Detonation-gas apparatus for applying coatings

The essence of the invention resides in that the apparatus comprises a gas istribution unit for distributing inert gas, oxidant and fuel gas, and has a cylinder provided with a headpiece. Walls of the cylinder have ports communicating its interior with gas sources, whereas the headpiece includes passages to convey gases from the interior of the cylinder to a barrel.

FIELD OF THE INVENTION 
This invention relates generally to apparatuses for spraying and applying 
coatings to surfaces of bodies, and more particularly to detonation-gas 
apparatus for applying coatings to surfaces of bodies. 
The invention can find application for applying metal, metal-ceramic, 
ceramic, wear-resistant, heat-resistant, electroinsulating, 
electroconducting and other types of coatings to machine parts and 
equipment of various designation. In addition, the apparatus embodying the 
present invention can be used for grinding powder materials, cleaning and 
local heating of surfaces, welding some non-metal materials and piercing 
holes in them, obtaining powders with new properties, producing structural 
changes in the surface layers of materials, and elsewhere. 
At present, the ever increasing specific loads exerted on working surfaces, 
higher temperatures to which machine parts are subjected during operation, 
and more corrosive atmosphere in which they operate call for improved 
quality of coatings applied by utilizing detonation waves, as well as more 
efficient methods and devices for coating application. These requirements 
are met by a number of prior art apparatuses. 
For example, there is known as apparatus for applying coatings to surfaces 
of bodies utilizing detonation gas waves (cf., U.S. Pat. No. 3,150,828, 
Cl. 239-79, published 1964). This apparatus comprises sources of fuel gas, 
oxidant and inert gas, a gas distribution unit connected to these sources 
by way of gas conduit a gas flow restricting means having a gas conduit 
for connecting with the gas distribution unit, a powder sprayer, a barrel, 
a system for igniting the gases, and a cam mechanism cooperating with the 
gas distribution unit and with the gas ignition system. In this apparatus 
the gas distribution unit includes three valve arrangements, for each gas 
separately, each such valve arrangement comprising a valve having a valve 
head and a springloaded valve stem secured in a guide sleeve provided in 
the housing of the gas distribution unit. In order to ensure reliable 
valve operation and prevent gases from leaking through the guide sleeve 
and valve seat, it is necessary to provide a highly accurate fit of the 
valve stem in the sleeve and setting of the valve head on the valve seat. 
Opening and closing of the valves is done here by the cam mechanism in the 
form of two cams with substantially flat tappets, the cams being secured 
on a common shaft which also carries a belt drive pulley and a cam of the 
ignition system interrupter. Such a cam mechanism needs precise timing to 
adjust the working cycle. In addition, the housing of the gas distribution 
unit is provided with cavities to accommodate the valve heads in lifted 
position. 
When inert gas is passed through these cavities, the velocity of gas flow 
drops to result in the formation of stagnation zones occupied by a mixture 
of inert gas and detonatable constituents, which prevents proper purging 
of the gas distribution unit. When feeding the constituents of detonatable 
mixture, oxidant and fuel gas are vigorously mixed with nitrogen present 
in the valve cavities, whereby a low quality mixture with retarding 
additions of inert gas (viz., nitrogen) is obtained. In order to obviate 
this disadvantage, it is necessary to increase the flow rates of both the 
inert gas to purge the oxidant and fuel gas from the valve cavities and 
the oxidant with the fuel gas to purge nitrogen from these cavities. 
Another disadvantage of such gas distribution resides in that the jet of 
gas flowing along the tapered generating line of the valve head actively 
mixes with the gases present in the valve cavity rather than sweeps them 
out. 
In addition, the gas flow restricting means is connected to the barrel by 
means of two counter flow gas conduits, which fail to sweep the spent 
inert gases from the barrel when the detonatable mixture is admitted, but 
which promote mixing of detonatable constituents with the inert gases. 
This entails poor quality of the detonatable mixture, low purging 
efficiency, and inaccurately metered filling of the gas flow restricting 
means of the gas blanketing arrangement prior to detonation to result in 
increased flow of working gases, impaired efficiency of the apparatus and 
low quality coatings. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to obviate disadvantages 
inherent in the prior art devices and provide a novel and improved 
detonation-gas apparatus for applying coatings to surfaces of bodies. 
Another object is to provide an apparatus which would use less working 
gases for its operation. 
One more object is to provide an apparatus which would be highly efficient 
and ensure high quality coatings. 
Yet another object is to provide an apparatus which would be simple in 
construction. 
These and other objects and attending advantages are attained by that in a 
detonation-gas apparatus for applying coatings to surfaces of bodies 
comprising a barrel with a spark plug, a sprayer of powder materials 
arranged inside the barrel, sources of fuel gas, oxidant, and inert gas, a 
gas distribution unit connected to the gas sources, a gas flow restricting 
means communicating with the gas distribution unit and with the barrel, an 
ignition system for detonating the gases in the barrel, and a cam 
mechanism cooperating with the gas distribution unit and with the gas 
ignition system, according to the invention, the gas distribution unit 
includes a cylinder wall which is provided with radial ports arranged in 
three rows in terms of height thereof to communicate the interior of the 
cylinder with the gas sources, the cylinder having a headpiece with 
passages to convey the gases from the interior of the cylinder to the 
barrel through the gas flow restricting means, and a piston arranged in 
the interior of the cylinder to reciprocate and cooperate with the cam 
mechanism. 
Thanks to such a structural arrangement, the inert gas conveyed from the 
source of inert gas to the barrel has along its travel path practically no 
stagnation zones and cavities of substantial capacity, because the only 
cavity in the cylinder above the piston has at this point in time a 
minimum volume determined by the intermediate position of the piston, and 
therefore the interior of the cylinder is easily purged by several gas 
streams flowing from the walls of the cylinder to the center of the 
headpiece. This in turn provides a possibility to use small quantities of 
inert gas for purging the detonation chamber subsequent to detonation and 
the gas flow restricting means prior to detonation, which results in 
improved purging efficiency. The constituents of the detonatable mixture, 
viz. oxidant and fuel gas, entering the barrel after the inert gas along 
the tubular gas conduits are admitted to the interior of the cylinder 
above the piston during the low position assumed by the piston when the 
cylinder interior is expanded; however, the volumes used for providing a 
detonatable mixture of these gases considerably exceed the volume of the 
cylinder interior, whereas the gas streams flowing from the walls of the 
cylinder to the center of the headpiece promptly sweep the remnants of 
nitrogen away. In addition, by virtue of the fact that the pressure of 
gases present in the cylinder interior is somewhat lower than that in the 
passages of the cylinder, gases at various pressures can freely pass 
therethrough; in other words, no resistance to the gases at lower 
pressures is produced. It is therefore possible to obtain a high-quality 
composition of the detonatable mixture containing negligeable amounts of 
foreign constituents which might weaken detonation. 
Preferably, half of the ports in the row of ports remote from the headpiece 
communicate with the source of inert gas, whereas the other half of the 
ports in this row of ports communicate with the ports in the row of ports 
adjacent the headpiece; one port in the middle row of ports communicates 
with the source of fuel gas, whereas the other ports in this row of ports 
communicate with the source of oxidizing gas. 
Thanks to such an arrangement, the constitutes of the detonatable mixture 
are fed to the ports of the middle row of ports of the cylinder at a 
pressure substantially below the pressure of the inert gas and invariably 
from above, whereas from below these detonatable constitutes are 
surrounded or blanketed by the inert gas to thereby prevent the escape of 
the detonatable mixture outside. This results in higher explosion safety 
and more efficient operation. 
It is further advisable that the piston would have fitted thereon elastic 
seal rings end faces of which have the form of tapered concave surfaces, 
and interposed between these seal rings spacer rings and gas-valving rings 
end faces of which have the form of tapered convex surfaces corresponding 
to the tapered surfaces of the seal rings, the piston preferably carrying 
a nut adjacent the seal ring and serving to adjust a clearance between the 
cylinder and seal rings, the gas-valving ring also having a groove at the 
outer surface thereof to ensure the passage of inert gas from its source 
to the ports in the row of ports adjacent the headpiece of the cylinder. 
By virtue of the above piston arrangement, it is possible to maintain a 
minimum clearance between the cylinder and seal rings of the piston to 
ensure free travel of the piston and prevent mixing of the constituents 
through this clearance. This results in an improved composition of the 
detonatable mixture of gases, which in turn enables to consume less 
amounts of working gases and obtain higher quality coatings. 
Desirably, the gas distribution unit comprises a sealing connection of the 
piston with the headpiece of the cylinder formed by annular projections 
provided at the end face of the piston and annular recesses at the end 
face of the headpiece in the interior of the cylinder. 
Such a sealing connection provides a local hydrodynamic resistance to 
soften the back-flash of gases propagating from the detonation chamber 
through the gas flow restricting means to the gas distribution unit 
resulting in a more efficient operation of the apparatus. 
Favourably, the cam mechanism engageable with the piston comprises a cam of 
such a shape as to provide the travel of the piston to successively open 
and close the ports in the cylinder in accordance with the working cycle 
phases. 
This arrangement makes it possible to dispense with bringing into 
synchronism several cams to adjust the cycle, since the sequence and 
timing of the cycle are guaranteed by the configuration of a single cam; a 
change in the rotational speed of the cam entails corresponding variations 
in timing. This is advantageous, because the frequency of detonation 
pulses can be varied within a wide range to again make the apparatus more 
efficient. 
Advisably, the gas flow restricting means comprises gas conduits arranged 
tangentially to the cross-section of the barrel and communicating the 
interior of the cylinder through the passages of the headpiece with the 
barrel. 
The tangential positioning of the inlet of the gas conduits in the 
detonation chamber of the barrel promotes the formation of a stable vortex 
flow of gases which acts to sweep by its wave front the spent and inert 
gases while failing to mix therewith behind the wave front line. It is for 
this reason that the detonatable mixture fed to the barrel contains 
negligible amounts of detonation-retarding ingredients, whereby high-power 
detonation pulses are developed to result in improved quality of coatings 
and higher production efficiency.

BEST MODE OF CARRYING OUT THE INVENTION 
Description in the Statics 
The proposed detonation-gas apparatus for applying coatings to surfaces of 
bodies represented in FIG. 1 comprises: a water-cooled barrel 1 having an 
acceleration portion 2 and a detonation chamber 3 accommodating a spark 
plug 4; a feeder 5 of powder materials including a metering means 6 and a 
sprayer 7 arranged inside the barrel 1; a source 8 of inert gas, a source 
9 of oxidizing gas, and a source 10 of fuel gas; a gas distribution unit 
indicated at 11 and connected to the gas sources 8, 9 and 10; a gas flow 
restricting means 12 communicating with the gas distribution unit 11 and 
with the barrel 1; an ignition system for detonating gases in the barrel 1 
including a direct current source 13, a voltage transformer 14, and a 
current interrupter 15 electrically wired to the spark plug 4; and a cam 
mechanism cooperating with the gas distribution unit 11 and gas ignition 
system. 
According to one feature of the invention, the gas distribution system 11 
comprises a cylinder 17 (FIGS. 2 and 3) terminating in a headpiece 18, and 
a piston 19 arranged in interior 20 of the cylinder 17 with a clearance to 
ensure that it reciprocates and cooperates with the cam mechanism 16. 
Walls 21 of the cylinder 17 have radial ports 22, 23 and 24 communicating 
the interior 20 of the cylinder 17 with the gas sources 8, 9 and 10 and 
arranged in three rows in terms of the height of the cylinder 17. Each 
such row has at least two ports. Alternatively, each such row may include 
any even number of ports. 
The headpiece 18 has a central passage 25 and radial passages 26 for the 
gases to flow from the interior 20 of the cylinder 17 to the barrel 1 
through the flow restricting means 12. 
Half of the ports 22 in the row of ports remote from the headpiece 18 
communicate by way of a gas conduit 27 (FIG. 1) with the source 8 of inert 
gas, whereas the other half of the ports in this row communicate in pairs 
with the ports 24 in the row of ports adjacent the headpiece 18 by way of 
a gas conduit 28. One port 23 in the middle row of ports communicates 
through a gas conduit 29 with the source 10 of fuel gas, the other ports 
23 of this middle row communicating by way of a gas conduit 30 with a 
source 9 of oxidizing gas. 
Fitted on the piston 19 are seal rings 31, spacer rings 32 interposed 
between the seal rings 31, and a gas-valving ring 33, all these rings 
being drawn together by a nut 34 having a stop 35 and serving to adjust 
the clearance between the cylinder 17 and seal rings 31. 
End faces 36 of the seal rings 31 have the form of concave tapered 
surfaces, whereas end faces 37 and 38 of the spacer rings 32 and 
gas-valving ring 33, respectively, have the form of convex tapered 
surfaces corresponding to the tapered surfaces of the end faces 36 of the 
seal rings 31. Provided at the outer surface of the gas-valving ring 33 is 
a groove 39 intended to ensure the passage of inert gas from the source 8 
thereof to the ports 24 in the cylinder 17 adjacent the headpiece 18. 
The gas distribution unit 11 comprises a sealing connection between the 
piston 19 and headpiece 18 of the cylinder 17 which is defined by annular 
projections 40 (FIGS. 2 and 3) provided at the end face of the piston 19, 
and annular recesses 41 made at the end face of the headpiece 18 in the 
interior 22 of the cylinder 17. 
The cam mechanism 16 cooperating with the piston 19 includes a cam 42 (FIG. 
1), a push rod 43 with a roller 44, and a spring 45. The cam 42 is rotated 
by an electric motor 46 through a reducing gear 47 and has a shape which 
ensures such a travel of the piston 19 as to successively open and close 
the ports 22, 23 and 24 in the cylinder 17 according to the working cycle 
phases, for which purpose it is defined by three arcuate surfaces 48 and 
four intermediate surface portions 49. Angles of the arcuate surfaces act 
to execute the cycle timing. 
The flow restricting means 12 includes gas conduits 50 (FIG. 4) arranged 
tangentially to the cross-section of the barrel 1 and communicating the 
interior 20 of the cylinder 17 with the barrel 1 through the passages 25 
and 26 of the headpiece 18. 
Operating Principle 
The proposed apparatus operates in the following manner. 
Inert gas, oxidizing gas and fuel gas are admitted, as shown in FIG. 1, to 
the ports 22, 23 and 24 of the gas distribution unit 11 through the gas 
conduits 27, 29 and 30, respectively. 
When the cam 42 is rotated, the piston 19 is caused to move down by the 
spring 45 to open the radial ports 24 in the row of ports adjacent the 
headpiece 18, while simultaneously registering the gas-valving ring 33 
with the radial ports 22 in the row of ports remote from the headpiece 18. 
Thereafter, the piston 19 stops temporarily in the intermediate position, 
and within this space of time the inert gas N.sub.2 (FIGS. 1 and 2) flows 
from the inert gas source 8 along the gas conduit 27 to the interior 20 of 
the cylinder 17, passes through the gas-valving ring 33 (FIG. 5) to escape 
from the interior 20 of the cylinder 17 and then be again received by the 
interior 20 of the cylinder 17 through the ports 24. The gas flows further 
along the passages 25 and 26 in the headpiece 18 of the cylinder 17 to be 
divided into two streams and enter through the flow restricting means 12 
along the tangential conduits 50 (FIG. 4) the detonation chamber 3 of the 
barrel 1 (FIG. 1), where it is swirled to sweep by the stream front 
detonation gases out of the chamber and thus execute the purging phase. 
The cam 42 continues to rotate, and the piston 19 is lowered a second time 
closing the ports 22 in the row of ports remote from the headpiece 18 to 
terminate the flow of the inert gas from the source 8 and, while opening 
the ports 23 in the middle row of ports, stops temporarily in the 
intermediate position (FIGS. 1 and 4). Within this space of time the 
oxidant and fuel gases flow along the gas conduits 29 and 30 to enter the 
interior 20 of the cylinder 17 to pass further along the passages 25,26 
and flow restricting means 12 directly to the detonation chamber 3 of the 
barrel 1, where they are swirled to force by the stream from the purging 
gas from the chamber 3 to the acceleration portion 2 thus completing the 
phase of filling the detonation chamber 3 with the fuel mixture. 
A still further rotation of the cam 42 causes the piston 19 to ascend, and 
while ascending to close the ports 23 in the middle row of ports, open the 
ports 24 in the row of ports adjacent the headpiece 18, and register the 
gas-valving ring 33 with the ports 22 in the row of ports remote from the 
headpiece 18. Then the piston 19 stops in the intermediate position (FIGS. 
1, 2 and 5), whereby the spring 45 is compressed. During this space of 
time only the flow restricting means 12 is filled with the inert gas thus 
providing gas blanketing. 
A subsequent rotation of the cam 42 makes the piston 19 ascend to close all 
the ports 22, 23 and 24 of the cylinder 17, stop the admission of gases, 
and mate the annular projection 40 with the annular recess 41 thus 
completing preparation procedures prior to detonation (FIG. 1). 
Concurrently, with the approach of the piston to the topmost position a 
lug of the pusher rod 43 forces the interrupter 15 to break the contact, 
whereby high voltage from the voltage transformer 14 is applied to the 
spark plug 4 to initiate detonation. Detonation is completed while the 
piston rests in the topmost position, and the powder material to be 
sprayed is heated and accelerated. The entire cycle is repeated after 
rotation of the cam 42. 
A specific feature of the aforedescribed gas distribution system is 
advantageous in that the detonatable gases are fed to the middle row of 
gas ports in the cylinder at a pressure substantially below the pressure 
of the inert gas and always from above thus blanketing them from below by 
the inert gas. Such a construction of the proposed apparatus makes 
operation less explosion hazardous. 
In order to change the frequency of detonation pulses, it is sufficient to 
vary the direct current voltage applied to the electric motor 30 and 
change the flow rate of gases accordingly. It is therefore possible to 
gradually attain the maximum frequency of detonation pulses to operate 
with the utmost efficiency.