Patent Document

BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to electrical wiring devices and more particularly to duplex electrical receptacles and housings therefor which are suitable for mounting in conventional wall boxes. 
     Duplex electrical receptacles may be categorized as either general purpose or self-contained receptacles. As is well known, general purpose duplex receptacles are typically designed to have two sets of two or three female contacts in each set, depending upon whether the receptacle is of the ungrounded or the grounded type. In the grounded type of receptacle, electrical connections are made to the ground terminals as well as to the power and neutral terminals. In ungrounded receptacles, ground terminals are eliminated. 
     General purpose receptacles usually have both a single and a split (or dual) circuit operating capability. Usually, the split circuit mode is used when each set of contacts is to be fed electrical power from independent circuit sources. The single circuit mode is usually used when it is desired that the electrical current supplied to the one set of contacts also feed-through to the other set of contacts and possibly to more downstream connected wiring devices coupled into the receptacle circuit. 
     A slotted tab provided in the electrical structure joining the different sets of contacts may be broken off by a screwdriver blade tip inserted into the tab or by pliers to convert the receptacle from the single circuit mode to a split (or dual) circuit mode. With the receptacle connected in a split circuit mode, both sets of contacts can be operated independently of each other. For example, one-half of the receptacle can be selectively energized by operation of an electrical wall switch connected to only the one set of contacts mounted in that one-half while the other set of contacts mounted in the other half of the receptacle can be energized continuously from conductors connected to the source of circuit power or through an upstream wiring device, such as another receptacle. 
     Self-contained receptacles as compared to general purpose receptacles, are designed to have only a feed-through or single circuit capability but do not have a split circuit capability. Moreover, because of their construction, fire code requirements presently limit installation and usage of self-contained devices to the first two levels of a building or other structure. The receptacles are primarily designed for assembly with special purpose assembly tools and usually can only be connected with non-metallic, sheathed cable. Because of their different-than-standard usage sizes and special mounting requirements, self-contained receptacles are usually not interchangeable with the aforedescribed general purpose receptacles. Moreover, the design of the housings of self-contained receptacles does not permit them to be mounted in the general purpose type of metallic wall boxes which are designed to accommodate various types of general purpose receptacles. 
     The insulated conductors may be connected to terminals of the self-contained receptacles by use of the so-called &#34;insulation-displacement&#34; technique. This technique typically involves pushing a conductor into a terminal slot such that the slot penetrates or cuts through the conductor insulation sufficiently to make electrical contact with the underlying conductor wire. One way to do this is by use of a special parts-clamping tool, resembling a large hand pliers. Proper operation of this tool requires a modicum of skill and dexterity by the installer and convenient access to the wire and terminal slots. The insulation-displacement technique is a wire connecting technique which has been used with male and female electrical contacts in single circuit types of wiring devices, as described in my U.S. Pat. No. 4,196,956, assigned to the same assignee as this application. 
     The invention constructed in accordance with this invention is a receptacle and a housing therefor of the general purpose type with single and split circuit capability. The receptacle is adapted for mounting in standard or general purpose wall or floor boxes and may be easily and readily wired to associated electrical conductors by forcing the conductors into terminals with the side covers of the receptacle which side covers then complete the enclosure of the receptacle housing. 
     More specifically, a receptacle made in accordance with the invention is virtually independent of the quality of workmanship used in its installation and is fully insulated when installed such that there are no exposed live parts. This is a particularly important safety feature because it ensures that the electrified terminals cannot inadvertently make electrical contact with the metal portions of the receptacle box in which such receptacles are usually mounted. The receptacle of this invention is constructed such that it can be used with conductors varying in size over a relatively wide range and, moreover, the receptacle is reusable and can be rewired repeatedly. The general size and manner of use of the instant receptacle is similar to that of a conventional screw-terminal receptacle, to minimize the chance of improper installation due to unfamiliarity. Additionally, a portion of the conductor on both sides of the contact terminal is provided with a measure of strain relief. This is an important feature because the receptacle must be pushed back into its wall box after connection is made between the contact terminals and conductors, and this movement may cause the conductors to loosen in their associated contact terminals leading to electrical failures. 
