Abstract:
A ground fault receptacle housing for an electrical device having a backing portion with a base and a wall extending from the base. The wall has a hoop portion that forms an exterior channel extending therethrough. A cover portion is adapted to couple to the backing portion and has a front face with apertures therein for access to the electrical device. A wall extends from the front face and has a substantially inflexible post extending from the wall. The post has a body portion and a tapered protrusion thereon, the protrusion having a largest perimeter that is greater than at least a perimeter in portion of the exterior channel. When the protrusion passes through the channel, at least a portion of the hoop portion stretches, while the wall extending from the base of the backing portion remains substantially stationary. The protrusion is adapted to engage the end surface of hoop portion after passing through the channel, while the body portion of the post is positioned within the channel without substantially stretching the hoop portion when the protrusion engages the end surface.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the assembly of an electrical receptacle housing. More particularly, the present invention relates to the assembly of a two-piece ground fault receptacle housing having multiple barbed posts on a first portion of the housing that couple to respective resilient hoops on a second portion of the housing. 
     BACKGROUND OF THE INVENTION 
     Many conventional electrical receptacle housings employ a two-piece housing that is formed by separate mateable front and back covers. The covers generally mate together using any know means, such as screws, rivets, or snap-fit. A mounting bridge with ears at opposite ends generally extends between the front and back covers and allows the housing to be attached to a suitable structure, such as a building wall or an electrical box. In some electrical receptacle designs, the mounting bridge has a generally U-shape so as to wrap around portions of the mated front and back covers of the housing and couples to the front and back covers. In other electrical receptacle designs, the mounting bridge is a relatively flat shape and is disposed between the mated front and back covers of the housing. The bridge can be coupled to the housing using any mechanical fasteners, such as screws or rivets. 
     In many conventional receptacle housings, the two-piece housing is coupled together using fasteners or screws, as described above. This fastener type housing forms a rigidly secured, hard to separate housing, but is cumbersome and difficult to assemble. In many situations, it is necessary to assemble many housings, each having multiple fasteners, creating a time consuming, tedious job. 
     Additionally, other conventional receptacle housings have a snap-fit design, wherein the front cover snaps to the back cover, holding the bridge in-between. Several designs of snap-fit of housings for electrical receptacles are disclosed in U.S. Pat. No. 4,872,087 to Brant, U.S. Pat. No. 5,510,760 to Marcou et al and U.S. Pat. No. 6,015,303 to Bonilla et al., which are herein incorporated by reference. A design of a snap-fit housing for an accessory strip to an outlet cover plate is disclosed in U.S. Pat. No. 5,613,874 to Orlando et al., which is herein incorporated by reference. While these prior art snap-fit designs allow a quick assembly of the housing without the use of screws or rivets, they do not provide a rigidly coupled housing. In many instances the two housing portions can be twisted or pulled apart relatively easily, thus exposing the electrical receptacle to the outside environment and the installer/user, and possibly causing electrical shock to the installer/user or damage to the electrical receptacle. 
     Consequently, a need still remains for a snap-fit housing for an electrical receptacle that is quick and easy to assemble, while simultaneously providing a housing that is difficult or unlikely to be pulled or twisted apart. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of this invention is to provide an improved electrical receptacle housing. 
     Another object of this invention is to provide an electrical receptacle housing, which can be easily and rapidly assembled. 
     Still another object of this invention is to provide an electrical receptacle housing having a two-part housing, which is difficult to disassemble. 
