US 3238492 A
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Description (OCR text may contain errors)
March 1, 1966 o. HOUSTON 3,233,492
SAFETY ELECTRIC RECEPTACLE Filed Jan. 16, 1964 ill!!! Jay. 4.
Wan/1M United States Patent 3,238,492 SAFETY ELECTRHC RECEPTACLE Douglas Houston, West Hill, ()ntario, Canada, assignor to Harvey Hubbeli, incorporated, Bridgeport, Qonra, a corporation of Connecticut Filed Jan. 16, 1964, Ser. No. 338,132 6 Claims. (Cl. 339-46) This invention relates to electric receptacles and, more particularly, to such receptacles of the safety type.
An electric receptacle, for example, the common duplex convenience outlet which is widely used in home, public, and commercial buildings, presents a distinct safety hazard to small children. This is because children, emboldened by curiosity, may attempt to insert metal objects such as hairpins or nail files into the slots in the front face of the receptacle. Should the child thereby contact the line side of the outlet, he may receive a serious, even a fatal shock.
A number of attempts have been made to produce a receptacle having safety features which would prevent the insertion of current carrying objects into the blade-receiving slots. However, all of the attempts heretofore made have resulted in devices having certain drawbacks. One approach which has been taken in several prior art devices involves the addition of a sliding plate, either to the cover or to the receptacle itself. The sliding plate is provided with slots for receiving the male blades of an electrical cap. These slots are normally nonaligned with the receptacle slots and a double motion is required to insert the cap. A first lateral motion displaces the plate so that the slots become aligned and the blades are then inserted to make electrical contact. Several disadvantages of a construction of this type will be apparent. To begin with, the user is required to perform a double movement in order to insert the cap. This is a commercial disadvantage and may also be difficult to perform under conditions of low illumination. A second disadvantage of such a construction is that, in most prior art devices of this type, the movable slots are interconnected so that the proper lateral motion of either slot alone will align the openings. This reduces the safety factor as a child could accidentally or purposely uncover both slots with a single instrument. Still another disadvantage arises from the present trend toward the use of three wire grounding caps and receptacles. In grounding caps of this type, the third, or grounding, blade is a semi-cylindrical plug which has a length greater than that of the line blades. Accordingly, the two blades could not be mated with the movable slots on the receptacle unless some type of special provision, such as an elongated grounding opening, were provided for the grounding plug.
Those prior art devices which overcome or avoid the disadvantages set forth above, are of a relatively complex nature. Such devices may require several moving parts and these moving parts tend to be complicated and, accordingly, expensive to manufacture, sell, and maintain.
Accordingly, it is a primary object of the present invention to provide an improved electric receptacle of the safety type. Other objects are to provide such a receptacle which allows the user to insert the cap in a single thrusting motion, as is the case with standard receptacles; to provide such a receptacle which cannot be actuated by insertion of a foreign object into either of the slots singly; to provide such a receptacle wherein the moving portions are few in number and are simple fiat elements which are inexpensive to manufacture; and to provide such a receptacle which may be used with either a standard two blade cap or with a three blade grounding cap.
Patented Mar. '1, 1956 The manner in which the foregoing objects are achieved will be more apparent from the following description, the appended claims and the figures of the attached drawing, wherein:
FIG. 1 is a front view of a grounding receptacle constructed in accordance with this invention;
FIG. 2 is a right side view of the body of FIG. 1;
FIG. 3 is a cross section taken along the line 33 of FIG. 2, illustrating the mechanical features of the invention;
FIG. 4 is a cross section taken along the line 44 of FIG. 3 and also illustrating a portion of an advancing p;
FIG. 5 is a view similar to that of FIG. 3, illustrating the mechanical operation of the invention during insertion of a three blade grounding cap;
FIG. 6 is an illustration similar to FIGS. 3 and 5 illustrating the positions of the mechanical elements of the receptacle when the grounding cap is fully inserted;
FIG. 7 is an illustration similar to FIGS. 3, 5, and 6 illustrating one possible modification of the mechanism of the invention; and
FIG. 8 is an enlarged cross section taken along the line 88 of FIG. 7.
FIGS. 1 and 2 illustrate a duplex grounding receptacle constructed in accordance with the invention. It Will be noted that on casual inspection the receptacle presents a standard appearance and that the mechanical safety features of the invention are not apparent. The receptacle includes a body it) which may be formed in the usual fashion from a suitable insulating material, such as a moldable plastic. The face of body 10 defines individual receptacles 10a, 10b, and the back of the receptacle is covered by a suitable closure plate 12. Terminals 14 provide means for connecting the line conductors to the receptacle line contacts, and a binding post terminal 16 is provided for connection of the receptacle ground con tactto a separate ground. Each of the individual re ceptacles, 10a, 10b, defines a pair of parallel spaced slots 18, 20 for receiving the blades of the electrical cap and a semi-circular opening 22 for receiving the grounding plug. As the construction of the mechanical safety features of the individual receptacles is identical, only the features of receptacle 10a will be described.
