US2831937A - Vibratory reed device and system employing the same - Google Patents

Description

April 22, 1958 w.A P. FOSTER ETAL 2,831,937

VIERATORY REED DEVICE AND SYSTEM EMPLOYING THE SAME Filed Feb. 17, 1954 United States Patent() VIBRATORY REED DEVICE AND SYSTEM EMPLOYING THE SAME William P. Foster, Lansdowne, Pa., and Charles A. Richardson, Linwood, N. J., assignorsto James G. Biddle Co., Philadelphia, Pa., a corporation of Pennsylvania Application February 17, 1954, Serial No. 410,857

3 Claims. (Cl. 200`91) This invention relates to vibratory reed devices and to systems employing a plurality of such devices tuned to different frequencies. Whilev the invention is applicable generally to such devices and systems, it is especially applicable to resonant reed relays and systems employing the same. Accordingly, the invention will be described herein with reference to such specific application. However, it is to be understood that in the broader aspect of the invention the resonant reed relay and relay system are to be regarded only as exemplary of vibratory reed devices and systems.

A resonant reed relay, like other vibratory reed devices, commonly employs at least one cantilever type resonant reed and an associated driving means and, preferably, such relay has `a primary reed and a secondary reed extending in parallel relation from a common mount. The resonant frequency of vibration `is directly proportional to the thickness of the reed and is inversely proportional to the square of the free length of the reed.

In prior constructionsof resonant reed relays the driving point has been located at the tip of the reed because the sensitivity is greatest at that point. In systems in which such relays are commonly employed, onepractice t has been to maintain the lengths of the reeds constant and ly requires increased input. This objection is partiallyy met by operating thereeds at reducedamplitude, and partially by increasing the magnetic bias which increases the driving force. However, if the input current is to'be maintained at a constant level, the necessary adjustments of amplitude and bias cause manufacturing difficulties.

One object of the present invention is to overcome the above-mentioned objection.

ing at the highest frequency, and by tuning the other relays of the series to lower frequencies by increasing the reed lengths while maintaining the driving point at the same distance from the reed mount. according to the present invention the relays are char- `acterized in that the reeds of the respective relays are of the same width and thickness but of different free lengths to operate at different frequencies within a predetermined frequency range, and the driving means of all of the relays are located at the same point along the free lengths of the reeds.

A further feature of the present invention is that the contact gap spacing is"approximately constant for allk relays in a series, and the contact gap is located at the same distance from the reed mount as the driving point.

Thus, at the critical contact-making instant, the `reed amplitude at the driving point is` approximately constant for This is achieved by locating the driving point at the reed tip only inthe relay operat- Thus, in a system all relays of a series. It has been found that this has tho effect of providing substantially uniform response characteristics in the series of relays.l

Another object of the present invention is to provide an improved vibratory reed device which is highly etlicient in operation and which has desirable operating characteristics.

A further object ofthe invention is to provide a resonant reed relay which is of simple compact construction, and which is economical to manufacture and easy to adjust. j

Other objects and features of the invention will be apparent from the following detailed description with reference to the accompanying drawings, in which:

Fig. 1 is an elevational view of a resonant reed relay constructed according to the present invention, with the casing or housing broken away to show the parts, and with certain elements broken away and shown in section for the purpose of illustration;

Fig. 2 is an elevational View taken from the right sidev of Fig. 1, with the casing broken away;

Fig. 3 is a cross-sectional view taken on line 3 3 of Fig. 1;

Fig. 4 is a longitudinal sectional view taken centrally through the device on line 4-4 of Fig. l;

Fig. 5 isa bottom view of the device;

Fig. 6 is a cross-sectional view taken on line 6-6 of Fig. l; n

Fig. 7 is a perspective view of the assembly which is contained within the casing; l

Fig. 8 is a graph showing the representative response curve fora relay constructed according to the invention; and f Fig. 9 is a diagrammatic illustration of a frequency responsive relay system according to the present invention.

Referring to the construction of a preferred embodiment of a resonant reed relay according to the present invention, as illustrated in Figs. l to 7, there is provided an elongate metal casing or housing 10 which is preferably of cylindrical shape and which is closed at its upper end and has an opening at its lower end to receive a closure member 11 which is also preferably formed of metal. The relay assembly containedwithin the casing 10 is supported as a unit by the closure member 11 which thus serves a dual purpose, i. e. both as a closuremeans for the casing and also as a support for the internal relay assembly.

