US2454771A - Drill bit assembly - Google Patents

Description

Nov. 30, 1948. V w. E. CARR 2,454,771

DRILL BIT ASSEMBLY Filed May 8, 1944 2 Sheets-Sheet l FiG. Z

lNVENTOR WALTER E. CARR BY 1 l ATTORNEY W- E. CARR Nov. 30, 1948.

K i mv OR WALTER E. CARR BY mu ATrbRNEY Patented Nov. 30, 1948 2,454,771 nnmr. arr ASSEMBLY Walter E. Carr, Spokane, Wash, assignor, by

decree of distribution,

Spokane, Wash.

to Sarah Jane Carr,

Application May 8, 1944, Serial No. 534,542

4 Claims. 1

The present invention relates to certain new and useful improvements in a drill bit assembly for detachable drill bits such as used in hard rock drilling, in mining, quarrying, etc.

According to the present invention, the drill bit is detachably secured to the drill rod by means of cam faces on the interior of the drill bit, frictionally engaging with corresponding cam faces on the drill rod. These cam faces are tapered, but

the taper is used solely for the purpose of disengagement and does not exert any force in effecting engagement, which is solely by relative rotation of the cam faces. The skirt of the drill bit seats against a collar on the drill rod so as to pre clude the impact of the drilling operation from driving the drill rod into tighter tapered engagement with the drill bit. In this manner, the drill bit is engaged with the drill rod, solely by the relative rotation of the cams, which is of prime importance in providing for quick and easy removal of the drill bit when dulled by use.

For removing the drill bit from the drill rod, the invention provides a driving block which saddles over the drill rod and butts against the drill bit at diametrically opposite sides, so that each blow of a hammer can be directed to both sides of the drill bit simultaneously, which is of paramount importance in removing the drill bit. This driving block eliminates all need to hammer directly upon the drill bit, which is a very ineflicient mode of removal, and exceedingly diflicult to accomplish by any attempt to hammer the bit in reverse rotation.

The drawings show the invention in the form in which it has been reduced to practice and thoroughly tested in various conditions oi hard rock drilling. Fig. 1 shows a drill rod having an integral collar against which the skirt of a bit is seated, and a driving block is shown (partly in section) bu ting against the head of the drill bit. in position for driving the bit off from the rod.

Fig. 2 is an enlarged sectional detail bit and rod of Fig. 1.

Fig. 3 and Fig. 4 each show a transverse section through Fig. 2 at the line X-X, Fig. 3 showing the cams in initial position, and Fig. 4 showing of the drill .the cams frictionally engaged for securing the drill bit upon the rod.

Fig. 5 is a diagrammatic showing of Fig. 3 for.

Fig. 8 is a transverse section of the driving block, taken along the line 88 in Fig. 7.

In carrying out the present invention the usual drilling rod R is here shown as round but may be hexagonal or any other suitable shape, and is usually provided with an axial bore as indicated at K, the purpose of which is exceedingly well known.

This drill rod R is expanded into an integral collar as indicated at C and provided with a bit shank E of smaller size so that the collar provides an annular shoulder 2.

This bit shank E is formed with cam sides 3 and 4 which are oppositely eccentric to the axis of the bit shank E which of course is axially aligned with the drill rod R. The arrangement of these cams is best seen in the diagrammatic showing of Fig. 5 (see also Fig. 3) and as shown in Fig. 2

these cams are tapered towards the end of the bit shank E.

The detachable drill bit B may have any suitable cutting head H as the present invention is not concerned with the kind of cutting faces employed. As best seen in Fig. 2, the bit B has an annular skirt S which is of the same size as the aforesaid collar 0, and as here shown, the cutting head H forms square shoulders T extending outwardly from the skirt S; however, it is conventional practice to flare the skirt instead of employing square shoulders and it will be understood that either mode may be employed in the present invention.

. The interior of this skirt S is provided with cams I and 6 which mate with the aforesaid cams 3 and 4, and are correspondingly tapered as will be seen from Fig. 2, the relative arrangement of the cams being best seen in the diagrammatic showing of Fig. 5 (see also Fig. 3)

In Fig. 3 and Fig. 5 these cams are shown in their initial position, and it will be seen that there is reasonable clearance between the sams on the skirt S and those on the bit shank E, so that the drill bit can be manually placed in position on the bit shank and then manually rotated to the position shown in Fig. 4 so that the cam surfaces will engage over considerable area and hold the drill bit upon the drill rod. In fact, a minor twist with the hand will afford suiliciently tight engagement to enable the drill rod to be lifted by grasping the bit. When the bit contacts the work in actual drilling, the constant rotation of the drill rod will urge the cam faces into exceedingly tight engagement and securely hold the bit upon the rod with assurance that the bit will not be lost in the bore hole.

