referring now to the drawings , there is illustrated in fig1 a wheelchair backrest mounting system , shown generally at 10 . the backrest mounting system 10 attaches a backrest shell 12 to a wheelchair frame ( shown at fig6 ). the backrest mounting system 10 includes a mounting block 14 that is fastened to the backrest shell 12 by attachment pads 16 . the mounting block 14 includes a bore 18 that extends therethrough and includes tapered or beveled receivers 20 . an offset locking tube 22 is configured to extend through and be supported by the bore 18 for rotation . the offset locking tube 22 terminates in locking teeth 24 . the illustrated locking teeth 24 are shown as tube end cutouts that have offset profiles along the tube longitudinal axis . other tooth arrangements , such as multiple teeth , may be provided if desired . the locking tube 22 maintains spaced - apart offset mounts 26 oriented in alignment relative to each other . the offset mounts 26 include pivot ends 28 , as shown in fig5 a and 5b . in the illustrated embodiment , the offset mounts 26 are configured such that locking bores 30 in the pivot ends 28 are coaxially aligned . the locking bores 30 include a locking profile 32 that mates with the locking teeth 24 of the offset locking tube 22 . alternatively , the locking teeth 24 may be multiple teeth distributed around the end perimeter of the offset locking tube 22 in order to permit the offset mounts 26 to be indexed relative to each other . when so indexed , the mounting block 14 may be oriented at an angle relative to the wheelchair frame to accommodate specific user conditions such as lateral spinal curvature issues which cause a tilted seated position . fig5 a illustrates the offset mount 26 a configured for one side , such as a left side of the wheelchair and fig5 b illustrates the mirror image offset mount 26 b for mounting on a right side of the wheelchair . where the offset mounts 26 have locking bores 30 with multiple teeth ( not shown ) distributed around the locking bore inner diameter , the offset mounts 26 a and 26 b may be adjusted to provide a lateral tilt to the backrest shell 12 . in order to provide the lateral angular adjustment described above , one offset mount 26 a may be rotated in a direction opposite of the other offset mount 26 b . both of the offset mounts will be described relative to one the offset mount 28 . as shown in fig5 a , the pivot end 28 includes a tapered surface or cone - shaped surface 34 that mates with the tapered or beveled receiver 20 of the mounting block 14 . the tapered surface 34 of the offset mount 26 is end loaded or compressed against the tapered receiver 20 to frictionally adjust the angular pivot orientation of the backrest shell 14 , as shown in fig2 b . an adjustable fastener 35 , such as a bolt , screw , or other length - adjustable connector extends through the offset locking tube 22 to end load the tapered surfaces 34 against the tapered receivers 20 . the tapered surface 34 and the mating tapered receiver 20 are shown having smooth profiles to provide a free range of adjustment . alternatively , this surface may be profiled , such as radially extending surfaces to provide a discrete series of adjustments . in operation , the bolt 35 may be loosened to permit rotation of the backrest shell 12 about the axis defined by the bore 18 , as shown by the arrows of fig2 b . in addition the backrest shell 12 may be moved toward or away from an edge of a wheelchair seat by moving the offset mounts 26 a and 26 b together in a clockwise or counterclockwise direction . as shown in fig2 c , the backrest shell 12 may include adjustment slots 12 a to permit height adjustment of the backrest shell 12 relative to the wheelchair seat of fig6 . referring again to fig1 , the offset mount 26 includes a frame mount 36 that engages a saddle 38 that supports the backrest relative to backrest frames or tubes 40 . in one embodiment , the backrest tubes 40 may terminate in a mounting point 40 a that permits attachment , either removable or permanent , to a wheelchair frame 52 of a wheelchair 50 , as shown in fig6 . the frame mount 28 may include a mounting face 42 that contacts the saddle 38 . in one embodiment , the mounting face 42 and the contacting face of the saddle 38 are smooth and permit a free range of angular adjustment , as shown by the arrows in fig2 b , of the backrest shell 12 relative to the backrest tubes 40 . alternatively , the surfaces may be profiled to permit discrete angular adjustment positions . a barrel nut 44 accepts a mounting screw 46 ; that extends through the frame mount 36 , the saddle 38 , and at least a portion of the backrest tube 40 ; to permit the connection to be tightened . in one embodiment , the barrel nut 44 is supported within a cap 48 that fits into an open end of the backrest tube 40 , proximate to the backrest shell 12 . in one adjustment operation , bolt 35 and mounting screws 46 may be loosened to permit the plane of the backrest shell 12 to be moved along a longitudinal axis of the wheelchair . in addition , the backrest shell may be rotated to an angular position relative to a side view of the wheelchair 50 , as shown in fig2 b . the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment . however , it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope .
a backrest mounting system provides angular and height adjustment of a backrest shell independent of backrest canes . the backrest mounting system attaches to a centrally located mounting structure on the backrest shell and defines at least two pivot axes that determine the angular position of the backrest shell relative to a wheelchair seat .