Patent Publication Number: US-6912443-B2

Title: Modular automated assembly system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application Ser. No. 09/522,633 of David W. Duemler, filed Mar. 10, 2000, now U.S. Pat. No. 6,535,786 entitled “Modular Automated Assembly System” the entirety of which is hereby incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to industrial assembly systems, and more particularly to modular automated assembly systems. 
   BACKGROUND OF THE INVENTION 
   Automated assembly systems have greatly improved the quality of manufactured products as well as the efficiency with which those products are made. These systems generally include a conveyor system that is controlled by a central computer. The central computer directs the conveyor system to move a product to successive work stations in order to accomplish a variety of operations on the product, such as loading, assembly, testing, rejecting, and unloading of the product. 
   Each work station typically includes an automated device for accomplishing a particular operation on the product. Typically, the majority of the operation of each device is directly controlled by the central computer. The central computer typically must be programmed with a very complex operating program that enables the computer to direct the operations of each individual work station device. The program may include the operating parameters and instructions for operating each device, code enabling the computer to communicate with each device, and a complex code structure interrelating the operation of each device to that of other devices in the system. 
   In smaller industrial applications, the central computer is typically directly wired to each work station, leading to a very complex web of connections. In larger industrial assembly systems, the central computer may communicate to each device through a network bus structure. In either application, each device is identified by a device address or network address. Therefore, each individual device must be programmed with an identifying address. If a device is removed from a network or its location in the assembly system is changed, that device must be reprogrammed with a new address identifiable to the central computer. In this manner, the central computer knows the individual location of each device and can direct the operations of each device individually. 
   Automated assembly systems such as just described are not easily modified and often are special purpose systems, i.e., they are only capable of assembling a single product or family of products. Significant changes to the automated assembly system require major reprogramming efforts for the central computer and any work station devices. These limitations produce a rather inflexible automation system that does not easily expand with a business or afford a business the ability to manufacture different products on the same assembly line. Further, it should be apparent that modifications to these automated systems require significant down time for the assembly system which in turn leads to costly production gaps. These systems also do not easily allow for reduced production during production cut-backs. Therefore, there is currently a need for a modular automated assembly system that is both cost effective, highly flexible, and easily adaptable. 
   SUMMARY OF THE INVENTION 
   The present invention is a modular assembly system and method of modular manufacturing. A modular assembly system includes a base unit and a plurality of detachable work stations. The base unit includes a base unit control processor, a plurality of work station ports, and a conveyor controlled by the base unit control processor. The detachable work stations are adapted to operate with the base unit and each work station includes a work station control processor for controlling the operation of the individual work station. Each of the work stations is detachably connected to one of the work station ports such that it can communicate with the base unit control processor. The base unit control processor is programmed to recognize at least one of said detachable work stations, monitor whether one of said detachable work stations successfully performs its operation on an individual product, and selectively direct the operation of at least a successive one of the detachable work stations. 
   The preferred embodiment of the assembly system of this invention is fully modular. Any number of combinations of work stations may be connected to the base unit to assemble modified or new products without reprogramming the base unit control processor or the work station control processor. The modular assembly system, therefore, provides an effective way for a manufacturer to minimize capital equipment expenses by offering significant opportunities to amortize equipment costs while maximizing the manufacturer&#39;s ability to react to ever-changing market demands. 
   The above and other features of the present invention will be better understood from the following detailed description of the preferred embodiments of the invention which is provided in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of an exemplary embodiment of a modular assembly system according to the present invention. 
       FIG. 2  is a top plan view of an exemplary base unit with dial index conveyor and two connected work stations according to the present invention. 
       FIG. 3  is a side elevational view of the unit of FIG.  2 . 
       FIG. 4  is a perspective view of an exemplary base unit and exemplary work stations according to the present invention. 
       FIG. 5  is a top plan view of an assembly system including manual base unit attached to exemplary work stations according to the present invention. 
       FIG. 6  is a side elevational view of the assembly system of FIG.  5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a block diagram of an exemplary embodiment of a modular assembly system  10  according to the invention. The modular assembly system  10  includes a base unit  20  indicated within the dashed lines and a plurality of detachable work stations  100 . 
