WO2005118457A1

WO2005118457A1 - Photoelectric operator position detector

Info

Publication number: WO2005118457A1
Application number: PCT/US2005/019327
Authority: WO
Inventors: Robert J. Lewis
Original assignee: The Raymond Corporation
Priority date: 2004-06-02
Filing date: 2005-06-02
Publication date: 2005-12-15
Also published as: US7259662B2; EP1751049A1; US20050270147A1

Abstract

A method and apparatus for reinforcing the training received by an operator of a material handling vehicle (10) to maintain the operator's feet and legs in the operator compartment (11) includes a first (1) and second (2) photoelectric beam extending across the entry (19) to the compartment. When a deadman brake (22) is released by operating the floor switch (20) and the vehicle is commanded to move or is actually moving, the detectors (7, 9) sense the presence of objects extending through the entry. When objects are sensed, a vehicle brake can be applied, a visual (55, 57) or audio (59) sensor can be activated, or the detected fault can be stored in memory. The faults can be used by a supervisor to calculate an operator rating.

Description

PHOTOELECTRIC OPERATOR POSITION DETECTOR

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to provisional application U.S. Serial Number

60/576,097, filed June 2, 2004, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION [0002] The present invention is related to material handling vehicles, and more

particularly to a method and apparatus to reinforce the training provided to an operator of a

material handling vehicle to maintain a proper position in an operator compartment while

driving the vehicle.

[0003] Employers are required by OSHA standards (29 C.F.R. 1910.178(1)) to train

operators of material handling vehicles in safe operation of the vehicle. The training includes

instructing the operator to maintain his or her feet and legs inside of the vehicle compartment

while operating the vehicle. These regulations also require the employer to prohibit operators

from placing their legs outside the running lines of the vehicle.

[0004] Electromechanical and photoelectrical systems are available for producing an

alarm or alert signal when an object extends into or out of the operator compartment of the

vehicle while the vehicle is in use, and therefore to provide an indicator when a leg or foot is

extended out of the vehicle..

[0005] One example of an electromechanical system for monitoring an operator in a

material handling vehicle is disclosed, for example, in U.S. Patent Number 6,137,398 to

Dunlap. Here, an electromechanical actuator is provided across the entrance to an operator

compartment. An alert signal is generated when a portion of the operator's body engages the

actuator, alerting the operator when a portion of the operator's body is extending outside of

the operator compartment. [0006] A photoelectric system is disclosed in U.S. Patent Number 4,840,248 to

Silverman. Here, a photoelectric light source and corresponding detector are positioned

across the entrance to an operator cab, and are activated whenever power is applied to the

vehicle. When an object extends into or out of the cab of the vehicle, the beam between the

source and the detector is broken, and an alarm is generated. The alarm can be a visual or

audio signal to the operator, or power can be cut off to the vehicle to force the vehicle to stop.

The alarm is activated whenever the operator leaves the compartment and is also used to

brake the vehicle when the operator exits.

[0007] These prior art systems, however, suffer from disadvantages which make them

unsuitable for either training or reinforcing the training of an operator. Both the

electromechanical and photoelectric prior art systems, for example, activate the sensors

whenever power is applied to the vehicle. An alarm is generated, therefore, not only when an

actual fault condition has been detected, but also whenever the operator intentionally enters or

leaves the vehicle. Therefore, alarm conditions are not consistently tied to actual "fault"

conditions, but rather are frequently encountered in normal operation. After a period of time,

therefore, operators may become immune to signals produced by these systems, and begin to

ignore actual fault conditions. These devices, therefore, have limited usefulness in training or

reinforce the training of operators to properly maintain a position within the vehicle.

[0008] There remains a need, therefore, for a system capable of providing alarm and

alert signals to an operator which are useful in reinforcing training to maintain the feet and

legs inside of the vehicle while in use. SUMMARY OF THE INVENTION [0009] In one aspect of the invention, a method to reinforce the training provided to

an operator of a material handling vehicle to maintain the operator's feet and legs in the

vehicle is provided. The method comprises the steps of mounting an emitter and a

corresponding detector across an entry to the operator compartment, monitoring the deadman

brake to determine when the deadman brake has been released to allow travel of the vehicle,

and determining whether the material handling vehicle has received a command to begin

travel. When the deadman brake is released and a travel request has been received, the

detector to is monitored determine whether an object is extending between the emitter and the

detector. A response sequence is activated when the vehicle is operational and the detector

indicates that an object has been detected. Therefore, the operator is alerted to fault

conditions only when the vehicle is in use.

