Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
1998-10-05
2001-12-18
Eley, Timothy V. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S005000, C451S010000, C451S259000
Reexamination Certificate
active
06331133
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to devices and methods for sharpening or re-pointing twist drill bits. More particularly, the invention relates to an apparatus for automatically re-pointing twist drill bits.
B. Description of Background Art
Printed wiring boards (PWB's) used to hold and electrically interconnect electronic circuit components are typically fabricated as laminated stacks of copper foil sheets alternating with insulating sheets made of fiberglass, the latter containing glass fibers solidified with a resin such as epoxy. The glass fibers are highly abrasive, and can quickly dull drill bits used to drill holes in the PWB for receiving component leads, or for forming passageways or vias through the PWB. A typical PWB has a thickness of about 0.062 inch, and has hundreds of holes drilled through it. Each contact with the upper surface of a PWlB to drill a hole is referred to as a “hit.” Since PWB's are usually arranged in stacks of two to five boards for drilling, a corresponding number of holes are drilled for each hit. Because the abrasive nature of the PWB board materials dulls typical drill bits after about 3000-5000 holes are drilled, the drill bit must be removed from service and re-sharpened after about 1,500-2,000 hits.
In conventional drill bit grinding apparatuses used to sharpen or re-point twist drill bits, the drill bit must be held in a chuck. Consequently, the operator must manually perform operations such as inserting the drill into the chuck of a drill bit holder mechanism, tightening the chuck to grip the drill, positioning or aligning the drill in relation to the drill bit holding mechanism and to a rotary grinding stone, advancing the drill bit towards a grindstone, retracting the re-pointed drill bit from the grindstone and removing the re-pointed drill bit. Because of all of the aforementioned operations, an operator can usually operate only a single drill bit grinding apparatus at a time. Thus, even an experienced operator can typically re-point no more than about 800 to 1,000 drill bits over an eight-hour work shift Therefore, there has been a strong demand for an automated drill bit re-pointing apparatus that has a higher throughput rate than existing re-pointing apparatuses, and which may be operated by less than highly skilled personnel. Despite a widespread need for an improved drill bit re-pointing apparatus, various difficulties have prevented the development of such an apparatus. The present invention was conceived of to provide an improved, automatic drill bit re-pointing apparatus in which functions performed manually in prior art devices are largely automated.
OBJECTS OF THE INVENTION
An object of the present invention is to provide an automatic apparatus for sharpening or re-pointing twist drill bits.
Another object of the invention is to provide a drill bit re-pointing apparatus which includes means for automatically aligning a drill bit with respect to a grinding wheel.
Another object of the invention is to provide a drill bit re-pointing apparatus having a drill bit holder mechanism which facilitates attachment of the drill bit to the apparatus for grinding, and removal of the bit upon completion of grinding.
Another object of the invention is to provide a drill bit re-pointing apparatus having a drill bit holder which incorporates means for rotating the bit about its longitudinal axis to a desired phase angle to orient the fluted, front cutting portion of the bit to a desired disposition relative to a grinding wheel.
Another object of the invention is to provide a drill bit re-pointing apparatus having fluted portion support means translatable transversely or perpendicularly relative to the longitudinal axis of the bit, between a position contacting the fluted portion of drill bits of various diameters and a non-contacting position.
Another object of the invention is to provide a drill bit re-pointing apparatus having a drill bit holder mechanism which includes means for axially advancing a drill bit to position the point of the bit at a desired extension distance from the holder mechanism.
Another object of the invention is to provide a drill bit re-pointing apparatus which includes means for aligning the phase angle and longitudinal protrusion or extension of a drill bit tip relative to an optical alignment device at a first, load/unload station, rotating the drill bit holder mechanism to second, grinding station where drill bit grinding stones grind the properly phased and extended drill bit, and rotating the drill bit holder back to the first load/unload station to permit the re-pointed drill bit to be removed from the apparatus.
Another object of the invention is to provide a drill bit re-pointing apparatus which includes a drill bit holder which has a pivotable shank retainer which may be pivoted upwards to allow the shank of a drill bit to be placed on a pair of phase-controlling roller wheels, and which may be pivoted downwardly to retain the shank in rotatable contact with the roller wheels.
Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims.
It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, we do not intend that the scope of our exclusive rights and privileges in the invention be limited to details of the embodiments described. We do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims.
SUMMARY OF THE INVENTION
Briefly stated, the present invention comprehends an apparatus for sharpening or re-pointing twist drill bits, in which functions required in the re-pointing process are largely automated.
An automatic drill bit re-pointing apparatus according to the present invention includes a drill bit holder mechanism having a rear, shank holder structure and a front, fluted holder structure which is actuable from a lowered, rear non-contacting position to a raised position contacting and supporting the fluted front portion of drill bits of various diameters. The drill bit holder mechanism includes a motor-driven shank retainer which is pivotable upwardly to a first position allowing placement of a drill bit in the apparatus, and removal of the bit after it has been re-pointed, and pivotable downwards to a second position bearirg against the shank of the drill bit to thereby secure the bit in the holder mechanism. The drill bit holder mechanism also includes a pair of laterally adjacent, “phase control” rollers which support the lower portion of a drill bit shank, the rollers being motor driven to permit rotating the bit about its longitudinal axis to a particular orientation or phase angle of the cutting lips of the fluted front cutting portion of the bit. A motor-driven lead screw in the drill bit holder mechanism pushes against the rear shank face of a drill bit in the holder mechanism to advance the drill bit axially with respect to the phase control rollers to a desired protrusion length or extension distance from the holder mechanism.
According to the present invention, the drill bit holder mechanism is pivotably mounted on a spindle rotatable by means of a connecting link coupled to a station position linear actuator cylinder from a first, load/unload station position to a second, grinding station position. At the load/unload station is located an optical alignment apparatus including an optical imaging unit that has an objective lens longitudinally aligned with and spaced outwards from the tip or point of a drill bit held in the drill bit holder mechanism. The optical imaging unit includes a CCD camera, on the focal plane of which i
Katayama Ichiro
Nakajima Yuichi
Shinbo Yoshiharu
Watanabe Yoshinobu
Berry Jr. Willie
Chapin William L.
Eley Timothy V.
Union Tool Company
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