Unitized fifth wheel and rear axle suspension

A modular suspension system adapted to a terminal tractor having a frame, comprises:

• a lift arm assembly having a front segment and a rear segment pivotally attached to a fifth wheel plate;
• a trailing arm assembly having a front segment and a rear segment attaching to a rear axle, said front segment of said trailing arm assembly pivotally connecting to said frame of said terminal tractor at two pivot bushing socket tubes housing elastomeric trailing arm pivot bushings which rotate on a common axis, said elastomeric trailing arm bushings holding an enforced longitudinal position of said trailing arm assembly while allowing limited vertical movement and side-to-side rotation of said trailing arm assembly relative to said frame, wherein said front segment of said lift arm assembly is joined to said trailing arm assembly by two large diameter composite bushings rotating on said outer surfaces of said pivot bushing socket tubes of said elastomeric trailing arm pivot bushings, said elastomeric trailing arm pivot bushings isolating said trailing arm assembly and said lift arm assembly from said frame, with at least one lift cylinder forcing said lift arm assembly from said trailing arm assembly to forcibly elevate and lower said lift arm assembly and said fifth wheel plate;
• said trailing arm portion further comprising a rear portion supporting two end housings behind said rear axle securing two ends of a spring means, said spring means having a center, said spring means further stabilizing side to side location of said rear axle and said lift arm assembly and providing controlled vertical and side to side rotational movement, with said spring means adjusted to a preferred riding characteristic;
• and
• a lower lift cylinder mount of said at least one lift cylinder at a lift cylinder mounting attachment positioned in front of said rear axle, said at least one lift cylinder having an upper lift cylinder mount which is pivotally mounted to a lift cylinder mounting attachment in said lift arm assembly in front of said fifth wheel plate, said lift cylinder, when activated, extending and raising said rear segment of said lift arm assembly and said fifth wheel plate, transferring relative lifting forces to said lift arm assembly and trailing arm assembly, isolating said relative lifting forces from said frame of said terminal tractor by said composite bushings, said elastomeric trailing arm bushings and said spring means at said rear segment of said trailing arm assembly.

A modular suspension system adapted to a terminal tractor having a frame, comprises:

• a lift arm assembly having a rear segment and a rear segment pivotally attached to a fifth wheel plate;
• a trailing arm assembly having a front segment and a rear segment attaching to a rear axle, said front segment of said trailing arm assembly pivotally connecting to said frame of said terminal tractor at two pivot bushing socket tubes housing elastomeric trailing arm pivot bushings which rotate on a common axis, said elastomeric trailing arm bushings holding an enforced longitudinal position of said trailing arm assembly while allowing limited vertical movement and side-to-side rotation of said trailing arm assembly relative to said frame, wherein said front segment of said lift am assembly is joined to said trailing arm assembly by two large diameter composite bushings rotating on said outer surfaces of said pivot bushing socket tubes of said elastomeric trailing arm pivot bushings, said elastomeric trailing arm pivot bushings isolating said trailing arm assembly and said lift arm assembly from said frame, with two tandem lift cylinders forcing said lift arm assembly from said trailing arm assembly to forcibly elevate and lower said lift arm assembly and said fifth wheel plate;
• said trailing arm portion further comprising a rear portion supporting two end housings behind said rear axle securing two ends of a transverse leaf spring, said transverse leaf spring having a center, said transverse leaf spring further stabilizing side to side location of said rear axle and said lift arm assembly and providing controlled vertical and side to side rotational movement, with said transverse leaf spring adjusted to a preferred riding characteristic;
• and
• lower lift cylinder mounts of said two lift cylinders at lift cylinder mounting attachments positioned in front of said rear axle, said lift cylinders having upper lift cylinder mounts which are pivotally mounted to lift cylinder mounting attachments in said lift arm assembly in front of said fifth wheel plate, said lift cylinders, under pressure, extending and raising said rear segment of said lift arm assembly and said fifth wheel plate, transferring relative lifting forces to said lift arm assembly and trailing arm assembly, isolating said relative lifting forces from said frame of said terminal tractor by said composite bushings, said elastomeric trailing arm bushings and said transverse leaf spring at said rear segment of said trailing arm assembly.