US 3681627 A
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Description (OCR text may contain errors)
I United States Patent Murry et al.
1 51 Aug. 1, 1972  SONICALLY OPERATED TOOL AND SONIC MOTOR THEREFOR  Assignee: Gulton Industries, Inc., Metuchen,
22 Filed: July 7,1969
 Appl.No.: 29,344
52 U.S.Cl. ..3l0/8.7,173/1l7,'228/l,
51 1111.0. ..H0lv7/00  FieldofSearch ..310/8.7,8.3,8.2,8.1,8; 173/117, 162; 228/1, 57
 References Cited UNITED STATES PATENTS 3,140,859 7/1964 Scaupa, ..3l0/8.2X
3,368,085 2/1968 McMasteretal ..310/8.3
3,511,323 5/1970 Riley ..173/117 3,101,419 8/1963 Rich ..3lO/8.3
3,283,182 11/1966 Jonesetal. ..3l0/8.7
2,815,430 12/1957 Weiss ..228/1X 3,110,825 11/1963 Miller ..3l0/8.7
Primary Examiner-J. V. Truhe Assistant Examiner-B. A. Reynolds Attorney-Wallenstein, Spangenberg, Hattis & Strampel  ABSTRACT A sonically operated tool unit preferably forming a half wave sonic vibrator comprising a piezoelectric transducer for producing longitudinal vibrations and sandwiched between a first relatively heavy assembly of parts forming, among other things, a supporting portion for the tool unit and a second relatively light assembly of parts forming a readily vibratory work.
performing portion of the tool unit and including at the end thereof a work performing element which is to engage and vibrate against a surface external to'the unit. The lighter second assembly of parts most advantageously includes a tapered velocity transformer having its wide end immediately contiguous to the transducer and having a longitudinal bore aligned with openings extending through the transducer and first assembly of parts. The work performing element has a long shank extending freely through the first assembly of parts, the transducer and the front end portion of the velocity transformer. The shank is rigidly secured to the rear end portion of the velocity transformer so the high velocity vibration of the narrow end of the velocity transformer is transmitted to the work performing element through the long shank thereof.
11 Claims, 7 Drawing Figures i GENERA 111/1 SONICALLY OPERATED TOOL AND SONIC MOTOR THEREFOR The present invention relates to sonic motor apparatus, and has its most important application in sonically operated hand-portable tools, such as soldering irons, drills and the like.
The application of sonic energy to tools of all kinds has been the object of much development in recent years. One such application, for example, has been to soldering irons for soldering materials which are readily oxidized. In such case, the use of sonic energy to vibrate the head of a soldering iron to remove oxide coatings without the use of contaminating fluxes is especially useful. However, to obtain adequate abrading action and good cavitation of the molten solder has been difficult to achieve without the use of devices which are large, heavy and cumbursome to use. It was usually found necessary to operate the tool at higher frequencies such as 40 to 50 kilocycles per second to keep the cost of the expensive piezoelectric materials commonly used in the transducers of such tools low and to reduce the overall weight and size of the soldering iron. However, the use of such higher frequencies mitigates against the obtainment of satisfactory cavitation of the molten materials to produce the best results.
Accordingly, an object of the invention is to provide an improved sonic motor which has use in sonically operated hand-supported tools, such as soldering irons and the like, and which, for a given frequency of operations, are much smaller and lighter than sonic motors previously developed.
Another object of the invention is to provide a sonic motor which produces the maximum velocity of vibra- 'tions at the working end of the motor for a given size and weight thereof.
A further object of the invention is to provide a sonically operated device which, for a given power input, size and/or weight of the device produces a maximum particle velocity at the work performing end thereof.
Still another object of the invention is to provide an extremely light, compact and eflicient sonically operated tool, such as soldering irons and drills, which can operate at frequencies of kilicycles and lower. A related object of the invention is to provide a vibrating soldering iron as described which, for a given size, weight and cost, produces a maximum amount of heat and vibration at the tip of the soldering iron.
