US 3837121 A
Disclosed is a machine for drilling into hard materials.
Description (OCR text may contain errors)
United States Patent 11 1 1111 3,837,121 Schirmer Sept. 24, 1974 DRILLING MACHINE 2,652,732 9/1953 Frye 408/17 ux Inventor: Kenneth L Schirmer, Redondo 2,850,854 9/1958 Levy 51/59 SS Beach, Calif. Primary Examiner-Al Lawrence Smith  Ass1gnee: TRW Inc., Redondo Beach, Cahf. Assistant Ramsey  Filed; Aug 97 7 Attorney, Agent, or FirmDaniel T. Anderson;
Stephen J Koundakjan  Appl. No.: 387,057
 US. Cl 51/56, 51/59 SS, 125/30 WD,  ABSTRACT 408/17, 408/700 Disclosed is a machine for drilling into hard materials.  Int. Cl B28d 5/02  new of Search 125/30 WD; 5156, 59 SS; The machine comprises a conventional miniature drill 408/17, 238 press, improved by the addition of a camming device to cause the drill to reciprocate while rotating, and a  References C'ted shock absorber interposed between the drill motor UNITED STATES PATENTS and bit to absorb a portion of the impact of the bit tip 1,318,466 1919 Taylor 125 30 WD against the Work p In Certain embodiments means 1,902,055 3/1933 Beste ..-125/30 WD are provided to introduce quantities of an abrasive 2,334,363 11/1943 Vann 408/238 suspension to the bit tip. 2,409,415 10/1946 Blomquist 51/56 UX 2,412,101 12/1946 Smyers 125/30 WD 12 Claims, 5 Drawing Figures l6 ll 14 I l y l 22 11 3, u T 24 /32 I 1 m 1 1 II so 54/, H l' 82 E15 .1. 11. I l 55 .1,. Q1? 66 I 76 l l 1 1 11 111 11 1 1 1 1 64 PATENTEU 39241974 3.837. 1 2].
sum 1 or 2 v BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to the field of drilling and, in particular, to precision drilling into hard materials, such as aluminum oxide.
2. Description of Prior Art Precision drilling into hard materials, such as aluminum oxide, is an expensive procedure as currently practiced. Ordinarily a specially fabricated diamondtip bit is placed in a miniature drill press, and the tip is simply forced onto the workpiece by manual or controlled mechanical pressure.
This procedure has several disadvantages. First, if the material drilled is relative brittle (as many hard materials are), constant pressure of the bit against the workpiece will cause fractures to occur and, frequently, will completely shatter the material. Likewise, especially when holes of small diameter are being created, the compressional forces on the bit caused by the constant contact with the workpiece over a period of time will collapse the necessarily fine bit. Also, in a normal highspeed drilling operation, the diamond tip will become quickly cluttered with material removed from the workpiece, the coolant/lubricant liquid and other debris, rendering the bit useless and requiring replacement. Since diamond tip bits are relatively expensive, the cost of such an operation is frequently considerable. In addition, since diamond bits are made only in standard sizes, custom-made bits must be specially ordered, if it is desired to create holes of non-standard diameter, resulting in time delays and even greater expense.
SUMMARY OF INVENTION Accordingly, it is an object of the present invention to provide an improved machine for drilling into hard materials.
Briefly, the present invention comprises a substantially conventional drill press, improved by the addition of means to cause the drill bit to reciprocate in a controlled fashion while rotating, together with means for absorbing a portion of the impact created each time the tip of the bit strikes the workpiece. The reciprocation means may comprise a cam/camshaft arrangement, with the free end of the camshaft engaging the drill chuck or other portion of the drill mechanism to cause it to receiprocate while the cam rotates. The impact absorbing means may comprise a shock absorber (for example a spring-loaded piston interposed between the bit and the drill chuck). In other embodiments, means such as a reservoir/drain tube device may be provided for introducing quantities of an abrasive suspension (for example diamond dust in water) to the bit tip, so that relatively soft, non-helical bits, which are easily replaceable, can be employed.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partially sectional, side elevation view of the preferred embodiment of the present invention.
FIG. 2 is a perspective, partially cutaway view of the impact-absorbing device shown in FIG. 1.
FIGS. 3A, 3B, 3C are perspective (partially cutaway, in the case of 3C) views of portions of drill bits of various styles adapted to use in connection with the preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Since the backbone of the preferred embodiment of the present invention is essentially a conventional miniature drill press, the detailed features of this aspect of the drilling machine will not be described in great detail. Accordingly, the motor 12 is mounted within the holder 14 by means of an upper arm 16 and a lower arm 18 in such a manner that axial motion of the motor relative to the holder is substantially prevented. The holder is slideably mounted to the standard 20 by means of an upper ring 22 and a lower ring 24. In the preferred embodiment, the standard is substantially square in cross-sectional area, in order to prevent rotation of the holding rings about the standard.
