Abstract:
The present invention is directed to an apparatus and method for transfer of various objects along a multi-level conveyor in a number of pallets, which are transported between levels by two elevators simultaneously going up or down on each end of the conveyor. Since there are two elevators and several conveying levels, it is possible to change the path of movement of pallets along the conveyor, thus, providing control over the path and number of cycles the objects spend on the conveyor. Hence, such configuration allows to change position of one pallet relative to another. Present invention significantly minimizes the size of conveyor systems as well as it allows to manipulate the amount of time each pallet spends inside the system. Furthermore, since each pallet moves one step at a time different technological processes (i.e. loading/unloading, testing, measuring etc.) can be done with products when pallets are stationary.

Description:
FIELD OF THE INVENTION 
     The present invention relates to moving objects on a conveyor. In particular, the invention relates to a multi-level conveying apparatus and a method of moving objects on a multi-level conveyor. 
     BACKGROUND OF THE INVENTION 
     Multi-level conveying systems are widely used in manufacturing facilities, such as assembly lines or the like, for treating products. One example of a well known treatment is drying painted articles. Typically, the product being mass produced is placed into a series of trays or the like, which move along the conveyor from level to level while the product is treated. In order for the particular treatment, such as drying, to be completed, the product requires a predetermined retention time in a designated space. One example of a designated space is a dryer chamber. 
     U.S. Pat. No. 1,881,063 discloses a multi-level conveyor apparatus which include a conveyor bounded by two elevators which advance trays through the entire conveyor from the top level sequentially to the bottom level. An additional track structure is required to return the trays to their starting position on the top level. However, the additional track structure reduces the efficiency of the multi-level conveyor by occupying space which could be used to increase the length of the conveyance path. 
     U.S. Pat. No. 5,466,290 discloses a multi-level conveyor which includes two sections and three elevators. Two of the elevators are located on the sides of the conveyor and and a third elevator is located in the middle between the two sections. 
     The carrier units are sequentially moved from the bottom level to the top level of the 1St section of the conveyor using the left and middle elevators. Then the carrier units are moved to the 2nd section via the top level directly connecting the first and the second sections. The carrier units then are moved from the top level to the bottom level of the 2nd section using the middle and right elevator this time. In Berta&#39;s invention there are a number of limitations. For example, the side elevators are only designed to move carrier units in one direction; more specifically the left elevator moves the objects only up and the right elevator moves the objects only down. Secondly, Berta&#39;s invention offers no control over the retention of objects on the conveyor, meaning once the objects have entered the system, they all undergo a similar treatment with no variation. Furthermore, possibility of changing the order of carriers on the conveyor might be of great importance and the Berta&#39;s invention offers no such flexibility. 
     Consequently, there is a need for an improved multi-level conveyor and a method of moving objects on a multi-level conveyor, which reduces the space required for a given length of conveyance path and offers better efficiency, control and flexibility. 
     There are 3 key aspects to the current invention. The first aspect of this invention covers a multi-level conveying apparatus with one set of transfer means. The second aspect of this invention covers the said conveying apparatus comprising multiple sets of transfer means. The third aspect covers the method of moving objects along specified predetermined paths. 
     SUMMARY OF THE INVENTION 
     The first aspect of this invention is a conveying apparatus comprising a plurality of levels and one set of transfer means. One set of transfer means includes separate, but identical devices for vertical transfer of pallets each located in the elevators on different sides of the conveying apparatus. 
     The second aspect of this invention is a conveying apparatus comprising a plurality of levels and multiple sets of transfer means. Each set of transfer means includes separate, but identical devices for vertical transfer of pallets each located in the elevators on different sides of the conveying apparatus. 
