Abstract:
Electrical connectors use magnetic repulsion for orienting themselves in the right polarity and magnetic attraction for holding together. When inserted into the ends of a conduit, a pair of these electrical connectors can transfer electricity through the conduit. Each electrical connector includes a housing with top and bottom surfaces and a fixed and a movable terminal both of which are recessed below the top surface of their respective, parallel passages. A spring controls terminal movement. Each terminal carries an electrical contact. A torus-shaped magnet surrounds the contact of the contact in the movable terminal so that its magnetic field energizes that contact. The magnets in movable terminals of each electrical connector are oriented in the same way so movable terminals of electrical connectors repel each other but fixed terminals attract movable terminals from their passages and into the passages of the fixed terminals so that two electrical connectors lock together.

Description:
TECHNOLOGICAL FIELD 
     The disclosure relates to electrical connectors for passing electrical current. More particularly, the present disclosure relates to electrical connectors that connect magnetically. 
     BACKGROUND OF THE INVENTION 
     Most electrical connectors are joined by mechanical means, typically using a male/female, frictionally-fitting connection, so that they can pass an electrical current from one connector to the next. Mechanical connectors require manual effort to join. Connectors that use magnetism rather than a mechanical connection are known. The magnetic force may be used to join the two connectors rather than manual effort. U.S. Pat. No. 8,936,472, which is incorporated herein in its entirety by reference and which is owned by the present applicant, discloses such a connector. Magnetic connectors are useful in circumstances where the two connectors cannot be easily joined by manual effort. 
     One example of circumstances in which access to couple two connectors is limited is in artificial holiday trees. Electrical current is passed by conductors via tubes or poles that simulate the trunk of an evergreen tree. Existing pole construction for artificial holiday trees uses an indentation and protrusion interlock system to serve as a key and keyway arrangement for correctly orienting the connectors. This method is old and, because the connecting poles tend to come apart when the tree is lifted or get stuck together, results in tree assembly, disassembly, and safety issues. 
     A set of connectors that is reliable and that is readily connect in the proper polarity without having to be physically oriented and physically joined, yet is inexpensive to manufacture in quantity, durable, effective, and safer, would be advantageous. 
     SUMMARY 
     The present electrical connectors use magnetic repulsion for orienting one connector properly with respect to another, and use magnetic attraction for holding two connectors together in the right polarity. Each electrical connector is identical so there are fewer parts required for manufacturing and assembly of the electrical connectors is greatly simplified. The present electrical connectors may be used to improve electrical connection in applications where electrical connectors may be difficult to join because of limited physical access or because of low light conditions. 
     When inserted into the ends of a conduit, a pair of the electrical conduits can be used to add electricity transfer to the structural conduit, which may have numerous uses as temporary barriers that carry electricity for temporary lighting. 
     An aspect of the disclosure is an electrical connector having a housing with a top surface and a bottom surface, a first passage and a second passage, and a fixed and a movable terminal in the first and second passages respectively. The first and second passages are spaced apart, open to both the top and bottom surfaces of the housing and run in parallel. There is a first contact on the fixed terminal and a second contact on the movable terminal. There is a magnet in the second passage proximate to the second contact, and its magnetic field runs through the second contact. 
     Another aspect of the disclosure is that the movement of the movable terminal is limited so that the second contact rises above the top surface of the housing by a predetermined distance. 
     Another aspect of the disclosure is that the electrical connector has a ferromagnet in the first passage proximate to the first contact of the fixed terminal. A ferromagnet is a device made of ferromagnetic material, that is, material attracted to a magnet but which material is not magnetic. 
     Still another aspect of the disclosure is that the first and second contacts have complementary surfaces on their expanded portions that interleave when the complementary surfaces are brought together. 
     An aspect of the disclosure is that the ferromagnet and magnet are torus-shaped and surround but do not touch the first and second, respectively. 
     Another aspect of the disclosure is that the first and second contacts both comprise an expanded portion, an upper shaft connected to the expanded portion, and a lower shaft. The lower shafts each have hole that receives the upper shaft. 
     Still another aspect of the disclosure is that the electrical connector has a compression spring in the second passage, which spring is connected to the second contact. The compression spring resists movement of the magnet, which surrounds the contact, toward ferromagnetic material that might be brought near the top surface of the housing. 
     Yet another aspect of the disclosure is that the fixed terminal is held in place by a spring washer. The spring washer is attached to the lower shaft of the first terminal. 
     An aspect of the disclosure is that both the first passage and the second passage have a wall therein dividing these passages into upper chambers and lower chamber. Each of the walls has a hole formed therein dimensioned to receive the lower shafts of the first and second contacts, respectively, passing from the upper chambers into the lower chambers. A spring washer in the lower chamber of the first passage is attached to the lower shaft and engages the wall of the first passage to hold the fixed terminal against movement of the first contact with respect to said housing. In the second passage, the lower shaft extends through the wall of the second passage and through a compression spring and a spring washer. The compression spring and the spring washer cooperate with the wall to limit movement of the second contact of the movable terminal above the top surface when the magnet surrounding the second contact is attracted to a ferromagnetic material. 
     Another feature of the disclosure is that two electrical connectors, can be joined by a pair of wires, one wire running from the first contact of the first of two electrical connectors to the first contact of the second electrical connector and the other wire running from the second contact of the first of the two electrical connectors to the second contact of the second electrical connector. 
     Another aspect of the disclosure is that the two electrical connectors can be carried near the ends of a conduit with one electrical connector flush-mounted with the first end of the conduit and the other recessed in the second end of the conduit. 
     Other features and their advantages will be evident to those skilled in the art of electrical distribution from a careful reading of the following detailed description, accompanied by the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures, 
         FIG. 1  is a perspective, top view of a connector according to an aspect of the disclosure; 
         FIG. 2  is a top, side-by-side, perspective view of the two terminals in normal position in an electrical connector shown in phantom lines so details of the two terminals can be seen, according to an aspect of the disclosure; 
         FIGS. 3A and 3B  show side view of a terminal in an exterior view and a cross-sectional view, respectively, according to an aspect of the disclosure; 
         FIG. 4  is a top perspective view of two contacts showing their complementary top surfaces, according to an aspect of the disclosure; 
         FIGS. 5A and 5B  are top perspective and side cross-sectional views, respectively, of the spaced-apart contacts of  FIG. 4 , according to an aspect of the present disclosure; 
         FIGS. 6A-6F  show in cross section the movements of the terminals of two electrical connectors and one of the connectors itself in response to an attempt to connect them improperly, according to an aspect of the disclosure, with  FIG. 4A  showing poles facing each other but with the wrong polarity,  FIG. 4B , showing connectors brought together with the wrong polarity,  FIGS. 4C, 4D, and 4E  showing connectors rotating in response to the magnetic field to self-organize the polarity, and finally with  FIG. 4F  showing connectors in the right polarity and aligned; and 
         FIG. 7  illustrates electrical connectors in a conduit, according to an aspect of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes a universal electrical connector. It also describes a pair of such connectors in electrical connection with each other to serve as an extension cord. That extension cord can be carried in a conduit to enable electrical power to be delivered in a structural member for use in temporary barriers with lighting, for example. 
     The term universal connector means that the connector is neither a “male” connector nor a “female” connector; the same configuration for the present electrical connector is used for both “plug” and “socket,” although the housing shapes may be varied depending on the context of use. Two such connectors can be joined together to pass electricity from one connector to another or the present connector can be used on both ends of an extension cord. Therefore, for example, in an extension cord with an electrical connector according to the present disclosure on each end, either end of the extension cord can be connected to a wall outlet, provided that the wall outlet mates with the present connector. The remaining end of the extension cord can be connected to, for example, an appliance having the same type of electrical connector. 
