Note: Descriptions are shown in the official language in which they were submitted.
2~ 7
METHOD_AND APPARATUS FOR VENTLESS TIRE MOLDING
FIELD_OF IllC INVENIION
This invention relates to a method and
apparatus for molding tires and more particularly
to a method and apparatus for the prevention of air
~ entrapment within a mold during tire molding. More
; specifically, this invention relates to methods and
apparatus for the molding of tires without the
necessity for employing mold vents.
BACKGROUND OF THE INVENTION
Tires, conventionally, are produced by
~ forming or ~laying up~ of uncured or so-called
; 15 green tire components on a tire building machine.
The resulting green tire is then removed from the
tire building machine and placed into a tire mold.
The tire mold generally is configured to apply heat
and pressure to the green tire forcing the green
~- 20 tire to conform to the configuration of a cavity
within the tire mold, and through curing, retain
that desired configuration. It is desirable that
the cured tire conform quite closely to the
confi~uration established by the tire mold, and
such conformance is in significant measure
dependent upon avoiding air entrapment between the
green tire and molding surfaces of the mold.
~ ~ :
Conventionally, the presence of air
between the green tire and molding surfaces of the
mold during molding operations is substantially
precluded by the provision of a substantial
plurality of small-bore passages or apertures
extending from molding surfaces of the mold through
the structure of the mold to points external to the
mold. Thus, as the green tire is moldingly forced
into close conformance with molding surfaces of the
.~
mold, air entrapped between the green tire and
molding surfaces of the mold tends to be forced
from the mold cavity via the apertures or
passages. These apertures or passages
conventionally are termed ~vents~.
While such vents typically provide for an
acceptable evacuation of air from the mold, green
or uncured rubber forming a portion of the green
tire being molded enters these vents subsequent to
entrapped air having been forced from the mold.
This green rubber cures within the vents, remaining
attached to the tire being molded after curing so
that when the mold is opened, and the cured tire is
removed, these vents provide a plethora of needle
like projections protruding generally
perpendicularly from the surface of the cured
tire. These projections are also termed ~ventsa
conventionally and provide the tire with an
external appearance generally regarded as
; 20 objectionable.
Such protrusions or projections protruding
from the cured tire generally are removed by
placing the tire on a machine whereby the finished,
cured tire can be spun, and cutting, either
~; 25 automatically or by hand labor, these projections
from the tire. Termed ~vent trimming~, this
projection cutting procedure typically adds to the
manufacturing cost of the finished cured tire and
results often in the generation of a significant
quantity of waste or blemished tires where the
trimming operation goes awry, producing a cut or
surface blemished tire. In addition, after vent
trimming, the tire surface remaining often is
considered to be possessed of a general, overall
unattractive appearance.
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It has been suggested that were air to be
removed from the mold cavity employing a vacuum
during the molding process, the necessity for at
least some mold vents may be obviated.
Accordingly, in one proposal exemplified by U. S.
Patent 1,276,411, a plurality of tire molds were
placed within a large press cavity, and the press
cavity was evacuated thereby evacuating the
plurality of molds. The press was then actuated to
compress the molds within the cavity in order to
form finished tires.
In another proposal exemplified by U. S.
Patent 2,779,386, vacuum was introduced to the mold
along a mold parting line and the tread portions
and ply portions of the green tire were punc'cured
so as to create air pathways from a zone adjacent
an interface between the tire interlayer and the
carcass of the tire to remove any entrapped air
from this zone.
In still another proposal exemplified by
;~ U. S. Patents 4j347,212; 3~842,150; and 3,854,852,
a plurality of valves were positioned embeddedly
within the mold along, particularly, sidewall
portions of the mold. The valves in this proposal
were configured to open as the mold closed, and to
evacuate air from within the mold as the green tire
~; was pressed against the molding surfaces of the
mold. The valves were configured, hopefully, to
close before being contaminated with rubber forced
into the valves during the molding processO Each
~-- valve was connected to a source of vacuum so as to
provide for evacuation of the mold. Others have
~ ~ employed poppet valves in tread but not sidewall
;~ ~ 35 portions of the mold.
In yet another proposal exemplified by
U.S. Patent 3,983,193, green tire portions being
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applied in a retreading operation have been
surrounded with an elastomeric bag having a vacuum
suction port whereby a vacuum cavity may be created
surrounding the tire being retreaded.
The foregoing proposals have generally
failed to meet with commercial success for a
variety of reasons. Where a plurality of molds are
contained within an evacuated press for molding,
time constraints associated with assembling and
disassembling molds containing green tires for
introduction into a hydraulic press has generally
proven excessively costly. For processes wherein
vacuum is drawn along a parting line to evacuate,
particularly interior interfaces of portions of the
green tire carcass, a failure to achieve a
significant, reliably effective vacuum has
contributed to commercial disinterest in such
processes. Where a plurality of poppet type valves
are employed positioned for example along a
sidewall portion of a tire mold, difficulties in
evacuating tread portions of the mold frequently
have resulted in the production of an unacceptably
elevated number of less than acceptable quality
tires. In processes wherein`a polymeric bag
surrounds a green tire portion being applied as a
retread, difficulties in assembling and
disassembling such a bagged green tire has
contributed substantially to commercial disinterest.
A process wherein a quality tire is
produced without the necessity for providing vent
holes or so-called vents in a tire mold reliably
and without significant extension to the processing
cycles of existing tire mold presses could find
substantial utility in the commercial manufacture
of tires by elimination of costly tire vent
trimming and by savings of rubber otherwise lost in
the vent trimming operations.
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The presen-t invention provides a method and apparatus
for subs-tantially evacuating a tire mold containing a green tire
to be cured and molded immediately prior -to -the onset of the
molding and curing operation. Particularly, in those processes
wherein a green tire tha-t includes -tread, sidewall and bead
por-tions is formed and then molded within a tire mold having
tread, sidewall and bead componen-ts, a-t least some components
separated by a parting line, the present invention provides for
evacuation of the mold prior to the curing and molding of a green
tire so that no ven-t holes or apertures are necessary between
molding surfaces of the tire mold and points external to the tire
mold.
The green tire is placed wi-thin the mold, and the
mold is partially closed so as to be open along the parting line
not more than about 5.08 and not less than about 0.10 centimeters.
The parting line is circumferentially sealed radially outwardly
so that movement of air into the mold along the parting line is
substan-tially precluded. Any other pathways by which air may
enter the mold are similarly sealed to substantially preclude the
movement of air into the mold.
A source of vacuum is then applies -to the conduit
means whereby the mold is evacuated to an absolute
pressure not exceeding abou-t 16932 Pa in a time period of not
more -than about 60 seconds. The mold is then fully closed
and the -tire is cured in accordance with usual and customary
procedures.
