U.S. patent application number 10/842356 was filed with the patent office on 2004-10-21 for tire mold and a method of rapidly depressurizing the mold.
This patent application is currently assigned to The Goodyear Tire & Rubber Company. Invention is credited to Ciesa, Clifford Jack, Fortin, Jean-Marc Francois, Incavo, Joseph Alan, Porter, Michael Eugene.
Application Number | 20040208945 10/842356 |
Document ID | / |
Family ID | 25277612 |
Filed Date | 2004-10-21 |
United States Patent
Application |
20040208945 |
Kind Code |
A1 |
Ciesa, Clifford Jack ; et
al. |
October 21, 2004 |
Tire mold and a method of rapidly depressurizing the mold
Abstract
A tire mold 2 for curing new or retreaded tires 20 has an upper
platen 4, a lower platen 6, and a central rim 30 with a frangible
member 50 designed to open when a predetermined pressure P.sub.1 in
excess of the normal curing pressure P.sub.c is observed. The
frangible member 50 preferably includes a rupture disk 60 that
breaks upon exposure to the pressure P.sub.1.
Inventors: |
Ciesa, Clifford Jack;
(Akron, OH) ; Fortin, Jean-Marc Francois; (Delano,
PA) ; Incavo, Joseph Alan; (Uniontown, OH) ;
Porter, Michael Eugene; (Hudson, OH) |
Correspondence
Address: |
The Goodyear Tire & Rubber Company
Intellectual Property Law Dept. 823
1144 East Market Street
Akron
OH
44316-0001
US
|
Assignee: |
The Goodyear Tire & Rubber
Company
|
Family ID: |
25277612 |
Appl. No.: |
10/842356 |
Filed: |
May 10, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10842356 |
May 10, 2004 |
|
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09838623 |
Apr 19, 2001 |
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6733702 |
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Current U.S.
Class: |
425/21 ; 425/36;
425/58 |
Current CPC
Class: |
B29D 30/0662 20130101;
B29C 35/049 20130101; B29C 43/104 20130101; B29L 2030/00 20130101;
B29D 30/0602 20130101; B29C 2043/5808 20130101; B29C 2037/94
20130101; B29C 35/049 20130101 |
Class at
Publication: |
425/021 ;
425/036; 425/058 |
International
Class: |
B29C 035/00 |
Claims
1-9. (canceled)
10. An improved tire apparatus for curing a retreaded or new tire
in a mold, the apparatus comprising: a central rim having mounting
flanges for mounting the beads of said tire, the central rim having
a central portion having an inner surface open to atmospheric
pressure and an exterior surface for forming a toroidal pressure
chamber with the tire; a frangible member connected to the central
portion of the rim, the frangible member opening to atmospheric
pressure P.sub.o when the chamber pressure reaches a predetermined
pressure P.sub.l, P.sub.l being greater than the tire curing
pressure P.sub.c,.
11. The improved tire apparatus of claim 10 wherein the frangible
member has a rupture element breakable at the predetermined
pressure P.sub.l.
12. The improved tire apparatus of claim 10 wherein the frangible
member opens at predetermined pressures in the 200 to 250 p.s.i.
range.
13. The improved tire apparatus of claim 10 wherein the frangible
member redirects the flow 90.degree. relative to the path exiting
the rim.
14. The improved tire apparatus of claim 10 wherein all exhaust
flows are centrally directed initially within the central rim.
15. An apparatus for use in a tire mold for curing tubeless tires,
said apparatus comprising: a central rim having mounting flanges
for sealing said tire at the beads, the central rim having a
central portion having a first side at atmospheric pressure and a
second side at the mold internal pressure, a frangible member
mounted in a hole of the central portion, and said frangible member
having a rupture element breakable at a predetermined pressure
greater than the tire curing pressure whereby dangerous vapors may
vent from the mold through the frangible member out into the
atmosphere.
16. A frangible member comprising a body having a first end for
mounting to a pressure chamber, said body having an interior
threaded surface, a rupture element breakable at a predetermined
pressure exceeding the chamber pressure, said rupture element being
mounted within the threads of said interior threaded surface of
said body.
17. The frangible member of claim 16 wherein said frangible member
further comprises a distal end having an end cap with holes wherein
the exhaust flow is redirected ninety degrees.
Description
[0001] This application claims the benefit of U.S. patent
application Ser. No. 09/838,623 filed on Apr. 19, 2001.
TECHNICAL FIELD
[0002] This invention relates to tire molds generally more
particularly to large molds for off road tires. The invention is
particularly useful in a class of molds commonly used in retreading
large tires.
