US2540496A - Safety electrical receptacle - Google Patents

Description

Feb. 6, .1951 -J. J. sPr-:RRAzzA SAFETY ELECTRICAL RECEPTACLE Filed April 13, 1948 FIG. l

. MOMVIAIAU\.

FIG.

INVENTOR Jrme J @verfazza I Bv umzlmmm 55am/*wv ATTORNEYS Patented Feb. 6, 1951 UNITED STATES GFFICE SAFETY ELEoTRIoAa mies-erwin.

Jerme yJ. sperrazzay BurralmN.' y.

Akpplication AprillS, 1948, Serial No. 20,632

8 Claims.

This invention relates to improvements in .shock-proof electr-ical connection. receptacles of the plug'receptacletype commonly used asWall `outlets in buildings-vandin.electrical fixtures.

t Conventional: types: of: plug, receptacles-.are

Aknown to presentA alrpotential source of danger because Va person inserting.:awforeignmetal-obj ect into an openingin sucha receptaclermaybe subjected-to a: severe electrical. shock or burn: This is. particularly true. in the` case of children: who,

.throught curiosity, may'insert nails, hairpins-or other objects into the-openings of such receptacles. c y f The present inventionzisfan improvement upon Y safety electrical plugreceptacles -of thekind'v hav.-

ingapair of openings to receive'. theprongs-ot. an

:electric plug, an Veleetricalcontact locatedin leach opening for` engagementby aplugprong; afmovable member partly locatedin-each' of the, openings in a po'sitiontobe engagedand movedA by thefprong of the plug, and `electrical..connections .actuated vby the movement of the :movable-mem- 4 ber associated with either. of the .openings .when

a prong Yof the plugfenters that opening to closea path -for electric currenttorthe electrical contact v located in the other` opening of the .pair. Afplug receptacle -havingV these `features. and construction is disclosed .inmy pending application Serial No. 725,455, .ledzJ'anuary `3i, .1947, Afor Electrical Connection Receptacle, now-4 Patent No; 2,500;

474, March 14; 1950.: In such .a .receptacle-:the electrical contacts' in bothnofL the openings are normallyv dead* and either of t them can.. only be made alive by the movement. of the.' movable "member associated". withtithe.; other; opening: in

of .faiplugisz inserted inffeitherlopenin'g itfirstengagesiand': moves fthe :movable member 'therein'ato a'ctuate' the relectricalconnecti'ons'to' close'a .path

inserted prongs offthe plug arewwithdrawnirom the -opr-rningsfthey circuit through. the` receptacle Aand`-4 the plug1 Willfbeybrokenby the initialimovef toIthein respective; contactsis broken onlyr after the prongsfdisengage `the contacts.V and break-the circuit toftheI plug.

Inthei preferred construction the` movable membersin g thev form of cam blocks fof insulating material.i-are.locatednear the upperportion=of thefopeningsxof the receptacleandthe contacts associated-v with @the :openings/areflocated. only?A in thelower` portion of such openings, that is; below the camblocksfivsothat. Whenthe prongszor blades of aplugare-inser-ted, they iirst 'move-the cam?. blocks.` to connect.' the contacts with their respective current supply'terminals,` and thereafter: engage' thel'respective-contacts in thefreceptacle vcpeninga,y Arcing in the' electricalcon- ,nection's.betweenithecontacts and their current supply; terminalsy isY therefore'positively avoided, since :.-they contacts andr terminals" are connected upzby the-'camvblocks beforethe prongs ofgthe plug engage the vcontacts to form acircuit. Whileftliere'm'aybe arcingy between the prongs and: their contacts in?" the: openings; thisis: no more serious than in: conventional receptacles, land 'one'.cansafely -concludeffthat when the' plug y isfwitlidrawn, .'the'contactsin `the openingsare for electric current from a current-'supplyterminal to theelectrical contactlocated inthe other openinggand thereafter'. as.` the prong'fis further inserted 'in theY opening, an'dor'the rst'tim'e, it=

engagesvthe electrical contact located in that opening, V Y

`-vvriealzne .elec-mear Contact andifmvame ;riicrriberassociatarwithv rhelrrvespetivef-openings 'off-the receptaclehaveethis relationship' and "theL deans-.and liavemotbeenrmade aliveby Welding-sin the-econnections'to thel-currenttsupply' terminals.