In a par-ticular embodiment a conduit means is pro-
vided along the parting lines in-terruptedly joined to the source
of vacuum. The parting line is, in particular,
circumferentially sealed radially outwardly of the conduit means
and the tread components.
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Typically the tire mold includes at least
one bead component moveable with respect to an
adjacent sidewall component and the process
therefore includes a step of sealing between the
moveable bead component and the adjacent sidewall
component so as to preclude substantially the
movement of air between the components into the
mold. Preferably the mold is evacuated to not more
than about 8466 Pa in a tlme period not exceeding
approximately 45 seconds. Most preferably, the
evacuation pressure does not exceed 2000 Pa. It is
much preferred that the mold be open between about
1.27 and 3.81 centimeters during vacuum
evacuation. Additionally, it is preferable that
the mold remain sealed against movements of air
from points external to the mold into the mold once
; fully closed for tire curing.
The seals employed in practicing the
process of the instant invention are preferably
those having one surface exposed to pressure within
the mold and an obverse surface exposed to pressure
sourced outside the mold, typically ambient
pressure, so that evacuation of the mold, by
inherent seal configuration, urges the seal into a
tighter sealing relationship.
The process of the instant invention can
be practiced in an improved tire mold having tread,
sidewall, and bead components typically radially
divided by a circumferential parting line with some
of the mold components being moveable to open and
close the mold along the parting line. The bead,
tread and sidewall components provide an inner mold
surface free of venting outlets by which a fluid
may pass from within the mold to without and visa
versa. At least one conduit means is positioned
along the parting line radially outwardly of the
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mold tread component and radially inwardly of a
parting line seal with the conduit means being
configured for interruptable inconnection with the
source of vacuum. The conduit means and vacuum
source are configured whereby the mold, upon being
sealed, may be evacuated to not more than about
16932 Pa within a time period of not more than
about 60 seconds.
A parting line seal, preferably self
actuating or inflatable-tube is circumferentially
arranged radially outwardly of the conduit means
and configured to sealingly engage at at least one
point in a range of parting lines openings of
between 0.10 and not more than 5.08 centimeters to
substantially preclude the movement of air into the
mold. The seal is configured to be capable of
continuing to preclude such air movement during and
even after mold closure. Such seaIs are comprised
of a surface exposed to pressure within the mold
~; 20 and an obverse surface exposed to a pressure
;~ sourced outside the mold, typically ambient
pressure.
In preferred embodiments of the improved
mold useful in the practice of the process of the
instant invention, at least one of the bead
components is moveable relative to an adjacent
sidewall component. The mold includes a bead seal
circumferentially sealing between the moveable bead
component and the adjacent sidewall component,
while the circumferential parting line seal is
sealingly engaged. The bead seal is affixed to one
of the components and is of a nature wherein one
seal surface is exposed to a pressure within the
mold and an obverse surface is exposed to a
pressure sourced outside the mold so that ~ere
- evacuation of the mold, by inherent seal
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configuration, urges the seal into a tighter
sealing relationship. The seal is configured to
continue to exclude movement of air into the mold
after ~old closure. The parting line
circumferential seal and the bead seal are either
so-called self actuating seals or inflatable-tube
` type configurations.
Preferably the vacuum source includes a
plurality of stages configured for being
consecutively interconnected with the conduit means
whereby the mold cavity may be evacuated in a
staged manner from an initial, modest vacuum to a
desired final vacuum.
The seals, as set forth, provide a means
for sealing a tire mold along the parting line and
along any bead-sidewall component interface in a
manner sufficient to support evacuation of the mold
to at least lÇ932 Pa, preferably to at least 8466
Pa, more preferably to not more than 6600 Pa, and
most preferably to at least 2000 Pa.
Employing the process and apparatus of the
instant invention, a tire is produced, which, when
.
removed from the mold, is characterized by having
no sidewall, bead, or tread vents protruding beyond
the periphery of the tire as established by the
outermost surface of the bead, sidewall, and tread
portions of the tire.
~ The above and other features and
; ~ advantages of the instant invention will become
~; 30 more apparent when considered in light of a
detailed description of the invention and drawings,
together forming a part of the specification.
~:~ DESCRIPTION OF THE DRAWINGS
Figure 1 is a partial side elevational
view of a tire mold and tire molding press
embodying the instant invention.
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Fiyure 2 is a partial side elevational
view of a tire mold and tire molding press
embodying the instant invention.
Figure 3 is a schematic representation of
a vacuum source for use in conjunction with the
practice of the method of the instant invention.
Figure 4 is a partial side elevational
view of a mold and molding press embodying an
alternate lower bead ring seal.
Figure 5 is a partial side eievational
view of a mold and molding press depicting an
alternate lower bead ring seal,
Figure 5 is~a depiction of a tire made in
accordance with the instant invention.
Figure 7 is a partial side elevational
view of a mold and molding press embodyina the
instant invention.
Figure 8 is a partial side elevational
cross sectional view o portions o~ a ti.e ~old and
tire molding press embodying the instant inYenticn.
BEST EMBODIMENTS!GF THF IMVENTION
The present invention provides a method
and apparatus for moldingly making a tiee, the
finished tire emèrging frcm the mold with~ut the
customary plurality of projections from the outer
surface of the tire formed by the curing of tire
rubber compound in vent holes provided in a
conventional tire mold. Referring to the draw~ngs
a mold 10 suitable for use in the p~actice of the
instant invention is depicted in FigurQs 1-2 and S.
~ .
Referring to Figure ~ the mold 10 is
employed in a tire press i2 which is shown only
partially in Figure 7. The mold 10 includes a
lower or male section 14, and an upper o, female
section 15. A parting line 16 separates thC ~ale
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and female sections 14, 15, with at least one of
the sections 14, 15, being moveable in a direction
perpendicular to the parting line away from the
remaining section. ~y separating the sections 14,
15, the mold is opened for introducing a green tire
to be moldedO
Each mold section 14, 15, includes tread
ring components 19, 20; sidewall components 23, 24;
and bead ring components 27, 28. The bead
components 27, 28 in some press-mold configurations
may be more properly associated with the press 12,
; but for purposes of simplicity in describing the
instant invention are considered together with the
tread 19, 20 and sidewall components 23, 24 of the
mold 10.
.
A green tire 30 is received in the mold;
the green tire is possessed of tread 31, sidewall
32, and bead 33 portions~ When the mold 10 is
closed along the parting line 1~l a molding surface
35 is defined by the tread 19, 20, sidewall 23, 24,
and bead 27, 28 components of the mold. The
molding surface 35 may be textured in known manner
to facilitate air movement during mold evacuation.
