Information
-
Patent Grant
-
6443118
-
Patent Number
6,443,118
-
Date Filed
Tuesday, December 19, 200023 years ago
-
Date Issued
Tuesday, September 3, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Mancene; Gene
- Castro; Arnold
Agents
- Sidley Austin Brown & Wood, LLP
-
CPC
-
US Classifications
Field of Search
US
- 123 260
- 123 267
- 123 268
- 123 280
- 123 283
- 123 286
- 123 46 R
- 123 46 A
- 123 46 H
- 123 292
-
International Classifications
-
Abstract
A portable, combustion-engined tool including a combustion chamber (1) in which a fuel gas in combusted upon ignition for building up pressure in the combustion chamber for driving the tool piston (8), an ignition device (20) for igniting the fuel gas in the combustion chamber (1), and gas drain means (43) provided in the combustion chamber (1) for controlling a pressure build-up therein.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a portable, combustion-engined tool and, in particular, a setting tool having a combustion chamber for receiving a fuel gas, and an ignition device for igniting the fuel gas for building up pressure in the combustion chamber for driving a setting piston adjoining the combustion chamber.
2. Description of the Prior Art
The drive energy in the tool described above is obtained by combustion of a fuel gas mixture, e.g., an air-fuel gas mixture, in the tool combustion chamber, and is transmitted to a fastening element, which need be driven in an object, via the piston.
The combustion-engined tool can have only one combustion chamber. However, a combustion-engined tool can have a combustion chamber that is divided in several chamber sections. In each case, the fuel gas mixture can be present in the chamber sections in different mixture ratios. For the sake of clarity, a combustion chamber would be considered which is divided only into chamber sections, a forechamber section and a main chamber section.
The combustion starts in the forechamber section by an electrical spark generated by the ignition device. 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 in the separation plate into the main combustion chamber section, creating there turbulence and pre-compression.
As the flame front reaches the through-openings, flame penetrates therethrough, due to the small cross-section of the openings, in a form of flame jets into the main chamber section, 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 substantially increases the effect of combustion as the losses which are caused by cooling, remain small.
A combustion chamber, which is divided in several chamber sections, can be formed as a collapsible combustion chamber having limiting opposite walls movable relative to each other.
An object of the present invention is a combustion-engined tool of a type discussed above having an increased capability of adjusting the energy transmitted to the piston.
SUMMARY OF THE INVENTION
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a gas drain arrangement that permits to control pressure build-up in the combustion chamber by draining a controlled amount of the fuel gas mixture. The fuel gas mixture can be drained through one or more drain channel(s) formed in the bottom region of the combustion chamber or in the main chamber section. By controlling the amount of the fuel gas mixture in the combustion chamber, an energy transmitted to the piston can be directly controlled.
In accordance with one embodiment of the present invention, the gas drain arrangement has a drain channel with an adjustable cross-section. For controlling the channel cross-section, an adjustable throttle or an adjusting screw with a radial through-channel can be used. In both cases, the channel cross-section can be changed to drain a controlled amount of the gas upon pressure build-up in the combustion (main) chamber.
According to an advantageous embodiment of the present invention, the gas drain arrangement includes a check valve for closing the combustion chamber when an underpressure prevails therein. The return of the piston into its initial position, after the attachment element has be drived in, is effected as a result of thermal feedback, i.e., during a phase when underpressure prevails in the combustion chamber or the main chamber section. The piston is displaced into its initial position until it engages a stop. To maintain the underpressure in the combustion chamber, it should remain closed during the return movement of the piston. This function is performed by the check valve.
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 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
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; and
FIG. 2
a cross sectional view along line A—A in FIG.
1
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A combustion chamber
1
of an 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
3
. 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 X 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
.
FIG. 1
shows a non-operational position of the setting tool in which the piston
8
is 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
.
Sealing rings
12
are 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. For fixing the piston
8
in its rearward off-position, there is provided a stop
13
.
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 X of the combustion chamber
1
. For separating the chambers on opposite sides of the movable wall
14
, an annular sealing
15
is provided on the circumference of the movable wall. The movable wall
14
has a central opening
16
, with an annular sealing
17
provided in the wall of the opening
16
. Sidewise of the central opening
16
at a distance therefrom, there is provided a through-opening
19
. An ignition device
20
is sealingly mounted in the opening
19
. The ignition device
20
has two electrodes
21
,
22
forming an electrical path for generating an ignition spark. The electrodes
21
-
22
face in a direction toward the bottom
3
of the combustion chamber
1
.
A separation plate
18
is provided between the bottom
3
of the combustion chamber I and the movable wall
14
. The separation plate
18
likewise has a circular shape and has an outer diameter corresponding to the inner diameter of the combustion chamber
1
. The separation plate
18
has a plurality of axial through-openings
38
spaced from the center of the separation plate
18
. The separation plate
18
is fixedly connected with a central projection
18
a
that extends into the through-opening
16
of the movable wall
14
. At the free end of the central projection
18
a
, there is provided a ring-shaped circumferential flange
18
b
which is engaged by the movable wall
14
when it is displaced in the axial direction. A spring
18
c
, which is provided between the flange
18
b
and the opposite rear side of the movable wall
14
and is supported on the projection
18
a
, always biases the separation plate
18
toward the movable wall
14
by applying a biasing force to the flange
18
b.
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
. Each of the openings
25
is provided win a circumferential seal located in the surface defining the opening
25
for sealing the combustion chamber
1
from outside. The movable wall
14
is connected with drive rods
23
by, e.g., screws
27
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
30
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
. The displacement of the movable wall
14
in a direction away from the bottom
3
is limited by a stop shackle
32
which is formed as a plate-shaped member. The shackle
32
is mounted in a circumferential groove
33
formed in the upper portion of the combustion chamber
1
. The shackle
32
is secured in the groove
33
with a locking ring
34
. The shackle
32
has an upwardly bulging section which serves as a stop for the central projection
18
a
of the separation plate
18
.
An aeration/deaeration valve is provided in the bottom
3
of the combustion chamber
1
. The aeration/deaeration valve serves for admitting fresh air into the combustion chamber
1
and for removal of waste gases from the combustion chamber
1
, as it will be described in more detail further below. In the condition of the combustion chamber
1
shown in
FIG. 1
, the aeration/deaeration valve is open. The condition of the combustion chamber
1
shown in
FIG. 1
corresponds to the off-condition of the tool.
At the lower end of the guide cylinder
5
, there are provided openings
39
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
.
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
21
,
22
, communicate the combustion chamber
1
with a metering valve (likewise not shown) and provide for injection of, e.g., liquefied fuel gas into respective combustion chamber sections which are formed when the movable wall
14
and the separation wall
18
are displace to the operational end positions determined by the stop shackle
32
, as also will be described in more detail further below.
In the bottom
3
of the combustion chamber
1
, there is also provided a drain valve arrangement
43
. The drain valve arrangement
43
includes a drain channel
44
, an adjusting screw
45
with a radial channel
46
, and a check valve
47
. The check valve
47
is shown schematically and includes a flap valve
48
which is biased by a compression spring
49
against an outlet side of the drain channel
44
, with the compression spring
49
being supported against a shoulder
50
provided on the cylindrical wall
6
of the guide cylinder
5
. The check valve
47
insures flow of waste gases from the combustion chamber
1
through the drain channel
44
outside, on one hand, and prevents any flow of air from the surrounding environment into the combustion chamber
1
through the drain channel
44
, on the other hand, when an underpressure is created in the combustion chamber
1
.
FIG. 2
, as discussed above, shows a cross-sectional view along line A—A in FIG.
1
. The cross-sectional view is taken through the drain valve arrangement
43
. As shown in
FIG. 2
, for the actuation of the adjusting screw
45
, there is provided a hand wheel
51
. The adjusting screw
45
is screwed tangentionally in bottom
3
of the combustion chamber
1
. The radial channel
46
of the adjusting screw
45
lies in the region of the drain channel
44
so that it becomes open or closed to a greater or lesser extent upon rotation of the adjusting screw
45
.
Below, the operation of the setting tool, shown in
FIGS. 1-2
, will be described in detail.
FIG. 1
shows the condition of the combustion chamber
1
in the off position of the setting tool. The combustion chamber
1
is completely collapsed, with the separation plate
18
lying on the bottom
3
of the combustion chamber
1
and the movable wall
14
lying on the separation plate
18
. In order to distinguish the movable wall
14
from the separation plate
18
, for the clarity sake, they are shown slightly separated. The piston
8
is in its rearward off-position, which is determined by the stop
13
, so that practically no space remains between the piston
8
and the separation plate
18
if one would disregard a small clearance therebetween. The position, in which the movable wall
14
lies on the separation plate
18
, results from the compressing spring
30
biasing the drive ring
28
away from the bottom
3
, with the ring
28
pulling the movable wall
14
via the drive rods
23
. In this position, the drive ring
28
is still spaced from the aeration/deareation valve, which remains open.
When in this condition, the setting tool is pressed with its front point against an object, the fastening element should be driven in, a mechanism shown only schematically by an element
57
, applies pressure to the drive ring
28
displacing it in the direction of the bottom
3
of the combustion chamber
1
. This takes place simultaneously with the setting tool being pressed against the object. At that, the movable wall
14
is lifted off the separation plate
18
and entrains therewith, via the compression spring
18
c
and the flange
18
, the separation plate
18
. Upon displacement of the separation wall
18
, a so-called main chamber section, which is formed between the separation plate
18
and the bottom
3
, expands. During the expansion of the main chamber section, air is aspirated thereinto via still open aeration/deaeration valve.
Upon further pressing of the tool against the object, the drive ring
28
is displaced further in a direction toward the bottom
3
, and, in a while, the projection
18
a
engages the shackle
32
. If the drive ring
28
is displaced further toward the bottom
3
, the movable wall
14
separates from the separation plate
18
, whereby a so-called forechamber section is formed between the movable wall
14
and the separation plate
18
. Air into the forechamber section is aspirated through the aeration/deaeration valve and the through-openings
38
formed in the separation plate
18
.
As soon as the movable wall
14
and the separation plate
18
pass the respective openings
41
,
42
, in principle, an injection of a metered amount of the liquified fuel gas into the forechamber and main chamber sections can start. At the end of the displacement of the movable wall
14
, the aeration/deaeration valve is closed by the drive ring
28
.
In the completely expanded position of the forechamber and main chamber sections, the movable wall
14
and the separation plate
18
become locked. This is effected by actuation of an appropriate lever or a trigger of the tool. The locking can take place shortly after the actuation of the trigger or shortly after ignition of the fuel gas mixture in the combustion chamber
1
of the setting tool. Upon actuation of the ignition device
20
, an electrical spark ignites a preliminary formed mixture of the air and the fuel gas in the forechamber section of the combustion chamber
1
. 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, creating there turbulence and pre-compression.
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, 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 bums with a high speed which substantially increases the effect of combustion.
The combustible mixture in the main chamber section 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 in discharged therethrough. The piston rod
10
effects setting of a fastening element.
The amount of energy transmitted to the piston
8
depends, among others, on the pressure build-up in the main chamber section. This pressure depends on the extent of opening of the drain channel
44
determined by a selected adjustment position of the adjusting screw
45
.
After setting or following the combustion of the air-fuel gas mixture, the piston
8
is brought to its initial position, which is shown in
FIG. 1
, 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. This means that the aeration/deaeration valve also should remain closed, as well as the drain valve arrangement
43
. The closing of the drain channel
44
is effected with the valve flap
48
, which is biased by the spring
49
into a position in which it closes the channel
44
until the underpressure exists in the main chamber section of the combustion chamber
1
.
After it is insured that the piston
8
reached its initial position, which is shown in
FIG. 1
, again, the movable wall
14
and/or the drive ring
28
, and/or the aeration/deaeration valve is (are) unlocked. The compression springs
30
bias the drive ring
28
in a direction away from the bottom
3
of the combustion chamber
1
, whereby the aeration/deaeration valve completely opens. Upon movement of the drive ring
28
away from the bottom
3
, the drive rods
23
pull the movable wall
14
in a direction toward the bottom
3
. Upon the movement of the movable wall
14
in the direction toward the bottom
3
, the compression spring
18
c
biases, via the flange
18
b
of the projection
18
a
of the separation plate
18
, the separation plate
18
toward the movable wall
14
. Thus, first, the forechamber section is deaerated, with the flue gases exiting through the aeration/deaeration valve. After the movable wall
14
abuts the separation plate
18
, both move in the direction toward the bottom
3
, with now the main chamber section being deaerated through the aeration/deaeration valve. In a while, the separation plate
18
abuts the bottom
3
, with the movable wall
14
lying on the separation plate
18
. The combustion chamber
1
becomes completely collapsed and free of flue gases. Now, an aeration process can begin anew upon the next setting of a fastening element.
The structure and operation of the tool was discussed above with reference to an embodiment with a collapsible combustion chamber. However, it should be clear that the present invention can be used with a setting tool or another tool in which the combustion chamber wall and/or separation plate are not displaced in the axial direction of the combustion chamber. In effect the present invention can be used with any tool the combustion chamber of which consists of a single chamber section and is not divided into forechamber and main chamber sections.
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.
Claims
- 1. A portable, combustion-engined tool, comprising a piston (8); a combustion chamber (1) in which a fuel gas is combusted upon ignition for building up pressure in the combustion chamber for driving the piston (8); an ignition device (20) for igniting the fuel gas in the combustion chamber (1); and gas drain means (43) provided in the combustion chamber (1) for controlling a pressure build-up thereinwherein the gas drain means (43) comprises a drain channel (44) with an adjustable cross-section, and wherein the gas drain means (43) comprises an adjusting screw (45) having a radially extending through-channel (46) and aligned with the drain channel (44) for adjusting the cross-section of the drain channel (44).
- 2. A portable, combustion-engined tool as set forth in claim 1, wherein the gas drain channel is formed by an adjustable throttle.
- 3. A portable, combustion-engined tool as set forth in claim 1, wherein the gas drain means (43) comprises a check valve (47) for closing the combustion chamber (1) when an under-pressure prevails therein.
- 4. A portable, combustion-engined tool as set forth in claim 1, wherein the gas drain means (43) is located in the bottom region of the combustion chamber (1).
Priority Claims (1)
Number |
Date |
Country |
Kind |
199 62 698 |
Dec 1999 |
DE |
|
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
3638632 |
Boling |
Feb 1972 |
A |
4773581 |
Ohtsu et al. |
Sep 1988 |
A |