Suspension systems and grounds maintenance vehicles incorporating the same are disclosed. The suspension system may include biasing elements or springs that may be adjusted to vary the preload and thus change the spring and dampening characteristics of the suspension system. In some embodiments, the system may include an adjustment mechanism that permits simultaneous adjustment of two springs via a single action. In other embodiments, features adapted to assist an operator with mounting/dismounting the vehicle are disclosed.

A body weight adjustment mechanism for automatic adjustment to a balanced point is provided to improve vibration absorption characteristics and impact absorption characteristics. A torsion angle of a lower frame-side torsion bar when an upper frame is at a balanced point is found in advance, a torsion angle of the lower frame-side torsion bar in a state in which a person is seated is detected, the detected torsion angle is compared with the aforesaid balanced point torsion angle, a control signal is sent to an elastic force adjusting unit, and torsion angles of upper frame-side torsion bars are adjusted so that the torsion angle of the lower frame-side torsion bar becomes equal to the balanced point torsion angle. The upper frame can be set to an appropriate position in an initial state and a static state in which a person is seated and vibration and impact absorption characteristics are improved.

Suspension systems and grounds maintenance vehicles incorporating the same are disclosed. The suspension system may include biasing elements or springs that may be adjusted to vary the preload and thus change the spring and dampening characteristics of the suspension system. In some embodiments, the system may include an adjustment mechanism that permits simultaneous adjustment of two springs via a single action. In other embodiments, features adapted to assist an operator with mounting/dismounting the vehicle are disclosed.

Suspension systems and grounds maintenance vehicles incorporating the same are disclosed. The suspension system may include biasing elements or springs that may be adjusted to vary the preload and thus change the spring and dampening characteristics of the suspension system. In some embodiments, the system may include an adjustment mechanism that permits simultaneous adjustment of two springs via a single action. In other embodiments, features adapted to assist an operator with mounting/dismounting the vehicle are disclosed.

A seat support mechanism including a lifter, and configured to perform a cushion frame suspension function no matter to what height a cushion frame is adjusted. Torsion bars extending in the width direction of a cushion frame and elastically supporting the cushion frame are supported by a link mechanism disposed between sliders and the cushion frame. Even if the attitude of the link mechanism is displaced when the lifter adjusts the height, the positions of the torsion bars are displaced so as to follow the displacement. The torsion bars elastically support the cushion frame no matter to what height the torsion bars are displaced. Thus, no matter to what height the cushion frame is adjusted, the torsion bars are able to support the cushion frame with predetermined elasticity and to exhibit predetermined vibration absorption characteristics.

Suspension systems and grounds maintenance vehicles incorporating the same are disclosed. The suspension system may include biasing elements or springs that may be adjusted to vary the preload and thus change the spring and dampening characteristics of the suspension system. In some embodiments, the system may include an adjustment mechanism that permits simultaneous adjustment of two springs via a single action. In other embodiments, features adapted to assist an operator with mounting/dismounting the vehicle are disclosed.

Embodiments related to active vibration isolation systems for a vehicle seat, as well as their methods of use, are disclosed. In some embodiments, an active suspension system may be configured to support a seat above a floor of a vehicle. The active suspension system may include two or more actuators that may be operated cooperatively to control both the roll and heave of the vehicle seat. In some instances, these actuators may also be non-back-drivable actuators. Additionally, in some embodiments, an active suspension system may include one or more torsion springs that apply torques in parallel with associated actuators of the active suspension system to support at least a portion of the loads applied to the active suspension system during operation.

There are improved a vibration absorption characteristic and an impact absorption characteristic. In a suspension mechanism 1 of the present invention, first and second dampers (150, 160) are suspended in parallel between an upper frame (120) and a lower frame (110) with mounting angles different from each other. For this reason, the smaller mounting angle the damper has, the smaller a vertical component of damping force becomes, and the damping force which acts on the upper frame (120) and the lower frame (110) which move up and down relatively is moderate in effectiveness as compared with a case of disposing all the dampers at the same mounting angle. Thus, a sense of incongruity in which strong damping force acts abruptly is suppressed and the vibration absorption characteristic and the impact absorption characteristic are improved, which leads to improvement in ride comfort.

There are improved a vibration absorption characteristic and an impact absorption characteristic. In a suspension mechanism 1 of the present invention, first and second dampers (150, 160) are suspended in parallel between an upper frame (120) and a lower frame (110) with mounting angles different from each other. For this reason, the smaller mounting angle the damper has, the smaller a vertical component of damping force becomes, and the damping force which acts on the upper frame (120) and the lower frame (110) which move up and down relatively is moderate in effectiveness as compared with a case of disposing all the dampers at the same mounting angle. Thus, a sense of incongruity in which strong damping force acts abruptly is suppressed and the vibration absorption characteristic and the impact absorption characteristic are improved, which leads to improvement in ride comfort.

Embodiments related to active vibration isolation systems for a vehicle seat, as well as their methods of use, are disclosed. In some embodiments, an active suspension system may be configured to support a seat above a floor of a vehicle. The active suspension system may include two or more actuators that may be operated cooperatively to control both the roll and heave of the vehicle seat. In some instances, these actuators may also be non-back-drivable actuators. Additionally, in some embodiments, an active suspension system may include one or more torsion springs that apply torques in parallel with associated actuators of the active suspension system to support at least a portion of the loads applied to the active suspension system during operation.