US1162249A - Rock-drill. - Google Patents

Description

V. J. OBRIEN.

ROCK DRILL.

APPLICATION HLED APR.8. I9I3- RENEWED FEB. 3.1914.

Patented NOV. 30, 1915.

5 SHEETS-SHEET I.

` A ROCK DRILL. -APPLCATION FILED APR.8. i913. RENEWED FEB. 3. l914. 1,162,249.

Pateted Nov. 30, 1915,

5 SHEETS-SHEET Z.

A v.1. Q'BRIEN.

ROCK DRILL. PPLICATION FILED APR-8 l9l3 RENEWED FEB. 3,194,

Patented Nov. 30, 191.5,

...hm fl NM\N.% I

i -:---!:-|--------TMI! III 1111 1 ----IWNIIMMIMWA.:

bkk w l y v.1. oBmEN.

ROCK DRILL. APPLlc/mow man Ame. 1913. RENEwED fz-:8.3.19l4.

Patented Nov. 3,0, 1915.

s sH'EETs`sHEET 5.

l.EEE-

VINCENT JOHN OBRIEN, OF DENVER, COLORDO.

ROCK-DRILL.

Specification of Letters Patent.

Patented Nov. 3G, 19rd.

Application filed April 8, 1913, Serial No. 759,593. Renewed February 3, 1914. Serial No. 816,316.

To all 'whom it lmay concern p Be it known that I, ViNoENT JOHN OBRIEN, citizen of the United States, residing at 514e Galapago street, in the city and county of Denver and State of Colorado, have invented certain new and useful Improvements infRock-Drills; and I do declare the following to be a full, clear, and exact descriptionfof the invention, such as will enable others skilled in the art to which it appe'tains. to make and use the same,.ref

Ierence being had to the accompanying draw-- in the art, so far as I understand it, consists 1n making prov1sion tor a graduated exhaust from the hammer cylinder, the exhaust being regulated to harmonize with the supply of air to the cylinder for reciprocating .the hammer. In other words, the throttle valve is so constructed that .as the. supply of; air to the hammer cylinder for reciprocating the latter is increased, the exhaust port in the valve is correspondingly increased. This feature has an important advantage over constructions heretofore in vogue and in which a permanent or' fixed exhaust is employed. In constructions of the last-named character it is necessary that the exhaust shall be so restricted as to hold the cylinder valve in the closed position during the re- 'seriously interferes with the lective opera--l tion of the construction.v M improved con-` struction, whereby the exhaust is regulated in harmony with the supply of air *to the drill cylinderk overcomes-this difficulty and makes itk practicable vto obtain not only a lconstruction whereby the pressure withr vtheifeed cylinder 1s less during the return hard blow with the travel of the hammer no rmal but also makes it practicable to obtain a relatively rapid light blow. This is accomplished by opening the exhaust port of @0 the throttle valve to permit the maximum volume of motive iiuid to pass therethrough, while at the same time the maximum amount of motive fini-d is entering the drill cylinder'. In this case the result is that by increasing the exhaust, the pressure on the rear and enlarged extremity ot the cylinder valve upon which reliance is made for retaining he latter in the closed position during the return stroke of the hammer, is so reduced' that the valve will open under the action of the contant live air pressure on ay shoulder of the valve, after the hammer has traveled only a small proportion ot' the length of the drill cylinder between the rear extremity of 7s the hammerand the rear end of said cylinder. This opening movement ot the valve d permits the entrance of the live air for driv.h ing the hammer forwardly and in this manner a very rapid, light blow may be obso tained, which is impossible in constructions having afixed or non-varying exhaust pas sage. f A

Another feature of novelty consists in a stroke of the hammer than during the forward 'stroke thereof. 1This result is obtained by taking the air from the feed cylinder which produces the returnmovement oit the hammer and so arranging the ports and passages thatthe amount ot air taken from the feed cylinder is greater than that which is delivered thereto simultaneously from the supply source. In this way pressure within the feed cylinder is weakened as compared with the pressure during the forward stroke of the hammer, since during thelast named hammer movement there is no escape of motive fluid from the feedE cylinder; consei quently, there is full line pressure in the feed cylinder for holding la'drill against the rock. By reducing the pressure Within the feed cylinder, the force of the pressure of' the drill bit against the rook; reduced. durn los ing the return `stroke of the` ammer, thus `making the rotary movement of lthe drill 5 easier for the'operator and at the same time diminishing the Wear upon the drill bit.