Elevation and lowering of the motor 12 is accomplished by means of the rack 26, integral to the standard 20, to which the pinion 28 is engaged. The pinion rotates about the pinion axle 30 which is sildeably mounted within a hole in the holder 14 in a direction transverse to the motor axis. Raising and lowering of the motor is accomplished by rotating the elevation lever 32, one end of which is rigidly secured to the pinion axle. The other end of the elevation lever possesses a rigid cylindrical projection 36 which is parallel t0 the axle.
Turning now to the drive train of the drill 10, the shaft 38 of the motor 12 terminates in a chuck of conventional design. Secured within the chuck is one of the novel features of the present invention the impact absorbing means 42. The purpose of the impact absorbing means is to eliminate a portion of the shock created when the drill bit strikes the workpiece. The
' effect of this shock-absorbing means is to prevent fracturing ofthe workpiece when repeatedly struck by the tip 56 of the bit 54 during the drilling operation, and to prevent concommitant damage to or destruction of the bit itself.
As shown in FIG. 2, the impact-absorbing device 42 comprises a shaft 44 which is rigidly engaged by the chuck 40. The lower end of the shaft terminates in a hollow cylinder 46 having a longitudinal slit 47 projecting upward from its lower end. In the preferred embodiment of the present invention, the cylinder contains a helical spring 48. Slideably mounted within the cylinder is a cylindrical plunger 50 having a rectangular projection 51. The purpose of the projection is to prevent relative rotation between the plunger and the cylinder when the plunger is slid into the cylinder such that the projection enters the groove 47.
In order to prevent the plunger 50 from falling completely clear of the cylinder 46 when the lower end of the drive train of the drill 10 is unsupported, the upper end of the spring 48 is attached to the upper interior portion of the cylinder 46, while the lower end of the spring is attached to the upper end of the plunger 50. The exact means of attachment are not shown, as these are well within the skill of an ordinary machinist.
In other embodiments of the present invention, the impact absorbing means 42 may comprise an ordinary fluid shock absorber, or such a shock absorber in combination with the helical spring device just described. Doubtless other means of inpact-absorption will become apparent to those skilled in the art to which this invention pertains, who read this disclosure and understand thefunction of this element.
The plunger 50 of the impact-absorbing device 42 terminates in the bit check 52 which is, in the preferred embodiment, a rather conventional chucking device. Rigidly engaged within the bit check is the bit 54, which is an elongated, substantially cylindrical piece of metal terminating in a bit tip 56. As shown in FIGS. 3A, 3B and 3C, bits 54A, 54B and 54C may terminate, respectively, in bit tips 56A (conical) 56B (rectangular) or 56C (a hollow cylinder). Depending on the particular type of hole to be drilled, bits having other tip styles may be employed as desired.
While an ordinary helical bit could be used with the drilling machine of the present invention, such bits are not ordinarily usable in the application for which the present device is particularly desirable drilling into hard, brittle materials. Such drilling operations require the use of very hard abrasive materials such as carborundum. or diamond. Accordingly, I have found it advantageous to employ bits having smooth outer surfaces to which a granular abrasive is applied. Normally, diamond dust in a liquid suspension (e.g., aqueous) is employed for this purpose.
The bits, themselves, are constructed from a relatively soft metallic material, such as a beryllium-copper alloy. The reason is that where an abrasive dust is used for the actual drilling operation, the bit is merely a support for the dust. The advantage of employing a soft bit is that the force of drilling tends to imbed the abrasive granules into the bit material, which provides excellent abrasive support for the continuing drilling operation.
It will be noted that another important advantage of utilizing smooth bits with an overcoating of abrasive powder is that such bits may be easily fabricated in any machine shop. Ordinary bar stock may be used, and a bit of any diameter may be quickly fabricated by means of an ordinary lathe. Thus, when the drilling machine 10 of the present invention is employed, the diameter of the hole sought to be made in the workpiece is not in the least critical.
In the preferred embodiment of the present invention, the abrasive suspension is introduced to the bit tip 56 by means of a gravity feed tube 82 emanating from a reservoir 80 which is placed above the position of the bit tip, as shown in H6. 1. Other means of introducing the abrasive, such as pumping or utilizing a wick, may be employed as desired.
Another novel feature of the present invention is the means for introducing reciprocating motion to the drill bit during the drilling operation. This is accomplished, in the preferred embodiment, by the cumming structure shown in FIG. 1. .lournalled onto the cylindrical projection 36 emanating from one end of the elevation lever 32 is the cylindrically perforated upper end 70 of the cam shaft 68. The lower end 72 0f the cam shaft, likewise cylindrically perforated, is journalled onto a cylindrical projection 78, placed off-axis on the camining flange 74, which rotates about the cam axle 76. The motive power which creates rotational motion in the camming flange is not shown, but may consist of a separate motor or, with suitable gears, belts or the like, be the'primary motor 12 which operates the drilling machine 10.
ln operation, the flange 74 rotates, causing the upper end 70 of the cam shaft 68 to reciprocate. This, in turn,
causes the elevation lever 32 to rotationally oscillate within a certain angle. The latter motion revolves the pinion 28 which, because it engages the rack 26, causes the holder 14 (and thus, the motor 12 and associate drive train of the drill 10) to reciprocate axially.
The purpose of this reciprocating motion is to avoid many of the difficulties encountered with the state-ofthe-art high speed drilling machines. Each downward movement of the drive train causes the bit tip 56to briefly engage the workpiece 66, resulting in the removal of the small amount of material from the workpiece. A portion of the impact of this engagement is absorbed by the impact absorbing means 42. The engagement between the bit tip and the workpiece is brief since the reciprocating motion causes the bit tip to be withdrawn rather quickly. During the period of withdrawal, the material removed from the workpiece will be driven away by centrifugal force or may be washed away (by means not shown), and the workpiece and the bit tip will cool. Thus, the drilling machine 10 of the present invention prevents the creation of large mechanical and thermodynamic stresses at the bittip/workpiece point of contact. This, in turn, prevents destruction of the workpiece and prolongs the useful life of the bit, advantages which are not enjoyed with state-of-the-art high speed devices used for drilling hard materials, which do not combine the reciprocating motion with the shock absorbing means of the present invention.
The parameters of operation of the drilling machine of the present invention may be readily adjusted for specific applications by any operator skilled in the art to which the invention pertains. For example, the cycle speed of either or both of the primary motions reciprocating and rotational may be set as desired for the particular job requirement. In particular, the machine may be constructed so that either or both may be varied at will, by operating a line rheostat, variable-speed clutch assenbly, or other suitable device.
Similarly, the stiffness" of the impact absorbing device may be adjusted as desired. In the case of the preferred embodiment of this invention, where a helical spring is incorporated into this device, this may be accomplished by selecting a spring having a specific spring constant. In general, the softer and less brittle the workpiecs, and the larger the diameter of the hole, the stiffer would be the spring. I
In order to assure precision drilling, a bit guide 58 may be employed. This device consists of a plate having a hole (or holes) 60 through which the bit 54 is inserted during the drilling operation. The guide is rigidly attached to, or integral with, the guide base 62. The latter is connected to the standard base 64 in such manner as will prevent transverse motion of the guide 58 relative to a desired axial alignment of the bit 54. This may be done by bolting the guide base to the standard base or, more simply, by providing cylindrical hole in the top surface of the standard base and mating cylindrical pro- 60 jections from the bottom surface of the guide base.
drilling operation has been accomplished, these projections may be simply sawed or ground away if desired.
1 claim: 1. The apparatus for drilling into a workpiece, comprising:
an elongated bit; mechanical means to impart rotational motion to said bit, comprising:
a bit holder having an axis, a first end and a second end, said first end of said bit holder being operably connected to said motor in such manner that upon rotation of said motor, said bit holder is caused to rotate about said axis, said bit being substantially rigidly attached to said second end in such manner that rotation of said motor causes rotation of said bit;
mechanical means to impart reciprocating longitudinal motion to said bit, said motion intermittently bringing said bit into contact with the workpiece; v and means, operably associated with'said rotational motion impartingmeans, for absorbing at least a portion of the impact created by contact of said bit with the workpiece, comprising:
' a first portion of said bit holder, said first portion possessing a substantially axial cavity having an opening at one end thereof;
a second portion slideably mounted within the cavity of Said first portion and extending out of said first portion through the opening therein;
means to substantially prevent rotational motion of i said second portion within said first portion; and
a flange operably connected to said driving means in such manner that said motor imparts rotational motion thereto;
a substantially longitudinal member, a first region of said longitudinal member being operably connected to said flange in such manner that upon rotation thereof, a second region of said longitudinal member, longitudinally displaced from said first region, is caused to reciprocate, said second region being operably connected to said bit holder in such manner as to cause said bit holder to responsively reciprocate.
5. The apparatus as recited in claim 1, further including bit guide means, said bit guide means adapted to restrict transverse motion of said bit.
6. The apparatus as recited in claim 5, when said bit guide means comprises a plate having a hole, said plate substantially secure to said motor, in such manner as to restrictmotion of said plate in a direction transverse to said bit, said bit being inserted through the hole in said plate.
7. Theapparatus as recited inclaim 1, further including means to introduce, to-the tip portion of'said bit, a granular abrasive substance.
8. The apparatusas recited in claim 7, wherein said abrasive is in 1a pulverized form and'in liquid suspension, and said introduction means comprises a reservior for saidsuspension and means to transport quantities of said suspension from said reservoir to said tip portion.