Abstract:
A system for enclosing an instrument, module or other assembly in an explosion-proof housing. The system includes an upper housing portion that includes a first threaded portion and, optionally, a transparent window portion; a lower housing portion that has a second threaded portion that is structured and arranged to cooperate with the first threaded portion to provide a tight, air- and water-tight fit; and an inner mounting assembly for supporting an instrument, module, electrical circuit, electrical device, display device, or other assembly. In pertinent part, the lower housing portion includes integrated bosses that provide horizontal surfaces for supporting the inner mounting assembly and for releasably attaching the inner mounting assembly to the lower housing portion. The number of positioning of the bosses and the number and positioning of mounting studs on the inner mounting assembly are designed to mount the inner mounting assembly within the lower housing portion in a manner that is independent of the mounting orientation of the lower housing portion.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    (Not Applicable) 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    (Not applicable) 
       BACKGROUND OF THE INVENTION 
       [0003]    An enclosure for containing an electrical meter or other instrument, module or device in an explosion-proof manner is disclosed. 
         [0004]    Explosion-proof enclosures or housings are generally known for containing electrical and electronic equipment which is used in hazardous environments in which a spark or flame could ignite flammable gasses or other constituents in the operating environment. Explosion-proof housings are designed and constructed to meet industry standards such as the explosion-proof standards contained in the National Electrical Code (NEC). Such explosion-proof housings generally comprise a first housing portion which contains the associated meter or other instrument or device, and a second housing portion threadably attached to the first housing portion to fully enclose the device. Housing of known construction have deficiencies which limit their applicability and which limit their ease of use. Conventional housings usually require internal electrical fittings which must be carefully aligned to properly seat and install the electrical device being contained in the housing. Often such fittings must be preassembled in the housing before installation of the device. Examples of known explosion-proof housings are shown in U.S. Pat. Nos. 6,882,523 and 7,233,154. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    In accordance with the invention, an explosion-proof enclosure is provided for containing an electrical meter or other instrument, module or device. The enclosure includes a lower housing portion adapted to be mounted on a mounting surface or structure, an inner mounting assembly to which the meter or other device can be attached, and an upper housing portion which is threadably attachable to the lower housing portion to fully enclose the meter or other device. The upper housing portion has a transparent window for viewing the visual display of the meter or other device. The lower portion has a plurality of bosses that are spaced about the periphery of the interior chamber of the lower housing portion. The inner mounting assembly contains a plurality of recesses about the periphery thereof that cooperate with the bosses of the lower housing portion and which allow the mounting assembly and device attached thereto to be oriented in different rotational positions. The mounting and the device attached thereto can be oriented to readily read the display of the mounted device irrespective of the orientation of the mounted lower housing portion. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0006]    The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0007]      FIG. 1  shows an isometric view of a lower housing portion in accordance with the present invention; 
           [0008]      FIG. 2  shows a cross section of a lower housing portion with an inner mounting assembly attached thereto in accordance with the present invention; 
           [0009]      FIG. 3  shows an isometric view of an upper housing portion in accordance with the present invention; 
           [0010]      FIG. 4  shows an exploded view of the lower housing portion, inner mounting assembly and upper housing portion in accordance with the present invention; and 
           [0011]      FIG. 5  shows a cross-sectional view of the upper housing portion in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring to  FIGS. 1-5 , there are shown various views of an explosion-proof enclosure. The enclosure  10  includes an upper housing portion  12 , a lower housing portion  14 , and an inner mounting assembly or module  16 . The upper and lower housing portions  12  and  14  are fabricated of a material, e.g., steel, cast iron, and the like, that is capable of preventing a spark or flame from within the housing from reaching the environment external to the enclosure. Preferably the upper and lower housing portions are each cast as a single integral unit. The inner mounting assembly or module  16  is fabricated from a durable and preferably non-conductive material such as plastic. 
         [0013]    The lower housing portion  14  ( FIG. 1 ) includes a sidewall portion  20 , a bottom portion  22 , and a threaded attachment portion  24 , which are structured and arranged to provide an open chamber  26  therein. The chamber  26  accommodates the device and associated wiring, fittings, and the like. 
         [0014]    The sidewall portion  20  is substantially cylindrical and includes a substantially planar rim portion  28  and first and second ports  21  and  23  into each of which a conduit (not shown) for cables, wires, and the like can be threaded or otherwise affixed. Although the sidewall portion  20  shown in  FIG. 1  is substantially cylindrical and two ports  21  and  23  are also shown, this is for illustrative purposes only. The sidewall portion  20  can have a shape other than cylindrical and the number of ports can be more than or less than two. In addition, the ports may be differently disposed than the illustrated embodiment in which the ports are in line with each other. 