As shown in Fig. 2, the bit shank E is of the same length as the depth of the interior of the skirt S, so that the bit seats on the end of the shank E, and also, the skirt S seats on the collar C, so that it is impossible for the impact of the drilling operation to urge the bit shank any deeper into the drill bit, which would drive the cams into o'bjectionably tight tapered engagement and also be likely to split the skirt and also split the head of the drill bit, as sometimes occurs in the prior art. Also, this seating of the drill bit, both internally and externally, is of considerable advantage in. keeping out refuse which would otherwise be forced inside the skirt and cause difllculties, as sometimes occurs with threaded bits, when a workman carelessly fails to fully screw the bit on before starting to drill. With the present invention, the loose fit of the bit in the initial position assures that the skirt S will seat on the, collar C without any effort on the part of the work'- men; and since the bit seats both internally and externally upon the drill rod, it affords about twice as much area for the impact of the drilling operation and therefore enhances the drilling eificiency of the bit, and also eliminates the well known fault of objectionably driving the rod into the drill bit and the disadvantages resulting therefrom. When the drill bit seats only on the end of the rod, the greatest wear occurs in the center of the bit, and when the bit seats only on the skirt, the greatest wear occurs on the outer portions of the bit, and the center of the bit gradually caves in by the impact of drilling. The double seating on the skirt and also on. the end of the bit shank as afforded by the present invention, assures uniform wear over the entire cutting surface of the bit, and thus prolongs the useful life of the bit and enables it to be sharpened a greater number of times.

For removing the drill bit from the rod, I provide a driving block such as shown at D in Fig. 1 or at D in Fig. 6, Fig. 7 and .Fig. 8.

As shown in Fig. 6 this driving block D has a body portion l I which is channelled on its underside as best seen at l2 in Fig. 8 where this channel is shown as of inverted U-shape so as to saddle over a round rod or else a hexagonal rodor octagonal rod of the same size. This channel extends full length of the block and is enlarged at l4 so as to clear the collar and the skirt S of the bit B, and thereby enable the forward end IE to butt against the shoulders T on diametrically opposite sides of the drill bit. This driving block is freely slidable upon the drill rod so that it can readily be moved into contact with the drill bit.

This driving block is thick walled to give suitable mass and weight, and its rear end is provided with a thickened head H to add further mass and weight, and also to provide for suitable impact with a hammer, by means of which the drill bit can be quickly and easily removed by a few blows.

In some instances, the drill bit canbe removed by the driving block alone, without resorting to the use of a hammer. That is to say that the driving block can be slidably moved along the drill rod in a few quick blows against the drill bit, and by reason of the fact that the driving blockcon.- tacts the drill bit at diametrically opposite sides, removal can be accomplished with less force than would otherwise be required by pounding with a hammer directly on the bit. Due to the fact that this driving block saddles over the rod. it is effectualiy guided to squarely contact the bit at each blow. -The body'portion H affords a convenient hand grasp for the workman in slidably moving the driving block upon the rod at each pounding stroke; and to afford a more secure hand grasp it is advisable to provide a flange as shown at [6.

In instances where a hammer is not employed, the thickened head I! affords weight and mass to enhance the manual pounding with the driving block itself, and where greater force is required this head I! affords a convenient and efficient face for impact with a hammer.

As shown in Fig. 1 the driving block may be provided with a handle such as l8 instead of the aforesaid head l1, and in this instance the workman uses the handle l8 to hold the driving block in position against the drill bit while the end I9 is pounded with a hammer to drive the drill bit ff the rod in the same manner as previously described, this driving block D being otherwise essentially the same as already described and having the aforesaid inverted U-shaped channel so as to saddle over the drill rod.

Either of these driving blocks can also be used on bits having a flared skirt instead of the illustrated square shoulder.

It will be noted that the driving block confines the force of the hammering, solely to endwise movement, of the drill bit, so as to dislodge the tapered surfaces of the rotary engaged cams. Thus the driving block precludes any attempt to rotate the cam engagement by hammering, which is a far more diflicult mode of removal than endwise driving. Moreover the driving block affords endwise driving on both sides of the bit simultaneously, and. greatly enhances the efliciency of removal, thus saving much time and effort, which can otherwise be spent in actual drilling. No matter whether the driving is by pounding with the driving block itself or by hammering upon the driving block, the saddle arrangement upon the rod precludes any glancing blows upon the bit which would be likely to break off corners of the bit and endanger the workman by flying pieces of metal.

It will be seen that the present invention effectually solves the problem with which the prior art was concerned but failed to solve in like manner. It will also be seen that the disclosed structure unites the various forces so that they function in proper relation to each other without setting up contraindicated forces objectionably affecting each other. The problem has long been of considerable consequence to the industry, and the present invention meets the existing need and want, with better success and satisfaction than has heretofore been obtained.

