Plastic Tube Screen Fills and Fabrication Thereof

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

Not Applicable.

BACKGROUND OF THE INVENTION

1. Filed of the Invention

The present invention relates to fill media for use in evaporative water cooling and air refreshing apparatuses. More precisely, the present invention relates to the screen type plastic tube fills, being able to be used in evaporative cooling apparatus such as open loop cooling towers, evaporative chiller or cooler, and in airborne fumes removal apparatus like ammonia gas removal apparatus used in livestock facilities, which are fabricated with plastic tubes.

2. Description of the Related Art

The fill media used in an evaporative water cooling and air cooling apparatuses like cooling tower, evaporative chiller or air cooler, and flue gas removal apparatuses are string screen fills (SSF), plastic-rod-screen-fills (PRSF) which are recently applied to U.S. patents (U.S. patent application Ser. Nos. 13/053,382 and 13/888,327), and honeycomb style commercial fabric cooling pad. The SSF and PRSF were invented by the present inventor and the present invention directly relates to the SSF and PRSF, since the present invention is invented to exclude their disadvantages of fabrication. The SSF is in thin plate type and made by winding one long string over a rectangular aluminum frame of the SSF and the PRSF is fabricated using solid plastic rods. The former has disadvantages such as high fabrication cost and difficulty to provide mass production within a relatively short time because of using two steps of manufacturing lines. The later was invented to reduce the former's disadvantages, but still it has a weakness in the reduction of manufacturing cost. The fabrication methods of the SSF and PRSF are described in detail in the previous patents of the present inventor (U.S. patent application Ser. Nos. 13/053,382 and 13/888,327). As the PRSF employs solid rods, the high manufacturing cost cannot be avoided for fabrication of large PRSFs fabricated using large solid rod, whose solid rod needs a large amount of plastic materials, compared with tube. To eliminate such a problem to cause unexpected high manufacturing cost of plastic screen fill media, the plastic solid rods used in the PRSF must be replaced with plastic tubes. Namely, a plastic-tube-screen-fill (PTSF) must be fabricated. For the fabrication of small size rod or tube fill media, the PRSF fabrication is preferred, because the one step fabrication cost of PRSF is cheaper than three step fabrication cost of the PTSF as described in the section of Detailed Description of Preferred Embodiment. Hence, there is a size criterion of rod for the fabrication cost of PRSF to be higher than that of PTSF, considering their costs of required materials and fabrication costs due to fabrication method. For the fabrication of larger size rod fill media than the size criterion of rod, the PTSF fabrication method is employed to minimize the fabrication cost of large size fill media.

The PRSF is fabricated by one step casting of molten plastics into a plastic-rod-screen-fill molder, which has a hollowed cavity of the PRSF in one structure, using plastic injection molding machine. Such one step injection molding method is possible for fabrication of PRSF using plastic solid rods, as solid rods can be molded using the injection molding machine. However, the one step injection molding method is not applicable to the fabrication of PTSF, because the tube cannot be molded using the injection molding machine. Therefore, the plastic tubes must be inserted into the tube holders of the tube holding frame of PTSF, after the tube holding frame and tubes are separately fabricated. To achieve such an aim of fabrication of PTSF using plastic tubes, the fabrication method of PTSF is invented in the present invention.

The purpose of the present invention is a fabrication of the PTSF being able to eliminate a problem to cause the high manufacturing cost of PRSF. Another purpose of the present invention is a supplying of new cooling fill media for replacement of current commercial evaporative cooling media.

SUMMARY OF THE INVENTION

The plastic-tube-screen-fill, PTSF, of the present invention consists of top and bottom perforated frames, tubes holding frames, and tubes (spiral corrugated tubes and plain tubes), which are assembled into one structure in the shape of rectangular plate with tubes suspending from between the top and bottom frames and parallel to the length of the rectangular plate as shown in FIG. 1. The PTSF is used for fabrication of a rectangular column pack, PTSFs pack, shown in FIG. 2, whose fabrication method and operational function are same with those of PRSFs pack invented by the present inventor, but the fabrication method of a single unit of PTSF is different. See the U.S. patent application Ser. No. 13/888,327 for the description of the fabrication method and operational functions of the PRSFs pack. Only fabrication of PTSF is described in the present invention.

The PTSF of the present invention shown in FIG. 1 is the single unit of PTSF which looks like a string screen and a configuration of PTSF is illustrated in FIGS. 3-1, 3-2, and 3-3. FIG. 3-1 illustrates left and right side partial schematic views of cross section I-I of PTSF as shown in FIG. 1, FIG. 3-2 shows the schematic view of cross section II-II of PTSF shown in FIG. 1, and FIG. 3-3 illustrates the left and right side partial schematic top view of top and bottom frames of PTSF. Hence, the PTSF is fabricated by assembling five pieces, top and bottom frames, top and bottom tube holding frames, and tubes. The PRSF comprises of three parts, top and bottom frames and solid rods suspending from between them, but they are made in one piece instead of assembling five pieces used to fabricate PTSF. As it is in one structure with solid rods, the PRSF is molded by casting molten plastics into a PRSF fabrication molder using an injection molding machine. However, the PTSF of the present invention is made with tubes instead of solid rods and the holes in the perforated frame are perfect holes, so that one step injection molding method being used to fabricate PRSF is not applicable to the fabricating of PTSF. Therefore, the top and bottom perforated frames, top and bottom tube holding frame, and tubes of PTSF are separately fabricated and then assembled into one structure.

The top and bottom perforated frames have same configuration as shown in FIGS. 4-1, 4-2, 4-3, and 4-4. Hence, only one perforated frame is fabricated by using the injection molding machine and then used as the top and bottom perforated frame. To meet this condition, as shown in FIG. 3-1, the position of circular holes on the frame are differently arranged in the left and right side of PTSF in order to use the perforated frame in two ways. Namely, intervals between adjacent circular holes are same, but the first circular hole from the left edge of frame is located at the half distance of a distance between the right edge and the first circular hole on the right side of frame. Such arrangement of the circular holes on the frame is helpful to provide a staggered perforated plate attaching one PTSF to the other PTSF horizontally rotated by 180 degree. See U.S. patent application Ser. No. 13/888,327 for the detailed description of the rotational attachment method. Next, the fabrication of the tube holding frame is described.

The configurations of the top and bottom tube holding frames are same as shown in FIGS. 5-1, 5-2, and 5-3, and also one tube holding frame is fabricated as shown in FIG. 5-1 and used as top and bottom tube holding frame. Tube holding frame consists of long male push-fit band connector and small tube holders, which are in one structure. Several tube holders are attached on the male push-fit band connector and the tube holders are apart from each other by maintaining in same interval between adjacent tube holders as shown in FIG. 5-3. The tube holders on the left and right side of tube holding frame are located in same way as the perforated holes of perforated frame are positioned. The tube holder is comprised of solid rod as an upper part and male push-fit tube connector as a lower part of tube holder as shown in FIGS. 5-1 and 5-2. As shown in FIGS. 5-1 and 5-2, the solid rod is formed in a cylindrical shape to be inserted into a cup-shaped circular hole on the perforated frame to create a ring hole shown in FIG. 3-3. The male push-fit tube connector is formed like a round attachment tag attached to the underside of the solid rod of tube holder as shown in FIGS. 5-1 and 5-2. The male push-fit band connector is long as same as length of the tubes holding frame and inserted into the female push-fit band connector on the underside of perforated frame. The male push-fit band connector is located passing through the lower partial vertical centerlines of tube holders as shown in FIGS. 5-1, 5-2, and 5-3. And also the female push-fit band connector is positioned passing through the lower partial vertical centerlines of the cup shaped circular holes on the perforated frame as shown in FIGS. 4-3 and 4-4.

