Machine and method for producing and blasting dry ice particles

Abstract

 A machine and a method for producing and blasting dry ice particles are disclosed, wherein a grinding unit including a grinding roller is fed by gravity with dry ice pieces having different shape and dimensions from a tank placed upper to the same roller.

Description

[0001] The present invention concerns a machine and a method for producing and blasting dry ice particles in order to clean surfaces with sublimable material.

[0002] The use of solid CO₂ particles and pellets for cleaning surfaces is already known and particularly appreciated in a large kind of applications. In fact, the solid carbon dioxide particles do not make abrasions on the hit surface and, after knocking the surface to be cleaned, they sublime in a short time and dissipate in the atmosphere in a gas form and without leaving residual products.

[0003] An example of machine for cleaning surfaces which uses this kind of technology is described in the European patent n. EP-0768934. The machine includes a feeding tank in which is inserted a dry ice block with a parallelepiped form. A transporting and thrusting device in the tank presses the block against a rotating plate with blades which remove dry ice grains from the block and carry them directly to a blast system which uses compressed air to transport dry ice grains against the surface to be cleaned. Because it is not realized any temporarily storage of the dry ice grains, it is provided the possibility to automatically control the production speed of dry ice grains operating on the transporting and thrusting device on the tank.

[0004] However this known machine can be fed only with dry ice block with form and dimension determined by those of the feeding tank, otherwise the transporting and thrusting device would be ineffective.

[0005] It is also known, in this kind of technique, another machine for producing and blasting dry ice particles which has a vertical tank for the feeding of dry ice to be ground. On the bottom of the tank there is a rotating plate with perforated teeth which remove the particles from the dry ice pieces.

[0006] However this machine can be fed only with dry ice pieces with little dimensions, for example pieces with a cylindrical form (usually named pellets) with a variable diameter from 3 to 5 mm and variable length from 5 to 40 mm. A weight is necessary to push the dry ice pieces to be ground against the rotating plate, because the weight of the material it is not sufficient to bring the material in contact to the grinding plate and in any case this weight changes as a function of the filling grade of the tank.

[0007] The object of the present invention is to propose a machine for producing and blasting dry ice particles which could be fed with different types of dry ice pieces as regards their forms and dimensions.

[0008] Another object of the present invention is to propose a machine of the above mentioned type that is particularly simple ed economical to realize.

[0009] A further object of the present invention is to propose a machine which allows to change in a simple and immediately way the granulometry of the dry ice particles produced between at least one pair of different values.

[0010] According to a first aspect of the invention, these objects are reached thanks to a machine for producing and blasting dry ice particles, including at least one feeding tank in which the dry ice is loaded in the form of pieces to be ground, the feeding tank having at least one exit opening near at least one grinding unit, and means for blasting dry ice particles produced by the grinding unit through a delivery nozzle, characterized in that the grinding unit includes a toothed roller rotated near the exit opening of the feeding tank.

[0011] Further to perform the grinding of the dry ice pieces, the toothed roller exercises a moving and pulling action on pieces with different shape and dimensions, without requiring thrusting or transporting elements of the pieces, and such as to allow a simple feeding by gravity.

[0012] In fact, the feeding tank for the dry ice pieces to be ground is preferably located on the top of the toothed roller, with a symmetry axis substantially perpendicular to the support surface of the machine.

[0013] A machine according to the present invention is thus suitable to receive many typologies of dry ice pieces among the more common ones as regards shape and dimensions. For example, further to the above mentioned pellets, it is possible to use pellets with a diameter of 10-16-19 mm and length of 30-70 mm, cylindrical "tablets" with variables diameters between 50 and 70 mm and thickness of 10-20 mm, or even tablets or tiles with thickness up to 50 mm. The machine is anyway suited to receive even pieces with irregular shape with respect to the most common ones, for example pieces recycled from blocks or crushed tiles.

[0014] The toothed roller is preferably located upper to a temporary storage hopper of the dry ice particles. An auger is put in rotation by an electrical motor on the bottom of the hopper for transporting the dry ice particles to the blasting means. The temporary storage allows to provide the blasting means with a uniform flow rate of dry ice particles, so as to allow a continuous and constant particles outflow.

[0015] According to a possible embodiment, the symmetry axis of the tank is incident with the rotation axis of the toothed roller. In this case, the toothed roller can be turned both clockwise and anticlockwise direction, without affecting the moving and pulling action exercised by the toothed roller on the pieces to be ground.

[0016] The rotation of the toothed roller in both directions can be easily obtained through control means, including for example an inverter or the like, which operate on an electrical motor which drives in rotation the toothed roller, and which allow the regulation of the rotating speed of the roller.

[0017] The toothed roller preferably includes a plurality of grinding teeth protruding from the surface of the roller and having essentially a triangular cross section. When the roller is driven in one of the rotating directions, the impact of the teeth with the dry ice pieces to be ground happens according to a major surface, or vice versa minor, with respect to the case in which the roller is activated in the opposite rotating direction. With the same machine it is therefore possible to easily obtain dry ice particles with a granulometry with two different values, so giving the possibility to select the desired granulometry as a function of the type of the surface on which the cleaning operation must be performed and/or as a function of the type of dust or fouling to be removed.

[0018] According to an alternative embodiment, the symmetry axis of the tank is offset with respect to the rotating axis of the toothed roller. In this alternative embodiment the machine can be fed even with tiles having major thickness compared with those useable with the previous embodiment.

[0019] According to another aspect of the present invention, it is provided a method for producing and blasting dry ice particles according to claim 11. Other features and advantages of this method according to the present invention are mentioned into the respective dependent claims.

[0020] Further characteristics and advantages of the present invention will be more apparent from the following description, made as an example, with reference to the attached schematic drawings:

• Figure 1 is a side elevation view of some components of a machine according to the present invention;
• Figure 2A is a front view of some components of the machine according to a possible embodiment of the present invention;
• Figure 2B is a front view of some components of the machine according to another embodiment of the present invention;
• Figure 3 is an enlarged plan view of the teeth present on the grinding roller according to a possible embodiment of the present invention;
• Figures 4A and 4B show two possible dispositions of the teeth on a grinding roller in a machine according to the present invention;
• Figure 5 is a section view of the grinding roller according to the embodiment of Figure 3; and
• Figure 6 is a section view of a further embodiment of the grinding roller in a machine according to the present invention.

[0021] In Figures 1, 2A e 2B are illustrated some of the components of a machine for producing and blasting dry ice particles according to some possible embodiments of the present invention.

[0022] The machine includes a casing 1 which contains a feeding tank 10 in which the dry ice pieces to be ground are charged through a closable hatch 2. All parts of the tank and of the machine which are in contact with the dry ice, which is at a temperature no more than about -78°C, are of course insulated or anyway thermally insulated with respect to the casing 1. The machine according to the invention can be realized with particularly limited dimensions, so that it will be easy to move it, and it can also have wheels fixed at the bottom of the casing 1 or it can be placed and/or installed on a trolley provided with wheels (not shown).

[0023] The feeding tank 10 vertically extends with symmetry axis S essentially perpendicular to the support surface P of the machine, in such a way as to favour the feeding of the dry ice pieces by gravity to a grinding roller 20 located in underlying position to the tank 10 in correspondence with an opening 15 (Figures 2A and 2B).

[0024] The grinding roller is activated in rotation by an electrical motor 30 through motion transmission means 31 which connect the respective shafts, and the rotation of the grinding roller 20 is subject to control means (not shown) which are able to regulate the rotation speed of the roller 20 and to change its rotating direction. The manual command of the principal functions of the machine is available to an operator by a command panel 3 located on the front part of the machine.

[0025] The dry ice particles obtained by grinding are temporarily collected into a hopper 40 before being transferred to the blasting means 50 through a rotating auger 45 driven in rotation on the bottom of the hopper 40 by a motor 55. The temporary storage of the particles allows to obtain a constant and uniform outflow of the particles, which is necessary to obtain a good quality of cleaning and removal.

[0026] The blasting means 50 can consist of any type of known suitable means. For example, the particles can be taken out by a Venturi effect from a pressurized air flow and thus directed to the delivery nozzle through a suitable flexible tube which is connected to a pipe fitting 51 on the machine.

[0027] Alternatively, the blasting means 50 can include a distributor of the "revolver" type, with a rotating drum provided with suitable seats in which the particles are deposited and thrown away by a pressurized air flow. The rotation of the drum can also be given by the same motor 30 which activates the roller 20.

[0028] In Figures 2A and 2B are illustrated two possible embodiments of the machine according to the present invention.

[0029] In Figure 2A the tank 10 is located with its symmetry S axis incident to the rotating axis R of the grinding roller 20. In this embodiment the machine is suitable to work with many typologies of dry ice pieces and the grinding roller 20 can be rotated in both directions (bi-directional arrow CA) to take advantage of some favourable characteristics which will be described below in a more detailed way.

[0030] In the embodiment of Figure 2B, the symmetry axis S of the tank 10 is offset with reference to the rotating axis R of the grinding roller 20. In this case it can be eventually provided a guide chute 41 (shown in dotted line) to facilitate the descent of the pieces fed into contact with the roller 20. In this embodiment the machine according to the invention is suitable to be fed with "tiles" of about 50 mm of thickness but maintaining the rotation of the roller 20 according to the direction indicated by the arrow A. With other pieces of different shape and/or smaller dimensions it is instead possible to let the grinding roller 20 rotates in both directions.

[0031] Referring to Figures 3, 4A and 4B, the grinding roller 20 is preferably constituted by a roller having a plurality of teeth 21 protruding from the surface of the roller and having a substantially triangular cross section. In the embodiments here represented the surface of the roller 20 is preferably without holes, so that the dry ice particles removed from the pieces subject to grinding are directly released in the hopper 40.

[0032] The teeth 21 are aligned on the roller 20 along helical lines 22 of one or more principles. The helical lines of one or more principles for example can converge to the centre of the roller as schematically represented in Figure 4A, or they can be oriented in the same direction as indicated in Figure 4B. In any case, the number of principles, their disposition an their orientation can be selected according to the more suitable moving effect for the shape and dimensions of the dry ice pieces that are usually fed to the machine.

[0033] In the section view of Figure 5 the configuration of the teeth 21 can be appreciated, which essentially show a "front" face 23, a "back" edge 24 and a cusp 25. The terms "front" and "back" have to be interpreted according to one of the possible rotating directions of the roller 20, that is the anticlockwise direction indicated by the arrow A.

[0034] When the roller 20 is driven in anticlockwise rotation, each tooth 21 meets the dry ice pieces with the larger surface, that of the face 23, and so it produces particles with a greater granulometry with respect to the case in which the roller 20 is driven in the opposite direction. In fact, when the roller 20 is rotated in the clockwise direction (arrow C), only the edge 24 essentially works on the dry ice pieces to be ground, so it produces dry ice particles with a smaller granulometry.

[0035] According to another possible embodiment, some of the teeth 21 can have a cusp 25 inclined with reference to a radial axis passing through each of them. This embodiment is schematically illustrated in Figure 6, in which some teeth 21' are inclined in the opposite direction with reference to other teeth 21", always with reference to radial axes D passing through each of the teeth 21', 21".

[0036] Various modifications can be made with reference to the exemplary embodiments here represented without go out from the scope of the present invention. For example, even a toothed roller can be used which has through holes, on condition that suitable means and/or configurations are provided to facilitate the transfer of the dry ice particles to the hopper and/or the relative rotating auger. Even a roller having the shape of a truncated cone, instead of the cylindrical one, can be used for this purpose.

Claims

1. A machine for producing and blasting dry ice particles, including at least one feeding tank in which the dry ice is loaded in the form of pieces to be ground, said feeding tank having at least one exit opening located near at least one grinding unit, and means for blasting the dry ice particles produced by said grinding unit through a delivery nozzle, characterized in that said grinding unit includes a toothed roller which is rotated near the exit opening of said feeding tank.

2. The machine according to the claim 1, wherein said feeding tank is located upper to said toothed roller with a symmetry axis substantially perpendicular to the support surface of the machine.

3. The machine according to claim 1 or 2, wherein said toothed roller rotates around to an axis substantially parallel to the support surface of the machine, and wherein the symmetry axis of said tank has an angle of incidence with the rotating axis of said toothed roller.

4. The machine according to claim 1 or 2, wherein said toothed roller rotates around to an axis substantially parallel to the support surface of the machine, and wherein the symmetry axis of said tank is offset with reference to the rotating axis of said toothed roller.

5. The machine according to the claim 1, further including at least one hopper for a temporary storage of the dry ice particles, and wherein at least one rotating auger rotates on the bottom of said hopper to transport the dry ice particles to said blasting means.

6. The machine according to the claim 1, wherein said toothed roller includes a plurality of grinding teeth protruding from the surface of said roller and having a substantially triangular cross section.

7. The machine according the claim 6, wherein at least part of said grinding teeth have a cusp inclined with reference to a radial axis which passes trough each teeth.

8. The machine according to claim 7, wherein some of said teeth have a cusp inclined in the opposite direction with reference to other of said teeth.

9. The machine according to claim 1, wherein at least one first motor is provided to rotate said toothed roller and means to control the speed and the rotating direction of said first motor.

10. The machine according to claim 1 and 5, wherein at least one second motor is provided to rotate at least said rotating auger located on the bottom of said hopper.

11. A method for producing and blasting dry ice particles, wherein said particles are obtained by grinding dry ice pieces located in a feeding tank, said feeding tank having at least one exit opening located near at least one grinding unit, and wherein the dry ice particles produced by said grinding unit are successively blasted by a delivery nozzle, characterized in that the grinding of said dry ice pieces is performed by a toothed roller which rotates near the exit opening of the feeding tank.

12. The method according the claim 11, wherein the feeding of said dry ice pieces to said toothed roller is made by gravity.

13. The method according to claim 11, wherein there are provided the temporary storage of the dry ice particles in an hopper and the subsequent transfer of said particles from said hopper to said delivery nozzle.

14. The method according to the claim 11, wherein said toothed roller includes a plurality of grinding teeth protruding from the surface of said roller and having a substantially triangular cross section.

15. The method according to the claim 14, wherein at least part of said teeth has a cusp inclined with reference to a radial axis which passes trough each teeth.

16. The method according to the claim 15, wherein some of said teeth have a cusp inclined in the opposite direction with reference to other of said teeth.

17. The method according to the claim 11, wherein the rotating speed of said toothed roller is manually regulated.

18. The method according to the claim 11, wherein the grinding of said dry ice pieces is made by rotating said toothed roller in clockwise direction.

19. The method according to the claim 11, wherein the grinding of said dry ice pieces is made by rotating said toothed roller in anticlockwise direction.

Drawing