US3811515A

US3811515A - Percussive drilling machine

Info

Publication number: US3811515A
Application number: US00323405A
Authority: US
Inventors: A Mishkin; A Bessarab; A Bazhal
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-01-15
Filing date: 1973-01-15
Publication date: 1974-05-21
Anticipated expiration: 1991-05-21

Abstract

A machine in which of an air-operated striking rearhead has a body accommodating a hammer piston reciprocating under the action of compressed air so as to deliver blows at a drill steel located at the front end of the machine, and a reversible rotary impulse fronthead has a body accommodating two rotatable and axially movable annular pistons provided with impact projections and indentations formed between the projections, with the pistons being coupled by an interengagement of the respective projections and indentations thereof, the projections and walls of the fronthead body forming work and idle stroke air chambers which are periodically placed in communication via passages with a source of compressed air and the atmosphere, and the projections of one of the annular pistons performing, under the action of air pressure, high-frequency reciprocatory angular oscillations so as to deliver blows with their impact projections at the respective projections of the other annular piston. The rotary impulse fronthead has a ratchet mechanism which ensures the rotation of one of the annular pistons and the drill steel only in one direction. In addition, the rotary fronthead is provided with means adapted to switch over the ratchet mechanism from one rotational direction to the other (from lefthand rotation to righthand rotation, and vice versa) so as to enable right- and lefthand rotation of the drill steel.

Description

United States Paten [191 Bazhal et a1.

[ PERCUSSIVE DRILLING MACHINE [76] Inventors: Anatoly Ignatievich Bazhal, ultisa Franko, 30, kv. 42; Alexandr llich Mishkin, ulitsa G agarina 8, kv. l8; Anatoly Antonovich Bessarab, ulitsa Shevchenko 8, kv: 24, all of Zheltye Vody Dnepropetrovskoi oblasti, USSR.

22] Filed: Jan. 15, 1973 21 Appl. N0.;323,40s

[52] US. Cl 173/93, 91/120, 173/108, 418/33 [51] Int. Cl B25d 15/00 [58] Field of Search l73/9393.7, .173/105-109, 9497;-4l8/33 [56] References Cited UN1TED STATES PATENTS 2,457,969 l/l949 Anderson 173/107 1,160,648 11/1915 Peck 173/108 3,552,363 1/1971 Funakoshi 418/33 Primary Examiner-Henry C. Sutherland Assistant Examiner-William F. Pate, lll Attorney, Agent, or Firm--Holman & Stern [57] I ABSTRACT A seaside nearer; of an snapsrma striking rear- May 21, 1974 head has a body accommodating a hammer piston reciprocating under the action of compressed air so as to deliver blows at a drill steel located at the front end of the machine, and a reversible rotary impulse front:

head has a body accommodating two rotatable and axially movable annular pistons provided with impact projections and indentations formed betweenT'Ie projections, with the pistons being coupled by an interengagement of the respective projections and indentations thereof, the projections and Walls of the fronthead body forming work and idle stroke air chambers which are periodically placed in communication via passages with a source of compressed air and the atmosphere, and the projections of one of the annular pistons performing, under the action of air pressure, high-frequency reciprocatory angular oscillations so as to deliver blows with their impact projections at the respective projections of the other annular piston. The rotary impulse fronthead has a ratchet mechanism which ensures the rotation of one of the annular pistons and the drill steel only in one direction. In addition, the rotary fronthead is provided with means adapted to switch over the ratchet mechanism from one rotational direction to Y the other (from lefthand rotation to righthand rotation, and vice versa) so as to enable right and lefthand rotation of the drill steel.

5 Claims, 15 Drawing Figures PATENTEDHAYZI m4 v 3,811,515

sum 3 or s w a, 4am.

s h I minimum 21 I974 8 l 1. 515

saw u or 6 v PERCUSSIVE DRILLING MACHINE BACKGROUND OF THE INVENTION a percussive drilling machine with independent nonl reversible rotation of a drill steel comprising an airoperated striking rearhead consisting of a body with a cylindrical bore which accommodates an airdistribution means and a hammer piston reciprocating under the action of compressed air so as to deliver, at the end of the work stroke, a blow to a drill steel located in the front part of the drilling machine, and a rotary impulse fronthead located in the front part of the drilling machine arrd comprising a body with a cylindrical bore which accommodates, located in the rear part thereof,

an annular striking piston having annular projections, a rotary anvil having cooperative projections and indentations so arranged that their side surfaces and walls of said fronthead body define, during each work and idle stroke, air chambers periodically placed in communication via passages with a source of compressed air or atmosphere, with the projections of the annular striking piston performing under air. pressure high-frequency reciprocatory angularj oscillations so as to deliver, at the end of the work stroke, a blow with hammer projections at the re-' spective projections ofv the rotary anvil, thereby rotating the rotary anvil connected to the drill steel; v ia intermediate parts, and a ratchet mechanism arranged in the front part of the fronthead body and comprising a ratchet wheel integral with the fronthead body and pawls mounted on the end face of the rotary anvil facing the drill steel. In the prior art drilling machine, the ratchet pawls are mounted in such a manner as to enable the rotation of the rotary anvil only in one direction, thereby preventing the rotation of the anvil, which is connected to the drill steel, in the opposite direction under the action of the elastic rebound reactive force of the drilling string being twisted due to the engagement with the rock. I

The prior art drilling machine permits the rotation,-' of the spindle with the drill steel only in one direction; which does not allow it'to be used in drilling deep? holes since it cannot provide for mechanization of f the process of disassembling the drilling string.

Furthermore, in the prior art drilling machine the degree of accuracy in fitting frictional end faces of the annular pistons as well as the size of gaps therebetween,

are determined by their initial mechanical adjustment only. However, since during the operation of the drilling machine under mining conditions, these surfaces are subject tointensive wear, and this results in the expansion of axial gaps, changes in theoperational.

parameters of the impulse rotary fronthead and in an excessive air consumption.

O BIE C TS AND SUMMARY OF THE INVENTION object of the invention ibiibvide a percussive steel, but also offers an opportunity of reversing the rotation of the drill steel.

Another object of the invention is to provide a percussive drilling "rarest as having a morfia'abie 5 structure.

Still another object of the invention is to provide a percussive drilling machine which has minimum axial gaps between the end faces of the annular pistons,

with the predetermined size of the gaps being automatically maintained constant.

These and other'objects of the invention are accomplished by the provision of a percussive drilling machine with independent rotation of a drill steel comprising an air-operated striking rearhead define by of a body with a cylindrical bore which accommodates an air-distribution arrangement and a hammer piston reciprocating under the actiongf compressed air so as to deliver, at the end of the work stroke, a blow to the drill steel disposed in the front part of the drilling machine, and a rotary impulse fronthead located at the front end of the drilling machine and comprising a body with a cylindrical bore which accommodates rotatably mounted annular pistons having imp ac tprojections and indentations formedbetween the projectionswith the annular pistons being coupled by an interengagement of the respective projections and indentations thereof so that the side surfaces of the projections and walls of the fronthead body define, during each work and idle stroke, air chambers which are periodically communication with a source of compressed air or atmosphere via passages, and the projections of one annular "piston performing under the action of air pressure, high-frequencyreciprocatory angular oscillations to deliver blows with the impact projections at the respective projections of the other annular piston at the end of the work stroke so as to rotate the drill steel via intermediate parts, and a ratchet mechanism arranged at thefront end of said fronthead body and comprising a ratchet wheel integral with the housing of the ratchet mechanism, said housing accommodating asleeve' provided with movable spring loaded pawls mounted therein, said pwals engaging the teeth of the ratchet wheel (housing), with the ratchet mechanism ensuring the rotation of one of the annular pistons and the drill steel in only one I direction. In accordance with the invention, the

annular pistons are arranged in a sleeve having a cylindrical projection located on the side opposite to the drill steel, the end face of said projection, which faces the annular piston, being provided with linkage members for cooperation with said piston so as to ensure their combined movement in the inner cavity of the fronthead body with the formation of an additional air chamber'between the end face of the annular piston, which is arranged on the side opposite to the drill steel, and the end face of the cy lindrical pr ojection o f the sleeve, and another additional chamber between the end face of the annular piston, which faces the drill steel, and the end face of a sleeve having pawls, said end face also being provided with linkage members for cooperation with the annular piston, one of the additional chambers communicating with a source of compressed air so as to cause combined axial movement of the annular pistons towards the opposite additional chamber under air pressure,'the end faces of the pistons, which define the walls of the additional chambers, being provided with linkage ratchet mechanism or to the sleeve having the cylindrical projection, said sleeve being permanently linked up with the sleeve of the ratchet mechanism and with the spindle of the drill steel by means of a drive sleeve,

while the annular saiaaraemg'uie 'dfillstel and the ratchet pawls, which are divided into the pawls for lefthand rotation and the pawls for righthand rotation, are providedwith linkage members for cooperation therebetween, switching members also being provided for these pawls, with said switching members and said linkage members causing simultaneous movement and switching of the left and righthand rotation pawls during the axial movement of the annular pistons, whereby the direction of rotation of the sleeve of the ratchet mechanism is changed over when it is connected by means of the linkage members to one of the annular pistons where this piston, which rotates in one direction, is blocked, and the other piston is placed in operation, thereby reversing the rotation of the drive sleeve and the spindle of the drill steel. 7 g 7 lt is advantageous that the linkage members providing for cooperation between the annular pistons and the cylindrical projection of the sleeve supporting them, as well as the linkage members of the sleeve having the pawls should be fashioned as axial clutch cams which secure engagement of the annular pistons during the transmission of powerful high-frequency torsional impact pulses to the drill steel.

It is also advantageous that the linkage members for cpgperation of the ratchet pawls with an annular piston be defined on these pawls in the form of cylindrical rods having annular projections, while the linkage members of the annular piston facing the drill steel be defined as an annular groove on the end face of this piston, which faces the drill steel, with said groove permanently receiving the annular projections of said rods and being adapted to cause, during the movement of the annular pistons, the displacement of the pawls, the length of the rods of the pawls for lefthand and righthand rotation being different by the amount of this dis placement whichres ulfs in simultaneous switching of the pawls for both lefthand and righthand rotation during the reversing of the.

rotation and the switching members for the pawls comprise the internal conical chamfers provided in the cylindrical projection of the end face of the fronthead body facing the drill steel, and in the cylindrical projection of an intermediate disc mounted in the end face recess of the housing of the ratchet'rnechanism, said chamfers being extended by cylindrical bores of a diameter which is smaller than the inside diameter of the ratchet wheel (housing), so that during the combined movement of the ratchet pawls and the annular pistons towards or away from the drill steel, the working edges of the pawls slide over the conical surface of these chamfers, whereby the pawls both for lefthand and righthand rotation are simultaneously rotated in the sockets of the sleeve of the ratchet mechanism, the pa\ v ls of one rotational directionbeing disengaged from the teeth of the ratch et wheel and being received in the I cylindrical bores which represent the extensions of the conical chamfers, while the pawls of the other rotational direction are caused to engage with the teeth of the ratchet wheel, thereby reversing the rotation.

This makes it possible to reverse the rotation of the drive sleeve with the spindle and the drill steel at any position of the annular pistons by means of a reliable and simple arrangement of minimum size. 4

It is also advantageous that the drilling machine, be provided with passages adapted to periodically place the work and idle stroke air chambers in communication with a source of compressed air and atmosphere, said passages comprising an annular inlet passage located on the outside surface of the annular piston, which is arranged on the side opposite to the drill steel, and in constant communication with a source of compressed air, and an annular exhaust passage located on the outside surface of the annular piston, which faces the drill steel, and in constant communication with the atmosphere, said passages being in constant communication with longitudinal inlet and exhaust passages respectively which are provided in the projections of the annular pistons, with said longitudinal inlet and exhaust passages terminating on the end faces of the projections of the annular pistons which are constantly in contact with the end faces of the bottom of the indentations and are communicated with concentric inlet and exhaust passages, which are locatedton the end faces of these indentations and terminate in the work and idle stroke chambers, the longitudinal inlet passages being periodically communicated with the concentric inlet passages terminating in the identical work and idle stroke chambers during the reciprocatory angular oscillations of the projections of the annular piston, which at the same time functions as a hammer, while the longitudinal exhaust passages beir lg i n constant communication with the concentric exhaust passages, with the concentric inlet and exhaust passages being defined in such a manner as to communicate the inlet and exhaust passages with the work and idle stroke chambers while the length of the concentrical inlet passages terminating in the identical chambers should be selected proceeding from the condition:

L1/L2 1, which provides for the formation of an air cushion only in the chambers of the work stroke at any rotational direction, wherein L, is angular length of the concentrical inlet passage terminating in the work stroke chamber;

L is angular length of the concentrical inlet passage terminating in the idle stroke chamber. i V, This ensures stable starting and operating conditions of the impulse rotary frontheadin any intermediate position of the annular pistons and within either rotational direction.

It is furthermore advantageous that the ratio between the areas of the end faces of each annular piston subjected to the action of compressed air on the side of the additional air chambers and the work and idle stroke chambers fulfil the following condition:

7.5 .45 211W. t M

which ensures a constant pressurei for urging the annular pistons against each other and for reducing compressed air leakage from the work and idle stroke chambers, wherein F, is area of the end face opposite to the impact projections of one of the annular pistons;

F is area of the end faces of the bottom of the indentations of one of the annular pistons on the side of reversible rotation of the drill steel shown in FIGS. 2 the impact projections in the work or idle stroke 'through 9 comprises an air-operated striking rearhead chambers. g V j 6 and a rotary impulse fronthead 7. This Provides for constant minimum p 5 The air-operated striking rearhead 6 has a body 8 tween the end faces of the annular pistons, which are rovided with a V cylindrical bore accommodafiigan in frictional engagement therebetween, to reduce comair-distribution arrangement (the air-distribution arpressed air leakage, and thereby increase the effirangement and an on/off arrangement are not shown ciency of operation of the impulse rotary fronthead of i the drawihgs and may be of any appropriate eFlIilEE lhEeE e o ..M .,W, 10 type), and a movable hammer piston 9. The body 8 is According to the m e there 13 Provided a P operably coupled with the rotary impulse fronthead cussive drilling machine with independent reversible by way of an adapter Sleeve 10.

rotation of a drill steel which has a reversible rotary T reversible impulse rotary fromhead 7 has.a body frohtheafi with e e of Constant minimum axial P 11 provided with a cylindrical bore accommodating automaheaiiy maintained w e Compressed F? the rotatably mounted axially movable annular leakage s eliminated and the efficiency of the

machine pistons

12 and 13 fitting into each other, and a Sleeve is increased. In addition, the machine is compact and 14 provided with a Cylindrical projection 15 (on the a e ih ep side opposite to the drill steel 2), with the sleeve being BR F DESCRIPTION OF THE rotatably mounted and accommodating the annular D DRAWINGS a'igisn' i'zafifi'si" The invention Wlll now be described in detail with The body 11 of the fromhead 7 p i e a cylindril' i t0 the p i embocjimeht thefeof cal tubular member with a sleeve 16 press fitted hated the accqmpanymg drawlhgi m which: thereon, so that their outside and inside surfaces re-' FIG- 1 schem y shows drilling rig e f spectively define passages therebetween. An inlet pasdrill deep holes underground using a percussive dl'llllflgl sage 17 communicates with a Source of compressed machine according s i visa'pi aisaaran'ahaust atsagersraaiaaaeate 2. a longitudinal sequonal l of f with the atmosphere via radial passages 20. The sive drilling machine according to t e invention e toutside Surface of the body 11, the Sleeve 16, is also hand rotation) provided with an inlet pipe 21 for lefthand rotatlon FIG. 3 a, b is a cross sectional view taken along the which is adapted to establish communication be L LI I II in F IG 2 the View looking in the direc' tween a source of compressed air via an inlet poit 22 ilgnrofgle ZP -T-- and the internal cavity of the body ll, which defines i aEi P i. i ii %g a reverse chamber 23 located between the end faces IV"IV m vlew ookmg m t 6 of the cylindrical projection 15 and the annular piston tion of th e arrows;

FIG. 5 a, b is a cross sectional view taken along the 12 on the'slda Opposite to the u 2.

