Electricity supply structure for a piezoelectric vibrator

An electricity supply structure for a piezoelectric vibrator includes a circuit board and a coil spring having one end positioned in contact with the circuit board and the other end with a portion extending toward the center of the spring and a rising contact portion which stands on the extending portion at a central portion of the coil spring. A piezoelectric vibrator is in contact with the free end of the rising contact portion of the coil spring and a positioning rod for positioning the coil spring is formed integrally with the base plate and is provided at the distal portion thereof with a groove in which the extending portion is insertable to prevent radial movement of the rising contact portion relative to the piezoelectric vibrator.

BACKGROUND OF THE INVENTION 
This utility model relates to an electricity supply structure for a 
piezoelectric vibrator for use in an alarm buzzer of a timepiece or the 
like. 
A conventional electricity supply structure for a piezoelectric vibrator 
for use in a timepiece buzzer is known in which one end of a coil spring 
is positioned in contact with a predetermined circuit pattern on a circuit 
board, while another end of the coil spring is positioned in contact with 
the outer periphery of the piezoelectric element of the piezoelectric 
vibrator. The coil spring has opposite annular end surfaces which are 
formed flat or coplanar. 
SUMMARY OF THE INVENTION 
As is well known, in order not to prevent the vibration of the vibrator in 
buzzer and a speaker which utilize a piezoelectric vibrator, a connecting 
coil spring is preferably positioned in contact with the outer periphery 
of the piezoelectric element of the vibrator. 
However, if it is intended that the coil spring with the structure 
described above is positioned in contact with the outer periphery of the 
piezoelectric element, a part of the annular coil spring whose two ends 
are formed flat or coplanar is inevitably disposed adjacent to a central 
portion of the vibrator. As a result of this, an adequate sound volume 
cannot be obtained. This phenomenon is especially remarkable in the case 
of a buzzer for a watch provided with an alarm mechanism having a 
small-diameter piezoelectric vibrator. 
An object of the present invention is therefore to provide an electricity 
supply structure for a piezoelectric vibrator in which one end of the 
electricity supply coil spring can be positioned in contact with a portion 
in the vicinity of the outer periphery of the piezoelectric vibrator in a 
point contact manner, and in which, furthermore, an adequate sound volume 
can be obtained. 
Another object of the present invention is to provide an electricity supply 
structure for a piezoelectric vibrator in which a coil spring can be 
easily and quickly installed. 
In order to achieve the abovementioned objects, this invention comprises: a 
circuit board; a coil spring having a base portion which is positioed in 
contact with the circuit board, and in which a portion extending toward 
its center is provided at the front end thereof, and in which a rising 
contact portion which stands at a central portion of the coil spring is 
provided in the extending portion; a piezoelectric element to which a 
front end of the rising contact and portion of the coil spring is 
positioned in contact; means for positioning the coil spring.

BRIEF DESCRIPTION OF THE INVENTION 
Referring to the accompanying drawings, an embodiment of the present 
utility model will now be described. 
As shown in FIG. 1, a back cover 2 is secured to the rearside of the body 1 
of a timepiece. A sound emitting hole 2a is bored in this back cover. In 
order to provide a good sound effect, it is preferable to arrange the 
sound emitting hole 2a at a position close to the band connecting portion 
1a of the body 1 and which the user's hand does not come into close 
contact. 
The inside of the sound emitting hole 2a is arranged to be a resonance 
chamber 3. In this resonance chamber, a piezoelectric vibrator 4 is held 
between the back 2 and a holder 5. The piezoelectric vibrator 4 is, as is 
well known, formed by way of putting a piezoelectric element 42 on a 
vibrating plate 41. 
In the rear portion of the holder 5 (right portion of FIG. 1) is disposed a 
circuit board 6. A positioning rod 71 which is integrally formed with a 
base plate 7 penetrates through a penetrating hole (not shown) bored in 
this circuit board. The front end of the positioning rod 71 is, as shown 
in FIG. 4, disposed in a penetrating hole 5a in the holder 5. 
A coil spring 8 which is wound to an outer periphery of the positining rod 
71 is, as shown in FIGS. 2 and 3, has a base portion 8a thereof which is 
positioned in contact with a circuit pattern 6a of the circuit board 6. 
The front end of the coil spring 8 comprises a extending portion 8b which 
extends toward a center portion and a rising contact portion 8c of the 
extending portion which stands in the center portion of the coil spring. 
The front surface of the rising contact portion 8c is, as shown in FIG. 4, 
positioned in contact with an outer periphery of the piezoelectric element 
42 in a point contact manner. 
The positioning rod 71 which serves as means for positioning the coil 
spring 8 is, as shown in FIGS. 4 and 5, provided with a groove 71a in 
which the extending portion 8b of the coil spring 8 is fitted at the front 
end thereof. The front surface of the positioning rod 71 is, as shown in 
FIGS. 5 and 6, formed by guide surfaces 71b and 71b which are slanted to 
each other with respect to the groove 71a. The groove 71a is, as shown in 
FIG. 5, arranged to be substantially disposed along an outer periphery of 
the piezoelectric element 42. Therefore, by way of keeping the clearance 
between the extending portion 8b and the inner surface of the groove 71a 
small, the radial movement of the coil spring 8 can be prevented, 
furthermore, the rising contact portion 8c formed in the coil spring 8 can 
be assuredly brought into contact with the outer periphery of the 
piezoelectric element 42 of the piezoelectric vibrator 4 in a point 
contact manner. As shown in FIG. 1, a dial 9 is secured to the base plate 
7, and a front cover 10 is provided in front of the dial 9. 
When the coil spring 8 is fitted from the front end of the positioning rod 
71, if the extending portion 8b of the coil spring 8 rides over the front 
surface of the positioning rod, it slides along the slanted guide surfaces 
71b and 71b, whereby the extending portion can be smoothly fitted in the 
positioning groove 71a. As a result, the coil spring 8 can be easily and 
quickly fitted. 
FIG. 7 illustrates another embodiment according to the present invention, 
wherein the positional relationship between a circuit board 6A and a base 
plate 7A is arranged inversely to that described in the aforementioned 
embodiment. Namely, a positioning hole 71A which serves as positioning 
means is provided on a base plate 7A. The coil spring 8 is disposed in the 
positioning hole 71A. Reference numeral 61A indicates a circuit pattern. 
[Effect of the Invention] 
According to the present invention whose structure has been described 
above, since the front end of the rising contact portion of the coil 
spring can be positioned in contact with the outer periphery of the 
piezoelectric element in a point contact manner, an adequate sound 
pressure can be obtained. As a result, it can exhibit a great sound 
volume. Furthermore, since a guide surface is provided at the front end of 
of the positioning rod, a coil spring can be easily and quickly mounted.