[1]0 3 @ 5 2 6 9 1 5 8 United States Patent Office Patented Sept. 1, 1970 2 dle moved progressively toward the work, while the drill penetrates the work, and the work engaging foot and clamp means, i.e., clamp foot or expansive clamp collet, remain stationary. 5 SUMMARY OF THE INVENTIO N The invention, in a present preferred embodiment, employs two motors, which can be air motors, though not necessarily sD. These motors exert torque jointly 10 through a planetar y gear set to drive the drill spindle, and their combined power is sufficient to drive the drill through the workpiece. During such drilling, and before the drill point "breaks through," the point of the drill is 15 drilling a bore of predete rmined diameter , and cutting edges along the flutes of the drill shank ream the bore to a predete rinined taper. The power of the two motors is used during this part of the operatio n, and the drilling and reaming operatio n can proceed at an optimum rate 20 by using such gear reductio n between the motors and the drill spindle that a drill rotation speed of the order of say approxi mately 1,000 r.p.m. is establish ed. This rotationa l speed can be a little lower, or substanti ally higher. The axial drill rate in inches per minute is regu25 lated in a conventi onal manner and remains constant through out the operatio n. Once the drill point has broken through and the drill is performi ng only taper reaming, drilling resistanc e is very greatly reduced , and a single motor can easily do the job alone, with mainten ance of 30 the initial axial feed rate. During drilling to this point, the work engagin g foot, and clamp means also, have been approac hing (relative ly) the drill body, and after breakthr ough, the approac h become g sufficien tly close that a trip member, carried by the work engagin g foot, 35 engages and then trips or moves a device which shuts off one of the two motors. Gear ratios are made such that with this motor stationar y, the planetar y gear set is then operate d by the remainin g motor, but at a much reduced speed at the drill spindle. In practice, and with aluminu m 40 as the material being drilled, the drill spindle speed is thereby reduced, for example, but without limitation, to say 250 to 350 r.p.m. The one motor is powerful enough, with the reduced lo;ad owing to cessation of drifling with the point of the drill, to easily continue rotation of the 45 drill without reductio n of forward feed of penetrat ion, to t@rn the drill at the reduced r.p.m., i.e., with, for example, a 75 percent reduction in speed. The important point is that at this reduced r.p.m., the flutes of the taper drill, or reamer, can cut a chip from the bore rather 50 than "wearin g" in a taper, and that by thus cutting a chip, a smooth superior taper bore is obtained, much improved over that obtainable in high speed reaming. It has been determined that, to assure attainment of a highly superior taper bore, reaming, at reduced speed, with the one 55 motor drive should be continue d for an approxi mate minimum distance equal to one and one-half diameters of the taper bore at the breakthrough point. The reduc ed r.p.m. is also helpfu l in the final cutting df the counte rsink. 60 BRIE F DESC RIPTI ON OF THE DRA WIN GS The inventi on will be better under stood, and certain additio nal featur es thereo f disclos ed and explai ned, in 65 the course of the followin g detailed descri@ tion of an illustrati ve embodi ment thereof, referen ce for this purpose bein.- had to the accompa nying drawing s, in which: FIG. I is a side elevati onal view, partly in vertica l medial sectio n, showi ng an illustra tive embod iment of the 70 inventio n; FIG. 2 is a section taken on line 2-2 of FIG. 1; FIG. 3 is a section taken on line 3-3 of FIG. 1; 3,526,158 TWO-SPEED POWER TAPER DRILL Ralph D. Adams, Glendora, and Rudolf R. Schindler, Los Angeles, Calif., assignors to Omark-Winslow Aerospace Tool Co., Portland, Oreg., a corporation of Oregon Filed July 10, 1968, Ser. No. 743,791 lnt. Cl. B23b 45114 U.S. Cl. 77-13 10 Claims ABSTRACT OF THE DISCLOSURE A power drill for drilling taper holes with provision for drilling at a high rotational speed until the drill bit breaks through the work, and then at a lower rotational speed for taper reaniing, the lower speed being conducive to a superior finish. Two motors drive the drill bit enough through a planetary gear set at the high rotational speed while the bit is boring through the workand means are provided whereby at breakthrough ' one of the motors is stopped, and the planetary gear set then driven solely by the other motor, rotates the bit at the reduced speed. The reduced or low speed rate is such that a chip can be taken by the taper bit, such as cannot be accomplished at the high speed rate, and under this condition a taper hole of superior finish is produced. BACKGROUND OF THE INVENTION In taper drilling or reaming in certain metals, notably aluminum, but also in steel, titanium, or others, and particularly at small tapers, as e.g., 1/4" per foot, or even in coiintersinkin.