AU603015B2 - Percussive mole - Google Patents

Description

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3A5IBKA, OIIYBJIH A C 0 BET C o~rQBOPQM 0 IIATEHTHO6 PA H CT) Me.WiyuapoiaaA KJnaccet4Jfrauifm (11) Homep msewgziapo~jifoft ny~snM~aiimn: WO 89/02011 Mio6peTeIIIIA Al (43) A1aTa rM*ewA~yfaPo,11wo I1y6JIIIKaIWII: EO2F 5/18 E21B 4/14, EMi 3/24 9 miapTa 1989 (09,03,89) (21) Homep tewa2y~aPotffoff 3a.aDKH PCT/SU88/00175 (22) /AaTamewariapoxioik no~A341; aaryC~a. 1988 (30.08.88) (31) 110 10P UPHOPHTeTiIOi IlaM4aI; 4300605/31 (32) ZAaTa IlpiiopmeTa: (33) Cirpauwa upiiopwrc'ra; 2 ceirrsg6psi 1987 (02.09.87)

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(71 3aen,~ ceryKa~~ xz ocy~apcmne, Kpome US); 1'HHiTYT ropuoro ALE4IA CHBIipcKoFo QTLIEJEBIAW AKAXIEMIII'1 HAYK CCCP [SU/ H0Eaocg6oPCi Q009 1, Kpaclhf rip,, 54 (SW) [INSTITUT GORNOGO DELA S$IB IRSKOGO OT- DELENIA AKADEMII NAUK SSSR, Novosibirsk (72) llrso6PQrarenw, Ai 1Lho~pe'raenaw/3a.HiIfemn (imomo 04,1 TYnH1 LlbII- XmonoaHT~IM IKoiictaw soawlt (SU/S H- B00I1HPM 630070, yxr, 0pywi4e, A, 57a, KBa, 115 (SU) [TUPITSYN, Konstantint Konstantinovich, Novosibirsk TYT1UUI QOPre~r KoIcTajrmopwi [SU/SU1; Hoocm~gpc 630112, yjr, Koul~oa 18, ixa. 18 (SU) [TUPITSYN, Sergei Konstantinovich, Novosibirsk KAMEHCKHRI BeHxma- N1mri BHIcTopoBaq (SU/SU]; Hoaoc~i6mpCK 630091, yii, JAepwia3f!Ha, 5, icB, 78 (SU) [KAMENSKY, Veniamnin Viktorovich, Novosibirsk (SU)J. KI4CE- JIEB HHnconaft IOpbenj~q [SU/SU]; HO~ocx16Hpcc 630049, yg,. .lHneAHaR, 37/1, IKB, 33 (SU) (KISE- LEV, Nikolai Jurievich, Novosibirskc (74) Arciffr; TOPTOBO-I'IPOMbIIJIEHHAA rIAJIATA CCCP; Mocrcaa 103735, ymi 1Kyfii~bneaa, 5/2 (SU) [THE USSR CHAMBER OF COMMERCE AND INDUSTRY, Moscow (SU)i.

(81) YI~a3ammine rocynapcmna: AT (eaponQAcK14f1 nawemT), AU', BE (efnponefiClcHf Hia-e wr), CH (eaponeficxC11h rlaTenT), DE (ei~poneftcKA rnaTeHr), F1, FR (eapouetqcn naTeHT), GB (eaporeucKA rnameiT), HU, iT (elnponeicicii unTelT), JP, JLU (eaporneICiKuAi naTeHiT),. NL, (eiponecKcx4l naTeiiT), SE (eap reficiii aaTeHT), US C ornwemotf 0 MeoIc6cvtapodIoAl( noucge A6b ucmeqernuq opowa 04y nsee'j gON~~lU opemewbo 41 C noo~p~'ol PY644K011110~ a .,14"y (54) T tiW; PNEUIVATICALLY-OPERATED PERCUSSION DEVICE x 11. La P. 1I (54) Hainfue II3QOPeTcHiA; flTIEBMATIWECICOE YtCTPOIf1TBO YJAPHO I E1TBU AUSTRALIAN A 7 1 13, 21/1 8 17 24 311 MAR 1989 PATENT OFPICk (57) Abitract 6 A pnceumaticaiiy-operated percuision devico compdses ai caming Iside which 4s moVilbis MOUnted A percUlsionl pistoo dividing the hollow of the casing Into (wo chambers, One chamnber is altornately connecotod toia compres air source and to thle atmosphere by meanis or an air distributor provided with a movwable execuating etenient and mounted In the casing Furthermore, the chamber 11 connectcd, through a throttle channel to thle chamber of the air distributor the pressure In said chamber being maintained by the nioveniont of the excuting Qlemlent to ono or the extreme positions# (S)P94eps 4$ .1~ 4.

