US3055441A

US3055441A - Percussive rock drill

Info

Publication number: US3055441A
Application number: US772332A
Authority: US
Inventors: William A Morrison
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1958-11-06
Filing date: 1958-11-06
Publication date: 1962-09-25
Anticipated expiration: 1979-09-25

Description

United States Patent T 3,055,441 PERCUSSIVE ROCK DRILL William A. Morrison, Easton, Pa., assiguor to Ingersoll- Rand Company, New York, N.Y., a corporation f New Jersey Filed Nov. 6, 1958, Ser. No. 772,332

8 Claims. (Cl. 175-139) This invention relates to percussive rock drills of the type employing a rotation mechanism including a rifle bar and an associated pawl and ratchet device, and it has for its object to prevent rifle bar failure in such a drill under severe rotational strain.

Another object of the invention is to provide a novel and improved resilient connection between the rifle bar and the ratchet holding mechanism in a rock drill of the above type.

Another object is to provide such a resilient connection between the parts of a two-piece chuck driver in a drill of the type specified, either as an alternative or supplement to the resilient connection between the rifle bar and the ratchet holding mechanism.

Still another object is to provide such a resilient connection or connections having inexpensive and easily replaceable shear pins which will fail under extreme load conditions before any damage occurs to the rifle bar in a drill of the type specified.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

The rotating mechanism of conventional percussive rock drills usually includes a fluted rifle bar having a head carrying pawls engageable with the ratchet teeth of a fixed ratchet ring. The rifles of the bar cooperate with a rifle nut fixed in the head of the hammer piston, so that during each stroke of the piston in one direction the piston is made to rotate while the rifle bar pawls are engaged with the teeth of the ratchet ring, while during each piston stroke in the other direction the rifle bar is made to rotate while its pawls ride over the teeth of the ratchet ring.

Serious difliculty has been encountered with the rifle bar breakage in various rock drills of the above type, which is usually caused by conditions requiring operation of the drill at full throttle to withdraw a tight bit from the drilled hole. Under such conditions, the shock load and strain are taken on the very end of the rifle bar and breakage frequently results.

The present invention overcomes the above difliculty 'by providing a novel torsionally resilient joint in either one or both of two locations in a rock drill of the foregoing type. One of such locations is between the stem of the rifle bar and the head of said bar, while the other is between the parts of a two-piece chuck driver which, through the intermediary of the chuck, rotates the drill rod. As a result of such construction, suddenly applied shock load is gradually applied and is distributed over the full bearing of the rifle nut instead of being concentrated in a small part of the bar as before.

In one embodiment disclosed herein for the purposes of illustration, the torsion-opposing joint mentioned above comprises a plurality of pins which are seated in mating holes in the rifle bar stem and the toothed ratchet member. These holes are tapered as hereinafter described to provide hollows into which the pins can bend under the torsional force imparted to the rifle bar by the piston of the rock drill. As a result, this torsional force is applied to the rifle bar more gradually than heretofore, permitting it to rotate to a limited extent without being twisted. Under extreme load conditions said pins, which are inexpensive and easily replaceable, will shear 011 before the rifle bar can be damaged. In the other embodiment Patented Sept. 25, 1962 hereinafter described, the resilient pins connect the two parts of the two-piece chuck driver, but the operation is the same in both embodiments of the invention.

The invention is described more in detail in connection with the preferred embodiments illustrated in the accompanying drawing, in which:

FIG. 1 is a broken longitudinal sectional view of a rock drill embodying the invention;

FIG. 2 is a transverse section through the rifle bar and associated parts, taken on line 22 of FIG. 1; and

FIG. 3 is a transverse section through the chuck driver and associated parts, taken on line 33 of FIG. 1.

The drawing shocks a rock drill cylinder 1 having a bore or chamber 2 containing the usual reciprocable hammer piston 3 for delivering impact blows to the shank of a conventional drill rod as hereinafter described.

Any conventional valve structure 4 may be used to supply air through

passages

5 and 6 to reciprocate the piston 3. The exhaust passage is illustrated at 7 in FIG. 1.

As is customary in rock drills of this type, a rotation mechanism operated by the hammer piston is provided for rotating the drill steel as the latter is percussively actuated. This rotation mechanism includes a rifle bar 8 having a spirally fluted or splined lower end portion slidingly interlocked with a rifle nut 9 fixed within the head of the piston.

The annular head 10 at the top of cylinder 1 carries pivotally mounted sets of pawls 12 which are urged inwardly by air operated plungers 13 into engagement with the teeth 14 of ratchet ring member 15. The ring 16 serves to hold one or the other of each set of pawls out of action as the ratchet moves in one direction or the other.