[0010] In another aspect of the invention, the operator is prompted to include an

operator identifier, and the response sequence includes associating the fault occurrence with

the operator identifier. Based on the stored fault occurrence data, an operator rating for can

be determined by supervising personnel.

[0011] In yet another aspect of the invention, a second emitter and a second detector

are mounted across the entrance to the compartment, offset a distance above the emitter and

detector. The first emitter and detector can, for example, be mounted adjacent a floor of the

compartment in a position selected to detect a toe or foot of the operator, and the second

emitter and detector can be mounted above the floor of the compartment in a position selected

to detect a leg of the operator.

[0012] In still another aspect of the invention, a method is provided to reinforce the

training provided to an operator of a material handling vehicle to maintain the operator's feet and legs in the vehicle. The method comprises the steps of mounting a first emitter and a first

corresponding detector adjacent a floor of the operator compartment to produce a first light

beam across an entry to an operator compartment substantially at the floor level. A second

emitter and detector is also mounted across the entry to the operator compartment to produce

a second light beam. The second light beam is positioned above the first light beam at a

position selected to detect a leg of the operator. A deadman brake is monitored and, when the

deadman brake has been released to allow travel of the vehicle and the material handling

vehicle has received a command to begin travel, the first and second detectors are monitored

to determine whether an object is extending between at least one of the first emitter and the

first detector or the second emitter and the second detector. The number of faults detected

during operation are used to provide a rating of the operator.

[0013] In yet another aspect of the invention, a material handling vehicle is provided.

The material handling vehicle includes an operator compartment, a deadman brake, a switch

for deactivating the deadman brake, and an emitter and a detector. The emitter and detector

are coupled to opposing sides of an opening to the operator compartment and are aligned such

that a beam emitted by the emitter is received by the detector unless broken by an object

extending through the opening. A traction motor is provided for driving the vehicle and is

adapted to provide a feedback signal indicating that the material handling vehicle is moving.

The vehicle further includes a vehicle control system and a control handle for providing a

travel request signal to the vehicle control system to drive the traction motor. The vehicle

control system is coupled to the switch to receive a signal indicating that the deadman brake

is to be deactivated, to the traction motor for receiving the feedback signal, and to the control

handle for receiving the travel request signal. The vehicle control system is programmed to monitor an output of the detector when the deadman brake is deactivated, and at least one of the travel request signal and the feedback signals is active, and to institute a response when

the output of the detector indicates that the beam is broken.

[0014] These and still other advantages of the invention will be apparent from the

detailed description and drawings. While a particular preferred embodiment has been

disclosed hereafter, it should be recognized that the invention is not so limited. Rather, the

claims should be looked to in order to judge the full scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a perspective view of a lift truck constructed in accordance with one

embodiment of the invention.

[0016] FIG. 2 is a block diagram of a lift truck constructed in accordance with the

invention.

[0017] FIG. 3 illustrate the operator's compartment and the position of the emitter and

sensor in the operator's compartment.

[0018] FIG. 4 is a flow chart illustrating an algorithm for determining the position of

the operator and for selectively inhibiting movement of the truck based on the position of the

deadman switch and a determination that the operator has crossed the line between the emitter

and the detector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0019] Referring now to the Figures, and more particularly to FIG. 1, a material

handling vehicle 10 constructed in accordance with the present invention is shown. The truck

10 includes an operator compartment 11 comprising an enclosure 17 with an opening 19 for

entry and exit of the operator. The compartment 11 include a control handle 14 which is

mounted to the enclosure 17 at the front of the operator compartment 11 proximate the forks 31, and a floor switch 20 positioned on the floor 21 of the compartment 11. A steering wheel 16 is also provided in the compartment 11. First and second light beams 1 and 2, each

extending from an infrared source 3 and 5, respectively, to a corresponding infrared detector,

7 and 9, respectively, are provided across the opening 19 of the operator compartment 11, as

described more fully below. Although the material handling vehicle 10 as shown is a

standing, fore-aft stance operator configuration lift truck, it will be apparent to those of skill

in the art that the present invention can also be provided in a side stance truck, or in other

truck configurations.

