US2729132A

US2729132A - Electrical pick-up for vibrating bodies

Info

Publication number: US2729132A
Application number: US252080A
Authority: US
Inventors: Jacob T Kunz
Original assignee: SCHULMERICH ELECTRONICS Inc
Current assignee: SCHULMERICH ELECTRONICS Inc
Priority date: 1948-11-17
Filing date: 1951-10-19
Publication date: 1956-01-03
Anticipated expiration: 1973-01-03

Description

Jan. 3, 1956 J. T. KUNZ 2,729,132

ELECTRICAL PICK-UP FOR VIBRATING BODIES Original Filed Nov. 17, 1948 LO0ASPEAKER TONE A MPL f/ERS INVENTOR. k/A cos 7 A uA/Z ATTORNEYS "ilnited States Patent 6 ELECTRICAL PICK-UP FOR VIBRATING BODIES Jacob T. Kunz, North Hills, Pa., assignor to Schulrnerich Electronics, Incorporated, Sellersville, Pa., a corporation of Pennsylvania Original application November 17, 1948, Serial No. 60,470, new Patent No. 2,606,474, dated August 12, 1952. Divided and this application October 19, 1951, Serial No. 252,080

4 Claims. (Cl. 841.14)

This invention relates to musical instruments and particularly to an electric musical instrument for producing bell or chime tones and the like, and is a division of copending application S. N. 60,470, filed November 17, 1948, now Patent No. 2,606,474, August 12, 1952.

Various means have been employed previously for producing electrically hell or chime tones. In the prior instruments, bars or rods, both solid and hollow, as well as other types of vibrating elements, have been used for the purpose of generating the vibrations. The vibrations produced have been picked-up electrically by various means, amplified, and then translated by an electro-acoustic mechanism to produce musical tones. The tone generated usually has been modified in the amplifier circuit in various manners. Instruments employing bars or rods have used fixed-free vibrators wherein one end of the vibrator is fixed and the other end of the vibrator is free to vibrate, and free-free bar vibrators wherein both ends of the bar are unrestrained and free to vibrate.

It has been diflicult in the previous devices to obtain all of the desired partials in their proper relationship to correctly produce a bell tone, particularly a bell tone of the Flemish or harmony type bell.

The object of the invention of this divisional application is to provide an improved collector plate and shield arrangement so that the collector plate or electrode has a minimum of capacity relative to the shield and adjacent vibratory bodies.

The terms characteristic tone or note" are used herein to mean the whole sound which identifies the note involved to the listener. The term fundamental tone is used to mean the lowest vibration present in the vibrator. When a rod is struck, various tones appear as the result of the vibrating pattern of the rod. A person listening to the note produced as a result thereof will select a characteristic tone by which he identifies the note. As will be explained hereafter, the characteristic tone in the case of a fixed-free rod is a synthesized tone, not actually present in vibrations in the rod, formed by a combination of the fourth and fifth partials or tones of the rod. The term partial or tone refers to a single tone and not to a combination of tones, first partial" meaning the first tone above the fundamental.

in one aspect of the present invention, a tone generator, which will be described in detail hereafter, has vibrations therefrom picked-up electrically to produce electrical vibrations or oscillations in an amplifier circuit. The vibrations picked-up are modified by locating the pickups in a predetermined relationship along the tone generator. Other vibrations in the tone generator can be modified in the amplifier circuit by suitable filters or electrical arrangements. The amplifier circuit used is connected to an electro-acoustic transducer or loud speaker to produce the desired note. A plurality of tone generators can be employed and actuated from a key board so that carillon music can be produced.

One of the features of the invention is a tone generator comprising a pair of vibrators for each note, preferably ice in the form of fixed-free rods, said pair of rods being strikable simultaneously by a striker. Merely as an example, twenty-five or more tone generators representing twenty-five notes of the chromatic scale can be employed for the production of carillon music, an instrument employing as many as sixty-one tone generators having been used. A greater or less number of tone generators may be employed as desired. The two fixed-free rods of each tone generator have their lengths or vibratory patterns selected relative to each other so that one rod will vibrate at a higher fundamental frequency than the other rod. As previously mentioned, the fundamental frequency is the lowest normal vibration in the rod.

The normal characteristic tone of such a rod or the tone identifying the note to the listener is not actually present in the vibrating pattern of the rod but is a tone which is synthesized as a result of the difference between two partials, such as the fourth and fifth partials of the rod.

