Field of the Invention
[0001] The present invention relates to a pneumatic striking tool, preferably to a pneumatic
submersible boring hammer.
Background of the Invention
[0002] Submersible boring hammers cannot increase their output characteristics by increasing
their lateral dimensions, e.g. by increasing the working cylinder diameter, as the
dimensions are delimited by the bore diameter and by the annular space necessary to
exist between the bore wall and the external diameter of the hammer, whereby, this
space is used to raise borings out of the bore by exhaust air.
[0003] But it is known to increase the installed output of submersible hammers not only
by increasing the air pressure used, but also by a system of compressed air distribution
and by the following arrangement of the filling and the exhaust ducts and recesses
that supply compressed air into the working compartments of the cylinder and take
away exhaust air.
[0004] The known and commonly used plate, ring, slide and flap distribution systems usually
operate on the principle of an air pressure drop in the cylinder compartment which
is being filled after opening of the exhaust duct. From the point of view of the installed
output and efficiency it is disadvantageous that the moment of closing one working
cylinder compartment at the same time is the moment of opening the filling of the
opposite working compartment. This makes impossible to use a controlled air expansion
in the cylinder compartment that is being filled without simultaneous backpressure
growth in the opposite compartment. Moreover, the so arranged distribution systems
are sensitive to the used lubricant, moisture and impurities in the supplied compressed
air. They are intricate and, therefore, also cost intensive in production and they
incline to be defective and unreliable in service.
[0005] A better solution is a system without any independent distribution system, where
the compressed air distribution to the working compartments of the cylinder is controlled
by the striking piston directly in relationship to its momentary position.
[0006] For example, the specification EP 40026 discloses a valveless boring tool having
a cylinder and a piston that form the upper and the bottom working compartments together
with the cylinder. The piston comprises an axially arranged filling opening, a separate
axially arranged exhaust opening and filling and exhaust ducts formed at least partially
in the wall of the working cylinder. Subject to the piston position in the cylinder
in co-operation with the input pipe they provide for compressed air distribution into
the working compartments and for output of exhausted air from the hammer. The input
pipe axially passing across the upper working compartment can be fixed in an input
body or it can be carried by a piston.
[0007] Specification US 5,318,140 discloses a submersible hammer that is comprised of a
working cylinder and a piston mounted so that it can move in a cylinder. The input
body of the hammer is provided with an extension that comprises a valve part, whereby,
the valve part co-operates with the central opening of the piston. A lightening is
made in the central opening of the piston that makes possible to interconnect the
compartments above and under the valve part in certain piston position.
[0008] Document US 4 591 004 A describes a pneumatic percussion machine. However, US 4 591
004 A does not hint at a means of a filling groove, provided on the surface of the
striking piston, in order to interconnect the front working compartment of the working
cylinder with the rear cavity of the input body.
[0009] Generally, the known solutions of this kind differ in detailed design of the filling
and the exhaust ducts and the recesses in the piston, the cylinder and in other connected
parts of the hammer and the boring bit. Usually, they make possible in one or in both
working compartments of the cylinder to close the intensive filling of the respective
working cylinder compartment and the subsequent air expansion in it before opening
the exhaust independently of circumstances in the opposite cylinder compartment. From
the point of view of the output installed and the efficiency, it remains as a disadvantage
that the closure of the filling of the given working cylinder compartment in the given
piston stroke position means opening of the filling of the same working compartment
and, therefore, it brings about rising of back pressure in the same position of the
opposite stroke. In the reverse stroke such relations are desirable, as the piston
has to be halted in the back dead centre without an impact on the face of the rear
working compartment. This can be utilised advantageously by intentionally making a
compression compartment that is closed by piston in the rear dead centre, function
of which is to act as an accumulator that makes possible to utilise a part of the
energy passed on the piston during the reverse stroke for its acceleration in the
initial phase of the striking stroke. However, in case of the striking stroke the
backpressure produced by premature opening of the filling of the front cylinder working
compartment causes undesirable piston breaking. Another disadvantage of this system
is that for accelerating the piston it is not possible to utilise the whole length
of the striking stroke because in its last phase before a blow, the exhaust duct is
opened, what brings about a rapid drop of air pressure in the rear working compartment
of the cylinder. Together with the mentioned backpressure rise in the front working
compartment in this phase of the piston movement the piston starts to be significantly
braked with a consequent decrease in its striking speed and impact energy, i.e. a
decrease of the installed output of the tool and of its total effectivity.
[0010] A disadvantage of the known designs is also the interconnection between the front
working compartment and the cavity in the input body that is always at least partially
formed in the wall of the working cylinder. Thereby, the cylinder is made thinner
in the front part which is the most stressed one by abrasion caused by the bored off
rock exhausted.
Summary of the Invention
[0011] The above mentioned disadvantages are eliminated by the embodiment of a pneumatic
striking tool, in this,case of a pneumatic submersible hammer according to the present
invention, which is comprised of a front cover with a working tool and with its arrestment,
a rear input body with a built in water valve and a working cylinder, wherein a striking
piston is guided that is provided with axial and side filling and exhaust ducts, whereby,
said piston extends into a cavity of said input body by its rear extended part with
a filling recess on its surface.
[0012] According to the invention, there is provided a pneumatic submersible boring tool
as set forth in claim 1.
[0013] According to one preferred embodiment of the present invention said closing pin is
formed by a front part of a water valve body.
[0014] According to another preferred embodiment, in an axial exhaust duct, made in the
front part of said striking piston, wherein apart from said side exhaust duct passing
through said wall of said striking piston, also said side release duct is mouthed,
which passes through said striking piston wall and which follows in said filling groove
made on the surface of said striking piston and which is connected with said cylinder
bottom working compartment, an exhaust inertial slide valve of pipe-like shape is
placed so that it can slide and in said axial filling duct of said striking piston
said filling inertial slide valve of pipe-like shape is placed so that it can slide.
[0015] It is also advantageous, when on the rear extended part of said striking piston is
between said filling recess and said adjacent rear working face of said striking piston
a cylindrical part is made which in said rear cylinder working compartment defines
length of the compression compartment that is delimited by said input body front face,
said adjacent internal diameter of said working cylinder, said striking piston rear
working face and by external surface of said cylindrical part of said striking piston
rear extended part.
[0016] Another advantageous embodiment of the present invention is when said rear extended
part of said striking piston is formed as a separate part mounted in the rear part
of said striking piston and this separate part is made of a plastic.
[0017] By making a pneumatic striking tool according to this invention it is possible to
fill the front and the rear cylinder working compartment during the selected sections
of the striking and the reversing stroke at full input air pressure directly from
the input body cavity, and each of both working cylinder compartments independently
of each other, using short and substantially straight and sufficiently dimensioned
sections without losses that would otherwise be caused by cross-sectional and directional
changes in the compressed air flow route. Also independently of each other, it is
possible, from the point of view of tool effectivity, to use in both cylinder working
compartments the desired compressed air expansion in an interval between the closing
of filling and the opening of exhaust. The full piston working stroke from the rear
dead centre up to the blow moment is utilised during the striking stroke to accelerate
the piston as a consequence of the exhaust and filling inertial valve and release
duct activities, and this without the counter-pressure effect in the cylinder front
working compartment, which would otherwise be formed by opening the filling of the
front working compartment and by compression caused in it. The so, according to the
invention, controlled cycle of filling and exhausting the cylinder working compartments,
combined with reverse stroke energy accumulation in the compression compartment of
the rear dead centre increases blow rate of the striking piston combined with a growth
in its impact velocity and consequently also of its impact energy, what indicates
a growth in installed output of the striking tool and in its effectiveness. Creation
of a rear extended part of said striking piston by using a separate part mounted in
the rear part of said striking piston and the possibility to make this separate part
from plastic is practical considering the impact fatigue stress of said piston and
inertial forces acting on the rear extended part of said striking piston. This embodiment
simplifies production of said tool and increases its operational safety. For design
and production simplicity it is preferable if the closing pin controlling, in co-operation
with the mouth of said axial filling duct, opening and closing of filling the cylinder
front working compartment is formed by the front extended part of the water valve
body.
Industrial Use
[0018] Design according to the present invention can find use in case of all input air pressures
that come into consideration. The design is compact, non-demanding in production and
consequently also in price. The design is simple and consequently insensitive to operational
conditions, staff and maintenance.
Brief Description of the Drawings
[0019] The attached drawing shows an example of an embodiment of a pneumatic striking tool,
in this case of a submersible boring hammer, according to this invention, where Fig.
1 shows a section along its longitudinal axis and Fig. 2 shows a partial section through
an alternative embodiment of the rear extended part of a striking piston and through
the adjacent part of an immersible hammer.
Detailed Description of the Invention
[0020] Fig.1 shows a striking piston
2 deposited so that it can move in a working cylinder
1. A front cover
4 with an arresting ring
5, and a boring bit
6 with an exhaust pipe
38 fixed in it, are fastened by means of a front thread
3 in the front part of the working cylinder
1. By means of a rear thread
7 an input body
8 is fixed in the rear part of the working cylinder
1. A water valve body
9 with a spring
10 and a cone
11 and a valve seat
12 are placed in the input body
8. The valve body
9 is provided with openings
13 that interconnect the compartment adjacent to the cone
11 with a cavity
14 of the input body
8. The front part of the valve body
9 is extended and forms a closing pin
15. A filling groove
16 is provided on the surface of the front part of the striking piston
2 that interconnects the front working compartment
17 of the working cylinder
1 with a side filling duct
18 that passes through the wall of the striking piston
2 and is a continuation of an axial filling duct
19. This duct
19 passes through a rear face
20 of a rear extended part
21 of the striking piston
2 and mouths into the cavity
14 of the input body
8. The surface of said striking piston
2 is also provided with an exhaust groove
22 that is interconnected by a side exhaust duct
23 that passes through the wall of the striking piston
2, with an axial exhaust duct
24 that passes through a striking face
25 of the striking piston
2 and is a continuation of a drilling
39 of a drilling bit
6. The rear extended part
21 of the striking piston
2 passes through an opening in the front face
26 of the input body
8. A filling recess
27 is provided on the surface of the rear extended part
21, whereby said recess
27 is delimited by two cylindrical surfaces. The front cylindrical part
28 of the rear extended part
21 of the striking piston
2, adjacent to the rear working face
29 of the striking piston
2, determines the length of the compression compartment that is formed during the reverse
stroke of the striking piston
2 in the rear working compartment
30 of the working cylinder
1. The internal wall of the cylinder
1 is provided with an exhaust recess
31 that is adjacent to the rear working compartment
30 of the working cylinder
1. In an axial exhaust duct
24 an exhaust inertial slide valve
32 is placed so that it can slide, whereby its front position is delimited by a front
stop
33 and the rear one by the bottom of an axial exhaust duct
24. A release duct
34 is also mouthed into an axial exhaust duct
24, whereby said duct
34 passes through the wall of the striking piston
2 and it is interconnected by a filling groove
16 with the front working compartment
17 of the working cylinder
1. A filling inertial slide valve
35 is placed in the axial filling duct
19 so that it can slide, whereby its rear position is delimited by a rear stop
36 and its front one by the bottom of the axial filling duct
19.
[0021] Fig. 2 shows an alternative embodiment of the striking piston
2, where its rear extended part
21 is formed by an independent part
37 with a passing axial filling duct
19, a filling recess
27, a rear face
20 and a front cylindrical part
28. The front part of the separate part
37 forms the rear stop
36 of the filling inertial slide valve
35.
[0022] A tool according to the present invention operates in the following way:
[0023] When compressed air is brought into the striking tool, the cone
11 opens flow of compressed air through the openings
13 of the valve body
9 into the cavity of the input body
8. From there, compressed air is led through the axial filling duct
19, the side filling duct
18 and the filling groove
16 into the front working compartment
17 of the working cylinder
1. The striking piston
2 is accelerated by the force of compressed air in the front working compartment
17 towards the rear dead centre. From the rear working compartment
30 exhaust air from the previous cycle of the piston
2 escapes through the exhaust recess
31, the exhaust groove
22, the side exhaust duct
23, the axial exhaust duct
24, the exhaust pipe
38 and the boring
39 of the bit
6 to the bottom of the bore and thereby to atmosphere. The striking piston
2 carries away with it the exhaust inertial slide valve
32 and the filling inertial slide valve
35, that are leaned against the respective stops as a consequence of action of inertial
forces, so that they are held shifted into their front positions, i.e. flows through
the side exhaust duct
23 and the side filling duct
18 are open, flow through the release duct
34 is closed. At certain phase of the reversal stroke, the rear working face
29 closes the exhaust recess
31 and thereby also all exhaust from the rear working compartment
30. The striking piston
2 continues in reverse movement and at the moment when the axial filling duct
19 is closed by the closing pin
15, filling of the front working compartment
17 by compressed air is terminated, and in the next phase of the striking piston
2 reverse movement expansion takes place in it. In the next phase of the striking piston
2 reverse movement, the filling recess
27 interconnects the rear working compartment
30 with the cavity
14 of the input body
8 and the rear working compartment
30 starts to be filled with compressed air that, in relation to the pressure circumstances
in the front
17 and the rear
30 working cylinder
1 compartments, gradually slows down movement of the striking piston
2. In the next movement phase of the striking piston
2, the striking face
25 opens flow into the exhaust pipe
38, through which the exhaust air from the bottom working compartment
17 escapes to atmosphere through the boring
39 of the bit
6. After closing of the filling recess
27 by the front face
26 of the input body
8, air in the rear working compartment
30 is compressed, what, together with a pressure drop in the front working compartment
17, causes a rapid breaking of the striking piston
2 up to a halt in the rear dead centre. The exhaust
32 and the filling
35 inertial slide valves continue in their movements because of inertia and so they
shift themselves into their rear positions delimited by their rear stops. Thereby,
closing of the side filling duct
18 and the side exhaust duct
23 and opening of the release duct
34 take place. By compression the striking piston
2 is accelerated forward towards the striking stroke, together with both inertial slide
valves
32 and
35 that are held by inertia in their rear positions. In the next phase of the striking
stroke, the filling recess
27 opens entry of compressed air from the cavity
14 of the input body
8 into the rear working compartment
30. Then, the striking piston
2 closes the exhaust from the front working compartment
17 by its striking face
25. Compression that would otherwise rise in the front working compartment
17 is released through the filling grove
16, the release duct
34, the axial exhaust duct
24 and the boring
39 of the bit
6 to atmosphere during the whole remaining part of the striking stroke of the piston
2. The striking piston
2 continues in its striking stroke up to a position when the compressed air input into
the rear working place
30 through the filling recess
27 is closed. In the next phase of the forward movement of the striking piston
2 expansion in the rear working compartment
30 takes place and during further movement of the striking piston
2, the closing pin
15 opens input of compressed air into the axial filling duct
19 at certain moment, but air flow into the front working compartment
17 through the side filling duct
18 and the side filling groove
16 is closed by the filling inertial slide valve
35. Before a blow of the piston
2 on the bit
6 the exhaust recess
31 is opened by the rear working face
29 of the striking piston
2, but an exhaust from the rear working compartment
30 through the exhaust groove
22 and the side exhaust duct
23 does not take place, as the side exhaust duct
23 is closed by exhaust inertial slide valve
32. The striking piston
2 is accelerated by expanding air in the rear working compartment
30 up to the moment of a blow, without any back pressure in the front working compartment
17. Not sooner than when the piston
2 strikes on the boring bit
6, the inertial slide valves
32 and
35 slide into their front positions by inertia. Thereby, the side filling duct
18 is opened by the filling inertial slide valve
35 and compressed air is brought to the front working compartment
17 through the filling duct
18 and the filling groove
16. Simultaneously, by opening the side exhaust duct
23 by the exhaust inertial slide valve
32 exhaust from the rear working compartment
30 through the recess
31, the exhaust groove
22, the side exhaust duct
23, the axial exhaust duct
24 and the boring
39 of the bit
6 to atmosphere is made possible. After a blow, the striking piston
2 is accelerated into the reverse movement and its working cycle is repeated. By a
controlled filling and releasing of the working compartments
17 and
30 according to this invention the output characteristics and effectiveness of this
tool can be increased, whereby its design simplicity and undemanding production and
operation are maintained.
1. A pneumatic submersible boring tool comprising a front cover (4), a working tool (6),
an arrestment (5), a rear input body (8) with a built in water valve (9), and a working
cylinder (1) in which a striking piston (2) is guided, the striking piston (2) being
provided with an axial filling duct (19), side filling duct (18) and a side exhaust
duct (23), wherein a rear extended part (21) of the striking piston (2) extends into
a cavity (14) of the input body (8), the rear extended part (21) having a filling
recess (27) on its surface, wherein a front working compartment (17) of the working
cylinder (1) is connected, by a filling groove (16) provided on the surface of the
striking piston (2), with the side filling duct (18), the side filling duct (18) passing
through the wall of the striking piston (2), wherein the axial filling duct (19) is
arranged in the rear extended part (21) of the striking piston (2) and is connected
with the cavity (14) of the input body (8), and wherein the axial filling duct (19)
is also connected to the side filling duct (18), wherein a closing pin (15) extends
axially in the cavity (14), wherein the front face of the pin (15) is placed within
an axial longitudinal section that is delimited by the front and the rear dead centres
of the rear face (20) of the rear extended part (21) of the striking piston (2), and
wherein the external diameter of the closing pin (15) is smaller than the internal
diameter of the axial filling duct (19).
2. A pneumatic tool according to claim 1, wherein the closing pin (15) is formed by the
front part of a water valve body (9).
3. A pneumatic tool according to claim 1, further comprising an axial exhaust duct (24)
provided in the front part of the striking piston (2), opening into the side exhaust
duct (23), the side exhaust duct (23) passing through the wall of the striking piston
(2) and connected to an exhaust groove (22) formed on the surface of the striking
piston (2), and also comprising a side release duct (34) passing through the wall
of the striking piston (2), connected to the filling groove (16) and connected with
the front working compartment (17) of the working cylinder (1), wherein an exhaust
inertial slide valve (32) of pipe-like shape is slidably mounted in the axial exhaust
duct (24).
4. A pneumatic tool according to claim 1, wherein a filling inertial slide valve (35)
of pipe-like design is slidably mounted in the axial filling duct (19) of the striking
piston (2).
5. A pneumatic tool according to claim 1, wherein, on the rear extended part (21) of
the striking piston (2) between the filling recess (27) and an adjacent rear working
face (29) of the striking piston (2), a cylindrical part (28) is made that, in said
rear working compartment (30) of said cylinder (1), defines the length of a compression
compartment which is delimited by front face (26) of the input body (8), by the adjacent
internal diameter of said working cylinder (1), by the rear working face (29) of the
striking piston (2) and by the external surface of the cylindrical part (28) of the
rear extended part (21) of the striking piston (2).
6. A pneumatic tool according to claim 1, wherein the rear extended part (21) of the
striking piston (2) is formed of an independent part (37) which is fastened to the
rear part of the striking piston (2).
7. A pneumatic tool according to claim 6, wherein the independent part (37) is made of
plastic.
1. Pneumatisches tauchfähiges Bohrwerkzeug, umfassend eine Vorderabdeckung (4), ein Arbeitswerkzeug
(6), eine Anlage (5), einen hinteren Eingabekörper (8) mit einem eingebauten Wasserventil
(9), und einen Arbeitszylinder (1), in dem ein Aufschlagkolben (2) geführt wird, wobei
der Aufschlagkolben (2) mit einem axialen Füllkanal (19), einem Seitenfüllkanal (18)
und einem Seitenauslasskanal (23) versehen ist, wobei sich ein hinten erweiterter
Teil (21) des Aufschlagkolbens (2) in einen Hohlraum (14) des Eingabekörpers (8) hinein
erstreckt, wobei der hinten erweiterte Teil (21) eine Füllausnehmung (27) auf ihrer
Oberfläche aufweist, wobei ein vorderes Arbeitsfach (17) des Arbeitszylinders (1),
über eine Füllnut (16), die auf der Oberfläche des Aufschlagkolbens (2) vorgesehen
ist, mit dem Seitenfüllkanal (18) verbunden ist, wobei der Seitenfüllkanal (18) durch
die Wand des Aufschlagkolbens (2) geht, wobei der axiale Füllkanal (19) in dem hinten
erweiterten Teil (21) des Aufschlagkolbens (2) angeordnet ist und mit dem Hohlraum
(14) des Eingabekörpers (8) verbunden ist und wobei der axiale Füllkanal (19) auch
mit dem Seitenfüllkanal (18) verbunden ist, wobei sich ein Schließstift (15) axial
in dem Hohlraum (14) erstreckt, wobei die Vorderseite des Stifts (15) innerhalb eines
axialen longitudinalen Abschnitts platziert wird, der durch die vorderen und hinteren
Totzentren der Rückseite (20) des hinten erweiterten Teils (21) des Aufschlagkolbens
(2) abgegrenzt wird und wobei der externe Durchmesser des Schließstifts (15) kleiner
als der innere Durchmesser des axialen Füllkanals (19) ist.
2. Pneumatisches Werkzeug nach Anspruch 1, wobei der Schließstift (15) durch den vorderen
Teil eines Wasserventilkörpers (9) gebildet ist.
3. Pneumatisches Werkzeug nach Anspruch 1, ferner umfassend einen axialen Auslasskanal
(24), der in dem vorderen Teil des Aufschlagkolbens (2) vorgesehen ist, wobei er sich
in den Seitenauslasskanal (23) hinein öffnet, wobei der Seitenauslasskanal (23) durch
die Wand des Aufschlagkolbens (2) geht und mit einer Auslassnut (22) verbunden ist,
die auf der Oberfläche des Aufschlagkolbens (2) gebildet ist, und auch umfassend einen
Seitenfreigabekanal (34), der durch die Wand des Aufschlagkolbens (2) geht, mit der
Füllnut (16) verbunden ist und mit dem vorderen Arbeitsfach (17) des Arbeitszylinders
(1) verbunden ist, wobei ein Auslass-Trägheitsverschiebeventil (32) einer rohrartigen
Form verschiebbar in dem axialen Auslasskanal (24) angebracht ist.
4. Pneumatisches Werkzeug nach Anspruch 1, wobei ein Füllträgheitsverschiebeventil (35)
in einer rohrartigen Konstruktion verschiebbar in dem axialen Füllkanal (19) des Aufschlagkolbens
(2) angebracht ist.
5. Pneumatisches Werkzeug nach Anspruch 1, wobei auf dem hinten erweiterten Teil (21)
des Aufschlagkolbens (2) zwischen der Füllausnehmung (27) und einer angrenzenden hinteren
Arbeitsfläche (29) des Aufschlagkolbens (2) ein zylindrisches Teil (28) gebildet ist,
das in dem hinteren Arbeitsfach (30) des Zylinders (1) die Länge eines Kompressionsfachs
definiert, welches durch die Vorderseite (26) des Eingabekörpers (8), durch den angrenzenden
internen Durchmesser des Arbeitszylinders (1) durch die hintere Arbeitsseite (29)
des Aufschlagkolbens (2) und durch die externe Oberfläche des zylindrischen Teils
(28) des hinten erweiterten Teils (21) des Aufschlagkolbens (2) abgegrenzt ist.
6. Pneumatisches Werkzeug nach Anspruch 1, wobei der hinten erweiterte Teil (21) des
Aufschlagkolbens (2) aus einem unabhängigen Teil (37) gebildet ist, der an dem hinteren
Teil des Aufschlagkolbens (2) befestigt ist.
7. Pneumatisches Werkzeug nach Anspruch 6, wobei der unabhängige Teil (37) aus Plastik
gebildet ist.
1. Outil de forage pneumatique submersible comprenant un cache avant (4), un outil de
travail (6), un arrêt (5), un corps d'admission arrière (8) comportant un clapet à
eau incorporé (9) et un cylindre de travail (1) dans lequel est guidé un piston frappeur
(2), le piston frappeur (2) comportant une conduite de remplissage axiale (16), une
conduite de remplissage latérale (18) et une conduite d'évacuation latérale (23),
une partie à extension arrière (21) du piston frappeur (2) s'étendant dans une cavité
(14) du corps d'admission (8), la partie à extension arrière (21) comportant un évidement
de remplissage (27) sur sa surface, un compartiment de travail avant (17) du cylindre
de travail (1) étant raccordé par l'intermédiaire d'une rainure de remplissage (16)
agencée sur la surface du cylindre frappeur (2) à la conduite de remplissage latérale
(18), la conduite de remplissage latérale (18) traversant la paroi du piston frappeur
(2), la conduite de remplissage axiale (19) étant agencée dans la partie à extension
arrière (21) du piston frappeur (2) et étant raccordée à la cavité (14) du corps d'admission
(8), la conduite de remplissage axiale (19) étant également raccordée à la conduite
de remplissage latérale (18), une broche de fermeture (15) s'étendant axialement dans
la cavité (14), la face avant de la broche (15) étant agencée dans une section longitudinale
axiale délimitée par les centres morts avant et arrière de la face arrière (20) de
la partie à extension arrière (21) du piston frappeur (2), le diamètre extérieur de
la broche de fermeture (15) étant inférieur au diamètre intérieur de la conduite de
remplissage axiale (19).
2. Outil pneumatique selon la revendication 1, dan lequel la broche de fermeture (15)
est formée par la partie avant du corps du clapet d'eau (9).
3. Outil pneumatique selon la revendication 1, comprenant en outre une conduite d'évacuation
axiale (24) agencée dans la partie avant du piston frappeur (2), ouverte vers la conduite
d'évacuation latérale (23), la conduite d'évacuation latérale (23) traversant la paroi
du piston frappeur (2) et étant raccordée à une rainure d'évacuation (22) formée sur
la surface du piston frappeur (2), et comprenant également une conduite de relâchement
latérale (34) traversant la paroi du piston frappeur (2), raccordée à la rainure de
remplissage (16) et raccordée au compartiment de travail avant (17) du cylindre de
travail (1), un robinet à tiroir d'évacuation à inertie (32) de forme tubulaire étant
monté par glissement dans ladite conduite d'évacuation axiale (24).
4. Outil pneumatique selon la revendication 1, dans lequel un robinet à tiroir de remplissage
à inertie (35) de forme tubulaire est monté par glissement dans la conduite de remplissage
axiale (19) du piston frappeur (2).
5. Outil pneumatique selon la revendication 1, dans lequel est agencée sur la partie
à extension arrière (21) du piston frappeur (2), entre l'évidement de remplissage
(27) et une face de travail arrière adjacente (29) du piston frappeur (2), une partie
cylindrique (28), définissant dans ledit compartiment de travail arrière (30) dudit
cylindre (1) la longueur d'un compartiment de compression délimité par la face avant
(26) du corps d'admission (8) par le diamètre intérieur adjacent dudit cylindre de
travail (1), par la face de travail arrière (29) du piston frappeur (2) et par la
surface externe de la partie cylindrique (28) de la partie à extension arrière (21)
du piston frappeur (2).
6. Outil pneumatique selon la revendication 1, dans lequel la partie à extension arrière
(21) du piston frappeur (2) est constituée par une partie indépendante (37) fixée
sur la partie arrière du piston frappeur (2).
7. Outil pneumatique selon la revendication 6, dans lequel la partie indépendante (37)
est composée de plastique.