     Yet Another object of the present invention is to provide an electrical receptacle housing having a two-piece housing, which are coupled together using a snap-fit connection, rather than the more conventional fastening means. 
     The foregoing objects are basically attained by providing a electrical wiring device housing, comprising a first section having a first wall, a first side wall extending from the first wall, and a connecting unit extending from the first side wall. The connecting unit has a connecting wall that has a normally substantially planar configuration and is spaced from the first side wall and an end wall that is adjacent the connecting wall. The housing also comprises a second section that has a second wall, a second side wall extending from the second wall, and a post extending from the second wall. The post has a barb at the distal end thereof, the barb is adapted to pass between the connecting wall and the first sidewall and engage the end wall of the connecting unit. The first side wall remains substantially stationary while at least a portion of the connecting wall flexes away from the first side wall when the barb passes therebetween, and the connecting wall returns to the normally substantially planar configuration when the barb engages the end wall. 
     By forming a electrical wiring device housing in this manner, the housing is quick and easy to assembly and is extremely difficult to disassemble. 
     Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention. 
     As used in this application, up, down, upper and lower refer to relative directions depending on the orientation of the two pieces of the housing relative to each other, and do not limit the housing to any specific orientation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings which form a part of this disclosure: 
     FIG. 1 is top perspective view of a two-piece housing according to the preferred embodiment of the present invention, prior to engagement of the first and second pieces of the housing. 
     FIG. 2 is a top perspective view of the housing of FIG. 1, after engagement of the first and second pieces of the housing and with the electrical receptacle therein. 
     FIG. 3 is a bottom perspective view of the housing of FIG. 1, prior to engagement of the first and second pieces of the housing. 
     FIG. 4 is a bottom perspective view of the housing of FIG.  2 . 
     FIG. 5 is a top plan view of the second piece of the housing of FIG.  1 . 
     FIG. 6 is a side elevational view of the second piece of the housing of FIG.  5 . 
     FIG. 7 is a top plan view of the first piece of the housing of FIG. 1 
     FIG. 8 is a side elevational view of the first piece of the housing of FIG.  8 . 
     FIG. 9 is an end view in section of the housing of FIG. 2, after engagement of the first and second pieces of the housing. 
     FIG. 10 is a side view in section of the housing of FIG. 9, taken along lines  10 — 10 . 
     FIGS. 11 a-e  is a partial side view in section of the barb and hoop portion of the housing in FIG. 1 being coupled together. 
     FIGS. 12 a-e  is a partial end view in section of the barb and hoop portion of the housing in FIG. 1 being coupled together. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-4 illustrate an electrical wiring device housing  10  in accordance with a preferred embodiment of the present invention. Wiring housing  10  is a ground fault interrupter receptacle for preferably housing an electrical duplex outlet  11 ; however, wiring housing  10  can house any electrical device desired. Housing  10  preferably has a first section  12  and a second section  14  that can be coupled together in such a manner that they are difficult to disassemble. 
     The electrical duplex outlet  11  is preferably a conventional electrical duplex outlet as is known to one skilled in this art and has a bridge  218  for coupling to an outlet box or any other device, attaching members or screws  216  for connecting electrical wiring, specifically hot and neutral wires, and attaching member or screw  220  for connecting electrical wiring, preferably a ground wire. 
     First section or backing portion  12  (FIGS. 3 and 4) is preferably formed of a plastic material, such as nylon (specifically, ZYTEL 101F-NC10) but can be any thermoplastic, polymer or synthetic nonconductive material. ZYTEL 101F NC010 is sold by DuPont and is an internally lubricated PA 66 that has been developed for fast cycles and high productivity and has the following mechanical properties measured at about 23° C.: 
     
