Patent Publication Number: US-6220940-B1

Title: Micro-finishing apparatus

Description:
FIELD OF THE INVENTION 
     This invention relates to a micro-finishing apparatus capable of providing continuous through-feed. More specifically, this invention is used to place a repeatable micro-finish on cylindrical workpieces having a relatively small diameter. 
     BACKGROUND OF THE INVENTION 
     Micro-finishing is a surface finishing process wherein an abrasive is brought to bear against a workpiece having a rough outer surface. By improving the surface finish, less friction will be produced between the workpiece and any contact surface thereby extending the life of the workpiece. Non-metallic products, such as wood, glass, rubber and plastic can also be micro-finished. 
     How a workpiece is micro-finished depends on its shape and size. Viewing FIGS. 1-4 herein, “centerless” or “center” operations dictate how a workpiece is held in place during the finishing process. Center operations are appropriate when the workpiece is large enough in diameter and length to be supported at each end for rotation, such as with a chuck on a lathe. However, when the diameter or the length of a workpiece is too small to be supported by a lathe, centerless operations may be used by placing the workpiece, for example, between two rotating rollers, as seen in FIGS. 2 and 4. 
     In addition, a workpiece contacts the abrasive either through “plunge” or “transverse” operations. A workpiece is subject to finishing by plunge operations when the workpiece&#39;s length is less than or equal to the width of the available abrasives. The entire length of the workpiece is constantly in contact with the abrasive. Transverse finishing is used when the workpiece is longer than the width of any available abrasives. In which case the abrasive must travel along the longitudinal axis of the rotating workpiece as it micro-finishes. 
     It is therefore well known in the art that the shape and size of the metal product will determine which one of the various micro-finishing machines would produce the best finish: 1) plunge-center; 2) plunge-centerless; 3) transverse-center; or 4) transverse-centerless. 
     For purpose of this invention, it is important to expand upon the typical transverse centerless micro-finishing machine known in the art. When cylindrical metal workpieces are micro-finished using the transverse centerless micro-finishing type machine, the workpieces are placed between two rollers as seen in FIG.  4 . The rollers are located beneath the abrasive and are offset at an angle for feeding the part through the micro-finishing apparatus. Hence, this process is also often referred to as “through-feed centerless” micro-finishing. The rollers rotate in the same direction very quickly, thereby rotating the part along the abrasive. Problems occur when workpieces are very small, such as those having diameters less than {fraction ( 3 / 8 )} of an inch or 8 millimeters. Particularly, transverse centerless cylindrical workpieces are difficult to micro-finish, if not impossible for small parts, because the abrasive cannot reach the small workpiece positioned between the rollers. This is due to the large difference in diameter between the rollers and the workpiece. More specifically, the diameter of the workpiece is so small that the abrasive contacts the rollers and never reaches the workpiece positioned therebetween. Also, conventional methods of holding the workpiece during finishing, such as using a lathe, cannot be used because the workpieces are just too small to be held by the chuck. 
     Art in the field may also be directed to grinding machines, as opposed to micro-finishing machines. Typical grinding machines are shown in FIGS. 5 and 6. These machines are comprised of a regulating mechanism, an abrasive and a means of supporting the workpiece at a fixed location. However, none of the grinding machines in the art can be used to solve the problem of micro-finishing miniature cylindrical workpieces. Problems exist in traditional grinding processes because of the abrasive used. In traditional grinding processes, the abrasive is a wheel or continuous belt that travels very fast, constantly being reused. As a result, the finish varies as the abrasive wears. Also, the contact surface of the abrasive is short if a plurality of workpieces are continuously fed through typical grinding machines. The preferred apparatus should repeatably produce consistent micro-finishing results to the entire outside surface of very small centerless workpieces. 
     In summation, there is nothing currently in the art capable of micro-finishing small workpieces. The purpose of this invention is to provide an apparatus that can micro-finish the outer surface of very small cylindrical workpieces with repeatability and consistency. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a micro-finishing apparatus, satisfying the need for finishing small cylindrical workpieces. This is accomplished by feeding the workpiece through two planar surfaces, one surface being a regulating mechanism and the other being a micro-finishing spool drive mechanism. The regulating mechanism rotates the workpiece against the abrasive of the micro-finishing spool drive mechanism and feeds it through the apparatus. 
     More specifically, this invention comprises a regulating mechanism having a planar contact surface for rotating the workpiece. The micro-finishing drive mechanism advances a roll of non-continuous abrasive belt over a planar grinding work face, which is substantially parallel to and forms an opening with the planar contact surface of the regulating mechanism. The invention also comprises a guide bar that passes through the opening and traverses at an angle between the planar contact surface of the regulating mechanism and the planar grinding work face of the micro-finishing drive mechanism. 
     Accordingly, it is an object of the present invention to provide a micro-finishing apparatus that is capable of micro-finishing small cylindrical workpieces that cannot be micro-finished on center machines or machines that support a workpiece on rollers. 
     Another objective of the present invention is to provide a micro-finishing apparatus that provides repeatability in finishing results by always introducing the workpiece to new abrasive. 
     Still another objective of the present invention is to provide a micro-finishing apparatus that more efficiently utilizes abrasive material by moving the abrasive at a very low rate of speed. 
     Another objective of the present invention is to provide a micro-finishing apparatus that can adjust to accommodate cylindrical workpieces of various diameters. 
     Further, another objective of the present invention is to provide a micro-finishing apparatus that has continuous through feed so that a plurality of workpieces can be micro-finished without constant and direct manual intervention. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The figures listed below have been selected to illustrate a preferred embodiment of the present invention. These figures along with the accompanying description are sufficient for those skilled in the art to practice the invention as claimed. Included are: 
     FIG. 1 illustrates a plunge-center micro-finishing machine used in the art; 
     FIG. 2 is a perspective illustration of a plunge-centerless micro-finishing concept used in the art; 
     FIG. 3 illustrates a transverse-center micro-finishing machine used in the art; 
     FIG. 4 is a perspective illustration of a transverse-centerless micro-finishing concept used in the art; 
     FIG. 5 illustrates an elevational side view of a centerless grinding machine used in the field; 
     FIG. 6 illustrates an elevational side view of another type of a centerless grinding machine used in the field; 
     FIG. 7 is a top plan view of the apparatus of the present invention; 
     FIG. 8 is an enlarged perspective detail showing the present invention as indicated at dashed circle  8  on FIG. 7; and 
     FIG. 9 is an elevational front view of the apparatus of FIG.  7 . 
    
    
     PREFERRED EMBODIMENT 
     Viewing FIGS. 7,  8  and  9 , a micro-finishing apparatus  10 , comprises a base  15  supporting a regulating mechanism  20 , a micro-finishing spool drive mechanism  40  and a guide bar  60 . The base  15  supports the micro-finishing spool drive mechanism  40  mounted below the regulating mechanism  20 . However, any other feasible orientation could be used. The regulating mechanism  20  has a planar contact surface  34 . The micro-finishing spool drive mechanism  40  has a grinding work face  42  being substantially planar and parallel to the planar contact surface  34  of the regulating mechanism  20  forming an opening  55  therebetween. The working width of the work face  42  and contact surface  34  are substantially equal. Their lengths may vary, however, as seen in FIG.  9 . 
     A workpiece  50  is fed through the micro-finishing apparatus  10  lateral to and at an angle with the contact surface  34  and grinding work face  42 . As the workpiece is fed through, it is supported by the guide bar  60  while the regulating mechanism  20  rotates the workpiece  50  against the grinding work face  42  of the micro-finishing spool drive mechanism  40 . The angled guide bar  60  and regulating mechanism  20 , shown in FIGS. 7 and 8, cooperate to continually feed each workpiece  50  through the micro-finishing apparatus  10 . 
     The regulating mechanism  20  further comprises a drive belt housing  22  which acts as a frame for drive belt components  24 - 36 . The drive belt housing  22  supports a drive belt  24 , a drive belt motor  26 , a drive belt tension device  28 , a plurality of drive belt pulleys  32 A, 32 B and a tracking device  36 . Via friction, the drive belt  24  provides the force to rotate the workpiece  50  against the grinding work face  42 . The speed of the drive belt  24  also determines the through-feed rate of the micro-finishing apparatus  10  as well as the number of times the workpiece  50  rotates while it is passing through the micro-finishing apparatus  10 . The drive belt  24  has a high coefficient of friction and should be a non-abrasive material such as cork or rubber so as not to interfere, scratch or otherwise damage the micro-finish of each workpiece, but it is not limited to these materials. 
     The drive belt motor  26  powers the drive belt  24  through the plurality of drive belt pulleys  32 . The drive belt motor  26  is preferably electric, although it may be pneumatic or hydraulic. The drive belt tension device  28  keeps the drive belt  24  taut as it goes around the plurality of drive belt pulleys  32 . The tracking device  36  maintains the drive belt  24  laterally in the appropriate position in relation to the grinding work face  42  while the drive belt  24  is rotating as shown in FIG.  7 . In another embodiment of the invention, the regulating mechanism  20  further comprises a drive belt platen  30  to provide a flat support for the drive belt  24  so that the height of the opening  55  formed by the drive belt  24  and the grinding work face  42  is substantially uniform. The drive belt platen  30  can be rigidly attached to the regulating mechanism  20 , or it can be attached so that it has a spring effect. 
     As shown in FIG. 9, the micro-finishing spool drive mechanism  40  comprises an abrasive  43 , an abrasive supply roll  44  which houses new abrasive  43 , an abrasive take-up roll  46  which houses used abrasive  43 , an abrasive advance motor  48  and a plurality of working surface pulleys  49 . The abrasive advance motor  48  drives the abrasive take-up roll  46  which pulls the abrasive  43  from the abrasive supply roll  44  over the plurality of working surface pulleys  49 . The abrasive supply roll  44  may further comprise a tension mechanism (not shown), such as a clutch, for maintaining tension on the abrasive  43 . Also, the abrasive advance motor  48  may be a gear motor, but it is not limited thereto. It is preferred that the abrasive  43  move slowly so that the workpiece  50  always contacts new abrasive  43  for repeatability in micro-finishing results. The abrasive  43  should not move too fast, however, so as to waste the abrasive  43  which is generally very expensive because of the type of material used, i.e. diamond fines. 
     Continuing to view FIG. 9, the opening  55  between the drive belt  24  of the contact surface  34  in the regulating mechanism  20  and abrasive  43  of the working face  42  in the micro-finishing spool drive mechanism  40  has a distance substantially equal to the diameter of the workpiece  50 . A vertical adjustment device  70 , affixed to the micro-finishing apparatus  10  changes the height of the opening  55  to accommodate different workpiece  50  diameters. 
     As previously stated, the guide bar  60  passes into the opening at an angle and holds the workpiece  50  in the micro-finishing apparatus  10  during processing. More specifically, the guide bar  60  is located relatively upstream of the forward moving belt  24  so that the workpiece  50  rests against the guide bar  60  during the micro-finishing operation. The angle of the guide bar  60  influences the through-feed rate of the micro-finishing apparatus  10  as well as the number of times the workpiece  50  rotates while it is in the micro-finishing apparatus  10 . More specifically, the greater the angle the shorter the residence time. Likewise, the smaller the angle the greater the residence time. Of course, the number of times the workpiece  50  rotates while it is in the micro-finishing apparatus  10  is directly proportional to the residence time. 
     The micro-finishing apparatus  10  is operated by placing the drive belt  24  into rotation via the drive belt motor  26  and drive belt pulleys  32 . The optimum speed of the drive belt  24  is approximately 400 surface feet per minute, although it can be adjusted to accommodate different workpiece materials and abrasive  43 . The abrasive  43  is then set into motion by the abrasive advance motor  48  driving the abrasive take-up roll  46 . The abrasive advance motor  48  rotates the abrasive take-up roll  46  by pulling the abrasive  43  from the abrasive supply roll  44  and over the planar grinding work face  42  at a rate of approximately ½ inch per minute. To maximize the efficiency of the abrasive material, the abrasive  43  is preferably pulled in the opposite direction as the belt  24 , although they can be pulled in the same direction without substantial changes in results. The guide bar  60  is positioned at an angle relative to the driving belt  24 , and the cylindrical workpiece  50  is fed through the micro-finishing apparatus  10 . The drive belt  24  rotates the cylindrical workpiece  50  along its longitudinal axis against the abrasive  43  of the planar grinding work face  42  as the workpiece  50  is fed in the opening  55  and passes laterally across the abrasive  43  before exiting the micro-finishing apparatus  10 . 
     Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.