A mold cavity, indicated generally at reference
numeral 37 is thereby defined within the mold.
A bladder 39 is provided within the mold
cavity 37. A lower clamp ring 40 and an upper
clamp ring 41 function to retain the bladder within
the mold cavity. The upper clamp ring 41
cooperates with an upper mold ring 43 to retain an
upper ring 44 of the bladder while the lower clamp
ring 40 cooperates with a lower bead ring 45 to
retain a lower bladder ring 46. An upper bead ring
47 is retained in the mold 10. The lower clamp
ring 40 is retained to the press 12 employing a
threaded ring 48.
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In use, a pressurized fluid is introduced
into the bladder 39 which causes the bladder 39 to
expand against the green tire 30. The green tire
is thereby pressed against the forming or tire
molding surface 35 of the mold cavity; the tire
molding surface 35 or forming surface may include
protrusions 50 which can assist in forming desired
shapes in a final cured tire. While the mold 10 is
being heated, the green tire 30 is pressed against
10 the molding surface 35 and curingly conforms to the
configuration of the molding surface 35 and
protrusions 50 to produce a final tire having
rubber components thereof cured or vulcanized.
The mold 10 as described herein is typical
15 of many tire molds used in the forming of,
particularly, tubeless tires in industry. One
noticeable difference between the mold 10 of Figure
7 and conventionally employed molds is a complete
absence of a plurality of small bore passageways or
20 apertures extending from the molding surface 35
through the mold to points external to the mold and
press. Such small bore passageways, commonly known
as vents, provide for releasing air that would
otherwise become trapped between the molding
25 surface 35 and the green tire 3~ during the tire
molding operation. Where not properly eliminated
by venting, such entrapped air can prevent the
green tire 30 from conforming fully to the contours
of the molding surface 35 and thereby introduce
30 deformities in the resulting final tire
particularly in the cured rubber outer surface of
the cured tire. Entrapped air may also function as
an insulator, slowing the curing process and
contributing to an incompletely cured final tire.
In the instant invention the mold is
modified to include a conduit means 52
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interruptedly connectable to a source of vacuum
(not shown in Figure 7). The conduit means 52 or
vacuum conduit means communicates between a point
53 on the parting line 16 and the vacuum source.
The point 53 is positioned radially outwardly of
the tread portions 19, 20. Typically such a
conduit means 52 can be formed by cross boring the
mold 10; the cross bores may range in size from
about 0.635 centimeters to about 5008 centimeters
in diameter. At least one conduit means 52 is
provided along the parting line, but depending upon
the diameter of the tire mold 10, the volume of the
mold cavity 37, and the size of the conduit means
52, a plurality of conduits 52 may be desirable at
annularly spaced intervals around the tire mold 10
along the parting line 16.
A seal 54 is provided circumferentially on
the parting line radially outwardly of the point 53
~; of vacuum conduit means 52. The seal 54 is
received in a recess 55 in one of the mold sections
14, 15; a similar recess may be provided in the
opposite mold section for receiving the seal when
the mold is closed. The seal in the embodiment of
Figure 7 is an 0-ring type seal formed from any
suitable elastomer. Preferably, the seal 54 is
highly deformable and is configured whereby a
sealing relationship between the mold sections 14,
15 can be`established at one or more points while
the mold sections 14, 15 remain separated along the
parting line by between 0.10 centimeters and about
5.08 centimeters. The seal 54 must provide
continuous sealing from point of initial engagement
in a range of 0.10 to 5008 centimeters until the
mold has fully closed for curing the tire. The
seal 54 should seal in such a way that movement of
air along the parting line 16 from points exterior
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12~4C97
to the mold into the internal mold cavity 38 is
essentially precluded.
A bead seal 58 is provided between the
lower bead ring 45 and the male mold section 14. A
similar bead ring seal 58 is provided between the
upper bead ring 47 and the female mold section 15.
In the embodiment of Figure 7, these bead ring
seals 58 are typically an 0-ring formed from a
suitable elastomeric material. The bead ring seals
58 function to preclude substantially, the movement
of air between points exterior to the mold 10 and
the molding surface 35.
It is important in selecting the seals 54,
58 that the seals 54, 58 be configured to be
substantially resilient. Where the seals
permanently deform or otherwise become
insufficiently resilient to reliably seal between
the sections 14, 15 of the mold 10 and between the
sections 14, 15 of the mold 10 and the bead rings
45, 47, then the seals will require replacement,
since otherwise air will tend to move both along
the parting line 16 and between the mold sections
14, 15 and the bead rings 45, 47 from points
exterior to the mold 10 into the mold cavity 37.
Inadequate evacuation of air from the mold cavity
37 can result, substantially increasing the
likelihood for improper formation of the green tire
30 to produce a final tire having a properly shaped
and cured outer surface, free of lightness.
Alignment of the mold sections in the
embodiment of Figure 8 can be accomplished in any
suitable or conventional manner.
Referring to Figure 2, a similar mold 10
is employed in a tire press 12 which is shown only
partially in Figure 2. The mold 10 includes a
lower or male section 14, and an upper or female
$~7
-14-
section 15. A parting line 16 separates the male,
and female sections 14, 15, with at least one of
the sections 14~ 15, being moveable in a direction
perpendicular to the parting line away from the
remaining section. By separating the sections 14,
15, the mold is opened for introducing a green tire
to be molded.
Each mold section 14, 15, includes tread
ring components 19, 20; sidewall components 23, 24;
and bead ring components 27, 28. The bead
components 27, 28 in some press-mold configurations
may be more properly associated with the press 12,
but for purposes of simplicity in describing the
instant invention are considered together with the
tread 19, 20 and sidewall components 23, 24 of the
mold 10.
A green tire 30 is received in the mold;
the green tire is possessed of tread 31, sidewall
32, and bead 33 portions. When the mold 10 is
closed along the parting line 16, a molding sur~ace
35 is defined by the tread 1~, 20, sidewall 23, 24,
and bead 27, 28 components of the mold. The
molding surface 35 may be textured in known manner
to facilitate air movement during mold evacuation.
A mold cavity, indicated generally at reference
numeral 37 is thereby de~ined within the mold.
A bladder 39 is provided within the mold
cavity 37. A lower clamp ring 40 and an upper
clamp ring 41 function to retain the bladder within
the mold cavity. The upper clamp ring 41
cooperates with an upper mold ring 43 to retain an
upper ring 44 of the bladder while the lower clamp
ring 40 cooperates with a lower bead ring 45 to
retain a lower bladder ring 46. An upper bead ring
47 is retained in the mold 10. The lower clamp
ring 40 is retained to the press 12 employing a
threaded ring 48.
