Communications: electrical – Audible indication
Reexamination Certificate
2001-04-19
2002-11-05
Tweel, John (Department: 2632)
Communications: electrical
Audible indication
C340S388100, C340S391100, C381S396000
Reexamination Certificate
active
06476710
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic sound generator for generating sounds by vibrating a vibration plate by an electromagnet, and more particularly to an electromagnetic sound generator mounted on a printed circuit board by the surface mount technology.
In recent years, there is a tendency to mount small electric parts on a printed circuit board, the electromagnetic sound generator as a small buzzer is accordingly mounted on the printed circuit board. Such a printed circuit with the electromagnetic circuit board is used as a signaling device of the portable telephone and beeper.
Referring to
FIGS. 5 and 6
, which are a plan view of a conventional electromagnetic sound generator and a sectional view taken along a line A—A of
FIG. 5
respectively, a case
50
of the electromagnetic sound generator comprises a lower case
51
and an upper case
52
.
The lower case
51
has a circular bottom
51
d
and a cubic portion
51
e.
An annular projection
51
a
is formed on the lower case
51
and a pair of cylindrical projections
51
f,
each having a hole
51
b
are formed in the cubic portion
51
e.
A yoke
53
made of magnetic material is secured to the bottom
51
c.
A core
53
a
is formed at a central portion of the yoke
53
and a notch
53
b
is formed at a side of the yoke. An annular magnet
55
and a coil
54
are mounted on the yoke
53
. An annular vibrating plate
56
having an armature
57
is secured on the annular projection
51
a.
Thus, a magnetic circuit for a buzzer is formed by the yoke
53
, core
53
a,
magnet
55
, and vibrating plate
56
.
A pair of lead plates
58
, each of which is made of an elongated metal plate, are embedded in the lower case
51
. Each of the lead plates
58
is extended between a side wall of the lower case
51
adjacent the hole
51
b
and an end
58
a
exposed in the notch
53
b
of the yoke
53
. A coil spring
59
is inserted in each hole
51
b.
An upper end
59
a
(
FIG. 7
a
) of the coil spring
59
is inserted in a hole
58
c
formed in an end portion
58
b
of the lead plate
58
and electrically connected to the lead plate
58
by solder
65
(
FIG. 7
b
). The lower end of the spring
59
is projected from the underside of the lower case
51
.
Both ends of the coil
54
are soldered to ends
58
a
of lead plates
58
. Thus, the coil
54
is connected to the coil springs
59
.
The upper case
52
has a sound emanating hole
50
a.
The upper case
52
is adhered to the lower case
51
so that a resonance room
66
is formed in the case
50
.
Here, it is necessary to accurately assemble the coil spring
59
in the hole
51
b
so as not to contact with the inner wall of the hole
51
b.
FIGS. 7
a
and
7
b
are sectional views showing a method for assembling the coil spring. A positioning jig
70
is provided for positioning the lower case
51
. The positioning jig
70
has a pair of positioning holes, each comprising a spring positioning hole
70
a
and a projection positioning hole
70
b.
In the assembling of the coil spring
59
, the lower case
51
is mounted on the jig
70
, engaging the cylindrical projection
51
f
with the projection positioning hole
70
b
as shown in
FIG. 7
a.
The coil spring
59
is inserted in the spring positioning hole
70
a
of the jig
70
and the hole
51
b
of the lower case
51
. The upper end
59
a
of the coil spring
59
is inserted in the hole
58
c
of the end portion
58
b
of the lead plate
58
and the coil spring is compressed by a pressing jig
71
. The upper end
59
a
of the coil spring
59
is connected to the end portion
58
b
by the solder
65
as shown in
FIG. 7
b.
Referring to
FIG. 8
a,
the case
50
is mounted on a printed circuit board
81
. The end of the coil spring
59
is pressed against a terminal on the circuit board
81
so that the electric current is applied to the coil
54
to vibrate the vibrating plate
56
. The generated sound is emanated from the sound emanating hole
50
a.
If the case
50
is inadvertently lifted and there is formed a gap G between the lower end of the cylindrical projection
51
f
and the printed circuit board
81
as shown in
FIG. 8
b,
the coil spring
59
expands accordingly. Consequently, the connection between the coil spring and the circuit of the circuit board
81
is kept.
FIG. 9
is a sectional view showing a connecting portion of another conventional buzzer. A U-shaped connecting spring pate
62
is connected to a lead frame
61
secured to a case
60
of the buzzer by solder
63
at an end thereof. Another end of the spring plate
62
is pressed against a terminal of a printed circuit board
82
.
When the case
60
is mounted on a circuit board
82
, the connecting spring plate
62
is bent and the end of the plate is contacted with a terminal of the circuit board
82
.
Therefore, if there is formed a gap between the case
60
and the circuit board
82
, the contact of the spring plate
62
with the terminal is kept.
However, when each of the above described conventional sound generators falls and collides with a hard ground, the coil spring
59
or spring plate
62
disengages from the terminal. Furthermore, there must be provided a plurality of jigs for accurately soldering the coil spring or spring plate, which requires multiple manufacturing steps.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electromagnetic sound generator having an external connecting terminal structure which has a high reliability and may be simply manufactured without accuracy jigs.
According to the present invention, there is provided an electromagnetic sound generator having a case provided with a yoke, a magnet, a vibrating plate and a coil, and a pair of leads, wherein an end of each of the leads is connected to an end of the coil and the other end of the leads is secured to the case so as to be connected to an outside terminal, a terminal connecting device is provided for connecting the end of the lead to the outside terminal, the terminal connecting device comprises a cylindrical case secured to the case, a connecting rod slidably mounted in the cylindrical case, and a coil spring provided in the cylindrical case to outwardly urge the connecting rod so as to be contacted with the outside terminal at an end of the rod, and means for contacting the cylindrical case with the end of the lead.
The means is engagement of the cylindrical case with a inside wall of a hole formed in the case so as to keep the contact of the cylindrical case with the end of the lead.
The means comprises a ball provided with the cylindrical case so as to be outwardly urged by the coil spring to be contacted with an inside wall of a hole formed inn the end of the lead.
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.
REFERENCES:
patent: 3774200 (1973-11-01), Heath
patent: 3869855 (1975-03-01), Sodler
patent: 5287084 (1994-02-01), Sone
patent: 5878149 (1999-03-01), Hamada et al.
patent: 5894263 (1999-04-01), Shimakawa et al.
patent: 6023518 (2000-02-01), Kuwabara et al.
patent: 6208238 (2001-03-01), Ohta
patent: 6265965 (2001-07-01), Lee
Asahina Masato
Ohta Yoshizumi
Togawa Shinichi
Citizen Electronics Co. Ltd.
Dennison, Schultz & Dougherty
Tweel John
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