Abstract:
A zone control module for a conveyor system includes a manifold unit having oppositely facing first and second surfaces. A valve unit is mounted to the first surface of the manifold unit and includes an electrical valve actuator and a movable valve element. An electrical control unit mounts to the second surface of the manifold unit and is spaced from the valve control unit by the manifold unit. The valve unit includes first and second conductors extending into conductive apertures in the manifold unit for electrical contact with the electrical control unit, such that electricity from the electrical control unit can be transferred to operate the valve unit. The control modules can be utilized with a slug module to control a conveyor. Optical sensors are used to provide drive signals for respective zones of the conveyor system. The optical sensors can be overridden by an electrical slug signal from the slug module.

Description:
FIELD OF THE INVENTION 
     This invention relates to a zone control system for sensing and advancing articles in selected zones of a conveyor system and more particularly to an improved zone control module therefor. 
     BACKGROUND OF THE INVENTION 
     It is common practice to utilize conveyors for moving articles about a factory, warehouse or loading dock. Such conveyors generally include rollers, at least some of which are driven, to advance goods along respective conveyors. Prior conveyor systems have utilized air pressure to power actuators moving articles along conveyors. Some conveyor systems have optically sensed the position of articles from below conveyor rollers. 
     FIGS. 1-3 illustrate parts of a known conveyor system  10  of the type extensively used in factories, warehouses and the like to permit supporting and advancing of articles such as boxes thereon. The conveyor  10  includes power-driven article support elements such as rollers  12  which are disposed to define an elongate path, and the rollers are typically rotatably supported so as to extend transversely between a pair of elongate side rails, one such side rail  11  being illustrated in FIG.  1 . The conveyor  10 , when configured to function as an accumulating conveyor, typically has the rollers  12  defined into adjacent zones which can be independently driven from one another. For this purpose, the rollers  12  of each zone are typically independently driven from a main drive device such as a continuously driven line shaft  14  which extends lengthwise of the conveyor. The rollers  12  of the individual zones are then independently and selectively driven from the line shaft  14  through an intermediate drive transmitting device  17  which can be selectively actuated. This intermediate drive transmitting device, in the illustrated embodiment, includes an elongate twisted belt  16  which is engaged between the line shaft  14  and drive hubs associated with one or more of the rollers  12  defining the respective zone. The drive belt  16  in turn has an actuator  18  associated therewith for appropriately tensioning or de-tensioning the drive belt. The actuator  18  in the illustrated embodiment includes an extendable and contractible fluid pressure device such as an air cylinder, the latter causing appropriate extension or contraction of a wheel  19  which contacts the drive belt  16  and can be moved into or away from the drive belt to effectively tension or de-tension same. By tensioning the drive belt  16 , the frictional contact between the drive belt and the drive rollers  12  and line shaft  14  is sufficiently increased to effect driving rotation of the rollers  12 , whereas conversely when the belt is de-tensioned the drive belt slips relative to the line shaft so that the rollers of the respective zone are not driven. 
     The general arrangement of the conveyor as described above, when used as an accumulating and advancing conveyor, permits individual articles to be supported on and advanced from zone to zone without permitting the articles to contact or stack against one another. This advancing of the articles from zone to zone is facilitated by a conveyor control system  21  which includes a series of zone control modules  22 , only one of which is shown in FIGS. 1 and 2, disposed serially along the conveyor for controlling the individual zones. 
     In the known control system  21  illustrated by FIGS. 1 and 2, the zone control module  22  includes an optical sensor  33  which is disposed so as to project a sensing path  34  transversely across the rollers of an adjacent downstream zone so as to sense the presence or absence of an article in the zone which is located downstream from the zone being controlled by the respective control module  22 . When the sensor  33  senses the absence of an article or box in the adjacent downstream zone, it transmits a signal to the controller  22  which in turn supplies pressure fluid to the air actuating device  18  associated with the adjacent upstream zone to activate the rollers  12  so that an article in the upstream zone is advanced into the adjacent downstream zone. Due to the presence of such control modules  22  being located in series and controlling the respective zones, articles can be sequentially advanced from zone to zone. 
