Hydraulic tire repair method

A method and apparatus for vulcanizing a rubber repair patch on a tire incorporating an internal fluid pressure bag placed within the interior of the tire and against the patch, an inflatable mandrel within the tire and against the internal bag, an external fluid pressure bag engaging the exterior of the tire radially opposite the internal bag, and a retainer device, such as a retainer strap radially encircling and engaging the external bag and the mandrel to cause the internal and external bags to be forced toward each other to squeeze the patch and tire between them, upon inflation of the mandrel. This invention is paticularly characterized in utilizing internal and external fluid pressure bags having walls of two-dimensional flexibility and utilizing a heat-conductive hydraulic fluid within both bags having a boiling point greater than the vulcanizing temperature.

BACKGROUND OF THE INVENTION 
This invention relates to a method and apparatus for the repair of tires, 
and more particularly to a method and apparatus for vulcanizing a repair 
patch on a tire. 
In the repair of injured tires, whether bias-ply or radial, in which 
unvulcanized rubber patch material is used, various methods are employed 
to vulcanize the patch material to the injured area of the tire. 
In some vulcanizing processes, a mold apparatus is utilized utilizing heat 
pads and air bags for applying heat to the rubber patch material. 
In one process, a heated mandrel of solid material, such as metal, 
pre-shaped to fit the interior of the tire, is inserted within the tire. 
An external heat pad is placed against the exterior of the tire, and then 
an external air bag is placed against the external heat pad. The assembly 
is then placed within a solid mold and heat is applied to the solid 
mandrel in order to heat the patch material to a vulcanizing temperature. 
In another form of the mold vulcanizing process, an internal heat pad may 
be placed against the patch material and the surrounding tire area and an 
inflatable mandrel or inflatable air bag placed within the tire. When the 
mandrel or air bag is inflated, pressure is applied against the internal 
heat pad. An external heat pad and an external air bag are retained 
against the exterior of the tire within the mold cavity of the mold 
apparatus, while the internal air bag or inflatable mandrel is clamped in 
place within the tire. 
In one form of the mold vulcanization process, an inner tube has been 
substituted for the inflatable air bag mandrel for exerting pressure 
against the inside heat pad. 
In all of the above mold vulcanization processes, both the external heat 
pad and the internal heat pad, although having some cross-sectional 
curvature, are made of solid rubber encasing the electrical heating coils 
and therefore have limited flexibility. Accordingly, when the heat pads 
are placed against the interior or the exterior surface of the tire, the 
heat pads are not flush with the corresponding surfaces of the tire. Since 
the tire curves in both its radial dimension and its circumferential 
dimension, the heat pads, although conforming to the shape to some degree 
in one dimension, do not conform to the shape in both dimensions of the 
tire. Accordingly, the heat pad bridges certain areas of the tire surfaces 
to create air gaps, and the heat is applied unevenly to the corresponding 
surfaces of the tire, creating localized hot spots. 
Furthermore, because of the relative inflexibility of the conventional heat 
pads, they are not readily adaptable to fit tires of different sizes and 
shapes to compound the problem of even heat distribution to the repair 
area as well as the surrounding tire surfaces. Moreover, the relatively 
stiff heat pads cause distortions in the tire shape during the 
vulcanization process. 
Because the patch on the interior surface of a tire projects inwardly 
beyond the plane of the tire surface, a rigid mandrel made of metal, or 
relatively inflexible heat pads, when applied to the interior surface of 
the injured area, creates uneven pressure against the raised patch and the 
surrounding tire surface, since the plane of the inner surface of the 
patch is not flush with the surrounding interior surface of the tire. 
Examples of such mold apparatus are the Vulcan section repair molds 
manufactured and distributed by Vulcan Equipment Company, Limited, of 
Scarborough, Ontario, Canada. 
Another disadvantage of the above mold-type repair apparatus is that the 
tire repairs have to be made at sites in which the tire mold apparatus is 
located, and field repairs would be highly impractical and expensive. 
Another process of vulcanizing tire repairs, which can be accomplished in 
the field is the Monarch vulcanizing repair system produced by IMC 
(Engineers) Ltd., of Hartfordshire, England, and distributed in the United 
States. This system substitutes flexible, but inelastic, straps for the 
mold hardware for encircling the section of the tire to be repaired and 
for containing the exterior and interior heat pads, exterior and interior 
flat air bags and an inflatable mandrel fitted within the tire. The 
mandrel is inflated to exert pressure against the interior flat air bag 
and the interior heat pad, in a somewhat similar manner as the 
above-described processes incorporating the mold apparatus. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide a tire repair 
vulcanizing system which will apply heat uniformly to the unvulcanized 
tire repair material, as well as to the surrounding surface of the tire, 
which will not distort the shape of the tire, regardless of different 
sizes, and which can easily and quickly be utilized in the field. 
