US2879494A

US2879494A - Electric plug with disabling means

Info

Publication number: US2879494A
Application number: US493128A
Authority: US
Inventors: Herman C Teetor
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-03-09
Filing date: 1955-03-09
Publication date: 1959-03-24
Anticipated expiration: 1976-03-24

Description

March 24, 1959 H. c. TEETOR 2,379,494 ELECTRIC PLUG WITH DISABLING MEANS Filed March 9, 1955 3 Sheets-Sheet 1 .6. 7 22 3 25 s 36 :35 INVENTOR.

\ fi/erman/ Cfeezmj BY PM ,QCLJ A) W 27 852 57 7 March 24, 1959 Filed March 9, 1955 @MiZIEQLEl ELECTRIC PLUG WITH DISABLING MEANS TEETOR 2,879,494

3 Sheets-Sheet 2 7g (90 9 94 63 62 INVENTOR. f ermaw/C Z5826)? H. c. TEETOR 2,879,494

ELECTRIC PLUG WITH DISABLING MEANS March 24, 1959 Filed March 9, 1955 3 Sheets-Sheet 3 I 96 INVENTOR.

figv'mcm/ Cjez ar United States Patent ELECTRIC PLUG WITH DISABLING MEANS Herman C. Teetor, Hagerstown, Ind. Application March 9, 1955, Serial No. 493,128

16 Claims. (Cl. 339- -37) This invention relates to improvements in electric connector or attachment plugs and more particularly to an electric plug having novel means for disabling the plug when desired in order to prevent its use.

In the case of many types of electrically operated devices and appliances, such as radio and television sets, record players, power tools, etc., it would be extremely desirable to have an inexpensive and convenient means for preventing unauthorized use of the device, i.e. by children or others. Along these lines, it has been suggested heretofore to provide a separate cover or shield adapted to be locked around and to enclose the contact prongs of the attachment plug on the electric cord of the device or appliance and thereby prevent the device from being used without permission. Other suggestions toward the same end have also been made but there are various objections to the different schemes heretofore proposed on the grounds that they are too inconvenient and cumbersome in use or that they are not entirely effective and safe.

Accordingly, it is a primary object of the present invention to provide an improved electric plug having novel means for disabling the plug at will in order to prevent unauthorized use thereof.

A further object of the invention is to provide in an electric attachment plug a novel key locked mechanism for disabling the plug and rendering it inoperable.

Another object of the invention is to provide a novel electric plug having means for disabling one of the contact prongs of the plug and thereby rendering the plug inoperative.

Other objects and advantages of the invention will become apparent from the subsequent detailed description taken in conjunction with the accompanying drawings wherein:

V Fig. 1 is a top plan view of an attachment plug comprising one specific embodiment of the invention;

' Fig. 2 is an end view on an enlarged scale as seen from the left-hand end in Fig. l;

Fig. 3 is a longitudinal sectional view as taken along the line 3-3 of Fig. 2 and showing the plug in operative position; a

Fig. 4 is a view similar to Fig. 3 but showing the plug in inoperative position;

Fig. 5 is a transverse sectional view as taken along the line 5-5 of Fig. 3;

Fig. 6 is a transverse sectional view as taken along the line 6-6 of Fig. 4;

Fig. 7 is atop plan view of an electric plug comprising a dilferent embodiment of the invention;

Fig. 8 is an end view on an enlarged scale of the device shown in Fig. 7 as seen'from th'left-handfend thereof; 1 Fig. 9 is a longitudinal sectional view as taken along the line 9-9 of Fig. 8;

Fig. 10 is a' transverse sectional view astalten along 'theline 10-10 of Fig. 9;

2,879,494 Patented Mar. 24, 19 59 Fig. 11 is a transverse sectional view as taken along the line 11-11 of Fig. 9;

Fig. 12 is a fragmentary sectional view taken along the line 12-12 of Fig. 9;

Fig. 13 is an exploded plan view of still another em bodiment of the invention; 7

Figs. 14 and 15 are end views on an enlarged scale showing the. plug in two different positions;

Fig. 16 is a longitudinal sectional view as seen along the line 16-16 of Fig. 15; and

Fig. 17 is a transverse sectional view of the plug as taken along the line 17-17 of Fig. 16.

