Abstract:
A controller assembly utilizes a base unit that receives a dockable processor unit. The controller assembly typically is a programmable logic controller that permits base units and processor units to be interchanged according to the requirements of a specific application. The base unit includes a power supply, I/O circuitry and interface circuitry, and the processor unit includes a processor, such as a CPU. A unique latching mechanism secures the processor unit to the base unit. The latching mechanism also includes a lever assembly that facilitates removal of the processor unit from the base unit.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to controller assemblies, such as those used in a programmable logic controller (PLC) system, and particularly to packaged controllers utilizing a base unit and a processor unit. 
     BACKGROUND OF THE INVENTION 
     Controllers are used throughout industry to control and monitor a wide range of machines and other movable components and systems. In an exemplary controller, such as that used in a PLC system, the controller may have power supply circuitry, I/O circuitry, interface circuitry, etc. combined with a processor, such as a CPU. 
     Generally, controllers are available with a wide range of capabilities and processing power. Conventional PLC systems utilize a plurality of modules that are mechanically mounted in a rack system and electrically connected along a back plane. The individual modules can be interchanged or replaced as required by a given system application. 
     Some PLCs, referred to as packaged controllers, typically are used for smaller machines or systems and include a single integral system having its own power supply, input/output circuitry, interface circuitry and processor in a single unit. 
     With packaged controllers, the entire controller e.g., PLC, must be purchased with appropriate power supply, I/O circuitry, interface circuitry, processor, etc. for the particular task or environment in which it will be used. The purchaser is limited to the available preconfigured controllers and has limited ability to upgrade a packaged controller system without purchasing a new system. Additionally, the purchaser is limited to the capabilities and features of the commercially available control systems. 
     It would be advantageous from both the customer&#39;s perspective and the manufacturer&#39;s perspective to design packaged controller assemblies having modular components that could be selectively interchanged. For example, it would be advantageous to have a PLC separated into two interchangeable components, such as a base unit containing a power supply, power supply circuitry, I/O circuitry, interface circuitry, etc., and a separate processor unit containing a control device, such as a CPU, for the base unit. Such a design would provide both the customer and the manufacturer great flexibility in delivering many configurations of a controller assembly with a smaller number of manufactured components. 
     SUMMARY OF THE INVENTION 
     In one preferred embodiment, the present invention features a dockable processor unit system. The system comprises a processor unit and a base unit configured to receive the processor unit. A latching mechanism is provided to selectively latch the processor unit to the base unit. The latching mechanism includes an integral lever disposed to facilitate separation of the processor unit from the base unit. 
     According to another aspect of the invention, a programmable logic controller system is provided. The system comprises a base unit and a processor unit configured to engage the base unit. A latching mechanism is designed to selectively hold and release the processor unit with respect to the base unit. 
     According to another aspect of the present invention, a method is provided for selectively latching a processor unit to a base unit of a programmable logic controller system. The method includes configuring a base unit with a receptacle for receiving a processor unit and selectively engaging the processor unit with the base unit. The method further includes connecting a latching mechanism to the base unit and the processor unit to selectively hold the processor unit in engagement with the base unit and to selectively release the processor unit from the base unit. Also, a lever is incorporated with the latching mechanism to provide a user with mechanical advantage in disengaging the processor unit from the base unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
     FIG. 1 is a perspective view of an assembled controller assembly, according to a preferred embodiment of the present invention; 
     FIG. 1A is a partial cross-sectional view taken generally along line  1 A— 1 A of FIG. 1; 
     FIG. 2 is a perspective view similar to FIG. 1, but showing the processor unit removed; 
     FIG. 2A is a schematic illustration representing exemplary functionality of the base unit and processor unit illustrated in FIGS. 1 and 2; 
     FIG. 3 is a perspective view of a portion of the base unit of the controller assembly according to a preferred embodiment of the present invention; 
     FIG. 4 is a perspective view of the right end of the processor unit illustrated in FIG. 2; 
     FIG. 5 is a partial top view of the processor unit and base unit taken generally along line  5 — 5  of FIG. 1, according to a preferred embodiment of the present invention; 
     FIG. 6 is a partial cross-sectional view taken generally along line  6 — 6  of FIG. 5; 
     FIG. 7 is a partial left end view of the processor unit mounted in the base unit taken generally along line  7 — 7  of FIG. 1; 
     FIG. 8 is a perspective view of the lever assembly illustrated in FIG. 1; 
     FIG. 9 is a front perspective view of the processor unit illustrating interlocking features; 
     FIG. 10 is a rear perspective view of the processor unit illustrating interlocking features; 
     FIG. 11 is a left side view of the lever illustrated in FIG. 8; 
     FIG. 12 is a right side view of the lever illustrated in FIG. 8; 
     FIG. 13 is a top view of the lever illustrated in FIG. 8; 
     FIG. 14 is a bottom view of the lever illustrated in FIG. 8; 
     FIG. 15 is a cross-sectional view taken generally along line  15 — 15  of FIG. 8; and 
     FIG. 16 is a cross-sectional view similar to that in FIG. 15 but showing the lever assembly in an actuated position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring generally to FIGS. 1 and 2, a controller assembly  20  is illustrated according to a preferred embodiment of the present invention. Controller assembly  20  comprises a base unit  22  and a processor unit  24 . Processor unit  24  is dockable in base unit  22  and selectively held in place by a latching mechanism  26 . 
