WO1992000912A1

WO1992000912A1 - Load positioning method and apparatus

Info

Publication number: WO1992000912A1
Application number: PCT/US1990/004813
Authority: WO
Inventors: William R. Mueller; Joseph F. Sabo
Original assignee: Caterpillar Industrial Inc.
Priority date: 1990-07-05
Filing date: 1990-08-27
Publication date: 1992-01-23

Abstract

A material handling vehicle (100) has a load engaging implement (210) for controllably loading and unloading a load (200). The load engaging implement (210) has a stationary portion (300) and a movable portion (305). The movable portion (305) is connected to the stationary portion (300) and is movable between extended and retracted positions. The vehicle (100) produces a position signal when the vehicle (100) is positioned adjacent a load (200). A device (400) pivotally connects the load engaging implement (210) to the vehicle frame (115) and pivotally moves the load engaging implement (210) in a first direction to a first angular position in response to receiving a first signal and in a second direction to a second angular position in response to receiving a third signal. A first driving unit (310) extends the movable portion (305) in response to receiving a second signal and retracts the movable portion (305) in response to receiving a fourth signal. A controller (705) produces the first signal in response to receiving the position signal, produces the second signal in response to the load engaging implement (210) being at the first angular position, produces the third signal in response to the movable portion (305) being at the extended position, and produces the fourth signal in response to the load engaging implement (210) being at the second angular position. The vehicle (100) automatically positions the load engaging implement (210) in a manner that provides for an optimum amount of flexibility for a material handling system.

Description

Load Positioning Method and Apparatus

Technical Field

This invention relates generally to a material handling vehicle and more particularly, to an automated material handling vehicle and method for retrieving and delivering a load.

Background Art

Material handling vehicles, and particularly automated material handling vehicles of the driverless type are typically utilized for transporting loads between work stations and storage locations. The degree of flexibility is often the key factor in determining the usefulness of this type of system. Oftentimes an automatic material handling vehicle which operates effectively in one application cannot adjust to a different application. Of course, numerous factors determine the overall flexibility of an automated material handling system, including: the organization of the operating environment, the programmability of the material handling system, and the physical architecture of both the operating environment and the material handling vehicle. For example, if the programmability of the material handling vehicle is relative low, then the organization of operating environment should be relatively high to produce efficient results. Since attempting to organize every operating environment is difficult and expensive, the programmability of automated material handling systems is increasing in order to adapt to changing operating environments. One important attribute for flexible material handling systems is the ability to automatically recognize, receive, and carry a load. Automated material handling systems employ markedly different loading systems. Many of these loading systems are directed towards a specific application, while others are adaptable to various applications. Automated material handling vehicles, for instance, find usefulness in a diversity of applications. Many applications of loading systems for automated material handling vehicles work in conjunction with workers on an assembly line. For example, an automated material handling vehicle carries a load to an assembly line where workers move parts from a container or pallet. In order to pick up and move a load, prior systems rely on a lift mast and complex assemblies. These types of material handling vehicles are cumbersome and difficult to work with because of their size constraints. Also, situations may arise where the attitude of the lift mast is forwardly inclined. This creates a potential for the load to inadvertently slide off the load engaging device carried on the lift mast assembly.

Another constraint of an operating environment is the confined area of the warehouse.

Load handling vehicles often operate in narrow aisle environments. These vehicles are normally guided for movement down the center of the aisle and in close proximity to the sides of the aisle. Therefore, it is difficult for many front loading vehicles to be in a position to pick up and move a load. Consequently, it is also desirable to allow loading and unloading to be done on both sides of the vehicle. A single sided capability limits the possible approach path of the vehicle to the load. Accordingly, this limitation forces the vehicle to turn around prior to receiving a load. The factory environment is not always so forgiving, as to provide sufficient maneuvering space for the vehicle to turn around. Therefore, it would be advantageous for an automated material handling vehicle to be able to approach a load from any one of four possible directions.

The present invention is directed to overcoming one or more of the problems as set forth above.

Disclosure of the Invention

In one aspect of the present invention, a material handling vehicle having a front portion, a rear portion, a frame and spaced apart sides, in coordination with a load positioned on a load supporting device is provided. A load engaging implement having a stationary portion and a oveable portion wherein the moveable portion is connected to the stationary portion and moveable relative to the stationary portion between extended and retracted positions is also provided. A sensor is provided for delivering a position signal in response to the vehicle being positioned adjacent the load. A device pivotally connects the load engaging implement to the frame and pivotally moves the load engaging implement in a first direction to a first angular position in response to receiving a first signal and in a second direction to a second angular position in response to receiving a third signal. A first driving unit extends the moveable portion in response to receiving a second signal and retracts the moveable portion in response to receiving a fourth signal. A controller produces the first signal in response to receiving the position signal, produces the second signal in response to the load engaging implement being at the first angular position, produces the third signal in response to the moveable portion being at the extended position, and produces the fourth signal in response to the load engaging implement being at the second angular position.

In a second aspect of the present invention a method for retrieving a load in a material handling vehicle is disclosed. The material handling vehicle has a frame and spaced apart sides, a load engaging implement having a stationary portion and a moveable portion connected to the stationary portion and moveable relative to the stationary portion between extended and retracted positions, in coordination with a load positioned on a load supporting device. The method includes positioning the vehicle adjacent the load. The method further includes moving the load engaging implement in a first direction to a first angular position, extending the moveable portion to an extended position in a direction transverse the first direction engaging the load supporting device, and moving the load engaging implement in a second direction to a second angular position and elevating the load to the second angular position. The final step of the method include retracting the moveable portion to a retracted position in a direction transverse the second direction.

The instant invention advantageously provides bidirectional loading and unloading capabilities to material handling vehicles and automatically positions a load engaging implement for a material vehicle in a sequence which retrieves and delivers a load. Such an arrangement has advantages in increasing the flexibility of the paths taken by the vehicle and the type of loads to be handled and is especially advantageous in those instances where the vehicle has limited space for maneuvering.

Brief Descri tion of the Prayings FIG. 1 is a diagrammatic side elevational view of an embodiment of the present invention showing a self guided material handling vehicle;

FIG. 2 is a top view of the vehicle showing a load supporting device positioned adjacent the vehicle;

FIG. 3 is a top view of the vehicle showing the vehicle in greater detail, and showing the load engaging implement;

FIG. 4 is a diagrammatic side view of a canting means embodying a portion of the present invention;

FIG. 5 is a diagrammatic front view of the canting means embodying a portion of the present invention; FIG. 6 is a diagrammatic front view of a ground engaging stabilizer;

FIG. 7 is a block diagram of an embodiment of an electronic control system;

FIG. 8 is a electrical schematic of an embodiment of the electronic control system; and

FIG. 9 illustrates the vehicle positioned adjacent the load support device, and showing a sequence of events to retrieve the load.

pest Mode for Carrying Qvit the Invention

Referring first to FIG. 1, a material handling vehicle 100 having a front portion 105, a rear portion 110, a frame 115 and spaced apart sides is shown. The material handling vehicle 100 depicted is driverless, computer controlled, and commonly referred to as a self guided vehicle (SGV) . It should be noted that the invention is particularly suited for use on a free ranging SGV but should not be limited to this use, as it can be advantageously employed on other material handing vehicles, such as driver operated material handling carriers and transporters, towed trailers, wire and strip following automatic guided vehicles, and the like. The vehicle 100 has a navigational system which includes a laser scanner 120 mounted on the vehicle 100 which reads bar coded targets (not shown) located at spaced apart locations within the facility. The vehicle has an on board computer 125 which receives information from the laser scanner 120, and wheel rotation and steering angle sensors (not shown). The on board computer 125 controls travel of the vehicle 100 based on preprogrammed instructions and triangulation calculations using target location information and sensor information. Typically a load 200 positioned on a load supporting device 205, as shown in FIG. 2, has at least one opening to accommodate a load engaging implement 210. The load 200 is engaged and lifted by the load engaging implement 210. The load 200 is then transferred to a vehicle deck 215 and transported to a remote location.

The vehicle 100 has a load engaging implement 210 having a stationary portion 300 and a moveable portion 305 where the moveable portion 305 is connected to the stationary portion 300 and is moveable relative to the stationary portion 300 between extended and retracted positions as shown in FIG. 3. The load engaging implement 210 is similar in construction to that supplied by Bolzoni as part number C115AAA. A first driving unit 310 composed of an electric motor or the like moves the moveable portion 305. The linear movement of the load engaging implement 210 is achieved through interconnecting chains 320 which connect the moveable portion 305 to the stationary portion 300. The moveable portion 305 is movable in response to the rotation of the motor. The moveable portion 305 may have either two or three telescopic stages to extend to varying lengths. An end portion 325 of the moveable portion 305 is a single platform of low profile used to handle post-pallets and boxes. The first driving unit 310 moves the moveable portion 305 between the extended position at which the moveable portion 305 is positioned outward from either of the vehicle sides and the retracted position at which the moveable portion 305 is positioned between the vehicle sides.

A canting means 400 for pivotally connecting the load engaging implement 210 to the frame 115 and pivotally moving the load engaging implement 210 in a first direction to a first angular position in response to receiving a first signal and in a second direction to a second angular position in response to receiving a third signal is shown in FIGS. 4 and 5. The vehicle 100 has a longitudinal axis 405 in which the load engaging implement 210 is pivotally movable about the longitudinal axis 405 between the first and second angular positions. The end portion 325 of the load engaging implement 210 is at a position elevationally below the longitudinal axis at the first angular position and at an elevational position above the longitudinal axis at the second angular position. The vehicle 100 has a surface portion 410. The load engaging implement 210 is movable to an intermediate position wherein the load engaging implement 210 is parallel to the surface portion 410, in response to the moveable portion 305 being at the retracted position. The canting means 400 includes a second driving unit 415 connected to the stationary portion 300, the stationary portion 300 is pivotally movable in response to the second driving unit 415. An angular sensing means 420 detects the angular rotation of the load engaging implement.

Referring to FIGS. 4 and 5, the second driving unit 415 includes an electric motor which drives a transmission 425. The transmission 425 has a rod 430 which extends and retracts in response to the rotation of the motor. The canting means 400 also includes a first link 435, a second link 440, a third link 445, and a fourth link 450 wherein each link 435,440,445,450 has first and second spaced apart end portions. The second end portion 455 of the first link 435 is rigidly connected to an end portion 457 of the rod 430 and the first end portion 459 of the first link 435 is pivotally connected to the first end portion 461 of the second link 440. More specifically, a spherical bearing assembly 505 of a conventional design is disposed in an aperture 510 pivotally connecting the first end portion 459 of the first link 435 to the first end portion 461 of the second link 440. All the pivotal connections of the linkages 435,440,445,450 are connected in the same manner. The second end portion 465 of the second link 440 and third end portion 466 of the third link 445 are connected at spaced apart longitudinal locations on a cross sleeve 467 in any suitable manner. For example, the end portions 465,466 may be welded to the cross sleeve 467. The cross sleeve 467 is of tubular construction containing a bore 515. Disposed within the bore 515 is a shaft 520 with first and second ends 525,526. Each end of the cross shaft 525,526 is pivotally connected to a flange 530,531 which is connected to the frame 115. The cross sleeve 467 allows the second and third link 440,445 to translate about the cross shaft axis 469. The first end portion 471 of the third link 445 is pivotally connected to the first end portion 473 of the fourth link 450. The second end portion 475 of the fourth link 450 is pivotally connected to a first end 477 of a coupling 479. The second end 481 of the coupling 479 is pivotally connected to the stationary portion 300 of the load engaging implement 210.

The operation of the canting means 400 is as follows. The motor rotates, extending or retracting the rod 430. The rod 430 which is fixedly connected to the first link 435 causes the second link 440 to pivotally move about the cross shaft axis 469 which in turn causes the third link 445 to pivot about the cross shaft axis 469 causing translation of the fourth link 450 and moving the coupling 479 which pivots the load engaging implement 210 about the longitudinal axis 405.

Adverting back to FIG. 3, a driving means 330 extends the moveable portion 305 in response to receiving a second signal and retracts the moveable portion 305 in response to receiving a fourth signal. The driving means 330 includes the first driving unit 310. A linear sensing means 335 detects the degree of extension of the movable portion 305 of the load engaging implement 210. A means is provided for sensing the vehicle

100 being positioned adjacent a load 200 and delivering a position signal in response to the vehicle 100 being positioned adjacent the load 200. The means for sensing the vehicle position can be accomplished in many ways. Preferably, the vehicle 100 uses the navigational system along with the on board computer 125 to determine its own position, utilizing triangulation and dead reckoning techniques in a manner that is well known in the art. Other possible sensing techniques can be employed such as infrared communications between the vehicle 100 and the load 200.

Referring to FIG. 2, a radiant energy means 220 detects the presence or absence of a load 200 on the load supporting device 205. The radiant energy means 220 directs electromagnetic energy diagonally outward from the vehicle 100 towards the load supporting device 205 and detects reflected electromagnetic radiation, and produces an enabling signal in response to detecting the reflected electromagnetic radiation. More particularly, the radiant energy means 220 includes an electromagnetic-reflective sensor 221. Positioned on the lower leg 230 of the load supporting device 205 is a retro target 235. Preferably, the retro target 235 contains strips of reflective material for reflecting electromagnetic radiation. The electromagnetic-reflective sensor 221 detects reflected electromagnetic radiation from the retro target 235, and preferably produces an enabling signal in response to detecting the reflected electromagnetic radiation. Therefore, the electromagnetic-reflective sensor 221 produces a signal indicative of the presence or absence of a load 200 in the path of the electromagnetic radiation. There are many commercially available electromagnetic-reflective sensors and targets of this type and consequently their operation will not be discussed.

The vehicle 100 includes at least one ground engaging stabilizer 600 for supporting the front portion of the vehicle 105. The ground engaging stabilizer 600 is positioned on the front portion 105 adjacent the vehicle sides as shown in FIG. 6. The ground engaging stabilizer 600 has a fixed portion 605 and a translatable portion 610, wherein the fixed portion 605 is attached to the vehicle frame 115. The ground engaging stabilizer 600 extends in response to receiving the first signal and retracts in response to the load engaging implement 210 being at the intermediate position and in the absence of the position signal.

A controlling means 700 produces the first signal in response to receiving the position signal, produces the second signal in response to the load engaging implement 210 being at the first angular position, produces the third signal in response to the moveable portion 305 being at the extended position, and produces the fourth signal in response to the load engaging implement 210 being at the second angular position. Additionally, the controlling means 700 only produces the first signal in response to receiving the enabling signal delivered by the radiant energy means 220. More specifically, the controlling means 700 includes a controller 705. FIG. 7 is a block diagram of an embodiment of the controlling means 700. As shown the controlling means 700 utilizes signals from the linear sensing means 335, the angular sensing means 420, the radiant energy means 220 and the on board computer 125, but it is understood that this is a preferred embodiment and that other types of sensing means fall within the scope of this invention. The controller 705 under software control receives signals from the various sensors. Moreover, the controller 705 may receive signals from a remote controller (not shown) . The controller 705 is capable of controlling angular and linear movement of the load engaging implement 210 via respective drive systems 415,310 as well as movement of the ground engaging stabilizer 600. The controller 705 typically includes a microprocessor, static and dynamic memory, and controlling software, since these are well known in vehicle control, a detailed description is not provided herein.

Referring to FIG. 8 the angular and linear sensing means 420,335 provide an indication of the angular and linear position of the load engaging implement 210 relative to the vehicle frame 115.

The angular sensing means 420 may include many types of sensors such as Hall effects devices, rotary potentiometers, etc. In the preferred embodiment, an optoelectronic sensor 800 is used which produces a four-bit digital signal. The optoelectronic sensor 800 is connected to the load engaging implement 210 via a mechanical linkage (not shown) in such a manner that the sensor 800 is responsive to the angular movement of the load engaging implement 210 indicating one of sixteen angular positions. The output terminal of the optoelectronic sensor 800 is connected to the cathode of a diode 805. The anode of the diode 805 is connected to a pull-up resistor 810 and a lowpass filter 815. The lowpass filter 815 includes a series resistor 820 connected at a first end to the anode of the diode 805 and connected at a second end to a capacitor 825. The capacitor 825 is also connected to ground. The lowpass filter 815 is connected to the controller 705 via an amplifier 830. The optoelectronic sensor 800 delivers a digital signal corresponding to the angle of the load engaging implement 210 to the input terminal of the controller 705. The lowpass filter 815 filters high frequency noise from the signal, and the amplifier 830 delivers and amplifies the signal to the controller 705.

The linear sensing means 435 includes a belt assembly 835 mounted on the moveable portion 305 of the load engaging implement 210. Preferably the belt assembly 835 is of a rugged construction having ^Mrungs^H or "teeth" adapted to engage a gear. A gear 840 connected to a resolver 845 is rotatably engaged with the belt assembly 835. As the belt assembly 835 moves, the gear 840 rotates. The rotary motion of the gear 840 transfers via a shaft 850 to the resolver 845. The resolver 845 is known in the art in that it is excited by a constant frequency signal and delivers a pair of constant frequency signals which have a magnitude and phase relationship proportional to the angular position of the resolver 845. A gear box 846 may be connected intermediate the shaft 850 and the resolver 845 should a gearing change be desirable. The resolver 845 is connected via analog lines to a resolver-to-digital converter (R/D) 855. The R/D converter 855 accepts analog signals produced in response to the rotation of the shaft 850, and produces a multi-bit digital signal correlative to the angle of shaft 850 rotation. The multi-bit signal is indicative of the horizontal movement of the moveable portion 305, which is supplied to the controller 705 via a bus.

Industrial Applicability

Operation of the vehicle 100 is best described in relation to FIG. 9. For the purposes of the following discussion, it is assumed that the vehicle 100 has arrived at the load supporting device 205 and is in the process of either receiving or depositing the load 200. The controller 705 monitors the sensors 335,420 and controls the load engaging implement 210 based on preprogrammed instructions. Preprogrammed instructions dictate the loading status of the vehicle 100 and orientation of the load support device 205. Using preprogrammed instructions to guide an automated vehicle is well known in the art and is not further discussed herein. The navigational system along with the on board computer 125, using triangulation and dead reckoning techniques, positions the vehicle 100 adjacent the load supporting device 205. Responsively, the on board computer 125 sends a position signal to the controller conveying information that the vehicle 100 is adjacent the load supporting device 205. The radiant energy means 220 detects the load 200 positioned on the load supporting device 205 and sends an enabling signal to the controller 705. The controller 705 delivers the first signal to the ground engaging stabilizer 600 nearer the load 200, and responsively the ground engaging stabilizer 600 extends, engaging the ground in a manner that provides stability to the vehicle 100 as shown in FIG. 9A.

Additionally, the canting means 400 receives the first signal from the controller 705, and responsively the canting means 400 controllably lowers the load engaging implement 210 in a first direction to a first angular position as shown in FIG. 9B. The angular sensing means 420 detects the angular rotation of the load engaging implement 210 and responsively delivers a signal corresponding to the rotation of the load engaging implement 210 to the controller 705. The canting means 400 continuously lowers the load engaging implement 210 until the first angular position is reached, which is predefined in the software of the controller 705. More particularly, the first angular position is at an angle which lies just below the load 200.

In the preferred embodiment, the controller 705 has a memory element. The memory element includes a plurality of values which correspond to the desired angle and extension/retraction of the load engaging implement 210. Therefore, the desired orientation of the load engaging implement 210 can readily be determined by merely accessing the appropriate memory location of the memory element contained within the controller 705.

Next, the driving means 330 receives the second signal from the controller 705 and responsively the driving means 330 controllably extends the moveable portion 305 of the load engaging implement 210 transverse the first direction to the extended position engaging the load supporting device 205 through the opening, as shown in FIG. 9C. The linear sensing means 335 determines the linear movement of the moveable portion 305 and responsively delivers a signal corresponding to the degree of extension of the load engaging implement 210 to the controller 705. The driving means 330 continuously extends the moveable portion 305 until the extended position is reached, which is predefined in the software of the controller 705.

Once the load engaging implement 210 extends to the extended position, the controller 705 sends a third signal to the canting means 400. Responsive to the third signal, the canting means 400 controllably raises the load engaging implement 210 in a second direction to the second angular position, lifting the load 200 off the load supporting device 205 as shown in FIG. 9D. Once again the angular sensing means 420 detects the angular rotation of the load engaging implement 210 and responsively delivers a signal correlative to the rotation of the load engaging implement 210 to the controller 705. The canting means 400 continuously raises the load engaging implement 210 until the second angular position is reached which is predefined in the software of the controller 705.

After the load 200 is lifted off the load supporting device 205 and the load engaging implement 210 is at the second angular position, the controller 705 delivers a fourth signal to the driving means 330. Responsive to the fourth signal, the driving means 330 controllably retracts the moveable portion 305 of the load engaging implement 210 transverse the second direction, transferring the load 200 interjacent the sides of the vehicle 100 as shown in FIG. 9E. Again the linear sensing means 335 determines the linear movement of the moveable portion 305 and responsively delivers a signal corresponding to the degree of retraction to the controller 705. The driving means 330 continuously retracts the moveable portion 305 until the retracted position is reached, which is predefined in the software of the controller 705. Responsive to the moveable portion 305 being at the retracted position, the controller 705 sends a fifth signal to the canting means 400. In response to the fifth signal, the canting means 400 controllably moves the load engaging implement 210 to an intermediate position stabilizing the load 200, as shown in FIG. 9F. The angular rotation of the load engaging implement 210 is determined by the angular sensing means 420. Consequently, the angular sensing means 420 delivers a signal correlative to the angle of the load engaging implement 210 to the controller 705. The intermediate position is defined in the software of the controller 705.

At this time the controller 705 sends a sixth signal to the ground engaging stabilizer 600 in which the ground engaging stabilizer 600 responsively retracts, as shown in FIG. 9F.

Finally, the loading of the vehicle 100 is complete and the vehicle 100 is free to travel to the next location as dictated by preprogrammed instructions.

The unloading sequence is substantially similar to the loading sequence previously discussed with the exception that the events in FIG. 9B through FIG. 9E are reversed and consequently is easily understood.

Other aspects, objects, and advantages of this invention can be obtained from a study of the drawings, the disclosure, and the appended claims.

Claims

1. A material handling vehicle (100) having a front portion (105) , a rear portion (110) , a frame (115) and spaced apart sides, in coordination with a load (200) positioned on a load supporting device (205) , comprising: a load engaging implement (210) having a stationary portion (300) and a moveable portion (305) wherein said moveable portion (305) is connected to said stationary portion (300) and moveable relative to said stationary portion (300) between extended and retracted positions; means (125) for sensing said vehicle (100) being positioned adjacent a load (200) and delivering a position signal in response to said vehicle (100) being positioned adjacent said load (200) ; canting means (400) for pivotally connecting said load engaging implement (210) to said frame (115) and pivotally moving said load engaging implement

(210) in a first direction to a first angular position in response to receiving a first signal and in a second direction to a second angular position in response to receiving a third signal; driving means (330) for extending said moveable portion (305) to said extended position in response to receiving a second signal and retracting said moveable portion (305) to said retracted position in response to receiving a fourth signal; and controlling means (700) for producing said first signal in response to receiving said position signal, producing said second signal in response to said load engaging implement (210) being at said first angular position, producing said third signal in response to said moveable portion (305) being at said extended position, and producing said fourth signal in response to said load engaging implement (210) being at said second angular position.

2. A material handling vehicle (100), as set forth in claim 1, wherein said vehicle (100) has a longitudinal axis (405) and said moveable portion (305) has an end portion (325) , said load engaging implement (210) being pivotally movable about said longitudinal axis (405) between said first and second angular positions, said end portion (325) being at a position elevationally below said longitudinal axis (405) at said first angular position and at an elevational position above said longitudinal axis (405) at said second angular position.

3. A material handling vehicle (100), as set forth in claim 1, wherein said vehicle (100) has a surface portion (410) , said load engaging implement (210) being movable to an intermediate position wherein said load engaging implement (210) is parallel to said surface portion (410) in response to said moveable portion (305) being at said retracted position.

4. A material handling vehicle (100), as set forth in claim 1, wherein said driving means (330) moves said moveable portion (305) between said extended position at which said moveable portion (305) is positioned outward from either of said vehicle sides and said retracted position at which said movable portion (305) is positioned between said vehicle sides.

5. A material handling vehicle (100), as set forth in claim 1, wherein said driving means (330) includes a first driving unit (310) driving a chain (320) connected to said moveable portion (305) , said moveable portion (305) being movable in response to said first driving unit (310) .

6. A material handling vehicle (100), as set forth in claim 1, wherein said canting means (400) includes a second driving unit (415) wherein said load engaging implement (210) is pivotally movable in response to said second driving unit (415) .

7. A material handling vehicle (100), as set forth in claim 1, including at least one ground engaging stabilizer (600) for supporting said front portion (110) of said vehicle (100), said ground engaging stabilizer (600) being positioned on said front portion (110) adjacent to the one of said vehicle sides nearer said load (200) .

8. A material handling vehicle (100), as set forth in claim 7, wherein said ground engaging stabilizer (600) extends in response to receiving said first signal and retracts in response to said ground engaging implement (210) being at said intermediate position and in the absence of said position signal.

9. A material handling vehicle (100), as set forth in claim 1, including an angular sensing means (420) for detecting the angular rotation of the load engaging implement (210) .

10. A material handling vehicle (100) , as set forth in claim 1, including a linear sensing means (335) for detecting the degree of extension of said moveable portion (305) .

11. A material handling vehicle (100), as set forth in claim 1, including a radiant energy means (220) for sensing a presence of said load (200) on said load supporting device (225) and delivering an enabling signal to said control means (700) wherein said control means (700) only produces said first signal in response to said enabling signal.

12. A material handling vehicle (100), as set forth in claim 11, wherein said radiant energy means (220) is mounted on said vehicle sides and directs electromagnetic energy diagonally outward from said vehicle (100) and detects reflected electromagnetic radiation, and produces an enabling signal in response to detecting said reflected electromagnetic radiation.

13. A method for retrieving a load (200) in a material handling vehicle (100) having a frame (115) and spaced apart sides, a load engaging implement (210) having a stationary portion (300) and a moveable portion (305) connected to said stationary portion (300) and moveable relative to said stationary portion (300) between extended and retracted positions, in coordination with a load (200) positioned on a load supporting device (205) , comprising the steps of: positioning said vehicle (100) adjacent said load (200) ; moving said load engaging implement (210) in a first direction to a first angular position; extending said moveable portion (300) to an extended position in a direction transverse said first direction engaging said load supporting device (200) ; moving said load engaging implement (210) in a second direction to a second angular position and elevating said load (200) to said second angular position; and retracting said moveable portion (305) to a retracted position in a direction transverse said second direction.

14. A method, as set forth in claim 13, including the step of moving said load engaging implement (210) to an intermediate position.

15. A method, as set forth in claim 13, including at least one ground engaging stabilizer (600) connected to said frame (115) , including the step of moving said ground engaging stabilizer (600) to an extended position.

16. A method, as set forth in claim 15, including the step of moving said ground engaging stabilizer (600) to a retracted position.