---- The

annular pistons

12 and 13, which are accommogfi lx f 2 the vlew lookmg m the dlrectlon; idated in the cylindrical bore of the body 11, comprise FIG. 6 is a longitudinal sectional view of the drilling islfieves having annular Impact Projectlons 25 t th hth d t f (FIGS. 3, a, b and 4, a, b). The impact pro ections 24 sjg accor mg 0 e an to and 25 of the

annular pistons

12 and 13 are received P16 7 a b is a cross fictional View taken alon t e. in the respective indentations formed between these line VII vrrm ro' K the View looking in the diicthat they are f l mmable and the side surfaces of the

pro ections

24 and 25 and the of mews; v... cylindrical surfaces of the body ll and the sleeve 14 F 8 b is a cr9cnonal View taken along the! provide

air chambers

26 and 27 for the work and idle F YIH VHI in G 6 the View looking in the ,strokes. The end faces of they bottom of the indentadlrectlon of the arrows tic r s pf th annular pistons are provided with con;

FIG. 9 a, b is a cross sectional view taken along the jrcjehtric passages namely; inlet 'g m in line IX-IX in FIG. 6 the view looking in the direc-- the piston 12 and

exhaust passages

30 and 31 in the t qiiqith arr ws;..- a MAM aa L piston 13.

DETAILED DESCRIPTION OF THE 7 The outside cylindrical surface of the annular piston INVENTIQN 12 is provided, on the side opposite tothe impact pro- AS Show" in the pg adaRted to drill, jections 24, with an annular inlet passage 32 in con holes underground using the drilling machine accord-T stant communication with the end faces of these 8 to the invention Comprises a drilling machine projections via longitudinal passages 34 provided in which is provided with adrill Steel 2 having a the impact projections 24. The outside cylindrical at the tip inserted in the front part and a feed arrange-' surface of the annular piston 13 is provided, on the merit 4 for imposing an axial feed load- The g'. side opposite to the impact projections 25, with an machine 1 and the feed arrangement 4 are located annular exhaust passage 33 in constant communicaa carriage 5 Which tfaiispoi'is these components to tion with the end faces of thesev projections via face and Performs an manipulations associated longitudinal passages 35 in the impact projections 25. With the setting "P of the machine and feed g The annular inlet passage 32 and the annular exhaust mer t for drill holes passage 33 of the

annular pistons

12 and 13 are con- Arrows A, B, C and D indicate the connections of the. nected by means of radial passages 36 and 37 .to the drilling machine to the compressed air mains of the inlet passage 17 a source of compressed air and to the mine. 7 Iexhaust passage 19 atmosphere.

The percussive drilling machine with an independent:

mounted cylindrical sleeve 47. The sleeve 47 is 38 during axial movement of both annular pistons 12,

13 away from the drill steel 2, with the sleeve 14 which is provided with respective axial cams 41 disposed on the cylindrical projection thereof. The sleeve 14 is provided with sector earns 42 facing the drill steel 2 which ensure constant engagement of the s le eve wit h a ratchet mechanism denoted generally 43 (or with a free-wheel mechanism of any other type).

8 The ratchet mechanism 43 is arranged in the front part of the reversible impulse rotary fronthead 7 (on the side of the drill steel 2) and is accommodated in a housing 44 which is provided with internal ratchet teeth 45. The housing 44 is provided with a cylindrical bore on the side opposite to the drill steelwhich seats,

on an aligning cylindrical projection 46 of the body 11' of the impulse rotary fronthead 7. The housing 44 of the ratchet mechanism '43 accommodates a rotatably provided with through notches and cylindrical bores which are adapted to accommodate rotatable and axially movable spring loadedithesprings are not s hFWn in the drawings) pawls 48 for lefthand rotation and pawls 49 for righthand rotation. The pawls 48. and 49 are provided, on the side opposite to the drill steel 2, with cylindrical rods of different length having annular projections 50 which are constantly received in the circular groove 40 of the annular piston 13 and which are adapted to transmit linear motion to the

pawls

48 and 49 during the movement of the annular piston 13.

The end faces of the sleeve 47 acc ommodates, on the side opposite to the drill steel 2, earns 51 adapted to engage the respective cams 39 of the annular piston 13, and on the side of the drill steel 2, internal sector cams 52. in addition, on the side of the drill steel 2, the sleeve 47 receives a drive sleeve 53 which engages the sector cams 52 of the sleeve 47 with its sector cams 54.

The drive sleeve 53 is accommodated in a cover cap 55 which is fixed to the housing 44 of the ratchet mechanism 43 and to the body 11 of the impulse rotary fronthead 7 by means of an intermediate disc 56 and bolts 57 with nuts 58.

The intermediate disc 56 is fixed to the housing 44 of the ratchet mechanism 43 by means of a cylindrical projection 59 and is provided, on its outside cylindrical surface, with a pipe 60 for righthand rotation which is communicated through a port 61 with a cylindrical bore 62, whose diameter is smaller than the inside diameter of the ratchet wheel. The cylindrical bore 62 is communicated through the notches of the sleeve 47 with a reverse chamber 63 for righthand rotatipn which is provided between the end faces of the annular piston 13 on the side of the drill steel 2 and of the sleeve 47 on the side opposite to the drill steel 2. The cylindrical projection 59 of the disc 56 is provided with a conical chamfer 64 by means of which the engagement and disengagement of the pawls 49 is performed during the reversing of the rotation. The pawls 49 for righthand ro-: tation, while sliding over the surface of the conical chamfer 64, are moved together with the annular pistons l2 and 13 away from the drill steel being rotated at the same time in their sockets, and are received in the cylindrical bore 62 thereby disengaging from the ratchet teeth 45 of the housing 44, or in other words. they are disconnected. The engagement of the pawls 49 takes place in the reverse order. During the movement of the annular piston 13 away from the drill steel 2, the pawls 49 leave the cylindrical bore 62 of the disc 56 and, while sliding over the generatrix of the conical chamfer 64, engage the ratchet teeth 45 of the housing 44, or in other words, they are engaged. The engagement and disengagement of the pawls 48 for lefthand rotation is performed in the same manner by means of a conical chamfer 65 of the aligning cylindrical projection 46 of the body 11 of the impulse rotary fronthead 7 and a cylindrical bore 62a during the movement of the

annular pistons

12 and 13 away o he dr lst s a V o,

Mounted in the drive sleeve 53 for rotation together therewith is a spindle 66 which is adapted to receive the drill steel 2. The drilling mschmerufiefibism theiairswifigway, the starting position is shown in FIGS. 2, 3a, 4a, 5a, in which the annular piston 13 functions as a rotary anvil, and the annular piston 12rests on the air cushion in the Work stroke chamber lefthand rotation.

