Abstract:
A multi-head centerless belt grinder for removing material from a workpiece includes a common base and a plurality of grinding heads spaced apart from one another and mounted to the common base. Each grinding head includes a moveable work rest blade, a moveable regulating wheel and a moveable grinding belt positioned by servomotors to centerless grind the workpiece along a common axis of rotation. The grinder is programmable for rapid machine changeover and set-up typically within 2-5 minutes to accommodate a large range of workpiece diameters. This feature results in improved productivity and output as well as greater flexibility for scheduling numerous workpiece diameters within a normal eight-hour work shift. A trough may extend beneath and between each of the grinding heads to more efficiently collect and transfer grinding swarf generated during the grinding process to a filter operable to separate solids within the swarf from coolant.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/858,077 filed on Nov. 9, 2006. The disclosure of the above application is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to multi-head centerless belt grinding systems for heavy stock removal, intermediate tolerance grinding, and fine surface polishing, normally performed in a single-pass-through operation for rods, bars, tubes, pipe, and other cylindrical workpieces, typically in lengths from 2′ (610 mm) long to over 60′ (18.3M) long, and in part diameters from 0.500″ (12.5 mm) to over 12.000″ (300 mm). 
         [0003]    More particularly, an improved belt grinding head mounting arrangement with programmable electronic servomotor controls is provided for rapid machine changeover and set-up for multiple workpiece diameters. Furthermore, an improved grinding coolant system efficiently disposes of large amounts of grinding swarf and coolant from the grinding heads and common machine base into a separate recirculating coolant system. 
         [0004]    Early multi-head grinding machines were configured with separate standalone grinding heads to perform sequential operations utilizing high powered abrasive belt drives from 20 HP (15 kW) to 100 HP (75 kW). The individual grinding heads sometimes moved relative to one another requiring frequent realignment for machine set-up. 
         [0005]    Furthermore, known grinding machines typically are oriented with each grinding belt head horizontally. During the grinding operation, a large amount of coolant mixed with the material removed from the workpiece to create a grinding slurry called swarf. The horizontally oriented belt grinding head tended to collect and accumulate the swarf within the belt head assembly and machine frame. Removal of swarf from the grinding heads was very time consuming and often required major downtime and operator maintenance for cleaning and partial disassembly of the grinder. 
       SUMMARY 
       [0006]    A multi-head centerless belt grinder for removing material from a workpiece includes a common base and a plurality of grinding heads spaced apart from one another and mounted to the common base. Each grinding head includes a moveable work rest blade, a moveable regulating wheel and a moveable grinding belt assembly positioned to simultaneously centerless grind the workpiece along a common axis of rotation. 
         [0007]    Additionally, a multi-head centerless belt grinder for removing material from a workpiece includes a plurality of spaced apart grinding heads aligned with one another and adapted to simultaneously remove material from the workpiece. A coolant spray system supplies coolant to each of the grinding heads. A trough extends beneath and between each of the grinding heads to collect and transfer swarf generated during the grinding process to a filter operable to separate solids within the swarf from coolant. 
         [0008]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0009]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0010]      FIG. 1  is a plan view of a grinder constructed in accordance with the teachings of the present disclosure; 
           [0011]      FIG. 2  is a side view of the grinder shown in  FIG. 1 ; 
           [0012]      FIG. 3  is a fragmentary end view of the grinder shown in  FIG. 2 ; 
           [0013]      FIG. 4  is a schematic depicting the major components of a grinding head associated with a workpiece; 
           [0014]      FIG. 5  is a plan view of a regulating wheel assembly; 
           [0015]      FIG. 6  is a side view depicting a first ball screw assembly; 
           [0016]      FIGS. 7-10  are views depicting a rest blade assembly; 
           [0017]      FIGS. 11-14  depict various views of a column assembly including a driven grinding belt; 
           [0018]      FIG. 15  is a fragmentary cross-sectional view of an idler pulley of the column assembly depicted in  FIGS. 11-14 ; 
           [0019]      FIGS. 16-18  depict the column in a finished state prior to assembly of the drive motor and grinding belt components; 
           [0020]      FIGS. 19-21  depict various views of a grinding cooling spray system of the grinder; 
           [0021]      FIG. 22  is a plan view of an alternate grinder; and 
           [0022]      FIG. 23  is a side view of the grinder depicted in  FIG. 22 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0024]      FIGS. 1-21  depict a multi-head centerless belt grinder  20 . Grinder  20  is useful for removing material from an outer diameter of a cylindrically shaped workpiece  22 . Workpiece  22  may be formed as a solid bar or a hollow tube typically ranging between 2 and 60 feet in length. Grinder  20  is operable to machine workpieces having outer diameters ranging from ½″ to 12″. One exemplary type of workpiece is a drawn-over-mandrel tube used to construct a telescopic cylinder in the hydraulics industry. 
         [0025]    Grinder  20  includes seven individually operable grinding heads  24 ,  26 ,  28 ,  30 ,  32 ,  34  and  36 . Grinding heads  24 - 36  are spaced apart from one another and each mounted to a common base  38 . Separate handling tables (not shown) may be positioned adjacent to base  38  to introduce workpiece  22  to grinder  20  and also accept finished workpieces after the grinding operations have been completed. Depending on the length of the workpiece to be ground, the number of grinding heads  24 - 36  simultaneously removing material from the workpiece may range from one to seven. The workpiece enters at grinding head  24  where a rough grind operation is performed. Grinding head  24  removes the greatest quantity of material from workpiece  22 . Workpiece  22  is axially driven toward grinding head  26  where a finer grit belt is engaged with the workpiece. The simultaneous grinding processes continue until workpiece  22  exits grinding head  36 , which may perform a micro-grinding operation. 
         [0026]    A controller  40  controls operation of each grinding head  24 - 36  as will be described in greater detail hereinafter. Controller  40  is also in communication with a graphical interface  42 . An operator may interact with graphical interface  42  to control grinder  20 . Grinding heads  24 - 36  are substantially similar to one another. Accordingly, only grinding head  24  will be described in detail. 
         [0027]    Grinding head  24  includes a column assembly  50 , a regulating wheel assembly  52  and a work rest blade assembly  54 . Regulating wheel assembly  52  includes a regulating wheel  56  in contact with an outer surface  57  of workpiece  22  and an electric motor  58 . Electric motor  58  is operable to rotate regulating wheel  56  about an axis  60  extending at an angle not parallel to an axis  62  about which workpiece  22  rotates. By arranging regulating wheel assembly  52  in this manner, regulating wheel  56  and electric motor  58  are operable to rotate workpiece  22  about axis  62  while simultaneously axially driving workpiece  22  in the direction indicated by an arrow  64 .  FIG. 5  depicts further details relating to regulating wheel assembly  52 . For example, a coupling  66  drivingly interconnects an output shaft  68  of electric motor  58  with an input shaft  70  of a gear reduction unit  72 . The output of gear reduction unit  72  provides torque to regulating wheel  56 . 
         [0028]      FIG. 3  shows a first ball screw assembly  80  mounted to base  38 . Regulating wheel assembly  52  is coupled to first ball screw assembly  80  such that regulating wheel assembly  52  may be axially translated in a direction substantially parallel to the ground. First ball screw assembly  80  includes a first servomotor  82  coupled to a slide assembly  84 . A precision ball screw  86  is driven by first servomotor  82  to linearly translate slide assembly  84 .  FIG. 6  depicts first ball screw assembly  80  in greater detail showing a first servomotor  82  being mounted to a screw housing  88 . A coupling  90  is positioned within screw housing  88  to interconnect an output shaft  92  of first servomotor  82  with a ball screw  94 . A bearing assembly  96  rotatably supports ball screw  94  within screw housing  88 . 
         [0029]    A nut housing  98  is spaced apart from screw housing  88  and coupled to a portion of slide assembly  84 . A nut  100  is threadingly engaged with ball screw  94  such that rotation of ball screw  94  causes axial translation of nut  100  and nut housing  98 . The interconnection and arrangement of first ball screw assembly  80  and regulating wheel assembly  52  allows precise positional control of regulating wheel  56 . Varying diameters of workpieces may be accommodated by axial translation of regulating wheel assembly  52  during selective energization of first servomotor  82 . Workpieces  22  are aligned along common axis of rotation  62  at each grinding head. 
         [0030]      FIGS. 7-10  depict blade assembly  54  including a jack housing  120  fixed to base  38 . A rest blade  122  is fixed to sleeves  124   a  and  124   b . A drive mechanism  126  is operable to move sleeves  124   a  and  124   b  between retracted and extended positions within jack housing  120 . Because sleeves  124   a  and  124   b  are substantially similar to one another, drive mechanism  126  relating to only sleeve  124   b  will be described in detail. 
         [0031]    Drive mechanism  126  includes an input shaft  128  rotatably supported by jack housing  120 . Worms  130   a  and  130   b  are fixed to or integrally formed with input shaft  128 . With reference to  FIG. 10 , worm  130   b  drivingly engages worm gear  132  to transmit torque to a jack screw  134 . Jack screw  134  drivingly engages a jack nut  136 . Jack nut  136  is fixed to sleeve  124   b . Jack screw  134  is free to rotate but restricted from axial movement. Jack nut  136  is restricted from rotation but allowed to axially translate within jack housing  120 . Therefore, rotation of input shaft  128  rotates worm  130   b  causing worm gear  132  to rotate in response thereto. Jack screw  134  is fixed for rotation with worm gear  132 . Rotation of jack screw  134  causes axial translation of jack nut  136 , jack sleeve  124   b  and rest blade  122 . 
         [0032]    A second servomotor  140  is mounted to base  38  and includes an output shaft  142  drivingly coupled to a longitudinally extending driveshaft  144 . Driveshaft  144  is fixed for rotation with an input shaft  146  of a right angle gear box  148 . An output  150  of right angle gear box  148  is fixed for rotation with input shaft  128  of blade assembly  54 . Second servomotor  140  is in communication with controller  40  such that the position of rest blade  122  may be varied to properly position workpiece  22 . Rest blade  122  and sleeves  124   a  and  124   b  are movable between the retracted and extended positions to account for various workpiece outer diameters. A surface  152  of rest blade  122  contacts outer surface  57  of workpiece  22 . 
         [0033]      FIGS. 11-15  depict column assembly  50  having a column  180 , a drive motor  182 , a contact wheel  184 , an idler pulley  186  and a belt tensioner  188 . Column  180  includes a flange  190 , a vertical rib  192  and a shell  194  defining a cavity  196 . Shell  194  includes a bottom wall  198  positioned at an angle “A” of approximately 30° to a mounting plane  200  located on flange  190 . Mounting plane  200  is positioned substantially parallel to the ground. As such, bottom wall  198  extends at approximately 30° to the ground. It should be appreciated that angle “A” may deviate from 30° as long as a swarf shuttling function is performed. Accordingly, it is contemplated that angle “A” ranges from 20°-70°.  FIGS. 16-18  depict column  180  in the finished state prior to assembly of the drive motor and grinding belt components. 
         [0034]    With reference once again to  FIGS. 11-15 , a grinding belt  208  is drivingly engaged with contact wheel  184  and idler pulley  186 . In the embodiment disclosed, grinding belt  208  is 12″ wide and 120″ long. Grinding belt  208  engages outer surface  57  of workpiece  22  to remove material from the workpiece. A bearing assembly  226  rotatably supports contact wheel  184  and an idler pulley yoke  212  rotatably supports idler pulley  186 . Belt tensioner  188  interconnects bearing assembly  226  and idler pulley yoke  212 . Belt tensioner  188  includes a pneumatic cylinder  214  in receipt of pressurized air to maintain a proper tension on grinding belt  208 . As the workpiece is being ground, the material removed by grinding belt  208  mixes with coolant to form a slurry called grinding swarf. Because grinding belt  208  is 12″ wide and typically has a grit ranging from No. 36 grit to a fine polishing grit, such as No. 600 grit, a relatively large quantity of swarf is generated during the grinding processes. A grinding coolant spray system  218  ( FIG. 20 ) operable to clear grinding belt  208  of swarf and keep the swarf from interfering with the grinding operation will be described in greater detail hereinafter. 
         [0035]    Drive motor  182  is mounted to column  180 . A drive belt  220  transfers torque from drive motor  182  to contact wheel  184 . More specifically, drive belt  220  engages a pulley  222  mounted on a driveshaft  224 . Driveshaft  224  is supported by a bearing assembly  226  mounted within column  180 . Driveshaft  224  is rotatably fixed to contact wheel  184  such that rotation of an output shaft  228  of drive motor  182  causes a drive pulley  230  to transmit power through drive belt  220 , pulley  222 , driveshaft  224  and provide power to contact wheel  184 . 
         [0036]    Idler pulley yoke  212  supports a cross shaft  231  as shown in  FIG. 15 . Idler pulley  186  is rotatably supported by a pair of bearing assemblies  232  positioned on cross shaft  231 . Each bearing assembly  232  is protected from exposure to the swarf by a cap  234  coupled to idler pulley  186 . Idler pulley  186  includes a recess  236  having a flared surface  238  angled in a direction to encourage swarf to sling outwardly from idler pulley  186  and contact inner surfaces of shell  194 . The swarf is washed out of cavity  196  by the grinding coolant spray system  218 . 
         [0037]    A grinding belt tracking adjustment apparatus  240  includes a first thumb wheel  242  and a second thumb wheel  244  coupled to shafts operable to rotate a cam  246 . Rotation of cam  246  varies the position of idler pulley yoke  212  within cavity  196 . By moving idler pulley yoke  212 , the positional relationship between an axis of rotation  248  of idler pulley  186  and an axis of rotation  250  of contact wheel  184  may be varied. Proper contact and alignment of grinding belt  208  with contact wheel  184  and idler pulley  186  may be maintained by adjustment of the relative alignment or misalignment between axes  248  and  250 . 
         [0038]    A second ball screw assembly  260  is mounted to base  38 . Column  180  is coupled to second ball screw assembly  260  such that column assembly  50  may be axially translated in a direction substantially parallel to the ground. Second ball screw assembly  260  includes a third servomotor  262  coupled to a slide assembly  264 . A precision ball screw  266  is driven by third servomotor  262  to linearly translate slide assembly  264 . Slide assembly  264  and ball screw  266  are substantially similar to slide assembly  84  and ball screw  86  previously described and depicted in detail in  FIG. 6 . 
         [0039]    Controller  40  is in receipt of signals indicative of the positions of column assembly  50 , regulating wheel assembly  52  and work rest blade assembly  54 . The position signals may be provided by encoders associated with the first, second and third servomotors, the first and second ball screw assemblies or other suitable position indicating devices. Axial translation of column assembly  50  allows grinder  20  to accept a wide variety of workpiece diameters and also facilitates the centerless grinding process where contact wheel  184  may be moved toward workpiece  22  during the grinding operation. Controller  40  is operable to simultaneously actuate first, second and third servomotors  82 ,  140 ,  262  for each grinding head  24 ,  26 ,  28 ,  30 ,  32 ,  34 ,  36  to allow changeover from a first workpiece diameter to a second workpiece diameter in two to five minutes time. Furthermore, controller  40  is in receipt of a signal indicative of the current being drawn by each drive motor  182 . The magnitude of current being drawn provides an indication of the load on contact wheel  184 . Graphical interface  42  may display a graphical representation of the current being drawn by drive motor  182  such that an operator may adjust the position of contact wheel  184  and increase or reduce the load on contact wheel  184  as desired. 
         [0040]      FIGS. 19-21  depict a portion of grinding coolant spray system  218  having a pump (not shown) providing pressurized fluid to a first coolant manifold  300  and a second coolant manifold  302 . First coolant manifold  300  and second coolant manifold  302  extend longitudinally along each side of grinder  20 . Each of the coolant manifolds  300 ,  302  are mounted to base  38 . The Figures depict portions of grinding coolant spray system  218  cooperating with grinding head  24 . It should be appreciated that grinding coolant spray system  218  includes additional components similarly cooperating with grinding heads  26 - 36 . Because the other portions of grinding coolant spray system  218  are substantially similar to one another, only one set of hardware providing coolant to grinding head  24  will be described in detail. A first coolant supply line  304  is in communication with first coolant manifold  300 . First coolant supply line  304  provides pressurized fluid to a column branch  306  and a workpiece branch  308 . Column branch  306  terminates at a plurality of spray nozzles  310  mounted to column  180  and positioned within cavity  196 .  FIG. 20  depicts five nozzles  310  directing a pressurized fluid spray on grinding belt  208  and inner surfaces of shell  194  to wash swarf out of cavity  196  and toward a trough  320  coupled to base  38 . A valve  312  is positioned in column branch  306  to allow an operator to selectively supply pressurized coolant to spray nozzles  310 . 
         [0041]    Trough  320  includes a first shed plate  322  and a second shed plate  324  extending inwardly from edges of grinder  20  at an angle “B” approximately 20° relative to the ground. It should be appreciated that angle “B” may deviate from 20° as long as a swarf shuttling function is performed and may range at least between 5° and 45°. The inclination of shed plates  322  and  324  force swarf to travel toward another portion of trough  320  having more vertically oriented side walls  326  and  328 . 
         [0042]    More particularly, side walls  326  and  328  define a “V” shaped arrangement having an included angle “C” of approximately 30°. Side walls  326  and  328  have lower terminal ends  330  and  332  abutting legs  334  and  336  of a bottom plate  338 . Legs  334  and  336  extend substantially perpendicular to one another. A corner  340  is defined at the intersection of legs  334  and  336 . Corner  340  is positioned at the lowest point of trough  320 . The deepest portion of trough  320  is defined by side walls  326 ,  328  and legs  334 ,  336  and is sized to suspend a large quantity of solids within the coolant of the swarf to facilitate moving the solids within the swarf to an end  342  ( FIG. 1 ) of trough  320 . 
         [0043]    Trough  320  includes a transition from the “V” shaped arrangement shown to a substantially circular cross-section at end  342 . Trough  320  may be inclined to force swarf toward one or more ends of the trough or some other location intermediate the ends. The first grinding head  24  encountered by workpiece  22  will typically remove the most material therefrom. Subsequent grinding heads may remove less material to more accurately shape and size the outer surface to a predetermined target. The grinding head that removes the most material from workpiece  22  may be positioned closest to the portion of trough  320  where the swarf is removed from grinding coolant spray system  218 . A filter  344  separates the solids from the coolant in the swarf at or near this location. Filtered coolant is pumped back into first and second coolant manifolds  300  and  302 . 
         [0044]    Branch  308  terminates at a spray nozzle  350  that may be directed to spray pressurized coolant at or near the interface between the workpiece  22  and grinding belt  208 . A valve  351  is plumbed in series within branch  308  to allow an operator to selectively supply pressurized coolant to nozzle  350 . Swarf generated by the grinding operation is washed down toward trough  320 . 
         [0045]    A second coolant supply manifold line  352  is integrated with second coolant supply manifold  302  to provide pressurized coolant to a second plurality of nozzles  354 . Nozzles  354  are mounted to regulating wheel assembly  52  and operable to selectively spray pressurized coolant on regulating wheel  56 . A valve  356  allows an operator to selectively provide pressurized coolant to nozzles  354 . 
         [0046]    It should be appreciated that grinder  20  is designed to accommodate a very large range of workpiece diameters. This may be accomplished by positioning parallel coolant supply manifolds  300 ,  302  along the sides of base  38  while trough  320  extends substantially along the longitudinal centerline of grinder  20 . Further design flexibility is provided by positioning first servomotor  82 , second servomotor  140  and third servomotor  262  outboard of first and second coolant supply manifolds  300 ,  302 . It may also be beneficial to note that each grinding head  24 - 36  is mounted on a common surface of base  38  to accurately maintain a common axis of workpiece rotation over time. 
         [0047]    Another grinder configuration  400  is depicted at  FIGS. 22 and 23 . Grinder  400  is substantially similar to grinder  20  except that the grinding heads are not substantially equally spaced apart from one another. On the contrary, a first grinding head  402  is spaced apart from a first end  404  of grinder  400  and a group of subsequent grinding heads  406 . By positioning grinding head  402  in this manner, a workpiece may be initially supported on a bed  408  and transferred in either direction relative to grinding head  402  to complete the first grinding operation along the entire length of a workpiece. Because the stock used to create ground components varies greatly, it may be desirable to perform a first, or several, rough grinding operations with grinding head  402  and subsequently inspect the workpiece prior to performing grinding operations with grinding heads  410 ,  412 ,  414  and  416 . After the rough grinding and inspection processes have been completed, it is determined if the workpiece exhibits certain characteristics to either be rejected or be further ground to create a finished product. Accordingly, the workpiece is either shuttled toward a reject station  419  for removal and scrap or shuttled toward a second end  418  where subsequent grinding operations are performed. 
         [0048]    Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings, that various changes, modifications and variations may be made therein without departing from the spirit and scope of the disclosure.