FR2485401A1 - METHOD AND APPARATUS FOR PROJECTING A POWDER TO THE PULVERIZED CONDITION - Google Patents

Abstract

THE INVENTION CONCERNS A PROCESS AND AN APPARATUS FOR SPRAYING A PULVERIZED STATE A POWDER. FOR THE SPRAYING OF A DRY POWDER FROM A FLUIDIZED BED POWDER TANK 10 THROUGH A 12 PUMP HAVING A CHAMBER WHICH IS OPEN TO THE ATMOSPHERE OF THE FLUIDIZED BED TO ADMIT A CERTAIN QUANTITY OF POWDER OR FLUIDIZED BED 'AIR IS INSUFFED IN THE PUMP TO SPRAY THE SAID FLUIDIZED POWDER THROUGH AN ASSEMBLY 16 FORMING A CYLINDRICAL BODY, WE CAN PULVERIZE A MORE CONCENTRATED QUANTITY OF POWDER AT HIGH SPEED OVER A GREATER DISTANCE IF THE CHAMBER IS MAINTAINED AND IS ISOLATED. TO GASES 44, 66 OPPOSITE THE TANK ATMOSPHERE BEFORE BREATHING AIR INTO IT.

Description

248540 1

  The present invention relates to a method and apparatus for spraying powder. In various finishing processes of the steel where the steel is shaped or formed in the hot state, it is often desirable to mark the hot steel for example for the identification or the identification of defects. Since steel is hot, marking materials such as paint can not be used because they would be quickly destroyed by heat. So far, the practice has been to apply dry powder pigments or metal powders to the surface of the steel

  hot, preferably by pneumatically projecting these powders.

  While there is a wide range of equipment on the market for blasting dry powders, these prior art equipment is not fully suitable for spraying the types of powders used to mark hot steel. Thus, the powders that are most commonly preferred for marking hot steel, for example titanium dioxide or zinc oxide, tend to agglomerate when pumped pneumatically, which frequently has the effect of clogging and close the equipment

powder projection.

  U.S. Patent No. 3,899,131 discloses a method and apparatus for projecting such powders.

  than the agglomerated titanium dioxide according to which the

  The problems associated with agglomeration are somewhat reduced. Although this method and this apparatus are commonly used successfully in a number of commercial operations, they have certain limitations which make them impractical to implement certain conditions, for example the marking of hot products such as bars, billets or slabs moving to large

  linear velocities, that is velocities greater than 300 m / min.

  Specifically, the impact of the marking powder on fast-moving products has not proved sufficient to ensure permanent adhesion to the product and, or the volume of the marking powder reaching the product does not provide a marking of a suitable contrast to give visibility at a distance. In reality, such a system requires that the marking apparatus be in the immediate vicinity of a fixed or slow moving product to provide a desired contrast, but this is not always possible on certain

  production lines, because the projection apparatus would be rapidly

  damaged, or since it is not possible to stop or

slow down the production chain.

  According to the invention there is provided a method for pneumatically spraying a powder through an apparatus comprising a powder reservoir in a fluidized bed, a pump body mounted inside the reservoir and having a a chamber that communicates with an assembly forming a cylindrical body

  and an opening in its wall which communicates with the

  tank, a valve that selectively opens and closes

  said opening, a gas-tight seal disposed between said

  pope and said pump body in order to hermetically seal said

  relative to the interior of said tank when the

  pope is closed, and means for blowing a gas into said pump body and said assembly forming a cylindrical body; the method of activating said powder reservoir in a fluidized bed so as to fluidize the powder contained therein, opening said valve to admit a quantity of fluidized powder into the chamber, closing said valve to retain said amount of fluidized powder inside said chamber, and to

  service said insufflation means in order to

  said amount of fluidized powder via.allied together

a cylindrical body.

  The invention also proposes a device for setting

process.

  The following description, designed as an illustration

  of the invention, aims to give a better understanding of its features and advantages; it is based on the accompanying drawings, among which: - Figure 1 is a partial sectional elevation showing an apparatus for projecting in powder form a dry powder according to the invention; - Figure 2 is a partial sectional plan view of the apparatus of Figure 1 along the lines II-II of Figure 1; FIG. 3 is a simplified diagram of the pneumatic control circuit making it possible to actuate the apparatus of FIGS. 1 and 2;

  FIG. 4 is a sectional view of an injection model

  an improved embodiment adapted to an embodiment of the invention; and FIG. 5 is a sectional view of another embodiment of

  realization of the advanced injector model.