         [0015]    The attachment portion  24  is substantially cylindrical and further structured to include threads  25  for releasably attaching the lower housing portion  14  and the upper housing portion  12 . Preferably, a sealing element, such as an O-ring  15 , is disposed in a groove  29  adjacent to the rim  28  for providing an air- and water-tight seal between the upper and lower housing portions  12  and  14  when the upper and lower housing portions  12  and  14  are in threaded attachment. 
         [0016]    Within the chamber  26  of the lower housing portion  14  and along the inner face  30  of the sidewall portion  20  is a plurality of bosses or ribs  32 . The bosses  32  are spaced about the periphery of the chamber and preferably are integrally formed with the lower housing portion  14 . Alternatively, the bosses  32  can be separate elements which are attached to the lower housing portion  14 . Although four bosses  32  are shown in  FIG. 1 , the invention is not to be construed as being limited to four as the number of bosses  32  can be greater than or fewer than four. 
         [0017]    The bosses  32  serve two primary purposes. First, they provide structural support and reinforcement to the lower housing portion  14 . Second, the bosses  32  provide guides for orienting and supporting the inner mounting assembly or module  16 . As will be further described below, the mounting assembly has recesses which are cooperative with the bosses to orient and mount the mounting assembly  16  in the chamber  26 . After installation of the mounting assembly  16  in an intended position in chamber  26 , the mounting assembly can be secured by an appropriate fastener. For example, as shown in  FIG. 1  and  FIG. 2 , each boss  32  can include a threaded opening  47  for receiving a fastener  46 , such as a thumbscrew, machine screw or bolt. 
         [0018]    For mounting the enclosure  10  to an external surface or structure, the lower housing portion  14  includes mounting flanges  49  that each include an opening  48  through which a fastener or other mounting element (not shown) can be accommodated. The flanges  49  and openings  48  are adapted to attach the enclosure  10  to a supporting structure, e.g., wall, beam, column, and so forth, in any orientation so that the first and second ports  21  and  23  are oriented horizontally, vertically or at any angle therebetween. 
         [0019]    As mentioned above, the plural bosses  32  also provide multiple guides for supporting and/or securing the mounting assembly or module  16 . Advantageously, the plural bosses  32  enable mounting the mounting assembly or module  16  to the lower housing portion  14  independently of the orientation of the mounted lower housing portion  14 . Consequently, the mounting assembly or module  16  can be disposed against and attached to the plural bosses  32  so that the device contained in the chamber  26  is always right-side up or otherwise oriented to facilitate observing the display of the device regardless of how the lower housing portion  14  is externally mounted. In the illustrated embodiment, four bosses  32  are provided in the lower housing portion  14  and cooperate with four recesses in the mounting assembly  16  to provide four different mounting positions for the mounting assembly and device attached thereto. 
         [0020]    The upper housing portion  12  ( FIG. 3  through  FIG. 5 ) includes a sidewall portion  34  and a top portion  36  that are structured and arranged to provide a chamber  38  that provides space for the portion of the mounting assembly  16  and device attached thereto which extends outwardly of the lower housing portion  14 . 
         [0021]    The top portion  36  of the upper housing portion  12  includes a transparent window  31  for viewing a readout or display of the meter, instrument or other device contained within the chambers of the housing. The window  31  can be made, for example, of glass, acrylic, polycarbonate, and the like, and is in sealing engagement with the surrounding portion of the housing  12 . 
         [0022]    The upper housing portion  12  includes a circular groove  71  in which a first O-ring  75  or other sealing element is disposed. The first O-ring  75  is seated in the circular groove  71  and is structured and arranged to abut the confronting surface of the window  31 , to provide an air- and water-tight seal. The window  31  is retained in place by a retaining ring  73  that is adapted to exert pressure against the window  31  to form the seal with the first O-ring  75 . 
         [0023]    The retaining ring  73  also includes a circular groove  72  in which a second O-ring  79  or other sealing element is disposed. The second O-ring  79  is structured and arranged to abut the reverse surface of the window  31 , so that when the retaining ring  73  is inserted in the housing portion and tightened, the second O-ring  79  provides another air- and water-tight seal. 