- When the drilling machine is activated, compressed air (air-and-oil mixture) is fed in the direction indicatedby arrows A, B, C (FIG. 1) from a source of compressed air to.the striking rearhead 6 (A), the inlet pipe 1 8 jBj/a'nd the pipe 21 (C) of the impulse rotary fronthead 7 (FIG. 2).

When subject to the pressure of the air admitted into the striking rearhead 6, the hammer pis ton 9 reciprocates was to deliver, at the end of the work stroke,

blows at the spindle 66 which receives the drill steel 2.

When compressed air is fed through the inlet pipe 21 :of the body ll of the impulse rotary fronthead 7, the air enters the reverse chamber 23 for lefthand rotation via the inlet port 22. Under the action of air pressure in the reverse chamber 23, the

annular pistons

12 and 13 are axially displaced towards the drill steel 2, while moving over the outside surface of the sleeve 14. Accordingly, the annular piston 13 during the movement in the above-mentioned direction causes the pawls 48 and 49't0 move towards the drill steel 2 by means of its circular groove 40 and annular projections 50 of the pawls which are received in this groove. The pawls 48 for lefthand rotation of the ratchet mechanism 43 are caused to disrfice axfilly tbwfils the drill steel 2, leave the cylindrical bore 62a of the body 11, whose diameter is smaller than the inside diameter of the ratchet wheel and. while sliding with their working edges over the surface of the conical chamfer 65 of the cylindrical projection 46 of the body 11, are shifted away from the central axis of the machine under the action of springs (not shown in the drawing) and come into engagement with the ratchet teeth 45 of the housing 44 (ratchet wheel), which means they are engaged.

away from the c eiitral axis ofthe machinefdisengaged from the ratchet teeth 45 and enter the cylindriv cal bore 62 of the disc 56 tafing their new position l3 'awa'y from the drifls t e el 2, the axial cams 39 of the annular piston 13 engage the respective axial cams 51 of the sleeve 47 of the ratchet mechanism 43, which is in constant engagement through its sector earns 52 (FIG. 5), with the respective sector earns 54 of the drive sleeve 53 having the spindle 66 of the drill steel received therein, thereby coupling the

annular pistons

12 and 13 with the drive sleeve 53 and the spindle 66.

After the annular pistons 12 and l3'have takentheir starting position (FIG. 2), compressed air from a source is fed through the pipe 18 and the inlet passage 17 of the body 11 into the annular inlet passage 32 and into tl 1 e lorgitudinal passages 34 (FIGS. 3 l' l 4) of the annular piston 12 in communication therewith. Then, the compressed air is fed, via the longitudinal passages 34 of the impact projections 24 of the annular piston l2 into the concentric inlet passages 28 located on the end faces of the indentations of the annular piston 12, which passages terminate in the work stroke chambers 26. Since the idle stroke chambers 27 communicate with the atmosphere via the

concentric exhaust passages

30 and 31 disposed on the end face of the bottom of the indentations of the annular piston 12 provided between the projections of the annular piston 12, which passages are in communication with the longitudinal exhaust passages 35 in constant communication with the annular exhaust passage 33 of the annular piston 13 and with the

exhaust passages

37, 19 and 20 of the body 11 of the rotary fronthead 7, the pressure in the idle stroke chamber 27 is close to the atmospheric one.

The pressure in the work stroke chamber 26 is abruptly increased, and the impact projections 24 of the annular piston 12 begin to turn towards the projections 25 of the annular piston 13 under the action of the pressure difference between the

chambers

26 and 27. In so doing, despite the fact that the compressed air,

which entered the work stroke chambers 27, exerts pressure upon both side surfaces of the impact projection 24 of the annular piston 12 and of the impact projection 25 of the annular piston 13, only the projec tions 24 of the piston 12 will start to move, since the piston 13 is coupled, by means of the axial cams 51 and 39, with the sleeve 47 of the ratchet mechanism, whose ratchet pawls 48 are in engagement with the ratchet teeth 45 of the housing 44 and block the sleeve 47 of the pawls and the piston 13 in this position prethe piston 13.

During further movement of the annular piston 12,.

after the longitudinal passages 34 have passed the space Between the concentric inlet passage; 28 and 29, compressed air enters the idle stroke chambers 27 via the longitudinal passages 34 of the annular piston 12 and the concentrical inlet passages 29 of the piston 13. The annular piston 12, while continuing its movement under inertia and compressing the volume of compressed air in the chamber 27, delivers with its impact projections 24, ablo w at the. projections 25 6f the annular piston 13. Upon delivering the blow, theannular piston 12 will move in the opposite direction under the action of the increased pressure in the chambers 27 and partially as a resplt of the rebound fromthe projections 25 the beginning of the idle stroke.

During the movement of the annular piston 12 away from the point of impacting between the

projections

24 and 25, the longitudinal inlet passages 34 of the annular piston 12 are disconnected from the concentric inlet passages 29 of the piston 13, thereby shutting off the admission of compressed air into the idle stroke chambers27. During further movement of the annular piston 12 under inertia theidle stroke chamber-5273K; comgmu riicated'with th atr'nosph ere ia the

concentric exhaust passages

30 and 31 of the piston 12, and longitudinal passages 35 and annular passages 33 of the annular piston 13, while the work stroke chambers 26 are communicated with a source of compressed air via the 30 concentric'inlet passages 2 8 of the piston 13, the longitudinal inlet passages 34 and the annular inlet passage 32 of the piston 12. Since the concentric inlet passages 28 of the annular piston 13, which terminate in the'work stroke chambers 26, are longer than the con- 35 centnc passaQQsQT, which terminate in the idle stroke chambers 27, the admission of compressed air into the chambers 26 respectively anticipates the admission into the chambers 27, whereby the annular piston 12, which moves under inertia, will begin to be decelerated by the air cushion formed in the chamber 26 also with anticipation, and will stop on the air cushion thus formed without reaching the projections 25 of the piston 13 the end of the idle stroke. At that instant, the pressure in the work stroke cham- 5 bers 26 is abruptly increased, and the projections 24 of venting them from rotating under the action of compressed air upon the projections 25. Accordingly, the annular piston 12 performs an angular travel work stYikd-th direction of movement afifi'isi'stiffi is indicated by arrows in FIGS. 3a, b and 4a, b.

During its movement, the annular piston disconnects its longitudinal inlet passages 34 from the concentrical inlet passages 28 of the annular piston 13 so as to shut off the admission of compressed air into'the

work exhaust passages

30 and 31 of the moving annular piston 12 and the longitudinal exhaust passages 35 of the annular piston 12 will move towards the projections 25 of the piston 13 under the action of the pressure difference between the chambers 26 and '27 (the work stroke cycle is repeated). I

Since one of the concentric inlet passages 28, which terminates in one of the work-stroke chambers 26, and one of the concentric inlet passages 29, which terminates in one of the idle stroke chambers 27, are longer than other

concentric inlet passages

28 and 29, the occurrence of a dead center during the starting period of the rotary fronthead is eliminated at any of intermediate angular positions of the

projections

24 and 25 of the

annular pistons

12 and 13.

During the operation of the impulse rotary fronthead 7, the sealing of the work and

idle stroke chambers

26, 27 and the reduction of air leakage between the end faces of the

projections

24, 25 of the

annular pistons

12 and 13 in contact therebetween, as well as between these end faces and the bottom of the indentations prowded between the projections are ensured due to the difference between the areas of the annular piston tw l sbar ybisqts tq hesqn ta t f sq of 9.

pressed air. Thus, the values of forces acting upon the end face areas of the annular piston 12 on'the side opposite to the projections 24,2111 area F I, 21d those facing the projections 24, an area F2, are directly proportional to the values of these areas, and the constant urging of the piston 12 against the piston 13 is ensured due to the force difference.

