U.S. patent number RE30,518 [Application Number 06/016,834] was granted by the patent office on 1981-02-17 for pneumatic tire wear indicating tread pattern.
This patent grant is currently assigned to Dunlop Holdings Limited. Invention is credited to Tom French.
United States Patent |
RE30,518 |
French |
February 17, 1981 |
Pneumatic tire wear indicating tread pattern
Abstract
A pneumatic tire and moulding matrix therefore, the tire tread
incorporating a traction pattern which changes distinctively when
only a predetermined amount of tread rubber remains, thus warning
the tire user that his tire is approaching the legal or safe limit
and will soon have to be replaced or retreaded.
Inventors: |
French; Tom (Sutton Coldfield,
GB2) |
Assignee: |
Dunlop Holdings Limited
(Birmingham, GB2)
|
Family
ID: |
10319492 |
Appl.
No.: |
06/016,834 |
Filed: |
March 2, 1979 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
834714 |
Jun 19, 1969 |
03653422 |
Apr 4, 1972 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Jun 29, 1968 [GB] |
|
|
31199/68 |
|
Current U.S.
Class: |
152/209.1;
152/154.2; 152/209.21 |
Current CPC
Class: |
B60C
11/00 (20130101); B60C 11/24 (20130101); B29C
33/42 (20130101); B29C 2037/80 (20130101); B29D
2030/0612 (20130101); Y10T 152/10027 (20150115); B29D
2030/0613 (20130101) |
Current International
Class: |
B60C
11/24 (20060101); B60C 11/00 (20060101); B29C
33/42 (20060101); B60C 011/00 () |
Field of
Search: |
;152/29R,29D,19NW,29NT,33A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
631215 |
|
May 1936 |
|
DE2 |
|
1203290 |
|
Jul 1959 |
|
FR |
|
1294744 |
|
Apr 1962 |
|
FR |
|
1061564 |
|
Mar 1967 |
|
GB |
|
Primary Examiner: Ball; Michael W.
Attorney, Agent or Firm: Stevens, Davis, Miller &
Mosher
Claims
Having now described my invention what I claim is: .[.1. A
pneumatic tire comprising a tread provided with at least one main
drainage groove and a first, radially outer, and a second, radially
inner, pattern each comprising at least one tread element selected
from the group consisting of slots, sipes, grooves, incisions and
the like, the first pattern changing to the second pattern at a
level situated radially inwardly of and substantially parallel to
the tread ground contacting surface of the tire, said level being a
predetermined amount less than the depth of the main drainage
groove, the second pattern being distinctively different from the
first and being located immediately radially inwardly of and in
radial alignment with said first pattern..]. .[.2. A pneumatic tire
according to claim 1 wherein the second pattern is substantially
undetectable from the exterior of the tire until at least a portion
of the tread equal in depth to the first pattern has been worn
away..]. .[.3. A pneumatic tire according to claim 1 wherein the
second pattern is in the form of at least one warning word..].
.[.4. A pneumatic tire according to claim 1 wherein the second
pattern is in the form of at least one warning word repeated around
the tire circumference..]. .[.5. A pneumatic tire according to
claim 1 wherein the second pattern is in the form of at least one
warning word repeated across the tire tread width..]. .[.6. A
pneumatic tire according to claim 1 wherein the second pattern
comprises a plurality of chambers..]. .[.7. A pneumatic tire
according to claim 1 wherein the second pattern is at least
partially filled with a material distinctively different from the
tread rubber..]. .[.8. A pneumatic tire according to claim 7
wherein the said material comprises a rubber or plastics material
of a color different from the tread rubber..]. .[.9. A pneumatic
tire according to claim 7 wherein said material has an abrasion
resistance different from that of the tread rubber..]. .[.10. A
pneumatic tire according to claim 1 wherein the second pattern
changes to at least one subsequent pattern radially-inwardly
thereof..]. .[.11. A pneumatic tire copmrising a tread provided
with at least one main drainage groove and a first, radially outer
pattern of no particular visual significance and a second, radially
inner, pattern having visual significance, each pattern comprising
at least one tread element selected from the group conisting of
slots, sipes, grooves, incisions and the like, the first pattern
changing to the secnd pattern at a level situated radially inwardly
of and substantially parallel to the tread ground-contacting
surface of the tire, said level being a predetermined amount less
than the depth of the main drainage groove, the second pattern
having a lesser number of tread elements than the first pattern
with all of the second pattern tread elements being in radial
alignment with corresponding elements of the first pattern and
located immediately radially inwardly of similar tread elements in
the first pattern so that when the first pattern
is worn away the second visually significant pattern is exposed..].
12. A pneumatic tire comprising a tread provided with at least one
main drainage groove and a first, radially outer, and a second,
radially inner, pattern each comprising at least one tread element
selected from the group consisting of slots, sipes, grooves,
incisions and the like, the first pattern changing to the second
pattern at a level situated radially inwardly of and substantially
parallel to the tread ground contacting surface of the tire, said
level being a predetermined amount less than the depth of the main
drainage groove, the second pattern being distinctively different
from the first, being located immediately radially inwardly of and
in radial alignment with said first pattern, and being in the form
of
at least one warning word. 13. A pneumatic tire comprising a tread
provided with at least one main drainage groove and a first,
radially outer, and a second, radially inner, pattern each
comprising at least one tread element selected from the group
consisting of slots, sipes, grooves, incisions and the like, the
first pattern changing to the second pattern at a level situated
radially inwardly of and substantially parallel to the tread ground
contacting surface of the tire, said level being a predetermined
amount less than the depth of the main drainage groove, the second
pattern being distinctively different from the first, being located
immediately radially inwardly of and in radial alignment with said
first pattern, and being in the form of at least one warning word
repeated
around the tire circumference. 14. A pneumatic tire comprising a
tread provided with at least one main drainage groove and a first,
radially outer, and a second, radially inner, pattern each
comprising at least one tread element selected from the group
consisting of slots, sipes, grooves, incisions and the like, the
first pattern changing to the second pattern at a level situated
radially inwardly of and substantially parallel to the tread ground
contacting surface of the tire, said level being a predetermined
amount less than the depth of the main drainage groove, the second
pattern being distinctively different from the first, being located
immediately radially inwardly of and in radial alignment with said
first pattern, and being in the form of at least one warning word
repeated across the tire tread width.
Description
This invention relates to pneumatic tires.
According to the invention a pneumatic tire comprises a tread
provided with at least one main drainage groove and a first,
radially outer, and a second, radially inner, pattern each
comprising one or more radially-disposed slots, sipes, grooves,
incisions, holes or the like, the first pattern changing to the
second pattern at a level situated radially inwardly of and
substantially parallel to the tread ground-contacting surface of
the tire, said level being a predetermined amount less than the
depth of the main drainage groove, the second pattern being
distinctively different from the first and comprising a wholly
radial continuation of part only of said first pattern.
Preferably the second pattern is substantially undetectable from
the exterior of the tire until at least a portion of the tread
equal in depth to the first pattern has been worn away.
Preferably the said predetermined amount is somewhat greater e.g. 1
mm. greater, than the minimum tread pattern depth allowed under
local laws or regulations, e.g. 1 mm. or 2 mm., so that adequate
prior warning is given to a tire user that the legal limit of wear
is approaching.
The second pattern is preferably so distinctively different from
the first pattern that the tire user's mind is directly associated
with the fact that in due time the tire will become unsafe or
illegal if it is continued to be used and that it should be
changed. For example, the second pattern may be in the form of a
warning word or several warning words repeated around the tire
circumference and/or across part at least of the tire tread
width.
The invention also includes a pneumatic tire as described in any of
the preceding paragraphs in which said second pattern changes to a
third pattern, and perhaps to subsequent patterns, below the tread
ground-contacting surface.
All of the patterns previously referred to are preferably formed by
moulding, but any other suitable method e.g. cutting or drilling,
may be used.
According to the invention also a tire moulding matrix comprises a
plurality of projections on the tread moulding surface of the
matrix the projections being for moulding a first, radially outer,
and a second, radially inner, pattern in the tread of the tire
incorporating at least one main drainage groove, the configuration
of at least part of at least one of the said projections changing
distinctively at a predetermined level which is substantially
parallel to the surface of the matrix for moulding the tread
ground-contacting surface of the tire and which is situated at a
depth which is a predetermined amount less than the depth of the
projection for moulding the main drainage groove, the said second
pattern comprising a wholly radial extension of part only of said
first pattern.
Embodiments of the invention will now be described by way of
example with reference to the accompanying drawings of which:
FIG. 1 shows a fragmentary perspective view of a tread moulding
matrix according to a first embodiment of the invention.
FIG. 2 shows a fragmentary perspective view of a tread moulding
matrix according to a second embodiment of the invention.
FIG. 3 shows a plan view of part of the first pattern of the tread
of a tire according to the second embodiment.
FIG. 4 shows a plan view of part of the second pattern of the tread
of a tire according to the second embodiment.
A first embodiment comprises a pneumatic car tire the tread pattern
of which is moulded by a conventional method using a mould
comprising a matrix 1 (part of which is shown in FIG. 1) which is
provided with a plurality of ribs 2 and pins 3 and 4. The ribs, 8
mm. high and of zig-zag configuration extend generally
circumferentially of the mould and form generally circumferential
grooves, each 8 mm. deep, in the tire tread. The pins, some
(indicated by the reference numeral 3) of which are 6 mm. high and
the remainder (indicated by the reference numeral 4) 8 mm. high,
form a pattern of holes in the tire tread ribs between the
grooves.
The construction of the mould matrix is such that the pins and ribs
thereof can be readily withdrawn in a radial direction from the
tread of the moulded tire. When 6 mm. i.e. the first pattern, of
tread has been worn away in use of the tire that part of the tread
pattern formed by the 6 mm. holes disappears leaving only that
portion formed by the 8 mm. deep holes, i.e. the second pattern and
the grooves. The 8 mm. deep holes form the word STOP repeated round
the tire circumference which is not readily apparent in the unworn
state of the tire, (being camouflaged by the 6 mm. deep holes) and
which warns the motorist that there is only 2 mm. of tread rubber
remaining in that area of the tread surface i.e. his tire will soon
become unsafe and probably illegal and that he should replace the
tire before further wear may render it unsafe to use. Words other
than STOP could be used either additionally or alternatively.
In a modified form (not illustrated) of the first embodiment some
or all of the pins are enlarged at their extremities so that a
bulbous chamber is formed at the base of some or all of the holes
formed in the tire tread. Preferably only the 8 mm. pins are
enlarged 2 mm. from their ends so that a chamber 2 mm. deep is
formed in the tire. Thus when 6 mm. of tread has been worn away a
more distinctive pattern appears to warn the motorist. In addition
the drainage of a tire tread provided with bulbous chambers is
better compared with that of a tire not so provided, especially at
the time of the tire's life when only 2 mm. of tread remains.
A second embodiment (as shown in FIGS. 2, 3 and 4) of the invention
comprises a tire (see FIG. 3) having a tread provided with a
plurality of grooves 5 and slots 6 some of the slots or part of
each slot opening out into a substantially cylindrical chamber
situated radially inwardly of the tread surface with its axis
parallel thereto. This tire is moulded by means of a moulding
matrix 7 (see FIG. 2) provided with ribs 2 (to form grooves) and
knife blades 8 (to form the slots) some of which or part of each of
which have joined thereto, e.g. by welding, or have integrally
formed therewith a cylindrical portion 9 e.g. a wire or rod, of
diameter greater than the thickness of the knife blades. The
cylindrical portion 9 wire or rod is bent into the form of a letter
in a plane parallel to that surface 10 of the matrix for moulding
the ground-contacting surface of the tread, while the knife blade
to which it is joined has a similar form with one or more
additional features (for example that part of a blade shown as 11
in FIG. 2) so as effectively to disguise the identity of the
letter. Several of these blades with the wire letters attached are
incorporated in the tire moulding matrix, the several letters
forming the mirror image of the warning word STOP. The knife blades
thus form the first pattern in the tread while the wires or rods
form the second pattern.
In use of a tire moulded in this way when most of the tread has
been worn away the chambers appear (as shown in FIG. 4) and because
they are wider than the slots and in the form of a warning word
should be sufficiently distinctive to cause the motorist to be
conscious of the need soon to renew the tire.
In a first modification (not shown) of this second embodiment, the
tire tread is provided with a pattern of slots some of which or
part of each of which do not open out into chambers but merely are
constructed to be deeper than the remainder of each slot or slots.
This pattern is moulded using a matrix incorporating knife blades
some of which or part of each of which are deeper than the
remainder of each blade or the blades. The difference between the
two depths of blade or blades can be 2 or 3 mm. i.e. equal to the
local minimum allowable tread depth plus an amount to provide a
warning of the need to replace the tire without undue delay.
In a second modification (not shown) of the second embodiment the
slots and chambers are moulded by means of a matrix provided with
knife blades and to which are weakly attached e.g. by means of a
weak adhesive or thin textile fibers the aforementioned wire
letters. In addition these letters are all wired to each other to
form a ring which extends around the internal circumference of the
tire mould on the radially inner extremities of the blades.
After moulding and on removal of the moulding matrix from the tire
the ring of letters remains embedded in the tire tread, the textile
fibers or the adhesive bond having broken during said removal. The
ring of letters is removed in a separate operation.
It is an advantage of this modification that the second pattern
i.e. the letters may be changed without changing the complete mould
matrix.
In a third modification (not shown) of the second embodiment the
wires or rods are replaced by U or V channels in which a thin strip
of material may be retained during moulding but leaves the channel
on removal of the tire from the mould. Thus the moulding operation
effectively embeds this strip into the tread rubber at the base of
the slot or slots.
The material inserted into the chambers should be such as to make
the appearance of the second pattern, when the tread has worn away
sufficiently to expose it, even more distinctive. For example,
vulcanized or unvulcanized rubber or plastics material may be
inserted of a color different from the remainder of the tread
rubber. Thus, for example, when sufficient tread has worn away a
colored word appears in the tread to warn the motorist of the small
amount of tread rubber remaining. Other examples of materials which
may be inserted are materials which generate a noise on becoming
uncovered when the tread is sufficiently worn, textile cords, or
rubber of greater or lesser abrasion resistance than the tread
rubber. In this last example the words of rubber will stand proud
of or recessed below, respectively, the tread surface. It can be
arranged either that the inserted material remains to form part of
the wearing surface of the tread or becomes detached under the
influence of centrifugal force to leave remaining a recognisable
impression in the tread rubber.
* * * * *