Note: Descriptions are shown in the official language in which they were submitted.
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Title: "Foam Extrusion Apparatus and Method"
TECHNICAL FIELD
This invention relates to an improved foam extrusion method and
apparatus using adjustable traction shaping rolls for shaping and forming
elongated bodies of plastic foam during formation of such bodies upon
extrusion through a die orifice to obtain foam or cellular boards, slabs,
billets or the like of substantially uniform thickness requiring little
subsequent processing.
BACKGROUND OF THE INVENTION
In the production of rigid foam billets, boards, slabs, logs, or the
like, a foamable thermoplastic resin, such as styrene or the like, incor-
porating a blowing agent is extruded through a die orifice. As soon as the
extrudate leaves the die orifice, it is at a much lower pressure, preferably a
vacuum, and immediately begins to expand three dimensionally and move
away from the die orifice. If such expansion is not properly controlled and
the extrudate properly drawn from the die orifice, particularly as the
extrudate cools and begins to cure or to set, undesirable dimensional
variations may result, such as corrugations and density and/or cell
orientation variations. Also, it is desirable to finish the product as nearly aspossible at a uniform thickness with planar top and bottom surfaces as the
ao product is so formed. The finished product, then, need only be cut
transversely with perhaps lateral edge trimming, or tongue and grooving. It
is important that the product be of uniform density and uniform thickness
and have minimum cell distortion; and i~ also is important that the finished
surface be free of distortions, surface blemishes or cracks.
In U.S. Patent No. 4,234,529 there is disclosed a method and
apparatus for shaping plastic foams extruded through an arcuate extrusion
die with the extrudate being conducted past several sets of curved rolls.
- Each set of curved rolls includes two of the same respectively located on
opposite sides of the extrudate pass line. The center of curvature of each
curved roll is approximately at the center of curvature of the arcuate
extrusion die orifice. At least one curved roll of each set thereof is
independently driven to rotate the same, and at least one curved roll of each
set thereof is movable to adjust the spacing between the same and the other
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curved roll of such set. The extrusion die, curved rolls,
and a surface finisher, if employed, are located in a
controlled environment, such as a vacuum.
While angularly related high pressure pinch rolls are
employed for stretching of non-foaming extrudates such as in
biaxially orienting film, as seen in Japanese publication
No. 1159~/71, an expanding board or billet of some thickness
presents problems of a different sort, particularly where the
foaming and shaping occurs in a vacuu~.
The several features and advantages of the method and
apparatus disclosed in U.S. Patent No. 4,234,529 also are
relevant to the instant invention.
It is desirable to provide additional forming and
shaping capability for an extruding apparatus, such as that
disclosed in such patent, especially to facilitate maintaining
high quality in the production of relatively wide boards or
billets of extruded plastic foams.
SUMl~iARY OF THE INVENTION
The invention, then, relates to an apparatus for and
method of providing such additional capability by means of
adjustable edge forming or shaping rolls and in the
combination of such rolls or use thereof in an extruding
apparatus and method of the type disclosed in U.S. Patent No.
4,234,529. The edge rolls preferably are located downstream
of the extrusion die and the curved rolls. Although the
curved rolls preferably extend fully across both major surfaces
of the extrudate, the edge rolls are arranged in pairs with at
_ least one pair near one edge portion of the extrudate, and a
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second pair near the other edge of the extrudate. Preferably
the edge roll pairs are located only near respective edges of
the extrudate.
An auxiliary edge roll pair includes two linear rolls
respectively on opposite sides of the extrudate pass line.
The angle of attack of such rolls, e.g. the angular relation
of the rolls or their linear axes to the principal direction
of movement of the extrudate between the rolls, may be remotely
adjusted. Remote adjustment capability facilitates adjustment
without interfering with the controlled environment in which
the extruding, foaming and shaping occur. The auxiliary rolls
may be adjusted to change the spacing
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between the rolls, for example by moving one roll while maintaining the
other roll in a plane that is substantially common with that of the curved
rolls and a surface finisher on the same side of the extrudate pass line to
accommodate extrudates of different thicknesses and to adjust the forces
S applied by such rolls to the extrudate. The spacing between pairs of rolls at
opposite edges of the extrudate also can be adjusted to alter the extent of
the edge portions of the extrudate over which the rolls extend or the width
of the extrudate that can be accommodated by such rolls. Such adjustability
allows an operator to vary the controlling forces applied by such rolls to
form the extrudate to a desired width.
To assure accuracy of the aforesaid remote adjustment and to
maintain a high quality of the finished product, it is desirable to hold sub-
stantially constant the relative orientation of the two rolls of each pair.
Accordingly, the two rolls are mounted for pivoting about a common pivot
axis, and a remotely operable actuator may be employed accurately to
control such pivoting.
According to the method of the invention, a method of controlling
and shaping a foaming extrudate exiting from a die orifice includes the steps
of directing the extrudate through and in engagement with sets of rolls that
extend at least substantially across the surfaces of the extrudate on opposite
sides thereof, further directing only the opposite edge portions of the
extrudate through and in engagement with respective pairs of further rolls
downstream of the sets of rolls, and respectively adjusting such pairs of
further rolls.
With the foregoing in mind, it is a principal object of the present
invention to provide an improvement in foam extrusion.
Another object is to facilitate production of relatively wide
boards, billets, or the like of plastic foam, especially while maintaining high
quality of production.
An additional object is to provide adjustable edge forming rolls for
use in a foam extrusion apparatus and method.
A further object is to adjust the shaping compression force applied
to the edge portions of a board, billet or like extrudate.
Still another object is to adjust the pulling force applied,
especially by driven edge rolls, to edge portions of a board, or like foam
extrudate.
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Still an additional object is to adjust the angle of attack of edge-
located rolls used in extruding, shaping and forming a foam extrudate.
Still a further object is to effect remote adjustment of the angle
of attack of such rolls relative to a foarn extrusion passing therebetween,
especially without interfering with the controlled environment in which
extruding, forming, and/or shaping are carried out.
Even another object is to combine an adjustable edge roll
assembly and use thereof in an expanding foam extrusion apparatus and
method, especially to form a relatively wide extrudate emanating initially
10 from an appreciably narrower extrusion die.
These and other objects and advantages of the present invention
will become more apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends, the
invention, then, comprises the features hereinafter fully described and
15 particularly pointed out in the claims, the following description and the
annexed drawings setting forth in detail certain illustrative embodiments of
the invention, these being indicative, however, of but a few of the various
ways in which the principles of the invention may be employed.
BRIEF DESCRIPTION OF DRAWINGS
In said annexed drawings:
Fig. 1 is a plan view of a foam extrusion apparatus using edge rolls
in accordance with the present invention;
Fig. 2 is a side elevation view of one edge roll assembly and a
remotely operable angle of attack adjusting mechanism therefor;
Fig. 3 is an enlarged section view of the actuating arm for the
remotely operable angle of attack adjusting mechanism looking generally in
the direction of the arrows 3-3 of Fig. l;
Fig- 4 is an enlarged side elevation view of an adjustable edge roll
assembly looking generally in the direction of the arrows 4-4 of Fig. 1,
Fig. 5 is a top plan view of the upper mounting bracket assembly
for mounting an upper edge roll of an adjustable edge roll assembly; and
Fig. 6 is a plan view of the lower mounting bracket assembly for
the lower edge roll of an adjustable roll assembly.
DETAILED DESCRIPTION
Referring now in detail to the drawings, and initially to Fig. 1, a
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foam extrusion apparatus in accordance with the present invention is
generally indicated at 10. The apparatus 10 includes an extrusion die 11,
preferably having an arcuate orifice 12, several sets or pairs of curved
shaping rolls schematically illustrated at 13 with the rolls of each pair being
5 located, respectively, on opposite sides of the extrudate pass line, and a
conveyor and/or surface finisher 14, all of which preferably are generally of
the type disclosed in U.S. Patent No. 4,234,529. The components 11-14
preferably are located within a controlled environment 15, such as a vacuum,
confined within partially illustrated chamber walls 16 and end wall or
10 bulkhead 17. A liquid barrier or other means may be provided at the
downstream end of the controlled environment 15 to maintain isolation
between the vacuum therein and the external atmosphere, for example, as it
is disclosed in U.S. Patent No. 4,199,310.
A rigid frame support 20 supports the conveyor 14 and may provide
15 support for the sets of curved rollers 13 and/or the extrusion die 11. Other
means of support also may be provided, for example, as is disclosed in the
'529 patent, to obtain the desired interaction of parts in forming, shaping, or
directing the extrudate 21 from the extrusion die 11 to an exit, not shown,
from the controlled environment 15 preferably as a substantially finished
20 product of expanded foam board or like type material.
The foam extrusion apparatus 10 also includes, as is seen in Fig. 1,
an edge roll apparatus 22. The edge roll apparatus 22 has two adjustable roll
assemblies 23 positioned, respectively, at opposite edge portions 24 of the
extrudate 21 to extend across only such respective edge portions9 this being
25 in contrast to the sets of curved rolls 13 which extend fully across the
extrudate 21. Support plates 25 support the roll assemblies 23 from the rigid
frame support 20 opposite respective edges of the extrudate 21, substantially
. opposed to each other, and approximately equidistant from the center of the
i extrudate and from the extrusion die 11 at a location between the sets of
30 curved rollers 13 and the conveyor 14. Slots 26 permit lateral adjustment of
the roll assemblies 23 relative to each other. Fasteners 27 may be tightened
to secure the roll assemblies 23 to the rigid frame support 20. By adjusting
the relative lateral spacing between the roll assemblies 23, the magnitude of
the distance such roll assemblies extend across the extrudate 21 can be
35 adjusted thereby to effect corresponding adjustment of the engaged width of
the extrudate edge portion 21.
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Each roll assembly 23 also can be pivoted angularly about a pivot
shaft 30. To effect such pivoting, an actuating arm 31 may be moved
substantially longitudinally from a location 32 outside of the controlled
environment 15, as will be described in further detail below. Such remotely
5 controlled pivoting by the mechanical linkage of the actuating arm 31
permits accurate control of the pivot swing of the roll assembly 23 about the
pivot axis 30 with facility and without disturbing the controlled environment
15.
Turning now to Fig. 2, a roll assembly 23 includes a pair of
cylindrical rolls 40, 41. The rolls 40, 41 preferably are straight cylinders
provided with the elastomeric sleeve illustrated. Each has parallel
vertically aligned longitudinal axes, and such rolls are mounted for rotation
about respective shafts 42, 43, which are supported, in turn, by respective
split mounffng brackets 44, 45 secured to a main support tube/shaft 46. The
15 top of the lower roll 40 preferably is approximately in a common plane with
the top of the conveyor 14 and with the top of the bottom curved rolls (not
shown) in the sets of curved rolls 13. Although that common plane is shown
in Fig. 2 as a horizontal one to facilitate the illustration, it should be
appreciated that in the preferred embodiment such common plane would be
20 sloped downwardly from the extrusion die, for example, as is disclosed in
U.S. Patent No. 4,234,529. The upper roll 41 is movable vertically relative
to the lower roll 40 to vary the spacing therebetween on opposite sides of
the extrudate pass line. Moreover, both rolls 40, 41 are commonly pivotable
about the axis 30 of the main support tube/shaft 46. Such pivotal movement
25 is effected by pushing or pulling on the~ actuating arm 31 of the remotely
- operable angle of attack adjusting mechanism 47, which ~lso includes a rigid
linkage 50 (Fig. 1) for coupling the arm 31 to the lower mounting bracket 44.
The rigid linkage 50 includes an elbow rod 51 connected by a jam nut 52 to
the lower mounting bracket 44, as is seen in Fig. 6, and a clevis type
30 connector 53 for coupling the rod 51 to the actuating arm 31. The rigid
elbow rod 51 in its angled configuration and length is designed to provide the
necessary movement arm for swinging the roll assembly and to exLend
directly normal to the extrudate path providing a substantially right angle
connection with arm 31 at the mi~point of the range of adjustment of the
35 angle of attack.
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Referring now to Fig. 3, the actuating arm 31 provides a sub-
stantially rigid mechanical linkage between the adjustment end 54 thereo~
and the rigid linkage 50 capable of accommodating different angles of
attack and heights of the rolls. The actuating arm 31 includes an adjustable,
partly hollow shaft 55, adjustable rod 56, a first clevis connector 57,
adjustable rod 58, and a second clevis connector 59 of which the clevis 53 is
part. The adjustable shaft 55 passes through an opening 60 in the bulkhead
17. A vacuum seal 61 is held in position about the shaft 55 by a bracket 62
secured by fastener 63 to the bulkhead 17. The bracket 62 has a hollow
longitudinal extension 64 through which the shaft 55 passes. A pair of split
shaft collars 65, 66 and Oilite thrust washers 67, 68 secure the shaft 55 in
fixed longitudinal relation relative to the bulkhead 17. Needle bearings 69
maintain the longitudinal axis thereof relatively fixed while permitting
rotation of the shaft 55. Such rotation may be effected manually or
automatically by the application of a torque to the squared adjusting end 54.
The adjustable shaft 55 has an internally tapped bore 70 opening
toward the controlled environment 15, and the threaded rod 56 is threadedly
secured in the passage 70. The rod 56 also is attached at a threaded
connection 71 to the clevis 72 of the first clevis connector 57 and is locked
in connection therewith by a jam nut 73. The clevis connectors 57, 59 also
have spherical rod ends 74, 75 attached to the respective clevises 72, 53 by
pins 76 in turn held in place by cotter pins 77. The threaded ends of the
adjustable rod 58 are attached to the respective spherical rod ends 74, 75 at
the illustrated threaded internal psssages 78, 79 and are locked in position
by jam nuts 80.
It will be appreciated that the effective length of the actuating
arm 31 may be adjusted, for example during set-up of the foam extrusion
apparatus 10, by adjusting the connections between the adjustable rod 58 and
the clevis connectors 57, 59. By turning the shaft 55 in one direction or the
other, for example using a torque applied to the adjusting end 54, the
adjustable rod 56 is moved longitudinally relative to the shaft 55. Such
longitudinal movement is coupled via the clevis connectors 57, 59 and rod 58
to the rod 51 to pivot the rolls 40, 41 about the main vertical support shaft
46.
Referring now to Figs. 4-6, the lower roll 40 is rotatably mounted
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on the shaft 42. A split collar 90 and thrust washer 91 at the outer end of
the roll hold the roll on the shaft. At the inner end of the roll 40 a thrust
washer 92 and sprocket assembly 93 is provided with the latter journaled on
shaft 42 and secured to roll 40. The thrust washer is interposed between the
5 assembly 93 and a split mounting bracket 94, which in turn supports air
motor 95 from an angle bracket 96. The motor 95 drives the roll 40 through
chain 97 between the sprocket assembly 93 and sprocket 98 on the motor
drive shaft 99. Controlled air pressure from a conventional supply, not
shown, drives the air motor 95 thereby to rotate the roll 40 at a controlled
10 speed.
The shaft 42 is secured in horizontally slotted recess 100 in the
lower mounting bracket assembly 44 by clamp fasteners 101 (~ig. 6).
Moreover, the lower mounting bracket assembly 44 is vertically split at 102
to permit clamping thereof by fastener 103 securely to the support tube 104
of the tube/shaft support 46. The support tube 104 is vertically movably and
swingably mounted in a main support sleeve 105, which in turn is attached at
a bottom flange to the support plate 25 (Fig. 1).
Ball bushings 106 mounted in the support tube 104 against lands 107
secure the main support shaft 108 of the tube/shaft 46 to maintain its axis 30
2G also in common with those of the support tube 104 and main support sleeve
105. The ball bushings 106 further facilitate vertical or axial movement of
the main support shaft 108.
Rotatably mounted about the outside of the main support sleeve
105 and in engagement with the land 110 thereof is a lower rod support 111
held in place by a split collar 112. Threaded through a tapped opening 113 in
the support 111 is the lower threaded end of guide shaft 114. The guide shaft
114 has a reduced cross section upper end 115 which passes through an opening
117 through the lower mounting bracket assembly 44, being positionally held
therein by Oilite bushings 118 and a split shaft collar 119.
The upper end 115 of the guide shaft 21 also passes vertically
through a ball bushing 120 in an opening 121 through rearward extension plate
122 secured on the upper mounting bracket assembly 45. The guide shaft 114
helps to maintain the upper roll 41 in true parallel relation with the lower
roll 40 as the former is raised and lowered. The guide shaft 114 also may be
turned by force applied at its lower squared end 123 when the clamp fastener
103 of the lower mounting bracket assembly 44 is loosened to adjust the
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vertical height of the lower roll 40, for example, to bring the same below,
into or above the plane of the conveyor 14 and/or of the lower rolls of the
curved set of rolls 13. After such vertical height adjustment of the lower
roll 40 is made, the fastener 103 is tightened again to secure the lower
mounting bracket assembly 44 to support tube 104.
In the illustrated embodiment of the invention the upper roll 41 is
not driven, although, if desired, it may be by the motor shown or by its own.
The roll 41 is rotatably mounted on the upper shaft 43 by a pair of split shaft
collars 130 and thrust washers 131. The shaft 43 in turn is seeured by
fasteners 132 to the top of the upper mounting bracket assembly 45.
Appropriate bearings or other means may be provided to facilitate rolling of
the respective rolls 40, 41 about the respective shafts 42~ 43.
The upper mounting bracket assembly 45 is also vertically split at
its rear end and is secured to the upper end of the main support shaft 108 by
tightening a clamp fastener 140. The shafts 108 and 114 cooperate to
maintain parallel alignment of the upper roll 41 relative to the lower roll 40,
such that the straight longitudinal axes of such rolls remain parallel and in a
common vertical plane as the upper roll 41 is displaced vertically relative to
the lower roll.
An air cylinder assembly 141 effects such vertical movement of
the upper roll 41. The air cylinder 141 is attached by a rod end cap 142 to the
underside of lower mounting bracket assembly 44. The piston rod 143 of
cylinder assembly is connected to a rod extension 144, which has a nanged
upper end 145 captured in a rod retainer plate 146. Such rod retainer plate is
attached to the underside of upper mounting bracket assembly 45 by
fasteners 147 (Fig. 5). The rod extension 144 passes through an opening
provided therefor in the lower mounting bracket assembly 44 and in the
lower roll shaft 42. The air cylinder 141 preferably is of the type disclosed inU.S. Patent No. 4,234,529; such air cylinder is coupled to a controlled source
of air pressure and venting (not shown) accurately to control both the
spacing between the rolls 40, 41 and the pressure exerted thereby on the
extrudate passing therebetween. As in such patent, pressure is applied
3 beneath the piston to cause the upper roll to float compensating for its tare
weight, and finely controlled pressure above the piston controls the pressure
of the roll against the foaming extrudate, and, of course, the pressure of the
extrudate against the lower driven roll.
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OPERATION
In operation of the foam extrusion apparatus 10, for set-up
purposes the spacing between the roll assemblies 23 is adjusted by adjusting
the relative positions of the support plates 25, and the length of respective
5 actuator arms 31 and the initial orientation for the angle of attack of the
rolls 40, 41 relative to the extrudate 21. Other fine adjustments may be
obtained by the clevis connectors 57, 59 and rod 58. Such angle of attack
also may be adjusted by turning the adjusting end 54 of the shaft 55. An
initial vertical separation of the respective pairs of rolls 40, 41 also may be
10 adjusted by appropriately controlling the air supply to and venting from the
air cylinder 141, and similar adjustments can be made at the sets of curved
rollers 13 and conveyor 14, for example, as is described in U.S. Patent No.
4,234,529. Also, the speed of rotation of the air motor 95 and, thus, the
lower roll 40 is initially set.
Using the foam extrusion apparatus 10 in the extruding process,
the extrudate is conducted through the sets of curved rolls 13 being shaped
thereby to an extent tending to obtain a relatively wide finished extrudate
although the width of the issuing extrusion die orifice 12 is relatively narrow.The roll apparatus 22 has a further drawing and control shaping effect on the
20 extrudate downstream of the curved rolls 13 tending further to control the
extrudate to the desired width. Accurate control of the height of the upper
rolls 41 by the air cylinder 141 will affect the force applied by the rolls to the
extrudate and thus any traction or draw; such force ordinarily would be
selected to exert on the extrudate 21 a force of desired controlled magnitude
25 to obtain the desired width with a minimum of distortion or destruction of
the individual cells of the foam extrudate. Further, by enlarging the angle
of attack of the roll assemblies 23, for example by rotating respective shafts
55 and, thus, lengthening or shortening the arms 31 even while the extruding
process is proceeding in a vacuum, the vector of applied force can be
30 increased or, conversely, by decreasing such angle, can be decreased.
STATEMENT OF INDUSTRIAL APPLICATION
In view of the foregoing, it will be appreciated that the method
and apparatus of the present invention is useful in the extruding of a
foamable material from a relatively narrow extrusion die orifice to form a
35 relatively wide extrudate.