In accordance with one embodiment of the invention, a plurality of cylindrical steel pins 17 provide a torsionally resilient or elastic connection between the rifle bar 8 and the toothed ratchet ring member 15. These pins 17, here shown to be six in number, are seated in mating holes 18 and 19 which are equally spaced about the flange 2d of rifle bar 8 and the adjacent surface of ratchet ring member 15, respectively. The holes 18 and 19 are taper-ed longitudinally so that they are wider at their mating inner ends than they are at their outer ends. The said wide regions of holes 18 and 19 thus form enlarged hollows into which the cylindrical pins 17 can bend under the influence of the torsional force presently to be described.

With the spiral flutes or splines of the rifle bar 8 inclined in the direction shown in FIG. 1, the rifle bar will tend to rotate clockwise in FIG. 2 during each return stroke of the piston 3. However, such rotation of the rifle bar is prevented by the operative engagement of certain pawls 12 with the teeth 14 of ratchet ring member 15, as shown in FIG. 2. As a result, piston 3 is caused to rotate, and this rotation is in turn transmitted to the drill steel in a manner well understood in the art. During each down stroke of the piston, rotation in a counter-clockwise direction in FIG. 2 is imparted to rifle bar 8, but the pawls 12 ride over the teeth 14 of ratchet ring member 15, or over the ring 16, so that the piston 3 moves axially without rotating.

0n the return stroke of piston 3, as described above, the piston is rotated as the ratchet mechanism holds the rifle bar 8 against rotation. The torsional force im parted to the rifle bar by the piston at this time is applied much more gradually than it otherwise would be because the pins 17 will bend or flex into the tapered holes 18 or 19 and thus permit rotation (about five degrees) of the rifle bar without any twist of the bar. In practice the piston will travel approximately one-fifth of its return stroke during the period the pins 17 are flexed to the maximum extent. This means that the turning force is applied more gradually to the rifle bar than when the rifle bar is held rigidly against rotation.

The rock drill shown in FIG. 1 has a chuck driver which is made in two

parts

22 and 23. The rear or upper part 23 of said chuck driver has a splined connection with the nose of piston 3 at 24 and rotates therewith. This rotation is transmitted from the chuck driver to the chuck 25 which in turn rotates the drill rod 26. In accordance with the invention, torsionally resilient cylindrical pins 27, here shown to be six in number (FIGS. 1 and 3), are seated in

mating holes

28 and 29 which are equally spaced about the adjacent surfaces of

chuck driver sections

22 and 23, respectively. As in the case of the holes 18 and 19 previously described, the

holes

28 and 29 are tapered so that they are widest at their mating ends, thus affording enlarged hollows into which the pins 27 can bend under the influence of the above-described torsional force. The operation is the same as that described above in connection with the rifle bar and ratchet joint.

The above-described action is particularly important when the drill is running on so-called cushion, i.e., when the drill is operated but the drilling tool or bit is not in contact with the rock. At such time the piston does not strike the working implement but its forward motion is halted by air trapped in the chamber 2. At this time the piston travels forward a greater distance than during normal operation and accordingly a shorter length on the rifle bar 8 is in engagement with the rifle nut 9. In the absence of the flexible connection between the rifle bar and the ratchet holding mechanism, and/or the flexible connection between the two sections of the chuck driver, an extremely high load would be applied to the tip of the rifle bar at the time the piston is reversed.

The

pins

17 and 27 herein described also act as shear pins when an extreme load condition is encountered on the rifle bar, the pins in such case being weaker than the rifle bar or the chuck driver and failing before any damage occurs to the rifle bar. The pins are cheap and easily replaced.

Although certain specific embodiments have been shown and described herein for purposes of illustration, it will be evident to those skilled in the art that the invention is capable of various modifications and adaptations within the scope of the appended claims.

The invention claimed is:

1. In a rock drill, the combination with a cylinder having a piston reciprocable therein, :of a rotation mechanism for said piston including a rifle bar extending into said piston, spiral means on said bar coacting with spiral means within said piston, a head surrounding the outer portion of said rifle bar, a rotatable ring associated with said rifle bar within said head, means for rotationally locking said ring in one direction to said head, and a plurality of resilient torsion-opposing pins connecting said rifle bar to said ring.

2. In a rock drill, the combination with a cylinder having a piston reciprocable therein, of a rotation mechanism for said piston including a rifle bar extending into said piston, spiral means on said bar coacting with spiral means within said pistons, a fixed annular head surrounding the outer portion of said rifle bar, a rotatable ring concentric with said rifle bar within said annular head, means for rotationally locking said ring in one direction to said head, mating holes in said rifle bar and said ring, and pins in said holes locking said rifle bar and said ring in rotational engagement with each other, said holes being enlarged in parts to permit said pins to bend therein.

