Abstract:
The axial rotation of a honing tool head and the radial advance of the co-rotating honing stones are accomplished simultaneously by a magnetic coupling. The magnetic coupling connects an inner and drive axle that are driven independently. When the inner axial is driven at a differential speed than the drive axle, a connected pinion gear mechanism is engaged to transfer torque and radially displace the honing stones in response to the speed difference.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of priority to the US Provisional Patent Application of the same title having application Ser. No. 61/859,414 which was filed on Jul. 29, 2013, and is incorporated herein by reference. 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates to an improved honing tool and method, and more particularly to a means for moving the honing stoning radially during the honing process. 
     Prior methods of honing require the oscillation and rotation of the honing head to advance in a stepwise fashion as the honing stones are advanced or retracted. This reduced machine throughput potential, and limits process control means. 
     It would be an advance in the art to have a simple convenient way to move the honing stone positions continuously while material is removed in the honing process and appropriate control means during such a process to avoid excess material removal. 
     SUMMARY OF INVENTION 
     In the present invention, the first object is achieved by providing a rotary machining tool comprising a rotating magnetic coupling having a first cylindrical bore, a drive axle having a first primary cylindrical axis and work tool end and a driving end opposite the work tool end, wherein the drive axle is supported by one or more rotary couplings in the rotating magnetic coupling, an inner axle having a second primary cylindrical axis disposed concentrically within at least a portion of the drive axle, wherein the inner axle is supported by one or more rotary couplings in the drive axle, in which the first and second primary cylindrical axis are co-incident with a geometric center of the cylindrical bore, a magnet coupling means having a portion attached to the outer periphery of the inner axial that is operative co-rotate the inner axle with the external rotation of the magnetic coupling, a tool head coupled to the working tool end of said drive axle, said tool head having a third primary cylindrical axis and comprising, a plurality of abrasive member tangential spaced apart about the third cylindrical axis, each abrasive member coupled to a radial positioning means for radial position adjustment from at least partially within the tool head to beyond an outer periphery of the tool head, at least one drive means for coupling torque from the inner axle to the radial positioning means. 
     A second aspect of the invention is characterized by each of the honing stones is set in a gear driven support member which is geared to advance or retract in the radial direction with respect to the third cylindrical axis, and the radial positioning means is a pinion gear drive coupled to the inner axial that urges the simultaneous drive of the geared support members when the inner and out axle rotate at different speeds. 
     Another aspect of the invention is characterized by the rotary machining tool having a magnet coupling means further comprises a first plurality of magnets disposed about the inner periphery of the first cylindrical bore, wherein the magnets in said plurality are arranged with opposing polarity to each adjacent magnets and the portion of the magnet coupling means attached to the outer periphery of the inner axial is a second plurality of magnets, wherein the magnetic in the second plurality are arranged with opposing polarity to each adjacent magnet in the second plurality. 
     The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is schematic longitudinal cross-section elevation view of a honing tool deploying a magnetic coupling in boring a work piece. 
         FIG. 2  is a detailed longitudinal cross-section elevation view of the magnetic coupling shown in  FIG. 1 . 
         FIG. 3  is a split axial cross-sectional elevation through the magnetic coupling at the section line A-A in  FIG. 1 . 
         FIG. 4  is a cur-away perspective view of the magnetic coupling. 
         FIG. 5  is a perspective view of an alternative drive motor for the magnetic coupling showing the drive motors used to rotate the honing tool via the drive shaft and axially oscillate the honing head. 
         FIG. 6  is a schematic cross-sectional elevation of an alternative embodiment of the magnetic coupling. 
         FIG. 7  is a schematic diagram of a control scheme for the drive motors in  FIGS. 1 and 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 7 , wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved Honing Tool and Method, generally denominated  100  herein. 
     In accordance with the present invention, a honing tool  100  has a rotary magnetic coupling  110 , which contains a rotating drive axle  120 , as well as a concentrically disposed inner axle  130 . The rotating drive axle  120  is connected to the tool head  140 . Pluralities of spaced apart abrasive or sharpened cutting members  145  are disposed about the circumferential direction of the tool head  140 . The abrasive/cutting members  145  are commonly referred to as honing stones, and can be adjusted in the radial displacement from the central cylindrical axis  101 . 
