Material handling vehicle load retention apparatus

Load retention devices for material handling vehicles are inadequate in maintaining load position and inflexible in load transfer operations. First and second blocking devices having elevationally movable gates are mounted adjacent opposite sides of the frame of a material handling vehicle and adjacent a load supporting apparatus. The first and second gates are guided for elevational movement between a first position above the load supporting apparatus at which a load on the load supporting apparatus is blocked from side passing movement and a second position beneath the load supporting apparatus at which the load is free to pass the first and second sides. A first power device is provided for selectively moving the first gate member between the first and second elevational positions and a second power device is provided for selectively moving the second gate between the first and second positions. Due to the flexibility in operation of the first and second blocking devices they are particularly suited for use on automatic guided vehicles.

DESCRIPTION 
1. Technical Field 
This invention relates to a device for retaining a load on a supporting 
apparatus of a material handling vehicle, and more particularly to a 
material handling vehicle having first and second spaced apart sides, a 
load supporting apparatus, and first and second spaced apart load blocking 
devices which are movable between a first position at which the load is 
blocked and a second position at which the load is free to move on the 
load supporting apparatus in a passing relationship relative to the first 
and second sides. 
2. Background Art 
Material handling vehicles and particularly automatic guided material 
handling vehicles have an apparatus for supporting a load on the vehicle. 
The load supporting apparatus may include a stationary load carrying 
horizontal deck, an elevationally movable horizontal load carrying deck, a 
horizontal roller deck having freely rotatable rollers, a powered 
horizontal roller deck having rollers with a single direction of rotation, 
a single direction of operation conveyor deck, and the like. Typically, 
the load supporting apparatus supports a load on the vehicle and permits 
transportation of the load between pick up and deposit locations for 
machining, storing, assembly and the like purposes. During transportation 
of the load between pickup and deposit locations there exists a 
significant potential for the load to inadvertently move due to vibration, 
impact, tipping, and the like of the vehicle. This movement results in 
inaccurate and unidentified load positioning on the vehicle which is 
detrimental to accurate and acceptable load transfer between an accurately 
docked vehicle and the deposit site. This is especially the case in 
flexible manufacturing systems, automated storage and retrieval systems, 
and the like where automated guided vehicles (driverless computer 
controlled vehicles) are utilized. Systems such as these are intolerant to 
load movement that is uncontrolled, unidentified, and of a magnitude 
greater than a preselected amount. This is due to the fact that any 
deviation in the position of the load on the vehicle greater than the 
preselected amount will not permit proper alignment between the load and 
the load transfer station. Because automated systems do not have a vehicle 
operator to correct and adjust the position of the vehicle relative to the 
docking location the accuracy of load position is of great importance. 
Therefore, it is important that the amount of free movement of the load be 
limited to an amount within an acceptable tolerance range while permitting 
transfer of the load on the load supporting apparatus between the vehicle 
and the load transfer station. 
Material handling vehicles having a load supporting apparatus for example; 
powered roller decks, unpowered roller decks, powered conveyor decks, and 
the like have been known to have a stop rigidly and fixedly mounted on the 
material handling vehicle adjacent a first side of the vehicle, to 
eliminate the potential for a load carried on the vehicle from 
inadvertently exiting the vehicle from the first side adjacent the stop. 
These transporting decks facilitate and direct the transfer of the load in 
a first direction toward a second side of the vehicle opposite the first 
side, past the second side, and onto a load transfer station such as a 
stand, rack, conveyor, machining table, and the like. Conversely, these 
load supporting apparatuses permit the transfer of a load from the load 
transfer station, past the second side of the vehicle, and onto the load 
supporting apparatus of the vehicle for transportation purposes. However, 
the rigid stop prevents a load from exiting the vehicle at the first side 
or being received by the vehicle from the first side. This greatly reduces 
the flexibility of operation of the automated system because the vehicle 
must always have the second vehicle side face the load transfer station. 
Therefore, additional time is required to properly position the vehicle 
which increases costs of operation and ultimately the finished product. It 
is advantageous that a vehicle of this type is capable of passing the load 
on either side. 