~.2~C~97
In use, a pressurized fluid is introduced
into the bladder 39 which causes the bladder 39 to
expand against the green tire 30 The green tire
is thereby pressed against the forming or tire
s molding surface 35 of the mold cavity; the tire
molding surface 35 or forming surface may include
protrusions 50 which can assist in forming desired
shapes in a final cured tire. While the mold 10 is
being heated, the green tire 30 is pressed against
the molding surface 35 and curingly conforms to the
configuration of the molding surface 35 and
protrusions 50 to produce a final tire having
rubber components thereof cured or vulcanized.
The mold 10 as described herein is typical
of many tire molds used in the forming of,
particularly, tubeless tires in industry. One
noticeable difference between the mold 10 of Figure
2 and conventionally employed molds is a complete
absence of a plurality of small bore passageways or
apertures extending from the molding surface 35
through the mold to points external to the mold and
press. Such small bore passageways, commonly known
as vents, provide for releasing air that would
otherwise become trapped between the molding
surface 35 and the green tire 30 during the tire
molding operations. Where not properly eliminated
by venting, such entrapped air can prevent the
green tire 30 from conforming fully to the contours
of the molding surface 35 and thereby introduce
deformities in the resulting final, cured, tire
particularly in the cured rubber outer surface of
th~ ~u~ed t~re. Entrapped air may also ~unction as
an insulator, slowing the curing process and
contributing to an incompletely cured final tire.
In the instant invention the mold is
modified to include a conduit means 52
~16-
interruptedly connectable to a source of vacuum
(not shown in Figure 2). The conduit means 52 or
vacuum conduit means communicates between a point
53 on the parting line 16 and the vacuum source~
The point 53 is positioned radially outwardly of
the tread portions 19, 20. Typically such a
conduit means 52 can be formed by cross boring the
mold 10; the cross bores may range in size from
about 0.635 centimetets to about 5.08 centimeters
in diameter. At least one conduit means 52 is
provided along the parting line, but depending upon
the diameter of the tire mold 10, the volume of the
mold cavity 37, and the size of the conduit means
52, a plurality of conduits 52 may be desirable at
annularly spaced intervals around the tire mold 10
: along the parting line 16.
An interface 90 exists between the upper
bead ring 47 and the mold section 15 and between
the lower bead ring 45 and the mold section 14.
The upper bead ring 47 is retained to the mold
section 15 employing fasteners 98. The interface
90 between the mold section 15 and the upper bead
ring 47 typically fills with rubber during a first
tire cure cycle; the rubber thus filling the
interface 90, once cured effectively seals the
interface 90 to movement of air from a point
external to the mold 10 into the mold cavity 37. A
small wedge 99 formed in either the section 15 or
the bead ring 47 along the interface 90 can
~ 30 substantially assist in sealing this interface 90.
: The embodiment of Figure 2 is a
representation of a mold 10 and portions of a press
- 12 known as a McNeil B.O.M. press, commercially
available. The mold 10 of Figure 2 includes a
recess notch 80 for receiving a shroud seal 81
having a bevel 83, the shroud seal being retained
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within the notch 80 employing a clamp ring 82
tightened to retain the seal 81. A chamfer or
radius 84 assists sliding motion of the seal 81. A
bead seal 92 is provided retained in a recess or
notch 96 provided in a lower bead ring 45. A bead
seal retainer 94, retained by fasteners 95,
functions to retain the bead seal 92 within the
notch 96. The bead seal 92 is resiliently
deformable from a resting position shown in phantom
at 97 to an actuated position achieved as the bead
ring 45 is seated compressing the seal 92 against
the mold section 14.
A dowel pin assembly 110 is provided
having a dowel bushing 112 and a dowel pin 114.
Fasteners 115, 116 function to retain the dowel pin
~ and dowel bushing 112 in the assembly. The dowel
; pin assemblies 110, a plurality of which are spaced
along the parting line 16 radially outwardly of the
tread sections 19, 20, function to align the mold
during closure to assure a uniform tire formation.
A vacuum conduit means 52 is provided
positioned radially inwardly of the shroud seal 81
and the shroud seal 81 and bead seal 92 are
configured to engage sealingly at one or more
points while the mold remains partially open at a
point at least between about 0.10 and 5.08
centimeters and to remain in sealing engagement
during subsequent full closure of the mold.
Typically the bead ring 45 is seated and the seal
92 engaged before mold 10 closure,
Preferably, the seals 81, 92 are highly
deformable and the seal 81 is configured whereby a
sealing r~lationship between the mold sections 14,
15 can be established at one or more points while
the mold sections 14, 15 remain separated along the
parting line by between 0.10 centimeters and about
12g4G97
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5.08 centimeters. The seals 81, 92 must provide
continuous sealing from point of initial seal 81
engagement in a range of 0.10 to 5.08 centimeters
until the mold has fully closed for curing the
tire, The seals 81, 92 should seal in such a way
that movement of air along the parting line 16 and
interface 90 from points exterior to the mold into
the internal mold cavity 38 is essentially
precluded.
It is important in selecting the seals 81,
92 that the seals 81, 92 be configured to be
~; substantially resilient. Where the seals deform or
otherwise become insufficiently resilient to
reliably seal between the sections 14, 15 of the
mold 10 and between the sections 14, 15 of the mold
10 and the bead ring, then air will tend to move
both along the parting line 16 and between the mold
sections 14, 15 and the bead rings ~rom points
exterior to the mold 10 into the mold cavity 37.
Inadequate evacuation of air from the mold cavity
37 can result, substantially increasing the
likelihood for improper formation of the green tire
30 to produce a final tire having a properly shaped
and cured particularly outer surface, free of
lightness.
~; Referring to the drawings, Figure 1 is a
representation of an alternate mold 10 and press 12
embodiment suitable for the practice of the method
of the instant invention. In Figure 1, items
functionally or structurally similar to items in
Fl~ur~ 2 and 8 have been aq~igned identical
re~eren~e numerals. The mold 10 and press 12 of
~gur~ 1 is ~ypical o~ mold lO and press 12
arrangements found on so-called Auto-Form Bagwell
presses available from NRM Manufacturing Company.
~- Such presses and general mold configurations are
; widely employed in the tire industry.
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In Figure 1, the mold 10 includes a male
section 14 and a female section 15 separated by a
parting line 16. The sections 14, 15 are moveable
away one from the other in a direction
perpendicular to the parting line 16. The mold 10
includes tread components 19, 20, sidewall
components 23, 24, and bead components 27, 28. As
in Figure 2, the bead components 27, 28 are defined
by bead rings 45, 47.
