Abstract:
Various designs of a spiral accumulator apparatus are disclosed for controlling the flow of articles. The accumulator may have an infeed conveyor driven in a first direction to convey articles therealong in the first direction along a first path that is at least partially curved, and an outfeed conveyor driven in an opposite direction to convey articles therealong in the opposite direction along a second path that is at least partially curved. The infeed and outfeed conveyors may be spaced apart and generally parallel along at least a portion of the first and second paths so as to define a space therebetween. A movable transport member may be disposed generally across and movable along the space, and an article transfer member may be carried by the transport member and operably disposed between the infeed and outfeed conveyors to transfer articles between the infeed conveyor and the outfeed conveyor. A transport member mover may be connected to the transport member. A differential drive mechanism may be located at a fixed position spaced from the transport member, the differential drive mechanism including an output portion for contacting and moving the transport member mover when a relative speed difference exists between the infeed and outfeed conveyors thereby causing the transport member to travel in the direction of the faster of the infeed and outfeed conveyors. The differential drive mechanism may include a plurality of gears, or it may include condition responsive devices and related motors and controls, for driving the transport member mover.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a spiral accumulator apparatus for controlling the flow of articles from an upstream delivery station to a downstream receiving station using a differential drive; and more particularly to an apparatus including an article transfer member moved via a remote differential drive mechanism. 
     BACKGROUND OF THE INVENTION 
     Accumulators have been utilized between an upstream delivery station and a downstream receiving station to accumulate articles when the capacity of the downstream receiving station is either shut down or run at a speed wherein it cannot handle the number of articles being fed by the upstream delivery station. One particular accumulator is disclosed in U.S. Pat. No. 4,018,325. One problem with such accumulators is that the last article fed into the accumulator is the first article fed out of the accumulator and, as a result, it is difficult to keep track of the batch from which a particular article came from, and the sequence in which the articles are fed from the upstream delivery station. 
     Accumulators have been made wherein the first article in is the first article out. Such “first in, first out” accumulators are sometimes known as “FIFO” accumulators. For example, the owner of the present application is also owner of U.S. Pat. Nos. 6,152,291, 6,182,812, 6,230,874, 6,260,688, 6,382,398, 6,497,321, 6,523,669, 6,533,103, 6,550,602, 6,585,104, and 6,612,420, all disclosing various aspects of FIFO conveyors, and all incorporated by references herein for all purposes. 
     Various of the above patents disclose accumulators having conveyors extending along multi-level curved paths, with a transfer mechanism disposed between the conveyors for transferring the conveyed objects between the conveyors. Such accumulators are commonly called spiral accumulators. As disclosed, the transfer mechanisms of such spiral accumulators may be driven by rotatable members which contact the oppositely moving conveyors (or attachments thereto) at the point of transfer. The rotatable members travel with the transfer mechanism along the conveyors, at a position dictated by the relative speeds of the conveyors. 
     SUMMARY OF THE INVENTION 
     According to some aspects of the invention, a spiral accumulator apparatus is disclosed for controlling the flow of articles. The accumulator includes a support structure, an infeed conveyor mounted to the support structure and driven in a first direction to convey articles therealong in the first direction along a first path that is at least partially curved, and an outfeed conveyor mounted to the support structure and driven in an opposite direction to convey articles therealong in the opposite direction along a second path that is at least partially curved. The infeed and outfeed conveyors are spaced apart and generally parallel along at least a portion of the first and second paths so as to define a space therebetween. A track is mounted to the support structure along at least a portion of the space, and a movable transport member is disposed generally across and movable along the space on the track. An article transfer member is carried by the transport member and operably disposed between the infeed and outfeed conveyors to transfer articles between the infeed conveyor and the outfeed conveyor. A transport member mover is connected to the transport member, the transport member mover including an endless loop. A differential drive mechanism is located at a fixed position spaced from the transport member. The differential drive mechanism includes an output portion for contacting and moving the transport member mover when a relative speed difference exists between the infeed and outfeed conveyors thereby causing the transport member to travel in the direction of the faster of the infeed and outfeed conveyors. Various options and alternatives are also available. 
     For example, if desired, the endless loop may be a belt, a cable, or any equivalent. The differential drive mechanism may include a plurality of gears. If so, the plurality of gears may include two input gears and a differential gear, one of the input gears being attached to an axle rotating at a speed related to that of the infeed conveyor and the other of the input gears being attached to an axle rotating at a speed related to that of the outfeed conveyor, the differential gear being driven by the two input gears so as to drive the output portion of the differential drive mechanism. 