     The third aspect of this invention is the method of moving objects, which allows for efficient, controlled and flexible movement of the pallets. Said method permits for pallets to circulate throughout the said conveying apparatus along the same or different paths in cycles numerous amounts of times or to transfer pallets from any starting point to any ending point. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described by way of example only with reference to the accompanying drawings, in which: 
     FIG. 1A is a plan view of a conveying apparatus according to a preferred embodiment of the present invention; 
     FIG. 1B is an elevation view of the apparatus; 
     FIG. 2A is a plan view of a pallet for the apparatus; 
     FIG. 2B is a side view of the pallet; 
     FIG. 2C is an elevation view of the pallet; 
     FIG. 3A is a partial plan view of the apparatus showing a first and second elevator; 
     FIG. 3B is a partial elevation view of the apparatus showing a first and second elevator; 
     FIG. 3C is a partial side view of the apparatus showing an elevator; 
     FIG. 4A is an enlarged side view of the second elevator; 
     FIG. 4B is a partial cross-sectional view of the apparatus showing the grapple mechanism secured to the grapple housing in a position to withdraw the pallet from the conveyor; 
     FIG. 4C is a partial cross-sectional view of the apparatus showing the grapple mechanism secured to the grapple housing in a position to insert the pallet into the conveyor; 
     FIG. 4D is a partial cross-sectional view of the apparatus showing the grapple mechanism in a position to disengage from the grapple housing of the pallet; 
     FIGS. 5A-5M are schematic views of the advancement of pallets through one cycle of the elevators in accordance with the preferred embodiment present invention; and 
     FIGS. 6A-F are schematic views of the advancement of pallets through several cycles of the elevators, in accordance with the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1A and 1B, a conveyor  100  according to a preferred embodiment of the present invention is shown. To demonstrate the full potential of the present invention the preferred embodiment is presented with three sets of transfer means. Furthermore, for convenience, the preferred embodiment of the present invention is described in connection with drying plastic panels after, for example, assembly. However, it will be understood by those skilled in the art that the present invention may be used for any suitable application for a multi-level conveyor, including without limitation, freezing, warming, heating, irradiating, disinfecting, assembling, testing or melting of a wide variety of products. 
     Continuing to refer to FIGS. 1A and 1B, the conveyor  100  includes a plurality of spaced apart preferably horizontal levels  111 . Preferably, a plurality of pallets  103  are provided on the conveyor  100  for receiving and retaining the product. However, it will be understood by those skilled in the art that any other suitable means for retaining a product may be provided. Alternatively, the product, such as, for example a car or the like, may be advanced along the surface the conveyor  100  without the use of pallets. 
     The pallets  103  are moved along the conveyor  100  from level to level by cooperative actions of first and second elevators  200 ,  300 , as described in further detail below. Preferably, the starting position for each pallet  103  is below station A, where a plastic panel  101  is unloaded from each pallet  103 , as it passes under Station A. A new plastic panel may be loaded onto each pallets  103  as it passes under station B. Preferably, the end position is indicated by reference number  109 . The conveyor  100  may include additional stations C, D, and E where additional operations are performed. For example, glue may be applied to an item on each pallet  103  under station C, and an additional panel may be attached under station D. At station E, a conventional viewing station  108  may be provided to examine the contents of each pallet  103  and remove an article which does not meet quality control standards. Stations A-E utilize conventional robotic arms  102  or assemblers, which align, orient and dispense the products in each pallet  103 . 
     The conveyor  100  is preferably located in a conventional dryer  110 . The first elevator  200  and the second elevator  300  are located adjacent to each end of the conveyor  100 . The dryer  110 , and the elevators  200 ,  300  are aligned to permit airflow to pass over the pallets  103 . 
     As shown in FIGS. 2A-2C, each pallet  103  preferably includes frame  104 , holder  105  which retains the panel in the pallet during drying, grapple housing  106 , and preferably four wheels  107 . As best shown in FIG.  4 B, the grapple housing  106  has a cylindrical inner surface  402 . A groove  404  is defined in the inner surface. Three spring-loaded latches  406  are movably received in the groove  404 . 
     FIGS. 3A-3C show first and second elevators  200  and  300 , respectively. Each elevator  200 ,  300  includes a lift mechanism  201 ,  301  for raising and lowering thereof. Both first and second elevators can transfer pallets from higher to lower levels as well as from lower to higher. 