In the preferred form illustrated, the relay assembly comprises a generally U-shaped support 12, also preferably formed of metal, having a pair of spaced arms 13 and 14 extending upward from the bottom portion 15 whichhas an 'extension 16 and is provided with a central threaded passage 17 to receive an attachment screw 18. As may be seen in Fig. 4, the closure membery 11 has a central aperture 19 to receive the screw 18, the aperture preferably being shaped to provide counter-sinking of the screw head which may be sealed by solder 20 afterv the device'has been assembled. The supported assembly further comprises a generally U-shaped reed structure formed of magnetic material, e. g. steel,`and having a base 21 and a pair of reeds 22 and 23extending upward from the base in substantially parallel relation to one another. The generally U-shaped reed structure is disposed at right angles to the U-shaped support 12 withv the base 21 interposed between the arms 13 and 14 of the support. As may be seen in Figs. l, 2 and 4, the

apertures ..25 to ,ac ccmrncdate the screws, the apertures being enlarged at their outer portions to accommodate insulating washers 26. The screws 24 threadedly engage apertures in the base 21 of the U-shaped reed structure. An insulating sheet V26a is interposed between base 21 and arm 14.

Referring more particularly to the reed structure, the base 21 is in the form of a metal block, and the reeds 22 and 23 are in the form of at metallic strips secured to the base 21 as by silver soldering or brazing. The reed 22 is the primary reed and it carries an electrical contact l27 secured thereto as by spot welding. The reed 23 is a secondary reed which serves simply to provide a balanced twin reed structure. A dummy contact 28 is secured to reed 23, as by spot welding, to better balance the twin reed structure. Associated with the primary reed 22 is a resilient contact arm 29 carrying an electrical contact 30 which is cooperable with the contact 27. Arm 29 has a lateral extension 31 by which it is mounted on arm 13 of the rigid support 12 by means of screws 32, being insulated from the metal support by insulating strips 33 and 34 (see Fig. 6). Reed 22 is electrically connected to one of a number of contact pins 35 through a connection 36. The contact pins 35 are insulated from the metallic closure member 11 by extending through fused glass seals 37. The contact arm 29 is also connected to one of the pins 35 through a connection 38. The pins 35 are similar to the projecting contact pins of an electron tube, the device being adapted to be plugged into a socket in the manner of an electron tube. The contacts 27 and 30 serve to control a controlled circuit, in response to actuation of the reed 22 by the driving means now to be described.

The driving means comprises an electrical coil 39 which is interposed between the reeds 22 and 23 and is so oriented that its axis lies in the direction of vibration of the reeds. The coil is formed of insulated wire wound on an insulating spool 40 to provide a coil unit which is held by the arms 13 and 14 of the rigid support 12. To this end the arms 13 and 14 are machined to provide recesses 41 and 42 in order that the coil unit may be inserted and embraced by the support arms. The coil unit is held securely in place by means of screws 43 and 44 on opposite sides of the support arms with their heads engaging the opposed faces of the coil spool 40. Within the coil spool is a permanent magnet coil 45 which not only provides a magnetic core for the coil but is utilized during tuning as hereinafter described. ln the form i1- lustrated, the permanent magnet core is of square crosssectional shape and it lits snugly within the spool 40 so as u to remain stationary therein. The ends of the coil 39 are connected respectively to two of the contact pins 35 by means of conductors 46 and 47.

It will be seen from the foregoing description that the entire internal structure of the relay is assembled as a unit with all of the component elements mounted on the common rigid support 12 which in turn is secured to and supported by the closure member 11. As may be seen in Figs. l, 2 and 4, the lower end of the metallic casing 10 is formed to provide an internal shoulder 48 to seat the closure member 11, and the member 11 is held within the lower end of the shell-like casing by means of a ring of solder 49.

