Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to the art of applylng
rubber treads to tires, and more particularly, to methocls of
re-treading used pneumatic tire bodies with a full circle
camelback or tread of new rubber.
Two systems are often used for ~etreading tires.
- One system uses a metal mold to apply a vulcanizable rubber
tread band, frequently called a camelback regardless of
whether the outer surface -thereof is curved or straight in
cross-section, to a carcass or a tire body while simultane-
ously embossing and vulcanizing it. The other system be-
gins with a previously embossed and vulcanized tread band
which is bonded to the carcass or tire body in a heated `
pressure vessel.
- The first of these systems uses a rigid, toroidal
metal mold or cavity which opens to receive the tire body and
then closes to process the retread and design. If the tire
body is very carefully placed in a perfect position within
the mold, there are no problems. E~owever, if the tire `~
.. : .
- body is not properly placed, the retread will be asymmetrical.
Accordingly, the existing system for embossing and vulcanizing
~ retread camelbacks in rigid metal molds entails a risk of
- deformation of the tire. ~
; After the mold is closed, the tire body usually is ;
subjected to internal pressure during vulcanization. If
the internal size of the mold is the same as the unstretche~
- size of the final tire there usually is little stretching of
:-
the tire body, but many different molds are required to per-
mit retreading of the many different tire sizes. The in-
- ternal size of the mold can be such that it may be used for
a few different tire body diameters, thereby reducing the
- 2 -
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7~
number of molds required, but for smaller body diameters the
material of -the tire is exposed to a substantial stress
through pressure and extension during vulcanization in the
rigid mold. Furthermore, the newer radial tires are sub-
stantially inextensible in the ~adial direction and, there-
fore, a different mold for each tire size is almost always
necessary to provide the desired retreading. Accordingly,
. .
when using this system, it is necessary to have a great num~
- ber of molds to accommodate different tire diameters.
: . .
The second of the systems mentioned above, in a
first step, uses hydraulic presses with flat metallic molds
to vulcanize the tread band and then in a second step uses a
. . I .
heated pressure vessel to bond, by means of a vulcanizable
rubber interlayer or an adhesive, the prevulcanized tread
band to the tire body. This system eliminates the deforma~
- . .
tion of the tire' however, it also greatly increases the
~- working operations~ The tread band has to be prevulcanized
. ~. .
and embossed in special vulcanizers. Thereafter, the en-
gagement surfaces of the tire body and the tread band must
be suitably cleaned, roughened, and coated with a rubber
~i adhesive and a vulcanizable rubber interlayer which bonds
.
' the tread band to the tire body. This method also has the ~;
,:-
disadvantage that the retreaded tires have different outside
.~ diameters. The thickness of the tread band is the same,
hut the initial tire body diameter varies, dependent on make
, and the number of ply or cord layers~ If two tires with
different diameters are used on the same vehicle, treads tend
to wear unequally and rapidly~
.... - ~ , ~
~ Accordingly, an ob3ect of the present invention is ~
r ,','~ '
to provide new and improved tire retreading methods.
~ :
Another object is to eliminate expensive and rigid
,.
- 3 -
,.,: .
~ `~
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molds heretofore used for retreading tires.
Yet ano-ther object is to save costs by eliminatiny
many operations which ~ere heretofore necessary for retread-
ing tires with prevulcanized tread bands such as the use of
presses, grinding and trimming machines.
A further object is to p;rovide an inexpensive re-
silient mold for retreading tires which may be used for re-
treading tire bodies which have different sizes within a re-
latively wide range and which do not require radial extension
- 10 of the bodies during retreading.
In ~eeping with an aspect of the invention, these
and other objects are accomplished by providing an elastic
mold which may be snapped over an unvulcanized camelback
- tire band previously attached to a tire body. The elastic
band may be centered on the tire body while it is turning.
Then, the entixe unit (elastic mold, camelback and tire
body) may be heat treated to vulcanize the camelback and
emboss the tread design thereon.
