US2950368A - Resonant reed relay - Google Patents

Description

w. J. LONDELL, JR, 2,950,368 RESONANT REED RELAY Aug. 23, 1960 Filed Nov. 4, 1957 INVENTOR. WILLIAM J. LONDELL, JR.

LENGTH v QTTO RNEY United States Patent RESONANT REED RELAY William J. Londell, In, North Plainfield, N.J., assignor to Gulton Industries, Inc., Metuchen, N.J., a corporation of New Jersey Filed Nov. 4, 1957, Ser. No. 694,274

7 Claims. (Cl. 20087) My invention relates to resonant reed relays and in particular to those resonant reed relays which are excited by transducers vibrating in flexural mode. My invention is also directed to the use of ferroelectric ceramic transducers vibrating in flexural mode and to resonant reed relays wherein a plurality of reeds of different lengths are formed from a unitary member which is rigidly held at one end.

At the present time, there are no reed relays available which may be excited at several resonant frequencies by a single electromechanically sensitive body nor are there reed relays available wherein a single electromechanically sensitive body is employed to excite a plurality of reeds and each reed excites an associated electromechanically sensitive body to produce an electrical output.

Accordingly, it is a principal object of my invention to provide a resonant reed relay which is excited by a ferroelectric ceramic transducer.

It is a further object of my invention to provide a resonant reed relay with a plurality of reeds of different lengths formed from a single piece of material.

It is a still further object of my invention to provide such a reed relay wherein the plurality of reeds areexcited by a single, flexural-mode electroacoustic transducer.

It is a still further object of my invention to provide such a reed relay wherein each of said plurality of reeds is separately excited by a flexural-mode electroacoustic transducer.

It is a still further object of my invention to provide such a reed relay wherein a single, flexural-mode electroacoustic transducer excites the plurality of reeds and an electrical output is obtained from each reed by means of a ferroelectric ceramic transducer aflixed thereto.

Other objects and advantages of my invention will be apparent during the course of the following description.

In the accompanying drawings, forming a part of this application, and in which like numerals are employed to designate like parts throughout the same.

Figure 1 is a side elevational view, partly in crosssection and partly schematic, of a preferred embodiment of my invention,

Figure 2 is a horizontal plan view of the embodiment illustrated in Figure 1,

Figures 3, 4 and 5 are horizontal plan views of further embodiments of my invention, and

Figure 6 is a diagrammatic view illustrating the operation of my invention.

In the drawings, wherein, for the purpose of illustration, are shown preferred embodiments of my invention, the numeral 9 designates the base or frame which is formed of metal such as steel, brass or similar material to which vibratory reed 10 is affixed at 11. Transducer 12 may comprise any element constructed to vibrate in the flexural mode, such as, for example, a sheet of barium titanate ceramic 13 prepared in the manner set forth in detail in United States Patent 2,486,410 issued Patented Aug. 23, 1960 November 1, 1949, to Glenn N. Howatt. Element 13, to the opposite major faces of which are affixed electrodes 14 and 15 comprising, for example, air-drying silver paste, is suitably affixed to 10 by soldering 15 to 10 or by similar means; 10 being formed of shim steel, spring brass or similar resilient material of a thickness of the order of .003".0O5". Generator 16 with an output of, for example, 10 volts R.M.S., is electrically connected to 14 and 9 and, when operated at the resonant frequency of 10, serves to cause 10 to vibrate. Contact 17, which may be fixed or adjustable in length, is insulated from 9 by insulator 18 of hard rubber, Bakelite or similar material and serves to close electrical circuit 19 which comprises a battery, resistor 19a and capacitor 1%, through coil 20, frame 9 and reed 10 when 10 makes contact with 17. The relay contact assembly, which is actuated by 20, is designated generally by 21 and comprises movable contact arm 22 and fixed contacts 23. 12 should be placed so as not to restrict the displacement of 10 and should not touch 9 so that its vibration is damped. It should be as close to 9 as practicable to avoid lowering the sensitivity of 10.

In Figures 3 and 4, sheet 24 is afiixed to 9 at 24a and is formed of shim steel, spring brass, beryllium copper or similar resilient material of a thickness of the order of .003".0O5". Vibratory elements 26, 27, 28, 29 and 30 are of different lengths and are formed together with 24 from a single, unitary piece of material. 25 is a ceramic transducer of the type previously described with an electrode afiixed to each face and afiixed to 24 in a manner similar to that in which 12 is affixed to 10. Contacts 31, 32, 33, 34 and 35 are similar to 17 and are placed so that contact is made with 26, 27, 28, 29 and 30, respectively, when the reeds vibrate. Generator 41 serves to cause the various reeds to vibrate when its output frequency is equal to the resonant frequency of the various reeds. Ferroelectric ceramic transducers 36, 37, 38, 39 and 40 are each provided with electrodes on each surface and are affixed to reeds 26,27, 28, 29 and 30, respectively in the manner described above. These transducers serve to provide an electrical output when the reed on which each one is mounted is vibrated. 42 designates a voltmeter which is used to measure the electrical output but the output may as readily be connected to telemetry or other circuitry.

