US2493298A - Distributing valve for rock drills - Google Patents

Description

Jan. 3,1950 E. B. LEAR 2,493,298

I DISTRIBUTING VALVE FOR ROCK DRILLS Filed March 29, 1947 2 Sheets-Sheet 1 //7(/enf0r Afforney Jan. 3, 1950 E. B. LEAR 2,493,298

DISTRIBUTING VALVE FOR ROCK DRILLS Filed March 29. 1947 2 Sheets- Sheet 2 .a W 41 Z /5 59 ii 5f 86 i & /7 74 57 '38 MVeh/or 4 5 45. Lear Patented Jan. 3, 1950 DISTRIBUTING VALVE FOR ROCK DRILLS Earl B. Lear, Detroit, Mich., assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application March 29, 1947, Serial No. 738,157

6 Claims. (Cl. 12119) This invention relates to pneumatic tools, and more particularly to a distributing valve for a pneumatic tool, such as a rock drill, containing a reciprocating piston which functions as a hammer.

An object of the invention is to provide a valve designed to respond quickly to fluid pressure, such as live air, and act positively to control the supply of the pressure fluid which reciprocates the hammer element of the tool.

A further object of the invention is to provide a valve having surfaces exposed both to the high pressure of the supply fluid and to the pressure of fluid compressed in the piston chamber in such novel manner and relation that the valve will be efficiently actuated in' timely and rapid reciprocation.

A still further object is to provide a valve so designed and so arranged within the valve chest that it will cooperate with a splined rifle bar to streamline the passage of live air into the piston chamber thereby to effect maximum eificiency in operation and also to channel the flow of lubricating fluid, as carried by the live air, di-

rectly against the rifle bar and nut.

A still further object is the provision of such a valve having a relatively large diameter and so disposed within the valve chest that its periphery forms a narrow gap with the valve chest, the arrangement of the valve being such that only a relatively short travel of the valve is required to effect distribution of the pressure fluid.

Still another object is the provision of a valve which is adapted for arrangement within the valve chest so that the pressure fluid will flow into the piston chamber between the inside diameter of the valve and the rifle bar of the piston.

Other objects will be apparent in the course of the following description in connection with the drawings, in which:

Fig. 1 is a longitudinal'section of a rock drill provided with a valve constructed in accordance with the invention, the valve being shown in forward operative position and the piston being near the end of its forward stroke;

Fig. 2 is a cross section of the tool taken on the line 2-2 in Fig. 1, the outer cylinder being omitted;

Fig. 3 is a longitudinal section on a larger scale of a half portion of the valve and valve chest, the valve being in forward operative position and having its flange modified by the provision of a starter port; and v Fig. 4 is a longitudinal section, as in Fig. 3,

showing the valve in rear operative position with a starter port in the valve as in Fig. 1.

Still referring to the drawings, the invention is shown embodied in a reciprocating percussive tool or rock drill which includes a cylinder I!) having a chamber II, a piston l2 reciprocable therein, a valve chest generally indicated at l3 comprising an annular valve block l4 and an annular valve cap IS, a valve chamber l6 formed between the valve block 14 and valve cap 15, and an annular distributing sleeve valve I! disposed within the valve chamber I6 for limited axial reciprocation to distribute pressure fluid, such as live air, to actuate the piston 12 as hereinafter described.

The rock drill is provided with conventional rotation mechanism for imparting step-by-step rotary movement to the piston. Such mechanism seats in the central bore l8 of the valve chest and may comprise a rifle nut (not shown) screwed to the piston and reciprocable therewith, a rifle bar [9 having helical splines 21 slidably engaging the rifie nut, a head22 on the rifile bar, a series of pawls 23 carried by the head, and a stationary ratchet ring 24 surrounding the head and pawls. The ratchet ring 24 and the rifle bar head 22 are maintained against axial movement by a back head (not shown) which is exterior thereto and is secured to the cylinder by conventional means. As the piston and included rifle nut reciprocate, intermittent rotary motion is imparted thereto by the splined rifle bar whose rotary movement is limited to one direction by the engagement of the pawls and ratchet in the well known manenr. The forward or outer end of the piston is guided in its reciprocations by the washer 25 rigidly mounted in the forward or outer end of the cylinder l0.