     A receptacle forming a specific embodiment of the invention is made up of two molded components composed of suitable polymeric compositions and several stamped sheet metal components, and is assembled with the help of standard assembly screws. One of the plastic components is a receptacle body which may be composed of a thermosetting or a thermoplastic compound, such as nylon, and the other is a receptacle front cover having two side covers hinged thereto by respective integral web hinges. A pair of terminal members each having power contacts and power insulation-displacement (or insulation penetrating) terminals are inserted into the receptacle body. A metal yoke, with a metal piece having ground contacts and an insulation displacing ground terminal secured to the yoke, is mounted on the receptacle body such that the rearward part of the yoke cradles the receptacle body. The yoke has several frontwardly-extending yoke projections which are received with interference fits in slots formed in the underside of the receptacle front cover. The yoke projections engaging the walls of the slots serve as the principal connective means for joining the receptacle body to the front cover. The ground contacts and a wall plate screw tab also extend through a suitable pocket in the receptacle body. 
     The insulation-covered ends of power and ground wires are placed opposite their respective terminal slots, which face outwardly from two sides of the receptacle body, and the side covers are pivoted toward the receptacle body to push the conductors into the slots, displacing portions of the insulation coverings in the process to make electrical connections therebetween. The side covers are secured by way of suitable assembly screws, which when tightened, help ensure that good electrical connections are maintained between the conductors and their respective terminal slots. The side covers are constructed to grip the insulation coverings of wires so as to provide strain relief for the wire terminations. More detailed aspects of the invention will become apparent from the detailed description below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the main parts of a receptacle which embodies the invention. 
     FIG. 2 is a perspective view of a receptacle front, shown as molded, which forms a part of the receptacle shown in FIG. 1 and is seen from the back side thereof. 
     FIG. 3 is a front view of the receptacle shown in FIG. 1, as assembled. 
     FIG. 4 is a sectional view along lines 4--4 of FIG. 3. 
     FIG. 5 is a sectional view along lines 5--5 of FIG. 3. 
    
    
     DETAILED DESCRIPTION 
     A receptacle which forms an embodiment of the invention comprises a receptacle front member 10, a pair of power blade connector straps 12 and 14, a receptacle body 16, a ground blade connector strap 18 and a yoke 20. The receptacle front member 10 comprises a front cover of generally rectangular shape and designated 10a, a pair of power contact side covers generally designated 10b and 10c, respectively, and a ground contact side cover generally designated 10d. 
     The front cover 10a has two sets of apertures or slots extending perpendicularly therethrough to accommodate the various conductive blades of one or two male plugs inserted into the receptacle. The number of apertures and their configurations will, of course, depend upon the particular application or use to which the receptacle is to be put. The receptacle as illustrated has two sets of power blade apertures, designated 11a and 11b, respectively; two sets of neutral blade apertures designated 13a and 13b, respectively, and two sets of ground blade apertures, designated 15a and 15b, respectively, to accommodate conventional three-blade plugs. If the receptacle is not a grounding type, the ground apertures 15a and 15b may be omitted and only two apertures provided in each set; a power and a neutral aperture oriented in substantially parallel alignment. The entire receptacle front member is integrally molded with the side covers hinged to the front cover by means of &#34;live&#34; or web hinges. 
     The ground connector strap 18 and yoke 20 are assembled into a unit by means of rivets 22 and 24 which pass through respective openings 26 and 28 in the yoke 20 and through respective openings 30 and 32 in the ground connector strap 18 and have their ends peened over to fixedly secure the strap 18 and yoke 20 together in good electrical contact. The receptacle further comprises a pair of side cover assembly screws 34 and 36 and a ground contact assembly screw 35 which, as described below, assist in the assembly and wiring of the receptacle. 
     To assemble the receptacle, the ground blade connector strap 18 is placed inside the yoke 20 and riveted together and the sub-assembly is inserted into the receptacle body 16 from the bottom thereof as seen in FIG. 1. A dovetail 40 of the yoke 20 fits within a mating guide slot 42 in the receptacle body to secure this end of the yoke to the receptacle body. In this position, a pair of projections 44 and 46 fit within pocket or cavity 48 in the receptacle body 16, another pair of projections 50 and 52 fit closely around the outside of the side walls forming another pocket 54 in the receptacle body 16, a pair of grounding blades 56 and 58 forming one of the ground contacts fit and are thereby housed within the pocket 48 in the receptacle body 16, toward the left-hand side of that pocket as seen in FIG. 1. 
