US3273288A

US3273288A - Ultrasonic grinding and honing

Info

Publication number: US3273288A
Application number: US190154A
Authority: US
Inventors: Kuris Arthur; Balamuth Lewis
Original assignee: Cavitron Ultrasonics Inc
Current assignee: Cavitron Ultrasonics Inc
Priority date: 1962-04-25
Filing date: 1962-04-25
Publication date: 1966-09-20
Anticipated expiration: 1983-09-20
Also published as: GB971530A; DE1502379B1

Description

P 1966 A. KURIS ETAL 3,273,288

ULTRASONIC GRINDING AND HONING Filed April 25, 1962 4 sheets-Sheet l INVENTORS LEWIS BALAMUTH 8.

ARTHUR KURIS p 1966 A. KURls ETAL 3,273,288

ULTRASONIC GRINDING AND HONING Filed April 25. 1962 4 Sheets-Sheet 2 INVENTORS LEWIS BALAMUTH 8. g, BY ARTHUR KURIS ATTORNEY Sept. 0, 1966 A. KURIS ETAL ULTRASONIC GRINDING AND HONING 4 Sheets-Sheet 3 Filed April 25. 1952 w & a MH R mwm MR Wmw 1A E 5 mm a 4 LA Hm J Z ATTORNEY P 0, 1966 A. KURIS ETAL 3,273,288

ULTRASONIC GRINDING AND HONING Fil d April 25 1953 4 Sheets-Sheet 4 fl/b' 3/9 ii 32/ i 26 w-fi/ jazz 3/95 INVENTORS LEWIS BALAMUTH & 17 g; 3 ARTHUR KURIS BYg ATTORNEY United States Patent "ice 3,273,288 ULTRASQNHC GRWDING AND HONING Arthur Kuris, Bronx, and Lewis Balamuth, New York, N.Y., assignors to Cavitron Ultrasonics lino, Long island City, N.Y., a corporation of New York Filed Apr. 25, 1962, Ser. No. 190,154 El Claims. (Cl. 51-72) This invention relates generally to grinding and honing, and more particularly is directed to improvements in apparatus for effecting grinding or honing in which the abrading surface is made to vibrate rapidly, for example, at ultrasonic frequencies, in directions generally normal to the area of that surface in contact with the workpiece.

It has heretofore been proposed, for example, in US. Letters Patent No. 2,695,478, issued November 30, 1954, to G. E. Comstock and G. Crompton, to effect radial vibration of a grinding Wheel for the stated purposes of permitting a high rate of stock removal even when grinding hard materials, reducing heating of the work and reducing wear of the grinding Wheel. In accordance with this previous suggestion, magnetostrictive elements are embedded in a resinous material, such as, phenolformaldehyde, forming an intermediate annular portion or zone of the grinding wheel interposed radially between inner and outer annular portions or zones of the wheel consisting of abrasive grains bonded with phenol-formaldehyde resins. The several annular zones or portions of the grinding wheel are molded integral with each other or formed separately and then subjected to heat and pressure so as to be united into an integral whole. The grinding wheel with magnetostrictive rods embedded in the resinous material thereof is rotated adjacent a circularly arranged series of electromagnets supplied with a biased alternating current at a suitable high frequency so that the resulting alternating electromagnetic fields cause vibration of the magnetostrictive rods at a corresponding frequency.

However, it has been found, in actual practice, that the vibrations of the magnetostrictive rods embedded in the resinous or other bonding material of the grinding wheel do not effectively produce radial vibrations at the active surface or periphery of the grinding wheel. The absence of any radial vibrations at the peripheral surface of the grinding Wheel that can appreciably afifect the grinding operation is due to the ineflicient transmission of the vibrations through the resinous or other bonding material forming the grinding Wheel. It is known that high frequency sonic and ultrasonic vibrations or compressional waves are only efiiciently transmitted through materials having a high mechanical Q or quality factor, whereas materials having a relatively low mechanical Q, such as, the resinous material of the above described grinding Wheel, absorb the vibrations rather than transmitting the same from the embedded magnetostrictive rods to the active peripheral surface of the grinding wheel.

Accordingly, it is an object of the present invention to provide means by which high frequency or ultrasonic vibrations of substantial amplitude directed generally normal to the surface of the workpiece are produced at the active periphery or surface of a grinding wheel, abrasive belt or honing tool so that such vibrations cooperate with the normal abrading action to actually achieve a high rate of stock removal, even when grinding or honing the hardest of materials, While reducing heating of the workpiece and wear of the grinding wheel, abrasive belt or honing tool.

In accordance with an important aspect of this invention, there is provided at least one abrading element consisting of abrasive grains bonded to a backing or of a mixture of abrasive grains and a suitable bonding resin, and having a relatively small thickness in the direction 3,273,288 Patented Sept. 20, 1966 normal to its active grinding or honing surface, and which may be in the form of a ring, belt or arcuate sections, moved across the workpiece and being subjected to high frequency or ultrasonic vibrations of substantial amplitude in directions normal to its active surface at least in the area of contact of the latter with the workpiece.

Since each abrading element has a relatively small thickness in the direction of the vibrations, the latter are effectively transmitted therethrough to the abrading or active surface even though the material of the abrading element may have a relatively low Q or quality factor, that is, a relatively great tendency to absorb vibrations.

In accordance with one embodiment of this invention, a grinding wheel is provided with a generally circular metal body having a high mechanical Q or quality factor and a diameter which is only slightly smaller than the desired outer diameter of the grinding wheel, and an abrading element or elements in the form of a circular ring or sections of a circular ring, respectively, is or are suitably secured on the peripheral surface of the metal body so that, when high frequency or ultrasonic radial vibrations are produced in the metal body, such vibrations are effectively transmitted radially through the abrading element or elements to provide radial vibrations of substantial amplitude at the outer or active abrading surface .of the grinding wheel.