     The differential drive mechanism may be operatively interconnected with axles driven by the infeed and outfeed conveyors. Also, the differential drive mechanism may include condition responsive devices for detecting directly or indirectly a speed of the infeed and outfeed conveyors, a motor, and a drive control for driving the motor based on the speeds of the infeed and outfeed conveyors so as to move the output portion of the differential drive mechanism at a desired speed. 
     Guide members may be mounted to the support structure for guiding the transport member mover, and the guide members may include geared or grooved pulleys and/or idler rollers. 
     The differential drive mechanism may drive the transport member mover at a speed equal to half the difference between the speeds of the infeed and outfeed conveyors. Also, the differential drive mechanism may drive the transport member mover at a speed proportional to as 1 −bs 2 , where s 1  is the speed of the infeed conveyor and s 2  is the speed of the outfeed conveyor, and a and b are adjustable parameters. 
     According to certain other aspects of the invention, a spiral accumulator apparatus is disclosed for controlling the flow of articles. The accumulator includes an infeed conveyor driven in a first direction to convey articles therealong in the first direction along a first path that is at least partially curved, and an outfeed conveyor driven in an opposite direction to convey articles therealong in the opposite direction along a second path that is at least partially curved. The infeed and outfeed conveyors are spaced apart and generally parallel along at least a portion of the first and second paths so as to define a space therebetween, and a movable transport member is disposed generally across and movable along the space. An article transfer member is carried by the transport member and operably disposed between the infeed and outfeed conveyors to transfer articles between the infeed conveyor and the outfeed conveyor, and a transport member mover is connected to the transport member. A differential drive mechanism is located at a fixed position spaced from the transport member, the differential drive mechanism including an output portion for contacting and moving the transport member mover when a relative speed difference exists between the infeed and outfeed conveyors thereby causing the transport member to travel in the direction of the faster of the infeed and outfeed conveyors. Various further options and alternatives are also possible with this accumulator, as above. 
     According to another aspect of the invention, a spiral accumulator apparatus for controlling the flow of articles is disclosed. The accumulator includes an infeed conveyor driven in a first direction to convey articles therealong in the first direction along a first path that is at least partially curved, and an outfeed conveyor driven in an opposite direction to convey articles therealong in the opposite direction along a second path that is at least partially curved. The infeed and outfeed conveyors are spaced apart and generally parallel along at least a portion of the first and second paths so as to define a space therebetween. A movable transport member is disposed generally across and movable along the space, and an article transfer member is carried by the transport member and operably disposed between the infeed and outfeed conveyors to transfer articles between the infeed conveyor and the outfeed conveyor. A transport member mover is connected to the transport member. A differential drive mechanism is located at a fixed position spaced from the transport member. The differential drive mechanism includes two input gears and a differential gear, one of the input gears being attached to an axle rotating at a speed related to that of the infeed conveyor and the other of the input gears being attached to an axle rotating at a speed related to that of the outfeed conveyor, the differential gear being driven by the two input gears so as to drive an output portion of the differential drive mechanism. The output portion contacts and moves the transport member mover when a relative speed difference exists between the infeed and outfeed conveyors thereby causing the transport member to travel in the direction of the faster of the infeed and outfeed conveyors. Again, various options and modifications are possible with this accumulator, as above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating an apparatus for controlling the flow of articles in its basic form. 
         FIG. 2  is a plan view of the apparatus of  FIG. 1  showing articles being loaded into the apparatus. 
         FIG. 3  is a plan view of a modified form of the design of FIG.  1 . 
         FIG. 4  is a schematic diagram illustrating an apparatus storing articles in a vertical spiral. 
         FIG. 5  is a perspective view of a transport member mounted on a track and attached to a transport member mover according to certain aspects of the invention. 
         FIG. 6  is a perspective view of a differential drive mechanism according to certain aspects of the present invention. 
         FIG. 7  is a partially exploded perspective view of the differential drive mechanism of FIG.  6 . 
         FIG. 8  is a perspective view of an alternate differential drive mechanism as in claim  6 , but with cable and pulley. 
         FIG. 9  is a schematic diagram of an alternate differential drive mechanism according to certain aspects of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1-4 , there is broadly illustrated an apparatus  10  for controlling the flow of articles A from an upstream delivery station to  12  a downstream receiving station  14 . The articles are carried on a main conveyor  16  that is driven by any conventional conveyor drive mechanism. The articles are fed along the main feed conveyor  16  until they reach apparatus  10 , at which point they exit conveyor  16  and enter apparatus  10 . Eventually, the articles are returned to main conveyor  16  in a FIFO sequence. 
