Patent Application
20150380856
The present invention relates to tamper resistant electrical receptacles. More particularly, the present invention relates to tamper resistant electrical receptacles using laterally sliding shutters spring biased to block access to the device's electrical contacts.
Tamper resistant receptacles are known in the art. “Tamper Resistant” or “TR” receptacles are a class of electrical receptacle outlets configured to deny access to the device's electrical contacts unless force is applied simultaneously to both the hot and neutral plug openings of the device pursuant to NEC Code 406.11 et seq. The Code and related regulatory requirements provide that not only must the outlet openings remain blocked unless force is applied to both openings at the same time, but also that any foreign object 1/32 inch or larger, must be prevented from bypassing the blocking member of a plug opening.
As will be appreciated, these requirements were enacted in response to the phenomena of small children curiously inserting a small toy or metal object into the hot or neutral opening of a receptacle and suffering electrical shock, burns, or even death.
In meeting the standard and providing the level of protection sought from these devices, the art has gravitated towards a configuration of receptacles utilizing cooperating shutter members to block access beyond the faceplate openings of the outlet. Specifically, to ensure that force directed into only one of the two blade openings is prevented from reaching the electrical contact that lies beneath, a sliding shutter mechanism is spring-biased into a position blocking (or “shuttering”) the blade opening from underneath the faceplate. The shutter physically prevents an object entering the blade opening from reaching the electrical contact below that shutter. In order to allow the shutter of a respective blade opening to be uncovered, the spring-bias must be overcome by a camming action caused by the other plug blade during insertion in the other blade opening.
To this end, the most common prior art configuration of a TR receptacle includes a shutter assembly comprising a pair of cooperating shutters. Each of the shutters includes a blocking portion positioned below a respective one of the blade openings blocking access to the contacts. Each of the shutters also includes a cam portion that extends to the opposite blade opening that receives contact from a plug blade and translates the vertical force of a plug blade and camming action into a lateral sliding displacement of the blocking portion. Thus, force by vertical insertion of a plug-blade on the neutral blade opening will move the shutter from obstructing access to the electrical contact below the hot blade opening, and vice versa. Specifically, for example, during insertion of a plug, the neutral blade tine will cam against and past the shutter cam surface forcing the shutter cam arm to move laterally, thereby overcoming the spring bias of the shutter and causing the hot blade shutter blocking portion to slide into a position away from and revealing the electrical contact beneath the hot blade opening. Likewise, force on the hot blade opening will contact the cam surface and allow the blade to cam past and move the arm and compress the spring to move the shutter blocking portion that covers the neutral blade opening out of the way. As will be appreciated, with this configuration, when a child tries to insert a toy into either opening of the outlet, the blocking portion of the shutter remains immobile from the spring bias of the opposite shutter and prevents the child from reaching the electrical contact. However, when both blades of an electrical plug contact the shutters simultaneously, the simultaneous force and camming action allows both blades to continue their downward insertion by simultaneously sliding respective shutter blocking portions laterally out of the way of the electrical contacts of the opposite shutter until the blades cam past the shutters and are able to properly “plug in” to the outlet's internal face contacts.
Existing prior art TR receptacle designs and their operational details are available in U.S. Pat. No. 4,379,607 to Bowden, Jr.; U.S. Pat. Nos. 7,645,148 to Carbone et al.; and U.S. Publ. No. 2013/0295788 to Baldwin, et al. and the references cited therein, the entire contents of which are hereby incorporated by reference in their entirety.
The proliferation of these important safety devices has led to an appreciation of the issues affecting their effective life span. A presently appreciated issue recognized by the present inventors stems from the translation of the vertical force of the plug blade into lateral movement of the shutters. With cooperating shutter assemblies, the shutters of each blade opening are frictionally forced to slide against each other in opposite directions. Additionally, the shutters are seated in a housing and frictionally side within the housing. Typically, the shutters and housing are generally planar and are in frictional contact along a substantial portion of their bodies. Sliding two or more materials against each other results in increased force needed to compensate for the frictional forces attendant to the areas of contact. The greater the contact area, the greater the frictional force to be overcome to cause the desired movement.
