GB2408250A - Fork-lift truck monitoring arrangement - Google Patents

Abstract

A monitor system, for monitoring the angle of both upward and downward fork tilt associated with fork-lift trucks, comprises a laser beam transmitter module (8, Fig 2) a multi-faceted laser beam detector module having a white light filter and a visual display module, having a servo driven indicator arm, for showing the measured angle of tilt. The invention is particularly characterised by each of the modules having magnetic means so as to allow them to be attached thereby to an associated fork-lift truck. The laser beam transmitter module is attached to the mast of the truck so as to align the laser beam with the corresponding detector module that is attached to the main body of the truck and is also connected to a pulse generator 16 which sends negative signals to a servo decoder mounted in the display monitor 14, preferably positioned in the drivers cab. The display includes a pointer 15 and a scale 12. The laser transmitter module is enclosed in container (7), having lid (10), a battery supply (9) and a control switch (11).

Description

RIONUOR FOR IISE: Wll]I IFORX LED TRUCKS.

This invention relates to a monitor for use with forklift trucks, Forklift trucks FLT of the type used to pick up and transport heavy loads, usually mounted on pallets comprise of a motorised vehicle, the forward part of which houses a steel upright sectional mast structure which can be extended vertically by mechanical or hydraulic means.

The upper part of the mast carries a pair of steel forks which project forward from the mast and are used for picking up pallets on which the load rests, the forks are inserted into the pallet bearing the load by firstly raising or lowering the forks and then adjusting the attitude of the forks in relation to the pallet, this is done by tilting the mast forwards or backwards so that the forks are level and parallel with the load that you wish to pick up, the FLT is then driven forward until the forks are positioned fully underneath the pallet. The forks are then raised by the operator of the FLT to lift the load clear of the surface on which it was resting, the mast of the FLT is then tilted slightly backwards to prevent the load slipping from the forks, the FLT can then transport the load to the next desired location.

Accident statistics in the UK involving fork lift trucks indicate a large number of serious mishaps caused by loads falling from the forks of FLTs. These have resulted in severe and sometimes, irreparable damage to the load or apparatus impacted to the load, worse still injury or even deaths have resulted from a heavy load falling onto or against workers in the vicinity of the FLT. The root cause of such accidents can be put down to the fact that the FLT operator has no means of verifying the exact attitude of the forks of the FLT, the fork attitude becomes even more critical when pallets are stored on high level racking.

One particular problem is that the steering wheels undergo greater wear than the driving wheels, when this occurs the angle of the FLT chassis changes accordingly, the change in the chassis angle also changes The angle of the forks which disappear from view whilst carrying a load.

Training FLT operators is a difficult task which could be made much easier for both pupil and instructor if a device were fitted to the FLT which would indicate to the operator the exact attitude of the forks, such a device would be invaluable to all FLT operators and may save many accidents from happening.

A monitor will now be described, which when fitted to the FLT will give the FLT operator a clear indication of any tilting of the FLT forks, by means of a head-up display mounted in the operators cab thus allowing the operator to adjust the inclination of the mast until the forks are positioned to the required angle.

According to the present invention there is a sealed enclosure which will be fixed to the mast of the FLT, the enclosure houses a low output laser module powered by replaceable internal batteries, the power of which is controlled by a switch fitted to the laser module case.

The laser beam is directed onto a laser detector module which is fixed to the main structure of the FLT.

The detector module consists of a vertical row of light dependent resistors LDRs which are fitted into a light resistive housing, the housing has a narrow vertical aperture which is directly in front of the sensitive area of the LDR.s.

This aperture allows the movable laser beam fitted to the movable FLT mast to fall upon whichever LDR is in the path of the laser beam.

The aperture is covered by a RED SPECTRUM light filter which shields the LDRs from white light IE sun light ETC, but readily passes the red beam of the laser.