~ccording to a broad aspect of the present invention, `
there is provided a method of treading tires comprising the ;
steps of fitting a vulcanizable cameLback tread band over a
tire body, expanding over said band and tire body a resilient
matrix ring mold having an internal embossing negative pattern
which applies a tread design to said band, said ring mold
having an inner diameter which is smaller than the diameter of
:
the tire with said tread band over the tire, when the mold is `
in an unexpanded condition, allowing the expanded matrix ring
- mold to contract, responsive to its own inherent tension, over
the tread band on the tire body, and heating the matrix ring` 30 mold, tire, and tread band to a temperature which converts the
tread band into a plastic form, embosses the tread design from
the matrix ring mold onto the tread band, and vulcanizes the
~ - 4 -
`' '
7 ~
tread band onto the tire body.
According to a further broad aspect of the presentinvention, there is provided a resil:ient, stretchable mold for
- embossing a pattern in unvulcanized rubber on the peripheral ~:
surface of a supporting body, salcl mold having the shape of a
generally circular, continuous band having an inner face ex-
tending around and facing the axis o~ said band, said band
. having a pair of lips of at least a prede-termined radial dimen--
sion extending from said inner face toward said axis and having
a plurality of spaced, pattern forming projections of a radial .
-. dimension less than said predetermined radial dimension on said
. inner face intermediate said lips and extending toward said
.. axis, and wherein a plurality of said projections are arranged
-. in a plurality of circumferentially extending, axially spaced
r rows, wherein said inner face between said rows and in cross- .
section being substantially flat and wherein the radial thick- :
ness of said band between said rows is greater than the thick-
. ness of said band radially outward of said rows.
. Reference may be made to the following specification . . ~
and the accompanying drawings describing and showing pre~erred ~-
.: embodiments of the invention, wherein~
. Fig. 1 is a transverse, axial, cross-sectional ~ ~:
. ,:- ',
.. view of an elastic mold constructed according to the inven-
tion and showing the mold as being stretched around a tire -
-~- body with the tread rubber thereon, .
;-. Fig. 2 is a cross-sectional view similar to Fig. 1
showing the elastic mold in its contracted molding position, .
..,.
.. Fig. 3 is a schematic, axial view of the stretched
. elastic mold and the tire body shown in Fig. 1
.. , ~ .
:, ~` ''
~:: - 4a -
., ~ .
~ . .
' Fig. 4 is a view similar to Fig. 3 of the con-
tracted elastic mold and the tire body shown in Fig. 2,
Fig. 5 is a perspective view of the elastic mold;
Fig. 6 is a cross-sectional view similar to Fig. 2 ;~
showing the elastic mold and tire body with a superimposed
rubber diaphragm,
,r Fig. 7 is a fragmentary, cross-sectional view,
similar to Fig. 6, of a modified embodiment of the invention
e in which the mold contains re-enforcing wires and in which
an internal bladder is used during vulcanizing,
i - ,. . .
Fig. 8 is a fragmentary, cross-sectional view, ;
~- similar to Fig. 7, of a modified embodiment of the invention
in which a sealing ring and a tube-like bladder are used
.
during vulcanizing; and
3'- Fig. 9 is a fragmentary, cross-sectional view,
similar to Fig. 7, of a modified embodiment of the invention
in which the air removal holes in the mold are formed by
hollow metal pins, one of the mold lips has rib forming re-
cesses, and a centering groove is provided.
In accordance with a preferred embodiment of the
ii:. .
invention, as illustrated in Figs. 1-4, a tire body 2 which ;~
is to be retreaded is first treaded on its radially out-
ward surface, in a conventional manner, such as by grinding, ~-
, . . .
etc., to provide a tread rubber receiving surface. A tread
layer on band 1 of unvulcanized rubber, without the tread
pattern thereon, is then placed around the tire body 2 in
contact with such prepared surface, such as by winding one
~;,' ~ , . ~ .
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or more ribbons of such rubber therearouncl, forming a band
o~ rubber of the proper size and placiny it therearound.
The thickness of the band 1 is selected rela~ive to the
diameter of the tire body 2 so tha-t the outside diameter Oe
the retreaded tire will be uniform and standard.
- Thereafter, an elas-tic mold or embossing ring 9
having tread pattern projections 10 on its inner side or
~- face 3 and treated on its inner face 3 with an anti-adhesive
agent, is stretched radially, as indicated by the arrows 12,
and placed around the tire body 2 and treadbandl as shown
in Fig. 1 and is then released permitting the mold 9 to
contract, as indicated by the arrows 13, and assume the posi- -
tion shown in Fig. 2, i.e., with the projections 10 engaging
the tread ban 1 and usually, penetrating into the band 1.