     An extension cord as disclosed herein can be inside a conduit with one of the electrical connectors flush-mounted to one end of the conduit and the other electrical connector recessed in the opposing end of the conduit so that a portion of the conduit extends past the connector. That end of the conduit can receive the end of a second such conduit that has an electrical connector flush mounted so the two mating connectors are inside the conduit. Each such conduit added to the previous conduits not only increases the total length of conduit but connects extension cords using the present electrical connectors together in a continuously conductive chain so that not only is the conduit available for a structural purpose (a barrier, a railing or trim piece) but so, too, is the electricity carried by a series of extension cords inside. 
     The term conduit is used herein to refer to any structural member that has a passage formed in it that generally follows the major dimension of the conduit. 
     In the present disclosure, electrical connectors are said to connect when they are in a position relative to each other with their contacts touching so as to be able to transfer electricity from one contact of one electrical connector to the other. 
     Referring now to  FIG. 1 , there is illustrated in perspective an electrical connector  10 . Electrical connector  10  has a housing  14  which may be primarily cylindrical or have a different shape, and it may have an axial groove  18 , as shown in  FIG. 1 , for certain applications. For example, axial groove  18  in connector  10  may allow it to slide into a conduit (not shown in  FIG. 1 ) that has an internal axial ridge. Axial groove  18  corresponds to such an internal axial ridge, which may be used to align adjacent sections of conduit with each other. Electrical connector  10  would need to have a housing shape that conforms to the interior shape of the conduit in that example but does not otherwise require axial groove  18  for its primary purpose, which is to connect to a second electrical connector  10 . 
     Housing  14  may have other features that adapt it to its environment, such as a flange  22  on its top surface  26  and plural ribs  30  that allow it to be inserted flush with the end of a conduit (not shown) and fit there tightly. 
     Electrical connector  10  has two terminals, a fixed terminal  34  and a movable terminal  38 . Fixed terminal  34  includes a contact  42 ; movable terminal  38  has a contact  46 . 
       FIG. 2  shows connector  10  with housing  14  drawn in phantom lines so that fixed terminal  34  and movable terminal  38  can be viewed more easily.  FIGS. 3A and 3B  show contacts  42 ,  46  from the side and in cross section, respectively. Housing  14  has two passages formed therein, passage  50  and passage  54 . Passages  50  and  54  are spaced apart and may be parallel. Both passage  50  and  54  have an upper chamber  58 ,  62 , and a lower chamber  66 ,  70 , respectively that are defined by a wall  74 ,  78 , respectively, that separates them. There is a hole  82 ,  86 , formed in wall  74 ,  78 , to allow upper chambers  58 ,  62 , to communicate with lower chambers  66 ,  70  Fixed terminal  34  is in first passage  50 ; movable terminal  38  is in second passage  54 . Every terminal  34  is identical to every other terminal  34 , and every terminal  38  is identical to every other terminal  38 . Terminals  34  and  38  are very similar to each other except for a few differences, which will be described presently. Passage  50  and  54  may also be dimensionally the same. 
       FIGS. 3A and 3B  show exterior and cross-sectional view of a terminal  90  identical to terminals  34 ,  38 . Terminal  90  has a contact  94  with an expanded top  98  and an upper shaft  102 . Upper shaft  102  has external threads and, where it meets expanded top  98 , its outer diameter may flare slight. 
     Terminal  90  has a lower shaft  106  with a hole  110  formed therein that has interior threads and is dimensioned to receive upper shaft  102 . Lower shaft  106  has a cylindrical groove  114 , that is, a portion of its length that has a reduced diameter and beyond which on lower shaft in both directions away from groove  114 , the diameter of lower shaft  106  is larger. Terminal  90  also has a top flange  118  that, between expanded top  98  and top flange  118 , define an annular recess  122 . For convenience, reference numbers applied to terminal  90  will be used on the equivalent structures on terminal  34 ,  38 . 
