Note: Descriptions are shown in the official language in which they were submitted.
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CUTTING METHOD AND APPARATUS
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Backgrollnd of the Invention
Field of the Invention
This invention relates to a method and apparatus
for cutting elongated material into shorter lengths having
predetermined dimensions. More particularly, this
invention relates to a method of cutting fiber, preferably
continuous filament, into shorter lengths for use as
reinforcement in plastic products. The preferred
elongated material of the present invention is continuous
filamentary material, preferably of polyester, nylon,
Cavalier, fiberglass, etc.; elongated material may equally
be applicable to strips, ribbons, tapes, film, wire or any
other flexible material.
The Prior Art
In the current practice of forming a sheet for
molding of plastic products such as hard hats, automotive
parts, etc., glass fibers are fed from a creel package to
a cutter mechanism which chops the fiberglass into staple
lengths for gravity feed into a resin paste passing
thereunder, usually on a conveyor belt. The cutter
mechanism includes cutting blades rotated against a
polyurethane covered roll and between which the fiberglass
is passed to be cut or broken into lengths corresponding
to the spacing of the cutting blades. The design has not
US proved satisfactory in cutting less brittle materials such
as polyester yarn. The present invention is intended to
allow elongated materials to be cut into staple lengths
for inclusion in a sheet of molding composition which
subsequently will be molded into a plastic product.
A portable device adapted to break fibers into
short lengths and to direct the same onto a surface being
coated is disclosed in U.S. Patent 3 011 257 to Bamberger.
Glass rovings are continuously drawn into the bite of
oppositely turning rollers, one of which has
circumferential spaced chopping bars thereon which
engage the other roller and breaks the fiber into short
sections when passed there between.
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Many other types of cutting devices and methods
for dividing elongated material into shorter lengths are
known. Specifically, reference should be had to U.S.
Patents 3 485 120 to Keith, 3 733 9~5 to Cook, 4 120 222
to Potter and 4 300 422 to Potter. ~11 of these cutters
are broadly used for cutting tow of very high denier into
staple length fibers. The cutter o-f the Keith patent
includes a rotatable reel having outwardly facing cutting
blades against which the -tow is wound; a fixed pressure
roller pressing upon the tow wound around the reel results
in cutting of the innermost layers of tow by the cutting
blade. As cutting progresses a wad of cut staple fibers
is forced inwardly between adjacent pairs of blades. The
other patents are directed to modifications of the Keith
apparatus for removal of the cut fibers.
U.S. Patents 3 9~12 401 and 3 945 280 to Reenact
teach a method and apparatus for cutting thread which
includes a rotating drum carrying a plurality of radially
extending cutting blades operating in conjunction with a
rotating support drum which carries and supports the
thread. Ejector elements carried by the cutting drum and
positioned in the spaces between the cutting blades are
urged radially outwardly by centrifugal force and
compress the thread against the surface of the support
drum. Compression of the thread is continuous, both
transversely and along its length.
U.S. Patent 3 118 336 to Hampshire teaches a
fiber cutter which includes a pair of rolls having
resilient covers, means rotatable mounting the rolls on
parallel axes and in pressure engagement with each other
to flatten the rubber covers of the rolls against each
other, means for passing a strand between the rolls to
hold the strand firmly between the flattened covers, and
at least one knife blade` carried by a roll and normally
surrounded by and circumferential supported by the
resilient cover. The blade is supported against radial
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deflection and becomes exposed between the flattened
covers to cut the firmly held strand. The strand is in a
state of continuous compression until cut.
U.S. Patent 4 406 196 to Reenact et at. teaches
yet another device for cutting thread wherein the device
has a first rotatable smooth faced drum and a second
rotatable blade bearing drum with a plurality of radially
extending circumferential spaced cutting blades on the
outer periphery thereof. Centrifugal force responsive
means comprising fins connected to a deformable ring are
positioned between the blades, and on rotation of the
drums act to press a thread onto the smooth faced drum,
i.e., to put the thread under continuous compression.
U.S. Patent 3 426 632 to Lucy et at. also
teaches a staple cutter which includes a pair of
rotatable, contiguous tow-clamping disks, having affixed
at their peripheries a series of flanged teeth in abutting
relationship adapted to grip and advance tow there between,
and a rotatable cutting member or flying-kniEe cutter
synchronized to pass through or cut tow and pass between
pairs of the abutting teeth.
Summary of the Invention
method and apparatus for cutting elongated
material into short lengths is provided. The method
comprises the steps of: compressing the elongated
material at discrete intervals transversely, slightly
tensioning the elongated material along its length between
intervals, pressing the slightly tensioned elongated
material between intervals against a cutting edge, and
cutting the elongated material with the cutting edge. It
is preferred that the cutting blades be mounted in a
spaced relationship and define a closed geometrical
figure, the cutting blades being rotated as a unit.