The LDRs in the detector module are electrically separate, each having there own specific IE different resistive values, these differing values are fed to a pulse generator which in turn sends the appropriate negative signal to a servo decoder which is mounted in the head-up display monitor situated in the drivers cab.

The decoder incorporates a geared servo motor, the output shaft of which cavities the pointer of the display meter.

The scale of the meter is graduated either side of a centre zero mark to indicate upwards and downwards tilt of the forks, the centre zero mark corresponds to the centre LDR indicating that the forks are level, upper and lower LDRs correspond to the upper and lower graduation marks on the scale of the meter of the head-up display monitor.

The head up display monitor requires a low voltage switched D.C supply, ideally 6 VOLT DC which can be self contained in the display housing or from an external source.

Further electronic modules may be added to facilitate voice commands of extent of tilt of the forks. , .

Referring to the drawing FIG. 2 a sealed enclosure 7. with lid 10. houses a laser module 8. and a battery power supply 9., an ON-OFF switch 11. is fitted into the cover lid 10.

The laser assembly FIG. 2 is attached to the mast of the fork lift truck FLT, having firstly made sure that the forks are perfectly horizontal.

The laser detector module FIG. 1 is mounted on the main structure of the FLT, so that the aperture 6 of FIG. I is vertical, and the laser beam is aligned with the centre of the aperture 6 of FIG. I. Referring to the drawing FIG. 1 a sealed enclosure 1. with enclosure front cover 5. houses a vertically stacked array of light dependent resistors LDR,s 30f FIG. 1.

The LDR,s are attached to a mounting board 2 of FIG. 1 and a RED SPECTRUM filter 4 of FIG. 1 is attached to the inside of the enclosure front cover 5 of FIG. 1., the filter shields the entire area of the aperture from white light IE sunlight etc. Tilting of the mast and hence the forks causes the laser beam of FIG. 2 to vertically traverse the aperture 60f FIG. 1.

When the laser beam falls onto any LDR 3 OF fig I that particular electrical circuit is switched on by the LDR.

All l,DR electrical circuits are separate from each other and have there own specific electrical resistance, these differing resistance values are fed into a pulse generator 160f FIG. 3 mounted in the head-up display monitor 14 of FIG. 3 situated in the drivers cab.

Electronic schematics are as FIG. 4.

The pulse generator 16 of FIG. 3 sends negative signals to the servo decoder NOT SHOWN mounted in the head-up display monitor 14 of FIG 3, the signals from the pulse generator vary in accordance with the different resistance values fed from the LDR array 3 of FIG. 1.

The decoder incorporates a geared servo motor, the output shaft of which carries the pointer of the display meter 15 of FIG. 3, the scale of the meter 12 of FIG.3 is graduated either side of a centre zero mark to indicate upwards and downwards tilt of the forks.

The resultant angular position of the servo output shaft and hence the display pointer 15 of FIG. 3 is directly proportional to the angular movement of the forks, each I,DR corresponds to a different graduation mark on the scale of the meter 12 of FIG. 3.

Claims (6)

1. CLAIMS: 1. A monitor for use with fork lift trucks, comprising of a laser

   beam transmitter module, A multi faceted laser beam detector module fitted with a white light filter and A visual Display module, Where the transmitter module, detector module and the visual display module are each fitted with a magnetic means of attachment to a fork lift truck.
2. 2. A monitor as claimed in CLAIM 1. where a white light inhibitor lens is fitted to the Active face of the detector module.
3. 3. A monitor as claimed in CLAIM 1. where the laser beam transmitter module Incorporates an electrical power supply and an ON-OFF SWITCH.
4. 4. A monitor as claimed in CLAIM 1. where the visual display monitor unit incorporates A servo driven indicator hand.
5. 5. A monitor as claimed in CLAIM 1. wherein means of a attaching the laser module, And the detector module and the visual display module to a fork lift truck is provided By means of a magnetic source NOT SHOWN.
6. 6. A fork lift monitor substantially as described herein with reference to figures 1-3 of the accompanying drawings.