     The modular approach to the construction of controller assembly  20  permits a range of base units  22  and processor units  24  to be interchanged. For example, by making available 6 types of base units and 3 types of processor units that may be selectively coupled together, 18 configurations of controller assembly  20  are possible. This type of modular system can be incorporated into many controller assembly designs, and the specific design illustrated is merely exemplary. The specific configuration of the base unit  22  and processor unit  24 , as well as the layout of features, may be varied without departing from the scope of the present invention. 
     In the illustrated embodiment, base unit  22  includes a mounting mechanism  28  comprising a plurality of bosses  30  having apertures  32  for receiving fasteners (not shown) therethrough. Additionally, base unit  22  includes an LED panel  34  through which inputs and outputs of controller assembly  20  may be monitored. Base unit  22  also includes a plurality of contact terminals  36  through which input and output signals flow from and to devices to which controller assembly  20  may be connected. 
     As illustrated in the diagram of FIG. 2A, processor unit  24  includes a processor  38 , such as a CPU. The base unit  22 , on the other hand, includes supporting circuitry, such as a power supply and power supply circuitry  40 , input/output (I/O) circuitry  42  and interface circuitry  44 . Base unit  22  potentially can be designed in many configurations with specific supporting circuitry for desired applications, and processor unit  24  can include a variety of processors designed to interact with base unit  22 . 
     A preferred embodiment of the base unit  22  is illustrated in FIGS. 2 and 3. Base unit  22  includes an outer housing  46  that may have a variety of configurations. Outer housing  46  is designed with a docking area  48  that permits processor unit  24  to be docked with base unit  22 . In the illustrated embodiment, docking area  48  comprises a cavity  50  formed in outer housing  46 . Cavity  50  is sized to slidingly receive processor unit  24  therein. 
     Preferably, base unit  22  includes a plurality of interlock slots  52  formed in outer housing  46  along the side of cavity  50 . Interlock slots  52  are designed to engage corresponding, mating interlocking features  54 , such as protruding lips  55 , on processor unit  24  (see also FIGS.  5  and  6 ). Base unit  22  also includes a base unit interface connector  56  disposed for conductive engagement with a processor unit interface connector  58  (see FIGS.  3  and  4 ). Base unit interface connector  56  provides a conductive path between the processor unit  24  and the various circuits of the base unit  22 . Base unit interface connector  56  and processor unit interface connector  58  may have a variety of configurations. For example, base unit interface connector  56  may include a plurality of pins  60  arranged for mating engagement with a plurality of receptacles  62  disposed in processor unit interface connector  58 . 
     Latching mechanism  26  cooperates both with base unit  22  and processor unit  24  to selectively lock or hold processor unit  24  in engagement with base unit  22 . Additionally, latching mechanism  26  is designed to facilitate release of processor unit  24  from base unit  22  when servicing or changing the processor unit. 
     In the preferred illustrated embodiment, latching mechanism  26  includes a lever assembly  64  pivotably mounted to base unit  22  for pivotable movement about a pivot axis  66 . (See FIGS.  2  and  7 ). Lever assembly  64  includes a lever handle  68  having a thumb grip area  70  for insertion of a thumb or finger to pull lever handle  68  and pivot lever assembly  64  about pivot axis  66 . The pulling of lever handle  68  and the consequent pivoting of lever assembly  64  in the direction of arrow  72  (see FIG. 1) disengages processor unit  24  from base unit  22 , as is described more fully below. 
