US3784944A

US3784944A - Adjustable electric buzzer

Info

Publication number: US3784944A
Application number: US00264899A
Authority: US
Inventors: S Schantz; W Berry
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-06-21
Filing date: 1972-06-21
Publication date: 1974-01-08
Anticipated expiration: 1991-01-08

Abstract

A ferromagnetic pole piece with a coil therearound is attached at one end to a ferromagnetic frame and a ferromagnetic armature is pivoted to the frame for vibratory movement toward and away from the other end of the pole piece to form a buzzer. The pivotal attachment of the armature includes non-magnetic pivot bearings which are so positioned as to direct the flow of magnetic flux between the frame and armature into a path which enters the armature transversely and thus eliminates undesirable vibration of the armature at the pivot bearings when the armature is pivoted on a conical end face of the pole piece in the ''''off'''' position. The intensity of the buzzing sound is controlled by a variable abutment member which varies the maximum air gap between the free end of the armature and the pole piece, which abutment member includes a rotatable shaft with a cam member positioned to vary the limit of movement of the armature away from the pole piece.

Description

United States Patent [1 1 Primary Examiner1-larold Broome Att0rneyArthur L. Morsell, Jr.

Schantz etal. [45] J 8, 1974 ADJUSTABLE ELECTRIC BUZZER [57] ABSTRACT [75] Inventors: Spencer C. Schantz, 16608 W. A ferromagnetic pole piece with a coil therearound is Rogers Dr., New Berlin, Wis. attached at one end to a ferromagnetic frame and a 53151; William R. Berry, ferromagnetic armature is pivoted to the frame for vi- Menomonee Falls, Wis. bratory movement toward and away from the other 4 end of the pole piece to form a buzzer. The pivotal at- [73] Asslgnee: f schamz New Berlm, tachment of the armature includes non-magnetic pivot bearings which are so positioned as to direct the flow [22] Fi d; June 21 1972 of magnetic flux between the frame and armature into a path which enters the armature transversely and thus [21] Appl 264899 eliminates undesirable vibration of the armature at the pivot bearings when the armature is pivoted on a coni- [52 us. Cl. 335/276, 335/128 eel end face of the p Pieee in the Position- 51 1nt.C1. 1101: 7/14 The intensity of the buzzing sound is controlled y a [58] Field of Search 335/276, 128 variable abutment member which varies the maximum air gap between the free end of the armature and the [56] References Ci d pole piece, which abutment member includes a rotat- UNTED STATES ATENTS able shaft with a cam member positioned to vary the limit of movement of the armature away from the pole 2,471,181 5/1949 Wilson .1 335/276 piece. 2,398,657 4/1946 McMaster et a1.... 335/276 2,884,574 4/1959 Jaidinger 335/276 9 Claims, 7 Drawing Figures /0 L1 ni i l// //////Df 7" I 1 54 28 v I 25 I -54 I 1 ADJUSTABLE ELECTRIC BUZZER BACKGROUND or THE INVENTION This invention relates to electromagnetic buzzers, relays, and other electromagnetic devices in which an armature is magnetically attracted to a pole piece when an alternating current is passed through a coil around the pole piece. Many such devices have been manufactured in the past, but all have tended to vibrate and hum at the pivotal connection between the armature and the frame thereof unless a means is provided to hold the parts together in intimate contact. This undesired vibration is caused by the alternating magnetic flux that traversed the pivotal connection between the armature and frame at right angles to the armature attracting said armature to the frame. In accordance with this invention, however, it has been found that such undesired vibration and hum can be eliminated by pivoting the armature on non-magnetic pivot bearings which are so positioned as to direct the flow of magnetic flux between the frame and the armature into a path which enters the armature transversely and thus eliminates the undesired vibration.

Accordingly, one general object of this invention is to provide an electromagnetic device in which undesired vibration of the armature at its pivot points is eliminated.

In its more particular aspects, this invention relates to improvements in electric buzzers such as utilized in doorbells, interoffice communication systems, and in various types of warning devices. Many different types of buzzers have been manufactured in the past, but although these buzzers fulfilled their primary function as noise emitters, they have suffered from shortcomings in terms of ease of adjustment, adjustment stability, range of adjustment, reliability, and economy.

Accordingly, another object of this invention is to provide an improved electric buzzer.

An additional object of this invention is to provide an electric buzzer having a volume adjustment mechanism which can be easily varied from zero sound output to a maximum sound output.

A further object of this invention is to provide an electric buzzer having a volume adjustment mechanism which can be adjusted in small increments from zero sound output to a maximum sound output.

Yet another object of this invention is to provide an electric buzzer having a volume adjustment mechanism which has improved stability.

A further object of this invention is to provide an electric buzzer having improved reliability.

A more specific object of this invention is to provide an electric buzzer in which the armature is pivoted upon non-magnetic bearings, the bearings being so positioned as to direct the flow of magnetic flux into a path which enters the armature transversely and thus eliminates undesirable vibration of the armature adjacent to the pivot bearings, particularly when the unit is adjusted in the non-buzzing mode and when the armature is lifted from the hinge point by an adjusting cam.

A further, more specific object of the invention is to provide a buzzer in which an end face of the pole piece is conical to form a novel fulcrum for the armature when it is moved to the off position by the action of an adjusting cam. This positively prevents buzzing and also compensates for manufacturing tolerances as it serves to lift the hinge end of the armature off of the non-magnetic bearings.

SUMMARY OF THE INVENTION In accordance with this invention, the above-noted objects are attained by providing a ferromagnetic pole piece which is attached at one end to a ferromagnetic frame. An electric coil is positioned around the pole piece and a ferromagnetic armature is pivotally attached to the frame for vibratory movement toward and away from the other end of the pole piece. The pivotal attachment of the armature includes non-magnetic pivot bearings which are so positioned as to direct the flow of magnetic flux between the frame and the armature into a path which enters the armature transversely and thus eliminates undesirable vibration of the armature at the pivot bearings. When the coil is energized by alternating current, the free end of the armature vibrates and produces a buzzing sound. The intensity of the buzzing sound is controlled by a variable abutment member which varies the maximum air gap between the free end of the armature and pole piece.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational sectional view of one illustrative embodiment of the invention;

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken on the line 3--3 of FIG. 1;

FIG. 4 is a perspective view of the variable abutment member for the embodiment shown in FIGS. L3;

FIG. 5 is a perspective view of the coil bobbin for the embodiment shown in FIGS. 1-3;

FIG. 6 is a perspective view of an electric terminal for the embodiment shown in FIGS. l3; and

FIG. 7 is a fragmentary sectional view of the bobbin to show the crushable ring which compensates for manufacturing tolerances.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. ll, one illustrative embodiment of the invention is enclosed in a housing consisting of a top member 10 and a bottom cupmember 12 which may be made of a suitable insulating plastic material. A U-shaped frame 14 which is made of ferromagnetic material is suitably attached through slotted engagement as at 16 and 18 to the top member 10 and projects downwardly into the cup member 12. A ferromagnetic core 20 forming a pole piece is staked at its lower end to the bottom of the U-shaped frame 14 as at 15 (FIG. 1) and has an electric coil 22 positioned therearound. The electric coil 22 is wound upon a nylon bobbin 24 which has a concentric hole 26 (FIG. 5) through which the pole piece 20 passes. The pole piece 20 has an enlarged upper end face 28 which holds the bobbin 24 in position on the frame 14 and which is seated on a slightly crusted annular ring 23 around the core opening, as shown in FIG. 7, for a purpose to be hereinafter described.

A ferromagnetic armature 30 is pivoted on frame 14 in a novel manner on bearing pivots 32 (FIG. 1) for movement toward and away from the end face 28 of pole piece 20, there being a slot 27 in the armature through which a reduced width portion 15 of the frame loosely passes. The pivot bearings are formed on the ends of legs 34 which project from opposite sides of the bobbin, as shown in FIG. 5. In order to provide support, these legs rest on shoulders 31 on each side of the reduced portion of the frame, as is shown in FIG. 2, and serve to rotationally position the bobbin. The armature 30 is normally urged away from the pole piece end face 28 by an extension spring 36, which also urges the armature 30 toward the pivot bearings 32 and, being on an angle, urges armature 30 against the frame in a transverse direction. The pivot bearings 32 are made of a non-magnetic material and are so positioned with respect to the U-shaped frame 14 and the armature 30 as to direct the magnetic flux into a path which enters the armature transversely and thus eliminates undesirable vibration of the armature at its pivot points. In the past, the armature 30 was allowed to rest directly on shoulders on the frame 14, and this allowed the magnetic flux at the pivot point to enter the armature 30 in aperpendicular direction which caused undesirable vibration and hum when the magnetic flux alternated. Although the pivot bearings 32 can be made of any non-magnetic material, they are preferably made of Nylon or some other suitable wear-resistant plastic and are preferably an integral part of the Nylon bobbin 24 as shown in FIG. 5. As an important feature of the invention the end face 28 of the pole piece is conical in form for a purpose to be hereinafter described.

The ends of electrical coil 22 are soldered to L- shaped

electrical terminals

38 and 40 which are supported in pockets in a projection 42 on bobbin 24, as will be described in detail later, and project through openings in the bottom member 12 of the housing. When an alternating or pulsating current is applied between the

terminals

38 and 40, an alternating magnetic flux field is established in a magnetic circuit that ex tends from the bottom of pole piece through frame 14 and armature to the top 28 of pole piece 20. This causes the armature 30 to be alternatingly attracted to pole piece end 28 and then released for movement away from end 28 under the impetus of spring 36 which produces a buzzing sound. The volume of this buzzing sound can be varied from zero to a maximum value by a variable abutment member which will be described in detail later.

The

electric terminal elements

38 and 40 can be supported in any suitable manner, but their bent upper portions are preferably supported in pockets 44 and 46 (FIG. 5) in the projection 42 of bobbin 24. The downwardly-projecting portions of the terminals 38 and 40 (upwardly in FIG. 5) are surrounded by nylon barriers 45 which fit in notched-out side recesses 47 in the bottom portion of the metal frame 14. Thus these nylon barriers serve to insulate the terminals from the frame 14 and also aid in holding and positioning the bobbin on the frame.

Protrusions

48 and 50 from the plastic are formed in the interior of

pockets

44 and 46. Each

terminal

38 or 40 has a hole 52 (FIG. 6) in the end which fits into its pocket. Each hole 52 is positioned beneath a

plastic protrusion

48 or 50 so that when the wires from coil 22 are soldered to the terminals, the heat will be conducted through the terminals to soften the

protrusions

48 and 50 and cause the nylon material to flow into the openings 52 as shown in FIG. 3. This anchors the

terminals

38 and 40 securely in place in the

pockets

44 and 46.

The volume of the sound produced by the buzzer can be varied in a novel manner by means of an adjustable abutment member. The latter consists of a shaft 54, a sector-shaped cam member 56 which projects laterally from the shaft 54, and a manually-operable extension 58 for the shaft 54. The shaft is rotatably mounted parallel to pole piece 20 in openings in toplO and frame 14. The cam member 56 is interposed between the free end of armature 30 and the top 10. As best shown in FIGS. 3 and 4, the cam member 56 varies in thickness along its periphery so that when the shaft is rotated, the effective thickness of the cam member interposed between the tip of armature 30 and top 10 is varied, the cam having an abrupt change of slope 31 leading to a portion of maximum thickness 33. This varies the maximem air gap between the armature 30 and the pole piece end 28 from zero to a maximum value and thus varies the volume of buzzing from zero to a maximum level. The shaft portion 58 is flattened along its length to fit into a manual adjustment knob which is not shown in the drawings.

The cam member 56 has serrations 60 formed on its upper surface which engage a rib 62 that is pressed into the top 10 and projects downwardly a short distance therefrom. A spring 64 urges the cam member 56 toward the top 10 and resiliently holds the serrations 60 in contact with rib 62 to produce a ratchet effect with a pleasing feel when the shaft 58 is rotated. This holds the cam member 56 in position after it has been adjusted in spite of the vibration of the armature 30.

The cam member 56 is, in its peripheral dimension, shaped like a sector of a ring and the radial edges of cam member 56 abut against the ferromagnetic frame 14 when the shaft 58 is turned to extreme position. One extreme position is where the thinnest portion of cam member 56 is interposed between armature 30 and top 10. This is the position shown in FIGS. 1-3, and in this position, the thickest portion 66 (FIG. 4) of cam member 56 abuts against the frame 14 to limit rotation. The other extreme position is where the thickest portion 66 of cam member 56 is interposed between armature 30 and top 10. In this position, the thinnest portion of cam member 56 abuts against the frame 14.

By having the end face 28 of the pole piece conically shaped as shown in FIG. 1 it is possible, when te adjustment cam is rotated to bring its thickest portion 66 into effective engagement with the end of the armature, to cause the armature to rock on an intermediate fulcrum provided by the top of the conical end face 28 whereby the left hand end of the armature is lifted off of the pivots 32. This positively prevents buzzing action and also compensates for manufacturing tolerances.

It is to be noted that the spring 36 extends obliquely between the end of the armature and the frame thereby tending to pull the margin of the armature slot into metal-to-metal contact with the frame portion 15 to complete the magnetic circuit.

The crushable or yielding annular ring 23 which projects upwardly from the bobbin around the core opening (as shown in FIG. 7) is integrally molded with the bobbin. During assembly, after the core 20 has been inserted through the bobbin, its lower end is staked to the underside of the base of the frame 14, as is common practice and as shown at 15 in FIG. 1. During such staking, however, there is a controllable slight reduction of the height of the core to compensate for manufacturing tolerances and this may vary slightly from one lot of parts to another. The ring 23, being made of yieldable or crushable plastic material such as Nylon, will yield or be in a condition of having been controllably reduced in height a required amount, as the core is being staked in place, to allow for such manufacturing tolerances. At the same time, because of the presence of the ring, the bobbin is always kept tight against axial movement relative to the core. This is an important feature as it insures accurate assembly and eliminates the necessity of using a spring washer to absorb tolerances.

From the foregoing description it will be clear that this invention provides an improved electric I buzzer. And although this invention has been described with reference to one specific embodiment thereof, it should be understood that the invention is not limited to the disclosed embodiment since many modifications can be made in the disclosed structure without changing its essential principles. For example, although the armature pivot bearings have been disclosed as being attached to the coil bobbin, they could be otherwise supported if desired. This and many other modifications of the disclosed structure will be apparent to those skilled in the art, and this invention includes all modifications falling within the scope of the following claims.

What is claimed is:

1. An electromagnetic device comprising a ferromagnetic frame, a ferromagnetic pole piece attached at one end to said frame, an electric coil on said pole piece, a ferromagnetic armature loosely pivoted to said frame for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and said frame in such position as to normally urge part of said armature against said loose pivot and another part away from the end of said pole piece, and said pivot including at least one wear resistant pivot bearing integrally molded with bobbin.

2. An electromagnetic device comprising a magnetic frame, a magnetic pole piece attached at one end to said frame, an electric coil on said pole piece, a magnetic armature loosely pivoted to said frame for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and said frame in such position as to normally urge part of said armature against said loose pivot and another part away from the end of said pole piece, and said pivot including at least one nonmagnetic pivot bearing so positioned between said armature and said frame as to direct the flow of magnetic flux between said frame and said armature into a path which enters the armature transversely and thus eliminates undesirable vibration of said armature on its loose pivot, said electric coil being wound upon a bobbin made of nonmagnetic material, and said non-magnetic pivot bearing being integrally joined to one end of said bobbin and projecting laterally therefrom.

3. An electromagnetic device as defined in claim 2 wherein said frame has a side portion spaced laterally from the pole piece and extending in the same general direction, said side portion having spaced shoulders, and whereinthere are spaced arms projecting from the bobbin on which said pivot bearings are formed, said arms being supported on the spaced shoulders of said frame and serving to locate and support the adjacent end of the bobbin.

4. An electromagnetic device as defined in claim 3 in which said frame side portion has an upper end of re duced width to provide said spaced shoulders and wherein said armature has a transverse slot through which said portion of reduced width loosely extends.

5. An electromagnetic device such as defined in claim 3 in which said pivot bearing is located at one end of said non-magnetic bobbin, and further comprising pockets formed in the other end of said bobbin, and electric terminals having portions secured in said pockets.

6. An electromagnetic device such as defined in claim 5 in which said bobbin is made of a thermoplastic material, andin which there is a protrusion in each of said pockets and an opening in each of said electric terminals, said protrusions being positioned to overlie said openings in said electric terminals with portions thereof in heat-flow interlocking relationship therewith.

7. An electromagnetic device comprising a magnetic frame, a magnetic pole piece attached at one end to said frame, an electric coil in said pole piece, a magnetic armature loosely pivoted to said frame for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and said frame in such position as to normally urge part of said armature against said loose pivot and another part away from the end of said pole piece, and said pivot including at least one non-magnetic pivot bearing so positioned between said armature and said frame as to direct the flow of magnetic flux between said frame and said armature into paths which are parallel to the plane of the armature, the non-magnetic pivot bearing being positioned to block flow of the magnetic flux in a direction which would effect seating of the armature on said pivot bearing, thus eliminating undesirable vibration of said armature on its loose pivot.

