Shock-absorbing seat structure

Claim 1

A seat-mounting structure including a stationary base and generally horizontal seat-support means disposed above the base, spring controlled mounting means supporting the seat-support means from the base for vertical movement relative thereto between upper and lower limit positions while maintaining the support means generally horizontally disposed, said spring controlled mounting means including first spring means progressively tensioned throughout movement of said seat-support means from said upper limit position to said lower limit position and second pretensioned-spring means maintained in pretensioned condition throughout movement of said seat-support means from said upper limit position to a lower intermediate position above said lower limit position and progressively further tensioned during movement of said seat-support means downwardly from said intermediate position to said lower limit position, said seatsupport means including opposite ends and opposite sides, a first pair of front to rear extending mounting levers pivotally secured at their front ends to opposite sides of the front end of said support means for oscillation relative thereto about first horizontal transverse axes and pivotally secured, at points forward of but adjacent their rear ends to opposite side portions of said base for oscillation about second horizontal transverse axes, a second pair of front to rear extending levers pivotally secured at their front ends to opposite sides of the front end of said support means for oscillation relative thereto about third horizontal axes and pivotally secured, at points forward of but adjacent their rear ends, to opposite side portions of said base for oscillation about fourth horizontal transverse axis, the rear ends of said first levers being spaced below the rear ends of the second levers, a pair of elongated upstanding connecting levers pivotally secured at their upper and lower ends to corresponding rear ends of said second and first pair of levers, respectively, upper and lower cross members extending between the rear ends of said first and second levers, respectively, a pair of upper and lower rearwardly and downwardly inclined and upstanding arms journaled at their upper and lower ends, respectively, from said upper and lower cross members for oscillation about horizontal transverse axes, the lower and upper ends of said upper and lower arms being pivotally secured together, said first spring means being connected between said upper cross member and said upper arm yieldingly urging said upper arm in a direction to swing its lower end downwardly and forwardly.