Abstract:
A lockable electrical socket has a pair of grasping jaws which can retain an electrical plug in place. The plug can be released by pushing in the plug and then allowing the plug retaining assembly and the plug to be thrust out under spring pressure. In a second embodiment a key is required to thrust out the plug in order to prevent unauthorized removal of the plug from the socket. A dummy or safety plug can be used in place of an electrical plug to make the lockable socket child-proof.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electrical sockets having releasable locking mechanisms to lock the contact prongs of electrical plugs therein. 
     2. Description of the Prior Art 
     Typical household electrical sockets normally include an insulated housing having two or three openings for receiving the prongs of an electrical plug. Such electrical sockets suffer many draw backs. For example, as the socket wears, the plug is no longer tightly retained in the socket. The plug may then partially slip out of the socket either due to gravity or minor tugs on the socket. If the plug is grasped in this condition, a risk of electrical shock exists because of the partially exposed prongs. Also the exposed prongs may present a fire hazard. 
     In addition, conventional sockets present an annoying inconvenience to users who repeatedly have to reinsert inadvertently disconnected plugs. 
     Further, children are extremely fascinated with electrical outlets, and have a tendency to remove electrical plugs from their outlets and insert objects such as paper clips or other metallic items into the outlet, thus subjecting themselves to the risk of electrocution. 
     For the aforementioned reasons, many electrical sockets that releasably lock the electrical plug in place, have been proposed in the prior art. The following United States patents all show releasably locking electrical sockets. 
     
         ______________________________________U.S. Pat. No.       Name______________________________________5,286,213           Altergott et al.5,129,836           Ursich4,969,833           Lindow et al.4,909,749           Long4,846,707           Pirkle4,530,556           Bonus4,167,658           Sherman4,136,919           Howard et al.4,085,991           Marshall et al.4,061,409           Bealmear3,805,211           Moore3,543,218           Archer3,350,675           Misencik et al.______________________________________ 
    
     However, none of the cited references teach or suggest a pair of hinged jaws for grasping the prongs of a plug, with the jaws being mounted to a carrier capable of reciprocating movement within the socket. 
     None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a lockable electrical socket that has a pair of grasping jaws which can retain a plug in place. The plug can be released by pushing in the plug and then allowing the plug retaining assembly and the plug to be thrust out under spring pressure. 
     Accordingly, it is a principal object of the invention to provide an electrical socket that releasably locks electrical plugs in place. It is another object of the invention to provide a lockable electrical socket which can be locked and unlocked by simply pushing in the plug. 
     It is a further object of the invention to provide a lockable electrical socket which can be unlocked by a key to prevent unauthorized access thereto. 
     Still another object of the invention is to provide a socket that can releasably retain a safety plug to prevent children from inserting metal objects therein. 
     It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of the locking socket of the present invention. 
     FIG. 2 is a top cross sectional view of the locking socket of the present invention showing the locking assembly in the locked position. 
     FIG. 3 is a top cross sectional view of the locking socket of the present invention showing the locking assembly in the unlocked position. 
     FIG. 4 is a bottom view of the locking socket of the present invention with the locking assembly in the locked position. 
     FIG. 5 is a perspective view of the locking assembly of the present invention showing the cam track on the bottom thereof. 
     FIG. 6 is a fragmentary view showing the profile of the cam track on the bottom of the locking assembly. 
     FIG. 7 is a front view of the twin locking sockets of the present invention. 
     FIG. 8 is a cross sectional side view of the twin locking sockets of the present invention showing both locking assemblies and the key operated lock in the locked position. 
     FIG. 9 is a cross sectional side view of the twin locking sockets of the present invention showing both locking assemblies and the key operated lock in the unlocked position. 
     FIG. 10 is top cross sectional view of the twin locking sockets of the present invention showing the key operated lock. 
     FIG. 11 is perspective view of the safety or dummy plug used with the locking socket of the present invention. 
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-6, the present invention is directed to an electrical outlet or socket 10 which releasably locks a plug 11 in place. The socket 10 includes a decorative face plate 12, a sliding cap 14, a housing assembly, and a locking assembly. 
     The socket 10 is generally secured within an opening in the wall 16 using the flange 18 and the screw 20. The face plate 12 fits around the sliding cap 14 and serves to conceal the opening in the wall 16. The housing assembly includes a housing 22, an overhang 24, and a spring guide 26. The locking assembly includes a carrier 28 and arms 30. At the end of each arm 30 is a pair of locking jaws 32 and 34. 
     The housing 22 has a pair of passages 36 for allowing the arms 30 to pass therethrough. Each passage 36 extends from the face of the housing 22 adjacent the spring guide 26, to the face of the housing distal to the spring guide 26. The ends of the passages 36, distal from the spring guide 26, have cavities 38 extending therefrom to accommodate guide extensions 40. The guide extensions 40 ride in respective guide grooves 42, which are provided on the underside of the overhang 24 and extend from the cavities 38. The guide grooves 42 act to keep the jaws 32 and 34 apart when the locking assembly is in the unlocked position, thus keeping the jaws 32 and 34 ready for receiving the plug 11. 
     Each of the passages 36 has a lateral cavity 44 adjacent thereto. The cavities 44 are in open communication with passages 36 and house spring steel contacts 46. The spring steel contacts 46 contact the jaws 32 and 34 when the locking assembly is in the locked position. The spring steel contacts are resiliently biased to press against the arms 30 and the jaws 32 and 34 at all times. Each of the spring steel contacts 46 is connected to the household current supply via respective lead wires 48 and 50. Lead wires 48 and 50 are maintained in contact with contacts 46 by screws 52. 
     The jaws 32 and 34 are made of a conductive material so that the plug 11 will be conductively connected to lead wires 48 and 50 when the plug 11 is inserted in the socket and the locking assembly is in the locked position. The arms 30 may or may not be made of conductive materials. The carrier 28 must be made of none conductive materials such as plastic if the arms 30 are conductive. However, the only constraint on the choice of materials for the various components of the socket 10, is that the materials should be chosen such that short circuits between the pairs of locking jaws 32 and 34 are prevented. Each of the jaws 32 has a bulge 54 which matingly engages the holes 56 in the prongs 58 of the plug 11. 
     The cap 14 is spring biased to project outward from the face plate 12, so as to remain in contact with the plug 11 at all times. This feature prevents the prongs 58 from being exposed to the touch. In the example shown in the illustrations, a guide rod 60 telescopes within a guide cavity 62. A spring 64 surrounds the guide rod 60, and extends between a shoulder within guide cavity 62 and the cap 14. The spring 64 biases the cap 14 toward constant contact with plug 11. Alternatively, the jaws 32 and 34 can be dimensioned to abut against cap 14 at all times. Under these circumstances, the locking assembly acts to bias the cap 14 toward constant contact with plug 11 thereby obviating the need for spring 64. 
     The spring guide 26 is generally a hollow cylindrical tube attached to the rear face of the housing 22 at a first end, the rear face being the face distal from the guide cavity 62. The second end of the spring guide 26 is closed and acts to retain the main spring 66 within the spring guide 26. A boss 68 is provided at the second end of the spring guide 26. The guide pin 70 has one end fixedly embedded in the boss 68. Alternatively, the guide pin 70 may be free to rotate within the boss 68. The other end of the guide pin 70 passes through the curved slot 72 in the underside of spring guide 26, and rides in the cam track 74 in the underside of the carrier 28. 
     The medial portion 76 of the carrier 28 rides in the spring guide 26. Lateral portions 78 of the carrier 28 protrude from lateral slots on either side of the spring guide 26, and have the arms 30 rigidly fixed thereto. Therefore, the carrier 28, the arms 30, and the jaws 32 and 34, move as a unit. The lateral slots on either side of the spring guide 26 extend along the length of the spring guide 26 for substantially the entire length of the spring guide 26, in order to allow the carrier 28 to reciprocate within the spring guide 26. 
     To illustrate the operation of the socket 10, the socket 10 is initially considered in the unlocked state as shown in FIGS. 1 and 3. In the unlocked state the carrier 28 is fully forward along the spring guide 26, the cap 14 extends fully outward from face plate 12, and jaws 32 and 34 extend fully outward from the housing 22. The guide extensions 40 keep the jaws 32 and 34 apart by virtue of their position along guide grooves 42. Main spring 66 urges the carrier 28 forward, and the guide pin 70 engages the cam track 74 at its rear most point. 
     When a plug 11 is being inserted in the socket 10, the prongs 58 pass through the corresponding openings in the cap 14 until the face of plug 11 abuts against cap 14. As the plug is pushed in further, the prongs 58 engage respective arms 30 between the hinges which hold jaws 32 and 34 to the arms 30. As the plug is pushed in still further, the entire locking assembly, which includes jaws 32 and 34, arms 30, and carrier 28, begins to move toward the rear of the spring guide 26. At this time, the rearward movement of the carrier 28 within the spring guide 26 begins to compress main spring 66. 
     Also, as the carrier 28 moves to the rear, the end of the guide pin 70 engaging the cam track 74 is forced to the side and outward within cam track 74 by the ramp 80 (see FIG. 6) and the camming surface 82. The guide pin 70 is sufficiently resilient to allow its end, engaging cam track 74, to follow the camming profile of the cam track 74. In addition, rearward movement of the locking assembly causes the jaws 32 and 34 to come together under the influence of guide extensions 40 riding in guide grooves 42. As the locking assembly nears the limit of its rearward travel, the guide grooves 42 cause the jaws 32 and 34 to tightly grasp the prongs 58 with the bulges 54 engaging holes 56. 
     When the locking assembly reaches the limit of its rearward travel, the end of the pin 70 engaging cam track 74 snaps over the end of ramp 80 and engages the deepest point of ramp 84. When pressure on plug 11 is released, the carrier 28 moves forward under the thrust provided by main spring 66. This forward movement is limited and is not sufficient to disengage jaws 32 and 34 from the prongs 58. During this limited forward motion, the guide pin 70 is urged upward within cam track 74 by ramp 84. At the end of this limited forward motion, the guide pin 70 snaps over the shallow end of the ramp 84 onto the deepest part of the ramp 86. Because the main spring 66 constantly urges the carrier 28 forward, the end of the guide pin 70 engaging cam track 74 becomes trapped in the point of the forward V-shaped portion 88 of the cam track 74. In this position the guide pin 70 acts as a stop preventing further forward movement of the carrier 28 and maintaining the socket 10 in the locked state. 
     To unlock the socket 10 and remove the plug 11, the plug is first pushed in to move the guide pin 70 out of the point of the forward V-shaped portion 88 of the cam track 74, under the influence of the ramp 86. When the carrier 28 reaches the limit of its rearward motion, the guide pin 70 snaps over the shallow end of the ramp 86 and onto the deep end of the ramp 90. When pressure on the plug 11 is released, the carrier 28 moves forward under the influence of main spring 66. During this forward motion, the guide pin 70 is in continuous contact with ramp 90 and allows the carrier 28 to move to its fully forward position. Also during this forward motion, the guide grooves 42 acting on guide extensions 40, urge the jaws 32 and 34 apart thus releasing plug 11. At the end of this forward motion the guide pin 70 snaps over the shallow end of the ramp 90 and comes to rest at the point of the rearmost V-shaped portion 92 of the cam track 74. With guide pin 70 in this position the socket 10 is in the unlocked state and the plug 11 can be removed. 
     FIGS. 7 to 10 show the second embodiment of the present invention. The second embodiment of the present invention includes two vertically spaced locking sockets 10a and 10b, which are substantially identical in structure and function to the locking socket 10 described previously. The locking sockets 10a and 10b differ from the locking socket 10 in that openings 94 and 96 are provided in spring guides 26a and 26b respectively. The holes 94 and 96 are positioned slightly forward of the frontmost face of respective carriers 28a and 28b, when the carriers are in the rearmost position. 
     A key lock 102 is provided between the locking sockets 10a and 10b. The key lock 102 includes a C-shaped key hole 103 which allows only the key 104, which has a matchingly shaped cross section, to be inserted into the key way 106. The key way 106 extends from immediately behind the key hole 103 to the rear of the housing 108. 
     A spring guide 110, similar in structure to spring guide 26, is provided at the rear of the housing 108. The spring guide 110 houses a wedge carrier 112 and main spring 114. The wedge carrier 112 carries a wedge 116 and has a cam track 118 which functions in the same manner as cam track 74 discussed previously. Cam track 118 is engaged by a guide pin 120 which functions in exactly the same manner as described previously in reference to guide pin 70. 
     The arm 122 is fixed to the wedge carrier 112 and extends into the key way 106 for the entire range of movement of the wedge carrier 112. The arm 122 extends sufficiently into the key way 106 at all times to allow the key 104 to impart movement to the wedge carrier 112. 
     The spring guide 110 further includes pin housings 124 and 126 provided on the top and bottom of the spring guide 110. each of the pin housings 124 and 126 are open to the interior of the spring guide 110 at one end. The pin housings 124 and 126 house respective jamming pins 98 and 100. The jamming pins 98 and 100 protrude from pin housings 124 and 126 and register with holes 94 and 96 respectively. The jamming pins 98 and 100 are spring biased to move toward the wedge carrier 112. 
     In the same manner as described with regard to carrier 28, the wedge carrier 112 can be moved into the locking position by pushing the wedge carrier 112 in with the key 104. Once the wedge carrier 112 reaches its rearmost position, releasing the key 104 allows the wedge carrier 112 to move slightly forward under the influence of main spring 114, to trap the pin 120 in the forward V-shaped portion of the cam track 118. To release the key lock 102, the wedge carrier 112 is first pushed in with key 104 and then allowed to move forward to its forwardmost position under the force of main spring 114. The release of wedge carrier 112 is effected through the interaction of the guide pin 120 and the cam track 118 in the same manner as described in reference to carrier 28 and guide pin 70. 
     As the wedge carrier 112 moves into the locked position, the wedge 116 forces jamming pins 98 and 100 into the interior of respective spring guides 26a and 26b. With the wedge carrier 112 in the locked position, jamming pins 98 and 100 protrude into respective spring guides 26a and 26b and act to retain the carriers 28a and 28b in the locked position. When the wedge carrier 112 is released, the jamming pins 98 and 100 move out of the path of carriers 28a and 28b under the influence of the respective biasing springs. Sockets 10a and 10b can then be unlocked in the normal manner described with respect to socket 10. 
     It should be noted that socket 10a and 10b are suited for plugs of the three prong type to illustrate the applicability of the locking socket of the present invention to three prong plugs. Hence, the need for the additional ground contacts 128 and 130, which are shown in sockets 10a and 10b. 
     Also, the illustrated embodiments are provided as examples only. The guide grooves 42 can be replaced by spring which bias jaws 32 and 34 in the open position. Then as the jaws are pushed into passages 36, they are clamp about the prongs 58. In addition, the jaws need not be as long as they are shown in the examples. They need only be long enough to extend from the tips of prongs 58 to the holes 56. Both these modifications allow a design having sliding socket caps and a key lock which are substantially flush with the face plate 12, when in the locked state. 
     FIG. 11 shows a non-conductive safety or dummy plug 132, which can replace the standard plugs. With the dummy plug in place in a locked socket, children are prevented from inserting objects into the sockets. Thus rendering the locking sockets of the present invention far safer than ordinary sockets. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.