In Figure 1, a tire has been omitted for
clarity in showing the mold. Likewise, a bladder
has been omitted for depiction clarity. In the
mold embodiment of Figure 1, any bladder is
retained within the press employing a bladder well
61. A spider 63 and a plurality of sector plates
65 co~perating to retain the bead ring 45.
The tread components 19, 20, sidewall
components 23, 24, and bead components 27, 23
cooperate to define a molding surface 35,
optionally textured in well known manner,
surrounding a mold cavity 37. As in Figure 2,
expansion of a bladder against an inner surface of
~ a tire contained within the mold 10 when closed,
;~ functions to force the tire against the mold for
shaping while heat supplied to the bladder and
typically to the tire mold 10 functions to cure the
tire.
Alignment of the mold 10 sections 14, 15
; ~ for closure along the parting line desirably is
facilitated by the provision of a plurality of
dowel pin assemblies 69 positioned
~ circumferentially surrounding the mold cavity 37
;~ along the parting line 16. Each mold section 14,
15, includes a shoulder 70 formed in conjunction
with a bore 71. A dowel bushing 72 and a dowel pin
73 are received within the bores 71 and are
- ,:
.
~Z~4~
-2~-
retained against the shoulders 70 by through
fasteners 74. The fasteners 74 can be of any
suitable or conventional nature such as machine
screws abutting a shoulder 75.
~t least one vacuum conduit means 52 is
provided within the sector 15 communicating between
the parting line and a point exterior to the mold
for the transmission of air therebetween. A vacuum
system (not shown in Figure 1) is interconnectably
configured for drawing a vacuum through the vacuum
conduit means 52. Interconnection between the
vacuum conduit means 52 and the vacuum means can be
of any suitable or conventional form such as manual
or solenoid operated valving.
A parting line keyway 80 is provided in
one of the sections 14,15. A shroud seal 81 is
provided configured for being retainably received
within the keyway 80. A ring clamp 82 is provided
which, upon tightening, is configured to compress
the shroud seal 81 retainably into the keyway.
Desirably, the shroud seal includes a beveled
portion 83 which facilitates movement of the shroud
seal over a chamfer or radius 84 provided adjacent
the outer edge of the parting line 16 on the mold
section 14.
The shroud seal 81 can be made from any
suitable or conventional elastomeric material but
should be shaped to be capable of forming a seal
~; ~ between the sectors 15, 14 along the parting line
16 while the mold 10 is partially open along the
parting line 16 and also when the mold 10 is fully
closed along the parting line 16. It is desirable
that the seal 81 function to substantially preclude
the passage of air along the parting line 16 into
the mold cavity 37 beginning at a point where the
mold 10 is open in a ranye of between about 0.10
~'
-21-
and 5.08 centimeters as measured perpendicularly
between the mold sections 14, 15 along the parting
line 16. The shroud seal 81 is positioned radially
outwardly of the vacuum conduit means 52 so that
when a vacuum is applied to the vacuum conduit
means 52, the mold cavity 37 can be evacuated while
air external to the mold is substantially precluded
from entering the mold cavity 37 along the parting
line 16.
Suitable or conventional materials finding
acceptance in the manufacture of shroud seals 81 in
both Figures 1 and 2 include resin cured butyl
xubbers, silicone rubbers, phenolic cured butyl
rubbers, and fluorocarbon rubbers such as Viton
rubber and Kel ~ rubber, all readily commercially
available. Inclusion of lubricants such as oils
and/or graphite may prolong seal life.
An opportunity for air to move from points
, external to the mold cavity 13 into the mold cavity
37 also exists along interface lines 90 between the
bead ring 45 and the mold section 14, and between
:~ the bead ring 47 and the mold section 15. The bead
ring 4~ in the embodiment of Figure 1 is moveable
away from the mold section 14 whereas the bead ring
: 25 47 is stationary relative to the mold section 15.
The interface 90 between the mold section 15 and
the bead ring 47 may be sealed by rubber entering
along the interface line 90, filling a notch 99 and
curing therein during a first tire cure. The cured
rubber remains within the notch 99 throughout
subsequent cures performed within the mold 10.
The interface line between the mold
section 14 and the bead ring 45 can be sealed
~ employing a flexible bead seal 92 circumferentially
: 3s surrounding the bead ring 45 mold and retained to
.~ the bead ring 45 employing a bead ring seal clamp
~'~
~ t7
94. The bead ring seal clamp 94 can be retained to
the bead ring in any suitable or conventional
manner such as employing fasteners 95. The bead
ring seal 92 is resiliently biased, joining a
keyway 96 formed in the bead ring 45 and assuming a
position 97 shown in phantom when the bead ring 45
is out of contact with the mold section 14.
Upon seating of the bead ring, the bead
ring seal 92 is resiliently biased away from the
phantom position 97 to effect sealing. The bead
ring seal 92 can be made from the same materials as
are used in forming the shroud seal 81. The bead
ring seal 92 should function to preclude
essentially all movement of air from points
exterior to the mold 10 into the mold cavity 37
during the drawing of vacuum and the molding of a
tire. Where the bead ring 45 is not seated prior
to mold closure, the range of mold openings at
which the bead ring seal 92 should preclude the
movement of air into the mold desirably should be
co-extensive generally with the range of partial
-~ mold openings for which the shroud seal 81
substantially precludes the movement of air aIong
the parting line 16 into the mold cavity 37.
Preferably this range is 0.10 to 5.08 centimeters
along the parting line and most preferably between
about 1.27 and 3.81 centimeters. Regardless of
when seated, the bead ring seal 92 should function
when the mold is completely closed to substantially
preclude the movement of air into the mold cavity
37.
Referring to the drawings, Figure 4
depicts an alternate preferred bead ring seal 92.
The seal 92 is configured to be received within a
keyway 96 formed in the mold section 14 in lieu of
being received in a keyway or notch 96 formed in
the moveable bead ring 45 as shown in Figures 1 and
2.
~.2~ f~ ~7
-~3-
~eferring to Figures 1, 2 and 4, the bead
seal depicted in each of these figures includes one
seal surface 120 which is exposed via the interface
90 between the moving bead ring 45 and the mold
section 14 to whatever pressure exists within the
mold cavity 37. An obverse surface 122 is exposed
to a pressure sourced elsewhere, generally ambient
atmospheric pressure surrounding the mold 10. As
the pressure within the mold cavity 37 is
decreased, for example by the application of vacuum
to the mold cavity 37 via the parting line 16
employing the vacuum conduit means 52, a
differential between the pressure at surface 122
and the pressure at surface 120 increases, pressing
the seal 92 more firmly into sealing contact. Such
a seal is often termed ~self-actuating~, that is,
one capable of seating more tightly as a pressure
differential between the surfaces 120, 122
increases.
Likewise, the shroud seal 81 includes a
surface 124 exposed to pressure within the mold
cavity via the parting line 16 and an obverse
surface 126 exposed to a pressure sourced
elsewhere, typically ambient atmospheric pressure
surrounding the mold. As with the bead ring seal
92, evacuation of the mold cavity 37 via the
parting line 16 imposes a reduced pressure upon the
surface 124 of the shroud seal 81 and a
; differential between the pressures perceived by the
surfaces 124, 126 effectively forces the shroud
seal 81 more tightly into sealing contact with the
-~ mold section 14.
The seals 81, 92 should be sufficiently
;~ resilient to be capable of being forced by the
differential pressures perceived between the
surfaces 124, 126, 120, 122 during evacuation of
'
.
-24-
the mold to allow resilient movement for
establishing tight sealing. Conversely, the seal
should not be so resilient as to be capable of
being sucked into the parting line 16 or the
interface gn under the influence of a pressure
differential between the surface pairs 120, 122 and
124, 126.
Referring to the drawings, Figure 5
depicts an alternate seal configuration for use in
sealing between a lower bead ring 45 and a mold
section 14. A recess 96 is formed in the mold
section 14, but equally could be formed within the
lower bead ring 45, and a hollowly tubular seal 130
is received within the recess 96. The seal 130
includes an outer surface 132 exposed to pressure
within the mold cavity 37 and an inner or obverse
surface 134. The obverse surface 134 defines a
tube within the seal this tube is charged with a
~; fluid under a pressure, typically a liquid or air.
As the mold cavity 37 is evacuated, the
differential between pressure within the mold
; cavity perceived by the surface 132 via the
interface 90 decreases relative to the pressure
perceived by the surface 134 thus expanding the
seal into sealing contact. While not essential, it
is frequently desirable that the tube defined by
the obverse surface 134 be inflatable employing a
liquid or a gas under pressure in known manner.
; Alternately, thermal expansion of a fluid within
the tube, or the presence of a spring such as a
helical spring or a rubber ~O~ ring within the tube
can expand the seal.
Referring to the drawings, Figure 7
depicts a radially opening mold 10 together with a
mold press 12 upon which the instant invention may
- be practiced. The mold 10 includes mold sections
~",
-25-
or plates 14, 15. A parting line 16 separates the
mold plates 14, 15. The upper mold plate 14,
includes a tread ring component 19, a sidewall
component 24, and a bead ring component 28. The
bead ring component 28 is integral to the mold
portion 14. The mold portion 15 includes a
sidewall component 23 and a bead ring component 27
formed by a moveable bead ring 45.
The mold sections 14, 15 define a molding
surface 35. Upon mold closure a mold cavity 37 is
created within the mold 10~ A bladder 39 is
retained in suitable or conventional mannee within
the mold cavity 37 and functions to shape a tire 30
received in the mold outwardly against the molding
surface 35.
The press 12 includes a top platen support
150, a top platen 152, and a plurality of actuator
ring sections 155 one or more of which may
optionally include a steam chamber 156 by which an
; 20 actuator ring segment 155 may be heated. The top
platen support 150, top platen 152 and actuator
rings segments 155 are retained one to the next
employing a plurality of bolts 154. Interfaces
between the top platen support 150, top platen 152
~ 25 and actuator ring segments 155 should be sealed
- ~ ~ employing suitable or conventional gasketing ~O~
rings, or the like tnot shown).
The press 12 also includes a press base
160. The press base supports a bottom platen 162
that may include at least one steam chamber 164 by
which the bottom platen may be heated. The bottom ?
platen 162 supports the mold section 15.
The mold section 14 is supportably carried
by a mold adaptor ring 158 having an elongated
shaft portion 170 slidably received within a
bushing 171. The bushing 17 is supported by the
:
~Z~ 7
-26-
top platen support 150. A pair of O-rings 172, 174
function to seal between the top platen support 150
and the bushing 171 and between the bushing 171 and
the shaft portion 170. Air movement into the mold
cavity 37 from points external to the mold along
interfaces between the top platen support 150 and
the bushing 171 and between the bushing 171 and the
shaft portion 170 is thereby substantially
precluded.
A parting line seal 81 is received in a
keyway 80 formed in the mold section 150 The seal
81 is configured to circumferentially surround the
mold 10. A band clamp 82 functions to retain the
seal 81 within the keyway 80. The seal optionally
includes a beveled portion 83 for facilitating
sliding engagement with the tread component 19 of
the mold section 14. The seal 81 includes a
surface 126 exposed to pressure external to the
mold cavity 37 and a surface 124 exposed to
pressure internal to the mold cavity 37 whereby
evacuation of the mold cavity 37 results in an
; increased pressure differential between the
surfaces 124, 126 and urges the seal more tightly
into sealing engagement with the tread component 19
of the mold section 14.
A self-actuating seal 92 is provided
received retainably within a keyway 96 formed in
: the moveable bead ring 45. The seal includes a
surface 122 exposed to pressure external to the
: 30 mold cavity 37 and a surface 120 exposed a pressure
internal to the mold cavity 37. Evacuation of the
~: mold cavity 37 produces a pressure differential
between the surfaces 122, 120 resulting in the seal
: being urged more forcefully into sealing contact
; 35 with the mold section 15.
~ :
, . .
-27-
A vacuum conduit 52 is formed through the
mold section 15, the bottom platen 162, and the
press base 160. The vacuum conduit includes a
point 53 of interface or intersection with the
parting line 16.
Referring to the drawings, Figure 3 is a
schematic representation of a vacuum system 140
suitable for use in the practice of the instant
invention. The vacuum system 140 includes a vacuum
source 141 that can be of any suitable or
conventional nature such as conventional vacuum
pumps, ejectors, or jets. The vacuum system 140
includes a valve 142 by which the mold vacuum
conduit means 52 may be isolated from the vacuum
system 140, and a vent valve 143 via which the
vacuum conduit means 52 may be vented. A valve 144
interruptably joins the vacuum source 141 to the
vacuum system 140.
.
A plurality of accumulators 145, 146, 147
are joinable to the vacuum source 141 employing
valves 148, 149, 150.
By opening the valve 144 and the valve
150, and by operating the vacuum source 141 with
the valve 142 in a closed position, the accumulator
147 may be evacuated to a desired vacuum. In
similar manner, the accumulators 146, 145 may be
evacuated to a desired vacuum. After closing the
valves 148, 149, 150 and the valve 144, the valve
142 may be opened to initiate evacuation of a mold
cavity 37 employing the vacuum conduit means 52.