In grinding wheels embodying the invention, the metal body of the grinding wheel may be formed of a magnetostrictive material and have exciting coils or windings associated therewith so that, upon the feeding of biased high frequency alternating current to such coils, the body of the grinding wheel acts as a magnetostrictive transducer for producing the desired radial vibrations at the periphery thereof. Alternatively, the shaft carrying the metal body of the grinding wheel may be longitudinally vibrated and have the metal body of the grinding wheel located at a nodal plane of the longitudinal vibrations and diametrically dimensioned so as to be resonant at the frequency of the longitudinal vibrations, whereby the metal body of the grinding wheel is vibrated radially. In either case, the metal body of the grinding wheel embodying this invention may be formed as an acoustic impedance transformer for magnifying the amplitude of the radial vibrations transmitted to the abrading element or elements.

In accordance with another embodiment of this invention, the abrading element is in the form of an endless flexible or rigid member made to travel along a closed path having an area of contact with the workpiece, and being backed up, at such area of contact with the workpiece, by a member vibrated generally normal to the active or abrading surface of the abrading element. Where the abrading element is in the form of a flexible abrasive belt, the member backing up the latter at its area of contact with the workpiece may be in the form of a contact Wheel which is vibrated radially and mounted for rotation so as to have the same peripheral speed as the abrasive belt traveling around the contact wheel. Since the abrasive belt is flexible, the peripheral surface of the radially vibrated contact wheel may be contoured for similarly shaping the abrasive belt running thereover, thereby to permit contour grinding of the workpiece.

Further, since high frequency or ultrasonic vibrations directed normal or perpendicular to two relatively movable surf-aces have the effect of very substantially reducing the frictional resistance to such relative movement, the vibrated member backing up the endless abrasive element at the area of contact of the latter with the workpiece may be stationary and merely made to vibrate in directions substantially normal to the path of the endless abrasive element moving thereacross, so that such vibrations are relied upon both to improve the abrading characteristics and to substantially eliminate friction between the vibrated member and the moving abrasive element.

The above, and other objects, features and advantages of this invention, will be apparent in the following detailed description of illustrative embodiments thereof which is to be read in connection with the accompanying drawings, forming a part hereof, and wherein:

FIG. 1 is an elevational view, partly broken away and in axial section, of a grinding wheel embodying the present invention;

FIG. 2 is a transverse sectional view taken along the line 2-2 on FIG. 1;

FIG. 3 is a view similar to that of FIG. 2, but showing a modification thereof;

FIG. 4 is an elevational view similar to that of FIG. 1, but showing a grinding wheel constructed in accordance with another embodiment of this invention;

FIG. 5 is a fragmentary sectional view corresponding to a portion of FIG. 3, but illustrating another modification thereof;

FIG. 6 is a fragmentary perspective view showing a grinding wheel constructed in accordance with still another embodiment of the invention, and with a portion of the abrading element thereof being broken away so as to disclose the arrangement of the body of the grinding wheel;

FIG. 7 is a side elevational view of an abrasive belt grinding machine embodying the present invention;

FIG. 8 is a front elevational view of the machine of FIG. 7;

FIG. 9 is a fragmentary front elevational view illustrating a modification of the machine shown in FIGS. 7 and 8 which makes possible the grinding of contours;

FIG. 10 is a side elevational view of a grinding machine employing an endless abrading element moving along a closed path and associated with a stationary vibrating member or transducer in accordance with still another embodiment of this invention;

FIG. 11 is a side elevational view of a grinding machine similar to that shown in FIG. 10, but employing a flexible abrasive belt as the abrading element;

FIGS. 12, 13 and 14 are enlarged fragmentary views illustrating various contours that may be given to the stationary vibrating member or transducer in the grinding machine of FIG. 11;

FIG. 15 is an enlarged fragmentary sectional view taken along the line 1515 on FIG. 11;

FIG. 16 is a vertical, axial sectional view of a honing machine embodying this invention;

FIG. 17 is a sectional view taken along the line 1717 on FIG. 16; and

FIG. 18 is a view similar to that of FIG. 17, but illustrating a modification of the honing tool in accordance with the invention.

Referring to the drawings in detail, and initially to FIGS. 1 and 2 thereof, it will be seen that a grinding wheel in accordance with the present invention, and there generally identified by the reference numeral 10, includes a body 11 of generally circular configuration which may be brazed, soldered or otherwise secured on a supporting shaft 12, and in which radially directed compressional waves are set up. In order to effect rotation of the body 11, shaft 12, which is supported in bearings 13 of a suitable frame 14, may be connected either directly, or through a suitable transmission, to the shaft of a driving electric motor (not shown).

In the case where the 'body 11 of grinding wheel 10 is in the form of a magnetostrictive transducer so that the compressional waves are generated directly therein, as illustrated in FIGS. 1 and 2, the body 11 is formed of magnetostrictive material, such as, nickel, Permanickel, Permendur, or other metals which have high tensile strength and are highly magnetostrictive in character. Thus, the body 11 vibrates radially to a maximum degree when subjected to the influence of an alternating electroa}. magnetic field established by the supplying of biased alternating current to windings 15 provided directly on body 11, as hereinafter described in detail.

