IL117428A - Apparatus and method for manufacturing drip irrigation hose - Google Patents

Description

117,428/2 rV lLin H]1^ *7(U ΙΠΙϋ-11^ nUPUTI 1Ϊ?ΠΠ APPARATUS AND METHOD FOR MANUFACTURING DRIP IRRIGATION HOSE T-SYSTEMS INTERNATIONAL, INC.

C:24592 -1- 117,428/2 DRIP IRRIGATION HOSE AND METHOD FOR ITS MANUFACTURE Background οΓ the Invention This invention relates to drip irrigation and, more particularly, to' a drip irrigation hose with an improved outlet construction and a method for its manufacture.

Drip irrigation hose can be classified into two types-hose having discrete emitters and hose having continuous , integral emitters. An example of a drip irrigation hose having discrete emitters is shown in U .S . Patent No . 4, 850,53 1 . An example of a drip irrigation hose continuous , integral emitters is shown in U .S . Patent No . 4,247,05 1 . Drip irrigation hose havi ng continuous integral emitters offers the possibil ity of lower cost and ease of manufacture and instal lation.

The design of die inlets to and outlets from the emitters is critical . If the effective outlet area of the emitters is too large, dirt and debris can collect externally in the outlets, thereby caus ing external clogging . If the effective inlet and outlet areas of the emitters are too small , they become clogged internally and cease to serve their purpose . Further, if the "effective outlet areas of the emitters are too smal l , water squirts out of the hose instead of dripping, and soil erosion results .

U .S . Patent 4,247,05 1 discloses a drip irrigation hose formed by bending a strip plastic fil m along its length to form an overlapping longitudinal seam between opposing longitudinal margins of the film. First and second longitud inally extending , laterally spaced, transverse ribs interconnect the opposing margins along their length to seal the overlapping longitudinal seam. The ribs are formed by one or more molten plastic beads extruded onto the film. As a result, a flow regulating passage is defined by the ribs and the opposing margins and a supply passage is defined by the remainder of the film. Water flows from the supply passage to the flow regulating passage through a plural ity of longitudinally spaced inlets . Water flows from the flow regulating passage to the exterior of the hose through a plural ity of longitudinally spaced outlets longitudinally spaced from the respective inlets to provide a substantial path length from each inlet to a respective outlet. In one embodiment, the outlets each comprise two parallel sl its that form between them a flex ible flap. The rlap serves as an outlet valve, opening arid closing as the hose is pressurized and depressurized . However, unless the plastic fil m is very thick and rigid , the flaps do not close consistently when the hose is depressu rized and therefore, the outlets can become clogged by soil d rawn into the sl its . - A problem encountered in the manufacture of continuous emitter drip irrigation hose is coordinating the position of the outlets and the track pattern of the ribs . If care is not taken, the track pattern of the ribs may overlap the outlets, and thereby cause the outlets to be on the h igh pressure side of the flow regulating passages .

Summary of the Invention One aspect of the invention, as defined in IL 109737, is a drip irrigation hose of the continuous emitter type in which the outlets from the regulating passage each comprise a single longitudinal sl it. By controll ing the length of the sl its and the flexibil ity of the fil m, water drips from the outlets when the hose is pressurized without clogging when die hose is depressurized . The sl its are su fficiently long and the fil m is sufficiently flexible so the water drips from the outlets when the hose is pressurized. The sl its are sufficiently short and the film is sufficiently rigid so the outlets close completely when the hose is depressurized .

Another aspect of the invention is a metliod for making a drip irrigation hose having longitudinal single sl it outlets and/or inlets . A first outlet and/or inlet forming wheel has one or more knife blades on its periphery. A second backing wheel engages the first wheel to establish a first nip therebetween. The backing wheel has on its periphery a circumferential slot into which the knife blade fits at the first n ip. A third rib forming wheel has around its periphery impressions that define a desired track pattern for the ribs . A second nip is establ ished with a th ird wheel in wh ich the desired track pattern is formed . The first and second wheels are mounted on Ϊ common shaft to operate in synchronism. A continuous strip of plastic film is directed in the following path in the order recited . The fil m is wrapped around the second wheel to reverse direction and pass into the first nip, thereby forming the outlet sl its . The direction of the film is reversed l a in the first nip to transport the film toward the first wheel . The film is wrapped around a portion of the periphery of the first wheel spaced lateral ly from the knife blade to reverse direction. The d irection of the fil m is reversed to transport the film toward the th ird wheel . The fil m is transported under an extruder to deposit a bead of molten plastic on the film before the third wheel . The film is transported into the second nip to form the desired track in the molten plastic . After the film leaves the third wheel , the hose is finished . The described method forms the outlet sl its and the track pattern in a coordinated fashion . As a result, the outlets are not restricted or plugged by the ribs .

