Abstract:
An insulting cover for industrial control components employs a cover support that may simply attached to existing or specially prepared structures on the control component, which supports a door that may be opened or closed for access to the control component. A variety of different covers may be simply generated using CAD templates executed to cut sheets of plastic that may be formed with relatively simple and low cost techniques.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
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     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     BACKGROUND OF THE INVENTION 
     The present invention relates generally to industrial control components such as fuse blocks and electrical disconnects as may be panel mounted, and in particular to a protective cover for these components. 
     Industrial control electrical equipment including components such as fuse blocks, electrical disconnects, and contactors, are typically mounted on a panel with interconnecting wiring run point-to-point between terminals on these devices. The mounting panel may be enclosed within a cabinet and the cabinet may have a door that may be closed to reduce the chance of accidental contact with the terminals and wiring of the components. The cabinet door may have an interlock, for example, working with the electrical disconnect to remove power from the components and wiring when the door is opened. However, often, an electrical interlock is not installed. 
     During testing and routine maintenance of the components and wiring within a cabinet, it may be necessary to have the cabinet door open while the wiring is live. For example, it may be desired to perform infrared thermography on the operating components to check for hot spots while power is applied. Alternatively, it may be necessary to probe voltages at points on the components while they are operating or to verify if fuses have blown. It may also be necessary to verify tightening torque at the termination points or electrical connections 
     In these situations, it is known that providing a secondary insulating cover over individual components to minimize the opportunity for inadvertent contact with electricity when the cabinet door is open is desirable. Such secondary covers may, for example, be molded of an insulating plastic or constructed of cardboard and may attach to the particular component by hooks or tabs or screws or other means. 
     One problem with these individual insulating covers is that they are not always replaced, particularly in circumstances where repeated access to the component is required. Removal and installation of the cover may be difficult requiring a removal of power and then a reapplication of power before the testing is performed. In components that may have multiple sizes as mounted on a panel, for example, an electrical disconnect with a trailing fuse block accommodating different sizes of fuses, providing covers is cumbersome and costly. Covers that are optional for a component, and thus purchased in small quantities, make special plastic molds impractical, yet inexpensive covers manufactured of paper or the like may not be suitable for the purpose or sufficiently durable. 
     SUMMARY OF THE INVENTION 
     The present invention provides a transparent cover that may be attached to individual panel-mounted electrical components and that may be readily manufactured from standard plastic sheet using simple folding operations. The cover has a door that may be opened for access to the components, simplifying such access and eliminating the problem of the cover being misplaced or removed entirely. The cover is suitable for components of varied sizes and shapes and having different available attachment points. A wide variety of cover plates may be manufactured in small quantities using stored computer-aided machining (CAM) files to cut the plastic sheet prior to folding. 
     Specifically, the present invention provides a cover system for electrical control components comprising an electrically insulating cover support detachably engaging structure of the electrical control component when the electrical control component is attached at a rear surface to a panel. The cover support presents a cover surface positioned in front of and having an opening providing access to electrically conducting elements of the electrical control component. An electrical insulating door is hingeably attached to the cover support to cover the opening when the door is in the closed position. 
     Thus, it is one object of the invention to provide a cover that reduces the chances that it will be misplaced or removed. The door may be opened for complete access while retaining attachment to the control component. 
     The electrically insulating door may be a transparent polymer material, for example, a polycarbonate such as Lexan. 
     Thus, it is another object of the invention to provide a cover that provides for visual inspection of the component prior to removal. 
     The electrically insulating cover support may also be a transparent polymer such as Lexan. 
     It is another object of the invention to provide improved illumination of the component and to simplify the construction and manufacture of the cover by making all parts of a single material. 
     The electrically insulating cover support and electrically insulating door may provide portions which together form a latch releasably holding the door in a closed position. 
     Thus, it is another object of the invention to allow the door to be stably held in a closed position reducing the chance of inadvertent contact with electrical components. 
     The latch and hinge may be integrally formed from the materials of the electrically insulating cover support and electrically insulating door. 
     Thus it is another object of the invention to provide a cover employing few parts (as few as two) and to allow all components of the cover to be, for example, insulating and transparent to provide the benefits of the material of the door and support. 
     The hinge may be at a side of the door to allow the door to open about a vertical axis. 