The valve 148 may then be opened to evacuate a
substantial portion of the air from the mold cavity
37. The valve 148 may then be closed and the valve
149 opened to evacuate still more air from the
cavity 37 of Figures 1-2 and 7. Such staged
evacuation enables rapid achievement of very high
~:
;'
.
.
~29~g7
-28-
vacuum levels in lieu of merely waiting for a
vacuum pump to ~catch up~. The valve 149 may then
be closed and the valve 150 opened so that
remaining air in the cavity 37 may be evacuated to
the accumulator 147. The valve 142 may then be
closed and the process of evacuating the
accumulators 145, 146, 147 reinitiated employing
the vacuum source 141.
A process configuration by which the
accumulators may be evacuated and then employed to
evacuate a mold cavity is set forth in Table I.
TABLE I.
EVACUATE
1a413ve # RoADY STEP 1 STEP 2 STEP 3 STEP 4 STEP 5
: 142 C 0 0 0 0 C
148 0 C 0 C C 0
149 0 C C 0 C 0
150 0 C C C 0 0
144 0 C C C C 0
TIME (Range)
(secs)1/2 10 2-15 2-15 2-15 15-300
TYP I CAL
(secs) 1/2 3 3 3 150
: 25 Evacuation should be accomplished in not
~: more than approximately 55-60 seconds and
~: preferably is accomplished in less than 45 seconds
` and most preferably within approximately 10-15
seconds. The accumulators 145, 146 147, and the
vacuum conduit means 52 by which vacuum may be
~: drawn on the mold cavity 37 should be configured to
permit evacuation of the mold cavity 37 to a
pressure not exceeding 16932 Pa and preferably not
exceeding 8466 Pa within at least one minute and
preferably in less than 45 seconds. More
preferably evacuation is accomplished to less than
:
:: -
:LZ9~97
-29-
8466 Pa, even more preferably less than 6600 Pa and
most preferably less than 2000 Pa, within not more
than approximately 15 seconds. These pressures are
necessary to eliminate sufficient air from the mold
cavity so that the final, cured, tire properly
conforms to the molding surfaces 35 and that an air
layer between the molding surfaces and the curing
tire within the mold does not insulatingly
interfere with the curing process.
It is important to note in Figures 1-2 and
7-8 that no provision is made for mold venting
through traditional vent passageways provided
through the tread and sidewall components of the
mold l9, 20, 23, 24 to release air trapped within
the mold as the mold is closed. Instead, the
instant invention employs use of a vacuum drawn
through the vacuum conduit means 52 rapidly and
deeply to evacuate quickly air from the mold cavity
37 in preparation for the actual tire molding
operation.
; The process for making a tire employing
vacuum evacuation of a molding cavity begins as do
most tire making processes with the building of a
green tire. A green tire is constructed from
uncured or so-called green rubber and other
components upon a tire building machine in well
known manner. Typically, for radial tire, the
green tire building machine includes a building
drum to which a tire liner and-tire body plies are
applied. Material overlapping the drum is turned
down and a bead assembly is applied to the edge of
,
the building drum. The overlapping plies are then
turned up over the bead package and back onto the
building drum. An extruded rubber sidewall is
applied to the tire plies and the carcass is
expanded to a desired diameter. Reinforcing belts
&~7
-30-
then are applied, an extruded tread is applied over
the belts and any air trapped between the belts and
the tread is removed in any suitable or
conventional manner such as by a so-called
~stitching~ operation. The tire is now ready for
vulcanization or curing.
Referring to Figures 1-2 and 8, the mold
is opened by moving the sections 14,15 apart in a
direction perpendicular to the parting line 16
whereby a green tire 30 may be placed within the
mold cavity 37. Once the green tire is positioned
within the mold cavity 37, the bladder 39 is
inflated with low pressure or so-called shaping
steam having a gauge pressure of between about 6895
and 68947 Pa or more which causes the bladder to
expand filling the tire.
The press is then closed until the mold
sections 14, 15 are spaced apart between about 0.10
and 5.08 centimeters as measured perpendicularly to
the parting line 16 between the mold sections 14,
15, and preferably to a point whereby the mold
sections 14, 15 are separated by between about 1.91
and 3.81 centimeters and most preferably to between
2.54 and 3.18 centimeters, as measured
perpendicularly to the parting line 16. The gauge
pressure of shaping steam being supplied to the
bladder 39 is then reduced to between about 6800 Pa
and about 41000 Pa and vacuum is applied to the
~ mold cavity through the vacuum conduit means 52
; 30 along the parting line 16.
Preferably, the vacuum source comprises a
-~ plurality of accumulators such as are shown in
Figure 3 and vacuum from the accumulators 145, 146,
147 is successively, that is consecutively, applied
to the mold cavity 37 to rapidly reduce the
absolute pressure within the mold cavity to not
:
I
p~
more than 16932 Pa, and preferably not more than
8466 Pa, more preferably not more than 6600 Pa and
most preferably not more than 2000 Pa. Typically,
the absolute pressure within the mold cavity is
reduced to approximately 1300 Pa. During
evacuation of the mold the seal 81, 92 must firmly
engage to preclude essentially all movement of air
from points external to the mold into the mold
cavity 37. Failure of the seals 81, 92 to
adequately prevent such air movement will result in
an improper vacuum being drawn upon the mold cavity
37 potentially resulting in a surface blemished or
so called ~light~ tire being produced as a result
of the curing process.
lS The mold 10 subsequently is fully closed
and the curing cycle started. The seals 81, 92
must continue to preclude essentially all ~ovement
of air from points external to the mold into the
mold cavity as the mold 10 closes and while the
2~ mold 10 remains closed. The tire is then subjected
to either a hot water cure or a so-called steam
cure. Under a steam cure, the bladder 39 is filled
with steam at a gauge pressure of approximately
1379-1724 kPa for approximately 15 minutes after
which the steam is blown down to atmospheric
pressure and a vacuum is applied to collapse the
bladder 39~ The press 12 is opened and the tire,
now havin~ curable components thereof having been
cured or so-called vulcanized, is removed.
Where a hot water cure is employed, the
bladder 39 is filled with high pressure steam at
b~we~n a~pEo~mat~y 137~ kP~ for
approximataly 2 minute~, a~ter which high pressure
hot water is circulated through the bladder at
between approximately 1724-2758 kPa at
approximately 198C ~or between about 10 and 14
-32-
minutes. Hot water within the bladder then is
removed and displaced by high pressure steam for
approximately 2 minutes after which steam contained
within the bladder 39 is blown down to atmospheric
pressure and a vacuum is applied to collapse the
bladder 39. The press is opened and a cured or
vulcanized tire then is removed.
