FR2957832A1 - MOBILE TANK FOR ICE PARTICLE DISTRIBUTION - Google Patents

Abstract

The invention relates to a dispensing tank (10) for storing ice particles. It comprises a hopper (12) having an upper loading opening (18) and a lower flow opening (22). Said distribution tank (10) further comprises first drive means (30, 52) mounted inside said hopper (12), and comprising on the one hand a transmission shaft (52) and on the other hand part of the mechanical members (30) mounted on said transmission shaft (52), said distribution tank further comprising second drive means (54, 60) for rotating said transmission shaft. According to the invention, said mechanical members (30) are helically installed around said transmission shaft; while said second drive means (54, 60) is adapted to drive said transmission shaft (52) in rotation over a fraction of a turn to drive at least a portion of said charged ice particles in motion.

Description

1 Mobile ice particle distribution tank

The present invention relates to a distribution tank for dry ice particles for supplying a plant for projecting these particles against surfaces to be treated. The projection of dry ice particles, particularly dry ice particles, against surfaces to be treated is similar to sandblasting for example and makes it possible to clean and degrease these surfaces, especially for subsequent treatment. The advantage of dry ice vis-à-vis the usual sand blasting techniques is that it sublimates after the impact under the effect of the heat energy produced precisely by this impact. Consequently, unlike conventional sandblasting where the sand is to be recovered with complex specific installations, with dry ice, it is sufficient to capture and then channel the gaseous carbon dioxide product to possibly filter it before rejecting it in the atmosphere. The equipment to be implemented is simpler and less expensive. In addition, by nature this technique generates much less particles than sanding. However, the implementation of dry ice particles, made of rods of a length of 10 to 20 mm and a diameter of about 3 mm, or "pellet" in English, for treatment surface, requires a relatively large installation including a reserve of liquid carbon dioxide, located near the place where they are projected. Indeed, the dry ice has a sublimation temperature of -78.2 ° C at atmospheric pressure so that it can not be stored for long periods. Moreover, it is inconceivable to wear a facility for the production of dry ice particles near the place, for example treatment chains, where the surfaces are treated. Also, it has been imagined to design mobile dry ice particle distribution tanks for transporting them between the production facility and modestly sized projection facilities located near the processing line. Reference can be made in particular to document EP 0 521 794, which discloses such a mobile distribution tank. It comprises on the one hand a hopper having an upper opening for loading the ice particles and a lower flow opening and, on the other hand, means for driving the particles mounted inside said hopper, comprising a hopper shaft. transmission and mechanical members mounted on said transmission shaft. The transmission shaft is oriented from said lower flow opening to said upper loading opening and said mechanical members comprise both blades and a worm which extends through the lower opening. The dispensing reservoir further comprises a motor for rotating said drive shaft to drive the moving ice particles into said hopper and forcing the ice particles to through the lower opening. If the flow of particles to the flow opening is relatively smooth, on the other hand, the rotation of the blades and worm in contact with the ice particles, causes them to settle which can lead to blockage. Also, such a reservoir causes operational impossibilities with stop and recovery. Also, a problem which arises and which the present invention aims to solve is to provide a dispensing reservoir which not only allows to promote a smooth flow of ice particles through the lower flow opening, but also which can stop and resume distribution without blocking. For this purpose, the present invention proposes, in a first aspect, a dispensing tank for storing ice particles for feeding a projection installation of said ice particles, said dispensing reservoir comprising a hopper having on the one hand a upper loading opening for loading said ice particles inside said hopper, and secondly a lower flow opening adapted to be connected to said projection installation, said dispensing tank further comprising first means for drive mounted within said hopper, said first drive means including a drive shaft oriented from said lower flow opening to said upper loading opening and mechanical members mounted on said drive shaft, said reservoir distribution system further comprises second drive means The invention relates to rotating said transmission shaft so as to cause said mechanical members to move against said ice particles. According to the invention said mechanical members are installed helically around said transmission shaft; and said second drive means is adapted to drive said transmission shaft in rotation a fraction of a turn to drive at least a portion of said charged ice particles in motion away from said lower flow opening, so as to allowing another portion of said particles to flow to said lower flow opening. Thus, a feature of the invention lies in the implementation of the mechanical parts helically around the transmission shaft so that they extend radially, and in the rotation of the transmission shaft on a fraction of a turn, so as to lift and cause at least a portion of the ice particles to the top loading opening and opposite the bottom flow opening, to allow the flow of another portion particles towards the lower opening. In fact, the ice particles tend not only to stick to each other because of the water in the form of vapor contained in the air and to agglomerate en bloc, but also to exert efforts towards the lower flow opening and maintain the blocks in front of the opening by closing the flow of ice particles. Also, by rotating the transmission shaft, not only the blocks of the lower opening are discarded, but in addition the blocks which break up into free ice particles are dislocated. In this way, the continuous flow of ice particles continues without stopping. According to a particularly advantageous embodiment of the invention, said second drive means are adapted to give a mechanical impulse in rotation to said transmission shaft when it is rotated, to cause the oscillation of said mechanical members. . Thus, the mechanical members which are elastically deformable connected to the transmission shaft, oscillate when the transmission shaft is subjected to a mechanical pulse of relatively low amplitude and high acceleration. The oscillation movement is of course quickly amortized, but its amplitude and its damping time nonetheless make it possible to break up the blocks of ice particles formed. In addition, the amplitude of rotation of the transmission shaft is of the order of ten degrees, for example 20 °, and is sufficient to drive in vertical motion and lift a substantial portion of the ice particles and the away from the flow opening. In this way, the hopper, towards the flow opening, is decongested and the free ice particles then flow continuously through this opening. Furthermore, preferably, the transmission shaft is rotated alternately in two opposite directions, as will be explained below. Advantageously, said mechanical members comprise grids. These grids have meshes allowing the flow of free ice particles through, and also allowing to drive the ice particles is more or less aggregate en bloc, in vertical movement when the transmission shaft is rotated. According to a particularly advantageous characteristic, the dispensing reservoir further comprises a lower shutter member for closing off said lower flow opening, and said shut-off member is controllable by means of a rod which extends to the interior of said transmission shaft. The rod extends outside the hopper above the upper opening and outside the shaft so as to be driven in translation to precisely control the closure member. According to a particular embodiment, said hopper comprises an intermediate duct installed in the extension of said lower flow opening, and said intermediate duct is equipped with a controllable stop valve. Thanks to the intermediate duct, the hopper is thermally isolated during momentary interruptions of use of the ice particles. In fact, in this case, the lower flow opening 30 is first sealed by applying the shutter member therethrough, and then, when the ice particles no longer flow, the valve is controlled. stopping to form an insulating free space opposite the lower flow opening.

