Warehousing system
i United States Patent Zollinger et al.  
 1 Apr. 29, 1975 1 WAREHOUSING SYSTEM [75] Inventors: Howard A. Zollinger, Ada Twp.,  
 Kent County; Leroy Lubbers; William K. Stubbs, both of Grand Rapids, all of Mich.  
 [73] Assignee: Rapistan, Incorporated, Grand Rapids, Mich.  
 [22] Filed: July 17, 1972 [21] Appl. No.: 272,287  
 [52] 11.5. C1 214/16.4 B; 104/48; 2l4/l6.4 A; 2l4/l6.1 EA [51] Int. Cl. B65g l/06 [58] Field of Search 214/16.l E, 16.1 EA, 16 B, 214/l6.4 B, 16.4 A, 16.4 C; 104/48 [56] References Cited UNITED STATES PATENTS 3,387,723 6/1968 Lemelson 2l4/l6.4 A  
 3,417,879 12/1968 Gough 214/16 B 3,519,150 7/1970 Keenan et a1. 214/164 B 3,557,973 l/l97l Kouviers 214/16 B 3,602,379 8/1971 Bosse 214/16.4 B  
 3,709.383 1/1973 Jennings et a1 214/16 B 3,746,189 7/1973 Burch et a1 214/16.4 B  
 FOREIGN PATENTS OR APPLICATIONS 262,893 6/1968 Austria 2l4/l6.4 B  
 Primary Examiner-Robert J. Spar Assistant E.ruminerR. B. Johnson Attorney, Agent, or FirmPrice, Heneveld, Huizenga &amp; Cooper storage bins arranged in vertical tiers with the tiers arranged in rows and having aisles between the rows. A mobile vertical lift moves across the ends of the aisles and carres thereon a mobile transfer vehicle which can be elevated by the mobile vertical lift to any desired storage level. The self-powered mobile transfer vehicle is adapted to be automatically dispatched from the mobile vertical lift at a predetermined aisle and level and is programmable to travel via tracks down the aisle to a predetermined bin location, extend retrieving mechanism from the vehicle under a pallet load in a bin, lift it and retract thereby transferring the pallet load onto the mobile transfer vehicle. The transfer vehicle then returns to the mobile vertical lift. The process can be reversed for transferring a pallet into storage. The mobile vertical lift travels between a home station which serves as an interface for the storage section of the system and various aisle positions to receive and discharge mobile transfer vehicles such that while one transfer vehicle is moving down an aisle to discharge or retrieve a palletized load from a bin, the mobile vertical lift can be transporting a different mobile transfer vehicle. The mobile vertical lift includes selfaligning means thereon such that the mobile vertical lift is accurately aligned with an aisle at the desired vertical and horizontal position to facilitate the dispatching of the mobile transfer vehicle along the aisle. The mobile transfer vehicle also includes self-aligning means to accurately position the transfer vehicle with a predetermined storage bin. In a broader aspect of the system, the mobile transfer vehicle serves as an interface between a storage facility and other facilities such as an assembly line or shipping area to automatically carry articles between the several facilities.  
 [ ABSTRACT A warehouse storage system comprises an array of 19 Claims, 26 Drawing Figures 10 1?. l0 12 10 395 I I I I 2 510 n my 00 J im L l J 1 1 l a 1?. 10 12 no 1?. \o  
 SHEET [1301 14 PATENTED APR 2 91975 SHEET BQUF 14 [HIIHIII NIP  )LLLL| NIP  \LIIIHHHIIIIIIIII] o l lllHllNlIlIllllllllllllllllllllllllllllllllll SHEET [ESUF 14 HGJO PATENTEDAPRZSIQYB SHEET 08 0F 14 HGJS PATENTED 3,880,299  
 SHEET lUGF 14 PATENTEDAPRZQIQYS SHEET 1 2 BF 1 4 LOCATOR CONTROL UNIT  LI FT C! U NDER CONTROL INFO XFER PANEL MOTOR V CONTROL CKT COMPUTER CONTROL CIRCUIT DATA KEY BOARD BPJDGE CONTROL cm- CARD READER LOGHZ CKT ; OUTPUT V 200-% ENPUT l FIG 24 PATENTEU 2 7 3.880299 SHEET 1 4 [1F 1 4 TalAlrlsFghR g o gg k DIGITAL REVERSIME E PANEL COUNTER common COUNTER SE N S O R 550&#39; 610 ass PA N EL PosmoN men/u. POSlTION REGISTER commnmq DETECTOR era 1 see ,659 6B2.  