     A first spring washer  126  is attached to lower shaft  106  or first terminal  34  just above groove  114  and against wall  74  so that expanded top  98  of fixed terminal  34  is held fixed below top surface  26  of housing  14 . First spring washer  126  is selected and dimensioned to hold tightly to lower shaft  106  where it is placed because at that location, diameter of lower shaft  106  is slightly larger than the diameter of groove  114 . Terminal  34  is restrained from upward movement with respect to passage  50  because of the position of first spring washer  126 , which is on one side of wall  74 , and top flange  118  is on the other side preventing downward movement of fixed terminal  34  with respect to first passage  50 . 
     In second passage  54 , downward movement of terminal  38  is restricted because of top flange  118  but upward movement is not restricted, although it is limited. A second spring washer  130  is mounted to lower shaft  106  at the lower end of groove  114  to prevent vertical movement of terminal  38  that would otherwise enable removal of movable terminal  38  from second passage  54 . A compression spring  134  encircles lower shaft  106  above second spring washer  130  and resists vertical movement of movable terminal  38 . As movable terminal  38  moves upward, compression spring  134  is loaded and urges movable terminal to recede into second passage  54 . When compression spring  134  is fully compressed, second spring washer  130  and compression spring  134  prevent further movement of movable terminal. At that point, expanded top  98  of movable terminal  38  extends above top surface  26  by the same distance that fixed terminal is recessed inside fixed terminal  34 . 
     In  FIG. 2 , both fixed terminal  34  and movable terminal  38  are shown in their “at rest” positions. 
       FIG. 4  shows first and second contacts  42  and  46  side by side. Each contact  42 ,  46 , has an expanded top  98  and an upper shaft  102 . Expanded tops  98  of first and second contacts  42  and  46  are configured with concentric rings  44  separated by concentric grooves  48 . See also  FIG. 1 .  FIGS. 5A and 5B  show first and second contacts  42 ,  46 , with expanded tops  98  facing each other in perspective and cross-sectional views, respectively. In  FIGS. 5A and 5B , concentric rings  138  and concentric grooves  142  of first and second contacts  42 ,  46 , are beveled so that they interleave more easily than concentric rings  44  and concentric grooves  48  of  FIGS. 1 and 4  when first and second contacts  42 ,  46  are brought together. Concentric rings  138  enter concentric grooves  142  of second contact  46 , and concentric grooves  142  of first contact  42  receive concentric rings  138  of second contact  46 . Although concentric rings  138  and concentric grooves  142  are shown, other examples of surface features that interleave are possible, such as spaced rows of parallel ridges or a saw-toothed pattern or cylindrical pins on first contact  42  and holes in second contact  46 . Expanded tops  98  of first and second contacts  42 ,  46 , may be different or may be identical, but they interleave. When expanded tops  98  of first and second contacts  42 ,  46  interleave, there is more surface area in contact for the electrical current to pass from one to the other. Moreover, expanded tops  98  are less subject to coming apart in the event they are subjected to horizontal forces. 
     The particular configuration chosen is complementary whether identical or not identical. In this context, complementary  FIG. 4  shows non-identical concentric rings  138  and concentric grooves  142 . Other shapes of first and second contacts  42 ,  46  may be identical, but nevertheless first and second contacts  42 ,  46  interleave. Complementary means that expanded top  98  of first contact  42  is the negative of expanded contact  98  of second contact  46 . Where expanded top  98  of first contact  42  has mass, expanded top  98  of second contact  46  has a recess shaped to accommodate that mass; and where expanded top  98  of first contact  42  has a recess, expanded top  98  of second contact  46  has mass shaped to fill that recess. 
     Fixed terminal  34  and movable terminal  38  differ in another respect that that one is fixed and the other is movable. Annular recess  122 , seen best in  FIG. 3B , of movable terminal contains a magnet  146 . Magnet  146  has a torus shape and surrounds upper shaft  102  between expanded top  98  and top flange  118 . Magnet  146  may be a rare earth magnet. A non-conductive spacer  150  may be placed between magnet  146  and upper shaft  102 . 
