U.S. patent number 3,770,578 [Application Number 05/142,499] was granted by the patent office on 1973-11-06 for method for controlling caliper.
This patent grant is currently assigned to Midland-Ross of Canada Limited. Invention is credited to William Gordon Spurrell.
United States Patent |
3,770,578 |
Spurrell |
November 6, 1973 |
METHOD FOR CONTROLLING CALIPER
Abstract
Method for controlling the caliper of sheet material being
calendered by calender rolls, comprising selectively directing air
at one temperature onto a region of at least one of the calender
rolls corresponding to that region of the sheet passing over the
roll which has a thickness different than the thickness of adjacent
regions of the sheet to bring the thickness of this region of the
sheet closer to the thickness of the adjacent regions, while
simultaneously directing air at a second temperature onto the
adjacent regions of the roll corresponding to the adjacent regions
of sheet passing over the roll in order to retain the thickness of
the sheet at these regions.
Inventors: |
Spurrell; William Gordon
(Lasalle, Quebec, CA) |
Assignee: |
Midland-Ross of Canada Limited
(Quebec, CA)
|
Family
ID: |
22500076 |
Appl.
No.: |
05/142,499 |
Filed: |
May 12, 1971 |
Current U.S.
Class: |
162/206;
100/162B; 34/481; 100/333; 100/329 |
Current CPC
Class: |
D21F
7/06 (20130101) |
Current International
Class: |
D21F
7/00 (20060101); D21F 7/06 (20060101); D21f
007/06 () |
Field of
Search: |
;162/205,206,207
;34/25,48 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bashore; S. Leon
Assistant Examiner: D'Andrea, Jr.; Alfred
Claims
I claim:
1. A method of adjusting the thickness of a web of paper passing
through a calender, wherein the web has a thickness in one region
which is greater than the desired thickness, comprising directing a
treating medium at a temperature greater than 300.degree.F. onto an
area of a calender roll corresponding to said region of said web
passing over said roll to adjust the web thickness toward the
desired thickness and simultaneously directing a treating medium at
a temperature of less than 90.degree.F. onto the area of the
calender roll corresponding to regions of the web adjacent said one
region, to minimize the effect of the treating medium at the
temperature greater than 300.degree.F. on these adjacent
regions.
2. A method of adjusting the thickness of a web of paper passing
through a calender, wherein the web has a thickness in one region
which is less than the desired thickness, comprising directing a
treating medium at a temperature less than 90.degree.F. onto an
area of a calender roll corresponding to said region of said web
passing over said roll to adjust the web thickness toward the
desired thickness and simultaneously directing a treating medium at
a temperature greater than 300.degree.F. onto the area of the
calender roll corresponding to regions of the web adjacent said one
region, to minimize the effect of the treating medium at the
temperature of less than 90.degree.F. on these adjacent
regions.
3. A method as defined in claim 1, wherein the temperature of the
treating medium directed against the area of the roll corresponding
to the one region is between 300.degree.F. and 350.degree.F.
4. A method as defined in claim 2, wherein the temperature of the
treating medium directed onto the adjacent regions is between
300.degree.F. and 350.degree.F.
5. A method as claimed in claim 2, including adjusting the volumes
of the different temperature treating mediums directed onto the
regions.
6. A method as claimed in claim 1, including adjusting the volumes
of the different temperature treating mediums directed onto the
regions.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved method and apparatus for use
in calendering a web to obtain a web of more uniform thickness.
2. Description of the Prior Art
A common problem in the manufacture of paper webs is the uneven
thickness or caliper of the web, across its width, due to
variations in the machine and process forming the web. This problem
is accentuated when passing the finished web of paper through a
calender stack and winding it into a reel. When wound into a reel,
the uneven thickness of the web shows up as hard spots, where the
web is thicker than adjacent portions of the web and as soft spots,
where the web is thinner than adjacent portions of the web.
In an attempt to obtain a more uniform thickness or caliper in the
web and thus reduce soft spots in the reel, cold air has been
selectively directed onto calender rolls in the calender stack to
reduce the calender roll diameter at locations corresponding to
those portions of the web passing over the roll which are thinner
than adjacent portions of the web. This effectively increases the
thickness of the thinner portions to a value more closely
approaching the thickness of the remainder of the web. This method
is of no use, however, in eliminating hard spots or raised portions
in the reel which are caused by a greater thickness in those
portions of the web than adjacent portions of the web.
In an attempt to obtain better caliper control by being able to
eliminate either hard or soft spots in the reel, it has been
proposed to selectively direct hot or cold air onto the calender
rolls, to adjust roll diameter, and thereby effectively obtain a
more uniform thickness or caliper in the web. See U. S. Pat. No.
2,981,175, issued Ap. 25, 1961, Francis H. Goyette, inventor, for
example.
The apparatus shown in the patent employs a series of nozzles, each
of which, through the use of a single, manually adjustable, control
valve, can selectively direct either hot or cold jets of air
against selected portions on the calender rolls corresponding to
selective portions of the web being calendered. One or more nozzles
corresponding to a particular portion of the web to be treated are
operated to blow either hot or cold air only onto a portion of the
calender rolls corresponding to that particular portion of the web
passing over the rolls, depending upon whether the portion of the
web is thinner or thicker than adjacent portions of the web.
Devices of this type have not, however, been all that more
effective in obtaining a web having a more uniform thickness. Upon
further investigation, it has been found that one of the main
reasons in failing to obtain a more uniform thickness is the fact
that when employing one or more nozzles to direct hot air against
the calender rolls, to reduce the thickness of the web, or hard
spots in the reel, to substantially the same thickness as adjacent
regions, the jet of hot air from the nozzle or nozzles tends to
adversely affect the adjacent regions of the web which are already
of desired thickness. This is due to the dissipation of heat in the
steel calender rolls which causes the rolls to expand in the
regions immediately adjacent to the areas where the nozzle or
nozzles are directed. Conversely, when blowing cold air on the
calender rolls, corresponding to regions of the web to be
thickened, adjacent regions, already of desired thickness, are also
increased in thickness. It has also been found difficult to
satisfactorily control the selective blowing of hot and cold air in
proper amounts in order to obtain a more uniform web thickness,
particularly during high speed operation, because of the use of a
single, manually adjustable, control valve to control both the hot
and cold air.
SUMMARY OF THE INVENTION
Applicant's invention relates to a method and apparatus for
obtaining more uniform web thickness which overcomes the above
disadvantages. More particularly, the invention relates to a method
of adjusting the thickness of a web of paper passing through a
calender, wherein the web has a thickness in one region which is
different from the desired thickness, comprising directing a
treating medium, at one temperature, onto the regions of a calender
roll corresponding to said region in said web passing over the roll
to adjust the web thickness towards the desired thickness and
simultaneously directing a treating medium, at a different
temperature, onto regions of a calender roll corresponding to
regions of the web passing over the roll adjacent said one region,
to minimize the effect of the treating medium at the one
temperature on those adjacent regions.
The invention is further directed toward an apparatus for adjusting
the thickness of a web of material having an uneven thickness to
obtain a more uniform thickness, which apparatus comprises a first
duct for carrying a first treating medium, a second duct for
carrying a second treating medium adjacent the first duct, a series
of spaced apart nozzles, first and second conduit means connecting
each nozzle to the first and second ducts respectively, valve means
in each conduit, operator means for opening and closing the valves,
and control means for selectively actuating said operator
means.
One operator means preferably is provided for each valve, there
being two operator means associated with each nozzle. Preferably,
the conduits and operator means are enclosed in a third duct
connected to the first and second ducts.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in detail having reference to
the accompanying drawings, wherein:
FIG. 1 is a cross-sectional view of the apparatus for treating a
web of material;
FIG. 2 is a schematic view of the apparatus shown in FIG. 1 shown
in partial section; and
FIGS. 3A, 3B and 3C are graphs representing the caliper profile of
a web showing:
a. the original profile of a web before treatment;
b. the profile after directing hot air only against a region of the
calender roll corresponding to a thick region in the web passing
over the roll; and
c. the profile after directing hot air against a region of the
calender roll corresponding to a thick region in the web passing
over the roll with simultaneous direction of cold air onto regions
of the calender roll on opposite sides of the region on which the
hot air is directed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 1, the improved caliper control apparatus 1 is
mounted to extend along and adjacent a roll 3 in a calender over
which the web 7 passes. The apparatus 1 includes a hot air duct 9
and an adjacent cold air duct 11 extending the length of the roll
3. The hot air duct is insulated. A plurality of nozzles 13 are
carried by the ducts 9, 11 pointing toward the surface of roll 3
and being spaced apart longitudinally of the roll. Each nozzle 13
is connected to main conduit 15 which has branch conduits 17, 19
connecting it to the hot and cold air ducts 9, 11 respectively.
Located in each banch conduit 17, 19 is a valve 21 for controlling
the flow of hot or cold air through the respective branch conduit
to the nozzle 13. An operator 23 carried by a bracket 25 on the
branch conduit closely controls the setting of the valve between
and including closed and fully open positions. Preferably, the
operator 23 is of the rolling diaphragm type, pneumatically
controlled. A suitable rolling diaphragm operator is one
manufactured by Bellofram Corp. under Model No. B10530. A rack
section 27 is attached to the shaft extending from a piston within
the casing of the operator. The rack section 27 cooperates with a
pinion segment 29 axially connected to a shaft 31 mounted
diametrically through the wall in the conduit, the shaft carrying
the valve 21 within the conduit. A casing 33, connected to ducts 9,
11, forms a duct 34 enclosing the main conduits 15, branch conduits
17, 19 and operators 23 for each nozzle 13, with each nozzle
extending through an opening 35 in the casing wall. Preferably, the
wall 37 of the cold air duct 11, forming a part of the wall
defining duct 34, has perforations 39 permitting the cold air to
pass into the duct 34 to provide an over-pressure in the duct and
thus keep out dust or particles which might otherwise enter the
duct and interfere with the operation of the valves or
regulators.