Thus, the end faces of the

annular pistons

12 and 13, which are in frictional contact therebetween, are rather sufiiciently oiled and cooled with an air-and-oil mixture, which is supplied from an air source and distributed via the inlet passages terminating in these end faces, namely via the longitudinal passages 34 and

concentric passages

28, 29.

The above-described cycles of operation of the annular pistons are repeated at high frequency, and the'annular piston 12 performsreciprocatory angular oscillations so as to deliver, at the end of every work stroke, a blow with its projections 24 at the projections 25 of the piston 13.

Under the action of torsional impact pulses created as a result of impacting between the impact projections- 24 and 25 of the

annular pistons

12 and 13, the annular piston 13, which performs the functions of an anvilduring lefthand rotation, is rotated in the direction of the blow and, by means of its axial earns 39, and the axial cams 51 of the sleeve 47 of the ratchet mechanism, rotates the sleeve 47 and the drive sleeve 53 coupled therewith by means of the sector earns 52 and 54, and hence the spindle 66 of the drill steel 2. V

The work and idle stroke cycles are repeated at high frequency, and the sleeve 47 receives periodical rotation under the action of torsional impact pulses created as a result of the impacting between the impact projections 24 of the annular piston 12 and the projections 25 of the annular piston 13, and transmits this rotatio through its own sector earns 52 and the sector cams I of the drive sleeve 53 to the spindle 66 with the drill steel 2.

During the angular motion of the sleeve 47 through some angle a, the spring loaded pawls 48 (FIGS. 5a, b)

accommodated therein are rotated, said pwals, while springly rocking over the ratchet teeth'45 of the housing 44 of the ratchet mechanism 43 and being displaced through the same angle a, block the sleeve 47 and the parts associated therewith at every new variable position, that is they block the drive sleeve 53 and the spindle 66 with the drill steel 2. The pawls 48 prevent these parts from rotating in the opposite direction under the action of the elastic rebound reactive force of the drill steel being twisted as a result of its engagement with the rock being destructed, 55a mfih tdrsiohal impa ct pulses received by the sleeve 47 are delivered at high. frequency, the sleeve 47 and the parts associated therewith, that is the drive sleeve 53 with the spindle 66 and the drill steel 2, receive substantially continuous lefthand rotation in one direction only.

In order to reverse the rotation, that is, in order to change over for righthand rotation, the pipe 21 for lefthand rotation is communicated with atmosphere, while the pipe 60 (the arrow D) for righthand rotation is communicated with a source of compressed air (FIG. 1). In this case, compressed air is admitted via the inlet port 61 and the cylindrical bore, 62 of the disc 56 and via the through notches of the sleeve 47 into the space between the end faces of the sleeve 47 and of the annu lar piston 13, that is into the reverse chamber 63 for righthand rotation (FIG, 6).

Under the action of pressurejn the reverse chamber 63, the annular pistons 1 3 and 12 are axially displaced away from the drill steel 2 moving over the outside surface of the sleeve 14. Therefore, the annular piston 13, while moving in the above-mentioned direction, causes the

pawls

48 and 49 to move away from the drill steel by means of the circular groove 40 of the piston and of the annular projections 50 of the pawls which are re ceived in this groove. The pawls 49 for righthand rotation of the ratehet mechanism 43 are c aused to move aiiallmay from the drill steel 2, leave the cylindrical bore 62 of the disc 56 and, while sliding with their working edges over the surface of the conical chamfer 64 of the cylindrical projection 59 of the disc 56, are shifted away from the central axis of the machine under the action of springs (not shown in the drawing), and come intoengagernent with the ratchet teeth 45 of'the Housing 44, that is they are engaged. At the same time,

the pawls 48 for lefthand rotation, which were earlier displaced towards the drill steel 2, are caused to move together with the pawls 48 away from the drill steel 2 so that their working edges slide over the surface of the conical chamfer 65 of the cylindrical projection 46 of the body 11, and the pawls are shifted away from the central axis of the machine so as to be disengaged from the ratchet teeth 45 and take their new position in the cylindrical bore 62a of the body 11, that is they are disconnected.

During the movement of the

annular pistons

12 and 13 away from the drill steel 2, the axial earns 38 of the annular piston 12 come into engagement with the respective axial earns 41 located on the cylindrical projectio n l a of the sleeve 14, and which sleeve is in constant engagement with the sector earns 52 and 54 of the sleeve 47 of the ratchet mechanism and of the drive sleeve 53 with the spindle 66 received therein by means of the sector earns 42 of the sleeve 14 (FIG. 5), thereby coupling the annular pistons and the drive sleeve with the spindle (FIG. 6).

After the

annular pistons

13 and 12 have taken their starting position (FIGS. 6; 7a, b; 8a, b; 9a, b), compressed air is admitted from a source through the inlet pipe 18 and the inlet passage 17 of the body 11 into the annular inlet passage 32 and the longitudinal passages 34 of the annular piston 12 in communication therewith. Then the compressed air flows via the longitudinal passages 34 of the annular piston 12 into the concentrical inlet passages 28, which are located on the end faces of the indentations of the annular piston 13, and terminate in the work stroke chambers 26. Since the idle stroke chambers 27 are communicated with the atmosphere via the

concentrical exhaust passages

30 and 31, which terminate on the end faces of the bottom of the indentations of the annular piston 12 provided between the projections 24 of the annular piston 12 and are in communication with the longitudinal exhaust passages 35 in constant communication with the annular exhaust passage 33 of the annular piston 13 and with the

exhaust passages

37, 19 and 20 of the body 11 of the rotary fronthead 7, the pressure ,in the idle stroke chambers 27 is near to the atmospheric pressure. p I 7 V The pressure in the work stroke chamber 26 is abruptly increased, and the impact projections 25 of the annular piston 13 begin to turn towards the projections 24 of the annular piston 12 under the action of the pressure diference between the

chambers

26 and 27. 1n this case, despite the fact that the compressed air admitted into the idle stroke chambers 27 exerts the pressure against the both side surfaces of the impact projection 25 of the annular piston 13 and of the impact projection 24 of the annular piston 12, only the projections 25 of the piston 13 will start to move, since the piston 12 is coupling by means of its own axial earns 38 and

thaxial cams

41 and 42 of the sleeve 14, with the drive sleeve 53 and with the sleeve 47 of the ratchet mechanism, whose ratchet pawls 49 are in engagement with the ratchet teeth 45 of the housing 44 and block the sleeve 47, the drive sleeve 53, the sleeve 14 and the piston 12 in this position, thereby preventing them from rotating under the action of pressure of compressed air upon the projections 24. As a result, the annular piston 13 performs an angular travel-work stroke the direction of movement M51565 13 isindicated by arrows in FIGS. 7a, b and 8a, b.

During its movement, the annular piston l3 disconnects its concentric inlet passages 28 from the longimama: 'inle'fpa'ssages 34 'ofthe piston iraas 165m off the admission of compressed air into the work stroke chambers 26, and further movement of the impact projections 25 takes place due to the energy expansion of the volume of compressed air admitted into the chambers. At the same time, the work stroke chain: bers 26 are communicated with the annular exhaust passage 33, and hence with atmosphere, via the concentric exhaust passagest) and 319i" the annular piston 12 and the longitudinalexhaust passages 35 of the moving annular piston 13.