     In movable terminal  38 , in annular recess  122  is a ferromagnet  154 . Ferromagnet  154  is not a magnet but is a material that, while producing no magnetic field of its own, responds to the magnetic field of a magnet or electromagnet regardless of polarity. 
       FIGS. 6A-6F  show two opposing connectors  10 ,  10 ′, being brought together.  FIG. 6A  shows connector  10  fixed in place while connector  10 ′ is being lowered toward connector  10 . In this example both fixed terminals  34  and  34 ′ and movable terminals  38 ,  38 ′ of electrical connectors  10 ,  10 ′ are directly opposite each other. The magnets  146 ,  146 ′ in movable terminals  38 ,  38 ′ are all oriented the same way, so the poles of two electrical connectors  10 ,  10 ′, when brought together face-to-face, repel each other. The mutual repulsive forces of magnets  146 ,  146 ′ move terminals  38 ,  38 ′ apart and thereby prevent contact, as seen in  FIG. 6B . Ferromagnets  170 ,  170 ′, in electrical connectors  10 ,  10 ′, neither attract each other nor repel each other. Because they are not movable and they are recessed in upper chambers  58 ,  58 ′ of passages  50 ,  50 ′, they also are not in contact so no current passes through between contacts  42 ,  42 ′ or  46 ,  46 ′. 
     However, to the extent that the magnetic fields of the adjacent magnets  146 ,  146 ′ influence ferromagnets  170 ,  170 ′, and repel each other, connector  10 ′ starts to twist and reorient itself, as seen in  FIG. 6C . 
     As this process of reorientation continues, best seen by comparing  FIGS. 6D and 6E , connector  10 ′ rotates so that fixed terminal  34 ′ is moving to oppose movable terminal  38  and movable terminal  38 ′ is simultaneously aligning with fixed terminal  34 . Finally, in  FIG. 6F , realignment is complete, and the magnetic fields of magnets  146 ,  146 ′ of movable terminals  38 ,  38 ′ are drawn partially out of their second passages  54 ,  54 ′ and their respective contacts  46 ,  46 ′ interleave with the contacts  42 ,  42 ′ of opposing terminals  34 ,  34 ′. The combination of interleaving and the movement of movable terminals  38 ,  38 ′ out of their second passages  54 ,  54 ′ helps to maintain the connection despite lateral forces. 
     Referring now to  FIG. 7 , there is shown two conduits, a first conduit  158  and a second conduit  162 . First conduit  158  has a reduced diameter portion  166  and an expanded diameter portion  170 . Likewise, second conduit  162  has a reduced diameter portion  174  and an expanded diameter portion  178 . Inside first conduit  158  at its reduced diameter portion  166  is a first electrical connector  182  in electrical connection with a second electrical connector  186  that is flush mounted to the end of the reduced diameter portion of  174  of second conduit  162 . Placing first electrical conductor  182  at the end of reduced diameter portion  166  inside first conduit  158  and placing second electrical conductor  186  flush with the end of reduced diameter portion  174  of second conduit  162  allows first and second electrical connectors  182 - 186  to be joined electrically when conduits  158  and  162  are joined physically. 
     Second electrical connector  186  and a third electrical connector  190  are connected in the same manner in second conduit  162  as if they were an extension cord: second electrical connector  186  is at one end and third electrical connector  190  is at the other end of a pair of wires  194 ,  198 , which may be joined in parallel with insulation and connected to the ends of the terminals ( 34 ,  38 , in  FIG. 2 ) of second and third electrical connectors  186 ,  190 . To preserve polarity, fixed terminal  34  of second electrical connector  186  would be joined to fixed terminal  34  of third electrical connector  190  and movable terminal  38  of second electrical connector  186  would be joined to movable terminal  38  of third electrical connector  190 .