     Thus it is another object of the invention to provide a door which is naturally bi-stable remaining open or closed so as not to interfere with the inspection process nor require biasing springs or the like. 
     The invention may include an extensible shield attached to the door and vertically adjustable to provide an additional covering area of varying vertical extent. As before, the shield may be transparent such as manufactured from a polymer material like polycarbonate. 
     Thus, it is another object of the invention to provide a cover adaptable to a variety of different installation configurations of a particular control component. 
     The extensible shield may be held by electrically insulating connectors passing through at least one hole of a series of holes in the extensible shield and at least one hole in the door. The height of the extensible shield may be determined by selection of the hole of the series of holes in the extensible shield through which the insulating connectors are placed. 
     Thus it is another object of the invention to provide for a simple method of adjusting the size of the cover that may be performed in the field, for example, when a fuse block component is configured for different sizes of fuses. 
     The insulating cover support may detachably engage to the structure of the electrical component by means of side panels extending inward from the cover surface of the cover support about the electrical control component. In one embodiment, the side panels may include access cutouts. 
     Thus, it is another object of the invention to provide minimal interference with adjacent wiring needed for the control component. 
     The side panels may include holes engaging outwardly extending tabs on the electrical control component or may include inwardly extending fingers engaging holes in the electrical control component. 
     Thus it is another object of the invention to provide an attachment method that does not require the drilling or tapping of holes in the mounting panel such as would be difficult, time consuming, and raise the possibility of contaminating the control system with conductive metal fragments. 
     When holes are used in the side panels to attach it to the electrical control component, they may be adjacent to V-channels to align the side panels with the tabs on the control component prior to engagement of the holes with the tabs. 
     Thus, it is another object of the invention to allow simple engagement of the cover with the control component after it has been mounted on the panel and in situations of relatively low accessibility. 
     The electrically insulating cover may have legs extending inward from the cover surface about the electrical control component to abut a rear panel supporting the electrical control component to align the electrically insulating cover. 
     Thus, it is another object of the invention to provide a simple method of aligning the cover with the rear panel without requiring permanent attachment to the rear panel. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is an exploded perspective view of an electrical disconnect with a trailing fuse block mounted on a panel showing positioning of the cover of the present invention including a cover support, a door, and a door extension; 
     FIG. 2 is a detailed view of the hinge connecting the door and cover support showing its construction out of the same sheets of plastic used for the door and cover support; 
     FIG. 3 is a view similar to FIG. 2 showing the formation of the latch from the same sheets of plastic used for the cover support and door; 
     FIG. 4 is a side elevational view of a side panel of the cover support having a hole for engaging a corresponding tab on the electrical disconnect and a V-notch for helping the user to align the tab and hole; 
     FIG. 5 is a side cross-sectional view similar to that of FIG. 4; 
     FIG. 6 is an alternative view of side panels of the cover support illustrating an alternative method of attaching the cover support to the control component  12 ; and 
     FIG. 7 is a perspective view of a plurality of control components mounted on a panel, and a cover support covering one of the control components. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, the cover system  10  of the present invention is designed to work with a control component  12  such as an electrical disconnect with a trailing fuse block. In this example, the control component  12  includes an electrical disconnect portion  14  and a trailing edge fuse block portion  28 . 
     The electrical disconnect portion  14  has terminals  16  for accepting power leads  18  from a three phase source and supports first fuse ferrule or blade holders  20  for holding one end of standard fuses  22 . The electrical disconnect portion  14  may be attached to a mounting panel  24  such as may be contained in a cabinet according to techniques well known in the art. 
     A disconnect lever arm  26  may extend from the side of the electrical disconnect portion  14  allowing electrical connection and disconnection of the power leads  18  to the fuses  22 . As is understood in the art, the disconnect lever arm  26  may be interlocked with a door handle mechanism (not shown) or the like to allow unhindered opening of the door of the enclosure only when the disconnecting means is opened. This interlock may be defeated so that power may be applied with the cabinet door open for routine maintenance. 
     Referring still to FIG. 1, the trailing edge fuse block portion  28  may be attached to the mounting panel  24  below the electrical disconnect portion  14  to receive a second end of the fuses  22  and provides for an electrical connection of power leads  30  to the second end of the fuses  22 . The power leads  30  may pass to a piece of equipment to be controlled. The trailing edge fuse block portion  28  may be moved up and down on the mounting panel  24  depending on the size of the fuses  22  required. 