3. In a rock drill, the combination with a cylinder having a piston reciprocable therein, of a rotation mechanism for said piston including a rifle bar extending into said piston, spiral means on said bar coacting with spiral means within said piston, a fixed annular head surround- 4 ing the outer portion of said rifle bar, a rotatable ring concentric with said rifle bar within said annular head, means for rotationally locking said ring in one direction to said head, mating holes in said rifle bar and said ring equally spaced about the axis of said rifle bar and ring, and pins in said holes locking said rifle bar and said ring in rotational engagement with each other, said holes being tapered longitudinally and being widest at their mating ends to form hollows into which said pins can bend under applied torsion-a1 force.

4. In a rock drill, the combination with a cylinder having a piston reciprocable therein, of a rotation mechanism for said piston including a rifle bar extending into said piston, spiral means on said bar coacting with spiral means within said piston, a ratchet mechanism including a fixed annular head surrounding the outer portion of said rifle bar, a rotatable ratchet ring concentric with said rifle bar within said annular head, ratchet teeth on the outer annular edge of said ratchet ring, spring biased pawls carried by said annular head and engageable with said ratchet teeth to rotationally lock said ratchet ring in one direction to said head, mating holes in said rifle bar and said ratchet ring equally spaced about the axis of said rifle bar and ratchet ring, and pins in said holes locking said rifle bar and said ratchet ring in rotational engagement with each other, said holes being widened at their mating ends to permit said pins to flex transversely therein.

5. In a rock drill, the combination with a cylinder having a piston reciprocable therein, of a chuck driver rotatably and slidably connected to said piston, a drill rod rotated by said chuck, a rotation mechanism for said piston including a rifle bar extending into said piston, spiral means on said bar coacting with spiral means within said piston, a ratchet mechanism including a fixed annular head surrounding the outer portion of said rifle bar, a rotatable ratchet ring concentric with said rifle bar within said annular head, ratchet teeth on the outer annular edge of said ratchet ring, pawls carried by said annular head and engageable with said ratchet teeth to rotationally lock said ratchet ring in one direction to said head, mating holes in said rifle bar and said ratchet ring equally spaced about the axis of said rifle bar and ratchet ring, and pins in said holes locking said rifle bar and said ratchet ring in rotational engagement with each other, said holes being tapered longitudinally and being widest at their mating ends to form hollows into which said pins can bend under applied torsional force.

6. In a rock drill, the combination with a cylinder having a piston reciprocable therein, of a chuck driver composed of two members, one member having a connecting portion connected to said piston to resist relative rotation therebetween while permitting relative longitudinal movement, the other member having a connecting portion connected to a drill rod for rotation therewith, a rotation mechanism for said piston including a rifle bar extending into said piston, spiral means on said bar coacting with spiral means within said piston, a head surrounding the outer portion of said rifle bar, a rotatable ring associated with said rifle bar within said head, means for rotationally locking said ring in one direction to said head, means connecting said rifle bar to said ring, each of said members having holes for receiving resilient torsion-opposing means for connecting the two members of said chuck driver.

7. In a rotary driving mechanism having a bore con taining a reciprocable hammer piston for delivering impact blows to the shank of a drill rod of a rotary percussive rock drill, the combination comprising:

(a) ahead,

(b) a ratchet ring rotatably disposed in said head and having an outer perimeter edge,

(0) said ratchet ring having ratchet teeth disposed on said outer perimeter edge and spring biased pawls carried by said head and engageable with said 6 ratchet teeth to rotationally lock said ratchet ring in (g) resilient pins disposed within said longitudinally one direction to said head, tapered holes and to secure said rotation means and (d) rotation means rotating said hammer piston to said ratchet ring in rotational engagement with each thereby rotate said percussive rock drill, and other. (e) pins means between said rotation means and said 5 ratchet ring to gradually apply and to evenly dis- References cued m the file of thls patent tribute sudden shock load therebetween. UNITED STATES PATENTS 8. The rotating driving mechanism according to claim 5 5, 2 w Sept 19 1393 7 including said pins means in which: 1,148,649 Bayles Aug. 3, 1915 (f) said rotation means and said ratchet ring are pro- 10 2,439,479 Mackmann Apr. 13, 1948 vided with longitudinally tapered holes, and 2,737,818 Feucht Mar. 13, 1956 UNITED STATES PATENT UFFICE CERTIFICATE OF CORREQTIUN Patent No. 3,055,441 September 25, 1962 I William A. Morrison It is hereby certified that error appears in the abov e numbered patent requiring correction and that the said Letters Patent should read as corrected below In the grant, line -l,

. name of inventor, for "William A.

Norrison" read William A. Morrison column 2, line 13,

for "shocks" read shows column 3, line 63, for "pistons" read piston Signed and sealed this 5th dey of February 1963.

(SEAL) Attest:

ERNEST W. SWIDER DAVID LADD Attesting Officer Commissioner of Patents