US3162850A - Alternating current bell - Google Patents

Description

Dec. 22, 1964 F. E. WELD 3,162,850

ALTERNATING CURRENT BELL Filed Sept. 21, 1961 2 Sheets-Sheet 1 FIG. I 9

JNVENTOR. FOSTER E. WE LD 30 U ATT RNEYS Dec. 22, 1964 F. E. WELD 3,162,850 ALTERNATING CURRENT BELL Filed Sept. 21, 1961 2 Sheets-Sheet 2 FIG. 3

5| cycle i l V T :08 i I FIG. 4 T? Current 2s Y 29 I 78 INVENTOR 68 FOSTER E, WELD FIG. 5

ATTORNEYS United States Patent 3,162,859 ALTERNATENG (IURRENT BELL Foster E. Weld, Newton Highlands, Mass assignor, by mesne assignments, to E. W. Bliss Company, Canton, ()hio, a corporation of Delaware Fiied Sept. 21, 1361, Ser. No. 139,652 2 Ciaims. (Cl. 349-699) The present invention relates generally to bells of the type having a vibrating striker for actuation by alternating current, and more particularly to a bell that strikes at half the frequency of the energizing current without the use of current-interrupting electrical contacts.

An object of this invention is to provide a bell adapted for use in installations including fire alarms, industrial signal application, program dismissal systems in schools and other installations where alternating current power is supplied.

Hitherto, one of the means used to achieve vibration of the striker in alternating current bells has consisted of make and break contact elements for interruption of the electrical current supplied to a striker actuating solenoid. These contact elements are a mapor source of difficulty in maintenance because of imperfect electrical connection between the elements caused by dint or the like, corrosion and contact wear. In many applications bells are subjected either to the weather or to other conditions whereby water, smoke, corrosive gases and foreign matter may reach the contact elements and result in faulty operation. Also, even under ideal conditions the opening and closing of electrical contact elements produces radio and television reception interference. Accordingly, a second object of this invention is to provide a bell which does not depend for its operation upon electrical contact elements.

A common alternating current power frequency is 60 cycles per second. Hitherto, most bells adapted for operation at this frequency have been of a type producing one heat per cycle with gong shells of from about four to ten inches in diameter. This frequency is con sidered too great for a clear, pleasant-sounding ring. Accordingly, a third object of this invention is to provide a bell adapted for operation at a given energizing frequency, but striking the gong at a lower frequency at which a more satisfactory ring is obtained.

A further object is to provide a bell mechanism of a type characterized by a high speed of response in starting and stopping upon the initiation and interruption of the actuating current.

With the foregoing and other objects hereinafter described in view, a feature of this invention resides in the provision of a striking mechanism actuated by an electromagnet in association with a permanent magnet to produce a gong striking frequency equal to half the alternating current frequency applied.

Another object of the invention is the provision of a bell mechanism of the type described including a readily and cheaply fabricated fixed assembly portion of a magnetic circuit, said fixed assembly including a coil or solenoid, a polarizing permanent magnet and pole pieces.

Another feature resides in the provision of a pair of magnetic circuits having a common leg including the oscillating striker mechanism.

A further feature resides in the provision of a bell having the foregoing features while at the same time having the actuating mechanism totally disposed within the gong in a weather-proof assembly.

A still further feature resides in the provision of ad justment means for the striker mechanism to insure a quick response upon the initiation and interruption of energizing current and to control the force of striking the "ice gong to insure a pleasing tone with the desired distance carrying power.

Other features of the invention reside in certain details of construction, assemblies and arrangements of the parts and modes of operation that will be more clearly understood from the following description of a preferred em ibodiment, having reference to the appended drawings in which:

FIG. 1 is a central vertical longitudinal section;

FIG. 2 is a vertical radial section taken on line 2-2 FIG. 1;

FIG. 3 is a horizontal longitudinal section taken on line 33 of FIG. 1 rotated counterclockwise from that of FIG. 1;

FIG. 4 is a composite time curve and schematic diagram illustrating the relationship between the actuating alternating current frequency and the gong striking frequency; and

FIG. 5 is a fragmentary View similar to FIG. 1 illustrating a modification of striker actuating means.

Referring to the drawings, there is provided a cast metal base 12 which is of dished shape and provided with a boss 14 to support a dish shaped metal gong 16. The base 12 is step-shaped to provide annular shoulders 18 and 21? between which there is disposed a cylindrical portion 22. A gong mounting screw 24 is threaded into a hole in the boss 14 which lies in the central axis of the base. This screw is provided with a flanged eccentric bushing 26 and a resilient sealing washer 23. The bushing 26 has an annular surface 29 eccentric to the screw axis which fits in a circular hole through and coaxial with the gong 16. This arrangement permits lateral adjustment of the axis of the gong in relation to the axis of the base while maintaining these axes in parallel relationship. This adjustment changes the space between the gong and a non-magnetic striker rod 30 which is suported within the cylindrical portion 22 of the base and constrained to move in a direction transversely of the axis of the base and gong. After adjustment by rotation of the bushing 26, the screw 24 may be tightened to clamp the gong in position whereupon the washer 23 provides a weather tight seal for the opening through the gong.

The base 12 has a flange portion 32 having an annular lip 34- extending rearwardly of the gong and an inwardly-facing shoulder 36 to provide a seat for an annular gasket 38. The base, in conjunction with the gasket 38, is adapted for sealed mounting upon a cast junction box 4i) having a tapped hole 42 for a conventional electrical cable or conduit connection. The box 40 is provided with a plurality of inwardly-projecting integral bosses forming screw suports 44 each of which is disposed parallel to the central axis of the box 4% and bored and tapped to receive a mounting screw 46. The screws 46 secure a flat circular metal receptacle mounting plate 48 in a plane at right angles to the central axis of the box. The plate 48 supports an insulating prong receptacle 5% in position to receive a pair of prongs 52 supported by the base 12 and extneding rearwardly of the gong. It will be understood that a pair of wires (not illustrated) is led from an external power source to the box 40 and connected with receptacle Si in a conventional manner to provide a circuit for the bell through the prongs 52. The prongs are inserted in the receptacle 50 as the base 12 is placed in position upon the box 40. The base is held securely on the box 443 by a pair of clamps 54 (FIG, 3) received over the flange portion 32 of the base and an annular flange 56 on the box 40, the flange 56 having a rearwardly-extending sloping surface matching a surface of the clamps 54-. A pair of mounting screws 53 provided with split lock washers 60 are threaded through holes in has a central integral portion 92 of larger diameter.

' associated magnetic actuating parts are shown secured to the base 12 by a pair of bolts 62 preferably of nonmagnetic material. The heads ofthese bolts are received in recesses in the base 12 with resilient sealing Washers 6 4 which provide a weather-tight seal for the holes in the base. The base is provided with a pair of bosses 66 projecting rearwardly of the gong against one of which is secured by a form-magnetic pole piece 68. An electromagnet coil 78 is received over one ofthe bolts 62 and against this pole piece. A pair of permanent magnetic slugs 72, preferably provided with circular metallic backing plates 73 in the case of ceramic slugs, and preferably ferro-magnetic cylindrical spacers 74 are placed over the other bolt 62. The axial length of the coil 7% is preterably equal to the sum of the axial lengths of the slugs '72, the backing plates '73 and the spacers '74. It will be understood that while two magnetic slugs are illustrated, fewer ora greater number of slugs may be assembled on the bolt, depending upon the residual magnetic strength of the slugs employed and the size of the gong to be used. To facilitate this modification, each of the spacers 74 is preferably .of the same axial thickness as one individual slug.

A second pole piece 78 which is preferably substantially identical to the pole piece 68 is received over the bolts 62. Insulation plates 8% spaced by suitable washers 82 are placed over the pole piece 78 and are provided with holes through which the bolts e2 are passed. Nuts 84 are threaded on the bolts s2 and tightened to form a rigid assembly. The plates 3% thereby form clamps for tangs 86 integral with and extending at right angles from the prongs 52 (FIG. 1). The tangs 86 project radially outwardly between the plates 8% (FIG. 1) to provide solder lugs, each lug being connected by a wire (not shown) to one terminal of the electromagnct 7%. The pole piece 7?; which is provided with a central opening 88 (PEG. 2) incycle, that is, only once every two cycles.

d springs preferably having identical'spring' characteristics and being opposed to one another. When the bell is in the unactuated condition, the initial compression of each spring is added to the attraction which the permanent magnetic field exerts on the respectiveadjacent plate 94, and the sums of these two forces represent equal and opposed rcsultants at the top and bottom of the rod.

A further feature of the foregoing adjustment is that the position of the striker rod is arranged to bring one of the plates 94 slightly closer to its associated projections ht? than in the case of the other plate. With the foregoing adjustments, the bell is in condition for actuation. FIG. 4 illustrates the currentin the elcctromagnet 70 as a function of time when an alternating potential is applied between the prongs 52. In the lower part of this figure the striker rod Ellis shown schematically in corresponding relation to the gong 16 at time intervals of one-fourth cycle. It will be noted that the gong is struck only at the alternate positive. peaks of the current This operation will next'be explained in further detail.

