Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
APPARATUS AND METHOD FOR BLASTING M TALL~C SURFACES
This invention pertains to an apparatus and method
for blasting the cylinder walls of aluminum engine blocks in
preparation for the coating of the same with a
wear-resistant coating material. It also broadly pertains
to an apparatus and method for blasting other products for
subsequent treatment.
BACKGROUND OF THE INVENTION
In recent years, aluminum pistons and aluminum
engine blocks have been used in automotive engines, but
scuffing and wear due to the motion between the piston and
the cylinder wall has created a problem. United States
Patent 5,080,056, which issued on January 14, 1992,
discloses this problem and the efforts made to solve it.
Patent 5,080,056'teaches a method of forming a scuff- and
wear-resistant liner in a relatively low-silicon content
aluminum alloy cast engine block. It discloses that engine
block casts of a suitable low-silicon aluminum alloy, such
as the aluminum 319 alloy, are easily cast into an engine
block, and aluminum-bronze alloy compositions are applied by
a thermal spray process onto the internal diameter of the
cylinder bores of the aluminum casting. The patent
discloses that before the thermal sprayed composition is
applied to the cylinder bore it is thoroughly gleaned and
degreased so as to be in suitable condition for the thermal
sprayed coating to be adhered to the walls of the cylinder
bore.
The owner of United States Patent 5,080,056
approached the assignee of this application requesting that
an apparatus be developed for pr~pari.ng the surface of the
cylinder bore portion of the castin-; :For application of the
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1 thermal sprayed coating material. The obvious method for
preparing the surfaces was believed to be by dry or slurry
blasting a grit such as small ground pieces of glass,
aluminum oxide, silican carbide, etc. that would roughen the
surface of the cylindrical bore portion to which the coating
could be more firmly attached and held. Use of blasting a
grit creates the problem of ensuring that all of the grit is
removed from the engine block in order to avoid the grit or
abrasive contaminating parts of the engine. Further, the W
grit itself could probably lodge in crevices of the engine
block or the cylinder bore surface itself. Thus, the use of
grit or abrasives to roughen the surface requires subsequent
cleaning of the entire area where the grit may be which is a
time-consuming operation. Also, there is no assurance that
all of the grit has been washed out completely. In fact, it
is practically impossible to assure all the grit has been
removed from the areas where it may be contained as a result
of the blasting operation.
Another disadvantage of using grit or abrasive
slurries is that the abrasive or grit can even contaminate
the surface being treated and although in many instances the
roughed surface is suitable to hold the coating, increased
tenacity of the roughed surface is desired. In -_ccordance
with the preferred embodiments of our invention, these
problems are eliminated in a more economical way than one
skilled in the art would ever conceive.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with our invention, I use
substantially pure water as the blasting media. By pure
3p water, we mean, there is no grit and essentially no other
materials added to the water. Further, we use a high
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1 pressure pump that pumps water through very small orifices
to create water jets that are directed onto the cylinder
bore surfaces at a pressure exceeding twenty-five thousand
pounds per square inch (25,000 psi). The water jets have
pressures between 25,000 and 60,000 psi and preferably about
fifty thousand pounds per square inch (50,000 psi)
particularly for the very best results in the preparing
aluminum 319 alloy for coating as disclosed in Patent
5,080,056.
I have discovered that water jets will roughen the
surface of the aluminum cylinder bore and clean them at the
very same time. The water jets not only roughen the surface
to increase the surface area to which the thermal sprayed
composition can attach but, also, attack the pores of micro
structure, that is the interstices of the metal, so as to
form undercuts that provide superior adhesion for the
coatings as compared to prior known methods. Thus, our
invention cleans the surface to eliminate leaving any
preexisting contaminated material on the surfaces, etches
the surface to provide superior adhesion for the coating and
leaves no harmful residue of itself.
A more detailed description of the apparatus and
method of our invention will be found below. These and
other objects and advantages of our invention will become
more clear particularly when described with relation to the
attached drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective cutaway, schematic view of
a four cylinder aluminum cast engine block with the major
3p part of our apparatus in the cylinders so as to illustrate
our invention;
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1 Fig. 2 is a perspective cutaway view of a cylinder
with the major part of our apparatus contained therein and, s
further, illustrating my invention;
Fig. 3 is a perspective cutaway view of a cylinder
illustrating the step of the coating being thermally sprayed
on the inside surface of the cylinder, such surface, having
previously been prepared by my invention as illustrated in
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Figs. 2 and 3.
Figs. 4a, 4b and 4c illustrate the sequential
condition of a metal surface treated in accordance with our
invention and then coated. Fig. 4a showing the surface
untreated; Fig. 4b showing the surface after being treated
by our method and apparatus and Fig. 4c disclosing the
coated surfaces
Figs. 5 and 6 disclose another embodiment of our
invention as it applies to the treatment of a flat surface
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rather than a cylindrical surfaces and
Fig. 7 discloses an apparatus for moving either of
the two rotating heads as disclosed in Figs. 1, 2, 3 and 5.
ZO DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, Figs. 1, 2 and 6
disclose the apparatus and method of this invention. Figs.
1 and 2 disclose a schematic representation of a cast
aluminum engine 1 having four cylinder chambers 2, one of
which is cutaway to disclose the cylinder walls 3. The
engine block 1 is a casting of a suitable aluminum alloy
such as the aluminum 319 alloy, which is well-known as an '
alloy that can be readily cast into complex configurations
such as engine blocks. The aluminum 319 alloy is a
low-silicon aluminum alloy having the composition and
characteristics as set forth in the Metals Handbook, 8th
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1 Edition, America Society of Metals. It not only contains by
weight 90.2% aluminum, 6.3% silicone and 3.5% copper, but :,a.t
is a malleable ductile metal having a surface hardness of
Brinell 70-95. Although the 319 aluminum alloy is the only
metal that we are familiar with as being easily cast into an
engine block and which can be treated by our method and
apparatus to produce the objects and advantages of our
invention, it is believed that other malleable ductile
metals can be treated by our method to produce the same
objects and advantages. It is believed that the criteria
necessary for our invention to properly treat the surface
requires a metal that has a Brinell hardness of between
about 50-100. These alloys are the zinc alloy AG40A which
has a composition of 95.96% zinc, 4% aluminum and 0.04%
magnesium and a Brinell hardness of 82; a copper-hardened
rolled zinc having the composition of 99% zinc and 1% copper
and a Brinell hardness of 60p a rolled zinc alloy having a
composition of 98.99% zinc, 1% copper and 0.010% magnesium
and a Brinell hardness of 80; a magnesium alloy AM100A
having a composition of 89.9% magnesium, 10% aluminum and
0.1% magnanese with a Brinell hardness of 52-69; a magnesiu:~n
alloy AZ63A having a composition 90-98% magnesium, 6%
aluminum, 3% zinc and 0.2% manganese with a Brinell hardness
of 50-73; a magnesium alloy AZ92A having a composition of
88.9% magnesium, 9% aluminum, 2% zinc and 0.1% manganese
and a Brinell hardness of 63-81; and the magnesium alloy '
AZ31B having a composition of 95.8% magnesium, 3% aluminum,
1% zinc and 0.2% manganese with a Brinell hardness of 49-73.
The only composition that I have tested is the 319 aluminum
3p alloy, although I believe my method and apparatus will
properly treat the above-listed other alloys.
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1 As briefly disclosed in Figs. 1 and 2, water is
pumped at a high pressure through the rotating conduit 4 to
the cylindrical head 5 which is rotating with the conduit 4.
The head 5 has a plurality of orifices 6; a very small
diameter preferably between .005 and .006 inch. The pressure of
the water forced through the conduit 4 and out of the
orifices 6 creates a number of water jets 7 that have a
pressure at least as high as twenty-five thousand pounds pe:r
square inch (25,000 psi) and, as high as 60,000 psi, or
higher. The preferred pressure of water jets 7 is about
fifty thousand pounds per square inch (50,000 psi). As they
conduit 4 and head rotates, they are moved upwardly and ._,."" . ..
downwardly so that the water jets strike the surfaces 8 to
be treated. In treating a 319 aluminum cylinder bore
surface, we have found that the speed of rotation between .
500-1500 rpm rotation with a traverse movement of the head
at a rate of 5.0 inches per minute produces a satisfactory
result if two passes are made: each pass being approximately
5.5 inches. The ideal standoff distance, that is the
distance from the edge of the head to the wall of the
cylinder bore, was one-half to one inch. Obviously,
variables in the standoff distance, the speed of rotation
and the traverse rate will vary depending upon the metal
being treated, the extent of the aggressive surface desired
and the pressure of the water jets. Greater water jet
pressures and/or increases in the time of treatment produce
more aggressive surfaces.
After the surface 8 has been treated and prepared
as disclosed above, the surface 8 or portions thereof are
coated by the method as described in Patent 5,080,056.
Briefly, aluminum-bronze alloy is supplied to the center of
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1 the coating head in the form of a wire 16, which is provided
on a spool. A commercially available thermal spray gun
apparatus is employed to coat the cylinder. This is
accomplished by using a high velocity oxy-fuel thermal spray
method. A combustion mixture of propylene and oxygen (HVOF)
flowing at a supersonic speed is introduced down the center
of the coating head 17 and ignited using an electric spark
(not shown) of high voltage and low amperage inside the tip
of the coating head 17. Once ignited, the flame is
self-sufficient. The aluminum-bronze alloy is melted and
blown as a spray by the high velocity gas of the head 17 and
deposited on the interior surface 8 of the cylinder wall 3.
The metal spray gun apparatus automatically rotates the
coating head 17 about the wire 16 and directs the droplets
18 of the molten wire material against the cylinder walls
surface 8 by moving the head up and down the axis of the
cylinder walls.
Fig. 7 discloses a robot mechanism for producing
the motions as described in relation to Figs. 1 ~.nd 2. In
Fig. 7, reference numeral 4 designates the conduit 4 as
disclosed in Figs. 1 and 2. It is rotated by a rotary lance
drive mechanism 10. A motor 11 drives the lance 12 to which
the conduit 4 and the cylinder head 5 are attached and
rotatable therewith. The unit 10 includes a passageway
member extending from one side to which the water conduit 13
is connected. A high pressure pump 14 of the type known as
an ultra-high pressure water intensifier sold by Flow
Systems International as Model 12XT is connected to
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1 the conduit 13 for supplying water under pressure to the
rotating conduit 4 and cylinder head 5.
The unit 10 is secured to the bottom end of a mast
assembly 20 which extends upwardly through the roof of
compartment 21 and is adapted~to be moved upwardly and
downwardly as disclosed by the arrows 22. This is
accomplished by the mast being connected to a screw 23
located in the housing 24. The screw 23 is rotated by the
motor 24. The actuation of this mast in a vertical up and
down direction is similar to that disclosed in the
assignee's U.S. Patent No. 5,067,285, issued
November 26, 1991 entitled~FIVE ACCESS ROBOT.
Although when the lateral position of conduit 4
and the cylindrical head 5 is once established, it is not
necessary to change such lateral position in the treatment
of one cylinder, when one head 5 is to be utilized to treat
5
different cylinders such as those disclosed in Figs. 1 and
7, it is desirable to move the entire unit 10 an~_ mast 20
v laterally from right to left as disclosed in Fig. 7. For
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that purpose, a carriage 30 is provided which is attached to
a nut 31 which is mounted for movement on the screw 32. The .
screw 32 is actuated by a motor 33 so that turning of the
screw 32 moves the nut 31 and the carriage 30. An example
of this type of apparatus is disclosed in United States
Patent No. 5,067,285, which issued November 26, 1991, and is
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owned by the assignee of this invention.
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1 Figs. 4a, 4b and 4c illustrate the unusual result
obtained by the present method and apparatus. Fig. 4a
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discloses a surface such as a very small section of the
surface 8 of one of the cylinders 2. It discloses a
relatively smooth surface which has been prepared as
disclosed in Patent 5,080,056. Fig. 4b discloses the
surface 8 after it has been treated by our method and with
our apparatus. It will be noted that the high pressure
water jets have, in fact, eroded the surface. It is not cut
into the surface such as might occur with grit such as glass
particles, but has actually eroded and formed undercut
portions 9a, 9b and 9c. It is believed some metal
structures have a porosity which is exposed by the erosion
of the surface leaving a surface that is undercut. The
addition of the undercuts in the surface advances the
adhesive characteristics of the surface. Also, the erosion
greatly increases the surface area. Therefore, the
configuration of the irregular surface 8 after treatment by
our method and apparatus provides for superior adhesion.
This is illustrated by Fig. 4c which discloses the coating
40 that is held to, and retained by, the increased surface
area and particularly by the undercuts 9a, 9b, 9c and others
not specifically designated.
MODIFICATION
Having conceived this method and apparatus for
treating the cylindrical walls of an aluminum engine block
by subjecting the walls to extremely high pressure water
jets, I also conceived that our method and apparatus could
be utilized in flat pieces or other forms of metal,
particularly malleable ductile metal having surface
hardnesses like that of the aluminum 319 alloy as referred
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1 to above. Figs. 5 and 6 disclose schematics of apparatus
for treating such surfaces.
Fig. 5 discloses a tubular water conduit 104
connected to a cylindrical head 105. The head has a
plurality of orifices 106 the same size as orifice 6 of
Figs. 1 and 2. Orifices 106 are located on the bottom
surface of the cylinder 105. Thus, the jets 107 are
directed downwardly on the surface 108; the spacing between
the bottom of the cylindrical head 105 being approximately
one to one-half inches. It should be understood that the
speed of the rotation of the conduit 104 and head 105, the
pressure of the water jets 107 and the standoff distance,
i.e., the distance between the bottom face of the head 105
and the surface 108, are preferably the same as that
previously disclosed with relation to Figs. 1 and 2,
although such parameters can change depending upon many
circumstances all as described above.
The conduit 104 and head 105 is moved by an
apparatus such as disclosed in Fig. 7. Thus, the conduit
104 would be attached to the lance 12 and in place of the
engine block 1 the workpiece 100 would be substituted. All
of the advantages enumerated above with relation to Figs. 1
and 2 would also be obtained by our invention as applied to
a flat or contoured piece such as the workpiece 100 of Figs.
5 and 6 . _ .~.._.. ~. . . .r
Having described my invention, it should be
understood that although a preferred embodiment has been
disclosed herein, other modifications and embodiments can be
utilized without departing from the spirit of this
3p invention. Therefore, this invention should not be;limited '
to only the embodiment illustrated.
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