     Referring to FIGS. 1,  4 , and  5 , a tab hook  32  may be molded in the left and right sides of the electrical disconnect portion  14  to extend outward therefrom generally parallel to the mounting panel  24 . The tab hook  32  may have a lower ramp surface  34  and an upper hook portion  36  so as to provide a point of attachment for the cover system  10  as will be described below. 
     The cover system  10  includes a cover support  40 , a door  42 , and an optional extension  44  and rivets  86 , each constructed of insulating material and preferably (all but the rivets  86 ) constructed of a transparent polycarbonate plastic sheet, such as Lexan, cut and folded as will be described. 
     When the cover system  10  is attached to the control component  12 , the cover support  40  provides a front cover surface  46  generally parallel to the mounting panel  24  but positioned in front of the conductive components of the control component  12 , for example, the fuses  22  toward the door of a cabinet. The front cover surface  46  includes a rectangular central aperture  48  allowing access to those conductive elements for the purposes of measurement and repair. 
     The front cover surface  46  of the cover support  40  is supported at the left and right sides by side panels  50  which extend rearward from the front cover surface  46  at right angles to cover the left and right side of the control component  12  when the cover support  40  is in place. Each side panel  50  includes an upper engagement arm  52  having an engagement hole  54  and its rear edge ends most removed from the front cover surface  46 . Each side panel  50  also includes a lower standoff leg  56  generally parallel to upper engagement arms  52  but positioned at the lower edges of the front cover surface  46 . An access cutout  58  separates lower standoff leg  56  from upper engagement arms  52 . 
     Referring now to FIGS. 4 and 5, the engagement hole  54  in each upper engagement arm  52  is positioned beneath the point of a V-groove  62  cut in an upper edge of the upper engagement arm  52 . The V-groove provides a large target so that the upper engagement arms  52  may be aligned with the tab hook  32  on the control component  12  for installation of the cover support  40  after the control component  12  is in place in a cabinet or the like when access is reduced. The installation may be accomplished by grasping the front cover surface and tipping its top edge back to position the upper engagement arms  52  below the tab hooks  32 . 
     Once the tab hooks  32  are positioned at the point of the V-groove  62 , upper engagement arms  52  are flexed outward slightly so as to allow the engagement hole  54  to slip over the tab hooks  32 . An upward motion of the engagement arms  52  may provoke this outward flexing so that the upper edge of the V-groove  62  is pushed outward by the ramp surface  34  on the tab hook  32 . The cover is intentionally designed with a width dimension less than the dimension on which it is attached so that the arms press inward to abut against the sides of the disconnect component and reduce the likelihood of unintentional removal from the equipment. The engagement hole  54  is sized to allow a slight pivoting about a horizontal axis around the tab hook  32  of the upper engagement arms  52  to assist in this location process. 
     Upper engagement arms  52  may then be rotated downward until the lower standoff legs  56  touch the mounting panel  24  at their distal edges aligning the front cover surface  46  to be substantially parallel to the mounting panel  24 . Adjustment of the relative offset of the engagement holes  54  and lower standoff legs  56  from the front cover surface  46  allows the cover support  40  to be readily adapted to a variety of control components  12 . It will be understood that the attachment of the cover support  40  is simple and fast and requires no drilling of holes into the mounting panel  24  such as would generate possible metallic fragments and contaminants which could affect the performance of other components  12  inside the control panel. In addition, there is no need to use any power tools to add holes, tapped, or otherwise, to secure the cover. 
     Referring momentarily to FIG. 6 in an alternative embodiment, a hole  94  may be molded into the control component  12 , or preexisting holes used for other purposes may be utilized, the holes receiving a tooth  92  formed in the end of each of the upper engagement arms  52 . This tooth may be formed in a single planar thermoplastic sheet and then folded along line seam  100  in a manner described further below. 
     The engagement hole  94  and the tooth  92  allows a degree of rotation of the cover support  40 , simplifying installation of the cover support  40  in tight quarters. The cover support  40  need not be parallel to the mounting panel  24  at the time of installation but may be angled into position and then rotated until the lower standoff legs  56  abut the front surface of the mounting panel  24 . 
