Abstract:
A movable spindle tool machine, such as a printed circuit board line drilling machine includes a base and a spindle mounted to the base. A magazine is mounted proximate the spindle for storing a supply of tools. A pitch independent tool changer is moveably mounted relative to the base for transferring tools from the magazine for insertion into the spindle. A tool locator is mounted in line with the spindle. The tool changer is operable to initially transfer a tool from the magazine to the tool locator to align the tool with the spindle and thereafter transfer the tool to the spindle for insertion into the spindle. The spindle is mounted to a nested outrigger guide. A positioning system can move two or more spindles simultaneously. A bit detector in a pressure foot button uses fiber optics to detect broken bits.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to movable spindle tool machines and, more particularly, to improvements in a movable spindle tool machine to satisfy increased throughput requirements. 
     FIELD OF THE INVENTION 
     A movable spindle tool machine in one form comprises a drilling machine. Drilling machines have been used, for example, for printed circuit board applications, such as in laminated chip carriers (LCC). Many of these machines include many spindles. The spindles are positioned during set-up to various locations. The most common type of drilling machine is a beam mounted machine that provides a single spindle for each work station. Each station acts on a workpiece at one time. Thus, if there are six stations, then there are six spindles. Another type of drilling machine used in high production operations is a matrix drilling machine. The spindles are provided in an array. The location of the spindles are not changed. The movable spindle LCC line driller is a cross between the traditional beam-mounted spindle drilling machine and air spindle matrix drillers. The line driller has the advantage of being able to automatically move the spindles to a fixed spacing that maximizes the hit rate based on the pitch of the LCC pattern on the panel. 
     In movable spindle tool machines of the type discussed the multiple spindles must be positioned prior to running the desired application. It is desirable to provide a means to automatically position the spindles. The conventional method is to provide a separate positioning system for each spindle. This can be expensive and requires a separate positioning system for each spindle which takes up a substantial amount of space. This minimizes the number of tools that can be used in a given area thereby limiting enhancements in machine productivity. 
     It is often necessary to replace a tool used in the spindle. This can be done manually. Advantageously, the process is automated. The spindle typically has a collect for holding the tool. The position of the tool must be located properly so that it can be inserted and maintained in the collect during a tool change operation. Also, the typical tool changers are adapted to change each tool independently. This can increase set-up time. Further, a drive system should operate independent of pitch. 
     In drilling machine applications it is important to determine if a drill bit is broken. Known methods range from microwave guide distortion, to acoustic vibration, to optical chip detectors. The most widespread method uses an optical through-beam pair of sensors to detect the presence or absence of the drill. However, to complicate the matters, drill bits sometimes only break off the tip of the drill. This has a tendency to fool most detectors because a through-beam pair typically looks higher up the drill flutes. Through-beam pairs are also limited by the minimum separation in the accuracy of alignment between the sender and receiver tips which impacts reliable detection of smaller drill diameters. 
     The present invention is directed to overcoming one or more of the problems discussed above, in a novel and simple manner. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a movable spindle tool machine is adapted to increase production productivity. 
     In one aspect of the invention, a movable spindle tool machine includes a pre-spindle tool locator. 
     In another aspect of the invention, a movable spindle tool machine includes a positioning system for two or more movable assemblies. 
     In still another aspect of the invention, a movable spindle tool machine includes nesting movable tool carriages. 
     In accordance with still another aspect of the invention, a movable spindle tool machine includes a location independent tool or button changer for linear spindle arrays. 
     In accordance with a further aspect of the invention, a movable spindle tool machine includes a light pipe bit detector incorporated in a removable pressure foot button. 
     In one embodiment of the invention there is disclosed a movable spindle tool machine including a base and a spindle mounted to the base. A magazine is mounted proximate the spindle for storing a supply of tools. A tool changer is movably mounted relative to the base for transferring tools from the magazine for insertion into the spindle. A tool locator is mounted in line with the spindle. The tool changer is operable to initially transfer a tool from the magazine to the tool locator to align the tool with the spindle and thereafter transfer the tool to the spindle for insertion into the spindle. 
     There is disclosed in accordance with another embodiment of the invention a movable spindle tool machine including a base and a plurality of spindles. A plurality of bars, one for each spindle, and each supporting one of the spindles, are movably mounted to the base to position the spindles relative to one another. A drive assembly is mounted to the base for driving a linear actuator. Clamping means are operatively associated with each bar for selectively engaging the individual bars with the linear actuator to thereby selectively enable movement of the individual spindles relative to one another. 
     There is disclosed in accordance with a further embodiment of the invention a movable spindle tool machine including a base and a spindle mounted to the base. A magazine is mounted proximate the spindle for storing a supply of tools. A tool changer is movably mounted relative to the base for transferring tools from the magazine for insertion into the spindle wherein the tool changer comprises a relatively rigid fixed jaw and a relatively flexible movable jaw. An actuator selectively moves the movable jaw toward the fixed jaw to grip a tool therebetween. 
     There is disclosed in accordance with an additional embodiment of the invention a movable spindle tool machine including a base and a plurality of spindles. A plurality of carriages, one for each spindle and each supporting one of the spindles, are movably mounted to the base to position the spindles relative to one another. Each carriage comprises a narrow bar mounted to the spindle to provide minimal spacing between the spindles and an outrigger framework attached to the narrow bar to effectively increase the width of the bar. A linear drive stage is mounted to the base and the carriages for selectively positioning the spindles. 
     There is disclosed in accordance with yet another embodiment of the invention a spindle tool machine including a base and a spindle mounted to the base having a drill bit for drilling a workpiece. A pressure foot is operatively associated with the spindle to apply pressure to the workpiece during a drilling operation. The pressure foot includes a downwardly opening recess. A button is mountable in the pressure foot recess. The button comprises a two-piece button having first and second halves mateable to define a center opening for a drill bit. First and second light pipes are disposed between the two halves in alignment with each other and concentric with a center of the center opening. The light pipes are operatively associated with optical fibers for detecting a drill bit at the center opening. 
    
    
     Further features and advantages of the invention will be readily apparent from the specification and from the drawing. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevation view of a line drilling machine in accordance with the invention; 
     FIG. 2 is a left side elevation view of the line drilling machine of FIG. 1; 
     FIG. 3 is a front elevation view of a spindle block assembly used with the drilling machine of FIG. 1; 
     FIG. 4 is a front view specifically illustrating a carriage assembly for holding the spindle block assembly of FIG. 3; 
     FIG. 5 is a side elevation view, with parts removed for clarity, illustrating a tool changer and pre-spindle tool locator in accordance with the invention, 
     FIG. 6 is a bottom view illustrating the tool locator of FIG. 5; 
     FIG. 7 is a detailed side elevation view illustrating the tool changer in accordance with the invention; 
     FIG. 8 is a front elevation view, with parts removed for clarity, illustrating a positioning system in accordance with the invention; 
     FIG. 9 is a sectional view taken along the line  9 — 9  of FIG. 8; 
     FIG. 10 is a front elevation view, similar to that of FIG. 8, with parts removed for clarity, illustrating the nesting of movable tool carriages in accordance with the invention; 
     FIG. 11 is a sectional view taken along the line  11 — 11  of FIG. 10; 
     FIG. 12 is a perspective view illustrating a button in accordance with the invention; 
     FIG. 13 is a perspective exploded view of the button of FIG. 12; and 
     FIG. 14 is a sectional view of a pressure foot holding the button of FIG.  12 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention relates to a printed circuit board line drilling machine adapted for use with a Laminated Chip Carrier (LCC). The illustrated line drilling machine has fifteen movable spindle capability. As described more particularly below, the spindles are arranged in a line across a beam and are moved to position and clamped in place before drilling. The spindles are mechanically clamped in place throughout the drilling process to yield superior hole location results over types of machines that can position spindles on every drill cycle. The spindles comprise air drive spindles which require no special water jacket for cooling and present no thermal intrusion of the beam which also improves location stability. 
     The spindle includes a pressure foot to clamp the panel. A bit detector is mounted in the pressure foot which can detect a 6-mil drill. The drill changer is mounted to the XY table and requires no adjustment for spindle spacing. A removable button is provided in the pressure foot which allows minimum clearance between the drill and pressure foot opening. A vacuum chuck is included which is used in conjunction with fixed locators. An XY table with 6×30″ stroke is used to allow for manual tool change. 
     While the present invention is disclosed in connection with a line drilling machine, the various aspects of the invention can be used with other types of spindle tool machines or processing machines using multiple assemblies that have to be positioned prior to running the desired application, as will be apparent to those skilled in the art. 
     Referring to FIGS. 1-2, a line drilling machine  20  in accordance with the invention is illustrated. For clarity, various parts of the drilling machine  20  that do not relate to the various aspects of the present invention are omitted. Likewise, several of the views illustrated herein show only elements of the machine  20  relating to specific features to aid in understanding the operation of the various aspects of the drilling machine  20 . 
     The line drilling machine  20  includes a lower base  22  supported on legs  24 . The lower base  22  supports an XY table  26 . Additionally, legs  28  extend upwardly from the lower base  22  to support an upper base  30  in the form of the beam. The beam  30  comprises a granite beam above the table  26  on the 24-inch side of a panel. This allows use of fifteen spindle block assemblies, referred to herein simply as spindle blocks, two of which are shown at  32 . The spindle blocks  32  provide a minimum spacing of 1.5 inches. Each spindle block  32  is mounted to a carriage assembly  34 . The carriage assemblies  34  are nestable, as described below, and move the spindle blocks  32  into position using a positioning system  36 . 
     Z-axis motion is produced by a drive bar  38 . The spindle blocks  32  are spring-loaded upwardly against the drive bar  38 . The drive bar  38  pushes downward on contact points in the form of drive ears  40  built into the spindle block  32  shown in FIG.  2 . The contact points in the spindle blocks  32  act downward through air cylinders  42  to actuate a pressure foot  44  mounted at the lower end of the spindle block  32  thereby improving drilling accuracy and eliminating fixed connections between the spindle block  32  and the Z actuator allowing a more freely movable spindle block  32 . This eliminates or decouples the moment produced by the pressure foot  44  on the spindle block  32 . The drive bar  38  is driven by drive stages  46  comprising lead screws acting through a linkage  48  to the drive bar  38 . Thus, the drive bar  38  acts on plural spindle blocks  32  simultaneously, eliminating individual Z-axis servos as in prior systems. 
     The XY table  26  includes linear motors (not shown) on either side of each axis to produce a resulting drive. The structure of the XY table  26  may be conventional in nature and does not form part of the present invention. It is therefore not discussed in detail herein. 
     Referring to FIGS. 5 and 6, a pre-spindle tool locator  50  in accordance with the invention is illustrated. The tool locator  50  is mounted frontwardly of the spindle block  32 . A magazine in the form of a drill clip  52  extends frontwardly of the spindle block  32  and provides up to twelve (12) tools in the form of drills, also referred to as drill bits,  54  in a plastic holder  56 . The drill bits  54  are in a line and are generally in alignment with the bit locator  50  and a collect  58  of the spindle block  32 . 
     FIG. 5 illustrates a single spindle block  32  with the tool locator  50  and the magazine  52 . In addition, a tool locator  50  and magazine  52  are provided for each spindle block  32 . 
     Referring specifically to FIG. 6, the bit locator  50  comprises a “V” block  60  mounted in the spindle block  32  in precise relation to the collect  58 . Particularly, a center line  62  passing through a center of a V opening  63 , and intersecting a vertex of the “V” block  60 , is aligned with a center of the collect  58 . A ball plunger  64  having a spring-loaded ball  66  is positioned in the V opening  63 . The ball plunger  64  serves to push the tool  54  in contact with the V opening  63  thereby locating it both laterally and angularly when the tool  54  is released by a tool changer  68 . The travel of the ball  66  allows the tool  54  to be inserted into the device with a substantially more “off” location than the spindle block  32  would allow as is shown by the dotted lines on the view of FIG.  6 . 
     The tool changer  68  is mounted to the XY table  26 . In operation, the tool changer  68  moves up and grips a tool  54  from the clip  52  and moves rearwardly to a location below the bit locator  50 . The tool  54  is then inserted in the bit locator  50  and the tool changer  68  ungrips the tool  54  to allow the bit locator  50  to properly position it. The realigned tool  54  is then regripped and lowered and moved further rearwardly to be inserted in the collect  58 . 
     Referring to FIG. 7, the tool changer  68  is illustrated in greater detail. Rather than using individual tool changers associated with each spindle block  32 , as is on a conventional multiple spindle per station, adjustable spindle drill machine or router, the tool changer  68  is a single entity which changes tools on any number of spindles  32  on any spacing within a certain linear space. In the illustrated embodiment of the invention, if fifteen spindle blocks are used for performing a drilling operation, then the tool changer  68  can change tools for all fifteen simultaneously. In the illustration in FIG. 1, the eight left-most carriage assemblies  34  are in position where tools could be changed for associated spindle blocks  32 . The remaining seven carriage block assemblies  34 , and their associated spindle blocks, not shown, are in an unused spindle storage area. 