       
         
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Value 
               
             
          
           
               
                 Property 
                 Test Method 
                 Units 
                 50% RH 
                 DAM 
               
               
                   
               
             
          
           
               
                 Yield Stress 
                 ISO 527-1/2 
                 MPa 
                 53 
                 83 
               
               
                 50 mm/min 
               
               
                 Nominal Strain at Break 
                 ISO 527-1/2 
                 % 
                 &gt;50 
                 18 
               
               
                 50 mm/min 
               
               
                 Yield Strain 
                 ISO 527-1/2 
                 % 
                 25 
                 4,4  
               
               
                 50 mm/min 
               
               
                 Tensile Modulus 
                 ISO 527-1/2 
                 MPa 
                 1200 
                 3100  
               
               
                 1 mm/min 
               
               
                   
               
               
                 ISO = International Standards  
               
               
                 MPa = Mega Pascal  
               
               
                 RH = Relative Humidity  
               
               
                 DAM = Dry as Molded Organization  
               
             
          
         
       
     
     First section  12  is preferably a molded portion of the housing having a substantially smooth, planar surface or first wall  16 . Backing portion  12  has a first end  18 , a second end  20 , a first side  22 , a second side  24 , and is surrounded by a perimeter wall  26 . Wall  26  extends substantially perpendicularly from planar surface  16 . Wall  26  is formed of several different sidewalls or sections. 
     As can be seen specifically in FIGS. 1 and 7, perimeter wall  26  has a U-shaped portion  28  that extends from first end  18 . The U-shaped portion is comprised of three, preferably unitary or integrally formed sections or substantially rigid base walls  30 ,  32  and  34 . Section  30  extends along substantially the entire length of first end  18  and substantially perpendicularly from planar surface or base  16 . Sections  32  and  34  each extend along a portion of sides  22  and  24 , respectively and substantially perpendicularly from planar surface  16 . However, sections  30 ,  32  and  34  do not necessarily need to be unitary and can be separate if desired and can extend at any suitable angle relative to planar surface  16 . 
     As seen in FIGS. 1,  2 ,  7  and  8  section  30  has a substantially rectangular protrusion or extension  36  that projections away from planar surface  16  and is substantially coplanar with section  30 . Sections  32  and  34  each have a hoop portion or connecting unit  38  and  40 , respectively, integrally or unitarily formed thereon. However, hoop portions  38  and  40  may be coupled to sections  32  and  34  in any suitable manner desired. Hoop portions  38  and  40  are substantially similar so only one will be described herein. 
     Hoop portion  38  is formed from three separate walls or portions  42 ,  44  and  46 . The three walls of the hoop portion  38  and section  32  are integrally formed or coupled together to define a continuous resilient hoop having a substantially rectangular through passageway or external channel  52 . Channel  52  however, does not have to be substantially rectangular and the walls  42 ,  44  and  46  and section  32  can be configured to form any shape channel desired. Portion or connecting wall  42  preferably has a normally substantially planar configuration and is substantially parallel to and spaced from section  32 . Walls  44  and  46  preferably extend substantially perpendicular from and are preferably unitary with section  32  and wall  44 . Each hoop portion has a first end  48  and a second end  50 , which are defined by the end surfaces of walls  42 ,  44  and  46 , as shown in FIGS. 1-4. As seen in FIGS. 11 a-e  and  12   a-e  the interior portion of walls  42 ,  44  and  46  taper downwardly and inwardly. The interior portion of wall  42  is preferably about 0.242±0.005 inches at its shortest length D and about 0.342±0.005 at its widest. The interior portion of walls  44  and  46  are preferably about 0.08±0.005 inches at their shortest length E and about 0.10±0.005 at their widest. The short length of walls  42 ,  44  and  46  and wall  32  form a narrow portion  51  of in through passageway  52 . Narrow portion  51  has a perimeter A. Perimeter A is preferably about 0.644 inches, but may be any measurement that allows the housing to couple together as described herein and walls  42 ,  44  and  46  do not necessarily need to be the lengths stated and may be any length desired. Additionally, each wall  32  and  34  has a groove or trench  53  and  55 , respectively, on the exterior surface of the wall and a ridge  57  and  59 , respectively, in the interior surface. 