As is apparent in FIG. 1, body 11 is preferably formed of an axial series or stack of generally circular laminations 16 which may be stamped or otherwise fabricated from the selected magne-tostrictive metal. Each of the laminations 16 is formed with cutouts, as at 17 (FIG. 2), so that equally angularly spaced apart, generally radially directed sectors or portions 18 of the laminations are defined between adjacent cutouts 17. The energizing windings 15 are wound around the sectors 18 of the group or stack of laminations 16 which are axially superposed so that the high frequency alternating electromagnetic field established by the passage of a biased, suitable high frequency alternating current through the windings 15 induces or generates radially directed vibrations in the sectors 18 at the fundamental mode of radial vibration of the body 11.

The body 11 of grinding wheel 10 has an outer diameter which is only slightly smaller than the desired peripheral diameter of the grinding wheel, and the latter further includes at least one abrading element 19 bonded or otherwise suitably secured on the outer periphery of the body 11 and having a relatively small radial thickness.

In the grinding wheel of FIGS. 1 and 2, the abrading element 19 is shown in the form of a removable, and hence replaceable length of abrasive belting including a flexible backing having abrasive grains bonded to its outer surface. The abrasive belting is wrapped around the circumference of body 11 and has its ends directed radially inward between adjacent sectors 18 of the laminations forming body 11 and being secured to the latter by a clamping member or wedge 20 held against the inturned ends of the length of abrasive belting by a nut 21 on a screw 22 extending radially outward from the center of body 11. Although a particular arrangement is disclosed for securing the removable or replaceable abrasive belting 19 on the circumference of body 11, it is to be understood that other conventional means may be employed for releasably clamping the abrasive belting-19 on the circumference of the body. It is also to be understood that the belting may be merely adhesively secured on the body 11.

When the body 11 of grinding mvheel 11 is in the form of a magnetostrictive transducer, as illustrated in FIGS. 1 and 2, the biased, high frequency alternating current may be supplied to the energizing or exciting windings 15 through slip rings 23 (FIG. 1) carried by an insulating collar 24 on the shaft 12 and being connected by suitable conductors 25 to the windings. Stationary brushes 26 engage the slip rings 23 and are connected, as by conductors 27, to a suitable generator or other source (not shown) of biased, high frequency alternating current.

Since the abrading element 19 has only a small radial thickness, the radial vibrations from body 11 are efi'ectively transmitted therethrough to the outer surface of the abrading element even though the latter may be formed of a material having a relatively low mechanical Q or quality factor, that is, a material which tends to absorb vibrations when the latter are directed through a substantial thickness thereof. Since the body 11 forming the major portion of grinding wheel 111 is formed of metal having a high mechanical Q, the vibratory energy is efiiciently transmitted through the body, rather than being absorbed therein as in the case of a grinding wheel constructed in accordance with US. Letters Patent No. 7,695,478, identified more fully above, and a major portion of the generated vibratory energy is therefore available at the active outer surface of abrading element 19.

When the grinding wheel 10 embodying this invention is rotated on shaft 12 and a workpiece 28 is moved relative to the wheel along a path tangential to the outer surface of abrading element 19 so that the latter grinds the surface of the workpiece at the area of contact therebetween, the high frequency or ultrasonic radial vibrations produced at the outer periphery of grinding wheel in response to energization of the windings further cause erosion of the contacted surface of he workpiece. The vibrations imparted to the abrasive grains of element 19 assist the grinding action and, when the usual grinding coolant, such as, water having a rust inhibitor therein, is delivered to the grinding area by the usual nozzle 29, the ultrasonic vibrations cause cavitation of the coolant to further enhance the cutting action, particularly when the workpiece is formed of a hard brittle material, such as, hard carbides, oxides, borides or the like.

If desired, the metal body of the grinding wheel embodying this invention may be formed, as disclosed in detail in our copending application Serial No. 190,044 filed April 25, 1962 for Magnification of Radial Vibrations, granted June 30, 1964 as Patent No. 3,139,543, so that magnified or relatively larger amplitude vibrations are obtained at selected peripheral areas of the abrading element.

For example, as shown in detail in FIG. 3, a grinding wheel 19a embodying this invention, and hence formed of a metal body 11a consisting of a stack of laminations 16:: and a relatively thin abrasive element 19a adhesively secured or bonded on the periphery of body 11a, has generally radially extending slots or cutouts 171; formed in each lamination 16a so as to divide the latter into a circular series of sectors or portions 18a and 18b. The radial slots or cutouts 17a are dimensioned and disposed so that the sectors or portions 18a and 18b, which are arranged alternately around the lamination, have relatively small and relatively large masses, respectively. Further, each lamination 160 has equal odd numbers of the sectors or portions 18a and 18b, for example, five sectors 18a of relatively small mass and five sectors 18b of relatively large mass, as in the arrangement illustrated in FIG. 3, so that each sector 18a of relatively small mass is diametrically opposed by a sector 18b of relatively large mass.

In the grinding wheel We, the energizing windings 15a are wound around the relatively narrow stems of sectors 18a of small mass of a group or stack of the laminations 16:: which are axially superposed. Since the diametrically opposed sectors or portions 18a and 18b of each lamination have different masses, balancing of the momenta requires that the average radial velocity in each sector 18a of relatively small mass be greater than the average radial velocity in the diametrically opposed sector 18b of relatively large mass and, therefore, the amplitude of vibration in the radial direction at the outer end or periphery of each of the sectors 18a of relatively small mass is substantially greater than, or magnified with respect to the amplitude of the radially directed vibration at the outer edge or periphery of each sector 18b of relatively large mass. Further, since the sectors 18a and 18b are arranged alternately around each lamination 16a, the net center of gravity of each lamination, and hence of the body 11a made up of a series or stack of the laminations, remains at the central axis of body 11a, thereby to avoid gross vibrations or dynamic unbalance of the shaft 12a when rotated with the grinding wheel 10a thereon.

Since relatively large amplitude radial vibrations appear at the peripheral edges of the sectors 18a, it will be apparent that the corresponding portions of the abrading element 190 are similarly subjected to relatively large amplitude radial vibrations, while the intervening portions of the abrading element extending across the peripheral edges of the sectors 18b are subjected to relatively smaller amplitude radial vibrations. It has been found that, when the grinding wheel 10a is rotated in contact with a workpiece, the alternate engagement with the latter of portions of the abrading element 19a which are subjected to relatively large and relatively small amplitude radial vibrations serves to increase the rate of removal of material.

In the above described grinding wheels 10 and 10a, the energizing windings 15 or 15a are associated directly with the body 11 or 11a so that the latter functions as a transducer developing the desired radial vibrations directly within the body. However, it is to be understood that, in accordance with the present invention, longitudinal vibrations generated by a transducer may be first converted into radial vibrations which are then transmitted radially through the body of the grinding wheel to the abrading element at the periphery of the latter. Thus, as shown by way of example in FIG. 4, a grinding wheel embodying the present invention, and there generally identified by the reference numeral 10b may include a body 11b made up of an axially arranged stack of laminations 16b which may have the configuration of the laminations 16 of FIG. 2 or the laminations 16a of FIG. 3. The laminations 16b are formed of a suitably high strength material having a high mechanical Q, for example monel metal, but need not be formed of a magnetostrictive material. The laminations 16!) forming the body 11b are brazed, soldered or otherwise rigidly secured on a radial flange or enlargement 30 located at a nodal plane of longitudinal vibrations transmitted through a connecting body 31 from a magnetostrictive transducer 32. Transducer 32 may consist of a stack of nickel or other magnetostrictive laminations rigidly secured, at one end, to an end of connecting body 31, and extending loosely through a fixed insulating casing 33 carrying the energizing winding 15b to which biased, high frequency alternating current is supplied from a suitable generator or other source (not shown).

The mechanical vibrator consisting of connecting body 31 carrying body 11b of grinding wheel 10b and transducer 32 is rotatably mounted in bearings 13b carried by a frame 14b so that the entire assembly may be rotated about the longitudinal axis of the mechanical vibrator, for example, by a suitable transmission from an electric motor.

The length of the laminations of transducer 32 and the length of connecting body 31 are selected, with reference to the desired frequency of vibrations, so as to be equal to an integral number of half wavelengths of the compressional waves produced therein when biased, alternating current is delivered to the winding 15b at the desired high frequency, whereby the laminations of transducer 32 and connecting body 31 are resonant at such high frequency and standing waves are set up therein with loops of longitudinal motion at the ends of the transducer and at the ends of the connecting body. Further, body 11b of grinding wheel 10b is diametrically dimensioned so that it is radially resonant at the frequency of the longitudinal vibrations or standing compressional waves transmitted to connecting body 31 from the transducer 32. Since body 11b is located on the flange or enlargement 36) of connecting body 31 at a nodal plane of the longitudinal vibrations in the latter, the periphery of radial enlargement 3t vibrates radially, and such radial vibrations are transmitted radially through the laminations 16b of body 11b.

Grinding wheel 10b further includes an abrading element 1% having a relatively small radial thickness and being secured on the periphery of body 11b, either removably, as in FIG. 2, or by an adhesive bond, as in FIG. 3. The radial vibrations are transmitted through body 11b and may be magnified by providing the laminations 16b with the configuration shown in FIG. 3, and such radial vibrations are effectively transmitted through the thin abrading element 1% so that the outer or active surface of the latter is radially vibrated with a substantial amplitude at the desired high or ultrasonic frequency in order to enhance the grinding action on a workpiece.

Although the previously described grinding wheels have a single abrading element wrapped or extending around the entire periphery of the radially vibrated metal body of the grinding wheel, it is to be understood that the single continuous abrading element may be replaced by a series of abrading elements each in the form of a section of a circle and being suitably secured, by adhesive or other suitable bonding means, to the periphery of the metal body. As shown in FIG. 5, the use of a series of abrading elements on a grinding wheel 10c embodying this invention is particularly advantageous when the body 110 thereof is formed of laminations having alternately arranged sectors or portions 180 and 18c which, as in the embodiment of FIG. 3, are formed so as to have relatively small and relatively large masses, respectively. Thus, as previously described herein, the radial vibrations occurring at the outer edges or peripheries of the sectors 18c have amplitudes that are relatively large or magnified in relation to the amplitudes of the radial vibrations occurring at the outer edges or peripheries of the sectors 18's. In the grinding Wheel 10c, the abrading elements 190 secured to the peripheral Zones of the body 110 defined by the outer edges of sectors 18c of the laminations have relatively fine abrasive grains therein, while the abrading elements 19'0 secured to the peripheral zones of the body defined by the sectors 18'c have relatively coarse abrasive grains. Thus, the fine abrading elements 190 are subjected to relatively large amplitude radial vibrations, while the relatively coarse abrading elements 19'(: are subjected to relatively smaller amplitude radial vibrations. It has been found that the foregoing arrangement increases the rate of stock removal and yet maintains a superior surface finish on the workpiece being ground.

In the previously described grinding wheels having a body formed of laminations with alternately arranged sectors of relatively small and relatively large masses, for example, as in FIGS. 3 and 5, the several laminations have been axially superposed so that the zones of relatively large and small amplitude vibrations extend axially on the periphery of the body from one end to the other of the latter. However, it is to be understood that the laminations of the stack making up the metal body of the grinding Wheel may be arranged in groups each having the laminations thereof in axial alignment, and with the successive groups of laminations having their sectors of relatively small mass angularly offset with respect to the corresponding sectors in the adjacent groups so that the areas of relatively high amplitude radial vibrations are staggered both axially and circumferentially over the surface of the abrading element. Further, as shown particularly in FIG. 6, the successive laminations 16d making up the metal body 11d of the grinding wheel 10d may be angularly displaced or offset relative to each other so that the circumferentially alternating zones H of relatively high amplitude radial vibrations and zones L of relatively low amplitude radial vibrations extend helically on the periphery of body 11d to produce similarly located zones of relatively high and low amplitude vibrations at the active outer surface of the abrading element 19d extending around the periphery of the metal body.