Broadly speaking, the objects of the invention are achieved by providing in an electric plug a movable contact prong which can be retracted, rotated, or other- ,wise shifted or even completely detached from the plug it cannot again be rendered operative except by use of the key to unlock the disabling mechanism.

Referring first to Figs. 1 to 6 of the drawings, an electric attachment plug 21 is shown having 'a two-part casing 22-23 of suitable insulating material such as plastic or the like, the two casing sections being secured together by a screw 24 and a nut 24'. A pair of parallel contact prongs 25 and 26 project from one end of the casing for insertion in an electric socket or outlet. An electric cord, comprising in this instance two insulated wires or

conductors

27 and 28, extends into the opposite end of the casing 22-23 for electrical connection with the

prongs

25 and 26, respectively. The prong 25 is disposed in fixed relation with respect to the plug casing, and a screw 29 is threaded into the inner end of the prong (Fig. 5) for connecting the conductor 27 to the prong 25. The other conductor 28 is connected by means of a screw 31 to an outwardly extending flange portion 32 (Fig. 6) of a generally U-shaped elongated resilient clip member 33 fitted in a recess in the casing section 22.

The contact prong 26 is movably mounted in a narrow groove or channel 34 (Fig. 5) in the casing section 22 for longitudinal shifting movement relative to the easing, and the inner end of the prong 26 is received between the legs of the resilient U-shaped clip or contact member 33, as clearly seen in Figs. 3 and 4. A small projection or bump 35 is provided in one of the legs of the clip 33 for frictionally gripping the prong 26 between the legs of the clip 33 and thereby insuring positive electrical contact in all longitudinal positions of the prong. As will be evident from the drawing, when the movable contact prong 26 is in its outermost projected position (Fig. 3) the plug is operative in the usual manner and the bump 35 provides a detent action to assist in retaining the prong in projected position. However, when the prong 26 is retracted within the plug casing (Fig. 4), the plug is completely disabled since only the fixed contact prong 25 remains in condition for insertion in the electric outlet. A central partition structure 36 in the assembled plug casing serves to separate or isolate the

prongs

25 and 26 together with their connections to the

conductors

27 and 28.

For effecting shifting movement of the movable prong 26, a rotary locking mechanism is utilized having suitable operating connections for converting rotary movement of the lock to reciprocating rectilinear movement of the prong 26. Thus, a lock 37 having a rotary cylindrical barrel portion 38 with a plurality of spring pressed tumblers 39 of the usual construction is mounted in a bore 41 provided in the casing section 22 adjacent the outer side of the prong 26. Suitable grooves (not shown) are provided in the casing section 22 at the Wall of the bore 41 for receiving the projecting ends of the tumblers 39 in the usual manner when the barrel 38 is rotated to either of its extreme positions for locking and unlocking the plug mechanism. The lock 37 is retained in position in the casing section 22 by means of a collar 42 at the outer end of the barrel 38 which seats in a counterbore 43 and by an arcuate key or spline 44 which is received in a peripheral groove 46 in the barrel 38 and coacts with a corresponding groove 47 in the casing section 22. As hereinafter explained in connection with the operation of the device, the barrel 38 is adapted to be rotated about its axis by means of a key (not shown) which is inserted through an axial opening 48 (Fig. l) and releases the tumblers 39 in the usual manner to permit rotation of the barrel 38 by twisting of the key.

The portion of the opposite casing section 23 which overlies the lock 37 is formed with a generally circular recess 49 having a slight upright boss or projection 51 with a pivot pin 52 mounted therein in coaxial relation with the lock barrel 38. The inner end of the pin 52 projects beyond the boss 51 and carries a gear 53 which is made from an insulating or non-conducting material such as nylon or the like. Rotary movement of the rotatable lock barrel 38 is transmitted to the rotatably mounted gear 53 by means of an eccentric connecting pin 54 extending rigidly from the inner axial end of the lock barrel 38 and fitted in an aperture 56 in the gear 53 so that the gear 53 rotate coaxially and in unison with the lock barrel 38. As best seen in Figs. and 6, the movable contact prong 26 is provided along one edge thereof with an elongated toothed portion or rack 57 which is constantly in intermeshed engagement with the teeth of the gear 53 so that rotation of the lock barrel 38 and the gear 53 in a clockwise direction, as seen in Figs. 3 and 4, causes the shiftablc contact prong 26 to be projected into its operative Fig. 3 position, and rotation of the lock barrel and interconnected gear in the opposite or counterclockwise direction results in retraction of the prong 26 to its inoperative Fig. 4 position.

