U.S. patent number RE33,919 [Application Number 07/442,729] was granted by the patent office on 1992-05-12 for pneumatic starter for internal combustion engine.
This patent grant is currently assigned to Sycon Corporation. Invention is credited to Michael Elwer, John J. Kristoff.
United States Patent |
RE33,919 |
Kristoff , et al. |
May 12, 1992 |
Pneumatic starter for internal combustion engine
Abstract
A starter arrangement for an engine includes a fluid actuated
rotary vane motor which is adapted to engage an associated engine.
The rotary motor has a plurality of blades or vanes with each of
the blades being made from a fiber reinforced plastic material to
reduce friction. A sleeve, in which the rotary motor is positioned,
has on its inner surface a hard metallic coating to reduce
friction. A relay valve member selectively provides a pressurized
operating fluid to the rotary motor. The blade material and the
sleeve inner surface coating cooperate to enable the vane motor,
when it is actuated by the relay valve member, to rotate in the
sleeve with a minimum of friction thereby obviating the need for a
lubricating agent.
Inventors: |
Kristoff; John J. (Marion,
OH), Elwer; Michael (Marion, OH) |
Assignee: |
Sycon Corporation (Marion,
OH)
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Family
ID: |
27363869 |
Appl.
No.: |
07/442,729 |
Filed: |
November 29, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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31399 |
Mar 27, 1987 |
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781216 |
Sep 26, 1985 |
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Reissue of: |
167402 |
Mar 14, 1988 |
04846122 |
Jul 11, 1989 |
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Current U.S.
Class: |
123/179.31;
29/527.2; 29/888.025; 418/152; 418/178; 418/260 |
Current CPC
Class: |
F02N
7/08 (20130101); Y10T 29/49245 (20150115); Y10T
29/49982 (20150115) |
Current International
Class: |
F02N
7/00 (20060101); F02N 7/08 (20060101); F02N
017/00 (); F01C 001/344 (); F01C 021/00 () |
Field of
Search: |
;418/152,178,260
;123/179F ;29/156.4WL,527.2,527.4,888.025,888.061 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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22103 |
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Jan 1981 |
|
EP |
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2752233 |
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Jun 1979 |
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DE |
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Other References
McGraw-Hill Dictionary of Chemistry, p. 403. .
Hackh's Chemical Dictionary (Fourth Edition), p. 435. .
Metals Handbook (8th Edition), p. 509. .
Marks, Mechanical Engineers' Handbook, (Sixth Edition), McGraw-Hill
Book Co. Inc., 1958, pp. 13-65..
|
Primary Examiner: Vrablik; John J.
Attorney, Agent or Firm: Fay, Sharpe, Beall, Fagan, Minnich
& McKee
Parent Case Text
BACKGROUND OF THE INVENTION
This application is a continuation-in-part of patent application
Ser. No. 031,399, filed on Mar. 27, 1987 and now abandoned, which
in turn, is a continuation of patent application Ser. No. 781,216,
filed on Sept. 26, 1985 and now abandoned.
Claims
Having thus described the invention, it is now claimed:
1. A starter arrangement for an engine, comprising:
a fluid actuated rotary vane motor which is adapted to engage an
associated engine, said rotary motor having a hub and at least one
blade which is slidably mounted in said hub and is made from a
fiber reinforced plastic material to reduce friction, and wherein
said at least one blade has a wear surface made of the same
material;
a housing including a sleeve in which said rotary motor is
positioned, said sleeve having on its inner surface a hard metallic
coating to reduce friction, wherein said sleeve inner surface
coating comprises a chromium .[.electrocating.].
.Iadd.electrocoating .Iaddend.having a hardness which measures at
least 70 on the Rockwell C hardness scale and a microfinish of
.[.less than.]. .Iadd.approximately .Iaddend.10 micro-inches
R.M.S.; and,
.[.a relay valve means for selectively providing a pressurized
operating fluid to said rotary motor, .]. wherein said blade
material and said sleeve inner surface coating cooperate to enable
said motor to rotate in said sleeve with a minimum of friction
thereby obviating the need for a lubricating system for the starter
arrangement.
2. The arrangement of claim 1 wherein said fiber reinforcing
material for said at least one blade is selected from the group
consisting of aramid fiber, glass fiber, boron fiber or carbon
fiber.
