Abstract:
A method of accumulating products traveling in a conveyor system according to system conditions including: receiving products from an infeed conveyor onto a first conveyor in an accumulator; transferring by a carriage products from the first conveyor to a second conveyor in the accumulator; moving products from the second conveyor to an outfeed conveyor; detecting a density of products moving on the second conveyor; and moving the carriage with along the first and second conveyors if the detected density is above a certain density value.

Description:
CROSS-REFERENCE TO PRIORITY APPLICATION 
     This application is a non-provisional of and claims benefit of U.S. Provisional Application No. 62/031,256, filed Jul. 31, 2014, which is incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to the managing of a flow of products on a production or assembly line using an accumulator to compensate for variations in the flow of product on the line. The invention specifically relates to controlling a carriage (also referred to as a car) in an accumulator. 
     A production or assembly line often uses conveyors to move products, such as bottles, cans and boxed items. The lines include stations each of which perform a task associated with the product, such as filling the product package, labeling the product and arranging the products for bulk transport. Conveyors move the products from one station another. Excessive numbers of products do not to gather at any one station, because each subsequent station processes products at least as fast as, and often at least slightly faster than the preceding station. 
     If an event causes a station to stop or slow, the oncoming products on the line gather at the station. Difficulties arise due to excessive numbers of products attempting to enter the station. To avoid having products gather excessively at a station, it would be helpful to temporarily extend the upstream conveyor to provide additional area along the conveyor to gather products until the stopped or slowed station resumes normal processing of products. 
     Temporary extensions of conveyors are provided by accumulators. An accumulator is typically an adjustable spur in a conveyor, referred to as the main line conveyor. Products can be moved onto the accumulator to temporarily divert products from the main line conveyor. The accumulator generally includes a pair of side-by-side conveyors operating in opposite directions. Products move along one of the conveyors and are transferred by a carriage to another conveyor before the products are returned to the main line conveyor. 
     While the carriage is at the front of the accumulator, products move quickly through the accumulator and are returned to the main line conveyor with only a minimal delay due to the accumulator. While the carriage is at the rear of the accumulator, products travel the full length of both conveyors in the accumulator which causes a substantial delay before products are returned to the main line conveyor. The length of the period that products are on the accumulator, and thus off of the main line conveyor, depends on the position of the carriage. 
     The carriage is moved along the conveyors of the accumulator to adjust the period during which products are on the accumulator and diverted from the main line conveyor. The further the carriage moves from the front of the accumulator, the longer the products remain on the accumulator conveyors and off the main line conveyor. By moving the carriage, the accumulator provides a means for delaying the movement of products along a main line conveyor, and thus delays the movement of products towards a stopped or slowed station. 
     Accumulators are disclosed in, for example, U.S. Pat. Nos. 4,313,724; 6,497,321, and 8,573,380. These patents describe various techniques for controlling the movement of the carriage and the conveyors in an accumulator. Conventional accumulators typically move the carriage based on the movement of the conveyors or based on manual controls. 
     BRIEF SUMMARY OF THE INVENTION 
     There remains a long felt need for an accumulator that is responsive to the flow of products through a conveyor system and, particularly, to excessive numbers of products gathering on a conveyor or in a particular section of a conveyor. An accumulator has been conceived and is disclosed here that monitors the density of products on a conveyor. If the density increases beyond a threshold, the carriage of the accumulator moves to increase the length available for the products to travel on the accumulator before being returned to a main line, and thus increases the capacity of the conveyor system. By monitoring density of product on a conveyor, the accumulator automatically responds when additional conveyor capacity is needed and before an excessive number of products accumulate on a conveyor. 
     To aid in reliably and consistently maintaining the flow of goods being sent through a production line, a production line system featuring a density-based carriage control system has been conceived and is disclosed that includes: a pair of conveyor systems oriented and moving in different directions, an infeed section connected to a first conveyor of the pair on which products move from a main line conveyor, an outfeed section connected to a second conveyor of the pair on which products move back to the main line conveyor, at least one density sensor mounted over at least one of the pair of conveyors, and a carriage that moves over the pair of conveyors and is configured to transfer products form the first conveyor to the second conveyor, wherein the carriage is moved based on product density information gathered from the at least one density sensor. 
     A method of moving products along a main line conveyor has been conceived and is disclosed comprising: arranging a pair of conveyors of an accumulator to be adjacent to each other and oriented to receive products from the main line conveyor and return the products to the main line conveyor, providing at least one density sensor over top of a section of at least one of the conveyors and/or the main line conveyor, providing a carriage to transfer products traveling in a first direction on the first of the pair of conveyors to a second of the pair of conveyors, and moving the carriage based on the information gathered by the at least one density sensor to avoid an excessive density of product on the main line conveyor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic top view of an accumulator forming a spur in a main line conveyor. 
         FIG. 2  is a perspective view of the carriage of the accumulator shown in  FIG. 1 . 
         FIG. 3  is a schematic top view of another embodiment of an accumulator connected to a main line conveyor. 
         FIG. 4  is a schematic showing the logic process followed by the accumulator to determine the movement of the carriage. 
         FIG. 5( a )  illustrates a conveyor with a high density of products. 
         FIG. 5( b )  illustrates a conveyor with a lower density of products. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to the use of density sensors, e.g., image sensors, capable of measuring density of products being transported on a conveyor system in real time and using data on product density to control an accumulator and particularly the movement of a carriage in an accumulator. The term density may refer to, for example, the number of products within a field of view of a sensor, the intensity of light or the imaged area having more than a light threshold level or a certain color of light reflected from the products in the field of view, and the rate of products passing the sensor or a certain region of a main line conveyor. The sensors may have internal processing capacity such that they directly control the movement of the carriage. Alternatively, the sensors may send signals to an external computer system which controls the carriage. The sensors may employ conventional time-of-flight (TOF) camera technology, three-dimensional TOF camera technology, structured light projection and imaging technology and other types of machine imaging technologies to sense the density of products moving on a conveyor. 
     The sensors are positioned to monitor at least one or both of the flow of products approaching the carriage body from an upstream conveyor and the flow of products leaving from the carriage body to a downstream conveyor. The sensors provide density data that represents the density of products as they move along the conveyors, e.g., move in real time. The density data is used to control the movement of the carriage. The carriage may move independently of the movement of the individual conveyors bringing products to or directing products away from the carriage. 
     The system described herein incorporates sensors and a computer system comprising at least a processor or controller and a non-transitory storage apparatus. The storage apparatus is configured to contain at least one executable program with instructions for operating the accumulator system described herein. The processor may be embedded in one or more of the sensors or included in a separate computer or control system. 
       FIG. 1  illustrates an accumulator  100  that includes a first density sensor  103  over an infeed measurement section  102  of a first main conveyor system  101 . Density information from the first density sensor  103  indicates to a controller  110  the density in real time of incoming products moving in direction  104  on the first main conveyor. Density information from the first density sensor  103  indicating that the density of products passing under the infeed measurement system is below a threshold density causes the carriage body to be moved forward in direction  114  towards a first end  105  of the accumulator. The carriage body  120  moves forward until it (1) reaches a maximum forward point (indicated by first carriage limit sensor  107 ) or (2) the density sensed in the infeed measurement section reaches a predetermined value, at which point, forward movement of the carriage would cease. Carriage system  120  is moved towards the first end  105  by first end carriage body actuator  122  and first end carriage belt  124 . 
     In response to the first density sensor  103  indicating a density of products above the threshold passing the infeed section  102 , the accumulator may optionally consult a second density sensor  113  to measure the density of products successfully transferred from the first conveyor  106  to the second conveyor  116  by the carriage  120  which may have a curved portion  121  to facilitate the transfer of products between the conveyors of the accumulator. Curved portion  121  may be powered and may feature a moving surface to assist with transferring products from first conveyor  106  to second conveyor  116 . Curved portion  121  may extend the width of the carriage body, with the portion  126  on the discharge side of the sensor bridge  130  being any acceptable shape, including flat, slanted, or curved. 
     In the event that first density sensor  103  indicates a density, e.g., number, of products reaching the system via the infeed system  102  at or above the threshold and the second density sensor  113  indicates a density of products being transferred to the second conveyor  116  is above another threshold, the carriage system  120  will move in a direction towards the second end  115  of the accumulation system  100  until either (1) the density measured by one of the density sensors drops below their respective threshold values, or (2) the carriage system  120  reaches a maximum second location (indicated by second carriage limit sensor  117 ). Carriage system  120  is moved towards the second end  115  by second end carriage body actuator  123  and second end carriage belt  125 . 
