US2443894A - Distributing valve for rock drills - Google Patents

Description

June 22, 1948. w. D. cRAzE DISTRIBUTING VALVE FOR ROCK DRILLS Filed 061;. 5,1944

'M4/HM DY Tex-72.6

Patented June 22, 1948 UNITED STATES PATENT OFFICE William D. Craze, Farmington, Mich., assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of`New Jersey Application October 3, 1944, Serial No. 556,999

This invention relates to rock drills of the pneumatic percussive type with particular reference to automatically operated distributing valves therefor.

The main object of the invention is to provide a rock drill or other fluid operated tool with a distributing valve which is not only positively and automatically tripped or actuated, but has such a simple and improved streamlined form that the motive fluid can flow past said valve with substantially full power from the fluid source to the hammer piston.

Another object is to arrange the motive fluid passages and ports and especially the latter in as nearly straight lines as possible in order to avoid abrupt or sharp changes in direction being imposed on the flowing motive fluid and thereby largely eliminate power loss during operation. I

A further object is to provide a distributing valve of the character indicated` with two opposed holding areas which are only slightly different in size and individually effective at certain stages of the operation to constitute active pressure areas for positively tripping or shifting the valve.

It is also an object of the invention to `associate one of the mentioned holding areas of the valve with a working space or chamber so proportioned that it can cooperate with the valve in rearward movement of the latter and cause cushioning of the valve by braking the same in its rearward movement.

Other objects and the advantages of the invention will appear more fully in the following description when taken with the `accompanyin drawing, in which:

Fig. 1 is a fragmentary longitudinal section of the main portion of a rock drillhaving a distributing valve embodying the invention in practical form, the valve and hammer piston being shown in initial rearward operative positions;

Fig. 2 is a similar view showing the valve and piston in fully operated forward positions at the start of the return stroke of the piston; and

Fig. 3 is a section of the distributing valve of Figs. 1 and 2. I

In rock drills and other fluid operated tools of the percussive type it is quite evident that intensity of the blow delivered by the hammer piston or striking element of the tool is in great measure determined by the ease with which the motive fluid flows through the passages controlled by the distributing valve thereof as well as past the latter during the` forward working Claims.

l stroke of the piston.`

` a plurality of fluid inlet passages or ports. 24,

2 To` this end, the` design of the valveitself as well as the arrangement of the ports and passages for the motive fluid should obviously be as free as possible from sharp bends, corners and constrictions, etc., in order to provide a streamlined path for the uid travelling toward said piston to drive the latter as eiciently as possible. I

Referring again to the drawing, in the practice of the invention arock drill casing, generally indicated at I 0 contains a hammerpiston II reciprocable `wit'hina cylinder I2 divided into a rear piston chamber I3 and a front piston chamber I 4 by means of antintermediately located annular exhaust groove or channel I5 communicating with atmosphere through a main exhaust opening or port I 6. The forwardportion or shank Il of the piston is fluted at I8 and guided in a front cylinder washer I9 which forms a fixed part of the `casing I0. The washer also provides a closure for the front end of forward cylinderV chamber I 4, while the rear end of the cylinder chamber` I3 is `closed by a valve cap 2| seated against a shoulder 22 in a counterbore 23 `in the casing. Valve cap 2l isprovided with 2,4 fort supplying motive iiuid directly against the rear end or face 25 of piston I I, as will presently be explained. Located rearwardly of said valve cap in the same counterbore 23 isa valve block 26, beyond which is located `a ratchet ring 21 of `conventional type surrounding a pluralityof pawls (not shown) carried by a rie bar 28 `associated with the hammer` piston to rotate the latter. A .back head 29 completes the end closure of casing Ill and connes` the ratchet ring 2? in place between the` back/head and the casing, said back head being secured to the latter by the usual through. bolts (not shown).

