Drill-tip sharpening apparatus

Abstract: A drill-tip sharpening apparatus which facilitates attachment/removal of a drill. In an attachment (12) of the drill-tip sharpening apparatus, a pair of phase rotation rollers (54) rotatably attached to a main block (50) supports the shank portion of the drill (18), while a body receptor that is provided on a main plate (20) in a vertically movable manner supports the body portion of the drill (18). A shank pressing member (70) is swingably provided on the main block. Through operation of a shank pressing cylinder (48), the shank pressing member (70) swings to hold and release the drill (18) in cooperation with the phase rotation rollers (54). A tip end positioning motor (44) moves a positioning spindle (86) via a drive gear (84) and a slide gear (88) in order to move the drill in the axial direction. A phase adjustment motor (46) rotates a drive roller that is in contact with the phase rotation rollers (54), thereby rotating the drill (18) about its axis via the phase rotation rollers.

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to a drill-tip sharpening apparatus for grinding the tip of a drill, and more particularly to a drill-tip sharpening apparatus suitable for re-grinding a small-diameter drill such as a printed-wiring-board drill (PWB drill) for drilling printed wiring boards (PWBs) (see for example EP-A-0 299 915). Description of the Related Art: Printed wiring boards are formed such that glass fibers and copper foil serving as a conductor are laminated and united together through use of a resin such as epoxy. Therefore, when holes are formed in such printed wiring boards through use of a PWB drill, the drill wears and finally breaks after 3000 to 5000 drilling operations. Therefore, a worn drill must be ground (re-ground) to thereby increase its service life. Under such circumstances, the applicant of the present application, a tool maker, has developed a pioneering sharpening apparatus for small-diameter drills, based on manufacturing techniques and experiences that the applicant has accumulated for years. The developed sharpening apparatus allows the tip end portion of a worn drill to be re-ground at appropriate timing for sharpening, allows a single drill to perform two 3000 drilling operations, and maintains the quality of drilled holes within an allowable range. Thus, cost due to consumption of drills for drilling printed wiring boards decreases, resulting in reduced machining cost. The above-described sharpening apparatus copes with an increase in density of parts mounted on PWBs in accordance with rapidly-developing surface mount technology (SMT). Therefore various types of sharpening apparatus for PWB drills are manufactured and utilized effectively by manufacturers of PWBs and the like. However, conventional drill-tip sharpening apparatuses are difficult to automate, because a drill is held through use of a chuck. Therefore, a worker manually performs attachment/removal of a drill to and from an attachment, which serves as drill support means for advancing the drill toward a grinding stone, as well as positioning of the drill. Generally, one worker operates one sharpening apparatus, and even an experienced worker can grind only about 1000 to 1200 drills during an 8-hour shift. Further, the number of drills that can be ground in an 8-hour shift depends greatly on the experience of the worker. Therefore, automation of such sharpening operation has long been desired in order to improve the work efficiency for grinding drills. Although automation of the drill-tip sharpening apparatus has been demanded, it has been considered difficult to achieve, because various difficult problems must be solved in order to secure precision of the cutting edge of each drill. SUMMARY OF THE INVENTION The present invention has been accomplished in view of the above-mentioned demand, and an object of the invention is to facilitate attachment and removal of a drill. Another object of the present invention is to enable automatic positioning of a drill. Sill another object of the present invention is to enable the tip end surface of a drill to be ground automatically. In order to achieve the above-described objects, the present invention provides a drill-tip sharpening apparatus having drill support means to which a drill is attached and grinding means for grinding the tip end surface of the drill held on the drill support means, characterized in that the drill support means includes a drill holding mechanism comprising a shank reception portion for supporting the shank portion of the drill; a vertically movable body reception portion for supporting the body portion of the drill; and a shank pressing portion for pressing the shank portion of the drill against the shank reception portion. Preferably, the drill holding mechanism is constructed such that the drill held by the drill holding mechanism can be moved in the axial direction, and there are further provided feed means for