US3054380A - Mounting for ultrasonic resonator rod - Google Patents

Description

Sept. 18, 1962 w. G. SIELAFF MOUNTING FOR ULTRASONIC RESONATOR ROD Filed May 29, 1961 INVENTOR. h/zY/z'arzz Glfi'e/afz BY yams: ATT).

3,654,38 Patented Sept. 18, 1962 3,054,380 MOUNTING FOR ULTRASONIC RESONATOR ROD William G. Sielatf, Chicago, Iil., assignor to Admiral Corporation, Chicago, 111., a corporation of Delaware Filed May 29, 1961, Ser. No. 113,2?1 6 Claims. (Cl. 116-137) The present invention relates t an ultrasonic resonator rod and a special mounting therefor.

Prior to this invention, resonator rods of the type commonly employed in signal generating units for remote control systems were generally mounted to their housings by resilient wire segments that clamped the rods at their midpoints. Two such mountings are set forth in the patent to Ole E. Wold entitled Ultrasonic Generator, Patent No. 2,821,956, in which a similar longitudinal-mode ultrasonic resonator rod is employed.

Like Wold, the present invention employs a hammer that impinges sharply on one end of such a rod to excite the rod and generate an ultrasonic frequency wave. The frequency of the emitted wave is determined by the length of the resonator rod, the speed of sound in the resonating material, and the general physical configuration of the rod. A vibrational node appears at the center of the rod, and the oscillatory amplitudes at surfaces of the rod adjacent its center are less than elsewhere in the rod. Thus, a mounting which supports the rod at or near its longitudinal center will absorb a minimum of vibrational energy from the rod and dampen the resonant vibrations less severely than a mounting at any other position along the rod. To prevent significant translational movement of the rod following strike, the center supports of Wold and the present invention are received in grooves or notches in the rod.

In Wold and other mounts of the prior art the mounting elements resiliently clamp the rod and extract small portions of vibrational energy from the rod during each vibrational cycle. However, as will be described in greater detail, the present invention provides a mount that contacts the rod but a small proportion of the time during vibration. The rod is essentially free-floating, and vibrational damping is considerably reduced. The signal receiving apparatus used in conjunction with the transmitting rod does not have to be designed to such great sensitivity as formerly. Signals initiated to change an operational condition in the receiving apparatus may be more reliably distinguished from extraneous noise occurring in the same frequency band.

Therefore, it is an object of this invention to provide a mounting for an ultrasonic resonator rod that will dampen vibrations Within the rod to a lesser degree than prior mounts.

Another object of the present invention is to provide cooperating configurations for a resonator rod of the type herein described and its mount that will provide minimal contact between rod and mount and permit prolonged high vibrational intensity within the rod.

A further object of the present invention is to provide a durable, economical mount for a resonator rod that will insure positional stability of the rod while providing minimal damping.

An additional object of this invention is to provide resonator rod holding means which provide positive support for the rod and high resistance to shock damage from dropping or the like.

A still further object of the present invention is to provide an ultrasonic generator with a substantially freefloating resonator element.

Other and further advantages and objects of the present invention will become apparent from examination of the detailed disclosure and drawings and from a reading of the claims.

A preferred embodiment of this invention is illustrated by the accompanying drawings in which:

FIG. 1 is a perspective view of an ultrasonic resonator chassis incorporating the present invention.

FIG. 2 is an enlarged exploded perspective showing the elements of the rod mount in pre-assembled positions.

FIG. 3 is a further enlarged cross-section perpendicular to the rod axis at its midpoint, showing the assembled mount and rod.

FIG. 4 is a fragmentary view of the rod and adjacent portions of the mount with the mount portions shown in vertical section along the longitudinal center plane of the rod.

The structural and operational association of the components that provide the rod-striking action to be described are clearly illustrated in a copending US. application, Serial No. 81,382 of James E. Vistain, and will not be described in extreme detail herein, because they are not of the essence of the present invention. Although the illustrations in Serial No. 81,382 are somewhat schematic as compared with FIGURE 1 of the present application, the detailed description is in every way applicable to the physical striking apparatus disclosed in the present application.

Referring now to the drawings, in which like elements are designated by like reference numbers, an ultrasonic generator chassis 10 (FIG. 1) is provided with two longitudinal mode resonator rods 11 and 12 centrally mounted through identical mounting assemblies 13 and 14 to a common support plate 15. A push button 16 is provided for manual operation of a first lever 17 which is pivoted at 18 on the chassis 10. One leg 19a of a torison spring 19 is received in the free end of the lever 17, and a second triangular shaped lever 20 is adapted to receive the other leg of the spring 19. The triangular shaped lever 20 is normally urged against a flange 21 by the spring 19, and is provided with a hammer 22 mounted thereto through a spring 24. The levers 17 and 20 are so situated as to provide the following action as the first lever is manually depressed:

Energy is stored in the torsion spring 19 until it passes over center. Then, spring 19 acts to accelerate the second lever 20 and its hammer 22 toward the adjacent end of the rod 11. Before the hammer 22 can strike the rod, the lever 20 strikes a flange 26. The flange 26 extends laterally from a supporting top plate 53 to overlie the triangular shaped lever 20 and provide 2. terminus for the counterclockwise movement of the triangular shaped lever 20 as viewed in FIGURE 1. The hammer 22 is carried forward by its momentum against the bias of its mounting spring 24 to impinge upon the end of the rod 11. Upon rebounding from the rod 11 the hammer 22 is held from further r e-strike by the spring 24. A compressional Wave passes through the rod 11 and is reflected and re-reflected to provide a standing wave of given preselected frequency within the rod 11. The fundamental frequency of the wave is the resonant frequency of the rod 11 as determined primarily by its length, its other physical dimensions, and the material properties of the rod. All even harmonics are quickly suppressed by the center support, and all high odd harmonics are quickly attenuated by internal damping within the rod. However, the fundamental frequency persists, minimally attenuated by the novel configuration of the mount to be described.

The rod is provided with an annular groove 31 at its center section. The annular groove 31 has a rounded root 3i) and is adapted to receive a vertical diaphragm member 32 of nylon, plastic, fish paper, woven fabric, metal, or other material. Nylon or similar resilient plastic materials have been found preferable for this use. The diaphragm 32 is rectangular in shape with a symmetrical, eye-shaped hole 33- therein for receiving the rod.

3 The major axis of the hole 33, as viewed in FIGURE 3, is its maximum horizontal dimension and is greater than the diameter of the rod 11. The minor axis of the hole 33, as viewed in FIGURE 3, is its maximum vertical dimension and is less than the diameter of the rod 11.

.As best seen in 'FIGS. 3 and 4, the eye-shaped hole 33 is of sufficient cross-sectional dimension to provide slight clearances from the root of the annular groove 31. The thickness of the diaphragm 32 is slightly less than the width of the groove 31 in which it is disposed, thereby providing longitudinal clearance as well. The diaphragm 32 is clamped between two metal flange members 34 and 35. The first of these flange members 34 is substantially L-shaped, having a vertical rectangular leg 36 that is provided with a circular hole 37 substantially greater in diameter than the rod 11, and an upper, horizontal leg 38 that is secured to the support plate 15. The second of the flange members is of thin, easily bendable sheet metal. It is provided with two side flanges 39 and 40 adapted to straddle the rectangular leg 36 of the first flange member 34 and be bent therearound. Smaller top and bottom flanges 41 and 42 overlap leg 36 to retain the diaphragm vertically in position. The second flange member 35 is provided with a circular hole 43 of equal diameter and matching disposition with hole 37.

' Referring now, in particular, to FIG. 2, assembly of the mounting elements onto the rod 11 begins with the diaphragm 32. The narrow, vertical axis of the eyeshaped hole 33 is shorter than the rod diameter, but when the flexible diaphragm 32 is vertically bowed and forced against the rod end as by urging its top and bot- 7 tom edges toward one another and twisting the diaphragm against the rod, the hole 33 may be opened sufliciently to fit over the rod. The diaphragm is then slid along the rod to the center groove position where it is permitted ,to resiliently return to its planar configuration and engage the groove. The sturdy first clamping flange member 34 is then inserted over one end of the rod 11, while the thin second clamping flange member 35 is inserted over the other end of rod 11. The clamping flange members are brought together to sandwich the diaphragm 32 therebetween, and flanges 39 and 40 are tightly bent around the opposing rectangularleg 36 of the first flange members 34. The small flanges 41 and 42 protrude into cooperating notches 44 and 45 in the vertical leg 36 to restrain the diaphragm 32 and second clamping flange member 35 against vertical displacement. Thus, the diaphragm 32 is held in position to space the rod from'the metal clamping flange members. 7

It should be noted that the edge of the eye-shaped diaphragm hole 33 is square (see FIG. 4) and that it does not fit snugly within the curved root annular groove 31. .The amount of clearance between the diaphragm and the rod is critical. If this clearance is too small, the result will be unduly high vibrational damping, while if the clearance is too great, positional stability of the rod in its mount will be sacrificed. The clearances between the vertical surfaces of the diaphragm '32 and the adjacent vertical surfaces of the groove 31 should be greater than the peak oscillatory amplitude at these surfaces in the expansional phase of rod vibration; Likewise, the clearances between the horizontal edges of the diaphragm hole 33 and the adjacent portions of the annular groove root'30 should be greater than the peak oscillatory amplitude at these surfaces due to'the Poisson ratio effect:

If these' clearances are not ample, vibrational energy'is' lost each time the oscillations reach an expansional peak of motion, or once every cycle. However, with adequate clearance, the rod is permitted to bounce .or'dance on its supports and-actually be airborne or floating a great majority of the time. Due to the high'frequency of vibration in the rod, approximately 40,000 vibrations per second, vibrational acceleration of 'the' rod surfaces reaches values much greater than the acceleration of gravity. Thus, upon excitation of the rod by the hammer 22 and initiation of vibration therein, the rod will thrust itself upward a slight distance off of its support, drop back due to gravity, quickly rebound upwardly, and continue to bounce in this fashion so long as vibrations of suflicient energy level continue within: the rod. This bounce occurs very rapidly, but nevertheless only once every several hundred vibrations. Therefore, energy is extracted from the rod by the mount during but a small fraction of the cycles of vibration. Depending on the amplitudes of vibration and physical dimensions of parts employed, the clearances referred to above may be in the nature of .001 inch to .005 inch, and considerable experimentation is required to arrive at the optimum clearances for maximum vibrational response. As can be readily seen, the configurations of mount and rod groove described above provide a minimum of surface area contactwithout creating any possible wedging between diaphragm and groove. It is desirable to maintain the angle of contact p of diaphragm and groove near horizontal to minimize amplitude oscillations, the mount of the present invention is durable, long-lived, and economical. The eye-shaped hole facilitates assembly, provides minimal contact area between rod and diaphragm,-and functions well in any position of thehand generator.

The signal thus generated is damped when the button 16 is released by a damping wire 50 that pivots with the lever 17 out of contact with the front edge of the rod 11 during strike, butnormally rests against said front end. A return spring 51 is attached to a downwardly extending portion 52 of lever 17 to return the mechanisms to their rest positions. When button 16 is released, lever 17 comes to rest against the flange 26, toggle spring 19 is carried back over center and lever 20 comes to rest against flange 21. The chassis 10 is adapted to be mounted in a plastic case, not shown, which is fastened by screws or other means to a top plate 53 and a bottom plate 54 which is spaced from top plate 53 by a post 55.

The annular groove is preferred, but other shaped mounting grooves are also contemplated, such as an opposite pair of partial grooves similar to those of Wold in Patent No. 2,82l,956.

