GB1597642A

GB1597642A - Audible signal apparatus

Info

Publication number: GB1597642A
Application number: GB92278A
Authority: GB
Original assignee: Star Micronics Co Ltd
Current assignee: Star Micronics Co Ltd
Priority date: 1977-01-11
Filing date: 1978-01-10
Publication date: 1981-09-09
Also published as: DE2800863B2; DE2800863C3; DE2800863A1; JPS5397985U; JPS5653438Y2

Description

(54) AUDIBLE SIGNAL APPARATUS (71) We, STAR SEIMITSU KABUSHIKI KAISHA, a Japanese company, of 194 Nakayoshida, Shizuoka-shi, Shizuoka-ken, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to an electrical audible signal apparatus such as a small buzzer, and more particularly to the mounting structure of a vibration unit including a diaphragm which is used in the audible signal apparatus and which is electromagnetically excited by an electromagnetic transducer.

An audible signal apparatus having an electromagnetic transducer which produces a regularly changing magnetic field is well known, and a transistor oscillation circuit which is adapted to drive such a transducer is disclosed, for example, in U.S. Patents No.

3,887,914 and No. 3,945,004. In conventional audible signal apparatus, electrical components which form the transistor oscillation circuit are disposed on a printed circuit board, which is received within a housing together with an electromagnetic transducer.

However, for an audible signal apparatus which is used as an alarm in a quartz controlled electronic watch or clock, a separate oscillation circuit for the audible signal apparatus can be dispensed with, together with the achievement of a saving in the space requirement, since the watch includes a complementary metal-oxide-semiconductor circuit (hereinafter referred to as "C-MOS") having a plurality of stages which divide the frequency of a crystal oscillator, as disclosed in U.S. Patents No. 3,560,998 and No.

3,742,697, and an oscillation signal of a suitable frequency can be derived from one of the terminals on C-MOS and amplified to be used as the drive for the audible signal apparatus.

Audible signal apparatus having a vibrator onit which is excited by an electromagnetic transducer is known in a variety of configuration, according to the manner of exciting the unit. In one practical arrangement, the diaphragm is magnetically driven either directly or through an armature which is carried by the diaphragm. In another configuration, the diaphragm is physically impacted by a striker on an oscillation member which is positively driven. In these configurations, the audible signal is formed by the oscillation of the diaphragm. However, there is also known another configuration in which a striker on an oscillating member impacts the core of the electromagnetic transducer, thereby producing a percussion sound.

U.S. Patent No. 3,931,549 (Berns et al) proposes to clamp a diaphragm rigidly between a cup-shaped housing and a cover, while U.S. Patent No. 3,179,932 (Gregoroff) proposes a diaphragm freely supported therebetween. U.S. Patent No. 3,846,792 (Haigh) discloses a diaphragm which is cupshaped, having a rib on its side and which is snapped into groove formed in a housing wall. U.S. Patent No. 1,956,393 (Loeffier) teaches that the provision of a support member within a housing for mounting a diaphragm thereon is old.

A vibrator unit including a diaphram and an oscillating member having a striker is disclosed in our U.S. Patents No. 3,887,914 (Sato et al) and No. 3,974,499 (Shigemori et al). In the former arrangement, the vibrator unit is integrally mounted on a plurality of pillar-like support members which are disposed on the base of a housing. In the latter, the diaphragm is supported on the bottom of the cup-shaped housing.

U.S. Patent No. 3,945,004 (Myers) discloses an electromagnetic transducer having a U-shaped core which fixedly carries a coil on one limb and having a striker arm mounted on the other limb, with a diaphragm which cooperates with the transducer being molded on a sidewall of a housing so as to form a top wall thereof. U.S.

Patent No. 3,564,542 (Yukio Arai) discloses a diaphragm which is rigidly clamped between a housing a cover, with a striker arm mounted on a frame which is disposed within the housing.