Preferably, the distribution tank further comprises a frame for supporting said hopper. The chassis is equipped with wheels for driving said rolling tank on a given surface, and more specifically for conveying it between the dry ice particle production facility and the projection installation. In addition, said hopper is mounted movably on said frame and said frame and said hopper are connected together by a pulse drive device for oscillating said hopper relative to said frame. Thus, when the angular movements of the transmission shaft are not sufficient to break up the blocks of ice particles, in addition the pulse drive device is actuated. The latter comprises for example a deformable air sleeve, which is inflated and then released suddenly air, which gives a tipping impulse to the hopper. This sudden movement is enough to break up the blocks of ice particles. According to another aspect, the present invention proposes a cryogenic treatment unit comprising an ice-particle production facility and an ice-particle projection installation situated at a distance from said production facility. The installation comprises at least one reservoir. as described above, for transporting said ice particles between said production facility and said projection plant. Thus, despite the time elapsing between the production of the ice particles and the moment of their projection, their flow inside the hopper and through the lower opening, occurs regularly. Indeed, inevitably air loaded with water seeps into the hopper 25 during the loading of the ice and thus, the particles tend to stick with each other. With the aforementioned dispensing tank, at the time of projection, which can occur more than 24 hours after the production of ice, the particles are separated from each other through the implementation of mechanical devices. According to a preferred embodiment of the invention, said ice-particle production facility comprises means for storing carbon dioxide to produce dry ice particles, the sublimation of which occurs immediately after the impact on the surface. surface to be treated and does not generate any liquid effluent. Advantageously, said projection installation comprises means for receiving said dispensing reservoir, said receiving means comprising a weighing scale of said dispensing reservoir. In this way, the consumption of ice is controlled in real time by measuring the weight of the distribution tank, which may initially contain 100 kg of dry ice particles for example. Other features and advantages of the invention will appear on reading the following description of a particular embodiment of the invention, given by way of indication but not limitation, with reference to the accompanying drawings in which: - Figure 1 is a schematic view of a distribution tank according to the invention; Figure 2A is a schematic top view of the dispensing reservoir shown in Figure 1 equipped with complementary elements; Figure 2B is a schematic bottom view of the dispensing reservoir shown in Figure 2A; and - Figure 3 is a schematic view of a treatment unit according to the invention. Figure 1 schematically illustrates a distribution tank 10 according to the invention. It comprises a hopper 12 having an upper portion 14 of cylindrical symmetry and a lower portion 16 of frustoconical symmetry. The hopper 12 defines a volume of between 0.05 m3 and 1 m3, for example 0.5 m3. The upper portion 14 has an upper wall 17 in which is formed an upper opening 18 sealed by a cover 20, while the lower portion 16 has at the tip of the cone, a lower axial opening 22. The hopper 12 has an insulating wall 24 with a double envelope, an inner envelope 26 and an outer envelope 28 between which is housed an insulator. The insulation has a thickness between 50% and 90% of the distance between the two envelopes and is pressed against the inner wall. In addition, the inner casing 26 is covered with a layer of a plastic coating, for example polyethylene.