Another presently appreciated issue recognized by the present inventors stems from the sharpness of plug blades being found on electrical products imported from overseas. As will be appreciated, during insertion of the plug blades into the outlet face openings, the vertical force of the incoming blades has the same point of contact on the cam surface. The cam surface of most prior art devices is an inclined “ramp” of about 45O that is of a length sufficient to cause lateral displacement during insertion of a distance that is equal to the entire distance necessary to un-shutter a blade opening (typically about 1.8 mm). Over time, these sharp blades having a single point of initial contact begin to deform and cut into the ramp surface which makes movement more difficult as the blades get stuck in divets or scratches at the point of contact. With each successive insertion, more and more force is needed to friction force the camming action and concomitant lateral sliding of the shutters. At some point, the deformity of the ramp surface may make insertion of a plug excessively difficult or even impossible. At this point, the device has reached the end of its useful life.
When considered in combination, the large area of contact between the surfaces of the constituent components and the increasing force necessitated by deforming ramps equates to larger amounts of force being required to get these types of TR receptacles into the open and operational position. This, in turn, may be rationally extrapolated to mean a shorter useful life of the product unless mitigated.
Yet another presently appreciated issue recognized by the present inventors is that many convention TR receptacle designs cannot accommodate deployment in a 20 A receptacle due to the inability to provide sufficient clearance for the perpendicularly oriented neutral blade of the plug.
The foregoing underscores some of the problems associated with conventional TR receptacles. Furthermore, the foregoing highlights the long-felt, yet unresolved need in the art for a TR receptacle that may extend the useful life of the device. Moreover, the forgoing highlights the long-felt, yet unresolved need in the art for a TR receptacle that has an extended service life at a reasonable cost. Finally, the foregoing highlights the long-felt need for an improved TR receptacle configuration that is useful in 15 A and 20 A receptacles.
Various embodiments of the present invention overcome various of the aforementioned and other disadvantages associated with prior art TR receptacles and offers new advantages as well. Although not wishing to be bound by theory, the present inventors' recognize that limiting the areas of contact between the sliding shutter members and/or the shutter housing results in a more frictionally advantageous configuration that may extend the service life of some prior art TR receptacles.
According to one aspect of various embodiments of the present invention there is provided a TR receptacle having cooperating shutter mechanisms wherein the shutters are configured to minimize the points of contact between the two to reduce the frictional forces during lateral movement.
According to another aspect of various embodiments of the present invention, there is provided a TR receptacle having cooperating shutter mechanisms wherein the ramp area of each shutter includes a metal skin to resist gauging and deforming by plug blades.
According to another aspect of various embodiments of the present invention there is provided a TR receptacle configured for use in a 20 A receptacle. According to this aspect of the invention, in a presently preferred embodiment the receptacle includes a shutter assembly having a hot shutter member and a neutral shutter member comprising flexible arms for accommodating the perpendicular blade of a 20 A plug.
The invention as described and claimed herein should become evident to a person of ordinary skill in the art given the following enabling description and drawings. The aspects and features of the invention believed to be novel and other elements characteristic of the invention are set forth with particularity in the appended claims. The drawings are for illustration purposes only and are not drawn to scale unless otherwise indicated. The drawings are not intended to limit the scope of the invention. The following enabling disclosure is directed to one of ordinary skill in the art and presupposes that those aspects of the invention within the ability of the ordinarily skilled artisan are understood and appreciated.
Various aspects and advantageous features of the present invention will become more apparent to those of ordinary skill when described in the detailed description of preferred embodiments and reference to the accompany drawing wherein:
While the present invention will be described in connection with a TR receptacle of the type having cooperating shutters generally described above, it will be readily apparent to one of ordinary skill in the art armed with the present specification that the present invention can be applied to a multiplicity of fields and uses. In particular, the present invention may find use in connection with other types of TR receptacles where reduction in frictional contact between surfaces is desirable. One of ordinary skill in the art armed with the present specification will also understand that the present system may be easily modified to include different configurations, mechanisms, methods, and kits, which achieve some or all of the purposes of the present invention.
As will be discussed in more detail below, the basic concept described in an illustrative embodiment according to the present invention is that the hot slider does not make contact with the neutral slider. Rather, each slider slides along its own tracks in the slider housing. Specifically, the hot slider includes slide pads and slide tabs adapted to slide in tracks in an inside surface of the slider housing, and the neutral slider includes slide pads and tabs adapted to slide in other tracks in the inside surface of the slider housing. With this embodiment, friction is reduced during the plugging process,
when compared to a prior art embodiment in which the hot slider makes contact with the neutral slider, because there is no interface between the hot slider and the neutral slider. Specifically, there is no frictional force on the hot slider due to an interface between the hot slider and the neutral slider, and no frictional force on the neutral slider due to an interface between the hot slider and the neutral slider. Although not sliding against each other, the sliders still cooperate in a manner that only allows the electrical contacts of an electrical receptacle to be accessed if simultaneous force is applied to both the hot and neutral plug openings. If force is only applied to one of the openings, the electrical contacts cannot be reached.
Turning to the exemplary embodiment depicted in the Figures, the slider assembly 10 includes a slider housing 100; a neutral blade slide body, or “neutral slider” 200; a hot blade slide body, or “hot slider” 300; and a central spring 400. In operation, as with the prior art devices described above, the blades of an electrical plug cause lateral movement of the sliders 200, 300 by overcoming the bias of the central spring 400. However, in the embodiment depicted, the sliders and housing are configured to reduce the frictional forces of the assembly as compared to prior art devices. Additionally, the component parts are adapted for use with a 20 A receptacle.
To these ends, the slider housing 100 is configured as a unitary piece of plastic sized and shaped to fit within the footprint of an electrical receptacle. The housing 100 is generally tub shaped having a central planar portion 101 surrounded by an ascending perimetrical sidewall 102 of a height sufficient to house the assembly's operative components and rest flush with the faceplate of an electrical outlet (not shown).
The central planar portion 101 of the slider housing includes a hot plug blade opening 110 and a neutral plug blade opening 120. The neutral plug blade opening 120 is not only longer than the hot blade opening 110 for receiving the larger neutral blade of a plug, but also wider to accommodate the perpendicularly oriented neutral blade of a 20 A plug. Additionally, the neutral plug blade opening 120 includes a lateral neck portion 121 and a pentagonal head portion 122. As will be described in more detail below, this configuration serves as part of the safety features of the device.
The neutral slider 200 and hot slider 300 are disposed in the slider housing 100. In the depicted embodiment, the sliders 200, 300 are spring biased in the “closed” position by a centrally disposed helical spring 400 that extends between spring seats 201, 301 disposed on opposing lateral faces 202, 302 of the sliders 200, 300. The lateral faces 202, 302 are on the centrally facing side opposite each of the respective ramp portions 210, 310 of the sliders 200, 300. The ramp portions 210, 310 are the portions of the sliders 200, 300 that lie beneath the blade openings in the receptacle faceplate and receive the blades during the initial stages of plug insertion. As depicted, the neutral slider 200 has a ramp 210 that is contacted by the neutral blade of an electrical plug, and the hot slider 300 has a ramp 310 that is contacted by the hot blade of an electrical plug. The names of the sliders were chosen arbitrarily based on the blade of the electrical plug that contacts them. Thus, for clarity in understanding the discussion that follows, it is the neutral slider that includes a portion that blocks access to the hot electrical contact and the hot slider that includes a portion that blocks access to the neutral electrical contact.