During further movement of the annular piston 13, when the longitudinal passages 34 of the annular piston 12 have been passed by the space between the

concentric inlet passages

28 and 29, compressed air is admit-' ted into hematite champerswwa the longitudinal passages 34 of the annular piston 12 and the concentric inlet passages 29 of the annular piston 13. Then the annularpiston l}, while continuing to move under inertia and compressing, in the chamber 27, the volume of the air admitted therein, delivers a blow with its impact projections 25 at the projections 24 of the annular piston 12. Upon delivering the blow, under the action of the increased pressure in the chambers 27, and partially as a result of the rebound from the projections 24, the annular piston 13 will begin to move in the apposite direction the beginnin g of the idle stroke. During the movement of the annular piston 13 away from the point of impacting between the projections 25 $a r1d 24, the longitudinal inlet passages 34 of the annular P15 9". arsstesanssts i r m t wnsqitt sia st passages 29 of the piston 13, thereby shutting off the admission of compressed air into the idle stroke chambers 27. During further movement of the annular piston. 13 under inertia the idle stroke chambers 27 are com- 'municated with theatrisphere via the concentric

x haust passages

30 and 31 of the piston l2 and their own longitudinal passages 35 and circular passage 33, while the work stroke chambers 26 are communicated with a source of compressed air via the concentric inlet,

chambers 27, and compressed air is admitted into the chambers 26 with an anticipation with respect to the chambers 27 the annular piston 13 moving under inertia will begin to be decelerated by the air cushion fonned in the chamber 26 also with anticipation and will stop without reaching the projections 24 of the piston 12 to rest on the air cushion thus formed the end of the idle stroke,

At the same time, the pressure in the work stroke chambers 26 is abruptly increased, and the projections 25 of the annular piston 13 move towards the projections 24 of the piston 12 under the action of the pressure difference between the work stroke chambers 26 vand the idle stroke chambers 27 the work stroke cycle ispepe ated, A V, V, l We qoqns 9 .th i t n t, aassassalii which terminates in one of the -work stroke chambers 26, and one Qftheconeentric inlet passages 29, which te rriiinat es inone of the idle stroke chambers 27, are made longer than the other

concentric inlet passages

28 and 29, the formation of a dead center during the starting period of the rotary fronthead is eliminated, when the

projections

25 and 24 of the

annular pistons

13 and 12 are at any one of the intermediate angular positions.

During the operation of the impulse rotary fronthead, '7, the sealing of the work and

idle stroke chambers

22 and 27 and the reduction. of air leakage between theend faces of the

projections

24, 25 of the

annular pistons

12 and 13 and the bottom of the indentations provided therebetween are ensured due to the difference in the areas of the hammer piston 13 subjected to the constant action of compressed air. Thus, the values of forces acting upon the area of the end faces of the piston 13on the side opposite to the projections 25, an area F and on the side of the projections 25 an area F are directly proportional to thevalues of these areas,-and the annular piston 13 is permanently urged against the piston 12 due to the force difference.

Therefore, the end faces of the

annular pistons

12 and 13, which are in frictional engagement therebetween, are rather sufficiently oiled and cooled with an air-and-oil mixture supplied from a source of compressed air and distributed via the inlet passages located on these end faces, namely, via the longitudinal passages 34 and the

concentric passages

28, 29.

V The above-described cycles of operation of the annular pistons are repeated at high frequency, and the annular piston 13' performs reciprocatory angular oscillations so as to deliver, at the end of every work stroke, a blow with its projections 25 at the projections 24 of the annular piston 12. Under the action of torsional impact pulses created as a result of impacting between the

impact projections

25 and 24 of the

annular pistons

13 and 12, the annular piston 12, which functions as an anvil during righthand rotation, is rotated in the direction of the blow. Thus, the annular piston-l2, by means of its axial earns 38 and the cams 41 of the cylindrical projection 15 of the sleeve 14, cause the latter to rotate, with the sleeve 14 being coupled by means of its sector cams 42 facing the drill steel 2, with the sector cams 54 of ithe drive sleeve 53 and the cams 52 of the sleeve 47 of thflilchetrnechanism 43. V

The work and idle stroke cycles are repeated at high frequency, and the sleeve 47 of the ratchet mechanism receives periodical rotation under the action of torsional impact pulses created as a result of impacting between the impact projccttions 25 of the annular piston 13 and the projections 24 of the annular piston 12. During the angular motion of the sleeve 47 of the ratchet mechanism through some angle a, the spring loaded pawls 49 (FIGS. 9a, b) accommodated therein are rotated, said pawls, while springly rocking over the ratchet teeth 45 of the housing 44 of the ratchet mechanism 43 and being displaced through the same angle a, block the sleeve 47 and the parts associated therewith at every new variable position, that is they block the drive sleeve 53, and the spindle 66 with the drill steel 2. The pawls 49 prevent these parts from rotating in the opposite direction under the action of the elastic rebound reactive force of the drill steel being twisted as a result of its engagement with the rock being distructed, and since the torsional impact pulses received. by the sleeve 47 are delivered at high frequency, the sleeve 47 and the parts associated therewith, that is, the drive sleeve 53 with the spindle 66 and the drill steel 2 receive substantially continuous lefthand rotation in one direction only.

What is claimed is:

11 R pa'eus'srvedsriig'aaciirieaavideramr 1 independent rotation of a drill steel located in a front part of the machine, comprising: an air-operated striking rearhead 6 and a rotary impulse fronthead 7; said air-operated striking rearhead 6 comprising: a body 8 with a cylindrical bore; an air-distribution arrangement and a hammer 9 accommodated in the cylindrical bore of said body 8; said hammer 9 reciprocating under the action of compressed air so as to deliver, at the end of a work stroke, a blow at the drill steel 2 located in the front part of said drilling machine 1; said rotary impulse fronthead 7 comprising: a body 11 with a cylindrical bore; annular pistons 12 and 13 having impact projections 24 and 25 and indentations formed between said projections 24 and 25 rotatably accommodated in the cylindrical bore of said body 11, the pistons being coupled by inter-engagement of said projections 24 and 25 and the respective indentations thereof; work stroke air chambers 26 and idle stroke air chambers 27 provided between the side surfaces of said projections 24 and 25 of the annular pistons 12 and 13 and walls of said body 11 of the rotary impulse fronthead 7, said chambers being periodically communicated via pa'ssage means with a source of compressed air or atmosphere, and the impact projections 24 and 25 of one of said annular pistons 12 or 13 performing, under the action of compressed air, high-frequency reciprocatory oscillations with said impact projections 24 or 25 at the respective projections 25 or 24 of the other of said annular pistons 13 or 12 so as to rotate the drill steel 2 via intermediate partsya sleeve 14 mounted in a cylindrical bore of said body 11 of said rotary fronthead 7 having a cylindrical projection 15 on the side opposite to the drill steel 2, said sleeve supporting said annular pistons 12 and 13 so that the same can axially move together in the inner cavity of said rotary fronthead 7; a ratchet mechanism 43 located in the front part of said body 11 of the rotary fronthead 7 and comprising a ratchet wheel integral with a housing 44 of the ratchet mechanism 43, said housing accommodating a sleeve 47 having movably mounted 16 therein spring loaded pawls 48 for lefthand rotation and pawls 49 for righthand rotation which are in engagement with the teeth 45 of the ratchet wheel 44, said ratchet mechanism providing for rotation of one of said annular pistons 12 or 13 and the drill steel only in one direction; an additional reverse air chamber for lefthand rotation located between the end face of the annular piston 12, which is arranged on the side opposite to the drill steel, and the end face of the cylindrical projection 15 of said sleeve 14, and another additional reverse air chamber 63 for righthand rotation located between the end face of the annular piston 13, which faces the drill steel, and the end face of said sleeve 47 of the ratchet mechanism, one of said additional air chambers 23 or 63 being in communication with a source of compressed air, under the pressure of which a combined axial movement of the annular pistons 12 and 13 away from the opposite additional chamber 63 or 23 takes place; coupling members for providing cooperation between said annular pistons 12 and 13 on the one hand, and said sleeve 14 having the cylindrical projection 15 and said sleeve 47 of the ratchet mechanism 43 on the other hand, said coupling members being located on the end face of said cylindrical projection 15 of the sleeve facing the annular pistons 12 and 13, on the end faces of said annular pistons on the side opposite to the impact projections 24 and 25, and on the end face of said sleeve 47 of the ratchet mechanism facing the annular pistons, said coupling members being so arranged that by means of these coupling members 38, 41, the annular piston 12, which is arranged on the side opposite to the drill steel 2, can be coupled during the combined movement of the annular pistons 12 and 13 away from the drill steel 2, with the sleeve 14 via said annular projection 15, which sleeve is constantly connected to the ratchet mechanism 43 which transmits righthand rotation to the drill steel via intermediate parts at this position of the annular pistons 12 and 13, while the annular piston 13 facing the drill steel can be coupled, during the combined movement of the annular pistons 12 and 13 towards the drill steel, with said sleeve 47 of the ratchet mechanism which transmits lefthand rotation to the drill steel via intermediate parts at this new position of the annular pistons 12 and 13; switching members of the ratchet pawls for righthand and lefthand rotation of the drill steel, said switching members and I said coupling members being adapted to perform simultaneous movement and switching of both said ratchet pawls 48 for lefthand rotation and the ratchet pawls 49 for righthand rotation during the combined axial movement of the annular pistons 12 and 13 towards and away from the drill steel, whereby the rotational direction of said sleeve 47 of the ratchet mechanism 43 is changed over when it is coupled, by means of the coupling members, with one of said annular pistons 12 or 13, which rotated in one direction, where this piston 12 or 13 is blocked, and the other piston 13 or 12 is placed in operation, thereby reversing the rotation of the drill steel.

