Self-centering, torque-sensing joint assembly for a pallet truck power steering system

Abstract

A power steering assist system for a hand-steered pallet truck includes a joint assembly having a pivot joint, handle biasing mechanism, and a torque sensing arrangement. The pivot joint includes a pair of needle bearings and pivot pin disposed within a pivot block that provides a flexible connection between a handle and a tiller arm. The handle biasing mechanism includes a cantilevered beam spring and two cam rollers that resists an operator steering force applied to the handle and further, centers the handle with respect to the tiller arm after the force is released. The torque sensing arrangement includes a magnet and a non-contact magnetoresistive (MR) sensor that measures movement of the handle relative to the tiller arm which is used to determine operator steering intent, i.e., the amount of steering force applied to the handle. The MR sensor provides accurate torque measurements regardless of the angle of the tiller arm. The steering assist system further includes a driving unit with a steerable drive wheel, and a servomotor. The amount of steering assist provided by the servomotor to the drive wheel is at least partially determined based on the measured operator steering intent.