Spring connector

A spring connector comprises a supporting member, a cylindrical plunger, and a coil spring provided in the cylindrical plunger. The supporting member has a base, a pillar extended from the base, and a shoulder and a head having a diameter larger than that of the pillar. The upper end of the head has an inclined surface. The plunger has a closed upper end, an opening formed in an annular bent portion of a lower end thereof. An annular edge of the opening is slidably engaged with the supporting member at the shoulder thereof. The coil spring is provided between the closed upper end and the inclined surface of the head so that a shoulder formed on the head at a lower annular periphery is pressed against the annular bent portion of the opening.

BACKGROUND OF THE INVENTION

The present invention relates to a connector used for surface mounting on a circuit substrate in an electronic device, particularly relates to a connector having a plunger resiliently urged by a spring so that the upper end of the connector may press terminal electrodes of electric parts to be electrically connected to the circuit substrate in the electronic device.

In an electronic device such as a portable telephone, a portable computer, and a game console, there are provided spring connectors for connecting battery, acoustic parts, peripheral circuits and other electric parts to a circuit substrate of the electronic device. Japanese Patent Application Laid-Open 2002-25657 discloses on page 3 and inFIG. 2(D), one of these spring connectors. The spring connector has a plunger which is slidably mounted in a tube and outwardly urged by a spring. The spring connector is secured to a circuit substrate and the plunger is pressed against a terminal electrode of the electric part in assembling process of the part in the device, thereby electrically connecting the part to the circuit substrate.

Referring toFIG. 2, the spring connector comprises a cylindrical tube11made of metal, and a metal plunger13slidably inserted in the tube11and outwardly urged by a coil spring12. A shoulder13cof a flange13aof the plunger13is pressed against a bent edge11aof the tube11by the coil spring12so as not to slide out of the tube11. The outer surfaces of the tube11and the plunger13are covered by nickel and gold plating. Both the tube11and the plunger13are formed by cutting work.

FIG. 3shows another conventional spring connector provided with a plunger13A. The plunger13A has the flange13a, an underside13dof which is inclined so that the peripheral wall of the flange is pressed against the inner surface of the tube11in an inclined condition. Thus the flange is strongly pressed against the inner surface, thereby ensuring the electrical conductivity between the tube and the plunger. In the present spring connector, the plunger13A is formed using a header instead of by cutting so that the manufacturing cost is decreased. The header is a processing machine to press or squash a metal material to form into a predetermined shape.

In each of the above described spring connectors, there is a problem of dirt entering the tube. Accordingly, the contact resistance between the plunger and the spring is unstable. Particularly in the case of the spring connector ofFIG. 2, since the underside of the plunger is not inclined, the contact resistance is even more unstable. Moreover, although the plunger is formed with header in the spring connector ofFIG. 3, since the tube must be manufactured by cutting in both cases, the manufacturing cost cannot be sufficiently decreased.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a spring connector which is excellent in performance and may be manufactured at a low cost.

According to the present invention, there is provided a spring connector comprising a supporting member having a base, a pillar formed on the base, a head having a diameter larger than that of the pillar, an annular shoulder formed between the pillar and the head, and an upper end of the head having an inclined surface, a cylindrical plunger having a closed upper end, an inner space, an opening formed in an annular bent portion of a lower end thereof, an annular edge of the opening being slidably engaged with a peripheral wall of the pillar, a coil spring provided in the inner space of the cylindrical plunger between the closed upper end and the inclined surface of the head so that the shoulder of the head is pressed against the annular bent portion of the opening.

The supporting member is formed by using a header, that is a processing machine to press or squash a metal material to form into a predetermined shape, and the annular bent portion of the plunger is formed by squeezing. Namely, a squeeze machine, after the supporting member is inserted in the plunger, squeezes the end of the plunger. The squeezing is a processing method to press the annular opening end of the plunger to be bent inwardly.

The surfaces of the supporting member and plunger are coated with Au plating.

These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a sectional view of a spring connector according to the present invention.

Referring toFIG. 1, the spring connector comprises a cylindrical plunger2made of metal and a supporting member1made of metal and slidably inserted in the plunger2. The supporting member1comprises a base1aof a large diameter which is to be surface-mounted on a circuit substrate (not shown), a small diameter pillar1bformed on the base1a, and a head1dhaving a diameter larger than that of the pillar1b. The upper end of the head1dis inclined with respect to the axis of the supporting member1, thereby to form an inclined top surface1c.An annular shoulder1eis formed between the head1dand the pillar1b.Although the supporting member1may be machined, it is possible to manufacture the supporting member by press using a header comprising a die having a recess and a punch, in which case, the manufacturing cost can be reduced.

The cylindrical plunger2has a closed upper end2awhich is to be pressed against a terminal electrode of an electric part (not shown), and an annular bent portion2dformed at a lower end thereof by squeezing action of a squeeze machine. An opening2bis formed at a lower end of the cylindrical plunger2opposite the upper end2aso as to be downwardly opened. A coil spring3is inserted in an inner space2cinside the cylindrical plunger2. An inner surface of the cylindrical plunger around the opening thereof is slidably pressed against the annular shoulder of the supporting member. The entire outer surfaces of both the cylindrical plunger2and the supporting member1are plated with gold.

In order to assemble the spring connector, the coil spring3is inserted in the cylindrical plunger2through the opening2b. The head1dof the supporting member1is then inserted in the cylindrical plunger2through the opening2b. The periphery of the opening2bis bent inward to form the annular bent portion2dwhich covers the shoulder1eof the supporting member1. The bent portion2daccordingly holds the supporting member1at the shoulder1eso as to prevent the supporting member1from falling out of the plunger2. The inner diameter of the inner space2cof the cylindrical plunger2and the outer diameter of the head1dof the supporting member1are set so that the plunger2is contacted with the head at a proper pressure so as to be smoothly slidable inside the plunger2. The outer diameter of the pillar1band the inner diameter of the bent portion2dare set so that the pillar1bis smoothly slidable through the bent portion2d. The cylindrical plunger2is formed by cutting and squeezing.

In operation, the base1aof the supporting member1is mounted on a circuit substrate of an electronic device and the upper end2aof the cylindrical plunger2is in contact with a terminal electrode of an electric part provided in the electronic device. When the cylindrical plunger2is pressed against the terminal electrode, the supporting member1is inserted deeper into the plunger2against the urging of the coil spring3so that the electrical connection between the terminal electrode and the circuit substrate is ensured. Since the pillar1bof the supporting member1smoothly slides against the bent portion2dof the plunger2, and circumference surface of the head1dis contacted with the inner surface of the plunger2at a proper pressure by the operation of the inclination of the inclined surface1c, dirt is prevented from entering the cylindrical plunger through the opening2b. Due to the inclination of the inclined surface1c, the head1dis pressed against the inner surface of the plunger2. Thus the contact resistance is small and stable. Accordingly, the electrical conductivity between the cylindrical plunger2and the supporting member1, and hence between the terminal electrode of the electric part and the circuit substrate is ensured.

Thus in accordance with the spring connector of the present invention, the head of the supporting member1is wrapped by the plunger and the opening of the plunger is downwardly opened so that dirt is not liable to enter the plunger, thereby rendering the contact resistance stable. Since the supporting member is provided with the inclined portion, the contact resistance is further maintained small and constant. The supporting member can be pressed using a header or cut and the plunger is formed by bending or by cutting so that the manufacturing cost of the spring connector is decreased. Thus inexpensive and reliable spring connector is provided.

While the invention has been described in conjunction with preferred specific embodiment thereof, it will be understood that this description is intended to illustrate and not limit the scope of the invention, which is defined by the following claims.