In each of the above described grinding wheels embodying this invention, the abrading element or elements have been fixedly secured, either permanently or removably on the peripheral surface of the radially vibrated metal body so as to rotate and radially vibrate with the latter during operation of the grinding wheel. However, as shown particularly in FIGS. 7 and 8, the present invention may also be embodied in a grinding machine 110 of the type employing an endless abrasive belt 119 as the abrading element. In the machine 110, the abrasive belt 119 travels around a contact wheel 111 and an idler pulley 134 which are rotatable on spaced apart

parallel shafts

112 and 135 supported by a suitable frame 136 having a mounting or support bracket 137. A tension pulley 138 may be adjustably supported on frame 136 by an arm 139 to engage a run of abrasive belt 119 between contact wheel 111 and idler pulley 134.

The workpiece 128 may be fed past grinding machine 110, for example, on a movable table 140, so as to tangentially engage abrasive belt 119 as the latter passes around, and is backed up by contact wheel 111.

In accordance with the present invention, the periphery of contact wheel 111 is made to vibrate radially at a high or ultrasonic frequency so that vibrations are transmitted from the contact wheel through abrasive belt 119 to the active or abrading surface of the latter and thereby enhance the grinding action of the abrasive belt. As is apparent in FIG. 7, the contact wheel 111 may be formed of an axial series or stack of laminations 116 having a configuration the same as that of the laminations 16a described in connection with FIG. 3 so that radial vibrations of magnified amplitude are obtained at the periphery of the contact wheel. The radial vibrations may be generated directly in contact wheel 111, for example, by forming the laminations 116 of a magnetostrictive metal and providing energizing windings or coils wound around arms or sectors of the laminations, in a manner similar to that previously described with respect to the embodiments of FIGS. 1 and 2 and FIG. 3. Alternatively, contact wheel 111 may merely effect radial transmission of vibrations which are generated in the axial direction, for example, in the manner perviously described herein with reference to FIG. 4.

The abnasive belt 119 may be driven by effecting rotation of either contact wheel 111 or idler pulley 134. In the illustrated abrasive belt machine, the contact wheel 111 is directly driven by a suitable electric motor 141, but it is apparent that a belt and pulley or other transmission may be interposed therebetween. Since the radially directed vibrations occurring at the periphery of contact wheel 111 have the effect of substantially reducing the friction between the rotatably driven contact wheel and the abrasive belt 119, and since the abrasive belt is driven by rotation of the contact wheel, relative slipping of the contact wheel and belt is avoided by providing the inner surface of belt 119 with spaced apart projections 142 that are received in radially opening recesses 143 spaced apart circumferentia lly on the periphery of contact wheel 111. The recesses 143 are preferably defined by gaps between the adjacent sectors or portions of the laminations 116 making up the contact wheel.

The machine of FIGS. 7 and 8 is illustrated as a flat surface grinder, but it will be apparent from FIG. 9 that such machine may be provided with a modified contact wheel 111a having a contoured surface so that the flexible abrasive belt 119, in traveling around contact wheel 111a, follows the contoured surface of the latter and thereby grinds the surface of the workpiece 128a with a similar contour.

In all of the previously described embodiments of the invention, the high frequency or ultrasonic vibrations at the active surface of the abrading element or elements have been transmitted to the latter by a member (for example, the grinding wheel body 11 or the contact wheel 111) which moves with the abrading element or elements during the grinding operation. However, since the high frequency or ultrasonic vibrations employed for enhancing the grinding action may also substantially reduce the frictional resistance to relative movement between the abrading element and the member producing or transmitting the vibratory energy to the abrading element, grinding machines embodying this invention may have a stationary or fixedly positioned member for transmitting the vibrations to the abrading element as the latter travels across such member at the area of contact of the abrading element with the workpiece.

More specifically, as shown in FIG. 10, a grinding machine 210 constructed in accordance with another embodiment of this invention includes an abrading element 219 in the form of a rigid metal ring having abrasive grains bonded to its outer surface. The abrasive ring 219 is mounted for rota-tion, about its center, on a driving roller 242 rotated by a motor 241 and on an idler roller 243.

Rollers

242 and 243 are rotatably supported on parallel shafts supported by a frame 244 so as to effect rolling engagement with the inner surface of abrading ring 219 at points which subtend an angle of approximately 120 degrees and which are symmetrically located at opposite sides of the vertical plane passing through the center of rotation of ring 219. The workpiece 228 is moved tangentially past abrading ring 219 at the bottom of the latter, for example, on a movable table 240, and radial vibrations are transmitted to the abrading ring, at its area of contact with the workpiece, by a vibratory device 211 which is fixedly mounted on frame 244.

As shown in the drawing, the vibratory device 211 may include a magnetostrictive transducer 245 formed of a stack of magnetostrictive laminations and an energizing winding extending around the stack of laminations and supplied with biased, alternating current at a high or ultrasonic frequency. The laminations of transducer 245 are rigidly connected, as by brazing, soldering or the like, to an end of a connecting body 246 which is preferably in the form of an acoustic impedance transformer, and the lengths of the transducer 245 and transformer 246 are selected so as to be integral numbers of half wavelengths of the compressional or standing waves generated therein at the desired high frequency at which biased alternating current is fed to the winding of the transducer, so that a loop of longitudinal motion occurs at the free end of transformer 246. The vibratory device 211 is mounted on frame 244 by a flange 247 disposed on the acoustic impedance transformer 246 at a nodal plane of the longitudinal vibrations in the latter, with the axis of the vibratory device extending vertically and with the free lower or output end of the acoustic impedance transformer 246 being disposed for contact with the inner surface of abrading ring 219 at the bottom of the latter.