     Adjacent U-shaped portion  28  (FIGS. 1 and 7) are two shorter or lower portions or walls  58  and  60  that are preferably unitary with and extend substantially perpendicular to planar surface  16 . Walls  58  and  60  are recessed slightly inwardly toward the center of surface  16 , relative to U-shaped portion  28 , and each wall  58  and  60  has a protrusion  62  and  64 , respectively extending outwardly and substantially parallel with planar surface  16  therefrom. Protrusions  62  and  64  extend to about the same distance as U-shaped portion  28 . 
     Sections or substantially rigid base walls  66  and  68  are adjacent walls  58  and  60  and are preferably unitary with and extend substantially perpendicular to planar surface  16 . However, walls  66  and  68  can extend at any suitable angle relative to planar surface  16 . Walls  66  and  68  are preferably rectangular and have hoop portions  70  and  72 , respectively, which are substantially similar to design and use as hoop portions  38  and  40  and therefore will not be discussed in detail here. Each wall  66  and  68  has two ridges  74  and  76  that extend from planar surface  16  adjacent each wall&#39;s outside edges on the interior surface of walls  66  and  68  and terminate preferably before reaching the end of walls  66  and  68 . Additionally, as seen in FIGS. 1 and  3 , the exterior surface of walls  66  and  68  each have a groove or trench  77  and  79 , respectively. Section  66  and  68 , walls  58  and  60 , and sections  32  and  34  of U-shaped portion  28  form U-shaped apertures or openings  78  and  80 . 
     As shown in FIG. 7, adjacent sections  66  and  68  are two shorter or lower portions or walls  82  and  84  that are preferably unitary with and extend substantially perpendicular to planar surface  16 . Walls  82  and  84  are similar to walls  58  and  60  described above. Walls  82  and  84  are recessed slightly inwardly toward the center of surface  16 , relative to sections  66  and  68  and each wall  82  and  84  has a protrusion  86  and  88 , respectively extending outwardly and substantially parallel with coplanar surface  16  therefrom. Protrusions  86  and  88  extend to about the same distance outwardly sections  66  and  68 . 
     At second end  20 , section  12  has another U-shaped portion  90  (FIGS.  1  and  7 ). U-shaped portion  90  is comprised of three, preferably unitary or integrally formed sections or substantially rigid base walls  92 ,  94  and  96 . Section  92  extends along substantially the entire length of second end  20  and substantially perpendicularly from planar surface  16 . Sections  94  and  96  each extend along a portion of sides  22  and  24 , respectively and substantially perpendicularly from planar surface  16 . However, sections  92 ,  94  and  96  do not necessarily need to be unitary and can be separate if desired and can extend at any suitable angle relative to planar surface  16 . Section  92  is preferably slightly shorter or narrower than section  30  of U-shaped portion  28  and has a protrusion or extension  98  that projects away from planar surface  16  and is substantially coplanar with section  92 . Additionally, section  92  is higher on the side of the projection adjacent wall  24  than on the side of the projection adjacent wall  22  and has an indentation or recess  93  adjacent wall  22 . 
     Sections  94  and  96  each has a hoop portion or connecting unit  100  and  102  (FIGS. 1-4 and  7 ), respectively integrally or unitarily formed thereon. Hoop portions  100  and  102  are substantially similar and therefore only hoop portion  100  will be described herein. Hoop portion  100  is formed from three separate walls or portions  104 ,  106  and  108 , as shown specifically in FIG.  7 . The hoop portion also has a first end  110  and a second end  112 . The three walls of the hoop portion  100  and section  94  are integrally formed or coupled together to define a through passageway or channel  114 . Portion or connecting wall  104  has a normally substantially planar configuration and is substantially parallel to and spaced from section  94 . Wall  106  extends substantially perpendicular from and is preferably unitary with section  94  and wall  106 , while wall  108  is also preferably unitary or integral with section  94  and wall  106 , wall  108  extends at an angle other than 90-degrees from section  94  and wall  106 . However, each wall can extend at any desired angle relative to section  94 . The interior portion of walls  104  and  108  taper downwardly and inwardly. Wall  104  is preferably about 0.204±0.005 inches at its shortest length and about 0.213±0.005 at its widest. Walls  106  and  108  are preferably about 0.09±0.005 inches at their shortest length and about 0.11±0.005 at their widest. The short length of walls  104  and  108  and wall  106  and section  94  form a narrow portion  51  in through passageway  52 , narrow portion  51  having a perimeter A′. Perimeter A′ is preferably about 0.588 inches, but may be any measurement that allows the housing to couple together as described herein and walls  104 ,  106  and  108  do not necessarily need to be the lengths stated and may be any length desired. Additionally, sections  94  and  96  each have a ridge or wall  119  and  121 , respectively that extends along the exterior surface adjacent walls  82  and  84 , respectively. Sections  66  and  68 , walls  82  and  84 , and sections  94  and  96  of U-shaped portion  90  form U-shaped apertures or openings  123  and  125 . 
