US2553251A - Vibrating tool - Google Patents

Description

y 1951 R. P. GUTTERMAN 2,553,251

VIBRATING TOOL 2 Sheets-Sheet 1 Original Filed Jan. 2, 1947 INVENTOR.

R IJEP F '1 Eu ateman ATTORNEYS May 1951 R. P. GUTTERMAN 2,553251 VIBRATING TOOL Original Filed Jan. 2, 1947 2 Sheets-Sheet 2 1 1" PRE. POWER.

,DSEILLATU AMPLIFIER AMPLIFIER I,

a 7 12 III R13]: ET r 1 EUJEJE' ETTTLELTL ATTORNEYS Patented May 15, 1951 VIBRATING TOOL Robert P. Gutterman, St. Paul, Minn assignor to Engineering Research Associates, Inc., St. Paul, Minn, a" corporation Original application January 2, 1947, Serial No;

719,861.. Divided and this application April 2, 1948, Serial No. 18,629

4 Claims. 1 This invention relates to improvements in vibratory motors.

A primary object of this invention is the provision of an improved magnetostrictive vibratory structure particularly well adapted for use in connection with machining tools and the like.

This application is a division of my copending application Serial No. 719,861, filed January 2, 1947, and a full understanding of methods for adapting and using the present invention may be had with reference to that application.

Other objects and advantages of this invention will be apparent during the course of thefollowing detailed description and the appended claims.

In the accompanying drawings, forming a part of this specification, and wherein similar reference characters designate corresponding parts throughout the several views,

Figure 1 is a plan view of the improved vibrattory tool holder, showing casing cover removed.

Figure 1A is a partial exaggerated end view of the structure in Figure 1.

Figure 2 is a longitudinal cross sectional view taken substantially on the line 2- -2 of Figure .1, the cover being shown as a part of the holder.

Figure 3 is a transverse cross sectional view taken substantially on the line 33 of Figure 1.

Figure 4 is an inside view of an end wall of the casing.

Figure 5 is an enlarged transverse cross sectional view taken through the laminated magnetostrictive driving rod associated as a part of the holder, substantially on the line 5-5 of Figure 1.

Figure 6 is a diagrammatic view showing a circuit arrangement for oscillating the magnetostrictive driving member.

Figure '7 is a diagram of the preamplifier wiring circuit.

Figure 8 is a diagram of the power amplifier wiring circuit.

Figure 9 is a wiring diagram of a vibratory pickup for determining proper resonance frequencies,

Referring to the vibratory tool holder, the same includes a casing structure 30 having a compliant tool clamp 31 detachab'ly supported therein for holding the material operating tool 32. A lamina-ted magnetostrictive driving rod 33 is provided as a part of the tool holder having associated therewith a driving coil 34- and a pickupcoil 35 to be subsequently described.

ill

The casing structure 30 includes an integral casing body having a. bottom wall 40 andv side walls M and 12 paralleling each other and pro viding a channel or compartmen 4 he fibetween wherein the-details 3|, 33, 34 and 35 above described are reecived. The casing body is clone ated and at its fore end it detachably receives the compliant tool clamp 3| to be subsequently described.

A canvas l n d p ol c r sin i ulat on closure 42 is provided for the top of the casing structure 30, being secured by a plurality of bolts 43. They are marginally secured to the top edges of the walls ii and 42 in the tapped openings 14', Anend wall 50, of the same material as the :10..- sure, is secured as by bolts 5| to the side wallsof the body 30, The wall 50 supports coaxial cables 52, with clamp or nut structures secured in aps proved manner thereto. From these cables. the various conductors lead to the driving and pickup coils 34 and 35, as shown in Figure 1,

The compli nt clamp 31 for the cutting tool acts as a supporting diaphragm for the cuttin tool or bit, in order that high frequency vibrations can be properly transmitted f om the magnetostrictive driving rod 33 to the cutter. To that end the compliant tool clamp 3lllcomprises a b dy p .tion having at each end thereof laterally extending relatively thin diaphragm portions 5.6, ,to which are integrally connected attaching flanges 51. The latter are adapted to lie against the inside surfaces .of the side walls H and 42 and are secured thereto by bolts 51?, as shown in Figure 3. It will be noted that the flanges 51 extend the full height of the compartment 4| but the diaphragm sections 56 so Support the body 55 as to be free of surface contact with the inside surface of the bottom wall and inside surface of the top Wall of the casing structure. This is important, not only to enable proper vibration of the tool, but also to provide rather minute air passageways '60, shown in Figure 3 of the drawing, throughwhich the cooling medium passes on its way to discharge from the tool bit end of the casing.

An enlarged front view of one diaphragm portion 56 is shown in Figure 1A. This shows the detail of the air passageway 60.

It will be noted that the spring sections 56 are relatively narrow and long in the direction of maximum cutting force. Thus, this force'will be taken up in shear, rather than in bending, while the vibration forces are taken up in bending rather than in shear. These compliant sections are such as to prevent any transverse movement of the cutting tool, such as would normally ocour in the use of a conventional type single-disc diaphragm. They enable the tool to move only in the direction of the longitudinal axis of the casing, with a limiting amplitude of such motion of approximately .001" deflection from the position of rest.

The body portion 55 is provided with a passageway 6| therethrough preferably of polygonal cross section, adapted to receive the attaching end of the appliance or cutting tool 32; the same being secured in place upon the compliant tool clamp by means of set screws 63, shown in Figure 2. The head ends of these set screws clear the opening in the closure wall 42 provided therefor.

Referring to the magnetostrictive driving rod 33, the same is preferably of nickel or nickel alloy and is of laminated construction. Generally the driving rod consists of a pile of thin laminations of pure nickel separated by very thin electrical insulating layers and bonded together to form a mechanically strong assemblage by means of an adhesive. This is done by producing on all the surfaces of the individual laminations a thin coating of oxide and the bond is accomplished by means of sodium silicate. The individual laminations are cut to size and cleaned in an acid dip and acetone. They are then individually heated in air at 1850 F. for one hour, raising and lowering the temperature over a twenty-four hour cycle. That is, the temperature is raised during the first twelve hours to 1850 F., maintained at this temperature for one hour, and then lowered gradually over the following eleven hours. This produces a thin enclosing oxide coating on each lamination. They are then coated with 1.38 specific gravity NazSiOs solution. Thereafter they are assembled in a press and a total of 500 lbs. pressure is exerted. In this condition the assembled laminations are baked at 300 F. for two hours until the bonding is completed.

The rod as thus completed is approximately long; the individual laminations being .015" in thickness, and the rod in cross section is square. The end of the. rod is then trimmed to provide the stud socketing portion 6| shown in Figure 2, which is square and A" long. This completes the formation of the rod. It is tinned with solder at its stud end, placed within the passageway 6| of the compliant tool clamp 3| for the full length of the stud, and soldered in place. The exposed portion of the rod is then heated to approximately 150 F. and given a coat of G. E. Glyptal red varnish in order to exclude moisture and oil-vapor or oil, any of which agents would adversely affect the silicate bond. The driving coil 34 comprises a spool-shaped supporting form 65 which is of insulation and preferably canvas laminated phenolic resin. It has suitable winding thereon. The pickup coil 35 is similarly formed.

Before referring to a description of the magnetostrictive functioning, it will be understood that the entire tool. holder is adapted to be clamped upon some base portion 28 of the cutter supporting mechanism of the lathe. The manner of so clamping may be fully understood with reference to my previously mentioned copending application.

Means is provided to cool the internal parts of strictive driving rod. Any approved gaseous cooling means may be used. I prefer to provide air as the cooling medium. It is forced under pressure through a suitable line having a shutoff valve 8| provided to control the volume of air. This line extends into a suitable opening 82 through which air passes into the chamber or compartment 4 I. A small portion of the air exists through the passageways above described, at the fore end of the tool clamp. The major part passes between the outer surfaces of the driving rod 33 and the inner walls of the spools of the driving and pickup coils and exits through the ducts 84 provided in the rear wall or cap 50.