     Referring now to FIGS. 1 and 2, on the right side of the upper and lower horizontal edges of the central aperture  48  of the front cover surface  46 , hinge tabs  64  may be formed having vertically aligned and opposed holes  66 . When the cover support  40  is constructed of sheet polycarbonate plastic, these hinge tabs  64  may be cut to be cantilevered extensions into the central aperture  48  coplanar with the front cover surface  46 . These extensions may then be heated and bent out horizontally using a bending fixture. 
     Similarly referring to FIG. 3, at the center of the right vertical edges of the central aperture  48  of the front cover surface  46 , a latch tab  68  may be formed extending frontward substantially perpendicular to the front cover surface  46 . Again, this latch tab may be also cut as an extension into the central aperture  48  coplanar with the front cover surface  46  and may be heated and bent outward. Tab  68  may have a retention notch  70  extending vertically partway down from its upper edge such as may engage an upper edge  72  of a corresponding latch hole  74  cut in the door  42  as will now be described. 
     Door  42 , at its left upper and lower left corners is notched to provide upper and lower hinge pins  76  extending vertically upward from the upper edge of the door  42  and vertically downward from the lower edge of the door  42 . The hinge pins  76  are sized to fit within the hole  66  of the hinge tabs  64  and may be assembled therein by a slight flexing of either the door  42  and the front cover surface  46 . In this way, hinges that are transparent, insulating, and integrally formed with the cover support  40  and door  42  are provided, to reduce the number of parts and simplify assembly. 
     Referring also to FIG. 3, a slight play in the fit between the hinge pins  76  and the holes  66  of the hinge tabs  64  allows a counter clockwise tipping of the door  42  allowing the edge  72  of latch hole  74  to rise over the tab  68  and drop into the notch  70  retaining the door in a closed position absent a slight upward lifting of the door  42  and outward pulling of the door. 
     When the door  42  is closed, the central aperture  48  is covered preventing inadvertent contact with conductive elements of the control components  12 . Visual inspection of those elements can be conducted without opening a door  42 , however, the door may be opened so as to allow the insertion of probes or optical monitoring using infrared thermography. Because the door  42  remains attached to the cover system  10  via the cover support  40 , it is unlikely to be misplaced or discarded. 
     Good visibility of the contained control component  12  is provided by both the transparent material of the cover support  40  and the ample access cutout  58 . The ability to see through the cover prior to its opening also assists in the prevention of unnecessary contact with the live circuitry. 
     An extension  44 , being a planar sheet of transparent plastic in the preferred embodiment, may be fit to the door  42  to increase the area covered by the door  42 . The door  42  may have a pair of horizontally displaced holes  80  in its lower surface. The horizontal separation of these holes  80  corresponds to the horizontal separation of a set of pairs of holes  84  spaced vertically on extension  44 . By aligning particular ones of these pairs of holes  84  with the holes  80 , and insertion of snap rivets  86  through the holes, the height of the extension  44  may be adjusted. The extension  44  may include an expanded section  90  at its lower edge wider than the door  42  that may be further tailored to the particular area of the control component  12  being covered. In the example of the electrical disconnect, expanded section  90  is sized to align substantially with the conductive portions of the trailing edge fuse block portion  28 . 
     The rivets  86  may be well known snap-type plastic rivets having inter-engaging teeth so as to be pressed together to clamp the door  42  and extension  44  together. 
     It will be understood that the cover support  40 , door  42 , and extension  44  as described may be fabricated, for example, by cutting the necessary outlines and openings in one or more sheets of thermoplastic and then forming the sheet by bending it at the edges of the front cover surface  46  through heating and mechanical action. The forming of the hinge tabs  64  and latch tab  68  may be done by a low cost jig providing for the necessary shaping surfaces for bending the tabs after the material has been suitably heated. The simplicity of the manufacturing allows a wide variety of different cover systems to be developed simply by using different templates for cutting the various components of the cover support  40 , door  42 , and extension  44  from stock sheet. These templates may be implemented by data files stored on a computer-aided machine such as a milling machine. In this way, a variety of low cost covers may be manufactured in low volume on an as needed basis. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.