     Referring to FIG. 3A, the first elevator  200  includes a plurality of spaced apart first transfer means  220  and the second elevator  300  includes a plurality of spaced apart second transfer means  320 . The first and second transfer means  220 ,  320  are spaced apart the same distance as the levels  111  in order to align therewith. The first transfer means  220  and the second transfer means  320  may be vertically spaced apart by two levels of the conveyor  100 . In addition, each first transfer means  220  is aligned with a corresponding second transfer means  320  on opposite ends of the conveyor  100 . The first and second transfer means  220 ,  320  are moved between levels by the lift mechanism  201 ,  301  respectively. The first and second transfer means  220 ,  320  cooperate to remove pallets  103  from one level  111  of the conveyor  100  and insert pallets  103  in another level  111 , as described in more detail below. In the preferred embodiment, three first and second transfer means  220 ,  320  are provided in the first and second elevator  200 ,  300 , respectively, such that each of the corresponding pairs of first and second transfer means  220 ,  320  are positioned adjacent to opposite ends of three levels  111  and are spaced two levels apart, as best shown in FIG.  3 B. It will be understood by those skilled in the art that any number of first and second transfer means  220 ,  320  may be provided, so long as the relationship between the number transfer means at each end of the conveyor  100  and number of levels is in accordance with the equation: 
     
       
           N   L   =N   t   ×A+ 1  
       
     
     where N L  is the number of levels; N t  is the number of transfer means on one of the elevators; and A is the number of levels between transfer means on an elevator. 
     Continuing to refer to FIGS. 3A-3C, each first and second transfer means  220 ,  320  comprises a platform  203 ,  303 , for receiving pallets  103 , and a pusher  202 ,  302 . Each pusher  202 ,  302  includes a sliding push bar  211 ,  311  which bears against a side of the pallet  103  when on the platform  203 ,  303 . The platforms  203 ,  302  are moved by conventional vertical slide ball screw systems  204 ,  304 . Each vertical slide ball screw system  204 ,  304  includes an actuator  205 ,  305 , a screwed shaft  206 ,  306  which are connected with each other by endless chain  207 ,  307  and two vertical guide shafts  208 ,  308 . Pushers  202 ,  302  are moved to by corresponding conventional horizontal slide ball screw systems  210 ,  310 , which have a similar design to the vertical slide ball screw systems  204 ,  304 . The push-bars  211 ,  311  push out pallets  103  from first and second elevators  200 ,  300  onto the conveyor  100 . 
     Referring now to FIGS. 4A-D, push bar  311  includes a conventional self-releasing grapple mechanism  312  described in detail in  Mechanisms and Mechanical Devices Sourcebook  by Neil Selater and Nicolas P. Chironis, 3 rd  edition, p. 407, which is incorporated by reference herein. Referring to FIG. 4B, the grapple mechanism includes a rod  408  having a knob  410  connected to its distal end. The knob  410  has a recess  414  which accommodates a collar  412 . The collar  412  slides on the rod  408 . This grapple mechanism  312  removes pallet  103  from the conveyor  100  onto platform  303  of second elevator  300 , and pushes out pallet  103  from platform  303  onto the conveyor  100  at another level  111 , as described in more detail below. The grapple mechanism  312  releases pallet  103  from pusher  302  at the end of the stroke of the push bar  311 . 
     The operation of the conveying apparatus according to a preferred embodiment of the present invention will now be described. Referring to FIG. 4A, pusher  302  of each second transfer means  320  is simultaneously moved from the full stroke position to the dwell position shown in phantom at  313 . It will be understood by those skilled in the art that the word “simultaneously”, as used herein, means not only “at the same instant”, but can also include a delay between movement of transfer means, provided each transfer means in a particular elevator  200 ,  300  completes the appropriate action prior to movement of the elevator to its next position. 
