Fork level indicator for lift trucks

Abstract

A fork lift truck includes a fork level sensor located in the forks, away from the vertical mast of a lift truck for detecting the true level of the forks, and a vision system including a camera which may take several forms. In one form, a single camera is mounted in a housing which may be moved to a protected location vertically either by sliding in the carriage assembly, or by use of a parallelogram device. In another form, multiple cameras are employed where a second camera may be either mounted above the first camera in the same housing or mounted between the forks. Alternatively, the first camera may perform multiple roles by being moved vertically from a first predetermined location below the bottom of the forks to a higher elevation a second predetermined location relative to the forks. A video display terminal, which shows the view observed by the camera, may also include a fork level indicator, a reticle for assisting in adjusting the vertical position of the forks, and an indicator showing the specific truck function selected by the operator.

Description

BACKGROUND OF THE INVENTIONThis invention relates to a remote viewing method and apparatus for use on fork lift trucks. This invention has particular application to those fork lift trucks where the forks can be raised above the head of the operator causing the operator difficulty in visually aligning the forks to a load or a load on the fork to an opening in a storage rack.In many materials handling vehicles, such as a rider-reach truck or a three- or four-wheel counterbalanced truck, a pair of movable, load carrying forks are mounted on a carriage for vertical movement on the mast of the truck. A camera has sometimes been mounted near the heel of the forks to view the scene in front of the forks, and to display that scene on a monitor mounted in view of the operator. Such an arrangement is helpful, provided the camera is properly positioned so that its view is properly aligned with the forks; however, the view of a camera in this location will be blocked when a pallet is placed on ...

AI Technical Summary

Benefits of technology

This invention also includes a camera, which is equipped with a horizontal plane reticle and mounted on a vertically movable carriage assembly and which is protected from damage and contact with the floor when the forks are in their lowermost position. The camera is lowered to a first predetermined position below the forks and load when the forks are raised, which provides the camera with a view that is optimum for viewing a target for vertical height position of the forks or load. When used on a double reach truck with the forks extended, the camera is placed at a second predetermined location relative to the forks, which is above the first predetermined position and which provides the camera with a view above the load support beam or rail of a rack near which the truck is usually placed when operating in this mode. A second camera at a different height may also be used and switching means provided to allow the operator to obtain a view above the load support beam.

It is another object of this invention to provide a fork lift truck with a vision system that provides useful images to an operator regarding the elevation of the forks or load for position to a storage rack. It is also an object of this invention to provide the operator with a view of the forks or load while at the same time providing information regarding which function of the truck controls has been selected.

Problems solved by technology

With a load on the forks, the best position for the camera is below the bottom of the load for use in operator viewing under-clearance or viewing alignment with a target below the load; however, in this position, the camera is subject to damage when the forks are lowered near the floor on which the truck is operating.

If the camera is fixed positioned to be clear of the floor when the forks are fully lowered, then its view will be too high to be effective for viewing below the forks and load.

The operator view problem is exacerbated on double reach trucks, that is, trucks with scissors mechanisms that permit the forks to be doubly extended, and thus pick up and deposit loads twice the storage depth distance of a single pallet.

Further, monitoring fork tilt either by sensing the vertical component of the fork or at the heel of the fork will not take into consideration the deflection of the fork away from the mast due to the weight of a load.

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