In constructing and assembling the above-described resonant reed relay, the support 12 is first assembled to the member 11. The reed block 21 and the reeds 22 and 23 are assembled by silver soldering or brazing, after which the reed assembly is heat treated in order to provide optimum characteristics of the steel. The reed contacts are then spot welded to the reeds at the proper location, and the assembly is tuned to a predetermined frequency in a special Xture designed to vibrate the block. The preliminary adjustment is made by shortening the reed length, and the nal adjustment is made by weighting the reed tips slightly, using solder. The coil and vmagnet assembly comprising coil 39 and magnet 45 is then charged to a predetermined level and is assembled to the support 12. The reed assembly is then mounted on the support 12, and the contact arm 29 is also mounted thereon. At this point in the assembly the contact gap is adjusted by bending the arm 29 to provide a predetermined gap spacing between the contacts 27 and 30. The abovedescribed electrical connections to the contact pins are then made. At this point the magnet 45 is demagnetized by applying an alternating current of suiiicient magnitude to the coil 39. This reduces the magnetic ux so that the reed frequency increases to a final predetermined value which is somewhat different than the value predetermined for the original reed tuning. Finally, the assembly is inserted in the casing and the latter is hermetically sealed by applying the ring of solder 49.

Figure 8 shows a representative response curve for a relay constructed according to this invention. In order to determine this curve, an A. C. signal is applied to the driving coil and is maintained at some arbitrary level, and its frequency is changed from outside the band toward the nominal frequency. An ohmmeter, or suitable signal device, is used to determine when the contacts close. At signal levels within a certain range there will be two contact close points; one as the frequency is varied upward toward the nominal frequency, and the second as the frequency is varied downward toward the nominal frequency. In each case the contacts must be open as the frequency starts to sweep. This procedure is repeated for different signal levels to determine the points of the curve.

Fig. 9 shows a frequency selective relay system ernploying a series of resonant reed relays constructed according to the present invention. In the illustrated system the number of relays chosen for the purpose of illustration was arbitrarily selected as four, the relays being designated by reference numerals 50 to 53. The relays are diagrammatically illustrated, and it is to be understood that they are of the character illustrated in Figs. 1 to 7 and described above. The relays are characterized in certain novel respects which will now be explained.

In earlier designs of reed relays the driving point has been placed at the tip of the reeds because the sensitivity is greatest at this point. In a series of relays having different frequencies this practice results in diiferent characteristics among the relays in the series unless special precautions are taken. Where frequency is increased by making the reeds thicker, the driving force required to produce the same amplitude is greater. This is partially oifset by operating the reeds at reduced amplitude, and partially by increasing the magnetic bias which increases the driving force. If the driving coil input current is to be maintained at a constant level the necessary adjustments of amplitude and bias introduce manufacturing difficulties.

According to this invention, the driving point is at the tip of the reeds only for the highest frequency in the series. As frequency is reduced by increasing reed lengths while maintaining the width and thickness constant, the driving point remains fixed and is, therefore, applied at some fraction of the reed length, which becomes increasingly smaller as the reed length increases.

A further feature of the present invention lies in the contact gap spacing, which is designed to be constant for all relays in a series. This contact gap is located at the same distance from the reed clamp point as the driving point. Thus, at the critical contact making instant the reed amplitude at the driving point is constant for all relays of a series. It has been found that this has the effect of providing a substantial improvement in the uniformity of the response curve characteristics of a series of relays covering a range of frequencies as great as 4 to l in the lower audio frequency spectrum.

f A further feature of this invention is the arrangement ofthe driving means and the support for it and the reeds.

In a reed relay as small as those contemplated in this invention, driving at a point isnot possible in the strict sense of the word. The best that can be done is t0 concentrate the driving forces within a small area about the desired point. EvenL when this is done there is an appreciable distributed driving vefect because of the physical size of the drive coil and the close spacing of the twin reeds. Two distinct driving effects are present in all the known driving methods. The first is the reaction between the drive coil and the reeds. The second is the reaction of one reed on its twin. In some types of drive the reeds repel each other while being attracted toward a central driving system. For example, if the pole of a permanent magnet is placed between the reeds and acoil is wound around the reeds, the increase in ux that causes the reeds to be attracted to the permanent magnet also causes the reeds to repel each other. This results in a loss of etliciency and reduced discrimination between response at the design frequency and response at half the design frequency.

