Abstract:
A overhead transport system with load-bearing members, in particular transverse bars for attachment of loads, includes running rails which extend in at least two horizontal planes in spaced-apart, parallel disposition, and at least one crane which travels in an upper one of the planes transversely to the running rails for transfer of the load-bearing members from one running rail to another running rail. In order to provide the overhead transport system in a cost-efficient manner with two production or treatment planes while yet saving time as far as transfer of the load-bearing members is concerned, the transfer of the load-bearing members in a lower one of the planes is realized by at least one self-propelled transfer vehicle which travels transversely to the running rails.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of German Patent Application Serial No. 199 00 688, filed Jan. 5, 1999, subject matter of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates, in general, to an overhead transport system for moving loads, and more particularly to a transport system of a type including load-bearing members which travel along running rails extending at least in two horizontal planes in spaced-apart parallel disposition, and a crane which travels in an upper one of the planes transversely to the running rails for transfer of the load-bearing members from one running rail to another running rail. 
     It is known from the magazine “Materialfluss”, April 1982, pages 31-34, to provide a crane assembly with several production planes. A transfer of loads is normally realized by several cranes whereby the loads are suspended from load-bearing members which are provided with running gears. The cranes travel in the upper plane transversely to the running rails and are designed to transfer load-bearing members from a running rail of one plane to a running rail of another plane. In addition to the transfer of the load-bearing members in vertical direction, the cranes also carry out a transfer of load-bearing members between running rails in a same plane. This type of crane assembly suffers shortcomings because a time-efficient operation of the transfer procedures requires the use of several cranes. As a consequence, the overall costs are relatively high; yet the provision of several cranes still fails to effectively reduce the time for carrying out the transfer procedures as cranes of this type are slow in operation. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention to provide an improved overhead transport system, obviating the afore-stated drawbacks. 
     In particular, it is an object of the present invention to provide an improved overhead transport system which includes at least two production planes in a cost-efficient manner while still being able to effectively reduce the overall transfer times. 
     These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a first rail system positioned in a horizontal plane and including running rails for travel of load-bearing members; a second rail system located in a horizontal plane in parallel, spaced-apart disposition to the first rail system and including running rails for travel of load-bearing members; a crane traveling in an upper one of the planes of the first and second rail systems in a transverse direction to the running rails for transferring the load-bearing members from one of the running rails to another one of the running rail; and a self-propelled transfer vehicle traveling in a lower one of the planes of the first and second rail systems in a direction transversely to the running rails for transferring load-bearing members in the lower one of the planes. 
     Through the provision of a separate, self-propelled transfer vehicle, the transfer of load-bearing members in the lower one of, for example, two vertically spaced planes does no longer require the use of a crane but is assumed by the much more agile transfer vehicle which is of much simpler structure than the crane, and attain a reduction of transfer times. The crane is thus used primarily used for transfers in the upper plane and for transfers between the upper and lower planes. 
     The time for transfer of a load-bearing member from and to a running rail can be kept brief, when providing rail elements which are shiftable for alignment with ends of the running rails for receiving at least one load-bearing member from one running rail and transfer thereof to another running rail, with the rail elements being shiftable together with the one load-bearing member. Thus, the load-bearing members travel, for example, from one running rail onto the rail element of the transfer vehicle and can be placed into alignment with another running rail to enable the load-bearing member to travel from the rail element to this running rail. Suitably, at least one of the rail elements is arranged on the transfer vehicle. Thus, the transfer vehicle can then move he desired running rail in position for receiving or transfer of at least one load-bearing member. 
     According to another feature of the present invention, the transfer vehicle can self-propel to a position adjacent a desired end of the running rail for connection of the rail element with the respective running rail, so that short transfer periods are attained in the respective plane with the transfer vehicle. The time for travel as well as for precise positioning can thereby be kept small. 
     In a simple configuration, the rail element may be a running rail portion for support and guidance of the load-bearing member. This results in a cost-efficient design, as the running gears can be precisely matched to the shape and size of these running rails. Suitably, the running rail portion is designed rectilinear. 
     According to another feature of the present invention, the transfer vehicle may include two rail elements in parallel, spaced-apart disposition. This configuration is suitable when long travel paths are involved, as two running rails may be used simultaneously, or the same running rail can be used successively for reducing the travel time. 
     Suitably, the stability of the rail element can be increased by arranging each running rail on a support beam. The support beam is of massive configuration so that the overall system of support beam-rail element can be supported on both ends of the support beam. A transfer of the rail element by the crane can suitably realized together with the support beam in a same plane or from one plane to another plane. A precise positioning, in particular during placement of a support beam by the crane into the lower plane, can be realized by providing two funnel-shaped receptacles in which both ends of the support beam automatically position themselves. 
