CA1290996C - Single-blow pneumatic percussive tool - Google Patents

Abstract

SINGLE-BLOW PNEUMATIC PERCUSSIVE TOOL
Abstract A single-blow pneumatic percussive tool comprises a hollow cylindrical casing accommodating a reciprocatable hammer piston which divides the interior space of the cas-ing into an upper chamber and a lower chamber. A spring-biased valve is mounted on the side of the lower chamber and a working member is secured to the valve. An air dis-tribution device is mounted on the side of the upper cham-ber and has passages and a control lever. The hammer pis-ton has an axial passage in which a tube is mounted which has a shoulder on the outer surface and a continuous inner partition wall. The tube has upper and lower ports dispos-ed on either side of the partition wall. An air distribu-tion sleeve biased by spring on the side of the air dis-tribution device is mounted on the tube and has an inner recess. The air distribution sleeve is movable under the action of the hammer piston to the upper position in which it covers the lower ports and the air distribution sleeve is movable under the action of a spring means to the lower position defined by the shoulder, in which it establishes communication between the upper and lower ports through the inner recess.

Description

SINGI~-B~OW PN~UMATIC PERCUSSIVE T~O~

q`he invention relates to pneumatic percus~i~e tools used in the construction and mining indu~tries, mechanical engineering and metallurgy, and more specifically, it deals with single-blow pneumatic percussive tools.
The invention may be most advantageously used in tool~
designed for marking, center-popping, riveting, marking-out and gate trimming.
q'he invention may also be used in apparatuses for min-ing working roof trimming, for demolishing concrete, mak-in~ holes and performing other operations in the construc-tion industry.
Pneumatic percussive tool~, in particular, pneumatic ha~mers al~ used for marking, center-popping, riveting, marking-out and gate trimming. Depending on a specific ap-plication, the pneumatic hammer has a working member such as a ~tamp, center punch or chisel mounted in a ca~ing hav-ing an interior ~pace. q`he interior space of the casing accommQdates a hammer piston dividing the interior space of the casing into an upper chamber and a lower chamber.An air distribution device is mounted on the casing. An energy carrier i~ compressed air which i~ supplied to the tool from a portable or stationary compressor, along a flex-ible hose. During operation of the tool, the hammer piston axially reciprocates under the action of a gaseous fluid under pre~sure admitted to the working chambers through the air distribution device following the command of the operator to impart a blow to the end face of the working , 3~

~ ~g()~g6 member at every working cycle. rlhe working member performs work under the action of blows whereby, depending on the type of the working member, marking, center-popping, trimm-ing or riveting takes place.
Since operations performed by pneumatic hammers are effected with the direct participation of the operator,such hammers are to have minimum weight and ~ize.
Known in the art i9 a ~ingle-blo~ pneumatic percussive tool (cf. USSR Inventor's Certificate No. 946912, Int.Cl.
B 25 D 9/00), comprising a hollow cylindrical casing ac-commodating a riciprocatable hammer piston and an air dist-ribution device disposed in a handle mounted on the casing.
'l'he hammer piston divides the casing interior into lower and upper chambers. The tool alæo has a tube adapted to establish communication between the lower chamber and gase-ou8 fluid under pressure at regular intervals.
In this tool, the tube is mounted outside the casing so that auxiliary devices should be provided outside the tool. As a result, the size and weight of the tool held by the operator are increa~ed.
Known in the art i~ a single-blow pneumatic percus~ive tool (cf. USSR Inventor' 6 Certificate No. 683828, Int.Cl.
B 21 C 51/00), comprising a hollow cylindrical casing ac-commodating a reciprocatable hammer piston dividing the interior BpaCe of the casing into upper and lower chambers.
A ~pring-biased valve to which a working member i9 secur-ed is mounted on the side of the lQwer chamber. An air distribution deivce having passages and a control lever is 1~90996 ~ 3 --mounted on the side of the upper chamber. A tube ~or sup-plying gaseous fluid under pressure into the interior space of the chamber is mounted out~ide the casing.
The arrangement of the tube outside the casing leades to large size and heavy weight of the tool held by the ope-rator.
It i9 an object of the invention to reduce size of the tool.
This object is accomplished by that in a single-blow pneumatic percus~ive tool com~rising a hollow cylindrical casing acco~nodating a reciprocatable hammer piston which divides the interior space of the ca~in~ into an upper chamb-er and a lower chamber, a spring-biased valve having a work-ing member secured thereto and mounted on the ~ide of the lower chamber for establislling com~unicatioll of the lower chamber with atmosphere at regular intervals, an air dis-tribution device having passages and a control lever, mount-ed on the casing on the side of the upper chamber and es-tablishing communication of the upper chamber with gaseous fluid under pressure and atmosphere via the passages at re-gular intervals, a tube for adn~tting gaseous fluid under pressure to the lower chamber at regular intervals, and a ratainer for retainin~ the hammer piston in the upper posi-tion, according to the invention, the hammer piston has an axial passage and the tube is mounted in this pa~sage and has an outer shoulder, a continuous internal partition wall and upper and lower ports provided on either side of the in-ternal partition wall, a spring-biased air-distribution sleeve urged away from the air distribution device is mo-unted on the tube and has an inner recess, the sleeve be-ing movable under the action of the hammer piston towards the upper position in which the ilmer surface thereof cov-ers the lower ports and being movable under ~he action of the spring into the lower position defined by the shoulder in which it establishes communication between the upper and lower ports via the imler recess for supplying gaseous fluid under pressure to the lower chamber for moving the hammer piston upwards.
This construction of the tool makes it possible to mi-nimize its weight and size because the tube and air dis-tribution means are disposed inside the tool.
~ he invention will now be described witil reference to the accompanying drawings showing a specific embodiment thereof, in which:
Fig. 1 schematically shows a single-blow pneumatic percusæive tool according to the invention with the hammer piston in the uppermost position, in longitudinal section;
Fig. 2 schematically ~hows a single-blow pneumatic percussive tool according to the invention with the hammer piston in the lowe~nost position, in longitudinal section.
A single-blow pneumatic percussive tool shown in Figs. 1, 2 comprises a hollow cylindrical casing 1 accommodat-ing a recip~?ocatable hammer piston 2 which divides the in-terior space of the casing 1 into an upper chamber 3 and a lower chamber 4. A spring-biased valve 5 to which is se- `
cured a working member 6 is mounted on the side of the low-er chamber ~. The valve ~ e~tablishes communication of the lower chamber 4 with atmosphere at regular intervals. An air distribution device 7 having passages 8,9 and 1~ and a control lever 11 cooperating with a spring-bia~ed spool valve 12 are mounted on the side of the upper chamber 3. The upper chamber 3 alternately communicates, via the passagei 8,9,10 o~ the air distribution device 7, with gaseou~ flu-id under pressure and with atmosphere. An axial passage 13 i8 made in the hammler piston 2 and a tube 14 having an outer shoulder 15 and a continuous inner partition wall 16 is mounted in this passage. ln this embodiment, the tube 14 is made composite of two tubes of different diameters.
It should be noted that the tube may also be made integral.
'l`he tube 14 has upper port~ 17 above the partition wall 16 and lower ports 1~ below the partition wall 16. An air dis-tribution sleeve 19 is movably mounted on the tube 14. A
spring 2~ engageable with the air distribution sleeve 20 is mounted on the side of the air distribution device 7.
An inner recess 21 i9 made in the sleeve 19 for establish-ing ¢o~nunication between the upper and lower ports 17,18 for admitting gaseous fluid under pressure to the lower ch~mber 4. The hammer piston 2 has a retainer 22 for re-taining the h~mmer piston in the uppermost position.
q`he single-blow pneumatic percussive tool functions in the following manner~
Gaseous fluid under pre~sure is admitted through a socket pipe of the air distribution device 7 (~ig. 1), spool valve 12, passage 8, upper ports 17, recess 21, low-1X 9~ ~6 er port~ 18 and tube 14 to the lower chamber 4 and act~upon the h~mmer piston 2 to move the latter to the upper position. 'l`he hammer piston 2 will move the air distribution ~leeve 19 by its upper end face to compress the spring 2 80 that the sleeve will cover with its i~ner surface the lower ports 18 and ~aseous fluid under pressure will cease to get into the lower chamber 4, the h~nmer piston 2 being retained in the uppermost position by the retainer 22. ~he upper chamber 3 will thus communicate with atmosphere thro-ugh the pas~ges 9,1u of the air distribution device 6.
When the valve 5 (~ig. 2) is moved (uepre3sed) into the interior of the casing 1, the lower chamber 4 communicates with atmo~phere through the now open valve 5, and gaseous fluid under pressure iB discharged from the lower chamber 4 into atmosphere. ~Yhen the control lever 11 is depressed 80 as to move the spool valve 1, the passages 8 and 1~ are shut-off, and ga~eous fluid under pressure is admitted, via the pa~sage 9, to the upper chamber 3 to act upon the end face of the hammer piston 2 retained by the retainer 22. As 800n as pressure in the upper chamber re~che~ a pre-set value, the ha~mer piston 2 is released to rnoYe to the lower position (~ig. 2). The air distribution sleeve 19 will be moved by the spring 2V to the lowermo~t position deflned by the ~houlder 15 80 aQ to establish communication between the upper and lower ports 17, 18 throu~h the recess 21, and ~aseous fluid under pressure is discharged from the lower chamber 4 through the spring-biased valve 5 into atmosphere. At the end of travel, the hammer pi3ton 2 de-~L~9~99~;-- 7 ~

livers a blow at the ~pring-biased valve 5 to which is se-cured the working member ~ which i8 ill contact with a work-piece surface to perform useful work. If the tool is lift-ed above the workpiece surface, the valve 5 is moved by the spring 23 to the lowermo~t position so a6 to interrupt com-munication of the lower chamber 4 with atmosphere. When the control lever 11 is released ~ig. 1), the 8p~01 valve 12 will move so a~ to open the pa6sa~es 8 and 1~, and ad-mission of gaseous fluid under pres~ure through the pas-sage 9 is interrupted. I'he upper chamber 3 will communicate with atmosphere through the passages 9 and 1~. Gaseous flu-id under pressure is admitted to the lower chamber 4 thro-ugh the passage 8, upper ports 17, recess 21, lower ports 18 an~ tube 14 to act upon the end face of the ha~ner pis-ton 2. The hammer piston 2 will start movin~ towards the upper position under the action of fluid under pressure on the side of the lower chamber 4. During its movement, the harnmer piston 2 engages the air distribution sleeve 19 to move lt bo the u~per po~ition and to compre~s the spring 20. ~he air distribution sleeve 19 will cover the lower ports 18 with its inner surface, and gaseous fluid admis-sion to the lower chamber 4 is interrupted, and the hammer piston 2 is retained by the retainer 22. The cycle is then repeated.
In comparison with prior art ~ingle-blow pneumatic percussive tools, the tool according to the invention mak-es it possible to arra~ge the tube and air distribution means in the interior of the tool thus reducing the tool siz~ and imprDving its ergDnDmic characteristics.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
A single-blow pneumatic percussive tool comprising:
a hollow cylindrical casing having an upper part and a lower part;
a hammer piston movably mounted in said casing and having an axial passage;
an upper chamber defined in said upper part of said cas-ing by said hammer piston;
a lower chamber defined in said lower part of said casing by said hammer piston;
a valve which is biased by a spring on the side of said lower chamber for establishing communication of said lower chamber with atmosphere at regular intervals;
a working member secured to said valve;
an air distribution device having passages and a cont-rol lever, mounted on the side of said upper chamber and es-tablishing communication of said chamber alternately with gaseous fluid under pressure for moving said hammer piston down and with atmosphere, via said passages;
a tube mounted in said axial passage of said hammer piston for establishing communication of said lower chamber with gaseous fluid under pressure at regular intervals;
a shoulder on the outer surface of said tube;
a continuous partition wall in said tube;
upper ports in said tube above said partition wall;
lower ports in said tube below said partition wall;
an air distribution sleeve movably mounted on said tube and biased by a spring on the side of said air distribu-tion device;
said air distribution sleeve having an inner recess and being movable under the action of said hammer piston towards the upper position in which said air distribution sleeve covers said lower ports,and said air distribution sleeve being movable by a spring into the lower position defined by said shoulder in which the air distribution sleeve establishes communication between said upper and lower ports through said inner recess so as to admit gaseous fluid und-er pressure to said lower chamber to move said hammer pis-ton upwards.