CO2jet spray nozzles with multiple orifices

[0002] This is a continuation-in-part of application Ser. No. 08/804,450, filed Feb. 21, 1997, now abandoned, which was a continuation-in-part of application Ser. No. 08/356,606, filed Dec. 15, 1994, also abandoned.

[0003] 1. Field of the Invention

[0004] The present invention relates to CO₂jet spray nozzles, and more particularly, to CO₂jet spray nozzles having multiple orifices.

[0005] 2. Description of Related Art

[0006] The related prior art of CO₂jet spray nozzles is believed to involve the use of a variable orifice. Despite much literature on the subject, this aspect has not been well explained or documented. Exact geometries of the nozzles vary and can be considered proprietary by each manufacturer. Fixed orifice nozzles are disclosed in U.S. Pat. No. 4,806,171, issued to Whitlock et al., and U.S. Pat. No. 4,962,891, issued to Layden. In each case a set of two (consecutive) orifices is given as essential to good jet spray (snow) production. In both cases the source of CO₂is in gaseous form, and in that case two consecutive orifices appear to be needed. However, expanding CO₂gas is inefficient and does not have the aggressiveness of CO₂jet spray from liquid. In using liquid CO₂, two consecutive orifices are detrimental to snow production since the second orifice frequently clogs and causes sputtering of the CO₂jet spray.

[0007] Therefore, it is an objective of the present invention to provide for improved CO₂jet spray nozzles that overcome the problems of conventional CO₂jet spray nozzles.

[0008] The production of a CO₂jet spray requires an orifice to generate snow, and a nozzle to shape, control, and direct snow to a surface. In order to meet the above and other objectives, the present invention provides for nozzles for use in producing CO₂jet spray, these nozzles having multiple orifices. In the present invention, a pattern of orifices forms a critical orifice, which is an integral part of the nozzle. By fabricating different nozzles in which orifice size, orifice geometry (round, oval, or elongated slit), total orifice area, nozzle diameter and nozzle length is varied within a well-defined matrix, any desired intensity of CO₂jet spray may be obtained. By varying the arrangement of the orifices, nozzle geometry, and nozzle length, different spray patterns may be provided.

[0009] More particularly, the CO₂jet spray nozzle of the present invention comprises a body, an elongated nozzle tube extending from the body, and an orifice disk disposed in the nozzle tube adjacent the body that has a plurality of orifices disposed therein. The orifices are formed by any suitable means such as laser drilling through the orifice disk, or by means of electron discharge machining (EDM), for example. The body has an input aperture that mates with a source of CO₂and an elongated tube extending toward an output end. The body has a first axial hole of a predetermined depth disposed along an axis of the body adjacent the output end, and a centrally located second axial hole having a diameter that may be different than the diameter of the first axial hole disposed through the remaining length of the body. The orifice disk is disposed at the bottom of the first axial hole and has a circular input aperture that couples CO₂to the plurality of orifices. The elongated nozzle tube is disposed in the first axial hole so that it abuts the orifice disk and protrudes a predetermined length in front of the body. The orifice disk may have a circular pattern of orifices that provide a circular CO₂spray pattern. The orifice disk and nozzle tube are typically welded together to prevent leakage.

[0010] The present invention also contemplates a linear jet spray nozzle that contains multiple orifices each with different dimensions or one that uses a changing density of orifices, such that it starts out on one side of the nozzle with a large number of orifices per linear inch, and gradually changes to a relatively small number of orifices per inch on the opposite side.

[0011] The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:

[0012] FIG. 1 illustrates a cross-sectional view of a CO₂jet spray nozzle having multiple orifices in accordance with the principles of the present invention;

[0013] FIG. 2ais a cross-sectional view of the orifice disk employed in the CO₂jet spray nozzle of FIG. 1;

[0014] FIGS. 2b-2dshow several orifice patterns that may be employed in the CO₂jet spray nozzle of FIG. 1;

[0015] FIGS. 3aand 3bshow representations of linear nozzles having multiple orifices each with different dimensions;

[0016] FIG. 3cshows a representation of a linear nozzle having a changing density of orifices;

[0017] FIG. 4 shows an enlarged cross-sectional top view of a portion of a linear jet spray nozzle corresponding to that shown in FIG. 3a;and

[0018] FIG. 5 is a cross-sectional side view of the nozzle of FIG. 4 taken along the line 5—5.

[0019] Referring to the drawings, FIG. 1 illustrates a cross-sectional view of a CO₂jet spray nozzle 10 having multiple orifices 21, or a multiple orifice nozzle 10, in accordance with the principles of the present invention. The multiple orifice nozzle 10 is comprised of a body 12 that comprises a metal gasket seal fitting 12 having an input aperture 17 that mates with a source 30 of CO₂. The metal gasket seal fitting 12 is commercially available from Cajon, for example, part number SS-4-VCR-3, for example. The body 12 or fitting 12 has an elongated tube 13 extending toward an output end 14 of the nozzle 10. A first axial hole 15 is formed to a predetermined depth along the axis of the body 12 adjacent the output end 14 of the nozzle. A centrally located second axial hole 16 having a diameter that is smaller than the diameter of the first axial hole 15 is disposed through the remaining length of the body 12. Thus the body 12 has an axially disposed hole formed therethrough that has a smaller diameter adjacent an input end of the nozzle 10 and a larger diameter adjacent the output end 14 of the nozzle 10.

[0020] An orifice disk 20 or orifice button 20 is disposed adjacent to the bottom of the first axial hole 15 and has a plurality of small orifices 21 therein. The orifice disk 20 has a circular input aperture 23 disposed at an input end thereof. A series of round orifices 21, for example, may be laser drilled through the central portion of the orifice disk 20 and within the diameter of the input aperture 23 in a predetermined pattern. Alternatively, the orifices 21 may be formed by means of electron discharge machining (EDM), for example. An elongated nozzle tube 25 having an outer diameter slightly less that the internal diameter of the first axial hole 15 is disposed in the first axial hole 15 so that it abuts the orifice disk 20 and is welded in place along the length of the first axial hole 15. The nozzle tube 25 protrudes about two-thirds of its length in front of the body 12. The nozzle tube 25 has an opening 25adisposed therethrough that provides an opening between the plurality of small orifices 21 of the orifice disk 20 and the output end 14 of the nozzle 10 through which carbon dioxide is sprayed.

[0021] The orifice disk 20 and nozzle tube 25 are fabricated in two parts and then welded together to fix the nozzle geometry and to prevent leakage. The present multiple orifice nozzle 10 disclosed herein was fabricated to clean cutting tools prior to nitriding. The pattern of orifices 21 forms a critical orifice, which is an integral part of the nozzle 10. By fabricating different nozzles 10 that comprise different orifice disks 20 in which orifice size, orifice geometry (round, oval, or elongated slit), total orifice area, nozzle diameter and nozzle length is varied within a well defined matrix, any intensity of CO₂jet spray may be obtained. By varying the arrangement of the orifices 21, nozzle geometry, and nozzle length, different spray patterns may be provided.

[0022] FIGS. 2a-2dillustrate exemplary embodiments of the orifice disk 20. FIG. 2ashows a cross-sectional view of the orifice disk 20. Several typical orifice patterns that may be formed in the orifice disk 20 are shown in FIGS. 2b-2d.FIG. 2bshows a disk 20 having three orifices 21. The orifice 21 may have a 0.003 inch diameter, a 0.005 inch diameter, or a 0.008 inch diameter, for example. FIG. 2cshows a disk 20 having six orifices 21 each having a 0.003 inch, a 0.005 inch, or a 0.008 inch diameter. FIG. 2dshows a disk 20 having eight orifices 21 each having a 0.003 inch, a 0.005 inch, or a 0.008 inch diameter. FIG. 2dshows the disk 20 with eight orifices 21 that was used in a specific embodiment of the nozzle 10 for which the present invention was conceived.

[0023] Thus, the orifice disks 20 illustrated by FIGS. 2a-2drepresent nine different orifice disks 20 that were fabricated, having orifices 21 of 0.003 inch, 0.005 inch and 0.008 inch diameters. Although a circular jet spray pattern is normally not generated using an orifice disk 20 that contains several holes with different diameters, it is to be understood that different spray patterns may readily be produced by appropriately selecting orifices 21 of different diameters and using them in one orifice disk 20.

[0024] By way of example, to provide a circular spray pattern, a circular pattern of orifices 21 is used. With regard to the application for which the present invention was developed, a fine CO₂snow spray was desired, and therefore 0.003 inch diameter orifices 21 were used. The spray distance required a total orifice area of 6×10⁻⁵square inches, and therefore 8 orifices 21 were required. A footprint of 0.125 inches was considered optimum and when used with multiple orifice nozzle 10 having a 0.125 inch internal diameter for the first axial hole 15, a circular pattern of 8 holes were drilled around a 0.06 inch diameter circle. Finally, tight control of the CO₂spray pattern was achieved by separating the orifice disk 20 and the exit of the nozzle 10 by a distance of 1.5 inches. The orifice density of the above-described round or circular jet spray nozzle 10 typically varies from 1000 orifices per square inch (3 orifices 21 in a 0.0625″ diameter) to 2600 per square inch (8 orifices 21 in a 0.0625″ diameter).

[0025] The above described multiple orifice nozzle 10 was fabricated and tested and it was determined that it cleaned as well as a variable orifice nozzle operated at an equivalent setting. During extensive tests, the above-described multiple orifice nozzle 10 was able to clean fixtures to zero particles per item in a robotic system.

[0026] The present invention also contemplates a linear jet spray nozzle 10 that contains multiple orifices 21 each with different dimensions. FIG. 3ashows part of a end view of a representation of this type of linear nozzle 10. Another design for the linear nozzle 10 uses a changing density of orifice disks 20 and nozzle tubes 25, examples of which are illustrated in FIGS. 3band 3c.FIG. 3bshows part of an end view of a nozzle 10 having a single row 26 of orifice disks 20 and nozzle tubes 25, while FIG. 3cshows part of an end view of a nozzle 10 having a plurality of rows 26 of orifice disks 20 and nozzle tubes 25. The nozzles 10 of FIGS. 3band 3cstart out on one side with 100 orifice disks 20 and nozzle tubes 25 per (linear) inch, for example, and gradually change to about 25 orifice disks 20 and nozzle tubes 25 per inch, for example, on the opposite side of the nozzle 10.

[0027] FIG. 4 shows an enlarged cross-sectional top view of a portion of a linear jet spray nozzle 10 corresponding to that shown in FIG. 3a,and FIG. 5 is a cross-sectional side view of the nozzle 10 of FIG. 4. The nozzle 10 has a manifold 28 at its rear end that is coupled to the source 30 of CO₂by way of an inlet 17, which may be a common gas fitting, for example. The manifold 28 is sealed at both ends by means of welds 29, for example. The manifold 28 has sets of orifices 21 drilled in its front end that are aligned with a corresponding plurality of openings 25aformed in a linear nozzle tube 25. In this embodiment, each of the openings 25aare laser drilled through a block of metal to form the linear nozzle tube 15. The manifold 28 is pressed into a groove 25bformed at the rear end of the linear nozzle tube 25. Carbon dioxide is supplied by way of the inlet 17 and manifold 28 to each of the orifices 21 which in turn produce different spray patterns that are a function of the diameters of the respective openings 25ain the linear nozzle tube 25. This type of nozzle 10, as well as the other linear jet spray nozzles 10 shown in FIGS. 3band 3c,are able to generate CO₂spray patterns that are nonparallel to a surface that is to be cleaned, as well a provide variable force cleaning, such as to clean articles having grooves and flat surfaces, for example. Of course, it should be clear that the orifices could be all of the same size and equally spaced. The variations of FIGS. 3a-3care simply to show that that is not necessarily the case.

[0028] The present invention improves upon single orifice nozzles that generate CO₂snow. The first advantage of using a plurality of small orifices 21 is the ability to generate a smaller snow flake size while maintaining an output jet spray pressure required to provide precision cleaning. The second advantage is the ability to increase the output pressure far beyond the capacity of a nozzle that employs a single orifice. By laser beam drilling or electron discharge machining the plurality of orifices 21, more advantages are provided. The ability to fine-tune the nozzle 10 to provide certain operating parameters is provided by using a focused laser beam or electron discharge machining to increase the hole diameter by a fraction of a one thousandth of an inch, for example. Furthermore, a single orifice 21 is as easily drilled as two or more orifices 21 using the laser beam or EDM, thus providing an economic advantage with respect to fabrication of the nozzle 10. The orifice pattern need not comprise single-size orifices 21, and by varying the sizes of the orifices 21 within the nozzle 10, distribution of the snow flakes can be favorably changed to more desirable parameters. Finally, a multitude of spray patterns may be generated using the present invention including a simple point spray, a fan spray, axial or radial sprays, or other patterns conforming to complex geometric spray patterns depending upon the particular orifice disk 20 that is selected.

[0029] Thus there has been described new CO₂jet spray nozzles having multiple orifices. It is to be understood that the above-described embodiments are merely illustrative of some of the many specific embodiments that represent applications of the principles of the present invention. Clearly, numerous and other arrangements can be readily devised by those skilled in the art without departing from the scope of the invention.

[0030] For example, as explained above, the shape and distribution of the orifices may vary. It is not the shape and distribution of the orifices which results in the desired pressure drop, as much as it is their very small size. In referring to their size, the term “maximum” diameter is used, when intended to cover the situation where the orifices are not necessarily circular. The tiny orifice size results in the pressure drop which creates the desired snow quality. Relatively large orifice sizes could not be used effectively to produce CO₂snow, since the orifices would be too large to create the required pressure drop and tiny droplets. Large orifices may be used to break a fluid flow into individual streams, as in a water shower, if the pressure drop across the orifice is not too large. Small orifices as in the present invention generate a significant pressure drop and an aerosol with tiny droplets. Immediately past the orifice, the unique thermodynamic properties of carbon dioxide allow the tiny droplets to freeze into small snow particles. While liquid CO₂may enter the orifices, the tremendous pressure drop at the exit side of the orifices simply does not allow liquid CO₂to exist. The expansion of liquid CO₂causes a rapid rate of cooling, which generates solid CO₂and gaseous CO₂. This is quite different from what would happen with the much larger orifice sizes.

[0031] It should also be understood that several nozzles of the FIG. 1 type could be arranged together in a row or any other desired pattern. They could be mounted separately, or welded or otherwise secured to each other. As an alternative to this, however, it is generally more efficient to produce an orifice plate such as shown in FIG. 4, i.e. one plate with multiple.