2. The drilling machine according to claim 1, wherein the linkage members between the annular pistons on the one hand, and the cylindrical projection of the sleeve supporting the pistons, and the sleeve having the pawls of the ratchet mechanism on 3. The drilling machine according to claim 1,

wherein the coupling members for cooperation between the ratchet pawls 48 and 49 and the annular piston 13 are provided on said pawls in the form of cylindrical rods having annular projections 50 and on the annular piston 13 in the form of an annular groove 40 located on the end face of said piston facing the drill steel, said rods being permanently received with their annular projections 50 in said groove, and said rods causing the pawls 48 and 49 to more during the movement of the annular pistons 12 and 13, the length of the rods of the pawls 48 and 49 for lefthand rotation and for righthand rotation being different by the amount of this movement, whereby simultaneous switching of both the pawls 48 for lefthand rotation and the pawls 49 for righthand rotation is achieved during the reversing of the rotation, while the switching members for the pawls 48 and 49 comprise inner conical chamfers 65 and 64 in a cylindrical projection 46 of the end face of the body 11 of the rotary fronthead 7 facing the drill steel2 and in a cylindrical pro jection 59 of an intermediate disc 56 mounted in an end face recess of the housing 44 of the ratchet mechanism 43 also facing the drill steel 2, the conical chamfers being extended by cylindrical bores 62a and 62, whose diameter is smaller than the inside diameter of the ratchet wheel 44, and during the combined movement of the ratchet pawls 48 and 49 and the annular pistons 12 and 13 towards or away from the drill steel 2, the working edges of the ratchet pawls 48 and 49 slide over the conical surface of said chamfers 65 and 64, whereby both the pawls 48 for lefthand rotation and the pawls 49 for righthand rotation are simultaneously rotated in the sockets of the sleeve 47 of the ratchet mechanism 43, the pawls 48 or 49 for one direction of rotation being disengaged from the teeth 45 of the ratchet wheel 44 and received in the cylindrical bores 62 or 62a, which represent the extensions of the' conical chamfers 64 and 65, while the pawls 49 or 48 for a new direction of rotation coming into engagement with the teeth 45 of the ratchet wheel 44, thereby reversing the rotation.

4. The drilling machine according to claim 1, cornoutside surface of the annular piston 12, which is arranged on the side opposite to the drill steel 2, and in constant communication with a source of compressed air, and an annular exhaust passage 33 located on the outside surface of the annular piston 13 facing the drill steel 2 and in constant communication with atmosphere, said passages being in communication with longitudinal inlet passages 34 and longitudinal exhaust passages 35 respectively which are provided in the projections 24, 25 of the annular pistons 12 and 13, characterized in that the longitudinal inlet, passages 34 and exhaust passages 35 terminate on the end faces of the projections 24 and 25 of the annular pistons 12 and 13, which are constantly in contact with the end faces of the bottom of the indentations, and are in communication with concentric inlet passages 28, 29 and exhaust passages 30, 31, which are located on the end face of said indentations and terminate in the work stroke chambers 26 and idle stroke chambers 27, the longitudinal inlet passages 34 being periodically communicated with the concentric inlet passages 28 or 29 terminating in the identical workstroke and idle stroke chambers 26 and 27 during the reciprocatory angular oscillations of the projections 24 and 25 of the annular piston 12 or 13 which at the same time functions as a hammer, while the longitudinal exhaust passages 35 are in constant communication with the concentric exhaust'passages 30 and 31, the concentric inlet passages 28 and 29 and the concentric exhaust pas'sage 30, 31 establishingcommunication between the longitudinal inlet passages 34 and the longitudinal exhaust passages 35 on the one hand, and the work stroke and idle stroke chambers 26 and 27 on the other hand,

while the

concentric inlet passages

28 and 29 which terminate in the

identical chambers

26 and 27 are of such a length as to fulfil the following conditions:

which 5miae 'rafgng braaaaa artist cushion pistons against each other and for a reduction of comk