In Figure 5, sheet 43 is aflixed to 9 at 43a as described above for 10 and 25. 43 and reeds 44, 45 and 46 are formed from a single piece of shim steel, spring brass or similar material of thickness of the order of .003.005". Contacts 47, 48 and 49 are respectively associated with reeds 44, 45 and 46 and operate in the same manner as described heretofore in connection with the reeds and contacts of Figures 1 through 4. Ferroelectric ceramic transducers 50, 51 and 52 have electrodes applied to each face thereof and are affixed respectively to 44, 45 and 46 in the manner described above. Generator 53 serves to excite 50, 51 and 52 and thereby cause reeds 44, 45 and 46 to vibrate when the excitation frequency is equal to the resonant frequency of the particular reed or reeds.

In Figure 6, sheet 54 and reeds 55, 56 and 57 are formed from a single piece of shim steel, spring brass or similar material of a thickness of the order of .003.005 and is affixed to 9 at 54a. 54b is a ferroelectric ceramic transducer with an electrode affixed to each face and suitably aflixed to 54. 58, 59 and 60 designate the contacts associated with 55, 56 and 57, respectively. 55a, 56a and 57a are the plots of displacement against reed length for reeds 55, 56 and 57, respectively, when 545 is excited by a generator (not shown) at the resonant frequencies of the reeds.

I prefer to employ ferroelectric ceramic transducers formed largely of barium titanate but any other transducer material may be employed so long as it is piezoelectric in operation. While I prefer to solder or otherwise afiix the transducer to the resilient member so that there is electrical contact between them, I also may aflix the transducer to the resilient member by means of an epoxy resin such as a bonding agent comprising an epoxy system in which the base resin is combined with a hardener such as, for example, metaphenylene diamine, and inert mineral fillers. Consistency can be controlled by the addition of diluents in a manner well known in the art. Such agents have been described in the article by Jerome Formo and Luther Bolstad entitled Where and How to Use Epoxies on pages 99 to 104 of vol. 32, No. 11 of Modern Plastics, July 1955. The bonding agent then serves to insulate the electrode from the resilient member and then it is not possible to use the base as one connection to the transducer.

It is obvious to those skilled in the art that means other than those shown may be used to obtain output from the vibrating reed and those shown are for the purpose of illustrating the invention. I have also found that under some conditions it is advisable to aflix a contact point to the vibratory reed.

In operation, when the excitation frequency is equal to the resonant frequency of the reed (dependent on the reed dimensions and material), the reed vibrates and closes an electrical circuit or generates an electrical voltage. For example, in the embodiment illustrated in Figures 1 and 2, when the frequency of 16 is equal to the resonant frequency of 10 and is of sufficient amplitude, 10 vibrates and makes contact with 17. When 10 and 17 are in contact, circuit 19 is closed and relay arm 22 is pulled down toward the lower contact 23 and when 10 and 17 are out of contact, circuit 19 is opened and relay arm 22 is pulled up toward the upper contact 23 by a spring (not shown). Since the mass of relay arm 22 of relay contact assembly 21 is much greater than that of 10, 22 will not vibrate in synchronism with 10 while the contact between 10 and 17 is being broken at the rate of vibration of reed 10. The filter action of 19a and 19b will tend to smooth the output characteristics of 19 so that an essentially D.-C. voltage is applied to 20 during the time reed 10 is vibrating. When 16 stops supplying excitation voltage of the proper frequency to 12, reed 10 will stop vibrating and 2.2 will be pulled into contact with the upper contact 23. It can be seen by one skilled in the art that multiple or single contact relays may be employed in place of the assembly 21 illustrated without departing from the spirit of my invention.

The embodiment of Figure 3 illustrates a plurality of reeds of varying lengths and consequently of different resonant frequencies formed from a unitary piece of resilient material; each of which is caused to vibrate when signal of the proper frequency and amplitude are applied to 25. It can be seen that more than one frequency may be applied to 25 thereby causing those reeds which are separately resonant to each applied frequency to vibrate and thereby make vibratory connection with its associated contact.

Figure 4, like Figure 3, illustrates a plurality of reeds and in which each reed has a ferroelectric ceramic transducer affixed thereto. In operation, when a signal frequency equal to the resonant frequency of, for example, reed 26 is applied to 25, 26 vibrates and makes contact with 31 and also causes 36 to generate an electrical output which may be detected and measured in '42 or otherwise employed for control or operation of associated circuits (not shown). If desired, more than one of the reeds may be excited at the same time or the input may be applied to the individual transducers 36, 3'7, 38, 39 and 40 and the output taken from transducer 25.

Figure illustrates a three reed relay of unitary reed formation in which separate ferroelectric ceramic transducers 50, 51 and 52 are afiixed to reeds 44, 45 and 46, respectively. When the proper signal frequency is applied by generator 53, the reed 44, 45 or 46 which is resonant to that frequency vibrates and makes vibratory connection with its respective associated contact 4-7, 48 or 59. As pointed out heretofore, more than one reed may be caused to vibrate simultaneously if more than one resonant frequency is applied by 53.

Figure 6 illustrates the displacement of reeds. of varying length 55, 56 and 57 for a given signal amplitude at the resonant frequencies of 55, 56 and 57. The plots of displacement with respect to reed length are shown as 55a, 56a and 57a. The input signal level controls the amplitude of vibration until the respective reeds make contact with the points 58, 59 and 60, at which time the displacement is damped and restricted. Ideally, suflicient input signal to make contact should be used and no more.

By way of illustration and not by way of limitation, following are examples of resonant reed relays of my invention:

Reed 10 is formed of beryllium copper .003 in thickness. 10 is 1 /2" long and A wide and has a resonant frequency of 18 cps.

Element 12 is formed largely of barium titanate and has silver electrodes on both surfaces formed by applying air-drying silver paste thereto. The dimensions of 12 are long by A" wide by 15 to 20 mils thick. 12 is as close to 9 as practicable; being about from 9.

Frame 9 is A" by A" at the top and is high. The base portion of 0 below 10 is approximately 1 /2" long by A1 wide by A; high.

The resistance of coil 20 is approximately 8000 ohms, the resistance of 19a is 47 ohms, the capacitance of 1% is 1 microfarad and the battery voltage is approximately 30 volts.

fReeds composed of stainless steel .003" in thickness with a gold plating .001" in thickness on each surface and /8" wide have the following characteristics:

Resonant reed relays of my invention are capable of discriminating between frequency differences of 1 c.p.s. with changes in reed length of .01" when the reed is [formed largely of stainless steel .003" thick with a gold plating .001" thick on each surface. Reeds of other materials will possess somewhat different discrimination characteristics.

While I have described my invention by means of specific examples and in specific embodiments, I do not wish to be limited thereto for obvious modifications will occur to those skilled in the art without departing from the spirit of my invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. A resonant reed relay comprising a base member; a flat, unitary metallic member affixed at one end to said base member, said metallic member having formed therefrom a plurality of laterally-spaced, vibratory fingers of different lengths at the end opposite said end afiixed to said base member, an electromechanically sensitive body with electrodes affixed thereto on opposite faces thereof afi'ixed to each of said vibratory fingers such that one of said electrodes is in contact with said vibratory finger; and means for exciting said electromechanically sensitive bodies at the natural frequencies of said vibratory fingers.

2. A resonant reed relay as described in claim 1 which includes means for making contact with each said vibratory finger.

3. A resonant reed relay comprising a base member; a flat, unitary, metallic member aflixed at one end to said base member, said metallic member having'formed 5 therefrom a plurality of laterally-spaced, vibratory fingers of different lengths at the end opposite said end aflixed to said base member; a ferroelectric ceramic, electromechanically sensitive body with electrodes aflEixed thereto on opposite faces thereof affixed to said metallic member adjacent the end affixed to said base member such that one of said electrodes is in contact with said metallic member; and means for exciting said electromechanically sensitive body at the natural frequencies of said vibratory fingers.

4. A resonant reed relay as described in claim 3 which includes means for making contact with each said vibratory finger.

5. A resonant reed relay as described in claim 3 which includes a 'ferroelectric ceramic, electromechanically sensitive body with electrodes afiixed thereto on opposite sides thereof affixed to each said vibratory finger.

6. A resonant reed relay as described in claim 5 6 which includes means for making contact with each said vibratory finger.

7. A resonant reed relay as described in claim 5 which includes means for making electrical connection to at least one of said ferroelectric ceramic electromechanically sensitive bodies afiixed to said vibratory fingers.

References Cited in the file of this patent UNITED STATES PATENTS 1,190,923 Lindquist July 11, 1916 2,033,631 Gruetzmacher Mar. 10, 1936 2,167,254 Skellett July 25, 1939 2,195,417 Mason Apr. 2, 1940 2,640,889 Cherry June 2, 1953 2,650,957 Cohen Sept. 1, 1953 2,714,642 Kingsley Aug. 2, 1955

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