~ The mold or ring 9 must be sufficiently resilient in an out-
- wardly radial direction to permit it to be stretched around
the treadbandl, and it must withstand the vulcanizing
heat subsequently applied without deforming. Therefore, a
suitable high temperature elastic rubber or similar material
is used to make the ring mold 9. In one embodiment actually
used, the vulcanizing temperature of the rubber of the band
1 was about 100C. and the rubber of the mold or ring 9
vulcanized at about 150 -180C., and was otherwise resistant
~ to heat.
`- The projections 10 on the inner face 3 of the
.
` mold 9 form an embossing tread pattern, that is, they form
,~ grooves, etc. in the tread band 1 and the pattern may be
any desired pattern. The mold 9 also has a pair of radially
inwardly extending lips 9" and 9"' at axially opposite edges
6 and 7 thereof for purposes hereinafter described. When -
,; , . .
s expanded or stretched (Figs. 1 and 3), the smallest inner
~ - 6 -
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'. : ' ' :
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'
s~t~
diameter of the mold 9 is larger than the ou-ter diameter of
i the vulcanizable tread band 1 on the tire body 2. On its
`- outer slde, equatorial to the -tread, the mold 9 has a full- ;
~ circle projection bead or circumferential fin 11, which
"~ serves as a centering index when the ring is placed over the
tire body 2 and tread band 1, just before the vulcanization
,,
step. Preferably, the tire is rotated, on any suitable
supporting mechanism (not shown) while the bead or fin 11
;~ is inspected or measured for trueness of its position. Al-
.~ .- 10 though the unvulcanized rubber of the tread band 1 may be
relatively stiff, it is formable and during the centering
of the mold 9 with the aid of the fin 11, the mold 9 con-
~: tinues to contract, responsive to its own inherent tension.
'~ In any event, it is contracted to the extent permitted by
,....................................................................... .
~" the tread band 1 by the time that the centering steps are com-
pleted. Thus, the mold 9 presses radially inwardly, in the
direction of the arrows 13, against the unvulcanized tread
band 1 and the tire body 2. ~-
The unit comprising the tire body 2, the rubber -
camelback layer 1 and the ring mold 9 is thereafter placed
~; in a heated tank, using either gas or liquid as a heat
;,; transfer medium. In the hereinbefore cited example of camel-
.: :
,;- back rubber which vulcanizes at a low temperature, such as
100C., the heated tank temperature will usually be about
100C.
~, . .. .
While so heated, the rubber layer 1 is changed
rom a low plastic condition into a high plastic condition~
In this highly plastic state during the vulcanization pro-
cess, the inherent tension of the ring mold 9 causes it to
press against the layer 1 and transfers and embosses the
profile of its tread pattern projections 10 into the rubber
:,
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i
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1~ 7&i~
layer 1. The elastic pressure of the ring mold 9 is directed
radially toward the tread area of the enclosed tire body to
accomplish the corresponding embossing process. Preferably, ~ -
the plastic condition of the rubber camelback layer 1 is main- `
tained, as long as possible, through a slow temperature in-
crease of suitably selected rubber mixtures, so that the em-
bossing pressure exerted by the ring mold 9 will not have to
be high, and so that the profiles of the projections 10 on
the inner face of the ring mold which are deformable under
pressure, are not deformed. Also, suitable holes, similar to
those described hereinafter, may be formed in the ring mold 9
to enable an escape of air entrapped between the inner face
of the mold 9 and the tlre body 2.
The embossing part of the retread operation is con-
` cluded during the early part of the vulcanization process.
Later, because of the vulcanization, the rubber layer changes
from its plastic condition to a stable elastic condition.
After the completion of the vulcanization process, the pattern
of the tread has become stable and finished. The ring mold 9
is then stretched and removed from the tire, which is now re-
treaded, and such ring mold 9 is ready for re-use in the re-
treading of another tire body.