A blower 41 is provided for directing air into the hot and cold air
ducts. The feed from the blower 41 is split with one conduit 43
carryng a portion of the flow from the blower through a heating
means 45 and then into the hot air duct 9, and a second conduit 47
carrying flow from the blower means to means 49 for regulating the
temperature of the cold air and then into the cold air duct 11. The
heating means 45 can comprise steam coils 51 capable of heating the
air fed to the hot air duct to a temperature of 350.degree.F. The
regulating means 49 can comprise cooling coils 53 for maintaining
the temperature of the air fed to the cold air duct at a
temperature no greater than 90.degree.F. and preferably between
approximately 65.degree. to 75.degree.F.
An operating station 55 is provided remote from the nozzles and
associated valves. The station 55 includes a grouping of a
two-position, three-way switch 57, a pressure regulator 59 and a
pressure gauge 60 for each nozzle. The switch 57 is connected to
selectively operate the hot air operator or the cold air operator.
The pressure regulator 59 pneumatically operates the operator 23
selected by switch 57 from a pneumatic source 58 to cause rack
section 27 to move and thus control the amount of valve opening and
the volume of hot or cold air directed through the nozzle. The
gauge 60 measures the pneumatic pressure supplied to the selected
regulator to provide an indirect visual measure of the volume of
hot or cold air directed through the nozzle.
The apparatus operates as follows:
Assume that a sheet passing over the calender roll 3 produces a
hard spot region in the reel providing a caliper profile such as
that shown in FIG. 3A with the hard spot region designated as 61.
The hard spot is a thick region in the web. In order to reduce the
thick region and thus provide a more uniform thickness in the
sheet, one or more nozzles A at or adjacent the area of a calender
roll over which this thick region of the sheet travels, are
operated by opening the valve leading from the hot air duct so as
to direct hot air onto the area of the calender roll corresponding
to the thick region in the web and thus reduce the web thickness in
this region. If only hot air is directed onto the area of the
calender roll corresponding to the thick region of the web, after a
certain period of time, the hot air affects regions 63, 65 adjacent
to the hard spot region in the reel 61 to produce a web caliper
profile as shown in FIG. 3B. It will be seen from this that, while
the hard spot region in the reel 61 has been eliminated, soft spot
regions in the reel 63, 65 have been formed adjacent the former
hard spot and the uniformity of caliper of the web is no better
than before. It is, therefore, necessary, when raising the hard
spot in the reel, to direct cold air from nozzles B, located
adjacent those nozzles A supplying hot air onto the areas of the
calender roll corresponding to the hard spot region, against the
areas of the calender roll corresponding to the regions of the web
adjacent the hard spot regions so as to minimize the effect of the
hot air on the adjacent regions. When this is done, a profile is
obtained as shown in FIG. 3C. It will be seen that the streams of
cold air from nozzles B prevent the formation of soft spots in the
reel which would otherwise occur as shown in FIG. 3B, and thus
assist in providing a web with more uniform caliper as shown in
FIG. 3C.
The apparatus would be operated oppositely when treating a region
of the web which is thinner than adjacent regions and corresponding
to a soft spot or depression in the reel. Cold air would be
directed onto areas of the calender roll corresponding to the thin
region of the web from one or more nozzles adjacent thereto.
Simultaneously, hot air would be directed onto areas of the
calender roll corresponding to the regions of the web adjacent
either side of the thin region so as to control the effect of the
cold air to obtain more uniform caliper.
The volume of hot or cold air directed onto the region to be
treated, together with the volume directed onto adjacent regions,
is controlled, depending on the variations in caliper between the
regions, to obtain more uniform caliper.
It has been further discovered that the maximum temperature of the
air in the hot air duct should be no greater than 350.degree.F. If
the temperature is greater than this, corrugations are produced in
the web. Preferably, the temperature in the hot air duct should be
between 300.degree. and 325.degree.F. Suitable controls on the
steam coils 51 are provided to maintain this temperature range.
Considerable difficulty was experienced in selecting proper
operators 23 to control the valves 21 in each branch conduit so as
to obtain proper valve settings to thereby control the volume of
hot or cold air passed through the nozzles and also to operate
reliably in the high temperatures. It is important to use operators
23 which do not exhibit a hysteresis effect so as to always be able
to obtain repeatable volume settings regardless of whether the
valve is being opened or closed and thus properly control the
volume of hot or cold air. Pneumatic operated cylinders exhibit a
hysteresis effect which is detrimental to the control. The same
volume setting cannot always be obtained. It has been found that a
rolling diaphragm-type cylinder is best suited since the hysteresis
effect is substantially eliminated. In addition, the positive drive
of the rack 27 and pinion 29 connection operating the valves
further eliminates hysteresis, thus providing very effective volume
control in the flow of hot or cold air from the nozzle.
* * * * *