US2737818A - Intermittent rotation mechanism with overload release - Google Patents

Description

March 13, 1956 J. E. FEUCHT INTERMITTENT ROTATION MECHANISM WITH OVERLOAD RELEASE Filed Dec. 22, 1954 FIG.4

FIGI

INVENTOR. JACOB E. FEUC HT ATTORNEY United States Patent INTERMITTENT ROTATION MECHANISM WITH OVERLOAD RELEASE Application December 22, 1954, Serial No. 477,012

2 Claims. (Cl. 74-127) This invention relates broadly to rock drills, but more particularly to an improved rotation mechanism for rock drills of the percussive type.

As is well known in this art, rotation mechanism for rock drills generally includes a rifle bar havinga head carrying pawls engageable with the ratchet teeth of a fixed ratchet ring. The rifles of the bar are cooperating with a rifled nut fixed within the head of an impact delivering reciprocatory piston, so that during each stroke of the piston in one direction the piston is made to'rotate while the rifle bar pawls are in operative engagement with the teeth of the ratchet ring, and during each stroke in the other direction the rifle bar is made to rotate while its pawls ride over the teeth of the ratchet ring. This step by step rotation ,of the piston is transmitted to the drill steel by a chuck having the shank of the drill steel fitted therein against relative rotation, the

2,737,818 Patented Mar. 13, 1956 Figure 3 is a view similar to Figure 2 but showing a modified construction, and

Figure 4 is an enlarged partial longitudinal section taken on line 4- 4 in Figure 3.

Referring to the drawing, 10 designates the usual cylinder of a rock drill, in which is reciprocably mounted a piston 11. The upper portion of cylinder 10 is enlarged to form an annular step 12 on which rests a valve cap 13 having slidable' therein a valve 14 cooperating with a'stationary valve block 15 for automatically controlling supply of pressure fluid alternately to the ends of cylinder 10 for effecting reciprocation of piston 11 in the usual and well known manner.

Valve block 15 rests on a casing in the form of an outer ring 16, and on it a bearing plate 17 which protrudes from cylinder 10 into a block head 18. The valve cap 13, valve block 15, outer ring 16 and bearing plate 17 are clamped between shoulder 12 and back head 18 by twoside bo1ts'19, through which the back head is also fixed to the cylinder. Valve cap 13, valve block 15 and outer ring 16 are locked to cylinder 10 against rotation relative thereto by a locking pin or dowel 20.

In the usual rotation mechanism of the rifle bar type, the outer metal ring 16 constitutes a one piece ratchet ring with teeth" provided on the inner wall thereof. In the present construction, outer ring 16 has vulcanized, cementedor otherwise affixed to its inner wall a resilient ring 21 preferably made of rubber or the like, to the inner wall of which is similarly aflixed a metal inner ring 22 formed with ratchet teeth 23 on its inner wall.

In other words, in the present construction the usual one chuck being conneced to the piston by interengaging its cooperating nut were subjected to excessive load which often resulted in pawl and rifle bar breakage, If no breakage occurred, the piston by virtue of the engagement of the rifles of its nut with the rifle bar, was prevented from taking a full stroke and delivering impacts on the drill steel to release it from its stuck-condition.

It is therefore an object of this invention to produce an improved rotation mechanism for rock drills capable of automatically becoming inoperative when subjected to a predetermined maximum torque, thereby eliminating excessive wear or breakage of its operating parts.

Another object of this invention is to provide a rock drill with a rotation mechanism assuring complete strokes of its piston even though the drill steel becomes stuck or will not rotate. H

"An'other object of this invention is to provide a rotation mechanism of the ratchet type with resilient or cushion means for the rifle bar to work against during normal operation and to have an overriding elfect, should the riflebar be subjected to a load greater than its designed load.

Another object of this invention is to produce such an improved rotation mechanism of simple and eflicient design free of movable parts such as locks, detents or the like subjected to wear and possible breakage.

,. Other objects of this invention not at this time more particularly enumerated will be clearly understood from the following description.