     As seen in FIGS. 1 and 2, second section or cover portion  14  is preferably a plastic, such as nylon (specifically, ZYTEL 101F NC010, as described above) but can be any thermoplastic, polymer or synthetic nonconductive material. 
     Second section  14  is preferably a molded portion of the housing having a substantially smooth, planar surface or second wall  124 . Surface  124  preferably has openings or apertures  126  therethrough for two electrical plugs or outlets. However, surface  124  can have any number of openings for any type of electrical device or it can have no openings. Additionally, surface  124  preferably has openings or apertures  128  for test  129  or reset  131  buttons, as are known to one of ordinary skill in the art. The interior surface  135  of portion  14  has walls or raised portions  137  that generally trace or outline apertures  126  and  128 , as seen specifically in FIG.  3 . 
     Cover portion  14  has a first end  130 , a second end  132 , a first side  134 , a second side  136 , and is surrounded by a perimeter wall  138 . Wall  138  preferably extends substantially perpendicularly from planar surface  124 , but may extend at any suitable angle. Wall  138  is formed of upper portion  140  and lower portion  142 . Upper portion  140  is preferably smooth and preferably extends substantially entirely around surface  124 , except at second end  132 , wherein two small grooves are cut out of upper portion  140  forming tongue  144 . 
     Lower portion  142  is preferably unitary or integral with upper portion  140  and is comprised of two preferably substantially similar portions  146  and  148 . However, it is not necessary for the portions to be similar and each may be any configuration desired. Portion  146  extends downwardly from upper portion  140  and substantially the entire length of first side  134  and along a portion of first and second ends  130  and  132 , as seen specifically in FIGS. 1-3. Lower portion  146  is preferably substantially parallel to and extends from upper portion  140  in such a manner that inner surface  150  of lower surface  146  is in substantially the same plane as outer surface  152  of upper portion  140 , defining upper portion end surface  154  and lower portion end surface  155 . However, upper portion  140  and lower portion  146  do not necessarily have to be parallel or have coplanar inner and outer surfaces and one can extend from the other in any manner desired, such as coplanar or any other angle. Additionally, lower portion  146  has two sections  156  and  158  that extend from end surface  154  of upper portion  140  farther than the rest of lower portion  146 , as seen specifically in FIG.  3 . Sections  156  and  158  each have a groove or recess  160  and  162 , respectively. 
     Lower portion  146  has three substantially inflexible or rigid, rectangular posts or elongate members  164 ,  166  and  168  extending therefrom having a cross-sectional area B with a perimeter that is less than the narrow portion of channel  52  or perimeter A, as seen specifically in FIGS. 11 a-e  and  12   a-e.  Each post is coupled to and preferably integral or unitary with exterior surface  170  of portion  146 . As seen in FIGS. 1-4, posts  164 ,  166  and  166  each have a body portion  165 ,  167  and  169  that extend outwardly and downwardly from portion  146  and terminate into a tapered protrusion or barb  172 ,  174  or  176 , respectively, at the distal end thereof. Protrusions or wedges  172  and  174  are substantially similar and therefore, only protrusion  172  will be described herein. As seen in FIGS. 1 and 5, protrusion  172  is substantially coplanar or flush with surface  178  of barb  164 , but extends or protrudes substantially perpendicularly from surfaces  180 ,  182  and  184 , defining a rear substantially planar surface  186  having a perimeter C. Perimeter C has a cross-sectional area that is greater than the narrow portion of channel  52  or perimeter A, as seen specifically in FIGS. 11 a-e  and  12   a-e.  Perimeter C is preferably about 0.76 inches and has two sides F that are preferably about 0.10±0.005 inches and two sides G that are about 0.28±0.005 inches; however the perimeter and length of the sides of the barb may be any measurement that allows the housing to couple together as described herein. Protrusion or wedge  172  of barb  164  does not necessarily need to be perpendicular relative to surfaces  180 ,  182  or  184  and may extend at any angle (acute, obtuse or otherwise) from any of the sides and not necessarily the same angle from each side. Protrusion  172  tapers downwardly and inwardly to an end or point  186 . Additionally, both the body portions  165 ,  167  and  169  and the protrusions  172 ,  174  and  176  of the posts  164 ,  166  and  168  may be any configuration desired, such as oval, circular, triangular or any other suitable polygon. Post  168  is set in farther toward the center of portion  14  than posts  164  and  166 , but is otherwise substantially similar to posts  164  and  166 . 
