Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
Fleld of the Invention
This lnvention relates to an unwlnder unit for
a roll of sheet moldlng compound whlch recovers the vinyl
film coverlng on the sheet molding compound.
DESCRIPTION OF THE PRIOR A~T
Many plastic parts, partlcularly automobile
body parts and panels, are made from flberglass rein-
forced plastlc. The starting plastic flberglass mix ls,
ln most instances, sheet molding compound. Sheet molding
compound is a mixture of uncured plastic in a styrene
solvent containing short lengths of glass fibers. It
is formed in flat sheets covered on both sides to prevent
evaporation of the styrene solvent. The sheet molding
compound, after it is formed and covered with v~nyl sheet,
Acompacted by running lt through compactlon rollers simi-
lar to the rollers used in the unwlnder unit. It is
then rolled onto large rolls untll ready for use.
In use, the large roll of sheet moldlng compound
is placed on a reel posltioned next to a cutting table.
Here an operator pulls the sheet of sheet molding com-
pound from the reel, pulls the vlnyl film from the sur-
face of ~he sheet and cuts the sheet into proper size
pieces for the mold operator to use.
The operator at the cuttin~ table usually pulls
large sections of sheet molding compound from the roll
at one time and strips back large sections of vinyl film.
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Thls results in large areas of sheet molding compound
belng exposed to the atmosphere resultlng in loss of
tons of styrene solvent per year. The solvent loss
also results in areas of the sheet molding compound
being deficient in styrene. Upon cure these areas are
porous, discolored and sometimes sink. It is virtually
impossible for the cutting operator to neatly fold or
roll the vinyl film for recovery. Also, due to the size
and the weight of the rolls of sheet molding compound,
it i9 a physical strain for all but the very strongest
of individuals to pull the sheet molding compound from
the reel. In additlon, the strongest of indlviduals
are often not the neatest and the sheet molding compound
must be cut to the proper size for use in the m~ld.
~n attempt was made to insert a right angle
grlnder mechanism into the spindle of the roll to turn
it. This was not accepted by the workers because it
made things worse.
In molding, stacks of sheet molding compound
are placed ln preselected areas of the mold. The quan-
tity used and the placement of the stacks is important.
The mold then closes causlng the sheet molding compound
to flow and flll the mold ca~ity. The mold is heated
which causes the sheet molding compoun~ to cure. After
several minutes the mold is opened and the cured part
formed is removed.
The use of nipper rolls for the dispensing of
vinyl film is disclosed in U.S. Patent 3,949,918 of
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Golner et al (1976). This patent, however, is directed to the dispensing,
not the recovery of vinyl film.
SUMMARY OF THE I~VENTION
The invention provides in a method of removing from a roll, a supply
of uncured sheet molding compound (SMC) covered on both sides with vinyl film,
by pulling the sheet molding from the roll, removing the film from both sides
of the sheet molding compound and cutting the sheet molding compound into
pieces suitable for insertion into a mold cavity, the improvement which com-
prises:
a) wrapping each film around each of a pair of power driven rollers
to attach each film to each roller by frictional contact;
b) forcing the pair of power driven rollers together;
c) pulling the SMC, consisting essentially of a solution of uncured
resin containing chopped glass fibers, by driving at least one of the rollers
and generating tension in the film due to the film being attached to the
rollers by frictional contact, and winding the film from one side of the
sheet molding compound upon itself onto one of the rollers and winding the
film from the other side of the sheet molding compound upon itself onto the
other roller;
d) cutting the sheet molding compound which is uncovered, while
leaving the rest covered to prevent air pollution;
e) repeating steps c) and d) one or more times; then reusing the
recovered film.
The invention also provides in an apparatus for supplying cut sheet
molding compound to a rnold having a dispensing reel or container for holding
sheet molding compound, the sheet molding compound being covered on both
sides with vinyl film, and a table for cutting the sheet molding compound
into pieces suitable for insertion into a mold the improvement which com-
prises:
a sheet molding compound unwinder positioned between the reel and
the cutting table, the unwinder having a horizontal base and two vertical
support members spaced apart on the base;
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two nipper rolls with shafts journalled and mounted between the
two side walls;
a motor driving at least one of the nipper rolls, and a control
unit for starting and stopping the motor.