In the accompanying drawing:

Figure 1 is a partial longitudinal sectional view of a portion of a rock drill embodying the preferred form of the invention.

Figure 2 is a cross-sectional view taken on line 2--2 in Figure 1.

piece metal ratchet ring has been replaced by a three piece ring forming a single unit, with both the inner and outer rings made of metal, and the intermediate ring made of resilient material such as rubber. Except for this modified construction of the ratchet ring,'the rotation'mechanism is of standard design and includes the usual rifle bar head 24 rotatably mounted within the ratchet ring 22. This head carries the usual pivotally mounted pawls 2'5 urged outwardly into engagement with the teeth 31 by spring biased plungers 26. Rifle bar head 24 has a pilot 27 extending upwardly therefrom and journaled within bearing plate 17. From the, head 24 depends a bar 28 journaled within valve block 15, and having a rifle portion 29'extending into a rifle nut, not shown, fixed within the piston head 11.

Assuming that pressure fluid controlled by valve 14 is admitted alternately into the ends of the cylinder 10 for elfecting reciprocation of piston 11, the operation of the rotation mechanism is as follows: With the helical splines or rifles of the rifle'bar 28 inclined in the direction shown in Figure 1, during each down stroke of the piston, the

rifle bar will tend to rotate clockwise in Figure 2, which rotation is prevented by operative engagement of the pawls 25 with the teeth 23 of the ratchet ring 22, thereby causing piston 11 to rotate in a counterclockwise direction in Figure 2, or clockwise direction in Figure 1, which rotation is in turn transmitted to the drill steel in a well known manner. During the upward or return strokes of the piston, rotation in a counterclockwise direction ,in Figure 2 is imparted to the rifle bar 28, while. the pawls 25 ride over the teeth 23 of the ratchet ring 22. In this instance piston 11 moves axially without rota-ting.

As so far explained, the operation of the improved rotationmechanism is the same as that ofstandard; construction, and during normal operating conditions, it' func tions substantially in the same manner as the usual rotation mechanism of the rifle bar type.

Assuming now that instead of normal drilling operation, holes are being drilled in a formation of varying density which causes the drill steel to become stuck in relatively soft formation, or more broadly, assuming that 3 the drill steel becomes stuck in the bottom of the drilled hole and cannot be rotated in the usual manner. In such instance, during the down stroke of the piston which now is prevented from rotating, the rifle bar is subjected to counter forces tending to rotate it in a clockwise direction in Figure 2. In standard construction wherein the ratchet ring is made of a single piece fixed to the cylinder, rotation of the rifle bar in the clockwise direction is not possible by engagement of the pawls with the ratchet teeth, thereby causing breakage of the pawls and sometimes breakage of the rifle bar itself. In the improved construction the ratchet ring 22 being fixed to the cylinder through the medium of the resilient ring 21, is capable of limited clockwise rotation relative to the cylinder 10 by subjecting the resilient ring 21 to a torsional force causing it to stretch peripherally. This limited rotation of the ratchet ring relative to the cylinder has been found suflicient to release the excessive load to which the pawls 25 and rifle bar 28 would otherwi e be subjected to, and thereby prevent their breakage. Furthermore, the pistonll upon limited rotation of the ratchet ring 22 and consequently of the rifle bar 28 in a clockwise direction in Figure 2 is now capable of cornpleting its down strokes for delivering at least light impacts on the drill steel to dislodge it from its stuck position.

In practice, the pitch of the rifles or helical splines 29, together with the length of the piston stroke, the thickness of the resilient ring 21 and the resiliency of its material must be taken in consideration and correlated in a manner affording at least contact of the piston with the drill steel at the end of the down strokes of the piston for a maximum stretching or deformation of the resilientring 21.

In the modified construction shown in Figures 3 and 4, the outer ring 116 has its inner wall provided with two diametrically opposed longitudinally extending re cesses 50 of a given width and depth. The ratchet ring 122 has its outer wall provided with similarly disposed lugs 51 substantially reaching to the bottom of the recesses 50 but of a width about one half that of the recesses. Filling the other half of each recess and located ahead of the lugs with respect to the direction of rota tion of the ratchet ring imparted thereto by the pawls 25, is located a resilient pad 52 also made of rubber or the like and held longitudinally therein by the valve block and bearing plate 17. To facilitate assembly, the pads 52 may be vulcanized or cemented within the recesses 50.

