US1581668A - Rock drill - Google Patents

Description

April 0 1926.

L. c. BAYLES ROCK DRILL Filed Oct. 9, 1924 E. i m

Patented Apr. 20, 1926.

j UNITED STATES 1,581,668 PATENT OFFICE. r

LEWIS G. BAYLES, OI EASTON, PENNSYLVANIA, ASSIGNOR TO INGERSOLLBAND' COM-o PANY, 0J3 JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY. I

ROCK DRILL.

Application filed October a, 1924. Serial No. 742,615,

To all whom it may concern:

Be it known that I, Lnwrs O BAYLES, a.

citizen of the United States, and a resident of-i sEaston, county. of Northampton, State of Pennsylvania, have invented a certain Rock Drill, ofwhich the following is a specification, accompanied by drawings.

This invention relates to pneumatic drills;

In operating certain types-of pneumatic "drills, such as for instance, those that are a supported by hand, it is desirable that the operator-pressagainst the tool with considerable force in order that the drill may opi erate efficiently. Thisis particularly true ofing down hard on such tools with the result that the machine does not produce the desired result-s. It has been proposed heretofore to construct such tools so that they stop operating unless theoperator bears down on the tool. This has been accomplished by constructing the cylinder sothat the ham mer piston reciprocating therein will overruns the air admlsslon port at thevforward end of the cylinder unless suflicient weight is applied 'at'the handle end of the tool to keep the steel or anvil block shoved well up into the pathofthe piston. In this case the hammer piston stops, being'beyond the ad mission port so as to close it oif. This arrangement is not always effectual for the reason that compression forms on the forward blow of the hammer and causes it to bounce back and reopen theadmission port with the result that the machine continues to operate. V i

It is anobject of this invention to relieve such compression'and leakage of live air in the front end of the cylinder thereby pre venting the hammer piston from returning when insufiicient pressure is applied to the handle end of the drill.

Figure l is alongitudinal sectional view of a rock drill adapted to break concrete and shows the hammer piston n position cover ing the admission port at. the front end to prevent operation of the tool, 7

Figure 2 is a longitudinal section of the Other objects and advantages will be in rock drill shownin Figure 1 in vwhich the drill is shown pushed forward so that the piston cannot advance to cover the admis sion port, and a r i I Figure 3 is a cross sectional view taken along the line v 'lhedrawing illustrates a drill in theform of a concrete breakerwhich is provided with" a sharp pointed steel A for splitting ofi con crete in chunks and is a substitute for the old fashioned method of using a hand ham-Q;

mer and, chisel. The, drill for operating against thesteel A may be of anyisuitable type,that shownin the drawing being of the well known semi-valvelesstyPe. I

The drill comprises a cylinder B within which there isprovideda reciprocating pis ton iG adapted to strike against an anvil block 1) supported in the anvil block seat E 1 and in contact with the drill steelfA sup.-

ported by a front head F. The anvil block 1) is arranged to move forwardly or back in the seat E so as to provide a certain freedom of movement desirable to permit the steel A to move forwardly and backv with respect to thecylinderB. p i

As these tools have usually been con structed, it is necessary to press with con siderable force on a handle G provided at the, rear'end ofthe drill in order to keep the anvil block" D push-edowell up 'into the cylinder B, for if the anvil block D- is perk" mitted to slide forwardly while the piston O is reciprocating, the latter will either strike against" the anvil block seat E or will strike the anvil block when is in contact with the front head F as shown in Figure 1 and the force-of the hannnerblows is taken signed to withstand shocks of this sort and after a short time the drill is; ruined. It has heretofore been proposed to avoid this difficulty by locating the admission port H so that the piston O overruns it andcuts olf the/supply of motive fluidto the front end of the oylinder'B when the anvil block D 7 is permitted to advance in the seat E beyond a certain limit. The piston C is then sup posed to stop operating although the throttle valve J may still be opened because substantially no motive fluid is admitted inthe cylinder B vahead ofthe back. a

One dilficulty with this arrangement as" piston C todrive it 7 C for the reason that the space behindthe heretofore proposed is that when the piston is exposed to atmospheric pressure on its rearward face and to compression on its for- T )lock 1) piston isin communication with atmosphere while the space ahead of the piston is not; Practically full live air pressure slowly builds up at the front of the piston C which eventually drives the piston back to uncover the port H and therefore to recommence its reciprocation. If the drill is com paratively new the same result obtains for the reasonthat thecompression pressure, is relatively high ahead of the pistonrbecanse ofthe tight fit between it andthe cylinder B; The piston C bounces back and reopens the admission port H. This condition is probably worse than when the drill is old and the cylinder walls and piston become somewhat worn because" the reciprocation due to high compression is much more rapid.

