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Патент USA US3077013

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Feb. 12,- 1963
c. D. HOBSON
3,077,003
PLUNGER MOLD
Filed April 14. 1960
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INVENTOR.
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17/055076
BY:
United States Patent Oiiice
i
3,077,illl3
PLUNGER MOLD
Carroll l). Hobson, Goshen, lush, assignor to Goshen
Rubber (10., line, ?ashers, ind, a corporation of lndiana
Filed Apr. 14, was, Ser. No. 22,259
Claims. (Cl. lit-36)
This invention relates generally to rubber molding
apparatus and especially to apparatus for molding rubber
d?lld?d
Patented :Feb. 12, 1&53
i2
is shown; and while the shoulder-de?ning portion 16 may
take a number of advantageous shapes, it preferably takes
the shape of a laterally extending disc.
in the embodiment of the mold apparatus which is
shown, a four~piece die will be seen to include a base
plate 18 which is provided with an aperture 23. In
assembling the mold for use, insert 1% will be placed on
the base plate ltd, locating the tenon portion 14 in the
aperture 2%.
articles having rigid inserts.
The molding die or appartaus also includes a stripper
10
Many rubber parts are desirably molded with a rigid
plate 22, and this stripper plate 22 is fashioned with a
insert of metal, hard rubber or resinous plastic material;
bore 24 which is adapted to pass the body portion 32
and when such inserts are to be incorporated, provision
when the plate 22 is assembled over the base plate 18.
must be made for positioning them properly in the mold.
Stripper plate 22 also de?nes a counterbore 26 which is
Most commonly, the inserts are positioned by contact with 15 adapted to receive the shoulder— e?ning portion 16 for
the molding dies. This arrangement avoids the neces
purposes of holding the insert it) in place vertically and
sity of removable support pins. Removable support pins
retaining the insert when the molding operation is com
are, however, required when the insert is to be completely
pleted as will be described more fully hereinafter.
imbedded in the rubber. in other circumstances, per
The molding apparatus also includes an intermediate
manent magnets have been employed to hold steel in 20 plate 28 which is arranged to ?t over the stripper plate
serts in place.
22 and to define a mold cavity 3t} about the body por~
The general shape of a rubber part can also create a
problem, particularly when the part has a tapered or
parabolic shape.
Removal of such a part from a con
ventional two-piece mold has proved to be exceedingly
‘ tion 12 of insert ltl. Advantageously, the cavity 30 is
de?ned in an insertable member 32 which is carried in
an appropriately shaped recess 34 formed in the inter
mediate plate 23.
diflicult because of the partial vacuum formed between
in accordance with a feature of the invention, the
member 32 inciudes a projection 36 which is adapted
over, parts of this general nature are frequently intended
to enter the bore 24 in the annular space de?ned be
tween the sidewalls of bore 24 and the sidewalls of body
for special purposes which, of their nature, preclude the
existence of a ?ash line on the body of the part. The 30 portion 1?’. This arrangement of member 32 has e?ec
combined problems of, positioning a rigid insert, avoid
tively eliminated the occurrence of galling in operation
ing a ?ash line and extracting a tapering, ?nished part
of the molding die by not passing the metal of the die
from the mold have heretofore presented a substantial
over the metal of the insert in assembling or disassem
barrier to the commercial production of parts having such
bling the mold. Moreover, this arrangement of member
combined requirements.
has occasioned a shutting-off of the cavity Ed on
35
Accordingly, an important object of the present inven
the upper sur?ace or check 38 of the shoulder-de?ning
tion is to provide rubber molding apparatus which over
portion 16, thereby eliminating flash on the working sur
face of the ?nished part.
comes the limitations of the prior art by producing
rubber parts having a rigid insert and having a generally
Finally, the molding apparatus comprises a cover plate
4-0 including a plunger portion 42 which is adapted to
tapered body without the incurrence of ?ash on the work
ing surface of the part.
enter a relieved portion 44 in intermediate plate 23 in
A more general object of the invention is to provide
order to de?ne thereby a transfer well 46, best indicated
a new and improved rubber molding apparatus.
in Hit. 2. This well 46 receives a quantity of rubber
Another object of the invention is to provide appa—
compound which is to be molded about the body portion
ratus for molding a rubber part with a rigid insert, which
if} of insert Ill; and advantageously, the member 32 in
apparatus facilitates stripping of the individual part
cludes a sprue
communicating the well 46 with the
mold cavity 3%}.
from the mold.
