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Патент USA US3041679

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July 3, 1962
w. ,1. MARSHALL ETAL
3,041,659
VACUUM FORMING APPARATUS
Filed Oct. 19, 1959
INVENTORS
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$3
BY.
REID
15
Z‘
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a.
MARS
HORVA
14.
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//,
THE l R
ATTORNEY
Unite States ‘Patent O?ice
1
3,041,669
VACUUM FORMING APPARATUS
‘Wilfred J. Marshall and Julius B. Horvay, Louisville, Ky.,
assignors to General Electric Company, a corporation
of New York
Filed Oct. 19, 1959, Ser. No. 847,367
2 Claims. (Cl. 18-19)
The present invention relates to vacuum forming appa
ratus and is particularly concerned with an improved ap
paratus for both vacuum forming a ?anged article from
3,341,669
Fatented July 3, 1962
2
drawing and the features of novelty which characterize
the invention will ‘be pointed out with particularity in the
claims annexed to and forming part of this speci?cation.
vIn carrying out the present invention, there is provided
apparatus for vacuum forming a ?anged article from a
heated sheet of plastic material comprising a vacuum mold
including a cavity or principal shaping portion and a face
or ?ange portion surrounding the cavity. The mold
?ange portion terminates in a peripheral cutting edge over
which the warmed plastic sheet is anchored or clamped
at the ‘beginning of the molding operation. A trimming
a sheet of plastic material and molding and trimming the
and ?ange forming member is provided for cooperative
edge portion of the article to ?nished shape and size.
action to both trim the ?ange to the desired width and
In the usual method of vacuum forming hollow articles
also form the ?ange to the desired uniform thickness dur
such as refrigerator door panels and the like from plastic 15 ing the vacuum forming operation. For this purpose, the
sheet material, a heated sheet of the plastic material is
forming and trimming member comprises a shearing ele
brought into sealing contact with the edge or face portions
ment adapted to cooperate with the cutting edge provided
of a vacuum mold after which the space between the sheet
on the mold for trimming the ?ange to the desired width
and the mold is evacuated to cause the central portion of
and an adjacent face portion for contacting and com
the heated sheet to assume the shape of the mold cavity. 20 pressing the remaining portion of the ?ange to a,.uniform
The resultant product comprises a central portion having
thickness during the trimming operation. This face por
the shape of the mold and a peripheral edge portion cor
tion in cooperation with the mold face both compresses
responding to that part of the sheet which was in contact
the ?ange edge of the article to a uniform thickness and
with the edge or face portions of the mold. After the
also anchors this portion of the sheet which the shearing
formed sheet has cooled to the point whererit again be 25 element has separated from the clamping means to pre
comes rigid so that no distortion of the formed article
will take place upon removal from the mold, it is removed
from the mold. Thereafter the excess sheet material is
vent distortion of the formed article during the subse
quent cooling operation. In order to assure this anchor
ing operation, a groove is provided between the mold
trimmed from the edges of formed article by suitable cut
cavity and the cutting edge of the mold and extending
ting dies. A disadvantage of this two-step method is that 30 about the entire periphery of the cavity for receiving ex
since some portions of the heated sheet are stretched and
cess sheet material during the forming and trimming op
thinned during the vacuum forming operation to a greater
eration.
‘
extent than other portions, the peripheral edge or ?ange
For a better understanding of the invention, reference
portions of the ?nished article because they have been
is made to the following description and the accompany
stretched the least during the molding operation will nor 35 ing drawing in which:
‘mally be of a greater thickness than any of the remaining
FIG. 1 is a diagrammatic view of an apparatus em
portion of the article and in itself may have an irregular
ployed in the practice of the present invention illustrating
thickness due to greater stressing and elongation of the
one step in the forming process;
sheet along the sides of the cavity than at and adjacent
FIG. 2 is a view similar to FIG. 1 showing the formed
the corners of the cavity as it is drawn to the shape of 40 sheet material in position with reference to the vacuum
the mold cavity. In addition, conventional trimming
mold but prior to the molding thereof;
methods do not provide a completely satisfactory appear
FIG. 3 is a view similar to FIG. 2 showing the sheet in
ance for the exposed trimmed edges since many of the
its molded state;
”
plastic materials suitable for vacuum molding have very
FIG. 4 is an enlarged sectional view of a portion of
little cold ?ow with the result that the trimmed edges 45 the vacuum‘mold illustrating an initial stage of the trim
clearly exhibit cut or fracture marks rather than a smooth
ming and ?ange forming operation; and
hot molded appearance.
FIG. 5 is a view similar to FIG. 4 illustrating the ?nal
The present invention has as its principal object the
stage in the trimming and forming operation.
provision of a vacuum molding apparatus by means of
Referring now to FIG. 1 of the drawing, a sheet of
which the edges of ?anges of the formed article can be 50 thermoplastic material 1 suitably supported or enclosed
trimmed while the vacuum formed part is still in the mold
in a rectangular frame 2 is ?rst heated to a softening
and at an elevated temperature. '
temperature by an electric heating element 3 prior to
Another object of the invention is to provide a vacuum
the forming operation. The clamping frame 2 supports
molding apparatus including means for simultaneously
the sheet to limit sagging thereof the effect of the heat
trimming the vacuum formed part and molding the edges 55 ing element 3. After the sheet 1 has been heated to the
thereof to a substantially uniform thickness.
desired extent, it is placed as shown in FIG. 2 over a
A further object of the invention is to provide means
vacuum mold generally indicated by the numeral 4. For
for trimming and forming the edge portions of a vacuum
the purpose of illustrating the invention, the mold is dis
formed piece while still in the plastic stage which means
closed as comprising a dish-shaped cavity as va shaping
anchors the peripheral edges of the piece to prevent de
means, the cavity 5 comprising side walls 6 and a bottom
formation of the piece after separation thereof from the
wall 7. - A peripheral ?ange or face portion 8 surround
usual clamping means.
ing the vcavity 5 provides a surface against which the
sheet 1 is held in sealing engagement by the frame 2
during evacuation of the mold cavity 5 through the aper
Further objects and advantages of the present invention
will become apparent from the following description
thereof when taken in connection with the accompanying 65 tures 9 connecting the mold cavity with the evacuating
5
3,041,669
‘receiving excess plastic material during said compressing
operation, and thereby assist in anchoring said shaped
sheet to said mold ?ange portion after said sheet has been
sheared.
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,404,320
1,415,018
Roberts et a1. _________ __ Jan. 24, 1922
Coates _______________ __ May 9, 1922
6
2,234,839
2,886,828
2,891,280
2,911,677
2,953,814
2,967,328
Edwards ____________ __ Mar. 11,
Lattuca _____________ __ May 19,
Politis ______________ .._ June 23,
Weber ______________ __ Nov. 10,
Mumford ____________ __ Sept. 27,
Shelby ______________ .._ Jan. 10,
1941
1959
1959
1959
1960
1961
FOREIGN PATENTS
495,376
Belgium _____________ __ Oct. 27, 1950
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