     The control module  22  of the prior art, as shown by FIGS. 1 and 2, include an electrical unit  23  which plugs into an electrical solenoid unit  24 , and the latter is fixedly secured to and operates a shiftable valve which is positioned interiorly of a manifold/valve unit  25 . A cable  35  electrically connects the optical sensor to the electrical unit. The electrical control units  23  of serially adjacent modules  22  are in turn electrically interconnected by electrical conductors  37  which have plugs  36  at opposite ends for joining to connector parts  38  provided on opposite ends of the units  23  so as to electrically connect the adjacent control modules. 
     In similar fashion the valve/manifold unit  25  has a through flow passage  26  which terminates at connector hubs  27 , and the adjacent modules  22  are joined together in fluid communication by fluid supply lines  28  connected to the hubs  27 . The serially-connected fluid supply lines at a remote end are joined to an appropriate source of pressurized fluid, typically air. The unit  25  has a load port  29  which connects to a line  31  which in turn connects to the actuator device  18 . 
     The control module, as illustrated by FIGS. 1 and 2, is typically fixedly secured to an inner surface of the side rails  11 , such as by screws  32  extending therethrough and being secured directly into the housing of the valve/manifold unit  25 . 
     With the arrangement illustrated by FIGS. 1 and 2, when the sensor  33  senses the absence of an article in the adjacent downstream zone, then a signal is transmitted to the electrical unit  23  which in turn energizes the shiftable solenoid associated with the solenoid unit  24 , and this in turn activates the valve disposed interiorly of the valve/manifold unit  25 . The activation of the valve permits pressurized fluid (i.e. air) from the supply line to pass through the valve to the fluid actuator  18  so that the belt associated with the upstream zone is tensioned to effect driving of the rollers  12  of the upstream zone, thereby permitting any article in the upstream zone to be advanced forwardly along the conveyor for movement into the adjacent downstream zone. 
     While the system described above relative to FIGS. 1-3 has generally operated in a satisfactory manner, nevertheless the construction thereof has possessed disadvantages. The construction of the module and the interrelationship between the units and the mounting thereof on the frame rail of the conveyor have made it difficult to service and maintain the arrangement. For example, if the valve/manifold unit requires repair or replacement, then the entire module must be removed to permit such repair, and then remounted on the side rail. Further, access to the solenoid unit is also difficult because of the overall constructional and positional restraints on the system, and thus any replacement or servicing thereof substantially requires removal of the entire module. 
     With the conveyor control arrangement of FIGS. 1-3, it is occasionally necessary or desirable to simultaneously activate a series of zones so as to permit simultaneous advancing of all objects or articles therein, this being referred to as “slug” advancing movement. To permit the simultaneous movement of a “slug” or series of articles, the control system of FIGS. 1 and 2 has the discharge port associated with each valve/manifold unit  25  connected to a discharge line. The discharge lines of the series of modules in turn connect to and discharge through a control valve which under normal conditions is maintained open to permit the normal discharge of air. This control valve is also connected to a slug line which in turn connects to a source of pressurized air. When slug movement is desired, the control valve is activated so that the discharge lines are closed off from the atmosphere, but instead are connected to the slug pressure line. The pressurized air in the slug pressure line is thus fed through the discharge lines to the discharge ports of the valve/manifold units, and is then fed through the valves to the pressure actuators  18  associated with the driving devices  17  associated with the series of zones, thereby permitting simultaneous driving of the rollers  12  in all of the zones defining the slug series. This slug movement is terminated by returning the control valve to the position wherein the slug pressure line is closed off and the discharge line are again vented. This known slug arrangement, however, significantly complicates the overall construction and specifically the pneumatic piping of the system. 
     Another prior art conveyor control device includes an optical sensor mounted below the rollers and angled upwardly to sense the presence or absence of articles through a gap between rollers. The optical sensor automatically closes a solenoid valve, turning off a section of the conveyor to avoid a collision when articles moving down the conveyor approach another article. The manner of mounting the device and the optical sensor therefore makes it difficult to accurately detect the presence of all articles on the conveyor. 
     Thus, it is an object of the invention to provide a conveyor control system which overcomes and/or improves on the disadvantages associated with the above prior art systems. 
