Method to cure endless track belts and apparatus therefor

Details Method to cure endless track belts and apparatus therefor Method to cure endless track belts and apparatus therefor

1999-11-04

2001-09-04

Tentoni, Leo B. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

To produce composite, plural part or multilayered article

C264S296000, C425S034200, C425S195000, C425S343000, C425S384000, C425S394000

Reexamination Certificate

active

06284180

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the curing of large endless track belts such as are illustrated in U.S. Pat. Nos. 4,721,498; 5,211,609; 5,575,729 and 5,536,464.
BACKGROUND OF THE INVENTION
The use of double platen presses for curing endless belts and conveyor belts has been known for some time. Two major problems were generally encountered, the containment of the rubber within the molds and the movement of the reinforcement within the belts such as tension members. In U.S. Pat. No. 5,110,274, there is disclosed a mold for vulcanizing cogged V-belts including cooling water ports at each end of the mold and also cog peak cavities at each end which are narrower than the central part of the mold. In U.S. Pat. No. 5,536,464, there is described a set of molds and subplates and a method of curing rubber track. The first mold has cooling water ports at each end to provide a plurality of semi-vulcanized lugs at each end with fully vulcanized lugs between. The second set of molds have no cooling ports and the process is designed to have the semi-vulcanized lugs from adjacent sections within the cavities of the second set of molds. The apparatus and method of the '464 patent are complicated and tedious.
SUMMARY OF THE INVENTION
The present invention provides a much simpler method of curing rubber track belts using a minimum of equipment and with a fewer number of steps. In accordance with the practice of the present invention, there is provided a method for curing endless track belts comprising:
a) providing a pair of upper and lower heated mold assemblies having an entrance end, an exit end, cooling water ports at each end, outer tread lug cavities in one half of a mold assembly, inner guide lug cavities in the other half of the mold assembly and a pair of fully supporting indexing wheels on opposing ends of the mold assemblies;
b) placing a green track belt carcass having a slab of tread lug compound built up on the outer surface thereof in between the mold halves and around the indexing wheels;
c) placing non-preformed slugs of inner guide lug compound in the inner guide lug cavities of the upper mold assembly and on the carcass opposite the guide lug cavities of the lower mold assembly;
d) turning on the water to all the cooling ports;
e) closing the mold halves at such a designated high pressure to form the tread lugs and guide lugs in a series of alternating bumps between high pressure and a much lower or no pressure to form the lugs;
f) applying a constant lower pressure to allow the lugs to expand into the cavities and the molds to separate until the first heat is complete;
g) opening the mold halves and indexing the belt a distance x which is less than the length of the molds until the lugs that were formed in the cavities next to the cold entrance end are aligned with the cavities at the exit end;
h) shutting off the cooling water at the exit end of the molds;
i) placing additional slugs of guide lug compound in the empty cavities of the upper mold and on the carcass opposite the empty cavities of the lower mold and repeating steps e, f and g for the second and subsequent heats prior to the final heat;
j) shutting off the cold water to the entrance ends of the molds;
k) placing additional slugs of guide lug compound in the empty cavities of the upper mold and on the carcass opposite the empty cavities of the lower mold and repeating steps e and f to form the final track belt; and
l) removing the track belt from the mold assemblies.
There is also provided an apparatus for curing large endless belts comprising:
a) a pair of double platen mold assemblies having outer tread lug cavities, inner guide lug cavities, entrance ends, exit ends and cooling water ports at each end;
b) pressure cylinders to impart a cavity pressure of 1.4 to 8.4 MPa; and
c) fully supporting indexing wheels, wherein the indexing wheels provide support across the entire width of the belt with a force of 0.14-3.5 MPa during the curing cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an elevational cross-sectional view of the apparatus used in the method of the present invention, showing the finished track in phantom lines.
FIG. 2
shows the apparatus of
FIG. 1
with a built-up carcass and guide lug slugs added prior to the first heat cycle.
FIG. 3
shows the condition of the apparatus during the first heat cycle.
FIG. 4
illustrates the indexing of the track belt after the first heat cycle and preparation for the second heat cycle.
FIG. 5
illustrates the mold assemblies closed during the second heat cycle.
FIG. 6
is a cross-sectional view of that portion of the track and fully supporting indexing wheel taken along line
6
—
6
of FIG.
5
.
FIGS.
7
(
a
) and
7
(
b
) illustrate a cross-sectional view of an alternative embodiment of an indexing wheel similar to FIG.
6
.


REFERENCES:
patent: 4207052 (1980-06-01), Satzler
patent: 4283366 (1981-08-01), Grawey
patent: 4575445 (1986-03-01), Fujita et al.
patent: 4721498 (1988-01-01), Grob
patent: 5110274 (1992-05-01), Hatai et al.
patent: 5211609 (1993-05-01), Haines
patent: 5536464 (1996-07-01), Muramatsu
patent: 5575729 (1996-11-01), Feldman et al.
patent: 0 308 550 A1 (1989-03-01), None

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