Within the valve cap ZI and valve block 26 is mounted the xed bushing 3l virtually suspended bythe ends thereof, withone end secured in the valve cap and the other end secured in the rear portion of the valve block. The bushing has -a pair of separate locating flanges 32, 33 respectively engaging against flanges 34 and 35 of said valve cap and valve block' serving to retain the bushing in place. The forward end 33 of the valve block is fitted upon the rearward projection 31 of the valve cap against shoulder 38 thereof, with the result that said'valve cap- 2|, valve block 26, and bushing SI together form a valve casing or chest for a hollow reciprocable distributing` valve 39 surrounding the xed bushing 3| generally without inwardly extendingv contact therewith and mounted for longitudinal sliding movement within said valve cap in couny terbore 4I in the valve block.

In order to supply motive fiuid to the distributing valve, the throttle valve 42 is rotatably mounted in back head 29 and controlled by hand -lever 43, while the interior chamber 44 thereof is connected to a continuous supply of motive fluid under pressure (not shown). When the throttle valve is open, as illustrated, the path of the motive uid leads through passage 45 to chamber or reservoir 4G in the back head and thence through passages 41 within the ratchet ring 21 to uid reservoir 48 in valve block 256. From this reservoir the fluid path leads onward 4through several inlet ports 49 and a central bore 59 in block 25 to the annular passage 5I about bushing 3| and within the hollow valve 39. Bushing 3| extends throughout the interior of the distributing valve and the position of the latter valve with respect -to the bushing determines the further course of the fluid during operation.

The distributing valve 39 hasV a counterbore or increased internal diameter 52 within the forward end 53 virtually forming a clearance portion which terminates rearwardly in an inclined portion or shoulder 54, while the remaining internal diameter or bore 55 is substantially uniform from said shoulder to the rear end 56 but exteriorly the valve has a radially projecting flange 5l near the forward end located in a valve ange chamber 55. Uuon its rearward portion and spaced a short distance from the rear end portion 55 thereof the valve is exteriorly grooved to forma neck- 59 adapted to cooperate in a manner shortly to be explained with a pair of annular grooves 6I and 62 spaced apart in in block 26 by a partition 63. The first groove El serves as an exhaust groove vented directly to atmosphere through auxiliary exhaust port 64 while the other groove 62 is connected to piston return passage G5 which opens into the front piston chamber I4 through port E9. In somewhat similar fashion to the latter, the valve flange chamber 58 communicates withV a Valve operating fiuid passage 61 opening into the rear piston chamber I3 through port 68 just rearwardly of the exhaust groove I5 and main exhaust port I'Ei.y I*

Theidi'stributing valve just described and the hammer piston are the only moving parts in the apparatus driven by the motive `fluid which is preferably compressed-air, and the operation is entirely automatic as will now be noted in detail. Assuming thatpressure fiuid from a given source is supplied to the chamber 44 of throttle valve 4;?, and with the hammer piston II as well as the `distributing valvej39 occupying their initial rearwardl positions sho-wn in Fig. l, the motive uid travelsthrough ports `45 to rear chamber or reservoir 45, as Aalready indicated. and through ratchet passage y4'! into reservoir 48 and thence through inletports 49 and 'bore 5i! into annular passagefi! between the distributing valve and bushing 3l, past inclined shoulder portion 54 insa'id valve and over the shoulder formed by retaining fiange 32 into annular distributing chamber and thence through rear inlet ports 24 into 'the rear piston chamber I3 Where the motive uid :exerts its force against the rear end 25 of piston II, immediately driving the latter forwardtoward the position shown in Eig. 2. The valve is held in its rearward positionby the pressure of live motive fluid against the front en'd53 of the valve, which` is aided by the pressure 4 on internal shoulder 54 but opposed by the pressure on the rear end 56.