axially moving the drill held by the drill holding mechanism, tip-end detection means for detecting the tip end of the drill moved axially, and control means for controlling the feed means in order to project the drill from the drill holding mechanism until activation of the tip-end detection means. Preferably, the drill holding mechanism is constructed such that the drill held by the drill holding mechanism can be rotated, and there are further provided phase adjustment means for rotating the drill held by the drill holding mechanism, tip-surface-shape detection means for detecting a shape of the tip end of the drill held by the drill holding mechanism, and control means for controlling the phase adjustment means on the basis of a detection signal from the tip-surface-shape detection means in order to rotate the drill such that the reference line of the tip end surface of the drill is oriented at a predetermined angle. In this case, the control means may be configured to detect the center of the drill on the basis of an output signal from the tip-surface-shape detection means and to move the center of the drill to a predetermined position via the body reception portion. In the drill-tip shaping apparatus according to the present invention having the above-described structure, a drill is placed on the shank reception portion and the body reception portion of the drill holding mechanism, and the drill is pressed against the shank reception portion by use of the shank pressing portion. Therefore, the drill can be easily held by the drill support means, thereby facilitating attachment and removal of the drill. Further, the drill is held by the drill holding mechanism in an axially movable manner, and control means controls the feed means in order to project the drill until activation of the tip-end detection means. In this case, the positioning of the tip end of the drill; i.e., setting of a grinding allowance, can be performed automatically. In addition, since the body reception portion can be moved vertically, the center position of the drill can be easily adjusted by means of vertical movement of the body reception portion performed in accordance with the diameter of the drill. Moreover, the control means controls the phase adjustment means on the basis of an output signal from the tip-surface-shape detection means in order to rotate the drill―which is held by the drill holding mechanism in a rotatable manner― such that the reference line of the tip end surface of the drill is oriented at a predetermined angle. Therefore, the drill can be oriented at an optimal phase for grinding. Further, the control means is configured such that on the basis of the output signal from the tip-surface-shape detection means the control mean controls the body reception portion in order to move the center of the drill to a predetermined position. Therefore, the drill can be automatically positioned at a position suitable for grinding by the grinding means. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are explanatory views of an attachment according to an embodiment of the present invention, wherein FIG. 1A is a plan view of the attachment, and FIG. 1B is a side view of the attachment; FIG. 2 is a side view schematically showing the overall structure of a drill tip sharpening apparatus according to the embodiment of the present invention; FIG. 3 is a view for describing the action of the attachment according the embodiment; FIG. 4 is a detailed explanatory view of a body reception portion according to the embodiment; FIG. 5 is an explanatory view of a body reception portion having a different structure; FIG. 6 is a cross-sectional view of the attachment according the embodiment, showing the detail of the feed mechanism; FIG. 7 is an explanatory view of a phase adjustment mechanism having a different structure; FIG. 8 is an explanatory view of a phase adjustment mechanism having a further different structure; FIG. 9 is an explanatory view showing a modification of the phase adjustment mechanism shown in FIG. 8; FIG. 10 is a view showing the relationship of arrangement between the attachment, a grinding unit, and a sensor unit according to the embodiment; FIG. 11 is a detailed explanatory view of the sensor unit according to the embodiment; and FIG. 12 is a view showing an example of the shape of the tip end surface of a drill displayed on a monitor screen. DESCRIPTION OF THE PREFERRED EMBODIMENT A drill-tip sharpening apparatus according to an embodiment of the present invention will now be described with reference to the accompanying drawings. FIG. 2 is a side view schematically showing the overall structure of the drill-tip sharpening apparatus according to the embodiment of the present invention. As shown in FIG. 2, a drill-tip sharpening apparatus 10 includes an attachment 12 serving as drill support means, and a grinding unit 14. The attachment 12 is turned by an elevation cylinder 16 disposed between a drill attachment/removal position