By this invention the return of the pis' ton C after passing tlieport H and closing it as is prevented by means to-"eliminate compression at this point, including longitudinal grooves K in the cylinder walls, extending from the forward end ofithecyliin der B beyond the inlet port Hywhich are arranged to connect th spaces on opposite sides 'ofthe piston only when the piston is permitted to advance to "cover the inlet' port The grooves K extend fronithe extreme endjof the cylinder B to a'point'ilocated at r the rear end of the head of the piston G when the front edge of the piston is just covering the port H. Therefore, when the;

drill is operating normally, the" grooves Kf are inoperative, they do not relieve the compression at thefrontend' of the cylinder nor do tl1ey ,in'a1'1y way effect the operation of the tool. However when ithepressur'e I on the handle G is insuflicient to hold the drill properly down against the steel the anvil block D advances permitting the piston C tolengthen its stroke beyond the port H, and therefore, to ceasepperating, the compression ahead of the piston being relieved by leaking out through the grooves K to atmosphere through the main air exhaustL. Nor can the piston C be caused to start again by air leaking down past the piston from the port because such leakage'air also finds its way to atmosphere by' way of the gro'oves During normal, operation the piston 0 advances no farther than approximately half way covering the port H as shown in Figure 2fland the anvil block D is seated in the anvil block. seat E. However, as the pres- :ure is relieved on the handle G the anvil is pushed forwardly with respect to the seat- E and the return of the piston C on the back stroke is ,feebler since the admission of live air-through the port H is somewhat cut off.

Although the main objectof stopping the 7 operation of the piston C as above described is to prevent the piston from breaking the front parts of the drill, in addition the arrangement insures that the operator will press sufliciently hard against the handle G of the'tool to keep the steel Apressed hard against the work, and thereforejto prevent careless operation on the part of the operator. -Poor operators are apt to allow their tools to keep on operatingwith the least possible exertion on their part with the result that very little workis doneby'the tool.

\Vith the above described arrange 'ment' as soon as the operator relaxes the tool stops operating automatically.

Any suitable piston and valve action may be employed for the drill.

That shown in the drawing is ofthesemi-valvelesstype in'-- which the piston C is provided with the rearward-extension 0 working in a small bore P of the cylind-er'B and subjected to constant pressure admitted through the pas sage Q in the back head R. The control of the air for operating the piston is'w'ell' known, having been describedgin patent to L12. Bayles, No.1,096,987, issued May-19,

The throttle valve J is controlled by means of a lever S arranged to press against the stem of the valve J and adapted to be manually controlled by a lever T working in'a slot U in thehandle G. The steel Ais held within the'front head F by means of a suitable steel retainer V cooperating with I the usual form ofcollar shank of the steel. 1

I claim:

normally adapted to extend a substantial distance into said cylinder, a hammer piston in thecylinder for delivering blows-to the upset I on the i L 1. A rock drill comprising a cylinder havv ing inlet and exhaust ports, an anvil block der being provided with grooves to bypass leakage air from the front end of the cylinder to atmosphere when the inlet port is closed by the piston in order to prevent the piston from rebounding uponthe' completion of its forward stroke due to an air cushion built up in the forward end of the cylinder. 7

2. A rock drillcomprising a cylinder hav-:

ing inlet and exhaust ports, an anvil block normally adapted to "extend substantial distance into said cylmder, a hammer lpiston in the cylinder for delivering blows to forwardly and the port is covered by the the anvil block and adapted to close the inpiston in order to prevent the piston from 1 let port when the anvil is moved forwardly rebounding upon the completion of its forfrom its normal position, said cylinder hav- Ward stroke due to an air cushion built up ing longitudinal grooves on opposite sides of in the forward end of the cylinder.

the inlet port to permit the escape of leakt In testimony whereof I have signed this age air from the front end of the cylinder specification.

to atmosphere When the anvil block is moved LEWIS C. BAYLES.

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