U.S. patent application number 11/492318 was filed with the patent office on 2008-01-31 for recessed tread wear indicator.
Invention is credited to Paul A. Mayni, Nathan J. Panning.
Application Number | 20080023116 11/492318 |
Document ID | / |
Family ID | 38984945 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080023116 |
Kind Code |
A1 |
Mayni; Paul A. ; et
al. |
January 31, 2008 |
Recessed tread wear indicator
Abstract
A tread band having a primary groove opening onto a front face
of the tread band, a secondary feature molded into the tread band,
and a wear indicator molded into a section of an undertread portion
of the tread band. The wear indicator is useful for providing an
end-of-useable tread indication when the front face of the tread
band wears even with a top portion of the wear indicator.
Furthermore, the secondary feature may be characterized as opening
onto a back face of the tread band, a side face of the tread band
or combinations thereof. The section of the undertread portion may
extend less than about 4 mm or less than about 3 mm from the back
face of the tread band. In other embodiments, the section of the
undertread portion may extend less than about 1.5 mm from the back
face of the tread band.
Inventors: |
Mayni; Paul A.; (Greenville,
SC) ; Panning; Nathan J.; (Simpsonville, SC) |
Correspondence
Address: |
MICHELIN NORTH AMERICA, INC.;INTELLECTUAL PROPERTY DEPARTMENT
MARC BLDG 31-2, 515 MICHELIN ROAD
GREENVILLE
SC
29605
US
|
Family ID: |
38984945 |
Appl. No.: |
11/492318 |
Filed: |
July 25, 2006 |
Current U.S.
Class: |
152/154.2 ;
152/209.18 |
Current CPC
Class: |
Y10T 152/10027 20150115;
B60C 11/24 20130101 |
Class at
Publication: |
152/154.2 ;
152/209.18 |
International
Class: |
B60C 11/24 20060101
B60C011/24 |
Claims
1. A tread band, comprising: a primary groove opening onto a front
face of the tread band and a secondary feature molded into the
tread band, the secondary feature opening onto a back face of the
tread band, a side face of the tread band or combinations thereof;
and a wear indicator molded into a section of an undertread portion
of the tread band to provide an end-of-usable-tread indication when
the front face of the tread band wears even with a top portion of
the wear indicator.
2. The tread band of claim 1, wherein the section of the undertread
portion extends less than about 4 mm from the back face of the
tread band.
3. The tread band of claim 1, wherein the section of the undertread
portion extends less than about 3 mm from the back face of the
tread band.
4. The tread band of claim 1, wherein the section of the undertread
portion extends less than about 1.5 mm from the back face of the
tread band.
5. The tread band of claim 1, wherein the wear indicator extends
radially from the back face of the tread band and is molded into an
indicator portion of the secondary feature.
6. The tread band of claim 5, wherein a bottom of the secondary
feature extends to a greater distance radially from the back face
than a groove bottom of the primary groove.
7. The tread band of claim 6, wherein the wear indicator is molded
into a plurality of secondary features at the same circumferential
location so that a lateral bar comprising a top portion of the wear
indicator forms across the tread band as the end-of-usable-tread
indication.
8. The tread band of claim 5, further comprising: an access channel
opening from the front face of the tread band and extending
radially to a top surface of the wear indicator, wherein the access
channel is in fluid communication with the indicator portion of the
secondary feature.
9. The tread band of claim 8, wherein the access channel is not in
fluid communication with adjacent portions of the secondary feature
that are separated from the indicator portion by a barrier.
10. The tread band of claim 8, wherein the access channel is
between about 4 mm and 6 mm wide.
11. The tread band of claim 8, wherein the wear indicator molded
into the indicator portion of the secondary feature is less than
about 12 mm wide.
12. The tread band of claim 1, wherein the tread band is cured
rubber.
13. The tread band of claim 1, wherein the tread band is uncured
rubber.
14. The tread band of claim 1, further comprising: a cavity that
extends from the front face of the tread band to below a top face
of the wear indicator, wherein at least a portion of the wear
indicator is molded within the cavity.
15. The tread band of claim 14, wherein the section of the
undertread portion extends less than 4 mm from the back face of the
tread band.
16. The tread band of claim 14, wherein the section of the
undertread portion extends less than 3 mm from the back face of the
tread band.
