US2634378A - Vibratory reed signaling device - Google Patents

Description

April 1953 v w. J. MULDOON 2,634,378

V I BRATORY REED SIGNALING DEVICE Original Filed Jan. 15, 1948 Patented Apr. 7, 1953 VIBRATORY REED SIGNALING DEVICE William J. Muldoon, Garden City, N. Y., assignor to The Wheeler Insulated Wire Company, Incorporated, Bridgeport, Conn, a corporation of Delaware Original application January 15, 1948, Serial No. 2,500. Divided and this application July '7, 1950,

Serial No. 172,594

3 Claims.

The present invention relates to signaling devices. This application is a division of my copending application Serial No. 2,500, filed January 15, 1948, now Patent No. 2,533,136, granted December 5, 1950.

In my copending application, Serial No. 570,585 filed May 17, 1946, now Patent No. 2,523,775, granted September 26, 1950, I have described an inexpensive and efilcient sound powered transducer, which is especially suitable for toy telephones, inter-oiiice units, farm telephone systems and the like. In my patent, No. 2,492,056 granted January 19, 1950, I have described a ringing unit for telephones of that general type. The. particular form of ringing units there described is especially designed for use in a toy telephone and where only a small amount of power may be required.

The object of the presentinvention is to provide a ringing unit of the general type described in my last named copending application but arranged to provide a more powerful signal.

With this object in view and other objects as will hereinafter appear, the present invention comprises the various combinations and arrangements of parts hereinafter particularly described and claimed.

In the accompanying drawing, Fig. 1 is a side elevation of a signaling unit according to the present invention; Fig. 2 is a sectional elevation on line 22 of Fig. l; Sis an enlarged detail view of the receiving transducer; Fig. 4 is an enlarged sectional view of line 44 of 1; Fig. 5 is a. detail view of thereed release; and

Fig. 6 is a wiring diagram fora signaling system. In the illustrated embodiment of the invention, the complete set for one station comprises a telephone handset (shown in the diagram of Fig. 6-) which may be of any suitable form, and a casing 12 having an opening 13 into which the ear piece of the handset may be received. The casing I2 encloses the bell and other parts of the ringing unit as will now be described.

Within the casing is a generator ringing unit comprising a vibrating reed l4, preferably in the form of a fiat resilient strip of metal anchored at one end in a bracket It. The reed I4 is coupled to the armature ll of a transducer it. Also enclosed in the casing i2 is a bell-ringing reed 23 adapted to be driven by a second transducer here designated as the receiving transducer. The

It comprises two permanent. magnets 24 and 25 in series in the magnetic circuit, with the armature 23 between them. Two pole pieces 26 and 28 are secured to the magnets and their ends are closely adjacent to the armature whereby small air gaps are formed. The armature is surrounded by a coil 30 which carries the signal current. The transducer shown in Fig. 3 also includes means for biasing the armature, which is used only on the receiving unit and will be referred to later. Referring now to the generating transducer, it has a winding 38 and its armature I! is coupled with the reed l4 through a yoke 32. As shown in Fig. 4, the yoke is attached to the armature and it has a projecting portion with a slot 42 within which the reed I4 is received. Preferably the reed is not tightly received in the slot but there is a slight looseness for reasons to be explained later. It will be seen that upon vibration of the reed I4 the armature I1 is vibrated and a signal current at the frequency of vibration is generated in the coil. It has been found that the best resonant frequency is in the neighborhood of 60 cycles per second and for this purpose the reed i preferably of spring steel having a free length of about 5 inches, a width of and a thickness of .045". A weight 36 may be mounted on the reed for a purpose to be described later.

Received within the casing is a bracket 38 which serves to mount the bell 40. Pivoted on the bracket 38 is a bell crank lever 42 having an arm 44 extending outwardly through the casing and carrying a manual operating button 45. Upon depression of the button to carry the arm 44 down through the slot 48 in the casing, the bell crank is rocked. The arm 42 carries at the top a latching pawl 53 which extends over the reed H to exert a pulling motion thereon as shown in Fig. 5. The pawl is pivoted on a ledge 52 extending horizontally from the top of the bell crank lever. The pawl is provided with a tail 54 which is adapted to engage a projection 55 extending outwardly from the bell mounting bracket 3% when the bell crank approaches the limit of its movement. The pawl i normally held in its latching position by a wire spring 53. A coil spring it connected between the bell crank and the mounting bracket normally tends to hold the bell crank in its upward position. Upon depression of the button 45, the pawl 50 flexes the reed l 3 until the tall 54 of the pawl engages the projection 58 whereupon the pawl is turned to release the reed. The reed then undergoes a sharp powerful series of vibrations and causes generation of a signal voltage in the coil through the vibration of the armature H.

The bell crank lever a2 is provided with a third arm 62 to operate a switch 54 which will be described later. The switching arrangement is such that the winding 30 of the generating unit at the transmitting station is connected to the v V winding 3% of the receiving unit at the receiving station, whereby the reed 28 of the receiving unit is vibrated synchronously with the reed [4 of the transmitting unit.

It has been found that the ringing level is improved by permitting the reed I4 to store up energy for a portion of its vibrating cycle and then discharge the energy rapidly into the magnetic system whereby a sharply peaked wave form of voltage is obtained. This results in a high acceleration of the receiver reed by which the ringing is accomplished at the receiving station. This result is accomplished by providing the small amount of looseness in the coupling 42 between the yoke 32 and the reed M, which has been previously referred to in connection with Fig. 4.

Referring now to the receiver unit, it is in general similar to the transmitter unit heretofore described. The receiver unit includes the bell 0 and the vibratory reed 26, the latter being anchored as indicated at 6B. The reed is formed at its upper end with a suitable bent portion 68 entering within the bell and carrying a hammer E0.