Cylinder I0 is formed with a counterbore 26 within which is mounted the valve chest H3. The valve block l4, forming part of the valve chest, abuts forwardly against the shoulder 21 formed by the counterbore, and the valve chest assembly is maintained against axial movement rearwardly by the ratchet ring 24 which is in turn supported by the back head. Valve block I4 is provided in its rearward face with an outer annular groove 28 and an inner annular groove 29 between which is formed a rearwardly facing valve seat 3|. Valve cap is formed with an outer annular groove 32 whose outer marin or wall 33 forms a continuation of the outer margin or wall 34 of the valve block outer annular groove 28; and inwardly of groove 82 is a forwardly facing annular groove 35 which said chamber irrespective of the position of the" valve I! as long as the proper valve (not shown) is turned on. Such live air advances from said chamber through a pluralityof ports 41 which lead to the annular groove 32 in the valve cap; thus supplying live air, which in the Fig. 3 position of the parts flows inwardly over the valve seat 39 through the passage 42 to the inner groove 35 and thence to the piston chamber as hereinafter described.

The distributing valve I'F comprises a hollow cylindrical stem or sleeve 43- and a: radially extending flange 4'4, the stem and flange being oinedby a; curved portion 45. The'outer'wall 45 of the valve stem, as best shownin Fig. 3, has a el'oseslidin fit with the inner wall 41 of the valve block, andthe inner wall- 18' of' the valve StemiS spaced'from the outside diameter 38 of the rifle bar to form an annular passage 49 between the valve and the spli'ne'drifi'e bar. The outer periphery 51 of the valve flange M; is-s'paced from theouter margin or wall 33 of the valve cap groove 32 to form an annular gap 52 leading from thegroove 32- in the valve cap to the outer groove 28 of the valve block. Itis to be noted that the curved surface 36 of the" groove 35 is concentric"- witli the rear face; 53 of the valve curved portion 45', thereby forming a smooth for- Wardly leading assage 5 1' fromthe roove- 35 into the" passage 48 and the groovesin the splined rifll'e bar.

Gylinde'r I'Oha's-a longitudin'al pas'sage 5Fr'wh1'ch is connected by port 56 to the valve chamber t6 and: by port 5! to the front end 58' of the piston chamber whereby live air is transmitted fromthe valve, as shownin rear position Fig; 4,130 the piston chamber to drive the pistonrearward'ly. A laterally extending port 59 (Fig. 1) extends from the valve chamber l-B through the valve block l4 into the cylinder 1 0- where it connects to the passage 6 I leading to the blower v'alvegenerally indicated at 61- A shown in solid lines in Fig. 1*, the' blower valve is in drilling position, but when the handle 63 isshifted tothe broken line position, the valve will open passage 6| through port 64 to atmosphere and at the same time close the main exhaust port of the piston chamber. Distributing valve l1- will then shift into or remain in forward position, as the case may be, since live air pressurewi=llcontinue on its rear surface. Valve l-l willthereu-pon be held in forward position, the piston willremain in forward position and live air will escape forwardly between the riflle bar and rifle nut to the hollow drill steel (not shown).

Lubrication is supplied to the moving parts of the motor in the form of oil introduced in small amounts into the live air as it enters the tool, such air serving as a carrier to conduct the lubricant to the piston, the cylinder, the rifle bar, the rifle nut, and to the valve itself. The oil may be introduced into the live air in the air supply line (not shown) by means well known in the art; or it may be introduced, as shown in theillustrative embodiment, from a reservoir 65 within the body of the drill proper. Reservoir 65 is formed by the mating of the annular recess 66 in the washer 25 and the annular recess 61 in the forward extension 68 of the cylinder Hi. Flats 69 are formed in the washer adjacent the reservoir on opposite sides and provide restricted passages H to the small ports 12. Ports 12 lead into the longitudinal passage 13 which at its rear end: has aright angle extension 14 leading into the outlet passage 15 which is connected to the short longitudinal passage 16 in the ratchet ring 24. A forwardly leading restricted aperture '5? connects passage'ifi to the inner surface of the ratchet ring, and it is at this point that the lubricant is introduced into the stream of live air as hereinafter explained. A supply of oil may Ice introduced from time to time, as required, through the cylinder opening 18 which is threaded for reception of a plug closure (not shown).