and a horizontal drill grinding position. Specifically, as shown in FIG. 3, a main plate 20 of the attachment 12 is supported by a support-point housing 24 via a rotary shaft 22, and the rotary shaft 22 is connected to the elevation cylinder 16 via a link 26. Further, as shown in FIG. 2, the drill-tip sharpening apparatus 10 has a sensor unit 30 for detecting the position of the tip end of the drill 18 and the shape of the tip end surface. The sensor unit 30 has a lens barrel 32 for magnifying the tip end surface. The lens barrel 32 is attached to a stand 34 via a sensor holding member 36 such that the optical axis becomes coaxial with the drill 18 positioned at the drill attachment/removal position. Further, a CCD camera 38 serving as tip-surface-shape detecting means is attached to the upper end of the lens barrel 32 in order to capture the shape of the tip end surface. An output signal from the CCD camera 38 is fed to a monitor television and displayed on a monitor screen. The output signal is also input to an unillustrated controller (control means) and is used for adjustment of the phase (rotational position) of the drill 18 and for judgment as to whether grinding is performed properly. Further, on the sensor holding member 36 is provided a tip-end detection sensor (tip-end detection means) 40 for detecting the position of the tip end of the drill 18. As shown in FIG. 1A, the attachment 12 has a motor bracket 42 fixed on the upper face of the main plate 20. On the motor bracket 42 are attached a tip-end positioning motor 44 which constitutes feed means for moving the drill 18 in the axial direction, a phase adjustment motor 46 which constitutes phase adjustment means for rotating the drill 18 about its axis, and a shank pressing cylinder 48 which operates a drill holding mechanism for holding the drill 18. Also, a main block 50 is mounted on the main plate 20. The main block 50 supports a pair of parallel rotary shafts 52 via bearings disposed inside the main block 50. At the tip end of each rotary shaft 52 is attached a phase rotation roller 54 formed of rubber or the like which constitutes a shank reception portion of the drill holding mechanism and serves to rotate the drill 18. The shank portion of the drill 18 is disposed above the mutually proximate portion (or contact portion) of the phase rotation rollers 54, as shown in FIG. 7. At the tip end portion of the main plate 20 is disposed a body receptor 56 which constitutes a portion of the drill support mechanism and serves to support the body portion of the drill 18. As shown in FIG. 4, the body receptor 56 is fixed to a body reception block 58 which is disposed on the main plate 20 in a vertically movable manner. As indicated by arrow 62, the body receptor 56 is moved vertically by an actuator 60, such as a cylinder or a motor, and via the body reception block 58. As shown in FIG. 5, the body receptor 56 may be moved vertically by use of a structure such that the body receptor 56 is attached to a swing arm 64, which is swung as indicated by arrow 68 by a cam 66 or the like. As shown in FIG. 1B, on the main block 50 is provided a shank pressing member 70 for pressing the shank portion of the drill 18 against the phase rotation rollers 54. The shank pressing member 70 is attached to arms 72 which are swingably attached to opposite sides of the main block 50, and is swung as indicated by arrow 74 by the shank pressing cylinder 48 so as to hold the drill 18 in cooperation with the phase rotation rollers 54 and to release the drill 18. Further, the shank pressing member 70 comes into contact with the drill 18 in a state in which the shank pressing member 70 inclines forward. Thus, when the drill 18 is rotated, separation of the rear end of the drill 18 from a positioning spindle 86 is prevented, which will be described in detail. Specifically, a rod 76 of the shank pressing cylinder 48 is connected to an operation shaft 80 via a link mechanism 78, and one of the arms 72 is connected to the operation shaft 80 via a link mechanism 82. Therefore, when the shank pressing cylinder 48 is operated, the operation shaft 80 is rotated via the link mechanism 78, and rotation of the operation shaft 80 is transmitted to the arm 72 via the link mechanism 82, so that in FIG. 1A the arm 72 turns in the direction perpendicular to the paper. The tip-end positioning motor 44 constitutes a feed mechanism for moving the drill 18 in the axial direction, and, as shown in FIG. 6, a drive gear 84 is attached to the output shaft of the motor 44. The drive gear 84 is in meshing engagement with a slide gear 88 provided at the rear end of the positioning spindle 86. The positioning spindle 86 penetrates the main block 50, and the front end surface of the positioning spindle 86 is in contact with the rear end surface of the drill 18. At the intermediate portion of the positioning spindle 86 is formed a screw portion 90, which is in screw engagement with the screw portion of the main block 