Electroacoustic transducer

Details Electroacoustic transducer Electroacoustic transducer

2002-12-10

2004-03-09

Le, Huyen (Department: 2643)

Electrical audio signal processing systems and devices

Electro-acoustic audio transducer

Electromagnetic

C381S409000, C381S410000, C340S391100

Reexamination Certificate

active

06704430

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electroacoustic transducer which is adapted to be mounted on a printed circuit board.
2. Description of the Related Art
Many of electroacoustic transducers such as speakers and microphones are adapted to be mounted on a printed circuit board of electronic equipment such as a mobile phone. In such an electroacoustic transducer, a terminal plate is fixed on a casing at a position away from a casing surface opposite the printed circuit board (opposite surface). Then a conductive member is required to allow the terminal plate to be electrically connected to a conductive portion of the printed circuit board.
A coil spring is conventionally known as one of such conductive members. The coil spring is placed between the terminal plate and the conductive portion of the printed circuit board in a resiliently compressed state. See Japanese publication A-2001-242871.
FIG.
8
(
a
) shows part of the conventional electroacoustic transducer having such coil spring. A cylindrical recess
102
b
is formed on a casing
102
, extending from an opposite surface
102
b
to a terminal plate
104
. A through hole
104
a
is formed on the terminal plate
104
at a position corresponding to the cylindrical recess
102
b
. A coil spring
106
has a protruding pin
106
a
extending in the axial direction from an end of the coil spring
106
. The protruding pin
106
a
is passed through the through hole
104
a
to be fixed to the terminal plate
104
by solder
108
.
Such conventional electroacoustic transducer, however, possibly causes a problem as described below depending on how it is mounted on the printed circuit board.
In an assembly of a mobile phone, the top surface of the casing
102
(the counter surface of the opposite surface
102
a
) of the electroacoustic transducer is adhered to the inner surface of the upper case of the mobile phone by a double-stick tape, and then the electroacoustic transducer and the upper case of the mobile phone are pressed against the printed circuit board to be mounted thereto. It is very likely that the coil spring
106
is horizontally displaced with respect to the printed circuit board, generating stress concentration at the base part of the protruding pin
106
a
of the coil spring
106
.
FIG.
8
(
b
) shows a state where the casing
102
is displaced leftward with respect to the printed circuit board
2
with the coil spring
106
resiliently compressed against the printed circuit board
2
. The protruding pin
106
a
soldered to the terminal plate
104
is also displaced leftward as the casing
102
is displaced so. The other end of the coil spring
106
, however, remains in the place since it is compressed against the printed circuit board
2
. Then the coil spring
106
is suffered from horizontal distortion as shown in the figure, exerting a larger bending moment to the base part of the protruding pin
106
a
(a surrounded area by dotted line) and generating stress concentration thereon.
The coil spring is likely to be broken during the assembling process, or durability of the coil spring is deteriorated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved structure for accommodating and supporting a coil spring inside the cylindrical recess while fixing it to neither the terminal plate nor the casing.
The present invention relates to an electroacoustic transducer adapted to be mounted on a printed circuit board comprising:
a casing;
a terminal plate fixed on the casing at a position away from a casing surface opposite the printed circuit board; and
a coil spring for making electrical connections between the terminal plate and a conductive portion of the printed circuit board when the electroacoustic transducer is mounted on the printed circuit board;
wherein, a cylindrical recess is formed on the casing so as to extend from the casing surface to the terminal plate;
the coil spring has a coil length longer than that of the cylindrical recess by a predetermined dimension, and a coil diameter smaller than the inner diameter of the cylindrical recess by a predetermined dimension; and
the coil spring is accommodated and supported in the cylindrical recess while it is fixed to neither the terminal plate nor the casing.
Any type of the “electroacoustic transducer” is applicable such as speaker, buzzer, microphone, and receiver as far as it is adapted to be mounted on the printed circuit board.
Any type of the “printed circuit board” is applicable as far as a conductive portion is formed thereon to make electrical connections with the terminal plate via the coil spring.
Any type of the “casing” is applicable as far as the terminal plate is fixed thereon at a position away from the casing surface opposite the printed circuit board. The “casing surface opposite the printed circuit board” is a surface facing the printed circuit board when the electroacoustic transducer is mounted on the printed circuit board. After the electroacoustic transducer is mounted on the printed board, the surface may be contact with the printed circuit board or may be away from it by certain distance.
Any type of the “cylindrical recess” is applicable as far as it extends from the casing surface opposite the printed circuit board to the terminal plate. It does not always require a circumferential wall formed entirely.
Any type of the “coil spring” is applicable as far as it is made of conductive material and it is accommodated and supported in the cylindrical recess while it is fixed to neither the terminal plate nor the casing. The phrase “accommodated and supported in the cylindrical recess” means that the coil spring does not come off the cylindrical recess in a no-load state and part of the coil spring is accommodated in the cylindrical recess. The coil spring is supported but fixed to neither the terminal plate nor the casing.
The “coil length” is not limited to a specific value. It may be any value as far as it is longer than the length of the cylindrical recess and long enough for surely making electrical connections between the terminal plate and the conductive portion of the printed circuit board when resiliently compressed. The “coil diameter” is not limited to a specific value. It may be any value as far as it is smaller than the inner diameter of the cylindrical recess and it allows the coil spring to be compressed and shifted in the cylindrical recess.
According to the present invention, since the coil spring is accommodated and supported in the cylindrical recess while it is fixed to neither the terminal plate nor the casing, the coil spring is free from any stress concentration even if external force is exerted.
In state that the coil spring is pressed against the printed circuit board, any horizontal displacement between them would not cause stress concentration on the coil spring since the coil spring is only horizontally shifted in the cylindrical recess until the coil portion hits against the wall of the cylindrical recess. This prevents a breakage of the coil spring during the assembling process and also a possible deterioration thereof after the assembling process.
As described above, breakage or damage of the coil spring is prevented even when it is used as a conductive member for making electrical connections between the terminal plate and the conductive portion of the printed circuit board,
The present invention eliminates the need for soldering of the coil spring to the terminal plate, simplifying the manufacturing process of the electroacoustic transducer.
The present invention eliminates the need for positioning of the coil spring with respect to the cylindrical recess to insert the protruding pin into the through hole for soldering, simplifying the manufacturing process of the electroacoustic transducer.
The present invention eliminates the risk of soldering heat which is likely to deform the resin members or portions near the terminal plate.
Eliminating the need for soldering provides an environmental PB-free product.
According to the pre

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