,As here shown, the cams 3 and 4 constitute a pair of identical cams, each offset from the axis of the drill rod an equal amount and in opposite directions along the same diameter. In like manner the cams 5 and 6 constitute a pairof identical cams, slightly larger and mating with the paired cams 3 and 4. This aflfords a quicker take-up of the clearance between the paired cams 5 and 6 on the skirt S and the paired cams 3 and 4 on the bit shank E, than would otherwise be accomplished by employing one continuous cam instead of the paired cams 3 and 4, and a corresponding continuous cam instead of the paired cams 5 and 6. The pairedcams as herein discosed, greatly lessen the rotation required to take-up a given amount of clearance; and furthermore, the non-contacting portions of the tightly engaged cams, isdivided equally at diametrically opposite positions so as to equalize the stresses, in contradistinction to the aforesaid continuous cams which would of necessity result in the non-contacting portions being all on one side and setting up lateral stresses in the opposite direction and against the areas having the least contact.

The paired cam structure herein disclosed, eliminates the need of confining the clearance so closely as is required. by continuous cams, and thus the paired cams afford greater latitude of tolerance and are more economically practical to manufacture in large scale production. which is of course required for a device of this kind.

Furthermore, if continuous cams were used, their rotary engagement would be much more gradual, and the rotation of the drilling operation would consequently urge them into tighter frictional engagement than is necessary for the purpose. Thus the paired cams of the present invention, eliminate the inherent inaptitudes of continuous cams, and render it much easier to remove the drill bit, because the paired cams do not engage so exceedin ly tight as is needlessly the case with continuous cams. These paired cams engage sufilciently tight to securely hold the drill bit upon the rod, but are more easy to remove, than if continuous cams were employed; thus the paired cams save the time and effort of the workman and enable him to work with better efliciency.

I claim as my invention:

1. A drill bit assembly comprising a drill rod including a tapered bit shank having a pair of external cam faces thereon and eccentric to each other, a drill bit including an annular skirt having a pair of internal cam faces mating with said external cam faces and tapered to correspond therewith, said drill rod having an integral collar against which said skirt seats, said bit shank being the same length as the interior length of said skirt so as toseat therein when said skirt also seats on said collar, whereby the seating of said skirt indexes the maximum tapered engagement of said cam faces and whereby the internal and external seating of said bit excludes refuse from entering between said cam faces, the cam faces on said skirt having sufficient clearance from the cam faces on said bit shank to afford a loose fit in the initial position and to afford a tight frictional engagement when rotated a fraction of a turn.

2. A drill bit assembly comprising a drill rod including a tapered bit shank having a pair of external cam faces thereon and eccentric to each other, a drill bit including an annular skirt having a pair of internal cam faces mating with said external cam faces and tapered to correspond therewith, said drill rod having an integral collar against which. said skirt seats to thereby index the maximum tapered engagement of said cam faces and thereby preclude longitudinal driving of said tapers against each other, the cam faces of said skirt having suflicient clearance from the cam faces on said bit shank to afford a loose fit 6 in the initial position and to afford a tight frictional engagement when rotated a fraction of a turn.

3. A drill bit assembly comprising a drill rod inciuding a bit shank. having curved cam sides tapered towards thev axis of said rod, a drill bit including an annular skirt having internal cam sides mating with the. cam sides on said bit shank.

and tapered to correspond therewith, said drill rod having an: integral collar against which said:

tapered engagement of said cam sides and whereby the internal and external seating of said bit excludes refuse from entering between said cam sides, the cam sides onv said skirt having sufllclent clearance from the cam sides on said bit shank to afford a loose fit in the initial position and to afford a tight frictional engagement when rotated a fraction of a turn.

'4. A drill bit assembly comprising a drill rod including a bit shank having curved cam sides tapered towards the axis of said rod, a drill bit including an annular skirt having internal cam sides mating with the cam sides on said bit shank and tapered to correspond t erewith, said drill rod having an integral collar against which said skirtseats to thereby index the maximum tapered engagement of said cam sides and thereby prc elude longitudinal driving of said tapers against each other, the cam sides on said skirt having sufiicient clearance from the cam sides on said bit shank to afford a loose fit in the initial position and to afford a tight frictional engagement when rotated a fraction of a turn, said drill bit having a cutting head larger than said skirt, and square shoulders formed at the rear of said cutting head to engage a tool for longitudinally driving said bit off fromsaid shank.

WALTER E. CARR.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 803,911 Leyner Nov. 7, 1905 1,360,897 Dailey Nov. 30, 1920 2,234,486 Craig Mar. 11, 1941 2,307,507 Hutton Jan. 5, 1943 2,312,471 Low Mar. 2, 1943 FOREIGN PATENTS Number Country Date 7 110,872 Australia June 19, 1940 1,806 Great Britain Apr. 29, 1.876

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