Abstract:
An electrical control module provides a plastic insert fitting inside a housing and compressed by assembly of the housing lid and base to be held securely therein. Elastic components on the plastic insert are compressed during the assembly provide a secure retention in the face of normal manufacturing tolerances. The plastic insert includes features for attaching electrical components such as electrical contactors, motor starters, disconnect switches, circuit breakers, and overload switches without conventional screw fasteners or the like through channels and elastic detents.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to electrical control modules, for example, as used for motor control, and in particular to a method of assembling electrical components into such modules with reduced fastener use. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electrically powered equipment in a factory, such as conveyors or the like, may employ electrical control modules placed between electrical power lines and electrical motors used in such devices. Such electrical control modules may incorporate in a single housing multiple electrical components including, for example, power disconnects, circuit breakers, overload relays, motor starters, drives, terminal strips and the like. These electrical components are wired together to provide an integrated system controlling and protecting the motor and equipment operators. 
         [0003]    Electrical control modules of this kind may be assembled on a customized basis for particular motor sizes and then shipped to the factory site to be connected to other components and wired to the electrically powered equipment which they control. 
         [0004]    Assembling together the electrical components of an electrical control module is normally accomplished by attaching each electrical component to a mounting plate using machine screws passing through holes in flanges of the electrical components and corresponding holes in the mounting plate to be retained by nuts and lock washers. The mounting plate may be predrilled and attached through standoffs or other means to the housing to provide a strong physical connection between the housing and the various electrical components. This method of attaching electrical components together within an electrical control module is physically robust and flexible accommodating many different types of electrical components through the provision of multiple holes in a mounting plate. 
       SUMMARY OF THE INVENTION 
       [0005]    The present have recognized that a significant cost to the assembly of electrical control modules relates to the management and installation of multiple machine screw fasteners, lock washers, and nuts used to attach the electrical components. Accordingly, the present invention provides a polymeric insert that may be used to physically assemble electrical components together in a module and with reduced or no separate fasteners and to affix the polymeric insert firmly within the module housing relying on the fasteners used to assemble the housing without the need for separate fasteners to assemble the insert to the housing. 
         [0006]    Specifically, the present invention provides electrical control module having a housing defining a contained volume held between an interfitting housing base and a housing lid, the housing base providing a first inwardly facing support surface surrounded by upstanding side walls opposing a second inwardly facing support surface on the housing lid when the housing base and housing lid are inter fitting, the housing lid interfitting against upper edges of the upstanding side walls to be retained there by attachment elements. A polymeric insert is within the contained volume and provides mounting surfaces for electrical components selected from the group consisting of electrical contactors, motor starters, disconnect switches, circuit breakers, and overload switches. The polymeric insert includes multiple elastomeric elements and the housing base and housing lid have inwardly extending compression surfaces engaging the elastomeric elements when the housing base and housing lid are interfitting to compress the same and secure the polymeric insert within the housing. 
         [0007]    It is thus a feature of at least one embodiment of the invention to largely eliminate the need for time-consuming assembly of the electrical components to a mounting plate using multiple fasteners. It is a further feature of at least one embodiment of the invention to avoid the need for time-consuming assembly of the mounting plate to the housing of the electrical module. 
         [0008]    The elastomeric elements may be cantilevered polymeric beams deflected by the compression surfaces. 
         [0009]    It is thus a feature of at least one embodiment of the invention to employ structure of the polymeric insert itself as the elastomeric elements. 
         [0010]    The compression surfaces may be posts protruding from one of the inwardly facing surfaces. 
         [0011]    It is thus a feature of at least one embodiment of the invention to permit the elastic elements to be closely located to the structure supported by the polymeric insert for improved rigidity. 
         [0012]    The polymeric insert may further include guide surfaces engaging portions of a least one of the housing lid and housing base to position the polymeric insert in a predetermined location along the first inwardly facing surface between the upstanding side walls 
         [0013]    It is thus a feature of at least one embodiment of the invention to implement not only the compressive features of threaded fasteners but their location features as well to prevent lateral motion (perpendicular to the compressive force) of the electrical components within the housing. 
