U.S. patent application number 09/741289 was filed with the patent office on 2002-02-21 for portable, combustion-engined tool and a method of controlling the tool operation.
Invention is credited to Bonig, Stefan, Buchel, Franz, Thieleke, Joachim, Wolf, Iwan.
Application Number | 20020020374 09/741289 |
Document ID | / |
Family ID | 7934226 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020020374 |
Kind Code |
A1 |
Buchel, Franz ; et
al. |
February 21, 2002 |
Portable, combustion-engined tool and a method of controlling the
tool operation
Abstract
A method of controlling operation of a portable,
combustion-engined tool including a combustion chamber (1) an
inlet/outlet valve (26) of which is closed or is opened dependent
on an operational phase of the tool, with the method including
igniting a fuel gas mixture filling the combustion chamber (1) for
build-up of gas pressure therein and closing or opening the
inlet/outlet valves (26) dependent on the gas pressure developed in
the combustion chamber (1), and a tool in which the method is
implemented.
Inventors: |
Buchel, Franz; (Ruggell,
LI) ; Bonig, Stefan; (Wasserburg, DE) ;
Thieleke, Joachim; (Wasserburg, DE) ; Wolf, Iwan;
(Chur, CH) |
Correspondence
Address: |
DAVID TOREN, ESQ.
SIDLEY, AUSTIN, BROWN & WOOD, LLP
875 THIRD AVE
NEW YORK
NY
10022
US
|
Family ID: |
7934226 |
Appl. No.: |
09/741289 |
Filed: |
December 19, 2000 |
Current U.S.
Class: |
123/90.15 ;
123/90.16 |
Current CPC
Class: |
B25C 1/08 20130101 |
Class at
Publication: |
123/90.15 ;
123/90.16 |
International
Class: |
F01L 009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 1999 |
DE |
199 62 598.0 |
Claims
What is claimed is:
1. A method of controlling operation of a portable,
combustion-engined tool including a combustion chamber (1) an
inlet/outlet valve (26) of which is closed or is opened dependent
on an operational phase of the tool, the method comprising the
steps of igniting a fuel gas mixture filling the combustion chamber
(1) for build-up of gas pressure therein; and closing or opening
the inlet/outlet valve (26) dependent on the gas pressure developed
in the combustion chamber (1).
2. A method according to claim 1, wherein closing of the valve (26)
starts after an overpressure has been created in the combustion
chamber (1).
3. A method according to claim 2, wherein the closing starts after
the pressure has been increased to a predetermined value.
4. A method according to claim 1, wherein opening of the valve (26)
starts after an expiration of a predetermined time period after an
overpressure has been developed in the combustion chamber.
5. A method according to claim 4, when the predetermined time
period starts at a momen a maximum gas pressure has been developed
in the combustion chamber.
6. A portable, combustion-engined tool, comprising a combustion
chamber (1); an inlet/outlet valve (26) provided in the combustion
chamber (1); blocking means (54) providing for closing and opening
the inlet/outlet valve (26); and means for controlling operation of
the blocking means (54) dependent on a gas pressure developed in
the combustion chamber.
7. A tool according to claim 6, wherein the blocking means (54)
comprises a pneumatic device.
8. A tool according to claim 7, wherein the blocking means (54)
comprises a check valve (55) connected with the combustion chamber
(1); and a conduit (62) connecting the check valve (55) with a
pneumatic cylinder (56) of the pneumatic device; and wherein the
controlling means comprises a throttle (57) for communicating the
conduit (62) with a surrounding atmosphere.
9. A tool according to claim 8, wherein the blocking means (54)
comprises a blocking member (58), and the pneumatic device
comprises a piston (64) displaceable in the pneumatic cylinder (56)
and having a piston rod (65) connected with the blocking member
(58) for pivoting same between blocking and release positions
thereof.
10. A tool according to claim 6, wherein the tool further comprises
a drive ring (28) for effecting closing and opening of the
inlet/outlet valve (26); and the blocking means (54) comprising
means for blocking the drive ring (28).
11. A tool according to claim 6, wherein the combustion chamber (1)
is formed as a collapsible chamber having a plurality of walls (14,
18) displaceable along a longitudinal extent of the combustion
chamber (1); and wherein the blocking means (54) provides for
locking of the displaceable walls of the combustion chamber in
predetermined positions thereof and for release of the displaceable
walls.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a portable,
combustion-engined tool, in particular a setting tool for driving
in fastening elements and including a combustion chamber an
inlet/outlet valve of which is closed or opened dependent on an
operational phase of the tool, and to a method of controlling the
operation of such a tool.
[0003] 2. Description of the Prior Art
[0004] In the tool described above, a drive energy is obtained by
combustion of a fuel gas mixture and is transmitted by a piston to
a fastening element. By pressing the tool against an object in
which the fastening element is to be driven in, an ignition of the
fuel gas mixture in the combustion chamber is initiated. The
initiation of the ignition takes place upon actuation of an
ignition device by a trigger which is actuated upon the tool being
pressed against the object. The ignition device produces an
electrical spark that ignites the fuel gas mixture, starting a
combustion process. The increased pressure, which is produced by
the combustion of the fuel gas mixture, acts on the piston which
adjoins the combustion chamber, driving the same in the setting
direction. At the end of its displacement in the setting direction,
the piston passes past outlet openings which are formed in a guide
cylinder, in which the piston is located, and through which opening
exhaust or waste gases can be at least partially removed. The
piston then returns to its initial position as a result of an
underpressure created in the combustion chamber as a result of
cooling down of residual gases still remaining in the combustion
chamber. During the time the piston returns to its initial
position, the combustion chamber should remain sealed from the
surrounding environment. The inlet/outlet valve, through which
fresh air enters the combustion chamber, should open only after the
return movement of the piston has been completed. Generally, the
time necessary for return of the piston to its initial position,
increases with an increase of the tool temperature. In addition, a
high-energy tool requires that a large expansion volume be
available, which also increases the time of the return movement of
the piston.
[0005] In conventional tools, the inlet/outlet valve can be closed
with an appropriate latch fixedly connected with a trigger by a
toggle lever. The inlet/outlet valve becomes open as soon as the
trigger, which is associated with the piston, returns to its
initial position.
[0006] The locking of the inlet/outlet valve with a trigger means
that the shift point of the trigger cannot any more be arbitrary
selected. The ignition switch can only then be actuated when the
closing of the inlet/outlet valve has been completed, i.e., much
later after the trigger movement. However, a prolonged trigger
movement adversely affects or influences the customer acceptance of
such tools. Further, with a hot tool, the return movement of the
piston, as it has already been discussed above, takes more time. In
this case, the user has to hold the trigger in its pulled position
much longer in order to prevent the piston from occupying an
erroneous position.
[0007] Naturally, in order to increase the time during which the
piston returns to its initial position, the movement of the trigger
can be damped. However, damping of the trigger movement adversely
affects the trigger characteristics as the triggering force is
increased, and the trigger itself does not return to its initial
position sufficiently rapidly. Users view dampening of a trigger
very unfavorably as it reduces the output and increases actuation
forces that need be applied by a user.
[0008] A further non-insignificant problem consists in that not in
each case, return of the piston to its exact initial position is
insured.
[0009] Accordingly, an object of the present is a tool of the
above-described type and a method of controlling its operation
which would insure a complete return of the piston to its initial
position before the inlet/outlet valve opens, without any
manipulation of the trigger by a user.
SUMMARY OF THE INVENTION
[0010] This and other objects of the present invention, which will
become apparent hereinafter, are achieved by providing a tool
having blocking means providing for closing and opening of the
inlet/outlet valve, and means for controlling the operation of the
blocking means in accordance with the pressure in the combustion
chamber; and by providing a method according to which the closing
and opening of the inlet/outlet valve is effected dependent on the
gas pressure in the combustion chamber.
[0011] In this way, the closing of the inlet/outlet valve is
automatized and, in addition, ignition of the gas mixture in the
combustion chamber takes place independent of the displacement
position of the trigger. In this way, it is insured that the piston
always returns to its initial position before opening of the
inlet/outlet valve. The operation is effected completely
automatically, without intervention of the user, in particular,
because opening of the inlet/outlet valve is not any more
controlled by the trigger movement.
[0012] As soon as an overpressure is produced in the combustion
chamber after ignition of the fuel gas mixture therein, at least
one inlet/outlet valve can be closed (if the combustion chamber has
several inlet/outlet valves). This can in principle take place at
any overpressure as closing of the inlet/outlet valve(s) alone is
not absolutely necessary for displacement of the piston. However,
closing should take place in each case after the overpressure in
the combustion chamber has been created and the piston has been
displaced, as now retaining of the underpressure, which is
necessary for return of the piston to its initial position as a
result of cooling of the residual gases, should be insured. The
combustion chamber, in this case, should not be aerated, and the
inlet/outlet valve should remain closed, which requires locking the
valve in its closed position. Otherwise, a complete return of the
piston to its initial position would not have been possible. To
unsure this, closing already starts after the gas pressure have
reached a predetermined, relatively small value.
[0013] Opening of the inlet/outlet valve takes place after
expiration of a predetermined time period after overpressure in the
combustion chamber has been produced. The predetermined time period
can, e.g., be determined based on previous empirically determined
data. At that, the time, necessary for return of the piston to its
initial position, should lie within the predetermined time period.
It proved advantageous to count the predetermined time period
starting from the point the maximum gas pressure in the combustion
chamber has been reached, as a maximum gas pressure can be easily
achieved in the combustion chamber.
[0014] According to the present invention, as soon as the gas
overpressure has been detected, somewhat shortly after the
beginning of the ignition process, the closing takes place. Then,
the time-delay element, which provides for automatic opening after
a predetermined time period, is actuated. This time period, as it
has already been discussed above, is so selected that opening
starts after the piston has been completely returned to its initial
position. The return of the piston to its initial position can take
place independent of the actuation of the trigger which insures a
reliable operation of the tool.
[0015] The blocking device can be formed in any arbitrary manner.
It only should be insured that it reacts to the inner pressure of
the combustion chamber. When the blocking device is formed as an
electro-mechanical or purely electrical device, for determining the
inner pressure in the combustion chamber, a pressure/voltage
transformer can be used. According to the invention, the blocking
device can include a pneumatic device, in which case, its operation
is initiated directly by the pressure in the combustion
chamber.
[0016] According to preferred embodiment of the present invention,
the blocking device includes a check valve connected with the
combustion chamber, and a pneumatic cylinder located downstream of
the check valve, with the conduit connecting the check valve with
the pneumatic cylinder communicating with the surrounding
environment via a throttle. The check valve only permits gas flow
from the combustion chamber to the pneumatic cylinder for actuating
a piston having a piston rod and displaceable in the pneumatic
cylinder. After the over pressure in the combustion chamber reaches
its maximum and is them reduced, the check valve closes
automatically as the pressure in the conduit, which connects the
check valve with the pneumatic cylinder, is greater than in the
combustion chamber. The conduit, together with the throttle, forms
the time-delay element as the pressure in the conduit is gradually
reduced by the throttle. As the pressure in the conduit is reduced,
the piston is biased to its initial position by a compression
spring located in the cylinder, releasing the blocking member which
results in opening of the inlet/outlet valve. The speed of the
movement of the piston in the cylinder and the release of the
inlet/outlet valve can be selected by adjusting the throttle,
whereby the predetermined time period, which is determined by the
time necessary for return of the piston into its initial position
can be matched to corresponding environmental conditions and/or
constructive features of the tool.
[0017] The piston rod of the piston of the pneumatic cylinder can,
e.g., pivot the blocking member into the displacement path of a
drive ring, which is arranged outside of the combustion chamber,
for blocking the movement of the drive ring or releasing the drive
ring which actuates the inlet/outlet valve. Due to the use of the
pivotal blocking member, the dimensions of the entire construction
are only slightly increased.
[0018] The present invention can be used in tools having a
single-volume combustion chamber. However, the invention can also
be used in tools having a multi-sectional combustion chamber the
chamber sections of which are separated by one or several
separation wall(s) or plate(s) provided with a plurality of
through-openings. In the later case, the pressure in the chamber
section adjoining the piston controls the closing and opening of
the inlet/outlet valve or valves. The present invention can also be
used with tools having collapsible combustion chambers which
include a plurality of chamber sections separated by movable walls
which are pushed onto each other during deaeration of the
combustion chamber, which results in collapse of the combustion
chamber. As long as the aeration/deaeration valve(s) remains
closed, and as long as the piston has not yet returned to its
initial position, the collapse of the combustion chamber should be
prevented, so that the same pressure conditions, which control
closing/opening of the inlet/outlet or aeration/deaeration valve,
control the locking or release of the movable walls of the
combustion chamber.
[0019] The novel features of the present invention, which are
considered as characteristic for the invention, are set forth in
the appended claims. The invention itself, however, both as to its
construction and its mode of operation, together with additional
advantages and objets thereof, will be best understood from the
following detailed description of preferred embodiments, when read
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In the Drawings:
[0021] FIG. 1 shows an axial cross-sectional view of a
combustion-engined tool according to the present invention in the
region of the tool combustion chamber, with completely expanded
chamber sections but with the movable walls not yet locked in their
positions;
[0022] FIG. 2 shows a cross-sectional view of the tool shown in
FIG. 1 in a condition after ignition, with the movable walls being
locked in their positions and the piston being displaced;
[0023] FIG. 3 show a view similar to that of FIG. 2 but with the
piston on its way to its initial position;
[0024] FIG. 4 shows a view similar to that of FIG. 1 with unlocked
movable walls; and
[0025] FIG. 5 shows a cross-sectional view of the tool in the
region of its combustion chamber, with the piston in its initial
position and the chambers sections in their collapsed
condition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] A combustion chamber 1 of the inventive combustion-engined
tool, in particular, of a setting tool, which is shown in FIG. 1,
has a cylindrical shape and includes a cylindrical wall 2 and a
ring-shaped bottom 3 adjoining the cylindrical wall 2. In the
center of the bottom 3, there is provided an opening 4. A guide
cylinder 5, which as a cylindrical wall 6 and a bottom 7, adjoins
the opening 4 in the bottom 3 of the combustion chamber 1. A piston
8 is slidably displaceably arranged in the guide cylinder 5 for
displacement in the longitudinal direction of the guide cylinder 5.
The piston 8 consists of a piston plate 9 facing the combustion
chamber 1 and a piston rod 10 extending from the center of the
piston plate 9. The piston rod 10 projects through an opening 11
formed in the bottom 7 of the guide cylinder 5.
[0027] FIG. 1 shows a non-operational position of the setting tool
in which the piston 8 in its rearward off-position. The side of the
piston plate 9 adjacent to the bottom 3 of the combustion chamber 1
is located closely adjacent to the bottom 3, with the piston rod 10
projecting only slightly beyond the bottom 7 of the guide cylinder
5.
[0028] Sealing rings can be provided on opposite sides of the
piston plate 9 to seal the chambers on the opposite sides of the
piston plate 9 from each other.
[0029] Inside of the combustion chamber 1, there is provided a
cylindrical plate 14 further to be called a movable combustion
chamber wall or movable wall. The plane of the plate 14 extends
transverse to the longitudinal direction of the tool. The movable
wall 14 is displaceable in the longitudinal direction of the
combustion chamber 1. For separating the chambers on opposite sides
of the movable wall 14, an annular sealing is provided on the
circumference of the movable wall. The movable wall 14 has a
central opening 16, with an annular sealing provided in the wall of
the opening 16.
[0030] Between the movable wall 14 and the annular bottom 3 of the
combustion chamber 1, there is provided a separation plate 18. The
separation plate 18 has a circular shape and an outer diameter
corresponding to the inner diameter of the combustion chamber. The
side of the separation plate 18 adjacent to the movable wall 14 is
provided with a cylindrical lug 19 that projects through he central
opening 16 in the movable wall 14. The length of the lug 19 exceeds
the thickness of the movable wall 14 in several times. The annular
sealing sealingly engages the outer circumference of the
cylindrical lug 19. At its free end, the cylindrical lug 19 is
provided with a shoulder 20 the outer diameter of which exceeds the
outer diameter of the lug 19 and the inner diameter of the opening
16 of the movable wall 14. At the edge of the opening 16, there is
provided a hollow cylindrical projection 17 connected with the
movable wall 14. The hollow projection 17 surrounds the lug 19. The
free end of the projection 17 is located below the shoulder 20.
[0031] In the idle position of the tool, the separation plate 18
lies on the bottom 3, and the movable wall 14 lies on the
separation plate 18. The combustion chamber 1 is in its completely
collapsed condition. Upon the tool being pressed against an object
into which a fastening element is to be driven in, as it would be
explained later, the movable wall 14 is lifted and becomes
separated from the separation plate 18, moving away therefrom.
After a while, the projection 17 engages the shoulder 20 of the lug
19 of the separation plate 18. At that, the movable wall 14 and the
separation plate 18 are spaced by a predetermined distance
determined by the position of the shoulder 20. The movable wall 14
and the separation plate 18 form together a forechamber 21 which,
in effect, is a section of the combustion chamber 1 and which
further below will be referred to as a forechamber section 21. Upon
further displacement of the movable wall 14, the movable wall 14
and the separation plate 18 move together, so that a further
chamber section, which further will be referred to as a main
chamber section is formed between the separation plate 18 and the
bottom 3 of the piston plate 9. The main chamber section is
designated with a reference numeral 22. FIG. 1 shows both chamber
sections 21, 22 in their completely expanded condition.
[0032] For displacing the movable wall 14, there are provided
several, e.g., three drive rods 23 uniformly distributed along the
circumference of the movable wall 14 and fixedly connected
therewith. Only one of the drive rods 23 is shown in FIG. 1. The
drive rods 23 extend parallel to the axis of the combustion chamber
1 and outside of the cylindrical wall 6 of the guide cylinder 5.
The drive rods 23 extend through openings 24, respectively, formed
in the separation plate 18 and through corresponding openings 25
formed in the bottom 3 of the combustion chamber 1. The openings 25
are formed as ventilation openings and have a conical shape. The
movable wall 14 is connected with drive rods 23 by, e.g., screws
which extend through the movable wall 14 and are screwed into the
drive rods 23. The free ends of the drive rods 23 are connected
with each other by a drive ring 28 which is arranged concentrically
with the combustion chamber axis and which circumscribes the guide
cylinder 5. The drive ring 28 is connected with the drive rods 23
by screws which extend through the drive ring and are screwed into
the drive rods 23 through end surfaces of the free ends of
respective drive rods 23. Each of the drive rods 23 supports a
compression spring extending between the bottom 3 of the combustion
chamber 1 and the drive ring 28. The compression springs 30 are
designed for pulling the movable wall 14 toward the bottom 3.
[0033] As it has already mentioned above, the openings 25 in the
bottom 3 of the combustion chamber 1, which also serve as
ventilation openings, are conically widened outwardly. A valve
tappet 32 sealingly extends into each opening 25. The valve tapped
32 is located, with the opening 25 being open, outside of the
combustion chamber 1 or beneath the bottom 3 and is retained there
by a shoulder 33 provided on the drive rode 23. When the drive rods
23 are pushed in the direction toward the bottom 3, the shoulders
33 push the valve tappets 32 into the openings 25, closing the
valves 26 formed by the walls of the openings 25 and the valve
tappets 32. The valve 26 is formed as an inlet/outlet valve. It is
to be pointed out that the separation plate 18 has a plurality of
opening 38 equidistantly spaced from the axis of the combustion
chamber 1. Further, a plurality of openings 39 are provided at the
lower end of the guide cylinder 5 for letting air out of the guide
cylinder 5 upon movement of the piston 8 toward the guide cylinder
bottom 7. At the lower end of the guide cylinder 5, there is also
provided damping means 40 for damping the movement of the piston 8.
As soon as the piston 8 passes the openings 39, the waste gases are
expelled from the guide cylinder 5 through the openings 39.
[0034] Two radial through-openings 41, 41 are provided in the
cylindrical wall 2 of the combustion chamber 1. Two conduits (not
shown), which extend from outside into the through-openings 41, 42,
communicate the combustion chamber 1 with a metering valve and
provide for injection of, e.g., liquefied fuel gas into respective
combustion chamber sections 21, 22 which are formed when the
movable wall 14 and the separation wall 18 are displace to their
operational end positions.
[0035] As it has already been mentioned above, FIG. 1 shows the
tool with the chamber sections in their expanded condition, i.e.,
with the forechamber section 21 and the main chamber section 22
being expanded. The displacement positions of the movable wall 14
and the separation plate 18 are defined by a stop which is formed
by the valve tappets 32. The valve tappets 32, upon being inserted,
into the openings 25 form stops for arresting the displacement of
the drive rods 23 which are arrested as a result of the shoulders
33 engaging the valve tappets 32. The stoppage of the drive rods 23
results in the stoppage of the movable wall 14. The position of the
separation plate 18 is determined by the position of the shoulder
20 which, in turn, is determined by the length of the hollow
projection 17 of the movable wall 14.
[0036] The lug 19 forms, in its region adjacent to the separation
plate 18, an ignition cage 51 for receiving an ignition element 52.
The ignition element 52 serves for generating an electrical spark
for the ignition of the air-fuel gas mixture in the forechamber
section 21. As it will be described in more detail below, the
ignition device 52 is located in the central region of the cage 51
having openings 53 formed in the cage circumference. Through this
openings 53, a laminar flame front exits from the ignition cage 51
into the forechamber section 21.
[0037] As shown in FIG. 1, sidewise of the guide cylinder 5, there
is located a blocking device 54.
[0038] The blocking device 54 has a check valve 55, a pneumatic
cylinder 56, a throttle 57, and a pivotal blocking hook 58. The
check valve 55 is a one-way valve and is connected with fluid
conduit 59 extending through the bottom 3 and opening into the
combustion chamber 1. The check valve 55 provides for gas flow only
from the combustion chamber 1 and includes a ball 60 for blocking
the conduit 59. The ball 60 is biased into its blocking position by
a spring 61. The outlet side of the check valve 55 is connected by
a channel 62 with an inlet of the pneumatic cylinder 56. The
channel 62 is connected with a branch channel in which the throttle
57, which is adjustable, is provided. Inside the pneumatic cylinder
56, there is located a piston 64. The piston 64 is connected with a
piston rod 65 projecting out of the pneumatic cylinder 56. A
compression spring 66 surrounds the piston rod 65 inside the
cylinder 56 and is supported, at its opposite ends, against a rear
surface of the piston 64 and the bottom of the cylinder 56,
respectively. The free end of the piston 65, which is located
outside of the cylinder 56, is connected with the pivotable
blocking hook 58. The blocking hook 58 has an angular shape and
pivots about an axle 67. The axle 67 extends transverse to the
longitudinal extent of the piston rod 65. At its end opposite the
end connected with the piston rod 65, the blocking hook 58 has a
nose 68 facing the guide cylinder 5. The nose 68 is displaced into
the path of the movement of the drive ring 28 when the blocking
hook 58 pivots about the axle 67 in the clockwise direction. When
the nose 68 is located in the path of the movement of the drive
ring 28, the compression springs supported on the drive rods 23
cannot push the drive ring 28 away from the bottom 3. As a result,
the inlet/outlet valves 26 remain closed.
[0039] The closing takes place after the ignition of the fuel gas
mixture which increases the pressure in the combustion chamber 1.
The increased pressure is communicated, via the check valve 55, to
the cylinder 56. This results in the displacement of the piston 64
against the biasing force of the spring 66. Upon the displacement
of the piston 64, the piston rod 65 pivots the blocking hook 58
about the axle 67 in the clockwise direction, and the nose 68
engages the drive ring 28 from beneath. With a further increase of
the pressure in the combustion chamber 1, an increased pressure is
applied to the piston 64, retaining it in the position in which the
nose 68 blocks the drive ring 28. When the pressure in the
combustion chamber 1 reaches its maximum and then diminishes, the
check valve 55 remains closed as the pressure in the conduit 59 is
smaller than in the channel 62. At that, the blocking device 54
acts as an accumulator, and the blocking of the drive ring 28 is
maintained, resulting in maintaining of the locking of the valves
26 and the movable wall 14. The pressure in the channel 62 is
reduced, via the throttle 57, gradually or over a predetermined
time period determined by the adjusted cross-section of the
throttle 57. When the pressure in the channel 62 is reduced below a
certain value, the spring 66 biases the piston 64 in a direction
toward the check valve 55, pulling the piston rod 65 with it. Upon
the piston rod 64 being pulled toward the check valve 55, the
blocking hook 58 would pivot in the counterclockwise direction
about the axle 67, withdrawing the nose 68 from the displacement
path of the drive ring 28. The drive ring 68 can now displace away
from the bottom 3, which results in the opening of the valves 26
and the displacement of the movable wall 14, together with the
separation plate 18, toward the bottom 3, with the waste gases
being expelled from the chamber sections 21, 22 through the
openings 38 in the separation plate and the inlet/outlet valves 26,
respectively.
[0040] Below, the operation of the tool according to the present
invention will be discussed in detail with reference to FIGS. 2-5.
In FIGS. 2-5, the same element as those in FIG. 1 are designated
with the same reference numerals.
[0041] FIG. 2 practically corresponds to FIG. 1, only in FIG. 2,
the ignition device 52 has already been actuated by a trigger or a
lever (not shown). Upon actuation of the ignition device 52, a
spark is generated in the cage 51. After the ignition, an air-fuel
gas mixture starts to burn laminary in the forechamber section 21.
Upon ignition of the mixture, a flame front starts to propagate
radially with a relatively small velocity. The flame front pushes
the unconsumed air-fuel gas mixture ahead of itself, and the
unconsumed air-fuel gas mixture penetrates through the
through-openings 38 in the separation plate 18 into the main
combustion chamber section 22, creating there turbulence and
pre-compression.
[0042] As the flame front reaches the through-openings 38, flame
penetrates therethrough, due to the small cross-section of the
openings 38, in a form of flame jets into the main chamber section
22, creating there a further turbulence. The thoroughly intermixed
air-fuel gas mixture in the main chamber section ignites over the
entire surface of the flame jets. The mixture burns with a high
speed which leads to a sharp increase of the pressure in the main
chamber section 22.
[0043] The high pressure, which is generated in the main chamber
section 22, is transmitted, on one hand, to the piston 8 and, on
the other hand, via the check valve 55, to the piston 64 of the
pneumatic cylinder 56. The piston 64, together with the piston rod
65, is displaced away from the check valve 55, compressing the
spring 66. The free end of the piston rod 65 pivots the blocking
hook 58 about the axle 67 in the clockwise direction, whereby the
nose 68 is displaced into the displacement path of the drive ring
28. Thereby, a locking condition is obtained.
[0044] Simultaneously with the increase of pressure in the main
chamber section 22, the piston 8 moves with a high speed toward the
bottom 7 of the guide cylinder 5, forcing the air from the guide
cylinder 5 out through the openings 39. Upon the piston plate 9
passing the openings 39, the exhaust gas is discharged
therethrough. The piston rod 10 effects setting of a fastening
element, being displaced in the direction shown by arrow. As in the
course of movement of the piston 8, the pressure in the main
chamber section 22 decreases, resulting in the decrease of pressure
in the conduit 59. Because a maximum pressure has been stored in
the channel 62, the check valve 55 remains closed. The throttle 57
provides only for a very slow reduction of pressure in the channel
62, and the locking condition is still maintained.
[0045] After setting or following the combustion of the air-fuel
gas mixture, the piston 8 is brought to its initial position, as is
shown in FIG. 3, as a result of thermal feedback produced by
cooling of the flue gases which remain in the combustion chamber 1
and the guide cylinder 5. As a result of cooling of the flue gases,
an underpressure is created behind the piston 8 which provides for
return of the piston 8 to its initial position. The combustion
chamber 1 should remain sealed until the piston 8 reaches its
initial position shown in FIG. 1. This means that the locking
condition should remain, which is insured in a manner described
above with reference to FIG. 2. The locking condition in FIG. 3 has
not changed in comparison with that in FIG. 2.
[0046] FIG. 4 shows a condition at which the piston 8 is brought to
its initial position as a result of thermal feedback. The operation
of the throttle 57 is so adjusted that only after the piston 8 is
brought into is initial position, the pressure in the channel 62 is
reduced to an extent at which the spring 66 is able to displace the
piston 64 in a direction toward the check valve 55. With the piston
rod 65 movable together with the piston 64, the blocking hook 58
pivots about the axle 67 in the counterclockwise direction, with
the nose 68 being displaced out of the displacement path of the
drive ring 28.
[0047] Upon removal of the blocking hook 58 out of the displacement
path of the drive ring 28, the compression springs supported on the
drive rods 23 displace the drive ring 28 away from the bottom 3 of
the combustion chamber 1, opening the inlet/outlet valves 26.
Simultaneously, the movable wall 14 is displaced toward the bottom
3, entraining therewith the separation plate 18, with the waste
gases being discharged from the forechamber section 21 and the main
chamber section 22 through the openings 38 in the separation plate
18 and the valves 26, respectively. Upon subsequent expansion of
the forechamber section 21 and the main chamber section 22, as a
result of the movement of the drive ring 28 in opposite direction,
the air is aspirated into the main chamber section 22 and the
forechamber section 21 through the inlet/outlet valves 26 and the
through-openings 28 in the separation plate 18, respectively.
[0048] Although the present invention was shown and described with
references to the preferred embodiments, such are merely
illustrative of the present invention and are not to be construed
as a limitation thereof and various modifications of the present
invention will be apparent to those skilled in the art. It is
therefore not intended that the present invention be limited to the
disclosed embodiments or details thereof, and the present invention
includes all variations and/or alternative embodiments within the
spirit and scope of the present invention as defined by the
appended claims.
* * * * *