17. A tire, comprising: a tire carcass having a crown portion; a
tread band bonded to the crown portion of the tire carcass, wherein
the tread band comprises: a primary groove opening onto a front
face of the tread band and a secondary feature molded into the
tread band, the secondary feature opening onto a back face of the
tread band, a side face of the tread band or combinations thereof;
and a wear indicator molded into a section of an undertread portion
of the tread band to provide an end-of-usable-tread indication when
the front face of the tread band wears even with a top portion of
the wear indicator.
18. The tire of claim 17, wherein the tire carcass is cured and the
tread band is uncured.
19. The tire of claim 17, wherein the tread band is stitched to the
tire carcass.
20. The tire of claim 19, wherein the tread band is stitched to the
tire carcass with a layer of cushion gum rubber.
21. The tire of claim 20, wherein the cushion gum rubber is cured
to bond the tread band to the tire carcass.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to tires and more
particularly, to tire tread wear indicators.
[0003] 2. Description of the Related Art
[0004] It is known how to provide wear detectors on the tread
pattern elements of a tire tread for motor vehicles. One example of
a tread wear indicator is shown in FIGS. 1A-C. A tread band 10
includes grooves 13 opening from the front face of the tread band
10, these grooves 13 forming the treads of the tread band 10. Wear
indicators 11 are molded into the grooves 13 at a depth m 12, which
represents the minimum acceptable depth of the tread grooves 13.
FIG. 1B shows the tread band 13 worn down to the wear indicators
11, indicating that the tread band 10 has served its useful life.
FIG. 1C is a perspective view of the tread band 10 showing that the
tread wear indicators 11 are generally located at the same
circumferential location along the tread band 10 so that when the
tread is worn down to the wear indicators 11, a wear bar 14 is
formed laterally across the tread band 10, which indicates that the
useful life of the tread is ended. The undertread 16 portion of the
tread band 10 is that portion that is below the bottom of the
grooves 13 that are formed in and open to the front face 17 of the
tread band 10.
[0005] Other examples, of tread wear indicators may be found, for
example, in the British patent publications GB-A-2 330 808 and
GB-A-2 268 715. These references disclose visual wear detectors
consisting of layers of colored light-reflecting rubber that are
disposed over the entire circumference of the tire in the mass of
the tread. These colored rubber indicators become visible following
a given amount of wear on the tire that strips away the rubber
covering the colored rubber layers.
[0006] Tread bands are used for retreading tires as well as in new
tire construction. In either case, the tread band is bonded to a
tire casing to provide either a new tire (when bonded to a new tire
casing) or a retread tire (when bonded to a used tire casing that
has had the old tread buffed off). The tread bands are molded and
may be either cured or uncured before being bonded to the tire
casing.
[0007] The undertread portion of the tread band is typically 2-5 mm
thick and may facilitate demolding the tread band. It may further
assist in resisting lateral compression of the tread pattern during
the process of bonding the tread band to the tire casing. However,
this undertread does not provide any useful life for the tread
because it lies below the tread grooves that open to the front face
of the tread band.
[0008] While wear bars are useful indicators of the end of the
useful life for the tread, there is a need for improved tread wear
indicators that maximize the use of the entire tread band before
its end of life.
SUMMARY OF THE INVENTION
[0009] One embodiment of the present invention includes a tread
band having a primary groove opening onto a front face of the tread
band, a secondary feature molded into the tread band, and a wear
indicator molded into a section of an undertread portion of the
tread band. The wear indicator is useful for providing an
end-of-useable tread indication when the front face of the tread
band wears even with a top portion of the wear indicator.
Furthermore, the secondary feature may be characterized as opening
onto a back face of the tread band, a side face of the tread band
or combinations thereof.
[0010] In particular embodiments of the present invention, the
section of the undertread portion may extend less than about 4 mm
or less than about 3 mm from the back face of the tread band. In
other embodiments, the section of the undertread portion may extend
less than about 1.5 mm from the back face of the tread band.
[0011] The tread band of the present invention further includes
embodiments wherein the wear indicator extends radially from the
back face of the tread band and is molded into an indicator portion
of the secondary feature.
[0012] The present invention further provides embodiments that
include a tire having a tire carcass having a crown portion with a
tread band bonded to the crown portion, the tread band having the
features described above. Particular embodiments of the present
invention include tires that are new as well as tires that are
re-treaded with a tread band as described above.
[0013] The foregoing and other objects, features and advantages of
the invention will be apparent from the following more particular
description of a preferred embodiment of the invention, as
illustrated in the accompanying drawing wherein like reference
numbers represent like parts of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1A-C are drawings showing cross sectional and
perspective views of a tread band showing a wear bar as known in
the prior art.
[0015] FIGS. 2A-2B are drawings showing cross sectional views of a
tread band having a wear indicator extending radially from the back
face of the tread band and molded into the secondary grooves in
accordance with a particular embodiment of the present
invention.
[0016] FIG. 2C is a top view of a portion of the tread band having
the wear indicator of FIGS. 2A-2B.
[0017] FIGS. 3A-3B are drawings showing perspective views of a top
and bottom mold suitable for molding a tread band having a wear
indicator molded into the secondary grooves.
[0018] FIG. 3C is a drawing of a perspective view of a detail of
the wear indicator portions of the top and bottom molds that are
shown in FIGS. 3A-3B.
[0019] FIGS. 4A-4B are drawings of perspective and cross sectional
views of a tread band having a wear indicator molded into a cavity
that is open to the front face of the tread band.
[0020] FIG. 5 is a drawing of a perspective view of a portion of a
retread tire having a tread band in accordance with the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] The present invention provides a wear indicator molded into
the undertread portion of a tread band to provide an
end-of-usable-tread indication. Such indication is provided when
the front face of the tread band wears even with a top portion of
the wear indicator. The tread band includes both a primary feature
that opens onto a front face of the tread band and at least one
secondary feature molded into the tread band that opens onto a back
face of the tread band, a side face of the tread band or
combinations thereof. Primary and secondary features may include,
for example, sipes, holes and/or grooves as known to those having
ordinary skill in the art.
[0022] Treads on tires reach an end-of-usable tread when the total
tread depth provided by the features that are open to the front
face of the tread are below an acceptable minimum depth or below an
acceptable total volume. Such minimum depth and/or volume may be
set by regulation in a given jurisdiction or alternatively, may be
determined by the tire designer.
[0023] The wear indicator of the present invention is molded into
the undertread portion of the tread band to provide an
end-of-usable-tread indication for the secondary features. Since
the secondary features are molded into the tread band and are open
to the sides and/or back of the tread band, these secondary
features do not provide usable tread depth or volume until the
front face is worn to a depth that opens the secondary features to
the front face. As the primary features that are open to the front
face wear away, the secondary features become exposed and open to
the front face to provide the required open volume and/or depth in
the tread. This allows the tread band to be worn much closer to the
rear face of the tread band, allowing more of the tread band to be
utilized before the tire is discarded or retreaded. Preferably the
wear indicator is molded into a section of the undertread portion,
the section extending less than about 4 mm from the back face of
the tread band. More preferably the section may extend less than
about 1.5 mm from the back of the tread band. Alternatively, the
section may extend less than about 3 mm from the back face of the
tread band. It should be noted that since the tread band is
typically bonded to a tire carcass, the "radial" direction of the
tread band as used herein is in the perpendicular direction between
the front face and the back face of the tread band.
[0024] As disclosed above, the wear indicator that is molded into
the tread band provides an end-of-usable-tread indication when the
front face of the tread band wears even with a top portion of the
wear indicator. The top portion of the wear indicator may be, for
example, a front or top solid face of the molded indicator or the
top or front of a void space molded into the tread band. For
example, a series of small perforations may be molded into a
section of the undertread in a pattern that spells out "WORN." When
the front face of the tread band is worn to that section of the
undertread, the "WORN" indication will become visible, thereby
providing the end-of-usable-tread indication. Solid wear indicators
may be characterized as "positive" indicators and wear indicators
that consist of voids may be characterized as "negative"
indicators. However, whether the indicators are positive or
negative indicators, the indication provided to the user of the
tires is the same, i.e., that the end-of-useable-tread has been
reached.
[0025] In a particular embodiment of the present invention, the
wear indicator extends radially from the back face of the tread
band to a predetermined minimum tread depth and is molded into a
portion of one or more secondary features that open onto a back or
side face of a tread band.
[0026] In another particular embodiment, the top surface of the
wear indicator is exposed in a cavity that extends from the front
face of the tread band to below the top face of the wear indicator.
When the tread wears down to expose the wear indicators, the end of
the useful life of the tread band is indicated. Advantageously, the
wear indicator of the present invention is typically located in the
undertread of the primary features that open onto the front face of
the tread band so that a greater amount of the undertread can be
utilized as useful tread, thereby extending the useful life of the
tread band.
[0027] Particular embodiments of the present invention include a
tread band that may be bonded either to a new tire casing or to a
used tire casing. Bonding the tread band to a used tire casing that
has had the old tread buffed off is part of the retread process.
The tread band is molded with features that are formed by both the
top and bottom sections of the mold. The top mold section molds one
or more primary features that are open to the front face of the
tread band and the bottom mold section molds one or more secondary
features that are open to the back face of the tread band.
Optionally, other secondary features may be molded by other molding
elements, i.e., molds that interact with the top and bottom mold
sections to form a complete mold as known to those having ordinary
skill in the art, to form features that, for example are open to
one or more sides of the tread band.
[0028] In particular embodiments of the present invention, the
bottoms of the one or more secondary grooves extend to a greater
distance radially from the back face of the tread band than the
groove bottoms of the one or more primary grooves. This arrangement
allows, during the wearing of the tire, the secondary grooves to
open to the front face of the tread band and thereby provide
useable features as the primary grooves wear away. It should be
noted that the "bottom" of a feature is typically opposite the open
end of the feature.
[0029] Since the secondary features provide tread for use after the
primary features have worn away, placing the wear indicator in a
portion of the bottom of the primary features does not provide an
indication of the minimum tread remaining. Placing the wear
indicator in a portion of the primary feature bottoms would provide
the end-of-usable-tread indication long before the tread was worn
to its minimum acceptable depth because it does not take into
account the additional tread life that is added by utilizing the
secondary features.
[0030] In particular embodiments of the present invention, the wear
indicator extends radially from the back face of the tread band to
a predetermined minimum secondary feature depth such that the top
portion of the wear indicator lies below the bottom of the primary
features. In this manner, as the tread continues to wear past the
primary and into the secondary features, the wear indicator
provides the desired end-of-useful-tread indication as the
secondary features are worn to their minimum acceptable depth. In a
particular embodiment, the wear indicator may be molded into a
portion of the bottoms of the secondary grooves, preferably at the
same circumferential location so that as the wear indicators become
exposed, they form a wear bar laterally across the face of the
tread band. Alternatively, the wear bar may be molded into the
bottom of a cavity that opens onto the top surface of the tread
band.
[0031] Particular embodiments of the present invention further
include an access channel opening from the front face of the tread
band and extending radially to a top face of a wear indicator that
extends radially from the back of the tread band. If the wear
indicator is molded into a portion of a secondary feature, then
preferably the wear indicator is surrounded by barriers, thereby
forming a chamber surrounding the wear indicator. The walls that
separate the wear indicator from the secondary feature are
typically flashing.
[0032] The access channel provides access with a measurement device
to ascertain that the wear indicator is at the correct depth to
indicate the minimum tread depth when showing. Additionally, the
access channel provides a visual indication of the tread wear. The
observable presence of the access channel provides a visual
indication that the tire has not worn to its minimum acceptable
tread depth. After the access channel has been worn away through
normal tread wear during use of the tire, the wear indicator
becomes visible, thereby providing a visual indication as to
whether the tire has reached its end-of-useable tread
condition.
[0033] Although the access channel may typically be shaped as a
square, there is no limitation as to the acceptable shapes for the
access channel. For example, the access channel may be circular,
oval, rectangular, triangular, any other regular or irregular
polygon shape or combinations thereof. Furthermore, the access
channel may be, without limitation, between about 2 mm and 12 mm
wide or preferably, between about 4 mm and 6 mm wide.
[0034] Particular embodiments of the present invention further
include both new and retread tires. Such tires include a tire
carcass having a crown portion and a tread band as described above
that is bonded to the crown portion of the tire carcass. As known
to those having ordinary skill in the art, the tread band may be
either cured or uncured when first stitched to the crown portion of
the tire carcass. If cured, then the tread band is stitched to the
crown portion of the tire carcass with, for example, cushion gum
and then cured so that the cushion cum bonds the tread band
securely to the crown. If uncured, then the tread is cured after
being stitched to the crown.
[0035] FIGS. 2A-2B are cross sectional views of a tread band having
a wear indicator extending radially from the back face of the tread
band and molded into the secondary grooves and FIG. 2C is a top
view of a portion of the tread band having the wear indicator. FIG.
2A includes the tread band 20 having a set of primary grooves 13
that open onto the front face 24 of the tread band 20 and a set of
secondary grooves 21 that open onto the back face 12 of the tread
band 20. The wear indicator 22 is molded into a portion of the
bottoms of the secondary grooves 21 and the wear indicator 22
extends radially from the back face 12 of the tread band 20 to the
minimum groove depth m 26. An access channel 23 is open from the
front face 24 of the tread band 20 to the secondary grooves 21. The
access channel 23 provides access for a measuring device to measure
the depth of the wear indicator 22. The access channel 23 further
provides a visual indication that the tread depth has not reached
the minimum acceptable depth because as long as the open access
channel 23 is visible, the wear indicator 22 has not been
reached.
[0036] FIG. 2B is a cross sectional view of the tread band shown in
FIG. 2A after the band has been worn and the primary grooves 13
have nearly worn away. The bottoms of the secondary grooves 21 are
shown opening to the top face 24 of the tread band 20 to provide
useful tread to replace the worn primary grooves 13. The wear
indicator 22 becomes visible through the opening into the secondary
grooves 21 to a person inspecting the tire. It should also be noted
that at this point, the access channel 23 has worn away and is no
longer necessary since the wear indicator 22 is visible through the
bottom of the secondary grooves 21.
[0037] FIG. 2C is a top view of a portion of the tread band having
the wear indicator as shown in FIGS. 2A-2B. The wear indicator 22
is molded into the secondary groove 21 and barriers 27 are formed
within the secondary groove 21 to isolate the wear indicator 22
from the adjacent portions of the secondary groove 21. The barriers
27 may be flashing deposited within the secondary grooves during
the molding process or alternatively, may be a molded feature. The
barriers 27 prevent moisture and dirt from passing through the
access channel 23 into the secondary groove 21.
[0038] FIGS. 3A-3B are perspective views of a top and bottom mold
forms suitable for molding a tread band having a wear indicator
molded into the secondary grooves. It should be noted that the
solid portions on the interior of the mold will result in
rubber-free portions in the molded tread band while the void
portions of the interior of the mold will result in solid rubber
portions in the molded tread band.
[0039] The top mold form 30 shown in FIG. 3A provides the primary
groove form 31 and the access channel form 32 for molding the
primary grooves 13 and the access channels 23 as shown in FIG. 2A.
The top mold form 30 further provides the front face form 33 that
forms the front face 24 of the molded tread band.
[0040] The bottom mold form 40 shown in FIG. 3B provides the
secondary groove form 41 and the tread wear indicator form 42,
which fills with rubber during the molding process to form the
tread wear indicator 22, as shown in FIG. 2A. The access channel
form 32 of the top mold aligns with and fills the gap above the
tread wear indicator form 42 as shown in FIG. 3C. The distance
between the bottom of the access channel form 32 and the back face
form 43 is the distance m 26, which is the minimum allowable tread
depth as shown in FIG. 2A.
[0041] FIGS. 4A-4B are perspective and cross sectional views of a
tread band having a wear indicator molded into a cavity that is
open to the front face of the tread band. In this embodiment of the
present invention, a wear indicator 51 is molded within a cavity 52
that extends from the front face 54 of the tread band 50 to below
the bottom 53 of the primary grooves 13. As shown in FIG. 4B, the
top surface of the wear indicator 51 lies below the bottom surface
53 of the primary grooves 13.
[0042] FIG. 5 is a drawing of a perspective view of a portion of a
retread tire having a tread band in accordance with the present
invention. The portion of the retread tire 60 includes a tire
carcass 61 having a crown portion 64 to which the tread band 65 is
attached. The tread band 65 is attached to the crown portion 64
with cushion gum 62 as known to those having ordinary skill in the
art. The openings into the access channels 23 provide a visual
indication that the tire has not worn beyond its allowable minimum
tread depth.
[0043] The terms "comprising," "including," and "having," as used
in the claims and specification herein, shall be considered as
indicating an open group that may include other elements not
specified. The term "consisting essentially of," as used in the
claims and specification herein, shall be considered as indicating
a partially open group that may include other elements not
specified, so long as those other elements do not materially alter
the basic and novel characteristics of the claimed invention. The
terms "a," "an," and the singular forms of words shall be taken to
include the plural form of the same words, such that the terms mean
that one or more of something is provided. For example, the phrase
"a solution comprising a phosphorus-containing compound" should be
read to describe a solution having one or more
phosphorus-containing compounds. The terms "at least one" and "one
or more" are used interchangeably. The term "one" or "single" shall
be used to indicate that one and only one of something is intended.
Similarly, other specific integer values, such as "two," are used
when a specific number of things is intended. The terms
"preferably," "preferred," "prefer," "optionally," "may," and
similar terms are used to indicate that an item, condition or step
being referred to is an optional (not required) feature of the
invention.
[0044] It should be understood from the foregoing description that
various modifications and changes may be made in the preferred
embodiments of the present invention without departing from its
true spirit. The foregoing description is provided for the purpose
of illustration only and should not be construed in a limiting
sense. Only the language of the following claims should limit the
scope of this invention.
* * * * *