In addition, the distribution tank 10 comprises first drive means mounted inside said hopper, and comprising a longitudinal transmission shaft 52 and mechanical members 30 helically mounted on said transmission shaft 52. The shaft longitudinal transmission 52 extends vertically and axially inside the hopper 12 by sealingly passing through the upper wall 17 and extending to the lower flow opening 22. It is rotatably mounted through the upper wall 17 and is surmounted by a drive arm 54 rotatably connected to the shaft 52 outside the hopper 12. In addition, the drive arm 54 has an eccentric stud 56 connected to the end of a rod 58 of a jack 60 to form a crank. Thus, as will be explained hereinafter, the longitudinal transmission shaft 52 can be rotated alternately in one direction and then in the opposite direction, with an angle substantially close to 30 °. The mechanical members in contact with the ice particles comprise grids 62 helically arranged on and around the longitudinal transmission shaft 52, forming a worm 64, from the top wall 17 to the opening The grids then comprise a plurality of radial rods which extend radially in a helix of the transmission shaft 52, and these radial rods are interconnected by parallel wires 20 regularly spaced between the transmission shaft 52 and free end of the radial rods. These parallel wires extend helically around the transmission shaft 52 and are integral with the radial rods they intersect perpendicularly. The arrangement of the helical grids thus extends radially from the drive shaft 52 to the inner casing 26 without coming into contact therewith. Furthermore, in the lower part 16 of frustoconical symmetry, the radial rods are shorter than the upper part 14 and the grids 62 have a width which is reduced as one approaches the lower opening 22 to respect the frustoconical geometry. The grids 62 define trapezoidal orifices, the dimensions of which vary according to their radial position in particular. Their dimensions are included, according to an alternative embodiment, between 10 * 6 cm and 3 * 4 cm. It will be observed that the grids 62, made with stainless steel wires for example, are elastically deformable, to a certain extent, with respect to the longitudinal transmission shaft 52 itself is made of stainless steel. The stainless steel wires and rods are connected together by welding. The distribution tank 10 further comprises a lower closure member 51 formed of a frustoconical member for sealing the lower flow opening 22. The lower closure member 51 is controllable by means of a control rod 53 which extends inside the longitudinal transmission shaft 52. The control rod 53 extends outside the hopper 12 and outside the shaft through the drive arm 54 for s extending over the upper opening 18. In this way, the control rod 53 can be driven in translation to precisely control the lower closure member 51. The latter is held axially, the tip facing the the lower opening 22, and its maximum outside diameter is greater than the internal diameter of this opening 22. In this way, when the control rod 53 is driven in translation towards the opening 22, the lower sealing member 15 51 just apply bend against the edges to seal it. In addition, the lower part 16 of the hopper 12 is extended beyond the lower opening 22 by an intermediate conduit 55 equipped with a controllable guillotine stop valve 57, for example by means of a jack, here not shown. Thus, this arrangement makes it possible to form an insulating free space inside the intermediate duct 55 between the lower shutter member 51 and the stop valve 57. Thus, dry ice particles in the form of a stick of 10 at 20 mm and a diameter of about 3 mm are first loaded inside the hopper 12 through the opening 18, while the lower sealing member 51 closes the lower opening 22. The dry ice particles flow inside the hopper and through the grids 62 to completely fill the hopper 12 with an amount of 100 kg of ice, for example. As soon as the hopper 12 is loaded with dry ice particles, and the lower closure member 51 is moved away from the lower opening 22, the dry ice particles flow by gravity through the lower opening. 22. Thanks to the shape of the grids 62 arranged helically, the ice particles are progressively rotated about the longitudinal transmission shaft 52 and in translation towards the lower opening 22. This guidance of the dry ice particles makes it possible to to improve the regularity of the flow. However, under the effect of the warming and because of the water contained in the air, the carbon ice particles tend to stick to each other, and to form keystones in the lower part 16 of the Hopper 12. Also, to prevent the continuous flow of the dry ice particles from being interrupted, by the aggregation of these ice particles, the rotation of the transmission shaft 52 is controlled by means of the cylinder 60 Thus, at a given frequency, for example 1/30 hertz, control cylinder 60 which then causes the rotation of the drive arm 54 in an angular sector, for example less than 30 °. The jack 60 is for example a pneumatic jack, and is capable of providing a pulse to the drive arm 54, which transmits a rotational movement to the transmission shaft 52 with a strong acceleration followed by a sudden stop. . This rotational movement being printed on the grids 62 in a helix in a direction intended to raise the ice particles of the hopper 12 on a