Information
-
Patent Grant
-
6293175
-
Patent Number
6,293,175
-
Date Filed
Monday, June 7, 199925 years ago
-
Date Issued
Tuesday, September 25, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 083 554
- 083 13
- 030 210
- 030 216
- 030 229
- 030 2774
- 091 25
- 091 26
-
International Classifications
-
Abstract
A web cut-off device including a frame defining a piston chamber, a piston movable in the piston chamber, a cutter blade attached to the piston such that upon movement of the piston in a first direction, the cutter blade is adapted to engage and cut a web, at least one pressure chamber and lower connecting ducts for connecting the pressure chamber(s) to a lower part of the piston chamber. The ducts opening directly into opposed side walls defining the piston chamber such that the piston operates as a valve between the piston chamber and the pressure chamber(s). The device also includes at least one return pressure duct in communication with an upper part of the piston chamber such that upon introduction of pressure into the return pressure duct(s), the piston is moved in a second direction opposite to the first direction, and at least one bottom duct in communication with a bottom of the piston chamber such that by introducing pressure into the bottom of the piston chamber via the bottom duct(s), movement of the piston in the first direction is initiated and by evacuating pressure from the bottom of the piston chamber via the bottom duct(s), the piston is maintained stationary in the piston chamber. A method for cutting a web using the device is also disclosed.
Description
FIELD OF THE INVENTION
The invention concerns a web cut-off device for cutting a web in a web-handing machine such as a paper machine and a coating machine.
BACKGROUND OF THE INVENTION
In devices for processing of a paper web, such as, for example, paper machines and coating machines, cut-off devices are used, whose function is to cut off the web at a number of points when some disturbance of operation takes place in the machine, such as, for example, an uncontrolled web break. The purpose of the cutting off is to protect components that might be damaged when the paper web proceeds as wrinkled and having lost its tension inside the machine, for example, through a coating station or through a calender with soft rolls.
Further, a cut-off device is employed in reelers as a part of the machine reel change equipment. At present, for cutting off a paper or board web, among other things, the following methods are used:
Board and paper grades whose basis weight is high, typically >150 g/m
2
(grams per square meter), are cut off by using a so-called bag change or a cutting band or a cutting string. In bag change, the machine reel that is being completed is slowed down while, at the same time, pressurized air is blown to below the web. The web rises and forms a bag and enters into the nip. A sudden jerk cuts off the web. In change by means of a band, a separate band or string is fed to which an adhesion face has been fitted, for example, by means of an adhesive tape at the inlet side of the nip so that the adhesive tape affixes the band to the face of the reel spool outside the web, and the web tears the web apart in the nip while winding the web in spiral shape around the reel spool. In band change devices, the band that cuts off the board or paper web remains in the interior of the machine reel that is being completed on the face of the reel spool, where it produces bottom broke. The board/paper is glazed at the band over a thickness of several tens of windings. Nor is the reliability of operation of band change devices good, and their operation requires an abundance of manual work and great care.
With medium-weight paper grades, from about 80 to about 150 g/m
2
, a so-called swan-neck change is employed, in which a little cut is cut into the web before the nip, and after the nip pressurized air is blown to the cut area, in which connection the web is torn up to the edges.
With thin paper grades, about <100 g/m
2
, in reelers of the Optireel™ type marketed by the current assignee's, blowing from below the web or from the side is employed in order to pierce and to cut off the web. In particular with thin paper grades and at high running speeds, cutting off of a paper web by blowing produces detrimental paper chips, because the process of cutting is not controlled. With thicker paper grades, when blowing exclusively by means of pressurized air is employed, problems arise because the pressurized air cannot pierce the web or does the piercing untidily.
Further, there are applications in which a high-pressure water jet/jets is/are employed as the cutting element, which jets move across the web at a high speed. A problem of water-jet cutting is the necessity of very quick linear movements in the cross direction of the web and long cutting tails. In water-jet cutting, uncontrolled web breaks may also arise, in which case the web is torn by itself further from the cut that has been made by the jet.
There are also applications in which various mechanically striking blades are employed, which cut off the web as of full width.
The current assignee's FI Patent No. 97,339 constitutes the prior art most closely related to the present invention. In said patent, a cut-off device based on a mechanical blade is described. Said cut-off device includes a cut-off blade and an actuator that is fitted to act upon the cut-off blade to produce a cut-off stroke. The actuator consists of a number of cylinders fitted inside a chamber, each of which cylinders includes a piston and a piston rod. The piston rods have been attached with a certain spacing to a cut-off blade extending across the whole web width. A rapid stroke of the cut-off device is produced by means of rapidly opening pressure-controlled control valves of large area for the cylinders attached to the cut-off blade and by placing the cylinders in the interior of a pressure chamber so that the path of the compressed air from the pressure chamber into the cylinders is as short as possible.
In the cut-off device described in the FI Patent 97,339, variation may occur in the cutting speed. This comes at least from wear of the seals of the retainers and/or from problems related to the two-part structure of the instant-discharge principle used for the discharge.
However, when it operates correctly, cutting off taking place by means of a blade involves a number of advantages, such as controlled cutting off and tidy cutting result also at high speeds, as well as easy regulation of the cutting capacity by means of regulation of pressure in compliance with the paper grade to be cut off.
OBJECTS AND SUMMARY OF THE INVENTION
The object of the present invention is to provide a very rapid and precise cutting off of a web based on a mechanical cut-off blade extending across the whole web width.
In order to achieve this object and others, a web cut-off device in accordance with the invention comprises means defining a piston chamber having a pair of opposed side walls, a piston movable in the piston chamber, a cutter blade attached to the piston such that upon movement of the piston in a first direction, the cutter blade is adapted to engage and cut a web, means defining at least one pressure chamber and lower connecting ducts for connecting the pressure chamber(s) to a lower part of the piston chamber. The ducts open directly into the side walls of the piston chamber and at least at level of a bottom face of the piston chamber such that the piston operates as a valve between the piston chamber and the pressure chamber(s). The device also includes at least one return pressure duct in communication with an upper part of the piston chamber such that upon introduction of pressure into the return pressure duct(s), the piston is moved in a second direction opposite to the first direction, and at least one bottom duct in communication with a bottom of the piston chamber such that by introducing pressure into the bottom of the piston chamber via the bottom duct(s), movement of the piston in the first direction is initiated and by evacuating pressure from the bottom of the piston chamber via the bottom duct(s), the piston is maintained stationary in the piston chamber. Stop cushions may also be arranged in a top portion of the piston chamber for stopping movement of the piston in the first direction.
A cut-off device in accordance with the present invention can be used for cutting off of all paper and board grades.
The device is easy to manufacture, because its construction is very simple and it comprises just one mobile part. The tightness of the device also remains stable, because the backup face of sealing consists of the lower face of the piston, which retains its shape very well.
With a cut-off device in accordance with the invention, within normal pressure ranges of compressed-air systems, max. about 7 bars, very high rates of accelerations of up to 1000×g and very high speeds of 30 meters per second can be achieved. High speed is an essential property required in cutting off of a paper and board web. A particularly high speed is also required when the web is cut off in the unwind stand of a coating machine or when running at a high speed.
The solution in accordance with the invention permits wider dimensioning of flow ducts and uniform supply of air to below the piston. This is why, behind the piston, full pressure is obtained immediately, which pressure results in an acceleration as efficient as possible. On the other hand, owing to the efficient acceleration, it is possible to achieve high speeds even with a piston of relatively low weight. As a result of this, it is possible to use a short acceleration distance, in which case the blade and the piston assembly become of lower height. This again results in a reduced mass and in lower forces of deceleration, which has the consequence of better mechanical strength in particular at high speeds.
Since the acceleration is efficient, full system pressures do not have to be used in the cut-off device either. This is why an adequate allowance for regulation of the stroke power is obtained so that the cut-off device can be used for cutting off of paper and board grades of highly different thicknesses.
Owing to its speed reserve and to the simultaneous timing in the cross direction of the web, the cut-off device in accordance with the invention is also highly insensitive to different variables in a papermaking process, which are usually detrimental to the carrying out of changes, and to the maximal values of said variables, to ranges of variations, cross-direction profiles, etc. Such variables include, among other things, the web speed, web tension, basis weight/grade, tension profiles, moisture, moisture profiles, web strengths, strength proportions.
The cut-off device can also be placed very freely in a machine, because the cut-off device is compact, and the cut-off device also operates when turned upside down because of the pneumatic retainer. Since the retaining takes place by means of a vacuum, the top side of the piston can be kept free from pressure, which improves the accelerations and speeds that are achieved.
As regards the discharge, the cut-off device operates highly reliably, for it operates even if a significant proportion of the discharge valves were not in operating condition. Since there are several discharge valves and since their operation is very quick, being directly electrically controlled, it is possible to achieve a highly simultaneous start of movement (typically <0.5 ms) across the entire length of the device. This is why the web can be cut off highly simultaneously across its entire width, in which case the cutting off is controlled and the risk of web break and/or of an uncontrolled tear is very little.
The invention will be described in the following with reference to the figures in the accompanying drawings, in which a preferred cut-off device in accordance with the invention is illustrated, the invention being, however not supposed to be confined to the details of said embodiment alone.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic vertical sectional view of a preferred web cut-off device in accordance with the invention.
In
FIG. 2
the web cut-off device is illustrated in its home position.
In
FIG. 3
the web cut-off device has been shifted from its home position into contact with the web.
In
FIG. 4
the web cut-off device has been discharged and the web has been cut off.
FIG. 5
is an enlarged view of the cut-off device in the situation shown in FIG.
3
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The frame part
100
of the web cut-off device as shown in
FIG. 1
comprises a bottom piece
101
and a first
102
and a second
103
upper part to be attached to the bottom piece. Said first
102
and second
103
upper part are, in the direction of width X—X of the frame part
100
, preferably mirror images of one another in relation to a vertical plane Y—Y fitted in the middle. In its longitudinal direction, the frame part
100
extends preferably across the entire width of the web to be cut off. The bottom piece
101
of the frame part
100
and the first upper part
102
are interconnected preferably by means of bolts
110
, and the bottom part
101
and the second upper part
103
are, similarly, also interconnected by means of bolts
111
. In the bottom piece
101
of the frame part
100
, there are bores fitted for the bolts
110
,
111
, and in the upper parts
102
,
103
of the frame part, similarly, there are threaded bores adapted to the threads on the bolts
110
,
111
. The bolts
110
,
111
are placed with a suitable spacing across the length of the frame part
100
so that an adequate sealing can be achieved between the bottom piece
101
and the upper parts
102
,
103
.
In the frame part
100
of the cut-off device, there is a cutter blade
11
, which is attached directly to the piston
12
, e.g., by means of spring cotters. On the other hand, the piston
12
is fitted in a piston chamber
13
, in which it can move in the directions of the arrow S. The cutter blade
11
, the piston
12
and the piston chamber
13
extend preferably substantially across the entire width of the web to be cut off. The piston chamber
13
has been shaped so that the first half of the piston chamber
13
has been formed into the first upper part
102
and the second half has been formed into the second upper part
103
. The horizontal section of the piston chamber
13
is substantially shaped as an oblong rectangle. The first long side wall of the piston chamber
13
is denoted with the reference numeral
14
and the second long side wall with the reference numeral
15
.
Further, the frame part
100
includes a first pressure chamber
30
in direct vicinity of the first long side wall
14
of the piston chamber
13
and a second pressure chamber
31
in direct vicinity of the second long side wall
15
. From the first pressure chamber
30
a first short lower connecting duct
32
passes into the lower part of the first long side wall
14
of the piston chamber
13
to the level of the bottom of the piston chamber
13
, and from the second pressure chamber
31
, similarly, a second short lower connecting duct
33
passes to the lower part of the second long side wall
15
of the piston chamber
13
to the level of the bottom of the piston chamber
13
. The pressure chambers
30
,
31
extend substantially across the entire length of the frame part
100
. Moreover, the pressure chambers
30
,
31
communicate with an outside source of pressure, which is not shown in the figure. The lower connecting ducts
32
,
33
that pass from the pressure chambers
30
,
31
into the piston chamber
13
preferably consist of a number of separate ducts parallel to one another and fitted in the longitudinal direction of the frame part
100
, i.e. in the cross direction of the web. It is also possible to imagine that, in stead of two pressure chambers
30
,
31
, just one pressure chamber is employed, from which a number of separate lower connecting ducts pass into the piston chamber
13
.
In the bottom piece
101
of the frame part
100
of the cut-off device, in said vertical plane Y—Y, there are bottom connecting ducts
16
that pass into the bottom of the piston chamber
13
to below the piston
12
, which ducts can be connected through discharge valves
40
to a discharge pressure duct
50
and/or to a vacuum duct
51
. The discharge pressure duct
50
communicates with an outside source of pressure, which is not shown in the figure, and the vacuum duct
51
communicates with an outside source of vacuum, which is not shown in the figure either. Discharge valves
40
and connected bottom connecting ducts
16
as well as connecting ducts
41
,
42
passing from the discharge valves
40
to the discharge pressure duct
50
and to the vacuum duct
51
are fitted with a suitable spacing, for example 5 to 10 per meter, across the entire length of the frame part
100
.
Further, in the frame part
100
, there is a first return pressure duct
60
in direct vicinity of the first long side wall
14
of the piston chamber
13
, and a second return pressure duct
61
in direct vicinity of the second long side wall
15
. From the first return pressure duct
60
a first short upper connecting duct
62
passes to the top portion of the first long side wall
14
of the piston chamber
13
, and from the second return pressure duct
61
a second short upper connecting duct
63
passes to the top portion of the second long side wall
15
of the piston chamber
13
. The return pressure ducts
60
,
61
extend substantially across the entire length of the frame part
100
. Further, the return pressure ducts
60
,
61
communicate with an outside source of pressure, which is not shown in the figure. The upper connecting ducts
62
,
63
passing from the return pressure ducts
60
,
61
into the piston chamber
13
preferably consist of a number of separate ducts parallel to one another and fitted in the longitudinal direction of the frame part
100
, i.e. in the cross direction of the web. It is also possible to imagine that, in stead of two return pressure ducts
60
,
61
, just one return pressure duct is employed, from which a number of separate upper connecting ducts pass into the piston chamber
13
.
Further, in the top portion of the piston chamber
13
, there are piston
12
stop cushions
17
,
18
. Between the stop cushions
17
,
18
, a first slot
21
has been formed which guides the blade
11
. Between the upper parts
102
,
103
of the frame part
100
, at the vertical plane Y—Y, above the piston chamber
13
, a second slot
22
has been formed. This second slot
22
is slightly wider than the first slot
21
, and the blade
11
can move freely in this second slot
22
in the direction of the arrow S.
At the bottom of the piston chamber
13
, at the long side walls
14
,
15
of the piston chamber
13
, into the bottom piece
101
of the frame part, grooves have been machined for a seal band
19
,
20
. When the piston
12
is in its lower position pressed against said seal bands
19
,
20
, the pressure present in the pressure chambers
30
,
31
at the sides of the piston chamber
13
cannot act upon the bottom face of the piston
12
. Below the piston
12
, into the bottom of the piston chamber
13
, into the space defined by the seal bands
19
,
20
in the lateral direction X—X, further, a shallow recess
23
has been formed, into which the connecting bottom ducts
16
are opened. This recess
23
may also be provided on the piston
12
, in which case the bottom of the piston chamber
13
is smooth.
The upper parts
102
,
103
of the frame part
100
can also be made asymmetric if it is desirable, for example, to provide the apparatus with a blowing that facilitates the adhering of the cut-off web end to the face of a reel spool above the return pressure ducts
60
,
61
.
The bottom piece
101
, the upper parts
102
,
103
and the piston
12
of the device can be manufactured, for example, out of extruded profiles of light metal. The piston
12
and the blade
11
attached to the piston constitute the only mobile part in the frame part
100
.
The size of the pressure chambers
30
,
31
and the cross-sectional flow areas of the lower connecting ducts
32
,
33
have been measured by means of computing so that the accelerating working pressure behind the piston
12
remains high over the whole duration of the stroke and that no throttle occurs in the lower connecting ducts
32
,
33
, i.e. the losses of flow have been minimized. The return pressure ducts
60
,
61
have been measured so that the back pressure formed above the piston
12
during a stroke does not become very high. The return pressure ducts
60
,
61
also include instant discharge valves (not shown in the figures), by whose means the return pressure ducts
60
,
61
can be emptied quickly during a stroke, or, by means of the instant discharge valves, at least part of the air is allowed to pass out of the return pressure ducts
60
,
61
into the open air during the stroke.
In the following, the operation of the cut-off device will be described with reference to FIG.
1
.
First, a return pressure is passed into the return pressure ducts
60
,
61
placed in the upper parts
102
,
103
of the frame part
100
at both sides of the piston chamber
13
. This return pressure has access from the return pressure ducts
60
,
61
through the upper connecting ducts
62
,
63
passing into the piston chamber
13
to act upon the top part of the piston
12
. In this connection, the piston
12
moves into the lower part of the piston chamber
13
and is pressed against the seal bands
19
,
20
placed there. At the same time, the piston
12
closes the lower connecting ducts
32
,
33
passing from the piston chamber
13
into the pressure chambers
30
,
31
. When the piston
12
is pressed against the seal bands
19
,
20
provided at the bottom of the piston chamber
13
, the pressure passed into the pressure chambers
30
,
31
cannot pass to the bottom side of the piston
12
, but it acts upon the side faces of the piston
12
only.
Secondly, the vacuum present in the vacuum duct
51
is connected, by means of charge valves
40
, which are placed as densely spaced in the bottom piece
101
, which are directly electrically controlled and which operate very quickly, to the recess
23
provided on the bottom of the piston chamber
13
. From the vacuum duct
51
, a connecting duct
41
of its own passes to each discharge valve
40
, and, on the other hand, from each discharge valve
40
a connecting bottom duct
16
of its own passes to the recess
23
provided on the bottom of the piston chamber
13
. The vacuum that is passed into the space defined by the bottom face of the piston
12
and by the recess
23
provided on the bottom of the piston chamber
13
keeps the piston
12
in its place pressed against the seal bands
19
,
20
.
Thirdly, full working pressure is passed into the pressure chambers
30
,
31
. Since the pressure present in the pressure chambers
30
,
31
and attempting to raise the piston
12
can act substantially upon the side faces of the piston
12
only, the vacuum acting upon the bottom face of the piston
12
in the area defined by the distance between the seal bands
19
,
20
even alone is sufficient to keep the piston
12
down in a stand-by position ready for discharge.
As the fourth step, the return pressure which acts upon the top face of the piston
12
through the return pressure chambers
60
,
61
and through their upper connecting ducts
62
,
63
passing into the piston chamber
13
is removed. Depending on the work pressures and vacuums that are used, a security level can be defined for the construction in order to keep it in the stand-by position now formed. The security can be increased, if necessary, by allowing a slight return pressure to remain effective until the moment of discharge.
As the fifth step, by means of the discharge valves
40
, the connection of the vacuum duct
51
to the connecting bottom ducts
16
is cut off, and at the same time a connection is opened from the discharge pressure duct
50
to the connecting bottom ducts
16
and through said ducts to below the piston
12
. When the air pressure is increased in a very short time below the piston
12
to a certain limit value, the piston
12
starts moving upwards, in which connection the lower connecting ducts
32
,
33
passing from the bottom portion of the piston chamber
13
into the pressure chambers
30
,
31
are opened, and the pressure present in the pressure chambers
31
,
32
can flow to underneath the piston
12
. The piston
12
is accelerated very quickly to the desired stroke speed, which can be regulated by regulating the working pressure employed in the pressure chambers
31
,
32
. When the piston
12
moves upwards, the blade
11
attached to the piston also moves upwards and strikes against the web and cuts it off at the desired point.
As the sixth step, the pressure is removed from the pressure chambers
30
,
31
and the return pressure is connected to the return pressure ducts
60
,
61
, in which connection the piston
12
and the connected blade
11
move into the initial position to the bottom of the piston chamber
13
. The piston
12
positions itself against the seal bands
19
,
20
provided at the bottom of the piston chamber
13
.
In the following, the use of the cut-off device in a reel change situation at a reel-up will be described with reference to
FIGS. 2
to
5
.
In
FIG. 2
, the cut-off device is in its home position, in which it can operate, for example, as a pulper guard. The frame part of the cut-off device has been fitted on a suitable shield box
200
, and the shield box
200
is again attached, for example, to hydraulic arms
201
, by whose means the frame part can be shifted towards the web W and apart from the web. At the same time, the shield box operates as a rigidifier of the frame part.
In
FIG. 3
, the cut-off device has been shifted from its home position against the web W. The upper part or upper parts of the frame part is/are in contact with the web W and raise(s) the web W slightly. When a thin paper grade is being cut off, the cut-off device can be placed apart from the web, because the high stroke speed is sufficient to cut off the web even if the web were not supported against the device.
In
FIG. 4
, the web W has been cut off by discharging the cut-off device. After this, the cut-off device can again be returned to its home position.
FIG. 5
is an enlarged view of the cut-off device in the situation shown in FIG.
3
. In this situation, the frame part
100
of the cut-off device is ready to be discharged against the web W, and it raises the web W slightly in order that the web W should be tight when the cut-off blade is discharged against the web W.
In the following, the patent claims will be given, and the details of the invention can show variation within the scope of the inventive idea defined in said claims and differ from what has been stated above by way of example only.
Claims
- 1. A method for cutting a web, comprising the steps of:applying a return pressure at a top of a piston chamber to move a piston to a bottom of te piston chamber, maintaining the piston at the bottom of the piston chamber by applying a vacuum force below the piston, the piston having with a cutter blade attached to the top of the piston and adapted to engage and cut the web, introducing a pressure into at least one pressure chamber in flow communication with a lower side part of the piston chamber such that the pressure bears against a side of the piston when the piston is at the bottom of the piston chamber, removing the return pressure acting on a top of the piston, stopping the application of the vacuum force being applied below the piston, and introducing pressure below the piston to cause movement of the piston toward the top of the piston chamber such that upon movement of the piston, the at least one pressure chamber is in flow communication with the piston chamber and the pressure in the at least one pressure chamber is effective against a lower part of the piston to accelerate the piston and the cutter blade to thereby cut the web.
- 2. The method of claim 1, further comprising the steps ofevacuating the pressure from the at least one pressure chamber, and applying the return pressure at the top of the piston chamber to move the piston to the bottom of the piston chamber.
- 3. A web cut-off device, comprising:means defining a piston chamber, said means including a pair of opposed side walls, a piston movable in said piston chamber, a cutter blade attached to said piston such that upon movement of said piston in a first direction, said cutter blade is adapted to engage and cut a web, means defining at least one pressure chamber, lower connecting ducts for connecting said at least one pressure chamber to a lower part of said piston chamber, said ducts opening directly into said side walls defining in part said piston chamber and at least at a level of a bottom face of said piston chamber such that said piston operates as a valve between said piston chamber and said at least one pressure chamber, at least one return pressure duct in communication with an upper part of said piston chamber but not in communication with said at least one pressure chamber such that upon introduction of pressure into said at least one return pressure duct, said piston is move in a second direction opposite to the first direction, at least one bottom duct in communication with a bottom of said piston chamber but not in direct communication with said at least one pressure chamber, means for introducing pressure into the bottom of said piston chamber via said at least one bottom duct in order to move the piston in said first direction, and means for evacuating pressure from the bottom of said piston chamber via said at least one bottom duct in order to maintain the piston stationary at the bottom of said piston chamber.
- 4. The device of claim 3, wherein said lower connecting ducts are separated from one another along each of said side walls.
- 5. The device of claim 3, wherein said at least one return pressure duct comprises first and second return pressure ducts, further comprising upper connecting ducts for connecting said first and second return pressure ducts to the upper part of said piston chamber.
- 6. The device of claim 3, wherein said at least one bottom duct comprises a plurality of bottom ducts.
- 7. The device of claim 3, further comprisingstop cushions arranged in a top portion of said piston chamber for stopping movement of said piston in the first direction.
- 8. The device of claim 3, wherein said means for introducing pressure comprisesat least one discharge valve in communication with said at least one bottom duct, and a discharge pressure duct in communication with said at least one discharge valve for enabling the introduction of pressure into the bottom of said piston chamber via said at least one bottom duct.
- 9. The device of claim 8, wherein said means for evacuating pressure comprisesa vacuum duct in communication with said at least one discharge valve for enabling the evacuation of pressure from the bottom of said piston chamber via said at least one bottom duct.
- 10. The device of claim 3, further comprisingat least one discharge valve in communication with said at least one bottom duct, and a vacuum duct in communication with said at least one discharge valve for enabling the evacuation of pressure from the bottom of said piston chamber via said at least one bottom duct.
- 11. The device of claim 3, further comprisingseal bands arranged at a bottom of said piston chamber adjacent said side walls, said piston being arranged to abut against said seal bands when in a stationary position and thereby prevent communication between said at least one pressure chamber and the bottom of said piston chamber when said piston is in its stationary position.
- 12. The device of claim 11, wherein said means defining said piston chamber comprise a recess between said seal bands and in communication with said at least one bottom duct, said piston being urged against said seal bands upon introduction of a vacuum in said recess.
- 13. The device of claim 3, wherein said means defining said piston chamber comprise an elongate frame part defining a slot through which said cutter blade projects upon movement of said piston in the first direction.
- 14. The device of claim 3, wherein said means defining said piston chamber comprise a first frame part including a lower wall of said piston chamber, a second frame part attached to said first frame part and including one of said opposed side walls of said piston chamber and a third frame part attached to said first frame part and including the other of said opposed side walls of said piston chamber such that said piston chamber is defined by said first, second and third frame parts.
- 15. The device of claim 3, wherein said means defining at least one pressure chamber define first and second pressure chambers, at least one of said lower connecting ducts connecting said first pressure chamber to a lower part of one of said walls defining said piston chamber and at least one of said lower connecting ducts connecting said second pressure chamber to a lower part of the other one of said walls defining said piston chamber.
Priority Claims (1)
Number |
Date |
Country |
Kind |
972329 |
Jun 1997 |
FI |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
102e Date |
371c Date |
PCT/FI98/00455 |
|
WO |
00 |
6/7/1999 |
6/7/1999 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO98/55688 |
12/10/1998 |
WO |
A |
US Referenced Citations (10)
Foreign Referenced Citations (5)
Number |
Date |
Country |
320043 |
Apr 1920 |
DE |
3333233 |
Mar 1985 |
DE |
0739695 |
Oct 1996 |
EP |
97339 |
Aug 1996 |
FI |
8700776 |
Feb 1987 |
WO |