During operation of the vibratory device 211 simultaneously with rotation of abrading ring 219, the lower or output end of the acoustic impedance transformer 246 undergoes vibration in the vertical direction, that is, normal to the surface of ring 219 passing the output end of the transformer. Such vibrations are transmitted through abrading ring 219 to enhance the grinding action of the latter on workpiece 228, and the vibrations further substantially reduce or minimize the frictional resistance to rotation of ring 219 resulting from its contact with the fixedly located vibratory device 211.

As is apparent in the grinding machine 210a shown in FIG. 11, the rigid ring 219 forming the abrading element in the previously described machine 210 may be replaced by an endless flexible abrasive belt 219a running around a driving pulley 242a and an idler pulley 2430 which are rotatably supported on the upper portion of the frame 244a, and also running around the lower or output end of an acoustic impedance transformer 246a included in a vibratory device 211a which is fixedly mounted on the lower portion of the frame. The abrasive belt 219a may be tensioned by a tension pulley 247 engaging the run of the flexible belt between pulleys 242a and 243a so that the flexible abrasive belt conforms to the contour of the lower or output end of transformer 246a in traveling across the latter. As is apparent in FIGS. 12, 13 and 14, the lower end or output surface of transformer 246a may have various con-tours. For example, the transformer may have an output surface 248a with a crosssectional shape in the form of a section of an ellipse (FIG. 12); or a cross-sectional shape including an arcuate portion and a straight portion, as at 249 (FIG. 13); or a cross-sectional shape in the form of an arc of a circle, as at 250 (FIG. 14).

Since the flexible abrasive belt 219a conforms to the cross-sectional shape of the output end or surface of transformer 246a in traveling across the latter, a workpiece 228a transported by the table 240a in directions transverse to the direction of travel of the abrasive belt will have the contour of the output end of the transformer ground into the surface of the workpiece engaged by the abrasive belt. As in the machine 210, the vibrations transmitted by the transformer 24611 of the fixedly located vibratory device 211a serve to substantially reduce the frictional resistance of the latter to move ment of the abrasive belt 219a and further effect vibration of the active surface of the belt 219a at the area of contact of the latter with the workpiece so as to greatly enhance the grinding action.

When the workpiece 228 is moved relative to the stationary vibratory device 211a in the direction of the path of travel of abrasive belt 219a, the transformer 246a may have an output end surface 251 (FIG. 15) which is contoured or profiled in the direction across the width of the belt, thereby to grind a corresponding contour in the surface of the workpiece engaged by the abrasive belt.

Although the present invention has been described above in connection with grinding wheels and grinding apparatus, it is to be noted that the invention is also applicable to honing machines or tools. More specifically, as shown in FIGS. 16 and 17, a honing machine 310 embodying the invention includes a conventional head 311 rotatably supporting a spindle 312 which is driven through a belt and pulley drive 312a from a motor or the like (not shown). A shaft 313 of rnagnetostrictive material forming a transducer extends downwardly from spindle 312 and rotates with the latter. Shaft 313 extends loosely through an energizing coil 314 supported in a fixed housing 315 and supplied with biased alternating current at a high or ultrasonic frequency from a suitable source (not shown). Thus, the rotated shaft 313 constituting a transducer has longitudinal standing or compressional waves generated therein, and shaft 313 is longitudinally dimensioned so as to have a length equal to an integral number of half wavelengths of the compressional waves generated therein, whereby a loop of longitudinal motion appears at the lower end of shaft 313.

A honing tool 316 is rigidly secured to the lower end of shaft 313 for rotation and vertical vibration with the latter. In accordance with the invention, the honing tool 316 includes a metal body 317 formed of an axially arranged series of laminations 318 fixedly secured, as by brazing, soldering or the like, to the lower end portion of shaft 313.

As shown in FIG. 17, each lamination 3 18 may have a configuration generally similar to that of the laminations previously described herein with reference to FIG. 3. Thus, each lamination 313 includes alternately arranged sectors or

portions

319 and 320 of relatively small mass and relatively large mass, respectively. The laminations 318 are axially superposed so that their sectors or portions 319 are in alignment with each other, and energizing coils or windings 321 are wound around the aligned sectors 319. Thus, when biased, high frequency or ultrasonic alternating current is supplied to the windings 321, radially directed compressional or standing waves are generated in the magnetostrictive material of the laminations 318 forming body 317 of the honing tool. As in the embodiment of FIG. 3, each lamination 318 has equal odd numbers of the sectors 319 and the sectors 320 so that each sector 319 of relatively small mass is diametrically opposed by a sector 320 of relatively large mass. Accordingly, radially directed vibrations of magnified amplitude occur at the outer peripheral edges of the sectors 319 or relatively small mass.

Honing tool 316 further includes abrading elements 322. of relatively small radial thickness which are bonded or otherwise secured to the outer peripheral edges of sectors 319 of the laminations forming body 317, so that the relatively large amplitude, high frequency radial vibrations are transmitted to the abrading elements or honing stones 322 upon energization of the windings 321. The current for energizing windings 321 is conducted to 1 1 the latter from a suitable source (not shown) by way of conductors 323 connected to brushes 324 and slidably engaging slip rings 325 which are connected by connectors 326 to the windings and carried by an insulating collar 327 secured on shaft 313 immediately above the honing tool.

