US3927403A

US3927403A - Electric buzzer

Info

Publication number: US3927403A
Application number: US547411A
Authority: US
Inventors: Spencer C Schantz
Original assignee: Individual
Current assignee: Individual
Priority date: 1975-02-06
Filing date: 1975-02-06
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16
Also published as: CA1035978A

Abstract

An electric coil is wound on a plastic bobbin, the latter having a central sleeve within which a magnetic core is slideably positioned. One end of the sleeve is closed and projects beyond the coil. An inverted cup-shaped housing surrounds the coil and bobbin and has a central opening through which the closed end of the sleeve projects. The core projects into the closed end of the sleeve beyond the margin of the opening in the housing to augment the magnetic coupling between the housing and the core. The open end of the housing is attached to a support bracket of magnetic material, there being a spring between the bracket and bobbin normally urging the core toward the closed end of the sleeve.

Description

United States Patent 1 Sehantz Dec. 16, 1975 1 1 ELECTRIC BUZZER [76] Inventor: Spencer C. Schantz, 16608 W.

Rogers Drive, New Berlin, Wis. 53151 22 Filed: Feb. 6, 1975 21 Appl. No; 547,411

[56] References Cited UNITED STATES PATENTS 7/1954 Meleski 340/396 10/1970 Dolter 340/396 X Primary ExaminerHarold I. Pitts Attorney, Agent, or FirmArthur L. Morsell, Jr.

[57] ABSTRACT An electric coil is wound on a plastic bobbin, the latter having a central sleeve within which :1 magnetic core is slideably positioned. One end of the sleeve is closed and projects beyond the coil. An inverted cupshaped housing surrounds the coil and bobbin and has a central opening through which the closed end of the sleeve projects. The core projects into the closed end of the'sleeve beyond the margin of the opening in the housing to augment the magnetic coupling'between the housing and the core. The open end of the housing is attached to a support bracket of magnetic material, there being a spring between the bracket and bobbin normally urging the core toward the closed end of the sleeve.

9 Claims, 3 Drawing Figures US. Patent Dec. 16, 1975 3,927,403

ELECTRIC BUZZER BACKGROUND OF THE INVENTION SUMMARY: or THE INVENTION 5 In the buzzer of this invention, the bobbin has a cen-.

tral co re-receiving sleeve which is closed;at one end. The closed end of the, sleeve projects beyond the electric coil wound on the bobbin. v

An inverted cup-shaped housing surrounds the bobbin and coil and has a central opening in the closed end thereof through which the closed end of I the .sleeve 7 projectsfThe core projects beyond the margin of the opening in the housing to improve themagnetic coupling between the coil and the core. The open end of the housing is attached to a support bracket made of magnetic material, there being a spring between the bracket and bobbin normally urging the core toward the closed end of the sleeve.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the preferred embodiment of the invention.

FIG. 2 is a longitudinal sectional view taken on the line 22 of FIG. 1.

FIG. 3 is a sectional view taken on the line 33 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment includes a bobbin 10 (FIG. 2) which is made of a suitable non-magnetic material such as nylon or the like. Bobbin 10 has a central sleeve 12 and two annular flanges l4 and 16 which are axially spaced apart on sleeve 12 and act as retaining walls for an electric coil 18 wound on sleeve 12 between

flanges

14 and 16. A pair of electrical conductors 20 (FIG. I) are attached to the ends of coil 18 and terminate in terminals 22 for connection to a switchable source of alternating current for energizing the buzzer. The upper end 24 of sleeve 12 projects beyond flange 14 and beyond coil 18, and is closed at 26 to limit the upward movement of a core 28 which is made of magnetic material and which is dimensioned to slideably fit within the interior of sleeve 12. The lower end of sleeve 12 is open. Sleeve 12,

flanges

14 and 16, projecting end 24 and end closure 26 are all an integral part of bobbin 10, which can be formed by known injection molding techniques.

Bobbin l0, coil 18, and core 28 are contained within a housing 30 which is preferably but not necessarily made of magnetic material and shaped like an inverted cup. The lower end of housing 30 is open, and the upper end is closed at 32 and provided with a central opening 34 through which the upper end 24 of sleeve 12 projects. The upper end portion 35 of core 28 projects within the upper end 24 of sleeve 12 beyond the margin of opening 34, to enhance the magnetic coupling between housing 30 and core 28. When core 2 28 is .within and not below the margin of opening. 34, the magnetic reluctance therebetween is at a minimum value. y

. At'its lower open end, housing 30 has stake portions 36 extending downwardly a short distance therefrom and engagingmatching openings in .a banjo-shaped mounting bracket38 which is fastened thereby over the open end of housing 30. Mounting bracket 38 is made of magnetic material to complete the magnetic circuit formed by coil 30 and core 35. It is slotted at 40 (FIG. 1) for convenient insertion under a mounting screw (not shown). I i

Thebobbin flange 14 is preferably provided with raised projecting means 14a near its outer periphery.

This may take theform= of ,two or more raised dots spaced symmetrically about the axis of thebobbin, or

may take'the form of a circular raised rib. When the housing 30 is staked tothe mounting bracket 38 by means of the stakes 36, the projecting means 1421 engage the underside of the top 32 of the housing 30 to cause the outer peripheral portion of the flange 14 of the bobbin to be deflected-downwardly, as. shown in FIG. 2. Thiseliminates looseness of the bobbin26 in the assembly which might be caused by tolerance buildup. The deflection of the outer peripheral portion of the flange l4 compresses the coil 18 in an amount sufficient to absorb tolerances of piece parts.

The end closure 26 of sleeve 24 has a depression 26a to provide sufficient clearance for any burr 28a which might be left on the end of the core portion 35. Where metal items of this type are cut off by a screw machine operation, a burr such as the burr 28 is generally left, and, by having the recess 26a, the necessity of removing these burrs is eliminated.

The underside of flange 16 has diametrically aligned grooves 42 and 44 (FIG. 3) to receive a leaf spring 46, which is supported at its ends by mounting bracket 38 and urges core 28 upwardly toward the closed end 26 of sleeve 12. When coil 18 is energized by alternating current, core 28 vibrates axially within sleeve 12, moving spring 46 and causing the latter to strike mounting bracket 38, and then moving upwardly again in each half cycle of the alternating current as the magnetic field builds up to a maximum and then drops to zero, thereby producing a buzzing sound.

Core 28 is preferably long enough so that its upper end 35 does not drop below the level of the opening 34 in housing 30 when core 28 is drawndownwardly by the magnetic field. This maximizes the magnetic coupling between housing 30 and core 28, if the housing is magnetic, and thereby maximizes the buzz intensity produced by any given A.C. current flow through coil 30, or else minimizes the current required to produce a given buzz intensity. If the housing is not magnetic, such as plastic, the magnetic coupling is still enhanced by the length of core protruding beyond the coil. The mounting bracket 38 serves not only as a closure for the open ends of both the sleeve 12 and housing 30, but also serves as a support for the entire buzzer and as a sounding board for the vibration of core 28. This simplifies the structure of the buzzer and substantially reduces its cost.

An alternate construction may eliminate housing 30, with bobbin 10 being suitably attached to bracket 38.

What I claim:

1. An electric buzzer comprising a bobbin of nonmagnetic material having a central sleeve portion with a bore, an electric coil wound on said bobbin around said sleeve portion, one end of said sleeve portion projecting beyond an end of the coil and being closed to close said end of the bore, and the other end being open, a magnetic core slideably mounted in the bore of said sleeve portion and having an end projecting into the projecting portion of the sleeve, a bracket of magnetic material attached to the end of the bobbin opposite the end having the projecting sleeve portion and closing the open end of the sleeve bore, and spring means normally urging said core toward the closed end of the sleeve bore.

2. An electric buzzer as claimed in claim 1 in which there is an inverted cup-shaped housing having a portion surrounding the bobbin and having one end with a central opening through which said projecting sleeve portion projects and having its other end open, and wherein the bracket of magnetic material is connected to the open end of the housing to close said end.

3. The buzzer of claim 1 wherein said spring means is mounted between said bracket and said core.

4. The buzzer of claim 1 wherein the bobbin includes two spaced apart annular flanges on said sleeve, said coil being wound on said sleeve between said flanges,

4 one of said flanges being adjacent the open end of said sleeve and having aligned grooves accommodating said spring means.

5. The buzzer of claim 1 wherein said core is long enough to always project beyond the coil.

6. The buzzer of claim 2 wherein there are staking members projecting from the open end of said housing, and wherein there are openings in-said bracket receiving said staking members, said staking members being staked to hold the assembly together.

7. The buzzer of claim 1 wherein the bobbin flange which is adjacent the open end of the sleeve is relatively thick and fits against the bracket, wherein the aligned grooves of said flange face said bracket, and wherein there is a leaf spring accommodated in said grooves and having an upwardly bowed portion engaging the adjacent end of the core to act thereon.

8. The electric buzzer claimed in claim 2 wherein the housing is made of magnetic material.

9. The electric buzzer claimed in claim 2 wherein the core is long enough to always project beyond the margin of said central opening of the housing.

Claims

1. An electric buzzer comprising a bobbin of non-magnetic material having a central sleeve portion with a bore, an electric coil wound on said bobbin around said sleeve portion, one end of said sleeve portion projecting beyond an end of the coil and being closed to close said end of the bore, and the other end being open, a magnetic core slideably mounted in the bore of said sleeve portion and having an end projecting into the projecting portion of the sleeve, a bracket of magnetic material attached to the end of the bobbin opposite the end having the projecting sleeve portion and closing the open end of the sleeve bore, aNd spring means normally urging said core toward the closed end of the sleeve bore.

4. The buzzer of claim 1 wherein the bobbin includes two spaced apart annular flanges on said sleeve, said coil being wound on said sleeve between said flanges, one of said flanges being adjacent the open end of said sleeve and having aligned grooves accommodating said spring means.

6. The buzzer of claim 2 wherein there are staking members projecting from the open end of said housing, and wherein there are openings in said bracket receiving said staking members, said staking members being staked to hold the assembly together.