The drive employed in this invention makes use of ar coil wound around the permanent magnet and oriented between the reeds in such a way that an increase in ux causes an attraction of the reeds toward the center, and the reeds are so polarized that they attract each other. Thus, being in phase, the two effects add and give increased eiciency and better discrimination between response at the design frequency and response at half the design frequency. Because the coil is wound around the magnet it is also possible to magnetize using the coil. Thus, the magnet strength may be adjusted by applying appropriate signals to the external terminals. Since frequency can be adjusted by magnetic field intensity it is possible to adjust frequency after the relay is assembled in its casing and sealed. The reeds are tuned to some frequency about a half percent above the nominal frequency. The relay may then be assembled and sealed after which a magnetizing signal isapplied tothe coil by discharging a capacitor into it or by other means of applying a short, high intensity current pulse. The midband frequency of the relay is measured by locating the lowest point of the response curve (see Fig. 8). This measurement must be made without increasing the applied signal more than necessary. The frequency will be lowered as a result of magnetizing. An alternating signal of proper level is then applied in order to demagnetize the magnet and bring the frequency back-up to its nominal value. The determination of the proper demagnetizing signal is done experimentally in steps of increasing level similar tothe manner in which a precision resistor is adjusted by trimming wire.

While the invention has been described with particular reference to the drawing disclosure, it is not limited thereto but contemplates such modifications and further embodiments as may occur to those skilled in the art.

We claim:

1. In a vibratory reed device, a stationary mounting means, a primary reed and a secondary reed secured to and extending from said mounting means in opposed spaced relation to one another, a straight magnetic core permanently magnetized to provide a magnetic bias and extending transversely between said reeds, a coil wound about said core whereby magnetizing currents may superimpose a fluctuating magnetic field on the magnetic bias,

and means tixedly mounting said coil and core in relation to said reeds.

2. A resonant reed relay, comprising an elongate metal casing or housing having an opening at one end, a closure member at the said end of the casing, Support means within said casing secured to said member, a reed-supporting block within said casing secured to saidsupport means, a primary reed and a secondary reed within said casing extending from said blockin opposed spaced relation to one another,.a contact on said primary reed, a fixed arm secured to said support means and disposed adjacent to said primary reed within said casing, a contact arm cooperable with said rst contact, a straight magnetic core permanently rnagnetized to provide a magnetic bias vand extending ytransversely between said reeds, a coil wound about said core whereby magnetizing currents may superimpose a fluctuating magnetic field on the magnetic bias, andmeans xedly mounting said corel and core on said support means.

3. A resonant reed relay, comprising an elongate metal casing or housing having an opening at one end, a closure member at the said end of the casing, support means within said casing secured to said member, a reed-supporting block within said casing secured to said support means, a primary reed and a secondary reed within said casing extending from said block in opposed spaced relation to one another, contacts controlled by said primary reed, a straight magnetic core permanently magnetized to provide a magnetic bias and extending transversely between said reeds, a coil wound about said core whereby magnetizing currents may superimpose a uctuating magnetic field on the magnetic bias, and means fixedly mounting said coil and core on said support means.

ReferencesCited in the tile of this patent `UNITED STATES PATENTS Great Britain Apr. 12, 1950 UNITED STATES PATENT @ENCE CERTIFICATE 0F CORBCTN Pimm; NQ.- 2,831,937 April 22?, 1958 v Willian P* Fester It i hereby certified that error appears in Ehe prmed specification of the above numbered patent requiring correction and that the said Leters Patent should read as corrected below.

.Column lima 2l, before "rmf insert a on said 4 lnef 26,; car "core" read `--f'- cnil Signed' r-md sealed this 5th .day of August l9`58 (SEAL) Angst:

KARL H, AXLINE l y ROBERT C. WATSN Attesting Ofcer y 'I Cammissioner of Patents UNITED STATES PATENT @FFME CERTIFCATE F CRRECN mmm Nm 2,831,937 April 2z, w58

Willie-.m Pm Fuster ai: alf It ir hereby cer-bifd 'that error appaars in me printed specaton Gf. the above numbeed patent requiring correctian and that the said Liiers Patent should read yas corrected blow.

.001mm lilik? 2l, before "am" insert sa on said line Ef im "core" e'ad ,.L. mi; .ma

Signed' and saled this 5th day of August lQ (SEAL) ttst:

KARL 'H1 AXLINE l HBERT WA'N Attesting Ocer Cwmmissianer @E Fammi;

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