I1HeBmaTzIec ioe yoTC T 0 ygapioro gelcm- TBI ogep=T ICOPnYOC BHY1TIl ICOTojporo 0 BOSMMHOKCOTZI inepemeiemm ycTaHoJimeH 3yapHu.2 niopuleHL, Aej-rmt rroiocm ixopayca (I) Ha =e IcamepI. OA~ icamepa nocpegcTBom paameulemnoro B xcopnyoe Bo3;xopacpeeXTejLFI a c iiog Thmv1 zoroji.

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ia o flCOOTLI (10) :Bos~yxopacnpe~geJMTejmh ,gawiemPe B H0T0PO0I ode oneqmae T ne peiem~ ~eIICnaOJIIHTejiL H0Ir SazeMG Ta IICMJO'flTEJIJO AtIIMJI Hfl.OPMAIf ROM6, t I63bYOMI4 blfl I63ar~efl) OTP~IOHQ O" t T If TMhAItil-X JntCIa GOUUPM It XOTOpWX NiO"4CiiaPOAuie WIM 8 COOTBOTMUI~ 0 PCT.,

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mandrAckap ML Momn MR Manpilytiio MW ManAin Nil IbqOpA40,00 NO II00sarl4m DO PYM4WHI sD Cy~Anf St, usoiu SN Coertn SUt cossickA Coo TD 44A4 TG Toro C04411MqRn.4 Wtaiu AM#pH~lf 1AA PNEUMATIC PERCUSSIVE DEVICE Technical Field The present invention relates to the mining technology, and more specifically, it deals with a pneumatic percussive device.

The present invention may be most advantageously used in pneumatic percussive tools such as pneumatic moles 66# 10 designed for forming boreholes in soil and rocks.

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Background of the Invention aa 0 94. Known in the art are pneumatic percussive devices having valve and spool air distribution arrangements and neumatic devices in which air distribution is effected by the hammer piston. All such devices are characterized by the provision of a system of passages made either in the casing walls or in the hanmer piston, which are necessary for controlling operation of the spool or valve and also for supplyng compressed air to working chambers of the device and for discharging exhaust air from these oCembers. The provision of such passages results, on the one t, hand, in a decrease in the net area of the hammer piston *gR 25 which, in turn, lowers the specif'i impact power and, on the ot:er hand, complicates the hammer piston and oasing thus bringing about superfluos stress concentrators so as to su1bstantially reduce service life of these parts. This is true to the largest extent for underground tools such as pneumatic moles in whi-h dianater of the casing, hence of the hammer piston, is limited by the diameter of the hole, and the impact loads are taken up not only by the hammer piston, but also by the oacing which functions as a wor'king member as well.

Known in the art is a pneumatic peroussive device ~iiI -2- I. a a a a a

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a OOae (DE, G, 1132067), comprising a pile hammer lowered into a borehole and an independent air distribution arrangement installed on the ground level. The pile hammer is in the form of a trivial impact work consisting of a tubular casing closed at both ends and a hammer piston mounted therein for axial movement. The hamumer piston divides the interior space of the tubular casing into two chambers communicating with each other either through a throttling passage, or through a passage having a check 1O valve, or by means of both. At least one of these chambers, which is referred to as the control chamber, communicates through a hose with the air distribution arrangement provided on the ground level.

The air distribution arrangement is generally in 15 the form of an oscillating system consisting of a spool valve box and, an actuator provided therein and made in the form of a spool or a valve adapted to perform osoillations either automatically or positively under the action of a drive mechanism, e.g. a cam drive. The selfoscillating spool is connected by means of levers and pivot Joints to a pendulum having an adjustable weight.