-, it is found that a superior finish is produced if a low drill rotation speed is used. With a small taper such as 1/4" per foot, the taper drill or reamer, at high rotational speed, acts to "wear" the parent material to produce the taper bore, rather than to cut a chip. A smoother and much superior taper bore is made if a chip is taken. The iulstrative drill which incorporates the invention is of a type having a drill body mounting an axially fixed rotary drill spindle, and motor means for driving the spindle, together with a work engaging foot which is on a carriage arranged for reciprocation toward and from the drill body, along a line parallel to the spindle. In addition, there is a work clamping means, which is on a clamp carriage reciprocable, parallel with the drill spindle, towards and from the drill body. This clamping means can be either a clamp foot which, by retraction of its carriage from an extended position, with the work engagin.- foot in engagement with one side of a workpiece, moves toward the work engaging foot, and clamps the workpiece thereagainst. Or the clamp foot can be replaced by an expansive collet which may be projected through a hole already made in the work engaging foot, or to one side thereof, and then caused to expand radially as the clamp carriage moves it toward the work en.-aging foot. The collet has clamp means thereon which, in the radially expanded position, overlies the front side of the workpiece, and so engages it, and moves and clamps it a.-ainst the work engaging foot upon retraction of the clamp carriage. In either case, after such clamping is accomplished, the two carriages move in unison, at a slow, regulated feed rate, suitable for drilling, toward or into the drill body, moving the clamped workpiece relatively toward the drill body, whije the drill turns on its axis in the drill body without axial translation relative to the drill body. If the workpiece is a fixed plate as is most often the case, these relative actions will occur, but with the drill body and drill spin-
[2]3 FIG. 4 is a longitudinal sectional view taken on line 4-4 of FIG. 6a; FIG. 5 is a transverse section taken on line 5-5 of FIG. 4; FIG. 6 is a transverse section taken on line 6-6 of FIG. 4; FIG. 6a is a top plan view of a portion of the drill body;and FIG. 7 is a dia.-rammatic view of the motor, gear and planetary transmission system for driving the drill spindle. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT As shown in these fl.-ures, the drill coniprises an elongated aluminum body 20 formed with a pistol-grip handle 21. The drill spindle is shown at 22, with the two motors, in this case air motors, designated at Ml and M2- These motors are here shown as air motors, though hydraulic motors, or electric motors, could be substituted. The motors Ml and M2 will be seen to be located in the rearward end portion of the body casting 20, and they are on opposite sides of the drill spindle, with their longitudinal axes parallel to the latter. The motors Ml and M2 have rearwardly projecting drive shafts 27 and 28, respectively, and they drive, throu,ah gear trains designated generally at 29 and 30, respectively, a planetary gear set or transmission 32, which in turn, drives a drive shaft 34 axially aligned with and coupled to the aforementioned drill spindle 22. A rearward housing 35 is screwed to the rearward end of the body 20, actuary forming a part thereof, to house the gear trains 29 and 30 as well as the planetary transmission 32. Formed in the underside of the body 20, above the pistol-grip handle 21, are a pair of axially aligned cylindrical chambers 40 and 41, disposed parallel to the drill spindle 22, these being separated by a transverse partition 42. These chambers 40 and 41, and the component parts therein, are necessary to the operation of the drill, but form no part of the present invention, and therefore need not be illustrated or described in full detail. A sleeve 45 extends coaxially through body chamber 40 and into chamber 41, and is slidable in a bore 46 in a portion 20a of the body 20, just forwardly of the chamber 40. This sleeve 45 has mounted on