In myv improved construction, provision is further made foi-"regulating the supplyoI l motive fluid tothe motor or drill cylinder suppiy to the feed cylinder, thus regulating the pressure in the feed cylinder to lxarmov with that in the drill cylinder. This is accomplished by actuating the throttle valve which is interposed between the motor and thegieed cylinder in the usual manner., @ther features of novelty included in mi present invention will be understood by re erence to the accompanying drawing taken in connection with the specification. y

1n the drawing, ni'fure 1 is a top plan view, partly in horizontal section, illustrating. afhammer drili equipped with my improvements.. Fig. 2 is a section taken on the line 2-2 of Fig. Fig. 3 is an elevation of the cylinder valve forming a part of the valve mechanism o1 the engine or'motor. Fig. 1 is a fragmentary' longitudinal section 'taken through the drill cylinder on the line Fig. il, Aand cutting the throttle valve on the line L11--7 Fig. 12. Fig. 5 is a similar 'section taken `through the engine construction on the line 5-5, Fig. 9, and cutting the throttle vaive on the line 5--6, Fig. 1,2.v Fig,

6 is a. similar section'talren on the line 6 6, Fig. 9, andthe line 5-6, Fig. 12. Fig. 7,

is a. similar section taken through the e'ngine structure on 'the line 7--7, Fig. 9, and

the throttle valve on the line 4 7,

Fig. 12; Figi 8 is a, section taken through the engine on the line 8-8, Fig. 9, and through the throttle valvel on the line 8--8, Fig. 12. Figs. 9, 10 and 11 are cross-sections e taken on the lines 9&9, 1.6-1.0 and `11-11,

respectively, Fig. v7. Fig. 12 is a vertical section Ataken through the throttle valve mechanism on the line 12-12,4Fig. 13. Fig. 13 is a view of the throttle valve mechanism iooln'ng in the direction of arrow 13, Fig. 12. Fig. .TL-ii is a section taken through the block or casing of the throttle valve showing the latter in elevation. Fig. 15,'is a cross-section taken through the throttle valve mechanism on the line 155-15, Fig. 14. Fig. 16 is a cross-section taken through the throttle Valve mechanism on the line fw-7, Fig. 12,;the, valve piece being.; shown yin a different pos1` tion'from that illustrated in Figs. 4 and 7. The same reference characters indicate the same parts in all the views.

From the brief' description oi the figures as already given, it willbe understood that I the relative positions of the throttle valve mechanism and the engine structure in Figs. Lt to 8, inclusive, must, at least so far as some of the views are concerned, be considered diagrammatic, and the excuse for this style of illustration in this particular instance is that I am, by adopting this course, better enabled to illustrate the operation and construction of the drill mechanism. It will, for instance, be readily observed that if, in Fig. 4, the engine mechanism and throttle valve mechanism are relatively so arranged l`foi-mance of its function is concerned.

that if the section is taken on the line 4 4, Fig. 9, through the engine and cuts the throttle valve horizontally, as shown in Fig. 4, if a view as Fig. 7 be taken on the line `7-7, Fig. 9, or at right angles to line 4 4, 70 the section would not show the throttle valve in horizontal section as illustrated iny Fig. 7 of the drawing. It is, however, believed that the license which I have assumed in the preparation of this drawing may be excused, 1n 75 view of the great diflculty in clearly illustrat-ing -a structure of this character, where the ports and passages` are so complicated and where their relation to each other in the throttle valve and engine mechanisms is so .o diflicultof comprehension. In other Words,

it is thought that the clearness of illustration which is accomplished by these views will compensate for any inconsistency which a critical examination ofthe'drawing would 86 disclose. The license which I have indulged in is further believed excusable, in view of the fact that the correct illustration of the valve mechanism and its various parts is' accurately shown in Figs. 12 and 16; inclusive. 00

.The same reference characters indicate the same parts in all the views.