For putting the pile hammer in operation, the actuator of the air distribution arrangement is automatically or positively driven to perform oscillations. Du- 25 ring oscillations of the spool the hose connecting the controlled chamber of the pile hammer to the air distribution arrangement alternately communicates with a compressed air source and with the environment depending on position of the spool, whereby the controlled chamber of the pile hammer also alternately communicates with the compressed air source and with the environment. Consequently, pulsating pressure is built up in the controlled chamber. As both chambers of the pile hammer communicate with each other through the throttling passage or through the passage incorporating a check valve, It C 4' -3rather than through a free passage, pressure in theso chambers is always different. Under the action of the pressure difference in the chambers, the hammer piston performs reciprocations during which it imparts blows either to a working implement or to the casing-in the opposite direction. The desired direction of blows is ensured by a preset combination of parameters of the air distribution arrangement chosen by way of experiments.

In certain embodiments of the pile hammer there are I: 0 no passages in the hammer piston. and casing altogether.

this makes the abovedescribed device advantageous over prior art pneumatic percussive devices having a spool or valve air distribution arrangements that cannot be im~olemented without a system of passages which are required for controlling the spool or valve and for discharging waste air from the chambers and admitting comnpressed air to the chambers.

The provision of a hose connecting t-Ie controlled chamnber to the air distribution arrangement which is lo- .:20 cated at a substantial distance from the pile hammner results in an increase in the '?dead volume', of this chainber by the amount of the vol~ume of the interior space of the hose. At, the same time, an incr'ease in the ltea volume", of the chazitber is known to result in an additionosmtOf compressed air, hence in a lower efficiency. In addition, a substantial length off the hose limits the rate of pressure pulses effectively transmitted to the chamber, i.e. limits impact power of the pile hammer. in an ideal case, the rate of pressu~re pulses effectively transmitcted through the hose per unit of time is determined by the formunila: wherein 60 is the rate of pulses -4 L is the hose length; is the velocity of sound in the air.

In real life devices, the rate of effectively transmitted pulses is still lower.

Known in the art is a pneumatic percussive device (SU, A, 261319), comprising a casing aud a hammer piston mounted in the casting for movement. The hammer piston divides the interior space of the casing into two chambers.

0. O A working implement is incorporated in the front end part of the casing. A massive balancing piston is S: provided in the rear end part of the casing, which is in the form ot a spool adapted to perform self-oscillatory movement when compressed air is supplied to the 15 device. A longitudinal passage provided in the spool permanently communicates wit a controlled chamber on one side and is communicatable with either a source of compressed and or the environment on the other side depending on position of the spool. Owing to the fact that I the independent air distribution arrangement is incorporated in the casing of the percussive device, there is no need to use a hose for communication of the controlled chamber with the air distribution arrangement as was tIe case in the prior art pneumatic percussive device of D, c, iT32067.

When compressed air is sup;lied to this device, the spool provided in the rear end part of the casing performs self-oscillations with respect to the casing. Depending on position of the spool during its oscillatory movement, the controlled chamber alternately communcat- f es through the longitudinal passage of the spool with the compressed air source and %ith the environment. Therefore, the balancing piston which is made in the form of the spool functions not only as a balancing inertia member but also as an independent air distribution device establishing communication alternately between the controlled chamber of the device and the compressed air source and the environment.

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4r 9 5 Under the action of pulsating pressure in the controlled chamber and air pressure in the other chamber, the hammer piston performes reciprocations during which it imparts blows to the working implement.

However, as the balancing piston functions as a balancing member as well, it has substantial dimentions and mass as well as the amplitude of oscillations so that the size and mass of te device as a whole also increase without bringing about any increase in the impact power.

TO Consequently, the specific impact power of the device is lowered. Attempts made to reduce mass and size of this prior art device by way of rational choice of dimensions, mass and swing of oscillations of the balancing piston and by lowering amplitude of oscillations of the balancing piston by means of limiting abutments failed. Thus reducing mass of the balancing piston to lower mass of the device as a whole inevitably result in the increase in amplitude of its oscillations so that length of the casing increases and the reduction of mass of the device 20 as a whole is not achieved because of an increase in mass of the casing. Reducing amplitude of oscillations of the balancing piston by means of the limiting abutments as is the case in known pneumatic percussive devices with valve air distribution arrangements in which the valve remains stationary ,lterrately in one and other position is also impossible for two reasons. Firstly, the balancing piston cannot be stopped if one wants it to perform its function.

Secondly, this piston being a self-osoillating member, it cannot remain stationary after its engagement with the abutment since the very principle of its self-oscillation movement involves the development of a rebound force under the action of which the balancing piston is instantly reversed after its stoppage. As a result, frequency of oscillatory movement of the balancing piston is only determined by a very short time of it4 shift between the two abutments and it will become too high as to rule out i 6 Inormal operation of the device.

Sunmmary of the Invention The main object of the present invention is to provide a pneumatic percussive device with such a construction of an air distribution arrangement that will enable one to considerably reduce mass and size of the device and to retain its comparatively high impact power, with IO all the merits inherent in the pneumatic percussive device with a single chamber remaining unaffected.

This object is accomplished by that in a pneumatic percussive device having a casing accomodating a movable I hammer piston dividing the interior space of the casing 15 into two chambers, the first chamber being defined by the casing walls and the hammer piston and the second chamber being defined by* the hammer piston and an air distribution arrangement accomodated in the casing and having a movable actuator member dividing the interior space of S. 20 the air distribution arrangement into at least two cavities, the pressure in the first cavity ensuring movement of the actuator member to one of its limit positions, the second 'cavity permanently communicating with the second chamber and alternately communicating with a compressed air source and the environment, according to the invention, the first cavity of the air distribution arrangement communicates with the second chamber via a throttling passage. The provision of the throttling passage establishing communication between said second chamber and first cavity prevents an instantaneous development of a force that changes direction of movement of the actuator member after its stoppage in one of its limit positions. During its self-oscillatory movement between the two abutments, the actuator member can thus stop in each of its limit positions, the stoppage time i 4 4 I I *S e .5.5

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if Si" r~r 7 in one position being equal to the time for filling said first cavity of the air distribution arrangement with air through the throttling passage and the stoppage time in the other position being equal to the time for discharging compressed air through this passage from said first cavity. The law of oscillatory movement of the actuator member in this case is determined by parameters of the throttling passage and said first cavity of the air distribution arrangement, but it does not substan- Ic tially depend on its inertia properties. As a result, an actuator member may be used the size and amplitude of oscillations of which can be reduced to the values sufficient not only for enabling free admission and discharge of air. In comparison with the device disclosed T5 in SU,A, 261319, size and mass of this device are reduced as a whole without a reduction in its impact power so that the specific impact power, the impact power-to-mass or volume ratio of the device increases.

It is preferred that the first cavity of the air 20 distribution arrangement and the second chamber of the casing comunicate with each other through at least one auxiliary throttling passage, the outlet opening of which on the side of the first cavity of the air distribtion arrangement is provided with a check -valve secured to a wall of the air distribution arrangement.

This facility allows an optimum time for admission of compressed air to said second chamber to be chosen with a preset time for exhaust of waste air therefrome To provide for the possibility of choice of an optimum time for discharge of compressed air from said second chamber with a Preset time for air admission thereto, it is preferred that the interior space of the air distribution arrangement and the second cha.ber of the casing comunicate with each other through at least one auxiliary throttling passage having an outlet opening 8thereof' on the side of' the second chamber of' the casing provided with a check valve secured to a wall of' the air distribution arrangement.

To prevent uncontrolled air overflows. from the air line into the f'irst cavity of' the air distribution arrangement, it is pref'erred, on the contrary, that a diaphragm be provided on the surf'ace of' the actuator member acted upon by compressed air pressure in said first cavity, the diaphragm being secured to the periphery of the air distribution casing.