Although in this process of vulcanizing the tire repair material, an 
inflatable mandrel is utilized, nevertheless, the conventional heat pads 
and air bags have been eliminated. 
In this process, an internal fluid pressure bag, encapsulating a hydraulic 
fluid having a boiling point greater than the operating vulcanizing 
temperature, is utilized within the tire. The bag walls have 
two-dimensional flexibility. The internal fluid bag is preferably 
pre-molded to generally fit the contour of the interior of the tire to be 
repaired. An inflatable mandrel or air bag is fitted within the tire 
against the internal fluid bag to force the bag against the interior 
surface of the tire, when the mandrel is inflated. An external fluid 
pressure bag, of the same construction as the internal fluid bag and also 
encapsulating hydraulic fluid, is pre-molded to fit around and against the 
exterior surface of the tire in radial opposition to the internal bag. 
Both fluid pressure bags preferably incorporate heating elements within 
the bags and in contact with the hydraulic fluid. 
Flexible, but inelastic retainer straps, such as Nylon straps, encircle the 
tire and engage the exterior surface of the external fluid bag as well as 
the top portion of the inflatable mandrel, and are secured taut in 
operative position. 
Therefore, the only additional equipment needed for properly vulcanizing 
the repair patch material in a tire in accordance with this invention, is 
a source of energy, such as electricity, for energizing the heater 
elements within the fluid pressure bags, and a source of compressed air 
for inflating the inflatable mandrel. 
When the mandrel is inflated, its inward expansion toward the center of the 
tire is restrained by the retainer straps, while the mandrel exerts 
pressure radially outward against the internal fluid pressure bag, causing 
the heated hydraulic fluid to distribute itself throughout the fluid 
pressure bag and against the interior surface of the tire. Simultaneously, 
the exertion of the inflating mandrel against the retainer straps causes 
the pressure within the mandrel to be transmitted through the retainer 
straps to the exterior surface of the external fluid pressure bag, forcing 
the hot fluid and the bag tightly against the exterior surface of the 
tire. 
Because of the two-dimensional flexibility of the bag walls and the 
mobility of the heated hydraulic fluid, an even distribution of heat is 
applied to the corresponding surfaces of the tire as well as the patch 
material, and furthermore, the shape of the tire is not distorted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings in more detail, an apparatus 10 for 
vulcanizing patch material, such as the unvulcanized rubber patch 11 and 
plug 12 installed within the hole 13 of the injured area of a conventional 
vehicle tire 15, is disclosed in FIGS. 1 and 2. 
The apparatus 10 includes an internal fluid pressure bag 16 having an 
interior wall 17 and an exterior wall 18 and adapted to completely enclose 
or encapsulate a hydraulic fluid 20 (FIG. 3). The internal bag 16, is 
preferably pre-formed or molded so that the interior and exterior walls 17 
and 18 are curved in radial cross-section to generally the same curvature 
as the interior surface 21 of the tire 15. The length of the internal bag 
16 is immaterial, so long as the bag 16 is long enough, that is in the 
circumferential dimension of the tire 15, to adequately cover the injured 
area including the unvulcanized repair patch 11. In a typical truck tire 
15, the length of the bag 16 may be in the order of 15". The width of the 
bag 16 may be less than the curvilinear distance from bead-to-bead around 
the interior surface 21 of and in the radial plane of the tire 15, so that 
the internal fluid bag 16 may accommodate itself to the shape of the 
interior surface 21 of tires of different sizes and still fit flush 
against the tire interior surface 21. 
Projecting through one end wall 22 of the internal fluid bag 16 is an 
elongated heater element, such as the electrical heater cartridge 24, of 
conventional construction. The end of the cartridge 24 is sealed in the 
end wall 22 and is connected by an electrical line 25 to a source of 
electricity. The cartridge 24 is preferably provided with a thermostat, 
not shown, in order to control the temperature of the cartridge 24, as 
well as the heated hydraulic fluid 20. 
Also fitted within the interior of the tire 15, and within, and in flush 
engagement with, the internal fluid pressure bag 16, is an inflatable air 
bag, or mandrel 27, generally cylindrical in cross-section and having an 
exterior wall portion 28, an interior wall portion 29, and opposed end 
walls 30. In one of the end walls 30, is located an air valve 31 connected 
to an air hose 32, (FIG. 2). The hose 32, is connected to a source of 
compressed air, not shown. 
The mandrel 27 is designed so that its exterior wall portion 28 will 
preferably be in flush engagement with the interior wall 17 of the 
internal bag 16. Moreover, the height or radial extent of the inflatable 
mandrel 27 is such that the interior wall portion 29 preferably projects 
radially inward toward the center of the tire 15 and slightly beyond the 
bead area 34 of the tire 15, when the mandrel 27 is inflated, as 
illustrated in FIG. 2. 
Fitted around the exterior surface 35 of the tire 15, is an external fluid 
pressure bag 37 having a radial interior wall 38 and a radial exterior 
wall 39 and adapted to completely encapsulate the hydraulic fluid 40, 
which is identical to the hydraulic fluid 20. The walls 38 and 39 are 
preferably pre-formed to the general transverse curvature of the exterior 
surface 35 of the tire 15, as illustrated in FIG. 2. The external bag 37 
is also preferably pre-molded or pre-formed to have a longitudinal 
circumferential curvature generally conforming to the circumferential 
curvature of the exterior surface 35 of the tire 15, and may be of a 
length slightly greater than the length of the internal bag. For example, 
the circumferential length of the external bag might be in the order of 
18" while the circumferential length of the internal bag might be 
approximately 15". 
One of the end walls 42 of the external bag 37 also receives a heater 
element, such as the electrical heater cartridge 44, which may be 
identical to the cartridge 24. The cartridge 44, extends lengthwise within 
the space between the walls 38 and 39 of the bag 37, and is surrounded by 
the hydraulic fluid 40 for heating. The cartridge 44 is connected by an 
electrical conduit or line 45 to a source of eletrical power, not shown. 
In order to hold the inflatable mandrel 27, the internal bag 16, and the 
external bag 37, in operative position, that is in place for vulcanizing 
the patch 11 and plug 12, at least one, and preferably a plurality of 
elongated, flexible, inelastic retainer straps 48 are wrapped radially 
about the outside of the external bag 37 and the mandrel 27. The ends of 
the retainer straps 48 are secured together in fixed positions by means of 
the buckle mechanisms 49, so that the straps 48 tautly engage the exterior 
surface 39 of the external bag 37 and also extend across the interior wall 
portion 29 of the inflatable mandrel 27, before the mandrel 27 is fully 
inflated. After the buckle mechanisms 49 are secured, and compressed air 
is introduced into the inflatable bag 27, through the hose 32 and the 
valve 31, the increased air pressure creates a commensurately increased 
tension in the retainer straps 48. Thus, the mandrel 27 is retained 
against any further radial inward movement so that the major portion of 
the expansion of the mandrel 27 occurs in the expansion of the exterior 
wall portion 28 against the inner wall 17 of the fluid bag 16. Thus, the 
mandrel 27 transmits its pressure to the hot hydraulic fluid 20 and the 
outer wall 18 of the internal bag 16. Simultaneously, the tension created 
within the retainer straps 48 is transmitted to the exterior wall 39 of 
the external bag 37 exerting pressure upon the heated fluid 40, which in 
turn, transmits a uniform pressure to the inner wall 38 of the external 
bag 37 to snugly grip and lie flush against the exterior surface 35 of the 
tire 15. 
Preferably, prior to the inflation of the mandrel 27, energy is supplied 
through the electrical lines 25 and 45 to the respective heater cartridges 
24 and 44 to heat the corresponding hydraulic fluid 20 and 40 within the 
internal bag 16 and the external bag 37, respectively. Because of the 
mobility or fluidity of the hydraulic fluid, heat is uniformly transferred 
throughout the extent of the hydraulic fluid within the respective bags 16 
and 37 to create a substantially uniform vulcanizing temperature to both 
surfaces of the tire 15, as well as to the patch 11. 
The curing time for the vulcanization of the patch 11 and plug 12 depends 
upon many factors known in the art, such as the thickness of the tire 15 
at the location of the injury and the patch 11, as well as the type of 
material incorporated in the wall of the tire. 
In a preferred form of the invention, the hydraulic fluid is a 
heat-conductive hydraulic fluid, such as a silicone fluid, which has a 
boiling point of 450.degree. F. The boiling point of the hydraulic fluid 
may vary, so long as it is greater than the normal operating vulcanizing 
temperature of 270.degree. F. Such vulcanizing temperature may range 
220.degree.-300.degree. F., and is more commonly approximately 270.degree. 
F. One form of hydraulic fluid which has been used successfully is General 
Electric SF96 350 centistokes silicone fluid. 
Also in a preferred form of the apparatus 10, each of the internal fluid 
pressure bag 16 and external fluid pressure bag 37, is encased in a 
flexible cover 50 and 51 respectively, and is preferably made of Nylon. 
The retainer straps 48 are also preferably made of Nylon. 
Although not disclosed in the drawings, when the various elements of the 
apparatus 10 are assembled upon the tire 15, the tire is supported in an 
elevated position convenient to the tire repairman. One means of 
supporting the tire 15 is with a sling supporting the upper portion of the 
tire from an elevated position. The sling can be supported from a hoist of 
any convenient type to permit the sling and the tire 15 to be raised and 
lowered to the desired repair position. 
The apparatus 10 could be adapted to be used in combination with an 
existing tire mold, such as the Vulcan molds, previously discussed. In 
such event, the retainer straps 48 would be eliminated, and the remaining 
assembly of the apparatus 10, including the tire 15, could be inserted 
between the jaws of the mold, so that the external fluid bag 37 would fit 
within the mold cavities. In this event, the interior wall 29 of the 
mandrel 27 would be retained by an existing and conventional clamp 
mechanism of the conventional mold apparatus. 
A tire repaired in a mold apparatus incorporating the mandrel 27 and the 
two fluid bags 16 and 37, would have all the advantages of the uniformly 
heated hydraulic fluid within these bags and the two-dimensional 
flexibility of the fluid bag walls. 
It is also within the scope of this invention to substitute for the 
electrical heating cartridges 24 and 44, a fluid circulating system 
incorporating a pump and lines leading to and from each of the bags 16 and 
37, so that the fluid could be heated externally and pumped through 
external lines to each of the bags 16 and 37 in order to circulate the 
heated fluid uniformly throughout each of the bags. The heated fluid would 
then be returned to the heater and the pump through corresponding return 
lines, not shown. 
It is also possible to utilize a conventional electrical heating pad 
between the mandrel 27 and the fluid bag 16 to heat the hydraulic fluid 
20. 
Furthermore, a conventional heated, but non-inflatable, mandrel might be 
substituted for the mandrel 27, in order to heat the hydraulic fluid 20. 
In a preferred form of the invention, the walls of the respective fluid 
bags 16 and 37 are made from a heat-resistant rubber to provide the 
two-dimensional flexibility and long service life. 
Furthermore, when the apparatus 10, made in accordance with this invention, 
is utilized, it is immaterial what type of repair material is used to fill 
and cover the injury hole, so long as the material is unvulcanized rubber, 
and requires vulcanization to complete the repair process. For example, 
any unvulcanized rubber filler material might be used in the injury hole 
instead of the plug 12. 
Because of the flexibility of the bags, the apparatus 10 may be utilized on 
various types and sizes of tires. For example, one apparatus 10 might be 
used on truck tires having a width of 8.25 to 12.00". 
Also in a preferred form of the invention, any operating pressure may be 
used which is sufficient to vulcanize the particular patch on the 
particular tire. Although Michelin recommends a minimum of 15 psi, the 
operating pressure which would normally be used with the apparatus 10 
would be approximately 30 psi. 
When the fluid bags 16 and 37 do not extend transversely entirely from 
bead-to-bead, around the respective sidewalls, shoulders and tread areas, 
as disclosed in the drawings, the major portion of each fluid bag is 
placed on the side of the tire 15 in which the tire patch 11 is located. 
Thus, the particular dimensions, that is the radial and circumferential 
dimensions of the respective bags 16 and 37 are not critical, so long as 
they give maximum coverage and thermal exposure to the repair patch 11 and 
the surrounding areas on both the interior and exterior surfaces of the 
tire wall 15 to effect vulcanization. 
It is also evident from the description of the structure and function of 
the above apparatus 10, that the elements employed for the vulcanization 
of the tire repair materials, are not only minimal in number, but minimal 
in size, and therefore require minimal space for effecting the tire repair 
as well as for storing the tire repair equipment. 
Furthermore, the apparatus 10 made in accordance with this invention is 
particularly adapted for use in the field for repairing tires of various 
sizes at the site of the puncture or tire injury. The only external 
equipment needed for the repair of a tire with the apparatus 10, is some 
mechanism for suspending or supporting the tire 15 while it is being 
repaired, such as the previously described sling, a source of compressed 
air to which the hose 32 may be attached, and a source of electricity for 
the heater cartridges 24 and 44, or an equivalent heating system. 
Therefore, because of the minimal number of elements in the apparatus 10 
as well as the minimum amount of apparatus required, the tire may be 
easily and rapidly repaired without the necessity of transmitting the tire 
to a repair shop or site. 
Because of the uniformity of pressure and temperature and the continuity of 
the flush engagement between the fluid bags 16 and 37 and the respective 
interior surface 21 and exterior surface 35 of the tire 15, a complete 
vulcanized repair of the injured area is assured.