Reference to FIG. 3 will disclose that the inside of the front face of receptacle 18a is covered by a flat guide plate 24 apertured in a manner to be described. Guide plate 24, in turn, is covered by a back up plate 26 which serves solely to retain the moving elements of the safety mechanism and is here shown cut away to more clearly illustrate the essential features of the invention. Back up plate 26 is slotted and apertured so as not to interfere with the insertion of the blades of the male cap from slots 18, 20 or opening 22.
Guide plate 24 includes a cutout portion which defines a generally V-shaped opening 28. The right arm of V, as viewed in FIG. 3, is essentially a parallelogram. The right hand edge 30 of the opening 28 is aligned with the outer edge of slot 18. The left arm of the V-shaped opening 28 is generally U-shaped so as to define a pair of spaced parallel slots 32, 34. The vertical edge 36 which joins the slots 32, 34 is aligned with the outermost edge of the slot 20.
The right arm of V-shaped opening 28 is substantially completely filled by a female slide member 38. Slide member 38 is a planar member having generally the shape of a parallelogram so as to be freely slidable Within the right arm of opening 28. Its left edge, however, is cut away so as to form a generally rectangular recess 40. The corners formed by recess 40 and the left edge of member 38 are beveled and the lower left corner of member 38 is cut away to form an edge 42 which is parallel to 3 the edge of slot 34 of the left arm of the V-shaped opening 28. In addition, the front surface of member 38 (that adjoining the front wall of receptacle a) is tapered over the area covering slot 18. The taper feathers out at right edge 30, as is most clearly shown in FIG. 4.
The left arm of the V-shaped opening 28 contains a U-shaped male slide member 44. Slide member 44 includes a pair of spaced arms 441, 442 which are slidably positioned in the corresponding slots 32, 34. The right hand edge of male member 44 is separated from the left hand edge of female member 38 so as to leave an intervening space. Projecting outwardly and to the right from the right hand edge of member 44 is a locking lug 46, which is directly opposed to the recess 40 on the female member 38. That portion of male member 44 which covers the slot is tapered in a fashion similar to the corresponding portion of the female member. The thin edge of the taper ends at edge 36, as is most clearly shown in FIG. 4. A coiled compression spring 48 acts outwardly against members 38, 44 retaining them in a separated condition and against the edges 30, 36 of the V-shaped opening 28.
FIGS. 3 and 4 illustrate the closed position of the safety receptacle of the invention. It will be noted that the slots 18, 20 are closed by the corresponding female member 38 and male member 44. Accordingly, it is impossible to insert a foreign object into either of these openings. If such an insertion is attempted, one of the members 38, 44 may be forced sligthly inward along the V-shaped opening 28, but, almost immediately, misalign ment of the recess and lug 46 will occur, making it impossible for either of these members to be advanced sufficiently to open the corresponding slot. The opposing beveled corners of recess 40 and locking projection 46 will interfere and prevent further advancement, as is illustrated by dashed-dotted lines in FIG. 3. However, the operation is different when a standard electric cap 50, as shown in FIG. 4, is advanced toward the receptacle. Cap 50 in the illustrated embodiment of the invention is a grounding cap of standard design, having a pair of spaced parallel contact blades 52, 54 and a semi-cylindrical grounding plug 56. After reviewing the operation of the device, it will also be apparent that a standard two blade cap could be employed with equal facility. As cap 50 is advanced toward the receptacle, grounding plug 56 will enter the opening 22 without resistance. The ends of blades 52, 54 will then contact the tapered portions of the corresponding slide members 38, 44 and, as they are advanced simultaneously, will begin to cam them inwardly toward each other along the arms of V-shaped opening 28 as is illustrated in FIG. 5. Since blades 52, 54 are of substantially equal thickness, they will displace the slide members 38, 44 by equal amounts. As the angles made with the horizontal by the two arms of V-shaped opening 28 are also equal, it necessarily follows that the recess 40 and the locking lug 46 will remain aligned with one another during such relative movement of the members 38, 44 so that the lug 46 will be permitted to enter the recess 40 as is illustrated in FIG. 5. The spring 48 is meanwhile being compressed by the closing force exerted by the members 38, 44 caused by the advancing cap. The interengaging action between lug 36 and recess 46 continues until the blades 52, 54 are completely inserted, as shown in FIG. 6, and electrical contact is made with the female contacts contained within body 10. Upon withdrawing the cap 50, the blades 52, 54 will be removed and the spring 48 will expand, forcing the silde members 38, 44 back into their original positions covering the slots 18, 20.