its rearward or inner end a piston 47 slidable within the cylindrical chamber 41. A shaft member 50 is telescopically receivable within the sleeve 45, and includes a rearward part 51 secured to a piston 52 which is slidable within the chamber 41, rearwardly of piston 47. A piston 54 is mounted on sleeve 45, within chamber 40. The piston 54 has a restricted oil passage therethrough (not shown), and the chamber 40 is filled with oil. During the drilling operation, the piston 54 moves relatively towards the right, as seen in FIG. 1, and the flow of oil in chamber 40 from behind to in front of the piston 54, through this restricted passage, is utilized as a means regulating the feed of the drill, all as more particularly explained in the aforementioned patent. As stated before, the details of these parts and the explanation of their operation is set forth in said patent, and need not be dealt with herein. On the forward extreniity of the sleeve 45, which with its piston functions as a carriage for enga.- in@- the work, is a work engaging foot 54. This foot has a bore 55 foi receivin.- the taper drill bii 56, with its countersink 57, and it is adapted, in the area of the bore 55, for flush en-agement with the work, here designated by the numeral 60. As here shown, the work 60 comprises a plate which is to be taper drilled and countersunk, and it may be assumed to be composed of aluminum, which is a material offering a problem to the attainment of a superior finish in taper reaming. A clamp means for clamping the work @60 against the work en.-aging foot 54 is also provided, and is here designated in a simplified form at 62. Thus, in this instance, 3)5262158 4 it comprises simply a foot fixed on the end of the aforementioned shaft 50 which functions as a carriage for this clamp foot. The clamp foot 62 as here shown is formed with a bore 63 coaxial with the drill to receive the latter as it penetrates the work plate 60 and then projects beyond it for a distance. Instead of the clamp foot, I may use as the clamping means a radially expansive clamp collet, insertable through a previo.usly made hole in the workpiece and which includes clamp fingers en10 @a-eable with the front side of the work around this hole. Th-. drill is powered by air, led to it by hose 65 connected to the bottom of its pistol-grip;handle 21. Air under pressure conducted into the pistol-grip handle via this 15 hose 65 passes by way of various passageways and valve, unsder the control of a trigger 66, to the chamber 40, 41 and to the air motors, but since analo,-ous valves and passages are ftilly shown in the aforementioned patent, in a form suitable for use herein, t@hey will not be fur20 ther illustrated or described in this specification. Suffice it to say that at the beginning of the drillidg stroke, the sbaft 50 and its piston 47 are near the position shown in FIG. 1, but with the clamp foot 62, carriage 501, and the piston 52 displaced somewhat further toward the left, 25 piston 52 being closely adjacent piston 47. Work engaging foot -50 and clamp foot 162 are thus spaced apart, and the work plate 60 is easily receivable therebetween. The work enga,@ing foot 54 is then placed against the work plate 60, and actuation of trigger 66 causes an operation, 30 through the internal valve mechanism of the drill, to feed air Linder pressure to the ohamber space between the piston 47 and the piston 52. Piston 52 thereupon moves slowly toward the right, bringing clamp foot 62 (or the clamp element of a clamp collet, as the case may 35 be) against the outer or lefthand face of the plate 60, so that the work plate 60 becomes tightly clamped between the work engaging foot 54 and the clamp foot 62 (or collet). Tbereafter, eqtiivalently to the operations described in the aforementioned patent, the two pistons 47 40 and 52 move slowly toward the right in unison, at the predetermined forward feed rate, causing the carriage sleeve 45 and work engaging foot 54, and the, carriage shaft -50 and the clamp foot 6,2, to-ether with the workpiece 60 clamped therebetween, to move slowly and proely towards the body of the drill, and the workpiece 45 gressiv 60 thereby to be engaged and penetrated by the rotating but axially relatively stationary drill bit 56 on the extremity of the drill spindle 22. Often in practice, however, the workpiece 60 is actually stationary, so that 50 after being clamped by the work engaging foot 54 and tihe clamp foot 62, the drill body 20, slowly moves towards the stationarily held work 60 ' with the drill bit advancing through the workpiece. Fixed to and extending rearwardly from work en-aging 55 foot 54 is a sleeve 70-, which is slidably received in bushin.