US3489985A - Contiguous cam contact for convenience outlet - Google Patents

Description

CONTIGUOUS CAM CONTACT FOR CONVENIENCE OUTLET Filed Oct. 30. 1967 R. L. MARTIN Jan. 13, 1970 2 Sheets-Sheet 1 YNVENTOR. ROBE/F734 MART/1V foul (f A TTORNEY Jan. 13, 1970 R- L. MARTIN 3,489,985

CONTIGUOUS CAM CONTACT FOR CONVENIENCE OUTLET Filed Oct. 30, 1967 2 Sheets-Sheet 2 /N VE N TOR Poss/PTA MART/N fu a agme A T TORNEY United States Patent 3,489,985 CONTIGUOUS CAM CONTACT FOR CONVENIENCE OUTLET Robert L. Martin, Cranston, R.I., assignor to General Electric Company, a corporation of New York Filed Oct. 30, 1967, Ser. No. 678,969 Int. Cl. H01r 29/00 US. Cl. 339-31 8 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a grounded duplex convenience outlet and to electrical contacts for such an outlet having the conventional receptacles for receiving blades of a grounded cap. The contact of the outlet has severable contact strips to permit split-circuit wiring; and has wire attachment means, including screw terminals and push-in type wire connectors to permit multiple connection of wires in association with each portion of the strip to receive a power blade of the cap. A feature of the invention is electrical contacts with an economical combination of screw terminal and push-in type wire connection means.

The present invention relates to grounded duplex receptacles having multiple wire connecting means. More specifically it relates to an electrical contact for use in a duplex receptacle to provide dual push-in type wire connections and a single binding screw connection for each blade inserted into the duplex receptacle contact.

Throughout the United States there are many areas which have electrical codes of a local nature which permit the use of certain types of wiring devices and prohibit others. The local regulations are not uniform so that a wiring device which is found to be in conformity with a number of the code requirements of one locality will also be found to be unacceptable in an adjoining locality. A single wiring device which meets the code requirements of a number of localities having different requirements is a more valuable and useful wiring device to an electrician because the single device can be used, because of its versatility, in a number of locations having different local electrical wiring codes.

Another problem of a similar nature is the problem concerned with the supply of electric current to wiring devices through aluminum conductors. Certain types of electrical contacts are operable only with copper conductors which have heretofore been used so widely whereas these same electrical contacts are not usable with aluminum wire. A particular type of connector which is subject to this difference in performance is the so-called pushin type of connector. This type of connector is illustrated in the Patent 2,705,785 of Benander. Push-in type connectors of the type taught by Benander have not generally been found satisfactory for use with aluminum wire because of the tendency of aluminum wire to develop an increased resistance at the surface through which electrical energy flows due to a temperature increase at the surface and the formation of a surface oxide of appreciable electrical resistance. For this reason electrical receptacles which have only push-in type of connectors have not been found satisfactory for use in wiring installations in which the conductors are either all or partially of aluminum.

One problem in providing a single electrical wiring device which is usable with either copper or aluminum wire and which is usable in many areas having diflferent local code requirements, is that the cost of including the number of alternative capacities in the device raises the cost of the device. As the cost of a more versatile electrical convenience outlet or other wiring device goes up, those "ice making wiring installations will choose the less versatile device which is capable of performing only the more limited wiring functions needed for a specific wiring installation.

It is one object of the present invention to provide a contact for a duplex convenience outlet adapted for use in wiring with aluminum or copper wire.

A second object is to provide a grounded duplex convenience outlet usable in wiring with aluminum or copper wire at low cost.

Another object of the present invention is to provide a duplex grounded outlet usable in most locations regardless of the local electrical code requirements relating to push-in or screw terminal connections.

A further object of the present invention is to provide an electrical contact having a combination of screw terminals and push-in type wire connectors.

Still another object of the present invention is to provide a grounded duplex outlet having alternate wiring facility at a very reasonable cost.

Other objects and advantages of the present invention will be in part apparent andin part pointed out in what follows.