         [0014]    The guide surfaces may be pins received by corresponding holes in the polymeric insert. 
         [0015]    It is thus a feature of at least one embodiment of the invention to permit the points of engagement between the guide surfaces and the polymeric insert to be close to the elements supported by the polymeric insert for increased rigidity. 
         [0016]    The pens may include a key portion fitting in a corresponding hole within the polymeric insert and a ledge portion fitting against a lower face of the polymeric insert. 
         [0017]    It is thus a feature of at least one embodiment of the invention to provide both support and lateral location with simply constructed guide surfaces 
         [0018]    The polymeric insert may include a lower edge defining a plane fitting against the first inwardly facing surface. 
         [0019]    It is thus a feature of at least one embodiment of the invention to permit portions of the polymeric insert to be broadly supported by the housing components for improved rigidity. 
         [0020]    The mounting surfaces of the polymeric insert may include opposed channel elements for slidably receiving a corresponding flange surface on the electrical components. 
         [0021]    It is thus a feature of at least one embodiment of the invention to provide a simple method of robustly attaching multiple types of electrical components to the polymeric insert using features well implemented in polymer. 
         [0022]    The opposed channels may conform to the dimensions of a standard DIN rail. 
         [0023]    It is thus a feature of at least one embodiment of the invention to provide an attachment method that works with a wide variety of different electrical components manufactured for DIN rail mounting. 
         [0024]    The mounting surfaces further include a spring detents for capturing the electrical component once its flange surface is received within the opposed channel elements. 
         [0025]    It is thus a feature of at least one embodiment of the invention to provide a fastener less method of releasably retaining the electrical components in the respective channels. 
         [0026]    The spring detents may be cantilevered polymeric beams having upwardly extending hooks. 
         [0027]    It is thus a feature of at least one embodiment of the invention to implement the attachment mechanisms for the electrical components entirely through features molded into the polymeric insert. 
         [0028]    The mounting surfaces may include at least two spring detents at different locations on the mounting surface along an axis of insertion of the electrical component into the opposed channels to block advance of the electrical component into the opposed channels in a given direction. 
         [0029]    It is thus a feature of at least one embodiment of the invention to permit different electrical components having different axial dimensions to be used with the given polymeric insert. 
         [0030]    The housing may include tabs projecting laterally for attachment of the housing to a planar surface. 
         [0031]    It is thus a feature of at least one embodiment of the invention to provide a simple method of attaching the electrical module to associated equipment or the like. 
         [0032]    The housing may be metal. 
         [0033]    It is thus a feature of at least one embodiment of the invention to permit the polymeric insert to derive greater strength by intimate contact with a relatively rigid metallic housing. 
         [0034]    The housing base and housing lid may be assembled together using machine screws. 
         [0035]    It is thus a feature of at least one, embodiment of the invention to provide an attachment mechanism of the housing lid and base conducive to compressing the polymeric insert therein. The machine screws provide substantial mechanical advantage for an arbitrary amount of compressive force. 
         [0036]    Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a perspective view of a motorized conveyor suitable for use with the present invention indicating a mounting of an electronic control module there on and showing an exploded diagram of the housing of the control module incorporating polymeric insert onto which electrical components may be mounted; 
           [0038]      FIG. 2  is a fragmentary cross-section through the control module of  FIG. 1  showing retention of an internal polymeric insert through flexing cantilevered elements; 
           [0039]      FIG. 3  is a fragmentary perspective view of the assembled housing and polymeric insert showing a guide pin aligning the polymeric insert within the housing; and 
           [0040]      FIG. 4  is a detailed fragmentary perspective view of a mounting surface of the polymeric insert for receiving an electrical component between opposed flanges has retained by flexing detents. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0041]    Referring now to  FIG. 1 , a motorized conveyor system  10 , representative of one type of electrically powered industrial equipment, may provide an electrical motor  12  powering a movable conveyor belt  14 . The motorized conveyor system  10  may provide a mounting surface  18 , (for example a leg of the conveyer) on which an electrical control module  22  may be attached and interconnected by wiring (not shown) to the electrical motor  12  and a source of line power. The electrical control module  22  may include a switch operator  24  or the like projecting from a front face of the electrical control module  22  to allow control of electrical power applied to the motor  12  by a nearby individual. 