The tubes used in the present invention are a plain tube with smooth tube surface and spiral corrugated tube with corrugated surface of spiral wavy surface. The spiral corrugated tube is illustrated in FIG. 6. The spiral corrugated surface forms waves repeating bumps and grooves whose flute directions are slanted to the longitudinal length of the tube. The slant angle, 30 degree, of the corrugated flute is preferred in the present invention. Such perforated profile of tube surface offers stronger tube in any gauge thickness and large surface area of contacting water and air, and spiral corrugated surface increases the contacting time of water and air due to longer flutes for water to pass. Hence, the spiral corrugated tube is preferred in the present invention. Providing such essential advantages, the corrugated tubes are employed to increase a contacting time of air and water and their contacting area on the surface of tube, and to strengthen the tubes using thinner PVC film for saving of raw PVC material. However, there is a slant angle of the flutes to provide an optimum condition of water to flow down through the grooves of corrugated tube. The smaller slant angle provides a smaller length of the corrugated groove, while larger slant angle provides a longer length of groove. But conversely, the larger slant angle allows water to jump over the corrugated bumps instead of flowing down along the grooves. The corrugated grooves must be deep enough for water to flow down along the corrugated grooves, but if too deep, water flows over the grooves, because the peak of corrugated bumps are close each other. And also if the grooves are shallow, the water flows over the corrugated grooves and the surface area is not significantly different from that of plain tube. Hence, the corrugated grooves on the surface of corrugated tube require optimum slant angle and depth of groove, which are described in the sections of <Fabrication of Spiral Corrugated Lines on Surface of Tube> and Detailed Description of the Preferred Embodiment. See the reference of www.corrugatedmetal.com for more information of the corrugated profile and terminology of corrugated surface.

The fabrication of PTSF is accomplished by assembling the perforated frames, tubes holding frames, and spiral corrugated tubes. Their assembly is performed by following an assembly procedure, STEP 1 through 3 as shown in FIG. 7. In STEP 1, two perforated tube holder frames are fabricated by assembling perforated frame and tube holding frame. In STEP 2, one of the perforated tube holder frames is jointed with one edge of the corrugated tube and the other perforated tube holder frame assembled with other edge of the tube as shown in a final STEP 3. Through the assembly procedure of STEP 1 to 3, the PSTF shown in FIGS. 3-1, 3-2, and 3-3 is fabricated.

To fabricate PTSF, the perforated frames, tube holding frames, and spiral corrugated tubes are necessary. The perforated frames and tube holding frames are made using the injection molding processes, while the spiral corrugated tubes are fabricated employing an extrusion blow molding process. The fabrication of perforated frames needs upper and lower mold halves. The lower mold halve of perforated frame fabrication molder is a molder fabricating the lower part of the perforated frame of PTSF, which is shown in FIGS. 8-3 and 8-4, and the upper molder for fabricating the upper part of perforated frame is shown in FIGS. 8-5 and 8-6. The upper and lower mold halves are designed to be overlapped and to easily remove the complete perforated frame out of perforated frame fabrication molder. On the lower mold halve, the perforated frame, male attachments, and female attachments are carved as shown in FIGS. 8-3 and 8-4. The light parts of lower mold halve are the carved parts of perforated frame and male attachments. The dark parts of the lower mold halve are female attachments and a body of the lower mold halve. On the upper mold halve, the upper part of perforated frame is carved to create cup-shaped humps fabricating cup-shaped cylindrical holes in the perforated frame to be located on the right position as shown in FIG. 3-1. The light parts of the upper mold halve are the caved part of the frame and the dark parts are the cup-shaped humps and the body of upper mold halve. Joining together of the upper and lower mold halves becomes the perforated frame fabrication molder and creates a cavity of the perforated frame in the molder as shown in FIG. 8-1. The light parts created in the molder are the cavity of the perforated frame.

The upper and lower parts of the tube holding frame fabrication molder are same and so a half part of the tube holding frame is carved on each of upper and lower mold halve as shown in FIG. 9-3. The white part in the upper or lower mold halve shown in FIG. 9-3 is the carved half part of tube holding frame. Joining the upper and lower mold halves together, the cavity of tube holding frame is created in the tube holding frame fabrication molder as shown in FIG. 9-1. The white part in the tube holding frame fabrication molder shown in FIG. 9-1 is the cavity of tube holding frame and FIG. 9-2 shows the cross section view of the cross section VII-VII shown in FIG. 9-1.

The wall thickness of the spiral corrugated tube is as thin as the current PVC cooling media is, which is in the range of 10 to 23 mils (0.15 to 0.345 mm, average=0.245 mm) Thus, in the present invention, the thickness of the spiral corrugated tube used is 0.25 mm. Such thin tube is fabricated by employing the extrusion blow molding process. Application of the extrusion blow molding process to the fabrication of spiral corrugated tubes of the present invention requires a split mold made of two mold halves of spiral corrugated tube as shown in FIGS. 10-1 and 10-2. Two mold halves, left and right mold halves, are same in molding configuration and so they are carved in same configuration. One mold halve is illustrated in FIG. 10-1, which is a schematic picture of its top view. Dark part is a body of mold halve and white park is a carved half part of spiral corrugated tube. The cross sectional view of the cross section VIII-VIII on the spiral corrugated fabrication molder, fabricated by overlapping the two mold halves, is shown in FIG. 10-2. FIG. 10-2 shows that the spiral corrugated fabrication molder can be splitted into split mold halve 1 and 2, which is used as an extrusion blow molder in the extrusion blow molding process.

Determination of tube size criterion for PTSF requires a comparison of total fabrication cost of PTSF and PRSF, which is determined by summation of marketing prices of materials and mechanical fabrication cost of rod (solid rod) and tube. In this comparison, the marketing prices of PVC tubes and rods are used instead of PVC raw material and collected from U.S. Plastics Inc as tabulated in Table 1. The mechanical fabrication cost

TABLE 1

Prices of PVC tubes (schedule 40) and rods as

of August 2013(From U.S. Plastics, Corporation)

Tube
Rod

Price
price

Size
OD
ID
(dollars
(dollars

(in)
(in)
(in)
per foot)
per foot)

¼
0.54
0.354
0.55
0.7

⅜
0.675
0.483
0.72
0.84

½
0.84
0.608
0.44
0.95

⅝

1.14

¾
1.05
0.804
0.59
1.06

1
1.305
1.033
0.87
2.78

1¼
1.66
1.363
1.17
4.32

1½
1.9
1.592
1.29
6.26

1¾

8.79

2
2.375
2.049
1.73
11.25

of tube includes 3 step fabrication costs such as injection molding cost and two parts-assembling costs, but rod fabrication cost includes 1 step fabrication cost of injection molding. Under an assumption of 0.5 dollar/foot/rod or tube of each step, the mechanical fabrication costs of rod and tube are 0.5 and 1.5 dollars/foot, respectively, which are constant because the sizes of tubes and rods do not significantly affect the mechanical fabrication. However, the prices of rods rapidly increase as their sizes increase, while those of tubes slowly increase as shown in Table 1. To understand the effect of rod and tube sizes to their total fabrication costs, the variation of the total fabrication costs are plotted, using the prices of tubes and rods and assumption of mechanical fabrication costs, as shown in FIG. 11. Observing the variations of the total fabrication costs shown in FIG. 11, the small size fill media are preferred to be fabricated using small diameter rod PRSFs less than 0.5 inches in ID and the large size fill media preferred to be fabricated using large diameter tube PTSFs greater than or equal to 0.681 inches in OD. Eventually, the relatively small size apparatuses like evaporative chiller and cooler, air refresher, and small cooling tower prefer small diameter rod PRSFs using less than 0.5 inches OD of rod for fabrication of their fill media, while the fill media of large and medium size cooling towers are fabricated with large diameter tube PTSFs using tubes of greater than or equal to 0.681 inches in OD of tube to minimize the amount of PVC. Therefore, the tube size criterion for PTSF is 0.681 inches outside diameter of tube applied to the fabrication of PTSF.

