Fluent material handling – with receiver or receiver coacting mea – Fluent charge impelled or fluid current conveyed into receiver
Patent
1989-09-18
1991-04-02
Recla, Henry J.
Fluent material handling, with receiver or receiver coacting mea
Fluent charge impelled or fluid current conveyed into receiver
141249, 222636, 12820315, B65B 108, B67D 500
Patent
active
050040219
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates generally to apparatus for applying powder coatings to workpieces, and more particularly it concerns an arrangement for conveying powder to the barrel of a gas detonation apparatus.
The invention can be utilized with the utmost advantage for obtaining refractory, corrosion- and wear-resistant coatings by gas detonation to protect units and parts of machines and mechanisms operating in highly corrosive media against intensive abrasive wear.
BACKGROUND OF THE INVENTION
The essence of applying coatings by gas detonation rests in the following. A barrel open at one end is filled with an explosive gaseous mixture, a powder for obtaining a coating is fed, and detonation is initiated at the closed end of the barrel. The high-temperature (.about.4000.degree. C.) and high-speed (.about.1500 m/s) flow of detonation products heats and accelerates the powder particles which are thrown against the surface of a workpiece before the open end of the barrel to form a coating. Normally, the apparatus for applying coatings by gas detonation are automatically controlled, the detonation process being repeated at a frequency of about 10 shots per second.
One of the major units of the gas detonation apparatus is an arrangement for conveying a powder material to the barrel. This arrangement is intended to convey a preset quantity of powder to a preset section of the barrel at a preset point in time. The more accurately such conditions are conformed to the higher is the quality of coatings, expressed by such characteristics as stability of the coating, strong bond between the coating and the surface of the workpiece, porosity, and thickness of the coating after one shot.
Among factors complicating normal functioning of such arrangements in apparatuses for applying coatings by gas detonation are the following: penetration of the products of detonation from the barrel to the housing of the powder-feeding arrangement (backfire) and penetration of the explosive mixture to the housing of the arrangement as this mixture is fed to the barrel of the apparatus. These two factors can lead to failure of the apparatus.
Therefore, the arrangement for conveying powder to the barrel should be so constructed as ensure an extra service life, stable cyclical feeding of the powder with particle size of 5 to 50 mkm (at a frequency of 1 to 10 cycles per second), an accurately preset quantity of powder for each cycle, reliable protection of the arrangement against backfires, uniform distribution of the powder particles in the flow of detonation products, fluidity of the powder as it fills the powder-metering recess, amenability to automatic remote control over the quantities of powder and carrier gas, and provision for minimizing the quantity of powder-carrying gas entering the barrel.
At present, apparatuses for applying coatings by gas detonation use two types of powder feeding arrangements, particularly pneumatic and mechanical. In the pneumatic arrangements powder is conveyed to the barrel of the apparatus by a compressed gas continuously or in a pulse-wise manner. In the continuous feeding of the powder to the barrel the quantity of powder is spread in the barrel in the form of an elongated mist. In this case the difference in the initial position of the powder particles axially of the barrel leads to variations in the speed and heating temperature of the particles as they are accelerated and heated by detonation products in the barrel of the apparatus. Experiments have shown that for obtaining high-quality coatings from a preselected powder material it is necessary that during the escape of the powder particles from the barrel the speed and temperature of all the particles of the quantity of powder fed to the barrel be approximately equal. This condition cannot be complied with during continuous feeding of the powder to the barrel, and therefore continuous feeding of the powder to the barrel results in low quality coatings with unstable characteristics.
During pulsewise feeding of the powder to th
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Buteev Alexandr I.
Gavrilenko Tamara P.
Nikolaev Jury A.
Ulyanitsky Vladimir J.
Institut Gidrodinamiki Imeni M.A. Lavrentieva Sibirskogo Oldelen
Kupferschmid Keith
Recla Henry J.
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