Abstract:
A grinding machine has a machine bed, a first spool and a second spool mounted on the machine bed. The spools are capable of storing stock to be ground and are rotatable in a coordinated manner. A grinding wheel is mounted on the machine bed. The first spool is capable of continuously unwrapping the stock, the second spool is capable of continuously wrapping the stock and the grinding wheel is adapted to grind the stock during its travel between the first spool and the second spool. The grinding machine can be used to continuously grinding a slender stock. The stock is continuously unwrapped from the first spool and continuously wrapped on the second spool. The stock is ground during its travel from first spool to the second spool.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to centerless grinders. More particularly the present invention relates to grinders wherein the stock is continuously unwrapped from a first spool and wrapped on a second spool during the process of grinding. 
   2. Description of the Related Art 
   Centerless grinders are well known machines for grinding elongated cylindrical workpieces such as medical guide wires, rods, pins, golf club shafts, antenna, fishing rods and similar articles. Conventional centerless grinders include a supporting structure on which a grinding wheel and a regulating wheel are mounted with their working surfaces facing each other and slightly separated. The workpiece is positioned between these two wheels (“the working area”). These wheels rotate in the same direction about a substantially horizontal axis at different speeds. The profile of the finished workpiece is controlled by moving the regulating wheel toward or away from the grinding wheel as the workpiece passes through the working area. 
   Since the workpiece&#39;s forward movement between the grinding wheel and the regulating wheel is controlled by the regulating wheel&#39;s speed and tilt angle (among other factors), slight changes in either of these factors can result in errors in the workpiece&#39;s desired grinding profile. In order to prevent such errors, systems employing optical sensors, such as those disclosed in U.S. Pat. No. 5,480,342 to Royal Master Grinders, Inc., the assignee of the present application, are used to precisely detect the workpiece&#39;s position and to move the regulating wheel in response to this detected position. 
   However, for elongated workpieces fabricated from wire stock shipped on spools, the grinding process can begin for a particular set of workpieces only after the wire is dispensed by hand from the spool and cut into a plurality of equal lengths. Each length of wire then must be placed into a feeder for transmitting the wire through the working area. These steps substantially delay the manufacturing process. Therefore, there is a need for a grinding machine that would continuously feed the wire past the grinding wheel and simultaneously continuously wrap the ground wire on a spool. 
   SUMMARY OF THE INVENTION 
   The present invention, in one aspect, teaches a grinding machine having a machine bed. A first spool mechanism having a first spool and a second spool mechanism having a second spool mounted on the machine bed. The first spool mechanism and the second spool mechanism are capable of storing stock to be ground. The first spool mechanism and the second spool mechanism are rotatable in a coordinated manner to rotate the stock. A grinding wheel is mounted on the machine bed. The first spool is capable of continuously unwrapping the stock, the second spool is capable of continuously wrapping the stock and the grinding wheel is adapted to grind the stock during its travel between the first spool and the second spool. 
   In another aspect, the present invention teaches a method of continuously grinding a slender stock. The stock is continuously unwrapped from the first spool and continuously wrapped on the second spool. The stock is ground during its travel from first spool to the second spool. 
   In another aspect, the present invention teaches a machine tool for continuously processing a slender stock. The machine tool has a first spool assembly having a first spool, and a second spool assembly having a second spool. A tool is located between the first spool assembly and the second spool assembly. A bed supports the first spool assembly, the second spool assembly and the tool. The tool is capable of continuously performing an operation on a stock while it is being unwrapped from the first spool and wrapped on the second spool. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a centerless grinding machine of the present invention. 
       FIG. 2  is an isometric view of the spool mechanism of the centerless grinding machine of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of the spool mechanism of the centerless grinding machine of  FIG. 1  showing the internal components of the spool mechanism. 
       FIG. 4  is an isometric view of another embodiment of the spool mechanism of the centerless grinding machine of  FIG. 1 . 
       FIG. 5  is a cross-sectional view of the spool mechanism of  FIG. 4  showing the internal components of the spool mechanism. 
       FIG. 6  is a cross-sectional view along line zz shown in  FIG. 3 . 
       FIG. 7  is a top plan view of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a grinding machine  100 . Machine  100  includes a machine base  102  (alternatively called machine bed). Machine base  102  may be made using known methods. Machine base  102  may be an iron bed that is stress relieved and normalized and then ground for flatness and parallelism of the structures on the bed. A main spindle may be mounted on machine base  102 . The main spindle may be housed in a counterweighted weldment  106  that also houses the main spindle drive motor. Weldment  106  may also house adjustment plate, machine electronic, and optionally a hydraulic tank and pump assembly. 
   A machine control interface swingarm  108  is mounted on machine base  102 . Machine control interface swing arm  108  houses the machine&#39;s master computer including a touch screen interface  110 . All functions of grinding machine  100  may be controlled via machine&#39;s master computer. The master computer may be located in any other suitable position and connected to grinding machine  100 . 
   An electrical control cabinet  112  is located adjacent to machine base  102 . All machine control hardware, input/output modules, relays, servo drives and motion controllers may be located in electrical control cabinet  112 . Electrical connections to various parts of grinding machine  100  may be made through quick disconnect plugs for ease of movement. Electrical control cabinet  112  may be located at any suitable location and the electrical connections may be made using any method and hardware known to one skilled in the art. 
   A coolant tank and pump assembly may be located in machine base  102  or any other suitable location. In one exemplary embodiment, coolant and delivery pump may be housed in a sheet steel forty gallon tank  114 . The pump may be a 10 GPM centrifugal unit powered by a ⅙ hp sealed electric motor. Any other suitable pump may be used. Tank  114  may have two or more compartments separated by individual insertions (partitions) to improve settling of sludge produced during grinding. 
   A ram bed assembly  116  is mounted on machine base  102 . Ram bed assembly  116  has a linear motion axis. The movement of the ram along the linear motion axis may be computer controlled. The movement of the ram along the linear motion axis determines final size of the work piece. The movement of the ram along the linear motion axis, for example, is generated through a servo motor coupled to a planetary gearbox that drives a custom ground ball screw drive line. Any other suitable arrangement for movement of the ram along the linear motion axis may be used. The position of ram may be controlled via a motion controller that may be part of the master computer. A 0.1 micron linear glass scale may be used to precisely move and locate the ram. Alternatively, any other suitable method and scale for precise location and movement of the ram may also be used. Customer specific tooling, including bushings or support blades, may be mounted on the ram and moved toward and away from the work zone to determine final part geometry. Final part geometry may be controlled with tooling and the ram axis movement. If bushings are to be used, the bushing diameters may be of tight tolerance, within 0.0002 inch, and may be sized to match the work piece diameter. The work piece is inserted inside the bushing for machining. The movement of the ram along the linear motion axis moves the work piece into the work wheel. The glass scale controls the ram axis position, thus controlling the work piece size. Any other form of tooling may function in similar ways and hold the work piece in position while the ram axis moves the tooling along with the work piece into the work wheel. 
   A main spindle assembly (also known as head stock assembly) may be housed in counterweighted weldment  106 . The main spindle assembly includes a grinding wheel  120  mounted on a precision work wheel spindle. The work wheel spindle may be of a cantilever design to allow the operator easy access to the work wheel for wheel change and setup. Three duplex pairs of class seven ABEC angular contact ball bearings may be used in the design for extreme accuracy. The preloaded ball bearing design, such as the duplex pairs of class seven ABEC angular contact ball bearings, requires no spindle warm up time. Alternatively, any other suitable bearings or means of rotational mountings may be used. The spindle may be fitted with lubed for life bearings and labyrinth seals at each end to ensure a contamination free life. This complete unit is installed in a normalized and stress relieved cast iron headstock to assure vibration free operation. The head stock is mounted on machine base  102 . Grinding wheel  120  having a 12″ diameter, 4″ face and 5″ bore may be mounted on the main spindle. Alternatively, grinding wheel of a different size may be mounted on the taper lock main spindle. The spindle may be belt driven and may run at up to 3300 rpm. Such spindle speed may results in a maximum wheel surface velocity of 10,500 sf/m and thereby allow the use of super abrasive grinding wheels. In another embodiment, spindle speed above or below 3300 rpm may be used. 
   Grinding machine  100  may also include one or more spool-to-spool assembly  130 . Spool-to-spool assembly  130  includes two separate multi axis coordinated spool mechanism  132  ( FIG. 2 ) that will continuously feed material from a spool  134 , process it, and wrap it on another spool  135 . Spool-to-spool assembly  130  may be used, for example, in grinding, heat treatment, polymer coating or any other process where continuous feed of work piece is desired. One embodiment of the spool-to-spool assembly  130  is used in the grinding machine  100  used to grind diameter products including guidewires. Although an embodiment using the spool-to-spool assembly in a grinding operation is described, the assembly could be used in heat treatment or polymer coating operation or perform any other operation by replacing the grinding wheel by an appropriate set-up (or tooling) to continuously heat treat or polymer coat or perform any other continuous operation on the stock. 
     FIGS. 2 and 3  show an exemplary spool mechanism  132  that may be used to wrap or unwrap the stock. Spool mechanism  132  includes a main housing  200  that houses a main spindle  202 . Main spindle  202  may be 8 inches long and 5.5 inches in diameter. The size of the main spindle may be changed as necessary for different embodiments. Main spindle  202  is mounted in two angular contact spindle bearings  204 . Any other suitable bearing and bearing configuration may be used. Main spindle  202  is coupled to a main spindle gearbox  206 . Main spindle gearbox  206  in turn is coupled to a main spindle servo motor  208  that drives the main spindle via coupling between driven pulley  209  and driving pulley  211 . 
   A gearmotor  210  for level mounting mechanism is also included in spool mechanism  132 . Gearmotor  210  is coupled to a level winding mechanism  212 . Level winding mechanism  212  includes a level wind screw  214  and guide shoe  216  mated with the level wind screw  214 . Gearmotor  210  drives level winding mechanism  212  so that guide shoe  216  reciprocates on level wind screw  214  at appropriate speed so as to result in level winding of the stock on spool  135 . Level winding mechanism  212  also includes a replaceable carbide guide that would resist wear and thereby ensure long life at high speed. 
   Spool  135  is mounted on a spindle  220  that in turn is mounted in long bearing  222  and short bearing  224 . A timing pulley  230  is coupled with spindle  220 . The timing pulley  230  allows the rotations of the spool  135  to be coordinated with the rotations of the spool  134 . Spool mechanism  132  also includes a centering cone  228  located in the main housing  200 . Centering cone  228  centers the stock such that the stock is positioned suitably for the grinding. The centering cone also assures that the stock rotates around its own axis and does not revolve off-center around a central axis. A motor is coupled to spool  134  and a second motor is coupled to spool  135 . These motors rotate spools  134  and  135  to unwrap and wrap the stock, respectively. The action of these motors may be coordinated to ensure that there is no “bailing up” of the stock. The bailing up of the stock is a condition wherein the stock is unwound at a rate faster than it is wound resulting in collection of excess stock that is not tightly stretched. 
   One embodiment of spool-to-spool assembly  130  shown in  FIGS. 4 and 5  uses two rotary servo motors  302 , two linear servo motors  326  and two rotary servo motors  310 . Another embodiment of spool-to-spool assembly  130  shown in  FIG. 3  uses two rotary servo motors  208 , two rotary servo motors  210  and two rotary servo motors  217 .  FIG. 6  shows rotary servo motor  208 , rotary servo motor  210  and rotary servo motor  217 . The rotary servo motors  208 , rotary servo motors  210  and rotary servo motors  217  are rotary servo motors that may direct drive servo motors with no gear boxes. The load may be attached directly to the motor spindle. The linear servo motor may be a rotary motor that has been flattened. Rotary servo motors  208  rotate the Spools  134  and  135  around the work pieces longitudinal axis X-X ( FIG. 3 ). Rotary servo motors  210  drives the level winding mechanism  212 . Rotary servo motors  217  rotate each quick change spindles of spools  134  and  135  around their axis Y-Y ( FIG. 3 ) and thereby rotate spools  134  and  135  respectively around axes Y-Y. 
   Rotary servo motors  208  may be electronically or manually coupled for fully coordinated motion. In another embodiment, motor  217  for rotating spools  134  or  135  around axis Y-Y and rotary motor  210  may be electronically or manually coupled. Servo motor  208  that rotate the spool ( 134  or  135 ) around the work piece longitudinal axis may also be called the “main wire rotation motor.” Servomotor  208  that rotates spool  134  (around axis X-X) and servo motor  208  that rotates spool  135  (around axis X-X) rotate the spools at the same velocity throughout the grinding process. The velocity is checked and controlled with the use of an encoder on each axis. Servo motors  217  may also be called “wrap motors.” Servo motors  217  rotate the wrap/unwrap spools (i.e., spools  134  and  135 ), and are also electronically coupled. Servo motors  217  are computer controlled for proper rotation rates and are checked with encoders. 
   Main wire rotation encoder, wire wrap encoder and level wind encoder are used to check position of all axes of motion. The encoders are mechanically coupled to each axis of motion, rotary or linear. The encoders have two parts. The encoders have a reader and a scale. The scale is attached to the part whose position is to be determined. The encoder reads the scale and thereby determines the position of the part to which the scale is attached. This is done so that the precise positioning and placement of the work piece can be assured. The master computer may use the position on the respective rotation axis for each spool to calculate the proper rotation rate of the wrap motor and linear position of the level winding mechanism  212 . Using the known values for wire wrap rotation rate, wire diameter and through put rate the level wind position can be calculated. And, as the workpiece is continually ground the level wind position can be updated to ensure that the winding is smooth and even. The proper rotation rate of the wrap motor and linear position of the level winding mechanism  212  are essential to getting a neat and level wrap on spool  135 . Controlling the position of the ram axis allows control of the part profile. 
   The rotary electrical connections for the motors may be made through slip ring hardware. The use of slip ring hardware may result in maximum axial rotation rate of about 2000 RPM for the servo motors  208 . Programmable or settable stops for each multi axis coordinated spool mechanism  132  will allow use of spools  134  and  135  of various width and diameter to be used as desired. The diameter of the spool  134  (or spool  135 ), wire diameter, spool width, and the wrap rate will determine the position of the stop. 
   Programmable stops simplify the mechanical assembly and eliminate mechanical components. The level wind motor needs to move across the face of the spool  135  at a rate that will evenly distribute the wire on the spool  135  without building up in any one given spot. As the wire diameter changes the move distance across the spool  135  changes. The stops will keep the level wind function operating properly. The “stop” stops the level wind motor at a predetermined position and thereby avoids buildup. 
   For ease of stock change over the spool spindle may be of a quick change design. Any suitable quick change method and apparatus known to one skilled in the art may be used. In one embodiment, width of spool  135  (or  134 ) may be limited to 4 inch and the maximum diameter of the grinding wheel may be limited to 12 inch. 
   The programmable rotational rates for spools  134  and  135  allow for precise control of wrapping tension and also keep the unwrapping stock from “bailing up”. Rapid rewind of the stock is possible as each wrapping and unwrapping units are bidirectional. Maximum rotational wrapping rates of 5000 RPM are possible. A replaceable carbide guide is used on the level winding assembly to ensure long life at elevated speeds. The level winding assembly may be of any form known to one skilled in the art. 
   Spools  134 ,  135  and the stock may also rotate around an axis while processes (such as grinding, heat treatment or coating) are preformed on the stock. While a process takes place, the stock is unwrapped and rewrapped from two spools  134  and  135  respectively. The level winding mechanism keeps the stock uniformly distributed on the spool on which the processed stock is being wrapped. Thus, during the process such as grinding, spools  134 ,  135  each rotate around a separate axis Y-Y passing through their center to unwrap and rewrap the stock. Additionally, spools  134  and  135  and the stock rotate around a second axis X-X, thereby imparting rotation to the stock on which the process is being performed. In an alternative embodiment, in place of rotation of the stock around the axis X-X, grinding wheel  120  may be rotated around the stock while grinding wheel  120  also rotates around its own axis. 