In one of its broader aspects the objects of the present invention are achieved by providing a wire connecting means comprising a strip of metal having a threaded binding screw receiving aperture at one end thereof and having at the other end an F form of slits with the top of the F proximate the threaded aperture and with the F approximately centrally located in the strip to provide a section of metal at each side of the F, the strips formed by the F slits being bent out of the plane of the strip to form cams for the gripping of a wire inserted between the ends of the cams and the corner section of the strip serving as an anvil.

The manner in which the objects of the invention may be achieved will be made clearer in the following description of an embodiment of the present invention and by reference to the accompanying drawings in which:

FIGURES 1 and 1a are exploded perspective views of a duplex convenience outlet structure of the present invention showing the parts aligned for assembly in the spacial orientation in which they are assembled.

FIGURE 2, is a front perspective view of the structure after assembly has been completed.

FIGURE 3 is a rear elevational view of the assembled device seen in FIGURE 2.

FIGURE 4 is a perspective view of a contact provided pursuant to the present invention.

FIGURE 5 is another perspective view of the contact shown in a different orientation.

FIGURE 6 is a plan view of the inside of the cover of the insulating housing of the duplex outlet structure of FIGURE 1.

FIGURE 7 is a plan view of the inside of the base of the insulating housing of the duplex outlet structure of FIGURE 1.

Referring first specifically to FIGURE 1 a mounting strap 10 for a convenience outlet is disposed between a cover 12 and a base 14, the three of which are assembled together by means of screw members 20. To assemble the device, electrical contact members 16 are placed in receiving contours of the underside of the cover 12. A grounding contact 18 is also mounted in such receiving contours but in insulated relation between the contact members 16. The mounting strap 10 is superposed over the grounding contact 18 so that electrical contact is maintained there'between. This contact is maintained after assembly of the device under the pressure of the base 14 pressing the grounding strap against the contact 18 with the pressure developed by tightening screws 20. Such tightening reassures the electrical contact therebetween.

Referring now specifically to the mounting strap 10, it is evident that each of the two holes 22 and 24 is provided for the passage of a grounding prong of a cap inserted from the remote side of cover 12 after the grounding prong has passed through and made contact with spring contact 26 or 28 respectively of the spring metal grounding contact element 18. The holes 30 and 32 in the grounding strap receive the shanks of the screw members 20 respectively in assembly of the elements of the device as explained above, a screw passing through the hole 32 for example also passing through the hole 34. The mounting holes 36 and 38 allow use of mounting screws in a manner well known in th art to urge the strap and the device mounted thereon into its proper posture in a wall box of conventional configuration (not shown). Such connection provides also the grounding of the strap and accordingly of the elements in contact with the strap to the grounding elements of the box as well as to the grounding conductor of the cable furnishing power to the box. The pairs of ears 40 are for use in mounting the outlet in a wall box and include features described in the co-pending application Ser. No. 626,616 filed Mar. 28, 1967 of the same assignee of this application. A rivet or equivalent means for mounting the grounding strip 18 against the mounting strap may be provided through the holes 42 and 44 in the grounding contact strip 18 and mounting strap 10 respectively.

A grounding connection between a wall box or a grounding conductor and the strap 10 may be made through terminal screw 46 mounted through the grounding tab terminal 48.

Turning now particularly to the base element 14, it is evident that this portion of the device is an insulating base which will house the electrical contact strips 16 and which will receive the wires which supply electricity to the contact strips 16. Conveniently these contact strips may also be used in feeding electricity through the convenience outlet to remote convenience outlets through additional pairs of wires furnishing electricity to such remote devices. Four pairs of wire entrances 50 are formed integrally with the base 14 of the convenience outlet housing to permit entry of wire ends into contact with contact cams as described below. The individual openings 52 are adapted to receive a Wire the end of which has been partially stripped of its insulation to a length indicated approximately by the strip gauge guide 54.

After the contact strips and grounding strap are in place, the base 14 is mounted over the remaining assembled elements of the contact. The screws 20 are then inserted into the ports 56 and 58 respectively and are self threaded into holes on the underside of the cover 12 only one of which, 31, is seen in FIGURE 1. The push-in connections are made by pushing the partially stripped wire down through the hole 52 until the conductor comes into contact with the receiving cams of the contact strip 16.

Also as will be more fully explained below, the wire, once pushed into and gripped by the contact strip 16, can be released from this grip by insertion of an appropriate implement or tool through the rectangularly shaped port 60 one of which is provided adjoining each of the pairs of wire entry ports 50.