  As can be seen in the drawings, the apparatus

  takes a fluidized bed powder reservoir 10, a pump assembly 12, an air pneumatic cylinder 14 and an assembly 16 forming a cylindrical body. The pump 12 is supported in one piece by

  a frame consisting of two lateral bars 20, an anterior plate

  22 and a rear plate 24. The frame is mounted to the interior

  This arrangement isolates the pump body from the outside atmosphere. The pump itself consists of a tubular body 30 welded to the front plate 22 and is provided with a pair of opposed extended openings 34 and 36. A pump cylinder 38, consisting of a cylindrical body

  hollow metal coated with polytetrafluoroethylene is mounted

  inside a sleeve 40 of polytetrafluoroethylene which is retained inside the body 30 by a fixing plate 42.

  cylinder 38 acts as a valve shutter element

  both to selectively open and close openings 34 and 36.

  The front end of the cylinder 38 is provided with an injector 44 which can be replaced. In the closed position shown in the drawings, the injector 44 bears against a hollow cylindrical nozzle 46 which is fitted into the front end of the body 30. The

  nozzle 46 is also made of polytetrafluoroethylene.

  At the front end of the body 30, is fixed by means of a threaded nut 48 the assembly forming a cylindrical body 16, which is of the type that can be replaced and consists of a metal tube 50 at the inner end of which is welded a ring of

  52. The tube 50 contains a sleeve 54 in polytetramposite

  fluoroethylene which is retained by a welded metal cap 56

at the front end of the tube 50.

  The rear end of the cylinder 38 is provided with a

  an angled cord 60 which receives an air inlet pipe 62 and to which is attached a push rod 64. The push rod 64 passes through the rear wall of the tank 10 and its outer end is connected to a rod 66 of the pneumatic cylinder 14 by a coupling 68. A

  bellows 70 is mounted on the rod 64 and is attached to the plate

  24. As a result, the reciprocating movement of the pneumatic cylinder 14 causes the cylinder 38 to move back and forth between the closed position, which is shown in the drawings, and an open position in the which the inside of the body of

  pump 30 is exposed to the atmosphere prevailing inside the reservoir.

  see 10 via openings 34 and 36.

  As regards the operation, the cylinder 14 is actuated to the closed position and the powder is placed in the reservoir 10, which must be projected via the assembly 16 forming a cylindrical body, the powder being fluidized by means of air that passes through a porous membrane 72.

  via the air hose 62 or other low velocity purge gas.

  This low velocity purge gas passes into the cylinder 38, the nozzle 46 and the assembly 16 forming a cylindrical body. The device is then armed and ready to spray powders on demand. To project

  powders according to the practices of the prior art, it is necessary to

  should increase the speed of the air or gas admitted by the pipe 62 while the cylinder 38 has been opened by the pneumatic cylinder 14

  to admit the fluidized powder inside the pump body 30.

  Once admitted, the powder would be pneumatically ejected through

  the nozzle 46 and the assembly 16 forming a cylindrical body. For inter-

  to break the powder projection, the pneumatic cylinder

  14 to close the cylinder 38 while reducing the air admitted therein to a low velocity purge jet

  to keep the passage clear of accumulated powder.

  Thus, according to the prior art, the cylinder 38

  would be in the open position for the duration of the spray-

  authorization. In contrast to the prior art, the invention requires the cylinder 38 to be closed during spraying. Thus, the cylinder 38 opens just before the jet-so as to admit the

  desired amount of fluidized powder within the pump body 30.

  Then, the cylinder 38 closes and retains a small amount of fluidized powder. When the cylinder 38 is completely closed, the small amount of powder inside the cylinder 38 is projected through the cylindrical body assembly 16 by means of a relatively low pressure, for example a pressure of 2.8 kg / cm so as to achieve a speed substantially

  higher than this is possible with an open cylinder 38.

  Although a significantly smaller volume of powder is thus

  thrown, its higher speed gives it a higher impact force on a more concentrated contact area. The powder thus projected has a stronger adhesion on the target area and its more concentrated nature produces a more visible area. In addition, the powder can be projected over a greater distance while leaving a mark easily visible, even on products that

  move at linear speeds exceeding 300 m / min.