short path towards the opening 18 so as to decongest the lower part 16 of the hopper 12 at the level of which keystones were formed during the flow of the particles through the lower opening 22. In addition, besides the rotational movement which allowed to disaggregate by shear in particular, the ice particles agglomerated in a block, a vibratory movement cushioning is printed at the grilles 62 elastically deformable under the effect of the pulse. This vibratory movement further disintegrates the agglomerated ice particles. It will be observed that, between two pulses, the rod 58 of the jack 60 is retracted, while the transmission shaft 52 and the helical grids 62 are driven in the opposite direction to be able to be used again every 30 seconds according to the implementation example 30 mentioned above. Reference will now be made to FIGS. 2A, 2B on which is illustrated the dispensing reservoir 10 described above in cutaway and installed vertically on a frame 66 provided with four independent wheels 68. In the lower part of the frame 66 and in the center found, the lower flow opening 22 extended by the intermediate conduit 55, the latter being equipped with the stop valve 57 controlled by a pneumatic cylinder. FIG. 2A in plan view shows more precisely the drive arm 54 and the jack 60 enabling it to be actuated, whereas in FIG. 2B the transmission shaft 52 has no helical grilles, and lower closure member 51 at the end of the control rod 53. Thanks to the four independent wheels 68, the distribution tank 10 can be manually driven on the ground, between a production plant 70 of particles of dry ice illustrated in Figure 3, and a projection installation 72 of the dry ice particles. Thus, the cryogenic treatment assembly illustrated in FIG. 3 can be installed within the same building in two spaces distant from each other. Indeed, the dry ice production plant 70 comprises a reserve of liquid carbon dioxide 74 and an ice particle production device 76, which must be maintained in a confined space to preserve the safety of the people. The production device 76 supplies dry ice particles to the distribution tank 10 through its filling opening and away from the air. Then, the dispensing reservoir 10 is closed again by means of the aforementioned cover 20, to be driven near the projection installation 72. It is then engaged on rails to guide it in a determined position, where the lower opening flow 22 is adjusted opposite a frustoconical receiving ring not shown. This frustoconical receiving ring is capable of being driven vertically to fit around the lower flow opening 22 and to fully support the distribution tank 10. The frustoconical receiving ring, in addition to its guide means Ice particles comprising a flexible tubing which extends it, is supported by unrepresented weighing means in order to measure in real time the weight of the distribution tank 10. The projection installation 72 comprises for example a robot 78, the last of which arm is equipped with a spray gun 80, and the flexible tubing is connected thereto. Thus, the robot 78 is able to guide the spray gun 80 facing a workpiece 82, while the ice particles are projected against this piece 82, as soon as the lower flow opening 22 is released. and that the vibrator device 32 is implemented. Moreover, this set of cryogenic treatment is advantageously associated with a hot surface treatment device using, in particular, a plasma torch. Also, it includes a protective cabin, not shown, at the projection installation 72. However, the treatment process generates a significant amount of dust which is deposited in particular on the walls of the protective cabin. However, dry ice blasting tends to depolarise the treatment environment, and especially the protective cabin, so that the adhesion of the dust on its walls is at the same time attenuated. In addition, the weighing means controls the weight loss of the dispensing tank 10 and hence the amount of dry ice particles consumed. Thanks to the reciprocating movements of the mechanical members, the dry ice particles flow in a regular flow through the lower flow opening 22 of the hopper 12 and consequently regularly feed the spray gun 80 without interruption with a flow rate. For example between 20 kg per hour and 60 kg per hour. In addition, since the time between the moment of production of the ice particles and the filling of the distribution tank on the one hand, and the timing of the application of these projected ice particles on the other hand, is relatively For example, at least 24 hours, thanks to the reservoir of the invention, the dry ice particles are driven in movement relative to each other and tend to separate from each other. This promotes their flow through the lower opening 22. Advantageously, the dispensing tank is equipped with an RFID tag, to record the filling time of the hopper of the distribution tank 30, corresponding to the moment of production of the particles. of ice, while the production facility is equipped with an RFID tag reader so as to check whether the dry ice particles are still usable for projection. Indeed, it can be estimated that beyond 48 hours, the dry ice is no longer usable. A plurality of dispensing tanks is provided for the cryogenic treatment unit to be able to supply the projection installation continuously without interruption. This is usually located near a continuous process line.