The shape of the base 14 of the device is designed to optimize the performance capabilities of the device while making optimum utilization of the small amount of material employed in forming the device. For example the narrow end 62 of the base 14 accommodates the grounding prong which enters the face of the devic through an appropriate port such as 64. The grounding prong then makes contact with the contacts 28 of contact strip 18 after which it passes through the portal 24 of the mounting strap 10 and is received in the insulated enclosure within the narrowed end 62 of the base element 14.

Turning now specifically to the contact elements 16 it will be evident from the foregoing that these elements are housed within longitudinally extending troughs within the base 14 and that the two screw terminal portions form part of the sidewall of the assembled receptacle, the side wall being absent from the base 14 as is evident at 72. The sidewall center is completed by the depending elements 76 of the cover 12. The contact 16 is made up generally of two blade contacting end portions 80 and 82; two wire contacting intermediate portions 84 and 86 and by a central circuit separating portion 88.

In FIGURE 1a an enlarged view of the wire contacting intermediate portion is given with the portion illustrated as flattened out to make additionally clear the relation of the elements of this portion to the strip from which they are formed.

The breakolf portion has an easily severable tab 90 which extends externally of the device when the device is fully assembled as best seen in FIGURES 2 and 3 and which can accordingly be readily gripped by an electricians tool, such as a pair of pliers, and broken away from the remainder of the contact simply by bending it back and forth until the metal work'hardens and fractures. Because the central break-ofi tab 90 may be removed to separate the contact element 16 into two electrically separate halves, each half is equipped with mul tiple wire contact means. One such means provided as an integral element of each half of the contact is the conventional terminal screw 92. Two such screws are shown on each contact element 16 as represented in FIGURES 1, 4 and 5. The inner end 94 of each screw 92 is staked in the conventional manner to prevent accidental release of the screw when the screw is retracted in wiring the device.

The breakofi midportion 88 and th wire connection portions 84 and 86 are electrically joined respectively by the conducting shank 96 and 98 respectively.

The blade contacting end portion 80 of the electrical contact strips is formed with a more rigid contact finger 100 and a more resilient finger 102.

As is evident from the contact strip 16 shown free standing in the FIGURES 1, 4 and 5, the upper portion of finger 102 is cut back to give a narrower end section 104 and this narrower end section fits within a receiving recess 106 in the underside of the cover to reinforce the finger 102 against being deformed by the action of power blades inserted thereinto.

Referring now specifically to FIGURES 4 and 5, it will be evident that an optimum use is made of the material of this contact. For example, three wire connecting means are provided in each of the contact sections 84 and 86. Each wire connection section includes the screw member previously described and includes also push-in type contacts, the cams of which are seen to be contiguous. For example, referring specifically to the section 84.of the contact as seen best in FIGURE 4, the two cams 106 and 108 are shown to be formed from the strip metal of which the contact itself is formed by making a transverse cut in the strip metal to form the edge 110, and by making the two longitudinal and parallel cuts 112 and 114 in the strip metal. The cams 106 and 108 are accordingly established by the cutting action to form the edges 110, 112 and 114. To complete the cam, the cam ends 116 and 118 are next formed by bending the respective ends of the cams 106 and 108 at about the midpoint of their length upward toward the screw 92 and away from the edge 110.

Although the cam ends 116 and 118- as well as the cams 106 and 108 are shown to be formed from the same strip of contact metal, and are also shown to have a close parallelism of both the cam ends and the cam shanks, it will be realized that these contiguous cams operate essentially independently of one another.

This independence of operation is in part indicated by the separate wire entry holes and 152 seen in FIG- URES 6 and 7 which are aligned with the respective cams 116 and 118 when the contact strip 16 is in place in the base 14 of the duplex outlet structure of this invention. Accordingly, a wire inserted into either hole 150 or 152 will be gripped by the respective cam 116 or 118.

A gripping pressure is established between the edge of the cam 116 and 118 and the inner wall surface 155 proximate the receiving hole 154 or 156 in the underside of the cover 12 of the housing of the duplex outlet. The surface 155 against which the wire is thrust by the action of the cams on 116 and 118 is best seen in the perspective view of the underside of the top 12 in FIGURE 2. The surface 155 has grooves which are aligned with and which guide the wire to the receiving holes 154 and 156.