     The action of this stroke of the pusher  302  causes grapple mechanism  312  (secured to the grapple housing  106 ) to move pallet  103  from the conveyor  100  onto the platform  303  of the second transfer means  320 . As best shown in FIG. 3B, three pallets  103  are simultaneously removed from three levels  111  of conveyor  100  onto three second platforms  303  of three transfer means  320 , in accordance with the preferred embodiment of the invention. The lift mechanisms  201 ,  301  move the first and second elevators  200 ,  300  to another level where the pallets  103  are inserted as described in detail below. 
     The push bar  311  of pusher  302  of each transfer means  320  moves from dwell position  313  to the full stroke position shown in FIG.  4 A. The action of this stroke causes the three pallets  103  in second elevator  301  to be inserted into the conveyor  100 . In addition, the stroke of the push bar  311  moves the collar  412  of the grapple mechanism  312  from the position shown in FIG. 4B to the position shown in FIG.  4 C. 
     Referring to FIGS. 1B and 4A, pushers  202  and  302  are programmed by known means to work together, so that when pusher  302  pushes out pallet  103  from second elevator  301  onto conveyor  100 , pusher  202  is in dwell position  213 . The inserted pallet advances all of the other pallets on that level, such that pallet  103 , which is adjacent to the first elevator  200 , is transferred from the conveyor  100  onto the platform  203 . Pushers  302  are then moved back to the dwell position  313 . Simultaneously, grapple mechanism  312  releases the inserted pallet as described in detail below. 
     Referring in FIG. 4D, as the grapple mechanism  312  begins to move away from the pallet  103 , collar  412  is forced into the recess  414  (shown in FIG. 4B) in knob  410 . The shape of the collar  412  permits the collar  412  to push the latches  402  into the groove  404  (shown in FIG. 4B) of grapple housing  106 , thereby permitting the knob  410  to be released from grapple housing  106 . 
     Referring again to FIG. 3B, lift mechanism  201  moves the first elevator  200  with pallet  103  on platform  203  to a position aligned with another level  111 . The empty second elevator  300  is moved to align with the same level. The pusher  202  is moved from the dwell position  213  to the full stroke position. The action of this stroke causes the pallet  103  in first elevator  200  to be introduced into the conveyor  100  and to move the remaining pallets  103  on that level. Pusher  302  is then moved to the full stroke position and grapple mechanism  312  secures transfer means  320  to the adjacent pallet  103 , as described in detail below. This cycle is then repeated continuously to advance the pallets  103  along the conveyor  100 , as described in more detail below. 
     Referring now to FIG. 4B, the knob  410  of grapple mechanism  312  pushes latches  406  into groove  408  and enters the grapple housing  106 . After knob  410  passes the latches  406 , the latches spring back, thereby securing the knob  410  inside the grapple housing  106 . 
     FIGS. 5 and 6 show the movement of the pallets on the conveyor through one cycle of first and second elevators  200 ,  300 , in accordance with a preferred embodiment of the invention. To more clearly illustrate the pattern of movement, each the pallets  103  on the conveyor have been assigned reference numbers  1  to  41  in FIGS. 5 and 6. 
     Referring now to FIGS. 5A-B, pallets  6 ,  18 , and  30  are removed (as described above) from levels  111   a ,  111   c , and  111   e , respectively by each of the three second transfer means  320  of second elevator  300 . 
     Referring to FIG. 5C, first and second elevators  200 ,  300  move down one level, such that transfer means  220 ,  320  align with levels  111   b ,  111   d , and  111   f.    
     Referring to FIGS. 5D-E, second transfer means  320  insert pallets  6 ,  18 , and  30  onto levels  111   b ,  111   d , and  111   e , respectively. The insertion also advances all of the pallets on those levels toward first elevator  200 , such that pallets  7 ,  19 , and  31  are pushed onto each of the first transfer means  220 . 
     Referring to FIG. 5F, first and second elevators  200 ,  300  move down one level such that transfer means  220 ,  320  align with levels  111   c ,  111   e , and  111   g.    