Let the numeral 5 designate the drill cylinder; 6 the valve mechanism of theje'ngine; 7 the throttle valve mechanism; and 8 the 05 mechanism of the feed cylinder. l i

The feed cylinder is connected with the engine structure and throttle valve mechanism -by means of rods 9, in the usual manner. Into the rear extremity of the engine adjacent 'the throttlev valve mechanism is inserted a member 1 0 having a centrally located core 12, through whichis formed a central cavity 1B, theyforward portion of which is closed by a plug 14, threaded in the core, as shown at 15. Surrounding this' core is the cylinder valve 16, which for the most part is of the usual construction. The wall of the valve, however, is provided with, a number of separated shallow recesses or 110 cavities 17, which coperate with circumferential grooves 18, 19 and 20, formed in the chester casing 21 of the engine mechanism. By employing these shallow cavities'which are separated bv cvlindrical segments of the structure, the valve is relieved of considerable wear durin the operation of theA machine while the novel' structuredisclosed is equally effective so faras the proper erhis` cylinder vulve is slidably mounted on the.' core 12, and has a range of longitudinal' movement, sufficient for opening and clos- -ing purposes, the forward extremity of the valve when in the closed position being in engagement 4with ashoulder 22, formed in the valve chest and surrounding a forward "G51-With ports 4'6andv 47 formed in the valve open or in its rearward position, as illustrated in Figs. 4 and 5, by the action of the live air on a narrow shoulder 25, in the usual manner. In other words the circular' cavity 26' in the forward portion of the vvalve chest of the engine is always in communication with live4 air or yother motive Huid from the source of supply, the said fluid entering the throttlevalve 27, through a vertically disposed longitudinal .opening 2S, leading upwardly from the base 29 of' the valve block 30. From the opening 28, the motive `fluid passes forwardly through a port 31, formed in the throttle valve, thence. through a port ,32, formed in the Valveblock, thence into a forward cavity 33,

Vand thence in opposite directions through ports-34m passages 35, whose forward ex;- tremities `communicate with the cavityQG. Hence,whether the cylindrical valve is in the open position, as shown in Figs. 4 and 5,

. or in the closed position as shown in Figs.