     According to another aspect of the present invention, the load-bearing members are provided with running gears to permit the load-bearing members to self-propel themselves onto the rail element. This may be carried out immediately after connection of the running rails, so as to secure also in this case short transfer times. It is, however, also possible to pull the load-bearing member onto the running rail or to push the load-bearing member from the running rail. This is advantageous because transport assignments can be separated from one another. 
     According to another aspect of the present invention, the transfer vehicle and/or the crane travel in a corridor, with the running rails being arranged in at least one of the planes at either side of the corridor in a direction transversely to the longitudinal axis of the corridor. As a result continuous running rails are realized during traverse of the transfer vehicle so that aligned running rails, separated only by the corridor, are temporarily connected for through-passage for a load-bearing member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects, features and advantages of the present invention will be more readily apparent upon reading the following description of a preferred exemplified embodiment of the invention with reference to the accompanying drawing, in which: 
     FIG. 1 is a schematic illustration of an overhead transport system in accordance with the present invention; 
     FIG. 2 is a plan view of a lower production plane of the overhead transport system of FIG. 1; 
     FIG. 3 is a plan view of an upper production plane of the overhead transport system of FIG. 1; 
     FIG. 4 is a schematic illustration, on an enlarged scale, of a crane used in the overhead transport system of FIG. 1; 
     FIG. 4 a  is a schematic illustration, on an enlarged scale, of a transfer vehicle used in the overhead transport system of FIG. 1; 
     FIG. 5 is a schematic illustration of an overhead crane during transfer of a support beam from an upper production plane to a lower production plane; and 
     FIG. 6 is a schematic illustration of the transfer vehicle. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. 
     Turning now to the drawing, and in particular to FIG. 1, there is shown a schematic illustration of an overhead transport system in accordance with the present invention, including load-bearing members  1  in the form of traverse bars from which loads  2 , schematically illustrated here, are suspended. In the non-limiting example, involved here, the overhead transport system has two horizontal production planes  3 ,  4  which extend above one another in spaced-apart relation. Each production plane  3 ,  4  has running rails  5  along which the load-bearing members  1  travel via self-powered running gears  6  which have attached thereon the traverse bars of the load-bearing members  1 . The running rails  5  may be formed as profiled hollow rails along which rollers, schematically illustrated in FIGS. 2 and 3 and denoted by reference numeral  6   a , of the running gears  6  roll. The running rails  5  of the upper and lower production planes  3 ,  4  extend horizontally at vertical distance from one another. Persons skilled in the art will appreciate that it is also conceivable to combine the load-bearing members  1  with a suitable device by which the load-bearing members  1  can be pulled onto or pushed from the running rail. 
     In a mid-section thereof, the overhead transport system includes in the upper plane  4  a suspended crane  7 , which may also be configured as transport carriage with crane-inherent functionality through provision of a conventional drive  30 , symbolically shown in FIG. 3 by broken line, and in the lower production plane  3  a self-propelled transfer vehicle  8  including a conventional drive  31  symbolically shown in FIG. 2 by broken line. Both, the crane  7  and the transfer vehicle  8  travel transversely to the running rails  5  of the production planes  3 ,  4 . As shown in FIG. 2, which is a plan view of the lower production plane  3  of the overhead transport system of FIG. 1, the running rails  5  extend in a common plane on both sides of a corridor  9  in parallel relation. Demarcating the corridor  9  are rails  11  which extend perpendicular to the running rails  5  for travel of the transfer vehicle  8  in a direction transversely to the running rails  5 . Thus, the lower production plane  3  is separated by the corridor  9  into two zones, with one zone, shown on the left-hand side of FIG. 2, including several separate booths  12 ,  13 ,  22  for processing loads  2 , for example metal sheets, machine parts or other workpieces, transported by the load-bearing members  1 . Reference numeral  12  may constitute, for example, an automated booth  12  for automatic spray painting of the workpieces, reference numeral  13  may refer to manually-operated booths in which the workpieces are manually re-painted, and reference numeral  22  may refer to a booth in which the workpieces are finished by cleansing, priming and/or grinding. The other zone of the lower production plane  3 , shown to the right of the corridor  9  in FIG. 2, may include a flash-off chamber  14  in which the workpieces can also cool down and can be buffered. The flash-off chamber  14  includes a plurality of parallel running rails which are numbered consecutively to the right thereof, with running rails  5   c  being extended with exit rails  5   d  for discharge of load-bearing members  1 . 