         [0042]    Referring still to  FIG. 1 , the electrical control module  22  may collect electrical components  20  in a protective metal housing  26 . The electrical components  20  (a single disconnect module shown) may be preassembled to implement a desired function, for example power conditioning for motor  12 , including providing for disconnection of electrical power to the motor  12 , overvoltage and overcurrent protection of the motor  12 , and proper motor startup voltages, for example. The electrical components  20  may include: power disconnects, circuit breakers, overload relays, motor starters, drives, terminal strips, and the like. 
         [0043]    The housing  26  of the module  22  may be constructed of separable components including a housing lid  28  attachable to a housing base  30  to define a housing volume  32  therein. The housing lid  28  may include a movable switch operator  24  supported thereby and having a shaft (not shown) passing through the lid  28  to communicate with an internal electrical component  20 , in this case, an electrical disconnect module. 
         [0044]    The housing base  30  may present a first inner, upwardly facing, and generally planar, support surface  34  whose opposite side may be mounted against the mounting surface  18  by means of outwardly extending tabs  36  attachable to the mounting surface  18  by machine screws or the like. Surrounding the planar support surface  34  are upwardly extending side walls  38  whose upper edges form a continuous periphery that may be capped by a generally planar housing lid  28  attached to that periphery by means of multiple machine screws  40  passing through holes  41  in the corners of the lid  28  and into corresponding threaded bores  42  in the corners of the upper edges of the upstanding side walls  38 . 
         [0045]    One or more of the upwardly extending side walls  38  may have openings receiving customization plates  39 , for example, being electrical plates holding electrical connectors  43  or the like for communication with the electrical wiring within the housing  26 . The customization plates  39  and attached connectors  43  may be varied according to the particular application of the electrical control module  22 . 
         [0046]    Fitting within the housing volume  32  is a polymeric insert  44 . The polymeric insert  44  may have a lower edge  47  defining a surface that may abut the planar support surface  34  and upper mounting surfaces  49  for receiving electrical components  20  thereagainst as will be described. The polymeric insert  44  may be injection molded thermoplastic providing for good electrical insulation, low cold flow, and good elasticity. 
         [0047]    Referring now to  FIG. 2 , the underside of the lid  28  may provide a second inwardly facing support surface  46  opposite the support surface  34  when the lid  28  is attached to the housing base  30 . The support surface  46  may include one or more downwardly extending compression surfaces  48  which engage corresponding cantilevered spring element  50  when the lid  28  is attached to the housing base  30 . When the lid  28  is attached to the housing base  30 , the polymeric cantilevered spring element  50  presses upward against the downwardly extending compression surfaces  48  holding the polymeric insert  44  between the compression surfaces  48  and the interface between the support surface  34  on the lower edge  47  of the polymeric insert  44 . 
         [0048]    The spring element  50  makes use of the natural resilience of the polymeric material of the polymeric insert  44  to deflect elastically downward under compression by the extending compression surface  48  with assembly of the lid  28  to the housing base  30  so as to ensure vibration less retention of the insert polymeric insert  44  within the housing  26  while accepting reasonable manufacturing tolerances which may change the dimensions of the extension of the compression surfaces  48  or the size of the polymeric insert  44  or the separation between support surfaces  46  and  34 . Thus, the spring elements  50  provide a predetermined compressive force between the housing  26  and the polymeric insert  44  for a range of dimensional variations. It will be appreciated that the spring elements  50  formed from a polymeric material will have a high intrinsic level of dampening so as to help not only retain the components but to reduce vibration by dissipating the energy. 
         [0049]    Referring to  FIGS. 2 and 3 , the support surface  34  of the housing base  30  may include upwardly extending guide surfaces  52  provided by a pin or other feature engaging a corresponding notch  54  or like in the polymeric insert  44 . These guide surfaces  52  serve to laterally align the polymeric insert  44  within the housing  26  against vibration or lateral movement with respect to the side walls  38  and further ensure correct insertion into the housing  26 . 