50. Therefore, when the tip-end positioning motor 44 is driven, the positioning spindle 86 moves axially to push out the drill 18 from the body receptor 56 constituting the drill holding mechanism. A drive gear 92 is attached to the output shaft of the phase adjustment motor 46. The drive gear 92 is in meshing engagement with a gear 96 provided at the rear end of each rotary shaft 52 penetrating the main block 50. The phase rotation roller 54 is attached to the front end of the rotary shaft 52. Therefore when the phase adjustment motor 46 is driven, the phase rotation roller 54 is rotated; via the drive gear 92, the gear 96 and the rotary shaft 52; which in turn rotates the drill 18. The phase adjustment mechanism for the drill 18 may have a structure such that the output shaft of the phase adjustment motor 46 penetrates the main block 50 and a drive roller is provided on the output shaft of the phase adjustment motor 46 in order to rotate the phase rotation roller 54. Specifically, as shown in FIG. 7, the drive roller 98 attached to the output shaft of the phase adjustment motor 46 may be disposed below the mutual proximity portion of the paired phase rotation rollers 54 such that the drive roller 98 is in contact with the phase rotation rollers 54. Thus, the rotational force of the phase adjustment motor 46 is transmitted to the phase rotation rollers 54 via the drive roller 98 in order to rotate the drill 18 via the phase rotation rollers 54. Also, the phase adjustment mechanism for the drill 18 may have a structure as shown FIG. 8 or 9. In the phase adjustment mechanism shown in FIG. 8, the shank reception portion is constituted of a pair of rollers 102 formed of, for example, a metal, and a phase adjustment arm 106 is disposed above the rollers 102 such that the phase adjustment arm 106 can be moved in directions perpendicular to the axes of the rollers 102 as indicated by arrow 104. Further, a drive piece 108 formed of a material that has a relatively large friction coefficient, such as rubber, is attached to the bottom surface of the phase adjustment arm 106 and is brought into contact with the drill 18. Thus, when the phase adjustment arm 106 is driven, the drill 18 rotates. FIG. 9 shows a modification of the phase adjustment mechanism shown in FIG. 8. In the phase adjustment mechanism shown in FIG. 9, the shank reception portion is constituted of a block 110 having a V-shaped groove instead of the pair of rollers 102. Except for the shank reception portion all other components are the same. As shown in FIG. 10, the grinding unit 14 has a second-surface grinding stone 112 for grinding the second surface at the tip of the drill 18 and a third-surface grinding stone 114 for grinding the third surface at the tip of the drill 18. These grinding stones 112 and 114 are attached to rotation drive motors 116 and 118 and are properly slanted with respect to the drill 18 so as to grind the second and third surfaces. The grinding stones 112 and 114 are disposed on a table 120 which is slanted with respect to the drill 18, and by an unillustrated traverse mechanism provided on the table 120 the grinding stones 112 and 114 are integrally moved in directions slanting with respect to the drill 18, as indicated by arrow 122. As shown in FIG. 11, a light source 126 is fixed to an object lens portion 124 of the lens barrel 32. The light source 126 is formed in, for example, a ring shape and is adapted to illuminate the tip end surface of the drill 18. Further, the tip-end detection sensor 40 is composed of an optical positioning sensor 128 and a light source device 130 disposed at a location facing the sensor 128. When the tip end of the drill 18 is elevated to a predetermined position, the positioning sensor 128 outputs a detection signal to the controller. The present embodiment having the above-described structure operates as follows. After the attachment 12 is raised to the drill attachment/removal position, the shank pressing member 70 is turned in the direction for releasing the drill 18. When the drill 18 is placed on the phase rotation rollers 54 and the body receptor 56 by, for example, an unillustrated picking apparatus, an unillustrated controller drives the shank pressing cylinder 48 in order to turn the shank pressing member 70. As a result, the drill 18 is held between the pair of phase rotation rollers 54 and the shank pressing member 70. Then, the controller reads the outputs from the positioning sensor 128 and the CCD camera 38 and judges whether or not the tip end of the drill 18 is located at a predetermined position. When the output signal from the positioning sensor 128 indicates that the tip end of the drill 18 has not reached the predetermined position (height), the controller drives the tip end positioning motor 44 in order to advance the drill 18 via the positioning spindle 86. When the amount of projection of the drill 18 from the body receptor 56 reaches a predetermined value, the positioning sensor 128 detects this