In FIG. 7 there is illustrated a modification wherein guide plate 58 is substituted for guide plate 24. Guide plate 58 differs from guide plate 24 in that both arms of the V-shaped opening 60 resemble parallelograms. The female slide member 38 is the same. However, the male slide member 62 is shaped to conform to the corresponding arm of the V-shaped opening 60. A slot 64 is cut through the male member 62 and its right edge 64 is aligned with the left edge of the front slot 26. That portion of the front surface of slide member 62 adjoining the edge 64 is tapered as illustrated in FIG. 8 to present a camrning surface to the advancing contact blade. Upon insertion of blade 54, member 62 will be cammed to the right in the fashion previously explained. The blade 54 will then enter the receptacle through slot 64. It will be observed that the operation of this modification is substantially similar to the operation of the mechanism previously described.
It will be apparent to those skilled in the art that the novel safety receptacle herein described achieves all the objectives set forth above. Furthermore, it will be apparent that these objectives are achieved with a minimum of complexity and with inexpensive parts. All parts of the mechanism of this invention, with the exception of the spring, are fiat elements which may be easily and cheaply manufactured out of any suitable material, such as plastic. Furthermore, there are only two major moving parts, so that device is reliable, rugged and inexpensive, while still providing maximum safety in its intended application. It will also be apparent to those skilled in the art that a number of modifications and variations may be made in this invention without departing from its spirit and scope. Accordingly, it is to be understood that the foregoing description is illustrative only rather than limiting. This invention is limited only by the scope of the following claims.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. In an electric receptacle having a body including a front wall defining at least first and second spaced slots aligned with internal female contacts for receiving the contact blades of an electric cap, the combination comprising: first reciprocating member means positionable to close said first slot; second reciprocating member means positionable to close said second slot; first camming means on said first member means arranged to be contacted by a first contact blade of said cap to displace said first member means away from said first slot; second camming means on said second member means arranged to be contacted by a second contact blade of said cap to displace said second member means away from said second slot; and control means positioned to clearingly interengage in response to substantially equal displacement of said member means to uncover said slots, but to interferingly engage upon unequal displacement of said member means to prevent further displacement and keep said slots closed; said first and said second reciprocating member means being substantially planar and arranged to be separately slidable along an inner surface of said front wall and along the arms of a V-shaped guide opening disposed in said body to uncover said slots when positioned at substantially the apex of said V-shaped opening and to cover said slots when positioned at substantially the outer ends of said V-shaped opening.
2. The receptacle of claim 1 wherein said control means comprises a recess defined by said first member means and a lug positioned on said second member means.
3. An electric safety receptacle comprising: a body including a front wall defining at least first and second spaced slots for receiving the contact blades of an electric cap and enclosing female contacts therein positioned in alignment with said slots to mate with said contact blades; a guide plate mounted adjacent the inner surface of said front wall defining a V-shaped cutout portion, the apex of the V being intermediate said slots and each arm of said V being over a different one of said slots; a first slide member positioned for sliding movement within said cutout portion and along one arm of said V, said first slide member being arranged to cover said first slot at its outermost position along said one arm and defining along its inner edge a recess having spaced parallel edges normal to a bisector of said V; first camming means on said first slide member positioned to be contacted by a first contact blade of said electric cap when inserted into said first slot to displace said first slide member toward the apex of said V; a second slide member positioned for sliding movement Within said cutout portion and along the other arm of said V, said second slide member being arranged to cover said second slot at its outermost position along said other arm and carrying on its inner edge a lug protruding therefrom having parallel edges aligned with said recess; second camming means on said second slide member positioned to be contacted by a second contact blade of said electric cap when inserted into said second slot to displace said second slide member toward the apex of said V and cause said lug to enter into said recess only upon substantially equal displacement of said first and second slide members toward each other; and resilient means intermediate said first and second slide members urging said slide members outwardly from said apex.
4. The receptacle of claim 3 wherein each of said slide members is substantially planar and wherein each of said camm-ing means comprises a tapered surface portion of its corresponding slide member.
5. The receptacle of claim 4 wherein said resilient means is a spring.
6. The receptacleof claim 4 wherein said second slide member defines a contact blade receiving opening adjacent the thinnest edge of its tapered surface portion.
References Cited by the Examiner UNITED STATES PATENTS 2,545,536 3/1951 Von Holtz 339-40 FOREIGN PATENTS 224,186 11/1962 Austria. 443,794 3/ 1936 Great Britain. 508,415 6/ 1939 Great Britain.
JOSEPH D. SEERS, Primary Examiner.