A shock absorber is installed in a power wheelchair to absorb shocks
transmitted from rear wheels of the power wheelchair. The shock absorber
includes a bracket, a seat and a suspension device. The suspension device
is installed between the bracket and the seat and includes two suspension
springs. Each suspension spring has a different spring stiffness. The seat
is pivotally connected to the bracket at a pivot point between the two
suspension springs. Consequently, the suspension springs will balance
absorbing shocks caused by bumps while the power wheelchair is moving.