     Referring now to FIG. 5G, first transfer means  220  insert pallets  7 ,  19 , and  31  onto levels  111   c ,  111   e , and  111   g , respectively, thereby advancing all of the pallets on those levels toward second elevator  300 . Pallets  17 ,  29 , and  41  are advanced adjacent to second elevator  300 , where grapple mechanism  312  of each second transfer means  320  engages the pallets  17 ,  29 , and  41 . 
     Referring to FIGS. 5H-I, pallets  17 ,  29 , and  41  are removed onto second elevator  300 , and first and second elevators  200 ,  300  move up one level to align with levels  111   b, d , and  f  of the conveyor  100 . 
     Referring to FIGS. 5J-K, pallets  17 ,  29 , and  41  are inserted at levels  111   b, d , and  f , while at the same time grapple mechanism  312  releases the pallets. The insertion of pallets  17 ,  29 , and  41  advances all of the pallets on those levels, such that pallets  8 ,  20 , and  41  are moved onto the first transfer means  220  of first elevator  200 . 
     Referring to FIGS. 5L-M, pallets  8 ,  20 , and  41  move up one level to align with levels  111   a, c , and  e  and are inserted on these levels. 
     Grapple mechanism  312  engages pallets  5 ,  16 , and  28 , and the cycle repeats. 
     FIGS. 6A-E show the pattern of movement of the pallets through several cycles of the elevators  200 ,  300 , in accordance with a preferred embodiment of the invention. In particular, on levels  111   a, c, e , and g, the pallets move from left to right while on levels  111   b, d , and  f , the pallets move in the opposite direction. For example, pallet  2  is shown in FIG. 6A in the starting position and moves sequentially to the right, as shown in FIGS.  6 B-E. Referring to FIG. 6F, pallet  16  is transferred to level  111   b , where it moves to the left. Pallet  41  is shown in the end position in FIG.  6 A. As shown in FIG. 6B, pallet  41  is transferred to level  111   f . Pallet  41  then moves to the left along  111   f , as shown in FIGS. 6C-F, as it returns to the starting position. It will be understood by those skilled in the art that any position may be chosen as the starting position. 
     The described above cycle can be broken down into a number of basic procedures, which consist of lowering or raising the elevator with pallets one or more levels. This basic procedure can be performed many times. Changing the sequence in which one basic procedure is done after another allows to control the path of a pallet inside the system, thus, making it possible to predetermine and differ Paths for any specific group of pallets. This allows one group pallets loaded with the same product to undergo one treatment, while another group of pellets loaded with another product can undergo a different treatment. As a result of altering paths, relative position of any one pallet comparative to another can be varied according to the requirements. 
     Referring again to FIGS. 5A-M, when the elevators  200 ,  300  are empty (i.e. no pallets on platforms  203 ,  303 ), there is preferably an even number of pallets on each level  111   b-f . However, the preferred embodiment of the present invention does not require the number of pallets  103  on levels  111   b-f  to be equal, provided there is an even number of pallets  103  on each level  111   b-f . An even number of pallets  103  is not required for the top and bottom levels  111   a  and  111   g , respectively. 
     The present invention increases the conveyance path over prior art multi-level conveyors by returning the pallets to the starting position through the conveyor rather than using a separate apparatus outside the conveyor. Furthermore, the present invention increases the output of the conveyor by utilizing first and second elevators  200 ,  300  which can transfer multiple pallets between levels simultaneously. In a preferred embodiment of the invention, multiple pallets are transferred by multiple transfer means  220 ,  320  on each of the first and second elevators  200 ,  300 . In order to increase output in a system with one transfer means per elevator, a more complex and costly elevator and transfer means is required. Even with additional complexity and expense, the output of a conveyor using elevators with one transfer means is limited. Consequently, the present invention provides the advantage of maintaining output even as the number of levels on the conveyor are increased by increasing the number of transfer means. 
     While the present invention as herein shown and described in detail is fully capable of attaining the above-described objectives of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and thus, is representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described preferred embodiment that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it is to be encompassed by the present claims.