     Typical mechanism for adjustment of the abrasive members  145  in a honing tool are disclosed in U.S. Pat. Nos. 2,439,117; 3,216,155 and 4,524,549, which are incorporated herein by reference. One or more honing stones  145  can be set in tangentially spaced apart in mounts that are driven by a linear gear  137  that engages the pinion gear  135 . The direction of rotation of the inner axle  130  thus directs the direction of travel of the linear gears  137  to drives the honing stones  145  inward away from the work piece  10 , our outward toward the work piece  10 , which can then continues to expand the bore hole concentrically. The rotating drive axial oscillates in the axial direction (arrow  102 ) as it rotates to complete the honing process. In the former case, retracting the honing stones  145  permits the removal of the tool head  140  from the completed bore hole formed in a work piece  10 . These various drive mechanisms deploy some sort of pinion gear  135  that rotates with the inner axle  130  when the drive axle  120  is stationary. In conventional technology, the inner axle is activated via a clutch and slip rings, which requires stopping the drive axle  120  rotation. 
     The magnetic coupling  110  provides the desirable benefit of driving the honing stones  145  radially without having to stop or slow the rotation of the drive axle  120 . With appropriate process control as described further below, a boring or honing process can be continuous until a predetermined dimension is reached and/or the effective pressure exerted by the cutting or abrading tool (or feed rate) can be adjusted to optimize the removal of material. 
     In one embodiment, the magnetic coupling  110  comprises at least one first set of spaced apart magnets  1610  connected to the inner periphery of the magnetic coupling  110 . The magnets  1610  have their opposing north and south poles pointing radially, while immediately adjacent magnets alternate in polarity. 
     Likewise there is at least one second set of spaced apart magnets  1630  connected to the outer periphery of the inner axle  130 . The magnets have their opposing north and south poles pointing radially, while immediately adjacent magnets alternate in polarity. 
     The inner magnets  1630  connected to the inner axle  130  are separated from the outer magnets  1610  connected to the inner circumference of the magnetic coupling  110  by a gap  103 . The annular drive axle  120  passes through gap  103  and surrounds the inner axle  130  and attached magnets  1630 . As at least this portion of the drive axle  120  within the magnetic field of the magnetic coupling is non-magnetic, the magnets stay aligned so that the magnetic coupling  110  and inner axle  130  stay aligned and are co-rotated independently of the drive axle. Magnetic coupling  110  can deploy opposing magnets arrays  1610  and  1630  or magnets  1630  and an AC induction coil replacing magnets  1610 . 
     In a more preferred embodiment, the inner axle  130  has a polygonal cross-section to provide flat faxes for attaching a plurality of high strength magnets of opposing polarity, as indicated by the N and S poles in  FIG. 3 , with one magnet disposed on each face. In contrast, the magnets  1610  are preferably inset in cavities in the inner periphery of the bore of the magnetic coupling  110 . It is additionally preferable that the facing magnetic surface of magnets  1610  and  1630  are machined to having concave and convex surface respectively so that the annular gap  103  that contains drive axle  120  is substantially cylindrical in inner and outer circumference. Thus, the attraction between opposing pairs of oppositely oriented magnets stay aligned so that the magnetic coupling  110  and the inner axial rotate at the same speed. 
     It should be appreciated that as illustrated generally in  FIG. 1 , the magnetic coupler  110  and the drive motor  510  or  505  can be integrated into a common unit having a hollow central shaft that accepts the hollow drive shaft  120  and the internal central shaft  110  that drives the pinion gear that advances and retracts the honing stones. 
     A plurality of rotary bearings  160  separate the rotating magnetic coupling  110 , inner drive axial  120  and inner axle  130  that is connected to the pinion gear  135 . The rotary bearings  160  are provided as pairs disposed at opposing sides of the magnetic coupling  110  distal and proximal to the honing head  140 . 
     As illustrated in  FIG. 5 , the drive axle  120  is attached to motor  520 . Another motor  540  drives the axial oscillation of the platform  525  supporting motor  510  in the direction of arrows  102 , whereas motor  530  optionally rotates the magnetic coupling  110  via a planetary gear  535 . 
     It is also preferred that either the drive shaft  120  or a portion thereof within the magnetic field of coupling  110 , (drive shaft portion  120 ′ as illustrated in  FIG. 6 ), is both non-magnetic and non-conductive. It is more preferred that this portion  120 ′ is a fiberglass epoxy composite tube, and the like. If the drive tube  120  is made of non-magnetic material, such as 300 series stainless steel there will be some circulating currents, causing more power consumption in motor  510 , and possibly heating which would become greater during rapid extension and retraction of the honing stones. In such conditions, as additional embodiment of the invention is providing cooling fines to drive axle  120 . 
     The inner axial  130  is connected to the pinion gear  145  that drives the abrasive members  145 . When the inner and outer axial are driven to rotate at the same speed the pinion gear will not engage the gear mechanism that drives the honing/abrasive stones radially. However, when there is a difference in drive speed, the magnetic coupling  110  prevents slippage of the inner axial  130  by magnetic attraction, the differential speed will be converted into a torque that turns the pinion gear  135  urge the linear gear mechanism  137  coupled to the honing stones  145  forward or backward, depending on the which axle is being driven at a slower speed. 
     Hence, another aspect of the invention is at least one drive means for rotating the outer magnetic coupling  110  that transfers torque from the inner axle  130  to the radial positioning means for the honing stones  145 . 
     Drive means, such as for motor  510  to the magnetic coupling  110  can be direct, or via gears or an offset drive belt, as for example via an axial gap motor  505  in which the magnetic coupling  110  is essentially the hollow core central shaft to accommodate the drive shaft  120 . 
     One or more sensors  512  are optionally in communication with drive axle  120 , such as a rotary encoders or a means detect the motor current draw of motor  520  to determine the position and/or point of contact of the honing stones. Alternatively, in-line or equivalent torque sensor  513  can be deployed on a portion of axle  120 , such as a torque strain gauge to measure the load on the honing stones. 
     In a more preferred embodiment, Illustrated in  FIG. 7 , the primary drive motor  520  and position drive motor  510  is in communication with a master-slave control module  700  that deploys the sensor or rotary encode to measure the master (primary drive motor speed) and in a slaved arrangement, adjust to position drive motor speed according to a predetermined schedule or procedure (provided by a micro-processor in the control module or a separate Programmable Logic Controller (PLC)  710  based on the final part dimensions, wear rate of the material being removed by the honing stones, and desired surface finish. 
     The above controls can be used in at least 2 modes of operation. First, based on first establishing a zero reference for the hone stone or cutting tool position, the controller can track the position of the hones with the software in the PLC  710  or controller  700  deployed to adjust hone position based on average material wear rates. Alternatively, deploying a strain gauge along with or as sensor  512 , the load on the main drive  120  is detected to determine when the honing stones contact the work piece  10 . As work pieces vary in exact dimensions before honing, it is useful to be able to detect when the hone stones contact the surface of the work piece. This can be accomplished with the torque strain gauge  513 , or alternatively the load on the primary servo motor drive  520 . 
     The inventive magnetic coupling  110  can be deployed to achieve the benefit of a faster machining process, in that the rotary material removal does not need to stop for the adjustment of the stone position. The magnetic coupling process is expected to provide better process control due to continuous feedback of motor torque or other sensor output indicating wear rate, and hence greater process reliability as well as final product quality. For examples, as metals that may be deployed in different work pieces have variable properties, the application of a constant pressure of the hone stone against the work piece is frequently insufficient to obtain an intended surface finish in a single process. However, monitoring the loading of the primary drive enables the application of variable pressure of the honing stones against the work piece, according to a predetermined program, to routinely obtain a targeted metal surface finish directly from the honing process. 
     While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be within the spirit and scope of the invention as defined by the appended claims.