     As seen in FIGS. 1 and 6, protrusion  176  is similar to protrusions  172  and  174  and the discussion of protrusion  172  applies to protrusion  176 ; except protrusion  176  is substantially coplanar or flush with both sides  188  and  190  and extends or protrudes substantially perpendicularly from surfaces  192  and  194 , defining a rear substantially planar surface  196 . Surface  196  defines a cross-sectional area having a perimeter B′ that is less than the narrow portion of channel  114  or perimeter A′. Perimeter B′ is preferably about 0.68 inches and has two sides that are preferably about 0.10±0.005 inches and two sides that are about 0.24±0.005 inches; however the perimeter and length of the sides of the barb may be any measurement that allows the housing to couple together as described herein. Protrusion  176  tapers downwardly and inwardly to an end or point  198 . 
     Portion  148  is substantially similar to portion  146 , described above and the description of portion  146  applies to portion  148 . Portion  148  has three elongate members or posts  204 ,  206  and  208  that are substantially similar to posts  164 ,  166  and  168  described above, each post having a protrusion  210 ,  212  and  214 , respectively. However, portion  148  does not extend along second end  132  in the same manner as portion  146 . As seen in FIG. 3, portion  148  ends at comer  200  of upper portion  140  and along second end  132 , member  202  extends outwardly and away from end  132 . 
     It is noted that the housing  10 , as described above, preferably has six hoop portions and six posts that couple together on a one-to-one basis, but is possible that the housing can have as few as one hoop/post connection and as many as desired (i.e. 2-5 or greater than 6) to achieve the coupling of the two pieces of the housing described above. 
     Assembly 
     As seen in FIGS. 1-6, to assemble housing  10 , first section  12  and second section  14  are moved toward each other along longitudinal axis X of elongate members  164 ,  166 ,  168 ,  204 ,  206  and  208 . Protrusions  172 ,  174  and  176  are inserted into channels  52  of hoop portions  40  and  72  and channel  114  of hoop portion  102 , respectively, and protrusions  210 ,  212  and  214  are inserted into channels  52  of hoop portions  38  and  70  and channel  114  of hoop portion  112 , respectively. The tapered walls of the protrusions engage the tapered walls of the hoop portions. As the protrusions are further inserted, the perimeters A and A′ of the hoop portions are increased or resiliently expanded, as seen specifically in FIGS. 11 d  and  12   d,  while the base walls or sections ( 32 ,  34 ,  66 ,  68 ,  94  and  96 ) and the elongate members remain substantially stationary. In other words, as the protrusion or barb passes through channel  52  or  114 , at least a portion of the connecting walls resiliently flex outwardly or away from the sections or base walls of the hoop and the elongate members and base walls do not substantially bend. At least a portion of each wall and preferably each entire wall is adapted to stretch when the protrusion passes through the channel  52 . The walls expand since the length of walls D and E are shorter than sides G and F of the barb or protrusion, respectively. In other words, the ratio of the length of wall D to side G is between about 0.83 to 0.90 and the ratio of the length of wall E to side F is between about 0.70 and 0.90. When the protrusion passes entirely through the channel or aperture and the end surface of each protrusion engages the abutment or end surface of the hoop portion, as seen specifically in FIGS. 2,  9  and  10 , the walls of the hoop portions return to a normal, unstretched position under their natural resiliency with a portion of the elongate member, preferably the body portion, remaining in the aperture. The hoop portion is designed to withstand a certain outwardly directed hoop stress that allows it to expand without breaking or permanently deforming, and to contact inwardly once the barb passes therethrough. 
     When the sections  12  and  14  are assembled, lower portion  142  of section  14  and openings  78 ,  80 ,  123  and  125  preferably form a rectangular opening allowing access to the interior of the housing  10 . These openings enable a connection, for example, a screw  216  or other type of connection, for hot and neutral wires or any type of desired electrical connection as is know in the art. Additionally, the lower portion of section  92  allows another access opening in housing  10  for an electrical connection  220 , such as a grounding wire. Additionally, extensions  36  and  98  are slightly spaced from upper wall  140  of housing portion  14 , allowing the bridge  218  for the electrical duplex to pass therethrough. 
     This assembly allows the two parts of the housing to be snap-fitted together easily and simply while making it extremely difficult to pull or twist the two halves apart. Specifically, the perimeter of cross-section of the end surface of each protrusion or barb is significantly larger that the respective channel in the hoop portion, and therefore it is very difficult to pull the barb backwardly through the aperture, without using a device or mechanism to stretch each hoop portion. The end surface of the protrusion simply abuts or contacts the end surface of its respective hoop portion. Additionally, the redundancy of the posts and the general rigidity of the housing make the housing resistant to twisting and the two pieces of the housing are therefore not likely to be pulled apart. 
     While a specific embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.