Whenever a single fixed stop is provided there is the potential for the 
load carried on the deck to shift due to operational vehicle dynamics 
which may result in inadvertent load movement with the potential for 
excessive load displacement, a condition wherein the load partially 
extends past the second vehicle side (the unblocked side). Although 
automatic guided vehicles normally travel at speeds which are considered 
to slow and inadequate to cause excessive load displacement it would be 
advantageous to make provisions to prevent such a happening from taking 
place. Excessive load displacement is detrimental to the operation of an 
automatic guided vehicle for several reasons including; load alignment, 
maneuverability, stability, durability, efficiency of operation and the 
like and should be avoided. 
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 frame with first and second spaced apart sides and a means for 
supporting a load on the frame at a location between the first and second 
spaced apart sides is provided. A first means blocks movement of the load 
on the supporting means in a first direction transverse and in passing 
relationship relative to the first side, and a second means blocks 
movement of the load on the supporting means in a second direction 
transverse and in passing relationship relative to the second side. A 
power means elevationally moves the first and second blocking means 
between a first position at which the load is blocked from side passing 
movement in the first and second directions on the supporting means and a 
second position at which the load is free to move past the first and 
second sides in the first and second directions on the supporting means. 
In another aspect of the present invention an automatic guided material 
handling vehicle having a frame which has first and second spaced apart 
sides and a plurality of rollers rotatably connected to the frame and 
defining a supporting surface plane is provided. The rollers are adapted 
to guide movement of a load supported on the rollers in a first direction 
transverse the first side and in a second direction transverse the second 
side. A first gate member having upper and lower end portions is connected 
to the frame at a location adjacent the first side and a second gate 
member having upper and lower end portions is connected to the frame at a 
location adjacent the second side. A first power means elevationally moves 
the first gate member between a first position at which the upper end 
portion of the first gate member extends elevationally above the 
supporting surface plane and a second position at which the first gate 
member upper end portion is elevationally below the supporting surface 
plane. A second power means elevationally moves the second gate member 
between a first position at which an upper end portion of the second gate 
member extends elevationally above the supporting surface plane and a 
second position at which the second gate member upper end portion is 
elevationally below the supporting surface plane.

BEST MODE FOR CARRYING OUT THE INVENTION 
With reference to the drawings, and in particular FIGS. 1-3, a material 
handling vehicle 10 having a frame 12, first and second spaced apart sides 
14,16, and front and rear end portions 18,20 is shown. The material 
handling vehicle depicted is driverless, computer controlled, and often 
referred to as an automatic guided vehicle (AGV). It should be noted that 
the invention is particularly suited for use on a free ranging AGV but 
should not be limited to this use as it is suitable for use on other 
material handling vehicles for example, driver operated material handling 
carriers, and transporters, towed trailers, wire, and stripe following 
automatic guided vehicles, and the like. 
The vehicle 10 has a plurality of ground engaging wheels 22 which are 
rotatably connected to the frame 12 and a tower portion 24 which houses an 
on board control system 26 capable of controlling vehicle drive functions, 
navigation functions, load manipulation functions, and the like. A source 
of power 28, for example, a storage battery is provided for powering the 
vehicle drive system (not shown), as well as the control system 26, and 
other vehicle systems. 
A means 30 is provided for supporting a load 32 on the frame 12 at a 
location between the first and second sides 14,16. The load supporting 
means 30 defines a supporting surface plane 34 which extends at an angle 
to the first and second sides 14,16. Preferably, the load supporting means 
30 includes a plurality of elongate consecutively arranged rollers 36 
having first and second spaced apart end portions 38,40, and a cylindrical 
outer surface 42. The rollers 36 are each rotatably connected at the first 
and second end portions 38,40 to the frame 12 at spaced apart locations on 
the frame 12, are oriented so that the outer cylindrical surfaces 42 are 
substantially parallel to each other and to the first and second gate 
members 48,50, and extend transverse the front and rear frame end portions 
18,20. It is to be noted that the load supporting means 30 may include 
other embodiments, for example, stationary decks, elevationally movable 
decks, conveyor decks, and the like without departing from the spirit of 
the invention. The rollers 36 suitably guide movement of the load 32 in a 
first direction transverse the first side 14 and in a second direction 
transverse the second side 16. To insure this motion and limit load 
movement in directions towards the front and rear vehicle end portions 
18,20, tapered guides 37,39 are provided adjacent the first and second end 
portions 38,40, respectively, of the rollers 36. 