The necessity and determination method of the acceptable size of material used for fabrication of fill media like plastic strings or rods packs is described in U.S. patent (application Ser. No. 13/053,382) of the present inventor. Among the several factors for determination of diameter of strings and rods, key factors are the thickness of ring hole surrounding string or rod and the interval space between ring holes. The ring hole thickness is computed by multiplying a multiplication factor, 1.412 or 1.924, to the diameter of string or rod and subtracting their diameters and then being divided by 2. The ring hole space, interval between outer circle of ring hole is determined to be 0.394 inch which is added to ring hole thickness to equalize with average sheet spacing of current commercial cooling tower fill media. In the present invention, the ring hole thickness is determined by applying 1.924 for tubes of greater than or equal to 1.5 inches in diameter and 1.412 for tubes less than 1.5 inches to preserve optimum size ring holes for water to easily and evenly flow down through ring holes. The ring hole spacing for tubes of less than 1.5 inch in diameter is determined to be 0.394 and 0.572 is applied for tubes greater than and equal to 1.5 inch. Using these criteria, the specifications of tubes used for fabrication of PTSF, whose diameters are in the range of 0.1 to 1.75 inches, are determined as tabulated in Table 2. The determination of tube specification due to variation of tube sizes are described in detail in the section of Detailed Description of Preferred Embodiment. As a result of analyzing the specifications of tubes tabulated in Table 2, the specific surface areas of PTSFs pack fabricated with tubes of 0.1 to 1.2 inches in outer diameter are not significantly different as they are in the range of 12 and 20 ft²/ft³and the relatively large specific surface areas are gathered around the largest specific surface area, 20 ft²/ft³, of the tube of 0.251 inches. They are suitable for fabrication of PTSF, since the cooling effects of 12 to 20 ft²/ft³of the PTSFs pack are greater than those of the lowest specific surface area, 41 ft²/ft³, of the commercial PVC film fills pack having been used for the benchmarking experiment of verifying the cooling effect of SSFs pack. See U.S. patent (application Ser. No. 13/053,382) for benchmarking experiment of SSFs pack. However, for the tube diameters of greater than 1.2 inches, the specific surface areas of the PTSFs pack rapidly decrease lower than 12 ft²/ft³and therefore their cooling effects are lower than those of the commercial PVC film fills pack, which means the large tubes of greater than 1.2 inches in outer diameter are not suitable for fabrication of PTSF. Considering the tube size criteria and acceptable tube diameters described above, it is concluded that the acceptable tube sizes used for economical fabrication of PTSF are in the range of outside diameter 0.681 to 1.2 inches of tube.

The fabrication method of the spiral corrugated rods is described in detail in the previous patent, U.S. patent application Ser. No. 13/888,327 of the present inventor. In the present invention, a fabrication method of corrugated PVC tube shown in FIGS. 6 and 12, whose corrugated bumps are able to provide an optimum large surface area of tube, is described based on the dimension of NPS 1″ PVC tube. The optimum large surface area means that the corrugated surface area of the spiral-corrugated-tube (SCT) is properly large and has properly wide and deep grooves enough for water to flow down along the corrugated grooves. To satisfy these conditions, the corrugated bump angle shown in FIG. 12 must not be small and not too large. FIG. 6 illustrates the schematic picture of the SCT and FIG. 12 shows the cross section view of the SCT which has 8 spiral corrugated bumps forming 8 diamond shapes by combining two isosceles triangles as shown in FIG. 12. The height or thickness of corrugated bump is made to be same with the thickness of NPS 1″ PVC tube. As a result, the corrugated of bump peak spacing×corrugated thickness of 0.4994×0.136″ is obtained. The corrugated bump angle and leg length of isosceles triangle of corrugated bump are respectively 142 degree and 0.2642(6.7 mm) inches computed from 45 degree isosceles triangle. Then, using this information, the surface area of 8 corrugated bump tube is computed to increase by 3.2%, compared with that of plain tube. Judging the results employing the optimum conditions of proper corrugated bump angles “not too small and not too large” and proper depth of groove “not too shallow depth”, the fabrication of 8 corrugated bump on the surface of NPT 1″ PVC tube is acceptable. The determination method of the optimum large surface area is described in detail in the section of Detailed Description of Preferred Embodiment. When 11 corrugated bumps are made on the surface of NPT 1″ PVC tube, the surface area can be increased by 15% and the surface area of the 7 corrugated bumps tube is same with that of the plain PVC tube.

Advantages of Present Invention

One of major advantages of the present invention is the ability to substantially reduce the height of the PVC Fills pack by maximum 35% of its original height to meet the required temperature of the water to be cooled in the current PVC Fills packs because the entire surface area of spiral corrugated tube is used for contacting between water and cooling air to completely cool water and the cooling function of cooling air is totally employed for cooling water without being significantly resisted by the spiral corrugated tubes, thereby expecting to maximize heat exchange rate between water and cooling air.

Another major advantage of the present invention is the ability to save a large amount of PVC materials for fabrication of fill media since the spiral corrugated tube has thin film-like surface and entirely hollow inside of the spiral corrugated tube.

Yet another major advantage of the present invention is the ability to keep the spiral corrugated tube robust because the corrugated surface of the spiral corrugated tube strengthen the tube body.

Another major advantage of the present invention is the ability to cool the water much hotter than the warm water able to be cooled by the PTCFs pack because the stack height of the PTSFs packs piled can be extended without loss of their physical integrity or mechanical strength and because they can be of rugged construction with ability to withstand without their damage or loss of shape, since the cooling efficiency of the PTSFs pack has much higher than that of the PVC Fills pack.

The spiral corrugated tube of the present invention still has other advantages for usage of PTSFs as fill media, which are same with those of PRSFs and described in the previous patent of the present inventor, U.S. patent application Ser. No. 13/053,382.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic picture of PTSF plastic tube screen fill.

FIG. 2 illustrates a schematic picture of PTSFs pack fabricated by assembling several units of PTSFs.

FIG. 3-1 shows left and right partial schematic view of cross section I-I of plastic-tube-screen-fill shown in FIG. 1.

FIG. 3-2 shows schematic view of side II-II of plastic-tube-screen-fill shown in FIG. 1.

FIG. 3-3 shows left and right partial schematic view of outside surface of top and bottom ring hole perforated frame of plastic-tube-screen-fill.

FIG. 4-1 illustrates mid-partial schematic picture of outside surface view of top and bottom ring hole perforated frames of plastic-tube-screen-fill.

FIG. 4-2 illustrates mid-partial schematic picture of side view of top and bottom perforated frames of plastic-tube-screen-fill.

FIG. 4-3 shows side cross section view of top and bottom ring hole perforated frames of plastic-tube-screen-fills.