       FIG. 2  is a perspective view of the carriage body system from the side of the second conveyor system  216 . Viewing the carriage body from this perspective, understanding the flow of goods becomes more apparent, as products originating upstream travel along first conveyor system  206  until they pass under first carriage cross bar  208  and come into contact with the curved surface  221  of carriage body  220 . As mentioned, curved surface  221  may be powered and supply movement and/or grip to assist with moving products from first conveyor  206  to second conveyor  216 . As the products cross to the second conveyor  216 , they pass through outfeed density measurement area  212 , which is underneath outfeed density sensor  213 , and under second carriage cross bar  218  as they travel downstream on second conveyor  216 . 
     Additionally, the carriage body system  200  illustrated in  FIG. 2  demonstrates that an optional third density sensor  233  may be utilized as well to refine the carriage body movement using additional data points. Similarly, an optional fourth density sensor (not pictured) may be utilized similar to infeed density sensor on the outfeed side of the system to monitor conditions of the overall system further downstream. 
     Carriage body  220  can be moved either forward towards a first end  205  or rearward towards a second end  215  using a first end carriage belt  224  and first end carriage body actuator (not shown) or a second end carriage belt  225  and a second end carriage body actuator (not shown). The actuators serve to pull their respective carriage belt towards their respective end while maintaining a taut belt capable of preventing products from prematurely crossing from first conveyor  206  to second conveyor  216 . Actuation of either actuator is controlled by a controller (not shown) which interprets various data, and density data in particular. 
     One embodiment includes the following process, executed, for example, by controller  210 . Initially, the system checks to ensure there are products arriving to the system through the infeed section. Then, the system checks the density, e.g., rate or amount, of products being brought into the carriage system by the first conveyor system. A first sensor measures the density of products being delivered, preferably by measuring the density of products on the conveyor system, and communicates that information to a controller. If the controller determines that the density of products is less than a predetermined value, i.e., the “prime” value, the system checks the location of the carriage body. The system will consult the first carriage limit sensor. If the carriage body is not already at its maximum forward position, the system will move the carriage body forward until either 1) the carriage body is moved to its maximum forward position, or 2) the first sensor indicates that the density of products in the first sensor&#39;s observation zone is greater than or equal to the prime value. 
     If the system indicates that the density of products passing through the first sensor&#39;s observation zone is equal to or greater than the prime value, the system then moves on and again checks the location of the carriage body. In this step, the system checks the second carriage limit sensor. If the carriage body is not already at its maximum rearward position, the system may then check a second sensor to measure the density of products passing through the discharge side of the carriage body, corresponding to the section of the second conveyor system under the second sensor. If the density of products in the second sensor area, i.e., density, is less than a predetermined value, the carriage body will remain in its current position. However, if the second sensor determines that the density of products passing through the second sensor observation area is greater than or equal to the predetermined value, the system will move the carriage body rearward until either 1) the carriage body is moved to its maximum rearward position, or 2) the second sensor indicates that the density of products in the first sensor&#39;s observation zone is less than the prime value, in which case the carriage body will stop moving rearward. 
     The carriage may be moved at a constant speed. The control system determines whether the carriage is to be moved and may or may not adjust its speed. Similarly, the carriage may be moved independently of the first and second conveyor systems. There may be situations where one or both of the conveyors are stopped and the carriage moves. Further, the conveyors may be both moving at the same speed (but different or opposite directions) while the carriage is moving. 
     This is a continuous process, with the controller accepting input from both sets of sensors and continuously processing data from at least the first and second sensors described herein. The controller may optionally additionally receive information from at least a third sensor positioned, for example, over the intake side of the carriage, and a fourth sensor positioned, for example, over the outfeed section of the second conveyor system. The controller may optionally additionally receive information from upstream or downstream sensors that will allow the accumulator system featuring a density-based carriage control system to anticipate and compensate for situations encountered in other parts of the system, both locally and globally (within the overall production line) which would affect the accumulator system described herein. 