The reed is operated by the transducer 22, which has already been partially described in connection with Fig. 3. It has been found that greater ringing force is obtained by biasing the receiver armature to a point just short of that where the armature would strike one of the pole pieces. The reason for this will be explained presently. The means for obtaining the bias is preferably as follows: An adjusting spring 86, which is a piece of fiat metal, is secured at one end to the pole pieces and at the other end to a block 88 through which passes an adjustment screw bearing on the armature 23. By turning the adjustment screw Bil the required amount the armature can be biased toward one of the pole pieces in any suitable degree.

The reason for the improved operation with the biased armature is that the force on the armature is proportional to the product and m, where 5,. is the air gap flux due to the permanent magnets and ac is the alternating flux due to the signal current in the windings. When the armature is biased toward one side, both s and {baa are increased through one pole piece, and decreased through the other. A complete analysis shows that the effect of the increased s due to greater proximity to one pole piece considerably over balances the decreased 's due to the larger distance from the other pole piece.

It will be understood that a sufiicient overall air gap must always be provided to take care of minimum economical tolerances and to insure against large performance variations and critical adjustment of the armature in the gap. The biasing of the armature as herein described shortens one of the air gaps and the resultant effect is not unlike what would be obtained if the unit were originally constructed with air gaps of the diminished amount on both sides of the armature. However, it would be difiicult to construct such a unit and to adjust the armature for optimum performance. The biasing arrangement herein shown allows the armature to be adjusted to the optimum setting; in other words, for a given overall air gap, a maximum ringing force is obtained by biasing the armature toward one side.

Another feature of importance is that of using a relatively massive vibrating element for the generator and a relatively light one for the receiver. Thus the generating reed has the weight 35, which contributes to the mass of the vibrating system, while the mass of the receiving system is preferably less. Since the vibrating systems of the generator and receiver are to resonate at the same frequency, this requires that the elastance of generating reed it be greater than that of the receiving reed 2G; in other words, the reed I4 is necessarily stiffer than the read Zil. In such a case the energy is approximately proportional to the mass; accordingly, the generating reed can store a large amount of energy, While the receiving reed does not withdraw much energy from the system. Thus both reeds can vibrate for a longer time than if they were of the same characteristics.

The preferred wiring diagram is shown in Fig. 6. The switch 64 which is operated by the arm 62 of the bell crank has a movable contact normally closed on a fixed contact 9 3 which is connected in series with the movable contact 96 of a hook switch. The contact 92 is adapted to close on a contact 97 when the button 46 is depressed. The contact 96 is closed on a contact 88 when the handset 99 is supported by the easing l2 and is adapted to close on the contact its when the handset is removed. One line H32 is connected to the windings 30 and 3B and to the handset. The other ends of the windings 3B and 3B are connected to the contacts 98 and 91 respectively. The contact [G0 is connected with the handset and the contact 92 is connected with the line I06.

Upon depression of the button 66, the generator winding 38' is connected to the line by reason of the closure of contact 92 on 9?. Contacts $2 and 91 remain closed during the vibration of the reed [4. At the receiving end, however, the winding 30 is connected to the line through contacts 98, 95 and 94, 92. The proper'windings of the two units are thus connected together, whereby the bell is caused to ring at the receiving station by reason of vibration of the reed 20. Upon lifting of the handsets 99 at both ends, both hook switches are closed at 96, I60, and since contact 92 is then closed on 95, the handsets are connected together through the lines for ordinary telephonic conversation.

It will be seen that the construction is in gen.- eral similar to that used in the ringing device described in Patent No. 2,492,056. However, it difiers in some respects. Among other things, it has been found desirable to use separate transmitting and receiving units since both can be then constructed for maximum ringing en: ergy, as heretofore described. With the apparatus herein described, it has been found possible to obtain a substantial volume of ringing with only the energy that can be introduced by operation of the button 46. As heretofore stated, the unit is particularly suitable for point-to-point communication in batteryless systems and is found particularly useful in farm units where house-to-barn or house-to-field communication is desired.

I claim:

1. A transducer comprising two permanent magnets in series, an armature secured at one end between the magnets, pole pieces extending from opposite ends of the magnets into proximity with the free end of the armature to form an air gap between the armature and the tip of each pole piece, a coil wound about the armature, and spring means for biasing the armature toward one or the pole pieces to cause it to vibrate about an axis which is relatively nearer one of the pole pieces.

2. A transducer comprising two permanent magnets in series, an armature secured at one end between the magnets, pole pieces extending from opposite ends of the magnets into proximity with the free end of the armature to form an air gap between the armature and the tip of each pole piece, a coil Wound about the armature, and means for biasing the armature toward one of the pole pieces, said means comprising a spring member, and a screw carried by the spring member and bearing against the armature to cause it to vibrate about an axis which is relatively nearer one of the pole pieces.

3. A transducer comprising two permanent magnets in series, an armature secured at one end between the magnets, pole pieces extending from opposite ends of the magnets into proximity with the free end of the armature to form an air gap between the armature and the tip of each pole piece, the armature extending outwardly beyond the pole pieces, acoil surrounding the armature, and means for biasing the armature toward one of the pole pieces, said means including a leaf spring overlying the outwardly extending portion of the armature, and a connection between said spring and the armature, to cause it to vibrate about an axis which is relatively nearer one of the pole pieces.

WILLIAM J. MULDOON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,306,068 Lewis Dec. 22, 1942 2,328,831 Mendelson Sept. 7, 1943 2,433,740 Collins Dec. 30, 1947

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