state and outputs a detection signal. In response to this detection signal, the controller stops driving the tip end positioning motor 44. Also, the controller obtains the position of the center of the drill 18 on the basis of a signal representing a captured image of the tip end surface output from the CCD camera 38 and judges whether the center is located at a predetermined position. Specifically, the controller calculates the position of a chisel point 132 of the drill 18 shown in FIG. 12 and judges whether the chisel point 132 is located at a predetermined position of the CCD camera 38. The predetermined position of the CCD camera 38 is set to correspond to the predetermined position of a monitor image 134. When the center of the drill 18 does not coincide with the predetermined position of the monitor image 134 due to variation in drill diameter or the like, the controller drives the actuator 60 to elevate/depress the body receptor 56 in order to cause the center of the drill 18 to coincide with the predetermined position of the monitor image 134. Further, the controller calculates a rotational amount (phase)  with respect to a reference line 136 of the drill 18 and drives the phase adjustment motor 46 in order to rotate the drill 18 about its axis such that the phase  coincides with a predetermined reference value  0 After positioning of the drill 18 has been completed, the controller operates the elevation cylinder 16 in order to swing down the attachment 12 to the horizontal position. Thus, the drill 18 is held at the grinding position. Subsequently, the controller drives the traverse mechanism of the grinding unit 14 in order to move the third-surface grinding stone 114 and the second-surface grinding stone 112 integrally such that the third-surface grinding stone 114 and the second-surface grinding stone 112 grind the third-surface 138 and the second surface 140 at the tip end of the drill 18 in order to sharpen them. At this time, the controller controls the phase adjustment motor 46 to rotate the drill 18 in accordance with progress of the grinding. After the grinding of the tip end surface of the drill has been completed in this manner, the attachment 12 is swung to the drill attachment/removal position, and based on the shape of the tip end surface captured by the CCD camera 38, the controller judges whether the grinding has been performed properly. Subsequently, the ground drill 18 is transferred to a drill case or the like through use of the picking apparatus or the like.

Claims: A drill-tip sharpening apparatus having drill support means (12) to which a drill (18) is attached and grinding means (14) for grinding a tip end surface of the drill held on the drill support means (12), characterised in that said drill support means (12) includes a drill holding mechanism comprising a shank reception portion for supporting the shank portion of the drill (18), a vertically movable body reception portion (56) for supporting the body portion of the drill (18), and a shank pressing portion (70) for pressing the shank portion of the drill (18) against the shank reception portion. The apparatus of claim 1, wherein said drill holding mechanism comprises feed means (44, 84, 86, 88) for axially moving the drill (18) held by said drill holding mechanism, tip-end detection means (40) for detecting the tip end of the drill (18) moved axially, and control means for controlling said feed means in order to project the drill (18) from said drill holding mechanism until activation of said tip-end detection means (40). The apparatus of claim 1 or 2, wherein said drill holding mechanism comprises phase adjustment means (46, 54, 92, 96) for rotating the drill (18) which is rotatably held by said drill holding mechanism, tip-surface-shape detection means (38) for detecting the shape of the tip end surface of the drill (18) held by said drill holding mechanism, and control means for activating said phase adjustment means (46, 54, 92, 96) on the basis of a detection signal from said tip-surface-shape detection means (38) in order to rotate the drill (18) such that the reference line of the tip end surface of the drill (18) is oriented at a predetermined angle. The apparatus of claim 3, wherein said control means detects the centre of the drill (18) on the basis of an output signal from said tip-surface-shape detection means (38) and moves the centre of the drill (18) to a predetermined position via said body reception portion (56). The apparatus of claim 3 or 4, wherein said shank pressing portion (70) is swingable in a vertical direction.

Inventors: KATAYAMA ICHIRO, NAKAJIMA YUICHI, SHINBO YOSHIHARU, WATANABE YOSHINOBU, KATAYAMA, ICHIRO, NAKAJIMA, YUICHI, SHINBO, YOSHIHARU, WATANABE, YOSHINOBU, Nakajima, Yuichi c/o Nagaoka Factory, Shinbo, Yoshiharu c/o Nagaoka Factory, Watanabe, Yoshinobu c/o Nagaoka Factory
Applicants: UNION TOOL CO LTD, UNION TOOL CO., LTD.
Application year: 1998
Main classification: B24B3
IPC codes: B24B3, B24B47