Backstop socket structure for lamp string

A backstop socket structure to prevent a lamp string from turning-off upon a bulb dropped unintentionally, which comprises a fuse-type bulb mounted in a socket of a lamp string and a plurality backstop sockets; each backstop socket is furnished with two contact copper plates, which are furnished with two spring reeds in close contact state normally; the bulb base has a rod stub under the center of the bulb base; after the bulb base is plugged in place, the rod stub would push the two spring reeds separated from each other; in case of a bulb base being dropped or missing, the two spring reeds will be in close contact state as a result of the resilient force thereof so as to keep the lamp string in lighting up state.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a lamp string for Christmas, and particularly to a backstop socket structure to prevent a lamp string from turning-off upon a bulb dropped unintentionally.

2. Description of the Prior Art

The conventional Christmas lamp string is usually made of an elongate lamp string, which includes a plurality of separate lamp strings connected together; each separate lamp string includes a plurality of short power-supply wires connected between two sockets. The first bulb of the lamp string is connected, by using a longer wire, with the plug; the longer wire is twisted with the lamp string to form into a separate lamp string.

Each of the sockets in the lamp string is to be plugged with a connector, which is mounted with a bulb so as to facilitate the bulb to be replaced in case of being burned out. The number of sockets and the coefficient of resistance of each bulb are all pre-designed in accordance with the voltage and current of a given area.

The plug of each lamp string is furnished with a fuse to prevent the power-supply wire of the lamp string from being over-loaded. In case of the power-supply wire having a short circuit or being over-loaded, the fuse in the plug will be burned out automatically so as to avoid a hazard; however, the fuse furnished in the plug is not designed to prevent the socket from being overloaded.

The bulb plugged in the socket of each lamp string has two copper wires to be fixed in place with a positioning bead; the tail ends of the copper wires are mounted with a tungsten filament; the aforesaid parts are then mounted in a glass tube, of which both ends are to be sealed by means of different welding methods respectively so as to form into a bulb; the bulb is to be plugged in the socket of the lamp string. Since the sockets of the lamp string are connected one another in series, the whole lamp string is subject to having an open circuit and outage in the event of a tungsten filament being burned out.

In order to avoid the lamp string to turn off upon the tungsten filament of a bulb being burned out, an aluminum fuse of 0.065 m/m is wound around the two copper wires near the positioning bead; the number of turns of the fuse is designed in accordance with technical requirement, but it has at least 2.5 turns to enable the fuse to mount in place. The object of furnishing such a fuse is to maintain the whole lamp string to be in lighting-up condition in case of the tungsten filament being burned out; in that case, the fuse having lower resistance can still have the two copper wires maintained in conduction condition. The requirement of at least 2.5 turns of the aluminum fuse is to prevent the fuse from being burned out upon the current being not over a given value.

The aluminum fuse mounted between the two copper wires and near the positioning bead must have a resistance less than that of the tungsten; in case of the tungsten filament being burned out, the aluminum fuse can still maintain a current to flow through the two copper wires so as to avoid the lamp string to have an outage for a short time; however, since every bulb in the lamp string will lose at least a portion of the tungsten filament to share the power dissipation, the tungsten filaments of the rest bulbs will have a higher power dissipation; in other words, the serviceable life of the tungsten filament in the bulb will be reduced proportionally. Whenever the number of bulbs in a lamp string is reduced gradually, the bulb number of bulbs, which are not lit up, will be increased. Since the power dissipation of every bulb is increased, the temperature thereof will also be increased; then, the temperature of the connector of each bulb will be increased to an over-loaded condition. Generally, the material used for making the connector and the socket will be improved to withstand a given high temperature; in that case, the cost for the material thereof will be increased without solving the problem of a single bulb in a lamp string to suffer from a high temperature.

In a conventional lamp string, if one bulb is dropped or missing, the whole lamp string will be turned off immediately.

SUMMARY OF THE INVENTION

The prime object of the present invention is to provide a backstop socket for a lamp string, in which the two contact copper plates are furnished with two spring reeds respectively, and the spring reeds are normally in close contact state; as soon as a bulb base is plugged into a backstop socket, the rod stud under the bulb base will push the two spring reeds separated from each other; in case of the bulb base being dropped or missing, the two spring reeds will restore in close contact state automatically to keep the lamp string in lighting up condition.

Another object of the prevent invention is to provide a backstop socket for a lamp string, in which the two contact copper plates are furnished with two spring reeds respectively, which are normally in close contact state; further, the lamp string is furnished with a fuse-type bulb which will be burned out in case of a given plurality of bulb bases being dropped or missing so as to prevent the lamp string from having further danger.