In this modified construction, it will be understood that when the drill steel is prevented from rotating, the pawls transmitting torque to the ratchet ring 122 will cause the resilient pads 52 to be compressed by the lugs 51 to allow limited rotation of the ratchet ring and the continued reciprocation of the piston.

An important feature of the two constructions above described resides in the energy stored in the resilient ring 21 and pads 52 during their deflection, which energy in the form of rotary power is transmitted through the pawls and rifle bar to the piston, tending to rotate it and the drill steel during each down stroke of the piston. This takes place even though the drill steel is prevented from rotating, thereby submitting the drill steel to an intermittent torque assisting in dislodging it from the formation in which it is embedded.

It is to be understood that during normal operation, the resilient bond between the ratchet ring and its casing or cylinder, or more particularly between the ratchet ring and the outer ring ,16 or 116, which in turn is locked to the casing 10, while not subjected to sufiicient torque to cause it to deflect and permit rotation of the ratchet ring in a clockwise direction in Figures 2 and 3, nevertheless acts as a cushion for the ratchet ring capable of absorbing unusual impacts or the load of the pawls against the ring and softening the action of the pawls against the teeth of the ring.

The details of structure and arrangement of the resilient bonds between the ratchet ring and its casing may be variously changed and modified without departing from the spirit and scope of the invention.

I claim:

1. In a rock drill, the combination of a cylinder having a piston reciprocable therein, of a rotation mechanism for said piston including a bar extending into said piston, helical means on said bar coacting with helical means within said piston, a ratchet mechanism including a fixed outer ring, a ratchet ring concentric Within said outer ring, ratchet teeth on the inner wall of said ratchet ring, a resilient connecting ring bonded to said outer and ratchet-rings and forming therewith a single unit whereby said ratchet ring is resiliently held stationary as long as the resistance to rotation of piston remains below a predetermined maximum, spring biased pawl means operatively carried by said bar engaging said teeth to rotationally lock said bar in one direction to said ratchet ring and thereby translate each stroke of said piston toward one end of said cylinder into a fixed extent of rotation of the piston by virtue of said coacting helical means, the resiliency of said connecting ring enabling said ratchet ring and bar to rotate in said one direction an extent at least equal to the fixed extent aforesaid for each stroke of said piston toward said one end of the cylinder when said resistance to rotation exceeds said maximum, thereby rendering said rotation mechanism inoperative.

2. In a rock drill, the combination of a cylinder having a piston reciprocable therein, of a rotation mechanism for said piston including a bar extending into said piston, helical means on said bar coacting with helical means within said piston, a ratchet mechanism including a fixed outer ring, a ratchet ring within said outer ring, ratchet teeth on the inner wall of said ratchet ring, a resilient bond between said rings resiliently holding said ratchet ring against rotation as long as the resistance to rotation of said piston remains below a predetermined maximum, spring biased pawl means pivotally carried by said bar engaging said teeth to rotationally lock said bar in one direction to said ratchet ring and thereby translate each stroke of said piston toward one end of said cylinder into a fixed extent of rotation of the piston by virtue of said coacting helical means, said pawls riding over said teeth during the rotation of said bar in the other direction by virtue of said helical coacting means during the strokes of said piston toward the other end of said cylinder, the resiliency of said bond enabling said ratchet ring and bar to rotate in said one direction an extent at least equal to the fixed extent aforesaid when said resistance to rotation exceeds said maximum, thereby rendering said rotation mechanism inoperative.

References Cited in the file of this patent UNITED STATES PATENTS 1,946,956 Waseige Feb. 13, 1934 2,062,805 Campbell Dec. 1, 1936 FOREIGN PATENTS 299,913 Germany Aug. 13, 1917 Juan,

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