It will be noted that the tool clamp is so constructed that the magnetostrictively actuated cutting tool is free to move in a direction parallel to the longitudinal axis of the casing. The limiting amplitude of such motion is approximately .001" deflection from a position of rest. As before mentioned, the driving means employed is based on the principle of magnetostriction. This duced by the application of a magnetic field. Pure nickel demonstrates a large and comparatively regular magnetostrictive action. If the driving rod is placed in an alternating magnetic field the magnetostrictive effect will cause the rod to change its length at a frequency equal to twice the frequency of the alternating field. If a steady field is applied to the rod together with the alternating field and the relative strength of the two field components is properly adjusted, the rod will then change its length at a frequency equal to that of the alternating field, provided that the alternating field strength does not exceed that of the steady field. Since the curve of a relative change of length vs. applied magnetic field is strongly non-linear in the regions of very small and very large field strengths and since saturation may occur at large field strengths, it is possible to vary the steady field strength so that the material will be caused to operate magnetostrictively at an optimum point as regards magnitude of the effect. The alternating field is normally referred to as the driving field, while the steady component is referred to as the polarizing or biasing field. If the frequency of the driving field is made equal to the natural frequency for vibration in length of the rod, or one of the harmonies of this frequency, it is possible to build up a very large amplitude of mechanical vibrations in the rod. The maximum amplitude obtainable without exceeding allowable mechanical stresses in the rod is about 0.0001 x the total length of the rod. If it is desirable to operate such a rod at reasonably high frequencies with fair efficiency, it is necessary to reduce eddy current losses in the nickel by some appropriate means. This is accomplished in the present instance by laminating the rod as above described. Vibratory changes in length of the rod at a mechanical resonance frequency cause the body portion of the tool clamp to vibrate due to the reaction of the mass of the rod against the acceleration accompanying its vibratory change of length. This reaction causes the cutting tool to move.

The driving coil is connected thru one of the coaxial cables above described to a source of alternating current which produces a driving field and to a parallel source of direct current which produces the biasing field. Since the greatest stress for a given magnetic field in a vibrating rod is produced in the nodes of vibration, the

5. driving coil is located so that its center coincides with a node corresponding to the desired resonant frequency of the rod. In the particular rod described the length is such that its fundamental frequency is approximately 11,000 cycles per'second, with a strong harmonic resonance at 23,500 cycles per second, when mounted as described above. The latter frequency has been chosen as the normal operating frequency for the tool holder since it is high enough to be well with in the supersonic range and close enough to the fundamental resonance to allow stable and efiicient operation. At this frequency,. nodes occur at the juncture with the tool clamp and also at a point /9, of the distance back of this juncture. This is the position where the driving coil is located.

The alternating current for the driving coil is obtained from a power amplifier. The input for this power amplifier may be obtained from a standard oscillator such as the Hewlett-Packard type 200- or it may be provided by a pickup coil surrounding the driving rod in the location shown in Figure 2. This provides a feedback arrangement to the input of the power amplifier such that electrical oscillations of the system are controlled by the rod itself. Either means for obtaining the alternating current will suffice. In Figure 6 the feedback hookup has been shown in full lines and the oscillator in dot and dash lines. Of course, if the oscillator is connected in the circuit the feedback arrangement is not used.

In Figure 6 is shown a composite diagrammatic view of the radiant energy hookup, and in Figures '7 and 8 are respectively shown the preamplifier and power amplifier hookups. The conductor terminals for the oscillator or feedback areshown at 9B and Si in Figure 7 for the preamplifier, and the power amplifier conductor terminals 92 and 93 are shown in Figure 8 and also at the end of the circuit in Figure '7.

Using an oscillator as the source of alternating current, indicated at H30 in Figure 6, the same is connected in standard manner to the preamplifier of which the first amplifier stage is the tube lill, shown in Figure '7. The output from the oscillator is amplified in the tube Ill] and .its output is transferred through a phase inverter stage through the network [02-103. The purpose of the phase inverter stage is to develop equal voltages which are out of phase and may be applied through I04 and N35 to the grids of a push pull output stage consisting of the tubes I06. The plate circuit of these push pull output tubes is connected to the transformer I01 which is used as an impedance matching device for applying the output voltage to the grids of tubes )8 and W9 (see Figure 8) which constitute a power amplifier stage whose output may be con- .nected to the tool holder system by means of the output transformer H6. The secondary winding of the transformer H0 is tapped and provided with a switch 130 for selecting the taps so that various impedances are available teal- .low matching the impedance of transformer: H0

to the impedance presented by the tool holder system. One side of the output circuit is grounded at ill and the other side of this circuit is passed through a variable condenser H2 which is in series with the driving coil 34. The other side of the driving coil is grounded as shown. This completes the means for introducing high frequency alternating current through the driving coil.