~ Although ~a rubber, or other elastomer, having a ^~
,- vulcanizing temperature the same as or only slightly higher
than that of the rubber of the tread band 1 could be used
for the mold 9, and, in fact, the rubber could be the same
,, .-. ,
~ forlboth, the mold 9 tends to lose its elasticity after a ~ ~
,; "
~: few uses thereof if it has a vulcanizing temperature close
!i to that of the band 1. Accordingly, it is preferable to use
i 30 a rubber for the mold 9 which has a vulcanizing temperature
(degrees C) at least 20% higher than the w lcanizing
- - 8 -
~ ~ .
,,-
temperature of the rubber used for the band 1, thereby pro-
viding uniform characteristics ~or each use thereof, better
resistance to carburizing and hence, degeneration, and longer
life. There are, of course, many elastomers or rubbers known ;
to those skilled in the art, and the selecting of a suitable
elastomer or rubber for the mold 9 when the rubber for the
band 1 has been determined is readily accomplished by those
skilled in the art. For example, when the rubber of the band
1 is o-f the type generally used in the art, namely, natural
or synthetic rubber, the mold 9 may be made from butyl, chloro- `;~
butyl or silicone rubber~
The preferred characteristics for the mold 9 may be
.i ~.
generally stated as follows:
(1) The elastomer from which it i3 made
has a vulcanization temperature which is at least
20% higher than that of the rubber for the band 1 ~`~
and which is relatively constant,
(2) The hardness and stiffness of the pro-
` jections 10 and the elasticity of the mold 9 is '' ~ . ' ,
2C such as to permit the embossing of small or thin
tread grooves,
; (3) The heat conductivity of the elastomer
should be relatively high to aid in distributing
- the vulcanizing heat and known types of additives
may be used to increase the heat conductivity thereof,
(4) The stretchability and resiliency should
be such that it can be stretched from a normal
diameter, approximately the outer diameter of the
tire body 2, to a diameter greater than the outer
- 30 diameter of the unvulcanized tread band 1 on the
tire body 2, and thereafter, contract to such normal
_ 9 _
:
. .
....
- : .: . -, : : :. : ,, : ,
-. :,..... : . ,, ~ : .: - ' .. ;
diameter without damage, such as tears or cracks,
and such stretching and contracting should be re-
peatable many -times,
(5) If the tread pattern embossing pressure
r
is to be supplied only by the inherent contracting
forces of the mold 9, it should be relatively thick
in cross-section ~see Fig. 1), whereas with the ap-
plication of external pressure, as described herein-
after, the cross-section may be relatively thin
(see Fig. 6),
(6) The normal diameter of the mold 9 should
be such that the inside thereof is completely filled
by the rubber of the band 1 and the projections 10
are fully seated before the mold 9 is fully contracted
and hence, while it is still applying pressure to
the band 1. However, the normal diameter should not
be small enough to apply a pressure which forces ~
rubber of the band 1 from under the mold 9, at the ~ -
lips 9" and 9"', during the wlcanization step,
s-~ 20 ~7) If it is desired to use the mold 9 for
making retreaded tires of different diameters, the
stretchability should be such as to permit the mold
9 to be stretched over the largest diameter tire body ~ ;
and tread band to be processed and yet should have a ~ ~
.
~- normal diameter and hence, resilience, as set forth
in Paragraph (6) hereinbefore.
~r~r~ With respect to the hardness and stiffness of the
projections 10 mentioned in Paragraph (2) hereinbefore, it
~-~ is preferred khat the mold 9 be unitary and of the same
` 30 material throughout, in order to simpliy its manufacture
and reduce its cost. However, if desired, the mold 9 can be
~' - 10 - ~,
~" ~, ~
~ 3
made of dif~erent materials at different parts as long as the
desired stretchability and resiliency is retained. For example,
the projections 10, or some of them, may be circumferentially
discontinuous and may be formed of a relative stiff and hard
rubber or may be metal inserts in the rubber body of the mold 9.