   The base unit  20  includes a base unit control processor  30 . The control processor  30  may be any programmable processor, such as a desktop computer, microprocessor, microcontroller, programmable logic controller, or the like. A plurality of work station ports  40  are connected to base unit control processor  30  through network bus  50 . Network bus  50  is preferably a network bus that is suitable for industrial control systems. In the preferred environment, network bus  50  is a Control Area Network (CAN) bus, such as a DEVICENET bus, which allows base unit control processor  30  to communicate or interface with ports  40  using the open network standard DEVICENET protocol. Examples of other acceptable buses and protocols that may be used in industrial control systems are PROFI-BUS, LONTALK, CONTROLNET, and SDS buses and protocols. 
   The base unit  20  also includes a conveyor  60 . The conveyor  60  is controlled by the base unit control processor  30  and is adapted to move a product during automated assembly of the product. The conveyor  60  may be any number of conveying devices such as a dial index as shown in  FIG. 2 ,  FIG. 3 , and  FIG. 4 , a vertical or horizontal walking beam in-line machine, an automated conveyor belt, or other conveying devices used in assembly lines to move a product through an assembly system. 
   Modular assembly system  10  includes a plurality of detachable work stations  100  adapted to operate with the base unit  20 . Each work station  100  includes a work station control processor for controlling the operation of the individual work station. The work station control processor is preferably a microprocessor adapted for use in an industrial control system, such as a programmable logic controller (PLC). The work station microprocessor or PLC is desirably programmed to control the operation of the work station, such that each work station is functional outside of the modular assembly system. 
   The work stations  100  may be any number of operational work stations, particularly those operational work stations used in assembling any number of small products, such as valves used in medical devices, transformers, or fasteners. Examples of such work stations are pick-and-place stations, part presence probes, O-ring loaders, ultra-sonic welders, part torque or screw station, empty nest identifiers, part orientation probes, leak and flow testers, electrical characteristic testers, pneumatic rams, crimpers and formers, liquid dispensers, glue dispensers, ultra violet gluers, machining devices, soldering devices, grinders, finishing and polishing devices, and chargers, to name a few. 
   Each work station  100  may be detachably connected to the base unit  20 , such as by a removable fastener, like a bolt or screw, by an interference fit, or by other fastening means. In one embodiment of the invention, a work station  100  triggers a switch  50  when it is attached to the base unit  20 . Each switch is connected to base unit control processor  30 . A triggered switch  50  indicates to the base unit control processor  30  that a work station  100  has been attached to the base unit. It should be apparent to one of ordinary skill in the art that the switch may have any number of designs, such as an electromechanical switch triggered when contacted by a work station  100  or manually triggered by a technician connecting a work station  100  to the base unit  20 . 
   When base unit control processor  30  determines that a work station  100  has been attached to the base unit  20 , base unit control processor  30  looks to port  40  to identify whether a work station  100  has been connected to communicate with the base unit control processor  30 . The communication between the base unit control processor  30  and a work station  100  through a port  40  may be accomplished using a standard communication protocol for connecting industrial equipment to control processors. In the preferred embodiment of the invention, the protocol is the RS-232 standard established by the Electrical Industries Association. It should be apparent, though, that work stations  100  and the base unit control processor  30  may be adapted to communicate using other protocols, such as those mentioned above. As mentioned, the network communications between the base unit control processor  30  and the plurality of work stations  40  may be coordinated through network bus  50  according to a network protocol, such as DEVICENET. 
   Because each work station preferably includes a work station processor which allows the work station to function independent of the modular assembly system  10 , the communication and control requirements of the base unit control processor  30  are greatly simplified and the system thereby becomes truly modular, as is discussed hereafter. 
