seat back connection of a form which substantially offsets the weight-reduction achieved by the backrest frame. 
     One form of connection for cast or molded backrest frames has utilized steel reinforcement beams, each of which extends up a respective side of the backrest frame. Another form utilizes a much heavier recliner system with bolting or riveting of vertical arms which similarly extend up the backrest frame to enable multiple fixings. In each case, the overall weight saving is less than achieved in the backrest frame, while there also are disadvantages in costs, materials usage and assembly time. Also, the connections can utilize space which otherwise would be available for other mechanisms, such as inflatable air-cushions and at least part of an operating mechanism for an adjustable lumbar support. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a seat arrangement including a backrest frame and a base frame. The backrest frame is connectable, adjacent the lower extent of each of opposite sides thereof, to respective mounting means that facilitate pivotable mounting of the backrest frame to the base frame. Each of the mounting means includes a respective load dispersing member, and the backrest frame is connected to the mounting means by fasteners inserted laterally to the frame, through the frame and the load dispersing member of the mounting means, the fasteners on fastening, drawing each load dispersing member into a respective recess defined by the backrest frame. Each recess has a complimentary form with the load dispersing member to define respective base surfaces through which the fasteners extend, and opposes side surfaces. The fasteners, upon fastening the backrest frame to the mounting means, causes each of the load dispersing members to clamp into the respective recess, whereby respective adjacent side surfaces of the recess and the load dispersing member are urged into a surface to surface contact. 
     The side surface of each load dispersing member and each of the recesses may be substantially parallel, although they preferably diverge. 
     In a preferred arrangement, each mounting means includes a mounting member, separately formed from the load dispersing member. The fasteners extend through the frame and the member and through the load dispersing member. In an alternative arrangement, the mounting member and the load dispersing member are formed as a single component, either integrally or by suitable connecting means, such that the fasteners extend through the frame and the load dispersing member. 
     The fasteners may comprise threaded screws or bolts. Alternatively, they may comprise rivets. 
     There preferably are two fasteners, with these most preferably spaced from each other in the front to rear direction relative to the backrest frame when the latter is in a normal in-use orientation. However, the fasteners can be spaced in other directions, for example, such as upwardly spaced. 
     Each load dispersing member preferably is formed of steel. In that case, it can be pressed or stamped from steel plate to provide a central region between two opposed diverging wing portions. The load dispersing member may be open between adjacent ends of the respective opposed wing portions, or it may be closed. In latter arrangement, the load dispersing member is somewhat cup- shaped. The central region may have holes formed therein for receiving the fasteners. In the case of threaded fasteners, the holes may be threaded. Alternatively, threaded nuts can be provided, with the nuts preferably welded to the central region. Alternatively, the central region can have burst holes for use with self-threading fasteners. 
     Rather than being formed from steel plate, each load dispersing member can be cast from a suitable metal such as a light alloy, preferably a high strength alloy, which might undergo suitable strengthening treatment during formation, such as heat treatment. The load dispersing member might additionally, or alternatively, be coated with a suitable strengthening coating. In these cases, the load dispersing member again may have a central region between two wing portions, with the wing portions preferably diverging. However, strengthening ribs preferably are provided between the wing portions. Alternatively, the load dispersing member may be of solid form, defining a central surface between two diverging side surfaces. 
     The recess defined by the backrest frame, at each of the opposite sides thereof, opens laterally. Also, each recess is defined by a wall portion of the frame which provides two side surfaces, preferably two mutually inclined diverging side surfaces, separated by a base surface through which the fasteners extend. The recess may be open at one or each end thereof, i.e., between the side surfaces. Alternatively, it may be closed at each end so as to enclose the load dispersing member around the periphery of the latter. 
     In one convenient arrangement, the load dispersing member is pressed from steel plate to provide a central region between two similarly diverging wing portions. In that arrangement, an included angle between each wing portion, and the central region is slightly in excess of a corresponding included angle between each side surface and the base surface of the respective recess. The arrangement is such that, as fasteners are applied to draw the load dispersing member into the recess to achieve surface to surface contact, the wing portions are caused to flex so that each is substantially parallel to a side surface of the recess. It is preferable that the wing portions are caused to flex only slightly, so that the level of strain induced in the load dispersing member when drawn into the recess is relatively low. The flex principally has the effect of reducing or eliminating free play between the load dispersing member and the backrest frame, so as to prevent movement therebetween under load, and to provide surface to surface contact between the side surfaces of the recess and the diverging wings of the load dispersing member for acceptable load transfer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the invention may more readily be understood, description now is directed to the accompanying drawings, in which: 
     FIG. 1 is a rear perspective view of a vehicle seat backrest frame, shown connected to mounting members in an arrangement according to the present invention; 
     FIG. 2 is an exploded perspective view of the, arrangement of FIG. 1 for one of the mounting members; 
     FIG. 3 corresponds to FIG. 2, but shows the arrangement as assembled; and 
     FIG. 4 is a rear elevation of the arrangement as shown in FIGS. 2 and 3. 
     FIG. 5 is an exploded perspective view of a modified form of the FIG. 1 arrangement for one of the mounting members. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, the arrangement  10  as shown therein includes a vehicle seat backrest frame  12  which is connected, at the lower extent of each of opposite sides thereof, to a respective mounting member  14 . Each member  14  forms part of a respective coupling  16  for a seat recliner system, with each coupling  16  also including a lower mounting member  18  which is connectable to a seat base frame (not shown). 
     The frame  12  corresponds substantially to that shown in the illustrated embodiment of our co-pending Australian provisional patent application PO 2747, filed on Oct. 4, 1996. In relation to the overall detail of the construction of frame  12 , reference is made to PO 2747, the disclosure of which is incorporated herein by reference and to be read as part of the disclosure of the present invention. 
     The frame  12  is cast from a suitable light alloy, such as a magnesium alloy. Its overall form is somewhat rectangular. However, the peripheral frame members  11 ,  13 ,  15  and  17 , and also its transverse member  19 , are of rearwardly open channel form. Frame  12 , in being of a light alloy, has a relatively low overall weight but a relatively high strength to weight ratio. The strength is further enhanced by transverse fins  21  provided between the opposed sides of members  11 ,  13 ,  15  and  17  with the opposed sides being designated  11   a  and  11   b  and  15   a  and  15   b  for members  11  and  15 . 
     Referring to FIG. 2, each coupling  16  further includes a shaft  20  which extends through overlapping portions of its members  14  and  18 , and a mechanism by which members can be released for relative rotation on the axis of shaft  20  or held in a required angular relationship. The overall construction of the mechanism is not part of the present invention and it therefore need not be fully described herein. However, the respective couplings  16  may be inter-connected (by means not shown) but, in any event, they function in unison to enable frame  12  to be adjusted, as required, in its inclination relative to a seat base to which it is connected. Also, the inter-connection between the couplings  16  extends below member  17  of frame  12 . Thus, the upper extent of each member  14  is fastened against the lower extent of the respective one of members  11  and  15  of frame  12 , with frame  12  being indented at  22  below such fastening whereby the upper extent of the respective member  18  and of a gear  23  on the inner face of each member  18  are accommodated with slight clearances. As shown, the indents  22  are in the outer wall  11  a and  15   a  of members  11  and  15 . 
     Each member  14  and, hence, its coupling  16 , is connected to a respective one of members  11  and  15  by means of two fasteners  24 . Each fastener  24  extends through an aperture  26  in member  14  and an aligned aperture  28  in the respective one of members  11  and  15 . However, as shown, fasteners  24  are used in combination with a device  30  which functions to disperse loadings transferred to or from frame  12  which otherwise would concentrate in the immediate vicinity of each fastener  24 . 
     Each device  30  has a body  32  pressed from steel sheet of a suitable thickness, and two threaded nuts  34  welded to body  32 . Each nut  34  provides a continuation of an aperture (not shown) through body  32 ; with the spacing between centres for nuts  34  corresponding to that for each of apertures  26  and each of apertures  28 . Also, while not shown, fasteners  24  are threaded so as to threadably engage with nuts  34 . 
     Body  32  of each device  30  is pressed so as to define a central region  32   a  at which nuts  34  are provided and, at each side of region  32   a , a respective wing  32   b . The wings  32   b  are bent at similar but opposite angles with respect to region  32   a  such that they diverge away from each other in a direction beyond nuts  34 . Thus, over the surface of body  32  remote from nuts  34 , as viewed from one end of region  32   a  (i.e., in the direction of spacing between nuts  34 ), device  30  has the form of a truncated wedge. 
     In connecting the members  14  by fasteners  24 , each device  30  is drawn so as to locate firmly in a recess  36  defined within the respective one of members  11  and  15 . The recess  36  is in the inner surface of the outer wall  11   a  and  15   a  of members  11  and  15 . In the specific arrangement shown, each recess is defined in part by an abutment surface  37  resulting from the formation of each indent  22 , and an adjacent fin  21 . The surface  37  and the fin  21  are spaced from each other on opposite sides of apertures  28 , while they also are oppositely inclined with respect to the respective one of sides  11   a  and  15   a . The arrangement is such that each recess  36  is of substantially complementary form to the above-mentioned truncated wedge form of body  32  of its device  30 . However, the included angle between each of surfaces  37  and fin  21  and the respective one of sides  11   a  and  15   a  is slightly less than the inclination of each wing  32   b  to region  32   a  of device  30 . Thus, as device  30  is drawn into its recess  36  by tightening of fasteners  24 , the wings  32   b  are caused to flex inwardly to achieve good surface to surface contact with fin  21  and surface  37 . 