         [0024]    The retaining ring  73  is operatively disposed within the chamber  38  of the upper housing portion  12 . In one embodiment, the retaining ring  73  is threaded about its outer periphery. The threads in the retaining ring  73  mate with threadings  70  within the chamber  38  of the upper housing portion  12 . By threading the retaining ring  73  within the chamber  38  of the upper housing portion  12 , the retaining ring  73  will exert pressure against the second O-ring  79  and against the window  31 . The window is retained in sealing engagement with the upper housing portion  12  to provide an air- and water-tight seal. Although  FIG. 5  shows that the retaining ring  73  is threaded into a threaded portion  74  of the chamber  38  that is separate from the internal threaded attachment portion  33  for attaching the upper housing portion  12  to the lower housing portion  14 , this is done for illustrative purposes only. The internal threaded attachment portion  33  for attaching the upper housing portion  12  to the lower housing portion  14 , could, instead, be continuous so that the outer periphery of the retaining ring  73  mates with continuous internal threaded attachment portion  33 , rather than a separate set of threadings  70 . 
         [0025]    For applications in which the meter or other device contained in the enclosure has no display to be read by a user, the window  31  can be eliminated and in its place, a blind cover can be provided. Alternatively, the upper housing portion can be integrally formed with a solid cover portion. 
         [0026]    The sidewall portion  34  shown in  FIGS. 3 through 5  is substantially cylindrical and includes a threaded attachment portion  33  and a beveled portion  37 . Grooves  40  for accommodating human fingers can be provided on the exterior surface  42  of the sidewall portion  34 , to facilitate rotation and threading of the upper housing portion  12  to the lower housing portion  14 . The internal threaded attachment portion  33  mates with the external threaded portion  25  of the lower housing portion  14 . 
         [0027]    The beveled portion  37  is disposed at the bottom portion of the sidewall portion  34 . The beveled portion  37  is adapted to accommodate an O-ring  15  that has been fitted onto the rim portion  28  of the lower housing portion  14 , to provide an air- and water-tight seal when the upper and lower housing portions  12  and  14  are in threaded attachment. Also, disposed on the exterior surface  42  of the sidewall portion  34  of the upper housing portion  12  is a locking device  45 , such as a locking screw, for releasably locking the upper and lower housing portions  12  and  14 . 
         [0028]    The inner mounting assembly or module  16  is structured and arranged to accommodate and support at least one meter, instrument, or other electrical device. Referring to  FIG. 2  and  FIG. 4 , the inner mounting assembly or module  16  includes a first cylindrical portion  65 , a second cylindrical portion  60 , and a planar portion  51  that is orthogonal or substantially orthogonal to each of the cylindrical portions  65  and  60  and that connects the first cylindrical portion  65  to the second cylindrical portion  60 . 
         [0029]    The first cylindrical portion  65  of the inner mounting assembly or module  16  includes a plurality of recesses  58  that are configured to be cooperative with the bosses  32  of the lower housing portion  14  and one or more attachment studs  52  that is disposed on the planar portion  51 . The second cylindrical portion  60  is stepped inwardly from the first portion  65  and has openings  57  and  61  and threaded studs (not shown) for receiving a meter or other device mounted thereto. The mounting assembly  16  can be configured with openings and mounting elements to accommodate a particular type of device or a range of device types. 
         [0030]    The mounting assembly  16  and the device attached thereto is positioned in the lower housing portion  14  with the recesses  58  of the mounting assembly in cooperative engagement with the bosses  32 . The mounting assembly  16  is secured in position by one or more fasteners  46  which extend through associated mounting studs  52  into threaded attachment with threaded holes  47  on the outer surface of respective bosses  32 . 
         [0031]    In the illustrated embodiment, the mounting assembly  16  is secured in the lower housing portion  14  by two diametrically positioned fasteners  46 . It will be appreciated that in some instance a single fastener  46  can suffice to secure the mounting assembly  16 , while in other instances, a fastener  46  may be employed for attachment to each of the bosses  32  of the lower housing portion  14 . 
         [0032]    It will be further appreciated that the configuration of the inner mounting assembly  16  can vary to suit the particular meter or other device to be attached thereto. In use, the meter or other device is attached to the mounting assembly  16  by suitable fasteners or other attachment elements, and electrical connection is made to the device by wires which extend into the housing chamber via the one or more conduits. 
         [0033]    Internal wiring within the explosion-proof is highly variable being determined, in large part, by the particular internal device and the end-user application. Wiring can include—for purposes of illustration and not limitation—analog and/or digital input signals and/or serial communication lines that represent an industrial process variable or that are used for process control and/or transmission or retransmission of the input; contact closure, i.e. relay, or transistor output that are used for alarm indication and/or process control; DC voltage output supply for powering an external device; and DC or AC voltage input supply for powering an internal device. 
         [0034]    Many changes in the details, materials, and arrangement of parts and steps, herein described and illustrated, can be made by those skilled in the art in light of teachings contained hereinabove. Accordingly, it will be understood that the following claims are not to be limited to the embodiments disclosed herein and can include practices other than those specifically described, and are to be interpreted as broadly as allowed under the law.