A first means 44 is provided for blocking movement of the load 32 on the 
load supporting means 30 in a first direction transverse and in passing 
relationship relative to the first side 14, and a second means 46 is 
provided for blocking movement of the load 32 on the load supporting means 
30 in a second direction transverse and in passing relationship relative 
to the second side. The first and second blocking means 44,46 include 
first and second gate members 48,50, respectively. As best seen in FIGS. 
4,6 the first gate member 48 has an upper end portion 52 and a lower end 
portion 54, and as best seen in FIG. 5, the second gate member 50 has an 
upper end portion 56 and a lower end portion 58. 
Refering to FIGS. 3-6, the first gate member 48 is connected to the frame 
12 at a location adjacent the first side 14 and is elevationally movable 
relative to the frame first side 14. Similarly, the second gate member 50 
is connected to the frame 12 at a location adjacent the second side 16 and 
is elevationally movable relative to the second side 16. A power means 68 
elevationally moves the first blocking means 44 between a first position 
60 at which the load 32 is blocked from movement in the first direction in 
passing relationship relative to the first side 14 on the supporting means 
30 and a second position 62 at which the load 34 is free to move in the 
first direction in passing relationship relative to the first side 14 on 
the supporting means 30, and elevationally moves the second blocking means 
46 between a first position 64 at which the load 32 is blocked from 
movement in the second direction in passing relationship relative to the 
second side 16 on the supporting means 30 and a second position 66 at 
which the load 34 is free to move in the second direction in passing 
relationship relative to the second side 16 on the supporting means 30. 
More particularly the first gate upper end portion 52 extends above the 
supporting surface plane 34 at the first position 60 of the first blocking 
means 44 and is elevationally beneath the supporting surface plane 34 at 
the second position 62 of the first blocking means 44. Similarly, the 
second gate upper end portion 56 extends above the supporting surface 
plane 34 at a first position 64 of the second blocking means 46 and the 
second gate upper end portion 56 is elevationally beneath the supporting 
surface plane 34 at a second position 66 of the second blocking means 46. 
As shown in FIGS. 4,5, and 6 the power means 68 includes but is not limited 
to first and second power means 70,72. The first power means 70 is 
provided for moving the first gate member 48 between the first and second 
positions 60,62 and the second power means 72 is provided for moving the 
second gate member 50 between the first and second positions 64,66. 
As best seen in FIGS. 4 and 6 the first power means 70 includes a first 
lever assembly 74 having first and second spaced apart end portions 76,78 
and a middle portion 80 located between the first and second end portions 
76,78. The first lever assembly 74 preferably includes a pair of spaced 
apart aligned bellcranks 82 rigidly secured to each other at the middle 
portion 80 by a pivot shaft 84 welded to the bellcranks 82. The first 
lever assembly 74 is pivotally connected at the first end portion 76 to 
the lower end portion 54 of the first gate member 48 by a pin assembly 86. 
The pin assembly 86 includes a boss 88 welded to the first gate lower end 
portion 54, a bushing 90 disposed in an aperture 92 in the boss 88, and a 
pin 94 disposed in a bore 96 disposed in the first lever assembly first 
end portion 76 and secured thereto. The pivot shaft 84 pivotally connects 
the first lever assembly at the middle portion 80 to the frame 12 by a 
pair of spaced apart bearing assemblies 98. 
The first power means 70 includes a second lever assembly 100 having first 
and second spaced apart end portions 102,104 and a middle portion 106 
located between the first and second end portions 102,104. The second 
lever assembly 100 is identical in construction to the first lever 
assembly 74 and is pivotally connected at the first end portion 102 to the 
lower end portion 54 of the first gate member 48 in a manner identical to 
the first end portion 76 of the first lever assembly 74. Likewise the 
middle portion 106 of the second lever assembly 100 is pivotally connected 
to the frame 12 in an identical manner as the middle portion 80 of the 
first lever assembly 74. The pivotal connections of the first and second 
lever assemblies first end portions 76,102 are at spaced apart locations 
on the lower end portion 54 of the first gate member 52 and the pivotal 
connections of the middle portions 80,106 to the frame 12 are at spaced 
apart locations on the frame 12 and adjacent the first gate member 52. 