The workpiece 328 having a bore to be honed is supported on a rigid base 329 with the axis of the bore extending vertically, that is, in alignment with the axis of honing tool 316 which is inserted in the bore. During operation of the described honing machine 31th, the honing tool 316 is rotated, while its abrading elements or honing stones 322 are subjected to both high frequency vibrations in the axial or vertical direction, by reason of the longitudinal vibrations generated in shaft 313 by energization of winding 314, and also to high frequency radial vibrations by reason of the radially directed vibrations generated in body 317 of the honing tool in response to energization of the windings 321. The combined axial and radial vibrations imparted to the honing stones ensure an increased rate of stock removal and reduce the wear on the honing stones.

FIG. 18 illustrates a modified form of honing tool 316a that may be employed in connection with the honing machine 310. The honing tool 316a includes a metal body 317a made up of an axially arranged stack of laminations 318a having diametrically opposed arms 319a. The laminations 318a are centrally secured on the lower end portion of shaft 313a with their opposed arms 319a in axial alignment, and energizing windings 231a are wound around the aligned arms 319a so that, when biased high frequency or ultrasonic current is supplied to the windings 321a, radially directed compressional or standing waves are generated in the arms 319a. The body 317a of honing tool 316a further includes a metal cylinder or sleeve 320a which is concentric with the axis of shaft 313a and which is rigidly secured, at diametrically opposed locations, as by brazing, soldering or the like, to the outer end edges of the arms 319a. Metal ring 320a is diametrically dimensioned so that its fundamental mode of vibration is equal to the frequency of the compressional or standing waves generated in arms 31%, whereby sleeve or cylinder 320a vibrates radially in response to the transmission of radial vibrations to the sleeve from the arms 31%. Finally, honing tool 316a includes abrading elements or honing stones 322a which are bonded or otherwise secured to the outer surface of sleeve 320a at circumferentially spaced apart locations. It is apparent that the honing tool 316a will operate in the same manner as the previously described honing tool 316 so as to achieve an increased rate of stock removal and decreased wear of the honing stones.

It will be seen that, in all of the above described embodiments of the invention, the abrading element or elements have a relatively small thickness in the direction normal to the active grinding or honing surface which is moved relative to the surface of the workpiece being finished, and such abrading element or elements are subjected to high frequency or ultrasonic vibrations of substantial amplitude in directions normal to the active grinding or honing surface, at least in the area of contact of the latter with the workpiece.

Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention, except as defined in the appended claims.

What is claimed is:

1. An abrading device comprising (A) at least one abrading element having an active surface adapted to be moved relative to a workpiece in contact with a surface of the latter for finishing the workpiece surface,

(1) said element having a relatively small thickness in the direction normal to said active surface; and

(B) means applying high frequency vibrations to said abrading element at the side of the latter opposed to said active surface and in said direction normal to the latter,

(1) said applying means including a generally circular, radially vibrate-d metal body having diametrically opposed sectors of relatively small mass and relatively large mass, respectively, so that the average radial velocity in each sector of relatively small mass is substantially greater than the average radial velocity in the diametrically opposed sector of relatively large mass, thereby to provide radial vibrations of magnified amplitude at the peripheries of said sectors of relatively small mass,

(2) said radially vibrated metal body being rotated with a peripheral speed equal to the speed of movement of said abrading element relative to the workpiece,

(3) said sectors of relatively small mass and of relatively large mass having abrading elements on the peripheries thereof which respectively include relatively fine and relatively course abrasive grains,

(4) said vibrations being applied to said abrading elements at least over the area of the latter in contact with the workpiece so that the vibrations are effectively transmitted through the thin abrading elements to act at said active surface for enhancing the abrading effect of the latter.

2. An abrading device comprising (A) at least one abrading element having an active surface adapted to be moved relative to a workpiece in contact with a surface of the latter for finishing the workpiece surface,

(1) said applying means including a generally circular, radially vibrated metal body having diametrically opposed sectors of relatively small mass and relatively large mass, respectively, so that the average radial velocity in each sector of relatively small mass is substantially greater than the average radial velocity in the diametrically opposed sector of relatively large mass, thereby to provide radial vibrations of magnified amplitude at the peripheries of said sectors of relatively small mass,

(3) said vibrations being applied to said abrading element at least over the area of the latter in contact with the workpiece so that the vibrations are effectively transmitted through the thin abrading element to act at said active surface for enhancing the abrading effect of the latter,

(4) said body including an axially arranged stack of laminations each having diametrically opposed sectors of relatively small mass and relatively large mass, respectively, at least certain of said laminations having their sectors of relatively small mass offset circumferential'ly with respect 13' to the corresponding sectors of the other laminations so that said body applies radial vibrations of magnified amplitude to said abrading element at peripheral Zones which are circumferentially offset at successive axial locations along said body. 3. An abrading device comprising (A) at least one abrading element having an active surface adapted to be moved relative to a workpiece in contact with a surface of the latter for finishing the workpiece surface (1) said element having a relatively small thickness in the direction normal to said active sur face; and

(1) said applying means including a generally circular, radially vibrated metal body engaging, at its periphery, with said abrading element and being rotated with a peripheral speed equal to the speed of movement of said abrading element relative to the workpiece,

(2) said abrading element being in the form of an endless, flexible abrasive belt running around said generally circular body which constitutes a contact wheel for the belt at the are-a of contact of the latter with a workpiece,

(3) said vibrations being applied to said abrading element at least over the area of the latter in contact with the workpiece so that the vibrations are effectively transmitted through the thin abrading element to act at said active surface for enhancing the abrading effect of the latter.

4. An abrading device as in claim 3;

wherein the inner surface of said belt and the periphery of said circular body have interengageable projections and recesses spaced apart therealong to avoid slipping of said belt relative to said body.

5. An abrading device comprising (A) at least one abrading element having an active surface adapted to be moved relative to a workpiece in contact with a surface of the latter for finishing the workpiece surface,

(1) said element having a relatively small thickness in the direction normal to said active surface,

(2) said abrading element being endless and moving along a closed path including a portion where an area of the abrading element is brought into contact with a workpiece; and

(B) means applying high frequency vibrations to said .a brading element at the side of the latter opposed to said active surface and in said direction normal to the latter,

(1) said applying means including a body vibrated longitudinally at its resonant frequency and having a length equal to an integral number of half Wavelengths of the compressional waves therein so that loops of longitudinal motion appear at the ends of said body,

(2) said longitudinally vibrated body being fixedly mounted adjacent said portion of the closed path with its longitudinal axis normal to said active surface of the abrading element at said area of contact of the latter, and with one end of said longitudinally vibrated body against said side of the abrading element opposed to the active surface, so that the vibrations at said one end are transmitted through the abrading element and also serve to minimize frictional resistance to movement of said abrading element along said path relative to the fixedly mounted body.

6. An abrading device as in claim 5;

wherein said abrading element includes a rigid ring rotatable about its center and having abrasive grains on its outer periphery, and said longitudinally vibrated body extends radially within said ring.

'7. An abrading device as in claim 5;

wherein said abrading element is in the form of a flexible abrasive belt traveling across said one end of the fixedly mounted body.

8. An abrading device as in claim 7; wherein said one end of the longitudinally vibrated body has a contoured surface, and said abrasive belt is tensioned to follow said contoured surface and correspondingly shape a workpiece with which it is in contact.

9. An abrading device comprising (A) at least one abrading element having an active surface adapted to be moved relative to a workpiece in contact with a surface of the latter for finishing the workpiece surface,

(1) said element having a relatively small thickness in the direction normal to active surface; and

( 1) said vibrations being applied to said abrading element at least over the area of the latter in contact with the workpiece so that the vibrations are effectively transmitted through the thin abrading element to act at. said active surface for enhancing the abrading effect of the latter (2) said means applying high frequency vibrations to the abrading element including a generally circular, radially vibrated metal body of magnetostrictive material having diametrically opposed arms and a cylindrical sleeve secured to the ends of said arms and carrying said abrading element, said body being rotated with a peripheral speed equal to the speed of movement of said abrading element relative to the workpiece,

(3) said means applying high frequency vibrations to the abrading element further including energizing windings on said arms to generate said vibrations radially in the latter when biased alternating current is supplied to said windings at the fundamental mode of said body.

References Cited by the Examiner UNITED STATES PATENTS ROBERT C. RIORDON, Primary Examiner.

JOHN C. CHRISTIE, FRANK E. BAILEY, Examiners.

L. I. SHECHTER, J. A. MATHEWS,

Assistant Examiners.

Claims

1. AN ABRADING DEVICE COMPRISING (A) AT LEAST ONE ABRADING ELEMENT HAVING AN ACTIVE SURFACE ADAPTED TO BE MOVED RELATIVE TO A WORKPIECE IN CONTACT WITH A SURFACE OF THE LATTER FOR FINISHING THE WORKPIECE SURFACE, (1) SAID ELEMENT HAVING A RELATIVELY SMALL THICKNESS IN THE DIRECTION NORMAL TO SAID ACTIVE SURFACE; AND (B) MEANS APPLYING HIGH FREQUENCY VIBRATIONS TO SAID ABRADING ELEMENT AT THE SIDE OF THE LATTER OPPOSED TO SAID ACTIVE SURFACE AND IN SAID DIRECTION NORMAL TO THE LATTER, (1) SAID APPLYING MEANS INCLUDING A GENERALLY CIRCULAR, RADIALLY VIBRATED METAL BODY HAVING DIAMETRICALLY OPPOSED SECTORS OF RELATIVELY SMALL MASS AND RELATIVELY LARGE MASS, RESPECTIVELY, SO THAT THE AVERAGE RADIAL VELOCITY IN SAID SECTOR OF RELATIVELY SMALL MASS IS SUBSTANTIALLY GREATER THAN THE AVERAGE RADIAL VELOCITY IN THE DIAMETRICALLY OPPOSED SECTOR OF RELATIVELY LARGE MASS, THEREBY TO PROVIDE RADIAL VIBRATIONS OF MAGNIFIED AMPLITUDE AT THE PERIPHERIES OF SAID SECTORS OF RELATIVELY SMALL MASS, (2) SAID RADIALLY VIBRATED METAL BODY BEING ROTATED WITH A PERIPHERAL SPEED EQUAL TO THE SPEED OF MOVEMENT OF SAID ABRADING ELEMENT RELATIVE TO THE WORKPIECE, (3) SAID SECTORS OF RELATIVELY SMALL MASS AND OF RELATIVELY LARGE MASS HAVING ABRADING ELEMENTS ON THE PERIPHERIES THEREOF WHICH RESPECTIVELY INCLUDE RELATIVELY FINE AND RELATIVELY COURSE ABRASIVE GRAINS, (4) SAID VIBRATIONS BEING APPLIED TO SAID ABRADING ELEMENTS AT LEAST OVER THE AREA OF THE LATTER IN CONTACT WITH THE WORKPIECE SO THAT THE VIBRATIONS ARE EFFECTIVELY TRANSMITTED THROUGHT THE THIN ABRADING ELEMENTS TO ACT AT SAID ACTIVE SURFACE FOR ENHANCING THE ABRADING EFFECT OF THE LATTER.