@s in a bore 72 formed in body 20; concentrically with drill spindle 22, being annularly spaced from the latter, as shown. As here shown, the forward end portion of this sleeve 70 is externally screw-threaded, as at 74 and 60 is screwed into a threaded bore 75 in the foot 54. This sleeve 70 will be seen to be receivable inside the bore 72 as the work engaging foot 54 and the clamp foot 62 move relatively towards drill body 20 in the course of penetration of the drill bit through the work. 65 An adjustment sleeve 80 has a forward portion screwthreaded onto the screw-threaded section 81 of the sleeve 70, and a rearward somewhat enlarged section 82 which is slidable and rotatable on a forwardly projectin& cylindrical portion 84 of the body 20. Cylinder,$O is freely 7o manually rotatable on the screw threads 74 of the sleeve 70, and thus capable of longitudinal adjustment relative to the wor-k engaging head 54 and said sleeve 70. The sleeve 80 is operable in a manner and throi-igh meanssubsequently to be described to shut off one of the drive 75 motors just after breakthrough of the. drill, so that the
[3]5 drill bit will thereafter rotate at a stibstantially reduced r.p.m. Referring now to FIG. 4, the previously mentioned drill spindle drive shaft 34 is drivingly coupled to spindle 22 by a coupling 86, preferably using external splines on the rearward extremity of the spindle 22, engaging with internal splines in the coupling member 86 on the forward end of t-he drive shaft 34 (the splines not being shown since they are conventional). The rearward end portion of the drive shaft 34 is journalled in bearings 88 contained within a tubular rearward extension 89 of the housing member 35. Toward its forward extremity, the shaft 34 has an enlarged corar 90 whioh is journalled in a bearing 91 contained within a bore 92 formed in a transverse frame plate 94 (see also FIG. 6a), and which is to be understood as mounted suitably within the housing extension 35. The drive shafts 27 and ZS extending rearwardly from the motors Ml and M2 go through this frame plate to a pair of presently described gear trains 29 and 30 leading to the planetary gear transmission 32. Journalled on drive shaft 34 immediately to the rear of bearin-, 91, as by use of needle bearings 96, is a gear sleeve 98 having thereon a spur gear 99; and journalled on the portion of sleeve 98 to the reax of gear 99 is a gear sleeve 101, which has at its forward end a gear 102, of the same diameter as and immediately to fhe rear of gear 99. Gear sleeve 102 has at its rearward extremity an intemal gear :104, and meshing therewith are a plurality of planet gears 106 rotatable on studs 107 which are set into a planetary cage, spider, or carriage 108 tightly and drivingly mounted on drill spindle drive shaft 34. Planet gears 106 mesh with a sun gear 110 which is on the rearward extremity of gear sleeve 98. It will be seen that if the gears 99 and 102 were to be driven at the same r.p.m., and in the same direction, the intemal gear 104 and the sun gear 110 would also rotate at the same r.p.m., the planetary gears 106 would not rotate on their individual axes, and the carriage 10:8@ and drive shaft 34 would likewise turn at the same r.p.m. Thus, no planetary action occurs. Assume now that the internal gear 104 is driven through gear:102 and the gear train between it and motor Ml from said motor at a certain predetermined speed reduction drive ratio, and that the sun gear is driven through its gear 99 and the gear train between it and motor M2 frOM said motor in the same direction as before but at a predetermined larger speed reduction. The internal gear and now slower rotating sun gear now cause the planetary gears to rotate on their axes, causing the planetary gear carriage to rotate at a lesser r.p.m. than the internal gear. This r.p.m. is the "high" speed rate of the drill spindle. Now, by stopping motor Ml, the intemal gear 104 is stopped, and the driu spindle is driven by the planetary ,-ear carriage owing to rotation of sun gear 110, with planetary aears 106 rolling on now stationary internal gear 102. ne gear reduction, owing to the now stationary intemal gear, is now substantially greater than before, so that the drill spindle now rotates at "slow" speed. Other forms of planetary or epicyclic gear transmission may of course be used within the broad scope of the invention. Also, the gears of the two gear trahis 29, and 30 are capable of selection to afford any desired high and low speed drives of the drill spindle. The internal gear 102 may initiauy rotate at the same r.p.m. as the sun gear, or even rwith greater gear reduction. In general, but without implied limitation, a good low speed range for superior taper drilling with a 1/2" diameter &ill is of the order of 250 or 350 r.p.m.; and a good high speed ran.