Note: Descriptions are shown in the official language in which they were submitted.
TITLE OF THE INVENTION ~,033453
APPARATUS FOR RUBBER COATING OF CORDS
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an apparatus for coating a
suitable number of cords with a raw rubber material and winding up
the coated cords.
A predetermined number of cords (e.g., one to tens or more) are
coated with a raw rubber material to obtain a belt or strip (e.g.,
0.~ mm to 30 mm in width), for example, a single nylon cord band or a
nylon band of a narrow width for use in tires. Such belts or strips
are conventionally made from a cord fabric having a large width
(e.g., 900 to 1200 mm) and woven of wefts, by coating the fabric with
rubber using a topping calendar of large width to obtain a strip of
rubber-coated fabric, and then slitting the strip into strips of
desired narrower width.
However, when the strip of rubber-coated fabric is slitted in
the predetermined width, it is likely that some of the cords will be
also cut along with the rubber material or damaged. Difficulty is
therefore encountered in preparing a rubber-coated material of narrow
width (rubber-coated tape). Further coating fabric of narrow width
using at standard calendar is less justifiable in terms of efficiency,
since the width of the topping calendar is determined in conformity
with the maximum width of the material to be coated.
Such a rubber coated material is wound up on a take-up drum
usually with a liner made of cloth, thin plastics sheet or like the
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interposed between the adjacent layers of the coated material to
preclude adhesion between the superposed layers, whereas the required
length of the coated material is determined in accordance with the
specifications and the quantity of production of the product for
which the coated material is to be used, and is not always the same
as the length of the liner.
Accordingly, in the case where the liner happens to be shorter
than the rubber-coated material, it is conventional practice to stop
the production of the coated material (coating operation) and
replenish the apparatus with another length of liner before resuming
the production. This method is therefore no good in terms of
productivity.
SUMMARY~aF THE INVENTION
A first object of the present invention is to provide a coating
apparatus which is adapted to coat one to several tens of (a suitable
number of) cords with a raw rubber material easily and rapidly and to
wind up the rubber-coated material.
A second object of the present invention is to provide a liner
joining device which is adapted to join to a liner being applied to a
rubber-coated material another length of liner during the production
of the rubber coated material without interrupting the operation so
as to continuously supply the liner to a take-up drum for winding up
the rubber-coated material.
To fulfill the first object, the present invention provides as a
first feature thereof an apparatus for coating a suitable number of
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cords with a raw rubber material, the apparatus being characterized
in that the appara-tus comprises:
a cord feeder for sending out the cords in a downstream
direction,
an extruder for coating the cords with the raw rubber material
to produce a rubber-coated material while the cords sent out
from the cord feeder are traveling in the downstream direction,
a take-up assembly for winding up the rubber-coated material on
a take-up drum,
a supply adjusting assembly for adjusting the winding speed of
the take-up assembly in accordance with the line speed and the
variation in the diameter of the wound-up material, and
a liner feeder for supplying a liner to the take-up assembly
during the winding of the rubber-coated material on the take-
up drum of the take-up assembly.
The present invention further provides as a second feature
thereof an apparatus for coating a suitable number of cords with a
raw rubber material, the apparatus being characterized in that the
apparatus comprises:
a cord feeder for sending out the cords in a downstream
direction as p&id off from a bobbin,
a small-sized extruder hsving the interior of its extruder head
held at an optimum rubber pressure in accordance with the
characteristics of the cords for coating the cords with the
raw rubber material to produce a rubber-coated material while
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the cords sent out from the cord feeder are traveling in the
downstream direction,
a pull roll assembly for pulling the resulting rubber coated
material in the downstream direction,
a take-up assembly disposed downstream from the pull roll
assembly for winding up on a take-up drum the rubber-coated
material from the pull roll assembly,
a supply adjusting assembly disposed between the take-up
assembly and the pull roll assembly for adjusting the winding
speed of the take-up assembly in accordance with the line
speed and the variation in the diameter of the wound-up
material, and
a liner feeder for supplying a liner to the take-up assembly
during the winding of the rubber-coated material on the drum of
the take-up assembly to interpose the liner between the opposed
. upper and lower portions of the coated material on the drum and
prevent the rubber coated material from adhering to each other.
.
. According to the first and second features of the present
invention, one or several tens of cords are sent out from the cord
feeder into the extruder and coated with a raw rubber matorial within
, the 0xtruder, whereby a rubber-coated material is produced free of
; spew. The coated material is pulled by the pull roll
, assembly against the internal pressure of the extruder, guided
toward the downstream direction via the supply adjusting assembly
and wound up on the take-up drum of the take-up assembly at a speed
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adjusted by the adjusting assembly in accordance with the line
speed and the variation in the diameter of the wound-up material.
During the winding, a liner is supplied from the liner feeder to
the take-up drum and interposed between the opposed upper and
lower coated material on the drum. Thus, the coated material is
continuously wound on the take-up drum without sticking to each
other.
The coating apparatus according to the first and second features
of the present invention has the advantage that one cord or a rank of
cords of small width can be easily and reliably made into a rubber-
coated material, thus not necessitating the step of coating a cord
fabric having a large width and then slitting the rubber coated
fabric into a number of narrow width strips.
Further according to the first and second features of the
present invention, it is desirable to provide a traverse assembly for
reciprocatingly moving the rubber-coated material in directions
approximately perpendicular to the direction of travel of the
material while the coated material is being wound up on the take-up
drum.
The provision of the traverse assembly results in the advantage
of preventing the rubber-coated material from being wound up on the
drum locally concentrically to preclude the roll of the material from
collapsing, further permitting the drum to wind up an increased
length of coated material.
Further according to the second feature of the present
invention, it is desired that the pull roll assembly comprise a pair
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of upper and lower rolls having their axes positioned in separate
horizontal planes, the axes of the respective rolls being displaced
from each other by a small angle.
The pull roll assembly has the advantage that even when the
rubber-coated material is wound around the rolls several turns, the
coated material can be pulled toward the downstream direction under
definite tension without lapping over itself.
To accomplish the first object, the present invention further
provides as a third feature thereof an apparatus for coating a
suitable number of cords with a raw rubber material, the apparatus
being characterized in that the apparatus comprises:
a crosshead having a cavity for the raw rubber material to be
forced thereinto from a direction perpendicular to the axis of
the cord by the rotation of a screw having a diameter of at
least 20 mm,
a sensor for detecting the internal rubber pressure of the
, crosshead,
a control system for determining the number of revolutions of
the screw based on the detection signal of the sensor to
maintain the interior of the crosshead at an optimum rubber
pressure in accordance with the characteristics of the cords,
and
a servomotor or like motor for rotating the screw in response
to a rotation command from the control system.
.
According to the third feature of the present invention, a
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rubber-coated material of specified shape can be extruded free from
spew because the screw having a diameter of at least 20 mm is rotated
at a speed which is so determined from the detected internal rubber
pressure of the head that the internal rubber pressure will be an
optimum value in conformity with the characteristics of the cords to
be coated.
Further to achieve the second object, the present invention
provides a liner joining device which is characterized in that the
device comprises:
a pair of adhering rollers respectively arranged in the vicinity
of a pair of rolls of liner removably mounted on a holdert
a pair of holding assemblies for releasably holding the leading
end portion of the respective liners, and
pressing assemblies for moving the rollers toward each other
into contact with each other and causing the rollers to adhere
the leading end of one liner roll, the leading end held by one
of the holding assemblies, instantly with the running liner of
the other roll when the running liner approaches its rear end.
The liner joining device of the present invention is so adapted
that the leading end of one liner roll is held by one of the holding
assemblies while the other liner roll is being drawn out and when the
running liner of the other roll approaches its rear end, the pair of
joining rollers are moved toward each other into contact with each
other by the pressing assemblies, whereby the leading end of the
above-mentioned one liner roll is automatically adhered and joined to
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the other liner being drawn out. Upon the adhesion, the holding
assembly lets go of the leading end of one liner roll. Accordingly,
the liner of one roll can automatically be joined to the running
liner of the other roll without making any ~epP Of the operation.
Thus, the rubber-coated material of desired length can be wound up.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l is a front view showing an embodiment of the invention;
Fig. 2 is a plan view of the same;
Fig. 3 is an enlarged fragmentary view in section of an
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extruder;
Fig. 4 is an enlarged front view partly in sec-tion and showing
a pull roll assembly;
Fig. 5 is an enlarged front view of a supply adjusting assembly;
Fig. 6 is an enlarged sectional view of the same;
Fig. 7 is an enlarged side elevation of a traverse assembly;
Fig. 8 is an enlarged sectional view of a take-up assembly;
Fig. 9 is an enlarged sectional view of a liner feeder;
Fig. 10 is an enlarged front view of the same;
Fig. 11 is a block diagram of a line control system; and
Fig. 12 is a block diagram of a control system for the extruder.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment will be described below with reference to the
drawings.
Figs. 1 and 2 show a coating apparatus of the invention in its
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entirety. The apparatus is adapted to coat a suitable number of
cords, e.g., one cord 1 (see Fig. 3), with a raw rubber material (see
Fig. 3). The apparatus comprises a cord feeder 3 for sending out the
cord 1 in a downstream direction, an extruder 5 for coating the cord
1 from the feeder 3 with the raw rubber material 2 to produce a
rubber-coated material 4 (see Fig. 3), a pull roll assembly 6 for
pulling the coated material 4 toward the downstream direction against
the internal rubber pressure of the extruder 5, a take-up assembly 8
for winding up the coated material 4 from the pull roll assembly 6 on
a take-up drum 7, a supply adjusting assembly 9 disposed between the
take-up assembly 8 and the pull roll assembly 6 for adjusting the
speed of winding of the coated material 4 in accordance with the line
speed and the variation in the diameter of the wound-up coated
material, and a liner feeder 11 for supplying a liner lO to the take-
up assembly 8 to interpose the liner between the adjacent windings of
the coated material 4 on the drum 7.
The cord feeder 3, the extruder 5 and the pull roll assembly 6
are mounted on a carrier 13 having casters 12 and are movable.
The cord feeder 3 comprises a base frame 14 provided upright on
the carrier 13, a motor (d.c. servomotor) 15 mounted on the base
frame 14, and a shaft 17 connected to the drive shaft of the motor 15
by a helical coupling ]6. A bobbin 18 having the cord 1 wound there-
around is attached to the shaft 17. The bobbin 18 comprises an
unillustrated paper tube fitted around the shaft 17 and having the
cord 1 wound thereon. More specifically, the paper tube with the
cord 1 wound thereon is fitted around the shaft 17, and air is
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X033453
injected into the shaft 17, expanding an expandable member within the
shaft 17 to project the member from the shaft 17 through a slit
therein and thereby firmly attach the paper tube to the shaft.
The base frame 14 is provided with a tension sensor 19. The
cord 1 drawn out from the bobbin 18 passes through a cord guide
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member 20 and then through the tension sensor 19, by which the
tension on the cord 1 is measured. The tension sensor 19 is, for
example, a tensiometer. The tensiometer comprises a pair of guide
rollers and a sensor roller and measures tension with an image
sensor.
As shown in Fig. 3, the extruder 5 has a cross head 22. It is
a small-sized extruder having a screw diameter of at least 20 mm and
is adapted to produce extrudates free of spew. The head 22
comprises a main portion 23, and a flow guide 24 and a die 25
provided inside the main portion 23. The cord 1 is inserted through
an axial bore of the flow guide 24 and the hole of the die 25 in
alignment therewith. The raw rubber material 2 is forced into a
cavity 28 from a direction perpendicular to the axis of the cord 1 by
the rotation of the screw (not shown) which is rotated by a motor 33
such as an a.c. servomotor. The cord 1 is coated with the extruded
rubber material to make the rubber-coated material 4, which is forced
out from the extruder 5.
The thickness of the rubber coating varies with the internal
rubber pressure of the head (i.e., the number of revolutions of the
screw) and the speed of travel of the material through the cross
head. To obtain the extruda-te of specified shape, therefore, there
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is a need to establish the abovementioned relationship and determine
the internal pressure of the head. Accordingly, the pressure is
detected for the control of the speed of rotation of the screw in
order to maintain the pressure at a predetermined value. Since the
internal head pressure varies more rapidly when producing extrudates
free from spew than when allowing spewing, it is necessary to use,
for example, an a.c. servomotor which permits effective control of
the speed of rotation of the extruder. Furthermore, the size of the
extruder, i.e., the diameter of the screw, must be at least 20 mm so
that the rubber material can be fully plasticized at the rotational
speed of the screw which provides the predetermined head pressure.
As shown in Figs. 1 and 2, the extruder 5 has a body 35 which is
supported by upright legs 34 on the carrier 13, and the motor 33 is
mounted on the top of the body 35. The body 35 has the crosshead 22.
A d.c. servomotor or d.c. motor may be used as the motor 33.
The rubber-coated material 4 formed in the extruder 5 is pulled
toward the downstream direction by the pull roll assembly 6, which
comprises upper and lower rolls 36, 37 and a motor 38 for rotating
these rolls 36, 37. The upper and lower rolls 36, 37 draw the cord 1
out against the internal rubber pressure of the head 22 by rotating
with the coated material 4 wound therearound. With reference to Fig.
4, the upper and lower rolls 36, 37 are rotatably supported by a roll
holder 40 mounted on a base frame 39 provided upright on the carrier
13. The motor 38 is attached to a motor holder 41 mounted on the
base frame 39 flnd has a drive shaft 38a which is connected to the
shaft 43 of the upper roll 36 by a coupling 42. The shaft 43 carries
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a pulley 44. The shaft 44 of the lower roll 37 also carries like
pulley 46. Belts 47 are reeved around the pulleys 44, 46.
Accordingly, the motor 38, when driven, rotates the upper and lower
rolls 36, 37.
The axis of the upper roll 36 extends perpendicular to the axis
of the coated material 4, while the axis of the lower roller 37 is
slightly displaced in a horizontal plane from the axis of the upper
roll 36. This prevents the cords 1 from lapping over themselves even
if wound around the rolls several turns. The line speed is dependent
on the surface speed of the upper and lower rolls 36, 37.
The take-up assembly 8, the supply adjusting assembly 9 and the
liner feeder 11 are mounted on a base 48. The supply adjusting
assembly 9, which adjusts the winding speed to the line speed of
several hundreds of millimeters per minute, comprises a roller holder
49 extending upright from the base 48, an upper roller 50 rotatably
supported by the upper end of the holder 49, and a slide roller
supported by the holder 49 and movable upward and downward as seen in
Figs. 5 and 6. The coated material 4 from the pull roll assembly 6
is reeved around the rollers 50, 51 as fitted in grooves 50a, 51a
thereof, and the winding speed of the take-up drum 7 is controlled by
shifting the slide roller 51 vertically. The slide roller 51 moves
upward or downward by being guided by rollers 53 which move upward or
downward along guide members 52 on the front side of the holder 49.
Although the stroke length of the roller 51 is several tens of
centimeters, the assembly 9 so functions that the stroke length is
increased several times since the material 4 is reeved around the
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Z033453
rollers 50, 51 several turns. As a result, the winding speed can be
fully controllable in accordance with the variation in the diameter
of the winding on the take-up drum 7 and the variation in the line
speed even if the speed is several hundreds of meters. More
specifically stated with reference to the present embodiment, the
maximum speed of the rubber-coated material is 200 m/min, and the
variation in the winding speed at the adjusting assembly is 1/10 of
the value. The winding speed is so adjusted as to reduce the speed
variation to zero upon detecting the variation.
A traverse assembly 54 is provided at the upper end of the
holder 49 of the supply adjusting assembly 9. The coated material 4
is supplied to the take-up drum 7 while being traversed by the
assembly 54 over the entire width of the roll. The traverse assembly
54 comprises a pulley 55 for guiding the travel of the coated
material 4, a support 56 for rotatably supporting the pulley 55, a
bar 57 for holding the support 56, and a linear motor 58 for
reciprocatingly moving the holding bar 57 in directions perpendicular
to the direction of travel of the coated material 4. The
reciprocating movement of the holding bar 57 reciprocatingly moves
the pulley 55 in the directions perpendicular to the direction of
travel of the coated material 4 and traverses the material 4 within
the width of the liner 10 to increase the length of the material 4 to
be rolled up and prevent the resulting roll from collapsing. The
pulley 55 serves also to measure the length of the material 4.
Next with reference to Fig. 8, the take-up assembly 8 comprises
a base 59, a drum holder 60 provided upright on the base 59, the
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take-up drum 7 rotatably supported by the holder 60, etc.
The holder 60 comprises a front holder portion 60a for
supporting the front portion of the drum 7, and a rear holder portion
60b for supporting the rear portion of the drum 7. Shaft members 61,
62 are fixedly inserted in the respective ends of the body 63 of -the
drum 7 for rotatably supporting the drum 7. The shaft members 61, 62
are reciprocatingly movable axially thereof as indicated by arrows by
means of cylinder mechanisms 64, 65, respectively. The drum 7 is
removably supported by the holder 60.
The base 59 is mounted by interposed members 67 on guide members
66, 66 mounted on the base 48 and is connected by a connector 69 to a
piston rod 68a of a cylinder mechanism 68 disposed under the base 48.
The base 59 is reciprocatingly movable along the guide members 66, 66
in directions perpendicular to the direction of travel of the coated
material 4 by the piston rod 68a of the cylinder mechanism 68.
Indicated at 70 is a motor for rotating the shaft members 61, 62 to
rotate the drum 7. The speed of the drum 7 is dependent on the line
speed and on the s-troke of the supply adjusting assembly 9.
With reference to Figs. l, 2 and 9, the liner feeder 11
comprises a support 71 provided upright on the base 48, guide rollers
72, 73 rotatably supported by the support 71, shaft members 75, 75'
rotatably supporting a pair of liner rolls 74, 74', respectively,
etc. When ~running liner 10 of one of the rolls, 74, comes to run
. , short of during operation, the leading end of the liner 10' of the
other roll 74' is adhered to the liner 10 of the roll 74 by a liner
joining device 76 mounted on the support 71.
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As shown in Figs. 2, 9 and 10, the liner joining device 76
comprises two opposed pressing assemblies 77, 77' each in the form of
a cylinder mechanism, and adhering rollers 78, 78' attached to the
.piston rods 77a of the pressing assemblies 77, 77', respectively.
The opposed rollers 78, 78' are reciprocatingly movable between the
solid-line position and the phantom-line position as illustrated by
the operation of the pressing assemblies 77, 77'. In the phantom-
line position, the opposed rollers 78, 78' are in pressing contac-t
with each other to join the liners 10, 10' by adhesion. The pressing
assemblies 77, 77' are provided with holding assemblies 83, 83',
respectively, for holding the liner leading ends of the rolls 74, 74'
releasably. The holding assembly 83 comprises a cylinder mechanism
84 having a piston rod 84a reciprocatingly movable vertically, and a
bearing member 85 for the forward end of the piston rod 84a to bear
on. The holding assembly 85 holds the leading end of one liner of
the rolls, 74, between the forward end of the piston rod 84a and the
bearing member 85. Like the holding assembly 83, the holding
assembly 83' comprises a cylinder mechanism 84' and a bearing member
85'. Indicated at 86 in Fig. 10 are sensors for detecting the
diameter of the roll 74 of liner to be supplied.
When the roll diameter sensors 8fi detect the approach of the
rear end of the running liner 10 (on the left-hand side in Fig. 10)
being paid off from the roll 74 on the shaft member 75, the rollers
78, 78' move toward each other into contact with each other as
illustrated in phantom lines to adhere and join the leading end of
the liner 10' of the other roll 74' to the liner 10 being sent out.
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In this case, the liner 10' not yet sent out has its leading end
held by the holding assembly 83' as illustrated on the right-hand
side of Fig. 10, so that if the leading end is released upon
completion of advance of the adhering rollers 78, 78', the two liners
10, 10' pass as fitted together through the nip of the pair of
rollers 78, 78', whereby the two liners can be adhered to each other
effectively. Further when the liner 10 of the roll 74 on the shaft
member 75 has been sent out, the pressing assemblies 77, 77' are
operated to return the rollers 78, 78' to the standby position
indicated in solid lines, a new roll 74 of liner is set on the shaft
member 75, and the leading end of the liner thereof is held by the
holding assembly 83. The liner 10 can then be supplied continuously
without any interruption in the same manner as above.
The liner 10' of the roll 74' has an adhesive or adhesive tape
applied to a portion m close to its leading end and opposed to the
liner 10 of the roll 74 for the adhesion of the liners 10, 10' with
the adhesive or tape. Accordingly, when the rear end of the first
liner roll 74 is about to be paid off during the supply by the liner
feeder 11, the liner 10' of the adjacent roll 74' is joined to the
liner 10 during operation for continued operation.
More specifically, when the rear end of the liner lO approaches
during the supply, the sensors 86 detect the reduction of the roll
diameter, whereupon the pair of rollers 78, 78' move into contact
with each other, whereby the liner lO' held by the holding assembly
83' is automatically adhered and joined to the line 10 during the
operation.
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The liner is a strip of paper, cloth, plastics film, thin metal
sheet or the like, and has a width of about 100 mm for use in the
present embodiment. Indicated at 81 in Fig. 9 is a powder brake, and
at 82 a rotary joint.
A description will be given of the process for coating the cord
1 with the raw rubber material 2 by the coating apparatus having the
above construction.
First, the rubber material 2 is heated by a temperature
controller 79 (see Fig. 2) and filled into the body 35 of the
extruder 5. The cord 1 is inserted through the crosshead 22 of the
extruder 5, the rubber material 2 in the head 22 is heated to a
suitable temperature, the cord 1 is further wound around the upper
and lower rolls 36, 37 of the pull roll assembly 6 and passed through
the supply adjusting assembly 9 and the traverse assembly 54 and the
leading end of the cord is wound on the drum 7 of the take-up
assembly 8 in preparation for a winding-up operation.
Next, the cord 1 is set to predetermined tension for paying off
using a setting unit 91 of the line control system 90 shown in Fig.
11.
The interior of the head 22 is then set to a predetermined
rubber pressure using a head pressure setting unit 96 of the extruder
control system 95 shown in Fig. 12.
The pull roll assembly 6 and the take-up assembly 8 are then
driven to travel the cord 1, and the extruder 5 is subsequently
initiated into operation. Upon the internal rubber pressure of the
head 22 building up to about 90% of the set value, the control
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system 95 of Fig. 12 is turned on.
In the line control system shown in Fig. 11, the tension
determined by the setting unit 91 and the tension measured by the
tsnsion sensor 19 are compared to obtain a signal. The control
system 90 further checks the current line speed and gives a speed
command and torque command to the motor 15 connected to the bobbin 18
to control the tension on the cord to be sent out. In other words, a
regenerative braking force is applied to the cord by the d.c.
servomotor 15, that is, a torque opposite to the direction of
rotation is produced for braking to obtain optimum tension. In Fig.
11, the pull roll rotating motor 38 and the take-up drum rotating
motor 70 are controlled by detecting the position of the slide roll
51 of the supply adjusting assembly 9 and the line speed setting to
adjust the winding speed according to the variation in the line speed
and the variation in the wound-up roll. Indica-ted 92 is a position
sensor for the slide roll 51 of the adjusting assembly 9.
The extruder control system 95 shown in Fig. 12 controls the
extruder 5 independently of the line control. The internal rubber
pressure of the crosshead 22 needs to be altered since the optimum
value of the pressure varies with the characteristics of the cord 1,
i.e., the material (such as nylon, aramid fiber, steel or thc like),
size, shape and structure of the cord 1. The control system 95
therefore has a head pressure setting unit 96. The speed of rotation
of the screw must be different for starting the extruder and the
manual operation thereof, so that the control system 95 has a screw
speed setting unit 97. For manual operation, the screw of the
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extruder 5 only rotates according to the speed setting. For the
pressure control, the system gives a rotation command on compairing
the signal from a pressure sensor 98 with the setting signal so that
the extruder 5 can be maintained at a constant pressure at all times.
The line speed is controlled by the line control system 90, and
the extruder 5 by the control system 95 to prepare the rubber-coated
material 4.
When the coated material 4 is wound up on the take-up drum 7,
the liner 10 is supplied to the drum 7 by the liner feeder 11 to
interpose the liner 10 between opposed upper and lower portions of
the coated material 4. The liner 10 is about 100 mm in width as
already mentioned, while the coated material 4 is less than 1 mm to
several tens of millimeters in width. Accordingly, the coated
material 4 is traversed by the traversing assembly 54 within the
range of width of the liner 10. If wound up on the drum 7 without
traversing, the coated material 4 would be wound up on the drum
locally concentrically, rendering the resulting roll liable to
collapse.
Although one cord is used for the above embodiment, several
cords are of course usable as desired. While preferred coated
materials 4 are in the range of one to 30 in the number of cords 1
and about 0.8 mm to about 30 mm in width, tho~e comprising a larger
number of cords and having a larger width can of course be prepared.
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