As is well known, when an electric pick-up is placed at a point along a rod Where the node of a particular tone or vibration occurs there will be no energization of the pick-up by this particular vibration because there will be no relative vibration between the pick-up and rod at this point. By placing the pick-up at a selected node of the fourth partial, the fourth partial will be eliminated from the electrical vibrations picked up and fed to the amplifier circuit. By such a placement of the pick-up, the characteristic tone, which is an octave below the fourth partial, also will be eliminated because the characteristic tone is a result of the difference between the fourth and fifth partials. The electrical vibrations in the amplifier circuit then will have a characteristic vibration or tone differing from the natural or normal previous char acteristic tone. As will be explained hereafter, in a fixedfree rod, the new characteristic tone may be a minor third or a musical interval of one and one-half tones above the normal characteristic tone of the rod.

In a tone generator having two rods, one of the rods can have its electrical pick-up arranged as described in the preceding paragraph for the purpose of changing the characteristic tone thereof. The other, or second, rod is constructed and tuned so that the fundamental tone thereof is a minor third musical interval above the fundamental tone of the first mentioned rod. The pick-up for the second rod is arranged so as not to change the characteristic tone thereof. The rods can be termed A and B rods. It is apparent that the changing of the characteristic tone of the first rod to a minor third above the normal characteristic tone thereof will cause the two rods to have the same potential characteristic tones in the electrical system thereof. The characteristic tones of both rods do not necessarily have to be used for the final amplified note as long as it is available from one rod. Thus, it is not absolutely necessary that the characteristic tone of each rod be exactly tuned as long as the particular partials therefrom are correct and bear the correct relationship to the characteristic tone that is utilized.

As will be explained in detail, at a later point, each of the rods will have certain of the desired partials, which are to be combined with the characteristic or strike tone so as to produce a true bell note, including a hum tone an octave below the characteristic tone.

The other undesired partials and the fundamentals of each rod can be removed by placement of the pick-up means, by damping means, and by the amplifier circuit arrangement. Also the electro-acoustic transducer can be selected so as to attentuate certain of the undesired partials. It is, of course, possible to use various other combinations of rods, or numbers thereof, struck simul-. taneously so as to attain the desired final note, such rods being initially tuned as required for the particular systems involved, and in accordance with the numbers of rods.

In one aspect of the invention, each base is mounted resiliently and independently of the others. In this manner, when a pair of rods is struck, the partials from one pair of rods are not carried into other rods. A small amount of pick up is not objectionable or noticeable and thus it is practicable to install two rods on a common block. The collectors or plates are mounted adjacent each rod so as to be in capacitative relationship with the rod, a suitable polarizing voltage being provided. The collectors can be mounted on a holder which in turn is fitted on a vertical support projecting upwardly from the base, the collector itself being insulated from the holder. The holder is arranged to be at ground electrical potential so that adjustments can be made without ge crating spu rious noises in the connected amplifier circuit. The rods are firmly positioned in the base in such a manner that they can be hit simultaneously with a hammer, means being provided so that the hammer will correctly hit both rods.

A collector plate or electrode, which particularly is the subject of this divisional application, is contemplated to be arranged so as to be electrostatically shielded and to .collect vibrations only from the desired rod. The electrode can be made with a relatively wide face adjacent the rod and a narrow face facing the shield. Also the electrode may be held in a high dielectric block fastened to the shield with a large portion of the electrode itself separated from the block. By this means, the electrode will have a minimum of capacity relative to the shield and the electrode holder organization.

These and other objects, features, and advantages of the invention will becomeapparent from the following description and drawings.

Figure l is a perspective view of one of the tone generator assemblies of the present invention.

Figure 2 is a section taken along the line 2-2 of Figure 1.

Figure 3 is an enlarged fragmentary view looking in the direction 33 of Figure 2.

Figure 4 is a schematic wiring diagram.

Figure 5 is an alternative schematic wiring diagram.

Describing the invention generally, the tone generators are seen diagrammatically indicated at (Fig. 5), said generators being operable by strikers 21, only one rod being visible. The electrical pick-ups 22 are connected to a preamplifier 23 of suitable design, said preamplifier in turn being connected to an amplifier circuit 24. The amplifiers may have suitable circuits therein for attenuating the undesired partials or tones. Loud speaker 25 is connected to the amplifier 24, said speaser having the desired characteristics. Merely by way of example, speakers having an output of l kilowatt have been heard for more than two miles when connected to the apparatus disclosed herein. The manner in which the two rods are tuned and utilized to produce a bell tone is described in detail in the aforementioned parent application, S. N. 60,470.

An alternate wiring arrangement is seen in Figure 4 wherein the A rods can be connected to one amplifier and the B rods toanother amplifier, said two amplifiers then having their output connected together for feeding the loud speaker or other amplifier arrangements. if desired, separate amplifiers can be used for each set of rods in each'octave. I

In a preferred form of the invention, a support block or base (Fig. l) is mounted on resilient supports 31 carried on plate or support 32. The

rods

33 and 34 mounted on said block are tuned so that they have the proper frequency and tones for the particular note involved in the manner described in said parent application. Tuning can be accomplished by adjusting the length of the rod in any suitable manner such as by cutting off or 4 by an adjustable element and weights can be adjusted along the rod as needed.