Turning to the specifics of the neutral slider 200. As best discerned from
The underside of the neutral slider 200 includes a sliding pad 250 in the area of the blocking portion 220. The sliding pad 250 may include a sliding tab 251. The sliding tab 251 is sized to fit into a tab track channel 151 in the slider housing 100. The underside of the slider 200 in an area of the ramp portion 210 and side fins 240A, 240B includes slider pads 260 and may include slider tabs 261A, 261B that are sized to fit in tab track channel 161A, 161B provided in the slider housing 100. The frictional benefits of the slider pads and tabs will be readily appreciated and will be discussed in more detail below.
With respect to the hot slider 300, as best discerned from
The head portions 340A, 340B are prevented from being flexed open by the provision of respective halves of a raised guide 345A, 345B on the underside of the head portions. The guide 345 is sized to sit in, and be constrained by, the neck 121 of the neutral opening 120 of the housing 100 to maintain the gap in the closed. Only when the hot slider 300 is slid laterally does the guide 345 slide into the pentagonal area 122 of the neutral opening which provides enough room for the guide to be spread apart. This in turn means that the gap between the head portions 340A, 340B of the slider 300 can be spread to receive the perpendicular neutral blade of a 20 A plug. Thus, absent cooperative sliding of both sliders, the gap remains impenetrable by foreign objects. To this end, in a preferred embodiment, the terminal ends, or fingers 241A, 241B of the fins 240A, 240B of the neutral slider 200 extend into niches 390A, 390B in the head portions 340A, 340B and serve to hold the head portion gap closed unless the ramp 210 in engaged and the slider 200 laterally cammed away. Thus, only when both prongs of a plug blade are inserted into the receptacle can the gap be spread.
The underside of the hot slider 300 also includes slide pads 350A, 350B and tabs 351A, 351B disposed downwardly from the side fins 320A, 320B. The tabs 351A, 351B are sized to run in track channels 181A, 181B provided in the housing 100. The downward disposition of the fins and slide pads provides clearance for the blocking portion 220 of the neutral slider 200. Slide pads 360A, 360B are similarly disposed on the underside of the hot slider 300 in the area of the head portions 340A, 340B. The various slide pads (and tabs) serve to lessen the surface area of the sliders that rubs against the housing during plug insertion.
In this regard, the planar area comprising the blocking 220 and central portion 230 of the neutral slider 200 is narrower and disposed within the confines of the fins 340A, 340B and arms 330A, 330B of the hot slider 300. This configuration separates the hot and neutral sliders 200, 300 so they do not rub against each other during lateral movement. Similarly, the fins 240A, 240B of the neutral slider 200 are configured to provide safe passage of the hot slider 300 during movement to further minimize any friction between the surfaces.
As will be appreciated, in operation, each of the sliders 200, 300 is cooperatively configured to reduce or eliminate the points of contact between the two sliders when the ramps are engaged and the sliders lateral moved during the plugging process. Numerous configurations of the sliders may be envisioned to allow for operation of the cooperating sliders while reducing or eliminating the physical contact between the sliders.
One of ordinary skill will appreciate that the exact dimensions and materials are not critical to the invention and all suitable variations should be deemed to be within the scope of the invention if deemed suitable for carrying out the objects of the invention. In this regard, to combat the problem of plug blades gouging and deforming the ramp surfaces 210, 310 of the camming portions, the present inventors envision the provision of metal skins 500 on the ramp surfaces. The metal skins will resist scratching, gouging, and bending and hopefully extend the useful life of the product.
One of ordinary skill in the art will also readily appreciate that it is well within the ability of the ordinarily skilled artisan to modify one or more of the constituent parts for carrying out the various embodiments of the invention. Once armed with the present specification, routine experimentation is all that is needed to determine adjustments and modifications that will carry out the present invention.
The above embodiments are for illustrative purposes and are not intended to limit the scope of the invention or the adaptation of the features described herein to particular TR receptacles. Those skilled in the art will also appreciate that various adaptations and modifications of the above-described preferred embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.
The present application claims the benefit of priority under 35 U.S.C. 102(e) from U.S. Provisional Application 62/015,131, filed Jun. 20, 2014, the contents of which are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62015131 | Jun 2014 | US |