As discussed above, the conventional audible signal apparatus is provided with a housing which provides a protection for an internally housed electromagnetic transducer and which contributes to supporting a vibrator unit which is excited by the tranducer.

For these reasons, the provision of the housing has been believed essential in such arrangement. However, it will be seen that the provision of such housing is awkward from the standpoint of manufacturing an aubible signal apparatus which is simple and compact in construction.

In consideration of the fact that when the audible signal apparatus is assembled into certain ulitilization devices such as the watch or clock mentioned above. for example, it is unnecessary to provide a separate housing for the audible signal apparatus in order to protect its internal components, the inventOr noted that the prior practice of supporting the vibrator unit with such housing can be eliminated, thereby providing a compact audible signal apparatus which is free from housing and thus is simple in construction.

To achieve the intended end. it is found that the vibrator unit can be supported by a coil bobbin, which is one of the members forming the electromagnetic transducer.

Therefore, it is an object of the invention to provide a compact audible signal apparatus which is simple in construction.

In accordance with the invention, there is provided an audible signal apparatus comprising a vibrator unit including a generally planar diaphragm. and an electromagnetic transducer for electromagnetically exciting the vibrator unit, the transducer including a bobbin having a body with an axis substantially perpendicular to the plane of the diaphragm, an elongate magnetisable core disposed inside the bobbin body with its axis in alignment with the axis of the bobbin body and a coil assembly disposed around the bobbin body, the bobbin having a flange on at least one end of the bobbin body and extending substantially perpendicularly to the axis of the bobbin body, the flange having an axially raised annular portion arranged to support the diaphragm at its periphery at a spacing from one end of the core, said vibrator unit further comprising a permanent magnet armature which is attached to the diaphragm and disposed in opposing relationship with and spaced from the one end of the core. the diaphragm being forcibly held in contact with the end of the raised annular portion by the magnetic attraction acting between the armature and the core.

The vibrator unit may further comprise the diaphragm and an oscillating or percussion member, the diaphragm having a striker which impacts the oscillating or percussion member. If desired. an arrangement may be employed in which the armature impacts the core to produce a percussion sound in addition to the sound produced by the normal oscillation of the diaphragm. At any event, the vibrator unit is supported by the coil bobbin, and hence the audible signal apparatus can dispense with any form of integral housing or casing. However, if desired, the audible signal apparatus can be detachably covered with a simple cupshaped cover.

The audible signal apparatus of the invention may or may not contain an electronic oscillation circuit which drives the electromagnetic transducer. When such circuit is provided, components which are used to form the circuit may be disposed on a printed circuit board which is attached to the coil bobbin. In order to form a magnetic loop with the vibrator unit. the electromagnetic transducer may be provided with an annular yoke or permanent magnet extending around the coil assembly which is disposed on the bobbin.

Certain embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a schematic cross section of an audible signal apparatus according to the invention in its simplest form including a vibrator unit which comprises a diaphragm with an armature; Fig. 2 is a cross section of the apparatus of the invention in which the lower flange of the bobbin carries a plate of a magnetic material; Fig. 3 is a cross section of the apparatus including a pair of vibrator units which are disposed on opposite flanges of the bobbin; Fig. 4 is a cross section of the audible signal apparatus including a vibrator unit which comprises a diaphragm having a striker and an oscillating member; Fig. 5 is a cross section of the audible signal apparatus as it is mounted on an external printed circuit board; ; Fig. 6 is cross section of audible signal apparatus having a self-excited electronic circuit; Fig. 7 is a cross section of the apparatus of the invention in which the electromagnetic tranducer includes a cup-shaped yoke; Fig. 8 is a cross section of the audible signal apparatus in which both flanges of the bobbin are formed with mounting legs; Fig. 9 is a cross section of the apparatus in which the upper flange of the bobbin carries the vibrator unit and is also formed with mounting legs; Fig. 10 is a cross section of the apparatus in which the lower flange of the bobbin is formed with mounting legs; Fig. 11 is a cross section of the audible signal apparatus provided with a cover; and Fig. 12 is a cross section of the audible signal apparatus in which the upper flange of the bobbin carries the vibrator unit and also forms a resonance chamber.