By mechanically removing the vinyl cover from the sheet molding
compound right at the cutt~ng table, the invention greatly reduces styrene
loss, eliminates back strain of the operator and results in uniform parts
without porosity sinks and dark areas due to styrene loss.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side view showing the unwinder unit of the present
invention positioned between the cutting area of the cutting table and the
dispensing roll.
Figure 2 is a front view of the unwinder unit.
Figure 3 is a side view of the unwinder unit.
DESCRIPTI0~ OF THE PREFERRED EMBODIMENTS
In referring to the drawings in detail, Figure 1 in particular,
the sheet molding compound roll holder comprises a frame 10 having two roll
side supported members 12 and 14 and an axle 16. A roll of sheet molding
compound 18 is rotatably mounted on roll support members 12 and 14. The
roll of sheet molding compound 18 is supported on the axle 16. The sheet
molding compound is fed from the roll 18 and the end of the strip of sheet
molding compound is fed between two nipper rolls 24 and 26.
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Nlpper rolls 24 and 26 are separated for the insertion
of the sheet moldin~ compound between them by means of
two separated air cylinders 28 and 30. The air cylinders
are commercial items commercially available from McKay
Company, Grand Rapids, Michigan. The air cylinders have
a 4" stroke. The sheet molding compound is manually
pulled between the nipper rolls 24 and 26. In addition,
the vinyl film covering 40 on the lower surface of the
sheet 22 is removed and rolled up upon nipper roll 26.
The operator must assist in starting the vinyl film 40
to begln being wound on nipper roll 26. The operator
also starts vinyl film 38 by wrapping it around nlpper
roll 24 for the first revolution o~ wind-up. After the
initlal start-up, the wind-up of the vinyl film is auto-
matic.
~ oot operated air pressure valve 34 controlæair ~ressure motor 36 which drives nipper roll 26 which
pulls sheet molding compound from roll 18. For a long
table, two controls are used - one start control at
the exit of the unwinder and one stop control at the far
end of the table.
When the operator desires additional material
for his cutt~ng table, he merely pushes the foot pedal
operated air valve 34 whlch causes air motor 36 to draw
2~ sheet 22 from roll 18. When sufficient sheet molding
compound is delivered to his cutting table, he merely
releases foot presæure on valve 34 which stops motor 36.
Motor 36 was originally the motor from a hand-operated
grinding tool 5 an aero right angle or nut runner.
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Motor 36 could be any type of motor such as an electrical
motor, a steam driven motor, or a small internal combus-
tlon engine. An air motor is preferred.
As shown in the drawing, air motor 36 only drives
nipper roll 26. It could also drive nipper roll 24 or
both rolls directly. It was found in practice, however,
that it was not necessary for motor 36 to drive both
rolls and that driving one was sufficlent. The second
roll is driven by the forces of the sheet molding com-
pound being pulled through by the other driven roll.
The rolls are 77mm (3 inch) pipe which is plugged at both
ends with stub axles inserted into the plugger.
The air cylinders 28 and 30 could also be re-
placed by liquid operated cylinders, electrical selonoids
or even operated manually like old time ringers on
washing machlned.
The arrangement used to control the force exerted
urging the rolls toward each other ls shown in Figure 3.
The maximum ~orce urging the rollers together ls pre-
ferably from 14 to 70 kilopascals (2 to 10 psl). By
using this small amount of force should an operator get
his hands caught in the rollers, he will not be ln~ured
and will be able to remove his hands. Air cylinder 28
via shart 42 controls the downward force on bushin~
support 44. Bushing support 44 is slldably mounted on
frame 46 by sl~des 48 and 50. The bushing mount 52 for
nipper roller 26 is fixed ln place on frame 46.
Other embodlments of the present lnvention could
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also be employed. For example, the air valve 34 could be
operated by a tlmer so that preselected quantities of
sheet molding compound could be delivered to the cutting
table at preselected periods of time, see U.S. Patent
3,949~91~ of Golner et al for suitable timing de~ice
for nipper roll control.
It is contemplated that future development will
involve festooning about 5,000 pounds of the sheet molding
compound into a box. The unwinder unit will then be
employed to remove the sheet molding compound from the
box, remove the film and place the sheet molding compound
onto the cutting table.
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