As the piston is driven forward, the residual fiuid in its path in front piston chamber I4 is partly exhausted through groove I5 and exhaust port I6 which, however, are shortly covered by the advancing piston, despite kthe importance of clearing 'out all fiuid from before said piston so that 'the forward driving 'stroke of the latter may occur with maximum force. As the main exhaust groove and port are no longer useful to exhaustthe front chamber directly during the further forward travel of the piston, the auxiliary exhaust port 66 lwith associated passage E5 then serve to l"exhaust said front chamber by leading off thefiuid therefrom to groove 92, from which the fluid proceeds past the inner periphery of partitin 53 along neck 59 on the distributing valve-to annular groove 6I and then out to atmosphere through port 94 so long as the valve remains in the initial rear position Yof Fig. 1.

However, `during the forward travel of the hamme'rjpiston, and approximately Iat the position indicated by broken line il ('Fig. '2), the piston uncoversl port 63 in the upper cylinder wall,` allowingfpressure fluid from rear piston chambery I3 suddenly to'rush through passage 6l to Lannu'lar `fiarige chamber 58 and immediately exert pressure on the rear surface 'I2 of 'the valve flange 5i andtend to overcome the active Huid pressure Von `the vfront end T53 of the valve and shift the latter forward into the'position shown in Fig. I2. it is, of course, understood that the stroke Aof the `hammer' piston is very swift, so that the portion of the movement vthereof occurring from the :point indicated by broken line "I3 forward'while :uncovering `port 58 just described is substantially instantaneous. Shortly thereafter, when the valve has been shifted forward so as Lto cut o' the flow of' motive fluid vto the rear piston chamber the rear Yend 25 yof the `piston has attained the nal operating position in the forward .direction vand has also'uncovered the' annular Vexhaust groove I5 to the rear piston chamber for release of the more or less 'spent fluid therein through exhaust port I9.

Associated with Vthe Valveflange 51 is the usual exhaust 'port -or 'breather l5, venting the front face of the flange to facilitate forward tripping of the valve; yalso 'the usual bleeding passage 'i6 'which lgradually relieves rthe pressure on the rear face of vthe flange to permit the valve to return. l

When ydistributing valve 39 has tripped from th'erear position, it is held in the forward position by the fluid pressure on its rear face 56 resulting from the flow of motive fluid into chamber f4 and groove 52. The rear face or end 5G of the valve is designed to have an effective area slightly in excess of Athat of internal inclined shoulder 154, so' lthat a state of unbalance exists which causes the valve to be held in its attained forward position.

yIn the'attainedffforward position of the valve 39 (Ei'g. 2)' the .endV r53 thereof overlies flange 32 onbushing 3i in sufciently close contact with the periphery thereof to cut off thev motive fluid supply to therear piston chamber I3 and instead allow `active motive iiuid `to lenter front piston chamber I4, las the rear end 59 of the valve then allows 'direct communication between annular groove 62 and chamber T4 `which isin constant communication with the pressure .fluid entering through passages -49 and 5I. VDuring the travel of the motive "uid in the forward direction into passage B5 and thence into front piston chamber I4 through port 55 said fluid exerts its fonce on the forward end "il of the hammer piston and drives the latter rearwardly toward initial position.

During the return stroke the piston covers port 58 while beginning to compress the fluid in rear piston chamber 3. After the piston has returned to a predetermined position short of the fully returned initial position the fluid pressure due to piston compression rises to a sufficient height to act through ports 24 against the forward end 53 of valve 39 and overcome motive fluid pressure pressing on rear end 56 of the valve and thereby effect rearward tripping or shifting of the latter to the initial rearward position of Fig. 1. Both the piston and valve are now again in initial rear positions ready for a new cycle of operation, and such operation continues indefinitely and automatically as long as valve 42 remains open and motive fluid is supplied thereto.

Because of the high velocity of the valve on its rearward stroke, a packing or pumping effect is produced by face 56 of valve driving into space '14. This causes a building up of pressure on face 56 in inverse ratio to volume of space 14. Because this feature lends itself as a highly effective control of the valve movement and a consequent improvement in energy output of tool, it is imperative that dimensions of space 14 be held to fairly close limits.