3. The arrangement of claim 1 further comprising:
a source of pressurized operating fluid;
a conduit means for interconnecting said source of operating fluid
and .[.said.]. .Iadd.a .Iaddend.valve means; and,
a driving means for transmitting the rotation of said motor to the
associated engine and wherein said driving means includes a pinion
gear which cooperates with a flywheel of the associated engine to
rotate said flywheel.
4. The arrangement of claim 1 further comprising:
a muffler which is secured to said housing; and,
an eccentric cam which urges said at least one blade outwardly as
said vane motor rotates.
5. The arrangement of claim 1 wherein said at least one blade
comprises an aramid fiber reinforced resin material.
6. The arrangement of claim 1 wherein said at least one blade
comprises a plurality of superimposed layers of a reinforcing fiber
cloth coated with a resin binder.
7. The arrangement of claim 1 further comprising a hard metallic
coating provided on a portion of said hub adjacent said at least
one blade to reduce friction between said hub and said at least one
blade as said at least one blade slides in said hub.
8. The arrangement of claim 7 wherein said hub hard metallic
coating comprises a chromium electrocoating having a hardness which
measures at least 70 on the Rockwell C hardness scale.
9. A starter arrangement for starting an internal combustion engine
with compressed fluid, comprising:
a housing including a metallic sleeve wherein said sleeve has on
its inner surface a hard metallic coating which measures at least
70 on the Rockwell C hardness scale, said coating on said sleeve
having a microfinish of .[.less than.]. .Iadd.approximately
.Iaddend.10 micro-inches R.M.S.;
a fluid actuated rotary vane motor rotatably mounted in said
sleeve, said motor having a plurality of blades with each of said
blades being made from a plurality of layers of a resin-coated
fiber cloth material to reduce friction wherein each of said blades
has a wear surface made of the same material, and wherein as said
blades slide against said sleeve there is minimal friction
occurring thereby obviating the need for a separate lubricating
system for the starter arrangement.[.; and,
a source of pressurized fluid for actuating said rotary
motor.]..
10. The arrangement of claim 9 further comprising a motor housing
in which said sleeve and .[.said.]. .Iadd.a .Iaddend.relay valve
are positioned.
11. The arrangement of claim 9 wherein said blade reinforcing
material comprises an aramid fiber.
12. The arrangement of claim 9 wherein said sleeve inner surface
coating comprises a chromium electrocoating having a hardness which
measures at least 70 on the Rockwell C hardness scale.
13. The arrangement of claim 9 wherein said sleeve inner surface
coating comprises metallic particles encapsulated in a ceramic
material, and a slurry binder system.
14. The arrangement of claim 9 wherein said sleeve inner surface
coating comprises titanium nitride having a hardness on the
Rockwell C hardness scale of approximately 85.
15. The arrangement of claim 9 wherein said sleeve inner surface
coating comprises an electroless nickel alloy.
16. The arrangement of claim 15 wherein said nickel alloy coating
is infused with a polymer such as fluorocarbon.
17. An unlubricated, and hence environmentally desirable, pneumatic
starter for an internal combustion engine, comprising:
an integral housing including a sleeve having on its inner surface
a hard metallic coating to reduce friction, said coating comprising
a chromium electrocoating having a hardness which measures at least
70 on the Rockwell C hardness scale and wherein said coating on
said sleeve has a microfinish of less than 10 micro-inches
R.M.S.;
a fluid actuated rotary vane motor rotatably mounted in said
sleeve, said motor having a hub and a plurality of blades with each
of said blades being made from an aramid fiber reinforced plastic
material to reduce friction as said blades rotate in said sleeve,
wherein said blades have a wear surface made of the same fiber
reinforced plastic material;
a source of pressurized air for actuating said rotary motor;
and,
an eccentric cam for positively displacing said blades in relation
to said hub when said motor is actuated, the rotation of said vane
motor in said sleeve, causing a minimum of friction thereby
obviating the need for a separate lubricating system.
18. The starter of claim 17 wherein said hub has a plurality of
slots, one for slidably mounting each of said plurality of blades,
and further comprising a hard metallic coating provided on a
surface of said hub at each of said slots to reduce friction
between said hub and said blades as said blades slide in said
hub.
19. The arrangement of claim 18 wherein said hub hard metallic
coating comprises a chromium electrocoating having a hardness which
measures at least 70 on the Rockwell C hardness scale. .Iadd.
20. A starter arrangement for a compression ignition engine,
comprising:
an air actuated rotary vane starter motor which is adapted to
engage the compression ignition engine, said rotary motor having a
hub with a slot therein, wherein said hub slot includes a hard
metallic coating to reduce friction;
a blade which is slidably mounted in said hub slot, said blade
comprising a fiber reinforced plastic material to reduce friction;
and,
a housing including a sleeve in which said hub and blade are
positioned, said sleeve having on its inner surface a hard metallic
coating to reduce friction, wherein said sleeve comprises a ferrous
material and wherein said hard metallic coating on said hub slot
and on said sleeve inner surface is a material selected from the
group consisting of chromium, nickel and titanium, wherein said
blade material, hub slot coating and sleeve inner surface coating
cooperate to enable said motor to rotate with a minimum of friction
thereby obviating the need for a lubricating system for the starter
arrangement. .Iaddend. .Iadd.21. The starter arrangement of claim
20 wherein said housing sleeve hard metallic coating has a hardness
which measures at least 70 on the Rockwell C hardness scale.
.Iaddend. .Iadd.22. The starter arrangement of claim 21 wherein
said housing sleeve hard metallic coating has a microfinish of less
than 10 microinches RMS. .Iaddend. .Iadd.23. The starter
arrangement of claim 20 wherein said hub slot hard metallic coating
has a hardness which measures at least 70 on the Rockwell C
hardness scale. .Iaddend. .Iadd.24. The starter arrangement of
claim 23 wherein said hub slot hard metallic coating has a
microfinish of less than 10 microinches RMS. .Iaddend.
Description
This invention generally pertains to starters. More specifically,
the present invention relates to a pneumatic starter for an
internal combustion engine.
The invention is particularly applicable to an air starter designed
for truck applications. However, it should be recognized that the
pneumatic starter of the present invention may also be adapted for
use in othe engine environments such as off-highway equipment,
emergency generators, locomotives, dirt hauling equipment,
compressors and the like.
When a compression ignition engine is started, its crankshaft must
be rotated at a speed sufficient to compress the air in the
cylinder to a pressure at which its temperature is sufficiently
high to ignite the fuel injected into the cylinder. With the
unavoidable leakage of some air past the piston rings, it is
essential that the engine be turned over at a high rate of speed
and this requires a substantial power output from the starter
motor. A pneumatic motor or "air" motor is especially adapted for
such starter applications since the motor can generate a large
amount of power in a small frame size and since there is no
reduction of its power output at either low temperatures or high
temperatures as there would be with battery operated electric
starters. The pneumatic motor is operably connected to the engine
in such a way that the rotation of the motor causes it to engage
and crank the engine until the engine becomes self-sustaining.
Such a pneumatic motor system includes a tank which contains a
supply of pressurized fluid used to rotate the pneumatic motor.
Systems of this type also commonly utilize a relay valve interposed
between the pressurized tank and the pneumatic motor. This valve is
normally closed and is selectively opened to feed pressurized fluid
to the pneumatic motor to actuate the latter.
In one known positive displacement pneumatic motor, the blades or
vanes of the motor engage an eccentrically located inner surface of
a sleeve which provides a circumferential restraint but radial
freedom of movement for the blades. The pneumatic motor is thus
positioned within the sleeve in an eccentric manner so as to
provide a number of chambers with the sleeve. The vanes are thrust
into intimate contact with the sleeve and a considerable amount of
frictional heat is generated. There is thus a need to provide
lubrication to the motor to prevent undue wear of the vanes. If
such a lubricating means is not provided, or if the lubricating
means should fail, the sleeve and the vanes would become subject to
failure in a very short period of time due to friction. Generally
speaking, such a lubricating means includes a mechanism for
entraining a measured charge of atomized lubricant into the air
delivered to the starter at the beginning of each starting
operation.
However, such lubricators are relatively expensive in relation to
the cost of the entire air starter system, up to approximately one
sixth of the cost of the whole air starter. Moreover, lubricators
also add to the mechanical complexity of the entire system. Also,
even with a lubricator system, a conventional air starter only has
a lifetime of approximately 10,000 cycles by the end of which the
sleeve is usually scored and rusted, due to moisture in the ambient
air, and the vanes are worn.