It should be noted that throughout the drawings, similar parts are designated by like numerals. Referring to Fig. 1, an electromagnetic transducer is generally indicated by a reference numeral 1, and includes a spool or bobbin or 2 having a cylindrical body 3, a coil assembly 4 disposed on the bobbin 2, and a iron core 5 supported inside the body 3 of the bobbin 2. The bobbin 2 is formed with an upper and a lower flange 6, 7 at the opposite ends of the cylindrical body 3, these flanges extending in a direction perpendicular to the axis of the body. The upper flange 6 is formed with an annular extension 8 which extends axially from the periphery thereof in a direction away from the lower flange 7. The annular extension 8 has an upper end 9 which terminates in a single plane, with the periphery being provided with a rib 17 of a small height.The bobbin 2 is molded from a non-magnetic and non-conductive material such as ABS resin or polyacetal resin. The coil assembly may be formed by polyurethane clad copper wire, for example. The core 5 may be formed from SK steel, for example.

A vibrator unit is generally indicated by a reference numeral 10. In the example shown, it comprises a flat diaphragm 11 and an armature 12 which is supported thereon substantially at the center of the diaphragm.

The unit 10 is carried on the bobbin 2 by placing the peripheral edge of the diaphragm 11 in contact with the upper end 9 of the annular extension 8 of the upper flange 6. At rest, the armature 12 is spaced from the upper end of the core 5. The diaphragm 11 may be formed from either magnetic or non magnetic material, while armature 12 is formed of a permanent magnet. In one desirable form, the diaphragm 11 is formed of a thin film of polycarbonate resin, and an armature 12 formed of a rare earth magnet such as a samarium cobalt magnet is adhe sively secured thereto. However, the dia phragm 11 may be formed of a thin film of cold rolled steel, and a magnet armature 12 may be held magnetically attracted thereto.

Since the armature 12 comprises a perma nent magnet, the diaphragm 11 may be simply played on the end 9 of the annular extension 8 without securing to the bobbin 2 since the magnetic interaction between the magnet armature 12 and the core 5 forcibly brings the diaphragm 11 into contact with the bobbin 2.

The coil assembly 4 induces a regularly changing magnetic field through the core 5, thereby exciting the vibrator unit 10. Such coil assembly may comprise a pair of drive and control coils as is found in a known form of blocking oscillator, or may comprise a single coil which is electrically connected with a selected terminal of C-MOS of a quartz controlled watch or clock into which the apparatus of the invention is incorporated.

The excitation of the vibrator unit 10 may take place in several different modes. Specifically, an oscillation of the diaphragm 11 can take place without the armature 12 contacting the upper end of the core 5. Alternatively, the diaphragm 11 may be caused to oscillate as the armature 12 impacts the core 5. The selection between these modes depends on the spacing between the armature 12 and the core 5, and the intensity of the magnetic field produced in the core 5. Where the armature 12 impacts the core 5, the armature comprises magnetised iron piece firmly secured to the diaphragm 11. Where a cavity 16 formed between the diaphragm 11 and the upper flange 6 of the bobbin 2 represents an enclosed space, it functions as a damper for the diaphragm 11, contributing to achieve an increased resonance frequency of the diaphragm.

In the audible signal apparatus shown in Fig. 2, the lower flange 7 of the bobbin 2 has a magnetic plate 15 which is connected with the lower end 14 of the core 5. It will be seen that the plate 15 improves the magnetic coupling between the end 14 of the core 5 and the diaphragm 11 which is formed of a magnetic material. As a result, the acoustic output is increased over the audible signal apparatus shown in Fig. 1. The plate 15 may comprise cold rolled steel, for example.