     The tool changer  68  uses jaws  69  defined by a fixed jaw or blade  70  and a movable jaw or blade  72 . The fixed jaw  70  is relatively rigid. The movable jaw  72  is relatively flexible. The tools  54  are gripped by pushing the movable jaw  72  towards the fixed jaw  70 . The rigidity of the fixed jaw  70  determines the tool location left and right while the flexibility of the movable jaw  72  assures that all tools  54  are gripped securely. 
     Two lobes  74  on the fixed jaw  70  and a single lobe  76  on the movable jaw  72 , positioned vertically between the lobes  74 , assure a sufficient resistance to force that may be applied to the tool  54  perpendicular to the cross-section. 
     In the illustrated embodiment of the invention, the movable jaw  72  uses a flexure  78  at a lower end to allow it to be pushed toward the fixed jaw  70 . Alternatively, any type of continuous hinge could be used. The movable jaw  72  is actuated by pressurizing a flexible oval tube  80 , backed up by a fixed member  82 . Any type of actuator that applies a substantially constant force per unit length could be used in place of the oval-shaped tube  80 . 
     The tool changer  68  is mounted on the XY table  26 . In the illustration of FIG. 1, the tool changer is positioned below eight of the carriage assemblies  34 . Assuming each carried a spindle block  32 , the tool changer  68  would be operated to change eight tools simultaneously. After the spindle spacing has been set up, the open jaws  69  would move under the desired drill position  54  in the drill clips  52 . The tool changer  68  would then move upwardly relative to the tool clip  52 . The jaws  69  would be closed and then moved away from the tool clip  52 , pulling the desired tools  54  from the magazine  52 . In this manner the spacing of the tools  54  in the jaws  69  is determined by the spacing of the spindles  32 . After locating the drills precisely relative to each spindle using the locators  50 , as discussed above, the jaws  69  move under the spindles  32  and then move up. After the collets  58  are tightened around the tools  54 , then the jaws open and move down so that machining may proceed. To put used tools  54  back into the magazine  52 , the process is reversed without the step using the bit locator  50 . 
     The tool changer  68  could also be used for changing the removable button  84 . Alternatively, a similar device  86 , see FIG. 2, can be separately secured to the XY table  26  for changing the button  84 . The tool changer Z drive system is used to raise and lower the tool changer  68 . It can be implemented in a number of conventional ways and therefore is not considered part of this invention. 
     Referring to FIGS. 4,  10  and  11 , each carriage assembly  34  comprises a narrow bar  88  and an outrigger framework  90 . The narrow bar  88  has a width corresponding to that of the spindle block  32 . This allows the spindle blocks  32  to be spaced closely together. The outrigger framework  90  acts as a stabilizer arm and increases effective width of the bar  88  to provide required rigidity to process the part accurately. Referring to FIG. 10, a first carriage  34 - 1  is shown unnested. The width of the carriage  34 - 1  is defined by the distance L 1  . The relationship between carriages  34 - 2  and  34 - 3  shows how carriages can be nested on centers defined by an effective width L 2  much smaller than the width L 1 . 
     Each narrow bar  88  comprises a block that slides on opposite outer rails  92  using linear bearings  94 . The rails  92  are fastened to the beam  30 . The outrigger framework  90  comprises a V-shaped bar having ends  96  secured to the opposite ends of the narrow bar  88 . The V-bar  90  has a center portion  98  slideably mounted to a center rail  100  using a linear bearing  94 . The center rail  100  is fastened to the beam  30  centrally disposed between the outer rails  92 . 
     Thus, the carriage assemblies  34  use a relatively narrow bar to provide minimal spacing between the spindle blocks  32  and the V-bar framework effectively increases width of the bar  88  to provide rigidity. 
     Referring to FIGS. 8 and 9, the positioning system  36  is illustrated in greater detail. In this illustration the V-bars  90  are omitted from the carriages  34  for clarity. 
     FIG. 8 illustrates three of the narrow bars  88  of three corresponding carriage assemblies  34  attached to the base  30  with the linear bearings  94  and rails  92  to allow motion in the direction shown by the arrow  102 . An assembly drive rod  104  is attached to a single positioning system  106  which contains drive means, such as a linear motor, rotary motor and lead screw, etc., and usually a position feedback means, such as an optical encoder, magnetic encoder, etc. The positioning system  106  is affixed to the beam  30 . A fixed rod  108  is mounted to the beam  30  by a block  110  on each end, only one of which is shown. The fixed rod  108  is used to hold the movable carriage assemblies  34  in place while other carriage assemblies are being moved. The fixed rod  108  has a small diameter and is mounted in tension which allows it to thermally conform to the beam  30 . A drive clamp  112  is permanently attached to each narrow bar  88  and can be selectively actuated and released to clamp or release the drive rod  104 . Similarly, a fixed clamp  114  is permanently attached to each narrow bar  88  and can be selectively actuated and released to a clamp or release the fixed rod  108 . 
     In the illustration of FIGS. 8 and 9, the clamps  112  and  114  are shown secured to the bar  88 . In an alternative configuration, as shown in FIG. 4, the clamps  112  and  114  are secured to the V-bar framework  90 . 
     When the carriage assemblies  34  are all at rest, the fixed clamps  114  are all actuated to hold the carriage assemblies  34  in position, see FIG.  9 . When it is desired to move an assembly to a new position, the drive clamp  112  on that particular carriage assembly  34  is turned on. The corresponding fixed clamp  114  is turned off. The positioning system  106  moves the desired incremental amount taking the particular assembly  34  with it. Once in the desired position, the fixed clamp  114  is turned on and the drive clamp  112  is turned off to complete the assembly move cycle. In this manner any number of carriage assemblies  34  can be moved selectively one at a time or in groups by means of a single positioning system  106 . Additionally, each carriage assembly  34  is rigidly clamped while in process as opposed to being held on location by a servo control loop. 
     Referring to FIGS. 12 and 13, the pressure foot button  84  is illustrated in detail. The pressure foot button  84  is provided in two halves  120  and  122 . This allows the path or track where a light pipe is placed to be located with a high degree of accuracy. Particularly, a light pipe sender  124  and a light pipe receiver  126  extend downwardly at an angle towards a center opening  128 . The sender and receiver light pipes  124  and  126  are machined in alignment with each other and concentric with the center of the pressure foot  44  which is the drill location. The button  84  is held in the pressure foot  44  on location by a set of opposing Vlier screws  130  that seat on depressions  132  in an outer barrel  134  of the button  84 . The depressions  132  are machined so that the Velier screws  130  bias the button  84  up against the pressure foot  44  and to resist rotation of the button  84 . The button  84  has a face  136  that is square to enable more positive gripping of the buttons by parallel jaws of the pressure foot button changer  86 . 
     The two button halves  120  and  122  are held together using fasteners  138  with dowel pins  140  in the face  136  maintaining the proper positioning. 
     Referring to FIG. 14, the button  84  is shown mounted in the pressure foot  44 . The light pipe sender and receiver  124  and  126  mate with an optical fiber bundle  142  which carries light signals several feet back to an LED emitter and photocell. It is necessary for the light to jump the gap between the fiber bundle  142  and the light pipe sender and receiver  124  and  126 . The throughbeam pair can detect a 4-mil target with a separation of 1.8 inches. The separation in the illustrated configuration is about 190 mils. Also, the expected diameter of the light bundle  142  is 15 mils where the light pipe diameter is about 40 mils. The light pipe  124  and  126  does not need a jacket and can be significantly smaller than the fiber bundle  42  thereby reducing the criticality of alignment across the gap. Air blowoff ports  144  are provided to keep the light pipes  124  and  126  free of debris. By angling the light pipes  124  and  126  downwardly below an outer surface  146  of the pressure foot  44 , the sensing plane is moved down to the very tip of the drill  54  improving the chance of detecting a broken tip without adding excessive drill stroke. As can be seen, the button face  136  is disposed below the pressure foot lower surface  146 . 
     As is apparent, the drilling machine  20  uses various additional structure for its intended operation. Because such structure is unrelated to the invention, it is not illustrated or specifically discussed herein. The various controlled elements are controlled by a personal computer or the like connected via input/output interface circuits to the particular controlled devices. The controller is programmed accordingly for the necessary operation. 
     Thus, in accordance with the invention there is provided a movable spindle tool which implements a pre-spindle tool locator, a spindle positioning system, the use of nesting movable carriages, a multiple tool changer and a pressure foot button light pipe broken bit detector in accordance with the invention.