  I LOGIC a CIRCU|T 6T9 &#34;l l LT] G73\ G12 CLUTCH fi F FORK MOTOR CONTROL E CONTROL DRWE cmcun l CIRCUIT MOTOR 678 7] l ggy: ACTUATOR EX&#39;TENSION RAISING 293 MOTOR MOTOR I I 2:2 242 WAREHOUSING SYSTEM BACKGROUND OF THE INVENTION The present invention relates to a warehousing system and particularly to apparatus for automatically transferring articles to and from the system.  
  With the ever-increasing demands for moving articles, in commerce, it has become necessary to increase the through-put capacity of warehousing systems so as to efficiently store and retrieve such articles at these facilities which provide retail and other outlets with a variety of different items. In recent years, the use of semi-automated equipment in place of manual transferring equipment has been incorporated with limited success in an attempt to increase the efficiency of warehousing systems. More recently, stacker cranes have been developed which travel down aisles of multitiered storage bins. These cranes are guided by an operator who locates the stacker crane across from a desired storage location and then either manually picks from that storage location or can extend lifting forks or the like into the storage bin to store or retrieve articles therefrom. In the more sophisticated systems, the operator is replaced by some type of electronically operated control system.  
  Even more recently, a system has been developed that is described in US. Pat. No. 3,503,530, Arthur R. Burch, et al., issued Mar. 3l, 1970 and which employs a first vehicle which travels across the aisles of the storage rack on tracks and carries with it a second vehicle which can be dispatched down the aisles. The second vehicle includes a mobile vertical elevator for aligning a picking unit with a storage bin. The picking unit then can retrieve or discharge articles between the storage bin and the second vehicle. The first vehicle includes a load station for transferring the articles between the second vehicle and first vehicles.  
  Although such a system represents an improvement in efficiency over manual picking systems, this system as well as the semi-automatic stacker crane systems lacks the through-put capacity since the vehicle which travels in the aisle is adapted to move vertically as well as along the aisle and therefore, only one vehicle can be employed for each aisle end. Thus, the maximum numbers of vehicles that actually store and retrieve articles into and out of the system is limited to two for each multi-level aisle assuming that each end of the aisle has a first vehicle that can transfer an associated second vehicle from aisle to aisle. In many warehouses only one aisle end is available thereby limiting vehicles which accomplish the transfer of articles to and from the storage bin to one per aisle.  
  The use of a stacker crane or other systems which have the ability to travel the length of one aisle and elevate within the aisle to any of the storage bin heights requires that a single unit have enough through-put capacity to handle the through-put required for each aisle. Because of the input and output systems usually associated at one end of the system, it is not feasible to operate two such stacker cranes in one aisle. This provides, in some cases, a significant limitation to the through-put capacity of the system which is best suited for extremely long aisles of storage. If long aisles are employed, however, the throughput is limited by the efficiency of the operation of the stacker crane. On the other hand, if the storage location is laid out to include many short aisles to overcome this limitation, a plural ity of the relatively expensive stacker cranes or thei equivalent are necessary to obtain the desired through put. The expense of the system rises significantly, since each vehicle is relatively complex to provide along-the aisle movement as well as vertical movement in addi tion to the picking motion required to reach into a stor age bin. Thus, these systems have undesirable limita tions either as to efficiency in their ability to provide the desired through-put or as to their expense if em ployed with shorter aisles to provide the dSII6( through-put capacity.  
  Another important limitation upon existing system: of this type is the fact they require the entire aisle to be unobstructed vertically. This is considered a seriou: fire hazard and places a limit on the height to which ar ticles may be stored. This invention eliminates thi: problem because no or only limited vertical movemen&#39; of the articles is performed in the aisles.  
 SUMMARY OF THE INVENTION The system of the present invention, however, provides a mobile vertical lift that travels across the end: of the aisles in a storage location and carries a mobile transfer car that can be discharged to any level of 2 given aisle by the mobile vertical lift. In this system, the cross-aisle vehicle is vertically movable and can discharge one transfer car at one level of the aisle and second, third, or more transfer vehicles at different levels of the same or other aisles. In this system, therefore, the number of transfer cars which are used to transfer articles into and out of the storage bins and which can be dispatched along a single aisle is greatly increased. By employing several transfer vehicles with a single mobile vertical lift, the efficiency of the warehousing system it its ability to rapidly store and retrieve articles there from is greatly increased. Also, since the mobile transfer vehicles move only in a horizontal plane, they are less complex and, therefore, less costly than vehicles which travel both horizontally and. verticaliy within the aisles.  
  It is an object, therefore, of the present invention tc provide an improved automatic warehousing system which employs a mobile vertical lift that travels across the ends of the aisles in a storage area and is adapted to carry and discharge a second vehicle movable at 2 single aisle level along an aisle and which includes means for receiving and discharging articles from and to a storage bin.  
  It is another object of the present invention to pro vide an automatic warehousing system that employs 2 single mobile vertical lift and a plurality of mobile transfer vehicles which are adapted to move along at aisle receiving and discharging goods from and to stor age bins therein while the mobile transfer vehicle is transporting different mobile transfer vehicles to other locations within the system.  
  It is an additional object of the present invention tc provide a self-powered mobile transfer vehicle that car be discharged into a storage aisle and transfers goods from and to storage bins and which can leave the sys tem thereby providing an interface between the storage area and other facilities.  
  It is an additional object of the present invention tc provide a home station which serves as an interface between the storage system and input and output conveyors such that mobile transfer vehicles can be discharged and received by the mobile vertical lift at the home station for receiving goods into the system and discharging goods from the system thereby.  
  It is an additional object of the present invention to provide a transfer car storage area where the mobile transfer vehicles can be located when not in use and are readily available to the mobile vertical lift when needed.  
  It is still an additional object of the present invention to provide a retractable bridge between input and output stations at the home station such that mobile transfer vehicles can be transported between the input and the output stations when the mobile vertical lift is not at the home station.  
  Another object of the present invention is to provide programming means to automatically control the positions of either the mobile vertical lift or mobile transfer vehicle, or both.  
  A further object of the present invention is to provide locating means on the mobile vertical lift to accurately align the lift with an aisle and locating means on each mobile transfer vehicle to accurately align it with a storage bin.  
  These and other objects of the present invention will become apparent upon examining the drawings together with the accompaning description thereof.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view in schematic form showing a warehousing system embodying the materials handling apparatus of the present invention;  
  FIG. 2 is a side elevational view in schematic form of the warehousing system shown in FIG. 1;  
  FIG. 3 is a fragmentary perspective view of the warehousing system showing the detailed structural elements forming the storage racks, the guide rails, the transfer vehicles used in the materials handling system as well as the home station and retractable bridge employed therewith;  
  FIG. 4 is a detailed enlarged view of one of the elements of the warehousing system shown in FIG. 3;  
  FIG. 5 is a side elevational view of the mobile vertical lift shown in schematic form;  
  FIG. 6 is a detailed sectional view of a portion of the mobile vertical lift taken along section lines VI-VI of FIG. 5 showing one of the load carrying wheels and associated guide wheels;  
  FIG. 7 is a detailed front elevational view in cross section taken along the section lines VII-VII of FIG. 5 showing the lower drive mechanism for the mobile vertical lift and its relationship to the tracks;  
  FIG. 8 is a detailed front elevational view in cross section taken along the section lines VIIIVIII of FIG. 5 of the top drive mechanism associated with the mobile vertical lift;  
  FIG. 9 is a detailed plan view of the top structure of the mobile vertical lift;  
  FIG. 10 is a detailed side elevational view of the lifting platform assembly which fits within the mobile vertical lift and is vertically movable therein;  
  FIG. 11 is a plan view in schematic form of the mobile vertical lift;  
  FIG. 12 is a detailed plan view of the aligning means employed with the mobile vertical lift;  
  FIG. 13 is a detailed front elevational view in cross section showing a portion of the horizontal channel members employed in conjunction with the aligning means shown in FIG. 12;  
  FIG. 14 is a perspective view of a mobile transfer vehicle;  
  FIG. 14A is a front elevational view of one of the column labels employed to uniquely identify each storage bin;  
  FIG. 15 is a partial cutaway detailed view of the wheel assemblies in the mobile transfer vehicle taken along the lines XV-XV shown in FIG. 14;  
  FIG. 16 is a partial plan view of the mobile transfer vehicle;  
  FIG. 17 is a sectional view partially in cross section taken along the lines XVIIXVII shown in FIG. 16;  
  FIG. 18 is a side elevational view of a portion of the structure shown in FIG. 17;  
  FIG. 19 is a plan view in schematic form of a mobile transfer vehicle showing the location of various sensors thereon;  
  FIG. 20 is an electrical circuit diagram in block form of a portion of the control circuit used with the present invention;  
  FIG. 21 is an electrical circuit diagram in block form of the control circuit for the mobile vertical lift;  
  FIG. 22 is a diagram in pictorial form of an information transfer panel;  
  FIG. 23 is an electrical circuit diagram in block form of the control circuit for a mobile transfer vehicle;  
  FIG. 24 is a plan view in schematic form of an alternative embodiment of the warehouse of the present invention; and  
  FIG. 25 is a plan view in schematic form of still another embodiment of the warehouse system of the present invention.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to FIGS. 1 and 2, there is shown a warehousing system comprising a plurality of storage racks 10 separated by aisles l2 therebetween which extend along the length of the storage racks 10. The racks are divided into a plurality of levels and individual storage bins which form an array of storage locations adapted to receive palletized loads therein. A transverse aisle 120 extends along one end of the aisles 12 between the two sections of storage racks, and a mobile vertical lift adapted to engage monorails 14 and 16 traverses aisle 120. The mobile vertical lift (trans-aisle vehicle) 100 is adapted to receive any one of a plurality of mobile transfer vehicles 200 which are dispatched into the aisles 12 of the storage system so that materials can be transferred into and out of the storage bins by the transfer vehicles 200.  
  The mobile vertical lift 100 operates between a home station generally indicated at 300 which includes input and output stations 320 and 340, respectively, which serves as an interface between the warehousing system and other systems such as a receiving station or shipping station, respectively. The warehousing system further includes a transfer vehicle storage magazine 350 communicant with the output station 340 and adapted to storage transfer vehicles when not in use. A retractable bridge 400 facilitates the movement of transfer vehicles 200 between the output station 340 across the monorail l6 and the input station 320 area when the mobile vertical lift 100 is not at the home station. The mobile vertical lift 100 includes a vertically movable lift platform 150 thereon which has a carriage assembly which carries the mobile transfer vehicles 200 by means of guide rails 154 adapted to receive guide wheels on the mobile transfer vehicles 200. The lift platform 150 is shown in FIG. 2 moving upwardly as indicated by the arrow 152 to an aisle level where a transfer vehicle 200 is in position to be received by the mobile vertical lift 100. When the mobile vertical lift is in position, the guide rails 154 are aligned with horizontal guide rails 18 extending along the aisles 12 of the storage racks such that the transfer vehicle 200 can transfer between the mobile vertical lift 100 and aisles 12. The transfer vehicles 200 are self-powered and are guided within the storage racks 10 along the aisles 12 by means of the guide rails 18 at a predetermined vertical height such that palletized loads 210 can be automatically transferred between storage locations within the storage racks and the mobile transfer vehicles 200 by transfer means carried on the vehicles 200. In FIGS. 1 and 2, arrows accompanying the palletized loads 210 and the transfer vehicles 200 indicate the direction of movement of the loads into and out of storage and the transfer vehicle motion toward the mobile vertical lift 100.  
  The mobile vertical lift 100 can be directly coupled to a control station 330 (FIG. 1) by means of a festoon cable 325 as shown in FIG. 2 to receive positional information from a computer to control the movement of the vertical lift 100 and direct the movement of the transfer vehicles 200. The cable 325 also provides the mobile vertical lift 100 with operating power for its drive motors. The mobile vertical lift can also be controlled semi-automatically by employing a punched card or like system in which an operator inserts such a card into a reader on the lift to control its movement within the system. Likewise, it is possible to manually control the positioning of the lift by carrying an operator thereon and providing suitable operator controls.  
  Each mobile transfer vehicle 200 includes its own drive mechanism and power supply such that it is selfpowered in its motion within the aisles 12. The input- /output station rails (375 and 358) include an electrical supply bus or collector bar and each mobile transfer vehicle includes a contact shoe adapted to slidably engage the collector bar such that when the transfer vehicle is at the home station area, it can be externally powered to conserve the electrical energy stored in its batteries. It is noted that such a conventional power supply can be employed at various of the warehouse areas including the access aisles if desired, although in the preferred embodiment, the transfer vehicles are selfpowered when in the aisles. It is seen that by employing a system such as that shown in FIGS. 1 and 2 whereby the mobile transfer vehicles 200 are movable in a horizontal plane and are elevated and lowered by means of a mobile vertical lift at an end of the aisles, the storage racks can be horizontally divided at predetermined vertical intervals by, for example, fire barriers 30 (FIG. 2) which extend horizontally through the storage rack area but not through the transverse aisle 120 in which the mobile vertical lift 100 travels. Thus, when the racks extend, for example, to I00 feet or more in height, they can be divided at several vertical intervals by horizontal fire barriers to lessen fire hazards. It is seen that only the ends of the aisles, and not the storage rack, must be open for the use of the materials handling equipment of this invention. These open ends can be equipped with fire doors to close them off in case of emergency.  
  FIGS. 1 and 2 illustrate the use of the materials handling system to interface with the input and output stations 320 and 340. The input station 320 has a conveyor 322 for transferring materials from a receiving station, for example, in a warehousing facility to the input station where materials are picked up by a mobile transfer vehicle 200 at the input station 320 on guide rails 375. The output station 340 has a conveyor 345 associated therewith which receives materials from a transfer vehicle 200 at the output station on rails 358 also associated with and extending into the vehicle storage magazine 350. Conveyor 345 then transfers materials to a shipping dock, for example, that is associated with the warehousing system. In addition, the facility shown in FIGS. 1 and 2 may include additional input and output means such as the guide rails 375 which are adapted to guide transfer vehicles 200 to a different facility such as an assembly line within the system. A shunting or stub conveyor 385 may be located adjacent the rails 375 to receive preselected loads from some of the transfer vehicles 200 and carry them to a different area, such as a packaging station. Also, another set of guide rails 395 may be provided at an opposite end of the storage racks for guiding vehicles 200 to a repair facility, maintenance facility, or any other of a number of different facilities. Thus, it is seen, by employing a self-powered transfer vehicle 200, the vehicle itself may under its own power and programmed intelligence move between the warehouse facilities shown in FIGS. 1 and 2 to other facilities by means of rails 375 and 395 01 may transfer loads thereon to various facilities as indicated by the associated conveyors 322, 345 and 385. Any number of other variations are possible with such a system that employs a self-powered transfer vehicle which includes means thereon for transferring unitized loads between the vehicle and other means, such as conveyors. The transfer vehicles are, as explained in detail below, programmable to move under their own power to any preselected location within the storage area, or to one of the interface facilities. Having briefly described the overall system structure and operation, details of the preferred embodiment of the present invention are presented.  
  Referring now to FIG. 3, there is shown a perspective view of a portion of the warehousing system shown in FIGS. 1 and 2, showing a cutaway portion of a mobile vertical lift and a mobile transfer vehicle 200 within an aisle 12 between storage racks 10.  
  The storage racks 10 comprise vertical supports 20 and load supports 22 that define individual storage bins 21 forming an array along each aisle. The bins 21 are adapted to receive standard palletized loads 210 therein as shown. The warehousing system is divided in dual sections of arrays of bins 21 that are accessible from adjacent aisles 12. The guide rails 18 form a portion of the horizontal support members for the storage racks 10 as well as providing support for the transfer cars 200. As seen in the figure, the carriage assembly 170 on the mobile vertical lift 100 also includes guide rails 154 which are adapted to be aligned with the rails 18 such that a transfer vehicle 200 can be transferred from the storage rack 10 onto the lifting platform of the mobile transfer vehicle 100 on which the carriage assembly rests.  
  Each transfer vehicle 200 includes a drive motor 250 coupled to guide wheels 270 which ride within the guide rails 18. Additionally, each transfer vehicle includes means 230 (FIG. 3) for transferring palletized loads 210 between a storage bin 21 and the vehicle 200 or between the conveyors 322, 345 and 385 and the vehicle. In the preferred embodiment, means 230 comprise a pair of forks 240 each comprising a threesectional platform having a vertically movable base 232, a middle section 234 movable to either side of the vehicle 200, and a top section 236 extensible to either side in relation to the middle section 234 and which fits under a palletized load 210 for lifting and transferring the load to and from the vehicle 200.  
  The home station area 300 where the mobile transfer vehicles 200 are transferred to and from the middle vertical lift 100, includes a retractable bridge 400 as shown in FIG. 3. The bridge comprises a pair of guide rails 418 mounted above the monorail 16 on which the mobile vertical lift travels and which are lowerable and retractable under the guide rails 375 shown in FIGS. 1 and 3. When the mobile vertical lift 100 enters the home station area 300, the tracks 418 are retracted out of the way so as not to obstruct the movement of the mobile vertical lift. This is accomplished by mounting the guide rails 418 of the bridge 400 on a platform 420 which is mounted to an additional platform 430 by means of a pair of actuation cylinders 425. This arrangement allows the platform 420 to be elevated and lowered in relation to the platform 430. Platform 430 is at approximately ground level and is mounted by means of guide wheels within a pair of tracks 440 such that it is longitudinally movable in a direction parallel to the tracks 375 and perpendicular to the monorail 16.  
  A motor 445 with a drive belt 450 coupled to the platform 430 can be actuated to cause the platform 430 and, therefore, the platform 425 and rails 418 thereon to be drawn to the left in FIG. 3 out of the way of the mobile vertical lift 100, once the rails 418 have been lowered by means of the cylinders 425. The bridge 400 is positioned when the mobile vertical lift 100 is not at the home station to provide a transfer path for the mobile transfer vehicles 200 from the output station 340 into the input station 320. The bridge 400 allows the transfer vehicle 200 to receive a palletized load 210 from the input station 320 or to move along the tracks 375 to transfer loads to the stub conveyor 385 or otherwise operate between the input and output stations 320 and 340, respectively, without requiring the presence of the mobile vertical lift 100. By so designing the system, the transfer cars 200 can be utilized to their maximum efficiency as can the mobile vertical lift 100.  
  Both the guide rails 418 of the bridge 400 and the guide rails 154 of the carriage assembly 170 associated with the mobile vertical lift 100 have locating means 410 and 160, respectively, which are employed in conjunction with tapered ends of the guide rails 18 in the storage racks to accurately align the guide rails 154, 4l8 with the storage rack guide rails 18 such that the transfer vehicles 200 can easily be transferred to and out of the storage rack aisles 12. Details of the locating mechanism are shown and described with reference to FIGS. 11 through 13 and discussed below. The guide rails 18 each include stops 24 (only two shown in FIG. 3) at the ends of the rails 18 adjacent the aisle 120 to prevent the transfer cars 200 from accidentally slipping from the aisle level when the mobile vertical lift 100 is not in position to receive the transfer vehicle 200. The construction details of the guide rails 18 and stops 24 associated therewith are shown in FIG. 4.  
  As seen in FIG. 4, the guide rails 18 comprise a longitudinal channel member 19 having a generally C- shaped cross section. A slightly crowned rail 26 is mounted along the interior bottom surface of the channel member 19 as shown. Rail 26 carries the weight of the transfer vehicle 200 thereon by means of the tapered guide wheels 270 on the transfer vehicle which contacts rails 26.  
  Each of the stops 24 located at the end of each guide rail 18 comprises a plate 28 having a cross-sectional area sufficiently large to close off the open area of the guide rail 18. The plate 28 is pivotally coupled to the C-shaped channel 19 by means of a pivot pin 29. The stops 24 are weighted by means of a weight 31 attached to the plate 28 by means of an arm 33 such that they will normally be held in the position shown in solid lines. In this position, the plate 28 closes off the end of the channel 19 when the mobile vertical lift is not positioned such that its guide rails 154 are aligned with the guide rails 18 of the storage racks 10.  
  The aligning means 160 on the mobile vertical lift, however, are adapted to swing inwardly when the lift 100 aligns with an aisle and include members which contact the stops such that the left and right stops 28 are pivoted in a direction indicated by the arrows to the position shown in phantom lines in FIG. 4. In this position, the plates 28 will be out of the way and allow the transfer vehicle 200 to freely move between the guide rails 18 in the storage racks and the guide rails 154 on the mobile vertical lift 100. The stops associated with the guide rails 358 in the vehicle storage magazine 350 operate in a similar manner to allow the transfer vehicles 200 to cross the bridge rails or tracks 418 and enter the storage magazine 350 when the locating means 410 have positioned the tracks in alignment with the guide rails 358 of the vehicle storage area. The construction of the interface between the mobile vertical lift guide rails 154 and the guide rails 18 within the storage racks 10 will be discussed in conjunction with the detailed description of the mobile vertical lift 100 which follows.  
  Referring now in detail to FIGS. 5-13, there is shown a mobile vertical lift 100 comprising a base member 102 to which is attached vertical support members 104 that extend upwardly from the base member 102 to an upper structure 110 shown in detail in FIG. 9. The mobile vertical lift 100 rests on the lower monorail 16 by means of a pair of load support wheels 103 and 105 coupled to the base 102 by means of brackets 106 and 107, respectively. The front portion of the base member 102 is shown in detail in FIG. 6 which illustrates the member 102 as comprising a triangular frame 108 to which is attached the mounting bracket 106 that holds the front support wheel 103. A pair of support beams 109 extend rearwardly and are coupled to a similar shaped rear triangular frame member (not shown in detail) to complete the frame of the base member 102. Rotatably mounted within the frame 108, by means of axles 113 and brackets 111, is a pair of guide wheels 112 (FIG. 6). These guide wheels straddle the lower monorail 16 as shown in detail in the cross-sectional view of FIG. 7. The rear support wheel 105 also includes a pair of guide wheels and mounting bracket assembly similar to that in the front as shown schematically in FIG. and indicated generally at 114.  
  The mobile vertical lift 100 is coupled to the upper monorail 14 by means of a front pair of guide wheels 115 rotatably mounted to the upper assembly 110 by means of a pair of axles 116 coupled within a frame 117 forming the front portion of the upper structure 110 as shown in FIG. 9. It is seen in FIG. 9 that the forward frame section 117 is generally triangular shaped as is the rear frame member 118 coupled to the front frame member by means of four strut members 119. A pair of guide wheels 122 are rotatably coupled within the rear frame 118 by means of axles 124 coupled to the frame 118 by means of a-bracket 125.  
  The lifting platform 150 on the mobile vertical lift 100 is shown in detail in FIG. and comprises a frame assembly 151 having triangular shaped end segments 152 joined by struts 157. The lift platform 150 is vertically movable within the mobile vertical lift 100 by means of a plurality of wheels 155 rotatably mounted to the end segments 152 by means of axles 156. Guide wheels 153 are mounted to the ends 152 of platform 150 as shown in FIG. 10. These wheels straddle the vertical support members 104 of the mobile vertical lift 100 to insure the smooth operation of the raising and lowering of the platforms 150 within the mobile vertical lift 100. The platform 150 also includes a pair of pulleys 158 rotatably mounted to brackets 159 on each end 152 of platform 150 through which a lifting cable 162 (FIG. 5) is strung such that the platform 150 can be raised and lowered within the vertical support members 104 of the mobile vertical lift 100.  
  The lifting cable 162 is also strung through four pulleys 164 mounted between the struts 119 of the upper assembly 110 (FIGS. 5 and 9) and is anchored at one end to the structure 110 by anchoring means 165 shown in FIG. 5. The opposite end of cable 162 is attached to a hoisting reel and motor unit 167 which is selectively actuated as explained below to wind or unwind the lifting cable 162 thereon such that the lifting platform 150 is raised and lowered.  
  The mobile vertical lift is driven by means of a drive motor 130 having a lower axle 132 coupled to a drive gear 134 which engages a rack 17 mounted on the side of the lower monorail 16 (FIGS. 5 and 7). The motor 130 further includes an upper shaft 136 which is coupled to a drive gear 138 (FIGS. 5 and 8) that engages a rack mounted on one side of the upper monorail 14. Shafts 132 and 136 are rotated by the actuation of motor 130 in the same direction such that the teeth on the drive gears 134 and 138 which engage the teeth on the racks 17 and 15, respectively, causing the mobile vertical lift 100 to travel along the monorails 14 and 16.  
  A carriage assembly 170 is mounted on the lifting platform 150 and comprises a base member 172 which is attached to the base 152 of the platform 150 by means of a pivot assembly 175 which permits the carriage 170 to pivot a sufficient amount such that the aligning means 160 (FIGS. 3, 11 and 12) associated with the guide rails 154 mounted on the carriage assembly 170 can align the carriage assembly rails with the guide rails 18 within the storage racks 10 (FIG. 3). In some installations, the carriage can be mounted to the lifting platform with rollers which permit lateral motion therebetween for aligning the tracks. The operation of the aligning means 160 in conjunction with the guide rails 154 on the carriage assembly 170 is best understood by referring to FIGS. 11-13.  
  In FIG. 11, a portion of the mobile vertical lift is shown with the guide rails 154 being illustrated in approximate horizontal alignment with the guide rails 18 of the storage racks. Each of the guide rails 154 on the carriage assembly has an aligning means 160 at the end adjacent the aisle as shown in the detailed plan view of FIG. 12. The left aligning means 160 shown in FIG. 12 comprises a trapezoidal-shaped (as viewed from the top) channel member having a similar cross section as the C-shaped channel member 19 forming the guide rails 18. The member 180 further includes a short section of rail at the bottom (not shown) similar to rail 26 in FIG. 13. Member 180 is pivotally coupled to the guide rail 154 by means of a pivot pin and mounting bracket 186. A second bracket 187 is coupled to the member 180 and includes a roller 188 at the top edge thereof rotatably mounted to the bracket 187 by means of an axle 189. The bracket 187 includes a pivot pin 191 adapted to pivotally hold the end of a shaft 192 of a solenoid 195 mounted to the bracket 186.  
  As the mobile vertical lift is positioned in general alignment with the guide rails 18 of a predetermined aisle level, solenoids 195 are actuated such that both the left and right trapezoidal members 180 (FIG. 11) swing inwardly in a manner such that a downward extension of their leading edge 182 (FIG. 12) will contact the stop plate arm 33 (FIGS. 4 and 11) to swing the plate 24 downwardly and out of the way. The trapezoidal members 180 come into full contact with the rails 18 thereby joining the rails 18 with the rails 154 and completing the track over which a transfer vehicle can travel between the mobile vertical lift and the aisle.  
  To insure accurate alignment, the mobile vertical lift platform 150 is initially positioned such that the rails 154 are slightly above rails 18. As the members 180 are swung inwardly, the rollers 188 will fit within the tapered trough 183 formed by the plate 184 which is welded to the ends of the rails 18 as shown in FIG. 13. Once the solenoids 195 are actuated, the lift platform 150 is lowered somewhat to allow the rollers 188 to contact the inner surface 184 of the plate 184, thereby positively forcing the trapezoidal member 180 into aligned engagement with the rail 18. The laterally movable carriage assembly 170 allows the rails 154 and, therefore, members 180 to move such that alignment is achieved.  
  In this manner, accurate alignment between the rails of the mobile vertical lift and those of the aisles is accomplished. The trapezoidal member is held in vertical support by means of the flat bottom portion 181 (FIGS. 3 and 11) of the guide rails 18 which are not tapered as are the top portions of the C-shaped channel member 19 forming the rails 18. Thus, as the platform 150 is lowered into position, the rollers 188 in conjunction with the trough 183 assure horizontal alignment of the rails 154 with the rails 18 while the protruding bottom portion 181 of the channel members 19 contact the lower portion of the trapezoidal member 180 to assure vertical alignment and support between the rails 154 and 18.  
  Various sensors, limit switches, and other control devices are mounted to the mobile vertical lift 100 and the rack structure 10 as shown in FIGS. 5 and 11 to provide position information as well as various control