     The grounding strap 18 includes a tong 60 having at its top a threaded wallplate screw hole 62 aligned with wallplate aperture 62a. The tong 60 positioned against the inside surface of the projection 46 is, along with projection 46, housed by the pocket 48. To render greater stability to the cantilevered end of the tong bearing the screw hole 62, tip portion 63 of the tong may be shouldered to seat against the opposite inwardly inclined edges 44b of the projection 44, FIG. 4. In any event, the screw opening 61 of greater diameter than the screw 36 is substantially aligned with a threaded opening 47 in the projection 46 to permit unimpeded inward axial movement of the screw 36 through the opening 47 upon rotation of the screw during cover closure. 
     Another pair of ground contact blades 64 and 66, forming another ground contact of the ground connector strap 18 fit within and are thereby housed by the pocket 54. The guide slot 42 and pockets 48 and 54 in the receptacle body 16 extend through the entire receptacle body and are open at their bottom ends, which are not visible in FIG. 1. 
     The power connector strap 14 is inserted into the receptacle body 16, by dropping it into the body 16 from the top thereof as seen in FIG. 1, such that its blades forming a power contact, generally indicated at 68, fit within a pocket 70 in the receptacle body 16 and its blades forming another power contact generally indicated at 72 fit within another pocket 74 in the receptacle body 16, its pair of legs 76 and 78, which define a generally V-shaped insulation-displacement slot 80 therebetween, fit between abutments 82 and 84 of the receptacle body 16 and over a land 86 having a U-shaped slot 88 which is large enough to accommodate the largest conductor to be wired into the receptacle, and legs 90 and 92 defining between them a generally V-shaped insulation-displacement slot 94 fit between similar abutments 96 and 98 over a similar land 100 having a similar slot 102. When so positioned, a break-off tab 157 is located over a cavity 138 behind an upstanding land 97 extending between the abutments 84 and 96. Tabs 79 and 89 are positioned to abut the land 97 and thereby limit outward movement of the slots 80 and 94 in a direction perpendicular to the longitudinal axis of the device 10 whether the tab 157 is broken off or not. The land 97 also serves as a fulcrum for the blade of a screwdriver which may be inserted in a slot 155 to bend and thus break the tab 157 from its supporting tabs 79 and 89, respectively. As will be apparent, the outer edges of the legs 76, 78 and 90, 92 will bear against abutment 82, 84 and 96, 98, respectively, to restrain the contacts 90 and 94, respectively, against movement in directions parallel to the longitudinal axis of the device 10. The inward edges 81 and 95 of the respective contacts 80 and 94 bear against the surfaces of the pocket 48 adjoining the lands 86 and 100, respectively. 
     The power blade connector strap 12, which is a mirror image of the strap 14, fits similarly in the receptacle body 16 such that its power blades generally indicated at 104 and 106 fit within pockets 108 and 110, respectively, of the receptacle body 16, an its insulation-displacement slots fit between similar abutments and over similar lands. 
     The front member 10 is fitted to the thusly assembled components by aligning the tops of the projections 44, 46, 50 and 52, which protrude above the top of the receptacle body 16, with matching rectangular slots 112, 114, 118 and 116, respectively, formed in the back of the front cover 10a of the front member 10, FIG. 2. The projections 44, 46, 50 and 52 each have a plurality of sharp barbs on the outer edges of their top ends and are spaced apart far enough to bite into the opposite ends of the plastic walls defining the corresponding slots 112-118 in the front cover 10a. These barbs engaging the slot walls thereby secure together, with an interference fit, the entire assembly made up of the front cover 10a, the power blade connector straps 12 and 14, the receptacle body 16, the ground blade connector strap 18 and the yoke 20. The slots 112 and 114 receiving the barbed ends of the projections 44 and 46, respectively, are partially visible in FIG. 2, and may be positioned on opposite sides of the wall plate aperture 62a. 