     In an alternative embodiment, an analogous system may utilize at least one sensor, which may be reliant on density measurements, to control the movement of the conveyor systems in addition to, or instead of, the movement of the carriage body. In such an embodiment, similar concepts related to flow of products into an infeed area would result in a determination of, i.e., density, and a control system would then determine whether to activate, and at what speed, at least one, and preferably two, conveyors. Such an analogous system may also utilize additional sensors, including sensors on both the infeed and/or the outfeed/discharge side of the system. Likewise, such a system may also incorporate sensors farther upstream or downstream from a specific accumulator unit, the sensors reporting data such as flow density in other parts of the overall system. 
       FIG. 3  is a perspective view of the accumulator system. In the perspective view, products flow into the accumulator system in direction  304  and onto infeed accumulation bed  306 . As the products travel towards the load end  315 , the products encounter carriage body  320  as they come into contact with curve  321 , which may be powered. Products are then directed to discharge accumulation bed  316  by a force or combination of forces resulting from the movement of infeed accumulation bed  306  and/or curve  321 , which may be powered and/or outfitted with a surface capable of grasping or directing flow of products. The products then are directed in product flow direction  314  for discharge from the accumulator system  300 . As the system accepts products coming from upstream, carriage body  320  may be moved between load end  315  and unload end  305  by load end carriage drive  323  and unload end carriage drive  322 , respectively. Carriage body is moved in response to information measured by at least product level sensor  303  during the infeed portion of the accumulation system and product level sensor  313 . Information from at least sensor  303  and sensor  313  are sent to computer system  340 , where instructions are executed to run a program to check the location of the carriage body along the length of the accumulator system using at least first carriage travel limit sensor  307  and second carriage travel limit sensor  317 . 
       FIG. 4  is a logic diagram further describing an example of the instructions stored in a non-transitory memory and provided to the computer system  340  regulating the accumulation system depicted in  FIG. 3 . After checking that the system is powered on and no faults are indicated from a variety of sensors (step X), which may be located locally or globally (within the overall production line system), the system consults sensors locally to decide how to operate the accumulator system based on observed conditions. 
     In step  407 , the carriage travel limit sensor is checked to determine whether the carriage body is able to move farther forward (in the direction of the unload end of the system). If the limit sensor indicates that the carriage body is at its maximum forward position (and cannot be moved farther forward), the system determines, in step  416 , if the second conveyor (discharge conveyor) of the accumulator is moving and, if so, may activate the first conveyor (infeed conveyor) in step  406 . 
     In step  403 , the infeed density sensor  303  is checked to confirm that products are passing into the accumulator above a certain density level and, if so, the density is checked (step  410 ) for products moving on the second conveyor (outfeed) and whether (step  417 ) the carriage is at the rear of the accumulator. If the carriage is at the rear of the accumulator, the first conveyor (infeed) may move products towards the carriage in step  406 . Similarly, if the density of products is greater than a certain level on the second conveyor and the second conveyor is moving (step  416 ), the first conveyor may move products towards the carriage. 
     In step  418 , a check is made to confirm that the main conveyor system downstream of the accumulator is running correctly. If true, even if the density is not above a threshold of product on the second conveyor of the accumulator (step  410 ), the second conveyor of the accumulator may be operated in step  416 . 
     Before the carriage is returned to the front of the accumulator (step  422 ), the system checks if the second conveyor is moving in step  416 , confirms that the density of products on the second conveyor is below a threshold step  410 , checks that the density is below a threshold level (step  413 ) of products moving off the accumulator and that the carriage is not already at the front of the accumulator in step  407 . 
     Before moving the carriage towards the rear of the accumulator (step  423 ), the system confirms that the density of products entering the accumulator is above a threshold (step  403 ), determines whether the second conveyor has a density of products above a threshold (step  410 ) or second conveyor is not moving (step  416 ), confirms that products are moving from the accumulator to the downstream main line conveyor (step  413 ) and that the carriage is not already at the rear in step  417 . 
     While moving the carriage towards the rear of the accumulator (step  406 ) or towards the front (step  416 ), the speed of the carriage may be constant or varied (step  421 ) to gradually increase and slow to and from the constant speed. The speed of the carriage may vary, such as in a sinusoidal manner, about a constant level to assist in the movement of products between the conveyors of the accumulator. 
       FIG. 5( a )  is an example of a flow of products demonstrating a high number of products passing through the observation area, with such a flow density likely being greater than or equal to a predetermined, or prime, value.  FIG. 5( b ) , on the other hand, is an example of a flow of products demonstrating a lower number of products passing through the observation area, with such a flow density likely being less than a predetermined value. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.