Brief' Description of' the Drawings A

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The invention will now be described with reference to a specific embodiment illustrated in the accompanying drawings, in which: Figure I is a general view of' a pneumatic percussive device according to the invention; Figure 2 Is an embodiment of' an air distribution arrangement having its actuator member which is in a position allowing compressed air to be admiitted to one of' chambers of' the device; Figure 3 is ditto of' Figure 2 showing a position of' the actuator member allowing waste air to be exhausted 25 from said chamber of' the device; Figure 4 is an embodiment of an air distribution arrangement using, a spring, sLown in a position all~owing com,)ressed air to be admitted to one of' chambers of the device; Figure -5 I~s ditto of' Figure 4, but showing the actuator member is a position all~owing waste air to be exhausted f'rom said chamber of' the device; Figure 6 is an embodi.ment. of' an air distribution arrangement having two throttling passages )aowing comair to be admitted to one chamber of' the device only-, 1' fl 1 9 Figure 7 is an embodiment of an air distribution arrangement having two throttling passages allowing compressed air to be admitted only to the interior space of the air distribution arrangement; Figure 8 is an embodiment of an air distribution arrangement using a diaphragm.

Best Mode for Carrying Out the Invention *see .4 f 0 o I

I.

w f O f *l **OO i* O 1O A pneumatic percussive device comprises a casing I (Figure e.g. of a tubular shape.

A working implement 2 is attached to one end face of the casing, and an air distribution arrangement 3 with an air supply hose 4 is provided at the other end of the 15 casing. A hammer piston 5 is mounted for the axial movement in the casing 1. The hammer piston 5 divides the interior space of the casing into two chambers 6, 7. The first chamber 6 is defined by the walls of the casing I, the hammer piston 5 and the working implement 2. The se- 20 cond chamber 7 is defined by the walls of the casing 1, hammer piston 5 and the air distribution arrangement 3.

The first and second chambers 6, 7 communicate with each other by any appropriate known means (not shown), limiting overflows of air from the second chamber 7 to the first chamber 6. A known means limiting overflows of air between the first and second chambers 6 and 7 may be in the form of a throttling passage .'hc iwy be in th form of an annular space between the hammer piston 5 and the casing I or in the form of a passage incorporating a check valve, or both.

The air distribution arrangement 3 has a movable actuator member 8 (Figure 2) dividing the interior space of a casing 9 of the air distributiozn arrangement 3 into at least two cavities, and in this particular case, into three cavities 10, I1, 12 since the actuator member 8 is 4*

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4 4 0 0 9 made in the forma of a steoped spol mounted coa1xiatly with the hammer pia-ston 5 (.Fi~ue, I) in the casing 9 (Figure 2) of' the air distribion av-angewat 3 for .reciprocations betweeni abuitments 13 a-nd 14+ provided. in the casing 9 of the distrioutiop, arnanienient 3. The first cavity 10 is de-fined by the wal~s of the casin$ 9 of the qir dis~ributiona aaemeat 3 and an end face o f the cct~ator mebi S. Presoure in the first cavity ea sur es a s hi ft of t h e a -utog mem~ber 6 toDD oe of itsLiitpositions. The, second cavity, 11 i's defiedth e v~ias of the csn 9 n ~u.~edfces 16 and 17. The second cavity 11 OqeauetJ~y comuni~atei th..ro a8 h qomnmuaicatip xadial andl on-ItLdinal passa! es 18 arid 19 resqpectitvely, with the second charbeg 7 of the device, The ziatliato~r Member 8 has a Cavity 20 in- the f orm of sleeve having a bottoul 21I. The cavity 20, comn- Maunicates, via a~ pass,qe 22, ylith the ait' sUPPly bose Z+ and, Via! a X1adiaL passa,,e 25, and the second avity 11, arid the second cavty 11-, depending on positt-ta of the act4,ator mernbe 8, 4l texpately comutnicates with the ajr~ OqP- Ply !ine V4 w ti one POe9itton, via tfte gadiat pqassa ge 23, mad, 'via luhts radial passa 0 *it4 -the environMent wlhen the actuator mnember~ 8 is in thp othog' ppostion (Fi :Ug5) The t.,iiird cavity 14' defitned, by an end fa-,ce 25 and thO walls of the QasitnK 9 of the air dist..

xtbution device perm~ently co~ucaicates with the enrviron--ant via a ,cadiaL, pasable 26 CFiSu-re The first cavity 10 pormanently COMM~atcates with the second4 oharbe-r 7 via a thrott~inS passagje 27 anid ;Cxc Fj~re2 4, 5 aqhovi! za 4m diment of a caAinF 28$o the air dtr4gbtiton agangernt and sa 5ctuatog mom-~ boex 2.9 of Saother tytp0 in, which there to~ no Cavity in the fornm Of a SIeeve: inside the atuator Member 29. la tht CMOa fLirst Oavtty 30 Wined by the wnlls of~ the Casing 26 and an end t£ne 311 ot, the actuatu r ember, 29

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I 4: :i c~li directly communicates, via a throttling passage 32, with the second chamber 7 of the device and functions as a receiver. A second cavity 33 defined by a wall of the casing 28 and annular end faces 34 and 35 permanently commnicates with the second chamber 7 through communicating radial and longitudinal passages 36 and 37, respectively., Depending on position of the actuator member 29, the second cavity 33 may communicate either with the environment through a radial passage 3( (in te position 1O shown in Fiure 4) or with the interior of the air supply hose 4. through passages 39 and 22 (in the position of the actuator member 29 shown in Figre A third caity 40 defind, by the walls of the casing 28 ad an end face 41 of the actuator member 29 permanently communicates, via the passage 22, with the air supply hose 4. A spring 42 is provided In the first cavit 30 between tIhe wall off the casing 28 and the end face 31: of the actuator member 29,t the force of the spring placig the actuator maeMbez 29 in the ?osition shQW n Biue 4 in which the 4ecoad ch~asb 7 oomiaocates with the environXiient To allow for a Choice of an optimumt time for exha~tst of compressed air from the second, clhamber 7 With a, preset time for air admission tereto, te first oavity 10 gtutre 6) co mrnicates with the secord. chanber 7 trti-rgh an auaciliary throttlin- passage 43. The outlet opening of the throttling pasage on t.'ee side of the second chambe::r incorporates a Check valve 4.4 onZlred to the wall of the ca.sIing 9 of7 the air distrribution arrangement 3 for allowIng air to pass to the oeoaond chamber 7 only.

If it isq desired to makce Choice of an optimar ti'eO for compressed air admniasion to the aeOoM Chambar 7 With a preset tinme for exhatat of waatej air th ,erefrom, the ou'tlet opening of the auxiliary tilcrttling paq_-eag 43 incorpor'ates on the side of th*e frst cavity 10 a 12 It *a Ike jq check 'valve 45 secured to the wall of' the casing 9 of the air distribution arranonent 3 which allows compressed air to be only admitted to the first cavity Figure 8 shows an embodiment of the air distribution ari.angepmeent 3 similar to that described with reference to Figure 1, but having a, different structural formj of an actuator raenber 46. This actu~ator member 46 has an end face defining a first cavity 47 in the form of' a flexible diaphr'agm 48 secured to ti;e 'periphery of' the casing 9 of To the air distributioQn arrangement The pneu-'Rati, -,erciusqive device accordinZ to the invention. ft nct;Lona i rl the fq Iowing manner.

Whaen, compressed air is fed to the device according to the invenition through the air supply hoQse 4 (Fig'ure2.) 15from A oompresse-4 air &QUrCe (not shown) the aott~ator member 8 iri the form of' a qtepped spool move,9 undo the aotion. of' oom ressedt atr- ipres-ure upon the bottoM 21of the sleeve 24 unt i it enagages wtteabtment T_3 ie.

Until, it i: i n a position "I hc ~p5~d i p 2Qed thz'oi~h te hose 4 file. the seond T chamber 7 of' the cain Itro~htha, passag 22 h aifty, 20, the ra, di4a paogage 23 of- the aotUator member 8, the second c a- Vi ty 11, the radial, and 11gi dinal Passages 18 and 9 of' h a thfh a' itribution arrangement 3.

2 ,,Wh e n comressed a iW i s adm ,tritd to the second cha-ber 7, an additlional foroe app2Jed qn the part of the secon~d oav~tyr 11 to the end face 16 acts upon the 4aetalor mimbez' 8 to press the actqatop' inmer 8 against -abut matit 13. At tlhe sa.Te tirqet pessure in t.-e f'irst cavity o T0 inoreases gradually sinqe Its charging with compressed aiz' ocurs thirough the ti~rottling passag~e 27 connecting thio fizrst cavity~ f'inxctIinnas a r'civz to oh cn oham'oer 7. Adission of atpz'eqsedaitoheeon OhaM 7 lasts until. Pr1 re in the firnt cavity (Iahev duing its filln a valu~e WI;Uc is -jfi.one~t to a a a q J *0

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I: 0- 1, 13 shift the actuator member 8 to the other position, i.e.

until its engagement with the abutment T4 as shown in Figure 3.

In the new position of the actuator member 8, admission of compressed air to the second chamber 7 is stepped as the radial passage 23 is shut-o~ff', and waste air is: exhausted, i.e. in this piosition of the actuator member 8 the second chamber 7 communicates with the environiment via the longitudinal, and radial passages 19 and 18 of casing 9 of the air distribution arrangemeat 3, its second cavity 11 and rad-ia. passage 24. During air exhiaust, air pressure in the second chamber 7 abruptly decreases, but pressure in the first cavity decr'eases gizadua22.y since its discharge occurs through.

se .5the throttliig passage 27. The actuator member 8 remains in this position until pressgure in the first cavity JO .:deqreages to a value at which the force of pressure acting upon ta~e end Lace. 15 of, the actuator member 8 becomes lower than thae force of the air line pressure in the cavity 20 acting upon the bottom 21. Then the abovedesaribed process of the self-oscillationi movement of the actt .tor member 8 with stoppages at two limit positions is CI~rl~repeated,.

epending on position in whi-.ch theo actuator aember l ocated,~ tho second c amber 7 communicates either With a Source of comvpressed~ air and is inolAated from th e nvironment, or with the environmnent and is insul~ated fr'om the source of compressed~ air. Therefore, ptusating, pzresore develops in the second chamber 7 of the device Swhen compressed~ air is supplied through the air supply hole 4- As th;e first chamb~er 6 (7igure 1) and the second ohambor 7 communicate through any appropriate knjown means.

(not shown)' restr'icting air pasage from one chamber 7 to anot-her rather than throuEh an. unobstructed pa9ei~z' in the~ir~t nd nocoadcabr ,7i ~j7Aia 14 different. Under the action, of the pressure difference between the chambers 6, 7 of the device, the hammer piston 5 performs reciprocations in the casing I. One can choose such a combination of parameters df the air distribution arrangement 3 by way of experiments that the hammer piston 5 will impart blows to the working implement 2 during reciprocations in the casing I every cycle of operation of the air distribution arrangement 3.

Operation of the air distribution arrangement 3 the 1O embodiment of which is shown in Figures 4, 5 is identical to operation of the air distribution arrangement 3 shown in Figure 2,3 as regards functions, When compressed air is admitted to the device ses through the air supply hose 4 (Figure the actuator ember 29 is moved under the action of air pressure upon the end face 4 thereof in a position (Figure 5) in which the second chamber 7 of the casing I communicates, via the passages 37, 36, 39 and 22, with a compressed air source so that compressed air is admitted to the second chamber 7. During admission 'of compressed air, an a4 iaS.. tional force counteracting the QOe of the spring 42 Sand caaused by pressure acting upon the end face 34 acts u* pon the actuator member 29. The admission lasts until pressure in the first cavity 30 during its filling with compressed air through the throttling passage 32 reaches a value which is quffiient for phifting the actuator member 29 to a position in whioh the second amber 7 (Figure 4) communicates, via the passages 37, 36 and 3$, with the enrironment. In this position of the actuator 3 member 29 waste air is e hausted fromr the ecoond chamber 7. Simultaneously with the 0aths"t, the first cavity functioning as a receiver is dLsqharged through the throttling passage 32 o that the actuator member 29 is again shifted to a position allowin compressed air to be admitted to the second chamber 7. The abovedescribed processa nc~ t u +rur~r F~ J5 -so: fe* a S.s is then repeated. Operation of' the device as a whole is similar to operation of the device with the air distribution arrangement aescribed with reference to Figures 2,3.

Operation of' the device according to the invention using the air distribution arrangement 3 having an auxiliary throttling passage 43 (Figure 7) with an outlet opening thereof incorporating the check valve 27 differs fromt that described above only in the fact that charging of" the first cavity 10 is effected through the throttling Passage 27 and the auxiliary throttling passage 37 and discharging is effected through ony throttling passage only.

If the outlet opening of' the auxiliary throttling 15 passage 43 is provided with the check valve 44 (Figure 6), the first cavity TO is discharged through the throttling passage- 27 and the Auxiliary throttling passage 43.

Operation of the device using the air distribution arrangement 3 with the diaphragm 46 (Figure 8) is similar to operation of th+e device described with reference to Figures 2,3, The difference resides in that the diaphragm 48 Vinctions as the end face defining the first cavity 47 comm~Unioating with the second. chamber 7 through the throttling passgge 47.

The numrber of embodiments of the actu~ator member 8 and air dist.ibiuttion arlrangement 3 is not limited to the two embodimerits ghovm In Figures 203 and 4,5. Air distribU tion arz'arg~ments having different desigzis Of the actt.atozr member cani be used, howeverl with any ermbodiment thereof, it is noeze~ary that there shall be at least one throttlinkg pas,&agE) estabJAshing comm~unication between a chamber of" the casizi& altezrnately oom-anincating with a compresed air source azid the, environmenit with a cavity or the air distribu~tion axrran,-emont the p'esure in which ,iren movement of" the actu~ator' member to one of" its 7 16 I 16 limit positions.

In comparison with the prior art, the pneumatic percussive device according to the invention has an air distribution arrangement of minimum mass and size. This makes it possible to lower size and mass of the device as a whole without compromising its impact power while retaining all advantages of pneumatic percussive devices having a single controlled chamber. As a result, the specific impact power, i.e. the power-to-mass or volume ratio of the device increases. On the other hand, if mass and size of the device according to the invention remain the same as before, absolute impact power of the device increases by virtue of an increase in its specific power which, in the end of the day, results in an increase in S* 15 productivity in applications of this device.

*i Industrial Applicability The invention is most preferably used for forming holes used in construction engineering of underground utility systems of various use by tunneling.

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Claims (3)

1. 2. A pneumatic percussive device according to claim I, characterized in that the first cavity (10,30,47) of the air distribution arrangement and the second chamber of the casing communicate with each other through at least one auxiliary throttling passage (43) having its outlet opening on the side of the first cavity (10,30,47) of tLe air distribution arrangement incor- porating a oheck valve (44) secured to a wall of the air distribution arrangement
2. 3. A pneumatic percussive device according to claim I, characterized in that the first cavity (10,30,47) of the air distribution arrangement and the second cham- ber of tLte casiig oomutnicate with each other K^* _4ouh at least one auxiliary throttling passage (43) having its outlet opening on the side of the second chant- ber (10, 30,47) the air distribution arrangement in- corporating a check valve (45) secured to a wall of the air distribution arrangement
3. 4. A pneumatic percussive device according to claim 1, characteri-Aed in that a diaphragm (48) is provided on the gurface of the actuator member acted upon by comn- pressed air pressutre in the first cavity the dia- phragn bein- secured to the periphery of a casing of the air distribution arranigement Dated this 14th day of Augrust 1990 INSTITUT GORNOGQ DELA SIBIRSIK0GO OTDELENIA AKADEMII NAUK SSSR By their Patent Attorney GRIFFITH RLACK CO. *eg I 19 PNEUMATIC PERCUSSIVE DEVICE ABSTRACT A pneumatic percussive device has a casing (I) accomnodating a movable hammer piston dividing the inte- rior space of the casing into two chambers. One of these chambers alternately communicates, by means of an air distribution arrangement having a movable actuator member with a compressed air source and with the environment. In addition, said chamber (7) communicates, via a throttling passage with a S" cavity (10) of the air distribution arrangement the pressure in which ensures movement of the actuator mem- 15 bet to one of its limit positions. e g .e so e 9* f g et•