Air tight vehicle wheel with lightener pocket and process for manufacturing same

A layer of sealant is applied to a portion of the surface of a vehicle wheel to prevent air leakage therethrough.

BACKGROUND OF THE INVENTION 
This invention relates in general to vehicle wheels and in particular to a 
light weight wheel which has a layer of sealant disposed upon a portion of 
a surface of the wheel to assure that the wheel is air tight. 
Light weight vehicle wheels formed from an alloy of a light weight metal 
such as aluminum, magnesium or titanium, are replacing steel wheels on an 
increasing number of vehicles. Such light weight wheels provide both a 
reduction in weight from steel wheels and an attractive appearance. 
Referring now to the drawings, there is shown in FIG. 1 a fragmentary 
sectional view of a typical prior art one piece light weight wheel 10. 
The wheel 10 has an annular wheel rim 11 which is adapted to carry a 
vehicle tire. The outboard end of the wheel rim 11 includes an annular 
sidewall 12. Due to limitations of conventional casting processes, the 
sidewall 12 typically has a thick cross section. An outboard tire bead 
retaining flange 13, which extends in an outward radial direction, is 
formed upon the outboard end of the sidewall 12. An annular outboard tire 
bead seat 14 is formed in the outer surface of the sidewall 12 adjacent to 
the outboard tire bead retaining flange 13. The outboard tire bead seat 14 
extends axially from the outboard flange 13 to an annular outboard tire 
bead hump 15. The outboard tire bead hump 15 is connected by a radial deep 
well wall 16 to a recessed annular deep well 17. The deep well 17 extends 
axially to an annular leg portion 18 of the wheel rim 11. The inboard end 
of the leg portion 11 is formed as an annular inboard tire bead hump 19. 
The inboard tire bead hump 19 is adjacent to an inboard tire bead seat 20 
which extends axially from the inboard tire bead hump 19 to an inboard 
tire bead retaining flange 21. The inboard tire bead retaining flange 21 
extends in an outward radial from the inboard end of the wheel rim 11. 
The wheel 10 also has a wheel disc 25 which is formed across the outboard 
end of the wheel rim 11. The wheel disc 25 includes a wheel hub 26 having 
a central pilot hole 27 and a plurality of wheel lug holes 28 (one shown) 
formed therethrough. A plurality of spokes 29 (one shown) extend radially 
from the hub 26 to the wheel rim sidewall 12 and support the wheel hub 26 
within the wheel rim 11. 
A flow chart for a typical prior art process for forming the wheel 10 is 
shown in FIG. 2. In functional block 30, a one piece vehicle wheel casting 
is formed by a conventional casting process, such as gravity or low 
pressure casting. The wheel casting is machined to final shape in 
functional block 31. Typical machining operations include turning the tire 
bead seats, facing the inboard surface of the wheel hub, boring the pilot 
hole and drilling the wheel lug holes. 
Once the machining is completed, the wheel surface is cleaned in 
preparation for finishing, as shown in functional block 32. Preparation 
usually includes immersion in a mild acid bath to remove all machining 
lubricants and rinsing with water sprays to remove the acid. Additionally, 
the surface of the wheel may be polished to a high luster, as shown in 
functional block 33; however, this step is optional. Depending upon the 
process used, the polishing step may require additional surface 
preparation to clean polishing residue from the wheel surface. In 
functional block 34, the wheel is dried by heating to approximately 
250.degree. F. in a drying oven. The heating evaporates any rinse water 
which may have been retained in small pores formed in the surface of the 
wheel. If not removed from the surface pores, such water could be changed 
to steam during the curing of a coating applied to the wheel surface in 
the next step of the process. The expansion of the steam could rupture the 
coating, thereby marring the appearance of the finished wheel. 
In functional block 35, a coating is applied to the wheel. For a polished 
light weight wheel, the coating is usually a clear coat which protects the 
polished surface. The clear coat can be applied to the entire wheel or 
only to the outboard surface of the wheel disc 25. Alternately, a 
decorative coat of paint can be applied to all or a portion of the 
outboard surface of the wheel disc. The coating is cured in functional 
block 36 by heating the wheel in a curing oven to about 350.degree. F. A 
second clear coat (not shown) is usually applied over the coat of paint 
and cured to protect the painted surface. 
SUMMARY OF THE INVENTION 
This invention relates to a light weight wheel which is sealed with a 
surface coating to assure that the wheel is air tight. 
As shown in FIG. 1, one piece wheels typically include a thick sidewall 12 
which increases the total weight of the wheel 10. The thick sidewall is a 
result of the structure of the molds used to cast one piece wheels. The 
wheel weight would be reduced if a lightener recess or pocket were formed 
in the sidewall 12. However, as a charge of molten metal is poured into a 
wheel mold to form a wheel casting, gases often become entrained within 
the charge. The large volume of metal contained in the sidewall tends to 
retain pockets of entrapped gas as the molten metal solidifies. As a 
result, the sidewall 12 tends to have small voids or pockets formed 
therein. This is in contrast to the thinner portions of the wheel rim 
which comprise the deep well 17 and leg portion 18. The thinner portions 
of the wheel rim 11 allow the gas to migrate to the surface of the casting 
as the molten metal solidifies. Thus, when metal is removed from the 
sidewall 12 to lighten the wheel 10, the internal gas voids and pockets 
are exposed to the surface of the wheel. If one or more of these exposed 
voids or pockets extends through the remaining sidewall to either the 
opposite surface of the wheel rim 11 or the outboard face of the sidewall 
12, the void or pocket will provide a path for the inflation air to escape 
from a pneumatic tire mounted thereon. Such wheels are commonly referred 
to as "leakers" and are scrapped. Accordingly, it would be desirable to 
provide a process for forming a one piece wheel with lightener pockets 
which is not a leaker. It would also be desirable to prevent leakage from 
other portions of light weight one piece and multi-piece wheels. 
The present invention contemplates a vehicle wheel having an annular wheel 
rim adapted to support a pneumatic vehicle tire and a circular wheel disc 
formed across an end of the wheel rim. A layer of sealant is disposed over 
a portion of a surface of at least one of the wheel rim or the wheel disc. 
The sealant forms an airtight seal over the portion of the wheel surface 
covered by the sealant. 
In the preferred embodiment, the layer of sealant is formed from an epoxy 
resin. Additionally, the sealant can be a thermosetting epoxy resin. The 
invention also contemplates that a protective or a decorative coating can 
extend over at least a portion of the layer of sealant. 
The invention further contemplates that the wheel rim and the wheel disc 
cooperate to form a wheel sidewall which has at least one lightener recess 
formed therein with the sealant disposed over at least a portion of a 
surface of the sidewall recess. The recess can extend substantially around 
the circumference of the wheel sidewall or can include a plurality of 
individual pockets formed around the circumference of the sidewall. 
Alternately, the layer of sealant can be applied to a portion of a 
radially outer surface of the wheel rim. 
It will be appreciated that the invention can be practiced upon either a 
one piece wheel or a multi-piece wheel. One type of a multi-piece wheel is 
a two piece wheel which includes a wheel disc attached to the outboard end 
of a partial wheel rim. In the preferred embodiment of a two piece wheel 
the wheel disc is a full face wheel disc which includes a wheel sidewall. 
The wheel sidewall has at least one lightener recess formed therein and 
the sealant is disposed over at least a portion of a surface of the 
sidewall recess. 
The present invention also contemplates a process for forming a vehicle 
wheel comprising the steps of forming a vehicle wheel and applying a layer 
of sealant to a portion of a surface of the wheel, the sealant forming an 
airtight seal over the portion of the wheel surface. 
In the preferred embodiment, the wheel is formed with a sidewall portion 
which has at least one lightener recess formed therein and the layer of 
sealant is applied to a portion of a surface of the recess. Additionally, 
the sealant applied to the wheel is a thermosetting epoxy resin and, prior 
to applying the sealant, the wheel is heated. After applying the sealant, 
the wheel is maintained above a predetermined temperature for a 
predetermined time period to cure the sealant. Also, in the preferred 
embodiment, the sealant is sprayed onto the surface of the recess. 
Additionally, a decorative coating or a protective coating can be applied 
to a surface of the wheel. 
The process also contemplates applying the layer of sealant to a portion of 
a radially outer surface of the rim. 
Various objects and advantages of this invention will become apparent to 
those skilled in the art from the following detailed description of the 
preferred embodiment, when read in light of the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring again to the drawings, there is illustrated in FIG. 3A a 
fragmentary sectional view of an improved wheel 40 formed in accordance 
with the invention. Portions of the improved wheel 40 which are similar to 
the prior art wheel 10 shown in FIG. 1 are identified with the same 
numerical designators. As shown in FIG. 3A, a portion of the side wall 12 
has been removed to form a lightener pocket or recess 41 which extends 
axially beneath the outboard tire bead seat 14 from the drop well wall 16. 
As shown, the recess 41 is continuous; however, the recess 41 also can be 
interrupted for a small portion which contains a bore (not shown) for a 
wheel valve stem. Alternately, a plurality of webs which extend radially 
across the recess 41 (not shown) can be spaced equally along the recess 
41. The recess 41 also can be formed as a plurality of lightener pockets 
spaced uniformly about the face of the deep well wall 16 (not shown). 
A layer 42 of an air tight sealant covers the surface of the lightener 
recess 41. The sealant layer 42 fills the openings to any gas pockets 
formed in the sidewall 12 which communicate with the recess 41 and thereby 
prevents air leakage from a tire mounted upon the wheel rim 11 (not 
shown). In the preferred embodiment, the sealant layer 42 covers only the 
surface of the recess 41; however, as shown in FIG. 3B, the invention also 
contemplates extending a sealant layer 43 axially across the outer surface 
of the wheel rim 11. In FIG. 3B, the sealant layer 43 extends completely 
across the deep well 17 and leg portion 18 to the inboard tire bead 
retaining flange 21 to seal the entire rim 11. It is further contemplated 
that the sealant can be applied to portions of other surfaces of the wheel 
rim 11 and/or the wheel disc 25 (not shown) as needed to prevent air 
leakage therethrough. 
In the preferred embodiment, the sealant is a thermosetting epoxy resin 
which, upon heating, can be sprayed onto the wheel surface. Upon curing, 
the epoxy resin forms an air tight layer. An epoxy resin which has been 
successfully used to from the sealant layer 43 is Product 4X-017 which is 
available from Crosslink Technology, Inc. The invention contemplates 
spraying Product 4X-017 onto a wheel which has been heated above 
350.degree. F. The wheel is then maintained above 350.degree. F. for about 
15 minutes to cure the resin. The improved wheel 40 is both lighter than 
the prior art wheel 10 described above and sealed to prevent air leakage 
therethrough. 
As shown in FIG. 3B, the invention also contemplates that the wheel 40 can 
include a decorative or protective layer 44 which covers a portion of the 
sealant layer 43. The decorative/protective layer 44 is optional. The 
decorative layer would be formed from a paint while the protective layer 
would be formed from a clear coat. While the decorative/protective layer 
44 is shown in FIG. 3B as extending across the surface of the wheel rim 
11, the decorative layer also can cover the entire wheel 40 (not shown) or 
other portions than shown in FIG. 3B. The invention also contemplates 
applying both a decorative layer of paint and a protective clear coat 
layer to the wheel (not shown). Additionally, while the 
decorative/protective layer 44 is illustrated as covering the sealant 
layer 43, it will be appreciated that the sealant layer 43 can also be 
applied over a portion of the decorative/protective layer 44 (not shown). 
An alternate embodiment 45 of the improved vehicle wheel is shown in FIG. 
4. As above, portions or the wheel 45 which are the same as the prior art 
wheel 10 shown in FIG. 1 are identified by the same numerical designators. 
As shown in FIG. 4, a portion of the side wall 12 has been removed to form 
a lightener pocket or recess 46 which extends radially into the sidewall 
12 beneath the outboard tire bead seat 14 from an inner surface of the 
wheel rim 11. As shown, the recess 46 is continuous; however, the recess 
46 also can be interrupted for a small portion which includes a bore (not 
shown) for a wheel valve stem. Alternately, a plurality of webs which 
extend axially across the recess 46 (not shown) can be spaced equally 
along the recess 46. The recess 46 also can be formed as a plurality of 
lightener pockets spaced uniformly along the inner surface of the wheel 
rim 11 (not shown). 
A layer 47 of an air tight sealant covers the surface of the lightener 
recess 46. In the preferred embodiment, the sealant layer 47 covers only 
the surface of the recess 46; however, the invention also contemplates 
extending the sealant layer 47 axially across the inner surface of the 
wheel rim 11 (not shown). The sealant layer can extend completely across 
the inner surface of the deep well 17 and leg portion 18 to the outboard 
tire bead retaining flange 21. 
The present invention also contemplates a process for forming the improved 
wheels 40 and 45 shown in FIGS. 3A through 4. The process is illustrated 
by the flow chart shown in FIG. 5. Similar to the prior art process shown 
in FIG. 2, the process illustrated in FIG. 5 begins by forming a wheel 
casting in functional block 50 by a conventional casting method, such as 
gravity or low pressure casting. The wheel casting is machined to final 
shape in functional block 51. Then, a lightener pocket or recess is formed 
in the sidewall portion of the wheel in functional block 52 by a 
conventional process, such as undercutting. Alternately, the lightener 
pocket can be formed during the casting process. If a plurality of 
lightener pockets are desired, the sidewall can be ground away to form the 
pockets or the pockets can be formed during the casting process. The 
forming of the lightener recess is shown as an optional step in FIG. 5 
because it is contemplated that the process also can be applied to wheels 
which do not include lightener recesses. In functional block 53, the wheel 
surface is cleaned in preparation for finishing by immersion in a mild 
acid bath followed by a water rinsing. As before, the wheel can be 
optionally polished in functional block 54. The polishing process may 
include further surface preparation to remove polishing residue from the 
wheel surface. The wheel is dried in a oven in functional block 55 to 
assure removal of all moisture from any surface pores or pockets. 
A sealant is sprayed onto the surface of the lightener recess in functional 
block 56. A highly automated process is contemplated with the wheel 
rotated while a spray head propels a layer of sealant into the recess. 
Alternately, the sealant can be sprayed onto other surface portions of the 
wheel. In the preferred embodiment, the sealant is a thermosetting epoxy 
resin which is sprayed onto the wheel before the wheel has cooled from the 
drying step in functional block 55 to a temperature which is below the 
resin activation temperature. Accordingly, the residual heat retained by 
the wheel from the drying oven will activate the curing cycle of the 
thermosetting epoxy resin. 
In functional block 57, a protective and/or decorative clear coating or 
decorative paint coating is applied to the wheel; however, this step is 
optional. In the preferred embodiment, the clear or paint coating is 
applied only to the outboard face of the wheel disc, which will be visible 
when a tire is mounted upon the wheel. Thus, the epoxy resin and the clear 
coating or layer of paint are applied to different wheel surfaces. 
However, it will be appreciated that the invention also can be practiced 
with the clear coating or paint applied over the epoxy resin. 
In functional block 58, the wheel is inserted into a curing oven and both 
the epoxy resin and the coating are cured at approximately 350.degree. F. 
Depending upon the wheel design, additional coats of paint and/or clear 
coat may be applied to the wheel and cured (not shown). For example, a 
clear coat may be applied over the layer of paint to protect the paint. If 
the paint or clear coat is omitted, the epoxy resin is cured in functional 
block 58. Alternately, if the residual heat remaining in the wheel when 
the epoxy resin is applied is sufficient to cure the resin, a curing oven 
is not required for curing the resin. 
An alternate embodiment of the process is illustrated by the flow chart 
shown in FIG. 6. The initial steps of the process are the same as 
described above. Thus, a wheel casting is formed in functional block 60. 
The wheel casting is machined to final shape in functional block 61 and at 
least one lightener recess is formed in the sidewall in functional block 
62. Again, the forming of the lightener recess is shown as an optional 
step in FIG. 6 because it is contemplated that the process also can be 
applied to wheels which do not include lightener recesses. The wheel 
surface is prepared in functional block 63 by cleaning and optional 
polishing in functional block 64. As before, the cleaned wheel is then 
dried in functional block 65. 
In functional block 66 a protective and/or decorative clear coating or 
decorative paint coating is applied to the surface of the wheel and cured 
in functional block 67. As before, these steps can be repeated for 
additional clear and/or paint coatings. After the decorative coatings are 
cured, but while the wheel is still hot, the sealing epoxy resin is 
sprayed onto the surface of the lightener recess and/or other surfaces 
which are to be sealed in functional block 68. The epoxy is then cured in 
functional block 69. 
While the preferred embodiment of the invention has been illustrated and 
described as being applied to a one-piece wheel, it will be appreciated 
that the invention also can be practiced upon a multi-piece wheel. One 
example of a multi-piece wheel is a two piece wheel which comprises a 
circular wheel disc attached to annular wheel rim. A typical full face two 
piece vehicle wheel 75 is shown in FIG. 7. The two piece wheel 75 includes 
a full face wheel disc 76 which is formed by a conventional casting or 
forging process. The wheel disc 76 is attached to the outboard end of a 
partial wheel rim 77 with a continuous air-tight weld 78. Components of 
the wheel 75 which are similar to components shown in the preceding 
figures have the same numerical designators. As shown in FIG. 7, the wheel 
75 includes a sealant layer 42 which covers only the surface of the 
lightener pocket 41; however, it will be appreciated that the sealant 
layer 42 can extend across the wheel rim 77 (not shown) or cover other 
surface portions of the wheel 75 (not shown). 
The inclusion of the sealant layer allows enlargement of the lightener 
pocket which further reduces the weight of the wheel. Additionally, the 
sealant layer permits greater flexibility in the design of light weight 
wheels by eliminating the potential for air leaks in the finished wheels. 
In accordance with the provisions of the patent statutes, the principle and 
mode of operation of this invention have been explained and illustrated in 
its preferred embodiment. However, it must be understood that this 
invention may be practiced otherwise than as specifically explained and 
illustrated without departing from its spirit or scope. For example, the 
process of spraying the epoxy resin can be practiced upon a wheel which 
has been cooled by adding a step to preheat the wheel before spraying the 
resin onto the wheel surface. Additionally, the wheel disc may be recessed 
within the wheel rim. Furthermore, it is contemplated that the sealant can 
be applied to surfaces of wheels that do not include a lightener recess.