In order to provide a biasing or polarizing diroot current through the driving coil 34 in addition to the high frequency alternating current above described, a direct current supply I [3 (Figure 8) is provided. In order to prevent the passage of the high frequency alternating current through the direct current supply, filter circuit I14, tuned to the same frequency as the operating frequency. desired, is inserted in series with the high side of the direct current supply. This filter H4 is of the parallel resonant type and presents a very high impedance at the resonant frequency.

Since the chosen resonant frequency of the driving rod is subjected to some variations over a small range, due to changes in its temperature or conditions of load, the use of a fixed frequency oscillator, as above described, to provide the original driving voltage sometimes results in reduced efficiency due to disparity between the frequency produced by the oscillator and the resonant frequency of the rod. In order to provide a more efficient system the rod can act as the frequency controlling device. If this is done, slight shift in the resonant frequency of the rod will not have a significant effect on its amplitude of vibration. The means for allowing the rod to act as a frequency controlling device, as above described, consists of providing a pickup coil 35 upon rod 33, shown diagrammatically in the circuit in Figure 6. It is so wound that the voltage developed in it, due to magnetostrictive changes in the'driving rod, is out of phase with the voltage developed in the driving coil 34. The voltage from the pickup coil 35 may be applied directly to the terminals of the preamplifier normally connected to the oscillator, as shown in full lines in Figure 6. The driving rod is capable of several'different modes so that unless some auxiliary device is provided in the feedback circuit from the pickup coil to preselect the desired mode or frequency of oscillation, the motion of the rod would be unpredictable. Such a device comprises the filter H5, shown in Figure 6, which is of a series resonant nature. It is characteristic of such filters that their impedance is a'minimum at the resonant frequency and becomes high at other frequencies.

Some means for detecting and determining the resonant frequencies of the magnetostrictive rod is necessary. This may be done by means of noting theeffect of the cutting tool upon the work or more accurately by means of a vibration pickup, such as diagrammatically shown in Figure 9. This may consist of a steel shank, shown at I20 in Figure 9, which may be socketed in the toolclamp in place of the usual cutting tool as shown diagrammatically at 33 in Figure 9. The steel shank together with a stiff steel wire [2| is connected to the sensitive element of a massive vibration pickup. The entire weight of the pickup is supported by the steel wire connection. This steel wire 12] is connected to an armature ['22 torsionally mounted between two permanent magnets I23' and I24 each of which is surrounded by a coil. The coils of these magnets are interconnected in such relationship to the polarity of the magnets that oscillation of the armature produces a voltage in the coils which is proportional to the amplitude and frequency of the armature motion. The cells are arranged in such relationship to the polarity of the magnet that any external magnetic field of a varying nature will produce voltage in the -two coils which are equal and opposite in direction so that stray fields, due'to operation of the tool. holder, will not produce spurious voltages at the terminals of the vibrational pickup. The terminals of the vibrational pickup may be connected to a standard vacuum tube voltmeter I25.

The procedure for putting the described apparatus and entire system into operation is as follows:

Using the oscillator 100 shown in Figure 6 as the source of high frequency alternating current, after the various resonant frequencies possible in the magnetostrictive rod have been determined, the desired frequency is selected and the oscillator is tuned close to that frequency. The amplifying and direct current circuits are turned on and the output of the oscillatoramplifier is adjusted to provide a moderately powerful output. Some means appropriate for detecting the vibration of the tool is employed continuously during the tuning procedure, such as the vibrational pickup above described. The oscillator frequency is very slowly varied by appropriate and standard controls (not shown) on the oscillator in the neighborhood of the desired frequency and the vibration detecting means is observed so that maximum vibration of the tool can be established. When this is done the setting of the condenser I I2 is varied until the combination of H2 and coil 34 is brought into series resonance. This will be detected by a marked increase in the amplitude of vibration of the tool. It is characteristic of the series resonant combination of H2 and 34 that its impedance becomes a minimum at the resonant frequency. Therefore, when this resonant frequency is made to coincide with that of the rod a maximum alternating current is passed through the driving coil 34.

After the variable condenser H2 and driving coil have been brought to resonance at the proper frequency, the selector switch I30 (see Figure 8) is varied to try different output impedance until a new maximum of vibration has been established at the tool. This operation ensures most eflicient transfer of energy from the power amplifier to the tool holder system inasmuch as the output impedance of the power amplifier is thereby matched to the impedance presented by the tool holder.

Referring to the direct current supply shown in Figure 8, the filter H4 is now tuned to the same frequency as that applied to the rod. When this is done the parallel resonant nature of the filter H4 is such that its impedance to the high frequency alternating current is maximum. This prevents any significant amount of the high frequency current from being shunted by the direct current supply. The D. 0. current is now Varied until another new maximum of vibration of the tool clamp is noted. This notation can be made either by using the vibration pickup, or through notation of the effect of the cutter upon the work, as above mentioned, if the vibration pickup is replaced by a cutter.

After the desired frequency has been obtained, it is not necessary to vary the controls. They may be set and as thus adjusted will cover a very wide range of work, not only as to size of work but also material involved. The controls having been set all that is necessary to do is to turn the current on and off.

For self-excited operation as the source of supply of high frequency alternating current, the oscillator I of course is not used and is disconnected as is shown in Figure 6. The feedback circuit is connected as shown in full lines in Figure 6. Assuming that the controls have all been set, as determined for operation with the oscillator I00; the latter of course havin been subsequently disconnected, the condenser section of H5 is varied until a maximum of tool vibration is noted and the system is then in operating condition.

From the foregoing it will be apparent that I have disclosed a very useful vibratory motor structure, particularly for machine tools or the like.

It will be understood that the above detailed description has been made only for purposes of illustration, and is not intended to limit my invention. The true scope of my invention is to be determined from the following claims.

I claim:

1. In a vibratory motor the combination of a casing structure comprising a supporting casing, an elongated magnetostrictive core, a driving coil mounted upon the casing in operating relation with respect to said core, and means mounting the vibrating portion of the core upon the casing including a plurality of elongated thin and nar row strips of material capable of supporting the core for longitudinal vibration without lateral defiection, said strips of material being disposed at opposed sides of the core at a plurality of relatively spaced locations at each of said sides.

2. In a vibratory motor the combination of a casing structure, an elongated magnetostrictive core, a driving coil upon the casing structure for said core, and diaphragm means connecting the vibrating portion of said core to said casing structure including a body clamped to said core, attaching portions secured rigidly upon the easing structure at each side of the core and in spaced relation to said body, and thin elongated narrow diaphragm strips securing the body of the diaphragm means to the attaching portions for permitting longitudinal vibration of the core without lateral deflection thereof.

3. In a vibratory motor the combination of a casing structure, an elongated magnetostrictive core, a driving coil upon the casing structure for said core, and diaphragm means connecting the vibrating portion of said core to said casing structure including a body clamped to said core, attaching portions secured rigidly upon the casing structure at each side of the core and in spaced relation to said body, and thin elongated narrow diaphragm strips securing the body of the diaphragm means to the attaching portions for permitting longitudinal vibration of the core without lateral deflection, said strips bein provided at each side of the core and at a plurality of relatively spaced locations longitudinally of the core.

4. In a vibratory motor the combination of an elongated casing having a compartment therein, an elongated magnetostrictive rod for said compartment, a driving coil in the casing for said rod, diaphragm means securing the vibrating portion of the rod to said casing in spaced relation with respect to the driving coil, the driving coil and diaphragm means having passageways therethru opening externally of the compartment and open to said compartment, and means for forcing a cooling medium into the compartment of the casing between the driving coil and diaphragm means and thru said passageways for exit from said casing.

ROBERT P. GUTTERMAN.

(References on following page) 9 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 19,461 Pierce Feb. 12, 1935 607,589 Haines July 19, 1898 1,307,654 Bergonie June 24, 1919 1,682,364 Ballantine Aug. 28, 1928 10 1,966,446 Hayes July 17, 1934 2,166,359 Lakatos July 18, 1939 2,233,829 Blackwell Mar. 4, 1941 2,391,678 Bundy Dec. 25, 1945 10 FOREIGN PATENTS Number Country Date 553,176 Great Britain May 1 1943 OTHER REFERENCES Magnetic Properties of Compressed Powdered Iron, by B. Speed and G. W. Elmen, Bulletin of the American Institute of Electrical Engineers, pages 13211359, esp. p. 1327, 1921.

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