     With reference to FIGS. 2,  4 ,  6  and  8 - 10 , further aspects of controller assembly  20 , latching mechanism  26  and processor unit  24  can be explained more fully. Generally, processor unit  24  includes an outer processor unit housing  74  in which the processor  38 , e.g., microprocessor based CPU, is housed. Housing  74  preferably includes integrally molded interlocking features  54  to facilitate sliding engagement with base unit  22  at interlock slots  52 . At the opposite end of housing  74  is disposed processing unit interface connector  58 , as illustrated. The internal processor  38  is appropriately connected to interface connector  58  as dictated by the design of the processor and interface connector. 
     Additionally, processor unit housing  74  preferably includes portions of latching mechanism  26 . Specifically, housing  74  includes a boss or pin  76  that interacts with lever assembly  64  to facilitate disengagement of processor unit  24  from base unit  22 . Housing  74  also includes a pawl  78 , which is a spring loaded member, as best illustrated in FIG.  10 . Pawl  78  also is designed and disposed for engagement with lever assembly  64 . Preferably, pawl  78  is on a generally opposite side of pivot axis  66  from pin  76  when processor unit  24  is engaged with base unit  22 . 
     Additionally, housing  74  includes an elastomeric preload member  80 , preferably disposed on an opposite end of housing  74  from pawl  78 . Elastomeric preload member  80  is a resilient plastic or rubber member that extends from an end wall  82  of housing  74  as best illustrated in FIG.  4 . Preload member  80  is located for engagement with a boss  83  mounted to outer housing  46  of base unit  22  along an edge of cavity  50 , as best illustrated in FIGS. 1A and 2. When processor unit  24  is inserted into cavity  50  for engagement with base unit  22 , pawl  78  maintains processor unit  24  in the engaged position, while elastomeric preload member  80  biases pawl  78  and processor unit  24  into constant engagement with latching mechanism  26 . This ensures a secure, reliable connection between processor unit  24  and base unit  22  even in relatively harsh industrial environments subject to substantial vibration. 
     Referring generally to FIGS.  5  and  11 - 16 , a preferred embodiment of lever assembly  64  is illustrated, and its function can be described. Lever assembly  64  is designed for pivotable motion about pivot axis  66 . To that end, lever assembly  64  includes a pin and preferably two pins  84  that are generally aligned with the pivot axis  66 . Pins  84  are rotatably received in corresponding apertures  85  formed in outer housing  46  of base unit  22  (see apertures  85  in FIG.  1 ). 
     Lever assembly  64  also includes a tooth  86  and a disengagement bar  88 . Tooth  86  and disengagement bar  88  are substantially on opposite sides of pivot axis  66 . Tooth  86  is positioned for contact with pawl  78  when processor unit  24  is inserted into and engaged with base unit  22 . Additionally, disengagement bar  88  is positioned for cooperation with pin  76  when processor unit  24  is engaged with base unit  22 , as illustrated in FIG.  15 . 
     Tooth  86  preferably includes an abutment surface  90  disposed for abutment with a corresponding contact surface  92  of pawl  78  during engagement of processor unit  24  with base unit  22 . Contact surface  92  is biased against abutment surface  90  by elastomeric preload member  80 . The biasing force is directed against abutment surface  90 , as indicated by a force arrow  94 , at a position that tends to bias lever assembly  64  about pivot axis  66  towards the closed position of FIG.  1 . 
     Furthermore, tooth  86  includes a sloped surface  96  that facilitates engagement of tooth  86  with pawl  78 . Specifically, when processor unit  24  is inserted into cavity  50  of base unit  22 , pawl  78  is disposed to contact sloped surface  96 . 
     Disengagement bar  88  generally is positioned on an opposite side of pivot axis  66  from tooth  86 , and is disposed at an angle  98  (see FIG. 15) with respect to lever handle  68 . The angle  98  permits disengagement bar  88  to apply a disengagement force against pin  76  in a direction that facilitates disengagement of processor unit  24  from base unit  22  along a substantial portion of the range of pivotable motion of lever assembly  64 . Lever assembly  64  is illustrated in FIG. 16 at its pivoted or open position. 
     When processor unit  24  is engaged with base unit  22 , disengagement bar  88  is disposed to rest proximate pin  76 . Specifically, a small gap is disposed between bar  88  and pin  76  to permit disengagement as explained below. When lever handle  68  is pivoted from its “at rest” position in a direction indicated by arrow  72  of FIGS. 1 and 16, disengagement bar  88  pulls against pin  76  to facilitate disengagement of processor unit  24  and processor unit interface connector  58  from base unit  22  and base unit interface connector  56 . Because lever handle  68  extends substantially beyond disengagement bar  88 , there is substantial mechanical advantage provided to a user pivoting lever assembly  64 . This mechanical advantage enhances the users ability to quickly and easily remove and interchange processor units with base units. 