Inianladvantageouse'form"of *the'fpre'sen't invention; the' cam blocks,1.cam'surfaced members? of Y insulatingrmaterial -or equivalent mea-ns, are

.l positioned? in tliebodyfofthe'A- receptacle soth'at present invention. In this view the surfaces of some of the elements below the line I-I are shown.

Figure 2 is a vertical sectional View. taken on the line 2-2 of Figure 1.

Figure 3 is a broken vertical sectional view taken on the line 3-3 of Figure 1'.`

Figure 4 is a broken perspective View of parts of the mechanism shown in Figures 1 to 3 removed from the body of the receptacle, showing the position of the important elements with plug prongs inserted.

The receptacle shown in the figures of the 'drawings includes a body of insulating material comprising an upper section I and va lower section I2 held together by screws I4 to form a unitary structure having an external shape similar t'o lconventional receptacles. The receptacle as shown is provided with two pairs of openings or slots I5-i5a and IGV-Isa for the receptionrof the prongs or blades of electrical plugs of conventional design. The twin unit shown is illustrated in connection with a plug I8 with its prongs 0r blades 20 and 26a inserted respectively Yin the openings I5 and |511.

The receptacle is adapted to be connected into a pair of current supply wires in the usual way by means of a pair of screws 22 threaded through similarly shaped metal current supply' bars 24 and `2B fitted in recesses in section IB and adapted 'to supply current to both receptacles. The bar 24 is bent at one end to provide a contact terminal 24a and at the opposite end to provide a contact terminal 24h. The bar 26 is bent in the same way to provide contact terminals 26a and 2Gb.

The metal contact elements for allrof the receptacle openings have the same shape and construction, for example that for the opening I5 comprises a sheet metal member having a contact leaf 28 (Figs. 2 and 4) bent from a at horizontal portion 28a and extending downwardly in the portion of the opening I5 in the lower body'v section i2. The portion 28a extends laterally along the top of the section I2 and has attached thereto a long spring section 28b bent up edgewise from the section 28a extending through an opening in the body section I0 crosswise of the receptacle in iront of the terminal 24a which projects into the same opening in the upper body section i. The arrangement is such that current supplied by the terminal 24a is conducted through the spring section 28h, section 28a to the contact leaf 28 which is engaged by the plug prong ZIJ. The contact element for the opening ISa includes a contact leaf 3U therein attached to a horizontal section 30a and a contact spring section Sub which is adapted to Vengage the contact terminal 2Gb.

The contact element for the opening I6 includes a contact leaf 32 bent from a horizontal section 32a to which ispattacheda spring contact member 32o adapted to be moved into engagement with terminal contact 26a. The contact element for the opening Ia includes a leaf contact 34 extending along the lower part of the opening I6a and bent down from a lateral section 34a to which is attached a spring contact member 34D adapted to be moved into engagement with the terminal contact 24h. The contact elements for all openings 4are mounted in appropriate passages or cut-outs in the upper body section I@ except for the leaf contacts which extend downwardly in the lower portions of the respective receptacle openings.

Each receptacle opening has associated with it a block of insulating material having a cam element normally extending into the opening, These blocks are of the same construction for all openings and comprise a block 36 for the opening I5, a block 36a for the opening I5a, a block 38 for the opening I6 and a block 38a for the opening IGa. I

The structure of these blocks of insulating ma'- terial is shown more completely in Figure 4 in which the block 36a, for example, is shownv as comprising a substantially rectangular shaped block having a lateral projection 40 provided with a sloping cam surface 42. The projection 4B is of such a width and positioned to be movable laterally into one edge of the receptacle opening I5a so that it normally blocks off a portion of the opening. Each block, such as 36a, is mounted so as to slide on the lower body section I2 in an appropriate cavity in the body section Vlilas shown, vwhich communicates with the cavity or passageway housing the oppositely mounted contact spring and terminal contact.

Figure 1 of the drawings shows the position of the elements described above with the prongs of the plug I8 inserted in the openings I5 and |511, while the other receptacle including the openings I6 and Ia illustrate the normal position of the elements described with the plug removed. In this receptacle the spring contact sections 321) and 34h are shown as being substantially straight, at springs which are normally biased away from the respective terminal contacts 24h and 26a, this bias being sumciently strong to move the cam blocks 38 and 38a to a stop in the body section l0 with the sloping cam projections extending into the openings I6 and ISa above the contact leaves 32 and 34.

When the prongs 20 and 20a of the plug I8 are inserted in the openings I5 and IEa as shown, the edges of the prongs engage the cam surfaces 42 of the blocks 36 and 36a, and as the prongs are pushed down, move the blocks laterally respectively against the Contact springs Sb and 28h, so as to move them respectively into engagement with terminal contacts 26h and 24a. These steps are effected by the time the ends of the prongs 2l] and 20a reach the level approximating the lower ends of the cam surfaces 42. There'- after, further movement of the prongs into the openings brings them respectively into engagement with the now live metal contact leaves 28 and 30 to 'supply current through the plug to the desired source.

The portion of the Contact spring 2827 where it is joined to the portion 28a and somewhat beyond, is conned in a relatively narrow passageway 4 (Figs. l and 2) in the body section I0 terminating at a vertical corner 4E where' -it opens into the wider passageway for accommo- `dating the movement of the remainder ofthe spring 28h., `VfJith-the -bodydsections Iii andi2 'clamped together the pcr-tionsfZ` and -2 8a ofthe 'contact "element are inA fixed position so Vthat when the spring contact* 28E? is moved outto engage terminal 2da it is bent around the corner 46, as will be seen by comparison with the normal position Aof the corresponding elements B2b r anula-34p, Thefcorner .-636 and the., 1corresponding corners for all contact elements aid inbiasing the respective .spring .contacts .as described.

The plug vreceptacle of the present invention with its novel safety features `can be substituted .for\.conventional types of receptacles for .insta-l- -lation in homes or other lpoints-of use, lsince the contact elements mountedin the receptacle openings are normaly dead and ,free from the possibility of being made alive by the internal welding lof any of the internal Iconnections yin the "receptacle, since arcing or welding is prevented by the improved construction. The receptacle is also safe from external hazards. For example, if a child inserts a bobby pin 48 in the opening 16a as indicated in Figure 2, the pin cannot energize the contact 34 in opening |6a, but at most only energize the contact leaf 32 in the opening I6. However, in the illustration the bobby pin is fully inserted without affecting the cam block 38a so that no danger Whatever is involved. Even if a metal object of the width of a plug prong were inserted in the opening I 6a, it would only energize the contact leaf 32 and not the contact leaf 34, so that there still would be no danger of a shock,

The receptacle structure is also such that a fuse cannot readily be blown. For example, even if the two prongs of a bobby pin were inserted respectively into the two openings of the receptacle, they would not move the cam blocks or activate the contacts therein. The improved receptacle of the present invention may be single, twin or otherwise and constructed to provide for any number of openings such for example as polarity plug receptacles, provided that the contact element for any one opening can only be made alive by the movement of a cam member or equivalent means, in a different opening.

