Patent Publication Number: US-6984141-B1

Title: Power socket device with enabling switch

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a power socket with a switch for enabling power supply to the socket. More specifically, the present invention is related to a power socket that can be enabled using switches that are isolated from socket power, and actuated by some type of user intervention. 
     2. Description of the Related Prior Art 
     Power sockets that provide activation/de-activation switching of the power supplied to the socket are known in the art. For example, switched sockets are known that activate/de-activate a power socket based on safety criteria. U.S. Pat. No. 5,865,635 to Hsiang et al. is representative of this type of socket, in which power is supplied to the socket only upon insertion of a mating connector plug. The prongs of the mating connector plug activate contacts within the socket that provide power to the various legs of the plug prongs inserted into the power socket. Each prong of the inserted mating plug activates a contact which enables power to another prong of the mating connector socket. This arrangement provides a safety feature, whereby an object inserted into one of the socket receptacles will not cause that receptacle to be powered, thereby reducing the possibility of electric shock. 
     Other known socket configurations include that represented by U.S. Pat. No. 5,374,199 to Chung, in which a power socket is activated only upon activation of a plunger type mechanism, which closes contacts within a socket to provide power to the inserted prongs of the mating connector plug. This feature provides a safety and security feature, because the socket remains unpowered until an appropriately configured mating connector plug is inserted into the socket. 
     Similarly, U.S. Pat. No. 5,984,700 to Chang discloses a socket which remains unpowered until a mating connected plug is fully inserted and rotated 90 degrees. The mating connector plug only receives power once it has been inserted into the socket and rotated 90 degrees, upon which contacts within the socket are closed to provide power to the various socket terminals. In addition, once the mating connector plug is inserted and rotated 90 degrees in the socket, the mating connector plug is secured within the socket, thereby providing a feature which prevents the unintentional disconnection of the socket and plug once power is being supplied. 
     U.S. Pat. No. 3,781,495 to Splingaerd shows a socket provided with an access cover, which disconnects power to the socket once it is pivoted away from the socket receptacle. The pivoted socket cover interrupts power to at least one leg of the connector socket, which interrupts the power supply to the mating connector plug. In addition, since the socket cover prevents access to the socket unless it is pivoted open, the cover acts as a safety shut-off, useful for devices drawing power from the socket, in addition to preventing potential harm to an individual accessing the socket. 
     In all of the above disclosures, the actuating switches that provide power to the socket receptacles also carry socket power. That is, the switching elements are typically contacts which conduct power to a particular terminal of the socket once actuated. The devices of the prior art typically do not disable power to a socket completely, nor do they control switching of the power source that provides power to the socket. Moreover, the prior art does not show any way of determining whether the socket is powered based on simple visual observation. 
     The present invention overcomes the drawbacks of the prior art by providing a switched power socket in which the switching signal can be isolated from socket power. The present invention further provides an indication of whether the socket is powered. Furthermore, the present invention provides several safety features which help to ensure safe and proper operation of the socket. 
     An example of a power socket in which the enabling socket switch is electrically isolated from the output of the power source to the socket is shown in U.S. Pat. No. 6,495,775, assigned to the assignee of this application. The present invention is an improvement on the device of this latter patent. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the electrical socket according to the invention provides power to a mating connector plug when actuated by a switch contained in the socket. The switch is actuated by user action, i.e., inserting a connector plug. The switch is isolated from the power supplied to the socket and acts as a power supply signal to enable socket power. The socket is powered only when needed, i.e., when the connector plug is inserted. The switch actuation method provides safety by disabling power to the socket unless the socket is actually in use. The socket cover and slide cover also prevent access to the socket unless positioned to receive a connector. 
     According to an embodiment of the present invention, there is provided a socket for providing electrical power, comprising: a housing having an inner chamber, at least one electrically conductive terminal in the inner chamber, the at least one terminal being connectable to an electrical output of an electric power source, the at least one terminal being accessible through an opening in a wall of the housing to supply electrical power from the power source to an electrical connector insertable through the opening, a socket enable switch operable to permit application of the electrical power to the at least one terminal and the socket enable switch being electrically isolated from the electrical output of the electric power source, the socket enable switch comprising a plunger disposed to be moved by a portion of a connector inserted through the opening, the plunger actuating the socket enable switch, the plunger being biased to return to a position to disable power to the socket when the connector is removed from the socket. Preferably, the plunger is moved by a prong of the inserted electrical connector. Further, preferably there are two conductive terminals and a plunger and switch associated with each terminal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in greater detail in the following detailed description with reference to the drawings in which: 
         FIG. 1  shows a perspective view of the terminals and enabling switches of the power socket of the present invention with the casing removed; 
         FIG. 2  shows a bottom perspective view of the power socket of  FIG. 1 ; 
         FIG. 3  shows a top perspective view of the power socket with the casing in place; 
         FIG. 4  is a side perspective view of the power socket with the casing in place; 
         FIG. 5  is a top perspective view of the power socket showing the cover of the casing open 180°; 
         FIG. 6  shows one of the plungers which operate the enabling switches of the power socket; 
         FIG. 7  is a cutaway view of the plunger of  FIG. 6 ; 
         FIG. 8  shows one terminal of the power socket with the plunger in place; and 
         FIG. 9  is a cutaway view of the terminal and plunger. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to the drawings,  FIG. 1  shows the interior of the power socket according to the present invention. The external appearance, with the cover open, is shown in  FIG. 5 . The power socket  10  includes a base  8  on which is mounted a printed circuit board  14  which has mounted thereon two switches  16  and  18 . The two switches  16  and  18  are connected to terminals  20  mounted on the printed circuit board. These are visible in the bottom view of  FIG. 2 . These terminals are typically low voltage terminals which control a control circuit once the switches are actuated to provide the higher voltage/current electrical power to the terminals  22 , for example, to connect the AC hot and neutral power leads from, for example a DC-AC inverter, to the terminals  22 . Accordingly, only when switches  16  and  18  are actuated can the AC power be connected to the terminals  22  for energization of a device connected to the terminals  22 . In addition, an illumination source such as an LED  24  may be provided on the printed circuit board for illuminating a display portion of the socket when power is provided to terminal  22 . The other ends of terminals  22  are shown in  FIG. 2  in the bottom view and connect to a suitable AC connector. This connector would provide both the hot and neutral as well as the ground connection to the socket. 
     Although two enabling switches  16 ,  18  are shown, only one can be provided, mechanically actuated preferably by the hot connector of the device plugged into the socket. 
       FIG. 3  shows a top view of the power socket with the casing in place, but with the hinged top cover removed. 
     Preferably the casing  11  comprises a housing on which is provided a safety slider  27 . The casing  11  can be a snap-fit on base  8 . The safety slider has openings which align with the openings in the casing to expose the terminals  22  when the safety slider is slid to one side. Otherwise, the terminals  22  are not exposed when the slider is in the safety position. The slider may be spring loaded so that it slides back to the safety position although it need not be and instead can have a lock or detent to lock or hold it in the safety position. 
     As shown, a ground opening  25  is provided for the ground connector of an electrical plug. A light pipe  26  s provided which the LED  24  illuminates when power is on. A torsion spring  28  may also be provided to allow the cover  30 , as shown in  FIG. 5 , to spring back closed. 
       FIG. 4  shows a bottom perspective view of the power socket with the cover closed. The sockets  32  and  34  for terminals  20  and  22 , respectively, are also shown. Socket  32  is the low voltage connector coupled to the switches  16  and  18  and socket  34  is the AC connector. 
       FIGS. 6 and 7  show the plungers  35  which actuate the switches  16  and  18 . The plungers  35  are located in the center of the terminals  22  shown in  FIG. 1 . Each plunger comprises an actuating member  36  including a top holder  38  which holds a compression spring  40  in place. The compression spring is located in a bottom can  42  which has a shoulder  44  resting on a shoulder  46  of the actuating member  36 . Preferably plungers  35  are made of an insulating material such as plastic. Preferably plungers  35  are of integral construction, or made of a minimal number of pieces to allow insertion of spring  40 . Spring  40 , although shown as metal, may also be made of some other material providing a biasing force, and can be some other type spring, not necessarily a coil spring as shown. When the actuating member  36  is engaged by the spade prong of an electrical plug inserted into the openings in the socket, the actuating member  36  moves downwardly, applying pressure to compress the spring  40  which causes the bottom can  42  to move downwardly, thereby actuating respective switch  16  or  18 . As shown in the drawings, each terminal  22  includes two opposed surfaces for electrically and frictionally engaging the prong of the electrical connector and the plunger associated with the terminal is preferably disposed in a centered orientation with respect to the terminal opposed surfaces so as to be actuated by the connector prong when the prong is inerted. See also  FIGS. 8 and 9 . As shown in  FIG. 1 , two plungers are preferably provided, each actuating a respective switch  16  and  18 , although one could be used. 
     The power socket can be connected as shown in  FIGS. 10A and 10B  of U.S. Pat. No. 6,495,775, the entire disclosure of which is incorporated by reference herein. Preferably, to provide isolation, it is connected as shown in  FIG. 10A  of U.S. Pat. No. 6,495,775. Since two switches are provided in the embodiment described, the two switches can be connected in series so that power will be applied only if both switches are actuated. However, the switches can be connected in different ways. For example, only one of the switches need be used. As shown in  FIGS. 1 and 2 , three terminals  20  are provided connected to the switches so that one of the terminals may be common to both switches. Alternatively, four terminals can be provided, two for each switch. As shown in  FIG. 10A  of U.S. Pat. No. 6,495,775, when the switch(or switches) is closed, a relay coil is energized and the contacts of the relay complete a circuit to provide power to a DC to AC power inverter, which then provides AC power to the power socket  10 . A relay need not be used, of course. Some other suitable switching device could be used, e.g., a semiconductor switch, etc. If the current is low, the switches  16  and  18  could also switch the input power to the inverter directly, although a relay or other controlled switching device is preferable. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.