CA1095021A - Method of controlling the reversing of a device for driving holes in earth and device for performing same - Google Patents
Method of controlling the reversing of a device for driving holes in earth and device for performing sameInfo
- Publication number
- CA1095021A CA1095021A CA296,707A CA296707A CA1095021A CA 1095021 A CA1095021 A CA 1095021A CA 296707 A CA296707 A CA 296707A CA 1095021 A CA1095021 A CA 1095021A
- Authority
- CA
- Canada
- Prior art keywords
- bush
- port means
- housing
- compressed air
- impact member
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Earth Drilling (AREA)
- Percussive Tools And Related Accessories (AREA)
Abstract
A method of controlling the reversing of pneumatic reversible percussive devices for driving holes in earth, wherein, in order to reverse the operation of the device from forward to reverse and vice versa, the supply of compressed air through the feed line is cut off. Then suction is generated in the feed line, whereby the operation of the device is reversed, whereafter the supply of compressed air is restored. The device performing the method of reversing of pneumatic reversible percussive devices for driving holes in earth includes a hollow housing accomodating therein a reciprocable impact member having a rear working chamber and defining with the housing a front working chamber within the housing. The rear working chamber receives therein a stepped-diameter air supply bush secured in the rear part of the housing. Its greater-diameter stage has ports made therethrough. Accomodated within the greater-diameter stage of the bush is a hollow spring-biased valve element having openings made in the end face thereof, facing the greater-diameter stage of the bush, the apertures being associated with respective valves. The surface of the valve member, cooperating with the bush, has ports made therein, alternatingly aligning with and closing off the respective ports in the bush upon the hollow valve member being rotated about its longitudinal axis. This is attained by the internal surface of the bush and the external surface of the valve member defining therebetween a zigzag-shaped groove movably receiving therein a lug. The compressed air feed line has provided therein a an aspirator adapted to create suction in this line, when the operation of the device is to be reversed.
Description
~09SOZl ME~HOD OF CONTROLLING ~EE REVERSING OF A D~JICE
FOR DRIVING EOLES IN EARTE AND DEVICE
~OR PERFORI~I~G s~æ
The present invention relates to construction techno-lo~y and, ~r~ particularly it relates to a method of co~trolliDg the reversing of a device ~or driving holes in earth find to devices for performi~g same.
~ he inve~tion ca~ be used to utmost e~fectiveneso for driving or making holes in compacted soil.
The present inve~tion can be also used to advantage in drivi~g pipes and tubes into soil, e.g. at trenchless laying o~ underground li~es.
At present various holes are drive~ in earth with a wide use of devices actuated by pressurized fluid e.~.
compressed air. ~ore o~ten tha~ not the devices used are re~ersible, i.e. the~ ca~ be operated in the ~orward mode wherein they adva~ce through the soil bod~ and make a hole therein, as well as i~ the re~erse mode, so that they can be retracted from the soil bod~ back to surfare.
There are also know~ methods of controlling the reversing of such percussive devices ~or dri~ing or sinking holes in earth, based on the air suppl~ line being rotated. B~
rotating thi~ line in either direction, a member controlling the air distributio~ in the device ~or drivin6 holes in earth i8, respectivel~, turned either in or out in a thread bet~ee~
lO9SOZl two extreme positions. This operation results in the ~i-rection o~ the impacts in the percussive-action device being reversed, which is tantamount to reversing the direction c~
the progress of the device for driving holes i~ earth.
~ his method is embodied in a percussive device for driving holes in earth (see, for example, the USSR Inv~
entor's-Certi~icate No. 238-,424) comprising a cylindrical a c co rr~rn o,~te~
housing with a pointed forward end. The housing ~64i~K~r#;
therein a reciprocable impa~t member having a hollow space in the rear portion the~reo~. The space receives therein a stepp~d-diameter tubular part secured in the housi~ by a threaded connection. The t~bular part is movable between two positions whereat~ respectively, the device i8 advanced in the forward and reverse directions.
Co~nected to the reax or tail portion of the tubular part is a compressed-air supply hose. The impact member is arra~ged in the housing 90 that its exter~al surface defines with the internal surface of the housing the front wor~ing cham~er, ~hi-le the i~tex~al sur~ace of the hollow space in the tail portion-of the impact member defines ~ith the tu--bular part-the rea~ wor~ing chamber. The impact member has ma~e therein a port-ada~ted to establish commu~ication bet-ween the two ch~mbers, to effect reciprocation of the impact --member, t-he c-hambers being co~municated when the impact me~-ber is in the front part of the housing.
10~021 Thi~ hitherto known percussive device for driving holes in earth operates with compressed air being supplied via the hose and the tubular part into the rear chamber, whereby the impact member is driven forward and delivexs an impact upon the front part of the housing at the end of its forward stroke. At this moment compressed air is supplied through the port in the impact member into the front working chamber.-The ef~ective end face area of the impact member, actPdupon by compres~ed air in the front chamber~ being greater than the ef~ective end face area of the same impact member, acted upon by compressed air in the rear chamber, the force urging the impaet member in the rea~ward direction is greate~
tha~ the force urging the impact member in the forward di-rection. ~onsequent ly, the impact member is driven rear-wardl7. Upon the port-of the impact member clearing the rearmost end edge of the tubular part, compressed air is exhausted ~rom the front chamber into ambient air.
Now the pressure of compressed air in the ~ront chamber becomes short of the pressure in the rear cham~er, the last-me~tio~ed pressure equalli~g the supply line pressure, ~here-by the impact member is arrested a~d then driven forward on~e again~ through it forward stroke.
~ hen the abGvedescrib~d cycle of the operation of the device of the prior art in the ~orward mode repeats itself.
lO9SOZl ~ o make the de~ice for drivi~g hole~ in earth operate in the reverse mode, the tubular part is to be set to the position corresponding to the reverse operation. This is done by rotating the tubular part with aid of the supply hose connected thereto, until this tubular part is set at its rearmost position.
Now compre~sed air is again supplied into the rear chamber and al~o periodically supplied through the port in the impact member into the front working chamber, driv-i~g the impact member through successive reciprocations.
However, in this case the impact member delivers impacts upon the rear or tail part of the housing, in which wa~
the device is retraeted through the hole made in the course o~ the operation of the deviee in the fsrward mode~
A di~advantage of this technique of controlling the device ~r driving hole~ in earth arises from the fact that afte;r the hole ha8 been made to a considerable length, it is dif~icult and in certain cases altogether impossible to-transmit the co~trolli~g torque to the tubular part wIth aid of the supply hose. ~oreover, thi~ man~er of switching the device ~rom one mode o~ operation to the other one has proved to-be time-eon~iLg.
- There is aiso known a method o~ controlling the revers-ing o~ a percussive action device for driving hoies in earth, ~09S021 based on pulling a cable and then rotating the suppl~
hose to displace an air-distributing member, in which wa~
the advance of the device is reversed.
This method of controlling a percussive device for driving holes in earth is performed by a device (see the West German Patent No. 2,340,751) comprising a cylindrical housing accomiodating therei~ a reciprocable impact member.
The impact member ha~ a hollow space in its tail portion, receiving a tubular part secured in the housing. The external walls of the impact member defi~e with the internal wall of the housing the iront workin~ chamber, while the walls of the hollow space in the impact member define with the en~ fa¢e of the tubular part the rear working chamber.
The two chambers communicate via a port made in the impact member.
The tubular part has two an~ular lugs with tuo long-itudinal lug~ therebetween, limiting the displacement of this part in the axial direction, and also two recesses preventing rotation of this part relati~e to ths housing.
The tubular part iB mounted in the axial bore of a guide element se¢ured in the housing and having two longitudinal grooves and an aperture receiving a spring-urged retaining element connected ~ith the remote-control cable. The abutment of the retaining element in the tubular part-retaining pos-itio~ proaects into the recess in the body of the tubular lO950Zl part. Longitudinal grooves are made in the wall of the axial bore of the guide element. The annular and longitu-dinal lug8 retain the tubular part in either one of two positions corresponding to the forward and reverse mode of the operation of the device for driving hole in eart.
In the ~orward mode of the operation of the last-descr-ibed device of the prior art the tubular member is poæitio so that the pattern of air distribution in the device pro-vides for practically simultaneous impact of the impact member upon the foremost portion of the housing and admiss~
of compressed air into the ~ront working chamber. In this mo-de of operatio~ the impact member is reciprocated, deliver-in~ succes~ive impacts upon the foremost portion of the housi~g. Should it be neces~ary to reverse the device ~or driving holes in earth, the tubular part is to be set to the other extreme position. ~his is attained by manually pulling the retaiIling element remote control cable, to withdraw the retaining abutmen~ from the recess in the tubular part. The~
the supply hoæe is rotated to rotate the tubular part with respect of the guide element~ until its longitudinal lugY
align with the grooves o~ the guide elament. Under the aetio~ o~ the air pres~ure in the rear chamber, the tubular part is now displaced rearwardly of the device, into its other position. ~o retain the tubular part in this new po-sition, the hose is rotated to rotate the tubular part about 109~0~.
the latter's axis, and the cable is released for the retaining element to engage the tubular part.
I~ this new position it is ensured th~t the admissio~
of compressed air into the front working chamber takes place earlier than in the forward mode, while the exhaust takes plaee relatively later, whersby the impact member now delivers impacts upon the rear portion of the device, which -means that the device for driving holes in earth is now advanced in the reverse direction.
A disadvantage o~ this reversing control method is the very incorporation of the cable which is apt to get tangled with the supply hose, or else to get caught by some foreign object. Besides, the rotation o~ the hose in still required to reverse the device, which is difficult when the hole is relatively l~ng.
There is further know~ a method of controlling the reversing of a pere~ssive device for driving hole~ in earth,-wherein the reversing control function is e~fected by cutt-ing off and re-establishing the supply of compressed air through the feed line. In this way action is exerted onto an elem~nt controlling the direction o~ the progress o~
the device.
~ his reversing eontrol method is performed by a percuss-ive device for driving holes in earth (~ee the West German Auslegeschrift ~o. 2,105,229) comprising a cylindrical lO9~0Zl a cc~ m n~ ~ ~1 a t l r~
housing accc~vd~ting therein a reciprocable impact member.
The impact member ha~ a hollow space in the rear or tail portion thereof, receiving therein a tubular part secured in the housing. The external walls of the impact member de-fine with the inte mal walls of the housing the front work-ing chamber, while the walls of the hollow space of the im-pact member and the front end face of th~ tubular member define the rear working chamber. The impact member has a port made therein through which the two chambers communicate with each other to effect reciprocation of the impact member~
A specific feature o~ the construction o~ the device is the incorporation of a bush rotatable relative to the tubular member. ~he rotation of the bush relative to the tubular part is provided ~or by the tubular part having made therein a cam groove, and the bush having a lug rsceived in this groove.
The tubular part has in the greater-diameter portion thereof two rows of ports, while the bush has on the greate diameter portion thereof two -~ows of Clo~s~ so arranged that when the bush is rotated relative to the tubular part, it has its wall closing one row of the ports in the tubular member and opening up the other row. When the device for driving holes in earth is to be operated in the forward mode, those ports of the tubular member are closed, which are the nearest to the front portion of ths housing, a~d those ~,og5~1 ports are open which pertain to the tail portion of the housing. In this situation compressed air is supplied into the front working chamber upon the ports of the impact member having cleared the foremost edge of the tubul-ar part, and the exhaust is ef~ected through the open ports of the tubular part.
When compressed air is supplied via the hose and the tubular part into the rear working chamber, the impact member is driven toward the front portion of t~e housing, and in its foremost position it delivers an impsct upon the housi~g. At this moment compressed air is admitted from the rear working chamber into the front working chamber via the ports in the impact member. Owing to the pressure differential acting upon the impact member, with the effort applied thereto from the front chamber being greater tha~
from the rear one, the impact member commences its rearward motion. Upon the ports of the impact member aligning with the port~ o~ the tubular part, compres~ed air is exhausted-from the front working chamber into the ambient air.
To switch over the last-described device for driving holes in earth from forward to reverse operation, the supply o~ compresæed air thereto is to be cut of~. A spring then displaces the bush relative to the tubular part, a~d, owing to the action of the cam slot, the bush is rotated relative to the tubular part. When the compressed air supply is re-~, ,?
10~0~
-established, the bush rotates some more relative to the tubular part. Now the ports of the tubular part, which are closer to the frQnt ~ortion of the hou~ing, become open, and the rearmost ports therein are closed.
Now, when compressed air is supplied into the rear working chamber, the admission of compressed air into the front wor~ing chamber takes place earlier than at the for -ward mode of operation, whereas, in its turn~ the exhaust -is delayed, whereby the reC~pr!ocating impact member deli-vers impacts upon the rear or tail portion of the device.
A shortcoming of the last-described technique of re-versing the operation o~ a device for dIiving holes in earth is that operating the device becomes hampered when either the air supply thereto is incidentally cut off, or elRe ~hen the operation is to be interrupted ~or some reason, which involves outting off the compressed air supply, because in both cases the mode of operation of the device is reversed, which is quite uncalled for. This becomes particu-larl~ aw~ward when the device is launched into earth, and the supply of compressed air is to be repeatedly turned off-and on to correct the hole-making direction.
It is an object of the present invention to eliminate the disadvantages and shortcomings o~ the reversible devices for driving holes in earth, which have been described herein-above .
It is another object of the present invention to in-crease the capacity of the device.
It is still another object of the present invention to improve the reliability of the control, when the operation of the device is to be reversed.
According to a first aspect of the invention there is provided a method of reversing a pneumatic percussive device for making holes in the ground, the device having a forward mode of operation in which said device is driven into the ground and a reverse mode of operation in which said device is retracted from the ground, s~id device being connected to a supply of compressed air by a feed line, said method comprising disconnecting said feed line from the supply of compressed air, creating suction in the feed line to switch the device from one said mode of opera-tion to the other said mode ~} operation by actuating a valve arrangement in said device, and re-connecting supply of compressed air to said feed line to drive said device in said other mode of operation.
This pattern of controlling the reversing of a percus-sive device for driving holes in earth from one mode to theother one, e.g. from the forward mode to the reverse one, pro-vides for reliable remote control of such reversing.
According to a second aspect of the invention there is provided a pneumatic reversible percussive device, having a forward mode of operation in which the device is driven into the ground and a reverse mode of operation in which the device is retracted from the ground, said device comprising: a hollow housing~a reciprocable impact member accommodated in said hous-ing and defining front and rear working chambers; a bush member, having a stepped portion arranged axially in said housing and adapted to be connected to a compressed air feed line, a rear portion of said impact member being hollow and fitting over said stepped bush member to define therewith said rear working chamber; first port means provided in the rear hollow portion of said impact member such that in a forward position of the impact member said first port means provides communication between said front and rear working chambers, said first port means co-operating with the stepped portion of the bush member to be first closed off thereby as said impact member moves to the rear of said housing, and then to communicate said front working chamber with a further chamber in the rear of said housing as said first port means moves beyond said stepped portion of said bush member, said further chamber being commun-icable with the atmosphere, said impact member thereby recip-rocating in said housing when compressed air is supplied to said bush member by the feed line; second port means at an intermediate position in the stepped portion of the bush member;
a valve arrangement in said bush member actuable by suction applied to the feed line to open and close alternately said second port means; said first port means passing said second port means during each stroke of the impact member, said device being arranged such that with said second port means closed, said impact member strikes the front of said housing during successive strokes so as to drive the device in the forwards direction, whereas, with said second port means open, said front working chamber communicates with said rear working chamber as said first port means passes said second port means during each stroke and said impact member thereby strikes the rear of the housing during successive strokes so as to drive the device in the rearwards direction.
~-, -12-lO950Zl It is expedient that the aspirator should include an a~piration nozzle and a control valve operable to connect the aspiration nozzle to the air feed line and disconnect it therefrom.
~ he present invention will be further described in connection with a preferred embodiment thereof, with refer-ence being had to the accompanying drawings, wherein:
Fig. 1 schematically illustrates a system depicting the method of controlling the reversing of pneumatic percussive devices for making hole~ in earth in accordance with the in-vention, in the forward mode of the operation of the device;
~ ig. 2 shows the same, as ~ig. 1, with the operation mode being reversed;
Fig. 3 is a longitudinal sectional view of the area A in Fig. 1 of the pneumatic reversible device for driving holes in earth~ according to the invention;
~ ig. 4 ~hows an involute (rotated through 90) of the e~ternal surface of the hollow valve element at the diame-ter D;
Fig. 5 is a sectional view taken on line V-V o~
Fig. 3 Swith the port~ o~ the bush and the valve element driven apart);
Fig. 6 is the same sectional view, as in Fig~ 5, with the ports of the bush and o~ the valve element aligned.
, ~ he method of controlling the reversing of a pneumatic reversible percussive ~levice for making holes in earth, in accordance with the invention, includes the operation of supplying compressed air from an e~ternal source into the air feed line and into the reversible device for making holes in earth, as indicated with arrows in ~ig. 1. ~o clarify the description of the method, some of the elements of the device performing this method will be re~erred to hereinbelow. In the forward mode of the operation, when a hole is driven or made in earth, an impact member 1 acco~ -odated in a housing 2 delivers successive impacts upon the frontmost part of the housing 2. ~he gate 3 of a control t O ~ t~
valve 4 is i~ a position whereat the aspiration~ozzle 5 of an aspirating means is disconnected from an air feed li-ne 6, so that the reversible percussive device 7 for making holes in earth is connected via the air ~eed line 6 to a compressecl air source 8.
- Should it be necessar~ to reverse the operation of the percussive device 7 for ma~ing holes in earth, in accor-dance with the inventio~, the compressed air supply to the device 7 is cut off, e.g. by setting the gate 3 o~ the con--trol valve vertically, as shown in Fig. 2, thus creating suction in the percussive action reversible device 7 for making holes in earth by withdrawing air therefrom. This direction of the air flow in indicated with the arrow in Fig~. 2. ~he suction thus created acts upon an element controlling the operation mode of the device 7, this ele-ment being displaced, switching over the device 7 to opera-tion in the alter~ative mode, i.e. the reverse mode of ope-ration.
It is deemed appropriate to illustrate the herein disclosed method of controlling the reversing o~ the device 7 by describing the operation of the reversible percussive device for making holes in earth.
~ he pneumatic reversible percussive device 7 (~ig. 1) ~or driving or making hole~ i~ earth, performing the herein disclosed reversing control method, includes the housing 2 in the form o~ a ~ollow cylinder with a pointed foremost or front end, i.e. the end which acts upo~ the soil to ma~e a hole therei~. The housing 2 accom~odates therein the reci-procable impact member 1 having in the tail portion thereof a cylindrical space defining the rear working chamber 9. ~he external surface of the impact member 1-defines with the in-ternal ~ur~ace of the housing 2 the front wor~ing chamber 10. When the impact member 1 of the rever~ible device 7 for-making hole~ in earth reciprocates, the working chambers 9 and 10 vary their volume. The front and rear wor~ing chambe~s 10 and 9 communicate via ports 11 made in the impact member 109~02~
~ he tail space o~ the impact ~member 1 receives there-in a stepped-diameter bush 12 (Figs 3 and 1) which is coaxial with the impact member 1, and, hence, with-the housin~ 2, the bush 12 having its greater-diameter portion or stage received in the hollow space of the impact member 1, while its smaller-diameter portion or stage is secured to the tail portion of the housing 2 by means of a nut 13 haYing an opening 14 therethrough for exhausting spent com-presse~ air into ambient medium. The stepped-diameter air supply bush 12 has in the greater-diameter ~tage thereof ports 15 which are intended to supply compressed air from the rear working chamber 9 into the front working chamber 10 when the pneumatic reversible percussi~e device 7 for making holes in earth is operate~ in the reverse mode.
~ eceived within the greater-diameter stage of the stepped-diameter air supply bush 12 is a spring-urged hollow valve element 16 having in the surface thereof, coo-perati~g with the air supply bush 12, ports 17. ~hese ports 17 are alignable with the ports 15 in the steppsd--diameter air supply bush 12 upo~ the hollow valve element 16 having been rotated accordingly about its longitudinal axis. ~he hollow valve element 16 has made in the cylind~-ical surface thereof, cooperating with the ~tepped-diameter air suppl~ bush 12, a zigzag-shaped groove 18 movably rec~
eiving therein a lug 19 ~ast with the greater-diameter 10950~1 portion or stage of the air supply bush 12. Fig. 4 of the appended drawings shows an involute (rotated through 90) of the external surface of the valve element 16 at the diameter D (~ig. 3). The end face of the hollow valve ele-ment 16, facing the smal~er-diameter portion or stage of the air supply bush 12, has made there-through apertures 20 associated with valves 21. ~he hollow valve element 16 is urged forwardly of the housing 2 by a compression spring 22. The stepped-diameter air supply bush 12 carries a valve member 23 preventing ingress of soil into the reversible de~ice 7~
The air feed line 6 incorporates an aspirator 5 ~ith two conduits 24 25 and a control Yalve 4 having a gate 3 rotatable betwee~ a horizontal position and a vertical one.
In one of its positions (the horizontal one) the valve 4 eonnects the pneumatic reversible percussive device 7 for making holes in earth to the compressed air source B, while in its other position, the vertical one, the reversible de-vice 7 is connected to the suction conduit 24 of the aspira-tor 5, whereas the compressed air source is connected to the aspiration nozzle conduit 25 of the aspirator 5.
The aforedescribed pneumatic reversible percussive device 7 for making holes in earth operates, as follows.
To operate the pneu~atic reversible pexcussive device 7 for making holes in earth in the ~orward, or hole-ma~ing 10950~1.
mode, the gate 3 is turned into its horizontal position, and the reversible device 7 is connected to the compressed air source 8. Under the combined action of the spring 22 and compressed air the hollow valve element 16 is held in its foremost position~ In this position the lug 19 of the stepped-diameter air supply bush 12 sets at the peak or apex o~ the zigzag-shaped groove 18, facing the rear portion of the housing 2, and the ports 15 of the stepped--diameter air supply bush 12 are closed with the wall of the hollow valve element 16, as shown in Fig. 5. Shown in Fig. 1 of the appended drawings is the foremost position of the impact member 1, whereat the impact member 1 strikes the housing 2 (which correspond~ to the forward mode of operati~
of the reversible device 7 for ma~ing holes in earth).
~ hen the air is supplied now via the feed line 6 into the rear working chamber 9, it is admitted into the front working chamber 10 through the ports 11 in the impact mem- -ber 1. ~he pressure of the compressed air in the rear and ~ront working chambers 9 and 10~ respectivel~, being roughly equal, an~ the e~fective area of the end face surface of the impact me~ber 1, acted upon by compressed air in the front working Ghamber 10, being greater than the effective face area o~ the same impact member 1, acted upon by com-pressed air in the rear working chamber 9, the efforts acting upon the impact member 1 from the front and rear 10~5021 working chambers 10 and 9, respectively, are different, the effort developed in the front working chamber 10 being greater. Consequently, the impact member 1 is bci~g dis-placed toward the rear portion o~ the housing 2. Upon the ports 11 in the impact member 1 becoming closed off by the wall of the greater-diameter stage o~ the stepped-diameter air supply bush 12, compressed air is no lon~er admitted into the front ehamber 10. The volume of the latter increas-es~ as the impact member continues its rear~ard motion, and the compressed air contained therein e~pands. Upon the ports 11 in the impact member 1 having cleared the rear face edge of the greater-diameter stage of the air supply bush 12, the front wor~ing c-hember 10 becomes connected to the ambient medium via the ports 11 in the impact member 1 and the openingrs 14 in the ~ut 13. The compressed air coming from the fro~t working chamber 10 opens the val~e 23 and escapes into the ambient medium, whereby the pressure in the ~ork-ing eha~ber 10 becomes roughly equal to atmospheric press-ure; so that there is no longer a~ e~fort applied to the impact member 1 from the side of the front end of the housing 2. At the same time, from the side of the rear working chamber 9 continuously connected with the compressed air source ~ there acts upon the impact member 1 an effort developed b~ the action of compressed air upon the end sur-face of the impact member 1, facing the rear wor~ing chamber 9.
lO9S021 The laqt-mentioned ef~ort, first, arrests the rearward motion of the impact member 1 and then drives it forwardly until its foremost end strikes the housing 2. Approximately at the same mome~t the ports 11 in the impact member 1 clear the foremost edge of the greater-diameter stage of the air supply bush 12, and compressed air is admitted into the front working chamber 10. The impact member 1 is driven rearwardly, a~d the abovedescribed cycle repeats itself.
~ o reverse the operation o~ the pneumatic reversible device 7 ~or making holes i~ earth, the gate 3 of the con-trol valve 4 is turned into its vertical position.
The compre~sed air source 8 now supplies compressed air via the feed line 6 into the conduit 25 of t~e aspirator 5 where the dynamic head of the air stream is converted into a static sub-atmospheric pressure. This creates suction in the suction conduit 24 o~ the aspirator 5, and, hence, in the pneumaltic reversible device 7 for making holes in earth.
The air being withdrawn creates 3uction in the internal space of the stepped-diameter air supply bush 12 of the reversible pneumatic de~ice 7 ~or making holes i~ earth, and there is devel~ped an air ~low from the stepped-diameter air supply bush 12 towaId the aspirator 5. There is created a pressure drop betwee~ the rear working chamber 9 and the air in the internal space of the stepped-diameter air supply bush 12~ The ~auge pressure of the air in the rear working ~095()21 _ 21 -chamber 9 drives the valve 21 of the hollow valve element 16 to the end wall of the latter, which precludes a flow of air from the rear working chamber 9 into the internal space of the stepped-diameter air supply bush 12, through the port 20 of the hollow valve element 16. Under the action of the air from the rear working chamber 9 upon the end wall of the hollow valve element 16, the latter is driven rearwardly of the housing 2. While bei~g thus axially displaced, this hollow valve eleme~t 16, owing to its operative connection with the stepped-diameter air supply bush 12 with aid of the zigzag-shaped groove 18 in the surface of the valve element 16 and the lug 19 of the bush 12, received therein, is rotat ed about its longitudinal axis through a-specified angle.
With the hollow valve element 16 having been thus driven into its rearmost posi~ion, the lug 19 of the air supply bush 12 fi~d~ itself at the apex of the zigzag-shaped groove 18, facing the front portion of the housing 2.
Now, when the gate 3 of the control valve 4 is reset to its horizontal position, or else when no more suction is supplied to the reversible percussive device 7 for making holes in earth, the valve element 16 is returned by the spring 22 into its foremost position. While being thus displaced axially, the hollow valve element 16 is rotated thf~ough a certain angle about its longitudinal axis, owing to its operative connection with the stepped-diameter air 10~50Zl supply bush 12, because throughout this axial displacement of the hollow valve element 16 the lug 19 remains i}~mobile, while the walls of the zigzag-shaped groove 18 of the hollow valve element 16 cooperate with this lug 19 and thus rotate the valve element 16. In the foremost position of the hollow valve element 16 the lug 19 finds itself in the rearmost blind end (although, the different one from the abovemention-ed) of the zigzag-shaped groove 18.
In this angular position o~ the hollow valve element 16.-it~ ports 17 align with the ports 15 in the stepped-diame-ter air supply bush 12, as shown in Fig. 6.
With compressed air now being fed from the supply sour-ce 8 via the feed line 6 ~with the gate 3 of the valve 4 restored to its horizontal position, as sho~ in ~ig. 13 into the percussive reversible device 7 ~or driving or mak-ing holes i~ earth, the impact member 1 is sent forward under the action of compressed air filling the rear working chamber 9, toward the front portion of the reversible device 7 for mR~ing holes i~ earth. Upon the ports 11 in the impact member 1 having estab~hed communication with the ports 15 i~ the greater-diameter stage of the stepped-diameter air æupply bush 12, compressed air is admitted from the rear working chamber 9 through the ports 17, 15, respectively, o~
the hollow valve element 16 and the stepped-diameter air supply bush 12 into the front working chamber 10. As it has ~09~;02~.
been already stated, the effective area of the end surface of the impact member 1 in the front working chamber 10 is greater than that in the rear working chamber 9, and so the effort acting upon the impact member 1 from the front work-ing chamber 10 iæ greater than that acting upon the same impact member 1 ~rom the rear working chamber 9. ~his diffe-rence of the efforts starts slowing down the impact member 1. As the latter mo~es on forward, the ports 11 in the impact member 1 become closed of~ with the wall of the stepped-diameter air supply bush 12, while the volume of the ~ront workin~ chamber 10 continues to diminish, whereby the air pressure is rapidly built therein. This built-up pressure increases still further the effort applied to the impact member 1 from the ~ront working chamber 10. Under this effort the impact member 1 is arrested and starts mov-ing rearwardly, and at the end of its rearward stroke it delivers an impact upon the tail portion of the housing 2, i.e~ upon the nut 13, to be more precise. As a result of repeated impacts of this kind, the percussive reversible device for making holes in earth is dri~en backward, iØ
it is driven in the reverse mode o~ its operation. ~he ports in the impact member 1 clear the end edge of the greater-diameter stage of the air supply bush 12, whereby the compressed air is exhausted from the front working chamber 10 into the am~ie~t medium. Under the action of 109~0~1 compressed air filling the rear working chamber 9 the impact membex is sent forward once again, and the abovedescribed cycle of the reverse mode repeatæ itself.
Should it be necessary now to switch over the pneumatic reversible percussive device 7 from the reverse mode to the forward one, the sequence of switching it over from the forward to reverse mode is to be repeated, i.e. the gate 3 of the valve 4 is to be set to its vertical position, to create suction in the reversible device 7.
The hollow valve element 16 would be displaced into its rearmost position, while rotating through a certain angle about its longitudi~al axis. Then the supply of suc-tion is discontinued~ and the hollow valve element 16 is restored into its original ( i.e. the extreme foremost) posi-tion, whereat its wall closes off the ports 15 in the greater-diameter stage of the stepped-diameter air supply bush 12.
FOR DRIVING EOLES IN EARTE AND DEVICE
~OR PERFORI~I~G s~æ
The present invention relates to construction techno-lo~y and, ~r~ particularly it relates to a method of co~trolliDg the reversing of a device ~or driving holes in earth find to devices for performi~g same.
~ he inve~tion ca~ be used to utmost e~fectiveneso for driving or making holes in compacted soil.
The present inve~tion can be also used to advantage in drivi~g pipes and tubes into soil, e.g. at trenchless laying o~ underground li~es.
At present various holes are drive~ in earth with a wide use of devices actuated by pressurized fluid e.~.
compressed air. ~ore o~ten tha~ not the devices used are re~ersible, i.e. the~ ca~ be operated in the ~orward mode wherein they adva~ce through the soil bod~ and make a hole therein, as well as i~ the re~erse mode, so that they can be retracted from the soil bod~ back to surfare.
There are also know~ methods of controlling the reversing of such percussive devices ~or dri~ing or sinking holes in earth, based on the air suppl~ line being rotated. B~
rotating thi~ line in either direction, a member controlling the air distributio~ in the device ~or drivin6 holes in earth i8, respectivel~, turned either in or out in a thread bet~ee~
lO9SOZl two extreme positions. This operation results in the ~i-rection o~ the impacts in the percussive-action device being reversed, which is tantamount to reversing the direction c~
the progress of the device for driving holes i~ earth.
~ his method is embodied in a percussive device for driving holes in earth (see, for example, the USSR Inv~
entor's-Certi~icate No. 238-,424) comprising a cylindrical a c co rr~rn o,~te~
housing with a pointed forward end. The housing ~64i~K~r#;
therein a reciprocable impa~t member having a hollow space in the rear portion the~reo~. The space receives therein a stepp~d-diameter tubular part secured in the housi~ by a threaded connection. The t~bular part is movable between two positions whereat~ respectively, the device i8 advanced in the forward and reverse directions.
Co~nected to the reax or tail portion of the tubular part is a compressed-air supply hose. The impact member is arra~ged in the housing 90 that its exter~al surface defines with the internal surface of the housing the front wor~ing cham~er, ~hi-le the i~tex~al sur~ace of the hollow space in the tail portion-of the impact member defines ~ith the tu--bular part-the rea~ wor~ing chamber. The impact member has ma~e therein a port-ada~ted to establish commu~ication bet-ween the two ch~mbers, to effect reciprocation of the impact --member, t-he c-hambers being co~municated when the impact me~-ber is in the front part of the housing.
10~021 Thi~ hitherto known percussive device for driving holes in earth operates with compressed air being supplied via the hose and the tubular part into the rear chamber, whereby the impact member is driven forward and delivexs an impact upon the front part of the housing at the end of its forward stroke. At this moment compressed air is supplied through the port in the impact member into the front working chamber.-The ef~ective end face area of the impact member, actPdupon by compres~ed air in the front chamber~ being greater than the ef~ective end face area of the same impact member, acted upon by compressed air in the rear chamber, the force urging the impaet member in the rea~ward direction is greate~
tha~ the force urging the impact member in the forward di-rection. ~onsequent ly, the impact member is driven rear-wardl7. Upon the port-of the impact member clearing the rearmost end edge of the tubular part, compressed air is exhausted ~rom the front chamber into ambient air.
Now the pressure of compressed air in the ~ront chamber becomes short of the pressure in the rear cham~er, the last-me~tio~ed pressure equalli~g the supply line pressure, ~here-by the impact member is arrested a~d then driven forward on~e again~ through it forward stroke.
~ hen the abGvedescrib~d cycle of the operation of the device of the prior art in the ~orward mode repeats itself.
lO9SOZl ~ o make the de~ice for drivi~g hole~ in earth operate in the reverse mode, the tubular part is to be set to the position corresponding to the reverse operation. This is done by rotating the tubular part with aid of the supply hose connected thereto, until this tubular part is set at its rearmost position.
Now compre~sed air is again supplied into the rear chamber and al~o periodically supplied through the port in the impact member into the front working chamber, driv-i~g the impact member through successive reciprocations.
However, in this case the impact member delivers impacts upon the rear or tail part of the housing, in which wa~
the device is retraeted through the hole made in the course o~ the operation of the deviee in the fsrward mode~
A di~advantage of this technique of controlling the device ~r driving hole~ in earth arises from the fact that afte;r the hole ha8 been made to a considerable length, it is dif~icult and in certain cases altogether impossible to-transmit the co~trolli~g torque to the tubular part wIth aid of the supply hose. ~oreover, thi~ man~er of switching the device ~rom one mode o~ operation to the other one has proved to-be time-eon~iLg.
- There is aiso known a method o~ controlling the revers-ing o~ a percussive action device for driving hoies in earth, ~09S021 based on pulling a cable and then rotating the suppl~
hose to displace an air-distributing member, in which wa~
the advance of the device is reversed.
This method of controlling a percussive device for driving holes in earth is performed by a device (see the West German Patent No. 2,340,751) comprising a cylindrical housing accomiodating therei~ a reciprocable impact member.
The impact member ha~ a hollow space in its tail portion, receiving a tubular part secured in the housing. The external walls of the impact member defi~e with the internal wall of the housing the iront workin~ chamber, while the walls of the hollow space in the impact member define with the en~ fa¢e of the tubular part the rear working chamber.
The two chambers communicate via a port made in the impact member.
The tubular part has two an~ular lugs with tuo long-itudinal lug~ therebetween, limiting the displacement of this part in the axial direction, and also two recesses preventing rotation of this part relati~e to ths housing.
The tubular part iB mounted in the axial bore of a guide element se¢ured in the housing and having two longitudinal grooves and an aperture receiving a spring-urged retaining element connected ~ith the remote-control cable. The abutment of the retaining element in the tubular part-retaining pos-itio~ proaects into the recess in the body of the tubular lO950Zl part. Longitudinal grooves are made in the wall of the axial bore of the guide element. The annular and longitu-dinal lug8 retain the tubular part in either one of two positions corresponding to the forward and reverse mode of the operation of the device for driving hole in eart.
In the ~orward mode of the operation of the last-descr-ibed device of the prior art the tubular member is poæitio so that the pattern of air distribution in the device pro-vides for practically simultaneous impact of the impact member upon the foremost portion of the housing and admiss~
of compressed air into the ~ront working chamber. In this mo-de of operatio~ the impact member is reciprocated, deliver-in~ succes~ive impacts upon the foremost portion of the housi~g. Should it be neces~ary to reverse the device ~or driving holes in earth, the tubular part is to be set to the other extreme position. ~his is attained by manually pulling the retaiIling element remote control cable, to withdraw the retaining abutmen~ from the recess in the tubular part. The~
the supply hoæe is rotated to rotate the tubular part with respect of the guide element~ until its longitudinal lugY
align with the grooves o~ the guide elament. Under the aetio~ o~ the air pres~ure in the rear chamber, the tubular part is now displaced rearwardly of the device, into its other position. ~o retain the tubular part in this new po-sition, the hose is rotated to rotate the tubular part about 109~0~.
the latter's axis, and the cable is released for the retaining element to engage the tubular part.
I~ this new position it is ensured th~t the admissio~
of compressed air into the front working chamber takes place earlier than in the forward mode, while the exhaust takes plaee relatively later, whersby the impact member now delivers impacts upon the rear portion of the device, which -means that the device for driving holes in earth is now advanced in the reverse direction.
A disadvantage o~ this reversing control method is the very incorporation of the cable which is apt to get tangled with the supply hose, or else to get caught by some foreign object. Besides, the rotation o~ the hose in still required to reverse the device, which is difficult when the hole is relatively l~ng.
There is further know~ a method of controlling the reversing of a pere~ssive device for driving hole~ in earth,-wherein the reversing control function is e~fected by cutt-ing off and re-establishing the supply of compressed air through the feed line. In this way action is exerted onto an elem~nt controlling the direction o~ the progress o~
the device.
~ his reversing eontrol method is performed by a percuss-ive device for driving holes in earth (~ee the West German Auslegeschrift ~o. 2,105,229) comprising a cylindrical lO9~0Zl a cc~ m n~ ~ ~1 a t l r~
housing accc~vd~ting therein a reciprocable impact member.
The impact member ha~ a hollow space in the rear or tail portion thereof, receiving therein a tubular part secured in the housing. The external walls of the impact member de-fine with the inte mal walls of the housing the front work-ing chamber, while the walls of the hollow space of the im-pact member and the front end face of th~ tubular member define the rear working chamber. The impact member has a port made therein through which the two chambers communicate with each other to effect reciprocation of the impact member~
A specific feature o~ the construction o~ the device is the incorporation of a bush rotatable relative to the tubular member. ~he rotation of the bush relative to the tubular part is provided ~or by the tubular part having made therein a cam groove, and the bush having a lug rsceived in this groove.
The tubular part has in the greater-diameter portion thereof two rows of ports, while the bush has on the greate diameter portion thereof two -~ows of Clo~s~ so arranged that when the bush is rotated relative to the tubular part, it has its wall closing one row of the ports in the tubular member and opening up the other row. When the device for driving holes in earth is to be operated in the forward mode, those ports of the tubular member are closed, which are the nearest to the front portion of ths housing, a~d those ~,og5~1 ports are open which pertain to the tail portion of the housing. In this situation compressed air is supplied into the front working chamber upon the ports of the impact member having cleared the foremost edge of the tubul-ar part, and the exhaust is ef~ected through the open ports of the tubular part.
When compressed air is supplied via the hose and the tubular part into the rear working chamber, the impact member is driven toward the front portion of t~e housing, and in its foremost position it delivers an impsct upon the housi~g. At this moment compressed air is admitted from the rear working chamber into the front working chamber via the ports in the impact member. Owing to the pressure differential acting upon the impact member, with the effort applied thereto from the front chamber being greater tha~
from the rear one, the impact member commences its rearward motion. Upon the ports of the impact member aligning with the port~ o~ the tubular part, compres~ed air is exhausted-from the front working chamber into the ambient air.
To switch over the last-described device for driving holes in earth from forward to reverse operation, the supply o~ compresæed air thereto is to be cut of~. A spring then displaces the bush relative to the tubular part, a~d, owing to the action of the cam slot, the bush is rotated relative to the tubular part. When the compressed air supply is re-~, ,?
10~0~
-established, the bush rotates some more relative to the tubular part. Now the ports of the tubular part, which are closer to the frQnt ~ortion of the hou~ing, become open, and the rearmost ports therein are closed.
Now, when compressed air is supplied into the rear working chamber, the admission of compressed air into the front wor~ing chamber takes place earlier than at the for -ward mode of operation, whereas, in its turn~ the exhaust -is delayed, whereby the reC~pr!ocating impact member deli-vers impacts upon the rear or tail portion of the device.
A shortcoming of the last-described technique of re-versing the operation o~ a device for dIiving holes in earth is that operating the device becomes hampered when either the air supply thereto is incidentally cut off, or elRe ~hen the operation is to be interrupted ~or some reason, which involves outting off the compressed air supply, because in both cases the mode of operation of the device is reversed, which is quite uncalled for. This becomes particu-larl~ aw~ward when the device is launched into earth, and the supply of compressed air is to be repeatedly turned off-and on to correct the hole-making direction.
It is an object of the present invention to eliminate the disadvantages and shortcomings o~ the reversible devices for driving holes in earth, which have been described herein-above .
It is another object of the present invention to in-crease the capacity of the device.
It is still another object of the present invention to improve the reliability of the control, when the operation of the device is to be reversed.
According to a first aspect of the invention there is provided a method of reversing a pneumatic percussive device for making holes in the ground, the device having a forward mode of operation in which said device is driven into the ground and a reverse mode of operation in which said device is retracted from the ground, s~id device being connected to a supply of compressed air by a feed line, said method comprising disconnecting said feed line from the supply of compressed air, creating suction in the feed line to switch the device from one said mode of opera-tion to the other said mode ~} operation by actuating a valve arrangement in said device, and re-connecting supply of compressed air to said feed line to drive said device in said other mode of operation.
This pattern of controlling the reversing of a percus-sive device for driving holes in earth from one mode to theother one, e.g. from the forward mode to the reverse one, pro-vides for reliable remote control of such reversing.
According to a second aspect of the invention there is provided a pneumatic reversible percussive device, having a forward mode of operation in which the device is driven into the ground and a reverse mode of operation in which the device is retracted from the ground, said device comprising: a hollow housing~a reciprocable impact member accommodated in said hous-ing and defining front and rear working chambers; a bush member, having a stepped portion arranged axially in said housing and adapted to be connected to a compressed air feed line, a rear portion of said impact member being hollow and fitting over said stepped bush member to define therewith said rear working chamber; first port means provided in the rear hollow portion of said impact member such that in a forward position of the impact member said first port means provides communication between said front and rear working chambers, said first port means co-operating with the stepped portion of the bush member to be first closed off thereby as said impact member moves to the rear of said housing, and then to communicate said front working chamber with a further chamber in the rear of said housing as said first port means moves beyond said stepped portion of said bush member, said further chamber being commun-icable with the atmosphere, said impact member thereby recip-rocating in said housing when compressed air is supplied to said bush member by the feed line; second port means at an intermediate position in the stepped portion of the bush member;
a valve arrangement in said bush member actuable by suction applied to the feed line to open and close alternately said second port means; said first port means passing said second port means during each stroke of the impact member, said device being arranged such that with said second port means closed, said impact member strikes the front of said housing during successive strokes so as to drive the device in the forwards direction, whereas, with said second port means open, said front working chamber communicates with said rear working chamber as said first port means passes said second port means during each stroke and said impact member thereby strikes the rear of the housing during successive strokes so as to drive the device in the rearwards direction.
~-, -12-lO950Zl It is expedient that the aspirator should include an a~piration nozzle and a control valve operable to connect the aspiration nozzle to the air feed line and disconnect it therefrom.
~ he present invention will be further described in connection with a preferred embodiment thereof, with refer-ence being had to the accompanying drawings, wherein:
Fig. 1 schematically illustrates a system depicting the method of controlling the reversing of pneumatic percussive devices for making hole~ in earth in accordance with the in-vention, in the forward mode of the operation of the device;
~ ig. 2 shows the same, as ~ig. 1, with the operation mode being reversed;
Fig. 3 is a longitudinal sectional view of the area A in Fig. 1 of the pneumatic reversible device for driving holes in earth~ according to the invention;
~ ig. 4 ~hows an involute (rotated through 90) of the e~ternal surface of the hollow valve element at the diame-ter D;
Fig. 5 is a sectional view taken on line V-V o~
Fig. 3 Swith the port~ o~ the bush and the valve element driven apart);
Fig. 6 is the same sectional view, as in Fig~ 5, with the ports of the bush and o~ the valve element aligned.
, ~ he method of controlling the reversing of a pneumatic reversible percussive ~levice for making holes in earth, in accordance with the invention, includes the operation of supplying compressed air from an e~ternal source into the air feed line and into the reversible device for making holes in earth, as indicated with arrows in ~ig. 1. ~o clarify the description of the method, some of the elements of the device performing this method will be re~erred to hereinbelow. In the forward mode of the operation, when a hole is driven or made in earth, an impact member 1 acco~ -odated in a housing 2 delivers successive impacts upon the frontmost part of the housing 2. ~he gate 3 of a control t O ~ t~
valve 4 is i~ a position whereat the aspiration~ozzle 5 of an aspirating means is disconnected from an air feed li-ne 6, so that the reversible percussive device 7 for making holes in earth is connected via the air ~eed line 6 to a compressecl air source 8.
- Should it be necessar~ to reverse the operation of the percussive device 7 for ma~ing holes in earth, in accor-dance with the inventio~, the compressed air supply to the device 7 is cut off, e.g. by setting the gate 3 o~ the con--trol valve vertically, as shown in Fig. 2, thus creating suction in the percussive action reversible device 7 for making holes in earth by withdrawing air therefrom. This direction of the air flow in indicated with the arrow in Fig~. 2. ~he suction thus created acts upon an element controlling the operation mode of the device 7, this ele-ment being displaced, switching over the device 7 to opera-tion in the alter~ative mode, i.e. the reverse mode of ope-ration.
It is deemed appropriate to illustrate the herein disclosed method of controlling the reversing o~ the device 7 by describing the operation of the reversible percussive device for making holes in earth.
~ he pneumatic reversible percussive device 7 (~ig. 1) ~or driving or making hole~ i~ earth, performing the herein disclosed reversing control method, includes the housing 2 in the form o~ a ~ollow cylinder with a pointed foremost or front end, i.e. the end which acts upo~ the soil to ma~e a hole therei~. The housing 2 accom~odates therein the reci-procable impact member 1 having in the tail portion thereof a cylindrical space defining the rear working chamber 9. ~he external surface of the impact member 1-defines with the in-ternal ~ur~ace of the housing 2 the front wor~ing chamber 10. When the impact member 1 of the rever~ible device 7 for-making hole~ in earth reciprocates, the working chambers 9 and 10 vary their volume. The front and rear wor~ing chambe~s 10 and 9 communicate via ports 11 made in the impact member 109~02~
~ he tail space o~ the impact ~member 1 receives there-in a stepped-diameter bush 12 (Figs 3 and 1) which is coaxial with the impact member 1, and, hence, with-the housin~ 2, the bush 12 having its greater-diameter portion or stage received in the hollow space of the impact member 1, while its smaller-diameter portion or stage is secured to the tail portion of the housing 2 by means of a nut 13 haYing an opening 14 therethrough for exhausting spent com-presse~ air into ambient medium. The stepped-diameter air supply bush 12 has in the greater-diameter ~tage thereof ports 15 which are intended to supply compressed air from the rear working chamber 9 into the front working chamber 10 when the pneumatic reversible percussi~e device 7 for making holes in earth is operate~ in the reverse mode.
~ eceived within the greater-diameter stage of the stepped-diameter air supply bush 12 is a spring-urged hollow valve element 16 having in the surface thereof, coo-perati~g with the air supply bush 12, ports 17. ~hese ports 17 are alignable with the ports 15 in the steppsd--diameter air supply bush 12 upo~ the hollow valve element 16 having been rotated accordingly about its longitudinal axis. ~he hollow valve element 16 has made in the cylind~-ical surface thereof, cooperating with the ~tepped-diameter air suppl~ bush 12, a zigzag-shaped groove 18 movably rec~
eiving therein a lug 19 ~ast with the greater-diameter 10950~1 portion or stage of the air supply bush 12. Fig. 4 of the appended drawings shows an involute (rotated through 90) of the external surface of the valve element 16 at the diameter D (~ig. 3). The end face of the hollow valve ele-ment 16, facing the smal~er-diameter portion or stage of the air supply bush 12, has made there-through apertures 20 associated with valves 21. ~he hollow valve element 16 is urged forwardly of the housing 2 by a compression spring 22. The stepped-diameter air supply bush 12 carries a valve member 23 preventing ingress of soil into the reversible de~ice 7~
The air feed line 6 incorporates an aspirator 5 ~ith two conduits 24 25 and a control Yalve 4 having a gate 3 rotatable betwee~ a horizontal position and a vertical one.
In one of its positions (the horizontal one) the valve 4 eonnects the pneumatic reversible percussive device 7 for making holes in earth to the compressed air source B, while in its other position, the vertical one, the reversible de-vice 7 is connected to the suction conduit 24 of the aspira-tor 5, whereas the compressed air source is connected to the aspiration nozzle conduit 25 of the aspirator 5.
The aforedescribed pneumatic reversible percussive device 7 for making holes in earth operates, as follows.
To operate the pneu~atic reversible pexcussive device 7 for making holes in earth in the ~orward, or hole-ma~ing 10950~1.
mode, the gate 3 is turned into its horizontal position, and the reversible device 7 is connected to the compressed air source 8. Under the combined action of the spring 22 and compressed air the hollow valve element 16 is held in its foremost position~ In this position the lug 19 of the stepped-diameter air supply bush 12 sets at the peak or apex o~ the zigzag-shaped groove 18, facing the rear portion of the housing 2, and the ports 15 of the stepped--diameter air supply bush 12 are closed with the wall of the hollow valve element 16, as shown in Fig. 5. Shown in Fig. 1 of the appended drawings is the foremost position of the impact member 1, whereat the impact member 1 strikes the housing 2 (which correspond~ to the forward mode of operati~
of the reversible device 7 for ma~ing holes in earth).
~ hen the air is supplied now via the feed line 6 into the rear working chamber 9, it is admitted into the front working chamber 10 through the ports 11 in the impact mem- -ber 1. ~he pressure of the compressed air in the rear and ~ront working chambers 9 and 10~ respectivel~, being roughly equal, an~ the e~fective area of the end face surface of the impact me~ber 1, acted upon by compressed air in the front working Ghamber 10, being greater than the effective face area o~ the same impact member 1, acted upon by com-pressed air in the rear working chamber 9, the efforts acting upon the impact member 1 from the front and rear 10~5021 working chambers 10 and 9, respectively, are different, the effort developed in the front working chamber 10 being greater. Consequently, the impact member 1 is bci~g dis-placed toward the rear portion o~ the housing 2. Upon the ports 11 in the impact member 1 becoming closed off by the wall of the greater-diameter stage o~ the stepped-diameter air supply bush 12, compressed air is no lon~er admitted into the front ehamber 10. The volume of the latter increas-es~ as the impact member continues its rear~ard motion, and the compressed air contained therein e~pands. Upon the ports 11 in the impact member 1 having cleared the rear face edge of the greater-diameter stage of the air supply bush 12, the front wor~ing c-hember 10 becomes connected to the ambient medium via the ports 11 in the impact member 1 and the openingrs 14 in the ~ut 13. The compressed air coming from the fro~t working chamber 10 opens the val~e 23 and escapes into the ambient medium, whereby the pressure in the ~ork-ing eha~ber 10 becomes roughly equal to atmospheric press-ure; so that there is no longer a~ e~fort applied to the impact member 1 from the side of the front end of the housing 2. At the same time, from the side of the rear working chamber 9 continuously connected with the compressed air source ~ there acts upon the impact member 1 an effort developed b~ the action of compressed air upon the end sur-face of the impact member 1, facing the rear wor~ing chamber 9.
lO9S021 The laqt-mentioned ef~ort, first, arrests the rearward motion of the impact member 1 and then drives it forwardly until its foremost end strikes the housing 2. Approximately at the same mome~t the ports 11 in the impact member 1 clear the foremost edge of the greater-diameter stage of the air supply bush 12, and compressed air is admitted into the front working chamber 10. The impact member 1 is driven rearwardly, a~d the abovedescribed cycle repeats itself.
~ o reverse the operation o~ the pneumatic reversible device 7 ~or making holes i~ earth, the gate 3 of the con-trol valve 4 is turned into its vertical position.
The compre~sed air source 8 now supplies compressed air via the feed line 6 into the conduit 25 of t~e aspirator 5 where the dynamic head of the air stream is converted into a static sub-atmospheric pressure. This creates suction in the suction conduit 24 o~ the aspirator 5, and, hence, in the pneumaltic reversible device 7 for making holes in earth.
The air being withdrawn creates 3uction in the internal space of the stepped-diameter air supply bush 12 of the reversible pneumatic de~ice 7 ~or making holes i~ earth, and there is devel~ped an air ~low from the stepped-diameter air supply bush 12 towaId the aspirator 5. There is created a pressure drop betwee~ the rear working chamber 9 and the air in the internal space of the stepped-diameter air supply bush 12~ The ~auge pressure of the air in the rear working ~095()21 _ 21 -chamber 9 drives the valve 21 of the hollow valve element 16 to the end wall of the latter, which precludes a flow of air from the rear working chamber 9 into the internal space of the stepped-diameter air supply bush 12, through the port 20 of the hollow valve element 16. Under the action of the air from the rear working chamber 9 upon the end wall of the hollow valve element 16, the latter is driven rearwardly of the housing 2. While bei~g thus axially displaced, this hollow valve eleme~t 16, owing to its operative connection with the stepped-diameter air supply bush 12 with aid of the zigzag-shaped groove 18 in the surface of the valve element 16 and the lug 19 of the bush 12, received therein, is rotat ed about its longitudinal axis through a-specified angle.
With the hollow valve element 16 having been thus driven into its rearmost posi~ion, the lug 19 of the air supply bush 12 fi~d~ itself at the apex of the zigzag-shaped groove 18, facing the front portion of the housing 2.
Now, when the gate 3 of the control valve 4 is reset to its horizontal position, or else when no more suction is supplied to the reversible percussive device 7 for making holes in earth, the valve element 16 is returned by the spring 22 into its foremost position. While being thus displaced axially, the hollow valve element 16 is rotated thf~ough a certain angle about its longitudinal axis, owing to its operative connection with the stepped-diameter air 10~50Zl supply bush 12, because throughout this axial displacement of the hollow valve element 16 the lug 19 remains i}~mobile, while the walls of the zigzag-shaped groove 18 of the hollow valve element 16 cooperate with this lug 19 and thus rotate the valve element 16. In the foremost position of the hollow valve element 16 the lug 19 finds itself in the rearmost blind end (although, the different one from the abovemention-ed) of the zigzag-shaped groove 18.
In this angular position o~ the hollow valve element 16.-it~ ports 17 align with the ports 15 in the stepped-diame-ter air supply bush 12, as shown in Fig. 6.
With compressed air now being fed from the supply sour-ce 8 via the feed line 6 ~with the gate 3 of the valve 4 restored to its horizontal position, as sho~ in ~ig. 13 into the percussive reversible device 7 ~or driving or mak-ing holes i~ earth, the impact member 1 is sent forward under the action of compressed air filling the rear working chamber 9, toward the front portion of the reversible device 7 for mR~ing holes i~ earth. Upon the ports 11 in the impact member 1 having estab~hed communication with the ports 15 i~ the greater-diameter stage of the stepped-diameter air æupply bush 12, compressed air is admitted from the rear working chamber 9 through the ports 17, 15, respectively, o~
the hollow valve element 16 and the stepped-diameter air supply bush 12 into the front working chamber 10. As it has ~09~;02~.
been already stated, the effective area of the end surface of the impact member 1 in the front working chamber 10 is greater than that in the rear working chamber 9, and so the effort acting upon the impact member 1 from the front work-ing chamber 10 iæ greater than that acting upon the same impact member 1 ~rom the rear working chamber 9. ~his diffe-rence of the efforts starts slowing down the impact member 1. As the latter mo~es on forward, the ports 11 in the impact member 1 become closed of~ with the wall of the stepped-diameter air supply bush 12, while the volume of the ~ront workin~ chamber 10 continues to diminish, whereby the air pressure is rapidly built therein. This built-up pressure increases still further the effort applied to the impact member 1 from the ~ront working chamber 10. Under this effort the impact member 1 is arrested and starts mov-ing rearwardly, and at the end of its rearward stroke it delivers an impact upon the tail portion of the housing 2, i.e~ upon the nut 13, to be more precise. As a result of repeated impacts of this kind, the percussive reversible device for making holes in earth is dri~en backward, iØ
it is driven in the reverse mode o~ its operation. ~he ports in the impact member 1 clear the end edge of the greater-diameter stage of the air supply bush 12, whereby the compressed air is exhausted from the front working chamber 10 into the am~ie~t medium. Under the action of 109~0~1 compressed air filling the rear working chamber 9 the impact membex is sent forward once again, and the abovedescribed cycle of the reverse mode repeatæ itself.
Should it be necessary now to switch over the pneumatic reversible percussive device 7 from the reverse mode to the forward one, the sequence of switching it over from the forward to reverse mode is to be repeated, i.e. the gate 3 of the valve 4 is to be set to its vertical position, to create suction in the reversible device 7.
The hollow valve element 16 would be displaced into its rearmost position, while rotating through a certain angle about its longitudi~al axis. Then the supply of suc-tion is discontinued~ and the hollow valve element 16 is restored into its original ( i.e. the extreme foremost) posi-tion, whereat its wall closes off the ports 15 in the greater-diameter stage of the stepped-diameter air supply bush 12.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of reversing a pneumatic percussive device for making holes in the ground, the device having a forward mode of operation in which said device is driven into the ground and a reverse mode of operation in which said device is retracted from the ground, said device being connected to a supply of compressed air by a feed line, said method comprising disconnecting said feed line from the supply of compressed air, creating suction in the feed line to switch the device from one said mode of opera-tion to the other said mode of operation by actuating a valve arrangement in said device, and re-connecting supply of compressed air to said feed line to drive said device in said other mode of operation.
2. A method according to claim 1 comprising creating said suction by connecting the compressed air supply to a venturi nozzle.
3. A pneumatic reversible percussive device, having a forward mode of operation in which the device is driven into the ground and a reverse mode of operation in which the device is retracted from the ground, said device comprising: a hollow housing; a reciprocable impact member accommodated in said housing and defining front and rear working chambers; a bush member having a stepped portion, arranged axially in said housing and adapted to be connected to a compressed air feed line, a rear portion of said impact member being hollow and fitting over said stepped bush member to define therewith said rear working chamber; first port means provided in the rear hollow portion of said impact member such that in a forward position of the impact member said first port means provides communication between said front and rear working chambers, said first port means co-operating with the stepped portion of the bush member to be first closed off thereby as said impact member moves to the rear of said housing, and then to communicate said front working chamber with a further chamber in the rear of said housing as said first port means moves beyond said stepped portion of said bush member, said further chamber being commun-icable with the atmosphere, said impact member thereby recip-rocating in said housing when compressed air is supplied to said bush member by the feed line; second port means at an intermediate position in the stepped portion of the bush member; a valve arrangement in said bush member actuable by suction applied to the feed line to open and close alternately said second port means; said first port means passing said second port means during each stroke of the impact member, said device being arranged such that with said second port means closed, said impact member strikes the front of said housing during successive strokes so as to drive the device in the forwards direction, whereas, with said second port means open, said front working chamber communicates with said rear working chamber as said first port means passes said second port means during each stroke and said impact member thereby strikes the rear of the housing during successive strokes so as to drive the device in the rearwards direction.
4. A pneumatic percussive device according to claim 3, wherein said valve arrangement comprises a cylindrical member arranged in the stepped portion of said bush member, said cylindrical member having a third port means which is moved successively into and out of register with said second port means on rotation of said cylindrical member thereby to open and close said second port means, said cylindrical member being adapted to rotate when suction is applied to the feed line.
5. A pneumatic percussive device according to claim 4, wherein said cylindrical member is axially slidable in said stepped portion of said bushing, said stepped portion and said cylindrical member having a co-operating lug and groove, said groove having a wavy profile, arranged such that said cylindrical member is rotated on axial movement thereof.
6. A pneumatic percussive device according to claim 5, wherein said cylindrical member has one end facing said impact member open, and an opposite end closed, and facing a shoulder on said bush member forming said stepped portion, said opposite end having a fourth port means formed therein provided with a one way valve to admit air from the feedline into the interior of the cylindrical member, and means are provided for biassing such cylindrical member away from said shoulder, whereby when suction is applied said cylindrical member is drawn towards said shoulder, whereby said cylindrical member is rotated owing to the co-operation between said lug and said groove, said cylindrical member being further rotated when said cylindrical member is returned to its original axial position on removal of said suction, said third port means being located relative to the profile of said groove such that alternate complete recip-rocation of said cylindrical member relative to the stepped portion of the bush member bring said third port means into and out of register with said second port means.
7. A pneumatic percussive device according to claim 3, in combination with a venturi nozzle, and a two-way valve arrangement said two-way valve arrangement being arranged to connect the air supply either directly to said percussive device to provide compressed air thereto, or to said venturi nozzle, in which case said valve arrangement is arranged to connect said venturi nozzle to said percussive device to provide said suction.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA296,707A CA1095021A (en) | 1978-02-10 | 1978-02-10 | Method of controlling the reversing of a device for driving holes in earth and device for performing same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA296,707A CA1095021A (en) | 1978-02-10 | 1978-02-10 | Method of controlling the reversing of a device for driving holes in earth and device for performing same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1095021A true CA1095021A (en) | 1981-02-03 |
Family
ID=4110749
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA296,707A Expired CA1095021A (en) | 1978-02-10 | 1978-02-10 | Method of controlling the reversing of a device for driving holes in earth and device for performing same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1095021A (en) |
-
1978
- 1978-02-10 CA CA296,707A patent/CA1095021A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |