Patent Application
20250020384
A device for adjusting and metering of dry ice granulate for a device for mixing solid particles of dry ice with a flow of gaseous medium.
The invention relates to a device for adjusting and metering of dry ice granulate for a device for mixing solid particles of dry ice with a stream of gaseous medium.
In the operation of dry ice cleaning machines using solid carbon dioxide (CO2) granulate, known as dry ice, often a reduction or a complete cut-off of the supply of particles from a container to the mixing system occur due to the tendency of the dry ice particles to clump together. This clumping can be up to the size of big dry ice clusters that form in the dry ice container of the equipment. The mixing system is herein understood to be the part of the machine where the dry ice particles are mixed with a stream of gaseous medium, typically a stream of air, after which the stream of dry ice particles is led into the blasting gun.
The clumping of dry ice particles can occur for a number of reasons such as the method of production, degradation over time, poor storage, operating conditions and so on. In the same way, conventional dry ice pellet production typically produces cylindrical particles with an axial length several times the diameter of the particle, so for example, for a pellet diameter of 3 mm, the length of the pellet is typically 12 to 15 mm. This particle shape then adversely affects the quality, or consistency, of the feeding of the mixing systems. Various systems are known in the prior art to prevent clogging of the feeding ports of the devices, or transport rollers for removing the granulate from the container.
Irregular feeding, also known as pulsation, is also a common problem with mixing systems working with dry ice granulate, which is most pronounced when the granulate consumption requirement is low. This pulsation is caused by the rotation of the mixing member and its shaped parts. These rotating mixing members contain separate chambers or pockets that are filled with granulate, from which the granulate is then transported by a stream of air. These rotating mixing members known in the prior art are disc or cylindrical in shape.
The above problems are partially solved by the device described in the published U.S. application 2019/0321942 A1, the particle blast apparatus includes a metering portion, a comminutor and a feeding portion. The metering portion and comminutor may each be configured to provide uniformity in the discharge of particles. The metering portion controls the particle feed rate, and may include a rotor, which may have V or chevron shaped pockets. The comminutor includes at least one roller which may be moved between and including a position at which the gap of the comminutor is at maximum and a position at which the gap is at minimum. The metering portion may discharge direction into the feeding portion without a comminutor being present. The comminutor may receive particles directly from a source of blast media without a metering portion being present.
The device according to the said document, in the metering part, comprises a single rotating roller which rotates in one direction relative to a wiping edge on the body of said metering part. This rotating roller has chevron, “V”, grooves, pockets, of “U” cross-section, formed along its length from each end thereof, which meet at the center of the cylinder at a peak which faces in the opposite direction to the direction of rotation of the roller.
This arrangement is intended to ensure that the granulate in the grooves moves to their axial centre, providing a more uniform distribution of granulate along the length of the roller. Said wiping edge is then intended to ensure that the granulate is not forced into the grooves. Forcing of the granulate would lead to clumping of the granulate in the grooves and could lead to retention of the granulate in these grooves and unwanted irregular and unpredictable loss of the granulate, or clumps of granulate, into the next stages of the device. The metering device then controls the amount of granulate supplied into the mixing system instead of the feeding or mixing device itself. The feeding or mixing devices can then operate continuously in a speed range that does not cause pulsation of the dry ice particle stream, wherein the amount of dry ice particles may be small which would otherwise cause said pulsation due to the low speed of the feeding element of the existing mixing device.
As mentioned above, it is not rare for clumps of dry ice to form in the dry ice container in the form of clusters which, due to their size, are unable to pass through, for example, the roller of the metering device described above. Other additional devices are then added because of the formation of such clusters, which mechanically break up such clusters. However, these additional devices then add to the complexity of the device and also to the energy consumption of the device.
The object of the present invention is to eliminate the deficiencies of the prior art.
Said object is achieved by a device according to the present invention for adjusting and metering of dry ice granulate for a device for mixing solid dry ice particles with a stream of gaseous medium, comprising a body having a granulate input section and a granulate output section, between which a rotary element is arranged for transporting the granulate from the input section to the output section. The device according to the invention is characterized in that there are at least two rotary feeding elements arranged parallel to each other in the body, where between said rotary feeding elements a shearing member is arranged. The feeding elements are driven into rotation such that to rotate against each other relative to the direction of passage of the granulate from the granulate input portion to the granulate output portion. The rotary feeding elements are formed as rotary rollers which contain recesses for transporting the granulate arranged around their circumference. These recesses are oriented in the axial direction of the feeding element and are arranged in at least two rows in succession along the length of the feeding element roller, and each of the two adjacent rows of recesses for transporting the granulate are offset with respect to each other. The shearing member is arranged between the rotary feeding members, the shearing member comprising at least one shearing edge at each roller. The position of the shearing edges with respect to the rollers is in a range below the level of a connecting line of the axes of rotation of the feeding members, including the position of the shearing edges at the level of the connecting line. The angle between the connecting line of the axes of rotation of the feeding elements and the face of the shearing member is between 0° and 45°. There is a gap between the roller and the shearing edge, the size of which is less than the smallest dimension of the granulate to be transported.
Preferably, a device for grinding of dry ice granulate is connected to the device for adjusting and metering of dry ice granulate, to the output section thereof, characterized in that a driven grinding roller connected to a torque source is arranged in the body of the device for grinding of dry ice granulate, wherein parallel to this grinding roller a rotary support body connected to a regulation for rotating this support body is arranged in the body of the device. A second grinding roller is rotatably mounted in the rotatable body, off-axis of this body, continuously connected via a transmission and a driven grinding roller to the same torque source.
The invention is further explained by means of the figures in the accompanying drawings, in which
A device for adjusting and metering of dry ice granulate for a device for mixing solid particles of dry ice with a stream of gaseous medium according to the present invention will be described in the following example of embodiment with reference to
The device 1 for adjusting and metering of dry ice granulate in the example of the embodiment shown, comprises a body 2 in which at least two rotary feeding elements 3 are arranged parallel to each other, and a shearing member 4 is arranged between said rotary feeding elements 3.
The body 2 has an input section 5 of the device 1, through which the granulate is supplied to the rotary feeding elements 3. This section 5 is on the side of the dry ice container, not shown in the figures, and preferably comprises inclined surfaces for gravitational feeding of the granulate to the rotary feeding elements 3. On the opposite side of the body 2, in this case below the rotary feeding elements 3, there is an output section 6 of the device which guides the granulate to a device for mixing dry ice particles with a gaseous medium, such as the device described in the published international application WO/2014/182253 of the same applicant.
As will be described below, the outlet portion 6 may also lead the granulate to a device 7 for adjusting a particle size of dry ice granulate. Such device 7 for adjusting a particle size of dry ice granulate will then be positioned between the device 1 for adjusting and metering of dry ice granulate and the device for mixing of dry ice particles with a gaseous medium.
The body 2 may be provided as attachable to the dry ice container, as the bottom of the dry ice container, and may alternatively also be provided as a part of the dry ice container.
The rotary feeding elements 3 are housed in the body 2 by means of their shafts 31 and bearings 8, and are driven into rotation such that to rotate against each other. The drive arrangement in the example shown comprises an electric motor 9 connected to the shaft 31 of one of the rotary feeding elements 3, and a transmission 10 formed by toothed gears arranged on the shafts 31 of the rotary feeding elements 3, such that the feeding elements 3 rotate against each other, in the direction of passage of the granulate from the input section 5 to the output section 6 of the device 1.
Particularly, as shown in
The rotary feeding elements 3 are formed as rotary rollers 32, which comprise recesses 33 arranged around their circumference for transporting dry ice granules when the feeding element 3 is rotated. These recesses 33 are oriented in the axial direction of the feeding element 3 and are arranged in at least two rows in succession along the length of the roller 32 of the feeding element 3, and each of the two adjacent rows of recesses 33 for transporting the granulate are offset relative to each other, or rotated. This arrangement resembles a set of several adjacent toothed wheels arranged tightly side by side on a shaft, where these toothed wheels are rotated relative to each other, that is their teeth and spacing are not mutually aligned. This in fact provides jagged rollers 32.
In this particular example of embodiment of the feeding elements 3 according to
The size of the recess 33, that is its width and depth, is chosen in relation to the size of the dry ice granulate to be transported, such that the selected granulate can easily fall into the recess 33 and could be transported by the recess 33 and fall freely out into the outlet section 6 of the device 1.
In general, the size, shape, number and location of the recesses 33 may be chosen in relation to the characteristics of the granulate to be transported, while must be such as to allow the transport of granulate in required volume.
A shearing member 4 is disposed between the rotary feeding elements 3. This shearing member 4 has, in this example of embodiment, the shape of a prism, where one of the sides of the prism comprises a pair of shearing edges 41. Generally, the arrangement of the shearing edges 41 is such, that each rotary feeding element 3 has at least one shearing edge 41 associated with it. Thus, at each roller 32 of the feeding element 3 there is at least one shearing edge 41.
In the example of embodiment shown, the shearing edges 41 are positioned with respect to the rollers 32 of the feeding elements 3 at the level, or may be positioned even slightly below the level of the connecting line OS of the axes of rotation of the feeding elements 3. Thus, the range of positions of the shearing edges 41 is within the range below the level of the connecting line OS of the axes of rotation of the feeding elements 3, including the position of the shearing edges 41 at the level of the connecting line OS. For the sake of clarity, the position below the connecting line OS is the position towards the output section 6 of the device 1.
The geometry of the shearing edges 41 themselves then realizes a clean shear of the pellets and allows the residual pellets to be transported through following transporting recesses 33. For this reason, the angle γ between the connecting line OS of the axes of rotation of the feeding elements 3 and the face 42 of the shearing member 4 is in the range of 0 to 45°, while this applies for both shearing edges 41.
There is a specific gap X between the roller 32 and the shearing edge 41, which affects adjustment of the granulate. Generally, a dimension of the gap X is to be smaller than the smallest dimension of the granulate to be transported, which prevents unadjusted granulate from passing freely, while in respect to working function it must not be zero.
The described geometry of the rollers 32 and shearing edges 41 is shown in detail D in
In general, the position and geometry of the shearing member 4 must be such, that by rotation of the rollers 32 of the feeding elements 3 only adjusting the pellets and loading them into the transport recesses 33 occurs. Thus, the shearing member 4 will shear off the parts of the pellets which, after being loaded into the recesses 3, protrude from the outline of the rollers 32, while gripping the pellets and pressing them against the contact walls of the rollers 32 and of the transport recesses 33 will not occur. Otherwise, undesirable sticking of the particles to the walls of the rollers 32 and recesses 33 would occur and thus would a loss of the feeding function, with a simultaneous reduction of transport capacity of the feeding elements 3.
Regarding an assembly, the precise connection of the parts of the device 1 is preferably realized with standard fasteners with use of pin connections.
The device 1 for adjusting and feeding of dry ice granulate is working as follows.
From a dry ice container, not shown, dry ice granulate is supplied, usually gravitationally, to the input section 5 of the device 1. This granulate is usually in the form of cylindrical shaped particles having an axial length several times exceeding the diameter of this particle. The feeding elements 3 are rotated, driven by the electric motor 9 in the direction against each other with respect to the direction of passage of the granulate from the input section 5 to the output section 6 of the device 1. The recesses 33 in the cylinders 32 of the feeding elements 3 are thereby filled with the granulate, which is transported by the recesses 33 around the shearing edge 41 of the shearing element 4 to the output section 6 of the device 1.
At the shearing edge 41, the granulate is adjusted, that is, portions of the granulate protruding from the recesses 33 are adjusted to a size allowing it to pass by the shearing edge 41, while preventing undesired pressing of the granulate into the recesses 33 and its sticking to the surface of the rollers 32. Granulate that has not been allowed into the recess 33 after passing around the shearing edge 41 is directed to the next incoming recesses 33. After the recess 33 has passed around the shearing edge 41, the adjusted granulate and in a batch defined by the recess 33, falls freely out into the outlet section 6 of the device 1.
In the case, clusters, or clumps of dry ice granulate are formed in the dry ice container, thanks to jagged surface of the rollers 32 of the feeding elements 3, these are crushed during their rotation, without the need for any additional or other device for breaking up the clusters of granulate, such as those used in prior art devices. Moreover, the shearing member 4, due to its position, increases the axial distance of the rollers 32, thereby gaining an increase in the working space of the rollers 32. Such breaking up of clusters of the granulate proceeds smoothly, without affecting the continuity of loading of the transport recesses 33, and thus the accuracy of the quantity of transported granulate is not affected. The device 1 such designed, along with fulfilling the main required functions of adjusting and metering of the granulate, also eliminates a need for the presence of other anti-clustering systems and also continuously fulfils the function of freeing a passage for supply of the granulate for a dry ice container.
For the sake of completeness, the shearing member 4 may be formed in various way, as static, as adjustable and fixable in a new position after the desired adjustment, or realized as a permanently rotating element. This embodiment provides the potential for further treatment of the granulate. Another function of the shearing member 4, is also a safety function, where its presence prevents foreign objects, objects larger than the shearing gap X, from being drawn into the gap between the rollers 32.
In a further example of embodiment, described below with reference to
According to this example of embodiment, the device 7 for grinding of dry ice granulate is connected to the device 1 for adjusting and metering of dry ice granulate, as described in the previous example of embodiment, to output section 6 thereof.
The device 7 for grinding of dry ice granulate, in the example of embodiment shown, comprises a body 71 in which a driven grinding roller 15 is rotatably mounted. In this example, the grinding roller 15 is driven into rotation by an electric motor 16 connected to the shaft 151 of the roller 15 via a transmission 23. The grinding roller 15 could also be connected directly to a torque source without the transmission 23, but such a solution would be less preferable in regard of a space.
Parallel to the driven grinding roller 15, a rotary support body 17 is arranged in the body 71 of the device 7, on which a second grinding roller 18 is rotatably mounted off-axis of this body 17, that is, eccentrically.
The rotary support body 17 in this example of embodiment, as shown separately in
The spacing block 20 comprises, on the side opposite to the second grinding roller 18, a shaped outer surface 201 for providing an inlet surface for the granulate between the grinding rollers 15, 18. This surface 201, during the grinding of the granulate, is located on the side of the granulate supplied from the device 1 for adjusting and metering of the granulate, thereby facilitating the access of the adjusted granulate between the grinding rollers 15, 18.
The rotary support body 17 is operated by the regulation electric motor 24, which is typically a stepper motor, connected to the shaft 171 of the support body 17 via a transmission 25. The support body 17 could also be connected directly to the regulation without the transmission 23, but such a solution would be less preferable in regard of a space.
The transmissions 23 and 25 are located on the outside of the sidewall 72 of the body 71 and are closed by a cover 26. A front view of the transmissions 23, 25 is specifically shown in
A head 27 is attached to the end of the shaft 171 of the support body 17 for determining the zero position of the support body 17. A sensor 28 of the shaft 171 position is then associated with the head 27. In the embodiment shown, the sensor 28 is mounted on the cover 26 of the transmissions 23, 25.
The second grinding roller 18 is driven into rotation by the electric motor 16 via the shaft 151 of the driven grinding roller 15 via a transmission 29. The transmission 29 is located on the outer side of the body 71 opposite the sidewall 72. A front view of the transmission 29 is specifically shown in
The transmission 29 can also be provided in another known equivalent manner, but the condition of rotation of the driven grinding roller 15 and the second grinding roller 18 against each other must be maintained, which is achieved in the example shown, by an odd number of gear wheels in the transmission 29. However, the use of gear wheels is preferable in regard of a space.
Thus, the second grinding roller 18 is also driven by the electric motor 16, the torque of which is transmitted by the shaft 151 of the driven grinding roller 15 via the transmission 29 to the shaft 181 of the second grinding roller 18. The second grinding roller 18 is thus continuously driven into rotation in any position of the rotary support body 17.
The gear ratios of the gear wheels 291, 292, 293, 294, 295 of the transmission 29 can be selected to achieve a suitable circumferential speed of the second grinding roller 18. The circumferential speeds of the driven grinding roller 15 and the second grinding roller 18 can be the same or different. However, it is preferable for the grinding process if the second grinding roller 18 has a higher circumferential speed than the driven grinding roller 15.
The transmission 29 is closed by the housing 300, which also serves together with the body 71 of the device 7, for mounting of the separate shafts 296, 297 as described above. On the outer side of this cover 300, brackets 301 for the drives of the device 7 are preferably attached thereto, that is in this example the electric motor 16 and the regulation electric motor 24. The electric motors 16, 24 are then arranged alongside the body 71 of the device 7, which is preferable in regard of a space.
In regard of a design, the precise connection of the parts of the device 7 is preferably realized by standard fasteners with use of pin connections.
The device 7 for grinding of dry ice granulate working in following manner, whereby the working phases of the device 7 are shown in
In the phase without grinding of the granulate, the rotary support body 17 is located, that is, it is rotated, in a position where the gap between the grinding rollers 15, 18 is greater than the largest dimension of the granulate used. At this phase, no change in the size of the granulate occurs and the granulate falls gravitationally through the gap between the rollers 15, 18. This gravitational fall is enhanced by the rotation of the rollers 15, 18, the surface of which partially forms a passage aperture for the granulate.
In the granulate grinding phase, the rotary support body 17 is located, that is, it is rotated, in a position where the gap between the grinding rollers 15, 18 is smaller than the largest dimension of the granulate used. At the moment of contact between the granulate and the surface of the rotating rollers 15, 18, the size of the granulate changes, while this gap is continuously variable by means of the rotation of the support body 17, regulated by the regulation electric motor 24, that is, the stepper motor. The second grinding roller 18 is continuously driven into rotation. The extreme position of the second phase is the position of the grinding rollers 15, 18 when their axial distance is smallest and they are at the horizontal, or shortest, connecting line of their axes of rotation. This position is referred to as the zero position and the distance of the grinding rollers 15, 18 determined by the design is the smallest achievable. In the embodiment shown, a change of a fraction size below this value is not possible. This zero position however, can alternatively be set to a larger distance of the rollers 15, 18, at which grinding of the granulate could still occur, while the size of the ground granulate would be considered the smallest possible for given device.
| Number | Date | Country | Kind |
|---|---|---|---|
| PP 50060-2021 | Nov 2021 | SK | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SK2022/050010 | 11/23/2022 | WO |