     Other features of lever assembly  64  include a stop  100  (see FIG. 13) that prevents lever assembly  64  from pivoting beyond a desired maximum angle of rotation. Additionally, lever assembly  64  may include a return spring  102  designed to contact outer housing  46  of base unit  22  to bias lever assembly  64  towards a closed position. Thus, when lever assembly  64  is pivoted about pivot axis  66  to remove processor unit  24 , return spring  102  provides slight resistance to that rotation and tends to bias lever handle  68  and lever assembly  64  towards a closed position. 
     To utilize controller assembly  20 , a given processor unit  24  is aligned and slid into cavity  50  of base unit  22  by a user. As processor unit  24  moves into cavity  50 , interlocking features  54  of processor unit  24  engage interlock slots  52  of base unit  22  to securely hold processor unit  24  in a proper orientation. Additionally, processor unit interface connector  58  engages base unit interface connector  56  such that conductive paths are created between processor unit  24  and base unit  22  via engagement of pins  60  with receptacles  62 . 
     Furthermore, as processor unit  24  is slid toward its fully engaged position in base unit  22 , pawl  78  is flexed by sloped surface  96  of tooth  86 . Pawl  78  is flexed into a relief cavity  97  (best viewed in FIG. 10) until processor unit  24  becomes sufficiently inserted such that resilient pawl  78  snaps back to its original position. This leaves abutment surface  90  of tooth  86  adjacent contact surface  92  of pawl  78 . This orientation of tooth  86  with respect to pawl  78  prevents the processor unit  24  from inadvertent disengagement or removal from base unit  22 . Preferably, elastomeric preload member  80  of processor unit  24  engages boss  84  of base unit  22  to bias contact surface  92  against abutment surface  90  as indicated by force arrow  94 . This tends to pivot lever assembly  64  about pivot axis  66  to a closed position to ensure that processor unit  24  is held securely in engagement with base unit  22 . 
     Once processor unit  24  is fully engaged with base unit  22 , pin  76  of processor unit  24  resides proximate disengagement bar  88  of lever assembly  64 . When it is desirable to disengage and remove processor unit  24  from base unit  22 , a user simply pulls on lever handle  68  via thumb grip area  70  to pivot lever assembly  64  about pivot axis  66  in the direction of arrow  72 . Disengagement bar  88  contacts pin  76  and exerts a force against pin  76  in a direction that generally forces processor unit  24  and processor unit interface connector  58  away from base unit  22  and base unit interface connector  56 . The length of lever handle  68  and the orientation of pivot axis  66  and disengagement bar  88  provide the user with mechanical advantage in forcing the disengagement of processor unit  24  via disengagement bar  88 . The angle  98  assures that the disengagement force directed against pin  76  is in substantial alignment with the direction of movement of processor unit  24  during disengagement. As lever handle  68  is moved through its maximum angle of rotation, e.g., until limited by stop  100  acting against outer housing  46 , disengagement bar  88  continues to act against pin  76  in disengaging process unit  24  from base unit  22 . 
     It should be noted that during initiation of this process, tooth  86  pivots past pawl  78 , permitting the user to readily pull processor unit  24  from cavity  50 . To the extent tooth  86  and abutment surface  90  interfere with contact surface  92  of pawl  78 , processor unit  24  can be forced slightly inward against elastomeric preload member  80  as tooth  86  slides past contact surface  92  and pawl  78 . Disengagement bar  88  does not contact pin  76  until tooth  86  has cleared pawl  78 . 
     It will be understood that the foregoing description is of a preferred exemplary embodiment of this invention, and that the invention is not limited to the specific form shown. For example, a variety of base unit housing designs and processor unit housing designs may be used; multiple types of interface connectors between the base unit and processor unit may be implemented; the circuitry and functionality of the overall controller assembly can be split in various ways between the base unit and the processor unit. The various components, such as tooth, disengagement bar, pawl and pin can be integrally formed with their corresponding lever assembly or housing or added as separate components; the lever assembly potentially can be mounted on the processor unit with the pawl and pin mounted on the base unit; and the latching mechanism can be placed at different positions with respect to the overall structure of the controller assembly. These and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims.