Advancing material of indeterminate length – Threading device – With means to pull lead-end
Reexamination Certificate
1999-11-02
2001-06-05
Mansen, Michael R. (Department: 3653)
Advancing material of indeterminate length
Threading device
With means to pull lead-end
C034S120000, C162S193000
Reexamination Certificate
active
06241138
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a paper web threading apparatus and, more specifically, to an apparatus for threading a leading edge of a paper web through a series of rollers or rotating cans of a papermaking machine. Further, the present invention relates to a method for threading a leading edge of a paper web through a series of rollers or rotating cans of a papermaking machine.
BACKGROUND OF THE INVENTION
Papermaking machines consist of several sections such as the fourdrinier, press section, dryer sections, calendar section, a reel, as well as other sections that may be unique to a particular type or grade of paper being produced. Many of these sections consist of multiple rolls or “cans” over which the paper travels. To start a new paper sheet or web through the papermaking machine, ropes can be used to carry a narrow leading edge of the web of paper, commonly referred to as a “tail” through the rollers. At a junction of two sections, the tail must be transferred from one set of ropes to another. This procedure is illustrated in
FIGS. 1-3
.
Specifically,
FIG. 1
is a top plan view of two adjacent dryer sections
10
,
12
of a papermaking machine
14
. To feed the new paper web
16
through the dryer sections
10
,
12
, the web
16
is provided with a tail
18
or a narrow leading edge as illustrated. The tail is inserted between two endless ropes
20
,
22
that are wrapped partially around sheaves disposed at the ends of the dryer cans
24
,
26
as well as the sheaves
28
,
30
as shown in
FIGS. 1 and 3
. The upstream endless ropes
20
,
22
must carry the tail
18
to the nip
32
formed by the two endless ropes
34
,
36
that extend around the sheaves
38
,
40
,
42
as well as sheaves mounted at the ends of the dryer cans
44
,
46
as also shown in FIGS.
1
and
3
. Not shown in
FIGS. 1 and 3
are stretching apparatuses used to adjust the tension of the endless ropes
20
,
22
and
34
,
36
. Such stretching apparatuses are known in the art. Examples of such stretching apparatuses appear in U.S. Pat. Nos. 5,263,623, 5,375,753, 5,377,892 and 5,379,932. The sheaves mounted to the ends of the cans
24
,
26
,
44
,
46
are also not shown but such sheaves are known in the art and are mounted to the can or roll head and rotate with the can or roll. The flow of the paper web
16
is illustrated in FIG.
2
.
It will be noted that the downstream section
12
(cans
44
,
46
) can be operated at a higher speed than the upstream section (cans
24
,
26
) to apply an appropriate tension to the paper web
16
.
The primary disadvantage with the tail transfer system illustrated in
FIGS. 1-3
is the premature release of the tail
18
by the ropes
20
,
22
. Specifically, referring to
FIG. 3
, the ropes
20
,
22
separate or diverge prior to reaching the nip
32
or the can
44
. As a result, the tail
18
is released too early and towards the inside or the center of the papermaking machine before the downstream ropes
34
,
36
form the nip
32
and can carry the tail
18
further downstream past the cans
44
,
46
.
As a result, there is a need for an improved web threading apparatus and method which does not result in a high incidence of the tail being released prematurely by the upstream ropes prior to the formation of the nip by the downstream ropes or a premature release by the upstream ropes which results in the tail being released inside towards the center of the papermaking machine.
SUMMARY OF THE INVENTION
The present invention satisfies the aforenoted needs by providing a paper web threading apparatus for use in a papermaking machine. The threading apparatus is applicable to a papermaking machine including a plurality of rotating drums such as an upstream drum, a downstream drum and a middle drum disposed between the upstream and downstream drums. Each drum includes an end on which a sheave is mounted. In an embodiment, a transfer sheave assembly is mounted on the end of the middle drum. The transfer sheave assembly includes a first sheave attached to the middle drum and that rotates with the middle drum and a second sheave that rotates freely and independently of the middle drum. The transfer sheave assembly also includes at least four endless ropes including at least two upstream ropes and at least two downstream ropes. The upstream ropes extend adjacent to one another and wrap partially around the sheave of the upstream drum before wrapping partially around one of the first or second sheaves of the transfer sheave assembly before diverging from one another downstream of the transfer sheave assembly. The downstream ropes are spaced laterally divergent from one another before converging in assuming adjacent positions with respect to each other and wrapping partially around the other of the first or second sheaves of the transfer sheave assembly before wrapping partially around the sheave of the downstream drum.
In an embodiment, the middle drum is the last drum of an upstream section of the papermaking machine and the downstream drum is the first drum of a downstream section of the papermaking machine. In this embodiment, the downstream section is operated at a higher speed than the upstream section. Therefore, the downstream ropes are mounted to the second sheave of the transfer sheave assembly which rotates freely and independently of the middle drum. Because the middle drum is the last drum of an upstream section, it rotates at a slower speed than the downstream section. Accordingly, the upstream ropes wrap around the first sheave which rotates at the same speed as the middle drum and the downstream ropes wrap around the second sheave which is free wheeling and therefore free to rotate at the higher speed of the downstream section. In this embodiment, the second or free wheeling sheave is disposed between the first sheave and the end of the middle drum.
In an alternative embodiment, the upstream drum is the last drum of an upstream section of the papermaking machine and the middle drum is the first drum of a downstream section of the papermaking machine. Thus, the middle drum and the downstream section rotate at a faster speed than the upstream drum and the upstream section of the papermaking machine. As a result, the downstream ropes wrap around the first sheave of the transfer sheave assembly which rotates at the same speed as the middle drum and the upstream ropes wrap partially around the second sheave of the transfer sheave assembly which is free wheeling and therefore is free to rotate at the slower speed of the upstream section. In this embodiment, the first sheave or the sheave fixed to the middle drum is preferably disposed between the second free wheeling sheave and the end of the drum.
In an embodiment, the upstream ropes also pass through a stretcher.
In an embodiment, the downstream ropes also pass through a stretcher.
In an embodiment, the present invention provides a method for threading the leading edge of a paper web through a papermaking machine as described above. The method includes the steps of providing a web threading apparatus as described above, operating the downstream section at a higher speed than the upstream section, and inserting the leading edge of the tail between the upstream ropes at a point upstream of the transfer sheave assembly.
Additional features and advantages of the present invention are described in, and will be apparent from, the detailed description of the presently preferred embodiments and from the drawings.
REFERENCES:
patent: 1688267 (1928-10-01), Cram
patent: 3529755 (1970-09-01), Spangenberg et al.
patent: 4480801 (1984-11-01), Stone
patent: 4747254 (1988-05-01), Lancaster
patent: 4931141 (1990-06-01), Shafranski
patent: 5016831 (1991-05-01), Saukkonen
patent: 5184408 (1993-02-01), Kotitschke et al.
patent: 5255602 (1993-10-01), Mamberer et al.
patent: 5263623 (1993-11-01), Bracken
patent: 5375753 (1994-12-01), Barthauer et al.
patent: 5377892 (1995-01-01), Kimball
patent: 5379932 (1995-01-01), Bracken
patent: 5397044 (1995-03-01), Suzuki
Article entitled “What
Garrigan Bruce G.
Theut Patrick J.
Wozniak Michael C.
Lawton C. A.
Mansen Michael R.
Sonnenschein Nath & Rosenthal
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