FIG. 4-4 shows mid-partial schematic view of underside surface of top and bottom ring hole perforated frame of plastic-tube-screen-fill.

FIG. 5-1 is a mid-partial schematic picture of side view of top and bottom tube holder frame of plastic-tube-screen-fill.

FIG. 5-2 shows view of cross section III-III of top and bottom tube holder frame of plastic-tube-screen-fill in FIG. 5-1.

FIG. 5-3 shows top view of top and bottom tube holder frame of plastic-tube-screen-fill.

FIG. 6 is a schematic picture of spiral corrugated plastic tube.

FIG. 7 is an assembling procedure of top and bottom perforated frames, tube holders, and plastic spiral corrugated tubes.

FIG. 8-1 is a side view of perforated frame fabrication molder joined upper and lower mold halves together of perforated frame fabrication molder.

FIG. 8-2 shows a schematic view of cross section IV-IV of perforated frame fabrication molder joined upper and lower mold halves of perforated frame fabrication molder shown in FIG. 8-1.

FIG. 8-3 illustrates a top view of lower mold halve of perforated frame fabrication molder.

FIG. 8-4 is a picture of cross section V-V of lower part of tube holder fabrication molder shown in FIG. 8-3.

FIG. 8-5 shows a top view of upper mold halve of perforated frame fabrication molder fabrication molder.

FIG. 8-6 is a picture of cross section VI-VI of upper mold halve of perforated frame fabrication molder shown in FIG. 8-5.

FIG. 9-1 illustrates a side view of tube holder frame fabrication molder joined upper and lower mold halves of tube holder frame fabrication molder.

FIG. 9-2 is a picture of cross section VII-VII of tube holder frame fabrication molder shown in FIG. 9-1.

FIG. 9-3 is a top view of upper and lower mold halves of tube holder frame fabrication molder.

FIG. 10-1 shows a schematic top view of left and right mold halves of extrusion blow molder for fabricating of spiral corrugated tube.

FIG. 10-2 shows a view of cross section VIII-VIII of extrusion blow molder created by joining left and right mold halves of spiral corrugated tube fabrication molder shown in FIG. 10-1.

FIG. 11 shows a comparison of fabrication cost of PTSF and PRSF.

FIG. 12 illustrates a rough schematic drawing of 8 wavy corrugated tube based on commercial NPS 1 inch PVC tube.

FIG. 13 shows a picture of 8 wavy corrugated crest lines slanted by 30 degree shown on rectangular surface of circumference of NSP 1″ PVC tube×length of corrugated tube with one circular length of corrugated crest line as diagonal.

FIG. 14 shows a variation of increase of surface area and slant angles of corrugated crest lines on NPS 1″ PVC tube as a function of number of corrugated crest lines.

FIG. 15 illustrates the fabrication procedure of spiral wavy corrugated tube using extrusion blow molding process.

FIG. 16 shows a schematic picture of die-caster of molding fabrication of 3 perforated frames and 3 tube holding frames at one injection of molten plastic by extrusion machine.

DESCRIPTION OF NUMBER IN THE DRAWINGS

1 PTSF, 2 upper tube holding perforated frame, 3 lower tube holding perforated frame, 4 ring hole, 5 spiral corrugated tube, 6 PTSFs pack, 7 inside hole of tube, 8 tube holder, 9 male push-fit tube connector, 10 size reduction gap, 11 spacing between outer circle of ring hole, 12 upper and lower tube holding perforated frame, 13 male attachment tag, 14 female attachment tag, 15 thickness of tube holding perforated frame, 16 peak of spiral corrugated bump, 17 image line of male push-fit tube holder, 18 cup-shaped hole perforated frame, 19 cup-shaped circular hole, 20 female push-fit band connector, 21 image line of cup-shaped hole, 22 tube holding frame, 23 male push-fit band connector, 24 corrugated groove, 25 corrugated bump, 26 corrugated surface of tube, 27 perforated frame fabrication molder, 28 upper mold halve of perforated frame fabrication molder, 29 lower mold halve of perforated frame fabrication molder, 30 hollow cavity to create a body of perforated frame, 31 body of lower mold halve of perforated frame fabrication molder, 32 cylindrical humps to create holes in the perforated frame, 33 top image line of cup shaped cylindrical hump, 34 band hump to create female push-fit band connector, 35 body of upper mold halve of perforated frame fabrication molder, 36 location image line of cup-shaped cylindrical hole, 37 tube holding frame fabrication molder, 38 upper and lower mold halves of the tube holding frame fabrication molder, 39 body of upper and lower mold halve of the tube holding frame fabrication molder, 40 extrusion blow molder, 41 hollow cavity of corrugated tube, 42 peak image line of corrugated bump, 43 body of left and right mold halve of the extrusion blow molder, 44 extrusion head inserting hole, 45 corrugated bump angle, 46 corrugated thickness or tube thickness, 47 corrugated groove, 48 corrugated bump, 49 thickness of corrugated surface of corrugated tube, 50 length of one circular corrugated bump, 51 hot parison or pre-formed hot plastic tube, 52 air blow pin, 53 molten plastic, 54 extruder, 55 extrusion head, 56 air supplying hose, 57 hollow cavity of corrugated tube, 58 air pressure expanding parison, 59 plastics placed on the wall of hollow cavity, 60 molded product, 61 die-caster of molding fabrication of 3 perforated frames and 3 tube holding frames, 62 perforated frame fabrication molder, 63 tube holding frame fabrication molder, 64 cavity image line of tube holding frame, 65 cavity image line of perforated frame, 66 molten plastic distributer, 67 molten plastic inlet port, 68 molten plastic injector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The plastic-rod-screen-fill (PRSF) invented by the present inventor has a disadvantage in employing large size rods (large diameter rod), since they require a large amount of materials for making solid rod. To complement such disadvantage of PRSF fabrication, the fabrication method of the plastic-tube-screen-fill (PTSF) using PVC tube is invented in the present invention. Any solid rod can be fabricated using a molten PVC injection machine like one step fabrication of PRSF, but plastic tube is made through molten plastic extruder. Hence, the fabrication of the PTSF can be accomplished by employing both injection and extrusion machines. Namely, the frame parts of PTSF are fabricated by the injection machine and the tubes fabricated by the extrusion machine, and then those parts are assembled to complete PTSF. The frame parts of PTSF include whole circular holes frame and tube holders. The whole circular holes frame is required, while PRSF has semi-circular holes frame, because PTSF needs a large intervals between adjacent tubes due to large diameter tubes and the tube holders are located in the center of the whole circular holes in the frame parts of PTSF. Therefore, the frame part of PTSF cannot be fabricated by one step machining as in the fabrication of PRSF. Actually, the frame of PTSF is fabricated by two separate machining, whole circular holes frame fabrication and tube holder fabrication, because one step injection machining is not possible for handling whole circular holes with tube holders in it. In other words, the whole circular holes frame and tubes holder are separately fabricated by the injection machining.

There are several factors for designing of PTSF. The designing factors for fabricating fill media like SSFs and PRSFs are extensively examined and determined in U.S. patents (application Ser. Nos. 13/053,382 and 13/888,327) recently applied by the present inventor. Since the plastic tubes used in the present invention are similar plastic materials as used for the fabrications of SSF and PRSF, those results are applied to designing and fabrication of PTSFs without any significant modification. The factors for designing PTSF are PVC tube diameter, the number of PVC tubes in PTSF, diameter of holes on the frame of PTSF, and specific surface area of PTSF. Such factors are essential for the effective and economical designing of PTSF and described in the following descriptions.

To determine an optimum diameter of tube, the marketing prices of plastic tube and rod fabricated using same material, PVC, are compared. Major factors determining the marketing prices of PTSF and PRSF are material cost and fill media mechanical fabrication cost excluding material cost. The fill media mechanical fabrication cost is fixed, not affected by tube or rod diameter, as an injection molding and assembling processes used for fabrication of PTSF and PRSF are not depending on the tube or rod diameter, but the material costs of tube and rod increase as their diameters increase. The fill media mechanical fabrication cost is determined from the fabrication procedure of fill media. The PTSF is fabricated through 3 fabrication steps: injection and extrusion molding process, assembling of perforated frame and tube holding frame to fabricate perforated tube holder frame, and assembling of tubes and perforated tube holder frames to fabricate PTSF. However, PRSF is fabricated by one step: PRSF is fabricated through one step of injection molding process. A mechanical fabrication cost of each step described above is assumed to be same because the assembling process can be automatically carried out like the injection molding process. Hence, the fill media mechanical fabrication cost of PTSF is three times higher than that of PRSF using an assumption of same fabrication cost rate applying to each step process of mechanical fabrication. Then, the total fabrication cost of PTSF or PRSF is sum of the fill media mechanical fabrication and material costs.

To observe a variation of total fabrication cost of PTSF and PRSF depending on tube or rod diameter, total fabrication costs of PTSF and PRSF are plotted against tube and rod diameters as shown in FIG. 11. FIG. 11 shows the variations of total fabrication cost and fill media mechanical fabrication cost of PTSF and PRSF, and material price as a function of tube or rod diameters. It is understood from FIG. 11 that the total fabrication costs of PRSF using rods larger than 0.75 inches in diameter rapidly increases, compared with those of PTSF, while using tubes and rods smaller than 0.75 inches in diameter, the total fabrication costs of PRSF is slightly getting lower than those of PTSF. From such trending of cost and price observation, the tube and rods are categorized into three groups of large, medium, and small size fill media as shown in FIG. 11. The large size group includes tubes and rods greater than 0.75 inches of tube ID and rod OD and the small size group contains tubes and rods less than 0.625 inches. The medium diameter tubes and rods between 0.625 and 0.75 inches are categorized into the medium size fill media group. The large and small size fill media are fabricated using tubes of greater than 0.961 (equivalent to 0.75 inches ID) inches in outer diameter and rods of less than 0.456 inches (equivalent to 0.625 inches OD) in inner diameters, respectively. Medium size fill media can be fabricated using both tubes and rods, since their material costs are not significantly different, but to save material, the fabrications of PTSFs using tubes between 0.625 (0.456 inch ID) and 0.961 inches OD (0.75 inch ID) are preferred. Eventually, the relatively small size apparatuses like evaporative chiller, evaporative cooler, air refresher, and small cooling tower prefer small diameter rod PRSFs using less than 0.456 inches OD of rod for fabrication of their fill media, while the fill media of large and medium size cooling towers are fabricated with large and medium diameter tube PTSFs using tubes of greater than 0.456 inches ID to minimize the amount of PVC. Therefore, the tube size criterion for PTSF is 0.456, the outer diameter of the minimum size tube applied to the fabrication of PTSF.

For the fabrication of the small diameter tube PTSF (smaller than 0.75 inches in inner diameter), the number of tubes used in PTSF is determined using same method as used for determination of optimum number of rods in PRSF, which is described in U.S. patent application Ser. No. 13/053,382. However, the number of large diameter tubes (larger than 0.75 inches in inside diameter) used in PTSF is determined using current design information of a fill media used in the cooling tower. Standard fill media pack size of commercial plastic film fill media is 12(W)×24(D)×48(H) inches, which has a specific surface area of 40 ft2/ft3 with sheet spacing of 1.49 inches (38 mm) to 51 ft2/ft3 with sheet spacing of 0.75 inches (19 mm) (referred to Cooling Tower Depot, Cross How Fill With Louver or Drift Eliminator and STAR COOLING TOWERS, Counterflow and Crossflow Film Fills). Hence, the standard size of the commercial fill media pack can be used to make the size of standard PTSFs pack same to directly compared with each other. To determine the number of tubes in the standard PTSFs pack of 12(W)×24(D)×48(H), tube spacing is determined. The tube spacing is interval between the surfaces of adjacent tubes and is equal to summation of a thickness of ring holes around the tube and ring hole spacing between outer circle of adjacent ring holes. Therefore, the interval between adjacent tubes (distance between centers of tubes) is equal to the summation of tube diameter, twice of thickness of ring hole, and ring hole spacing. Namely, Interval=Ring Hole Diameter+Ring Hole Spacing. As in the previous U.S. patent (application Ser. No. 13/053,382), the outer diameter of ring hole is made to be 1.412 times outer diameter of tube and the ring hole spacing is kept constant spacing of 0.394 inches (10 mm) which is applied to every different tube diameters. Computation formula of interval is driven as follows. Tube Interval between adjacent tubes in PTSF=1.412×Tube OD+0.394. See the determination of the optimum spacing between adjacent rods in U.S. patent application Ser. No. 13/053,382. Applying this optimum spacing determination method to the present invention, the optimum numbers of tubes of 0.1 to 1.75 inches in outer diameter required for fabrication of PTSFs pack of 12(D)×24(W)×48(H) inches are determined and tabulated in Table 2. The optimum numbers of tubes for fabrication PTSF are indicated as bolt numbers in the column of Table 2. The tubes are located in a staggered position in PTSF pack. Up to the tubes of 1.2 inches in outer diameter, the staggered configuration of tubes is achieved with the ring hole spacing of 0.394 inches. However, for the tubes of greater than or equal to 1.5 inches in diameter, a little larger ring hole spacing, 0.572 inches, is necessary to fabricate a complete frame of PTSF shown in FIG. 3-3. If not, the thickness of the perforated frame becomes narrow to damage the ring hole. Table 2 shows that the surface areas of PTSFs packs of large diameter tubes greater than or equal to 1.5 inches in outer diameter are small,

TABLE 2

Variation of number of tubes in PTSF and specific surface

area of PTSFs pack depending on tube outer diameter.

Specification of PTSF

Dimension of PTSF: 24 (W) × 48 (H) inches

Dimension of PTSFs pack: 12 (D) × 24 (W) × 48 (H) inches

Interval

Interval

of ring

Specific

Specification

# of
# of
# of
Thick
of tubes
Thick
holes
Surface
surface

of
Tube
tubes
PTSFs
tubes
of
In PTSF
of ring
(OD to
area of
area

PVC film
OD
In
In
In
PTSF
(C to C)
holes
OD)
pack
of pack

fill
(in)
Pack
pack
PTSF
(in)
(in)
(in)
(in)
(ft2)
(ft2/ft3)

Dimension
1.75
32
4

8

2.622
3.043
0.361
0.572
59

7

12 (D) ×
1.5
45
5

9

2.318
2.691
0.309
0.572
71

9

24 (W) ×
1.2
77
7

11

1.799
2.088
0.247
0.394
97

12

48 (H)
1.0
104
8

13

1.556
1.806
0.206
0.394
109

14

(inches)

0.78

149

9.3

16

1.289

1.496(38)

0.1607

0.394

122

15

Specific
0.75
158
9.6

17

1.252
1.453
0.1545
0.394
124

16

Surface
0.625
207
11

19

1.100
1.277
0.1288
0.394
138

17

Area
0.5
276
12.66

21.82

0.948
1.100
0.103
0.394
144

18

40-69
0.456
308
13.4

23

0.894
1.038
0.094
0.394
147

18.4

(ft2/ft3)
0.375
390
15

26

0.796
0.924
0.0773
0.394
153

19

PVC film

0.307

493

17

29

0.7125

0.827(21)

0.0632

0.394

158

19.75

gauge =

0.251

608

19

32

0.6444

0.748(19)

0.0517

0.394

160

20

10-15 mils
0.25
608
19

32

0.6435
0.747
0.0515
0.394
159

19.88

Weight =
0.125
1008
24

42

0.4914
0.571
0.0578
0.394
132

16

2.3-2.9
0.1
1171
26.02

45

0.4611
0.5352
0.0206
0.394
123

15.4

lbs/ft3

Notes:

multiplication factor = 1.412;

OD = outside diameter;

C = center of tube.

compared with those of other tubes of less than 1.5 inches. Such an observation indicates that the small surface area of fill media leads to its low operation efficiency. Therefore, the operational efficiencies of the large diameter tube PTSF packs using greater than or equal to 1.5 inches are not acceptable for their commercialization. Eventually, the fill media using tubes should be fabricated with those of less than or equal to 1.2 inches in outer diameter which is a maximum diameter of tube applicable to the fabrication of PTSF. Considering the size criterion and maximum diameter of tube, it is concluded that the acceptable tube diameters used for fabrication of PTSF are in the range of 0.456 to 1.2 inches in outer diameter of tube.

Dimension of standard PTSF is determined using a small size commercial standard PVC film fills pack. The small standard PVC film fills pack has a dimension of 12(D)×24(W)×48(H) inches and the numbers of PVC film fills in it are mainly 15, 16, and 26 sheets/ft with sheet spacing of 0.827, 0.748, and 0.472 inches, respectively. See STAR COOLING TOWERS, Counterflow and Crossflow Film Fills in references for a detailed description of the standard PVC film fills pack. To determine the dimension of standard PTSF, the dimension of standard PVC film fills pack and the sheet spacing of the PVC film fills assembled in the pack. From the dimension of 12(D)×24(W)×48(H) inches, the width×height of PTSF can be determined to be 24×48 inches of rectangular PTSF as shown in FIGS. 1 and 3-1. The intervals between tubes in the PTSF is distance between the center of the adjacent tubes and is equalized with the sheet spacing of PVC film fills in the PVC film fills pack. Hence, the tube intervals in the PTSF are 0.827, 0.748, and 0.472 inches from center to center of the adjacent tubes. Using these tube intervals and width of the PTSF, the number of tubes in the PTSF is determined to be 29 (e.g. 24 inches/0.827 inches=29), 32, and 51 for the tube intervals of 0.827, 0.748, and 0.472 inches, respectively, which are tabulated as bolt numbers in Table 2. The thickness of PTSF can be determined by equalizing with the tube interval in the PTSF, because adjacent tubes are lined up on the depth of PTSF pack when two PTSFs are jointed together for assembling of PTSFs as described in the section of <Designing of PTSF>. By doing so, for tubes in each PTSF to be positioned on the tube interval between adjacent tubes in PTSF, the thickness of the PTSF is fabricated to be equal with the tube interval in PTSF. Then, among the tube intervals created by joining two PTSFs of same thickness with tube interval in the PTSF, the shortest interval is equal with the thickness of PTSF, where the tubes are located on the vertex of square or isosceles triangle with its height and base are equal with thickness of PTSF. To make all of tube intervals created by joining together of PTSFs equal, they are positioned on the vertex of equilateral triangle, since all three sides of the equilateral triangle are congruent. To do this, the height of the equilateral triangle whose sides are congruent with the tube interval in PTSF is computed using a computation formula of “Thickness of PTSF=0.8615×Tube Interval.” This formula shows that the thickness of PTSF is the reduced length of tube interval in PTSF by 13.85%, which means an increasing of the number of tubes in PTSF. In turn, the surface area of standard PTSFs pack is increased by that much ratio. Using the above formulas (indicated as bolt letters and numbers), the number of tubes in a single unit of PTSF, number of PTSFs and total number of tubes in PTSFs pack, and specific surface area of PTSFs pack are determined depending on the tube outer diameters and the results are tabulated in Table 2. The number of tubes able to economically fabricate PTSFs is in the range of 77 to 308 corresponding to the tube diameters of 1.2 down to 0.456 inches in outer diameter.

The specific surface areas of PTSFs pack for tubes of 0.1 to 1.75 inches in outer diameter are given as bolt numbers in the last column of Table 2. As described above, the economic fabrication of PTSF needs tubes of 0.456 to 1.2 inches in outer diameter. Their specific surface areas are in the range of 12 to 18.4 ft²/ft³whose corresponding outer diameters are 1.2 down to 0.456 inches. To evaluate whether the computed specific surface areas are acceptable or not, the results of the cooling tower benchmarking experiment carried out by the inventor of the present invention are employed. See U.S. patent application Ser. No. 13/053,382 for detailed description of benchmarking experiment. The benchmarking experiment compared the cooling capability of the String Screen Fills pack invented by the present inventor with that of the commercial PVC film fills pack. Their specific surface areas were 41 ft²/ft³for PVC film fills Pack and 14 ft²/ft³for String Screen Fills pack. The cooling efficiencies of the PVC film fills pack and String Screen Fills pack were 13 and 16%, which means the String Screen Fills pack has a higher cooling efficiency by 20%. Therefore, it can be understood that the cooling efficiencies of all PTSFs to be fabricated using the specifications of PTSFs given in Table 2 are higher than those of commercial PVC film fills, since the specific surface area, 14 ft²/ft³, of the String Screen Fills pack fabricated using strings of 0.098 inch in diameter is close to 15.4 ft²/ft³of PTSF pack using 0.1 inch tubes shown in Table 2.

The larger the surface area of the corrugated tubes is, the better cooling efficiency of the cooling media fabricated using the corrugated tubes with large surface area can be expected. However, there is a limit for the determination of the large surface area of the corrugated tube, because the corrugated bump angle gets smaller than an acceptable small angle. Such small angles cannot hold water in the corrugated grooves and allow water flow over the corrugated bumps instead of flowing down along the corrugated grooves. To determine the acceptable surface area and corrugated bump angle, an assumption is required as the shapes of spiral corrugated bumps are isosceles triangles as shown in FIG. 12 for an easy and possible computation of the surface area of spiral corrugated bumps on tube. Under such an assumption, the cross section of 8 bump corrugated tube can be divided into 8 of diamond shapes. One of them is highlighted with dark solid lines as shown in FIG. 12. The diamond shape is formed by combining short leg and long leg isosceles triangles, which has a long diagonal of 0.6525 inches and short diagonal of 0.3953 inches, respectively. The short legs of the short leg isosceles triangle are formed in the thickness of PVC tube and their lengths are 0.2642 inches. The perimeter of cross section of eight bump corrugated tube is covered with 16 short legs and therefore the perimeter of the cross section is 4.2272 inches which can be compared with the outer circumference, 4.098 inches, of NPS 1″ PVC tube. To compare them, the surface of the plain NPS 1″ PVC tube and 8 bump corrugated tube upto one circular length of corrugated line are drawn in one figure as shown in FIG. 13. FIG. 13 shows the flat surface of 8 corrugated bumps slanted by 30 degree which is larger than the original surface of plain tube. The dark rectangular area shown in FIG. 13 is the outer surface of the plain tube. From their comparison, it is understood that the surface area of the 8 bump corrugated tube increases by 3.2%. The corrugated bump angle can be computed from dark highlighted diamond shape rhombus whose vertex angle, small legs, long diagonal, and short diagonal are respectively 45 degree, 0.2642, 0.6525 (=0.4772+0.1753), and 0.3953 inches. With helping of the vertex angle of 45 degree, leg length of 0.2642 inches, and diagonal of 0.3953 inches, the corrugated bump angle can be computed to be 142 degree. The corrugated bump angle of 142 degree is large enough for water to be held and flow down in the grooves of the corrugated lines. Therefore, the 8 bump corrugated NPS 1″ PVC tube satisfies the condition of the optimum large surface area, as its surface area and corrugated bump angle are respectively large and wide and deep enough for water to be held in the grooves. Likewise, the surface areas and corrugated bump angles of other number of corrugated bumps on the surface of NPS 1″ PVC tube are computed and plotted as function of number of corrugated bumps as shown in FIG. 14, which shows that the surface area of the corrugated tube increases as the number of corrugated bumps does, while the corrugated bump angle decreases. Observing the plots of the corrugated bump angles and surface areas of the corrugated tube varying due to number of corrugated bumps, the corrugated bump angles and surface areas satisfying the conditions of the optimum large surface area are in the range of a dark square shown in FIG. 14. Namely, the numbers of the corrugated bumps economically fabricated on the surface of NPS 1″ PVC tube are 7 to 11 bumps, whose surface area can be increased by 0 to 15%, respectively. Eventually, combining the effects of corrugated bumps (0 to 15%), slant angle of corrugated bumps (0 to 5%), and surface area of the PTSF pack (10 to 15%), the cooling effect of the spiral corrugated tube PTSF (SCTSF) is higher than that of the PVC film fill by 10 to 35%.

The comparison of PVC amount required for fabrication of current PVC fills and SCTSF fills pack is necessary to be performed under the same conditions. Namely, a basic volume of fills pack used in their comparison is one cubic feet. To do so, the physical specification, surface area, dry weight of PVC per cubic feet, PVC film thickness (film gauge), and density of PVC film of current standard PVC fills pack are necessary for driving of PVC amount required for fabrication of SCTSF fills pack under the same physical conditions as used in PVC fills pack. They are respectively 48 ft²/ft³, 2.6 lbs/ft³, and 15 mils except for density, which are obtained from reference of STARCOOLINGTOWERS.COM. The density of 15 mils PVC film used on this PVC film pack is estimated to be 43 lbs/ft³(=2.6 lbs/(48 ft²×0.015 in)). Using this information concerning the basic volume in one cubic feet of fills pack, the weight of SCTSF fills pack in one cubic feet is calculated as follows. First, the surface area of SCTSF fills pack is calculated like the surface area of PTSF fills pack×1.15 (maximum) or 1.10 (minimum) since the surface area of SCTSF increases by 10 to 15% as described in the section of Optimum Large Surface Area of SCTSF. The surface areas of PTSF pack with tubes in various diameters are given in Table 2. The diameters of tubes applicable to economical fabrication of PTSFs are in the range of 0.456 to 1.2 inches in outer diameter, whose corresponding surface areas are 18.4 and 12 ft²/ft³. Hence, the maximum optimizing surface areas of SCTSF pack with small tube of 0.456 inches in diameter and large tube of 1.2 inches are 21.16 ft²(=18.4×1.15) and 13.8 ft²in a volume of one cubic feet. Then, their corresponding weights of CTSF packs are 1.137 lbs (21.16 ft²×0.015 in×ft/12 in×43 lbs/ft³) and 0.742 lbs (=13.8 ft²×0.015 in×ft/12 in×43 lbs/ft³) per volume of one cubic feet. Comparing the weights, 0.742 to 1.137 lbs/ft³, of SCTSF pack with 2.3 to 2.9 lbs/ft³of current standard PVC pack, the fabrication of SCTSF pack saves 61 to 68% of the amount of PVC required for fabrication of current PVC fills pack.

The fabrication of the PTSF 1 needs three molders: perforated frame 27, tube holding frame 37, and spiral corrugated tube fabrication molders 40. The spiral corrugated tube 5 requires one sort of tube, but the perforated frame 27 and tube holding frame 37 require respectively two kinds of frames and holders, as the tubes are arranged in staggered position. To achieve this requirement with the employment of one molder for each of them, the molder should be designed to fabricate the perforated frame 18 or tube holding frame 22 able to be used in two ways. To do these, the perforated frame fabrication molder 27 is fabricated for the first circular hole 19 from the left edge of the perforated frame 18 to be located at the half distance of the distance between the right edge and the first circular hole 19 on the right side of frame as shown in FIGS. 8-1, 8-3, and 8-5. And also the tube holding frame fabrication molder 37 is fabricated in the same way as the perforated frame fabrication molder 27 as shown in FIGS. 9-1 and 9-3. However, the attachment tags 13, 14 on the both end sides of the perforated frame 18 should be positioned on the same distance from both edges of the perforated frame 18 as shown in FIG. 8-1 for the overlapping of male and female attachment tags 13, 14 to be aligned and joined together when one of two perforated frames 18 is horizontally rotated by 180 degree. FIG. 8-1 shows the schematic side view of the perforated frame fabrication molder 27 produced by overlapping a lower mold halve 29 shown in FIG. 8-3 and a upper mold halve 28 shown in FIG. 8-5. The light part in the lower mold halve 29 shown in FIG. 8-3 is a hollow cavity 30 to create a body of perforated frame 18 and dark and light tags create respectively female and male attachment tags 13, 14. In the upper mold halve 28 shown in FIG. 8-5, the light part is a hollow cavity 30 to create a body of perforated frame 18 and dark circles on the center line of the hollow cavity 30 are cup-shaped cylindrical humps 32 to create cup-shaped cylindrical holes 19 in the perforated frame 18. The dark straight bar 34 connected all dark circles 32 in the upper mold halve 28 are straight bar hump 34 creating female push-it connector 23 as shown in FIG. 5-3. FIGS. 8-2, 8-4, and 8-6 show cross sectional views of cross section IV-IV, V-V, and VI-VI on the perforated frame fabrication molder 27, lower mold halve 29, and upper mold halve 28, respectively. To firmly join together PTSFs 1 when the PTSFs pack 6 is assembled, 2 male and 2 female attachment tags 13, 14 are properly carved respectively on one side near to left and right edge of the lower mold halve 29 of the perforated frame fabrication molder 27 as shown in FIG. 8-3, while 2 female and 2 male attachment tags 13, 14 are properly carved on the other side near to the edge of the lower mold halve 29. By doing so, the male attachment tabs 13 can join firmly together with female attachment tabs 14 on the same location by pressing them, when they are assembled together with horizontal rotation of one of two frames by 180 degree.

The tube holding frame 22 consists of several tube holders 8 and male push-fit band holders 23. The tube holders 8 are made of a round solid rod as an upper part of the tube holders 8 and push-fit tube connector 9 as a lower part and they are connected with male push-fit band connector 23 to be formed in one structure as illustrated in FIGS. 5-1, 5-2, and 5-3. This tube holding frame 22 in one structure is carved in two mold halves 37, 38 as shown in FIGS. 9-1, 9-2, and 9-3. FIG. 9-1 shows the side view of the tube holding frame fabrication molder 27 joined upper and lower mold halves of molder 38 and FIG. 9-2 shows the cross sectional view of cross section VII-VII shown in FIG. 9-1. The light parts 23 in the center of the molder 27 shown in FIG. 9-1 are hollow cavities 23 creating the body of the tube holding frame 27 and the dark parts are a body of molder. FIG. 9-3 shows the top view of upper and lower mold halves which are same.

The spiral corrugated tube 5 are fabricated using two mold halves 40 carved the half shape of spiral corrugated tube 5 as shown in FIGS. 10-1 and 10-2. Two mold halves 40, split mold halve 1 and 2, are same in molding configuration and so they are carved in same configuration. FIG. 10-1 illustrates a schematic picture of top view of one split mold halve 40. Dark part is a body of split mold halve 1 and 2 43 and white park 41 is a carved half part of spiral corrugated tube 5. The dot lines 42 are images of the peak of corrugated bumps 48 slanted by 30 degree to the length of the tube. At the center of the top of split mold halve 40 is a half cylindrical hole 44 to provide a insert hole inserting hot plastic injector and air blow pin 52 of extrusion head 55, through which a plastic hot resin 53 is transported and pressure air 58 is blown into the blow molder 40. Overlapping the two mold halves 40 together, the corrugated grooves 47 and bumps 48 are exactly put in a straight line without any discontinuity for water to flow along the corrugated grooves 47. FIG. 10-2 shows a cross sectional view of cross section VIII-VIII of the spiral corrugated tube fabrication molder whose schematic picture of overlapping split mold 1 and 2 is as shown in FIG. 10-1, with hollow cavity 41 of the 8 bumps wavy corrugated tube 5 created, when the split mold halve 1 and 2 43 are jointed together.

The fabrication of SCTSF 1 is accomplished by sequential fabrication activities of spiral corrugated bump tubes 5, perforated frames 18, tube holding frames 23, and their assembling into SCTSF 1. The spiral corrugated bump tubes 26 are fabricated through the extrusion blow molding process shown in FIG. 15 using the spiral corrugated tube molders 40 shown in FIGS. 10-1 and 10-2. The extrusion blow molding process is an extended process added to the outlet portion of the molten plastics extruded by the extrusion machine. The extended process is an expansion process of parison (pre-formed tube), which is an air blow molding like a balloon. Namely, the pre-formed plastic resin hot tube extruding from the extrusion machine is placed within a split mold, with a hollow cavity of a final end product, shown in FIGS. 10-1 and 10-2, and the mold sides are clamped together, pinching and sealing the pre-formed tube. Then, air is blown into the tube, which expands the hot resin wall of the pre-formed tube into the shape of the cavity and the mold is cooled with water solidifying the resin into the shape of the end product. Once cooled, the part is ejected from the mold and trimmed. Such an extrusion blow molding process applying to fabrication of the spiral corrugated bump tube 5 is shown in FIG. 15, which shows 5 stages of fabrication procedure of spiral corrugated tube 5 using the spiral corrugated tube fabrication molder 40 shown in FIGS. 10-1 and 10-2. In the first stage, STEP 1 shown in FIG. 15, the spiral corrugated tube molder 40 is set to the extrusion head of extruder 54 and parison or pre-formed plastic tube 51 is placed within the molder 40. In STEP 2, the two mold halves 43 are closed and clamped together, sealing the pre-formed tube 51 and then the air blow pin 52 is inserted into the parison 51. In STEP 3, the inflation of the parison 51 is started by pressure of air blown 58 into the pre-formed tube 51 through the long air blow pin 52. The air pressure expands the plastic wall of the pre-formed tube 51 to the wall of the hollow cavity 57 of the blow molder 40 as shown in STEP 3 in FIG. 15, so that plastic film is placed on the wall of the blow molder. Eventually, thin plastic spiral corrugated tube 60 is formed on the wall of blow molder 40, whose thickness is like dark line 49 plastic wall of corrugated tube 5 shown in FIG. 12. After cooled down, the thin plastic spiral corrugated tube 60 is ejected from the blow molder 40 in STEP 4. The final product 60 needs to trim scrap remained and to cut out unnecessary part on both ends of the final product tube 60. These trimming processes are performed in the final stage, STEP 5, of blow molding fabrication process of the spiral corrugated tube 5.

The molding fabrications of the perforated frame 18 and tube holding frame 22 are accomplished by respectively injecting of molten plastic into the perforated frame and tube holding frame fabrication molders 27, 37 shown in FIGS. 8-1 and 9-1 mounted on an injection machine. To fabricate them at one shot of the injection machine, the perforated frame and tube holding frame fabrication molders 27, 37 must be installed in one large die-caster 61, which can be inserted into a large injection machine. The determination of the machine size of injection machine is described in the U.S. patent application Ser. No. 13/888,327. Since the perforated and tube holding frames 27, 37 are relatively small, several frames can be fabricated in one die-caster. To fabricate 3 perforated frames 27 and 3 tube holding frames 37 at one injection, a large die-caster 61 handling 6 molders is fabricated as shown in FIG. 16. The die-caster 61 consists of perforated frame fabrication molders 62, tube holding fabrication molders 63, molten plastic distributer 66, molten plastic inlet port 67, molten plastic injector 68, support system (embedded in the die caster), and cast release system (embedded in the die caster). The molders are the ones shown in FIGS. 8-1 and 9-1. The cast release system releases the casted perforated frames 18 and tube holding frames 22 out of the die-caster and the injector of molten plastics 68 transfers the molten plastic injected from the injection system to the molten plastics distributer 66, which distributes the molten plastics to every hollowed perforated frames 65 and tube holding frames 64 carved in the perforated frame fabrication 62 and tube holding frame fabrication molders 63. The functions of support system are to receive the molten plastics injected from the injection system at the entrance of the receiver 67 and to transfer the molten plastics to every hollowed perforated 65 and tube holding frames 64 after passing through the distribute controlling lines 66. And also the support system has the functions of cooling molten plastics by circulating cold water surrounding the molten plastics filled every hollowed frames and ejecting the cooled frames from the frame fabrication molders 62, 63.

Following the assembly procedure Step 1 to 3 shown in FIG. 7, the assembly of perforated frames 18, tube holding frames 22, and spiral corrugated tubes 5 is performed to fabricate the PTSF 1. The Step 1 of the assembly procedure is the stage joining the perforated and tube holding frames 18, 22. To do this, the tube holders 8 and male push-fit band connector 23 of the tube holding frame 22 are properly aligned with the cup-shaped cylindrical holes 19 and female push-fit band connector 20 of the perforated frame 18 and then inserted into them by pressing. By doing so, the tube holding and perforated frames 18, 22 are firmly joined together. The completion of their insertion fabricates the perforated tube holding frame 12: ring hole perforated frame, as the insertion of tube holders into the holes on perforated frame creates a ring hole as shown in FIG. 3-3. In the Step 2, the ring hole perforated frame 12 is assembled with the spiral corrugated tubes 5. Their assemblies start by inserting of one side female edge of the spiral corrugated tube 5 into the male push-fit tube connector 9 of the ring hole perforated frame 12. The inserting process of tube in Step 2 continues until the insertion of all male push-fit tube connectors 9 of the ring hole perforated frame 12 into one side female edges of spiral corrugated tubes 5 is completed and then Step 3, the insertion process of the other side of tubes 5, starts. On completion of Step 2 and 3, the insertion processes of both side edges of tubes 5, the unit fill medium of SCTSF 1 shown in FIGS. 1 and 3-1 is fabricated.

While the present invention has been described as having an exemplary design, this invention may be further modified within the concept and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention relates.

Plastic Tube Screen Fills and Fabrication Thereof

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