Fig. 3 shows an audible signal apparatus having a second vibrator unit 20 in addition to the vibrator unit 10 mentioned above. In this audible signal apparatus, the lower flange 7 of the bobbin 2 is formed with an annular extension 21 which is similar to that formed on the upper flange 6, and the lower end 22 of the annular extension 21 represents a flat surface delineated by a rib 23. The second vibrator unit 20 has a diaphragm 25 having an armature 24 which is disposed in opposing relationship with and spaced from the lower end of the core 5, and the unit 20 is supported so that the peripheral edge of the diaphragm 25 is placed in contact with the lower end 22 of the annular extension 21.

This signal apparatus operates in substantially the similar manner as the embodiment shown in Fig. 1, but produces a greater acoustical output by the cooperation of the pair of vibrator units 10, 20.

Fig. 4 shows a slightly modified vibrator unit 30 which comprises a diaphragm 31 formed of the similar material as the diaphragm 11 and carrying on its one side an armature 32 of the similar material as the aforementioned armature 12 and disposed at a spacing from the upper end of the core 5 and carrying on its other side a striker 33, and a percussion member 34 adapted to be impacted by the striker 33 of the diaphragm 31. The diaphragm 31 is peripherally sup ported by the end face 9 of the annular extension 8 formed on the upper flange 6 of the bobbin 2, while the percussion member 34 is peripherally supported on the rib 10 of the annular extension 8. The percussion member 34 may be formed of a similar material as that utilized to form the diaphragm 11 mentioned previously.In the operation of the vibrator unit 30 when the diaphragm 31 is excited by the core 5 the striker 33 impacts the percussion member 34, causing the percussion member to oscillate.

Fig. 5 shows an audible signal apparatus 40 as mounted on an external printed circuit board 41. The audible signal apparatus 40 is substantially identical with that shown in Fig. 2 except that the lower flange 7 of the bobbin 2 is provided with a plurality of hard lead wires 42 which are fitted into a plurality of through-holes 43 formed in the flange 7, with one end 44 of the lead wire extending to the inner surface of the flange 7 and the other end 45 extending through the hole 43 and a corresponding through-hole formed in the printed circuit board 41 to project therefrom.

The end 44 is electrically connected with lead wires 46 from the coil assembly 4 while the other end 45 is electrically connected with the circuit board 41 as by soldering 47. In the example shown, the circuit board 41 carries thereon C-MOS 48 which forms a quartz controlled electronic clock, bias resistor 49 and amplifier transistor 50. While not shown, the transistor 50 has its base connected through resistor 49 with one of terminals 51 on C-MOS, and its emitter with the ground.

The coil assembly 4 of the audible signal apparatus 40 comprises a signal coil which is connected through the lead wires 42 with the positive terminal of a power source and with the collector of the transistor 50. In this manner, the coil 4 can be energized by C MOS at a frequency of 2048 Hz intermittently, namely with a repetition frequency of the order of 1 to 10 Hz, thus inducing an oscillating field through the core 5.

Fig. 6 shows an audible signal apparatus having a printed circuit board 53 carrying electrical components 52 which are used to form an electronic oscillation circuit. The circuit board 53 is secured across the upper and lower flanges 6, 7 by means of rivets 54, 55 which are applied to the respective flanges. The arrangement of an electronic oscillation circuit is disclosed in U.S. Patent No. 3,887,914, for example, where the coil assembly 4 comprises a pair of coils.

Fig. 7 shows a modification in which a yoke 60 is connected with the lower end of the core 5 and is provided with an annular magnetic portion 62. The yoke 60 cooperates with the core 5, and the armature 12 to form a magnetic loop.

Figs. 8 to 10 show various examples of mounting legs which are used to secure the audible signal apparatus of the invention to an external structure. In Fig. 8, both the upper and lower flanges 6, 7 of the bobbin 2 has an axially extending leg 65, but only one of them may be provided. In Fig. 9, there is shown an audible signal apparatus 66 having a vibrator unit 10 mounted on the upper flange 6 of the bobbin 2, and the flange 6 is shown having a pair of laterally extending mounting legs 67. When the apparatus 66 is mounted in an external mounting structure such as clock housing 68, the housing 68 is formed with a number of apertures 69 in the region of the vibrator unit 10 for allowing the sound output to be produced. The mounting legs 67 provide a reference surface so that a suitable spacing can be maintained between the diaphragm 11 and the housing 68.Fig. 9 also illustrates that a printed circuit board 70 which is similar to the printed circuit board 53 described in connection with Fig. 6 may be mounted on the other flange 7 of the bobbin 2 of the audible signal apparatus 66.

Fig. 10 shows mounting legs 71 which extend laterally from the peripheral edge of the lower flange 7 which is opposite to the upper flange 6 carrying the vibrator unit 10.

Referring to Fig. 11, a cup-shaped cover 75 is detachably mounted on an audible signal apparatus such as shown in Fig. 10. The cover 75 is placed over the bobbin 2 and is frictionally coupled with the peripheral edge of the upper and lower flanges 6, 7 of the bobbin. The cover 75 has a top 74 in which an aperture 76 is formed. The top cooperates with the diaphragm 1 of the vibrator unit to define a resonance chamber 77. The cover 75 may be formed of a synthetic plastic material, but may also be formed of a magnetic material to provide a magnetic shield against external apparatus.

Fig. 12 shows another audible signal apparatus in which the flange 6 supporting the vibrator unit 10 is integrally provided with a horn 79 which defines a resonance chamber 78 for the vibrator unit. The open end of the horn 79 is closed by a top plate 81 in which an aperture 80 is formed, but it should be understood that the closure plate may be omitted. The function of such resonance chamber is well known and therefore will not be described. What is important is that it may be formed simultaneously as the bobbin 2 is molded.

While various embodiments of the invention have been described in detail, it should be understood that they are illustrative only, and not limitative of the invention. It will be obvious to one skilled in the art that a number of changes and modifications can be made therein without departing from the scope of the invention. For example, a coil bobbin may be formed so as to have a flange only on the end which supports the vibrator unit while the other end may be configured to be connected with an external mounting structure. Therefore, it is intended that the scope of the invention be solely defined by the appended claims.

WHAT WE CLAIM IS: 1. An audible signal apparatus comprising a vibrator unit including a generally planar diaphragm, and an electromagnetic transducer for electromagnetically exciting the vibrator unit, the transducer including a bobbin having a body with an axis substantially perpendicular to the plane of the diaphragm, an elongate magnetisable core disposed inside the bobbin body with its axis in alignment with the axis of the bobbin body and a coil assembly disposed around the bobbin body, the bobbin having a flange on at least one end of the bobbin body and extending substantially perpendicularly to the axis of the bobbin body, the flange having an axially raised annular portion arranged to support the diaphragm at its periphery at a spacing from one end of the core, said vibrator unit further comprising a permanent magnet armature which is attached to the diaphragm and disposed in opposing relationship with and spaced from the one end of the core, the diaphragm being forcibly held in contact with the end of the raised annular portion by the magnetic attraction acting between the armature and the core.

2. An audible signal apparatus according to Claim 1 in which the or a flange has at least one mounting leg which extends in the axial direction of the bobbin from the periphery thereof.

3. An audible signal apparatus according to Claim 1 in which the or a flange has at least one mounting leg which extends in a direction perpendicular to the axis of the bobbin from the periphery thereof.

4. An audible signal apparatus according to Claim 1, 2 or 3 in which the flange has a cylindricl horn which extends in the axial direction of the bobbin from the periphery of the annular portion, the horn defining a resonance chamber for the vibrator unit.