In accordance with one of the aspects of the invention, a Langevin sandwich-type sonic motor which generally comprises two or more piezoelectric discs connected electrically in parallel and sandwiched under compression between two masses of substantially different weight, is constructed in a unique way greatly to increase the sonic efficiency of the sonic motor. Whereas previously a Langevin sandwich-type sonic motor wasdesigned so it formed a half-wave vibrator, that is a vibrator with a length having an integral number of half-wave lengths at the frequency involved, and was then mounted in a housing with other parts forming a complete sonically operated tool or other device, the aspect of the present invention now being described integrates all of the parts of the sonically operated device, such as the housing and the vibrating tool or other utilization element, into the Langevin sandwich-type sonic motor so that the entire device acts as a half-wave vibrator with the relatively heavy housing forming part of the heavy mass of the Langevin sandwich sonic motor and the vibrating too] or other utilization element forming the outer end portion of the lighter mass thereof. A Langevin sandwich-type halfwave vibrator as described produces a maximum particle velocity at the end of the lighter mass. In the sonically operated device first described, when the vibrating tool forms the end portion of the lighter mass of the Langevin sandwich, the outer end of the tool vibrates at a maximum velocity.
In accordance with another aspect of the invention, independently of whether or not the entire sonically operated device acts as a half-wave vibrator of maximum efficiency, a tapered velocity transformer made of aluminum or other light metal is substituted for the usual cylindrical light mass member of a Langevin sandwich-type sonic motor so that the sonic transformer fonns part of the sonic motor rather than merely being an element vibrated by the same. This reduces the power requirements, size, weight and cost of the sonic motor for a given desired amount of sonic energy output.
In accordance with a still further aspect of the invention, the overall length of a sonically operated device of a type like that described is materially reduced by forming a longitudinal shank-receiving passageway in the Langevin sandwich-type sonic motor extending from the end of the motor containing the heavier mass to the end containing the lighter mass, and passing the shank of the vibratable utilization element involved through the passageway where it connects with the lighter mass. In the preferred form of the invention, where the entire sonically operated unit involved is a. half-wave vibrator, a substantial portion of the length of the shank of the utilization element contributes to the length of a half-wave vibrator without increasing the actual length of the unit as a whole. In the most preferred form of the invention which utilizes a tapered velocity transformer on one side of the transducer portion of the sonic motor, the shank of the vibrating element makes connection to the velocity transformer within a longitudinal bore therein at the narrow end portion thereof wherein the velocity of the vibration thereof is a maximum.
The above and other objects, advantages and features of the invention will become apparent upon making reference to the specification to follow, the claims and the drawings wherein:
FIG. 1 is a fragmentary, longitudinal, sectional view through a sonically operated tool unit incorporating the unique sonic motor of the present invention;
FIG. 2 illustrates a unique hand-held sonically operated soldering iron unit incorporating a unique sonic motor construction and relationship between the soldering iron shank and sonic motor;
FIG. 3 is a transverse sectional view through the sonically operated soldering iron unit of FIG. 2, taken along section line 3-3 thereof;
FIG. 4 is a greatly enlarged, fragmentary, longitudinal sectional view through the velocity transformerforrning part of the sonic motor of the soldering iron unit of FIG. 2;
FIG. 5 is a perspective view of a socket terminalforming portion of the parts located within the velocity transformer of FIG. 4;
FIG. 6 illustrates the sonically operated tool unit of FIG. 2 with a drill tool bit replacing the soldering iron tip of the soldering iron unit to form a drill unit mounted on a drill frame; and
FIG. 7 is a greatly enlarged fragmentary sectional view through the modified velocity transformer portion of a sonically operated tool unit like that shown in FIG. 2, but devoid of any means for feeding heating current to the tool shank which forms part of a drill tool element or the like.
Referring now more particularly to FIG. 1, a sonically operated tool unit generally indicated by reference number 2 is shown which longitudinally vibrates a tool element 4 projecting from the forward end of the tool unit. The sonically operated tool unit as a whole forms a half-wave vibrator or sonic motor with a Langevin sandwich-type construction. The tool unit 2 includes an outer housing 6 of any suitable construction and preferably made of an insulating material. Anchored to the housing 6 by screws 8 is an annular member 10 which is made of a relatively dense metal like steel. The annular steel member 10 and the housing 6 together form the heavy mass of a Langevin sandwich-sonic motor. A piezoelectric transducer assembly generally indicated by reference number 12 is sandwiched between the annular steel member 10 and a forwardly tapering velocity transformer 14 made of aluminum or other relatively light metal. The tool element 4 is connected to the narrow end of the velocity transformer 14 from which it longitudinally extends.
The piezoelectric transducer assembly 12 as illustrated includes a pair of annular piezoelectric ceramic discs l2al2a separated by a metal annular electrode 12b. The tool element 4 and the velocity transformer 14 together form the light mass of a Langevin sandwich-sonic motor. The piezoelectric transducer assembly 12 is placed under an initial compression by an assembly including a stud 16 extending longitudinally through a central opening 10a in the annular steel member 10, openings l2cl2c in the annular piezoelectric discs l2al2a and opening 12d in the annular electrode 12b, all of which openings are aligned longitudinally of the tool unit 2. The inner end of the stud 16 is threaded at 16a where it is threaded into a tapped bore 14a in the velocity transformer 14. The outer end of the stud 16 is threaded at 16b and receives a nut 20 which bears against a pair of oppositely bowed spring washers 22-24 sandwiched between the nut 20 and the outer side of the annular steel member 10.
The stud 16 is insulated from the annular electrode 12 between the piezoelectrid discs l2al2a by an insulating sleeve 26 positioned around the stud 16. A pair of insulated conductors 26 and 28 in a cable 30 extending from a high frequency generator 32 are respectively connected to terminals 34 and 36. Terminal 34 is secured to the annular steel member 10 and the terminal 36 is an extension of the electrode 12b. It is thus seen that the piezoelectric ceramics discs l2al2a are effectively connected in parallel with one another since the outer faces of these discs are connected to the same electrical potential through the stud 16, the nut 20 and the spring washers 22 and 24. With the application of a high frequency voltage on the opposite faces of each of the piezoelectric discs l2al2a, the entire assembly is vibrated longitudinally.
The entire tool unit 2 is dimensioned to form a halfwave vibrator with the point of maximum velocity of vibration occuring at the tip 4a of the tool element 4 attached to the narrow end of the velocity transformer 14. In addition to the unique feature of the design of the entire tool unit 2 so it forms a half-wave vibrator, the position of the velocity transformer 14 constituted another unique feature thereof in that it forms an integral part of the half-wave vibrator and replaces the usually cylindrically shaped light mass forming part of a convention Langevin sandwich, thereby reducing the length, weight and cost of the sonic motor.
Refer now to FIGS. 2-4 which illustrates a combination soldering iron and tool-unit 2' which includes a sonic motor construction representing an improvement over that shown in FIG. 2 among other things, in that a substantial part of the length of the tool element 4 thereof, which is shown as a conventional soldering tion soldering iron and tool unit 2' of FIGS. 2-4 includes many parts in common with the tool unit 2 in FIG. 1, the corresponding parts have been similarly numbered. (Those parts which are or may be identical in construction to those in FIG. 1 have been given unprirned numbers whereas those parts which correspond with parts in FIG. 1 but are of modified construction are given the same numbers with a prime following the same.)
The shank 4a of the soldering iron 4' in FIG. 2 extends through a longitudinal passageway 166' formed in the stud 16' which is a hollow sleeve passing through the aligned openings in the annular steel member 10 and piezoelectric transducer assembly 12. The soldering iron shank 4a is spaced from the walls of the stud passageway 16c so that the tool element shank is free to longitudinally vibrate within the passageway 160'. The tool element shank 4a also passes into a longitudinal bore 14a in the velocity transformer 14' which, unlike the tapped bore 14a in the velocity transformer 14 of FIG. 1, extends deeply into the velocity transformer. The inner end of the illustrated soldering iron is externally threaded at 40' to engage a tapped portion 14b of the velocity transformer bore 14a. The inner end face of the shank 4a forms a flat axially facing shoulder 4d (FIG. 4) which tightly abuts an axially facing shoulder in the bore 14a to provide a good acoustic energy transferring interface between the velocity transformer 14' and the shank. Thus, except for the point where the shank 4a threads into the velocity transformer bore 14a, it is spaced from all portions of the tool unit 2' so it is free to vibrate longitudinally. Since the portion of the shank 4a within the velocity transformer 14', transducer assembly 12 and annular steel member 10 do not increase the overall length of the tool unit 2', it is practical to operate the soldering iron and tool unit 2' at much lower frequencies, such as 20 kilicycles, than was heretofore practical since the larger parts necessary to form a half-wave vibrator at the lower frequency do not result in a longer tool unit. The lower frequency produces much better cavitation of the solder.
The soldering iron 4' has a heater containing head portion 4e which is adapted to removably receive a soldering iron tool tip 4] The head portion 4e has extending from within the same a heating current carrying conductor 40 (FIG. 4) surrounded by insulation material 42 and projecting a short distance beyond the rear end of the tool element shank 4a. The illustrated soldering iron 4' is a stock soldering iron part flattened on the inner end 4d and wherein the heater current carrying conductor 40 projects only a small distance from the inner end of the soldering iron. To adapt it for proper use in a vibratable tool unit, the projecting end of the conductor 40 is tightly fitted within a metal ferrule 42 which, in turn, extends within a conventional vacuum tube socket member 44 best illustrated in FIG. 5, to provide good electrical contact between the socket member 44 and the conductor 40 of the soldering iron under the vibrating conditions imposed by the vibrating tool unit 2. The socket member 44 has a terminal tab 46 projecting from the rear end thereof to which an insulated A.C. current carrying conductor 48 is connected for carrying heater current to the soldering iron.
The socket member 44 and the metal ferrule 42 are held fixedly within a rear bore portion 14d of the velocity transformer by an externally threaded nut 50 which threads into the rear bore portion 14d and bears against an insulating sleeve member 52 which snugly surrounds the shank portion 42a of the metal ferrule 42 and bears against the inner face of the head portion 42b of the metal ferrule which is located within a hollowedout portion of the insulation 42 of the soldering iron shank 4a. The insulating sleeve member 52 has a shank portion 520 which passes through an opening 53 between the velocity transformer bores 14a and 14d and insulates the ferrule 42 from the metal surfaces of the velocity transformer 14'. The externally threaded nut 50 has a central longitudinal bore 55 through which the socket member 44 extends, the externally threaded nut interlocking with the socket member 44 to hold the same in place by means of an upwardly extending tab 44a wedged within the bore 55 of the externally threaded nut 50.
The soldering iron and tool unit 2' in FIG. 2 has an elongated housing 6' of circular cross section but of tapering configuration so as to be comfortably holdable by the user of the tool unit 2'. The housing 6' has a very narrow rear portion 6a (FIG. 2) from which extends a cable 30 carrying the aforementioned insulated A.C. current carrying conductor 48 and insulated conductor 58 which is attached to a terminal tab 36 extending from the annular electrode 12b forming part of the transducer assembly 12, and an insulated common conductor 60 secured to a terminal tab 34' secured to the velocity transformer 14'. The conductor 58 is connected to a high frequency generator 32' supplying the high frequency power for vibrating the piezoelectric discs 12a--12a in the manner previously described.
The forward portion 6b of the housing 6' has a forwardly flaring configuration which terminates in a reduced neck portion 60' forming a recessed annular surface 61 having an annular depression 63 at the inner end thereof. A housing head piece 65 having a flexible annular inwardly extending lip portion 65 is rotatably mounted upon the annular surface 61 and interlocks removably with the front portion of the housing 6' by the extension of the flexible annular lip portion 65 into the annular depression 63.
As best shown in FIG. 3, the neck portion 60' of the housing 6' is provided with three equally circumferentially spaced radial holes 68 which are alignable with three corresponding holes 70 in the head piece 65. When the head piece 65 is rotated into position where the various holes 68 and 70 are in alignment the aligned holes are adapted to receive securing screws extending therethrough and threading into corresponding tapped holes 71 in the annular steel member 10 to anchor the housing 6' to an external support frame to convert the tool unit 2 into a drilling tool or the like as shown in FIG. 6. As there shown, a vertically adjustable tool holding arm 70 extends from a vertical post 72. In a well known manner, the tool holding arm 70 is adapted to be progressively lowered to perform a drilling or other machining operation. The tool unit 2 is mounted upon the end of the arm by means of screws 74 which pass through the aforesaid aligned openings 68 and 70 formed in the neck portion 6c of the housing 6' and the rotatable head piece 65 and thread into the opening 71 in the annular steel member 10. The soldering iron tool tip 4f in FIG. 2 is replaced by a suitable drillimg tool bit 73 or the like. The longitudinal vibration of the tool bit 73 cuts through a suitable work piece 75 supported on a work holding surface 77, as illustrated.
In the form of the invention shown in FIG. 6, it is apparent that the parts of the tool unit 2' which carried heater current in the soldering iron embodiment of the invention of FIG. 2 are inactive and so carrys no current in the drill application of the invention, to substantially increase the particle velocity at the end of the tool element involved, the velocity transformer may be modified so that it has the construction shown in FIG. 7 which comprises an assembly of three tapered velocity transformers forming members 79, 84 and 90, ome within the other. The modified velocity transformer assembly, which is identified by reference number 14", is not designed to receive the soldering iron shank 41 and so is devoid of those parts of the apparatus shown in FIG. 4 which carrys heater current to the tool element. The outer tapered member 79 whose wide end is secured to the end face of one of the annular piezoelectric elements 12a and is provided with a tapered central cavity 80 having its narrow end nearest the wide end of the outer member 79. The tapered cavity 80 terminates at the wide end thereof in an annular shoulder 82 facing toward the narrow end of the cavity 80. Welded or otherwise rigidly secured to this annular shoulder 82 is the wide end of the first inner tapered member 84 which, except for its contact with the shoulder 82, is spaced from the other defining walls of the cavity 80. The first inner tapered member 84 thus forms a second velocity transformer connected in tandem with the outer member 79 also forming a velocity transformer so as to amplify the article velocity occuring at the annular shoulder 82 at the narrow end of the outer tapered member 79 without any increase in length of the tool unit. Similarly, the first inner tapered member 84 is provided with a tapered cavity 86 therein whose wide end is nearest the narrow end of the first inner tapered member 84. At the inner end of the cavity 86 there is a shoulder 88 against which is rigidly secured by welding or otherwise a second inner tapered member 90 which is somewhat smaller than the cavity 86 so that it is spaced from all the defining walls of the cavity except the annular shoulder 88. The second inner tapered member 90 thus forms a third velocity transformer which amplifies the particle velocity at the shoulder 88 of the first tapered member 84. The outer tapered member 79 of the velocity transformer assembly 14" and the two inner tapered members 84 and 90 are provided with aligned communicating openings 79a, 84a, and 90a to permit the free passage therethrough of a tool element shank 4a". The inner end of the tool element shank 4a" threads into a threaded portion of a tapped opening 84b at the narrow end of the second inner tapered member 90. Except for this point of connection of the tool element shank 4a to the tapered member 90, the tool element shank 4a" is spaced from the walls of the various openings within the velocity transformer assembly so that the tool element shank 4a" is free to vibrate longitudinally. It is apparent that the particle velocity at the threaded end of the tool element shank 4a" is greatly magnified from the particle velocity at the wide end of the outer tapered member 79 of the velocity transformer assembly 14".
It is apparent that the present invention has provided a highly unique and efficient and compact construction for sonic motors and sonically operated tools.
It should be understood that numerous modifications may be made in the various forms of the invention described above without deviating from the broader aspect of the invention.
1. A sonically operated, portable, hand-supported device comprising: a transducer for producing longitudinal vibrations, said transducer being sandwiched between a first assembly of parts forming a supporting portion for the device and a second assembly of parts, the outermost portion of said first assembly of parts forming a handle for the device, said second assembly of parts forming a readily vibratory work-performing portion of the device and including at the end thereof a workperforming element which is to engage and vibrate a material external to the device, said transducer being sandwiched between said first and second assembly of parts so the longitudinal axis of the assembly of parts coincides with the axis of vibration of the transducer, said first assembly of parts having a mass many times that of said second assembly of parts and said entire device comprising said first and second assembly of parts forming with the transducer therebetween a half-wave vibrator where the maximum particle velocity thereof is at or near the end of said work-performing element, said transducer and said first relatively heavy assembly of parts having aligned openings, and said work-performing element being exposed at the end of the device opposite to the side of '55 engage and vibrate a material external to the device, said transducer being sandwiched between said first and second assembly of parts so the longitudinal axis of the assembly of parts coincides with the axis of vibration of the transducer, said first assembly of parts having a mass many times that of said second assembly of parts and said entire device comprising said first and second assembly of parts forming with the transducer therebetween a half-wave vibrator where the maximum particle velocity thereof is at or near the end of said work-performing element, said relatively light second assembly of parts including a tapered velocity transformer having its wide end adjacent said transducer, and the velocity transformer having a longitudinal bore opening onto and extending from the wide end thereof and which bore communicates and is in alignment with said openings in said transducer and first assembly of parts, said connecting shank of said work-performing element passing freely through the end of said bore at the wide end of said velocity transformer and being rigidly secured to the velocity transformer at the other end of the bore.
3. A portable hand-supported sonically operated tool unit comprising: a housing having an opening therein through which extends a vibratable tool shank, and sonic motor-forming means within said housing and comprising a series of juxtaposed parts held together to form a compressed sandwich of parts including, in order from the front to the rear thereof, an annular member of a relatively dense metal anchored to said housing, annular transducer means which vibrates longitudinally on application of an alternating current thereto, and a rearwardly tapered velocity transformer made of a relatively less dense material than said annularmember and having a longitudinal bore extending from the front face thereof to a rear portion thereof, said annular member and annular transducer means having aligned central openings through which said tool shank passes, the tool shank also freely passing into said longitudinal bore of said velocity transformer and being rigidly secured to the rear end of said longitudinal bore at which point longitudinal vibrations are transmitted to the tool shank.
