Safety Sleeve for Attachment to the Prong of an Electrical Connector and Key for Its Removal

The invention concerns a locking device for electrical plugs, The locking device attaches to the prong of a male electrical connector to prevent its insertion in a corresponding female connector and thus prevent activation of an electrical apparatus to which it may be attached.

Such devices have been previously disclosed in U.S. Pat. Nos. 2,664,734; 2,955,272; and 3,345,600.

Earlier devices have generally been too complicated or costly to effectively become utilized by the mass consumer market. The invention provides a simple and inexpensive connector lock.

A sleeve which receives and retains within a central channel through the sleeve the prong of a male electrical connector of the type having a hole in the surface of the prong. A locking stud for engagement in the hole in the prong projects into the channel. A beveled tip on a locking stud contacts the prong tip on first insertion and deflects the locking stud aside by movement of a flexible arm on which it is mounted. In a preferred embodiment there are two locking studs on opposite sides of the channel mounted on separate flexible arms. Each locking stud engages one side of the prong. The surface of the locking stud opposite the beveled surface is perpendicular to the longitudinal axis of the channel so that when the locking studs engage the hole in the prong removal of the prong is prevented.

A key is provided to permit removal of the prong from the sleeve. The key consists of a body having slightly divergent projecting blades with oppositely beveled tips. The blades are inserted in the channel and are directed alongside the prong deflecting the flexible arms outward withdrawing the locking studs from the hole in the prong. The removal of the prong from the sleeve is thus permitted.

A preferred construction of the sleeve consists of two identical halves. Each half has a central groove which form together the central channel and each has a locking stud on a flexible arm which is defined by a U shaped groove. The key and the end of the channel where it is received is preferably larger than the prong receiving end to prevent placing the key in the wrong end when the sleeve is not in use. Preferably projecting ribs extend into the key receiving end of the channel to prevent insertion of a prong in the wrong end of the sleeve.

FIG. 1 is an exploded perspective view of the invention illustrating the separated positions of the key, sleeve and an electrical connector.

FIG. 2 is a sectional view through the sleeve and a prong of an electrical connector which is inserted in the sleeve.

FIG. 3 is a sectional view similar to FIG. 2 with the key inserted illustrating how the flexible arms are deflected.

FIG. 4 is a perspective view of a component of the sleeve which when mated with an identical component form a complete sleeve.

The preferred embodiment of the invention is illustrated in FIGS. 1 through 4. The invention is a sleeve 10 which may be attached to a prong 12 of a male electrical connector 14 of the type having a hole 16 in the surface of the prong. The sleeve 10 receives a prong of the connector and captively retains it by the engagement of locking studs 18 in the hole 16 in a manner more fully described below. This prevents the connector from being inserted in a corresponding female connector thereby preventing unauthorized and/or unsupervised use of an electrical apparatus, particularly by children. To release the prong 12 from the sleeve a key 20 is inserted in the sleeve 10. The key contacts the prong within the sleeve and, in a manner more fully described below, causes the locking studs 18 to disengage the hole 16 and permit removal of the prong from the sleeve.

The sleeve, in its preferred form, consists of a housing 22 having a central channel 24 passing centrally through it. The channel is preferably, approximately twice as long as a prong. Preferably the channel has the same transverse cross-sectional shape as a conventional prong 12. One end of the channel receives the prong and the opposite end receives the key 20. Preferably the end of the channel where the key is inserted and the key itself are slightly larger than the end where the prong is inserted so as to prevent the key from being inserted in the wrong end when the device is not in use. In the key end of the channel, preferably, there are ribs 25 extending into the channel which prevents the prong from being inserted in the wrong end. A locking stud 18 extends into the central channel. Preferably there are two such locking studs positioned on opposite sides of the channel from each other so that each may contact the prong from opposite sides. These studs are connected to the housing 22 by flexible arms 26. Preferably the arms 26, locking studs 18, and housing 22 are integrally constructed from a single piece material such as polystyrene plastic. In such a preferred construction the arms 26 are defined by a slot such as the U-shaped slots 28 shown in the drawings. The tip of the locking stud 18 is preferably beveled at 30 so that upon insertion of the prong 12 into the channel the tip 32 of the prong contacts the beveled surface 30 of the locking studs forcing the arms 26 outward allowing the prong to be inserted to a point where the locking studs engage in the holes 16 of the prong under the resilient force of the arm. The surfaces 34 of the locking studs opposite the beveled surface prevent removal of the prong and are preferably perpendicular to the longitudinal axis of the channel. Further travel of the prong inward is limited by the body of the plug 14 contacting the end of the housing 22. The sleeve 10 thus captively holds the prong preventing its removal and insertion of the plug into a female receptacle.

The key 20 is provided to release the prong from the sleeve 10. The key consists of a body 36 which provides a convenient means of grasping it and blades 38 and 40 which each act upon a corresponding arm and locking stud. In the preferred embodiment there are thus two such blades which pass on opposite sides of the ribs 25. The blades 38 and 40 have tips 42 and 44 respectively which are oppositely beveled. They are preferably beveled at ten (10) degrees. When the blades are inserted in the channel 24 when the sleeve 10 is holding a prong, the beveled ends 42 and 44 contact opposite edges of the prong tip 32. As the key 20 is inserted further the blades are deflected outward against their corresponding arms 26 drawing the locking studs 18 from the hole 16 in the prong and permitting removal of the prong from the sleeve 10. Preferably the blades 38 and 40 are angled from each other by approximately two (2) degrees at 46. This causes the blade tips 48 and 50 to travel along the walls 52 of the channel 24 during insertion and to be directed alongside rather than into the tip 32 of the prong.

Preferably the sleeve is constructed of components such as the component 54 shown in FIG. 4. The component consists of a body 56, preferably of a generally rectangular shape, of a semi-rigid material. A central groove 58 extends the length of the body and a U shaped slot 28 as previously described above outlines and defines the flexible arm 26 as also described above to which the locking stud 18 having the beveled tip 30 is attached. Preferably the component 54 is provided with indexing elements such as the pins 60 and receiving holes 62 as illustrated in FIG. 4. When such a construction is used a sleeve 10 can be constructed from two identical components 54. The indexing pins 60 fit into the receiving holes in the mating component and vice versa. The two halves may be held together with a suitable adhesive.

The sleeve and key together provide a very simply constructed and effective safety device. The key and the sleeve can be molded from an inexpensive and easy to handle plastic material to provide a simple, effective safety device.