It will be observed from the drawings that the axially
opposite edges 6 and 7 of the mold 9 have a pair of radially
inwardly extending, circumferentially continuous, lips 9" and
9"',which extend from the surface 3 by a distance greater than
` 10 the radial dimension of the projections 10. As mentioned here-
inbefore, the unvulcanized rubber tread band 1 becomes rela-
tively soft and plastic during the vulcanizing step, and the
main purpose of the lips 9" and 9"' is to confine the rubber
~ of the band 1 at its sides during such vulcanizing step. The
- lips 9" and 9"' also aid in centering the mold 9 wi-th respect
to the tire body 2, the lips 9" and 9"' having a radial dimen-
sion such that they engage the tire body 2 at least when the
mold 9 has fully contracted. Preferably, the radial dimension
of the lips 9" and 9"' from the surface 3 is slightly greater
than the radial dimension of the projections 10 plus the radial
dimension of the band 1 so that the lips 9" and 9"' engage
- the tire body before the mold is fully contracted, and the ~-
inner faces 4 and 5 thereof are divergent, as shown, ~o as
~ to increase the pressure of the lips 9" and 9"' against the
-~ tire body 2 as the mold 9 contracts and so as to provide ;
tapered sides for the band 1. Preferably, also, the minimum
distance between the lips 9" and 9"', i.e., the points of
inter~section thereof with the inner face 3, is less than the
width of the prepared surface of the tire body 2 to which the
band 1 is to be applied and radially innermost portions of -
i the faces 4 and 5 are spaced apart by a distance greater -than
-- 11 --
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7~
such width to assist in centering of the mold 9 with respectto the tire body 2. Pre~erably, the lips 9" and 9"' are cir-
cumferentially continuous, but, if desired, each lip may be
formed by a plurality of circumferential segments which are
closely spaced, contacting or overlapping at the segment ends
when the mold is in its contracted state. Although the inner
faces 4 and 5 have been shown as smooth, they may have tread
pattern projections thereon. Also, although it is preferred
that the lips 9" and 9"' be integral with the mold 9, the lips
9" and 9"' may be separate rings of an inner diameter which
will cause them 'co engage the side walls of the tire body 2
and of an outer diameter which will cause them to engage the
body of the mold 9 when it is fully contracted but without pre-
venting such contraction.
Accordingly, the preferred embodiment of the mold 9
of the invention is made of a resilient and stretchable elas-
i~ tomeric material and is in the shape of a generally circular,
continuous band having an inner face 3 extending around and
facing the axis of the band and a pair of axially opposite
. '~
edges 6 and 7. The band has integral therewith a pair of sub-
~stantially circumferentially continuous axially spaced lips -
9" and 9"' at the edges 6 and 7 and extending from said face 3
toward said axis and has a plurality of spaced tread pattern
projections 10 on said inner face 3 intermediate said lips ~ -
~ 9" and 9"' and extending toward said axis. When the mold 9
3- is unstretched, the inner diameters of the face 3 and the pro-
jections 10 are less than the outer diameter of the tread
kand land the inner diameter of the lips 9" and 9"' is less
than the inner diameter of said tread band 1. The projections
10 have a radial dimension from the face 3 less than the
~ radial dimension of the tread band 1, and the mold 9 is
5.-~ stretchable to a size such that the inner diameter of at least
- 12 -
~: :
;3'7t~
one of the lips 9" and 9"', and hence, of the projections 10,
is at least equal to the outer diameter of the tread band 1
In one method of making the ring mold 9, a new or
unused retread tire can be used as a form. First, a layer o~
any suitable high temperature, vulcanizable rubber of the
desired thickness is placed over the patterned tread surface
of the new or unused tire form, which preferably is pretreated
with an anti-adhesive agent. Thereafter, this layer, while
~ :.
-~ on the form, is vulcanized under both pressure and suitable
high temperature. Thus, the resilient rubber layer is inter~
;, ,.
nally embossed with a negative contour of the tread pattern ;~
on the tire which is used as a form and may be used as the mold
. :
9 The best results of creating said negative contour are
~- obtained when the tire with the unvulcanized rubber layer
i:-
~ thereon is inserted into a flexible tubular rubber envelope
: ~ :
~ which covers the tire on its entire surface. The air from the
,
~ open space between the tire body, rubber layer and tubular
: ' .
i envelope is evacuated by suction and the assembly is exposed
to heat and pressure in a ~hamber. Preferably, a tubular
, 20- envelope as is described in United States Patent ~o. 2,966,936 ~
is used for manufacturing the ring mold 9. Other methods of ~ -
using envelopes as known from the art of retreading may be
,~ utilized as well.