What I claim as new is:

l. An electrical plug receptacle comprising a body having a pair of openings, a first electrical contact means on said body for each opening adapted to be connected to a source of electrical. energy, a second electrical contact means on said body for and associated with each of the respective openings and normally out of contact with" the rst means, and an actuating means comprising a pair of movable cams mounted in said body above the second contact means and associated respectively with said openings, said cams being insulated from the first and second contact means and adapted to effect contact between the first and second contact means of one opening only upon the insertion of an object in the other opening of the the pair, the second contact means and the cam for each opening being arranged with respect to each other so that the insertion of an object into one opening rst moves the cam associated therewith toeffect Contact between the rst and second contact means for the other opening and thereafter thel object engages the second contact means associated said one opening;

2. An electrical plug receptacle having a plurality of openings for receiving the contact prongs of a plug, an electrical contact in the lower portion of each opening adapted to b e engaged by a contact-prong of a plug, a terminal connector 'for each vcontact Aadapted to be lconnectedto a 'source of 4electricity butfnor'mally disconnected from its contact, and means associated with each opening insulated-:from the contact therein land operable upon the insertion of -a plug'contactprong therein prior to its erigagementwith the `contact thereinfor electrically connecting only the contact in a different one of `said plurality of openings with its terminal connector.`

' 3.- An electrical plug receptacle as defined' by claim 2l inY which said means is a cam member mounted in a position to-l be actuated bya plug prong prior to vthe contact of such"prongwith Vthe electrical `contact in the opening into'which the-prong is inserted.-

4. An electrical plug receptacle as defined by claim '2 in which said means is a cam member movable into and out of the opening'witli which itis associated, and in which 4the contactin each opening includes a spring portion arranged to be moved into engagement with but which is biasedL away from its terminal connector.

5. An electrical plug receptacle comprising a body having a pair of openings for the reception of the prongs of a plug, a contact element for each opening including a portion thereof arranged in the lower part of the opening and a portion forming a spring contact linger extending along one side of the other opening, a movable cam member of insulating material operatively arranged in said body between each contact finger and the adjacent one of said openings, each spring contact finger being adapted to urge the adjacent cam member toward and into a portion of the adjacent opening above the contact element therein, a terminal connector arranged adjacent each of said vcontact fingers normally out of contact therewith and adapted to be connected to a source of electrical energy, each of said cam members being arranged to be actuated by a plug prong inserted in the adjacent opening whereby the adjacent spring contact finger is moved into engagement with the adjacent contact terminal to thereby close a circuit to the contact element in the remote opening.

6. An electrical plug receptacle comprising a body having a plurality of openings therein for the insertion of the prongs of a plug, a contact element mounted in the lower portion of each opening, a movable contact member connected to the contact part in each opening and extending alongside and spaced from a different outlet opening, a current supply terminal arranged in said body on the side of each movable contact member opposite the outlet opening alongside which it extends, and an actuating member of insulating material movably arranged in a passageway in said body between each movable contact member and the opening alongside which it extends at a position above the contact element therein, said actuating member being adapted to normally project into the opening adjacent to which it is mounted, and when moved therefrom by the insertion of a plug prong into the opening being adapted to move lthe movable contact member into engagement with the oppositely mounted current supply terminal.

7. In an electrical plug receptacle having a pair of outlet openings adapted to receive the prongs of a plug, a Contact element in each opening, a terminal connector for each element arranged to be connected therewith but normally disconnected therefrom, and `a member of insulating material associated with each opening and movable by the insertion of a plug prong therein for connecting the contact element of the other opening with its terminal connector, the improved structure in Which the movable member for each opening is arranged to be moved by an inserted plug prong prior to the engagement of the prong with the contact element for such opening, whereby arcing between the contact elements and their respective terminal connectors is avoided.

8. In an electrical connection receptacle having a pair of openings to receive the prongs of a plug, an electrical contact and a movable part located in each of the openings in position to be engaged by a prong, and electrical connections actuated by the movable part associated with 15 either opening when a prong enters that opening to close a, path for electric current to the contact located in the other opening, the movable part being located above the contact in each opening,

whereby upon withdrawal of the prongs from the openings the circuit through the receptacle will be broken at the said contacts.

JEROME J. SPERRAZZA.

REFERENCES CITED The following references are of record in the le" of this patent:

UNITED STATES PATENTS Number Name Date 2,201,875 Zelt May 21, 1940 2,221,345 Davis Nov. 12, 1940 2,487,560 Kuhn Nov. 8, 1949 A FOREIGN PATENTS Number Country Date 374,145 Italy Aug. 16, 1939

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