     Apparatus  10  includes a support structure  18  that, as shown, may include various vertical members  20  and horizontal members  22 . The layout of support structure  18  may take any desired form depending on the size of and application for apparatus  10 . Thus, support structure  18  shown herein is merely an example, and any modifications to that shown should be considered as within the scope of the present invention.  FIGS. 1-3  show only vertical members  20  of support structure for clarity. 
     Apparatus  10  includes a deflecting rail  24  for deflecting articles A off the main conveyor  16  onto an infeed conveyor  26  carried on support structure  18 . Infeed conveyor  26  is an endless conveyor and is driven by an infeed drive mechanism  28 , which may include a variable speed motor  30  and a motor control  32 . 
     An outfeed conveyor  34  is also carried on support structure  18 . A substantial portion of the runs of the infeed and outfeed conveyors  26  and  34  are parallel to each other providing a space  36  therebetween. An outfeed drive mechanism  42 , which may include a variable speed motor  44  and a motor control  46 , drives the outfeed conveyor  34 . A deflecting rail  24  is also located so as to deflect articles off outfeed conveyor  34  back onto main conveyor  16 . 
     A transport member  38  rides on a track  40  carried by support structure  18  that permits the transport member to move backwards and forwards along the length of the infeed and outfeed conveyors  26  and  34 . Infeed drive mechanism  28  drives infeed conveyor  26  in a first direction on one side of track  40 , and outfeed drive mechanism  42  drives outfeed conveyor  34  in a second direction on the other side of the track. 
     A transport member mover  48  is operably connected to the transport member  38  and is driven by a differential drive mechanism  50 . The transport member mover  48  may comprise an endless loop such as a belt, chain, cable, or the like, that rides in or along track  40 . If desired, guide members  41  such as geared or grooved pulleys or idler rollers may be utilized to guide transport member mover  48 . 
     Differential drive mechanism  50  is mounted to support structure  18  and is operatively engaged with infeed and outfeed conveyors  26  and  34 . As will be discussed below in greater detail, differential drive mechanism includes two axles  52  and  54  joined at a differential housing  56 . Axles  52  and  54  rotate respectively with infeed and outfeed conveyors  26  and  34 , as a function of the speed of the conveyors. As shown, axles  52  and  54  are driven directly by contact with conveyors  26  and  34  via rollers  53  and  55 . However, it would also be possible to obtain input rotation speed information from other idler or driven members, rotated by conveyors or motors, both directly or indirectly, if desired. Transport member mover  48  rotates around an output portion of housing  56  as the housing moves, dependent on the differential speeds of shafts  52  and  54 , based ultimately on the conveyor speeds (see FIGS.  6 - 8 ). Accordingly, transport member  38  is driven relative to conveyors  26  and  34  along a path parallel to the conveyors, at a speed and direction depending on the relative speed of the conveyors. An article transfer member  58  is carried by transport member  38  for deflecting articles from infeed conveyor  26  to outfeed conveyor  34 . 
     The speeds of the conveyors  26  and  34  are controlled by drive mechanisms  28  and  42 . If the speed of outfeed conveyor  34  is slower than the speed of infeed conveyor  36 , then transport member  38  is moved in the counter-clockwise direction (as shown in FIGS.  1 - 3 ), thereby increasing the number of articles on the surfaces of the infeed conveyor and the outfeed conveyor for temporarily storing the articles in the accumulator  10 . If the speed of outfeed conveyor  34  is greater than the speed of infeed conveyor  26 , transport member  38  will move in a clockwise direction (as shown in FIGS.  1 - 3 ), thereby reducing the number of articles stored on the infeed and outfeed conveyors, with FIFO sequencing. 
     Condition responsive devices may be positioned along the conveyors for generating signals responsive to various conditions. For example, a condition responsive device  60  may be positioned adjacent to main conveyor  16  for sensing a backup of articles on the main conveyor; and if such a condition occurs a signal may be sent to a motor control  32  which causes the motor  30  to shift to a higher speed, thereby speeding up infeed conveyor  26 . The condition responsive device  60  may be any suitable conventional sensor, but in one particular embodiment it is a photocell provided with a timer so that if the photocell is activated for a certain period of time by non-movement of the article a signal is generated. The articles A carried on the main conveyor are spaced apart, and as long as the space is sensed between the articles in a given period of time then no signal is generated by the photocell to trigger an increase in speed of the infeed conveyor  26 . One suitable photocell is manufactured by Sick A.G. having a part number of WT4-2P135S10. Sick A.G. is located in Wldkirch, Germany. It is to be understood that any conventional suitable condition responsive device could be used at any of the locations where one is required. 