-e can be of the order of one to several thousand r.p.m. Referring now most particularly to FIGS. 5-7, the two gear trains 29 and 30 between motors Ml and M2 and the planetary transmission will next be described. In addition to the transverse frame plate 94 already described as contained and mounted inside the housing part 3,526,158 6 35, and which is utilized to support bearings for various gear shafts presently to be described, there is a second and somewhat similar frame plate Ill mounted inside the housing patt 35, spaced rearwardly of the plate 94, and located immediately to the rear of the gear 102. This frame plate 111, which may serve also to afford bearing for certain gear shafts, is tied to the first-mentioned -frame plate 94 by means of spacers 120 and screws 121. 10 The gear trains between the motors and the two planetary transmission drive gears 99 and 102 are subject to variation and interchange for selection of preferred gear ratios, and those shown are merely illustrative and subject to wide modification. The shafts of the individual 15 gears of these trains may be afforded bearings in any fashion desired, but the frame plate 94 is intended primarily for this purpose, and the frame plate 111, or other fixtures, may also be utilized. As here shown, on the rearward end of shaft 27 of 20 motor Ml, which shaft may be journalled in a suitable @bearing carried by frame plate 94, is a gear 130 which meshes with an idler gear 131. The idler gear 131 meshes with a gear 132, which is on a gear shaft 133 extending rearwardly and carrying a gear 134 which meshes with the 25 aforementioned drive gear 102 for the internal gear 104 of the planetary transmission. The shaft 28 of motor M2, which may be understood to be loumalled similarly in the frame plate 94, has at its rearward extremity a gear 136, which meshes with 30 a gear 137. The latter is on a shaft 138, which carries also, in the plane of planetary transmission drive gear 99, a gear 139 meshing @with an idler gear 140 which in tum meshes with the planetary transmission drive gear 99. 35 As shown best in FIG. 4, planeta-ry transmission drive gear 102 meshes at the bottom with a gear 141, which is pinned on the disc-shaped rotary driving member 142 of a one-way clutch indicated generally by the letter C. The stationary outer part or casing 143 of the cILitch 40 is pinned to a stud 144 mounted on the frame plate 94. The clutch C may be of any known type capable of permitting free rotation of the gear 130 in the direction of normal rotation of gear 102, biit to act as instantaneously a brake against reverse rotation. Such oneway 45 or over-running clutches are common in the art in a number of different forms, and accordingly the details of any particular clutch need not be shown. The purpose of this one-way clutch is to prevent any possibility of drive of the gear 102 by the motor M,, 50. through a back reaction effect, upon stopping of motor Ml. From what has now been described, it should be understood that as the work engaging foot 54, clamp foot 62, and work 60 move progressively, relatively speaking, toward the drill body, the drill bit 56 will engage 55 and penetrate the work. Air under pressure for the drive of the two motors Ml and M2 enters the pistol-grip handle 21 via hose 65, to a chamber 150, and thence passes through passageway '151 to a circular chamber 152 surrounding the chamber 41, then from the top 60 thereof to passageway 154, a passageway 155 through an intermediate plate 156 (FIG. 3), and finally a passageway 157 leading to a chamber 158 in a slide valve assembly 160. In the position shown in FIG. 3, air in the chamber 158 is cut off. By movement, however, of 65 the slide valve 16@2 towards the right, as to the position indicated in dashed lines, air from chamber 159 is enabled to pass to and thence through tnvo outlet passages 164 and 165, the former leading to motor M2 and the latter to motor Ml. The passageway @164 leads to an 70 inlet passage 166 for motor Ml, and the passage 165 leads to an inlet passage 167 for motor M2 (FIG. 6a). The entire continuity of these passages is not shown in the drawings to avoid confusion, but it will be clearly understood that the passage 164 continues to passage 166 and 75 that the latter feeds the inlet to.motor M2 while the pas-
