DECORATIVE BULB UNIT WITH FILAMENT SHUNT MOUNTED IN BULB SOCKET THEREOF

Abstract

A light string includes electrical wires to which a number of bulb sockets are connected in series. Each bulb socket defines a receptacle for receiving and retaining a bulb with the bulb in electrical connection with the electrical wires. A shunt member made of alumina is incorporated in the socket. The shunt member is removably disposed in the receptacle of the socket, independent of the bulb, for being electrically connected to the electrical wires in parallel with the bulb whereby when the bulb burns out, the shunt member maintains the current flowing through the wires. The shunt member further includes an insulation sheath surrounding the alumina section.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to a decorative bulb unit, and more particularly to a decorative bulb unit with a filament shunt member mounted in the bulb socket thereof.

[0003] 2. Description of the Prior Art

[0004] Decorative light strings are commonly used in celebrations and festivals. The light string usually comprises a number of bulb sockets connected in series to an electric wire. Bulbs, usually incandescent ones, are mounted to the bulb sockets for connection with the wires. When a single bulb fails to illuminate, the whole string fails to light. It is very time-consuming to locate and replace the defective bulb. Thus, light strings with shunt circuits for overcoming the problems are known, such as U.S. Pat. Nos. 6,084,357 and 6,323,597 B1. These conventional designs of shunt circuits, however, require a shunt member to be encased in the bulb itself or are made with expensive electrical elements. The manufacturing process is also complicated.

[0005] Thus, it is desired to have a shunt circuit for a light string to alleviate the problem

SUMMARY OF THE INVENTION

[0006] A primary object of the present invention is to provide a decorative bulb unit with a filament shunt member. The shunt member is mounted in the bulb socket of the decorative bulb unit and electrically connected with the filament of the bulb in parallel.

[0007] The other object of the present invention is to provide a light string having a shunt circuit for each bulb of the light string to avoid defective bulbs causing Malfunction of the whole light string. The shunt member having a simple structure and low costs of material and manufacturing.

[0008] Another object of the present invention is to provide a light string comprising a shunt circuit for each bulb, the shunt circuit being formed easily with a simplified manufacturing process.

[0009] A further object of the present invention is to provide a shunt circuit for a light string, the shunt circuit being operative with regular bulbs whereby costs are reduced.

[0010] To achieve the above objects, in accordance with the present invention, there is provided a light string comprising electrical wires to which a number of bulb sockets are connected in series. Each bulb socket defines a receptacle for receiving and retaining a bulb with the bulb in electrical connection with the electrical wires. A shunt circuit is incorporated in the socket, including a shunt member made of alumina. The shunt member is removably disposed in the receptacle of the socket, independent of the bulb, for being electrically connected to the electrical wires in parallel with the bulb whereby when the bulb burns out, the shunt member maintains the current flowing through the wires. The shunt member may further include an insulation sheath surrounding the alumina section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which:

[0012] FIG. 1 is a schematic view of a light string incorporating a shunt circuit in accordance with the present invention;

[0013] FIG. 2 is a cross-sectional view of a bulb socket of the light string with a bulb received therein;

[0014] FIG. 3 is a perspective view of a bulb socket with a shunt member in accordance with a first embodiment of the present invention detached therefrom;

[0015] FIG. 4 is a perspective view of a shunt member in accordance with a second embodiment of the present invention;

[0016] FIG. 5 is a perspective view of the shunt member of the second embodiment of the present invention, which further comprises slots;

[0017] FIG. 6 is a perspective view of a shunt member in accordance with a third embodiment of the present invention; and

[0018] FIG. 7 is a perspective view of a shunt member in accordance with a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] With reference to the drawings and in particular to FIG. 1, a light string, generally designated with reference numeral 100, comprises electrical wires 102 connected to a power source device 104. A number of bulb sockets 106 are mounted to and in electrical connection with the electrical wires 102 via a first connection wire 102a and a second connection wire 102b. Each bulb socket 106 receives and releasably retains a bulb 108 therein whereby the bulb 108 is electrically connected to the wires 102 and powered by the power source device 104 to illuminate.

[0020] Also referring to FIG. 2, each bulb socket 106 forms a receptacle 110 in which first and second contacts 112a, 112b that are electrically connected to the first connection wire 102a and the second connection wire 102b are fixed. The bulb 108 with a filament 109 is provided with a first terminal 108a and a second terminal 108b respectively engaging the first and second contacts 112a, 112b when the bulb 108 is mounted and received in the receptacle 110.

[0021] Also referring to FIG. 3, in accordance with a first embodiment of the present invention, a shunt circuit is incorporated in each bulb socket 106. The shunt circuit comprises a shunt member 116 received in the receptacle 110. The shunt member 116 comprises an alumina wire 118 surrounded by an outer insulation sheath 120 with two ends 122a and 122b. The shunt member 116 is sized to be retained inside the socket 106 with the exposed ends 122a and 122b of the alumina wire 118 physically engaging the first and second contacts 112a, 112b of the socket 106. Thus, the shunt member 116 and the bulb 108 are connected in parallel with each other whereby when the bulb 108 malfunctions, such as burning out, electrical current from the wires 102 can continuously flow through the shunt member 116.

[0022] The reason that alumina is taken as the material for the alumina wire 118 is simply because, by properly shaping and sizing the alumina wire 118, the alumina wire 118 can provide a proper resistance that allows proper voltage drop, usually around 0.7 volts. Furthermore, alumina is a cheap and easily obtained material. Thus, costs can be reduced. Preferably, the shunt member 116 is removably received in the socket 106 for replacement and maintenance.

[0023] FIGS. 4 and 5 show a shunt member constructed in accordance with a second embodiment of the present invention, generally designated with reference numeral 116a for distinction. The shunt member 116a comprises an insulation base 120 around which alumina wire 122 made of aluminum oxide or other suitable material that has electrical characteristics similar to that of aluminum oxide as discussed above are wound. To ensure secure retention of the alumina wire 122 on the base 120, slots 124 are defined in opposite ends of the insulation base 120 for partially receiving the alumina wire 122 therein. Similarly, the shunt member 116a is received in the socket 106 with opposite ends of the wound alumina wire 122 in physical engagement with the first and second contacts 112a, 112b of the socket 106 to form a shunt circuit for the bulb 108 received in the receptacle 110 of the socket 106.

[0024] FIG. 6 shows a shunt member constructed in accordance with a third embodiment of the present invention, generally designated with reference numeral 116b for distinction. The shunt member 116b comprises a central section 126 and two leg sections 128a and 128b extending from opposite ends of the central section 126, forming a U-shaped member. The shunt member 116b can be formed as a single unit with aluminum oxide or other suitable materials. Similarly, the shunt member 116b is received in the socket 106 with opposite leg sections 128a and 128b in physical engagement with the first and second contacts 112a, 112b of the socket 106 to form a shunt circuit for the bulb 108 received in the receptacle 110 of the socket 106.

[0025] FIG. 7 shows a shut member constructed in accordance with a fourth embodiment of the present invention, generally designated with reference numeral 116c.for distinction. The shunt member 116c is a modification of the shunt member 116b with reference to FIG. 6 and the shunt member 116c has a structure similar to that of the shunt member 116b. Thus, the shunt member 116c comprises a central section 130 and two leg sections 132a and 132b extending from opposite ends of the central section 130 to form a U-shaped. An insulation sheath 134 surrounds the central section 130. Similarly, the shunt member 116c is received in the socket 106 with opposite leg sections 132a and 1332b in physical engagement with the first and second contacts 112a, 112b of the socket 106 to form a shunt circuit for the bulb 108 received in the receptacle 110 of the socket 106.

[0026] Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.

Claims

1. A decorative bulb unit comprising: a socket defining a receptacle for receiving and retaining a bulb having a filament, a first terminal and a second terminal; a first contact mounted in the socket; a second contact mounted in the socket and opposite to the first contact; and a shunt member being removably mounted in the socket, the shunt member having opposite ends respectively engaging the first contact and the second contact and electrically connected with the filament of the bulb in parallel through the first terminal and the second terminal, the shunt member comprising a portion made of alumina.

2. The decorative bulb unit as claimed in claim 1, wherein the shunt member comprises a core made of alumina surrounded by an insulation sheath and having two ends electrically engaging the first contact and the second contact.

3. The decorative bulb unit as claimed in claim 1, wherein shunt member comprises an insulation block with elongated elements made of alumina wound around the insulation block, portions of the elongated elements on opposite ends of the block being in physical engagement with the first contact and the second contact.

4. The decorative bulb unit as claimed in claim 3, wherein slots are defined in ends of the block for partially receiving and retaining the elongated elements.

5. The decorative bulb unit as claimed in claim 1, wherein the shunt member comprises a central section and two legs extending from opposite ends of the central section for physically engaging the first contact and the second contact.

6. The decorative bulb unit as claimed in claim 5, wherein the shunt member comprises an insulation sheath surrounding the central section.