         [0050]    Referring now to  FIG. 4 , the guide surfaces  52  may in some embodiments provide upwardly facing ledges  56  that can support the underside of the polymeric insert  44  instead of the support surfaces of the lower edge  47  to resist vertical movement. In this case, the guide surfaces  52  include a smaller diameter extension  52 ′ fitting within a hole or notch  54  to resist lateral movement. 
         [0051]    As noted, the mounting surfaces  49  of the polymeric insert  44  may include features intended for fastener-less attachment of electrical components  20  to the mounting surfaces  49 . In one embodiment, these features may include spaced parallel channels  60   a  and  60   b  extending upward from the mounting surface  49  and providing mutually opposed channel slots separated to receive flanges  62  extending in opposite directions from a base  64  of the electrical component  20 . In this way, the electrical component  20  may slide into the channels  60  along an axis  66  to be retained by the channels  60  against motion perpendicular to that axis  66 . The channels  60  may be preferably molded into the polymeric insert  44 . 
         [0052]    Detent elements  70   a  and  70   b  may be positioned at the edges of the mounting surface  49  along axis  66  and have upwardly extending hooks  72  mounted on cantilevered tabs  74  to project in a relaxed state above the upper plane of the mounting surface  49 . The tabs  74  of polymeric material (preferably formed integrally with the polymeric insert  44 ) may flex downward to allow passage of the base  64  over the hook  72  as the electrical component  20  is slid into engagement in the channels  60 , but then may spring upward to catch the vertical edge of an end of the component  20  against further axial movement once the hook  72  clears the base  64 . The use of two opposed upwardly extending hooks  72  on different separated cantilevered tabs  74  may block axial movement in either direction. In this way, electrical component  20  may be assembled to the mounting surface  49  and retained there without the need for screw fasteners or the like. 
         [0053]    It will be understood that the component  20  may be removed from the mounting surface  49  by reversing the above procedure and one of the hooks  72 , for example, with the blade of the screwdriver, to allow the base  64  to pass thereover. The use of two detent elements  70   a  and  70   b  arranged as mirror images, allow insertion or removal of electrical component  20  from the mounting surface  49  in either direction along axis  66 . 
         [0054]    The polymeric insert  44  may provide for multiple mounting surfaces  49  for a variety of components allowing selective insertion or installation of those components  20  into the module  22  for semicustom assembly of different components. 
         [0055]    The mounting surface  49  may further include one or more intermediate stops  76  which may also be cantilevered beams deformed upward to present a stop surface  77  for components  20  having relatively short length along axis  66  so that these components may be retained between one hook  72  and the stop surface  77 . On the other hand, the stop surface  77  may be pressed inward below the plane of the mounting surface  49  so that the channels  60  may receive longer electrical component  20  into the channels  60 . In this way, components at different sizes may be admitted into the channels  60 . 
         [0056]    Multiple spring elements  50  may be distributed around the mounting surfaces  49  in various portions on the polymeric insert  44  to provide in total a high degree of retention force (being the sum of each of the forces on each spring element  50 ) and to provide more uniformly distributed support of the polymeric insert  44  in the vicinity of the mounted components  20 . 
         [0057]    The elimination of the need to align and tighten multiple screws with lock washers and nuts and the like greatly simplifies the assembly process. 
         [0058]    Incorporation of the guide elements and mounting surfaces into the housing elements of the base and lid eliminates the need for standoffs or other separate components as well saving both assembly time and the need to stock multiple components and the possibility of incorrectly installed components becoming loose in the field. 
         [0059]    The polymeric insert provides a generally electrically insulating surface greatly reducing the possibility of ground faults from wires that may become disconnected or abraded and provides a damping quality beyond that obtained from a metal material. 
         [0060]    Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “left”, “right”, “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
         [0061]    When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0062]    Various features of the invention are set forth in the following claims. It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.