BACKGROUND OF THE INVENTION
[0003] In the manufacture of large tires for earthmoving,
construction, and in some cases, farm tire applications, very large
molds are employed to cure the tires.
[0004] Additionally, in most applications these tires are well
suited for retreading. Retreading involves the practice of taking
worn or used tires, grinding the remaining tread surface, and
applying a new layer of tread rubber, which when cured in a retread
mold, forms the tread pattern. This renewal process extends the
life of the tire and can result in a substantial cost savings to
the end user.
[0005] This added tread rubber is often 6 inches to over 12 inches
thick. In order to cure such a thick component the cure cycles can
take from 6 to almost 24 hours. Rubber products, when cured over
such a large period must be exposed to minimum temperatures at
reasonably low pressures, generally under 300.degree. F. and under
200 p.s.i., preferably about 180 p.s.i.
[0006] On rare occurrences when retreading a used tire, volatiles
are expelled from the interior of the casing and mixed with the
heated air. If a sufficient quantity of such volatiles are expelled
into the heated air chamber, an ignition can occur resulting in a
rapid increase in pressure. Due to the large size of the molds,
sometimes 10 ft. in diameter and larger, these rapid pressure
increases can result in damaged presses caused by warpage and
cracking. In most severe cases wherein a leakage does not occur,
then the upper platen can become dislodged or broken. Naturally due
to the very large size of these molds, dislodged components
weighing in excess of a ton are very undesirable.
[0007] Attempts to minimize such occurrences have led some to
consider employing nitrogen to pressurize the curing press instead
of air. Nitrogen will not support combustion. A primary drawback of
the use of nitrogen is that exposure by humans to high levels of
nitrogen results in nausea, headaches and asphyxiation. Containing
the chamber fluid is considered desirable, but experience shows
that repeated mixing of the nitrogen with the tires' normal
outgasing of volatiles and oxygen results in said systems being in
constant need of monitoring and replenishing.
[0008] The present invention attempts to achieve normal air curing
without requiring such extreme measures, such as nitrogen
curing.
[0009] The present invention has a primary objective of preventing
exposure to rapid increases in pressure with the purpose of
eliminating such conditions long before they can cause damage to
the molds.
SUMMARY OF THE INVENTION
[0010] A method of rapidly depressurizing a mold for curing
retreaded or new tires is disclosed. The mold has an upper platen,
a lower platen and a central rim for sealing the tire at the beads.
The central rim is open to atmospheric pressure P.sub.o at the
radially inner surfaces. The radially outer surfaces of the central
rim, in combination with the upper platen and lower platen, form a
toroidal pressure chamber for curing the tire.
[0011] The method comprises the steps of providing a frangible
member attached and open to the toroidal pressure chamber through
an opening in the central rim and opening the frangible member to
the atmospheric pressure P.sub.o when the chamber pressure reached
a predetermined pressure P.sub.l, P.sub.l being greater than the
tire casing pressure P.sub.c.
[0012] Preferably, the step of opening the frangible member
includes the step of rupturing a portion of the frangible member at
the predetermined pressure P.sub.l. Most preferably, once the
frangible member opens, the chamber exhaust flow is directed
orthogonal relative to the attachment to the rim.
[0013] The above method is practiced in an improved mold for curing
retreaded or new tires. The mold has an upper platen, a lower
platen, and a central rim.
[0014] The central rim has a radially inner surface open to the
atmospheric pressure and radially exterior surface which, in
combination with the upper platen and lower platen, form a toroidal
pressure chamber for curing a tire. The improved mold has a
frangible member attached to an opening in the central rim and is
connected on a radially inner surface of the rim. This frangible
member opens to atmospheric pressure P.sub.o when the chamber
pressure reaches a predetermined pressure P.sub.l, P.sub.l being
greater than the tire curing pressure P.sub.c. Preferably the
frangible member has a rupture element breakable at a predetermined
pressure P.sub.l. Most preferably P.sub.l is in the range of 200 to
250 p.s.i. The frangible member has a flow diverter for redirecting
the exhaust flow 90.degree. relative to the path exiting the rim.
Ideally, the exhaust flow is centrally directed within the central
rim.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a view of the mold according to the invention.
[0016] FIGS. 2A and 2B are cross-sectional views of the mold
according to the invention.
[0017] FIG. 3 is a view of the rim according to the invention.
[0018] FIG. 4 is a top view of the rim.
[0019] FIG. 5 is a cross-sectional view of the central rim.