wardly in the drill cylinder until it engages f theI lstriking pin 37 (see- F ig. l). In the hammer chamber a short distance forward of its rear extremity are formed two ports 88, which communicate with passages 39 extending rearwardly through the drill cylinder and the valve rchest and communicating -at their rear extremities with` a transverse passage 40 formed rlh the base .of thecore member 10,.the passage 40 communicating v'with the central, cavity 13 formed in.` the core, as heretofore explained. Leading from this central cavity are ports 4l formed in the'shell of the core and communicating :ith the space 42, in which the rear enlarged portion 43 l of the cylinder valve travels. These ports 41 are closed when the ,there will vbe no exhaust throughthis path while the valve 16 remains in the open pos1t1 on. As the hammer continues its for- '.ward -movement the motive iuid forward .of.tli e,ha1mner will first exhaust through ports", -2 and. `passages 3, extending rearwardly through the vshell of the cylinder A.nd communicating with lpassages 44 and 45, the passage 44 being iny'communication chest and core member l0, respectively, the line of communication being continued through a passage 48 of the valve block or casing 30, whose rear extremity communicates with the atmosphere. The exhaust the passage 45 passes inwardly through a port 49 to the space 4Q forwardof the rear extremity or face 43 of the cylinder valve, the exhaust from said cavity being through a lport 59., passages 53 and 54 f 'formed in the valve chest, and core member l0, respectively, and thence through a passage 55 formed in the valve block 30, thence into a port 56 formed in the valve piece of the throttle valve mechanism, and thence through a passage 57 formed in the valve block to the atmosphere. The port 5G varies in size whereby the exhaust from the cylinder may be regulated and controlled by the proper adjustment of a valve piece of the throttle valve mechanism to cause the exhaustto harmonize with the introduction of motive fluid to the hammer cylinder. After the hammer passes the ports 2 and closes` the latter, the exhaust from the cylinder forward of the. hammer is continued through aport 58, and. passage 59 formed the wall of the cylinden'and passage 60 ins-the valve chest,port G1 which communi- Cates with aA circumferential groove 19 formed in the valve-chest adjacent the cylin der valve and in communication with the cavities 1i' of the last-named valve. From this" groove exhaust continues rearwardly thro-ugh ,recesses 17 of the valve 16 lto the l space 42 forward of the shoulder 5l of the valve 1G. F rom this space exhaust contijnues tothe atmosphere through a4 port 7 5 and passagesy 76, 77 and 78 on one side of the machine; while on the opposite side the exhaust"continues from the said space 42 u forward of the/'shoulder 51 of the cylinder valve, through the ports 52, 53 and 54, the" passage 55, the graduated port 56, and the passage 57 .to the/atmosphere.

Just before the hammer engages the striking pin aport 65 is uncovered in the cylinl der and the lived, motive iuid acting on the passages QG and (57 to a port (38 communi-- cating with the extreme rear portion of the cavity'42 in the .rear of the enlarged area 43 of the cylinder valve and this live motive Huid acting on this enlarged area will serve to drive the valve forwardly since the pressure on this enlarged area in the forward direction is suiiicient to overcome the other tendency, namely, the action of the live air on the small end of valve. The valve then moves to the closed position illustrated in Figs. 6, 7, and 8. The live motive fluid is then cut off from the rear extremity of the hammer chamber and motive fluid from the feed cylinder 8 is introduced to the hammer chamber forward of the hammer by isa way of the following route, namely, from i the feed bar casing through an angular port cylindrical groove 19; thence through ras` sages 61, 60, 59 and portv58, heretofore described, into the hammer ylinder forward of the hammer. The latter then begins its rearward travel and the exhaust from the hammer chamber in the rear of the hammer begins through the ports 38, the passages 39- and 40, tothe cavity 13; thence through the'ports 41 to the space 43`in the rear of the cylinder valve, where the exhaust serves to hold the valve in the closed position, the

esxape of the exhaust, however, in a restricted manner being continued through a port 75, passages 76 and 77 formed in the valve chest, and core member and thence through the passage 7 8 to the atmosphere. The exhaust also passes from the space 43 in therear of the cylinder valve, through the ports 52, 53 and 54, the passage 55, the port 56 of the throttle valve piece and the passage 57 to the atmosphere.

VThe exhaust as just explained continues until the hammer closes the port 38, after which the air cushionsl l'ietween the hammer and the rear extremity of its chamber and acts on the forward extremity of the cylinder valve and in` conjunction with the action of'the live motive fluid or the small shoulder 25 serves to move t e cylinder valve rearwardly tothe open position. As soon as the. ports 3S are covered, the ports. 2 are opened forward of the hammer and the exhaust from. the hammer chamber in front ol the hitter commences through the passages 3, and continues on` one side of the machine through the ports 4G and 47 and the passage 48 to the atmosphere; while on the opposite side the exhaust from the hamm'er chamber in front of the hammer enters the space 42 and acts'upon the shoulder 51, which also aids in impartingr the opening movement to the cylinder valve. The exheretofore explained.

4that a the hammer inactive, thevfeed bar cylinder 8 isiin communication with the atmosphere through a cavity 79 in the throttle valve I block or casing, a port 80, 'a small recess 81 vin the throttle valve, a passage 82 in the.

throttle valve and a passage 83 in the lthrottle valve block or casing. This condi- 1 tion allows the air in the feed bar casing to exhaust to the atmosphere as there is no necessity for holding the drill against thev rock when not in use. vWhen this condition exists thethrottle -.valve piece 27l is turned considerably farther in the directimfof the arrow, in Fig. 15, than is illustrated, or so f port or passage 84 in the throttle valve will extend beyond the port in the direction of the valvesrotary movement, indicated by the arrow in said figure.

Now, when it is desired to set the drill against the rock'the throttle valve piece will be rotated in the direction opposite the said arrow, first to turn the port 84 into com.

munication with the port 80, .in which event the motive fluid which enters through the passage 28 of the throttle valve piece will pass to the feed bar casing and supply the necessary pressure therein to hold the drill against the rock. At this time, however;

the hammer is in a conditionof rest as the live motive fluid has not been introduced toe.,

the hammer chamber. start the hammer, the throttle valve piece is turned farther in the direction opposite that of the arrow, or until theport 31 in th' throttle valve piece ,is brought into communication with the port 32 ofthe throttlel live motive fluid passesvfr the source of Asupply to the hamner chamber in the rear of the latter to dri\'e the hammer forwardly'. as heretofore explained. f

lVhen the throttle valve 'piece is adjusted to deliver the maximum ply ofmotive fluid to the engine and thie,v Aeed bar casing, the exhaust port 56 in lili; throttle valve piece occupies approximafely the position illustrated in Figs. 5 and 1,6. rotary` action of this valvie` piece,until the exhaust port occupies slh position, the

opening movement of the. 7port 31 in the- During the' the opening of Then, in order to valve block or casing, in hich` event the-,-

it is desiredl to increase theexhaust through.

the variable port'G, the rotary' action of the throttlevalve continued in the direction A opposite, 'the arrow,L in Fig. 15, and this vportion/of this port is brought vwith rthe last-named passage.' .During this movement of the throttle. valve, the rearmovement will increase the exhaustthrough theport 5,6 inasmuch as this action of the valve? piece increases thedepthfof the portion of the port 'l'lwhich is brought into register with the passage- 7 until the deepest into register valve will open before the hammer reaches it should remain open or during the forward the rear extremity of itschamberfand when the exhaust through the portv 56 is` at itsA maximum the 'strokes of the hammer will vbe very shoitv and exceedingly rapid. Atrthe same time the portsl and 90 are so constructed that the adjustment of thethrottl'e valve for the purpose of increasing the ex haust through the port 56 does not vary the 'volume of motive liuid which passes to the engine sind the feedbar cylinder. rFhis is a very important feature of my. improve ment and enables me to accomplish an'object,

not heretofore attainable in 'previous constructions, so far as l amaware.

in further explanation of the construcf;y tion, it may be stated that a. relatively small w port 91 is in communication with the space or cavity 42. rhis port communicates with av small passage 92 leading to the atmospliers and permits the escape of any motive y fluid that may leak into the cavity 43 in the rear of the cylindervalve when the lat` ter is inthe open position and' obviates anytendency to close the cylinder valve whentravel of the hammer in the'cyli'nder.

In further explanation of the construction, it may be stated that a small port 4 (see Fig. 4) is for the purpose of compensating for uany slightlv irregularity,-should it occur-,

70. lt is of importance only as, on account of its relatively small cross-v sectional area, it does not interfere with the action of the mechanism of the 'machine as described, when the hammer 1s moving at medium or maxlmum speed.

Still another yfeature consists in' forming an interior annular groove 101 at the forf ward' extremity of lthe cylinder valve 1 6,

which communicates at its forward extremity when the cylinder valve is open, with the cavity 26, and at its opposite extremity with a port 100 communicating With Consequently, the last-named as regards the simultaneous opening ya passage 102 which leads to they central cavity 13. The said groove 101, the port 100 and the passage 102 are relatively small, their only object being to allow enough mot-ive fluid'to pass during the first part of the-forward movement of the hammer 36, i to ill the passages 39 and 40 by the'time the ports 38 are uncovered, thus obviating any dinnnution of the motive fluid pressure acting on the hammer, which diminution of preure would result by the filling ofthe said passages with the motive fluid from behind the hammer as soon as the ports 38 Wereuncovered, if the said passages had not already been lled.

`Iclaimv 1. In mechanism of the character described,'they combination with a motor inclutling a cylinder and a hammer mounted gto-'reciprocate therein, of a valve for varying .the 'supplyv of motive fluid to 4the motor, saidv valve bein also equipped to gradually and continuous y increase the exhaust from the motor as' the valve Ais moved from closed to.v fully open position.4

2. In mechanismof the class described,

the combination of 'a motor and feed bar casing, of' a Vvalve interposed between the motor and said fcasing and adjustable to control'the passage of motive fluid to both, the saidy valve being also' equipped to gradually and continubusly increase the exhaust from the motor as the valve is moved from the closed to the 'fully open position.

3. The combination with a motor, including a cylinder and a hammer mounted to re-` ciprocate4 t ereinl and a feed bar casing, of

a valve int rpcsed between the motorl and said .casing an passage of motive liuid to both the motor and casing,l thelsaid valve being also equipped to gradually and continuously increase the exhaust from the motor as the valve is sition.

4. vThe combination with a motor and feed barY casing, of a valve interposed between the motor and said casing to control the passage of motive fluid to both, and equipped with a port arranged to yary the exhaust from the motor while the supply to bothmotor and feed bar casing remains uniform. i l

5. Thef combination. with a motor and feed'barnasing, of a valve interposed between th said motor and casing to control the passageof motive fluid to both, and equipped with a port arranged. to increase the exhaust increased to both casingand motor until the moved from the closed to the fully open poadjustable to controlthe *i from the motor as the supply is n is reached and without varying the supply to either the motor or casing.

7. The combination with a cylinder and a piston mounted to reciprocate therein, a movable valve for controllingthe supply of motive fluid to and its exhaust from the cylinder, the valve ha vine; ditferential pressure areas and the pressure ol the exhaust 0n the larger area serving to hold the valve closed during the rearward movement of the hammer, and a second valve having a port ai ranged in the path of such exhaust and adjustable to vary the length of time during which the pressure of the exhaust on the larger area of the first-named valve is exerted for the purpose set forth.

S. rIlle combination with a cylinder, a hammer mounted to reciprocate therein and a movable valve for controlling the supply of motive fluid to and its exhaust from the cylinder, the valve having differential pressure areas and the pressure 'ot' the exhaust y on the larger area serving to hold the valve closed during the rearward movement of the hammer, against the tendency of the live motive fluid on the lesser area to open the said valve, and a second valve lhaving ports through which the supply and exhaust to and from.' the cylinder pass, the second valve being;v adjustable to 'increase both the supply and exhaust until the maximum supply is reached, and to furtherincrease the exhaust without tfhaluginpthe supply, until a predetermined maximum cxhaust is attained.

l). The combination with a cylinder, a hammer mounted to reciprocate therein and a movable valve `for controlling the supply of motive fluid to and its exhaust from the cylinder, the valve having` ditlerential pressure areas and the pressure of the exhaust on lthe larger area serving to hold the valve closed during the rearward movement of the hammer, and a second valve having ports through which the supply and exhaust to and from the cylinder pass, the second valve being adjustable to increase both the supply and exhaust until the maximum supply is reached and to further vary the exhaust within a pre-determined range after the' maximum supply limit is attained, without varying the supply for thev purpose set forth.

10. In a tool of the class described, the

combination with a motor including a cylinder and a motive Huid actuated hammer iounted to reciprocate therein, a feed cylinder for holding the motor to its work, the motor having a movable valve Ator regulating; the supply' and exhaust to and from. the cylinder, the said valve having,r dil'lerential pressure areas upon the larger of which the exhaust acts to hold the valve lclosed during' the return of thehammer, and a second val ve interposed between the motor and cylinder and having;` ports through which the supply to the `motor and t'eed cylinder passes and a port through which the exhaust from the motor cylinder passes, che second valve being adjustable to control the supply to both cylinders and the exhaust from the motor cylinder and to vary the lasts named exhaust. Within a Ipre-determined range Without varying the supply to the nio-I tor or feed cylinder.

11.x .Tn a rock drill, the combination of a motor and feed cylinder, 'the motor including a cylinder and a hammer mounted to reciprocate therein, the motor having a valve movably mounted to regulate the supply and exhaust of the motive luid to and from the hammer cylinder, and a second valve in.M terposed between the motor and feed cylinder and having; ports arranged. for the passage of the motive fluid supply directly from its source lto both cylinders, said drill hav-- mg a passage for the transmission ol me tive fluid from the feed cylinder to the motor cylinder for the return of the han/nner, said passage being larger than the said port leading to the feed cylinder and said passage being arranged toibe controlled by the motor valve.

12. In apparatus of the class describek the combination with a motor includi cylinder, a hammer mounted to reciprmate therein and a valve movably mounted to regulate the supply and exhaust of motive fluid to and from the cylinder, and meaf f r subjecting the valve to a portion of the haust from the cylinder forward of. the hammer shortly before the hammer has reached its limit of rearward travel to aid in openii the said valve.

13. In an apparatus of the class described, the combination of a motor, a feed cylinder, a movable piston therein and mechanism. whereby a lower pressure prevails in feed cylinder when the hammer is moving` rearwardly than when the hammer is moving forwardly or toward the striking `pin. z

14. In a Huid driven rock drill, a slide. valve having surfaces of different areas at its ends, means for subjecting the surface of greater area to the pressure of the exhf ing `fluid while the valve is in one po` and means for regulating the f exhaust.

mii

Valve having surfaces of different areas at its ends, said smaller surface being constantly under the influence of line pressure, means for subjecting the said larger surface to the pressure ot the exhausting Huid, while the valve is in one position, and means for regulating the speed of the exhaust.

16. In apparatus of the class described, the combination with a motor including a cylinder, a hammer mounted to reciprocate therein, and a `valve movably mounted to regulate the supply of motive fluid to the cylinder, said cylinder havingan exhaust passage arranged to be uncovered by the hammer when near its rear limit of movement only, said valve having a projection and said cylinder having a port adapted to maintain communication between the said passage and one side ot' said projection.

17. In a rock drill, a feed cylinder, a. hammer cylinder, a motor valve interposed between said cylinders, said drill having passages for feeding motive f luid continuously to said valve, a feed cylinder and a passage leading from the feed cylinder to the forward end of the hammer cylinder, said last named passagebeing arranged toV be controlled by the movement of the motor-valve.

18. In a rock drill, a feed cylinder, a harnmer cylinder, a motor valve interposed between said cylinders, said drill having passages for feeding motive fluid continuously .to said valve, a feed cylinder and a passage leading from the feed cylinder to thefor ward end of the hammer cylinder, said last named passage being larger than the feed passage to the feed cylinder and being ar' ranged to be controlled by the movement of the motor valve.

19. In a rock drill, a hammer, a hammer cylinder, a motor valve for controlling the flow of motive fluid to'said cylinder, the

latter having an exhaust passage extending through and controlled by said valve, and means for regulating the s1ze ot said pas- Sage at one polnt.

Images