GB2103112A - Apparatus for detonation coating - Google Patents

Abstract

A detonation coating apparatus comprises a detonation chamber (1), a spark plug (2) for initiating detonation, a gas mixture supply system (3), a powder supply system (4), and a control system (5). The gas mixture supply system (3) includes a mixer (6) communicating with sources (7), (8) and (9) of the gas mixture components and with the detonation chamber (1). The powder supply system (4) includes a batch meter (18) communicating with the detonation chamber (1). The control system (5) incorporates a control unit (26) electrically connected with the spark plug (2), the gas mixture supply system (3), and the powder supply system (4), a powder detector (33) mounted at the open end of the detonation chamber (1) and a protective shield (45) downstream of powder detector (33). If the powder discharged during two successive detonations falls below a predetermined amount the shield (45) is moved into position to prevent powder reaching the article (c) being coated during during the next detonation. If the amount of powder still falls below the predetermined amount operation of the apparatus is automatically interrupted. <IMAGE>

Description

SPECIFICATION Apparatus for detonation coating The present invention relates to the equipment for coating process using high-temperature spraying technique, and more specifically is concerned with an apparatus for detonation coating.

The invention is applicable in the metallurgical, oil, chemical, and machine-building industries, power engineering and all other industries where there is a need in manufacturing parts which when in use are subjected to high loads or exposed to a strong corrosion or erosion attack.

Though the detonation coating technique has been known since long ago, until now, however, there has been no apparatus proposed which would ensure both a high quality coating even in the case of accidental malfunctions and at the same time a high efficiency of its operation.

According to the present invention there is provided an apparatus for detonation coating comprising a detonation chamber in the form of a barrel, gas supply means for supplying a combustible gaseous fuel to the chamber, ignition means for igniting the fuel in the chamber, powder supply means for supplying coating powder to the chamber; a control means for controlling the gas supply means, the powder supply means and the ignition means, the control means including a powder detector located at the open end of the barrel for detecting powder in the detonation products emitted therethrough, a protective shield mounted movably at the open end of the barrel on the side of the powder detector remote from the barrel, and means for adjusting the shield to obstruct the flow from the barrel when the powder emitted from the barrel during one or more preceding successive detonations is less than a predetermined value.

With such a control arrangement continuation of the operation in the case of accidental malfunction of the apparatus is possibie. The surface of the article being coated is shielded by the protective shield until the operating characteristics of the two-phase flow are fully restored, the two-phase flow being the detonation products and the powder of the coating material the presence of which is detected by a powder detector.

The first detonation and the detonation subsequent to a misfire, i.e. detonations which contain either a very small amount of the coating powder or a very great amount thereof hit the protective shield, and do not reach the surface of the article being coated, thereby considerably enhancing the quality of the coating being applied.

It is expedient that means be provided for advancing the article being coated and connected to the control means so that the article is advanced only after a detonation during which the shield is withdrawn so as not to obstruct the flow of powder to the article.

The presence of the advancing means allows the article being coated to be moved according to the predetermined program during the coating operation. Its electrical connection with the control means makes it possible to stop the advancing means in the case of accidental malfunction of the apparatus. When after the restoring of the operating characteristics of the two-phase flow, the protective shield is withdrawn again, the coating is applied only onto that portion of the article which was to be but was not coated because the operation was discontinued. All this allows the quality of the coating being formed to be enhanced.

The invention will now be explained with reference to specific embodiments thereof which are represented in the accompanying drawings, wherein: Figure lisa functional diagram of the apparatus of the invention; Figure 3 is a functional diagram of the control unit constructed in the form of a master-controller; Figure 3 is a functional diagram of an alternative embodiment of the proposed apparatus which incorporates a manipulator.

An apparatus for detonation coating comprises a detonation chamber 1 (Figure 1 ) constructed in the form of a barrel closed at one end, a spark plug 2 mounted within the detonation chamber 1 and adapted to initiate detonation, a gas mixture supply system 3, a powder supply system 4, and a control system 5.

The gas mixture supply system 3 includes a mixer 6 adapted to prepare a gas mixture from a combustible gas, such as acetylene, an oxidizer, such as for instance oxygen, and an inert gas, such as nitrogen. The respective sources 7, 8 and 9 of said gas mixture components are communicated with the mixer 6 through feed pipes 10, 11 and 12 which are provided with valves 13, 14 and 1 5 respectively. The mixer 6 is communicated with the detonation chamber 1 through a check valve 16 and a coil pipe 17 intended for dampening the back surge produced by the detonation.

The powder supply system 4 includes a batch meter 1 8 provided with a hopper 1 9 having a first inlet 20 for charging a powdered coating material, a second inlet 21 for supplying a gas, and a discharge hole 22 connected with the detonation chamber 1 through a tube 23. Through a gas transmission pipe 24 connected with the second inlet 21 the batch meter 18 is communicated with a source of a carrier gas which source in this apparatus is an inert gas source 9. As a batch meter 1 8 use may be made of a feeder having a hopper connected with the source of carrier gas (for instance a pulse mode feeder, an impellertype stream feeder, or a gas-jet feeder with a perforated ring).Mounted on the gas transmission pipe 24 at the second inlet 21 of the batch meter 18 is a valve 25 through which the carrier gas is fed into said batch meter.

The control system 5 of the proposed apparatus includes a control unit 26 which is electrically connected, through control circuits 27, 28, 29 and 30, to actuating mechanisms, and namely: through the circuit 28 to the valve 1 5 of the gas mixture supply system 3, through the circuit 27 to the valve 13 and 14, through the circuit 29 to a spark ignition device 31 adapted to ignite a spark across the plug 2, and through the circuit 30 to the valve 25 via which the gas carrier is supplied to the powder supply system.

The control system 5 further includes a feedback circuit 32 which includes a powder detector 33 adapted to detect the presence of the powder in the detonation products and being mounted at the open end of the detonation chamber 1, and a signal converter 34 adapted to convert signals produced by the powder detector 33, which feedback circuit is electrically connected through a threshold element 35 with the control unit 26.

The powder detector 33 is constructed in the form of a photocell. Since during operation the detonation products leaving the detonation chamber 1 produce luminous radiation there is no need therefore of using additional source of light.

The signal converter 34 for converting signals from the powder detector 33 comprises a series connected voltage amplifier 36, power amplifier 37, integrating network RC, and power amplifier 39. The voltage amplifier 36 is connected to the powder detector 33, and the power amplifier 39 is connected to the control unit 26 through the threshold element 35.

The threshold element 35 is constructed in the form of an electromagnetic relay 40 which through contacts 41,42, and 43 is connected respectively to the control circuits 27, 29 and 30 of the control unit 26. At the input of the electromagnet relay 40 there is located a toggle switch 44 having two positions "a" and "b". By changing said positions of the toggle switch 44 the electromagnetic relay 40 is connected either to a d.c. current source E or to the power amplifier 39 of the signal converter 34 for converting signals from the powder detector 33.

According to the invention at the open end of the detonation chamber 1 there is mounted a protective blind 45 which is located after the powder detector 33 in the direction of the detonation products flow and is provided with an actuating mechanism 46 constructed in the form of an electromagnet. Connected to the actuating mechanism 46 is a control circuit 47 including a threshold element 48 through which said protective blind 45 is electrically connected to the signal converter 34 of the powder detector 33.

The actuating mechanism 46 of the protective blind 45 is connected through the control circuit 47 to the d.c. source E.

The threshold element 48 is made in the form of an electromagnet relay 49 having a contact 50 placed in the control circuit 47, and an input connected to the power amplifier 39 of the signal converter 34.

The electromagnet relays 40 and 49 are so selected that with the decrease of the voltage value at the output of the power amplifier 39 (which may be caused by malfunctions of the apparatus) the contact holding time of the contacts 41, 42 and 43 of the electromagnet relay 40 in a closed position (energized state) is longer than the contact holding time of the contact 50 of the relay 49.

The holding time of the contact 50 of the electromagnetic relay 49 in a closed position is longer than the time interval between two detonations but is shorter than that between three detonations. The contact holding time of the contacts 41, 42 and 43 of the electromagnetic relay 40 in a closed position is longer than the time interval between three detonations but is shorter than that between four detonations. This is conditioned by that the absence of the powder in the detonation product flow or a misfire of the apparatus i.e. malfunctions thereof repeating during a time interval corresponding to less than two successive detonations are assumed to be accidental ones.

The control unit 26 is designed for cyclic generation of electric pulses to activate at a predetermined sequence the actuating mechanisms. This unit may be variously constructed, for instance in the form of a master controller (as shown in Fig. 2).

The master controller comprises a shaft 51 coupled with a rotational drive 52. On the shaft 51 there are mounted cams 53, 54, 55 and 56. The cam 53 is in contact with a switch 57 of the control circuit 27 operating the valves 13 and 14, and the cam 54 is in contact with a switch 58 in the control circuit 28 operating the valve 1 5 of the gas mixture supply system 3. In a similar manner the cam 55 is in contact with a switch 59 in the control circuit 29 operating the device 31 for igniting spark across the spark plug 2, and the cam 26 is in contact with a switch 60 in the control circuit 30 operating the valve 25 through which a gas carrier is supplied to the powder supply system 4.

Shown in Fig. 3 of the accompanying drawings is a modification of the proposed apparatus, wherein the control system 5 includes a manipulator 61 adapted to move the article being coated, which manipulator is electrically connected with the threshold element 48 of the control circuit 47.

The proposed apparatus for detonation coating operates in the following manner.

Before starting operation an article C to be coated is positioned in front of the open end of the detonation chamber 1 (Fig. 1), and the toggle switch 44 is set in the position "a", in response to which the electromagnetic relay 40 operates and causes the contacts 41, 42, and 43 of the control circuits 27, 29 and 30 of the unit 26 to close. The contact 50 of the electromagnetic relay 49 is open and the protective blind 45 is shielding the surface of the article C to be coated.

After the pre-starting procedure has been accomplished, the operator presses a push button "START" on the control console (both said push button and control console are not shown), in response to which a drive 52 (Figs. 1 and 2) of the control unit 26 is energized, and a supply voltage from the source E is applied to the control circuits 27, 28, 29 and 30 to operate the actuating mechanisms of the apparatus in a predetermined sequence. In this case, first, the cam 53 actuates the switch 57 to close the control circuit 27 and to thereby to cause the valves 13 and 14 of the gas mixture supply system 3 to operate, while the cam 54 actuates the switch 58 closing the circuit 28 to thereby cause operation of the valve 1 5.As a result, a combustible, an oxidizer and an inert gas are fed from their sources 7, 8 and 9 through the pipe-lines 10, 11, and 12 into the mixer 6, wherein said components are mixed to produce an explosive mixture. The gas mixture thus produced is introduced through the check valve 1 6 and the coil pipe 1 7 into the detonation chamber 1.

At the moment when the detonation chamber is being filled with the gas mixture, the cam 56 of the control unit 26 actuates the switch 60 making the circuit 30 to thereby cause to operate tha valve 25 of the powder supply system 4. The valve 25 is opened for a period of time which is equal to the circuit-closing time of the control circuit 30, determined by the configuration of the cam 56, so as to provide feeding the inert (carrier gas) gas to the batch meter 1 8 and to inject said gas through the pipe 23 into the detonation chamber 1. The amount of powder thus supplied to the detonation chamber 1 (powder charge) depends on the gas carrier pressure and the time period during which the valve 25 is open.

After the detonation chamber 1 has been filled with the gas mixture and powdered coating material, the cam 53 of the control unit 26 releases the switch 57 to break the control circuit 27 and to thereby close the valves 13 and 14 of the pipelines 10 and 11 supplying combustible and oxidizer respectively. As the valve 1 5 still remains at that moment open, the inert gas continues to be supplied into the mixer 6 to force out the gas mixture from the cavities of the mixer 6, check valve 16 and coil pipe 17.

Thereafter the cam 54 releases the switch 58 to break the control circuit 28 and to thereby cause the valve 1 5 to close. Simultaneously the cam 55 actuates the switch 59 which in response makes the control circuit 29 to provide the formation of spark across the spark plug 2 and thereby initiate detonation in the detonation chamber 1.

The detonation products entrains the powdered coating material thereby heating and accelerating it. The detector 33 mounted at the outlet of the detonation chamber 1 detects the brightness of the two-phase flow, which brightness depends on the amount of the coating material powder contained in said flow. The signal from the detector 33 is applied to the signal converter 34 wherein, first the signal power is amplified by the power amplifier 36, and then the signal voltage is amplified by the voltage amplifier 37. The thus amplified signal from the detector 33 is applied to the integrating circuit RC 38 which incorporates a capacitor. In response to the signal from the detector 33 the capacitor of the RC-circuit 38 is charged to a voltage whose magnitude is proportional to the magnitude of the signal.The voltage across the capacitor of the integrating RC circuit 38 determines the voltage value at the output of the power amplifier 39.

The first detonation is caused to hit the protective blind 45, which is explained by that the first detonation is not sufficiently effective, since the content by weight of the explosive mixture components does not fully correspond to the predetermined operating parameters.

After the first detonation the toggler switch is changed over to the position "b", whereafter the apparatus operates depending on signals from the detector 33. In case the amount of powder contained in the detonation products corresponds to the predetermined one the voltage at the output of the power amplifier 39 corresponds to the predetermined value. Such being the case, the electromagnetic relay 49 operates to close the contact 50 of the control circuit 47, in response to which the actuating mechanism 46 of the protective blind 45 is connected to the direct voltage source E, and as a result the protective b!ind 45 is caused to be lifted and to thereby expose the surface of the article being coated. If the voltage value at the output of the power amplifier 39 is sufficient to operate the electromagnetic relay 49, the apparatus operates in the above sequence.The powder particles are ejected from the detonation chamber 1 as a result of explosion therein and impinging upon the article are bonded to the surface thereof, thereby forming a layer of coating thereon.

If the amount of the coating powder contained in the detonation products is below the predetermined value, or in case there is no powder detected in the detonation products, or in the case of a misfire of the apparatus, that is the detonation does not occur, the voltage magnitude at the output of the power amplifier 39 becomes not sufficient to cause the electromagnetic relays 40 and 49 to operate. The electromagnet relay 49 having a shorter contact holding time of the contact 50 in a closed position than that of the electromagnetic relay 40, break the control circuit 47 in response to which the actuating mechanism 46 operates to lower the protective blind 45 and to thereby screen the surface of the article C being coated. If, during the time equal to the corresponding time period between two successive detonations, the voltage value at the output of the power amplifier 39 does not attain the required value, the contacts 41,42, and 43 of the electromagnetic relay 40 will be opened and the operation of the apparatus will be ceased to aliow the determination of the reason of malfunction. If the voltage value at the output of the power amplifier 39 is restored, the malfunction of the apparatus is assumed to be accidental and the electromagnetic relay 49 operates to close the contact 50. As a result, the actuating mechanism 46 operates to lift the protective blind 45, whereafter the apparatus operates in the predetermined sequence.

A modification of the proposed apparatus shown in Fig. 3 operates in general in the same fashion as described above. In this case, however, the manipulator 61 causes the article C being coated to move only in the case when the contact 50 of the electromagnetic relay 49 is closed. Thus, the manipulator does not move the article C being coated either during the first detonation or in the case of malfunctions of the apparatus, that is when the voltage value at the output of the power amplifier 39 is lower than the required one.

When the voltage at the output of the power amplifier 39 corresponds to the predetermined one, that is when the contact 50 of the electromagnetic relay 49 is closed, the manipulator 61 causes the article C being coated to move along the predetermined path.

While particular embodiments of the invention have been shown and described various modifications thereof will be apparent to those skilled in the art and therefore it is not intended that the invention be limited to the disclosed embodiments and the departures may be made therefrom within the spirit and scope of the invention as defined in the claims.

Claims (6)

1. An apparatus for detonation coating comprising a detonation chamber in the form of a barrel, gas supply means for supplying a combustible gaseous fuel to the chamber, ignition means for igniting the fuel in the chamber, powde supply means for supplying coating powder to the chamber; a control means for controlling the gas supply means, the powder supply means and the ignition means, the control means including a powder detector located at the open end of the barrel for detecting powder in the detonation products emitted therethrough, a protective shield mounted movably at the open end of the barrel on the side of the powder detector remote from the barrel, and means for adjusting the shield to obstruct the flow from the barrel when the powder emitted from the barrel during one or more preceding successive detonations is less than a predetermined value.

2. An apparatus according to claim 1, wherein the control means is arranged to interrupt operation of the gas supply means, powder supply means and ignition means in response to the amount of powder emitted from the barrel remaining less than the said predetermined value for a number of successive detonations exceeding said one or more preceding successive detonations.

3. An apparatus according to claim 1 or 2, wherein said one or more preceding successive detonations is two in number.

4. An apparatus according to claim 1,2 or 3 wherein the powder detector is coupled to a signal converter, and the shield adjusting means is connected electrically to the signal converter through a control circuit including a threshold element.

5. An apparatus according to any one of claims 1 to 4, wherein means is provided for advancing an article being coated and connected to said control means so that the article is advanced only after a detonation during which the shield is withdrawn so as not to obstruct the flow of powder to the article.

6. An apparatus for detonation coating substantially as hereinbefore described with reference to the accompanying drawings.