[0020] FIG. 6 is an enlarged cross-sectional view of the frangible
member.
[0021] FIG. 7 is a partial view of the frangible member attached to
the inner surface of the rim.
DETAILED DESCRIPTION OF THE INVENTION
[0022] With reference to FIG. 1 there is shown one large earthmover
retread tire mold 2. The mold 2 has an upper platen 4 and a lower
platen 6. Interposed between the upper platen and lower platen is
shown the tire 20.
[0023] As in FIGS. 2A and 2B the cross-sectional view of the mold 2
shows both the upper platen 4 and the lower platen 8, including
segments 8, 9 for forming the tread pattern of the tire. As shown
in FIG. 2B the lower segments 9 interlock with the upper segments 8
and the upper and lower platens 4, 6 hold both segments 8, 9 in a
restrained position when the mold 2 is closed during curing.
[0024] The tire casing 22 and the uncured tread rubber 24 come in
contact with the tread forming segments 8, 9. The rim 30 presses
against the bead portion 26 of the tire 20.
[0025] With reference to FIG. 3, the rim 30 as shown is a
Compression Cure.RTM. System SuperRim from Ohio Machine and
Manufacturing Co. of Los Angeles, Calif. The rim 30 has an
adjustable bead width flange 32 which allows adjustments in width
bead 26 to bead 26 as required for the mold 2. This type of rim 30
allows for tubeless curing. While the particular type of mold or
rim is not relevant to the invention, it is important that the
central core forming the tire be a rim or rim type structure open
to the atmosphere in the center as will be appreciated with further
reading of this description.
[0026] Once the mold is closed as shown in the view 2B the heat and
pressure are applied to the internal surfaces 28 of the tire 20.
The pressure P.sub.c generally is in the range of 165 to 200 p.s.i.
and is held generally constant during the cure cycle. The cure
cycle can be from a few hours to over 12 hours or longer.
[0027] As discussed earlier, in rare occasions the tire 20 may
outgas volatile vapors that can result in an ignition causing a
rapid increase in pressure. This can result in mold damage and
product loss.
[0028] The present invention takes advantage of the rim 30 having a
central area open to atmospheric pressure. As shown in FIG. 4 a
hole or opening 40 is placed in the central portion of the rim 30
between the flanges 32, 34. The central portion 36 is in direct
open communication with the pressurized heated air in the tire 20.
Welded to the rim 30 at the opening 36 is a frangible member 50 as
illustrated in FIG. 7.
[0029] With reference to FIG. 7 the frangible member 50 is shown.
This device has a threaded first flanged pipe 51 fitting attached
to a thread flange 52 welded to the rim 30 on the internal surf ace
31 and another second threaded flanged portion 53 fastened to the
first portion 51 by a large coupling nut 54. The second portion 54
has an end cap 55 with holes 56 for diverting the flow exhaust
90.degree. relative to the opening in the rim 30. Internal to the
two portions 51, 53 is a rupture disk 60. The rupture disk 60 is
specifically designed to break at a predetermined pressure P.sub.l,
the pressure being set above the cure pressure P.sub.c. Once the
rupture disk 60 breaks, the chamber cure pressure P.sub.c rushes
out of the tire 20 and the mold 2 is quickly and safely vented.
[0030] The frangible member 50 shown is a BS&B Union Type
safety head. The fittings 51, 53, 54 are made of carbon steel or
316 stainless steel. Brass, nickel Monel aluminum and other types
of metals can be used. The rupture disks 60 can be made of metal or
composites and are commercially available in a variety of materials
and designs for the particular application.
[0031] While it is considered possible to accomplish this venting
action by using a pressure relief valve, it has several drawbacks,
the first being the reliability of such a valve. As those skilled
in the art know, such valves are prone to sticking and
malfunctioning over time. The rupture disks 60 are very reliable
and once they fail, a new one is substituted unlike valves that
once activated, they are simply reset. Applicants further find
valves occlude or block when exposed to rubber particulate matter.
Rupture disks 60 are immune to this problem.
[0032] A key feature of this invention is the fact that the
frangible member 50 must be open to the internal surfaces of the
tire 20. Relief valves are known to be used in molds, but in the
case of a tire mold, any pressure relief done on the exterior
surface of the tire 20 is prone to failure, the reason being the
tire itself would seal against the opening preventing the
depressurization from occurring. It is when the unique combination
of a mold 2 with a central core or rim 30 open to atmospheric
pressure is used in this type of molding that one can safely and
reliably vent the cure pressure P.sub.c in the manner described
herein.
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