Claims (11)

REVENDICATIONS1. A dispensing tank (10) for storing ice particles for supplying a projection apparatus of said ice particles, said dispensing tank comprising a hopper (12) having on the one hand an upper loading aperture (18) for loading said ice particles within said hopper, and secondly a lower flow opening (22) adapted to be connected to said projection installation, said dispensing reservoir (10) further comprising first means for drive (30, 52) mounted within said hopper (12), said first drive means including a drive shaft (52) oriented from said lower flow opening (22) to said upper loading opening (18) and mechanical members (30) mounted on said transmission shaft (52), said dispensing reservoir further comprising second drive means (54, 60) for rotating said transmission shaft so as to cause said mechanical members (30) to move against said ice particles; characterized in that said mechanical members (30) are helically installed around said transmission shaft; and in that said second drive means (54, 60) is adapted to drive said transmission shaft (52) in rotation over a fraction of a turn to drive at least a portion of said loaded charged ice particles in the opposite direction said lower flow opening (22) so as to allow flow of another portion of said particles to said lower flow opening (22). 2. Dispensing reservoir according to claim 1, characterized in that said second drive means (54, 60) are adapted to give a mechanical impulse in rotation to said transmission shaft (52), to cause the oscillation of said organs mechanical (30). 3. Dispensing tank according to claim 1 or 2, characterized in that said mechanical members (30) comprise grids. 4. Dispensing reservoir according to any one of claims 1 to 3, characterized in that it further comprises a lower shutter member (51) for closing said lower flow opening (22), and in that said shutter member is controllable by means of a rod (53) which extends inside said transmission shaft (52). 5. Dispensing tank according to any one of claims 1 to 4, characterized in that said hopper (12) comprises an intermediate conduit (55) installed in the extension of said lower flow opening (22), and said intermediate conduit is equipped with a controllable stop valve (57). 6. Dispensing tank according to any one of claims 1 to 5, characterized in that it further comprises a frame (66) for supporting said hopper (12). 7. Dispensing tank according to claim 6, characterized in that said frame (66) is equipped with wheels (58) for driving said tank (10) rolling on a given surface. 8. Dispensing reservoir according to claim 6 or 7, characterized in that said hopper (12) is movably mounted on said frame (66) and in that said frame and said hopper are connected together by a drive device. pulse to oscillate said hopper relative to said frame. 9. Cryogenic treatment assembly comprising a production facility (70) for ice particles and a projection installation (72) for ice particles located at a distance from said production facility, characterized in that it comprises at least one dispensing tank (10) according to any one of claims 1 to 8 for conveying said ice particles between said production plant (70) and said spraying plant (72). 10. cryogenic treatment unit according to claim 9, characterized in that said apparatus for producing ice particles has carbon dioxide storage means (74) for producing dry ice particles. 11. cryogenic treatment unit according to claim 9 or 10, characterized in that said projection installation (72) comprises means for receiving said distribution tank (10), said receiving means comprising a weighing scale of said distribution tank .