Assembly of the molding apparatus proceeds as has
Still another object of the invention is to provide appa
ratus for moldin'7 a rubber part with a metal insert, which
been indicated hereinabove, i.e. the insert lit) being ?rst
positioned over the base plate 13 with the tenon portion
apparatus e?ectively avoids galling with the insert.
‘14 entering the aperture 2%. Subsequently, the stripper
Additional objects and features of the invention per
plate 22 is positioned over the base plate 13 so that the
tain to the particular structure and arrangements where
by the above objects are attained.
shouldendeiining portion 16 enters the counterbore 2d
and the body portion 12 passes through the bore 24%.
The invention, both to its structure and mode of oper—
ation, will be better understood by reference to the follow
Thereafter, the intermediate plate 23 is assembled over
the molded part and its surrounding mold cavity. More
ing disclosure and drawing forming a part thereof,
the stripper plate 2-2, the projection 36 entering the an
wherein:
nular recess between the sidewalls of bore 24 and the
‘
sidewalls of body portion 12.
PEG. 1 is a disassembled View in cross-section showing
rubber molding apparatus constructed in accordance
A suitable quantity of a desired rubber compound is
60 then placed in the relieved portion 44 and the cover plate
with the invention;
PEG. 2 is an enlarged, sectional view showing the ap
44;" placed over the intermediate plate 2.3, plunger 42 en
tering the relieved portion 44. A compressive force tend
paratus of
l in its assembled condition; and
FIG. 3 is a central, cross-sectional view of a rubber
ing to move the cover plate lit} in the general direction
part with a rigid insert made using the apparatus of
of the base plate 18 is applied to urge quantities of the
H6. 1.
65 rubber compound through the sprue 48 into the mold
Referring now in detail to the drawing, speci?cally to
cavity 3%; and while pressure is still being: held on the
FIG. 1, a rigid insert 193, preferably fashioned from a
mold, heat is additionally applied to vulcanize the rubber
metal such as ‘brass, will be seen to include a body por
tion 12, a tenon portion 14 and a shoulder-de?ning por
compound.
‘When vulcanization has been completed, cover plate
tion 16 disposed integrally between the portion 12 and 70
may be easily removed after the molding die has been
1d. The body portion 12 ordinarily displays a gen
withdrawn from the press. The ?ash pad which is cured
erally tapered shape, such as the parabolic shape which
in the well 46 can then be stripped to remove with it the
aoraoos
3
rubber cured in the sprue 48.
When the intermediate
a counterbore disposable adjacent said ?rst plate for re
plate 28 is pried away from the stripper plate 22, the
ceiving said shoulder-de?ning portion to restrain said
?nished part 50 which is indicated in FIG. 3, will be re
insert against movement relative to said ?rst plate; a third
tained by the stripper plate 22 because of the abutting
relationship between the shoulder-de?ning portion 16 and
plate disposable over said second plate, said third plate
the counterbore 26.
charging material into said cavity, said cavity having a
Subsequently, the part 50 may be
including means de?ning a mold cavity and means for
easily pounded from the stripper plate 22 after the base
base, a vertex and sides tapering from said base to said
plate 18 has been removed, no partial vacuum being
vertex, the walls of said cavity surrounding the sides and
formed between the part and any of the mold units.
the exposed end of the body portion of said insert spaced
With reference to FIG. 3, the ?nished part 50 will be 10 apart therefrom, the walls of said cavity abutting a check
seen to include the rigid insert 10, its body portion 12 be
of said shoulder-de?ning portion to establish a mold part
ing enveloped in a general tapering mass 52 of cured rub
ing plane coincident with said cheek whereby to prevent
ber. As will be recognized, the mass 52 may be sub
the occurrence of ?ash on the tapering surface of the rub
sequently ground or otherwise ?nished in a desired man
ber part molded about said insert.