As viewed in FIGS. 1 and 2, the upper plate 94 is is adjusted to be closer to-its associated pole projections 90 than'is the lower plate 94, assuming'the current is 0E. The operation is as shown'in H6. 4 if current is applied at time t=G and if the first half-cycle of current induces a polarity in the electromagnet 7%) which aids the permanent magnetic field in attracting the upper plate toward sulates the components of the magnetic circuits from the prongs 52 and tangs 86.

The pole pieces 6% and 7d are each provided with integral fiat axially-extending right angle projections t which face one another in pairs. Space'is provided hetween'these projections for the striker rod 36 which A pair of flat circular ferromagnetic plates 94 are slidingly received against the shoulders of the portion 2 and extend radially of the striker rod 39 so that the surfaces of the plates are in opposed relationship tothe projections 96 of the pole pieces.

To mount reciprocably therod 3t threaded plugs )6 and 98 arereceived in tapped holes in the cylindrical portion 22 of the base 12. The plug 93 has a full-length drilled axial hole to receive the striking end of the rod 39. A portion of this hole is relieved to receive a closely fitted bushing 1% having a low coefiicient of friction with the rod 3! slidable therein. The plug 96 has a blind axial hole to receive the opposite end of the rod it this hole being similarly relieved to receive a bushing 1&2 for the rod. As shown for plug 96, these plugs have a screw slot 1 34- for radial adjustment of the plug.

The plugs as and 98 have inwardly projecting shouldered extensions to receive tapered compression springs 1556 bearing at their opposite ends against the plates 5 4.

In operation, initial adjustments of the plugs are made to control both the axial distance between the plugs and the axial distance of each plugr'rorn tbe central axis of the screw'fi l. It will be understood that this latter axis is also the central axis of the base 12 and of the magnetic circuit defined by the pole pieces. it will also be understood that the foregoing adjustment controls the initial com ression of each of the springs the, these the pole projection. In the first half-cycle the striker,

alreadybeingclose to the gong, strikes it and the upper plate M strikes or projections 9t The current in the electroniagnet ill thenbegins to decrease and the lower spring 1% begins to move the striker upwardly. As the upper plate 94 moves further from the upper projections 96 the air gap is increased,

reaches its closest position to the upper thus increasing the magnetic reluctance of the path through this plate and further decreasing the attractive force of the magnetic fields on it. In the secondhalf of-the first cycle the current reverses and produces a magnetic field in opposition to the permanent magnet, thus still further reducing the total field acting uponrthe upper plate 94.

At the beginning of the second cycle, the current again produces an aiding magnetic field, but at that time the upper plate he is further from the projections 96 than it was in the first cycle, and accordingly the ficlds I have a relatively smaller eflect on that plate. On the other hand, the lower plate @4 is relatively closer to its projections and the aiding fields draw it upwardly.

conclusion of one-fourth of the third cycle. the :striker again strikes the gong 16' Referring to PlGURE 5, there is illustrated another embodiment which utilizes only one armature or circular plate 94, and modified pole pieces 68 and '73. Y The bell according to this embodiment is also self-starting and, in addition, has increased plunger travel for increased sound output. The absence of the lower armature and the use of modified polerpieces r58, 73' substantially reduce the effectiveness of the attractive forces operating on the lower end of the striker rod 36 and permits long striker travel without altering the air gap between the upper plate $4 (FIGURE 1) and the upper ends of pole pieces 6,8, 73.

As showniin FIGURE 5, the lower axially-extending projections 9% from each of the pole pieces as, 73 have been omitted to form pole pieces 63, 78. Accordingly, pole pieces 68', 78' have each only one axially-extending projection 96 which corresponds to the upper projection 96 shown in FIGURE 1. It should be understood that where upper and lower springs are similar, the central I! 3 portion 92 of striker rod 30 will be extended a distance equal to the thickness of the absent plate 94. The lower spring 186 arranged in FIGURE 5 to bear against the lower shoulder of central portion 92, while the upper spring 106 (FIGURE 1) bears against upper plate 94. The relationship of upper plate 94 to the upper pair of projections 90 is maintained as in the embodiment of FIGURES 1-3. The embodiment utilizing one plate 94 and the modified pole pieces 68', 78 also provides a bell whose operation is substantially as described for the embodiment utilizing two plates 94 and pole pieces 68, 78.

