Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-10-27
2001-07-24
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C152S209600, C156S129000, C156S130000, C264S502000
Reexamination Certificate
active
06264779
ABSTRACT:
FIELD OF INVENTION
The invention relates to a tire having an improved precured tire tread for mounting to an unvulcanized or a vulcanized tire casing.
BACKGROUND OF THE INVENTION
Historically the use of precured treads was limited to retreaded tires exclusively. Tire casings are designed to survive several times longer than the tread. This is particularly true of truck tires and low aspect ratio passenger tires.
The Goodyear Tire & Rubber Company in the late 1980's introduced the Unicircle precured injection molded tread. This precured tread is disclosed in European Patent Publication 0-464-660A1. This annular or acutely shaped tread had short annular wings radially inwardly extending. The wings were flexible and adapted to accommodate casings of various axial widths. This tread introduced high-pressure injection molded rubber compounds having excellent wear and rolling resistance properties. Materials used in tread rubber compounds have also been improved making it feasible to transfer compression mold high quality treads for tires which can also achieve excellent wear and performance characteristics.
Later development efforts were concentrated on improved adhesion of the tread to the casing and in particular at better ways of adhering the wing edge to the casing. On May 24, 1994, U.S. Pat. No. 5,313,745 issued to Carl L. Mace, Jr., et al. relating to a tread edge grinning method which effectively created a chamfered edge enabling the cushion gum rubber to migrate over the chamfer effectively locking the annular wing of the precured tread to the cushion gum and the casing.
The advancement in the overall adhesion properties of the tread to casing bond coupled with the ability to meet or surpass the performance of conventional molded new tires means that it is now feasible for new tires to be made using precured treads. One aspect of the present invention describes an improved precured tread and a method for assembling it to a previously unvulcanized casing. A second aspect of the invention teaches how the tread can be applied to a precured new casing or a used prepared vulcanized casing. In each case, the invention permits the adhesion of the tread at the sidewall to exceed that achieved in the Mace patent while at the same time creating an almost imperceptible seam line between the casing and the tread.
A common concern in the tire art relates to the uniformity of tire construction and therefor tire performance. The inventors believe that once cause of poor and inconsistent tire performance relates to the non-uniform pressure distribution exerted on tire casings during the tire curing process. In particular, the inventors believe that belts can be distorted due to the non-uniform pressure exerted by the mold in the tread groove area. The present invention overcomes this problem by providing uniform pressure distribution on the casing during curing. Thus, tire life and performance is enhanced.
SUMMARY OF THE INVENTION
A tire
200
having an improved precured tire tread
10
for mounting to an unvulcanized or a vulcanized-precured tire casing
100
,
150
is disclosed. The tread
10
is made from an elastomeric material. The precured tire tread
10
has a radially outer ground engaging surface
20
. The tread
10
has grooves
22
extending radially inwardly from the ground engaging surface
20
. The tread material radially inwardly of the grooves
22
constitutes an inner tread
30
, the inner tread
30
having a radially inner surface
32
and a radially outer surface
3
. The tread
10
when in an annular configuration has a cross-section including first and second lateral surfaces
40
,
50
respectively extending radially inwardly and axially outwardly from an axially outermost point
24
,
26
on the ground engaging surface
20
. The lateral surfaces
40
,
50
extend radially inwardly to axially outermost and radially innermost point of the inner tread surface, preferably extending a distance less than two times more preferably about equal to or slightly greater than the thickness of the tread
10
, the tread thickness being measured at the equatorial plane (EP). The improved tread
10
has a pair of circumferentially continuous projections
60
. One projection
60
extending axially outwardly from each of the lateral surfaces
40
,
50
and being radially outwardly space above the intersections
36
,
38
of the radially inner surface
32
of the inner tread
30
and the lateral surface
40
,
50
. The projection
60
provides a means for air tight sealing the tread casing assembly at the lateral surfaces
40
,
50
during the vulcanization of the tread
10
to the casing
100
. It is preferred that the projection
60
has a uniform cross-sectional shape that is either trapezoidal, semicircular or triangular and that projection be spaced radially about 3 mm preferably less than 15 mm outward of the intersection
36
,
38
of the radially inner surface
32
of the inner tread
30
and the lateral edge surface
40
,
50
.
The precured tread
10
is best molded to an unvulcanized casing
100
by the method of placing the tread
10
and casing
100
in a smooth mold
70
inserting an inflatable bladder
80
inside the casing
100
then closing the mold
70
. The bladder
80
is then inflated expanding the casing
100
firmly into contact with the tread
10
, the tread
10
correspondingly expanding firmly engaging the smooth mold
70
and air tightly sealing the tread
10
at the annular projections
60
along the tread edges
40
,
50
. A strip or strips of cushion gum rubber
152
may be applied circumferential around the casing to facilitate bonding the tread to the casing. Additionally, an adhesive
153
can be employed if so desired. Heat and pressure is then applied causing a uniform flow of casing material radially outwardly along the tread edges
40
,
50
to the annular projection
60
.
In the case of attaching a precured annular tread
10
of the present invention to a previously vulcanized casing
150
the method includes the steps of applying a cushion gum layer
152
and an adhesive cement
153
if needed to the prepared casing
150
, expanding the tread
10
and positioning the tread
10
onto the casing, transferring the tread onto the casing
150
, attaching two shoulder rings
201
to the assembly, the shoulder rings
201
firm and air tightly sealing the tread
10
at the projection
60
and then forming an annular cavity
202
between the projection
60
and the casing
150
, placing the assembly into an autoclave or vulcanizing chamber and applying sufficient heat and pressure to cause a uniform flow of cushion gum material
152
radially outwardly along the tread edges to the annular projection
60
. Preferably the annular rings
201
are provided with a means
204
for evacuating entrapped air from the cavity to insure the cushion gum rubber
152
can be adequately fill the cavity
202
. Additionally, an adhesive cement coating
153
may optionally be applied to the tread
10
or the casing
150
or both to further enhance adhesion.
In the case of applying a precured strip tread
10
of the present invention the above step of expanding the tread
10
is replaced with the step of splicing the tread
10
all other steps being the same as the method of attaching a ring or annular tread as described above.
In another embodiment, a tire
300
has a precured tire tread
310
for mounting to an unvulcanized or a vulcanized-prepared tire casing
312
,
314
. The tread
310
is made from a an elastomeric material and has an inner tread surface
315
, a radially outer ground engaging surface
318
and first and second tread edges
320
,
322
. The tread
310
may have tread grooves
324
and preferably one of the grooves
324
is centered on the ground engaging surface
318
.
The tread
310
is molded to the unvulcanized tire casing
312
using a smooth mold
326
that has first and second annular radially extending projections
328
,
330
and preferably a third annular radially extending projection
332
that is positioned substantially equidistant between the firs
Cappelli Mathew Ray
Laurich Thomas Andrew
Rex William Allen
Vannan, Jr. Frederick Forbes
King David L
Knable Geoffrey L.
The Goodyear Tire & Rubber Company
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