Apparatus and method for refinishing a surface in-situ   

TECHNICAL FIELD

The present invention relates to rotary grinders and more particularly to vertically axised rotary grinders.

BACKGROUND ART

A rotary valve is a valve, a part of which rotates intermittently to control fluid flow, such as in an oil refinery. A rotary valve typically includes a track plate, a rotor plate and an upper pressure-tight shell or casing. The casing and the track plate form a fluid-tight housing totally enclosing the rotor plate. The rotor plate is maintained in fluid-tight contact with the track plate and typically rotates in a horizontal plane. The rotor plate has a slick, smooth surface, referred to as a “seal surface,” and a number of channels and holes and/or ports that communicate with corresponding channels, holes and/or ports in the track plate in order to direct the flow of fluid within the rotary valve.

Wear and tear to the surface of the track plate during use can cause it to become damaged to such an extent that the necessary sealing required for proper fluid control is impaired. Such damage can be caused by corrosion, erosion, friction or distortion, or by the presence of foreign objects. Once the surface is damaged, either repair or replacement is necessary to reestablish an acceptable seal, so that the function of the rotary valve for the particular fluid control application is restored. To avoid the significant cost of replacing a worn track plate, the surface of the track plate may be refinished by a process commonly referred to as “resurfacing.”

It is known in the prior art to use a rotary grinder to refinish a surface of an item (a “workpiece”), such as a track plate. Due to the complexity, time and expense required to remove or ship such items, it is advantageous to be able to refinish the surface of a track plate without shipping the track plate or the entire valve to a refinishing facility.

Apparatus, such as those described in U.S. Pat. No. 6,921,322, for refinishing the surface of a track plate on site generally include height adjusting mechanisms to control depths of cuts made by a traversing rotary grinding wheel. A typical prior art refinishing machine includes a lower frame member and an upper frame member connected to each other by three adjustable assemblies spatially distributed around the peripheries of the frame members. In use, the lower frame member is rigidly attached to the track plate, and the grinding wheel is attached to the upper frame member. Adjusting the assemblies changes the height and orientation of the upper frame member and, consequently, the height and orientation of the grinding wheel, with respect to the lower frame member and the track plate. The height of the grinding wheel determines the depth of a refinishing pass over the track plate.

Adjusting the height of the grinding wheel to set the depth of a refinishing pass requires separately and precisely adjusting each one of the three assemblies. For a given refinishing pass, all the assemblies must be adjusted by precisely the same amount, which is difficult to do efficiently and consistently without stopping the machine, even for skilled operators. Many passes of the grinding wheel are typically required to resurface a track plate, because each pass removes only a small amount of material. Consequently, refinishing a track plate can be time consuming and labor intensive.

SUMMARY

An embodiment of the present invention provides a rotary grinder system that may be coupled with a workpiece. The rotary grinder system includes a support frame, a grinder assembly and a grinder wheel. The support frame may include an upper frame coupled to a lower frame. The support frame has an engagement region configured to be coupled to the workpiece. The grinder assembly is coupled to the support frame. The grinder assembly includes an axial arm and a radial arm coupled to the axial arm. The radial arm is coupled to the axial arm in a substantially orthogonal orientation. The radial arm is coupled to the axial arm, such that the radial arm rotates about an axis of the axial arm. The grinder wheel is rotatably coupled to the radial arm of the grinder assembly via a grinder wheel driver. The grinder wheel is translatable along the radial arm. The rotary grinder system also includes a single point axial positioner configured to drive the radial arm of the grinder assembly along the axis of the axial arm. The single point axial positioner is configured to drive the radial arm translationally, with respect to the support frame.

The single point axial positioner may include a ball screw system and, optionally, a mechanical slide. Optionally or alternatively, the single point axial positioner may be configured to drive the radial arm though translation of the axial arm or through rotation of the axial arm or through extension of the axial arm.

The grinder assembly may be coupled to the support frame via at least one slide assembly connected to the axial arm of the grinding assembly and to the support frame.

The axial arm may include a telescoping arm configured to change length upon application of force from the single point axial positioner.

The grinder wheel may be coupled to a mechanical slide on the radial arm and configured to translate along an axis of the radial arm. In this case, translation of the mechanical slide along the radial arm displaces the grinder wheel.

The radial arm may include a telescoping arm, and the grinder wheel may be coupled to the radial arm.

The rotary grinding system may also include a counterweight coupled to the grinder assembly and to the support frame. Such a counterweight may be configured to urge the grinder assembly in a direction away from the workpiece, along the axis of the axial arm. The counterweight may include a hydraulic device, a spring and/or a mass-based counterweight.

The rotary grinding system may also include a counterweight that is movably coupled to the radial arm. Such a counterweight may be configured to move along the radial arm a distance proportional to, and in a direction opposite, the grinder wheel.

A rotary grinding system according to claim 13, wherein the counterweight includes at least one of a chain drive, a screw drive and a dual rack with an interconnecting gear drive.

A rotary grinding system according to claim 1, further comprising a micrometer adjustable dressing tool configured to dress the grinder wheel.

Optionally, the rotary grinding system includes one or more eccentric pins. Each such eccentric pin extends through a respective hole defined by the support frame and into the workpiece. Rotation of at least one of the eccentric pins laterally displaces the support frame, relative to the workpiece.

Optionally, the rotary grinding system includes at least one support member connected between the support frame and the grinder assembly. Such a support member may be configured to selectively support weight of at least a portion of the grinder assembly.

Optionally, the rotary grinding system may be computer numerically controlled. Actuators may be employed to adjust various elements of the rotary grinding system. A computer numerical control may be electrically connected to a first actuator, which may be configured to adjust the single point axial positioner. In addition, the computer numerical control may be electrically connected to a second actuator, which may be configured to translate the grinder wheel driver along the radial arm. Each of the actuators may include an encoder for measuring the magnitude of the respective adjustment and translation.

Optionally, the grinder assembly includes at least one slip ring configured to transmit electrical signals to the radial arm during rotation of the radial arm. Optionally or alternatively, the grinder assembly may include at least one hydraulic rotary union configured to transmit hydraulic fluid to the radial arm during rotation of the radial arm.

The grinder assembly may include at least one mechanical stop on the axial arm or on the radial arm.

The grinder wheel may be retractable translationally beyond a zero point on the radial arm, so as to expose a diameter of the workpiece.

The rotary grinding system may include an adapter plate. In this case, the support frame may be configured to be coupled to the workpiece via the adapter plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by referring to the following Detailed Description of Specific Embodiments in conjunction with the Drawings, of which:

FIG. 1 is a cut-away view of a prior art rotary valve assembly, with which embodiments of the present invention may be used;

FIG. 2 is an exploded perspective view of a rotary grinding system, in accordance with an embodiment of the present invention;

FIG. 3 is a close-up perspective view of a height-adjustable connector of the rotary grinding system of FIG. 2;

FIG. 4 is a perspective view of the rotary grinding system of FIG. 2, as seen from one side;

FIG. 5 is a perspective view of the rotary grinding system of FIG. 2, as seen from another side;

FIG. 6 is a cutaway view of the rotary grinding system of FIG. 2;

FIG. 7 is another cutaway view of the rotary grinding system of FIG. 2;

FIG. 8 is a perspective view of a rotary grinding assembly portion of the grinding system of FIG. 2;

FIG. 9 is a perspective view, from one side, of a radial arm portion of the rotary grinding system of FIG. 2;

FIG. 10 is a perspective view, from below, of the radial arm of FIG. 9;

FIG. 11 is a perspective view of a single point tool holder for a rotary grinding system, in accordance with an embodiment of the present invention;

FIG. 12 is a side view of an adjustable grinding wheel dressing tool holder, according to an embodiment of the present invention;

FIG. 13 is a schematic block diagram of a computer-controlled rotary grinding system, according to an embodiment of the present invention;

FIG. 14 is a perspective view, from below, of the rotary grinding system of FIG. 2; and

FIGS. 15, 16 and 17 are respective top, side and sectional views of an eccentric adjuster, according to an embodiment of the present invention.

DETAILED DESCRIPTION

In accordance with preferred embodiments of the present invention, methods and apparatus are disclosed for a rotary grinding system useful in resurfacing applications, particularly where a workpiece requires resurfacing without removal from its environment. Advantageously, the cutting depth of the grinding system can be adjusted at a single point. Consequently, depth-of-cut adjustments can be made more precisely, because equal adjustments need not be made on multiple connecting members. Furthermore, the depth-of-cut adjustments may be made while the grinding system is in operation, thereby significantly reducing the total amount of time to resurface a workpiece.

The rotary grinding system may be coupled to a workpiece via a support frame of the rotary grinding system. A grinding assembly, coupled to the support frame, may be axially re-positioned through precise adjustments made at a single location. The axial repositioning may be vertical re-positioning, or the grinding assembly may be disposed in an alternative orientation, for example horizontally, in which case the axial repositioning would be horizontal. As noted, such adjustments may serve to alter the depth of a grinding wheel that is coupled to a radial arm of the grinding assembly, thereby changing the amount of material the wheel removes from the workpiece in one pass across the workpiece.

The radial arm may be rotated in a plane parallel to the workpiece to move the grinding wheel in a circular pattern across the surface of the workpiece, and the grinding wheel may be translated radially across the surface of the workpiece. Accordingly, an entire circular area, or an annular portion, of a workpiece may be resurfaced using embodiments of the present invention, and the depth of the resurfacing cut may be accurately and quickly adjusted via adjustments of a single re-positioning mechanism, such as a single point screw adjuster. The grinding system makes the grinding/machining process more accurate and efficient, thereby decreasing the down time experienced by an end-user.

FIG. 1 illustrates a typical prior art rotary valve 100, with which embodiments of the present invention may be used. As noted, a rotary valve 100 typically includes an upper pressure-tight shell or casing 103 with a track plate 106 and a rotor plate 110 disposed within the shell 103. The rotor plate 110 is maintained in fluid-tight contact with the track plate 106 and typically rotates in a horizontal plane. The rotor plate 110 is driven by a drive assembly 113 and a drive shaft 116. If the track plate 106 becomes damaged, an upper portion 120 of the rotary valve 100, from (and including) the rotor plate 110 up, may be removed from the rotary valve 100. Upon removal of the upper portion 120, a rotary grinding system (not shown) according to the present disclosure may be mounted to the track plate 106 or another portion of the rotary valve 100, and the rotary grinding system may be used to refinish the surface of the track plate 106. Alternatively, the track plate 106 may also be removed, and the rotary grinding system may be attached to the track plate 106 to refinish it.

FIG. 2 is an exploded view of a rotary grinding system 200, according to an embodiment of the present invention. Also shown in FIG. 2 is an exemplary track plate 204, to which the rotary grinding system 200 may be attached. The rotary grinding system 200 includes four main subassemblies: a lower frame 206, an upper frame 210, an axial drive assembly 213 and a radial drive assembly 216, each of which is described in detail below. The lower frame 206 is attached to a workpiece, such as the track plate 204. The upper frame 210 is rigidly, but adjustably, attached to the lower frame 206. The lower frame 206 and the upper frame 210 are collectively referred to as a support frame. The axial drive assembly 213 is attached to the upper frame 210, such that the height of the axial drive assembly 213 above the track plate 204 can be adjusted by a single adjustment point. The radial drive assembly 216 is suspended by and below the axial drive assembly 213.

The upper and lower frames 206 and 210 are designed to provide a known and engineered amount of deflection, which allows for specific amounts of flexibility in the system. Various parts of frames 206 and/or 210 may include hollow or tubular members to minimize the weight of the frames 206 and/or 210.

As noted, the lower frame 206 may be rigidly attached, such as by bolts, to the track plate 204 or to another workpiece or to another portion of a rotary valve. The bolts (not shown) may be inserted through some or all holes 220 defined in the lower frame 206 and into corresponding holes 223 in the track plate 204. Optionally or alternatively, an adapter plate (not shown) may be placed between the lower frame 206 and the track plate 204 or another workpiece, in case the workpiece lacks holes 223 that align with the holes 220 in the lower frame 206 or in case the workpiece is of a size or shape that is otherwise incompatible with the lower frame 206. Such an adapter may have holes that align with the holes 220 in the lower frame 206 and additional holes that align with holes in the workpiece. Optionally or alternatively, the adapter may provide hooks, bosses, threads or other features that may be used to secure the adapter to the workpiece.

Prior to tightening the bolts to secure the lower frame 206 to the track plate 204, eccentric pins inserted through some of the holes 220 and into corresponding holes 223 in the workpiece 204 may be used to laterally adjust the position of the lower frame 206, relative to the workpiece 204. An exemplary eccentric pin 1500 is shown in FIGS. 15, 16 and 17. Each eccentric pin 1500 includes a lower portion 1503 and an upper portion 1506, as well as a hexagonal or other suitably shaped drive portion 1510. Centers 1513 and 1516 of the upper and lower portions 1506 and 1503 of the pin 1500 do not coincide, thereby providing the eccentricity. FIG. 17 is a cross-sectional view of a portion 1703 of the lower frame and a portion 1706 of the workpiece, with an eccentric pin 1500 inserted in corresponding holes defined by the lower frame and by the workpiece. Rotating the pin 1500 displaces the lower frame, relative to the workpiece.

Returning to FIG. 2, the rotary grinding system 200 includes a multi-point mounting system. The lower frame 206 may include a number (preferably three) of raised flats 226 to facilitate attaching the upper frame 210 to the lower frame 206. The upper frame 210 may include a corresponding number of ribbed flanges 230, only two of which are visible in FIG. 2. The flats 226 define through holes that correspond to holes defined in flanges 230. The upper frame 210 is oriented such that the holes in the flanges 230 register over the holes in the flats 226, and height-adjustable connectors, such as lockable bolts passed through the holes, are used to connect the upper frame 210 to the lower frame 206. Portions 231 and 232 of one such height-adjustable connector are shown.

FIG. 3 is a close-up view of an exemplary height-adjustable connector 300 installed between one of the flats 226 and one of the corresponding flanges 230. Two stress-offloading bolts 303 are also installed between the flat 226 and the flange 230 to support the weight of the upper frame 210 while the grinding system 200 is transported or stored, thereby relieving the connector 300 from bearing this weight. However, in use, the stress-offloading bolts 303 are loosened or removed, leaving the connector 300 to bear the weight of the upper frame 210 and to control the distance 306 between the flat 226 and the flange 230.

The connector 300 includes a lower portion 231 rigidly attached to the flat 226 of the lower frame 206. The connector 300 includes a bearing (spherical) for misalignment and flexibility, and a nut. The lower connector portion 231 defines a precision threaded hole, into which a precision threaded bolt 232 is threaded. The lower connector portion 231 may include a grease fitting 308 to facilitate lubricating the bolt 232. The bolt 232 is vertically captured above and below the flange 230 by capture members 310 and 313, such that the vertical position of the flange 230 is defined by the position of the bolt 232. The height of the upper frame 210 may, therefore, be adjusted, relative to the lower frame 206, by turning the bolt 232, such as via a square 316 or another shaped drive portion defined by the top of the bolt 232. Once a desired separation distance between the flat 226 and the flange 230 is achieved, further rotation of the bolt 232 may be prevented by tightening the capture member 313, which may include a split locking collar, or the bolt 232 may be self-locking to maintain its position.

Returning to FIG. 2, the height and orientation of the upper frame 210 may be adjusted, relative to the lower frame 206, by making suitable adjustments to one or more of the connectors 300 (not shown in FIG. 2, but visible in FIG. 3). Once the lower frame 206 is rigidly attached to the track plate 204, adjusting the connectors 300 also adjusts the height and orientation of the upper frame 210, relative to the track plate 204. It should be noted that the distances between respective corresponding flats 226 and flanges 230 need not be equal. That is, the connectors 300 may be adjusted as needed until the axis 233 of the upper frame 210 is perpendicular to the track plate 204. These adjustments may compensate for irregularities in the sizes or shapes of the frames 206 and 210 or for an imperfect mating between the lower frame 206 and the track plate 204. Once the upper frame 210 is properly oriented, relative to the track plate 204, the adjustable connectors 300 may be locked to prevent changes in the height or orientation of the upper frame 210 during the refinishing process. Alternatively, the connectors 300 may be non-adjustable.

The axial drive assembly 213 is height-adjustably attached to the upper frame 210. Thus, the axial drive assembly 213 may be moved up or down, relative to the upper frame 210, as indicated by arrow 234. In one embodiment, the axial drive assembly 213 is moveably attached to the upper frame 210 via two hardened way slides. One portion (not shown) of each hardened way slide is attached to the upper frame 210 at 236, and the other portion 240 of each hardened way slide is attached to the axial drive assembly 213. A suitable height adjuster, such as a ball thread, rack and pinion, chain and gear or telescoping hydraulic member, may be used to adjust the height of the axial drive assembly 213, relative to the upper frame 210. Advantageously, the height of the axial drive assembly 213 may be adjusted by a single point adjustment 235.

To prevent or limit stress on bearing assemblies of the axial drive spindle during shipment or storage of the rotary grinding system 200, the combined weight of the radial arm assembly 216 and the upper frame 210 may be borne by removable links, such as wires, cables, chains, hooks or the like, installed between the radial arm assembly 216 and the upper frame 210. The links may be shortened, and/or the height adjuster may be adjusted to lower the axial drive assembly 213 and the radial arm assembly 216, until the combined weight is borne by the links.

In one embodiment, the radial arm assembly 216 includes four lugs 241 (only two of which are visible in FIG. 2) and a lift eye 413 (not shown in FIG. 2, but shown in FIGS. 4 and 5) is attached to each lug 241. Four corresponding lift eyes 1413 (not visible in FIG. 2, 4 or 5, but shown in FIG. 14) are attached to the bottom of the upper frame 210. In preparation for shipment or storage of the rotary grinding system 200, a suitable link, such as a chain and turnbuckle, may be connected between each pair of corresponding lift eyes 413 and 1413. FIG. 14 schematically shows four such links 1400 and four pads 1403 on the bottom of the upper frame 210 to which the upper lift eyes 1413 may be attached. The links 1400 may be shortened as needed, such as by adjusting the turnbuckles (not visible) to tension the links 1400, thereby reducing or offloading the combined weight of the radial arm assembly 216 and the axial drive assembly 213. Optionally or alternatively, the axial drive assembly 213 may be adjusted to lower the radial arm assembly 216 until the links 1400 bear its weight. The load on the height adjuster 300 may be offloaded by placing sleeves around one or both bolts 303 and lowering the upper frame 210 until the sleeve(s) bear the weight.

Returning to FIG. 2, the radial drive assembly 216 (also referred to as a “radial arm”) is suspended by an axial drive shaft (not visible) (also referred to as an “axial arm”) below the axial drive assembly 213. Thus, the radial drive assembly 216 moves up and down with the axial drive assembly 213. The axial drive assembly 213 includes a motor coupled to the axial drive shaft for rotating the radial arm assembly 216 about the axis 233 of the upper frame 210, as indicated by arrow 243. The axial drive assembly may be capable of driving the radial arm assembly 216 in one or both of the directions indicated by the arrow 243.

The radial drive assembly 216 includes a grinding wheel 244 and a motor 245 to rotate the grinding wheel 244. The radial drive assembly 216 also includes a track 246 and another motor (not visible) to translate the grinding wheel 244 along at least part of the length of the radial drive assembly 216, as indicated by arrow 250. Thus, in operation, the combination of rotating the axial drive shaft and translating the grinding wheel 244 back and forth causes the grinding wheel 244 to work on all or a desired annular portion of the track plate 204. Adjusting the height of the axial drive assembly 213 alters the depth to which the grinding wheel 244 cuts.

FIG. 4 is a perspective view of the rotary grinding system 200 of FIG. 2. The grinding system 200 includes a support system 411 that includes the upper frame 210 and the lower frame 206. The lower frame 206 has a circular base that may be engaged with a circular workpiece (not shown in FIG. 4). The upper frame 210 is rigidly attached to the lower frame 206 via three connection assemblies 300, only two of which are visible in FIG. 4. As noted, in some embodiments, the connection assemblies 300 may be adjustable, whereby the level and/or orientation of the upper frame 210 may be varied, relative to the lower frame 206. Although an embodiment with three connection assemblies 300 is described, other embodiments may include other numbers of connection assemblies. The support frame 411 may be disassembled, such as by detaching the upper frame 210 from the lower frame 206, such as for ease of shipment, storage or installation.

The support frame 411 shown in FIG. 4 is merely exemplary, and various other configurations may be provided in accordance with other embodiments of the present invention. Alternative configurations of the support frame 411 include uni-body constructions and alternatively shaped support frame members. The shape(s) may be chosen to suit a particular grinding application, as dictated by a particular workpiece.

FIG. 4 also shows the axial drive assembly 213 attached to the support frame 411. The axial drive assembly 213 may be moved vertically along the axis 233 through adjustments to the single point adjustment screw 235. The axial drive assembly 213 maintains its alignment, with respect to the support frame 411, when moved along the axis 233 via sliders 405 (which may be implemented as hardened way slides, dovetail slides or any other suitable translating device) engaging the axial drive assembly 213 and the support frame 411. In this embodiment, sliders 405 are located on opposite sides of the axial arm 408 of the axial drive assembly 213. In other embodiments, other numbers (including one) of slides may be used and/or the slides may be positioned differently than shown in FIG. 4. The radial drive assembly 216, which may be rotated about the axis 233 of the axial drive assembly 213, is partially shown in FIG. 4.

FIG. 5 is a perspective view of the rotary grinding system 200 shown in FIG. 4 illustrating another side of the system. In this figure, a third connection assembly 300 between the lower frame 206 and the upper frame 210 is visible. Additionally, both of the vertical slides 405, each located on an opposite side of the axial drive assembly 213, are visible. The single point adjustment screw 235 is also shown. In this embodiment, the height of the axial drive assembly 213 and, therefore, the depth of cut, may be adjusted by turning the adjustment screw 235 on top of the axial drive assembly 213. In other embodiments of the invention, the single point adjustment 235 may be located at alternative locations.

Optionally, the single point adjustment 235 may be provided via an alternative adjustment mechanism capable of translating the axial drive assembly 213 along axis 233. For example, the axial arm 408 of axial drive assembly 213 may include a telescoping arm to move the radial drive assembly 216 and the grinding wheel attached thereto (not visible) closer to, or further from, the workpiece. A telescoping axial arm may be extended or retracted using hydraulic pressure or any other suitable driver.

The rotary grinding system 200 may also include a locking mechanism 512 or fixed or adjustable vertical stop to prevent and/or limit vertical travel of the axial drive assembly 213, relative to the upper frame 210, beyond upper and/or lower predetermined limits, for example so as to prevent grinding below a predetermined depth or to prevent back-driving during operation. Optionally or alternatively, the vertical locking mechanism 512 can be locked to prevent vertical movement of the axial drive assembly 213, such as during shipment or storage. Locking vertical movement of the axial drive assembly 213, relative to the upper frame 210, and then installing links to support the weight of the radial arm assembly 216 below the upper frame 210 (as described above) offloads roller bearings 705 (described below, in relation to FIG. 7) in the axial drive assembly 213.

FIG. 6 is a cutaway view of the rotary grinding system 200 shown in FIGS. 4 and 5. FIG. 6 further illustrates the single point vertical screw adjustment mechanism 235. A ball screw assembly 601 includes a ball screw and a housing and is used to impart linear motion to the axial drive assembly 213. The ball screw assembly 601 allows precision vertical, i.e., depth-of-cut, adjustments. The ball screw or the housing is secured to the support frame 611. Accordingly, when the screw is turned causing it to move with respect to the housing (or vice versa depending on which is secured to the support frame 611), the axial drive assembly 213 is translated along the axis 233, with respect to the support frame 611.

FIG. 7 is another cutaway view of the rotary grinding system 200 shown in FIGS. 4 and 5 showing both the axial arm 708 of the axial drive assembly 213 and the radial arm 706. The radial arm 706 is generally orthogonal to the axial arm 708. In this embodiment, an axle 702 is housed within a housing of the axial drive assembly 213. The housing also includes roller bearings 705, which maintain the orientation of the axle 702 while allowing it to rotate within the housing. The radial arm 706 is coupled to, and suspended below, the axle 702. Accordingly, rotating the axle 702 rotates the radial arm 706, which moves the grinding wheel 244 in a circular motion across the surface of the workpiece. The motor 245 rotates the grinding wheel 244.

A motor 710 directly or indirectly drives a ball screw drive shaft 715. The grinding wheel motor 245 is attached to a carriage that is translated by the ball screw drive shaft 715, as the ball screw 715 turns. In normal operation, the grinding wheel 244 is translated within a region 720, so as to refinish a portion of a workpiece. However, as shown, the grinding wheel 244 may be retracted a distance 723 beyond the center point or axis 233, i.e., to the left, in FIG. 7. This feature enables the grinding wheel 244 to be retracted, so as to expose a diameter of the workpiece. Thus, an operator or an automatic measuring system may measure flatness of a workpiece, such as by inserting a precision bar or by shining a laser beam across the diameter of the workpiece.

The axial arm 708 may also include a slip ring (not visible) to allow the use of electrical equipment options, such as cameras, lasers, inspection equipment, sensors, actuators or other tools that allow precision monitoring and/or maneuvering of components of the rotary grinding system 200. Such equipment increases the range of operations that are achievable by the grinding system. For example, embodiments of the invention may be used to machine contours into a workpiece.

FIG. 8 illustrates a grinding assembly 800 of the rotary grinding system 200 shown in FIGS. 4 and 5, without the support system 411. The axial arm 408 of the grinding assembly 800 is shown still connected, via the axial drive assembly 213, to the dual vertical slides 405. The axial arm 408 of grinding assembly 800 also includes a hydraulic piston 803, which serves as a counterbalance to relieve weight on the vertical height adjustment mechanism, i.e., the ball screw assembly. The piston 803 is connected between the axial drive assembly 213 and the saddles 405 by a bar 804. Optionally or alternatively, another suitable counterweight, such as a preloaded spring or a chain and mass, may be used.

FIG. 8 also illustrates a track 806, along which a carriage 810 may ride to translate the grinding wheel assembly 813, as driven by the ball screw 715 (FIG. 7), as indicated by arrow 816.

Some embodiments of the present invention include scales that provide position feedback, in the form of electrical signals, of the displacement of the grinding wheel 244 along the track 806 of radial arm 216, as well as the radial arm displacement in the vertical direction along the axis 233 of the axial arm 408. A rotational scale may be used to determine the rotational phase of the radial arm 216 about the axis 233.

FIG. 9 illustrates the radial arm 216 to show possible locations of mechanical stops 900 to limit travel of the carriage 810 along the track 806 to prevent the grinding wheel assembly 813 from being displaced further along the track 806 than desired predetermined distances. Multiple fixed mechanical stops 900 may be used, so that various stopping limits may be set for workpieces of different sizes. The mechanical stops 900 may be fixed, with respect to their radial distances along radial arm 216, or the mechanical stops 900 may be adjustable. One or more of the mechanical stops 900 may be positioned in a protruding manner (as further illustrated in FIG. 10) to prevent motion of grinding wheel assembly 813 along the track 806, or one or more of the mechanical stops 900 may be re-positioned in a retracted position to allow the grinding wheel assembly 813 to pass these stops 900 on track 806. Alternatively, one or more adjustable mechanical stops (not shown) may be used, each of which may be engaged at a desired location along the track 806.

In some embodiments, the radial arm 216 includes a dynamic counterweight (not shown). The counterweight may be dynamic in the sense that, as the grinding wheel assembly 813 is moved along the track 806, the counterweight automatically moves in equal and opposite directions to reduce any deflection that may occur in the radial arm 216. Such a dynamic counterweight may be implemented using a chain drive, a screw drive, a dual-rack with an interconnecting gear drive, or any other suitable drive. A screw with two opposing threads may be used to drive both the carriage 810 and the dynamic counterweight in opposite directions.

The radial arm 216 may also be equipped with lines (not shown) that allow cooling fluids or gases, such as air, to be introduced at the grinding wheel 244 as the surface of the workpiece is being machined, thereby allowing better surface finishes, more efficient machining and extended wheel life.

FIG. 10 shows the radial arm 216 of FIG. 9 from below. In this figure, the grinding wheel 244 and the grinding wheel motor 245 are omitted for clarity. The bottom of the carriage 810 (i.e. the portion that connects the motor 245 and wheel 244 to the track 806 of radial arm 216) is shown attached to track 806. The ball screw drive shaft 715 of the drive mechanism that displaces the carriage 810 is also shown. As noted, the carriage 810 may be displaced by rotational motion imparted by the motor 710 (not visible in FIG. 10) to the ball screw 715. Accordingly, the ball screw drive shaft 715 may be a threaded shaft whose spiral path is designed to engage ball bearings housed within a ball bearing housing connected to the base of the carriage 810. Thus, when the ball screw drive shaft 715 is rotated, the carriage 810 and the attached motor 245 and grinding wheel 244 translate along the path of the track 806. The track 806 helps maintain the carriage 810 in the proper orientation during this translation. Alternative drive mechanism may be used to impart linear motion to the carriage 810. Examples of other drive mechanisms include, but are not limited to, a lead screw system, a rack and pinion system, a chain drive system and hydraulic rod or rodless cylinder. Alternatively, some embodiments of the invention may include a linear motor to move the carriage 810.

The drive mechanism is used to propel the grinding wheel assembly along the tracks of the radial arm. The radial drive may be equipped to allow for slow or rapid traversing. The drive mechanism may be a rotary motor and may include a drive system to convert the rotary motion into linear motion of the grinding wheel assembly. As discussed above the drive mechanism may provide various drive speeds. The drive mechanism may use a hydraulic motor, clutch, brake. gearing, torque limiters, etc. to achieve a range of drive speeds.

FIG. 11 illustrates a single point tool holder 1100 in accordance with embodiments of the present invention. The tool holder 1100 may be configured for mounting to the grinding wheel assembly 813 (FIGS. 8 and 9). When a tool, such as a carbide cutting tool, is held by the tool holder and the tool holder is mounted to the grinding wheel assembly in lieu of a wheel guard, the tool may be positioned to engage the workpiece, instead of the grinding wheel engaging the workpiece. Rotation of the axial arm 408 (FIGS. 5, 7 and 8) causes the tool to make circular or spiral cuts in the workpiece. Such an arrangement may be used to more rapidly remove larger amounts of material from the workpiece than can be removed by the grinding wheel, albeit possibly resulting in lower surface finish quality than when using the grinding wheel. Such an operation may be advantageous when, for example, the workpiece is badly damaged. The single point tool may be used to remove the bulk of the workpiece material that is to be removed. After the bulk of the material is thus removed, the single point tool and holder 1100 may be removed, and the grinding wheel may be used to finish the workpiece, as described above.

FIG. 12 illustrates a tool holder 1200 for dressing the grinding wheel 244 (FIGS. 2, 7, 8 and 9), in accordance with various embodiments of the present invention. The tool holder 1200 may be manually slid into or out of a precision slot in the grinding wheel guard in order to prepare the wheel for grinding. The tool holder 1200 includes a micrometer adjuster, such that displacements of the business end 1203, with respect to the tool holder, may be precisely measured. The spindle 1202 of the micrometer may be coupled to a dressing tool, such as a dressing diamond, at the business end 1203. Thus, when the thimble 1204 of the micrometer is rotated, the dressing tool moves in or out, and the amount of motion is indicated on the scale located on the sleeve 1205 of the micrometer. Accordingly, the depth of the cut for the dressing tool may be precisely controlled.

FIG. 13 is a schematic block diagram of a computer-controlled embodiment of the present invention. In this embodiment, a computer numerical control (CNC) system 1300 controls various operations of the rotary grinding system 200 (FIGS. 2 and 4-7). A feedback control system consisting of sensors and/or actuators on components of the grinding system 200 connects with CNC 1300 to drive components and measure the corresponding displacements and rotations. For example, the CNC 1300 may be connected to motor A 1301, motor R 1302, and motor T 1308. Motor A 1301 may be used to translate the axial arm 1303 in an axial direction via a single point axial positioner, such as by rotating the single point height adjuster 235 (FIG. 4). The amount of translation may be controlled via CNC 1300. Sensor A 1305 provides feedback to CNC 1300 indicating the amount of axial translation that axial arm 1303 has experienced.

The amount or phase of axial rotation may also be controlled via CNC 1300. Motor R 1302 may be used to rotate the axial arm 1303. Sensor R 1306 provides feedback to CNC 1300 indicating the amount or phase of axial rotation that radial arm 1304 has experienced.

The amount of translation experienced by grinding wheel motor 1310 and grinding wheel 1311 along the radial arm 1304 may also be controlled via CNC 1300. Motor T 1308 may be used to drive the translation mechanism of the radial arm 1304. Sensor T 1309 provides feedback to CNC 1300 indicating the amounting of radial translation that grinding wheel motor 1310 and the grinding wheel 1311 have experiences. The CNC 1300 may also control the grinding wheel motor 1310. CNC 1300 may be electrically connected to the sensors and motors on the radial arm 1304 via slip ring 1307. Slip ring 1307 allows electrical signals to be sent and received from electrical components disposed on the radial arm during rotation of the radial arm.

The CNC 1300 may be used to automate all or part of a refinishing operation. For example, many track plates have annular “lands” that need to be refinished, while annular portions (“spaces”) between the lands need not be refinished. The CNC 1300 may be programmed to operate the motor T 1308 so as to move the grinding wheel 1311 back and forth over one of the land portions (and not over adjacent spaces) and to operate the motor R 1302 so as to rotate the axial arm 1303 one or a predetermined number of full revolutions, so the grinding wheel 1311 makes one or the predetermined number of complete passes over the land. The CNC 1300 may then operate the motor A 1301 so as to incrementally lower the axial arm 1303. Another complete pass or set of passes may then be made over the land. This process may be repeated as necessary to refinish the land to a predetermined height or smoothness.

The CNC 1300 may be programmed to skip over the spaces, i.e., operate the motor T 1308 to translate the grinding wheel 1311 over the spaces as quickly as possible, and refinish only lands of a workpiece. If a sector, rather than an annular portion, of the workpiece is to be refinished, the CNC 1300 may be programmed to operate the motor R 1302 so the grinding wheel 1311 traverses over only the sector of the workpiece. In either case, time may be saved by avoiding having the grinding wheel 1311 pass over portions of the workpiece that need not be refinished.

As the grinding wheel 1311 is used to remove material from a workpiece, the grinding wheel 1311 wears down, causing a reduction in the radius of the grinding wheel 1311. The CNC 1300 may be programmed to compensate for this decrease in radius by periodically or occasionally operating the motor A 1301 to lower the grinding wheel 1311 an amount approximately equal to the actual or estimated reduction in the grinding wheel\'s radius, while the rotary grinding system is refinishing a workpiece. The rate at which the grinding wheel\'s radius is worn down may be estimated, based on the composition of the grinding wheel, the type of material being worked, the amount of time the grinding wheel 1311 has been operating and/or the area of the workpiece that has been refinished. The area may be calculated or estimated, based on the cumulative distance the grinding wheel 1311 has passed over the workpiece. Optionally or alternatively, a laser or other measuring instrument may be used to automatically measure the radius of the grinding wheel 1311.

Thus far, use of the rotary grinding system has been described in the context of refinishing workpieces so as to leave level finished surfaces. However, the CNC 1300 may be programmed to operate the motors 1301, 1032 and/or 1308 so as to leave sloped or contoured (i.e., curved) surfaces. Furthermore, the smoothness of a finished surface may be controlled by adjusting the radial feedrate of the grinding wheel, the speed of the grinding wheel, the depth of cut, and the rotational speed of the radial drive assembly. Thus, the CNC 1300 may be programmed to finish different portions of a workpiece to different grades of smoothness.

The motors used in various embodiments of the present invention may be hydraulic, pneumatic or electric motors. Similarly, sensors, scales, etc. used in various embodiments may be electronic, electromechanical, pneumatic or any other suitable types of sensors.

While the invention is described through the above-described exemplary embodiments, it will be understood by those of ordinary skill in the art that modifications to, and variations of, the illustrated embodiments may be made without departing from the inventive concepts disclosed herein. Furthermore, disclosed aspects, or portions of these aspects, may be combined in ways not listed above. Accordingly, the invention should not be viewed as being limited to the disclosed embodiments.