     FIGS. 4 and 5  show another embodiment of spool mechanism  300 . Two spool mechanisms  300  are included in a spool-to-spool assembly  130  that will continuously feed material from one spool and wrap it on the other spool. Features described in context of the embodiment of  FIGS. 2 and 3  may also be used with the embodiment of  FIGS. 4 and 5  and vice versa. In the embodiment of  FIG. 4 , spool mechanism  300  includes a wire rotation servomotor  302 . Wire rotation servomotors  302  of the two spool mechanisms  300  are coupled either electrically and/or mechanically. Spool mechanism  300  includes a yoke assembly  304  coupled to the wire rotation servomotor  302  via a slip ring  306 . A spool  308  is coupled to the yoke assembly  130 . The spool  308  has a spindle  310  directly driven by a wire wrap servomotor  312 . Spindle  310  may be supported in bearings  320 . The spool  308  is mounted on the spindle  310  using two centering cones  314 . A circlip  316  is mounted on one end of the spindle  310  to prevent the spindle  310  from sliding out of position. The circlip  316  and a handle  322  on the opposing end from the circlip  316  help performing a quick change of spindle if necessary. A counter weight  324  is located adjacent the handle  322 . An encoder wheel  318  having an encoder read head  320  is mounted on the spindle  310  between the circlip  316  and the yoke assembly  304 . The rotation of the spindle  310  is monitored via the encoder read head  320 . 
   A level wind motor for level mounting mechanism is also included in spool mechanism  300 . Level wind motor  326  may be a servomotor. Level wind motor  326  drives level winding mechanism so that guide shoe  330  reciprocates on level wind screw  328  at appropriate speed so as to result in level winding of the stock on spool  308 . The action of level wind motor  326  is coordinated with the action of wire wrap servomotor  312  to ensure that the winding of wire stock  340  on spool  308  is level. Such coordination may be achieved via coupling the level wind motor  326  to the wire wrap servomotor  312  either electrically and/or mechanically. Level winding mechanism also includes a replaceable carbide guide that would resist wear and thereby ensure long life at high speed. Spool mechanism  300  may also includes a centering cone for centering the stock such that the stock is positioned suitably for the grinding. 
   A grinding machine using any one of the spool-to spool assembly  130  may be used to continuously process a piece of stock as described hereafter. The stock final diameter may have any combination of straight and tapered sections. To start continuous grinding of stock, the wire rotation servomotors  302  are coupled to each other, the level wind motor  326  is coupled to wire wrap servomotor  312  and the grinder set-up is completed. First spool mechanism  300  having the stock to be ground is mounted on one side of the grinding wheel and second spool mechanism  300  on which the processed stock is to be wrapped is positioned on the other side of the grinding wheel. Next, a length of stock is manually unwrapped from the first spool mechanism  300 , fed through the machine past the grinding wheel and loaded on second spool mechanism  300 . The presence of stock near the grinding wheel may be monitored via a proximity sensor. 
   After the “loading” process is complete the wire rotation servomotors  302  are electronically started through the master computer. After they reach their specified rotational rpm, the grinding process can be started. At this time the ram is brought into proper position for final stock size and the wire wrap servomotors  312  in each of the spool mechanisms  300  begin their appropriate rotation to unwrap and wrap the stock. At this time the grinding wheel is rotating at desired rpm and the stock passing by the grinding wheel is ground to the desired size and profile. The ground stock is wrapped on the spool of the second spool mechanism  300 . 
   During the grinding, wire rotation servomotors  302  are coupled matching their respective rotation rates. Their rotation rates are controlled via a motion controller and their encoders respectively. At level wind motor  326 , first spool mechanism  300  reciprocates across the width of the spool as wire  340  is fed into the grinder. The wrap motor  312  is varying the rpm according to the spool diameter and wire diameter to unwind the wire  340  at a constant rate. The wire wrap servomotor  312  is coordinated with the level wind motor  326  to ensure that the stock is properly fed to the grinder. At second spool mechanism  300 , level wind motor  326  reciprocates, coordinated to the wire wrap servomotor  312 , continuously laying the ground stock neatly across the width of the spool. The wire wrap servomotor  312  is varying rpm according to the spool diameter and the wire diameter to keep the layers neat and the through put rate of the machine constant. 
   Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.