What is claimed is:

1. A uid pressure actuated percussive tool comprising a cylinder, a piston mounted for reciprocation therein, a valve chest positioned adjacent the rear end of the cylinder, an annular distributing valve mounted in said chest for axial reciprocation, a bushing co-axially disposed within the valve and spaced therefrom to provide an annular passageway therebetween, a flange upon the bushing, means for delivering motive fluid constantly to the rear end of the annular passageway, a rear cylinder port or ports connecting the front end of the annular passageway with the rear end of the cylinder and adapted to be uncovered by the valve during rearward movement, a front cylinder passage connecting the rear end of the valve passageway with the front end of the cylinder and arranged to be uncovered upon forward movement of the valve, the front extremity of the valve being intermittently exposed to uid compressed by the piston to move the valve rearward and then being exposed to live motive fluid to hold the valve in rearward position, the rear extremity of the valve being constantly exposed to live air tending to shift or hold the valve forward, characterized in that the valve has a single counterbore adjoining its forward face to provide a sliding t for the valve upon the bushing flange to control communication past the front extremity of the valve, said counterbore being disposed in reference to the valve bore to form a shoulder exposed to live fluid pressure constantly opposing the pressure on the rear extremity, whereby to reduce the effectiveness of the latter, the counterbore being of uniform diameter from the shoulder to the front extremity of the valve.

2. A fluid pressure actuated percussive tool comprising a cylinder, a piston mounted for reciprocation therein, a valve chest positioned adjacent the rear end of-the cylinder, an annular distributing valve mounted in said chest for axial reciprocation, a bushing co-axially disposed within the valve and spaced therefrom to provide an annular passageway therebetween, means for delivering motive fluid constantly to the rear end of the annular passageway, a rear cylinder port or ports connecting the front end of the annular passageway with the rear end of the cylinder and adapted to be uncovered by the valve during the rearward movement, a front cylinder passage connecting the rear end of the valve passageway with the front end of the cylinder and arranged to be uncovered upon forward movement of the valve, the front extremity of the valve being intermittently exposed to fluid compressed by the piston to move the valve rearward and then being exposed to live motive fluid to hold the valve in rearward position, the rear extremity of the valve being constantly exposed to live air tending to shift or hold the valve forward, characterized in that the front portion of the valve is counterbored to provide a shoulder exposed to live fluid pressure constantly opposing the pressure on the rear extremity, whereby to reduce the effectiveness of the latter, the effective area of said shoulder being less than the opposing area on the rear extremity of the valve, the counterbored portion of the valve extending from the shoulder to the front extremity of the valve.

3. A fluid pressure actuated percussive tool according to claim 1 in which the shoulder is inclined or tapered in a rearward direction from the counterbored portion of the valve.

4. A fluid pressure actuated percussive tool according to claim 1 in which the valve chest is recessed to receive the rear end of the valve and cushion the rear stroke thereof.

5. A pneumatic percussive tool comprising a cylinder, a piston mounted for reciprocation therein, a valve chest at the rear end of the cylinder, said chest having a central bore adapted to be constantly supplied with live air and having a counterbore extending forwardly from said bore, an annular distributing valve mounted in said counterbore for axial reciprocation, a bushing coaxially disposed within the valve and spaced therefrom to provide an annular passageway therebetween, a fiange on the bushing near the front end of the valve, a port or ports arranged to connect the front end of the annular passageway with the rear end of the cylinder to supply live air thereto in the rear position of the valve, the interior surface of the valve comprising a forwardly ,facing shoulder, a cylindrical bore of uniform diameter extending from the shoulder to the rear extremity of the valve and a cylindrical counterbore of uniform diameter extending from the shoulder to the front extremity of the valve, the diameter of said valve bore being approximately equal to the diameter of said valve chest bore, the counterbore being of such diameter as to fit over the bushing flange and thus periodically cut off the iiow of live air through said port or ports.

WILLIAM D. CRAZE.

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

UNITED STATES PATENTS

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