5. An audible signal apparatus according to Claim 1, 2 or 3 further including a detachable cap which covers the vibrator unit and the electromagnetic transducer, the cap being frictionally coupled with the side of the flange.

6. An audible signal apparatus according to Claim 5 in which the cap cooperates with the vibrator unit to define a resonance chamber.

7. An audible signal apparatus according to Claim 5 in which the cap is formed of a magnetic material.

8. An audible signal apparatus according to any preceding claim in which the diaphragm is formed of a magnetic material.

9. An audible signal apparatus according to claim 1 in which the vibrator unit comprises the diaphragm and a percussion member, the diaphragm being adapted to strike the percussion member, and the percussion member being supported by the raised annular portion.

10. An audible signal apparatus according to Claim 9 in which the annular portion has a first and a second plane which are axially spaced, the diaphragm being on the first plane and the percussion member being on the second plane.

11. An audible signal apparatus according to Claim 1, in which the bobbin further comprises a second flange at the opposite axial end of the bobbin body to the firstmentioned flange.

12. An audible signal apparatus according to Claim 11, further including another vibrator unit including a second diaphragm adapted to be excited by the core, and wherein the second flange has a second annular portion extending axially of the bobbin body on the opposite face from the coil assembly, the second diaphragm being supported by the second annular portion in spaced relationship from the pther end of the core.

13. An audible signal apparatus according to Claim 11 in which the second flange carries electric hard leads which are electrically connected with the coil assembly and which extend through the second flange to project to the opposite face thereof from the coil assembly.

14. An audible signal apparatus according to Claim 11, further including a printed circuit board carrying electrical components which form an electronic circuit for supplying an oscillating current to the coil assembly, the circuit board being aligned with the axial direction of the bobbin body and supported by the flanges.

15. An audible signal apparatus according to either Claim 11 or 13, further including a printed circuit board carrying electrical components which form an electronic circuit for supplying an oscillating current to the coil assembly, the circuit board being supported on the face of the second flange which is remote from the coil assembly.

16. An audible signal apparatus according to either Claim 11 or 13, further including a magnetic yoke disposed on the side of the second flange remote from the coil and connected with the other end of the core.

17. An audible signal apparatus according to Claim 11, further including a magnetic yoke disposed on the face of the second flange which is remote from the coil and connected with the other end of the core, the magnetic yoke having magnetic portions extending around the coil assembly.

18. An audible signal apparatus accord

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. to be connected with an external mounting structure. Therefore, it is intended that the scope of the invention be solely defined by the appended claims. WHAT WE CLAIM IS:

1. An audible signal apparatus comprising a vibrator unit including a generally planar diaphragm, and an electromagnetic transducer for electromagnetically exciting the vibrator unit, the transducer including a bobbin having a body with an axis substantially perpendicular to the plane of the diaphragm, an elongate magnetisable core disposed inside the bobbin body with its axis in alignment with the axis of the bobbin body and a coil assembly disposed around the bobbin body, the bobbin having a flange on at least one end of the bobbin body and extending substantially perpendicularly to the axis of the bobbin body, the flange having an axially raised annular portion arranged to support the diaphragm at its periphery at a spacing from one end of the core, said vibrator unit further comprising a permanent magnet armature which is attached to the diaphragm and disposed in opposing relationship with and spaced from the one end of the core, the diaphragm being forcibly held in contact with the end of the raised annular portion by the magnetic attraction acting between the armature and the core.

18. An audible signal apparatus accord

ing to any of Claims II, 13 or 16 in which the second flange has at least one mounting leg which extends in the axial direction of the bobbin body from the periphery of the second flange.

19. An audible signal apparatus according to any of Claims 11, 13 or 16 in which the second flange has at least one mounting leg which extends in a direction perpendicular to the axis of the bobbin body from the periphery of the second flange.

20. An audible signal apparatus substantially as hereinbefore described with reference to any Figure of the accompanying drawings.