The first power means 70 has a tie rod 108. The tie rod 108 which has first 
and second spaced apart end portions 110,112 is pivotally connected at the 
first end portion 110 to the second end portion 78 of the first lever 
assembly 74 and the tie rod second end portion 112 is pivotally connected 
to the second end portion 104 of the second lever assembly 100. The tie 
rod 108 is preferably disposed between the pair of bellcranks 82 of each 
lever assembly 74,100. The pivotal connections of the tie rod 108 first 
and second end portions 110,112 are accomplished by a pin assembly 114 in 
a conventional manner. The tie rod 108 insures uniformity in movement of 
the first and second lever assemblies 74,100, establishes the distance 
between the first and second lever assemblies second end portions 78,104, 
and determines the relative position of the first and second link 
assemblies 74,100. In order to permit fine tuning of the attitude and 
distance between the first and second lever second end portions 78,104 a 
screw threadable adjustor 116 is provided at the tie rod second end 
portion 112. 
The first power means 70 includes a linear actuator 118 having a housing 
120 and a rod 122 slidably connected to the housing 120 and telescopically 
movable relative to the housing 120. The rod 122 is pivotally connected to 
the first lever assembly 74 first end portion 76 at a location on the 
first end portion 76 spaced from the connection with the first gate member 
52 by a pin assembly 124 of conventional design. The rod 122 is disposed 
between the pair of spaced apart bellcranks 82 of the first lever assembly 
at this connection. A housing mounting assembly 126 pivotally connects the 
housing 120 to the frame 12 at a location on the frame 12 near the first 
gate member 52. The housing mounting assembly 126 has a protrusion 128 
which extends from the housing 120 in a direction opposite the rod 122 and 
a pin 130 which is transversely disposed relative to the protrusion 128 
and connected to the protrusion in any suitable manner. The pin 130 is 
pivotally connected to the frame 12 in any suitable manner, for example, 
by a pair of spaced apart bearing assemblies 132. 
The second power means 72 is an identical mirror image of the first power 
means 70. Therefore, the second power means 72 will not be discussed in 
any great detail. However, elements of the second power means 72 not 
previously discussed will be identified with the same reference numerals 
as the first power means 70 but, with a prime following the numeral. 
The second power means 72 includes a first lever assembly 74', second lever 
assembly 100', a tie rod 108' and a linear actuator 118'. The first lever 
assembly 74' has first and second end portions 76',78' and a middle 
portion 80'. The first lever assembly 74' is pivotally connected at the 
first end portion 76' to the lower end portion 58 of the second gate 
member 50 and is pivotally connected at the middle portion 80' to the 
frame 12. The second lever assembly 100' has first and second end portions 
102',104' and a middle portion 106' and is pivotally connected at the 
first end portion 102' to the lower end portion 58 of the second gate 
member 50 at a location on the second gate member second end portion 58 
spaced from the pivotal connection of the first lever assembly first end 
portion 76'. The second lever assembly middle portion 106' is pivotally 
connected to the frame 12. The connections of the middle portions 80',106' 
to the frame 12 are at spaced apart locations on the frame 12 next to the 
frame second side 16 and adjacent the second gate member 50. It is to be 
noted that these connections are made in a manner identical to those of 
the first power means 70. 
The tie rod 108' has first and second spaced apart end portions 110',112' 
and is pivotally connected at the first end portion 110' to the second end 
portion 78' of the first lever assembly 74' and at the second end portion 
112' to the second end portion 104' of the first lever assembly 100'. It 
is to be mentioned that these pivotal connections are made in a manner 
identical to those of the first power means 70. 
The linear actuator 118' of the second power means 72 has a housing 120' 
and a rod 122' slidably connected to the housing 120' and extensibly 
movable relative to the housing 120'. The rod 122' is pivotally connected 
to the first end portion 76' of the first lever assembly 74' at a location 
on the first end portion 76' spaced from the pivotal connection of the 
first end portion 76' with the second gate member 50. The housing 120' is 
pivotally connected to the frame 12 at a location on the frame 12 near the 
second side 16 and adjacent the second gate member 50. These pivotal 
connections are made in a like manner as those of the linear actuator 118 
of the first power mean 70. 
The first and second power means 70,72 include identical motors 134,134', 
respectively. The motors 134,134' are preferably electric, but fluid 
operated motors are considered suitable substitutes and within the scope 
of the invention. Motor 134 is mounted on housing 120 and drivingly 
connected to the rod 122 in any suitable and well known manner such as by 
gearing, fluid coupling, and the like, and motor 134' is mounted on 
housing 120' and drivingly connected to the rod 122' in the same manner. 
The rods 122,122' are extensibly moveable in response to actuation of 
their respective motors 134,134' to move the first and second gate members 
48,50 between the first and second positions. The motors 134,134' are 
connected to power source 28 and the control system 26. The control system 
controls each motor 134,134' and provides for individual and dual 
operation in response to pre-programmed instructions. 
A roller drive motor 136 which is connected to the power source 28, 
controlled by the system 26, and mounted on the frame 12 is provided. The 
roller drive motor has an output shaft 138 connected to a chain and 
sprocket arrangement 140 of conventional design. The chain and sprocket 
arrangement is connected to the rollers 36 in any manner suitable for 
transmitting rotary motion from the shaft 138 to rotary motion of the 
rollers 36. The rollers 36 are rotatable about the first and second roller 
end portions 38,40 in response to rotation of the motor output shaft 138. 
The roller drive motor 136 is preferably a reversible electric motor 
capable of driving the rollers 36 in either clockwise or counterclockwise 
directions. The direction of rotation of the roller drive motor 136 and 
ultimately the rollers 36 is established by the control system 26. 
The frame first side 14 includes a first pair of spaced apart substantially 
parallel support members 142 which define a first guideway 144 
therebetween. The first gate member 48 which is preferably a flat steel 
plate, is slidably disposed in the first guideway 144 between the first 
pair of support members 142. A first pair of bearing pads 146 are disposed 
in the first guideway 144 and connected to the first pair of support 
members 142, respectively. The first pair of bearing pads 146 are 
preferably constructed of a nonmetalic plastic material and connected to 
the first pair of support members 142 in any suitable manner. The first 
gate member 48 is disposed between the first pair of bearing pads 146, 
bears against the first pair of bearing pads 146, and is slidably guided 
by the first pair of bearing pads 146. 
The frame second side 16 includes a second pair of spaced apart 
substantially parallel support members 148 which define a second guideway 
150 therebetween. The second gate member 50 which is preferably a flat 
steel plate, is slidably disposed in the second guideway 150 between the 
second pair of support members 148 A second pair of bearing pads 152 are 
disposed in the second guideway 150 and connected to the second pair of 
support members 148, respectively. The second pair of bearing pads 152 are 
preferably constructed of a nonmetalic plastic material and connected to 
the second pair of support members 148 in any suitable manner. The second 
gate member 50 is disposed between the second pair of bearing pads 152, 
bears against the second pair of bearing pads 152, and is slidably guided 
by the second pair of bearing pads 152. 
A first sensing means 154 senses the elevational position of the first gate 
member 48 and delivers a first signal in response to the first gate member 
48 being at the first position 60 and a second signal in response to the 
first gate 48 member being at the second position 62. A second sensing 
means 156 of construction identical to the first sensing means 154 senses 
the elevational position of the second gate member 50 and delivers a first 
signal in response to the second gate member 50 being at the first 
position 64 and a second signal in response to the second gate member 
being at the second position 66. 
The first sensing means 154 has first and second inductive proximity 
sensors 158,160 which are each capable of delivering a signal and 
receiving a reflection of the delivered light signal. The first inductive 
proximity sensor 158 is located on the frame 12 at a position on the frame 
12 adjacent the lower end portion 54 of the first gate member 48 at the 
first position 60 of the first gate member 48, and the second inductive 
proximity sensor 160 is located on the frame 12 at a position on the frame 
12 adjacent the lower end portion 54 of the first gate member 48 at the 
second position 62 of the first gate member 48. 
The second sensing means 156 like the first sensing means 154 has first and 
second inductive proximity sensors 162,164 which are each capable of 
delivering a light signal and receiving a reflection of the light signal. 
The first inductive proximity sensor 162 is located on the frame 12 at a 
position on the frame 12 adjacent the lower end portion 54 of the second 
gate member 50 at the first position 64 of the second gate member 50, and 
the second inductive proximity sensor 164 is located on the frame 12 at a 
position on the frame 12 adjacent the lower end portion 54 of the second 
gate member 50 at the second position 64 of the second gate member 50. The 
first and second inductive proximity sensors 158,162,160,164 are connected 
to the frame in any suitable manner, such as by brackets 166 and fasteners 
168. 
The first gate member 48 has a sensing edge 170 located on its lower end 
portion 54 and the second gate member 50 has a sensing edge 172 on its 
lower edge portion. The sensing edges 170,172 are elevationally aligned 
with the first inductive proximity sensors 158,162, respectively, to 
interrupt a portion of the light signal of the respective first inductive 
proximity sensors 158,162 at the first positions 60,64 of the first and 
second gate members 48,50, respectively. The sensing edges 170,172 are 
also elevationally aligned with the second inductive proximity sensors 
160,164, respectively, to interrupt a portion of the signal of the 
respective second inductive proximity sensors 160,164 at the second 
positions 62,66 of the first and second gate members 48,50, respectively. 
The first inductive proximity sensors 158,162 each deliver a control signal 
to the control system 26 in response to the gate members 48,50 being at 
the first positions 60,64 and the second inductive proximity sensors 
160,164 each deliver a control signal to the control system 26 in response 
to the gate members 48,50 being at the second positions 62,66. The control 
system 26 responds to these signals in a pre-programmed manner and 
controls operation of the vehicle 10, rollers 36, gate members 48,50 and 
the like in order to transfer the load 32 between the vehicle 10 and a 
load transfer station 174. 
Industrial Applicability 
With reference to the drawings, and in operation, the automatic guided 
vehicle 10 follows the pre-programmed instructions of the onboard control 
system 26 as well as instructions transmitted to the vehicle from a remote 
controller (not shown). In response to these instructions, the vehicle 10 
carries out its loading and unloading functions, as well as transporting 
the load 32 between load transfer stations 174. 
Assuming a load 32 on the vehicle 10, the control system 26 receives 
signals from the first and second sensing means 154,156 indicating that 
the first and second gate members 48,50 are in the first position 60,64. 
Because the load 32 is blocked from passing the first and second sides 
14,16 of the vehicle 10, the control system 26 will enable the vehicle 10 
to transport the load 32 to a preselected destination within the facility. 
As the vehicle 10 approaches the load transfer station 174 communication 
between the load transfer station 174 and the vehicle 10 are established 
which results in accurate positioning of the supporting means 34 and the 
load transfer station 174. Because the load 32 was maintained on the 
supporting means 34 between the vehicle sides 14,16 by the gate members 
48,50 the ability to maneuver close to the load transferring station 174 
without interference is made possible. Stated another way, the position of 
the load on the vehicle is controlled within preselected limits so that 
accurate load transfer may take place. 
As previously noted, the tower portion 24 and the rear end portion 20 of 
the frame 12 extend elevationally above the supporting means 30 and 
establish boundaries which limits load movement in directions toward the 
front and rear end portions 18,20 of the vehicle 10. They also serve to 
assist the supporting means 34 and particularly a roller deck 36, in 
guiding the load 32 transversely of the first and second gate members 
48,50. 
After the vehicle 10 is properly docked and the load supporting means 30 is 
aligned with the load transfer station 174, control system 26 actuates 
linear actuator 118 which lowers the first gate member 48 to the second 
position 62. At this position 62 the load 32 is free to be transferred 
past the first side 14 and on to the load transfer station 174. The first 
sensing means 154 determines when the first gate member 48 is at the 
second position, i.e.; when the second inductive proximity sensor 160 and 
the sensing edge 170 are aligned, and delivers a control signal to the 
control system 26. As a result, the roller drive motor 136 is actuated to 
rotate in a preselected direction as established by the first gate member 
48 being at the second position 62 and the vehicle 10 being successfully 
docked which rotates the rollers 36 and transfers the load 32. Upon 
completion a successful load transfer the roller drive motor 136 is 
stopped and the linear actuator 118 is actuated to raise the first gate 
member 48 to the first position 60. 
Because the first and second blocking means 44,46 are each movable between 
the first and second positions 60,62,64,66 as determined by pre-programmed 
instructions and in accordance with certain established parameters. The 
capability of transferring and receiving the load 32 past either the first 
and second sides 14,16 is possible. As a result speed and flexibility not 
present in flexible manufacturing and assembly systems, and automated 
storage an retrieval systems currently available is made possible. 
Other aspects, objects and advantages of this invention can be obtained 
from a study of the drawings, the disclosure and the appended claims.