     More specifically, this invention relates to a conveyor control system with simplified installation of the required wiring and plumbing, which system includes a control module having easy access and removal of the valve control unit without disturbing the manifold unit, and which can be used with a slug module to provide a simplified slug mode of operation. 
     SUMMARY OF THE INVENTION 
     Summarizing the invention, a conveyor control system includes a zone control module provided with a manifold unit, a valve unit, and an electrical control unit. The electrical control and valve units preferably are detachably mounted to oppositely facing sides of the manifold unit, and the latter is preferably attached to the conveyor frame structure. Such arrangement provides easy access to the electrical control and/or valve units without disturbing or requiring removal of the manifold unit and the fluid supply lines secured thereto. 
     An embodiment of the invention also includes an electrical slug module for controlling the zone control modules. An electrical slug signal is supplied by a third conductor included with first and second power supply conductors integrated into electrical connectors in series between the control modules to supply power to and control the valves of the individual zone control modules. The valves can be simultaneously activated to supply fluid pressure to corresponding actuators to simultaneously drive all of the rollers of the conveyor system in zones controlled by the slug module. Further, the number of zones controlled by the slug module can be adapted or changed merely by providing a slug terminator as an electrical connector between adjacent zone control modules, which slug terminator has an open circuit for the slug signal line. 
     Other objects and purposes of the invention will be apparent to persons familiar with arrangements of this general type upon reading the following specification and inspecting the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a prior art conveyor control system mounted onto a rail member of a conveyor system. 
     FIG. 2 is a side view of the prior art conveyor control system of FIG. 1 as viewed from line  2 — 2  in FIG.  1 . 
     FIG. 3 is a longitudinally extending sectional side view for diagrammatically showing the zones of the conveyor. 
     FIG. 4 is a block diagram of a conveyor control system according to the present invention and showing the arrangement between various components thereof. 
     FIG. 5 is an isometric view of a portion of an improved conveyor control system according to the present invention and shown mounted on a roller conveyor. 
     FIG. 6 is an isometric view of the zone control module having the valve control unit separated therefrom. 
     FIG. 7 is an exploded side view of the zone control module. 
     FIG. 8 is an exploded end view, partially in cross section of the control module as shown in FIG.  7 . 
     FIG. 9 is a schematic electrical control circuit for the zone control module. 
     FIG. 10 is a schematic electrical control circuit for a slug module. 
    
    
     Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the conveyor system of the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the system and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import. 
     DETAILED DESCRIPTION 
     Referring to FIG. 5, there is illustrated a conveyor system  10  which incorporates therein an improved control system  41  for permitting transporting and intermittent advancing movement of articles from zone to zone. The conveyor system  10  incorporates therein much of the conventional structure described above with respect to FIGS. 1 and 3, and accordingly the same reference numerals are utilized for designating the corresponding conventional parts of the conveyor. 
     Considering the improved conveyor control system  41  of this invention, and referring to FIG. 4, the control system includes a plurality of individual zone control modules  42  which are serially connected, both pneumatically and electrically, longitudinally along the conveyor so that each module  42  corresponds to and controls a respective zone on the conveyor, which zones are diagrammatically depicted as zones A, B, etc. in FIGS. 3 and 4 for illustrative purposes. The serially interconnected zone control modules  42  are substantially identical, and each comprises a small and compact structure which is defined primarily by three sub-modules or units which are directly fixedly but releasably interconnected. 
     More specifically, each zone control module  42  includes a valve unit  56 , a manifold unit  57  and an electrical control unit  58 . These three units are substantially vertically stacked together so that the manifold unit  57  is fixedly but releasably sandwiched between the valve and electrical units. 
     The manifold unit  57 , as shown in FIGS. 4-8, includes an elongate blocklike housing  75  having a main flow passage  76  extending longitudinally therethrough, which flow passage at opposite ends terminates in hubs or nipples  77  which project outwardly beyond opposite ends of the housing. These hubs  75  mount thereon one end of an elongate tubular conduit  45  which extends between the manifold units of serially adjacent modules. One of the modules also has a conduit connected thereto which in turn extends back to a source  46  of pressurized fluid, specifically air, whereby pressurized air is supplied through and to the manifold units  57  of all of the serially-connected modules  42 . 
