U.S. patent application number 10/097827 was filed with the patent office on 2002-10-31 for retreaded tires and method for making the same without spray cement.
This patent application is currently assigned to Bandag Licensing Corporation. Invention is credited to Bender, David L., Bundschuh, James E. JR., Carlson, Lawrence, Logsden, Johnathon Leslie, Myers, Floyd S., Schnedler, Gary W., Seiler, Ronald.
Application Number | 20020157761 10/097827 |
Document ID | / |
Family ID | 23578007 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020157761 |
Kind Code |
A1 |
Bender, David L. ; et
al. |
October 31, 2002 |
Retreaded tires and method for making the same without spray
cement
Abstract
A retreaded tire assembly and method for making the same is
disclosed. The method and assembly provide for the application of
new tread to a buffed tire casing with only a layer of cushion gum
disposed therebetween. The cushion gum is applied directly to the
buffed circumference of a tire casing without the use of
conventional spray cement normally applied to the buffed surface of
the entire casing.
Inventors: |
Bender, David L.;
(Muscatine, IA) ; Bundschuh, James E. JR.;
(Davenport, IA) ; Carlson, Lawrence; (Muscatine,
IA) ; Logsden, Johnathon Leslie; (Tipton, IA)
; Myers, Floyd S.; (Muscatine, IA) ; Schnedler,
Gary W.; (Letts, IA) ; Seiler, Ronald;
(Muscataine, IA) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
TWO PRUDENTIAL PLAZA, SUITE 4900
180 NORTH STETSON AVENUE
CHICAGO
IL
60601-6780
US
|
Assignee: |
Bandag Licensing
Corporation
Muscatine
IA
|
Family ID: |
23578007 |
Appl. No.: |
10/097827 |
Filed: |
March 14, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10097827 |
Mar 14, 2002 |
|
|
|
08773864 |
Dec 27, 1996 |
|
|
|
6368439 |
|
|
|
|
08773864 |
Dec 27, 1996 |
|
|
|
08399070 |
Mar 8, 1995 |
|
|
|
Current U.S.
Class: |
156/96 ;
156/128.1; 156/130; 156/130.3 |
Current CPC
Class: |
B29D 2030/544 20130101;
B29D 30/54 20130101; B29D 30/58 20130101; B29C 2793/0081
20130101 |
Class at
Publication: |
156/96 ;
156/128.1; 156/130; 156/130.3 |
International
Class: |
B32B 001/00 |
Claims
What is claimed is:
1. A method for retreading a tire, comprising the steps of:
removing tire tread from a tire casing to present a buffed surface;
applying a layer of cushion gum directly to the buffed surface;
wrapping a tread layer about the layer of cushion gum; and treating
the tire to form bonds between the casing and the layer of cushion
gum and between the tread layer and the layer of cushion gum.
2. The method for retreading a tire as recited in claim 1, wherein
the step of applying the layer of cushion gum includes the step of
pressing the layer of cushion gum against the buffed surface with
sufficient pressure to force any air from between the casing and
the layer of cushion gum.
3. The method for retreading a tire as recited in claim 2, wherein
the step of applying the layer of cushion gum includes stretching
the layer of cushion gum circumferentially about the casing.
4. The method for retreading a tire as recited in claim 1, wherein
the step of applying the layer of cushion gum includes the step of
applying a pair of shoulder strips to the buffed surface.
5. The method for retreading a tire as recited in claim 3, wherein
the step of applying the layer of cushion gum includes the steps of
cutting the layer generally transverse to the circumferential
direction and splicing the layer at the cut region.
6. The method for retreading a tire as recited in claim 5, wherein
the step of wrapping the tread layer includes the steps of cutting
the tread layer generally transverse to the circumferential
direction and splicing the tread layer at the cut region.
7. The method for retreading a tire as recited in claim 6, further
comprising the steps of enclosing the tire in an envelope; heating
the tire; applying a vacuum within the envelope; and applying
pressure to the outside of the envelope.
8. A method for retreading a tire, comprising the steps of:
removing old tire tread from a tire casing to present a buffed
surface; cutting a tread layer to a length sufficient to encircle
the buffed surface along the circumference of the casing;
maintaining the buffed surface free of tire retreading cement;
disposing a layer of cushion gum between the buffed surface and the
tread layer; squeezing the layer-of cushion gum between the buffed
surface and the tread layer; and heating the combined tire casing,
tread layer and layer of cushion gum to form a vulcanized bond
therebetween.
9. The method for retreading a tire as recited in claim 8, wherein
the step of removing old tire tread includes grinding the tire
tread from the tire casing.
10. The method for retreading a tire as recited in claim 9, wherein
the step of maintaining the buffed surface includes removing
contaminants from the buffed surface.
11. The method for retreading a tire as recited in claim 8, wherein
the step of disposing the layer of cushion gum includes applying
tension thereto in a circumferential direction as the layer of
cushion gum is wrapped about the circumference of the tire
casing.
12. The method for retreading a tire as recited in claim 11,
wherein the step of disposing the layer of cushion gum includes
stitching the layer of cushion gum to the buffed surface to drive
air from therebetween.
13. The method for retreading a tire as recited in claim 8, wherein
the step of squeezing includes the steps of placing the combined
tire casing, tread layer and layer of cushion gum within a pressure
chamber.
14. The method for retreading a tire as recited in claim 13,
wherein the step of squeezing includes the steps of placing the
combined tire casing, tread layer and layer of cushion gum within
an envelope and creating a vacuum within the envelope.
15. The method for retreading a tire as recited in claim 14,
wherein the step of heating occurs while the combined tire casing,
tread layer and layer of cushion gum are in the pressure
chamber.
16. A retreaded tire assembly prepared for insertion into a
pressurized heating chamber comprising: a tire casing having a pair
of sidewalls and a radially outer wall spanning the pair of
sidewalls, the radially outer wall having a buffed surface disposed
about the outer circumference of the tire casing; a layer of
cushion gum disposed directly against the buffed surface; and a
tread layer disposed against the cushion gum.
17. The retreaded tire assembly as recited in claim 16, wherein the
layer of cushion gum is mounted in tension about the circumference
of the tire casing.
18. The retreaded tire assembly as recited in claim 17, wherein the
layer of cushion gum includes a center strip and a pair of shoulder
strips.
19. The retreaded tire assembly as recited in claim 17, wherein the
tread layer is arcuate in both the circumferential and the
transverse directions.
20. The retreaded tire assembly as recited in claim 17, wherein the
tread layer is arcuate only in the circumferential direction.
Description
TECHNICAL FIELD
[0001] This invention relates generally to a method for making
retreaded tires and particularly to a method for making retreaded
tires that eliminates the need for spray cement normally applied to
the tire casing.
BACKGROUND OF THE INVENTION
[0002] Retreaded tires have been available for many years and
provide an economical way to gain additional use out of a tire
casing after the original tread has become worn. According to one
conventional method of retreading, sometimes referred to as cold
process retreading, the remaining tread on the used tire is removed
by a special buffing machine that grinds away the old tread and
leaves a buffed surface to which a new layer of tread may be
bonded.
[0003] Removal of the old tread from the tire casing provides a
generally smooth treadless surface about the circumference of the
tire casing. The tire casing may then be examined for injuries,
often called skives, which are filled with a repair gum. After
completion of the skiving process, the buffed surface is sprayed
with a tire cement that provides a tacky surface for application of
bonding material and new tread. Then a layer of cushion gum is
applied to the back, i.e., the inside surface, of a new layer of
tread. The cushion gum and tread are applied in combination about
the circumference of the tire casing to create a retreaded tire
assembly ready for curing. The cushion gum forms the bonds between
the tread and the tire casing during curing.
[0004] Following assembly of the tire casing, cement, cushion gum
and tread, the overall retreaded tire assembly is placed within a
flexible rubber envelope. An airtight seal is created between the
envelope and the bead of the tire. The entire enveloped tire
assembly is placed within a curing chamber, and subjected to
pressure and a raised temperature for a specific period of time.
The combination of pressure, temperature and time chemically bonds
the layer of cushion gum to both the tire casing and the new tire
tread.
[0005] The above-described method of cold process retreading works
well and provides high quality, retreaded tires. However, in
certain applications it would be advantageous to eliminate the
spray cement. This is particularly true in geographical areas where
there is increased regulation of the use of chemicals within spray
cement. Generally, available spray cements include either heptane
solvent or methyl chloroform. The heptane solvent has been found to
contribute to smog formation, and methyl chloroform, although it
does not cause smog, has tended to be substantially more expensive
than heptane solvent.
[0006] Use of spray cement can also add to the cost of producing
retreaded tires due to the product cost and equipment cost. For
example, because cementing of the tire casing should only be done
in a well ventilated spray booth, retreading shops must purchase
appropriate ventilation equipment. Elimination of the spray cement
thus eliminates the need to purchase ventilated spray booths.
[0007] A potential solution to smog problems associated with using
heptane solvent is the installation of solvent capture equipment at
each retreading shop. However, this solution is disadvantageous due
to the cost of the equipment and the operational and maintenance
costs. The present invention addresses the drawbacks associated
with using spray cement during retreading of tires.
SUMMARY OF THE INVENTION
[0008] The present invention includes a method for retreading a
tire that comprises the steps of removing the tire tread from a
tire casing to present a buffed surface. Then, a layer of cushion
gum is applied directly to the buffed surface without spraying
cement over the buffed surface. A tread layer is wrapped about the
layer of cushion gum, and finally, the tire is treated to form
bonds between the casing and the layer of cushion gum and between
the tread layer and the layer of cushion gum.
[0009] Another unique aspect of the invention is a retreaded tire
assembly prepared for insertion into a pressurized heating chamber.
The tire assembly includes a tire casing having a pair of side
walls and a radially outer wall spanning the pair of side walls.
The radially outer wall has a buffed surface disposed about the
outer circumference of the tire casing. A layer of cushion gum is
disposed directly against the buffed surface, and a tread layer is
disposed against the cushion gum about the outside circumference of
the cushion gum. After appropriate heat and pressure treatment, the
tire casing, cushion gum and tread layer become bonded into an
integral retreaded tire that may be used on an appropriate
over-the-road vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will hereafter be described with reference to
the accompanying drawings, wherein like reference numerals denote
like elements, and:
[0011] FIG. 1 is a cross-sectional view of an exemplary original
tire;
[0012] FIG. 2 is a cross-sectional view of the tire of FIG. 1 after
the tread layer has been removed from the tire casing;
[0013] FIG. 3 is a schematic representation of the layer of cushion
gum and the new tread layer being applied to a tire casing;
[0014] FIG. 4 is a cross-sectional view of the tire casing
illustrated in FIG. 2 with the addition of the layer of cushion gum
and the new tread layer; and
[0015] FIG. 5 is a perspective cross-sectional view of an alternate
embodiment of a retreaded tire according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] Referring generally to FIG. 1, an original tire is shown as
having a tire casing 12 from which extends a tire tread 14. The
illustrated tire 10 is a radial tire; however, the invention
applies equally to other types of tires, such as bias ply
tires.
[0017] More particularly, tire 10 includes a pair of side walls 16
bounded by a generally radially outward wall 18 that spans side
walls 16. Each side wall 16 extends radially inward from outer wall
18 and terminates in a bead area 20 designed for mounting on the
tire rim (not shown). Bead area 20 may be designed in a variety of
configurations depending on, for example, tire type, tire size or
rim configuration. In the illustrated embodiment, each bead area 20
includes a bead heel 22, a bead toe 24, and a bead sole 26. Each
bead area 20 may also include a bead bundle 28 and a chafer ply 30.
Both bead bundle 28 and chafer ply 30 may include, for example,
metal strands or wires to improve the strength of bead area 20.
[0018] Side walls 16 may also include multiple layers, such as a
rubber layer 32, a radial ply 34 and an inner liner 36 which
cooperate to provide a strong but flexible side wall. Side walls 16
are joined to radially outward wall 18 and tread 14 through a pair
of shoulder areas 38. Shoulder areas 38 extend towards tire tread
14 which, in turn, is disposed radially outwardly from wall 18 of
tire casing 12. Tire tread 14 may include a plurality of grooves 40
designed to channel water and provide added traction during certain
road conditions. Additionally, outer wall 18 may be strengthened by
a plurality of belts or cords 42 extending circumferentially about
tire 10 within wall 18 (see FIGS. 2 and 5).
[0019] After tire tread 14 wears beyond a certain limit, tire 10
must either be discarded or retreaded before it should be used on
the vehicle for which it was designed. In cold process retreading,
the remaining tire tread 14 is removed from tire casing 12 by a
buffing machine, such as the Model 8110 buffing machine
manufactured by Bandag, Incorporated of Muscatine, Iowa. During the
buffing operation, the original tire tread 14 is ground away from
tire casing 12, leaving a buffed surface 44 as illustrated in FIG.
2. Buffed surface 44 extends circumferentially about tire casing 12
and also extends transversely across the outside of outer radial
wall 18 until it terminates at buffed shoulder areas 46.
[0020] Following removal of the used tread layer, a process called
skiving and filling is performed on tire casing 12. Skiving is the
removal of damaged material from a tire prior to making a repair.
Often, the tire casing 12 accumulates holes, nicks or tears due to
stones or other sharp objects the tire comes in contact with during
use. The injured or damaged area is first ground smooth by an
appropriate grinding tool and then filled with repair gum, such as
Bandag extruder repair rope or repair gum or some other suitable
material. It is necessary to fill the injured areas to the level of
buffed surface 44 to avoid air pockets between buffed surface 44
and the later applied tread layer. Trapped air can have negative
effects on the longevity of a typical retreaded tire. Following the
skiving and filling operation, a building step occurs in which a
layer of cushion gum and a new tread layer are wrapped about the
circumference of tire casing 12 along buffed surface 44.
[0021] As illustrated best in FIG. 3, a building machine 48 (shown
schematically), such as the Bandag 5110 semiautomatic builder
manufactured by Bandag, Incorporated, may be used to apply a layer
of cushion gum 50, such as HD30 cushion gum manufactured by Bandag,
Incorporated. Although the layer of cushion gum 50 could be applied
to tire casing 12 in a variety of ways, the schematic
representation of FIG. 3 shows a roll of the cushion gum 52
rotatably mounted on building machine 48. The layer of cushion gum
50 moves about a tensioning roller 54 prior to being wrapped
circumferentially around buffed surface 44.
[0022] Preferably, cushion gum layer 50 is covered by a bottom
plastic sheet 56, e.g. a poly sheet, and a similar top plastic
sheet 58. As illustrated, bottom sheet 56 is peeled away from
cushion gum layer 50 shortly before the cushion gum is wrapped
about tire casing 12 along buffed surface 44. Bottom plastic sheet
56 may then be wrapped about tensioning roller 54 as shown in FIG.
3.
[0023] Cushion gum layer 50 is preferably applied to buffed surface
44 within eight hours of buffing. Additionally, the application has
been found to work best when the layer of cushion gum 50 is applied
under tension in the circumferential direction. Depending on the
application, it may be desirable to slightly stretch the cushion
gum layer 50 to achieve better adherence to buffed surface 44.
Cushion gum layer 50 is cut transversely and the cut edge is
spliced with the leading edge so there is no gap between the
beginning and the end of cushion gum layer 50. Any, overlap between
the leading edge and the trailing cut edge is preferably limited to
one-eighth inch or less.
[0024] After cushion gum layer 50 is applied to tire casing 12,
layer 50 is stitched, or in other words pressed, against buffed
surface 44 to drive out any air trapped between the cushion layer
and buffed surface 44. Following stitching, the top layer of
plastic 58 is removed from cushion gum layer 50 to permit a new
tread layer 60 to be applied over the cushion gum. The stitching
step also helps prevent the cushion from lifting away from buffed
surface 44 when plastic layer 58 is removed and tread layer 60 is
applied.
[0025] Preferably, tread layer 60 is also applied with the
assistance of building machine 48, although there are a variety of
ways to wrap tread layer 60 about the circumference of tire casing
12. When using building machine 48, a tread roll 62 is rotatably
mounted thereon, and tread layer 60 is guided onto tire casing 12
against cushion gum layer 50 by guide rollers 64.
[0026] Tire casing 12 is rotated an building machine 48 until a
sufficient length of tread layer 60 is unraveled from tread roll 62
to extend about the circumference of tire casing 12. Tread layer 60
is then cut generally transversely to the circumferential
direction, and the cut end is butted up against the leading edge of
tread layer 60 to form a splice. The tread layer splice is often
held together by a plurality of staples (not shown). It is also
preferred that the spliced area of cushion gum layer 50 and the
spliced area of tread layer 60 be disposed at different points
along buffed surface 44.
[0027] Although the application of cushion gum layer 50 and tread
layer 60 to a tire casing 12 by building machine 48 has been
generally known in the industry for many years, the unique aspects
of this inventive method of retreading allows the omission of a
previous step, namely the application of spray cement to buffed
surface 44. Previously, spray cement would be initially applied to
buffed surface 44. Then, cushion gum layer 50 would be applied to
the inside or lower surface of tread layer 60. The combination of
cushion gum layer 50 and tread layer 60 would be wrapped about
cement covered buffed surface 44 and spliced together.
[0028] The present method permits the elimination of the spray
cement which overcomes certain disadvantages described in the
background of the invention section above. By first stretching the
layer of cushion gum about the circumference of tire casing 12,
stitching the cushion gum and then applying tread layer 60 over the
combined tire casing 12 and cushion gum layer 50, the necessity of
using spray cement has been eliminated. It has been found that
retreaded tires made according to the new method have very
desirable characteristics without requiring an extra cementing
step.
[0029] After application of cushion gum layer 50 and tread layer
60, a retreaded tire assembly 66 is created and ready for curing
under appropriate heat and pressure conditions. A cross section of
the retreaded tire assembly 66 is illustrated best in FIG. 4. After
assembly, the overall tire assembly is inserted into a rubberized
curing envelop, such as the appropriate Bandag, Incorporated curing
envelope designed for the particular tire type and size being
retreaded.
[0030] The retreaded tire assembly 66 is sealed within the curing
envelope and placed within a curing chamber, such as the Model 4130
or 4120 curing chamber sold by Bandag, Incorporated. Pressure and
heat are applied to the retreaded tire assembly 66 within the
curing chamber. The amount of time necessary to cure a given
retreaded tire may vary depending on the size of the tire and the
materials used. However, the time must be long enough to create
sufficient bonding between the tire casing 12 and cushion gum layer
50 and between the tread layer 60 and cushion gum layer 50.
Generally, the bonding results from vulcanization between the tire
casing, cushion gum layer and tread layer. The times, pressures and
temperatures within the curing chamber would be known by one of
ordinary skill in the art. However, exemplary parameters during
curing within the curing chamber are temperature: approximately
210.degree. F.; pressure: approximately 85 psi; and time:
approximately three and one half hours. The above listed
temperature, pressure and time parameters are only provided as
examples, and are not meant to limit the scope of the invention. As
stated previously, the time within the curing chamber may vary
depending on the tire size and tire materials. Additionally, other
combinations of temperature and pressure can potentially provide
satisfactory results. After curing, the retreaded tire may undergo
certain minor trimming operations, but otherwise is ready for use
on a vehicle.
[0031] Another embodiment of retreaded tire assembly 66 is
illustrated in FIG. 5. The process used for this type of retreaded
tire is the same as that described above, except for the addition
of a pair of shoulder strips 68 of cushion gum that are added to
accommodate arched outer flanges 70 of a slightly different tread
layer 72. In this embodiment, tread layer 72 extends about the
circumference of tire casing 12 as described above, but the arched
outer flanges 70 curve in the transverse direction generally about
shoulder areas 46 of tire casing 12. Accordingly, additional
cushion gum must be added in the form of shoulder strips that run
generally along each shoulder area 46 of tire casing 12 and beneath
flanges 70.
[0032] Thus, after cushion gum layer 50 is applied to buffed
surface 44, and stitched thereto, the top layer of plastic 58 is
removed and shoulder strips 68 are applied along shoulder areas 46.
The tread layer 72 including its arched outer flanges 70 is applied
over cushion gum layer 50 and shoulder strips 68, measured, cut,
and spliced similarly to that described above.
[0033] The various parameters involved in cementless retreading of
tires may vary depending on the overall design of the tire being
retreaded and the composition of the retreading materials. However,
in general, it is preferred that the temperature of both tire
casing 12 and cushion gum layer 50 be at least 65 degrees
Fahrenheit when the cushion gum layer is applied to buffed surface
44. Additionally, the cushion should be applied to the uncemented
casing within eight hours of buffing or, if the buffed casing is
covered with poly, the cushion application should be within 72
hours of buffing. Furthermore, to ensure a high quality retreaded
tire, it is preferred that the centerline of cushion layer 50 be
aligned with the center line of the buffed casing within plus or
minus one eighth inch. When applying the flat style tread
illustrated in FIG. 4, there should be at least one eighth inch of
cushion layer 50 extending transversely past the base of the tread
on each side of tread layer 60. Similarly, cushion layer 50 should
be applied with enough tension to facilitate conformation to the
buffed surface 44, but the tension should not cause the width of
cushion layer 50 to be reduced by more than one eighth inch.
Generally, the length of cushion layer 50 is approximately 2-8
inches shorter than the circumference of buffed surface 44.
[0034] It will be understood that the foregoing description is of
the preferred exemplary embodiment of this invention and that the
invention is not limited to the specific form shown. For example,
the invention is directed to a tire assembly and a method for
retreading tires that does not require the use of spray cement, and
therefore a wide variety of equipment may be used to apply the
layers of cushion gum and tread to the tire casing. Additionally,
the invention encompasses a broad variety of tires, materials, and
tread designs that may be assembled according to the invention. The
methods of preparing the tire casing and curing the retreaded tire
assembly may vary substantially due to differences in materials,
equipment and techniques for creating retreaded tires. These and
other modifications may be made in the design and arrangement of
the elements without departing from the scope of the invention as
expressed in the appended claims.
* * * * *