Still another object of the present invention is to provide a backstop socket for a lamp string, in which the two contact copper plates mounted in the backstop socket are furnished with two spring reeds (punched in shape) having different length; after the two contact copper plates are mounted into the copper-plate plug grooves of the backstop socket, the two spring reeds on the contact copper plates are in close contact state; as soon as the bulb base is plugged into the backstop socket, the rod stub under the bulb base will push one spring reed to separate from the other spring reed so as to having the power supply passed through the bulb to keep the lamp string in lighting up state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention relates to a backstop socket structure to prevent a lamp string from turning off upon a bulb dropped unintentionally; as shown inFIG. 1, the lamp string11comprises a long power-supply wire12, a shorter power-supply wire13, a plurality of short power-supply wires14, and a plurality of backstop sockets15; each backstop socket15includes a bulb base16mounted with a bulb17. In each lamp string11, the bulb17A in one backstop socket15is a fuse-type bulb. In case of a given number of bulb bases16in a lamp string11being dropped to ground or missing, the backstop socket15can automatically have the circuit connected so as to enable the lamp string to be lighted up continuously. If the number of the dropped bulb bases16is over the number as designed originally, the fuse-type bulb17A will be burned out automatically without causing the safety of the lamp string.

As shown inFIGS. 2 and 3, every backstop socket15in a lamp string11includes a plug cavity20, a rectangular plug space21and a power-supply wire groove24; the plug cavity20is designed to facilitate the cylinder member29of the bulb base16to plug in. Both sides of the rectangular plug space21are furnished with two copper-plate plug grooves22and23respectively to facilitate two contact copper plates25and26to plug in respectively. The power-supply wire groove24is under the rectangular plug space21, and it is used for facilitating the short power-supply wires24of the two contact copper plates25and26to pull outwards.

The bulb base16is furnished with a plug cavity for receiving the bulb17. The bottom of the plug cavity is furnished with two through holes32to facilitate the two copper wires18and19of the bulb17to pull out and to attach to two side surfaces33. The center of the rectangular block30is furnished with a rod stub31, which is to be plugged into the rectangular plug space21under the plug cavity20of the backstop socket15; after the rod stub31is plugged in place, the end surface34of the rod stub31will touch and push the spring reed28of the contact copper plate26downwards until the spring reed28being separated from the spring reed27.

As shown inFIGS. 3 to 5, the two contact copper plates25and26in the copper-plate plug grooves22and23are furnished with two spring reeds27and28projected vertically out of the two plates25and26respectively; the spring reed28is longer in length than the spring reed27. The spring reed28is mounted in the lower part of the rectangular plug space21, i.e., in the copper-plate plug groove23; the spring reed28has a given flexibility; when the spring reed28is pushed with the rod stub31of the bulb base16, it will move downwards; the other spring reed27on the contact copper plate25is a shorter one, and is mounted fixedly in the copper-plate plug groove22. After the bulb base16is plugged into the rectangular plug space21of the backstop socket15, the spring reed28will be pushed downwards by the rod stub31of the bulb base16to separate from the spring reed27; in that case, the power supply will be connected through the bulb17to have the lamp string lit up normally.

As shown inFIGS. 1 and 5, the lamp string11is made of a plurality of backstop socket15; each backstop socket15is furnished with two spring reeds27and28to prevent the lamp string from turning off in case of a bulb base16being dropped. In the lamp string11, there is a safety socket assembly15A without spring reeds27and28; in the safety socket assembly15A, there is a bulb base16A which is mounted with a fuse-type bulb17A. In real use, the spring reeds27and28in every backstop15of the lamp string11are pushed with the rod stub31in open-circuit state. The power supply will go through the power-supply wire13, the short power-supply wire14A, the contact copper plate25, the copper wire18and the tungsten filament of the bulb17, the contact copper plate26, and the short power-supply wire14B in series to light up the lamp string11for ornament purpose.

As shown inFIGS. 3 and 6, the lamp string11is made of a plurality of backstop sockets15; in case of one bulb base16in a backstop socket15being dropped or not mounted in place, the spring reed28will move upwards automatically as a result of its resilient force and the pushing force from the rod stub31being removed to become in close contact with the spring reed27of the contact copper plate25; in that case, the power supply will be turned on via the two spring reeds27and28so as to keep the lamp string11lit up as usual.

The current in each bulb in the lamp string11should not be too high; whenever a bulb base16in the lamp string11is dropped or missing, the current flows through the rest bulbs16will be increased, and an over heating to them will be resulted. In order to prevent overheating danger, the lamp string11is added with a safety socket; as soon as the socket lost a bulb base16is overheated, the fuse-type bulb17A will be burned out to cut off the power supply of the lamp string11so as to prevent the lamp string form having an overheating danger to burn out a backstop socket15.

While the invention has been described with reference to specific embodiments it must be understood that those embodiments are susceptible to many changes, substitutions, and modifications that will be readily apparent to those having ordinary skill in the art without departing from the scope and spirit of the invention.