The present invention also provides an improved
apparatus for cutting elongated material into
predetermined lengths. The apparatus comprises a
rotatable cutting roll having a plurality of radially
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extending cutting blades, and a cooperating second roll.
The rolls rotate in opposite directions with the elongated
material passing there between. The improvement comprises
forming at least a coating of the second roll of an elastic
material and providing the cutting roll with a plurality
of projections radially extending therefrom
circumferential. At least one of the projections is
located on each side of a cutting blade and extends
further radially from the normal periphery of the cutting
lo roll than the blades. The coating of the second roll is
engaged by the projections in succession to compress the
elongated material there between.
The present invention also provides apparatus
for cutting elongated material into short lengths which
comprises: means for compressing the elongated material
at discrete intervals, means for tensioning the elongated
material between the intervals, and means for pressing the
slightly tensioned elongated material between intervals
against a cutting edge to ultimately cut the elongated
material therewith.
Brief Description of the Drawings
Figure l is a plan view of the cutter lo of the
present invention, without a cover or guide system,
Figure 2 is a front view of cutter 10 with guide
system 18.
Figure 3 is an end view of cutter 10.
Figures 4 and 5 are each detailed sectional
views of cooperating cutting roll 20 and pressure (backup)
roll 25,
Description of the Preferred Embodiment
In the accompanying drawings like numbers
indicate like apparatus. With reference to Figures 1-3,
the cutter 10, preferably for use in a sheet molding
compound (SAC) or spray up system, comprises cutting roll
20 and pressure roll 25, mounted in parallel with respect
to their longitudinal axes in a frame if for rotation in
opposite directions (see arrows in Figures 3 and 4).
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Frame 11 is designed to leave the area beneath the cutting
zone defined between rolls 20 and 25 open for the
horizontal passage of a conveyor belt. Cut staple lengths
fall (by gravity) into a sheet of resin paste on the
conveyor belt (unsown).
Any conventional drive system for rolls 20 and
25 is suitable. In the preferred system, a motor
(unsown) drives the shaft of cutting roll 20 via timing
belt 12 with associated timing pulleys. Spur gear 13,
which is keyed to the shaft of cutting roll 20, rotates
with the shaft to drive spur gear 14, which is keyed to
the shaft of pressure roll 25. This causes rotation of
pressure roll 25. Obviously, the shaft of pressure roll
25 could be driven by timing belt 12 to in turn drive spur
gear 13 for rotation of cutting roll 20.
Cutting roll 20 has a plurality of radial slots
21 therein which extend longitudinally and receive cutting
blades 24. Blades 24 are held in place by a retching cap
15 which is screwed into the ends of cutting roll 20. The
edges of blades 24 adjacent retaining cap 15 have a notch
therein (unsown) which aligns with a groove (also
unsown) in the end of cutting roll 20 for receipt of an
annular protrusion (unsown) from retaining cap 15. As
best seen in Figure 4, blades 24 radially extend from
cutting roll 20 and protrude from slots 21 slightly. The
cutting edge of blades 24 is honed to be razor sharp.
Cutting roll 20 also has a plurality of radially
extending projections, depicted as teeth 23 in Figure 4.
teeth 23 extend radially from the normal periphery of roll
20 beyond the cutting edge of blades 240 There must be at
least one tooth 23 on each side of a blade 24. Selected
slots 21, however, may be left empty to alter the length
of fiber cut. Teeth 23 are depicted as an integral part
of cutting roll 20, and this is preferred. Teeth 23 and
I the portion of cutting roll 20 between blades 24 are made
of a hard material, preferably metal, most preferably
steel. Cutting roll 20 may be hollow or solid, preferably
the latter, and preferably made of steel having a hardness
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of at least 20 on the Rockwell C Scale (ASTM E-18-61).
Pressure roll 25 is elastic in the sense that
its yarn contacting surface or coating (see Figure 4) is
temporarily deformable by teeth 23 to a depth of at least
the distance teeth 23 project from the surface of cutting
roll 20. This portion of pressure roll 25 preferably has
a range of 80 to 95 dormitory on A scale of hardness,
ASTM D-785. Polyurethane is the material of choice for
the roll itself or a coating for the roll due to its wear
characteristics. Cutting roll 20 and pressure roll 25 are
forced into mesh with jack blocks and screws 16 (see
Figure l); by into mesh is meant the relationship shown in
Figure 4.
Suitable covers and shields for cutter 10 may be
provided along with guides for fiber access. Fiber
strippers 17 (see Figures 1 and 2) are placed, one to the
side of cutting roll 20 and one to the side of pressure
roll 25, along the longitudinal axes thereof and 180 more
or less from the cutting zone. Each fiber stripper 17
constitutes an air duct having a plurality of apertures
facing the particular roll 20 or 25 adjacent thereto. Air
is supplied to strippers 17 to blow off any fiber which
tends to follow the rotating rolls 20 and 25 subsequent to
cutting.
A guide system 18 is provided which comprises a
plurality of spaced apart partitions, mounted directly
above the cutting zone, for separating yarn ends being
fed to cutter 10. The ends of yarn are segregated in
system 18 to permit cutting of different types of fiber
with a single cutting roll 20. That portion of a cutting
blade which has been used for cutting fiberglass cannot be
used to cut polyester without sharpening or coating the
blade. This machine therefore permits cutting of
different types of fiber by the same cutting blades of the
cutter apparatus.
The following steps detail operation of cutter
10. The cutter cover is removed to permit string-up of
guide system 18 wherein a yarn end is fed between each
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pair of partitions. The air supply is then cut on to
fiber strippers 17. The motor is cut on, which ultimately
results in rotation of cutting roll 20 and pressure roll
25. These rolls turn at about 50 to 1400 main
preferably 290 m/min. Yarn end 19 is compressed between
tooth 23 and pressure roll 25 which then carry end 19 with
them as they rotate through the cutting zone With
reference to Figure 4, when the succeeding tooth 23
compresses yarn end 19 against pressure roll 25, the yarn
end is tensioned between those two teeth and over the
cutting edge of blade 24. As rolls 20 and 25 continue to
rotate and the next succeeding tooth 23 engages roll 25
with yarn end 19 there between, the yarn is cut by blade
24~ With reference to Figure 4, the yarn is cut when
blade 24 has rotated to the position of blade 24', which
is the point of greatest deformation of roll 25. As can
be seen, the tensioned yarn 19 is pressed between teeth 23
against the cutting edge of blade 24 to be cut thereby.
As rotation continues, pressure roll 25 resumes its shape
and the cut staple length falls into the resin paste
below. Thus, a first tooth 23 compresses yarn I as it
engages polyurethane pressure roll 25. As the rolls
rotate and the second tooth 23 compresses yarn 19 against
polyurethane pressure roll 25, yarn 19 is stretched, or
slightly tensioned between teeth 23 and across the cutting
edge of blade 24. As rotation continues, blade 24 cuts
yarn 19. The number of cutting blades 24 chosen is
dependent upon the length of cut fiber desired. With
reference to the shape of teeth 23, any shape that deforms
cutter roll 25 without tearing yarn 19 is suitable, i.e.,
sharp teeth should not be used. It is preferred that
teeth 23 be symmetrical as in Figure 4 to permit the
addition or deletion of blades there between for
versatility in staple length.
Blades 24 preferably are made of steel; however,
they may be made of tungsten carbide. In the preferred
embodiment there is a six-inch (15 cm) pitch circle on
gears 13 and 14, and thus on rolls 20 and 25. Teeth 23
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project about 0.042 inch (0.107 cm) radially outward from
the normal surface of roll 20. The cutting edge of blade
24 projects approximately 0.025 inch (0.064 cm) radially
outward from the normal surface of roll 20. The preferred
number of projections/teeth 23 and slots 21 is 76; with a
blade 24 in each slot 21, 0.25 inch (0.64 cm) staple is
cut. Blades 24 are centered between teeth 23. With 38
blades 24 in every other slot, 0.50 inch (1.23 cm) staple
is cut. The number of partitions in guide system 18 is
25, for feeding 24 yarn ends.
When cutting roll 20 has a diameter of about 2.1
inches (5.4 cm) for use with handheld chopper guns cutting
0.25 inch (0.64 cm) staple, notches 26 are required in
pressure roll 25 (see Figure 5) at spaced intervals which
correspond to engagement of blades 24. This ensures that
the second tooth 23 engages pressure roll 25 prior to yarn
end 19 being cut. It is believed that a cutting roll 20
for cutting 0.25 inch (0.64 cm) staple and having a
diameter smaller than about 4 inches (10 cm) would require
notches 26 as in Figure S. Notches 26 have a depth and
arc length of 0~010 and 0.075 inch (0.025 and 0.191
cm), respectively for the 2.1 inch (5.4 cm) cutting roll
system. Further, teeth 23 project about 0.047 inch (0.119
cm) radially outward from the normal surface ox roll 20.
The length from the center of blade 24 to the closest edge
of tooth 23 (trailing blade 24) is about 0.060 inch (0.151
cm), i.e., blade 24 is not centered between teeth 23, but
is much closer to the succeeding tooth 23.