  - To obtain a high speed displacement of the powder

  through the assembly 16 forming a cylindrical body, it is necessary to

  that the seal between the injector 44 and the nozzle 46 is very effective. Any leakage at this level causes turbulence in the nozzle 46 and reduces the speed. In FIG. 4, it can be seen that the sealing face of the injector 44 is inclined so as to produce a contact angle α of between 40 and 50. According to another possibility, it is possible to provide a spherical contact surface, shown in FIG. 5, where the tangent to the radius R at the point of contact with the injector is at an angle of between 40 and. The inner surfaces of nozzle 46 and cylindrical body assembly 16 must be streamlined to minimize turbulence, i.e. any acute wedge at any orifice must be removed to avoid turbulence. which tends to reduce the speed of the air. The ideal speed must approach without

exceed the speed of sound.

  The pneumatic control circuit of the apparatus is shown in FIG. 3. A main line 76 for supplying air from a pipe 74 connects to a four-way valve 78 which delivers air to the pneumatic cylinder 14. either at its anterior end 80 or at its posterior end 82, according to

  the position of the valve 78. A solenoid 84, which actuates the

  Pope 78, is excited by an appropriate power source

  conch 86 via a switch 88 recalled by

  fate. A second solenoid valve 90 is placed on the pipe

  air 76 which supplies air to the supply pipe 62 of the pump.

  The solenoid 90 is energized by any suitable power source 92 via a switch 94 recalled by

  spring. Air is supplied continuously to the fluid bed 10

  said by a pipe 96 via a regulator 98.

  In operation, when the reservoir 10 is fluidized, the operator can push the switch 88 so as to supply air to the inlet 80 of the pneumatic cylinder 14. This brings about the withdrawal of the cylinder 38 and thus authorizes the admission of a fluidized powder in the pump body 30. The release of the switch 88 causes a reversal of the direction of movement of the pneumatic cylinder, which

  has the effect of closing the cylinder 38 by enclosing a certain quantity

  powder in the pump body 30.

  mutator 14 to open the solenoid valve 90 and allow all the air supply pressure to increase suddenly in the pipe 62 and the cylinder 38 by projecting the fixed amount of powder through the assembly 16 forming a cylindrical body. In an application

  on the actual production line, the switches 88 and 94

  ordinarily occur automatically in response to a signal in

view of the projection of the powder.

  Of course, those skilled in the art will be able to imagine

  from the process and the apparatus whose description has just been

  given by way of illustration and in no way limiting, various

  variants and modifications that are not outside the scope of the invention.

Claims (4)

R E V E N D I C A T IO N S   1. Method for pneumatically projecting to the state   sprayed powder through an apparatus that includes a reservoir   see (10) fluidized bed powder, a pump body (12) mounted within said reservoir and having a chamber communicating with an assembly (16) forming a cylindrical body and an opening   formed in its wall which communicates with the interior of said reservoir.   see, a valve (38) for selectively opening and closing said opening, and means (62, 90) for blowing a gas into said pump body and said cylindrical body assembly, the method being characterized in that it consists in activating said reservoir (10) of powder in a fluidized bed so as to fluidize the powder contained therein, to open said valve (38) in order to admit a certain quantity of fluidized powder into said pump body ( 12), closing said valve (38) to close   the inside of the pump body (12) with respect to the reservoir   see (10) and retaining within said pump body (12) said amount of fluidized powder, and actuating said insufflation means (62, 90) to blow out said amount of fluidized powder through said assembly (16) forming a cylindrical body.   Apparatus for pneumatically spraying a dry powder into the powdered state, comprising a fluidized bed powder reservoir (10), a pump body (12) mounted within said reservoir and having a chamber which communicates with a fluidized bed, an assembly (16) forming a cylindrical body and an opening in its wall which communicates with the interior of said reservoir, a valve (38) for selectively opening and closing said opening, and a means (62, 90) for insufflation of a gas through said pump body and said cylindrical body assembly, the apparatus characterized by comprising a gas-tight seal (44, 46) disposed between said valve (38) and said pump body (12) so as to seal said chamber relatively to   inside said tank when the valve is closed.   3. Apparatus according to claim 2, characterized in that said valve is an injector (38) slidably mounted in said pump body (12), and said gas-tight seal comprises a   nozzle (46) made of polytetrafluoroethylene attached to the inside of the   anteriorly of said chamber and in contact with the injector (38) according to a concordant surface inclined at an angle of between 40 and 50 with respect to the sliding direction of the injection. (38).   4. Apparatus according to claim 3, characterized in that said injector (38) and said nozzle (46) are in contact according to concomitant partially spherical surfaces, the tangent to the partially spherical portions at the contact area being inclined d an angle between 40 and 50 'in relation to the   sliding direction of the injector (38).