Claims

1. A percussive drilling machine provided with independent rotation of a drill steel located in a front part of the machine, comprising: an air-operated striking rearhead (6) and a rotary impulse fronthead (7); said air-operated striking rearhead (6) comprising: a body (8) with a cylindrical bore; an airdistribution arrangement and a hammer (9) accommodated in the cylindrical bore of said body (8); said hammer (9) reciprocating under the action of compressed air so as to deliver, at the end of a work stroke, a blow at the drill steel (2) located in the front part of said drilling machine (1); said rotary impulse fronthead (7) comprising: a body (11) with a cylindrical bore; annular pistons (12 and 13) having impact projections (24 and 25) and indentations formed between said projections (24 and 25) rotatably accomodated in the cylindrical bore of said body (11), the pistons being cOupled by inter-engagement of said projections (24 and 25) and the respective indentations thereof; work stroke air chambers (26) and idle stroke air chambers (27) provided between the side surfaces of said projections (24 and 25) of the annular pistons (12 and 13) and walls of said body (11) of the rotary impulse fronthead (7), said chambers being periodically communicated via passage means with a source of compressed air or atmosphere, and the impact projections (24 and 25) of one of said annular pistons (12 or 13) performing, under the action of compressed air, high-frequency reciprocatory oscillations with said impact projections (24 or 25) at the respective projections (25 or 24) of the other of said annular pistons (13 or 12) so as to rotate the drill steel (2) via intermediate parts; a sleeve (14) mounted in a cylindrical bore of said body (11) of said rotary fronthead (7) having a cylindrical projection (15) on the side opposite to the drill steel (2), said sleeve supporting said annular pistons (12 and 13) so that the same can axially move together in the inner cavity of said rotary fronthead (7); a ratchet mechanism 43 located in the front part of said body (11) of the rotary fronthead (7) and comprising a ratchet wheel integral with a housing (44) of the ratchet mechanism (43), said housing accomodating a sleeve (47) having movably mounted therein spring loaded pawls (48) for lefthand rotation and pawls (49) for righthand rotation which are in engagement with the teeth (45) of the ratchet wheel (44), said ratchet mechanism providing for rotation of one of said annular pistons (12 or 13) and the drill steel only in one direction; an additional reverse air chamber for lefthand rotation located between the end face of the annular piston (12), which is arranged on the side opposite to the drill steel, and the end face of the cylindrical projection (15) of said sleeve, (14), and another additional reverse air chamber (63) for righthand rotation located between the end face of the annular piston (13), which faces the drill steel, and the end face of said sleeve (47) of the ratchet mechanism, one of said additional air chambers (23 or 63) being in communication with a source of compressed air, under the pressure of which a combined axial movement of the annular pistons (12 and 13) away from the opposite additional chamber (63 or 23) takes place; coupling members for providing cooperation between said annular pistons (12 and 13) on the one hand, and said sleeve (14) having the cylindrical projection (15) and said sleeve (47) of the ratchet mechanism (43) on the other hand, said coupling members being located on the end face of said cylindrical projection (15) of the sleeve facing the annular pistons, (12 and 13), on the end faces of said annular pistons on the side opposite to the impact projections (24 and 25), and on the end face of said sleeve (47) of the ratchet mechanism facing the annular pistons, said coupling members being so arranged that by means of these coupling members (38,41), the annular piston (12), which is arranged on the side opposite to the drill steel (2), can be coupled, during the combined movement of the annular pistons (12 and 13) away from the drill steel (2), with the sleeve (14) via said annular projection (15), which sleeve is constantly connected to the ratchet mechanism (43) which transmits righthand rotation to the drill steel via intermediate parts at this position of the annular pistons (12 and 13), while the annular piston (13) facing the drill steel can be coupled, during the combined movement of the annular pistons (12 and 13) towards the drill steel, with said sleeve (47) of the ratchet mechanism which transmits lefthand rotation to the drill steel via intermediate parts at this new position of the annular pistons (12 and 13); switching members of the ratchet pawls for righthand and lefthand rotation of the drill steel, said switching members and said coupling members being adapted to perform simultaneous movement and switching of botH said ratchet pawls (48) for lefthand rotation and the ratchet pawls (49) for righthand rotation during the combined axial movement of the annular pistons (12 and 13) towards and away from the drill steel, whereby the rotational direction of said sleeve (47) of the ratchet mechanism (43) is changed over when it is coupled, by means of the coupling members, with one of said annular pistons, (12 or 13), which rotated in one direction, where this piston (12 or 13) is blocked, and the other piston (13 or 12) is placed in operation, thereby reversing the rotation of the drill steel.

2. The drilling machine according to claim 1, wherein the coupling members between the annular pistons on the one hand, and the cylindrical projection of the sleeve supporting the pistons, and the sleeve having the pawls of the ratchet mechanism on the other hand, comprise axial clutch cams respectively.

3. A drilling machine according to claim 1, wherein the coupling members for cooperation between the ratchet pawls (48 and 49) and the annular piston (13) are provided on said pawls in the form of cylindrical rods having annular projections (50) and on the annular piston (13) in the form of an annular groove 40 located on the end face of said piston facing the drill steel, said rods being permanently received with their annular projections (50) in said groove, and said rods causing the pawls (49 and 49) to move during the movement of the annular pistons (12 and 13), the length of the rods of the pawls (48 and 49) for lefthand rotation and for righthand rotation being different by the amount of this movement, whereby simultaneous switching of both the pawls (48) for lefthand rotation and the pawls (49) for righthand rotation is achieved during the reversing of the rotation, while the switching members for the pawls (48 and 49) comprise inner conical chamfers (65 and 64) in a cylindrical projection (46) of the end face of the body (11) of the rotary fronthead (7) facing the drill steel (2) and in a cylindrical projection (59) of an intermediate disc (56) mounted in an end face recess of the housing (44) of the ratchet mechanism (43) also facing the drill steel (2), the conical chamfers being extended by cylindrical bores (62 and 62), whose diameter is smaller than the inside diameter of the ratchet wheel (44), and during the combined movement of the ratchet pawls (48 and 49) and the annular pistons (12 and 13) towards or away from the drill steel (2), the working edges of the ratchet pawls (48 and 49) slide over the conical surface of said chamfers (65 and 64), whereby both the pawls (48) for lefthand rotation and the pawls (49) for righthand rotation are simultaneously rotated in the sockets of the sleeve (47) of the ratchet mechanism (43), the pawls (48 or 49) for one direction of rotation being disengaged from the teeth (45) of the ratchet wheel (44) and received in the cylindrical bores (62 or 62a), which represent the extensions of the conical chamfers (64 and 65), while the pawls (49 or 48) for a new direction of rotation coming into engagement with the teeth (45) of the ratchet wheel (44), thereby reversing the rotation.

4. The drilling machine according to claim 1, comprising passage means which are adapted to periodically communicate the work stroke chambers (26)and the idle stroke chambers (27) with a source of compressed air and atmosphere, said passage means comprising an annular inlet passage (32) located on the outside surface of the annular piston (12), which is arranged on the side opposite to the drill steel (2), and in constant communication with a source of compressed air, and an annular exhaust passage (33) located on the outside surface of the annular piston (13) facing the drill steel (2) and in constant communication with atmosphere, said passages being in communication with longitudinal inlet passages (34) and longitudinal exhaust passages (35) respectively which are provided in the projections (24, 25) of the annular pistons (12 and 13), characterized in that the longiTudinal inlet, passages (34) and exhaust passages (35) terminate on the end faces of the projections (24 and 25) of the annular pistons (12 and 13), which are constantly in contact with the end faces of the bottom of the indentations, and are in communication with concentric inlet passages (29, and 29) and exhaust passages (30, 31), which are located on the end face of said indentations and terminate in the work stroke chambers (26) and idle stroke chambers (27), the longitudinal inlet passages (34) being periodically communicated with the concentric inlet passages (28 or 29) terminating in the identical work stroke and idle stroke chambers (26 and 27) during the reciprocatory angular oscillations of the projections (24 and 25) of the annular piston (12 or 13) which at the same time functions as a hammer, while the longitudinal exhaust passages (35) are in constant communication with the concentric exhaust passages (30 and 31), the concentric inlet passages (28 and 29) and the concentric exhaust passage (30, 31) establishing communication between the longitudinal inlet passages 34 and the longitudinal exhaust passages (35) on the one hand, and the work stroke and idle stroke chambers (26 and 27) on the other hand, while the concentric inlet passages (28 and 29) which terminate in the identical chambers (26 and 27) are of such a length as to fulfil the following conditions L1/L2 > 1, which provides for the formation of an air cushion only in the work stroke chambers (26) at any rotational direction, wherein L1 is length (angular) of the concentric inlet passage (28) which terminates in the work stroke chambers; L2 is length (angular) of the concentric inlet passage (29) which terminates in the idle stroke chamber (27).

5. The drilling machine according to claim 1, wherein the ratio between the areas of the end faces of each of the annular pistons subjected to the action of compressed air on the side of the additional air chambers and on the side of the work or idle stroke chambers fulfils the following condition: F1/F2 > 1, which provides for a permanent urging of the annular pistons against each other and for a reduction of compressed air leakage from the work stroke chambers and idle stroke chambers, wherein F1 is area of the end face of one of the annular pistons on the side opposite to the impact projections; F2 is area of the end faces of the bottom of the indentations of one of the annular pistons in the work or idle stroke chamber on the side of the impact projections.