The pressure of the conductive cam end 116 or 118 against an inserted wire causes the wire to be pressed against the surface 155 by a wedging action as the wire is pushed into the contact and into the hole 154 or 156. One reason for the wedging is that the edge 110 overlays the wire entry holes 150 and 152 so that electrical contact is made both at the overlaying conducting edge 110 and at the conducting tip of cam end 116 or 118.

The release of a wire gripped by the cams of the contact strip 16 from such grip is accomplished by inserting a tool through the tool entry port 60 shown in FIGURE 1, the internal portal of which is shown in FIGURE 7 as 160.

The insertion of a broad bladed tool such as a screwdriver of width approximating that of the portal 160 results in a simultaneous deflection of the two cams 106 and 108 and a simultaneous release from the grip of the cams of any wires held in their grip.

One reason why use of contiguous cams had been avoided heretofore is explained in the recently issued Patent No. 3,339,170 assigned to the same assignee as the present application. It is therein pointed out that: The performance of prior art duplex plug receptacles which have been provided with spring type wire fastening means has been less than satisfactory where two or more wires of different sizes are fastened and it is desired to release only the larger of the wires while the smaller wire is under tension. The gripping elements of these spring type fastening devices have been designed in various ways, but these prior designs have been deficient in a number of respects. One principal defect is observed when line wires of different sizes are employed and this has also been found to be the case where wires of the same size are inserted.

Where an attempt is made to remedy this deficiency by utilizing a bifurcated spring to provide two spring locking elements for a fastening arrangement, this arrangement has also proven less than satisfactory in actual use in holding two wires of the same or different sizes. This arrangement is especially deficient during the releasing of the wires in that it is not possible to release only one of the wires without simultaneously releasing the other where both are held by the same spring element even though it is bifurcated where deflection of one prong of the spring serves to impart a similar deflection to the other rong. p The solution to this problem was stated in the prior patent to involve the use of the E formation of locking cams. Surprisingly, it has now been found feasible to obtain the advantageous separate gripping and separate release features in the form of push-in contact taught herein having contiguous cams.

Considering now the relation of blade receiving end portions 80 and 82 of the contact strip to the base 14, the wider portion of the more flexible contact finger 102 is received within the slot 122 when the contact strip 16 is placed in its conforming recess in the base 14. Slot 122 is formed in a vertical wall of the partition 120 dividing the base into the longitudinal left hand and right hand sections. The mounting strap 10 overlays the partition 120' and is spaced from the thinner tips 104 of the more flexible finger 102 at the necked down sections 23 of the strap 10. The insulating divider 107 depending from cover 12 separates the narrower tip 104 of the more flexible blade 102 from the necked section 23 of strap 10.

Grounding contact strip 18 overlays the grounding strap 10.

When the device is in the process of being assembled, the parts are mounted on the inverted cover shown in FIGURE 6. After all the metal parts are in place, the base 14 is mounted over the sub-assembly and the screws 20 are inserted and threaded into place to hold the device together.

As is evident from the left hand portion of the cover shown in FIGURE 1, when the contact strip is inserted in its position on the cover during the assembly, the edges 128 of the binding screw plate 130 are received in the slots 132 formed integrally with the cover member so that the binding screw plates 130 together with the depending side wall element 76 of cover 12 form a substantial part of the side wall of the device. The remainder of the sidewall is formed integrally as the side wall portion 134 of the base 14.

The slot 132 and depending side wall portion 76 not only position the screw terminal plate 130, but also keep the two portions of the contact in their respective positions in the duplex receptacle when the breakotf tab is removed in the manner explained above. The two anvil portions 111 of the contact strip are also kept separated after removal of the breakoff tab 90 by the cooperation of the boss 77 depending from cover 12 and the boss 136 extending upwardly from the center of the bottom of base member 14. It is important that the spacing of the two anvils 111 of each contact strip maintain a separation to keep the edges over a portion of the wire entry openings 150 and 152 as this provides a second high pressure contact with an inserted wire, the first being with the tip of the gripping cam 116 or 118.