In a tool such as shown in the illustrative embodiment, lubrication iseffected by the pressure fluctuations that occur during the reciprocation of the hammer piston. Pressure within the oil reservoir 65- remains substantially constant and sometimes greater than the pressure within the passage 55 while the piston isreciprocating. This results from the restricted dimensions of the passages 1| leading. intothe reservoir. Pressure variations occurring in the passage 55 are transmitted into the reservoir. Accordingly, the relatively high constant' pressure on the oil in the reservoir causes a small amount of the oil to be discharged from the reservoir through the portings connected thereto upon each drop in pressure in the passage 55' to the motor inlet passage. Such oil reaches the ratchet ringv 24 and passes therethrough by means of aperture 11 to become entrained by the live air flowing therethrough' to actuate the piston. The oil thus entrained is carried through the valve cap transmission passages 40, 41, 32, 42 and 35 into the valve chamber l6, and since the valve is in forward position (-Fig. 1') during the interval of pressure drop, the live air moves forwardly through the passage 54" inside the valve stem 43 and into the splined grooves 2| of the rifle bar I 9". The oil entrained in the live air is thus carried directly against the moving rifle bar to effect complete lubrication of the part. Obviously, the device will operate with the same effectiveness if the oil is fedthereto by atomization within the tool or inthe air conductor outside the tool.

In operation, with the valve l1 and the piston 12 in forward operative positions, as shown in Figs. 1 and 3, live air flows from the source of live air (not shown) through; the space between the pawls 23 and ratchet ring 24, into the chamber 40 and thence, in the course indicated by the arrows in Fig. 3, throughv the valve passages into the rear end of the piston chamber II. It is to be noted that when the valve is thus in its forward position, with live air pressing the valve forwardly at at and 84, apart of the live air also flows forwardly through the narrow annular gap 52 into the annular groove 28 in the valve block where it is prevented from further flow by the valve seat 3| which is then in contact with the valve flange. Live air pressure is thus exerted on valve surface 19 and tends tothrow the valve rearwardly or to partially offset the forward pressure on the rear actuating surfaces 8i and 84. It should also be noted that such live air, when the valve is in forward position, presses against the forward peripheral face 82 of the valve stem 43, likewise tending to throw the valve rearwardly. During the forward movement of the piston and after it has closed the exhaust port 84, the air in the front end 58 of the piston chamber is compressed and forced rearwardly through the port 51 into the passageway 55 and thence through the valve block port 56 into the valve chamber I6 and against the actuatin surface 83 of the valve. As the piston continues to advance, this pressure obviously builds up. But the pressure thus exerted to the rear on the actuating surface 83, combined with the live air pressure directed rearwardly on the valve surface 19 and on the forward peripheral wall 82, as described, is not sufficient to unseat the valve rearwardly so long as live air is contained in the rear of the piston chamber and maintains forwardly directed pressure on the valve actuating surface 8|. As soon as the advancing piston uncovers the exhaust port 84, however, there will be a drop in the pressure of the live air acting against the surface 8| and the foregoing described combined pressures on surfaces 19, 82 and 83 will thereupon shift the valve rearwardly to the position upon the valve seat 38 shown in Fig. 4.

The valve having shifted, the live air, as indicated by the arrows in Fig. 4, will flow from the chamber 48 throughports 4| into annular groove 32, through the gap 52, the annular groove 28, past the valve seat 3 I, into the valve chamber 5, thence outwardly through the port 56 into the passage 55 and thence into the forward piston chamber 58 to drive the piston rearwardly. In this course of the live air, pressure on surface 19 functions to press the valve rearwardly. The piston moving rearwardly will cover the port 84. Air confined in the rear end of the cylinder chamber will thereupon be compressed and will act upon the rear actuating surface 8| of the valve flange 44 to tend to shift the valve forwardly. But it should be observed that such compressed air will also act upon the forward peripheral face 82 of the valve stem to partially offset such forward pressure on surface 8|. At the same time, live air from the ports 4| will act upon the rear surface 84 of the valve flange 44 outwardly of the valve seat 39 and will tend to move the valve forwardly. However, the pressure of the live air acting upon the forward face I9 of the valve flange and the pressure of the compressed air in the cylinder upon the forward peripheral face 82 of the valve stem will maintain the valve in rear seated position against the combined forwardly urging forces of the live air on the surface 84 and of the compressed air on the rear surface 8|. But as soon as the port 64 is uncovered by the rearward movement of the piston, the live air pressure against surface 19 will drop and the aforesaid combined forwardly urging pressures will shift the valve forwardly to its forward seated position, as shown in Figs. 1 and 3.

The flange 44 of the valve, in the embodiment shown in Figs. 1 and 4, is pierced with a small through aperture 85 in the area between the seats 3| and 39 to connect the grooves 28 and 35. The function of this aperture is to assist in shifting the valve when the machine is started from idle position under certain conditions. If the valve should by chance come to rest in its rear position when the machine has been stopped in a preceding operation, it has been found that the force of the air which will be compressed in the rear of the piston chamber, and accordingly in the 6 groove 35, will sometimes be insufiicient to shift the valve forwardly. By the presence of the aperture 85, however, the rearward pressure exerted by the live air on the flange surface 19 is reduced sufiiciently to permit the compressed air to unseat the valve. In the embodiment shown in Fig. 3, a connecting aperture 86 is formed in the valve cap l5 leading from one of the ports 4| directly to the groove as an alternate means of shifting the valve in the event it may have come to rest in rear position. In this instance, live air flowing through the aperture positively increases the force of the compressed air in the groove.