     The devices  30  result in good dispersal of loads transferred to or from backrest frame  12  via fasteners  24 . That is, the loads are distributed over the area of surface to surface contact achieved by devices  30 , rather than being concentrated at the immediate vicinity of fasteners  24 . To further enhance the resultant load accommodating capacity of the connection of members  14  to frame  12 , the wall thickness of frame  12  preferably is increased at each recess  36 . Thus, the respective fin  21  which defines part of each recess  36  can be thickened, as shown, relative to the thickness sufficient for other fins  21 . Also, the thickness of each of sides  11   a  and  15   a , where forming part of recess  36  and defining a surface  37  can be of increased relative to the thickness that is sufficient in other parts of members  11  and  15 . 
     The devices  30  can, if required, be cast or formed by powder metallurgy from light alloy, or molded from a suitable engineering plastics material, rather than formed from steel sheet. However, if not made from steel sheet, fins preferably are provided across the body  32   a  between wings  32   b . Alternatively, the volume shown between wings  32   b  can be filled by metal or engineering plastics material, such that body  30  is solid, rather than provided with actual wings. 
     FIG. 5 illustrates a modified version of the arrangement  10  shown in FIGS. 1 to  4 . For convenience, features shown in FIG. 5 that correspond to those of FIGS. 1 to  4  have the same reference numeral, plus 100. 
     The coupling  116  shown in FIG. 5 is generally the same as, and operates in the same manner, as the coupling  16  of FIGS. 1 to  4 . However, the mounting member  114  includes a load dispersing member  130  which is shown as being integrally formed to the mounting member  114 . The member  130  could however be attached to the mounting member  114  by other means, such as by suitable fasteners, although that would detract from the advantages of the overall arrangement e.g. cost, weight saving etc. The mounting member  114  and the  20  member  130  could be formed from the materials and by the methods identified earlier for the separate member  14  and the device  30 . 
     In the arrangement of FIG. 5, each of the frame members  111  and  115  (not shown) includes a recess  136  in the outer surface of the outer walls  111   a  and  115   a . The recess  136  of FIG. 5 is disposed perpendicular to the recess  36  of FIG. 2, although the arrangement could equally provide a recess perpendicular to that shown in FIG. 5, by rearranging the connection or formation of the load dispersing member  130  relative to the mounting member  114 . The recess  136  has a central planar region  141 , which is flanked on opposite sides by inclined surfaces  142  and  143 . The included angle between the surfaces  142  and  143  is slightly less than the included angle between the wings  132   b  of the load dispersing member  130 , for the reasons discussed in relation to the FIG. 2 arrangement. 
     It is preferred that the angle A between the body  132   a  and each wing  132   b  is no more than 135° and preferably approaching 90°. That arrangement ensures proper transmission of load from the seat backrest frame  12  to the wings  132   b . This is particularly the case with horizontal loads. If the angle A between the body  132   a  and each wing  132   b  is greater than 135°, then the size, or surface area of the wings is required to be increased for proper transmission of load. 
     The coupling  116  is connected to the frame  112  by extending fasteners  124  through openings  140  in the central region  132   a  of the load dispersing member  130 , which fasteners then extend through the openings  128  in the recess  136 . The fasteners  124  may threadably engage nuts disposed on the obscured side of the wall  111   a , which may be welded thereto, or other arrangements as earlier described may be employed. The bolts may also extend through openings in a boss, or plurality of bosses (one for each bolt) provided on the wall  111   a , preferably on the obscured side of that wall. Fastening of the coupling  116  to the frame  112  in the manner shown in FIG. 5, results in the same benefits of load dispersion as the earlier described arrangement. The additional benefit of the FIG. 5 arrangement relates to a reduction of parts to be fitted, particularly if the member  114  and the load dispersion member  130  are integrally formed. 
     The connecting arrangement provided by the present invention is relatively simple. However, it also is found to be highly effective. The seat backrest frame is found to have a very significantly enhanced resistance to fracturing in both static and dynamic strength tests representing impact loads such as experienced in front and rear impact vehicle crash tests. Specifically, the arrangement has been found to perform satisfactorily in suitable sled tests which simulate vehicle crash tests. Moreover, this arrangement achieves this excellent level of performance without significant loss of the weight savings resulting from the backrest frame being cast from light alloy. 
     Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.