4. The hand-supported sonically operated tool unit of claim 3 wherein said tool shank has on the outer end thereof an abrading tool for removing the oxide coating of a surface to be soldered, said tool shank and abrading tool forming a soldering iron which heats the abraded surface and solder applied thereto.
5. The tool unit of claim 4 wherein there is a conductor in said tool shank which carries heater current for heating the abrading tool and said conductor terminates in a projecting pin at the rear of said tool shank fonning a terminal for the heater current, and a socketforming member in said housing into which said projecting pin frictionally fits.
6. The tool unit of claim 3 wherein the rear end of said tool shank is flat and abuts a flat end defining wall of said longitudinal bore to form a good vibration transmitting interface between the velocity transformer and the tool shank.
7. The tool unit of claim 3 wherein said annular transducer means comprises at least one piezoelectric annular disc to the opposite annular facing sides of which are connected a source of high voltage at a relatively high frequency producing longitudinal vibrations thereof; and there is provided means for pre-stressing said piezoelectric discs comprising a hollow stud passing through said annular transducer means and threaded into said velocity transformer at the rear end thereof, a spring washer means encircling said tool shank in spaced relation thereto and positioned against the front side of said annular member, and a nut threaded around the forward end of said stud and tightened around said stud to apply pressure against said spring washer means to draw the parts of said sandwich together to apply compressive stress to said piezoelectric disc.
8. An electromechanical transducer assembly comprising electromechanical transducer means sandwiched between two members of substantially different weight and constituting with said members a mechanical vibrating system which vibrates as a halfwave vibrator in the direction of a line extending through said members and said transducer means, the lighter of said members including a tapered velocity transformer having its longitudinal axis extending parallel to said line and its wide end nearer said transducer means than the narrow end thereof, the wide end of said velocity transformer being immediately contiguous to said transducer means, the heavier of said members and said transducer means having aligned openings extending completely therethrough and said velocity transformer has a longitudinal bore opening onto the wide end thereof and in alignment with said openings in the heavier member and said transducer means, and vibration coupling means passing freely through said aligned openings of said heavier member and said transducer means and the adjacent end of said bore of the velocity transformer and being rigidly secured to the velocity transformer at the other end of said bore.
9. In a sonic motor including transducer means for providing longitudinal vibrations in a given direction, the improvement comprising a first tapered velocity transformer having an axis extending in the direction of said longitudinal vibrations and whose wide end is connected to said transducer means, said velocity transformer having a tapered bore therein whose axis is aligned with the axis of the velocity transformer and whose narrow end is nearest the wide end of the velocity transformer, said tapered bore of said first tapered velocity transformer having at the wide end thereof a shoulder facing in the direction of the wide end of the velocity transformer, a second tapered velocity transformer mounted within said tapered bore of said first tapered velocity transformer with the wide end of said second tapered velocity transformer rigidly engaging said shoulder of said first tapered velocity transformer and spaced from the other defining walls of the tapered bore therein whereby to befreely longitudinally vibratable within said bore, and means to be vibrated mechanically coupled to said second tapered velocity transformer.
10. The sonic motor of claim 9 wherein said means to be vibrated is a third tapered velocity transformer mounted in a tapered bore within said second tapered velocity transformer the axis of the latter bore being aligned with the axis of the second tapered velocity transformer, the narrow end of the latter bore being neare t the wide e d of e sec nd ta ere velocit transfbrmer, and tire wiiie en ther of aving g shoulder facing in the direction of the wide end of the second tapered velocity transformer, and said third tapered velocity transformer, and said third tapered velocity transformer being rigidly secured to the latter shoulder, the rest of the third tapered velocity transformer being free to vibrate longitudinally within the latter tapered bore.
11. The sonic motor of claim 10 wherein said transducer means and said first, second and third tapered velocity transformers have aligned openings therein extending from the side of said transducer means remote from said velocity transformers to a point deeply within said third velocity transformer, and connecting shank means extending freely through the openings of said transducer means and said first and second tapered velocity transformers and through the end of the opening of said third tapered velocity transformer, and said connecting shank means being secured rigidly to the walls of said third velocity transformer at a point at the narrow end portion thereof.