Abstract: A bi-directional anti-tip system for a wheelchair includes a pair of anti-tip system subassemblies actively lifting a leading anti-tip wheel when traveling in either forward or reverse directions. The anti-tip system subassemblies operate to couple a leading anti-tip wheel to the drive assembly such that pivot motion thereof effects vertical displacement of the leading anti-tip wheel and to decouple a trailing anti-tip wheel from the drive assembly to null pivot motion inputs therefrom. In one embodiment, rheonetic links actively couple and decouple the anti-tip system subassemblies. The system may also include compliant bearings or extensible links for inward displacement of the anti-tip wheel upon impact with a curb.

Abstract: An active anti-tip system is provided for a wheelchair having a main structural frame and a drive assembly. The anti-tip system includes at least one anti-tip wheel, a suspension arm assembly pivotally mounting the anti-tip wheel to the main structural frame, a pendulum mount for coupling the drive assembly to the main structural frame and intermeshing gears for conveying the motion of the drive assembly to the suspension arm assembly. The pendulum mount causes the drive assembly to traverse in a substantially horizontal path in response to torque input from the drive assembly. The motion of the drive train assembly is converted to pivot motion of the suspension arm by the intermeshing gears. The pivot motion of the suspension arm assembly causes the anti-tip wheel to be raised for curb/obstacle climbing and effectively lowered for pitch stability.

Abstract: An anti-tip system is adapted for use in a powered wheelchair for purposes of curb-climbing and ride stability. The anti-tip system includes at least one anti-tip wheel, a suspension arm for mounting the anti-tip wheel and a pair of links coupling the suspension arm to the main structural frame of the wheelchair. Each of the links is pivotally mounted to the main structural frame of the wheelchair about a first pivot point and is pivotally mounted to the suspension arm about a second pivot point. In a first embodiment of the anti-tip system, the links include an upper and lower link, wherein the upper link is extensible to facilitate angular displacement of the suspension arm to permit rearward displacement of the anti-tip wheel in response to an externally applied load.

Abstract: An anti-tip system is provided for stabilizing a vehicle, such as a power wheelchair, about a pitch axis and relative to a ground plane. The anti-tip system includes at least one anti-tip wheel. The mounting assembly for the anti-tip wheel is configured such that it traverses linearly in a direction toward or away from the ground plane and is responsive to an acceleration or deceleration of the wheelchair. As the wheelchair accelerates or decelerates, rotational motion of the drive train assembly is transmitted to a guide subassembly within the mounting to effect translation of the anti-tip wheel. Upward translation of the anti-tip wheel enables the wheelchair to negotiate obstacles, e.g., curbs or steps, while downward translation or force enhances stability when stopping the wheelchair or while moving down sloping terrain or surfaces. The anti-tip wheels may be castors and normally contacting the ground during operation.

Abstract: A linkage arrangement for an active anti-tip system is provided for improving the stability of a powered vehicle, such as a powered wheelchair. The vehicle includes a drive-train assembly which is pivotally mounted to a main structural frame. A suspension system biases the drive-train assembly and its connected anti-tip wheel to a predetermined resting position. The drive-train assembly bi-directionally rotates about a pivot in response to torque applied to or acceleration forces on the vehicle. The linkage arrangement is characterized by a suspension arm pivotally mounting to the main structural frame about a pivot at one end thereof and an anti-tip wheel at the other end. The linkage further includes at least one link operable to transfer the bidirectional displacement of the drive-train assembly to the suspension arm and may also include a bell crank link member.

Abstract: A curb-climbing rear wheel drive power wheelchair is disclosed having a pair of drive wheels, at least one ground-engaging idler wheel connected to the frame forward of the drive wheels and at least one anti-tip wheel mounted above ground aft of the drive wheels. Each drive wheel and an associated drive assembly are mounted to a motor support bracket that is pivoted to the frame of the wheelchair. The drive assembly is mounted such that its motor is angled upward and rearward from the bracket. The anti-tip wheel is attached to one motor support bracket such that pivoting of the motor support bracket causes vertical displacement of the anti-tip wheel.