Wire tip grip opening 139 in the face of the binding screw plate permits the end of the wire to be inserted so as to facilitate wrapping the wire about the exposed shank of the screw 92 when the screw is loosened to its extended position and also permits the wire to be held as the screw is tightened. Another value of locating the wire tip grip opening 139 at the intersection of the vertical and horizontal portions of contact strip is that this facilitates the forming of the strip and while giving the opening additional resistance to bending moments resulting from working of the wire end around the shank of the screw.

It will be noted that the hollow end of the two parallel cavities on either side of the center partition 120 of base 14 are extended in the section 138 to accommodate the portions of inserted power receiving blades which pass through the blade receiving portals shown in FIG- URES 2 and 6. This minimizes the actual volume of the cavities and the resulting material needed to enclose the cavities.

A number of safety features are provided in avoiding improper assembly of the elements of the duplex outlet of this invention. By one such feature the fingers 102 of the blade receiving ends 80 and 82 of the contact strip 16 are seated in insulating relation to the mounting strap inasmuch as the finger 102 has a narrow end 104 and a broadened section 105 which must enter the slot 106. Also the broadened section 105 conforms to the slot 122 in the partition wall 120 of the base 14 and insures that the contact strip 16 will be properly positioned in the base 14 as the device is assembled.

As is evident from FIGURE 1, the upper portion 104 of the finger 102 is sufficiently narrow so that it fits into the groove 106 in the wall of the depending insulating divider 107 but if it straddles insulating divider 107 the base will not fit over the contact strip because broadened section 105 will not seat in slot 122. The depending insulating divider 107 is spaced to receive the neck portions 23 of the mounting strap 10.

What is also particularly advantageous about the contact of the present invention is the provision of these three separate means for attachment of wire in the wire attachment portions 84 and 86 of the contact and the provision of these means with a minimum of metal. Further the attachment may be either to the screw terminal or to the push-in type of connection.

It will be seen that if the break-01f link 90 is removed and if the blade gripping fingers 100 and 102 of the blade contacting portion 80 are also removed, that the Wire contact portion 84 or 86 is essentially a single strip of metal having a threaded hole for a terminal screw in the mid portion of one end of the strip and having a figure F cut into the other end of the strip at one corner section, and adapted to cooperate with the other corner section acting as an anvil to provide a gripping electrical contact with wires inserted thereinto.

The provision of this combination of binding screw and F form of push-in connector is deemed to provide eifective wire connection means with a minimum of metal.

What is claimed is:

1. Electrical connecting means adapted for connection of wires to a wiring device which comprises a strip of metal having a threaded binding screw receiving aperture at one end thereof and having at the other end an F form of slits with the top of the F proximate the threaded aperture and with the F laterally located approximately of the other end to provide a longitudinally extending edge portion of said strip at each side of said F, the strips formed by the F slits being bent out of the plane of the strip to form cams for the gripping of wire inserted between the end of a cam and the edge of the strip serving as an anvil.

2. The electrical connecting means of claim 1 in which the end having the screw receiving aperture and the end having the cams are bent at right angles along a junction therebetween.

3. The electrical connecting means of claim 2 in which an aperture is provided at the junction to facilitate the bending along the-junction and to receive a wire end to be looped around a screw member in said threaded aperture.

4. The article of claim 2 wherein the threaded aperture is spaced from the junction to align an axis through the aperture above the bent cams.

5. The article of claim 1 wherein the connecting means is electrically and mechanically paired with a mirror image connecting means.

6. The article of claim 5 wherein the pair of connecting means are for-med from the same strip of metal.

7. The article of claim 6 wherein the linkage between the mirror image connecting means is a frangible tab the removal of which electrically isolates the separated connecting means.

8. The article of claim 5 in which mirror image power blade contact means are provided at each end of the article.

References Cited UNITED STATES PATENTS 2,974,301 3/1961 Slater 339l4 3,001,168 9/1961 Smith 339-164 3,325,768 6/1967 Munroe.

3,339,170 8/1967 Martin.

RICHARD E. MOORE, Primary Examiner JOSEPH H. MCGLYNN, Assistant Examiner US. Cl. X.R. 33995, 164

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