   Very little communication is required between a work station  100  and the base unit control processor  30 . When a work station  100  is connected to a work station port  40 , and a switch  50  indicates to base unit control processor  30  to look to a work station port  40  associated with the switch  50 , then base unit control processor  30  initiates communications with the work station  100 . Each individual work station  100  is not programmed with a network address to identify its location to the base unit control processor  30  because each work station port  40  is associated with and identified by a network address. Further, base unit control processor  30  recognizes work stations  100  without being pre-programmed with operating instructions for work stations  100  that may be connected to the base unit  20 . 
   The interaction between the work stations  100  and the base unit control processor is best described using an example. Assume base unit  20  includes sixteen work station ports  40  and sixteen associated switches  50 . An assembly system including four work stations may be created by connecting work stations  100  to, for example, the first, fifth, ninth, and fifteenth work station ports  40 . There are preferably sixteen available locations for work stations to operate on products along the conveyor  60 , each location associated with a work station port  40 . Indeed, the work stations  100  can be connected to any four work station ports  40 , as long as they are connected in the correct assembly order. No addressing is required for the individual work stations  100 . Assuming the associated switches  50  indicate to the base unit control processor  30  that work stations  100  are attached to the base unit  20 , base unit control processor  30  looks to the associated work station ports  40 , here the first, fifth, ninth, and fifteenth work station ports  40 , to determine whether work stations  100  are connected to these work station ports  40 . Assuming work stations  100  are connected to the work station ports, the communication begins between the connected work stations  100  and the base unit control processor  30 . The work stations  100  are preferably connected to the work stations ports  40  through cables which permit data transfer, such as cables designed for serial or parallel data transfer. 
   The base unit control processor&#39;s function is much like that of a traffic cop. The base unit control processor  30  does not need to know what kind of work stations  100  are connected to the base unit  20  or the work station-specific detailed operating instructions particular to each work station. The base unit control processor  30  determines from each work station control processor whether each individual connected work station cycles on a good or bad product. A work station  100  that cycles on a bad product performs its operation when a prior work station  100  has not successfully performed its operation or a product has failed a work station test. An example of such a work station is an unload or dump work station or a work station that reconfigures or reforms a defective product in some manner. A work station that cycles on a good product performs its operation when the prior work stations  100  have successfully performed their respective operations on a product or have successfully tested a product. 
   A work station  100  may also communicate to the base unit control processor that it is a dual function work station. A dual function work station cycles on both a good and bad product. An example of dual function work station is a rotate station that rotates, flips, or otherwise orients a product to be operated on by a successive work station regardless of whether the product is good or bad. 
   The base unit control processor  30  also sends start signals to the work stations, receives completion signals from the work stations, and controls the conveyor  60  in order to move a product to successive work stations in accordance with these signals. Once the base unit control processor  30  recognizes each work station  100  and determines the cycle characteristic of each work station  100 , the base unit control processor sends a start signal to the first work station  100 , that work station connected to the first work station port  40  in the example. The first work station  100  may be a loader for example. The work station  100  loads a product onto the conveyor  60  and communicates a complete signal to base unit control processor  30 . The work station also communicates to the base unit control processor  30  whether it has completed its operation successfully or unsuccessfully. The operation of the work station  100 , though, is controlled entirely by the work station control processor. The base unit control processor records whether the operation has been completed successfully and, therefore, whether the product is a good or bad product. 
   The base unit control processor  30  then preferably directs the conveyor  60  to move the product one increment to the next work station location, i.e., the location where a work station would be if connected to the second work station port  40 . The base unit control processor  30  could direct the conveyor to move the product to the location where the second connected work station is located, i.e., to the work station  100  connected to the fifth work stations port, but the base unit control processor  30  would then have to account for the separation between each work station. In that situation, products would eventually be spaced on the conveyor such that each work station would not have a product on which to operate, unless the spacing between the work stations is equidistant, e.g., work stations connected to the first, third, fifth, and seventh work stations. After the product is moved to the next location, the base unit control processor again sends a start signal to the first work station  100 , and a second product is loaded onto the conveyor  60 . The work station control processor then sends a completed signal to the base unit control processor  30  and a successful operation or unsuccessful operation signal. 
   This same process is repeated until the first product reaches the second work station  100  connected to the fifth work station port  40 . The base unit control processor  30  does not know the operating instruction for the particular work station  100  in sufficient detail to direct the entire operation of the work station  100 , but the base unit control processor  30  does know whether this work station cycles on a good or bad product, or whether the work stations cycles on both a good and bad product. The base unit control processor also knows from the successful/unsuccessful operation signal for this product sent from the first work station control processor whether this individual product is a good or bad product. If the product is good, i.e., the first work station performed its operation successfully on the product, and the second work station  100  is programmed to cycle on a good product, then base unit control processor  30  sends a start signal to the second work station  100  to perform its operation. The second work station  100 , like the first work station  100 , eventually sends a complete signal to the base unit control processor  30  and a successful or unsuccessful operation signal. Before directing the conveyor  60  to move the product along the assembly line to successive work stations, the base unit control processor  30  also sends a start signal to the first work station. The base unit control processor awaits a complete signal and successful/unsuccessful operation signal from each work station before directing the conveyor  60  to move the product. The work stations preferably work simultaneously, if directed to do so, as the base unit control processor awaits complete and successful/unsuccessful information from each work station performing an operation. 
   In the manner described above, the products on the conveyor  60  eventually are moved before the third and fourth work stations  100  connected to the ninth and fifteenth work station ports  40 , respectively. The communication between the base unit control processor  30  and the individual work stations  100  is repeated. The base unit control processor  30  simply directs an individual work station  100  to perform its function based on whether the product presently before that particular work station  100  is a good or bad product and whether that particular work station  100  cycles on a good or bad part. 
   Because the base unit control processor  30  directs traffic and the operation of each work station  100  is directed by a work station control processor, the assembly system  10  is truly modular. The base unit control processor  30  does not identify what product is being assembled or how individual work stations  100  operate. The base unit control processor  30  performs the same simple routine regardless of the number, order, or type of work stations  100  connected to the base unit  20 . Further, because the work stations  100  are not programmed with network addresses, they are quickly and easily interchanged or replaced. An assembly line that assembles solenoids may quickly be transformed into an assembly that assembles relays by detaching each work station  100  that is not needed, or that needs to be relocated, from the base unit  10  and the work station ports  40 . The associated switches  50  are no longer triggered when the work stations are disconnected and therefore no longer indicate to the base unit control processor  30  that there is a need to communicate through their associated work station ports  40 . The work stations  100  needed to assemble the new product are connected to the base unit  10  and work station ports  40  in the correct assembly order, e.g., the loader should be located before other work stations along an assembly line, and the associated switches  50  are again triggered. The base unit control processor recognizes the presence of each work stations connected to a work station port, determines whether each work station cycles on a good or bad product, or on a good and bad product, and sends a start signal to the first work station  100 . In this manner, a new assembly system is created with little loss in production time and no reprogramming of either the base unit control processor or the work stations. 
   It should also be apparent that additional work stations  100  can, in the same manner, simply be added to a sequence of work stations  100  to modify the assembly of a product or perform an additional operation on a product. Similarly, work stations  100  may be removed to modify an assembly line or to be used outside of the automated modular assembly system  10 , since the individual work stations  100  control their own operations. This may be extremely valuable to businesses as they modify production emphasis from one product to another. The higher yield products may be assembled on an automated modular assembly system  10 , and the lower yield products or products that having reduced demand may then be assembled manually using the replaced work stations  100  without the base unit  10  and conveyor  60 . The removed work stations may similarly be used in a semiautomatic system. 
     FIG. 5  is a top plan view of a manual assembly system  300  including manual base unit  310  and two exemplary work stations  350 .  FIG. 6  is a side elevational view of the system of FIG.  5 . The work stations  350  may be manually triggered to perform their operations on products manually positioned on a nest table  340 . The work stations  350  are connected to a support plate  357  that may be connected to the manual base unit  310 , such as by fastening bolt  355 . Each work station includes a protective chamber  350  for housing a work station control processor (not shown). The manual base unit  310  may include an AC power outlet  330 , emergency shut down buttons  320 , and adjustable feet  370 . As a business grows or it become prudent to switch to an automated system, the work stations  350  may be removed from the manual base unit  310  and connected to an automated modular assembly system. Likewise, work stations from an automated modular assembly system may be removed from the automated modular assembly system and connected to the manual assembly system  300 , for example during reduced production periods or production emphasis changes. 
     FIG. 2  is a top plan view of an exemplary embodiment of a automated modular assembly system  500  according to the present invention including a dial or rotating index conveyor  510 .  FIG. 3  is a side elevational view of the modular assembly system  500  of FIG.  2 . The base unit  520  includes the base unit control processor (not shown) and inputs  530  to work station ports (not shown). Each work station  540  may include an enclosed chamber  545  for protecting the work station control processor and is connected to an input  530  through a connecting cable  550 . The work stations  540  may be attached to the base unit  520  at connectors  560 . Connectors  560  each include a switch (not shown) that indicates to the base unit control processor that a work station is attached to the base unit  520 . 
   The modular assembly system  500 , as shown in FIG.  2  and  FIG. 3 , may include, for example, sixteen inputs  530  to sixteen work station ports. The modular assembly system  500  as shown is capable of accommodating up to sixteen work stations and therefore includes sixteen connectors  560 . It should be apparent that the modular assembly system  500  can accommodate different combinations of sixteen or less work stations without reprogramming the work stations or base unit control processor. The base unit control processor simply recognizes which work station ports have connected work stations  540 , determines whether each work station cycles on a good or bad product, or both a good and bad product, sends a start signal to the first work station, and monitors the complete and successful/unsuccessful return signals. The base unit control processor of base unit  520  also directs the dial index conveyor  510  to rotate to move the products through assembly. 
     FIG. 4  is a perspective view of an exemplary embodiment of a base unit  700  according to the present invention with exemplary work stations that may be connected to the base unit  700 . Base unit  700  includes a dial index conveyor  790  that is controlled by a base unit control processor (not shown). The base unit  700  includes sixteen connectors  900  for mating with anchors  800  of the work stations. The connectors  900  may include switches (not shown) that are triggered when a work station is attached to the base unit  700 . The base unit  700  may also include an operating panel  780  which permits a technician to turn on the base unit  700 , turn off the base unit  700 , monitor the base unit  700 , or otherwise control the base unit  700 . Further, the base unit  700  may include selectively placed emergency shut down switches or buttons  1000 . Inputs  770  permit the work stations to plug into the work station ports (not shown) in order to communicate with the base unit control processor. 
   Several exemplary detachable work stations  710 ,  720 ,  730 ,  740 ,  750 ,  760  are shown which may be connected to base unit  700  to form and assembly system. The work stations are shown as examples of exemplary detachable work stations and are merely illustrative of work stations that may be used in a modular assembly system. Work station  760  is a glue dispenser. Work stations  760  includes a work station control processor (not shown) within chamber  765 . The work station control processor may be connected through cable  850  to an input  770  of the base unit  700 . Other work stations are also depicted in FIG.  4 . Work station  710  is an optical position sensor, work stations  730  is a rotary pick-and-place device, work stations  740  is another pick-and-place device, work station  750  is a light duty ram, and work station  720  is a ultraviolet curing device. 
   Work stations  720  is an example of a double-wide device. The work station occupies two locations along or around an assembly line, but is controlled by one work station control processor. The work station control processor of a double-wide work station indicates to the base unit control processor the additional information that it is a double-wide work station processor. The base unit control processor recognizes that a single work station processor is responsible for two locations along a conveyor, such as dial index conveyor  790 . The base unit control processor communicates through a single work stations port connected to the work station processor of work station  720 , thereby allowing the same work station processor to operate at two locations. 
   Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments of the invention that may be made by those skilled in the art without departing from the scope and range of equivalents of the invention. For example, an exemplary modular assembly system may include work stations that are not described herein or be used to manufacture numerous products not described. Further, the modular assembly system has been described using an exemplary base unit configured to accept sixteen work stations. This exemplary embodiment is presented for illustrative purposes only, and one of ordinary skill in the art should recognize that base units may be configured to accept fewer or more work stations.