For the lubrication of the valve in the area of friction between the outer wall 48 of the valve stem 43 and the inner wall 4! of. the valve block M, an annular groove 81 is formed in the inner wall 47 to which lubrication is supplied by the passage 88 leading from the reservoir 89. Reservoir 89 may be supplied from time to time through an aperture (not shown) in the cylinder.

What is claimed is:

1. In a rock drill of the class wherein the percussions to a working implement are derived from a reciprocating piston to which intermittent rotary movement is imparted, in combination, a helically splined rifle bar, a valve chest formed with a valve chamber and having a curved portion extending in the direction of the reciprocating piston and terminating contiguous the helical splines of the rifle bar, and a distributing valve in the valve chamber comprising a discal member integrally joined by a curved portion to a stem, said stem surrounding the rifle bar and said curved portion being in uniformly spaced relation to the curved portion of the valve chest thereby to form an annular channel connecting the valve chamber to the helically splined portion of the rifle bar.

2. In a rock drill of the class described, a valve chest comprising an annular block and an annular cap arranged in opposed relation to form a valve chamber therebetween, the cap being provided with a curved surface extending in the direction of said block; a rifle bar rotatable in the central aperture of the valve chest and having helical splines the grooves of which terminate in sloping end portions contiguous the curved surface of the valve cap; and a distributing valve within the valve chamber comprising a discal member disposed opposite a face of the valve cap and connected by a curved portion to a stem which is in spaced relation to the rifle bar, the curved portion being in spaced relation to the curved surface of the valve cap thereby to form in conjunction with the helical splines a series of channels leading from the valve chamber.

3. In a rock drill of the class described, a cylinder having a piston chamber; a piston adapted to be reciprocally actuated therein by live air and adapted upon forward motion to compress air in the front portion of the piston chamber and upon rearward motion to compress air in the rear portion of the piston chamber; an annular cap formed with an annular groove arranged in the direction of the piston chamber, a, second groove disposed inwardly of the first mentioned roove, an annular valve seat between the grooves, an annular sloping portion on the side of the cap nearer the piston chamber, and an inlet passage adapted for connection to a source of live air; an annular block formed with an annular groove on the side of the block farthest from the piston chamber, a second groove disposed inwardly of said first mentioned groove, an annular valve seat between the grooves, and a passage for connection to the splines the grooves of which slope at their rear end portions to terminate contiguous the sloping portion of the valve cap; an annular distributing valve adapted to be reciprocated within the valve chest and having a diseal portion disposed between the valve sea-tswith its periphery in spaced relation to the valve cap outer groove to form an annular gap for the passage of live air from the inlet passage to the piston chamber when the valve is in rear position and for the passage of live air into the outer groove of the valve block to exert differential rearward pressure upon the valve when the latter in forward position, said valve also having a stem surrounding the rifle bar in spaced relation thereto in the region of the annular block and connected to the discal portion by a curved portion the curve of which is substantially concentric with the curve of the sloping portion of the valve cap thereby forming a channel for the easy passage of live air into the rear portion of the piston chamber; opposed actuating surfaces on the valve each adapted to be subjected to intermittent compression from 8 the piston chamber to shift the valve upon the exhausting to atmosphere -'of the live air actuatmg the piston and opposed differential pressure surfaces on the valve constantly exposed to live air to assist in-shifting the valve.

4. In a rock drill, a combination, as in claim 3, wherein the inner groove in the valve cap is connected by an aperture 'to the live air supply thereby to admit live an to'assist in shifting the valve forwardl-y in the valve chamber when the valve is inrear position therein upon the initiating of operation.

5. In a rook dr'ill, a com'binattion, as in claim 4, in which the aperture'to'theiinner groove of the valve cap extends through the discal portion of the valve.

6. In a rock drill, .a combination, as in claim 4, in which the aperture to the inner groove of the valve block extends through the valve 'cap.

EARL B. LEAR.

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

STATES PATENTS Number Name Date 776,671 Maximillian Dec. 6, 1904 1,597,412 Lear Aug. 24, 1926 2,070,299 'Slatcher Feb. 9, 1937 2,141,727 Slater Dec. 27, 1938

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