When it is desired to render the attachment plug inoperative to prevent unauthorized use of the device or appliance to which the plug is connected, the user merely inserts the proper key in the opening 48 of the lock and rotates the barrel 38 thereof to retract the shiftable prong 26 to its Fig. 4 position. The user then withdraws the key from the lock and the tumblers 39 are automatically projected into one of the coacting grooves whereupon the barrel 38 is held against rotation and the prong 26 is thereby locked in its retracted position and cannot be released except by operation of the lock 37 with the proper key. Obviously, when the prong 26 i fully retracted and locked, it will be impossible for a child or other unauthorized person to use the electrical device or appliance because an operative electrical circuit cannot be completed with only one contact prong even if the plug is inserted in an electric socket or outlet. To unlock the plug, the key is utilized to rotate the lock barrel in the opposite direction for projecting the prong 26 into its normal operative position. Of course, when the key is withdrawn, the tumblers 39 are again automatically projected into a groove in the casing for holding the lock barrel in this position.

Referring now to Figs. 7 to 12, a somewhat different contact prong disabling means will now be described. In this embodiment of the invention the attachment plug, designated generally at 61, again has a two-part casing comprising

separate sections

62 and 63 which are detachably connected by means of a screw 64 and a nut 66. The casing section 62 has a transverse tubular portion 67 in which is mounted a lock 68 of the same type herein before described having a rotary barrel 69. The casing section 63 has mounted therein a fixed contact prong 71 connected to a conductor 72 by a screw 73. Another conductor 74 extends into the casing and is connected by aserew 76 to an ngular contact memberhaving an na- 4 standing contact portion 77 and an apertured portion 78 into which the screw 76 is threaded (Fig. 11). A central partition structure 75 in the assembled casing again serves to segregate the prongs and their electrical connections.

Whereas in the first described embodiment the movable contact prong was arranged for axial shifting movement relative to the plug casing, in this embodiment the movable prong is mounted forrotary movement about an elongated axis parallel with the fixed prong 71. Thus, I provide a generally cylindrical elongated body portion 79 located within the casing section 63 and having integral gear teeth 80 arranged circumferentially therearound. Projecting integrally from the body portion 79 through an opening 31 in the end of the casing is a thin flat contact prong portion 82 of the usual type. The body portion 79 is journaled in the casing section 63 at opposite ends of the toothed portion 80 for rotary movement about its longitudinal axis so as to permit rotation of the contact prong portion 82 between an opera: tive position parallel with the prong 71 as shown in full lines in Figs. 8 and 9 and an inoperative position at right angles to the prong 71 as shown in dotted lines in Figs. 8 and 9. For maintaining proper electrical contact with the conductor 74 in all positions of the movable prong ,82, the inner axial end of the cylindrical body portion 79 abuts the contact portion 77 of the connecting clip 77-78 in flatwise rotatable engagement therewith. An integral radial flange 83 carried adjacent the inner end of the body portion 79 is rotatably received in a groove 84 in the plug casing for fixing the position of the body p r i n axially f the casifig was to ns r cgnt st thereof with the member 77 and also to prevent removal of the member 79.f8;2 through the opening 81.

For interconnecting the rotary lock barrel 69 with the movable contact prong 82, a worm gear 86 made from an insulating or non-conducting material such as nylon or the like is rotatably mounted in the casing section 63 by means of a pin 87 in coaxial relation with the lock barrel 69. An eccentric connecting pin 88 extends from the barrel 69 and is received in an opening 89 in the opposed end of the gear 86 'for transmitting rotary move: ment of the lock to the worm gear. The helical thread of the gear 86 meshes with the teeth 88 on the rotatable body portion 79, and it will be evident that rotary move: ment of the lock barrel 69 will thereby eifect rotation of the prong between operative and inoperative positions. Of course, the key is again necessary to effect rotation of the lock barrel and upon removal of the key from the lock, the mechanism is secured in either operative or inoperative position.