     The housing of the valve manifold has opposite side surfaces, namely respective upper and lower surfaces as illustrated in the drawings, which face outwardly in opposite directions so as to abuttingly engage opposed surfaces defined on the valve and electrical units  56  and  58  respectively. The manifold housing also has a feed passage  78  formed therein which communicates with the main passage  76  and extends transversely so as to open outwardly through the upper surface  79  for communication with the valve unit  56 , as explained below. 
     The valve unit  56  includes an elongate and generally blocklike housing  61  which has a length corresponding generally to the length of the manifold housing  75 . The valve housing  61  mounts adjacent one end thereof a shiftable valve element  62  which controls flow between an inlet passage  63 , a load port  64  and a discharge port  65 . The inlet passage  63  opens through the lower face of the valve housing for direct communication with the feed passage  78  in the manifold housing. The load port  64  connects to a suitable tubular line  66 , such as a flexible conduit, so as to supply air to or return air from the respective zone actuating cylinder  18 . The discharge port  65  permits discharge of air directly to the atmosphere, but can connect to a discharge conduit if desired or necessary. The valve  62  is normally maintained in a closed position wherein the supply port  63  is closed off, and the load and discharge ports  64 ,  65  directly communicate with one another. The valve  62  can be shifted linearly into an open position, however, wherein the discharge port  65  is closed off, and the supply port  63  connects directly to the load port  64 . 
     The valve  62  is shifted from the closed to the open position by an electric solenoid actuator  67  which is disposed adjacent the other end of the valve housing  61  and which includes a conventional solenoid coil  68  disposed in surrounding relationship to a movable armature  69 , the latter being coaxially coupled to the valve  62  to effect shifting movement of the latter into an open position when the coil is electrically energized. A spring (not shown) is provided for returning the valve and armature to the closed position upon de-energization of the solenoid coil, such being conventional in valve arrangements of this general type. The construction of the shiftable valve  62  and its actuation by a solenoid is conventional, whereby further description thereof is believed unnecessary. 
     The manifold housing  75  in the upper side thereof is formed with a stepped channel-like recess  81  which opens downwardly therein and is elongated longitudinally thereof. This channel-like recess  81  enables the lower portion of the valve housing  61  to nest therein between the manifold housing sidewalls  82  so as to permit secure seating of the valve and manifold housings one on top of the other. A suitable fastener  73  such as a screw extends downwardly through the valve housing  61  for threaded engagement with the manifold housing  75  to permit fixed but releasable attachment of the valve unit  56  to the manifold unit  57 . 
     Considering the electrical control unit  58 , it includes a generally hollow boxlike housing  91  which is open on one side so as to permit containment of the electrical components therein. This housing  91  is disposed so that a rim  92  on the free edge thereof seats into a shallow recess  83  surrounded by a flange  84  as defined on the bottom side surface of the manifold housing  75 . The flange  84  effectively allows the rim  92  of the electrical control housing to nest therein. The electrical control housing  91  in turn is fixedly but detachably joined to the manifold housing  75  by fasteners  93  such as screws which project through the control housing and thread into the manifold housing. The electrical control unit housing  91  mounts therein, substantially adjacent the lower side of the manifold housing, a circuit board  94  on which appropriate electrical control circuitry is provided, as explained hereinafter. 
     The electrical control unit  58  also includes electrical connector parts  96  and  97 , such as plugs, grommets, or sockets, which are provided on and projecting longitudinally from opposite ends of the housing  91 . These connector plugs  96 ,  97 , in this example, are electrically joined to the circuit board for transmission of electrical energy to and through the electrical control unit. The connector plugs  96 ,  97  are releasably engaged to flexible electrical connectors  47  which extend between and couple to the connector plugs of serially-connected modules  42  for permitting transmission of electricity therebetween. The endmost zone module  42  in turn has the electrical unit thereof joined to an electric connector which in turn joins to an electrical power source  48 , preferably a direct-current power source such as 24-volt direct current. 
     The electrical connector  47  preferably defines therein three electrical conductors, the first conductor  104  (FIG. 9) supplying the DC voltage to the electrical units  58  of the serially-arranged modules  42 , the second conductor  106  being a ground conductor, and the third conductor  105  being a signal conductor for use when “slug” operation of the conveyor is desired, as explained hereinafter. 
     The control unit  58  also includes a further connector part  95  which is accessible exteriorly from one side thereof, which connector may involve any type of conventional plug-in, jack-type or socket-type electrical connector, for releasable connection to one end of a flexible signal transmitting line  44 , the latter having an optical sensor  43  provided at the other end thereof and mounted so as to project a sensing sight line transversely across the conveyor generally slightly above the upper surfaces of the rollers for sensing the presence of an object or article within the respective conveyor zone. The line  44  has a connector part  122  for releasable attachment to the connector part  95 . 
     To permit transmission of electricity from the electrical control unit  58  to the valve unit  56 , the manifold housing  75  has a pair of transverse openings  85  extending therethrough adjacent one end thereof. These openings fixedly mount therein a pair of elongate electrically-conductive pins  86  which extend transversely through and are fixedly mounted on the manifold housing. These conductive pins  86  at the upper ends define upwardly-opening cuplike sockets  88 . The pins at the lower ends have parts  87  which project downwardly in cantilevered fashion a limited extent below the lower surface of the manifold housing. These downwardly projecting pin parts  87  in turn plug into upwardly-projecting electrical sockets  99  which are defined in a connector part  98  which is mounted on and projects upwardly from the circuit board  94  associated with the electrical control unit  58  when the electrical control and manifold units are engaged one with the other. 
     In similar fashion, the solenoid  67  of the valve unit  56  has a pair of conductive pins  71  associated therewith and secured so as to project in cantilevered manner downwardly from the lower surface  72  of the valve housing. These pins  71  align with and project into the cuplike sockets  88  associated with the conductors  87  on the manifold housing  75  when the valve and manifold units are joined together. In this manner the electrical control and valve units individually have a releasable plug-type electrical engagement with the conductive elements  87  which are mounted on and extend transversely through the manifold housing  75  so as to permit direct transmission of electrical energy from the control unit  58  to the valve unit  56 , while at the same time permitting each of the valve and control units  56  and  58  to be easily detached from the manifold unit  57 . 
     Connector parts  95 ,  96 ,  97  of electrical control unit  58  may be plug-type connectors having at least three conductive pin elements, but other types of connector parts, either separable or permanently joined, can be utilized having the equivalent of three or more conductive elements as is well known in the electrical arts. 
     The electrical circuitry associated with the zone control module  42 , which circuitry is associated with the electrical control unit  58  and is provided on the circuit board  94  and by the electrical connector parts associated therewith, will now be briefly described with reference to FIG.  9 . 
     The circuitry includes three conductors  101 - 103  which enable the three electrical conductors  104 - 106  associated with the electrical connectors  47  to be connected to and pass through each of the modules  42 . These three conductors include the main voltage supply conductor  101  which joins to the conductor  104  of the connectors  47 , a ground conductor  103  which joins to the conductor  106  of the connectors  47 , and a slug line conductor  102  which joins to the conductor  105  of the connectors  47 . This arrangement enables electric power to be supplied to and through each of the zone modules  42  which are connected in series. 
     The circuitry also includes conductors  111  and  112  which respectively connect to the power and ground conductors  101  and  103 . The conductors  111  and  112  also join to the connector part  95 , and thus join to the sensor signal transmitting line  44 . The sensor  43 , in the arrangement illustrated by FIG. 9, comprises a transistor  121  which is open (that is, no signal) when an article is present in the conveyor zone being sensed. When no article is present, however, then the optical sensor closes the path through the transistor  121  between the conductors  113  and  112 , thus essentially closing the circuit path from the conductor  113  to the ground conductor  103 , whereby transistor  121  thus effectively grounds the conductor  113  except for a small voltage drop across the collector-to-emitter of the transistor. The previously open conductor  103  now enables current to pass from power conductor  101  through conductor  114  to one of the conductive pins  71 , thence through solenoid coil  68  to the other conductive pin  71 , and thence to the conductor  113 , through diode D 3 , which now connects through conductor  112  to the ground conductor  103 . This hence energizes the solenoid coil  68  which shifts the valve element  62  into an open position, thereby enabling pressurized fluid from the manifold unit to flow through the valve to the respective zone driving actuator  18 . At the same time, a resistor R 1  and a light emitting diode D 4  are connected in parallel with the solenoid coil  68  so that current passing through this parallel line activates the light emitting diode D 4  to visually indicate that the rollers of the respective zone are being operated. When the adjacent downstream zone acted on by the sensor  43  senses the presence of an article being moved into the zone so as to interrupt the sensor signal, then the transistor switch  121  effectively reopens, and the solenoid coil  68  is de-energized whereby the valve returns to its closed position, thus connecting the zone driving device  18  to the discharge port of the valve so as to de-pressurize the device  18  and thus stop the rotation of the conveyor rollers in the adjacent upstream zone. 
     While the optical sensor  43  in the illustrated embodiment comprises a transistor  121  as the sensing or switching element, it will be appreciated that the actual sensor or switching element can be of many conventional types, such as an infrared sensor or even a physical switch-type sensor positioned so as to make physical contact with the article contained in the zone. 
     For normal accumulating and advancing of articles on the conveyor, each of the serially-connected zone control modules  42  independently operates in the manner described above so that, upon sensing that the adjacent downstream zone is empty, the control module  42  activates its respective adjacent upstream zone so as to advance the article therein into the adjacent downstream zone, with the presence of the article in the adjacent downstream zone being sensed by the sensor so as to again de-activate the control module of the adjacent upstream zone. 
     With the above arrangement, each control module  42  can be readily maintained or serviced due to its being readily accessible adjacent the exterior side of the conveyor side rail, and the valve unit and the electrical control unit can each be readily disconnected from the intermediate manifold unit, and quickly replaced if necessary, without requiring that the entire module be removed from the conveyor. 
     The optical sensor  43  is preferably mounted by a support element (see FIG. 2) to send a beam across and above the rollers  12  and substantially parallel to the axes of the rollers, with the beam being reflected off of a reflector adjacent the other side. If an object or article is present, the beam is broken and in this manner the presence of an article in the zone can be sensed. 
     When it is desired to provide the conveyor with the capability of “slug” movement so as to permit simultaneous advancing of articles disposed in a plurality of adjacent zones, then the conveyor control system is provided with a slug control module  51  (FIGS. 4 and 5) connected electrically in series at one end of the number of zones defining the slug, and is provided with a slug terminator  54  connected electrically in series at the other end of the number of zones defining the slug. 
     The slug terminator  54  substantially corresponds to the electrical connector  47  except that the terminator  54  permits electrical transmission therethrough of only the power supply conductor  104  and the ground conductor  106 . The slug control conductor  105  does not extend through the slug terminator, thereby creating a break in the slug conductive line. 
     As to the slug control module  51 , it connects to a slug signaling device  52  through an intermediate signal transmitting line  53 . The slug signaling device  52  typically comprises some type of switching device, such as a manually or automatically actuated switch, a conventional transistor capable of performing a switching function, or any other type of input which provides a signal equivalent to a switching function. When the slug signal device  52  provides a slug signal or switching function, then the slug control module  51  through its appropriate circuitry causes activation of the valve solenoids  68  coupled to the plurality of control modules  42  which are connected in series with and controlled by the slug module, thereby permitting the rollers in the plurality of zones to be simultaneously driven, as explained in greater detail hereinafter. 
     The slug module  51  as illustrated in FIGS. 4 and 5 includes a hollow housing which can also be fixedly attached to the conveyor, such as to the side rail, as by fasteners such as screws. The slug control module  51 , in the housing thereof, mounts a circuit board  94 ′ (FIG. 10) which is substantially identical to the circuit board  94  associated with the zone control module  42  as shown in FIG.  9 . This circuit board  94 ′ again defines the same conductors  101 ,  102 ,  103  extending therethrough for connection to connector parts  96  and  97  which in turn join to ends of electrical connectors  47  so that the slug module is connected electrically in series with the electrical units  58  of the zone modules  42 . The connector  95  is connected to the slug signaling device  52  through the signal line  53 , which signaling device  52  typically comprises some type of switching arrangement, this being diagrammatically illustrated by the switch  126 . 
