Power cord with a leakage current detection conductor

[0001] This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) from China Patent Application No. 200620134167.8, filed Oct. 25, 2006, which is incorporated by reference in its entirety.

[0002] 1. Field of the Invention

[0003] This invention relates to a power cord. In particular, it relates to a power cord for an appliance that has a built-in leakage current detection conductor for detecting a leakage current in the power cord.

[0004] 2. Description of the Related Art

[0005] With the wide use of household electrical appliances, such as air conditioners, washing machines, refrigerators, etc., more attention is being paid to the safety of using such appliances. An appliance typically has a power cord of one meters or longer. As shown in FIG. 1, such a power cord is made of three copper wires 11, 6 and 8 for carrying power, three insulating layers (made of rubber or plastic) 10, 5, and 7 surrounding the respective copper wires, two metal sheaths 19 and 14 (made of thin copper wires woven together) surrounding two insulating layer, respectively, and an outer insulating layer 1 (made of rubber or plastic) enclosing the wires.

[0006] Such a power cord may age due to long-term use, or become damaged when the appliance is moved, which may cause a leakage between the phase line and the neutral or ground lines in the cord. Such leakage current may cause sparks, which may cause fire and property damages. To quickly and accurately detect leakage current in the power cord, an additional conductor is provided and electrically connected to the metal sheath 19, 14. Leakage current can be detected by detecting a voltage on the metal sheath.

[0007] The metal sheaths are conventionally made by weaving thin copper sires. The cost of the power cord has increased due to the increase cost of the copper material.

[0008] Accordingly, the present invention provides a power cord useful for appliances such as air conditioners, washing machines, refrigerators, etc. which has a built-in leakage current detection conductor for detecting a leakage current in the power cord.

[0009] An objective of the present invention is to provide a power cord with reduced manufacturing cost.

[0010] To achieve this and other objects and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention provides a power cord with leakage current detection function, which includes: three metal wires for carrying power; three insulating layers surrounding the three metal wires, respectively; at least two conductive layers surrounding two of the insulating layers, respectively; at least one leakage current detection conductor being in contact with the at least two conductive layers; and an outer insulating layer surrounding the metal wires, the insulating layers, the conductive layers and the leakage current detection conductor.

[0011] In one embodiment, one of the at least one leakage current detection conductor is located adjacent two of the at least two conductive layers and is in contact with both conductive layers. The power cord further includes a metal sheath surrounding the metal wires, the insulating layers, the conductive layers and the leakage current detection conductor, wherein the outer insulating layer surrounds the metal sheath. In another embodiment, the power cord includes two leakage current detection conductors, each leakage current detection conductor being located between one of the two conductive layers and the corresponding insulating layer.

[0012] In one embodiment, the metal wires are made of copper, the conductive layers are made of copper foil, tin foil, aluminum foil, or conductive rubber, and the leakage current detection conductor is made of copper or aluminum wires.

[0013] Advantages of power cords according to embodiments of the present invention include low cost, reliability, and the ability to quickly and accurately detect leakage current in the cord to protect safety of users and prevent damage to the appliance.

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

[0019] As shown in FIG. 2, a power cord according to an embodiment of the present invention includes three copper wires 11, 6 and 8 for carrying power and a leakage current detection conductor 3 for detecting a leakage current in the power cord. The three copper wires 11, 6 and 8 are surrounded by three insulating layers (made of rubber or plastic) 10, 5, and 7, respectively. Two insulating layers 10, 5 are surrounded by metal conductive layers 9, 4, respectively. The leakage current detection conductor 3 is provided adjacent the two metal conductive layers 9, 4 and is in contact with both of them. A metal sheath 2 encloses the three wires with their respective insulating layers and metal conductive layers as well as the leakage current detection conductor 3. An outer insulating layer 1 (made of rubber or plastic) is provided outside of the metal sheath 2.

[0020] To reduce manufacturing cost, the metal conductive layers 9, 4 may be made of a thin copper foil, tin foil, aluminum foil, or conductive rubber. The leakage current detection conductor 3 may be formed of one or more copper wires or aluminum wires.

[0021] When leakage current is present between copper wires 11 and 6, 11 and 8, or 6 and 8, the leakage current detection conductor 3 can quickly and accurately detect the leakage current via the metal conductive layers 9 or 4.

[0022] FIGS. 3 and 4 are cross-sectional views showing the structure of a power cord with leakage current detection conductors according to alternative embodiments of the present invention. As shown in the figures, the power cord includes three copper wires 11, 6 and 8 for carrying power and two leakage current detection conductors 3 for detecting a leakage current in the power cord. The three copper wires 11, 6 and 8 are surrounded by three insulating layers (made of rubber or plastic) 10, 5, and 7, respectively. Two insulating layers 10, 5 are surrounded by two metal conductive layers 9, 4, respectively. One leakage current detection conductor 3 is provided between the metal conductive layer 9 and the corresponding insulating layer 10; another leakage current detection conductor 3 is provided between the metal conductive layer 4 and the corresponding insulating layer 5. An outer insulating layer 1 (made of rubber or plastic) encloses the wires with their respective insulating layers and metal conductive layers as well as the leakage current detection conductors 3.

[0023] To reduce manufacturing cost, the metal conductive layers 9, 4 may be made of a thin copper foil, tin foil, aluminum foil, or conductive rubber. The leakage current detection conductors 3 may be formed of one or more copper wires or aluminum wires.

[0024] When leakage current is present between copper wires 11 and 6, 11 and 8, or 6 and 8, the leakage current detection conductors 3 can quickly and accurately detect the current leakage via the metal conductive layer 9 or 4.

[0025] By changing the metal sheath used in conventional power cords, which are made by weaving thin copper wires, into a thin metal foil of copper, tin or aluminum, manufacturing cost is significantly reduced. In addition, by using the leakage current detection conductor 3, which is in contact with the metal conductive layers 9, 4, leakage current can be quickly and accurately detected.

[0026] Advantages of the present invention include low cost, reliability, and the ability to quickly and accurately detect leakage current in power cord.

[0027] It will be apparent to those skilled in the art that various modification and variations can be made in the power plug embodiment of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations that come within the scope of the appended claims and their equivalents.