GB2100145A - Apparatus for detonation coating - Google Patents

Abstract

A detonation coating apparatus comprises a detonation chamber thereby made in the form of a barrel (1) having one end open and the other closed, a gas mixture supply system (2), a spark plug (6) for igniting an explosive gas mixture supplied to the chamber, and a powder supply system which includes a feeder (16) and a hopper (17) communicating with each other through a slide valve (24), a pipeline (21) including a valve (22) for supplying carrier gas to the feeder (16) to convey powder therefrom to the detonation chamber via pipeline (20), and control means including a powder detector (26) mounted at the open end of the barrel and producing a signal which is passed through an inverter (27) to an actuator of the slide valve (24) whereby to maintain the level of powder in the feeder substantially constant throughout operating time, and thereby ensure a substantial equal amount of powder injected into the detonation chamber during each operation cycle. <IMAGE>

Description

SPECIFICATION Apparatus for detonation coating The present invention relates to the practice of coating using a high-temperature spraying technique, and particularly to apparatus for detonation coating. The invention may be used in the metallurgical and chemical industries and power engineering, and is particularly useful for applying a coating onto parts which when in use are exposed to strongly corrosive and/or erosive conditions.

In accordance with the present invention there is provided a detonation coating apparatus comprising a detonation chamber in the form of a barrel closed at one end and open at the opposite end, a gas supply system for supplying explosive gas mixture to the detonation chamber, means for igniting the gas in the detonation chamber, and a powder supply system for supplying powdered coating material to the detonation chamber, the powder supply system including a powder receiver connected through a valve with a carrier gas source and connected to the detonation chamber for carrier gas to convey powder therefrom to the detonation chamber, a powder feed device connected through adjustable means to the receiver for feeding powder to the receiver and control means for controlling the amount of the powder supplied to the detonation chamber, the control means including a powder detector mounted adjacent the open end of the barrel and said adjustable means being responsive to a signal from the powder detector to control the supply of powder to the receiver.

The controlled adjustable means, preferably a slide valve, makes it possible to add powder to the receiver from the feed device if the amount of powder detected in the detonation products is below the required value, and thereby maintain the level of the powder in the receptacle substantially constant which in turn ensures uniform flow conditions for the carrier gas carrying the powder particles and hence a substantially constant amount of powder delivered to the detonation chamber during each cycle of operation of the apparatus.

Absence of threshold elements in an electric circuit connecting an actuator of the slide valve with a unit controlling the amount of powder in the detonation products makes the powder supply system highly responsive to quantitive variations of said powder in the detonation chamber. At the same time accidental loss of the detector signal, which signal influences the level of the powder in the powder receiver without having a direct effect on the amount of powder injected into the detonation chamber, cannot cause any significant quantitive changes in the amount of the powder fed to the detonation chamber during any operation.

The system for controlling the amount of the powder supplied to the detonation chamber thereby ensures a substantially constant quantity of powder without changing the flow rate of the carrier gas, which permits the proposed apparatus to be used for any powdered coating materials.

The invention will now be explained with reference to specific embodiments thereof which are represented in the accompanying drawings, wherein: Figure 1 is a functional diagram of the apparatus of the invention; Figure 2 is an alternative embodiment of the feeder incorporated in the apparatus of the invention.

An apparatus for detonation coating comprises a detonation chamber 1, a gas mixture supply system 2 and a powder supply system 3, both systems being communicated with the detonation chamber, a control unit 4 connected to said supply systems, and a unit for controlling the amount of the powder in the detonation products, electrically connected with the powder supply system 3.

The detonation chamber 1 is made in the form of a barrel closed at one end. Mounted inside the said barrel is a spark plug 6 adapted for initiating detonation in the detonation chamber 1 and electrically connected with the control unit 4.

The gas mixture supply system 2 includes a mixer 7 communicating through valves 8, 9 and 10 with a fuel source 11, an oxidizer source 12 and an inert gas source 13. As the fuel, oxidizer and inert gas use may be made of acetylene, oxygen and nitrogen respectively. The mixer 7 is communicating with the detonation chamber 1 through a coil pipe 14 adapted to protect the mixer 7 from the back surge, that is from the propagation thereinto of the detonation wave which is caused by the explosion in the detonation chamber 1.

The powder supply system 3 includes a batch meter 15 having a feeder 16 and a feed hopper 17 located above the feeder 16 and communicated therewith through a slide valve 18. Mounted in the feeder 16 are connection pipes 19 and 20, the ends of which connection pipes are introduced inside the feeder 16.

The connection pipe 19 is connected to supply a pipeline 21 connected with the inert gas source, which supply pipe is adapted for delivering the inert gas to the batch meter 1 5, with the inert gas being used as a transporting medium (carrier gas).

The supply pipeline 21 is provided with a valve 22. The connection pipe 20 communicates the feeder 16 with the detonation chamber 1 and is adapted for injecting into said detonation chamber the powder which is passed from the feeder 16 when the valve 22 is opened.

The slide valve 18 has an electromagnet 23 whose core is connected with the valve 24 of the hopper 17 discharge hole, said valve 24 being held in a closed position with the aid of a spring 25.

The control unit 4 includes a setting device constructed in the form of an electromechanical or electronic master controller. The control unit 4 is connected through control circuits to the spark plug 6, mixer 7 valves 8-10, and valve 22 of the powder supply system 3.

The unit 5 for controlling the amount of the powder in the detonation products incorporates a powder detector 26 mounted at the open end of the barrel, and a signal converter 27 for converting signals applied from the powder detector.

The powder detector 27 is constructed in the form of a photodiode responding to the radiation produced by the detonation products. Instead of said photodiode use may be made of any other suitable device, for instance a photoresistor.

The signal converter 27 comprises a series circuit including an input signal power amplifier and an intergrating circuit.

To the output of the signal converter 27, which output also serves as output of the unit 5, is connected through the invertor 28 to the electromagnet 23 coil, which electromagnet 23 functions as an actuator of the slide valve 18.

As a power source for the units 4 and 5 use is made of a direct voltage source 29.

Disclosed above is a preferred embodiment of the proposed apparatus wherein, however, some ports may be variously otherwise constructed. For instance, the batch meter 15 of the powder supply system 3 may be constructed as shown in Fig. 2 wherein the feeder 16 and the feed hopper 17 are located side by side and are communicated with each other through a tube 30 whose inlet opening located in the hopper 17 is covered by the valve of the sliding valve 18 coupled with the core of the controllable electromagnet 23.

Apart from the connection pipe 19 brought into the feeder 16, to the supply pipeline 21 is also connected a connection pipe 31 brought into the hopper 17 and adapted to deliver thereinto the carrier gas which is used for conveying the powder from the feed hopper 17 into the feeder 16 at the moments when the valve 24 is opened.

Below is described the operation of the proposed apparatus for the case when the coating process is conducted without presence of the inert gas in the gas mixture supplied into the detonation chamber, which is possible, for example, when coating material is alumina. In other cases the operation of the apparatus may be more complicated but for this particular case it does not matter.

When the power source 29 is switched on /Fig. 1/ the control unit 4 starts generating electric signals to cause the controllable mechanisms associated therewith to operate in the predetermined sequence. In this case first the valves 8 and 9 open to let the fuel and the oxidizer pass from their sources 11 and 12 respectively, into the mixer 7, wherefrom the explosive mixture formed therein is passed through the coil pipe 14 into the detonation chamber 1.Thereafter, the valve 22 opens to let the inert gas pass from the source 13, which inert gas passing through the connection pipes 19, the feeder 16 of the batch meter 15, and the connection pipe 20 entrains and carry a certain portion of the powdered coating material from the feeder 16 to the detonation chamber 1, the amount of the powder thus carried depending on the properties of the powder, pressure of the inert gas, and the time during which the valve 22 remains open. The valves 8, 9 and 22 are closed while the valve 10 is opened so that the inert gas passing from the source 13 into the mixer 7 forces the remainder explosive mixture therefrom into the explosion chamber 1, whereafter in this chamber detonation is initiated with the aid of the spark plug 6.The detonation products carrying the powder particles of the coating material heated thereby flowing at a great velocity from the barrel in the direction of the part C. Impinging upon the surface of the part C the powder particles are bonded thereto thereby forming a coating layer. Thereafter the detonation chamber is purged by the inert gas which is passed therein through the valve 10, the mixer 7 and the coil pipe 14, whereafter the valve 10 is closed and the operating cycle is repeated again.

At the moment when the power source 29 is switched on, the signal from the powder detector 26 is of a minimum magnitude and therefore a signal formed at the output of the signal converter 27 is also of a low value, which signal is applied to the input of the inverter 28, and as a result at the output thereof there appears a signal of a maximum value, which signal being applied to the coil of the electromagnet 23 causes the valve 24 to move down. As a result, the powder passes from the feed hopper 17 into the feeder 16.

When the two-phase stream (the powder and gaseous detonation products) are flowing from the barrel the powder detector produces a signal determined the brightness of the flow which depends on the amount of the powder contained therein. In case the amount of the powder in the detonation products is sufficient the signal from the detector 26 is amplified in the converter 27 to attain its maximum value in response to which at the output of the inverter 28 there is formed a signal having a minimum value. As a result, the electromagnet 23 of the slide valve 18 is deenergized and the valve 24 under the action of the spring 25 closes to cut off the flow of the powder from the hopper 17 into the feeder 16.

When the amount of the powder in the detonation product flow does not correspond to the predetermined value the valve 24 remains open and the powder pours from the hopper 17 into the feeder 16 until the powder content in the detonation products attains the predetermined value.

During the operation of the apparatus as the level of the powder in the feeder 16 lowers which results in that the amount of the powder in the detonation products decreases, the brightness of the flow also decreases, the signal at the output of the signal converter becomes small while at the output of the inverter 28 the signal attains its maximum value, which causes the electromagnet 23 to operate and to thereby open the valve 24 so as to let the powder pass from the hopper 17 into the feeder 17 and fill the latter to the required level. In this way the amount of portions of the powdered coating material injected into the detonation chamber are automatically stabilized.

The high degree of stability in amount of the powder in the stream of the detonation products ensures a high quality coating featuring uniformity of the physical properties.

The operation of the apparatus provided with the batch meter shown in Fig. 2 differs from that disclosed above in that the powder does not freely flow from the feed hopper 17 into the feeder 16 by gravity but is carried by the inert gas which while passing through the valve 24 and the connection pipe 31 into the hopper 17 entrains said powder and conveys it through the tube 30 to the feeder 16.

While particular embodiments of the invention have been described, various modifications thereof will be apparent to those skilled in the art and therefore this invention may be variously otherwise embodied within the scope of the appended claims.

Claims (6)

1. A detonation coating apparatus comprising a detonation chamber in the form of a barrel closed at one end and open at the opposite end, a gas supply system for supplying explosive gas mixture to the detonation chamber, means for igniting the gas in the detonation chamber, and a powder supply system for supplying powdered coating material to the detonation chamber, the powder supply system including a powder receiver connected through a valve with a carrier gas source and connected to the detonation chamber for carrier gas to convey powder therefrom to the detonation chamber, a powder feed device connected through adjustable means to the receiver for feeding powder to the receiver and control means for controlling the amount of the powder supplied to the detonation chamber, the control means including a powder detector mounted adjacent the open end of the barrel and said adjustable means being responsive to a signal from the powder detector to control the supply of powder to the receiver.

2. An apparatus according to claim 1, wherein said adjustable means comprises a slide valve.

3. An apparatus according to claim 1 or 2, wherein the feed device comprises a hopper arranged to discharge powder under gravity into the receiver.

4. An apparatus according to claim 1 or 2, wherein the feed device comprises a powder receptacle connected to the carrier gas source for carrier gas to convey the powder therefrom to the receptacle.

5. An apparatus according to claim 1, 2 or 3, wherein the control means includes an inverter for inverting the signal from the powder detector before it is supplied to the slide valve actuating means.

6. A detonation coating apparatus substantially as herein described with reference to the accompanying drawings.