     Another condition responsive device  62  may be positioned along main conveyor  16  closely adjacent to the front end of the rail  24 . This device is provided to sense a backup on conveyor  16 , and causes a signal to be produced to reduce the speed of conveyor  16  to a medium speed. Another condition responsive device  64  may be positioned near the entrance of infeed conveyor  26  for sensing a lack of articles on the infeed conveyor. This sensor generates a signal to the stop the infeed conveyor when such a condition occurs. 
     There may be still another condition responsive device  66 , positioned adjacent to main conveyor  16 , where the articles are fed back onto the main conveyor. When a backup of articles is sensed by condition responsive device  66  on the main conveyor  16 , a signal is sent to motor control  46  to stop the outfeed conveyor  34 . A backup is sensed when the articles exiting off of outfeed conveyor  34  are pressed against each other on main conveyor  16 . 
     Under normal operation, main conveyor  16  is running at a higher speed than outfeed conveyor  34 , and as the articles are transferred from the outfeed conveyor onto the main conveyor a space is developed between the articles. Condition responsive device  66  is thus provided for ensuring that this space remains between the articles, and if the space is lost as a result of a backup of articles then the outfeed conveyor  34  is stopped. 
     A still further condition responsive device  68  may be positioned further down the line on main conveyor  16 , and when it senses that there is no space between articles being delivered back onto the main conveyor a signal is generated, which is fed to variable motor control  46  for outfeed conveyor  34 , for reducing the speed of variable speed motor  44 . 
     All of the signals generated by condition responsive devices  60 - 68  are fed to motor controllers  32  and  46  (or the controller for conveyor  16 , not shown), which may comprise conventional controllers such as a programmable logic controller. One suitable programmable logical controller is manufactured by Allen Bradley and has a model number of SLC500 series. Allen Bradley is located in Milwaukee, Wis. Other controllers may also be utilized within the scope of the invention. 
     In order for transport member  38  to move from the position shown in  FIG. 2  to the position shown in  FIG. 1  the speed of infeed conveyor  26  must be running faster than the speed of outfeed conveyor  34 . As a result, when transport member  38  is moved in a counter-clockwise direction it is loading articles from infeed conveyor  26  to outfeed conveyor  34  for storing the articles. As previously mentioned when the demand at the downstream receiving station increases then the speed of outfeed conveyor  34  will increase over the speed of infeed conveyor  26  via transport member mover  48 , and the transport member will move in a clockwise direction from the position shown in  FIG. 1  to the position shown in  FIG. 2  to unload the articles stored in the accumulator. The configuration for the parallel run of infeed conveyor  26  and the outfeed conveyor  34  can vary depending on the amount of floor space that is desired to be utilized for the accumulator. In  FIGS. 1 and 2  the configuration of the infeed and outfeed conveyors is in a spiral. In  FIG. 3  the configuration of infeed conveyor  26  and outfeed conveyor  34  is also in a spiral but it has an elongated middle portion. If there is sufficient floor space the run of the two conveyors can be in a horizontal plane. 
     As shown in  FIG. 4  the configuration of infeed conveyor  26  and outfeed conveyor  34  is in a vertical spiral so that a substantial amount of storage can be placed in a relatively small space. Sometimes as the height of the spiral increases it is necessary to additionally drive the infeed and outfeed conveyors along the vertical path of the spiral so as to minimize the drag of the conveyors on the track. The additional drive mechanism is shown in schematic form in FIG.  4 . 
     As can be seen in  FIG. 4  infeed conveyor  26  and outfeed conveyor  34  are endless conveyors. Infeed conveyor  26  is driven by motor  30 , and its path extends upwards from adjacent main conveyor  16  in a spiral configuration to pass over a drive sprocket  70  then down a vertical run through an idle sprocket  72  and back to the track which holds the conveyor in a vertical spiral. The track (not shown) for holding the conveyor may be of any suitable construction and is supported on vertical members  20  and horizontal members  22 . Outfeed conveyor  34  is driven by outfeed drive motor  44  by means of drive sprocket  74 . The conveyor belt  34  passes around idle sprockets  76  and  78  in its run. Infeed conveyor  26  and outfeed conveyor  34  may be constructed of any suitable conventional chain belt that has connecting links  80 , and in one particular embodiment has an upper surface such as shown in FIG.  5 . 
