The present invention relates to forming solid particles of a cryogenic material, and is particularly directed to a method and apparatus for forming carbon dioxide particles from liquid carbon dioxide.
Solid cryogenic material, such as solid carbon dioxide, has many uses. Solid carbon dioxide has long been used to maintain items, such as food or beverages at desirable cool temperatures. In certain food service applications, solid blocks, or cakes, of carbon dioxide have been used, disposed within an given volume adjacent the items sought to be maintained at or below a desired temperature. It is known to cut form carbon dioxide blocks of the desired size or to cut them from larger blocks. It is also known to form the desired sized blocks by reforming carbon dioxide particles into blocks.
Solid carbon dioxide particles have also been used in carbon dioxide particle blasting systems for several decades. Typically, carbon dioxide particles, whether granular or pellets, also known as blast media, are fed into a transport gas flow and are transported as entrained particles to a blast nozzle, from which the particles and transport gas exit, being directed toward a workpiece or other target.
Solid cryogenic particles, in particular but not limited to carbon dioxide particles, may be formed by many ways. Such solid particles may be formed by transforming liquid cryogenic material into small solid particles (“snow”) and compressing them into larger parts (“pellets”). For example, carbon dioxide pellets may be formed by producing carbon dioxide snow, such as by passing liquid carbon dioxide through a phase change nozzle such as is described in U.S. Pat. No. 5,018,667, and forming that snow into carbon dioxide pellets by forcing the snow through die openings, such as is described in U.S. Pat. Nos. 5,301,509 and 5,473,903. The gas phase is a byproduct of this process that accompanies the formation of the solid phase as snow. U.S. Pat. Nos. 5,018,667, 5,301,509 and 5,473,903, all of which are incorporated herein by reference.
As described in the '509 and '903 patents, with reference to FIGS. 1 and 2 thereof, a pelletizer may be used to change the phase of carbon dioxide from liquid to the solid phase as snow by passing the liquid carbon dioxide through a phase change device, such as a phase change nozzle, and directing the snow into the internal chamber of the barrel of the pelletizer. The flow rate of carbon dioxide into the internal chamber of the barrel is affected not only by the pressure of the carbon dioxide upstream of the phase change nozzle, but also by the internal pressure of the internal chamber. Downstream of the phase change nozzle, the gaseous portion of the carbon dioxide flow directly affects the internal pressure of the internal chamber. To reduce the internal chamber pressure, the gaseous carbon dioxide is vented out of the internal chamber, to reduce the backpressure resulting from the gaseous carbon dioxide flow. Vents are provided in the barrel adjacent the phase change nozzle to vent the gaseous carbon dioxide. Without the vents, the flow of solid and gas carbon dioxide into the internal chamber would be constricted, reducing the efficiency of the process.
A collector may located adjacent and surrounding the vents to collect the off gassing of the carbon dioxide from the vents. The collector includes screens located adjacent the vents allowing the gas to vent while retaining the snow within the barrel internal chamber. The screens are disposed at the periphery of the barrel, aligned with the vents. This location allows snow to accumulate in the “wells” created by the thickness of the barrel wall and the vent screen, the snow being pushed into the wells by the travel of the piston. The accumulated snow impedes the out flowing of the gas.
As can be seen in FIGS. 1 and 2 of the '509 and '903 patents, the barrel is retained between a plate and an end cap by elongated fastening rods. The rods, four in number, may present problems. Uneven tension and misalignment may negatively affect concentricity along the length of the barrel, which can present problems of undesirable contact and wear between the wall forming the barrel internal chamber and the piston. The locations of the rods about the exterior of the barrel affects the size and shape of the collector, and therefore affects the location and number of vents, since the rods interfere with a collector reaching vents disposed under the rods.
There is a need for a method and apparatus, and therefore are objects of the present invention, that provide improved venting of the gaseous faction of the flow downstream of the phase change nozzle from the internal chamber, that provide reduced pressure within the internal chamber of the barrel, that opens up the peripheral access to the barrel, that provide vents configured to remain free from substantial accumulation of snow, and that reduce the potential to cause misalignment between the barrel internal chamber and the piston and wear resulting from such misalignment.
Although the present invention will be described herein in connection with carbon dioxide, it will be understood that the present invention is not limited in use or application to carbon dioxide.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.
Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.
In the following description, like reference characters designate like or corresponding parts throughout the several views. Also, in the following description, it is to be understood that terms such as front, back, inside, outside, and the like are words of convenience and are not to be construed as limiting terms. Terminology used in this patent is not meant to be limiting insofar as devices described herein, or portions thereof, may be attached or utilized in other orientations. Referring in more detail to the drawings, an embodiment constructed according to the teachings of the present invention is described.
Referring to
Referring also to
Pelletizer assembly 2 may be secured to hydraulic cylinder assembly 4 by any suitable means. In the embodiment depicted, end block 8 is secured to hydraulic cylinder 4 by a plurality of spaced apart fasteners 26. In this embodiment, fasteners 26 are multiple jackbolt tensioners in which include a plurality of jackbolts 26a are carried by a single threaded shaft and are tightened individually to tighten the single threaded shaft.
Referring to
Piston 30 includes two spaced apart grooves 40a and 40b in which respective wear bands 42a and 42b are disposed. Wear bands 42a and 42b may be made of any suitable material, such as nylon. Formed in the bottom of grooves 40a and 40b are O-ring grooves 44a, b, c and d in which O-rings 46a and 46b are disposed. The outer diameter of piston 30 is smaller than the inner diameter of barrel 6. Wear bands 42a and 42b, supported by O-rings 46a and 46b, allow piston 30 to float, minimizing contact between piston 30 and barrel 6 and allowing less precise alignment. Ends 30a and 30b of piston 30 are tapered, further reducing the potential for direct contact with barrel 6. Thus, as rod 28 is extended, the precision of the alignment required is less with this configuration.
Referring to
Collectors 24a and 24b may be retained in place by any suitable configuration. In the embodiment depicted, inner facing panels 24a′ and 24b′ of collectors 24a and 24b are connected to each other in a spaced apart arrangement by a plurality of fasteners 48, engaging the outer periphery of barrel 6. Access to fasteners 48 may be provided by removable outer panels 24a″ and 24b″. Collectors 24a and 24b may also include tabs (24′″ in
Collectors 24a and 24b include respective seal grooves 18a and 18b about their respective edges which are disposed adjacent the periphery of barrel 6. Respective seals 19a and 19b are disposed in seal grooves 18a and 18b. Any suitable material and shape may be used. In the embodiment depicted, seals 19a and 19b are nylon O-ring cord.
Referring to
Referring to
In the embodiment depicted, there are sixteen spaced apart countersunk bores 10a that align with threaded bores 6d (see
Adaptor 10 provides the mount for the die through which solid snow is extruded. In the embodiment depicted, die 12 is a solid plate with openings formed therethrough. Any suitable configuration of die 12 may be used, such including the use of a backing plate. Die 12, as depicted, includes sixteen spaced apart countersunk bores 12, which align with threaded bores 10b in adaptor 10. Fasteners (not shown) are used to secure die 12 to adaptor 10. With this configuration, potential damage resulting from changing dies 12 occurs only to adaptor 10, saving the more expensive barrel 6 from such damage. In the event that adaptor 10 becomes worn or damage beyond use, a new adaptor may be installed to the distal end of barrel 6.
To create pellets, pressurized liquid, such as liquid carbon dioxide, is forced through phase change nozzle 54 (see
As can be seen in
The foregoing description of an embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Although only a limited number of embodiments of the invention is explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the preceding description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiment, specific terminology was used for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. It is intended that the scope of the invention be defined by the claims submitted herewith.
The present invention claims priority from and incorporates by reference U.S. Provisional Patent Application, Ser. No. 61/487,837, filed on May 19, 2011, titled Method And Apparatus For Forming Carbon Dioxide Particles.
Number | Date | Country | |
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61487837 | May 2011 | US |