Information
-
Patent Grant
-
6532917
-
Patent Number
6,532,917
-
Date Filed
Tuesday, July 3, 200123 years ago
-
Date Issued
Tuesday, March 18, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Mancene; Gene
- Benton; Jason
Agents
- Sidley Austin Brown & Wood, LLP
-
CPC
-
US Classifications
Field of Search
US
- 123 46 H
- 123 46 R
- 123 46 SC
-
International Classifications
-
Abstract
A method of controlling operation a portable, internal combustion engined power tool including a combustion chamber (1), at least one suction/discharge valve (34)associated with the combustion chamber (1), and an operational piston (8) the method including inquiring a displacement position of the operational piston (8) of the power tool when it is being displaced to its initial position after having performed an operational stroke upon ignition of a fuel gas mixture filling the combustion chamber, and releasing the at least one suction/discharge valve (34) upon the piston (8) reaching its initial position; and a power tool which is controlled by the method.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a portable, internal combustion engined power tool, in particular a setting tool for driving in fastening elements, and including a combustion chamber, at least one suction/discharge valve connected wit the combustion chamber, and an operational piston which performs an operational stroke upon ignition of a fuel gas mixture filling the combustion chamber. The present invention also relates to a method of controlling operation of such a power tool.
2. Description of the Prior Act
With a power tool of a type described above, the drive energy is generated by burning a fuel gas mixture in a combustion chamber and is transmitted by the operational piston to a fastening element. Upon pressing a power tool against a constructional component into which a fastening element is to be driven, an ignitable fuel gas mixture is injected into the combustion chamber. Upon actuation of a trigger, a spark is produced which ignites the fuel gas mixture, initiating a combustion process. The operational piston, which adjoins the combustion chamber, is driven by the combustion gases. At the end of its operational stroke, the piston passes past discharge openings through which the waste gases can be at least partially discharged. The piston, after having performed the operational strokes, returns in its initial position as a result of underpressure which was created in the combustion chamber by cooling of the waste or residual gases. During the period of thermal return of the piston to its initial position, the combustion chamber should remain sealed from the surrounding it environment. Therefore, the suction/discharge valves, which provide for delivery of fresh air into the combustion chamber, should be open only after the piston has returned into its initial position. Generally, the time necessary for the return of the piston into its initial position increases with the increase of the tool temperature which heats during operation. In addition, high-energy power tools require a large expansion volume which results in that a greater time becomes necessary for the return of the piston into its initial position.
In some conventional power tools, closing of a suction/discharge valve can be effected with a pawl connected by, e.g., a toggle lever with the trigger. In this way, the suction/discharge valve becomes open as soon as the trigger returns into its initial position. This means that by the time the trigger returns to its initial position, the piston also must return into its initial position.
The locking of the suction/discharge valve by the trigger means that the switching point of the trigger cannot any more be arbitrary selected. The ignition switch can only then be actuated when the locking of the suction/discharge valve has been completed, i.e., long after the start of the displacement of the trigger. However, a long trigger displacement adversely affects acceptance by the customers. Moreover, as it has already been discussed above, with a heated tool, the return of the piston into its initial position lasts longer. The tool user must, in this case, hold the trigger in its pulled condition longer to prevent the piston from occupying a erroneous position.
In order to increase the time available for return of the piston into its initial position, the trigger displacement can be damped. However, damping negatively influences operational characteristics of the trigger as a larger force is needed for actuating the trigger, and the trigger does not return sufficiently rapidly into its initial position. A user does not look at dampening favorably as it reduces the maximum setting rate and requires a greater force for actuating the trigger, which the user has to apply.
German Publication DE 19962 598.0 suggests detecting of the gas pressure in the combustion chamber after the fuel gas mixture has been ignited and locking the suction discharge valve(s) dependent on the detected gas pressure.
Accordingly, an object of the present invention is to provide a method which would permit to precisely determine when the piston returns into its initial position and thereby would provide for a more precise control of release of the suction/discharge valve.
Another object of the present invention is to provide a power tool which would contain means that would permit more precisely determine the return of the piston into its initial position.
SUMMARY OF THE INVENTION
These and other objects of the present invention, which would become apparent hereafter, are achieved by providing a method according to which the displacement position off the piston is inquired, and the suction/discharge valve is released after the return of the piston in its initial position has been ascertained.
The tool according to the present invention includes inquiry means for inquiring the piston position and which actuates a locking/release device associated with the suction/discharge valve for opening same.
According to the present invention, the method for operating a portable internal combustion engined power tool including a combustion chamber, at least one suction/discharge valve for supplying fresh air into the combustion chamber and for discharging waste gases therefrom, and an operational piston displaceable in an operational direction upon ignition of a fuel gas mixture filling the combustion chamber, includes inquiring a displacement position of the piston when it is being displaced to its initial position after having performed an operational stroke; and releasing the at least one valve upon the piston reaching its initial position.
The foregoing method permits to precisely determined the geometrical position of the piston, in particular, its initial position. The release or opening of the suction/discharge valve is effected only when the piston has reached its initial position. The pressure variations of the residual gases in the combustion chamber do not lead any more to a faulty control during the valve release. The danger of the valve being released before th piston reaches its initial position is completely eliminated. The initial position of the piston is a position in which the opening between the combustion chamber and the guide cylinder is completely closed.
In principle, for inquiring the displacement position of the piston, a position of any portion of the piston can be monitored. However, because the piston is guided in a guide cylinder and has a piston rod at least a portion of which projects from the guide cylinder, according to embodiments of the invention, it is the position of the piston rod which is being ascertained. In this case, the access to the inside of the cylinder or the combustion chamber is not any more necessary. Therefore, the inquiring element or device for determining the displacement position of the piston can be formed much simpler, and it can be mounted much easier. The displacement position of the piston can be easily ascertained from the displacement position of the piston rod. Based on the principle that it is the initial position of the piston that need be ascertained, a corresponding clearly defined point on the piston rod can be monitored, e.g., by using a stationary sensor. Passing of the defined point of the piston rod past the sensor, upon returning of the piston to its initial position, is a clear indication that the piston has reached its initial position.
According to one embodiment of the present invention, as a defined point which has to be monitored for determining the displacement position of the piston rod, the end surface of the piston rod is used. The position of the end surface of the piston rod can be monitored very easily and very precisely. This permits to precisely determine the return of the piston to its initial position.
In case, the piston rod has not returned to its initial position after the performance of the operational stroke, according to a further development of the present invention, a forceful release of the suction/discharge valve is provided for. The forceful release is provided in order to discharge the waste or residual gases from the combustion chamber. In this case, the piston must be brought into its initial position by other means, namely, manually or by a subsequent ignition of a new fuel gas mixture injectable into the combustion chamber.
According to the present invention, the portable, internal combustion engined power tool includes a combustion chamber, at least one suction/discharge valve for supplying fresh air into the combustion chamber, and for discharging waste gases therefrom, an operational piston displaceable in an operational direction upon ignition of a fuel gas mixture filling the combustion chamber, a locking/release device for release the at least one suction/discharge valve after the piston has reached its initial position after having performed operational stroke, and inquiry means for inquiring a displacement position of the piston when it is being displaced to its initial position after having performed operational stroke and for actuating the locking/release device when the piston has reached its initial position.
According to the invention, it is, thus, provided for a piston location-dependent control of the locking/release device, with the control being independent from pressure variation of the residual gases in the region of the combustion chamber.
As it has already been discussed previously, the piston, which is displaceable in a guide cylinder, has a piston rod a portion of which projects from the guide cylinder. Therefore, according to the invention, the inquiry element for determining the position of the piston is located outside of the guide cylinder in vicinity of the guide cylinder. This simplifies the design of the tool and insures an easy mounting and monitoring of the inquiry element. This position of the inquiry element insures a precise determination of the displacement position of the piston rod.
The piston rod and the inquiry element are located immediately opposite each other, whereby the inquiry of the displacement position of the piston rod is effected directly.
As it has already been discussed above, for inquiring the displacement position of the piston, a displacement position of the piston rod is monitored. As it has further been discussed above, a clearly defined point on the piston rod, which corresponds to the initial position of the piston, can be monitored. As it has still further been discussed above, as a defined point on the piston rod, the piston rod end surface is used, which is monitored with suitable sensor means. As sensor means mechanical, electrical, optical, and magnetic sensors can be used. Besides the end surface of the piston rod, as a defined point, other geometrical elements of the piston or the piston rod can be used. Also, an external elements mounted on the piston or the piston rod, such as magnets, soft iron cores, optical bar codes, can be used. However, the most advantageous element for ascertaining the return of the piston into its initial position, proved to be the end surface of the piston rod as its position can be most easily detected.
According to one embodiment of the present invention, an inquiring element can be formed as a sensor located adjacent to the displacement path of the piston rod and generating an electrical release signal as soon as the piston rod leaves the region of the sensor. The sensor generates the electrical release signal when the free end of the piston rod passes the sensor, which position of the piston rod corresponds to the initial position of the piston. To this end, the distance of the location of the sensor from the initial position of the piston is so selected that the sensor is located immediately in front of the end surface of the piston rod when the piston occupies its initial position.
The electrical release signal actuates the locking/release device which releases the suction/discharge valve(s). When the locking/release device has a locking lever, the electrical release signal can be used for a actuating an setting device that lifts the locking lever off its locking position. The locking lever is brought into its locking position by the tool trigger. The setting device retains the locking lever in its locking position until it is actuated by the electrical release signal.
According to another embodiment of the present invention, the inquiry element for inquiring or ascertaining the displacement position of the piston rod is formed as a resilient feeler biased against the circumference of the piston rod and extending into the displacement path of the piston rod when the piston has returned to its initial position. In the initial position of the piston, the feeler end is located immediately in front of the free end surface of the piston rod. Forming the inquiry element as a feeler simplifies its structure and, at the same time, provides for an inquiry element which is robust and require little maintenance. It is also not sensitive to contamination. The end of the feeler adjacent to the piston rod can be formed as a spring element, in form, e.g., of a leaf spring with a convex end, with the piston rod extending tangentially to the convex end in the displacement direction of the piston.
The locking/release device locks or releases the suction/discharge valve(s) dependent on whether the feeler engages the piston rod or extends into the piston rod displacement path, respectively. The locking or release of the valve(s) can be effected by the locking lever of the locking/release device engageable by the feeler.
The feeler can be connected with the free end of the locking lever which is displaceable into its locking position by the tool trigger. The locking lever remains in its locking position after the ignition of the fuel gas mixture in the combustion chamber as long as the feeler engages the circumference of the piston rod.
According to an advantageous embodiment of the present invention, there is provided a setting device that displaces the locking lever in its release position as soon as the piston has returned into its initial position. As the feeler element is formed as a mechanical element engageable with the circumference of the position rod, it is formed as a resilient element as it need be compressed upon the pivotal movement of the locking lever in its release position.
As a setting device, e.g., an actuation button, which is actuated manually and is connected with the locking lever, can be used.
However, the setting device can be also formed as an angular lever pivotally supported at its apex, with one leg of the angular displacing the locking lever of the locking/release device into its locking position when the other leg of the angular lever is displaced by a press-on element, which is supported in the tool housing, upon the displacement of the press-on element to the rear of the tool. The displacement of the other leg provides for pivoting of the angular lever in a respective direction. If, for some reasons, the piston has not returned in its initial position after performing its operational stroke, the tool can again be pressed against the constructional component to displace the locking/release device or its locking lever into the release position, which insures release of the suction/discharge valves(s) and deaeration of the combustion chamber. With a subsequent press-against process, the fuel gas again is injected into the combustion chamber, and the working process is conducted with the piston spaced from its initial position. However, in this condition of the piston, no fastening element is located in the outlet channel of the tool, so that there is no any danger of injury. Upon return of the piston in its initial position, the normal operation of the tool is resumed.
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 is construction and its mode of operation, together with additional advantages and objects 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:
The drawings show:
FIG. 1
an axial cross-sectional view of a first embodiment of a power tool according to the present invention in the region of its combustion chamber in a completely collapsed condition of the combustion chamber sections;
FIG. 2
an axial cross-sectional view of the power tool shown in
FIG. 1
in its pressed-on condition with expanded combustion chamber sections;
FIG. 3
a view similar to that of
FIG. 2
in an ignited condition of the combustion chamber;
FIG. 4
a view similar to those of
FIGS. 1-3
illustrating a condition during return of the piston into its initial position;
FIG. 5
a view similar to that of
FIG. 1
after the piston has returned into its initial position;
FIG. 6
a view similar to that of
FIG. 1
in a release condition of the power tool;
FIG. 7
an axial cross-sectional view of a second embodiment of a power tool according to the present invention in the region of its combustion chamber;
FIG. 8
an axial cross-section view of a third embodiment of a power tool accordingly to the present invention in the region of its combustion chamber;
FIG. 9
an axial cross-sectional view of a fourth embodiment of a power tool according to the present invention in the region of its combustion chamber; and
FIG. 10
a cross-sectional view of a portion of a front region of the power tool shown in
FIG. 9
at an increased scale.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A combustion engined power tool according to the present invention, which is shown in
FIGS. 1-6
, includes a cylindrical combustion chamber
1
with a cylindrical wall
2
and an adjoining the cylindrical wall
2
, circular bottom
3
a,
3
b.
In the center of the bottom
3
a,
3
b,
there is provided an opening
4
a,
4
b.
A guide cylinder
5
, which has a cylindrical wall
6
and a bottom
7
, adjoins the opening
4
a,
4
b.
A piston
8
is slidably displaceable in the guide cylinder
5
in its longitudinal direction. The piston
8
is formed of a piston plate
9
adjoining the combustion chamber
1
and a piston rod
10
located centrally with respect of the piston plate
9
. The piston rod projects through an opening
11
formed in the bottom
7
of the guide cylinder
5
.
In
FIG. 1
, the piston
8
is shown in its initial position corresponding to a non-operational condition of the power tool which is formed as a setting tool for driving fastening elements into constructional components. A surface of the piston plate
9
, which is adjacent to the combustion chamber, adjoins, to a lesser or greater degree, the bottom
3
a,
3
b,
and the free end of the piston rod
10
only slightly projects past the bottom
7
of the guide cylinder
5
. The diameter of the piston plate
9
is stepwise reduced in the direction of the combustion chamber
1
, with a smaller diameter portion lying in the opening portion
4
b
and a larger diameter portion lying in the opening portion
4
a.
In this way, the larger diameter portion of the piston plate
9
abuts the bottom plate
3
b
which forms a stop for the piston
8
in the initial position of the piston. For sealing the space on opposite sides of the piston plate
9
, sealing rings (not shown) can be provided in the outer circumference of the piston plate
9
.
Within the combustion chamber
1
, there is located a cylindrical plate which can be called a combustion chamber wall
14
. The combustion chamber wall
14
is displaceable in the longitudinal direction of the combustion chamber
1
and is provided in its outer circumference with an annular sealing to seal the space in front of and behind the combustion chamber wall
14
. The combustion chamber wall
14
has a central opening
16
in the wall of which there is arranged an annular sealing.
An annular separation plate
18
is arranged between the bottom plate
3
b
and the combustion chamber wall
14
. The separation plate
18
has a diameter that corresponds to the inner diameter of the combustion chamber
1
. At its surface adjacent to the combustion chamber wall
14
, the separation plate
18
is provided with a cylindrical lug
19
which extend through the central opening
16
of the combustion chamber wall
14
. The length of the lug
19
exceeds the thickness of the combustion chamber wall
14
in several times. The sealing, which is provided in the wall of the opening
16
, snuggly surrounds the lug
19
. At its upper end, the lug
19
is provided with a shoulder
20
the outer diameter of which is greater than the inner diameter of the opening
16
. A hollow cylindrical lug
17
adjoins the combustion chamber wall
14
at the edge of the opening
16
. The hollow lug
17
surrounds the lug
19
. The free end of the hollow lug
17
is located beneath the shoulder
20
and, in the position shown in
FIG. 1
, is spaced from the shoulder
20
. A web
2
a,
which is connected with the cylindrical wall
2
of the combustion chamber
1
, serves as a stop for the lug
19
and thereby insures a proper positioning of the separation plate
18
in an expanded condition of the combustion chamber
1
.
In a non-operative position of the power tool, the separation plate
18
lies on the bottom plate
3
b,
and the combustion chamber wall
14
lies on the separation plate
18
. This position of the separation plate
18
and the combustion chamber wall
14
corresponds to a completely collapsed condition of the combustion chamber
1
. When the power tool is pressed against a constructional component (not shown) into which a fastening element is to be driven in, the combustion chamber wall
14
is, as it will be explain later, lifted and becomes spaced from the separation plate
18
or the bottom plate
3
b,
as the case may be. After a certain time period, the combustion chamber wall
14
engages the shoulder
20
of the lug
19
of the separation plate
18
. In this position of the combustion chamber wall
14
, it is separated from the separation plate
18
a predetermined distance, forming a so-called fore-chamber section of the combustion chamber
1
. The fore-chamber section is designated with a reference numeral
21
(FIG.
2
). Upon lifting of the combustion chamber wall
14
further, the combustion chamber wall
14
and the separation plate
18
are displaced together parallel to each other, and a further chamber section is formed between the separation plate
18
and the bottom plate
3
b
or the piston plate
9
. This chamber section is called a main chamber section and is designated with a reference numeral
22
(FIG.
2
).
FIG. 2
shows a condition of the combustion chamber
1
in which both combustion chamber sections, the fore-chamber section
21
and the main chamber section
22
, are completely expanded. In this position of the combustion chamber
1
, the shoulder
20
of the lug
19
of the separation plate
18
engages the stop-forming web
2
a.
For displacing the combustion chamber wall
14
, there are provided several, e.g., three actuation or drive rods
23
uniformly distributed along the circumference of the combustion chamber wall
14
and fixedly connected therewith. Only one of the drive rods
23
is shown in the figures. 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
a,
25
b
formed in the in the bottom
3
a,
3
b.
The openings
25
a,
25
b
simultaneously serve as ventilation openings, with the openings
25
b
having a conical shape. The drive rods
23
and the combustion chamber wall
14
are connected with each other, e.g., by screws in per se known manner. The free ends of the drive rods
23
are connected with the drive ring
28
which, thus, connects the drive rods
23
with each other. The drive ring
28
is arranged concentrically with the combustion chamber axis and surrounds the guide cylinder
5
. The drive ring
28
is connected with the drive rods
23
by screws, but other suitable connecting means can also be used. A shoulder
26
, through which the drive rods
23
extend, is formed on the guide cylinder wall
6
in a spaced relationship to the drive ring
28
. Compression springs
27
extend between the drive ring
28
and the shoulder
26
. The compression springs
27
are so arranged that they always pull the combustion chamber wall
14
in a direction toward the bottom plate
3
b.
As it has already been discussed above, the openings
25
a,
25
b
serve also as ventilation openings, and valve tappets
32
are provide for displacement into the openings
25
a.
In the open condition of the openings
25
a,
25
b,
the valve tappets
32
are located outside of the combustion chamber
1
, i.e., beneath the bottom plate
3
a.
The valve tappets
32
are supported on a shoulder
33
a
formed on the cylindrical wall
6
of the guide cylinder
5
. Compression springs
33
b
are arranged between the valve tappets
32
and the edges of respective openings
25
a,
applying pressure to the valve tappets
32
, biasing them toward the shoulder
33
a.
When the drive ring
28
is displaced in a direction toward the bottom plate
3
a,
shoulders
33
provided on the drive rods
23
engage the valve tappets
32
and carry them, against the biasing force of the compression springs
33
b,
into the openings
25
a,
25
b,
closing the valves
34
. The valves
34
are formed as suction/discharge valves. The shoulders
33
, which are provided on the drive rods
23
are displaced through the openings
33
c
provided in the shoulders
33
a.
A plurality of openings
38
are distributed over the circumference of the separation plate
18
at the same distance from the combustion chamber axis. In the lower end of the guide cylinder
5
, there are formed a plurality of outlet openings
39
for evacuating air from the guide cylinder
5
when the piston
8
is displaced toward the bottom
7
of the guide cylinder
5
. At the lower end of the guide cylinder
5
, there is provided damping means
40
for damping the movement of the piston
8
. When the piston
8
passes past the openings
39
, an exhaust gas can escape through the openings
39
.
Two radial, axially spaced openings
41
and
42
are formed in the cylindrical wall
2
of the combustion chamber
1
. A liquefied fuel gas is delivered into the combustion chamber
1
though the radial openings
41
,
42
.
FIG. 2
, as it has been discussed above, shows the inventive power tool, which is formed as a setting tool, in the expanded condition of the combustion chamber sections, i.e., in the expanded condition of the fore-chamber section
21
and the main chamber section
22
. The displacement positions of the combustion chamber wall
14
and the separation plate
18
is fixed upon the valve tappets
32
entering the ventilation openings
25
a,
25
b,
which prevents further displacement of the drive rods
23
and thereby the displacement of the combustion chamber wall
14
and with the shoulder
20
of the lug
19
of the separation plate
18
abutting the stop-forming web
2
a.
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 fore-chamber
21
. As it will be described in more detail below, the ignition element
52
is located in the central region of the cage
51
having openings
53
formed in the cage circumference. Through these openings
53
, a laminar flame front exits from the ignition cage
51
into the fore-chamber
21
.
As it is further shown in
FIG. 1
, adjacent to the guide cylinder
5
, there is provided a locking/release device
54
which is connected with an inquiry element
55
for inquiring the displacement position of the piston
8
or the piston rod
10
.
The locking/release device
54
serves for locking the drive ring
28
and thereby the suction/discharge valves
34
in their closed positions. To this end, the locking/release device
54
includes a locking lever
56
that extends parallel to the longitudinal extend of the guide cylinder
5
at a small distance from the cylindrical wall
6
of the guide cylinder
5
. The locking lever
56
is pivotally supported at its rear end on the bottom plate
3
a.
For supporting the locking lever
56
, a pivot support
57
is provided on the outer side of the bottom plate
3
a.
The locking lever
56
has its end remote from the support
57
extending through an opening
58
formed in the drive ring
28
. The locking lever
56
is formed integrally as one-piece with a feeler that forms the inquiry element
55
. The end of the inquiry element
55
is located immediately below an end surface of the piston rod
10
when the piston
8
is located in its initial position. The part, which forms the locking lever
56
and the feeler-shaped inquiry element
55
can be stamped out of a strong metal sheet. On its side remote from the guide cylinder
5
, the locking lever
56
has a locking edge
59
with which the locking lever
56
can engage the drive ring
28
from behind when the drive ring
28
has been pushed sufficiently far toward the bottom
3
a,
3
b
of the combustion chamber
1
. A portion of the locking lever
56
that extends from the support
57
to the locking edge
59
has a relatively small width which increase to form the locking edge
59
. The locking lever
56
is pivoted, at the support
57
, toward the guide cylinder
5
by a spring
60
supported against an element of power tool housing. Upon pivoting of the locking lever
56
, the locking edge
59
becomes disengaged from the edge of the opening
58
of the drive ring
28
, when the locking edge
59
is located behind the drive ring
28
, and the inquiry element
55
has its free end located in the displacement path of the piston rod
10
.
Sidewise of the guide cylinder
5
, there is provided a trigger
61
which is pivotally supported on the cylindrical wall
6
of the guide cylinder
5
. For pivotally supporting the trigger
61
, a support
62
is provided on the cylindrical wall
6
. The trigger
61
pivots in a direction toward the bottom
3
a,
3
b
against a biasing force of a compression spring
63
. An actuation section of the trigger
61
lies outside of the locking lever
56
. The trigger
61
is formed integrally with a lug
64
extending from the support
62
toward the bottom
7
of the guide cylinder
5
. Upon a pivotal movement of the trigger
61
in a counter clockwise direction, the lug
64
engages an edge of the locking lever
56
, pivoting the locking lever about the support
57
against a biasing force of the spring
60
.
Now, the operation of the first embodiment of a power tool according to the present invention will be described with reference to
FIG. 2
in which the same elements are designated with the same reference numerals as in FIG.
1
.
FIG. 2
shows a condition in which the tool, which is formed as a setting tool, is pressed with its tip against a constructional component into which a fastening element has to be driven in. Upon the tip being pressed against the constructional component, the drive ring
28
is displaced by a press-on cage (not shown) in a direction toward the combustion chamber
1
, causing an expansion of the combustion chamber sections
21
and
22
(with drive rods
23
), simultaneously closing the discharge/suction valves
34
. Shortly before the combustion chamber sections are completely expanded, the liquefied fuel gas is injected through the openings
41
,
42
. In its displaced condition, the drive ring
28
is located in front of the locking edge
59
. However, the locking edge
59
cannot yet engage the drive ring
28
from behind, as the trigger
61
has not yet been actuated. The free end of the inquire element
55
remains in the path of the piston rod
10
immediately in front of the end surface
10
a
of the piston rod
10
.
FIG. 3
shows a position in which the trigger
61
is actuated, i.e., is pivoted counter clockwise about its support
62
against a biasing force of the spring
63
. Upon the pivotal movement of the trigger
61
, the lug
64
pivots the locking lever
56
also in the counter clockwise direction about the locking lever support
57
, and the locking edge
59
engages from behind the driving ring
28
. Simultaneously with the pivotal movement of the locking lever
56
, the inquiry element
55
moves out of the path of the piston rod
10
. During the last portion of the pivotal movement of the trigger
61
and after the inquiry element
55
has moved out of the path of the piston rod
10
, ignition of the gas mixture filling the combustion chamber sections
21
,
22
is effected with the ignition element
52
. The ignition is effected with a spark produced by the ignition element
52
within the cage
51
. First, the mixture starts to burn luminary in the fore-chamber section
21
, and the flame front spreads rather slowly in a direction of the openings
38
. The unconsumaable air-fuel gas mixture is displaced ahead and enters, through the openings
38
, the main section chamber
22
, creating there turbulence and precompression. When the flame front reaches the openings
38
, it enters the main chamber section
22
, due to the reduced cross-section of the openings
38
, in the form of flame jets, creating there a further turbulence. The thoroughly mixed, turbulent air-fuel gas mixture in the main chamber section
22
is ignited over the entire surface of the flame jets. It buns with a high speed which significally increases the combustion efficiency.
The combustible mixture impacts the piston
8
, which 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
, moving in the direction indicated with an arrow, drives the fastening element in the constructional component against which the power tool is pressed.
Shortly after the ignition of the fuel gas mixture, the trigger
61
can be released. This results in the locking lever
56
moving, together with the inquiry element
55
, toward the guide cylinder
5
under the action of a biasing force applied by the spring
60
. However, this movement of the locking lever
56
does not lead to the disengagement of the locking edge
59
from the drive ring
28
because the free end of the inquiry element
55
engages the piston rod
10
, preventing further pivotal movement of the locking lever
56
about the support
57
in the clockwise direction. Thus, the drive ring
28
remains in its displaced position, the suction/discharge valves
34
remain, therefore, closed and the combustion chamber sections
21
,
22
remain in their expanded condition.
FIG. 4
shows a condition of the inventive power tool after setting of the fastening element or following the combustion of the air-fuel gas mixture. The piston
8
is being brought to its initial position 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
or behind the piston plate
9
which provides for return of the piston
8
to its initial position. The inquiry element
55
slides along the piston rod
10
as the piston
8
is being brought to its initial position so that the drive ring
28
remains engaged by the locking edge
59
, and the suction/discharge valves
34
remain closed as the piston
8
has not yet reached its initial position.
FIG. 5
shows a condition of the inventive power tool in which the piston
8
has completely returned to its initial position, with the piston plate
9
completely closing the central bottom opening
4
a,
4
b.
The piston
8
has been retracted into the guide cylinder
5
to such an extent that the free en
10
a
becomes located outside of the region of the inquiry element
55
.
FIG. 6
shows a position in which both the locking lever
56
and the inquiry element
55
have been pivoted to their original position, with the locking edge
59
being disengaged from the drive ring
28
which can now move to its initial position.
In a next step, not shown in the drawings, the drive ring
28
is pushed away from the bottom
3
a,
3
b
of the combustion chamber
1
by springs
27
, entraining with it the drive rods
23
. The shoulders
33
, which are provided on the drive rods
23
, likewise move away from the bottom
3
a,
3
b,
and the springs
33
b
push respective valve tappets
32
out of the ventilation openings
25
a,
25
b.
With the displacement of the drive rods
23
, toward the front of the power tool, the combustion chamber wall
14
and the separation plate
18
move toward the bottom
3
a,
3
b
of the combustion chamber
1
, leading to the collapse of the combustion chamber sections
21
,
22
. The residual gases, which remain in the combustion chamber
1
are discharged through the openings
25
a,
25
b,
with the suction/discharge valves
34
being open. The valves
34
also serve for admitting fresh air into the combustion chamber
1
upon the movement of the combustion chamber wall
14
and the separation plate
18
away from the bottom
3
a,
3
b.
FIG. 7
shows, as discussed above, a second embodiment of the power tool according to the present invention which differs from the first embodiment in that the inquiry element
55
is formed as an electric sensor unit. The sensor unit can be formed, e.g., as an electric photo barrier consisting of a light source, sender
65
, and a light receiver
67
arranged at the outer side of the bottom
7
of the guide cylinder
5
on opposite sides of the opening
11
in the bottom
7
in such a way that the light path extends beneath the end surface
10
a
of the piston rod
10
of the piston
8
in the initial position of the piston
8
, i.e., in the position of the piston
8
in which the piston plate
9
completely closes the opening
4
a,
4
b
in the bottom
3
a,
3
b
of the combustion chamber
1
.
After the ignition of the fuel gas mixture in the combustion chamber sections
21
,
22
and displacement of the piston
8
into its operational position, the piston rod
10
is located between the light sender
65
and a the light receiver
66
so that no light reaches the light receiver
66
. An electrically actuated setting device
67
continues to retain the locking lever
56
in its locking position even after release of the trigger
61
, with the locking edge
59
engaging the drive ring
28
. Only after the return of the piston
8
in its initial position, the piston rod
10
unblocks the light path between the sender
65
and the receiver
66
. After receiving a light signal, the receiver
66
sends a release signal to the setting device
67
which provides for pivotal movement of the locking lever
56
about its support
57
in the clockwise direction. As a result of this pivotal movement of the locking lever
56
, the locking edge
59
becomes disengaged from the drive ring
28
, providing for displacement of the drive ring
28
away from the combustion chamber
1
and for opening of the suction/discharge valves
34
.
The embodiment of the power tool shown in
FIG. 8
differs from the previously shown and discussed embodiments in that the inquiry element
55
is formed as a flexible element in form of a leaf spring. The rear end of this leaf spring is fixedly attached to a projecting heel
56
a
provided at the free end of the locking lever
56
. The opposite, front end of the leaf spring is convexly bent and is pressed against the circumference of the piston rod
10
. The front, convexly bent end of the leaf spring-shaped, inquiry element
55
is biased into engagement with the piston rod
10
by the spring
60
. However, the biasing force applied by the spring
60
is not sufficiently large to dislodge the locking edge
59
from engagement with the drive ring
28
. If for some reason, the piston
8
is not returned into its initial position, the condition shown in
FIG. 8
does not changed. Still, the release of the drive ring
28
can be effected with a push-button
68
which is displaceably arranged in the housing of the power tool. The push-button
68
is located in a support element
69
and is displaced against a biasing force of a return spring
70
. Upon displacement of the push-button
68
the actuation rod
71
displaces the locking lever
56
in a direction toward the piston rod
10
. The leaf spring-shaped inquiry element
55
bents resiliently further, and the locking edge
59
becomes disengaged from the drive ring
28
. With the drive ring
28
moving away from the combustion chamber
1
, the combustion chamber becomes deaerated. Upon release of the push-button
68
, the return spring
70
pushes the push-button
68
in its initial position in which the shoulder
72
provided on the rod
71
lies on the surface edge of the support
69
. The locking lever
56
remains in its release position because the drive ring
28
is located leftward of the locking edge
59
.
Upon subsequent displacement and locking of the drive ring
28
and ignition of the fuel gas mixture in the combustion chamber
1
, and a subsequent return of the piston
8
into its initial position, the front end of the leaf spring-shaped inquiry element
55
can be displaced, under the action of the spring
60
, into a position beneath the end surface
10
a
of the piston rod
10
, with the locking edge
59
being disengaged from the drive ring
28
.
FIGS. 9-10
, which show a fourth embodiment of the inventive power tool, show a condition of the power tool in which the piston
8
has not yet reached its initial position after the completion of the setting process and is immovable. In this case, likewise, a forced released is provided, which is needed because the setting tool is again pressed with its tip against the constructional component.
To this end, an angular lever
73
, which is supported for a pivotal movement about an axle
74
on the outer side of the bottom
7
of the guide cylinder
5
, is provided. The axle
74
is located in the apex region of the angular lever
73
which has two legs, a first leg
75
and a second leg
76
connected with each other at the apex. Both legs
75
and
76
lie in a plane extending perpendicular to the axial extent of the axle
74
which, e.g., can extend tangentially to the guide cylinder
5
. The first leg
75
extends toward the front of the setting tool whereas the second leg
76
extends toward the piston rod
10
.
At the free end of the first leg
75
, there is provided an axle stub
78
which is located in a slot
77
provided in the free end
56
a
of the locking lever
56
. The free end
56
a
is formed by tangent-bending an end section of the locking lever
56
remote from the locking lever support
57
. The slot
77
extends in the longitudinal direction of the setting tool or the piston rod
10
. A leaf spring-shaped inquiry member
55
is secured at its rear end to the free end of the free end section
56
a
of the locking lever
56
. The front end of the leaf-spring-shaped inquiry element
55
is convexly bent and is pressed against the piston rod
10
. The inquiry element
55
serves for sensing the position of the piston rod
10
.
The second leg
76
of the angular lever
73
is provided at its free end with an axle stub
79
on which set lever
80
is pivotally supported. The set lever
80
is formed as a unidirectionally extending section. The lever
80
has a slot
81
having a stop edge
82
against which a leg
83
of a leg spring
84
is pressed. The leg spring
84
is wound about the axle
74
and has its other leg
85
supported on the cylindrical wall
6
of the guide cylinder
5
. The leg
83
of the leg spring
84
is constantly pressed against the stop edge
82
for applying a biasing force, via the set lever
80
, to the angular lever
73
for rotating same about the axle
74
in the clockwise direction. The position of the stop edge
82
in the set lever
80
is so selected that the leg spring
84
so positions the set lever
80
that it extend toward the front end of the setting tool and at a predetermined angle to the piston rod
10
. This angle is so selected that, in case the piston
8
does not reach its initial position and the front end of the leaf-spring-shaped inquiry element
55
is pressed against the piston rod
10
, the free end
80
a
of the set lever
80
is surrounded by an extension
86
of a press-on cage (not shown) that upon the setting tool being pressed against a constructional component, is displaced toward the rear end of the setting tool.
The operation of the setting tool shown in
FIGS. 9-10
will be now described for a case when the piston
8
does not reach its initial position and is immovable, i.e., is in the condition shown in
FIGS. 9-10
.
For releasing the drive ring
28
and for dearating the combustion chamber
1
, the setting tool is again pressed with its tip against the constructional component. Upon the setting tool tip being pressed against the constructional component, the press-on cage, which was mentioned above, is displaced inward, together with its extension
86
. Because the leaf-spring inquiry element
55
is pressed against the piston rod
10
, the leg spring
84
can pivot the angular lever
73
only a small predetermined amount. The spring leg
83
, which is pressed against the stop edge
82
of the set lever
80
, so aligns the set lever
80
that the free end
80
a
of the set lever
80
is grasped by the extension
86
. The extension
86
presses the set lever
80
backward. As a result, the angular lever
73
is pivoted by the set lever
80
in a clockwise direction about the axle
74
. At that, the first leg
75
of the angular lever
73
moves toward the piston rod
10
, compressing the inquiry element-forming leaf spring. Upon displacement of the first leg
75
toward the piston rod
10
, the locking lever
56
is pivoted by the stub
78
about the support
57
, which results in disengagement between the locking edge
59
and the drive ring
28
. The drive ring
28
moves toward the front of the setting tool, causing deaeration of the combustion chamber
1
. When the press-on cage, together with the extension
86
, is displaced back to the front end of the setting tool, the angular position of the angular lever
73
does not change because locking lever
56
cannot move back because its thick section lies in the opening
58
of the drive ring
28
because of the movement of the drive ring
28
to the front of the setting tool. The locking lever
56
retains, with its slot
77
, the stud
78
and thus, the angular lever
73
, in its new position.
During the displacement of the set lever
80
by the extension
86
backward, the set lever
80
becomes engaged by a convex section of the extension
86
to prevent the set lever
80
from turning back. The displacement of the set lever
80
causes the rotation of the angular lever
73
in
FIG. 10
in the clockwise direction and, as a result, the leg
83
of the leg spring
84
forms an acute angle with the stop edge
82
. This acute angle opens in a direction toward the leg
85
. When, after the release or lifting off of the locking lever
56
, the extension
86
moves forward, the set lever
80
is further pivoted in the clockwise direction by the leg
83
about the axle stub
79
. The set lever
80
, at a subsequent application of the tool against the constructional component and rearward movement of the extension
86
, would not be engaged by the extension
86
, and the set lever
80
would be located above the extension
86
.
Upon the second application of the tool against the constructional component, the combustion chamber will again be filled with the fuel gas mixture that will be ignited. The piston
8
would be again actuated and finally would return into its initial position. As soon as the piston rod
10
passes the inquiry element-forming leaf spring, it can move back into the region of the piston rod
10
, with its front end lying immediately beneath the end surface
10
a
of the piston rod
10
.
It follows from the foregoing discussion that in the release condition of the tool, i.e., in the release condition of the drive ring
28
, the extension
86
is uncapable of engaging the set lever
80
during initial application of the tool against the constructional component. When after a subsequent application of the tool against the constructional component, the drive ring
28
becomes locked as a result of actuation of the trigger
61
, and the locking lever
56
is pivoted away from the guide cylinder
5
, the angular lever
73
in
FIG. 10
would pivot in the counterclockwise direction about the axle
74
. As a result the inquiry element-forming leaf spring would be displaced out of the path of the piston rod
10
, the free end
80
a
of the set lever
80
would engage the upper portion of the extension
86
, and the leg spring
84
would become preloaded, as a result of the actuation of the trigger
61
and the pivotal movement of the locking lever
56
. The engagement of the free end
80
a
of the set lever
80
with the extension
10
leads to an additional excursion of the leg
83
of the leg spring
84
which, however, ascends again as soon as the extension
86
, as a result of a recoil, moves relative to the guide cylinder
5
. When after the ignition, the piston rod
10
passes, on its displacement back, the inquiry element-forming leaf spring, it again is displaced by the leg spring
84
into the path of displacement of the piston rod
10
. As a result, a conventional release of the drive ring
28
takes place. The drive ring
28
becomes released as a result of pivoting of the locking lever
56
which leads to disengagement of the locking edge
59
from the drive ring
28
. In this case, a compression spring
60
, which is used in the embodiments of
FIGS. 1 and 3
, becomes unnecessary.
Though 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.
Claims
- 1. A portable, internal combustion engined power tool comprising a combustion chamber (1); at least one suction/discharge valve (34) for supplying fresh air into the combustion chamber and for discharging waste gases therefrom; an operational piston (8) displaceable in an operational direction upon ignition of a fuel gas mixture filling the combustion chamber; a locking/release device (54) for releasing the at least one suction/discharge valve (34) after the piston (8) has reached its initial position after having performed an operational stroke; inquiring means (55, 65, 61) for inquiring a displacement position of the piston (8) when it is being displaced to its initial position after having performed the operation stroke and for actuating the locking/release device (54) when the piston (8) has reached its initial position; and a guide cylinder (5) for guiding the piston (8),wherein the piston (8) has a piston rod (10) projecting from the guide cylinder (5), and wherein the inquiring means (55, 65, 66) is arranged outside of the guide cylinder (5).
- 2. A power tool according to claim 1, wherein the inquiry means (55; 65, 66) comprises sensor means (65, 66) arranged adjacent to a displacement path of the piston rod (10) for generating an electrical release signal when the piston rod (10) passes a region of the sensor means (65, 66).
- 3. A power tool according to claim 1, wherein the inquiry means comprises a feeler element (55) biased against a circumference of the piston rod (10) and displaceable into the path of displacement of the piston rod (10) when the piston (8) has reached its initial position.
- 4. A power tool according to claim 3, wherein an end of the feeler element (55) adjacent to the piston rod (10) is formed as an elastic end.
- 5. A power tool according to claim 3, wherein an end of the feeler element (55) adjacent to the piston rod (10) is formed as a spring.
- 6. A power tool according to claim 2, comprising means (67) for lifting the locking lever (56) off its locking position in response to the electrical release signal generated by sensor means (65, 66).
- 7. A power tool according to claim 3, wherein the feeler (55) has an end remote from the piston rod (10) and connected with the locking lever (56).
- 8. A power tool according to claim 4, further comprising means (68, 80) for displacing the locking lever (56) into its release position if the piston (8) has not reached its initial position after performing the operational stroke.
- 9. A power tool according to claim 8, wherein the displacing means (68) comprises an actuation button.
- 10. A power tool according to claim 8, wherein the displacing means further comprises an angular lever (73) privotable about an axle (74) and having a leg (75) for displacing the locking lever (56) into its release position when another leg (76) of the angular lever (73) is displaced by press-on means (86) provided on the power tool, pivoting the angular lever (73).
- 11. A method of controlling operation a portable, internal combustion engined power tool including a combustion chamber (1), at least one suction/discharge valve (34) for supplying fresh air into the combustion chamber (1) and for discharging waste gases therefrom, and an operational piston (8), the method comprising the steps of inquiring a displacement position of the piston (8) when it is being displaced to its initial position after having performed an operational stroke; and releasing the at least one suction/discharge valve (34) upon the piston (8) reaching its initial position,wherein the tool further includes a guide cylinder (5) for guiding the piston (8), wherein the piston (8) has a piston rod (10) projecting from the guide cylinder (5), wherein the inquiring step comprises inquiring a displacement position of the piston rod outside of the guide cylinder and comprises detecting a position of a free end surface (10a) of the piston rod (10).
- 12. A portable, internal combustion engined power tool comprising a combustion chamber (1); at least one suction/discharge valve (34) for supplying fresh air into the combustion chamber and for discharging waste gases therefrom; an operational piston (8) displaceable in an operational direction upon ignition of a fuel gas mixture filling the combustion chamber; a locking/release device (54) for releasing the at least one suction/discharge valve (34) after the piston (8) has reached its initial position after having performed an operational stroke; and inquiry means (55, 65, 61) for inquiring a displacement position of the piston (8) when it is being displaced to its initial position after having performed the operational stroke and for actuating the locking/release device (54) when the piston (8) has reached its initial position,wherein the locking/release device (54) comprises a locking lever (56), the inquiry means (55, 56, 66) lifting the locking lever (56) when the piston (8) reaches its initial position.
- 13. A method of controlling operation a portable, internal combustion engined power tool including a combustion chamber (1), at least one suction/discharge valve (34) for supplying fresh air into the combustion chamber (1) and for discharging waste gases therefrom, and an operational piston (8), the method comprising the steps of returning the piston to its initial position as a result of vacuum that was created in the combustion chamber upon displacement of the piston to its operational position; inquiring a displacement position of the piston (8) when it is being displaced to its initial position after having performed an operational stroke; and releasing the at least one suction/discharge valve (34) upon the piston (8) reaching its initial position to provide for aeration of the combustion chamber.
- 14. A method according to claim 13, wherein the tool further includes a guide cylinder (5) for guiding the piston (8), wherein the piston (8) has a piston rod (10) projecting from the guide cylinder, and wherein the inquiring step comprises inquiring a displacement position of the piston rod outside of the guide cylinder.
- 15. A method according to claim 13, further comprising the step of forcefully releasing the at least one suction/discharge valve (34) when the piston has not reached its initial position after having performed the operational stroke.
- 16. A portable, internal combustion engined power tool comprising a combustion chamber (1); at least one suction/discharge valve (34) for supplying fresh air into the combustion chamber and for discharging waste gases therefrom; an operational piston (8) displacement in an operational direction upon ignition of a fuel gas mixture filling the combustion chamber; means (39) for creating vacuum in the combustion chamber, the piston being returned to its initial position upon creation of vacuum in the combustion chamber; a locking/release device (54) for releasing the at least one suction/discharge valve (34) after the piston (8) has reached its initial position after having performed an operation stroke; and inquiry means (55, 65, 61) for inquiring a displacement position of the piston (8) when its is being displaced to its initial position after having performed the operational stroke and for actuating the locking/release device (54) when the piston (8) has reached its initial position.
Priority Claims (1)
Number |
Date |
Country |
Kind |
100 32 310 |
Jul 2000 |
DE |
|
US Referenced Citations (6)