ner. A part, such as the illustrated part 50, has been 15
3. Apparatus for molding a rubber part with a rigid
employed to advantage in, for example, gate valves. How
insert, which insert has a body portion, a tenon portion
ever, the invention is not intended to be limited to the
and a shoulder-de?ning portion therebetween, said ap
production of parts for any speci?c use.
paratus comprising: a base plate having a recess adapted
From the foregoing description, it will become ap
?ttingly to receive said tenon portion whereby to locate
parent that the present invention provides molding ap 20 said insert in position; a stripper plate disposable over said
paratus which e?iciently produces rubber parts having a
rigid insert, this production being achieved without the
base plate and having a bore therethrough for freely pass
ing said body portion, said bore being of greater diameter
incurrence of ?ash on the working surfaces of the part.
than said body portion to de?ne an annular recess there
Furthermore, galling of the insert is avoided and removal
about, said stripper plate further having a counterbore
25 disposable adjacent said base plate for receiving said
of the ?nished part from the mold is facilitated.
Accordingly, the speci?c example herein shown and
shoulder-de?ning portion to restrain said insert against
described should be considered as illustrative only. Var
movement relative to said base plate; an intermediate
plate disposable over said stripper plate; a cavity-de?ning
ious changes in structure will, no doubt, occur to those
skilled in the art; and these changes are to be understood
member in said intermediate plate adapted to enter the
as forming a part of this invention insofar as they fall 30 recess surrounding said body portion, said member in
within the spirit and scope of the appended claims.
cluding means de?ning a mold cavity having a base, a
The invention is claimed as follows:
vertex and sides tapering from said base to said vertex,
1. Apparatus for molding a rubber part with a rigid
the walls of said cavity surrounding the sides and the
exposed end of the body portion of said insert spaced
insert, said apparatus comprising: a ?rst plate; a second
plate disposable over said ?rst plate and having a hole 35 apart therefrom; a cover plate disposable over said inter
therethrough for freely passing a ?rst portion of said in
mediate plate, said cover plate cooperating with said
intermediate plate in de?ning .a rubber compound-receiv
sert, said second plate further having a recess aligned with
said hole and disposable adjacent said ?rst plate for re—
ing transfer well therebetween; and means de?ning a
ceiving a second portion of said insert to restrain said
sprue between said well and the vertex of said mold
insert against movement relative to said ?rst plate; and 40 cavity.
4. Apparatus in accordance with claim 3 wherein said
a third plate disposable over said second plate, said third
plate including means de?ning a mold cavity and means
insert is fashioned from a different metal than said plates
for charging material into said cavity, said cavity being
and said member and wherein the walls of said cavity are
of generally conoidal shape and having a base, a vertex 45 sutliciently spaced apart from the surfaces of said insert
to avoid contact therewith in assembling and disassembling
and sides tapering from said base to said vertex, the walls
of said cavity surrounding the sides and one end of said
said apparatus.
?rst portion of said insert spaced outwardly therefrom,
separation of said second plate and said third plate upon
References Cited in the ?le of this patent’
completion of a molding operation serving to extract the 50
UNITED STATES PATENTS
?nished part from the mold cavity.
1,621,000
Crowley _____________ __ Mar. 15,
2. Apparatus for molding a rubber part with a rigid
1,776,017
Brownson ____________ __ Sept. 16,
insert, which insert has a body portion, a tenon portion
2,279,208
Shaw _________________ __. Apr. 7,
and a shoulder-de?ning portion therebetween, said ap
2,456,615
Berglund ____________ _.._ Dec. 21,
paratus comprising: a ?rst plate having a recess adapted 55
1 2,465,276
Ryder _______________ .__ Mar. 22,
?ttingly to receive said tenon portion whereby to locate
2,717,793
Nenzell ______________ __ Sept. 13,
said insert in position; a second plate disposable over said
2,982,999
Stewart
_______________ __ May 9,
?rst plate and having a bore therethrough for freely pass
ing said,body portion, said second plate further having
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