[0020] Referring now to FIG. 2, a block diagram of a typical lift truck 10 in which the

present invention can be provided is illustrated. The lift truck 10 comprises a vehicle control

system 12 which receives operator input signals from the operator control handle 14, the

steering wheel 16, a key switch 18, and the floor switch 20 and, based on the received signals,

provides command signals to each of a lift motor control 23 and a drive system 25 including

both a traction motor control 27 and a steer motor control 29. The drive system 25 provides a

motive force for driving the lift truck 10 in a selected direction, while the lift motor control 23

drives forks 31 along a mast 33 to raise or lower a load 35, as described below. The lift truck

10 and vehicle control system 12 are powered by one or more battery 37, coupled to the

vehicle control system 12, drive system 25, steer motor control 29, and lift motor control 23

through a bank of fuses or circuit breakers 39.

[0021] As noted above, the operator inputs include a key switch 18, floor switch 20,

steering wheel 16, and an operator control handle 14. The key switch 18 is activated to apply

power to the vehicle control system 12, thereby enabling the lift truck 10. The floor switch

20 provides a signal to the vehicle control system 12 for operating the brake 22 to provide a

deadman braking device, disabling motion of the vehicle unless the floor switch 20 is activated by the operator. Light emitters or sources 3 and 5 and associated detectors 7 and 9 are also coupled to the vehicle control system 12. As described above, the source and detector pairs (3, 7; 5, 9) produce light beams 1 and 2, respectively, extending across the entry 19 to the operator compartment 11.

[0022] The operator control handle 14 provides a travel request signal to the vehicle

control system 12. Typically, the handle 14 is rotated in a vertical plane to provide a travel direction and speed command of motion for the lift truck 10. A four-way switch 15 located

on the top of the handle 14 provides a tilt up/down function when activated in the forward

and reverse directions and a sideshift right and left function when activated to the right and

left directions. A plurality of control actuators 41 located on the handle 14 provide a number

of additional functions, and can include, for example, a reach push button, a retract push button, and a horn push button as well as a potentiometer providing a lift function. A number

of other functions could also be provided, depending on the construction and intended use of

the lift truck 10.

[0023] The traction motor control 27 drives one or more traction motor 43 which is connected to wheel 45 to provide motive force to the lift truck. The speed and direction of the traction motor 43 and associated wheel is selected by the operator from the operator control handle 14, and is typically monitored and controlled through feedback provided by a

speed sensor 44 which can be an encoder or other feedback device coupled to the traction

motor 43. The wheel 45 is also connected to friction brake 22 through the traction motor 43, to provide both a service and parking brake function for the lift truck 10. The friction brake 22 can be a spring-activated brake that defaults to a "brake on" position, such that the switch 20 and associated brake 22 therefore provide the deadman braking function. The operator must provide a signal indicating that the deadman brake is to be released to drive the truck, here provided by the floor switch 20, as described above. The traction motor 43 is typically an electric motor, and the associated friction brakes 22 can be either electrically operated or hydraulically operated devices. Although one friction brake 22, motor 43, and wheel 45 are

shown, the lift truck 10 can include one or more of these elements.

[0024] The steer motor control 29 is connected to drive a steer motor 47 and

associated steerable wheel 49 in a direction selected by the operator by rotating the steering wheel 16, described above. The direction of rotation of the steerable wheel 49 determines the direction of motion of the lift truck 10.

[0025] The lift motor control 33 provides command signals to control a lift motor 51

which is connected to a hydraulic circuit 53 for driving the forks 31 along the mast 33,

thereby moving the load 35 up or down, depending on the direction selected at the control handle 14. In some applications, the mast 33 can be a telescoping mast. Here, additional

hydraulic circuitry is provided to raise or lower the mast 33 as well as the forks 31.

[0026] In addition to providing control signals to the drive system and lift control system, the vehicle control 12 can also provide data to a display 55 for providing information to the operator, and activate both light indicators 57 and audio indicators 59 to indicate fault conditions to the operator. Information provided on the display 55 can include, for example,

a weight of a load placed on the forks 31, the speed of the vehicle, the time, or maintenance

information. Furthermore, fault conditions detected by the detectors 7 and 9, as described below, can also be indicated on display 55. The display 55 can provide an interactive interface, allowing the operator to enter identifying information, such as an operator name or employee number, for use in calculating a number of faults encountered by a given operator driving the vehicle, as described below. [0027] Referring again to FIGS. 1, 2, and 3, in operation, objects extending through the entrance 19 to the operator compartment 11 are detected when the light beams 1 and 2 are

broken by the object. When the object extends between a source 3 or 5 and the associated

detectors 7 or 9, the light beam is broken, the detector 7 or 9 provides a signal to the vehicle control system 12, as described more fully below. Light beams 1 and 2, which, as shown in the figures, are disposed more or less horizontally across the entry to the operator's

compartment 19. The light produced by sources 3 and 5 can be modulated to a pattern, comprising a pulse mark-space ratio where the light source is alternately turned on and off, at

a high rate. The detectors 7 and 9 can be similarly tuned to this pattern to limit response to other light sources. The pattern timing and frequency can also be chosen to eliminate

possible false signals from ambient light such as fluorescent, HID, etc. Obstruction of the

beam is detected by the truck control system 12 according to an algorithm (FIG. 4), and an

appropriate response, as described below, ensues if the conditions of the algorithm are met.

In general terms, the beam 1 or 2 is broken or interrupted and a fault condition occurs when an object is positioned in the path of the beam between the source and the corresponding detector, either continuously or transitorily.

[0028] Referring still to FIGS. 1 , 2 and also to FIG. 3, the sources 3 and 5 and associated detectors 7 and 9 are provided in pairs across the entrance 19 of the operator

compartment 11 of the lift truck 10 to detect the position of the operator or other objects extending into or out of the compartment 19. The source 5 and detector 9 are mounted in a housing 4 provided adjacent the floor 21 of the compartment 19, while the mounted to individual housings 6 and 8 provided along the sides of the entrance 19.

[0029] The light beam 1 produced by source 5 is projected across the opening 19 adjacent the floor 21 of the compartment 11, preferably approximately .75" above the plane of the floor 21, and is positioned particularly to detect the operator's toe or heel, if it is

positioned improperly beyond the prescribed boundary. The output of detector 9 is fed to the

vehicle control system 12 which, after a signal is received from the detector 9, analyzes the

length of time the light beam 1 has been interrupted. Interruptions below a predetermined

time are ignored, reducing false triggers that could be caused, for example, by debris moving

around the operator compartment floor, while still reliably detecting an operator's foot or

other objects extending beyond the prescribed area. While a range of the time periods can be

used, depending particularly on operating conditions, a two hundred millisecond delay has

been experimentally shown to eliminate most false triggers.

[0030] The light beam 2 is positioned particularly to detect static or transitory

presence of the operator's leg or calf extending improperly beyond the confines of the

operator compartment 19. The light beam 2, and associated emitter 3 and detector 7, are

located in a range of about six to nine inches above the floor 21, and preferably at a height of

approximately eight inches above the floor plane 21. This height has been shown to

consistently detect fault conditions, and to prevent operators from stepping or jumping over

the beam 2. Here, again, the vehicle control system 12 receives a signal from the detector 7

and institutes a delay to filter false triggers. A quicker detection time of about forty

milliseconds has been shown experimentally to be appropriate for this purpose. Under these

conditions, the vehicle control system 12 will detect a rapidly moving leg or calf, and institute a response quickly, as described below.

[0031] Prior to operation of the lift truck 10, the operator can initially be prompted to

enter an operator identifier such as a name, operator number, employee number, or other

identifier into the vehicle control system 12 through the user display 55 or using other

methods known in the art. The vehicle control system 12 can then store this identifier in memory and associate driving information with the operator as described below to provide an

operator rating. Other types of identifiers could also be used.

[0032] Referring now to FIG. 4, in operation, the floor switch 20 is monitored by the

vehicle control system 12 to determine whether an operator has requested release of the

deadman brake (step 100). When the floor switch 20 is activated, the brake 22 is deactivated,

and an operator intends to drive the truck, the emitters 3 and 5 producing light beams 1 and 2

are activated or energized by the control system 12 (step 102). The vehicle control system 12

then determines whether travel has been requested, or if the truck is moving (step 104) by

determining whether a travel request command has been issued by control handle 14 or

feedback is received from the traction motor 43. If not, the vehicle control system 12

determines whether a broken beam has been detected and a fault condition has been set (step

106), indicating that continuity between either of the sources 3 and 5 and associated detectors

7 and 9 has been broken. If so, the broken beam fault is cleared (step 108), travel is allowed,

and the vehicle control system 12 returns to monitoring the deadman 20 (step 100). If not,

the vehicle control system 12 takes no action and returns to monitor the deadman 20 (step

100).

[0033] If travel has been requested or feedback indicates that the lift truck 10 is

moving, the vehicle control system 12 determines whether either beam 1 or beam 2 has been

broken, indicating a broken beam fault condition (step 110). If the broken beam fault is not

set, each of the detectors 7 and 9, are checked to determine if the respective light beam 1 or 2

has been broken. The upper set (3; 7) is checked first (step 112), and if a fault has occurred, a

delay is instituted for a period of about forty milliseconds, to filter any false triggers. If the

fault remains active through the forty millisecond period, a fault condition is set and a

response sequence is initiated (step 116). If the upper detector 7 does not indicate that the beam 1 has been broken, the vehicle control system 12 determines if the lower beam 2 has

been broken, again, continuously for a period of time, here selected as 200 milliseconds (step 114). If so, again, a fault is set and a response sequence is initiated (step 116). The response sequence can include inhibiting travel, limiting the speed of the truck 10, activating an audio

or visual alarm, or storing the occurrence of the fault condition in the vehicle control system 12. When the response sequence includes inhibiting travel, the fault is set, and the truck is

moving (step 118), regenerative braking (step 120) is applied to the truck at a rate determined experimentally to produce a smooth stop, irrespective of the weight of any load on the vehicle.

[0034] When the switch 20 is inactive such that the brake 22 is applied, the emitters 3 and 5 are de-energized by the control system 12. When the emitters are de-energized (step

122), the vehicle control system 12 continually monitors the detectors 7 and 9 to determine

whether either of the beams 1 and 2 have been sensed for a period of 20 milliseconds or more (step 124). If either of the beams have been detected, then a problem likely exists with one of

the emitter/detector pairs (3, 7 or 5, 9), a fault has occurred, and a response sequence is

initiated (step 126). Here, again, travel of the lift truck 10 can be inhibited, and a signal, such as a message provided on display 55, can be provided for the operator.

[0035] The present invention therefore provides a means to reinforce training received by operators to maintain their feet and legs within a prescribed space envelope in an operator- standing lift truck by instituting a response sequence warning the operator that an object, such as a foot or leg of the operator, is extending through the opening 19 of the operator compartment 11. The response sequence is instituted only when the lift truck 10 is either known to be moving, or a request for movement has been received, therefore limiting the response sequence to conditions encountered while the vehicle is moving, and filtering out activations that occur when the vehicle is stopped and the operator is merely entering or

exiting the vehicle normally. Moreover, the fault conditions can be counted and maintained

in memory, and associated with a particular operator to provide a rating of the operator's

driving of the vehicle. These ratings can be used, for example, to limit the speed of the

vehicle for a particular driver, or to identify operators who require additional training.

Various other uses for the rating information will be apparent to those of skill in the art.

[0036] The disclosed system, furthermore, provides a means for reinforcing the

training of an operator to maintain his or her limbs inside of the vehicle, but does not impact

operator positional flexibility and choice of foot position, allowing maintenance of comfort

over extended operational periods.

[0037] The disclosed system also tailors the sensitivity of the emitter/detector

producing beams 1 and 2 to provide individualized trigger levels. As described above, these

trigger levels are tailored to detect portions of the operator's foot or leg. The beam 1, which is

provided closest to the floor 21 of the compartment 11, is more easily accidentally triggered,

and detects mainly the foot or toe extending from the vehicle. The detector 7 is provided with

a comparatively longer delay period before activating the response sequence than the beam 2,

which can detect a leg extending from the compartment 11. When an object extends into or

out of the vehicle at a position above the floor 21, as detected by beam 2, the response

sequence is activated quickly.

[0038] In addition, the emitter/detector pairs producing light beams 1 and 2 are

monitored to detect possible equipment failures, providing a "self-test" to assure proper

system operation. Because the emitter/detector pairs producing beams 1 and 2 are bi-stable,

the sources 3 and 5 and detectors 7 and 9 have only two possible output conditions, on or off,

and appropriate operation can be verified based on expected on/off conditions. When a light is not detected as expected, a fault condition can be assumed to exist in either the source 3 or

5 or the corresponding detector 7 or 9. The appropriate conditions for the sources 3 and 5 and

detectors 7 and 9, moreover, can be provided in a state map and, in the event that one or both

of the emitter/detector pairs producing beams 1 and 2 is determined to be in an inappropriate

state, a defined response sequence can be initiated. As described above, the defined response

can include slowing or stopping the lift truck 10, inhibiting travel of the lift truck 10, or

providing a fault indicator to the display 55 (FIG. 2). All operating modes are tested during

normal truck operation, regardless of whether the operator's foot or leg is in a position to

block one of the beams.

[0039] Although an infrared emitter and detector pair has been described above, in

alternative embodiments, the invention can be implemented using any of the following types

of sensor devices:

[0040] Infrared sensor array. In this embodiment, a line of modulated infrared

sources and proximity receivers can be provided, arranged a few degrees from vertical,

pointing at an imaginary target above and behind the rear of the operator's compartment. An

object impinging into the infrared beam pattern established by the array of infrared sources

would reflect some amount of the energy back toward the infrared sensors, and this would be

detected and acted upon.

[0041] E-field sensor. An E-field sensor comprising an electronic transmitting

antenna, and corresponding receiving antenna could also be provided. This solution takes

advantage of the fact that an object disposed within an electrostatic field changes the balance

of the signal seen by an adjacent receiving antenna. The construction included a transmitting

antenna and a receiving antenna, aligned below and behind the operator platform. An object,

such as a foot, imposed into the beam pattern created by the transmitting antenna would impact the magnitude or phase of a signal received by a companion antenna. The steel

structure of the truck itself would make the system immune to the operator within the

compartment.

[0042] Full light curtain. An array of horizontally teamed transmitters and receivers

can be positioned across the entrance 19 of the operator compartment 11, effectively creating

a series of beams vertically disposed from one another and from the floor 21 of the operator's

compartment 19 by a small distance, such as, for example, 2 inches. The array defines the

vertical area from compartment floor level up to, for example, 24", detecting any portion of

the operator or other objects impinging upon one or more of the beam pairs.

[0043] Photoelectric System. The present invention can also employ a photoelectric

system, comprising matched beam sources and receivers, to detect an operator's extremity

beyond a designated area

[0044] In other embodiments, a system whose philosophy rests with reinforcing

training of an operator to maintain the operator's extremity is at specific points within the

prescribed area, rather than outside of a prescribed area, can also be used. Furthermore, use

of a self-test mechanism that validates operation of the system continuously as the truck is

used, validating correct operation of the elements of the system repeatedly during normal

vehicle operation, is also contemplated.

[0045] In addition, a plurality of sensors can be used, and discrete detection criteria

and timing can be applied for each detector, thereby tailoring the responsivity of each to the

target's velocity and length of time the respective beam would be interrupted, allowing a level

of compliance commensurate with the operator's actions, and a reduction of false triggers.

[0046] It should be understood that the methods and apparatuses described above are

only exemplary and do not limit the scope of the invention, and that various modifications could be made by those skilled in the art that would fall under the scope of the invention. To apprise the public of the scope of this invention, the following claims are made:

Claims

CLAIMS We claim:

1. A method for reinforcing the training received by an operator of a material

handling vehicle to help maintain the operator's feet and legs in the vehicle, the method

comprising the following steps:

(a) mounting an emitter and a corresponding detector across an entry to the

operator compartment;

(b) monitoring the deadman brake to determine when the deadman brake has

been released to allow travel of the vehicle;

(c) determining whether the material handling vehicle has received a

command to begin travel;

(d) when the deadman brake is released and a travel request has been

received, monitoring the detector to determine whether an object is extending between the

emitter and the detector; and

(e) activating a response sequence when the detector indicates that an object

has been detected.

2. The method as recited in claim 1, wherein step (c) further comprises the step

of monitoring a feedback signal indicating that the material handling vehicle is moving and

step (d) further comprises the step of monitoring feedback from a traction motor to determine

if the material vehicle is operating, and monitoring the detector to determine whether an

object is extending between the emitter and the detector when the deadman brake is

deactivated and the material handling vehicle is moving.

3. The method as recited in claim 1, wherein step (e) comprises the step of

storing a fault occurrence in memory.

4. The method as recited in claim 3, further comprising the steps of receiving an

operation identification from the operator of the vehicle, and of associating the fault

occurrence with the operator identification.

5. The method as recited in claim 4, further comprising the step of calculating a

rating for the operator based on the number of fault occurrences associated with the operator

identification.

6. The method as recited in claim 1, wherein step (e) comprises braking the

material handling vehicle.

7. The method as recited in claim 1, wherein step (e) comprises the step of

providing at least one of an audio and a visual signal.

8. The method as recited in claim 1, wherein step (a) further comprises the steps

of mounting a second emitter and a second detector corresponding to the second emitter

across the entrance to the compartment, the second emitter and second corresponding detector

being offset a distance above the emitter and corresponding detector.

9. The method as recited in claim 8, wherein step (a) further comprises the steps

of mounting the emitter and the detector adjacent a floor of the compartment to a toe or foot

of the operator, and mounting the second emitter and the second detector in a position above

the floor of the compartment in a position selected to detect a leg of the operator.

10. The method as recited in claim 9, further comprising the step of delaying for a

first predetermined period of time when the detector detects an object and for a second

predetermined period of time when the second detector detects an object.

11. The method as recited in claim 10, wherein the second predetermined period

of time is less than the first predetermined period of time to provide a quick response when a

leg is extended from the vehicle.

12. A method for reinforcing the training received by an operator of a material

handling vehicle to maintain the operator's feet and legs in the vehicle, the method

comprising the following steps:

(a) mounting a first emitter and a first corresponding detector to produce a

first light beam across an entry to an operator compartment in the material handling vehicle

adjacent a floor of the operator compartment to detect a toe or foot;

(b) mounting a second emitter and a corresponding second detector across an

entry to the operator compartment at a position above the first light beam to produce a second

light beam positioned to detect a leg of the operator;

(c) monitoring the deadman brake to determine when the deadman brake has

been released to allow travel of the vehicle;

(d) determining whether the material handling vehicle has received a

command to begin travel;

(e) when the deadman brake is released and a travel request has been received,

monitoring the first and second detectors to determine whether an object is extending

between at least one of the first emitter and the first detector or the second emitter and the

second detector; and

(f) counting the number of faults detected during operation and providing a rating of the operator based on the number of faults.

13. The method as recited in claim 12, further comprising the step of prompting

the operator of the vehicle to enter an operator identifier before allowing the operator to drive

the vehicle.

14. The method as recited in claim 12, wherein step (f) further comprises the step

of delaying for a predetermined period of time and checking a state of the first and second

detector to filter false triggers.

15. A material handling vehicle including an operator compartment, comprising: a deadman brake; a switch for deactivating the deadman brake; an emitter and a detector, the emitter and detector being coupled to opposing

sides of an opening to the operator compartment and aligned such that a beam emitted by the

emitter is received by the detector unless broken by an object extending through the opening; a traction motor for driving the vehicle and adaptable to provide a feedback

signal indicating that the material handling vehicle is moving; a control handle for providing a travel request signal to the vehicle control

system to drive the traction motor; and a vehicle control system, the vehicle control system being coupled to the

switch to receive a signal indicating that the brake is to be deactivated, to the traction motor

for receiving the feedback signal, and to the control handle for receiving the travel request

signal, the vehicle control system being programmed to monitor an output of the detector

when the deadman brake is deactivated, and at least one of the travel request signal and the

feedback signals is active, and to institute a response when the output of the detector indicates that the beam is broken.

16. The material handling vehicle of claim 15, further comprising a second emitter

and a second detector, the second emitter and second detector being positioned adjacent a

floor of the operator compartment to monitor a toe of the operator as it extends from the

compartment, the emitter and detector being offset at a distance above the second emitter and

second detector and above the floor of the operator compartment.

17. The material handling vehicle of claim 16, wherein the vehicle control system

is adapted to monitor the detector for a predetermined period of time before indicating a fault

condition.

18. The material handling vehicle of claim 16, wherein the vehicle control system

is adapted to monitor the second detector for a predetermined period of time before indicating

a fault condition.