|Title of Invention||
"AN IMPROVED HIGH VELOCITY OXYGEN AND LIQUID PETRILEUM GAS (LPG) OPERATED WIRE SPRAY GUN"
|Abstract||ABSTRACT OF THE INVENTION It is an improved spray gun of supersonic velocity of spray atomized metal from low as well as high melting point metal and non-metal wires using oxygen and liquid petroleum gas (LP6)/Propane as fuel to spray the metal. The gun is substantially identical to the existing gun consisting of siphon plug 2, nozzle 3, air cap 4 with the additional improvement of having an annular chamber 11 in the siphon plug 2, for the supply of auxiliary extra air in addition to usual air supply 8. The wire guide 5 is tapered 13 towards its nozzle end. The air cap 4 is made of reduced diameter of 7 mm against 8.3 mm.|
|Full Text||The present invention relates to an improved high velocity oxygen
and liquid petroleum gas operated wire spray gun in thermal
The known spraying method consists of generating heat by the
burning of a fuel with oxygen to melt the wire and subsequently
atomizing the molten droplets by gases and/or air. The atomized
droplets are propelled on to a substrate where they form a dense,
The presently known spray guns for thermal spraying have
A) Low velocity oxy fuel spraying guns for wire and rods;
These type of guns are available in the national and
international market and it is used for the spraying of wires and
rods at subsonic velocity (as opposed to the supersonic velocity
of spray particles like our newly developed gun). However, with
these guns it is not possible to spray materials like Molybdenum,
steel, using LPG as fuel. Generally LPG is used as fuel in these
guns only for the spraying of low melting materials like Zinc and
Alumunium. The flame velocity in this conventional gun is about
B) High velocity oxy fuel (HVOF) gun for spraying of powder:
This is a high velocity gun for spraying material in the form of
powders. Though in this existing device supersonic speed is
obtained, but the cost of operating this system is very high due
to higher consumption of fuel gas and oxygen.
Our area of invention is high velocity oxy fuel spraying as stated in para B. In the known HVOF guns the heat for melting of
the raw material is generated by the burning of a fuel gas. The
raw material which is in the form of powder is melted in the
flame and the molten particles are atomized by the gas and air
mixture. The atomized droplets then strike the substrate at a
high velocity where they form the coating. The temperature of
the flame depends upon the fuel gas used.
Our gun sprays the materials in the wire form and not in the
powder form as stated in para B. The materials available in the
wire form are much cheaper than their powders thus leading to
economy of operation. In the present invented high velocity oxy
fuel spraying, the particles are propelled at a supersonic
velocity. The heat energy for the melting of the wire comes from
the burning of LPG with oxygen.
A supersonic velocity is described by the MACH No. e.g. MACH 1,
MACH 2, MACH 3 etc. MACH 1 being the velocity of sound, MACH 2
being twice the velocity of sound and so on.
When a flame is having supersonic velocity (above the speed of
sound) diamond shaped profile is seen in the flame. These
diamonds are generated due to the shock waves generated by the
supersonic flow and hence these diamonds are know as shock
The presence of shock diamonds is a characteristics of the
In our present invention about 6 shock diamonds are seen in the
flame. Hence we can safely say that the flame obtained is
The materials to be sprayed by the above mentioned guns are
various metals and alloys ceramics, cermets etc. Any material
which does not sublime on heating can be sprayed by thermal
The coating may be given on a variety of substrates, like metals
and alloys, glass, wood, plastics, ceramics and paper.
The conventional HVOF guns use powder as the raw material for
melting and spraying. But the present invented improved gun can
give a supersonic flame and can be used for spraying of wires or
rods instead of powder. No such gun has been developed in India
till now. In this new gun molybdenum and high melting wire can
also be sprayed using LPG.
As the present developed gun is a flame wire spray gun, the
subsequent portions of the write up deal with the wire flame
spray process only.
In this present invented wire flame spray process a fuel of
comparetavely lower cost is burnt with oxygen to generate a flame
which provides the heat for melting. The fuels used are the
gaseous fuels like LPG and oxygen.
In the known process acetylene gas gives the flame with the
highest temperature and hence it is used most widely. The high
temperature obtained in the acetylene flame permits the spraying
of high melting point wires such as molybdenum and spray steel.
The high melting point wires melt in the flame of oxy-acetylene.
The flame temperature for oxy-acetylene flame is 3100 C and for
oxy-LPG flame is approximately 2760 C. But the cost of acetylene
In the conventional powder spray gun molybdenum coating can not
be produced by oxy-LPG flame due to the low temperature of the flame. The coating in this case shows the presence of large amount of unmelted particles and the coating does not bond to the substrate. In the conventional gun an oxy acetylene flame of higher 'cost has to be used to get a proper coating of high melting point powder.
In the present invented high velocity wire spray gun the coating quality produced is better than that produced by the conventional gun. Moreover the high quality coating is achieved by using LPG as fuel in place of acetylene which is much cheaper and safer fuel. The cost of acetylene is RS.175/M3. one cylinder of acetylene costs Rs.962/-. The cost of LPG as fuel is Rs.28/- per kg. one cylinder of LPG cost Rs.370/-. The above prices are for comparison only for a particular period of time. A LPG cylinder run approximately for 2.5 hrs and one acetylene cylinder run for approximately 3 hrs.
Thus the new high velocity wire spray gun brings down the operating cost of coating considerably with a great improvement in the thermal spray coatings characterized on the following basis.
2. Bond strength
3. Porosity (Density)
4. Surface Roughness
5. Deposition Efficiency.
The hardness of the molybdenum sprayed with the high velocity gun
are greatly increased. The conventional powder spray gun gives a molybdenum coating with a hardness of Re 60-62 while our newly developed wire spray gun gives a hardness of Re 68-70 in the molybdenum coating.
2. Bond Strength:
The tensile bond strength of the coating was checked on a tensile strength testing machine. Following results were obtained; High velocity wire gun ....Molybdenum....4001 psi Low velocity wire gun ....Molybdenum....2777 psi
The porosity in the H.V.spraying molybdenum and low velocity sprayed molybdenum (conventional process) are compared by the photo micrographs. It is observed that the percentage porosity in the H.V.Wire sprayed molybdenum is very less. Moreover, the size of the porosity is also very small. Thus the newly developed gun gives a dense coating when compared to the c onvent i onal gun.
4. Surface Roughness:
The surface roughness of the as sprayed coating was taken by the
Roughness measuring instrument. The values are given below.
Three reading were taken for each sample:
H.V.Velocity spraying of molybdenum... (4 . 74, 4.85, 4.79) Ra
L.V.Velocity spraying of molybdenum...(6.96, 13.3, 9.23) Ra (Ra-
Average roughness in microns).
So the H.V.Wire gun spraying of molybdenum gives a much finer
5. Deposition efficiency:
The deposition efficiency of the process is measured as the percentage of the ratio of the metal deposited to the metal (wire) sprayed. The deposition efficiency was measured for the spraying of spray steel wire containing 0.8% C.
The conventional process yielded a deposition efficiency of 57% i.e. 43% of the powder was wasted.
The newly developed H.V.Wire gun had a deposition efficiency of 78% i.e. only 22% wire was wasted.
According to the present invention, an improved high velocity oxygen and liquid petroleum gas (LPG) operated wire spray gun having siphon plug nozle and air cap being characterised by that the improvement comprising use of wires or rods(instead of powder) for being sprayed at a supersonic velocity and the use of LPG as fuel melting high melting point material in wire rod form, like molybdenum, steel and alloys, ceramics and cermets,the improved gun consisting of a wire guide of 2.5 mm dia at the feeding end, the wire guide being tapered towards its nozzle end; annular chamber in the siphon plug for the supply of auxiliary extra air through the gun, an improved cap of reduced diameter of 7 mm and an additional sleeve being fitted inside the nozzle of reduced diameter of 1.7 mm through which the wire is fed to the flame, the gun having the other conventional means like entry of air, oxygen and fuel (LPG) through different ports into the siphon plug and the mixing chamber before the nozzle. The present invented improved spray gun for achieving the above mentioned properties has been illustrated in the accompanying drawing.
The gun 1 is substantially identical to the existing gun
consisting of sipon plug 2, nozzle 3, air cap 4.
The improvement comprises providing wire guide 5 at the feeding
end for feeding wire 6. The gases, oxygen 5, air 8 and fuel gas 9
enter through different ports into the siphon plug 2 and carried
to the mixing chamber 10 and a flame is struck in the gases as
the gases exit though the nozzle 3.
Air 8 enters into the siphon plug 2 through a port provided for
the air. The air does the job of cooling the siphon plug 2 and
the nozzle 3. The cap 4 is provided on,the nozzle 3. The air
exits from the gun from the gap between the cap and the nozzle.
The air which passes between the nozle 3 and the cap 4 after
cooling the siphon plug 2 and the nozzle 3, additionally, does
the work of atomizing the molten particules obtained from the
feeding wire 6 through the centre of the gun 1 by the present
The following improvements have been made in the design of the
conventional gun to generate high velocity flame.
The high velocity wire gun has a special design of the siphon
plug 2 which makes the gun high velocity 1. Annular chamber 11
is provided in the siphon plug 2 for the supply of auxiliary,
extra air into the syphon plug 2 through openings 12. This extra
air is fed at a very high pressure.
Modification of the wire guide 5 inside the siphon plug 2. The
wire guide provided in the high velocity gun is tapered 13
towards its nozzle end to direct the flow of air. An 'O1 Ring 14
is also provided on the wire guide to prevent back fire. In the
wire guide of the conventional gun no 'O1 Ring is provided and
the guide is not tapered towards its nozzle side.
The air cap 4 of the high velocity is of reduced diameter of 7 mm
dia as compared to the conventional gun of 8.3 mm.
Thus the following novelties are obtained in the present
1. A method of producing a supersonic flame of gas mixture of
LPG and oxygen and Air.
2. A method by which metallic and alloy wires, and rods of
ceramic/cermets can be thermally sprayed at high supersonic
3. A method by which the High Velocity Spraying of wire/Rod is
being done by oxy LPG/Flame instead of conventional low velocity
OXY LPG flame.
4. The process by which the high melting point metals and alloys
like Molybdenum is thermally sprayed by Oxy/LPG combustion,
It is evident that detail of constuction or their arrangement may be modified in order to obtain the same result without departing from the scope of the invention.
1. An improved, high velocity oxygen and liquid petroleum gas (LPG) operated wire spray gun having siphon plug 2, nozzle 3 and air cap 4, being characterised by that the improvement comprising use of wires or rods(instead of powder) for being sprayed at a supersonic velocity and the use of LPG as fuel melting high
melting point material in wire rod form, like molybdenum, steel and alloys, ceramics and cermets, the improved gun consisting of a wire guide 5 of 2.5 mm dia at the feeding end, the wire guide 5 being tapered 13 towards its nozzle end; annular chamber 11 in the siphon plug 2 for the supply of auxiliary extra air through the gun, an improved cap 4 of reduced diameter of 7 mm and an additional sleeve being fitted inside the nozzle 3 of reduced
diameter of 1.7 mm through which the wire is fed to the flame,
the gun having the other conventional means like entry of air 8
oxygen 7 and fuel (LPG) 9 through different ports into the siphon plug 2 and the mixing chamber 10 before the nozzle 3.
2 . An improved high velocity oxygen and LPG operated wire spray gun as hereinbefore described and illustrated in the accompanying drawing .
|Indian Patent Application Number||2529/DEL/1997|
|PG Journal Number||10/2008|
|Date of Filing||05-Sep-1997|
|Name of Patentee||METALLIZING EQUIPMENT COMPANY PVT LIMITED|
|Applicant Address||E- 101, M.I.A, PHASE-II, BASNI, JODHPUR-342005, INDIA.|
|PCT International Classification Number||B05B 7/22|
|PCT International Application Number||N/A|
|PCT International Filing date|