Stabilizers 36, consisting of plates 37 firmly clamped on a support 38 may have springs 39 mounted thereon engaging a rod. The stabilizers will serve to laterally retard the free motion of the rod. The stabilizing springs will serve to restrict the fundamental tone of the rod, there being less effect on the first partial and substantially no effect on tones higher than the first partial. It is necessary to select the stiffness of the spring so that it has a resonant frequency outside of the range of the note. Stabilizers must also be placed so that they will not interfere or attenuate any of the desired partials in the rod. The stabilizer will add to the mechanical stability of the rod because the amplitude of the fundamental and first partial is high. In addition to the low frequency attenuation described, the stabilizer also makes it possible to place the pick-up close to the rod without danger of the rod striking the pick-up.

The stabilizers can be placed at any desired point along the rods such as for example, near the centers. Inasmuch as the lower partials are removed in the amplified circuit and not used, it is thus desirable to restrict the rod from vibration at these partials.

In the form shown, the

rods

33 and 34 are supported in slots 39 located in base 30, said rods being tightly held therein so that the rods, block, and collector plate support 38 will vibrate as a unit. The collector plate support 33 is held tightly in place on the base 30 by means of nut 40.

The collector plates, shown generally at 41, are mounted on collector plate support 38. The collector plates include an electrode element 42 (Figs. 1, 2, 3) arranged to be closely spaced relative to the rod from which vibrations are .to be collected by the particular plate. Preferably, the

electrode has a flat relatively wide face next to the rod, and a relatively thin side surface parallel to the shield or support plate. Shield plate 43 is provided so as to shield the collector electrode 42 from the vibrations of the other rod. The collector electrode is mounted on an insulating block 44 (Figs. 2, 3) carried by the collector frame in such a manner that it is insulated from the remainder of the collector structure. The block 44 may be made of Bakelite or other high dielectric material. The ends of the electrode are held in the block in such a manner as to provide a space 44A between a large portion of the electrode and the block. Screws 443 may be employed to hold the block in place on the collector frame. The collector frame may comprise two sheets of

metal

45, 45A joined together in abutting relationship at 66 and 67. Clamps 46 may be placed on the collector plate support 35 above and below each electrode. A spring 69 (Fig. 2) may be located between the collector and the support 38. Clamping screws 47 located at end 66 clamp the collector in place on the support 38. The flat face of the electrode is opposite the rod 33 so as to give maximum capacity whereas the shield 43 is arranged so that only an edge of the electrode is in close proximity to an angularly disposed part of the shield.

Various details of construction can be altered without departing from the spirit of the invention except as defined in the appended claims.

What is claimed:

1. In an electric musical instrument tone generator having a pair of vibrating rods, a collector plate device having an electrode with a fiat surface adjacent one of the rods, and a shield between said rods, said shield having a supporting portion angularly disposed relative to an edge of said electrode so as to have a minimum of capacity relative thereto.

2. In an electric musical instrument tone generator having a pair of vibrating rods, a collector plate device for each rod, each device having an electrode with a fiatsurface adjacent its respective rod, and a shield on each plate between said rods, said shields having a portion angularly disposed relative to an edge of said electrode between said rods so as to have a minimum of capacity relative to the electrode and adjacent rod.

3. In an electric musical instrument tone generator having a pair of vibrating rods, a collector plate device for each rod, each device having an electrode with a flat surface adjacent its respective rod, a shield on each plate between said rods, said shields having a portion angularly disposed relative to an edge of said electrode and between said rods, and a high dielectric supporting block holding said electrode in edgewise relationship with said shield, a large portion of said electrode being separated from said block, so as to have a minimum of capacity relative to the electrode and adjacent rod.

4. A collector plate assembly for picking up electrical vibrations from one of tWo adjacent vibrating rods comprising a flat electrode adjacent one of said vibrating rods, and a shielding plate disposed between the two vibrating 6 rods in spaced relation to said one vibrating rod, said plate extending to opposite ends of said vibrating rods and in a direction away from said electrode on the same side of the rods as said electrode so as to have a minimum of capacity relative to the electrode.

References Cited in the file of this patent UNITED STATES PATENTS 1,847,872 Hand Mar. 1, 1932 1,875,132 Peterson Aug. 30, 1932 2,234,998 Worrall Mar. 18, 1941 2,507,188 Weathers May 9, 1950 2,512,138 Butt June 20, 1950 FOREIGN PATENTS 109,597 Australia Feb. 1, 1940