Note: Descriptions are shown in the official language in which they were submitted.
555~
United State Patent 2,4~4~771 of March 15, 1949, to Van Guelpen
discloses an angularly tiltable extrusion head over which a web under tension
is passed for coating the under face, but no backer roll is used opposite the
orifice and a doctor, or smoothing, blade is in rear of the orifice along the
web path to actually produce the smooth coating. Such a device is not likely
to produce a commercially acceptable, thin~ low cost coating from viscous,
tacky, hot melt substances which range from 5,000 to 500,000 cps.
One solution to the problem of commerciaIly successfuIly handling
such hot melt coatings at high line speeds and with desired uniformity is found
in ~nited State Patent 3,556,832 of January 19, 1971 to Park. Apparatus is
disclosed in this patent wherein a web to be coated is passed over a station-
ary, somewhat rounded coating head having an elongate slito Paper moves over
the elongate slit bearing against the rounded coating head. Hot melt material
is extruded through the elongate slit onto the paper. An important part of
this process is the transverse stretching of the web as it approaches the coat-
ing head and the guiding of the web under tension into sliding contact with
the coating head itselfO me coating process described by Park generally in-
cludes the steps of simultaneously controlling the rate of flow of the coating
material to exert a pressure that is somewhat greater than an opposing force
on the tension web, a force normally achieved with a press roll.
In general, the process disclosed by Park has been a successful and
desir~ble commercial processO
Indeed the process has been found to be so broadly applicable that
there has been a need for improved apparatus that will permit full exploitation
of the process capabilitiesO
Therefore, it is an object of the invention to provide an improved
e~trusion head apparatus which can be used to achieve improved coating precision
of hot melt materials and is readily cleaned and adjusted to meet various pro-
cessing conditionsO
It is a further object of the invention to provide apparatus which has
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an improved self-cleaning characteristic during operation.
Another object of the invention is to provide a more efficient
coating apparatus, one characterized by a more dependable maintenance of web
tension.
Other objects of the invention will be obvious to those skilled in
the art on reading the instant application.
The above objects have been substantiaIly achieved by constructing
a coating apparatus comprising a coating head, or extrusion die, wherein the
web-support members forming an elongate slit comprise elongate lead-on members
and lead-off members at least one of which is adjustably mounted for overall
positioned adjustment with respect to the other member and also for adjustment
of slit width along the length of the slit by means of adjusting either com,
pression or tension on individual adjusting means spaced along the member
m is adjusting feature, permitting as it does finer control over the
slit wldth, also allows central feed to a plenum chamber from which the elon-
gate slit feeds hot melt extrudate. In the more advantageous embodiments of
the invention, the extrusion die formed of the lead-on and lead-off members
and plenum are mounted for skewing with respect to a fixed press roll which is
mounted to oppose extrusion pressure by backing the web proximate the slit.
~o In this application and accompanying drawings there is shown and
described a preferred embodiment of the invention and suggested various
alternatives and modifications thereof, but it is to be understood that these
are not intended to be exhaustive and that other changes and modifications can
be made within the scope of the invention. These suggestions are selected and
included for purposes of illustration in order that other~ skilled in the art
will more fully understand the invention and the principles thereof and will
be able to modify it in a variety of forms, each as may be best suited in the
condition of a particular case.
IN THE DR~WINGS
~, . .
Figure 1 is a partiaIly diagrammatic section in elevation and showing
i()4;~5S5~
the relationship of the apparatus of the invention to a web being coated there-
with.
Figure 2 is a section of the extrusion apparatus as defined by
section line 2:2 on Figure 40
Figure 3 is a section of the apparatus as defined by section line
3:3 on Figure 4.
Figure 4 is a sectional view of the coating apparatus of the inven-
tion taken through a planewhich is normal to the direction of the web being
coated.
Referring to Figure 1, it is seen that coating apparatus 10 comprises
a coating head 12 which is mounted for angular movement by an hydraulic ram 14
by means of a bracket 16 mounted for skewed movement on shaft 18 within arcuate
slot 20.
A paper web 22 is passed left-to-right across coating head 12 and
receives a layer 24 of a hot melt barrier coating 26.
A fixed press roll 28 is mounted on the opposite side of web 22
and forms means to support said web against pressure exerted by coating mater-
ial being forced under pressure onto the web from coating head 12. Idler rolls
30 form means to keep web 22 in snug contact with coating head 12.
Figures 3 and 4 show details of coating head 12~ The coating head
is formed of a primary housing which encloses a plenum, or a manifold chamber
32. Coating material is forced into this chamber trhough a conduit 34 and
thence through an elongate slit 36 onto the web to be coated. Slit 36 is
formed of two elongate members, each of which comprises a web-contacting sur-
face, one of which we shall refer to as lead-on surface 38, the other as lead-
off surface 40. Lead-on surface 38 forms the web supporting surface of static
lead-on member 42. Lead-off surface 40 forms the web-supporting surface of
the static lead-off member 440
Lead-on member 42 is fixed by bolt 46 to the housing of plenum
chamber 32. However, lead-off member 44 is not so attached~
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Lead-off member 44 is mounted for adjustment of its position with
respect to member 42 by means of a series of spaced threaded fa~teners 48
which form means to push or pull member 44 as is required to adjust the width
of slit 36. Member 44 is sufficiently distortable along its length that fast-
eners 48 can be utilized to, for example, m~ke the extreme ends of slit 36
wider than the center thereof, or make whatever other modification in slit
width is made desirable along the length thereof.
Fasteners 48 are held in a support plate 50 which in turn is fasten-
ed to plenum chamber housing 51 by fasteners 520 A clamp plate ~4 is utilized
to hold member 44 snugly against housing 51 with bolts 55.
Figure 2 shows end plates 56 which are fastened by bolts 58 to
housing 51 and thereby form the lateral walls of plenum chamber 32.
More detail of the apparatus is shown in Figure 4. Press roll 28
is equipped with ports 60 and a chamber 62 for accommodating heating or cool-
ing fluids as may be required for a given coating operation~
Unlike prior art coaters, the press, or backing, roll 28 is rotat-
able in fixed bearings 64 and 66 in frame 680 Thus the web path and web ten-
sion remain constant and are not affected by any displacement of the roll~
Because the roll cannot be elevated, flying splice operation is facilitated.
The backing roll 28 is not 9ubject to skewing, because skewing is accomplish-
ed with the adjustable movable coating head 120 For ~hreading of the web, the
coating head may be tilted and compensation may be made for non-parallelism by
skewing the coating head in a horizontal plane.
The center feed to the plenum 51 assures uniformity of distribution
of coating to both ends of the extrusion slot. It should be noted that there
are no gap adjusting screws which cross the extrusion slot to interfere with
flow, adjustment of slot opening being accomplished by screws exterior to the
slot and outside the coating path~
~hile the device of the above mentioned Van Guelpen patent relies
on a doctor, or smoothing, blade for achieving a thin smooth, uniform coating
1()43SS9
of tacky, viscous hot melt substance, the device of this invention achieves a
commercially acceptable coating by proper adjustment of the width of the slit,
or orifice, 36, together with angular adjustment of the coating head to the
web and to the fixed backing, or press roll 28
The extrusion orifice, slit or nozzle 36 of the apparatus of this
invention may also be used to extrude cold viscous material which includes a
predetermined percentage of solvents, such as dispersions, lacquers (nytro-
lacquers) and rubber cements with benzine solvents High viscosity materials
of m~ny types may be applied in thinner than conventional layers to thereby
save considerable drying time. Capital outlay for drying equipment, such as
heat tunnels, ovens and the like, and the floor space for coating apparatus
is thus greatly reduced.
It is also to be understood that the foIlowing claims are intended
to cover all the generic and specific features of the invention herein des_
cribed and aIl statements of the scope of the invention which might be said
to fall therebetween~