8. An electromagnetic device comprising a magnetic frame, a magnetic pole piece attached at a first end to said frame, an electric coil for said pole piece, a magnetic armature, pivot means on said frame on which said armature is loosely pivoted forvibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and frame in such a position as to normally urge part of said armature against said loose pivot means and another part away from the end of said pole piece, a bobbin on which said electric coil is wound, spaced arms projecting from said bobbin and having said pivot means thereon, said frame having a side portion spaced laterally from the pole piece and extending in the same general direction, and said side portion having spaced shoulders, said spaced arms which project from the bobbin being supported on said spaced shoulders of said frame and serving to locate and support the adjacent end of the bobbin.

9. An electromagnetic device comprising a magnetic frame, a magnetic pole piece attached at a first end to said frame, an electric coil for said pole piece, a magnetic armature, pivot means on said frame on which said armature is loosely pivoted for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and frame in such a position as to normally urge part of said armature against said loose pivot and another part away from the end of said pole piece, a bobbin on which said electric coil is wound, said bobbin being made of thermoplastic material and having pockets formed in its end which is remote from the armature, electric terminals having portions secured in said pockets, there being a protrusion in each of said pockets and an opening in each of said electric terminals, said protrusions being positioned to overlie said openings in said electric terminals with portions thereof in heatflow interlocking relationship therewith.

Claims

1. An electromagnetic device comprising a ferromagnetic frame, a ferromagnetic pole piece attached at one end to said frame, an electric coil on said pole piece, a ferromagnetic armature loosely pivoted to said frame for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and said frame in such position as to normally urge part of said armature against said loose pivot and another part away from the end of said pole piece, and said pivot including at least one wear-resistant pivot bearing integrally molded with bobbin.

2. An electromagnetic device comprising a magnetic frame, a magnetic pole piece attached at one end to said frame, an electric coil on said pole piece, a magnetic armature loosely pivoted to said frame for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and said frame in such position as to normally urge part of said armature against said loose pivot and another part away from the end of said pole piece, and said pivot including at least one non-magnetic pivot bearing so positioned between said armature and said frame as to direct the flow of magnetic flux between said frame and said armature into a path which enters the armature transversely and thus eliminates undesirable vibration of said armature on its loose pivot, said electric coil being wound upon a bobbin made of non-magnetic material, and said non-magnetic pivot bearing being integrally joined to one end of said bobbin and projecting laterally therefrom.

3. An electromagnetic device as defined in claim 2 wherein said frame has a side portion spaced laterally from the pole piece and extending in the same general direction, said side portion having spaced shoulders, and wherein there are spaced arms projecting from the bobbin on which said pivot bearings are formed, said arms being supported on the spaced shoulders of said frame and serving to locate and support the adjacent end of the bobbin.

4. An electromagnetic device as defined in claim 3 in which said frame side portion has an upper end of reduced width to provide said spaced shoulders and wherein said armature has a transverse slot through which said portion of reduced width loosely extends.

6. An electromagnetic device such as defined in claim 5 in which said bobbin is made of a thermoplastic material, and in which there is a protrusion in each of said pockets and an opening in each of said electric terminals, said protrusions being positioned to overlie said openings in said electric terminals with portions thereof in heat-flow interlocking relationship therewith.

8. An electromagnetic device comprising a magnetic frame, a magnetic pole piece attached at a first end to said frame, an electric coil for said pole piece, a magnetic armature, pivot means on said frame on which said armature is loosely pivoted for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and frame in such a position as to normally urge part of said armature against said loose pivot means and another part away from the end of said pole piece, a bobbin on which said electric coil is wound, spaced arms projecting from said bobbin and having said pivot means thereon, said frame having a side portion spaced laterally from the pole piece and extending in the same general direction, and said side portion having spaced shoulders, said spaced arms which project from the bobbin being supported on said spaced shoulders of said frame and serving to locate and support the adjacent end of the bobbin.

9. An electromagnetic device comprising a magnetic frame, a magnetic pole piece attached at a first end to said frame, an electric coil for said pole piece, a magnetic armature, pivot means on said frame on which said armature is loosely pivoted for vibratory movement toward and away from the other end of said pole piece, spring means attached between said armature and frame in such a position as to normally urge part of said armature against said loose pivot and another part away from the end of said pole piece, a bobbin on which said electric coil is wound, said bobbin being made of thermoplastic material and having pockets formed in its end which is remote from the armature, electric terminals having portions secured in said pockets, there being a protrusion in each of said pockets and an opening in each of said electric terminals, said protrusions being positioned to overlie said openings in said electric terminals with portions thereof in heat-flow interlocking relationship therewith.