Wheelchair backrest and rear wheel assembly

A rear wheel unit for a wheelchair comprising:

• a structure adapted to be secured to a seat frame member of the seat frame, the structure defining a cylindrical receptacle;
• a bushing adapted to support a rear wheel of the wheelchair along an axle axis, the bushing received in the cylindrical receptacle and rotatable in the cylindrical receptacle about a bushing rotational axis non coincident with the axle axis;
• a level on the bushing and positioned to indicate an orientation of the axle axis relative to the ground;
• and
• a tightening mechanism to block rotation of the bushing relative to the cylindrical receptacle.

A system of bracket assemblies for a wheelchair comprising:

• a pair of bracket assemblies adapted to be connected to respective sides of a seat frame of the wheelchair, each said bracket assembly having
• a base adapted to be secured to a seat frame member of the seat frame, the base including a clamp body, the clamp body configured to form a translational joint with the seat frame member until tightened to be fixed to the seat frame member,
• an arm adapted to be secured to a backrest frame member of a backrest frame, and
• a pivot pivotally connecting the base to the arm for rotational movement of the arm relative to the base;
• at least one blocking mechanism in at least one of the bracket assemblies to block the rotational movement of the arm relative to the base in a use orientation of the backrest frame;
• and
• a rod separate from the pivot and having opposed ends connected to the base of the pair of the bracket assemblies for spacing the bracket assemblies away from one another.

A system of bracket assemblies for a wheelchair comprising:

• a pair of bracket assemblies adapted to be connected to respective sides of a seat frame of the wheelchair, each said bracket assembly having
• a base adapted to be secured to a seat frame member of the seat frame,
• an arm adapted to be secured to a backrest frame member of a backrest frame, and
• a pivot pivotally connecting the base to the arm for rotational movement of the arm relative to the base;
• at least one blocking mechanism in at least one of the bracket assemblies to block the rotational movement of the arm relative to the base in a use orientation of the backrest frame;
• and
• a rod separate from the pivot and having opposed ends connected to the base of the pair of the bracket assemblies for spacing the bracket assemblies away from one another, the rod being a tie rod having an axial degree of expansion.