Tires resulting from the practice of the
instant invention are characterized by the absence,
when removed from the mold cavity, of so-called
vents or projections protruding generally outwardly
from the profile of the tire from the side~all,
tread, and bead portions of the tire and resulting
from the presence of cured rubber within mold vent
passageways normally provided within the sidewall
19, 20, tread 23, 24, and bead 27, 28 portions of
the tire mold 10 of conventional configurations.
The absence of such projections obviates a
requirement for trimming the tire by placing the
tire on a tire trimming machine and cutting off or
otherwise removing such projections to dress the
tire for sale, and can result in savings of
~; approximately one ounce of uncured rubber per tire
; manufactured because of the necessity for including
extra rubber in a green tire being built to allow
for losses associated with green rubber entering
the vents of the tire mold and curing therein. The
cured tire, removed from a mold after being formed
in accordance with the method of the instant
invention is possessed of particularly sharply
delineated sidewall surface and tread contouring
since, as a result of virtually complete air
.~
removal, the green tire is capable of conforming
most closely to contours of the molding surface 35
within the tire mold 10 during the curing process.
I
:~'
~,
.,
12~ 7
-33-
The desired vacuum must be achieved in the
mold cavity 37 within a relatively short time
period. Desirably, the desired vacuum is achieved
within not more than about 60 seconds and
preferably within not more than about 45 seconds.
Most preferably the vacuum is achieved within not
more than 30 seconds and typically, where a
multi-stage vacuum system such as is depicted in
Figure 3 is employed for evacuating the mold,
desired vacuum may be achieved in approximately 6
to 15 secondsO
In the event of elevated times for
achieving a vacuum within the tire mold, and
particularly those time periods exceeding about 60
seconds, there is a tendency $or the tire to
~ . .
overshape as a result of bladder pressure, becoming
pinched and thereby misshapen as the mold closes.
Also, in the event the time period for evacuating
the mold exceeds about 60 seconds, the bladder may
collapse, steam pressure within the bladder being
reduced during the drawing of vacuum in order to
avoid overshaping. In addition, an excessively
long time period for achieving evacuation of the
mold cavity 37 can cause rubber to enter the
.
parting line 16 and thereby at least partially seal
off channels by which air remaining within the mold
cavity 37 can be conducted to the vacuum system.
Lastly, during an excessively long period for
; ~ evacuating the mold~ the tire may objectionably
partially cure before the mold fully closes,
particularly in cure sensitive areas such as tire
sidewalls where the quantity of curable elastomeric
rubber is relatively limited as compared to, for
example, the tire tread.
It should be apparent, that one aspect
important in implementing the method of the instant
:
:
--` 12~LC~g7
invention is the relatively free and rapid movement
of air from the mold cavity 37 to the vacuum
conduit means 52 for transmission to the vacuum
; system 140. Where the mold lO is closed
excessively, particularly to an opening width of
less than 0.10 centimeters along the parting line,
free movement of air to the vacuum conduit means 52
is substantially restricted and evacuation times
can become excessively prolonged. Further, in
closing the mold to a parting line opening of less
than approximately 0.10 centimeters, a significant
opportunity arises for the tire, under impetus of
the expanded bladder and the virtually closed mold,
to expand, trapping air along the sidewall l9, 20,
bead 23, 24, and tread 27, 28 components of the
mold and precluding the entrapped air from being
evacuated from the mold. A light tire results.
The ultimate extent to which a mold may
remain open along the parting line 16 during
evacuation of the mold cavity 37 in preparation for
vulcanizing and shaping a tire is dependent on the
capability of the seals 81, 92 to substantially
preclude the movement of air from points external
to the mold into the mold cavity. Practically,
this limitation has been found to preclude mold
openings greater than approximately 5.08
centimeters however, with the availability of a
suitable sealing configuration, mold openings
somewhat in excess of approximately 5 centimeters
can be accommodated, provided that evacuation of
the mold cavity is accomplished sufficiently
rapidly to prevent overstressing of the green tire
being molded, and that movement of uncured
elastomeric tire component material into the
parting line 16 is precluded. The vacuum conduit
means 52 is conveniently configured to be of a size
,:
~ Cf~
amenable to connection with conventional piping;
typically, the vacuum conduit means 52 is
configured for connection to 3/4 or 1 inch nominal
size pipe. A plurality of such vacuum conduit
means 52 spaced circumferentially around the tire
mold 10 in a size sufficient given the particular
number of vacuum conduit means 52 being provided to
evacuate the mold cavity adequately within a
desired time period are contemplated as being
; 10 within the purview of this invention. At least with a staged system 140 of vaccum accumulators
configured for consecutive application to the
evacuation of a tire mold 10, a single vacuum
conduit means 52 of approximately 3/4 inch nominal
pipe size has been found adequate in accomplishing
the evacuation of the tire mold. The vacuum
conduit means 52 need not be circular in cross
section but may assume any cross-sectional
configuration desirable for fabrication within the
mold 10 and amenable to innerconnectable attachment
` with the vacuum system 140.
As set forth herein, a wide variety of
materials are available for fabrication of the
seals 81, 92. It is desirable in the fabrication
of seals for use in the practice of the instant
invention, that the seals be capable of delivering
a service life at least equal to a service life
available from the bladder 39O Therefore, silicone
rubbers, expoxy cured butyl rubbers, and so-called
flurorubbers find particular attractiveness in the
practice of the instant invention as being capable
of delivering an elevated surface life. It is
particularly important that such rubbers be
relatively free from permanent deformation at
whatever temperatures to which the mold and bladder
are heated in curing the tire. That is to say,
~; ,
: '
~2~ 3
-36-
.
that the seals 81, 92 should be capable of
surviving without substantial permanent deformation
temperatures of at least 198C.
Referring to the drawings, Figure 6
depicts a tire 230 made in accordance with the
instant invention upon emerging from the mold
cavity having outermost tread 231, sidewall 232 and
bead portions 233 define the tixe 230 profile free
of protrusions in the form of vents. No trimming
of such a tire 230 is required to remove
protrusions resulting from the curing of green tire
rubber in mold vents. A savings in green rubber is
thereby realized, as no losses to such trimming are
thereby incurred.
; 15 While specific preferred embodiments of
; the invention has been shown and described in
detail, it should be apparent that various
modifications may be made thereto without departing
from the scope of the claims that follow.
Particularly, while the invention has been depicted
upon the presses of Figures 1-2 and 8, ready
adaptation may be made to so-called radial-opening
~, presses such as are shown in Figure 7.
:
:
