High speed precision drilling system

{
  "publication_number": "EP0461733A2",
  "country": "EP",
  "kind": "A2",
  "title": "High speed precision drilling system",
  "abstract": "A high speed system (50) for drilling of very small holes in workpieces (137) such as printed circuit boards. The system (50) includes a conventional spindle (85) and a high speed spindle (81). The high speed spindle (81) includes a stationery body (156) carrying the stator (195, 196) of the drive motor. Only the spindle rotor (160) is translated along the Z axis to perform drilling movements. The rotor (160) is supported within the body (156) by rotary and linear air bearings (179, 187), and is axially driven by a linear motor (210, 220). A tool changer (95) loaded by clips (350) carrying the drilling bits (400) is mounted on the top work table (70). A high leverage centrifugal chuck assembly is provided for gripping a drill bit in the high speed spindle (81).",
  "claims": [
    "1. A high speed drilling spindle for a drilling system comprising a spindle body, a rotatable shaft supported within said spindle body for high speed rotation, a chuck assembly for securing a drilling tool at the lower end of the rotor shaft in alignment with the shaft axis, a rotary air bearing means for supporting the rotor shaft for high speed rotation with low frictional drag within said spindle body, and a rotary motor for imparting rotational drive forces to said rotor shaft so as to rotate said shaft on said rotary air bearing at high speeds, said drilling spindle characterized in that said spindle body is fixed and said shaft is supported within said spindle body for high speed rotation; said spindle further characterized by: a linear drive means for imparting an axially directed drive force to drive said shaft along said shaft axis to perform drilling movements; and means for coupling said linear drive means to said rotor shaft to impart said drive means to said shaft, said means comprising a thrust bearing and a linear air bearing; whereby said rotor shaft may be rotated at high speeds by said rotary motor and simultaneously translated along said axis to perform said drilling movements.",
    "2. A drilling spindle according to Claim 1, wherein said rotary motor comprises an electric motor having a stator comprising a ferrous stator core encircling said rotor shaft and a plurality of stator windings of electrically conductive wire wound about axial slots formed in said core about said shaft, and a rotor comprising an elongated rotor region to conduct the rotor electrical currents, said region extending along said rotor shaft in the region encircled by said stator and having an elongated length by a sufficient length to enable the shaft to translate along a range of movement without significant degradation of the rotary motor function.",
    "3. A spindle according to Claim 1 or 2, further characterized by a coolant system for conducting heat away from the spindle in the region of the rotary motor during high speed operation.",
    "4. A spindle according to Claim 3 wherein said coolant system comprises a plurality of coolant passages about the rotary motor, and means for conducting a coolant fluid through said passages.",
    "5. A spindle according to any of claims 1, 2, 3, or 4, further characterized in that said linear drive means comprises a linear motor having: a moving coil assembly having means for connection to a motor driver; a stator assembly comprising a permanent magnet assembly for co-action with said moving coil assembly to develop axially directed drive forces on said moving coil assembly in response to motor drive signals; and means for coupling said moving coil assembly to said rotor shaft for imparting said axial forces to said shaft.",
    "6. A spindle according to Claim 5, wherein said moving coil assembly comprises a metal cylinder having a conductive wire wound around the periphery thereof, with said wire being coupled to said motor driver, and wherein an electromotive force is exerted in an axial direction on the moving coil assembly in response to motor drive signals applied thereto.",
    "7. A spindle according to Claim 5 or 6, wherein said means for coupling said moving coil assembly to said rotor shaft comprises a plunger member having one end coupled to said rotor shaft by said thrust bearing and the other end coupled to said moving coil assembly are transmitted to said rotor shaft.",
    "8. A spindle according to Claim 7, wherein said plunger is mounted within the spindle body on an air bearing, and the thrust bearing comprises an air bearing for coupling the rotor shaft to the plunger so as to reduce frictional drag between the rotor shaft and the plunger.",
    "9. A spindle according to any of Claims 1 to 8, further characterized by means for biasing the axial rotor position against the force of gravity so as to equalize the force required to be exerted by the linear motor to axially translate the rotor in either axial direction.",
    "10. A high leverage centrifugal chuck assembly for gripping a drill tool in a high speed drilling spindle, comprising a chuck structure having an interior opening formed therein to accept the shank of a drill tool, said chuck structure characterized by: (i) at least one pair of opposed jaw members each comprising a jaw surface partially defining a circumferential region of said opening for contacting said shank; (ii) at least one pair of opposed lever arm members corresponding to said jaw members and extending along and adjacent to said opening; and (iii) a fulcrum, region encircling said opening between said jaw members and said lever arm members, said fulcrum region between each of said corresponding jaw members and said lever arms such that as said respective lever arm members are urged outwardly from said opening, reactive forces are transmitted through said fulcrum region tending to urge said jaw members inwardly to grip said drill tool shank; and (iv) means for positioning the chuck in concentricity with a spindle drilling axis and for aligning the tool shank with said drilling axis; whereby as said chuck is rotated at high speeds with a drill bit shank inserted in the chuck assembly, centrifugal forces urge said chuck lever arms outwardly, causing the jaws to grip the shank securely and concentrically with the drilling axis.",
    "11. A chuck assembly according to Claim 10, further characterized in that said chuck comprises two pairs of lever arm members and gripping jaw members disposed about said opening in a substantially uniformly spaced relationship so as to achieve substantially uniformly distributed gripping forces exerted on the drill bit shank.",
    "12. A chuck assembly according to Claim 10 or 11, further characterized in that the relative lengths of said respective lever arm and jaw members are cooperatively selected so that the center of mass of each lever arm member is located further from the fulcrum region than the center of mass of said respective jaw member, so as to achieve a gripping force amplification resulting from the centrifugal force leverage through said lever arm member and said fulcrum region on said gripping jaw member.",
    "13. A chuck assembly according to any of claims 10 to 12,,further characterized by means for applying a static gripping force on an inserted tool shank to retain the tool in the chuck assembly during the static spindle condition.",
    "14. A chuck assembly according to any of claims 10 to 13, further characterized in that said positioning means comprises a chuck bushing member having an opening formed therein for receiving said drill tool shank and an alignment surface for contacting said chuck to position the chuck in concentricity with said drilling axis.",
    "15. A chuck assembly according to Claim 14, further characterized in that said positioning means further comprises a tool shank alignment bushing having a central opening formed therein in alignment with said drilling axis for receiving the inserted end of the tool shank.",
    "16. A chuck assembly according to any of claims 10 to 15, further characterized in that said chuck structure comprises a unitary structure fabricated from a springy material, with said fulcrum region connecting said respective lever arm members and said jaw members.",
    "17. A chuck assembly according to Claim 16, further characterized in that said jaw members are disposed at a first end of said chuck and define a first cross-sectional chuck dimension, said lever arms extend back to a second end of said chuck and define a second cross-sectional chuck dimension, said second cross-sectional dimension being larger than said first cross-sectional dimension to increase the mass of the lever arm members in relation to said jaw members.",
    "18. A high speed drilling spindle comprising a spindle shaft having a shaft axis, means for driving said shaft at high rotational speeds, and a centrifugal chuck assembly for securing a drilling tool to said shaft in alignment with the spindle axis during spindle rotation, said chuck assembly characterized by: (i) a tool alignment bushing comprising a bore for receiving the inserted end of a drilling tool shank, the bushing mounted in said spindle such that said bore is aligned with said shaft axis; (ii) a chuck structure mounted adjacent the tool end of the spindle shaft and having an interior opening formed therethrough to accept said shank, the chuck structure further comprising at least one pair of diametrically opposed jaw members disposed about peripheral regions of the opening for contacting said shank, at least one pair of lever arm members corresponding to said respective jaw members, and a fulcrum region encircling said opening between said respective jaw members and said lever arm members such that as said respective lever arms are urged outwardly away from said opening, reactive forces are transmitted through said fulcrum region tending to urge said jaw members inwardly toward said axis to grip said shank; and (iii) a chuck alignment bushing mounted adjacent said tool end and having an opening formed therein for receiving the tool shank and an alignment surface for contacting said chuck and maintaining the chuck structure in concentricity with said shaft axis.",
    "19. A drilling spindle according to Claim 18 further characterized in that said chuck assembly further comprises means for applying a static gripping force on said tool shank when the spindle shaft is stationary, thereby retaining the tool in the inserted position within the chuck assembly.",
    "20. A drilling spindle according to Claim 18 or 19, wherein said chuck structure comprises two pairs of diametrically opposed lever arm members and jaw members arranged symmetrically about said spindle axis to provide gripping forces distributed uniformly about the inserted tool shank.",
    "21. A drilling spindle according to any of Claims 18, 19 or 20, wherein said lever arm members and jaw members are cooperatively arranged such that the center of mass of the respective lever arm member is located further from the fulcrum region than the center of mass of the jaw member so as to achieve a gripping force amplification resulting from the centrifugal force leverage through said lever arm member and said fulcrum region on said gripping jaw member.",
    "22. A tool changer for a machine tool system employing at least one tool head for mounting a tool along a predetermined axis and a work table which is selectively positionable with respect to the tool head for carrying a workpiece, said tool changer characterized by: magazine means for accepting a tool clip carrying a plurality of tools inserted in aligned clip apertures, and for securing said clip with said tools oriented along tool axes which are substantially parallel to said tool head axis; means for locking or unlocking each tool in the inserted clip such that in the locked condition the tools may not be removed from the tool changer, and in the unlocked condition the tools may be removed from the tool changer; means for translating the tool changer along an axis which is parallel to said tool head axis to transfer tools between said tool head and said tool changer; and means for mounting the tool changer to said work table.",
    "23. A tool changer according to Claim 22, further characterized in that said magazine means comprises a top plate member having at least one elongated slot formed therein, the width of said slot being selected to allow the tool shanks of the tools inserted in said apertures in said clip to be received between the edges of the slot as the clip is inserted into the magazine, and the means for locking the tools in the magazine comprises the cooperative engagement of the edges of the slot with an exposed region of reduced thickness formed about the tool shank, whereby the top plate captures the tools.",
    "24. A tool changer according to Claim 22 or 23, further characterized in that said unlocking means comprises a plurality of spaced enlarged openings defined by the slot edges, and means for laterally translating the top plate member to align the tool axis of the clip tools with respective ones of enlarged openings defined by the slot edges, whereby the tools in the clip are released by the top plate and may be removed from the tool changer through said openings to be loaded into the tool head.",
    "25. A tool changer according to any of Claims 22, 23 or 24 wherein said means for translating the tool changer comprises a pneumatic cylinder means having a piston carrying the tool changer, and arranged for translation between an extended position for inserting a tool into the tool head during a tool changing operation, and a retracted position during normal machine tool operation.",
    "26. A method for changing tools in a machine tool system employing a tool head for mounting a tool along a predetermined axis and a selectively positionable work table for carrying a workpiece, comprising a sequence of the following steps: mounting to the work table for translation along directions parallel to the tool head axis a tool changer having a magazine for accepting a tool clip carrying a plurality of tools inserted in aligned clip apertures; securing the tool clip in said magazine with the tools oriented along respective tool axes parallel to the tool head axis; locking the tools in the inserted clip to prevent removal of the tools from the magazine; positioning the table such that a predetermined one of the tools in the magazine clip is aligned with the tool head axis; translating the tool changer toward the tool head and inserting a portion of the tool into the tool head; unlocking the tools in the magazine to allow removal of the tool from the tool changer magazine; and withdrawing the tool changer from the tool head leaving the tool inserted in the tool changer.",
    "27. A method according to Claim 26 further characterized by the step of frictionally engaging the tool by the tool head as the tool is inserted therein during the tool insertion step so that the tool is retained in the tool head as the tool changer is withdrawn from the tool head.",
    "28. In combination with an elongated drilling tool having a shank for insertion into a machine tool and a drilling means projecting from one end of the shank, a container arrangement for containing a plurality of said drilling tools, characterized by: means for defining a region having a reduced cross-section dimension about the shank of said tool; means for defining a shoulder region about the periphery of said tool shank between the ends of the tool; and a clip body defining a first clip surface and a plurality of aligned tool receiving apertures in said surface into which the drilling means of said tools may be inserted, each aperture partially defined by a clip shoulder region for engaging against said tool shoulder region to control the depth of insertion of said tool in said aperture; said means for defining said reduced region and said means for defining a shoulder region being cooperatively arranged such that said groove is exposed from said first surface of the clip body when the tool is inserted in an aperture therein.",
    "29. A combination according to Claim 28 further characterized by: a clip cover member arranged to be removably installed on said clip body for providing an enclosure about said first surface to cover the exposed portions of tools inserted into said apertures, said cover member comprising at least one rib member extending inwardly therefrom to be engaged in said reduced region formed about said tool shank when the cover is installed on said clip body, thereby securing said tool in the inserted position.",
    "30. A combination according to Claim 28 or 29, further characterized in that said means for defining said reduced region comprises a collar received on said shank and frictionally retained thereon between the ends thereof, said collar having a groove formed in an outer surface thereof to provide said region of reduced cross-sectional dimension.",
    "31. A combination according to Claim 30 further characterized in that said means for defining a shoulder about said shank comprise said collar, said shoulder being defined by a surface of said collar extending outwardly from said shank.",
    "32. A combination according to Claim 28 or 29, further characterized in that said means for defining said region of reduced cross-sectional dimension about said shank comprises a groove formed in said shank.",
    "33. A combination according to Claim 29, further characterized in that said means for defining a shoulder about said shank comprises the intersection of the shank and the drilling means extending therefrom, the shoulder being defined by the relatively larger cross-sectional dimension of the shank in relation to that of the drilling means."
  ],
  "description_excerpt": "The present invention relates to high speed drilling systems for precision drilling of workpieces such as printed circuit boards and the like, and more particularly to systems for drilling very small diameter holes in such workpieces at high speed.\n\nPrinted circuit boards are in universal use today to mount and interconnect electrical components forming electrical circuits. Typically, the leads of the components are inserted through holes drilled in the boards to form predetermined hole patterns. Various systems are known in the art for automated drilling of the holes in printed circuit boards. Examples of such systems and components thereof are described in U.S. Patent Nos. 4,088,417; 3,578,827 and 3,973,863. Such systems typically employ multiple spindles, and are numerically controlled to drill the workpieces in accordance with a predetermined drilling sequence. The systems typically employ automatic tool-changing devices to allow the drill tool to be rapidly changed during the drilling sequence. The workpiece is mounted on a table supported for X-Y translational movement to accurately position the workpiece in relation to the drill spindles. Typically, the work table is supported by a plurality of air bearings on a granite beam, and a lead screw mechanism is provided to allow the capability of translation along one of the X-Y axes. The granite beam is in turn typically supported above a granite base by a plurality of air bearings and another lead screw mechanism provides the capability of translation along the other of the X-Y axes.",
  "cpc": [
    "F16C 32/06",
    "B23B 31/142",
    "B23B 39/161",
    "B23Q 1/03",
    "B23Q 1/032",
    "B23Q 1/38",
    "B23Q 1/4828",
    "B23Q 1/70",
    "B23Q 3/15536",
    "B23Q 3/15539",
    "B23Q 3/15706",
    "B25B 11/005",
    "F16C 2322/39",
    "F16C 29/025",
    "F16C 32/0603",
    "H02K 7/12",
    "H05K 3/0047",
    "Y10T 279/17231",
    "Y10T 279/247",
    "Y10T 408/08",
    "Y10T 408/554",
    "Y10T 408/675",
    "Y10T 408/907",
    "Y10T 483/10",
    "Y10T 483/179",
    "Y10T 483/1864"
  ],
  "ipc": [
    "B23B 31/00",
    "B23B 31/02",
    "B23B 31/14",
    "B23B 39/00",
    "B23B 39/16",
    "B23B 47/06",
    "B23Q 1/00",
    "B23Q 1/01",
    "B23Q 1/03",
    "B23Q 1/26",
    "B23Q 1/38",
    "B23Q 1/48",
    "B23Q 1/70",
    "B23Q 11/12",
    "B23Q 3/08",
    "B23Q 3/155",
    "B23Q 3/157",
    "B25B 11/00",
    "B65D 85/28",
    "F16C 29/02",
    "H02K 41/02",
    "H02K 7/12",
    "H05K 3/00"
  ],
  "assignees": [
    "DYNAMOTION CORP"
  ],
  "inventors": [
    "KOSMOWSKI WOJCIECH"
  ],
  "filing_date": "1987-04-09",
  "publication_date": "1991-12-18",
  "priority_date": "1986-04-18",
  "application_number": "EP-91202136-A",
  "family_id": "25316599"
}