; .
Any air entrapped between the rubber layer and the ;
~ form tire is evacuated through radially extending holes which
,~ :
~ are made in the body of the tire form at the deepest parts of
i -:: ..
~- the tread pattern. These holes are similar to the holes 15
~ shown in Fig. 6 except that they extend through the body of
;- the tire form instead of through the mold 9'~
When required, the embossing pressure of the ring
mold 9 may be augmented by any suitable means for applying
~; - 13 -
~,,;. , .
" ~:
' :' :
additional pressures, which are directed radially against
the mold 9.
Preferably, pressure of a fluid or gaseous vulcan-
izing medium is used in connection with a superimposed rubber
diaphragm to apply an auxiliary embossing pressure to the
assembly, Fig. 6 shows how this method is carried out in
practice. The tire body 2 with an unvulcanized rubber band
or layer 1 and matrix ring or ring mold 9 7 iS covered with a
resilient rubber diaphragm 14. This diaphragm 14 also
covers, with sealing, a surface portion of the tire body 2
which extends beyond the lips 9" and 9"' of the ring mold 9'.
The ring mold 9' is provided with radially extending
holes 15 and the rubber diaphragm 14 is provided with a suc-
tion valve 16. By means of a suction pump (not shown),
connected to this valve 16, entrapped air can be evacuated
from the spaces between the inner side of the ring mold 9'
and the outer side of the tread band 1 and between the outer
side of the ring mold 9' and the inner side of the rubber
diaphragm 14. Those surfaces of the ring mold 9', which are
directed radially outwards, can be roughened or suitably pat-
- terned to allow the passage of air from the holes 15 to the
suction valve 16.
- In order to facilitate the application of the -
ring mold 9' and the rubber diaphragm 14 onto -the tire body 2
provided with the tread band 1 and to have the first two ele-
ments positioned in controlled relation to each other, they
are preferably bonded together at the lateral edges 18 and 19 `
of the ring mold 9'. The rubber diaphragm 14 thereby will
-i accompany the ring mold 9' when this is expanded and contracted.
In order to assist, in this case, in the centering
of the matrix pattern projections 10 in relation to the tire
- 14 - ;-
,
~0~;~7~
body 2, the rubber diaphragm 14 and not, as before, the ring
` mold 9, is provided with a full-circle projection bead or
, circumferential fin 17.
, The entire assembly including the tire body 2 with
the tread band 1, the ring mold 9' and the rubber diaphragm
14 is introduced into a conventional pressure vessel (not
shown~, to which a heated fluid or gaseous vulcanizing medium
is then supplied under proper pressure, thereby applying pres-
sure to the rubber diaphragm 14 and thus, onto the ring mold :~
9~, such pressure being in addition to the contracting forces
~t of the mold 9'. During this vulcanizing process, the pressure
iS increased slowly.
In order to achieve a true print of the pattern of
projections 10 on the rubber band or layer 1, when using such
~ an additional pressure, the ring mold 9' should be designed as ~;
,~- is shown in Fig. 6. As shown therein, the thickness of the
~ ring mold 9', seen transversely, varies such that it is largest~
in the middle between two neighboring projections 10 of the
pattern and is decreased from the middle in both directions
towards these projections 10. Such a shape eliminates the
~ risks that the shape of the tread band 1 of the vulcanized
; tire will be concave between these two projections, the addi-
- tional thickness preventing bulging of the mold 9' intermediate
. ........................................................................ .
:~ the rows of projections 10. Thus, through the design mentioned
hereinbefore, the resistance to bending will be the largest in `
the middle between the rows of projections 10, where the lar-
gest bending moment is generated by the additional pressure. -~
*-` The bending of the mold 9' between the rows of projections 10
` thereby will be minimized, which is essential for a true tread
print.
When using an additional pressure as is described in
connection with Fig. 6, it is possible to dimansion the ring
~- - 15 -
:~ '.. :
~-" ~:
7~ 9
mold 9' to be -thinner, as it is not necessary for the ring
- mold 9' to have such a large inherent tension. The air en-
trapped between the tire band 1 and the ring mold 9' is
evacuated to insure a good duplication or printing of the
tread design. If the entrapped air were allowed to remain,
it would be compressed to deface the tread and thereby result
in an unsatisfactory imprinting of it into the embossed tire
~- band 1.
The embodiment of the invention shown in Fig. 7 is
similar to the embodiment in Fig. 6, except that the mold 20
corresponding to the mold 9' has a plurality of circumferen-
tially spaced, axially extending rods or pins 21 therein and
the interior of the body 2 is covered by an internal diaphragm
22. The pins 21, which are relatively rigid, aid in preventing
bending of the mold 20, intermediate the rows of projections 10 ~ `
for the purposes described hereinbefore.
It sometimes happens that a tire body 2 to be re-
~ treaded has holes extending from the interior thereof to the
5~ surface thereof to which the tread band is applied due to naiL
punctures, etc. Such holes may make it difficult to remove air
~ by way of the suction valve 16 and, in addition, steam is ofte~
t
' used as the vulcanizing heat medium. In the latter case, water -
can seep through such holes into contact with the underside
~ of the tread band 1 creating voids between the tread band 1
f~ and the tire body 2. For these reasons, it may be desirable
to employ an internal, fluid-impexmeable diaphragm 22 which
s~ covers the interior of the body 2 and extends around the out-
'~ side thereof and into contact with the diaphragm 14 during the
. .
removal of air by way of the valve 16 and the vulcanization of
the tread band 1.
~,
Fig. 8 shows an embodiment similar to the embodiments
'' in Figs. 6 and 7, except that in Fig. 8 the internal diaphragm
.~ .
~ - 16 -
: .
~., .
-. , , . . . ~
~ 3~ 'tj~ ~
22 is replaced by an inflatable bladder 23 supported inter- ;
nally by a ring 24, such bladder 23 and ring 2~D" serving the
same purposes as the internal diaphra~m 22 and also serving to
aid in maintaining the desired shape of the body 2 during vul-
canizing. Fig. 8 also shows a pair of 0-rings 25 and 26,
which may be of vulcanized or unvulcanized rubber, between the ~;~
diaphragm 14 and the side walls of the body 2 to assist in pro-
viding a fluid seal between the diaphragm 14 and the body 2.
Fig. 9 shows an embodiment similar to the embodirnents
in Figs. 6-8, except that the mold 27 has been modified to
include hollow metal pegs or pins 28, rib forming recesses 29
and 30, and a centering groove 31. The metal pins 28, which
are embedded in the mold 27, provide the holes 15 described
hereinbefore and may be incorporated in the mold 27 during ~ -
vulcanization thereof or inserted therein after vulcanization
thereof. ~ ~
The groove 31 in the rib 32 integral with the mold -
, -: .
27 may be used in centering the mold 27 with respect to the
body 2. Thus, a roller ~not shown) properly mounted with res~
pect to a rotatable support for the body 2 may ride in the ~-
' groove 31 as the body 2 is rotated, causing the rib 31, and ~
.
hence, the mold 27, to center properly with respect to the ~- ~
f' '~ :
; body 2.
~-~ Because of the presence of the rib 3~, the diaphragm ~`
14 may be made in two parts 14' and 14", sealed in any desired
manner at their edges 33 and 34 to the mold 27 and connected
~;- to two suction valves 16 and 16'.
In some cases, it is desirable for decorative pur- ;
poses to apply one or more ribs to the side wall, or to both
side walls of a tire body 2 being retreaded. In such cases, a
; lip, such as the lip 27', or both lips, may be provided with
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the necessary number of circumferential recesses, such as the
recesses 29 and 30, for receiving and forming unvuLcanized
~. rubber 1' extending from the tread band 1 downwardly to the
$` recesses 29 and 30 or merely applied to the portion of side
wall of the body 2 adjacent to the recesses 29 and 30, the
thickness of the rubber 1' being sufficient to at least fill
. such recesses 29 and 30. Such rubber 1' will assist in sealing
the diaphragm part 14' to the side wall during air removal and
vulcanizing of the tread band 1.
:.ç 10 Those skilled in the art will readily perceive modi- :
ficiations which fall within the scope and the spirit of the
~` invention. Therefore, the appended claims are to be construed
broadly enough to cover all equivalent structures.
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