Additionally, both bus operators and the marine industry have
experienced annoying and costly problems with conventional air
starters having lubrication systems. These problems emenate from
frequent lubricator malfunctions which cause an "over lubrication"
condition resulting in surplus lubricant being sprayed into the
engine compartment. The lubricant is eventually dicharged into the
atmosphere. In the case of diesel engine buses especially,
lubricant discharged into the atmosphere worsens air pollution in
urban areas. Generally, such lubricant fluid can be the diesel fuel
used by the engine itself. Even when the conventional air starter
lubricators are not malfunctioning, approximately 1 cc of lubricant
fluid is discharged into the atmosphere on each engine start.
It is evident that the use of unlubricated air starter motors would
be of great environmental benefit. Additionally, by providing an
unlubricated air starter, a considerable sum of money could be
saved in fuel costs per year, since the "saved" fuel would have
been expended to lubricate a conventional air starter.
Accordingly, it has been considered desirable to develop a new and
improved pneumatic starter for an internal combustion engine which
would overcome the foregoing difficulties and others while
providing better and more advantageous overall results.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, a new and improved
starter arrangement for an engine is provided.
More particularly in accordance with the invention, the starter
arrangement includes a fluid actuated rotary vane motor which is
adapted to engage an associated engine. The rotary motor has a
plurality of blades with each of the blades being made from a fiber
reinforced plastic material to reduce friction and wherein the
blades have a wear surface made of the same material. The rotary
motor is positioned in a housing including a sleeve which has on
its inner surface a hard metallic coating and a microfinish of less
than 10 micro-inches R.M.S. to reduce friction. A relay valve means
of the starter arrangement selectively provides a pressurized
operating fluid to the rotary motor. When such operating fluid is
provided, the blade material and the sleeve inner surface coating
cooperate to enable the motor to rotate in the sleeve with a
minimum of friction thereby obviating the need for lubricating
system for the starter arrangement.
In accordance with another aspect of the invention, a starter
arrangement for starting an internal combustion engine with
compressed fluid is provided.
More particularly in accordance with this aspect of the invention,
the arrangement includes a housing having a metallic sleeve and a
fluid actuated rotary vane motor rotatably mounted in the sleeve.
The motor has a plurality of vanes or blades with each of the
blades being made from a fiber reinforced plastic material to
reduce friction, wherein each of the blades has a wear surface made
of the same material. Also, the sleeve has on its inner surface a
hard metallic coating to reduce friction so that as the blade
slides against the sleeve, minimal friction occurs. A source of
pressurized fluid is provided for actuating the motor. The sleeve
has a microfinish of less than ten micro-inches R.M.S.
In accordance with still another aspect of the invention, a
pneumatic starter for an internal combustion engine is
provided.
In accordance with this aspect of the invention, the starter
includes an inner housing including a sleeve having on its inner
surface a hard metallic coating a reduce friction. The coating
comprises a chromium electro-coating having a hardness which
measures at least 70 on the Rockwell C Scale. Also, the sleeve has
a microfinish of less than 10 micro-inches R.M.S. A fluid actuated
rotary vane motor is rotatably mounted in the sleeve. The motor has
a plurality of blades with each of the blades being made from a
fiber reinforced plastic material to reduce friction as the blades
rotate in the sleeve. The fiber is made from an aramid material and
the blades have a wear surface made of the same fiber reinforced
plastic material. A source of pressurized air is provided for
actuating the rotary motor. An eccentric cam is provided for
positively displacing the blades when the motor is actuated.
One advantage of the present invention is the provision of a new
pneumatic starter motor which runs with less friction than previous
starters.
Another advantage of the invention is the provision of a starter
arrangement which obviates the necessity for a separate lubricating
system for the arrangement due to the reduced amount of friction
which is generated as the starter motor operates because of the
motor's improved self-lubrication properties.
Still another advantage of the invention is that the reduction in
the amount of friction generated as the starter motor operates
enables the elimination of the conventional expensive lubricator
system contained in a traditional air starter as well as its
attendant piping system. This reduces the cost of the air starter
by approximately one sixth.
Yet an another advantage of the present invention is the provision
of a lubrication-free air starter which eliminates a source of
environmental polution in comparison to a conventional air starter
have a lubricator system which discharges approximately 1 cc of
lubricant into the atmosphere per start of the engine.
Yet still another advantage of the present invention is its
provision of a lubrication-free air starter which can save a
considerable amount of money per year per engine in fuel. The saved
fuel would have been expended to lubricate a conventional air
starter.
An additional advantage of the present invention is its provision
of an air starter having an average life which can be up to ten or
more times as long as that of conventional air starter due to its
reduced friction characteristics.
Still other benefits and advantages of the invention will become
apparent to those skilled in the art upon a reading and
understanding of the following detailed specification.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take physical form in certain parts and
arrangements of parts, preferred embodiments of which will be
described in detail in this specification and illustrated in the
accompanying drawings which form a part hereof, and wherein:
FIG. 1 is a schematic side elevational view of a starter
arrangement and related components according to a first preferred
embodiment of the present invention;
FIG. 2 is an enlarged perspective view, partially broken away, of
the starter arrangement of FIG. 1;
FIG. 3 is a reduced exploded perspective view of certain components
of the starter arrangement of FIG. 2;
FIG. 4 is a schematic cross-sectional view of the starter
arrangement of FIG. 2;
FIG. 5 is a greatly enlarged view through a portion of the starter
arrangement of FIG. 4; and,
FIG. 6 is a greatly enlarged view through a portion of a starter
arrangement according to a second preferred embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, wherein the showings are for
purposes of illustrating the preferred embodiments of the invention
only and not for purposes of limiting same, FIG. 1 shows the
subject new starter arrangement in a complete starter installation.
While the starter arrangement is primarily designed for and will
hereinafter be described in connection with a diesel internal
combustion engine for a truck, bus, boat, or the like it will be
appreciated that the overall inventive concept involved could be
adapted for other engine environments, such as emergency
generators, locomotives, dirt hauling equipment, compressors, and
the like and also for engines other than diesel engines.
More particularly, the starter installation includes an air tank 10
which is connected by an air conduit 12 to a relay valve means 14.
A manually actuated valve control member 16, which is usually
positioned in the cab of a truck or other vehicle (not
illustrated), controls the actuation of the relay valve means 14 of
an air motor.
With reference now also to FIG. 2, the valve means 14 is preferably
positioned within a housing 20. Also positioned within the housing
20 is a sleeve 22 and a sleeve adapter 24 which admits pressurized
fluid from the valve means 14 into a sleeve interior 26. The sleeve
22 has a body section 28 which has on its interior surface a
coating layer 30 as best seen in FIG. 5.
In one preferred embodiment, the sleeve is made out of a metal such
as gray iron and the sleeve coating is made of an "armoloy"
material. Such a material is a hard chromium electrocoating having
a hardness which measures at least 70 on the Rockwell C hardness
scale. This coating is sold by the Armoloy Corporation of 118
Simonds Avenue, Dekalb, Ill. The coating is effective in increasing
wear resistance in sliding surface contacts and provides superior
corrosion and erosion resistance. This coating may be on the order
of 0.0002 inches in thickness. It is evident that the thickness of
layer 30 has been greatly magnified in FIG. 5 for easier
visibility.
Alternatively, a metallic ceramic coating may be used for the inner
surface of the sleeve. This coating combines metallic particles,
such as aluminum particles, encapsulated in a ceramic with a slurry
binder system. This coating also provides a great resistance to
corrosion, erosion and abrasion. The thickness of such a protective
film coating can vary from 0.001 to 0.006 inches. Such coatings are
available from Metallic Ceramic Coatings, Inc., Front and Ford
Streets, Bridgeport, Pa. Such a coating provides abrasion and
corrosion resistance and aids in reducing friction between
components.
Another such coating is a titanium nitride coating which is
available from the Star Cutter Company of Farmington Hills, Mich.
This type of coating can be applied through a physical vapor
deposition process and will result in a coating thickness of 0.0001
to 0.0002 inches. The coating has a Rockwell C hardness of
approximately 85. Such a coating effectively improves abrasion
resistance and corrosion resistance.
Still another possible coating is an electroless nickel alloy. Such
coatings may have a thickness of up to 0.001 inch if desired,
although thicknesses as small as 0.0003 inches can also be used. An
electroless nickel alloy also provides low friction properties and
a smooth surface finish. Such a nickel coating can be obtained from
the Armoloy Corporation of DeKalb, Ill. A nickel alloy coating of
this type can be infused with a polymer such as fluorocarbon to
provide an inherent lubrication. Such a polymer infused nickel
alloy coating is available from General Magnaplate Corp., of
Linden, N.J.
With reference now also to FIG. 3, positioned in the sleeve
interior 26 is a rotor 40 having at least one rotor vane or blade
42 thereon. In the preferred embodiment, five such rotor blades 42
are provided but, of course, any suitable number of blades can be
used. Driving the rotor blades 42 is an eccentric cam 44 as may
best be seen from FIG. 4. The eccentric cam 44 prepositions the
blades 42 into the air stream flow from the air tank through the
relay valve means 14. This design is considerably more tolerant of
contaminants and frost than most prior art designs and provides
instant torque and starting reliability even under adverse weather
conditions.
With reference now to FIG. 5, it can be seen that each blade has a
blade body 46 which is provided with a plurality of strand-like
reinforcing elements 48. In one preferred embodiment, the
reinforcing fiber is an aramid fiber, such as KEVLAR brand fiber
sold by E. I. duPont de Nemours Corp. of Wilmington, Del., which
also provides great flexural strength as the blade rotates in the
sleeve.
Other reinforcing fiber could, of course, also be used. Among these
fibers are glass fibers, boron fibers, and carbon fibers, i.e.
graphite fibers. The fibers are preferably woven into a "cloth"
which is then coated with a resin binder. The resin coated "cloth"
is set in a humidity chamber. A plurality of superimposed layers of
such cloth, depending on the thickbess desired for the blade, are
then provided in a sheet to a press. The press applies heat and
pressure to the sheet to bind the several layers together.
Thereafter, blades can be fabricated from the sheet.
If the fibers are made of glass, the resin can be an epoxy. On the
other hand, if the fiber are aramid, the resin can be phenolic. Of
course, the various layers of fibers in the blade can be oriented
in different directions or in the same direction, as desired. One
advantage of such reinforced plastic blades is that they are
friction resistant. Another advantage is that they are not prone to
rusting thereby increasing the life cycle of the air starter.
In order to provide an airtight chamber, the sleeve 22 is provided
on each end with a respective end plate 50, 52 as shown in FIG. 3.
With reference again to FIG. 2, a gear element 54, which is driven
by the rotor 40 through a shaft 56, is positioned adjacent the
second end plate 52. A second gear 58 is driven by the first gear
54.
The second gear 58 is part of a drive means 60 for transmitting the
power of the vaned motor to an internal combustion engine having a
flywheel ring gear 62 (see FIG. 1). Also positioned on the housing
20 is an integral muffler 64.
In the present invention it has been found that the use of a sleeve
coating 30 reduces the coefficient of friction of the rotor blades
42 as they rotate against the sleeve 22. Also, the rotor blades are
made of a suitable fiber reinforced plastic material which further
reduces friction. Such friction has in the past been responsible
for the wear and corrosion of the sleeve 22.
A conventional air starter has an average lifetime of approximately
10,000 cycles. Depending on the frequency of the starts per day,
such 10,000 cycles can be accumulated in 3 to 8 years of use. At
the end of this time, the sleeve of the starter may have rusted or
scored so as to be unusable and the blades generally have become
worn despite the use of a lubricating system which supplies
lubricant for the sleeve and the blades.
In a test of an air starter constructed according to the present
invention, however, the use of the "armoloy" material together with
aramid fiber reinforced plastic blades, resulted in minimal wear to
the blades over 10,000 cycles of the air starter despite the
absence of a lubricating system. It was found that blade wear was
less than 0.010 inches even without external lubrication. It was
also found that there was negligible wear on the sleeve. It is
estimated that the construction of an air starter from the
materials listed above will increase the life cycle of the air
starter up to at least 14,000 cycles and perhaps to as much as
30,000 cycles. Besides a longer life cycle for the air starter, the
elimination of an external lubrication system results in a
considerable savings on the cost of the air starter and also
results in a much simpler and mechanically less complex unit.
In the preferred embodiment, the blades are made of aramid fiber
reinforced plastic which can have a coefficient of thermal
expansion of approximately 35.3.times.10.sup.-6 inches/inch
.degree.C. linearly and approximately 32.9.times.10.sup.-6
inches/inch .degree.C. crosswise. In contrast, the sleeve, which is
made of cast iron can have a coefficient of thermal expansion of
12.96.times.10.sup.-6 cm/cm .degree.C.
With reference now to a second preferably embodiment of the
invention, as illustrated in FIG. 6, the invention is there shown
as having another construction. For ease of illustration and
appreciation of this alternative, like components are identified by
like numerals with a primed (') suffix and new components are
identified by new numerals.
In this FIGURE, the interior surface of a sleeve body 28' has been
given a very smooth surface. The surface was reduced from 40
micro-inches, as in the embodiment of FIG. 5, to approximately 8 to
10 micro-inches, and ideally to 5 micro-inches R.M.S. in the
embodiment of FIG. 6. This finish is achieved by honing the sleeve
interior surface using the finest honing stone presently available.
Previously, a rougher finish was acceptable for the sleeve inner
surface since lubrication was provided during each start of the air
motor. Now a smoother sleeve inner surface finish is considered
very desirable despite its additional cost.
Extensive testing has revealed that the surface finish of the inner
wall of the sleeve is critical in determining the life expectancy
of the air starter. In this regard, while a surface finish of 40
micro-inches might allow up to 15 to 20,000 cycles on the air
starter of FIG. 5 before failure, a microfinish of approximately 8
micro-inches has given a significantly longer life. More
specifically, a test run on such an air starter having such a
sleeve microfinish has exceeded 125,000 cycles without failure of
the blades. Eventually, a rotor shaft 56' of the air starter failed
due to metal fatigue. However, there was a minimum of scoring or
pitting on the sleeve surface and a minimum of wear on the
vanes.
The inner surface of the sleeve body 28' can be provided with a
coating 80 which can be made of hard chromium electro-coating, such
as armoloy, having a hardness which measures at least 70 on the
Rockwell C hardness scale. Hardness tests also indicate a
measurement of from 1020 to 1100 on the Vickers Diamond Pyramid
Hardness Scale. This equals 70 to 72 on the Rockwell C Scale. The
armoloy material conforms to the existing surface of a body
including threads, flutes, scratches, etc. with detail down to
approximately 8 micro-inches R.M.S. Additionally, armoloy will not
affect a growth on the surface of the material more than 0.0002
inches under normal circumstances thereby eliminating the need for
undersized design calculations in most applications. The coating 80
works its way into the surface of the sleeve material and adheres
so positively that it will not chip, peel, crack, or flake when
subject to standard ASTM bend tests over a radius equal to half the
thickness of the material to which it is applied.
Roughness, the finely spaced surface texture irregularity resulting
from the manufacturing process or the cutting action of tools or
abrasive grains, has in general a greater effect on performance
than any other surface quality. The control of roughness appears to
be very important in prolonging the life of the air starter.
If desired, a slot 82 in a hub in which a vane 42' reciprocates can
also be coated with a suitable hard material coating 84 such as
armoloy. This may be advantageous in preventing the pitting or
scoring of the slot 82 as well as in preserving the vane material
from scratches or other surface degredation. The coating material
84 may be the same as the coating 80 on the inner surface of the
sleeve or it may be another low friction coating material.
The subject invention thus provides an air starter arrangement
which produces less friction as the blades rotate in a sleeve than
do conventional systems. Therefore, the present arrangement enables
the elimination of conventional lubrication systems which are used
in air starters thus resulting in a considerable cost and material
savings on the starter arrangement.
Through a judicious selection of coating materials and vane
materials as well as through the provision of a microfinish on the
sleeve inner surface in the range of 8 to 10 micro-inches, a
tenfold increase has been achieved in the life expectancy of air
starters for engines. More specifically, while a conventional air
starter has a life expectancy of approximately 10,000 cycles by the
end of which the sleeve is usually scored and rusted and the vanes
are worn, an air starter according to the present invention can
have a life expectancy of more than 100,000 cycles.
The invention has been described with reference to preferred
embodiments. Obviously, modifications and alterations will occur to
others upon the reading and understanding of this specification. It
is intended to include all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents thereof.
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