It will be appreciated that the spring rates are chosen in relation to the size of the magnetic fields so that sufficientamplitude of motion of the striker and the plates 94 is obtained. Spring tension and the weight of the moving parts are chosen to be such that the natural frequency of vibration of the moving parts is 30 cycles per second, for best openation of the bell.

It will also be seen that the striking frequency will be thirty strokes per second if the applied current is sixty cycles per second which produces a pleasing tone in contrast with a sixty stroke rate.

The described embodiment is protected from the weather and since no electrical contacts are required, no interference to radio or television reception will occur and the bell will give dependable performance with a minimum of maintenance.

It will be understood that numerous variations in the described structure of the bell may be provided to adapt the mechanism to gongs of varying diameter and to alter the structure and relationships of the pants for various purposes consistently with the modes of operation and teachings herein described. These adaptations and variations may be carried out without departing from the spirit and scope of this invention.

What is claimed is:

1. In an alternating current bell, in combination: a base; gong means mounted on said base; a striker rod resiliently mounted on said base for oscillatory movement for striking said gong, said striker rod having at least one plate secured thereto and movable therewith, said plate extending outwardly from said striker rod; magnetic circuit means mounted on said base for imparting said oscillatory movement to said striker rod, including an electromagnet, a permanent magnet, and two pole elements; each said pole element comprising a vertical element and at least one arm horizontally extending from an end thereof, said pole elements secured to said base with said horizontal arms in spaced apart and opposed relation to each other; said electromagnet and permanent magnet secured to said base and located substantially equally between said poles; opposed striker rod biasing spring means for urging said rod to a normal position with said plate spaced from said arms; whereby when said magnetic circuit means is energized by alternating current said striker rod means will oscillate and strike said gong at a frequency substantially below that of the ternating current applied to energize said magnetic circuit means.

2. In an alternating current bell as set forth in claim 1, wherein the bias of said spring means and mass of said rod and plate is selected to tune the same to half the frequency of said alternating current.

References Cited in the file of this patent UNITED STATES PATENTS 1,134,758 North Apr. 6, 1915 1,815,853 Lake July 21, 1931 1,839,342 Richmond June 5, 1932 2,205,189 Edwards lune 18, 1940 2,220,979 Swanson Nov. 12, 1940 2,463,380 Harris Mar. 1, 1949 2,683,871 Meleski July 13, 1954 2,854,660 Best et a1 Sept. 30, 1958

Claims (1)

1. IN AN ALTERNATING CURRENT BELL, IN COMBINATION: A BASE; GONG MEANS MOUNTED ON SAID BASE; A STRIKER ROD RESILIENTLY MOUNTED ON SAID BASE FOR OSCILLATORY MOVEMENT FOR STRIKING SAID GONG, SAID STRIKER ROD HAVING AT LEAST ONE PLATE SECURED THERETO AND MOVABLE THEREWITH, SAID PLATE EXTENDING OUTWARDLY FROM SAID STRIKER ROD; MAGNETIC CIRCUIT MEANS MOUNTED ON SAID BASE FOR IMPARTING SAID OSCILLATORY MOVEMENT TO SAID STRIKER ROD, INCLUDING AN ELECTROMAGNET, A PERMANENT MAGNET, AND TWO POLE ELEMENTS; EACH SAID POLE ELEMENT COMPRISING A VERTICAL ELEMENT AND AT LEAST ONE ARM HORIZONTALLY EXTENDING FROM AN END THEREOF, SAID POLE ELEMENTS SECURED TO SAID BASE WITH SAID HORIZONTAL ARMS IN SPACED APART AND OPPOSED RELATION TO EACH OTHER; SAID ELECTROMAGNET AND PERMANENT MAGNET SECURED TO SAID BASE AND LOCATED SUBSTANTIALLY EQUALLY BETWEEN SAID POLES; OPPOSED STRIKER ROD BIASING SPRING MEANS FOR URGING SAID ROD TO A NORMAL POSITION WITH SAID PLATE SPACED FROM SAID ARMS; WHEREBY WHEN SAID MAGNETIC CIRCUIT MEANS IS ENERGIZED BY ALTERNATING CURRENT SAID STRIKER ROD MEANS WILL OSCILLATE AND STRIKE SAID GONG AT A FREQUENCY SUBSTANTIALLY BELOW THAT OF THE ALTERNATING CURRENT APPLIED TO ENERGIZE SAID MAGNETIC CIRCUIT MEANS.

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