Alternatively, the diaphragm may be mounted between the flanges at right angles to the position shown in the drawings, i.e. with the'eye-shaped opening vertical instead of horizontal. The actuator of the present invention is designed to be effectively useable in whatever position the operating individual may choose to hold the generator. While the preferred mounting is illustrated and described in detail above, the rod .will float freely, or relatively so, in any position the actuator assumes.

It is obvious that numerous other modifications and alterations not specifically mentioned in the preceding disclosure could be employed without departing from the spirit and scope of this invention, but it is not, intended to limit the scope of the appended claims by the omission from this disclosure of such modifications and alterations.

Therefore, what is claimed is:

1. In combination with a longitudinal mode resonator rod adapted for vibration at a predetermined frequency responsive to impact by a hammer, said rod having a generally cylindrical shape and having an annular groove centrally disposed thereabout; a mounting for said rod comprising flexible sheet material means forming a generally elliptical opening with the major dimension of said opening being greater than the diameter ,of said rod ad the minor dimension of said opening being smaller than the diameter of said rod; said sheet material means being deformable to allow positioning thereof in said annular groove; and meansclamping said sheet material means whereby a substantially rigid support for said rod is obtained.'

2. A mounting for a cylindrical resonator rod having a transversely oriented groove midway between its ends; said mounting comprising a thin sheet of flexible material forming an arcuate opening; said rod being received in said opening in the transverse plane of said groove, said opening having a minor axis which is smaller than the diameter of said rod but greater than the diameter of said rod at its grooved section; means clamping said sheet of flexible material over a substantial portion of its surface to impart rigidity thereto whereby said rod is free to move in a direction parallel to the plane of said sheet of flexible material but is restrained from substantial movement in a direction transverse to the plane of said sheet of flexible material.

3. A mounting as set forth in claim 2 wherein the thickness of said groove exceeds the thickness of said sheet of flexible material by a predetermined amount, said predetermined amount being greater than the peak oscillatory amplitude of the central portion of the rod.

4. A mounting as set forth in claim 3 wherein said sheet of flexible material comprises nylon.

5. In combination with a compressional wave generator including a longitudinal mode resonator rod having an annular groove at a predetermined nodal point, support means, a hammer for percussive engagement with one end of said rod, means mounted to said support means carrying said hammer into and out of engagement with said one end of said rod, exciter means operatively coupled to the means carrying said hammer, and means mounting said rod to said support means, said last-mentioned means including; a diaphragm of thin flexible material forming an eye shaped hole having major and minor dimensions, said major dimension being greater than the outside dimension of said rod and said minor dimension being greater than the inside dimension of said annular groove; said diaphragm being deformable to al-. low said rod to be slipped therethrough whereby said eye shaped hole engages said rod at said annular groove; and clamping means mounted on said support means, said clamping means clamping said diaphragm over a major portion of its surface to impart substantial rigidity to said diaphragm and consequent high resistance to translational movement of said rod.

6. In a mechanical resonator of the type for generating compressional waves of predetermined frequency including support means, a cylindrical, longitudinal mode resonator rod having an annular groove midway between its ends, mounting means mounting said resonator rod to said support means at said annular groove, and hammer means percussively engaging one end of said rod responsive to manual actuation of exciter means, the improvement in said mounting means comprising; a thin flexible diaphragm forming an aperture having two arcuately shaped portions, said diaphragm being deformable and receiving said rod in said aperture such that the edges of said arcuately shaped portions nest in said annular groove; the maximum distance between said arcuately shaped portions being less than the diameter of said rod, but greater than the diameter of said rod at its grooved section; and a pair of clamping members clamping said dia phragm therebetween over a major portion of the diaphragm surface whereby substantial rigidity is imparted to said diaphragm and said rod is restrained from substantial movement transversely of the plane of said diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS 2,920,604 McDonald Jan. 12, 1960

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