     The slug control module  51  also mounts therein a second circuit board  131  which defines thereon a pair of electrical connector parts  132  and  133 , the latter creating a plug-type engagement with connectors parts  98  and  116 , respectively, as defined on the circuit board  94 ′. The three terminals associated with the connector part  116  of board  94 ′ are joined to conductors  117 ,  118 ,  119  which in turn respectively connect to the conductors  113 ,  103 ,  102 . 
     The circuit board  131  includes a relay coil  135  which connects via conductor  134  to terminals on the connector parts  132  and  133 , which in turn respectively connect to the conductors  114  and  117 . The relay coil  135  therein, when energized, causes closure of a normally open relay switch  137 , the latter being provided in a conductor  136  associated with the circuit board  131 . This conductor  136  in turn is joined to the remaining two terminals of the connector part  133 , which two terminals in turn join to the conductors  118 ,  119  of the circuit board  94 ′. 
     In operation, in the absence of a slug signal, the slug switch  126  is normally open, and thus the conductor  114  and the coil  135 , while connected between power conductor  101  and conductor  113 , are nevertheless isolated from the ground conductor  103  so that the coil  135  remains unenergized, and the relay switch  137  remains open. 
     When slug operation is desired, the slug switch  126  is closed thereby connecting conductor  113  to ground conductor  103  through intermediate conductor  112 . This causes coil  135  to be energized, whereby relay switch  137  is closed, thereby creating a direct connection between the slug line  102  and the ground line  103  on the circuit board  94 ′, which direct connection is transmitted through the intermediate electrical connectors  47  to the serially-connected zone control modules  42 . In the individual modules  42 , the solenoid coil  68  is now connected through conductor  114  to the power conductor  101 , and the solenoid coil  68  is also connected at its other end to the conductor  113  which in turn connects to conductor  139  containing the diode D 2  therein. Conductor  139  connects to the slug conductor  102  which extends back to the slug module  51  and is joined through the conductors  118  and  117  to the ground conductor  103 . This thus provides a complete circuit so that the solenoid coils  68  associated with the plurality of serially-connected zone modules  42  are thus energized, causing each of the respective valves to be shifted into an open position, and thereby allowing pressurized air to be supplied to all of the pneumatic actuators associated with the plurality of zones defining the slug region. The conveyor rollers in all of the zones are thus rotatably driven so long as the slug switch  126  remains closed. Opening of this latter switch breaks the circuit by de-energizing the relay coil  135  and opening the relay switch  137  of the slug module  51 , and thereby causing de-energization of the solenoid coils  68  associated with the respective zone control modules  42 . Of course, if the sensor switch  121  associated with any of the zone control modules  42  is in a position effecting closure between the conductors  112  and  113 , then those specific control modules  42  will remain energized until the respective sensor switch  121  returns to its open position. 
     Diodes D 1  in FIGS. 9 and 10 and diode D 5  in FIG. 10 are present to merely prevent back voltages or currents from skewing operation of electrical control circuits. 
     Slug module  51  does not have a valve unit  56 , or a manifold unit  57 . Also, slug module  51  can be mounted below or between zone control modules  42  because of the lack of connection to fluid supply lines. Slug module  51  merely must be connected in series with the zone control modules  42 , such as via electrical connector lines  47 . 
     While the modules  42  and  51  are illustrated in FIGS. 9 and 10 as having separable connector parts  96 ,  107  and  97 ,  108  for electrically joining the flexible electrical connectors  47  to the modules, it will be appreciated that at least one of connections  96 ,  107  or  97 ,  108  could be permanent if desired so that the connector  47  would thus remain attached to a respective module. 
     The circuits of FIGS. 9 and 10 are merely a preferred circuit arrangement for implementing the invention. Other circuits including various elements having equivalent functions to the elements set forth in FIGS. 9 and 10 are known in the art. 
     While rollers  12  are described throughout the invention as the conveyor zone transporting members, other approaches are known and are within the scope of the invention. For example, a series of endless conveyor belts corresponding to the zones being controlled can be positioned on drive shafts or drive rollers and driven to move the articles. 
     Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.