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The invention comprises an electro-acoustic transducer mounted in a housing, said housing
having a wall or a hole or group of holes through which sound waves pass from the housing and
covering this hole more or less The invention relates to an electroacoustic calling device having a
closure member which is movable across the wall of the housing, the contour of the surface of
the closure member and the outer surface of the wall in the region of the bore being
complementary. Such a device may be used in a telephone and may be of the form shown in
British Patent Application Nos. 208201A or 2115648A. Conventional devices are mounted for
pivotal movement with respect to one point on the housing in order to vary the closure of one or
more holes and to control the intensity of the sound waves escaping the holes. Having a closed
closure. However, this device has the disadvantage that if there is a misalignment between the
outer surface of the wall of the housing and the contact surface of the closure member sound will
leak out between these surfaces. This means that the lowest sound level will be different from
one appliance to another, as the contact between these surfaces will vary with normal materials
and tolerances. It is an object of the present invention to provide an electroacoustic calling device
of the type described in the opening which allows a more effective seal to be obtained between a
wall having a hole and a closing member. According to the invention, in the electroacoustic
calling device described at the outset, the surface of the closing member has minimal acoustic
wave leakage between the closing member and the outer surface of the wall when the closing
member is moved so as to completely cover the hole. It is characterized in that it is pressed
against the wall of the housing by a universal bearing, as it is limited. By pushing the closure
onto the housing using a universal bearing, the alignment of the surface of the closure with the
surface of the 71 housing is improved, thus reducing the sound leakage to a low level. This can
be advantageous even if the sound output does not have to be zeroable, i.e. before the additional
leaks, where the size of the controllable holes may vary from device to device This is because the
minimum necessary sound output that is not affected can be output. The closing member has a
plate located in the recess of the arm which is pivoted about a point on the housing, so that
pivoting of the arm about the pivot allows the plate to move across the hole be able to. In this
way a relatively simple and inexpensive device can be made, the arms and the plate being
suitable for being made as injection molded plastic parts.
The plate may be provided with a projection that makes a point contact with the bottom of the
recess. In this structure, the projections can be formed in the same molding operation, especially
if the plate is made by injection molding, so that a particularly simple and inexpensive universal
bearing can be obtained. Alternatively, protrusions may be formed within the recess to provide
equally effective structure and effects. In one embodiment of the invention, the surface of the
closure member is planar. By providing a flat mating surface on the housing and the closure
member, it is relatively easy to ensure a good seal between these surfaces. For example, it may be
more difficult to align the spheres to ensure small sound wave leakage. The electroacoustic
transducer can have a piezoelectric disc. A speaker cone may be attached to this piezoelectric
disc. In this way, the volume produced by the device can be increased and the position of the
piezoelectric disc can be fixed in a direction parallel to its plane. The present invention will be
briefly described in the following with reference to the drawings. FIG. 1 shows a cross-sectional
view of an electroacoustical calling device suitable for use as a tone sounder in a telephone. Such
tone sun gear is increasingly being used in place of the bell as it is better adapted to the
electronics currently installed on the telephone in recent times. The device of FIG. 1 comprises an
upper casing 1 and a lower casing 2, which casings are connected together to form a housing
with holes 3 in the plane of the flat wall 4. As can be seen from FIG. 2 which shows a plan view of
the calling device of FIG. 1, the housing is circular in plan view. A piezoelectric disc 5 is mounted
between two circular projections 6.7 extending from the upper casing 1 and the lower casing 2
respectively. The upper casing 1 has a cylindrical projection 8 which serves as a pivot for an arm
9 having a recess 10 facing the flat wall 4 of the upper casing 1. A plate 11 is located in the
recess and is pushed by the arm 9 against the flat wall. The plate 11 is provided with a projection
12 which forms a point contact with the recess 10. Thus, the projection 12 and the recess 10
form a universal bearing between the arm 9 and the plate 11, so that the lower surface of the
plate 11 is in the same plane as the flat wall 4 and this plate 11 is optional in the plane of the
recess. You can freely turn around the axis. Said projections 12 are a simple and inexpensive
embodiment of a universal bearing, since it is easy to make said projections when the plate 11
and / or the arms 9 are formed by injection molding.
However, other forms of coupling between the arm 9 and the plate 11, for example ball and
socket joints, which allow universal movement of the plate relative to the arm can also be used. It
is clear that the recess is not necessary if any form of universal joint is used to join the arms and
the plate. The recess of the embodiment of FIG. 1 is one in which the plate 11 is placed between
the arm 9 and the upper casing 1. The advantage of the embodiment shown in FIGS. 1 and 2 is
that the plate 11 itself can be aligned with the face of the wall 4 of the upper casing, so that the
level of the noise produced is minimized when the holes 3 are covered It is to be done. As shown
in FIG. 3, the plate 11 may be in the form of a disc and may be provided with a conical projection
12 in contact with the bottom of the recess 10 of the arm 9. It goes without saying that it is also
possible to provide the above-mentioned projections at the bottom of the recess portion 0
instead. In any case, the projections acting on the relatively flat surface form a universal bearing,
i.e. the wall of the disc 11 in the upper casing l independently of the play of the pivoting joint
between the arm 9 and the cylindrical projection 8 It can be aligned to the 4th plane. It is not
essential that the arm 9 be pivoted to a point on the housing if the housing and the arm 9 are
separately fixed to another member, which may for example be the casing of a telephone.
Furthermore, said arm 9 may be replaced by a disc-shaped member of the type shown in GB-A2115648 A which is adapted to provide a recess in which the plate 11 is located. Furthermore,
the plate 11 can be changed to have the holes disclosed in the above-mentioned British patent
application if the plate is held by the spider rather than by the recess. FIG. 4 shows a second
embodiment of the electroacoustical calling apparatus of the present invention. The calling
device is mounted in a recess 106 of an arm 107 mounted around a lower casing 100, an upper
casing 101 having a hole 102, a piezoelectric disc 103, a speaker cone 104 and a boss 108 on
the upper casing 101. It has a closure member 105 in the form of a disc located. Piezoelectric
disc 103 is mounted between the two annular nipples 109 and 110. The first knife edge 109 is
integrally formed with the lower casing 100, while the second knife edge 110 is formed by an
upper and lower casing 10 (an annular member 111 clamped between 1, 101).
The speaker core is connected at its top to the center of the piezoelectric disc, for example by an
adhesive, and the annular flange is clamped between the annular member 111 and the upper
casing. The closing member 105 is pushed onto the upper surface of the upper casing 101 by
the arm 107 via a universal bearing having a projection 112 in the recess 106. The arm and
plate variants described with reference to FIGS. 1 and 3 are not to be applied to the embodiment
of FIG. 4 as well. The addition of the speaker cone 104 helps to increase the volume that can be
obtained from a given electric power, and furthermore, the piezoelectric disc 103 is placed, and if
this unit receives a shock, this disc will Stop moving to the This is preferable to minimize the
possibility of the edge of the piezoelectric disc 103 coming into contact with the housing when
the device is subjected to mechanical shock. The piezoelectric disc 103 is mounted so that the
annular projection of the nafetji 109. 110 is at the nodal point of the disc and the maximum
amplitude of the vibration is at the center of the disc with the apex of the cone 104. It is obvious
that the arms 9 or 107 can also be fixed with a housing pivoted about a point so that a relative
movement between the bore and the closing member takes place. The universal bearing may take
any convenient form, for example the projection may be hemispherical or the closing member
may be connected to the arm by means of a universal joint which may be of various known
forms. The closure member does not necessarily have to be in the form of a plate, especially
when different types of universal bearings are used, eg there is no limitation on its thickness, the
only constraint being the effectiveness and repeatability of the hole The contact surface must not
be convex in order to allow a certain sealing. The holes 3 or 102 of the housing do not
necessarily have to be a single hole, and a plurality of holes may be formed collectively.
Brief description of the drawings
1 is a cross-sectional view of a first embodiment of the electroacoustic calling device according to
the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3a is a plan view of a closing
member suitable for use in the device of FIG. Fig. 3b is a side view thereof, and Fig. 4 is a side
view showing a second embodiment of the electroacoustic calling device according to the present
DESCRIPTION OF SYMBOLS 1, 101 ... Upper casing 2, 100 ... Lower casing 3, 10.2 ... Hole 4 ...
Wall 5, 103 ... Piezoelectric disc 6.7 ... Circular protrusion 10, 106 ... recessed portion 11 ... plate
12.112 · projection 104 ... speaker cone 105 ... closure member 108 ... boss 109 ... first knife
edges 110 ... second knife edges 111, .. Annular members
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description, jps61149000
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