     The front cover 10a includes integrally molded projections 120 and 122 positioned and dimensioned such that projection 120, which is generally U-shaped in section with the open side facing outwardly, presses the legs 76 and 78 defining the slot 80 onto the land 86 and the projection 122, of generally U-shape in section, similarly presses the legs 90 and 92 defining the insulation-displacement slot 94 against the land 100. The free ends of the projections 120 and 122 press against the legs defining the respective insulation-displacement slots to resist bending and deformation of the respective legs by forces applied in directions transverse to the plane of the legs when conductors are pushed into the insulation-displacement slots. The projections also provide a three-sided insulated housing around the edges defining each slot. The open side of each housing is wide enough to accommodate the end of an insulation-covered wire which is forced into an underlying insulation-severing slot. Similar projections 124 and 126, of generally U-shaped in section, press the insulation-displacement slots of the power connector strap 12 against similar lands and between similar abutments, and another projection 128 fits over the surfaces of two legs 130, 132 which define a ground conductor insulation-displacement slot 134. The two legs 130, 132 are is located inwardly of two integrally formed, opposed legs 142 and 143 which define therebetween a U-shaped slot 145 dimensioned to accept the heaviest ground conductor for which the receptacle is designed. 
     When so assembled, the receptacle is ready to be wired. The unstripped ends of power and ground conductors are placed at the respective power and ground insulation-displacement slots, as illustrated in FIGS. 4 and 5, and the side covers are pivoted toward the receptacle body 16, initially by hand and then with the assistance of the assembly screws 34, 35 and 36. Referring as an example to FIG. 4, the unstripped end of a power conductor 130 is placed at the insulation-displacement slot 94, which is visible in FIG. 4, and the power side cover 10c is pivoted toward the receptacle body 16 such that the slot 131 in the cover 10c and the pusher block 134 on the inside of the side cover 10c engage the insulated sheath of the conductor 130. The web portion 135 of the pusher block 134 is aligned with the slot 94 and can freely enter it. The power assembly screw 34 passes through the opening 38, FIG. 2. The screw 34 also passes freely through the U-shaped insulating barrier 136 in the receptacle body and is threaded into the threaded opening 44a in the projection 44 of the yoke 20. Upon tightening the power blade assembly screw 34, the conductor 130 is pushed progressively into the insulation-displacement slot 94 until the slot cuts through the insulation and makes electrical contact with the underlying conductor wire 130a. It is noted that the pusher block 134, web 135 and the edges of the slot 131 engage a length of the insulated sheath of the conductor 130, pressing it against mating parts of the receptacle body 16, to provide a degree of strain relief against tensile forces applied to the conductor. Any other power conductor and the ground conductor are wired similarly and are similarly held to provide strain relief. A separate side cover 10d and a separate assembly screw 35, extending through opening 39 in side cover 10d and threaded in the opening 51 of projection 50, are used in a similar manner to wire the ground conductor. As illustrated in FIG. 4, assembly screw 36 passes through opening 37 (FIG. 1) in side cover 10b and threads into opening 47 of projection 46, with any protruding part of the screw tip extending through opening 61 in the grounding strap 18 and into the open area between the projection 44 and the tong 60 of the grounding strap. 
     The terminal action is not adversely affected by the offset loading produced by only one conductor each in the hot and neutral terminal. To use the receptacle as a split circuit receptacle, the tab 157 (FIG. 1) in the power connector 14 and the tab 161 in the power connector 12 can be broken off with the screwdriver used to effect wiring and installation of the receptacle. 
     To facilitate manufacture of the receptacle, the ground strap 18 and the yoke 20 could be made as a single integral metal part rather than two individual parts connected by the rivets 22 and 24. In addition, the projections 44 and 46 could be positioned at the end of the yoke 20 opposite that from which the projections 50 and 51 depend and the housing 16 recessed to receive these projections to depend therefrom in the same way as the projections 50 and 51 depend from their end of the yoke. Other similar changes could be made to the receptacle without departing from the scope of the invention. 
     As will be appreciated, when assembled and wired, the insulated housing of the receptacle fully encloses all electrically live parts to thereby reduce danger of electrical shock. 
     The orientation of the elements of the receptacle has been described for the usual case, that is, the receptacle is mounted with the front cover 10a extending along a vertical plane and being the &#34;front&#34; of the receptacle. As will be understood, it is possible to mount the receptacle in other orientations without departing from the spirit of the invention.

Technology Category: 5