     The transfer vehicle  8  includes two rail elements  15  in spaced-apart parallel relation, with each rail element  15  being configured as rectilinear running rail portion  15   a.  In the position of the transfer vehicle  8 , shown in FIG. 2, the running rail marked  5   a  to the left of the corridor  9  and the running rail marked  5   b  to the right of the corridor  9  are in alignment with the leading running rail portion  15   a  to thereby realize a continuous running rail. Thus, a load-bearing member  1  can travel in this constellation under the power of its running gear  6  without interruption from the automated booth  12  to the flash-off chamber  14 . Normally, the load  2  suspended from the load-bearing member  1  is moved or self-propels, however, from the automated booth  12  to the transfer vehicle  8  which then travels transversely to the running rails  5 —i.e. downwards in the illustration of FIG.  2 —for transfer of the load-bearing member  1  with the load  2 , for example, to the running rail  5  of one of the manually-operated booths  13  or to a running rail  5  of the flash-off chamber  14 . Reference numeral  24  designates doors which are open in areas where running rails  5  are located to provide access thereto. 
     It will be appreciated by persons skilled in the art that the transfer vehicle  8  contains additional mechanical apparatus which does not appear in the foregoing Figures, e.g. a drive unit to propel the transfer vehicle for travel along the rails  11  or a brake mechanism. Additionally, persons skilled in the art will understand that a suitable control mechanism must be provided to monitor the overall operation of the transport system, i.e. operation of the crane  7  and the transfer vehicle  8  as well as movement of the running gears  6  when the running rails  5  are aligned with the rail elements  15  of the crane  7  and/or the rail elements  15  of the transfer vehicle  8 . However, these components have been omitted from the Figures for the sake of simplicity. 
     As further shown in FIG. 21 both rail elements  15  of the transfer vehicle  8  can be brought simultaneously in alignment with two successive running rails  15  of the right hand booth  14  to thereby enhance the versatility of the transfer vehicle  8 , while only one of the rail elements  15  of the transfer vehicle  8  can be aligned with the running rails on the left hand side. 
     FIG. 3 shows a plan view of the upper production plane  4 . The crane  7  is located in the mid-section of the overhead transport system and travels along parallel rails  16  which demarcate the corridor  9  and extend perpendicular to the running rails  5 . The running rails  5  extend in parallel relation to the right of the corridor  9  in a compartment  17  which may be a kiln. 
     FIGS. 4 and 4 a  show, on an enlarged scale, cutaway views of the mid-section of the overhead transport system, illustrating in more detail the crane  7  and the transfer vehicle  8 , respectively. As shown in FIG. 4, the rail element  15  of the crane  7  is mounted to the bottom side of a support beam  18  which extends parallel to the rail element  15  and provides an even support of the rail element  15  over its entire length. Further shown in FIG. 4 is the aligned connection of the rail element  15  and a running rail  5  in booth  17 , to thereby allow a transfer of the load-bearing member  1  from the rail element  15  to the opposite running rail  5 . 
     The support beam  18  is formed on both ends with forked prolongations  19  which can be placed in receptacles  20  lined adjacent to the rails  16 , as shown schematically in FIG.  3 . Elevating and lowering of the support beam  18  is realized by the crane  7  via a lifting device  21 , which is shown in FIG. 4 only schematically Via the, lifting device  21 , the crane  7  can thus move the support beam  18  together with its rail element  15  in the upper production planes  4  into alignment with a desired running rail  5  for transfer of the respective load-bearing member  1 . In addition, the lifting device  21  can lower the support beam  18  to the lower production plane  3  which is lined adjacent the rails  11  with stationary receptacles  23  to receive the support beam  18 , as shown schematically in FIG. 5 which illustrates the phase during descent of the support beam  18  for placement in a respective one of the receptacles  23 . As shown in FIG. 4 a , the receptacles  23  have a funnel-shaped top to facilitate placement of the prolongations  19  when the support beam  18  is lowered by the crane  7 . During descent, the prolongations  19  can fold inwardly to prevent interference with other parts. Thus, as indicated by arrow  25 , the load-bearing members  1  can be shuttled by the crane  7  in the upper plane to the desired locations in the booth  17 , and in addition can be dropped to a desired location in the lower production plane  3 . 
     Transfer of load-bearing members  1  in the lower production plane  3  is, carried out by the transfer vehicle  8  which can run in a more rapid fashion than the crane  7 . Clearly shown in FIG. 4 a  is the alignment of the rail elements  15  on opposite ends thereof with a respective running rail  5  to thereby allow a traveling of the load-bearing member  1  from one running rail  5  to the opposite running rail  5 . As shown in FIGS. 4 a,    6 , the rail elements  15  of the transfer vehicle  8  are secured to a support beam  28  which is received on opposite sides via prolongations  29  in receptacles  24 . The support beam  28 , like the support  18  for the crane  7 , provides even backing of the rail elements  15  during operation over their entire length. Thus, as indicated by arrow  26 , in the lower production plane  3 , the load-bearing members  1  can be selectively shuttled from a running rail  5  of one zone to a running rail of another zone. 
     While the invention has been illustrated and described as embodied in an overhead transport system, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.