Referring next to Figs. 13 to 17, a modified form of the invention is illustrated wherein one of the contact prongs is not only movable but is also completely detachable from the plug for disabling the same. The plug, designated generally at 91, again has a two-part casing comprising

interfitting casing sections

92 and 93 with a pair of

electrical conductors

94 and 96 extending into one end of the casing. The conductor 94 is connected by a screw 97 to the inner end of an elongated flat contact prong 98 which projects from the opposite end of the plug casing. At the opposite side of the casing section 93, a fixed contact member is provided having a connecting portion 99 connected by a screw 101 to the conductor 96. An upright resilient arm or clip portion 102 extends from the portion 99 for the purpose described hereinafter. As before, the assembled casing has a partition structure which isolates the prongs and their connections.

A rotary lock rnec hanisrn 103, which is of the same genera t n zhsrem c de c be a a rotary ba re p91.- tion 104 rotatably mounted at one end of the plug'casing, as best seen i n Fig. 16. An electrical contact pin 106 extends from the inner axial end of the barrel portion 1051 in eccentric relation with respect to the axis of rotation of the barrel 104 and is adapted to be received recess or depression 107 in the clip 102 for completing an electrical circuit from the conductor 96 to the lock barrel 104. The lock barrel 104 is arranged for rotation through approximately 90 for positioning the contact pin 106 in either an operative position engaging the clip 102, as shown in full lines in Figs. 16 and 17, or an inoperative position shown in dotted lines wherein the circuit connection between the lock barrel 104 and the conductor 96 is disrupted.

In this case, the key for manipulating the lock mechanism consists of an elongated flat element 108 having a contact prong portion 109 at one end thereof and a key portion 111 at its opposite end. When the lock barrel is in the rotary position indicated in Fig. 14 (and also in dotted lines in Figs. 16 and 17), the key portion 111 of the element 108 is freely insertable in the lock. It will be noted from Fig. 14 that when the key is first inserted the contact prong portion 109 is oriented at right angles to the fixed prong 98 so that the plug is still inoperative and cannot be inserted in the usual socket member. However, upon rotation of the lock by manipulation of the projecting contact prong portion 109 to its opposite rotary position shown in Fig. 15 (and also in full lines in Figs. 16 and 17), the prong portion 109 is thereby disposed in parallel operative relation with the fixed prong 98 and at the same time the electrical circuit within the plug is completed from the conductor 96 through the contact means 99-402 and the lock means 106-104 to the prong 109. It will, of course, be understood thatwhen the plug is disabled by rotation of the prong 109 to its Fig. 14 position and subsequent removal ofthe prong, the lock mechanism is automatically retained in its inoperative position and cannot thereafter be returned to operative position except by use of the combined key and contact prong element 108. Even if a metal strip should be inserted in the end of the lock in an attempt to utilize a disabled plug, the disengaged relation of the pin 106 with respect to the contact clip 102 when the lock is in its Fig. 14 locked position will prevent the plug from operating in the normal manner by reason of the disrupted circuit.

The outer end of the element 108 may be provided with a small aperture 112 so that the element can be carried on a key chain or the like along with other keys.

Although the invention has been described with particular reference to certain specific structural embodiments thereof, it is to be understood that various alternatives and modifications may be resorted to without departing from the scope of the invention as defined in the appended claims.

I claim:

1. An electric plug comprising a casing, a plurality of contact prongs projecting from said casing for insertion in a socket, lock means having a portion rotatably mounted in said casing, and movable mounting means for one of said prongs, said mounting means being operably connected to said rotatable lock portion and movable in unison therewith andsaid rotatable lock portion having a recess for detachably receiving a key for operating said lock means, said one prong being movable in response to key actuated manipulation of the lock means for rendering said one prong non-insertable in a socket and thereby disabling the plug.

2. An electric plug comprising a casing, a pair of contact prongs extending from said casing for insertion in a socket, one of said prongs being mounted for bodily movement relative to the casing, rotary lock means mounted in said casing and having a recess for detachably receiving a key for operatingsaid lock means, and gear means rotatably mounted in said casing and operatively interconnecting said lock means and said one prong whereby to shift said one prong relative to the casing in response to key actuated manipulation of the lock means for rendering said one prong non-insertable in a socket and thereby disabling the plug.

3. An electric plug comprising a casing, a pair of contact prongs extending from said casing for insertion in a socket, one of said prongs being mounted for bodily movement relative to the casing, lock means having a barrel portion rotatably mounted in said casing, said barrel portion being operable by a detachable key cooperable with said barrel portion, a gear member rotatably mounted in said casing in coaxial relation with said barrel portion, means providing an operating'connection between said barrel portion and said gear member for rotation of the latter in unison with the barrel portion, and toothed means provided on said one prong in coacting engagement with said gear member whereby to eifect movement of said one prong in response to key actuated rotary movement of said barrel portion for rendering said one prong non-insertable in a socket and thereby disabling the plug.

4. The device of claim 3 further characterized in that said barrel portion extends transversely into said casing from one side thereof and the opposite side of said casing rotatably supports said gear member in coaxial relation with said barrel portion.

5. An electric plug comprising a casing, a pair of elongated contact prongs extending from said casing for in sertion in a socket, means supporting one of said prongs for longitudinal shifting movement thereof between projected and retracted positions relative to said casing, key actuated rotary lock means rotatably mounted in said casing and having a recess for detachably receiving a key for operating said lock means, and actuating means operatively interconnecting said lock means and said one prong for effecting movement of said one prong between said positions by rotation of the lock means whereby to render the plug operative or inoperative.

6. An electric plug comprising a casing, a pair of contact prongs extending from said casing for insertion in a socket, means supporting one of said prongs for longitudinal shifting movement thereof between projected and retracted positions relative to said casing, lock means including a barrel portion rotatably mounted in said casing and having a recess for detachably receiving a key for operating said lock means, a gear rotatably mounted in said casing and operatively connected to said barrel portion in coaxial relation therewith, and an elongated rack carried along one edge of said one prong and engaged by said gear whereby to effect movement of said one prong between said positions in response to rotary manipulation of said lock means.

7. An electric plug comprising a casing, a pair of contact prongs extending from said casing for insertion in a socket, one of said prongs being supported within said casing for longitudinal shifting movement thereof between projected and retracted positions relative to said casing for rendering the plug operative and inoperative, respectively, a generally U-shaped resilient clip member rigidly mounted Within said casing and receiving the inner end of said one prong, means coacting between said clip member and said one prong insuring electrical contact therebetween in both projected and retracted positions of said one prong, and key actuated lock means operably mounted in said casing and having an operating connection with said one prong for effecting shifting movement of the latter in response to manipulation of said lock means, said lock means having a recess for detachably receiving a key for operating the lock means.

8. An electric plug comprising a casing, a pair of contact prongs extending from said casing for insertion in a socket, one of said prongs being supported within said casing for longitudinal shifting movement thereof between projected and retracted positions relative to said casing for rendering the plug operative and inoperative, respectively, a fixed contact member rigidly mounted in said casing and adapted to have an electrical conductor connected thereto, said contact member including a generally U-shaped clip with resiliently connected parallel leg portions, the inner end of said one prong being regarages ceived between said leg portions, a projection extending from one of said leg portions and frictionally engaging said one prong under resilient pressure during both projected and retracted positions of said one prong for Insuring electrical contact therebetween at all times, lock means including a barrel portion rotatably mounted in said casing and having a recess for detachably receiving a key for operating the lock means, a gear rotatably mounted in said casing coaxially with said barrel portion and operatively connected thereto for rotation therewith, and a rack carried by said one prong along an edge thereof and engaged by said gear whereby to eifect shifting movement of said one prong in response to rotary manipulation of the lock means.

9. An electric plug comprising a casing, a pair of elongated flat faced contact prongs extending from said casing for insertion in a socket, means supporting one of said prongs for bodily rotary movement thereof about its longitudinal axis, rotary lock means rotatably mounted in said casing, and actuating means operatively interconnecting said lock means and said one prong for rotating the latter between an operative position with one fiat face parallel to a corresponding fiat face of the other prong and an inoperative position with said one face nonparallel to said corresponding fiat face in response to manipulation of said lock means.

10. An electric plug comprising a casing, a pair of elongated flat contact prongs extending from said casing for insertion in a socket, means supporting one of said prongs for bodily rotary movement thereof about its longitudinal axis, an operating body portion carried by said one prong and provided with circumferentially spaced gear teeth, key actuated rotary lock means rotatably mounted in said casing, said lock means being operable by a detachable key cooperable therewith, and a helical gear rotatably mounted in said casing and operatively connected to said lock means, said helical gear being meshed with said gear teeth whereby to effect rotary movement of said one prong in response to key actuated rotary manipulation of said lock means.

11. An electric plug comprising a casing, a fixed contact prong extending rigidly from said casing, an elon gated member rotatably supported in said casing parallel to said fixed prong, said member having a body portion with gear teeth arranged around the circumference thereof and said member also having a contact prong portion extending from the casing for insertion in a socket together with said fixed prong, rotary lock means having a barrel portion rotatably mounted in said casing, said barrel portion being operable by a detachable key cooperable with said barrel portion, and a helical gear rotatably mounted in the casing and operatively connected to said barrel portion for rotation therewith, said helical gear being meshed with said gear teeth whereby to effect rotation of said prong portion about its longitudinal axis in response to key actuated rotary manipulation of said lock means for rendering said one prong non-insertable in a socket and thereby disabling the plug.

12. The device of claim 11 further characterized in that said casing is provided with fixed contact means rigidly mounted in the casing and adapted to have an electric conductor connected thereto, said fixed contact means having a bearing portion with the inner axial end of said body portion rotatably engaging said bearing portion for electrical contact therebetween in all rotary positions of said member.

13. An electric plug comprising a casing, a fixed contact prong extending rigidly from the casing, lock means mounted in said casing, said lock means including a rotatable portion having a key receiving recess, and a detachable element having a contact prong portion at one end and a key portion at the other end adapted to be inserted in said recess, said key portion coacting with said lock means when inserted therein for rendering the plug operative upon rotation thereof whereby said contact prong portion is adapted to be inserted together with said fixed prong into a socket, and said element being removable from the lock means for disabling the plug.

14. An electric plug comprising a casing, a fixed contact prong extending from the casing, lock means having a barrel portion rotatably mounted in said casing for movement between operative and inoperative positions and having a key receiving recess therein, and a detachable contact prong having a key portion at one end thereof adapted to be inserted in said recess for rotating said barrel portion, said contact prongs being insertable in a socket in one rotary position of said barrel portion for rendering the plug operative, and said detachable contact prong being removable from said barrel portion in another rotary position thereof for disabling the plug.

15. An electric plug comprising a casing, an elongated fiat faced contact prong extending rigidly from the casing in fixed relation thereto, rotary lock means rotatably mounted in said casing for movement through approximately said lock means having a key receiving recess, and an elongated fiat faced detachable contact prong having a key portion at one end insertable in said recess and cooperable with said lock means for actuating the latter, said detachable contact prong having one fiat face aligned in parallel relation with the corresponding face of said fixed contact prong in one rotary position of the lock means for rendering the plug operative, and said one fiat face of said detachable contact prong being disposed in non-parallel relation with said corresponding face of said fixed contact prong in another rotary position of the lock means and also being removable from the lock means in said other rotary position of the lock means for disabling the plug.

16. An electric plug comprising a casing, a fixed contact prong extending from said casing, a fixed contact element mounted in said casing, lock means having a rotary member rotatably mounted in the casing adjacent said fixed contact element, said rotary member having a key receiving recess, means extending from said rotary mmber for making electrical contact with said contact element in one rotary position of said member and disengageable from said contact element in another rotaryposition of said member, and a detachable contact prong having a key portion adapted to fit in said recess for actuating said member between said positions for rendering the plug operative or inoperative, said detachable contact prong being removable from said member in said other rotary position thereof for disabling the plug.