     One example of a gear-based differential drive mechanism useful with the spiral accumulator designs disclosed above is shown in more detail in  FIGS. 6 and 7 . As shown, the mechanism includes four bevel gears  82  A-D. The outfeed axle  52 , rotating (as shown) at the speed of the outfeed conveyor  34  (not shown, but traveling around rollers  53 ), is connected to the bevel gear  82 A. The infeed axle  54 , rotating (as shown) at the speed of infeed conveyor  26  (not shown, but traveling around rollers  55 ), is connected to opposite bevel gear  82 B. The gears mesh with gears  82 C and  82 D, which are coaxially and rotatably aligned as pinion gears on pinion shaft  84 . Couplings  86  retain the bevel gears in place on the axles and pinion shaft. The ends of pinion shaft  84  extend from a spider  88 , which also provides supports for axles  52 ,  54 . The differential mechanism fits in a hollow  90  formed in the center of two mating central housing halves  92 . The ends of pinion shaft  84  fit in cavities  94  formed radially in the housing halves. Metal plates  96  serve as thrust bearings. Dowels  98  register the two housing halves, which are held together conventionally by bolts or screws through holes  100 . A toothed sprocket wheel  102  is attached to each housing half. The peripheral teeth of the sprocket wheel engage a driven belt, comprising the transport member mover  48 , to drive it. 
     The geared differential works conventionally in that relative motion of shaft output bevel gears  82 A and  82 B causes pinion gears  82 C and  82 D to rotate about the axis of axles  52 ,  54 . As the pinion gears rotate, the ends of pinion shaft  84  cause housing  56  and sprocket wheels  102  to rotate. The speed of rotation depends on the relative speeds of the rotation of the output shaft bevel gears. In the situation where the outfeed conveyor and the infeed conveyor are moving at the same speed in opposite directions, outfeed output bevel gear  82 A rotates in one direction at a certain speed and the infeed output bevel gear  82 B rotates in the opposite direction at the same speed, which causes the pinion gear assembly to rest with its pinion shaft stationary. As one of the conveyors  26  or  34  speeds up relative to the other, differential drive mechanism  50  causes the housing and sprocket wheel assembly to rotate in the direction of the faster moving rotating assembly, but at half the difference between the speeds of each rotating assembly. Thus, in this example, the speed s of transport member mover  48  is given by: S=½ (s 1 −s 2 ), where s 1  is the speed of the faster-moving belt and s 2  is the speed of the slower-moving conveyor. Of course, the gearing ratios can be altered by the use of gear reducers or other conventional techniques to derive other speed relationships that maybe generically defined by s is proportional to as 1 −bs 2 , where a and b are parameters set by the effective gear ratios, for example. This would allow the transport member mover to be driven at a speed that is influenced relatively more by one of the conveyors than the other in special applications. Also, the ratios could be changed if the widths of the conveyors were not equal, which could be desirable in some situations. 
     As shown in  FIG. 8 , it would be possible to modify transport member mover  48 ′, for example by substituting a cable for the illustrated belt. If so, members  41  could be a pulley or the like, and guide track  40  would have to also be modified accordingly. Also, housing  56  would likely be modified as well, so that the output portion driving transport member mover  48 ′ would not necessarily be two, toothed sprocket wheels, but would comprise a groove  102 ′ for receiving the cable. Various other modifications would also be possible to transfer differential rotational motion from a differential housing to transport member mover. It should be understood that all such modifications and options are considered to be within the scope of the invention. 
     Another example of a differential drive mechanism useful with the above spiral accumulators is shown diagrammatically in FIG.  9 . As shown, differential drive  50 ′ includes a housing  56 ′ disposed between conveyors  26  and  34  for driving transport member mover  48 . As shown, transport member mover  48  is a cable but, as above other structures could be used with suitable corresponding modifications. Condition responsive devices such as an infeed conveyor speed sensor  104  and an outfeed conveyor speed sensor  106  are also provided. As shown schematically in  FIG. 9 , sensors  104  and  106  may measure the rotational speed of axles  52  and  54  directly, or in another way such as via related rotational axles or via differential housing  56 ′. Accordingly, sensors  104  and  106  may comprise optical or mechanical transducers or the like. Alternatively, sensors  104  and  106  could directly measure the speed of conveyors  26  or  34 . Sensors  104  and  106  are in communication with a motor controller  108  that drives a motor  110  depending on the sensed speeds. Controller  108  can use logic, along the lines described above, to determine an output speed and direction for housing  56 ′ and can drive motor  110  accordingly. Controller  108  may be a programmable logic controller, as described above. 
     While preferred embodiments of the invention have been described above, it is to be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. Thus, the embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. While particular embodiments of the invention have been described and shown, it will be understood by those of ordinary skill in this art that the present invention is not limited thereto since many modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the literal or equivalent scope of the appended claims.