Brief Description of the Drawings The features of specific embodiments of the best mode contemplated of carrying out the invention are illustrated in the drawings , in which: FIG . 1 is a schematic block diagram of the method for making a drip irrigation hose of the continuous emitter type; FIG. 2 is a schematic view of a portion of the film path for making a drip irrigation hose in accordance with the invention; and FIG. 3 is a side partially cutaway view of a length of drip irrigation hose incorporating the principals of the invention.

Detailed Description »Γ the Speci fic Embodiment The disclosures of Patent Nos. 4,247,05 1 , 4,984,739 and 5, 123 ,984 art; incorporated fully herein by reference.

The drip irrigation hose of thei invention is made ;from a continuous strip of flexible, water impervious piastic film, generally ranging in thickness between 4 and 15 mil. As depicted by block 10 in FIG. 1, outlets and/or inlets are formed in the strip of film along one margin. As described in more detail below, each outlet and/or inlet comprises a single longitudinal slit in die film. Next, as depicted by block 12, one or more molten plastic beads made of material compatible widi die film are deposited by an extruder on one margin of the film on either side of the outlet slits. Next, as depicted by block 14, die track pattern of the ribs is formed in the molten beads by a rib forming wheel. The track pattern is repeated each time the rib forming wheel completes a revolution. As depicted by block 16, after the ribs are formed, the margins of the film are overlapped to position between them die track pattern. Finally, as depicted by block 18, die overlapping margins are sealed by the still, molten ribs to form the finished hose. The described steps, except for formation of the outlets and/or inlets, are shown in more detail in the referenced '984 patent. Alternatively, either the inlets or the oudets could be formed as interruptions in one of die ribs.

FIG. '2 illustrates die path of a continuous strip of film 38 from which die drip irrigation hose is made between die formation of the outlets and/or inlets (block 10) and the formation of die track pattern (block 14). An outlet forming wheel 20 and a rib forming wheel 22 are mounted on a common shaft 24 to synchronize dieir operation. Wheels 20 and 22 have die same diameter. A backing wheel 26 engages outlet forming wheel 20 to establish a nip 28 therebetween. A knife blade 30 is mounted on the periphery of wheel 20. Wheel 26 has a circumferential slot 32 into which knife blade 30 fits at nip 28. Direction changing wheels 34 and 36 also define part of die film padi. Wheels 20, 22, 26, 34, and 36 have flanges to guide film 38 laterally during die manufacturing operation.

Wheel 22 has, around its periphery, impressions (hot shown) diat define die desired track pattern, for example, one of the track patterns is shown in the '051 patent or in the '739 patent. The direction of movement of film 38 is depicted by the arrows in FIG. 2. Film 3S is wrapped around wheel 26 to reverse direction and pass into nip 28. As a result, a slit is formed . in film 3S each time blade 30 passes into nip 28. A slit is formed each time wheel 20 completes one revolution. After leaving wheel 26, film 38 is wrapped around wheel 34 to reverse direction and return toward wheel 20. Film 38 is wrapped around a portion of the periphery of wheel 20, spaced laterally from knife blade 30, to reverse direction. After leaving wheel 20, film 38 is wrapped around wheel 36 to reverse direction and move toward wheel 22. Wheel 22 could be canted slightly to provide a smooth transition in the film padi between wheels 20 and 22 , and the film could twist slightly between wheels 3 6 and 22 . Be tween whee l s 3 6 and 22 , f i lm 38 pas s es unde r ; ex t rude r ( no t shown ) whi ch dep o s i t s two molten plastic beads on die margin of film 38. A backing wheel (not shown) underlies wheel 22 to If the inlets also comprise slits another knife blade is mounted on the periphery of wheel 20 laterally spaced from knife blade 30 and wheel 26 has another circumferential slot laterally spaced from slot 32 into which the other knife blade fits. The inlets as well as the outlets are formed as the respective knife blades pass into nip 28.

In FIG.3, the completed drip irrigation hose is shown. Strip 38 is bent along its length to form an overlapping longitudinal seam between an interior margin and an exterior margin of the strip. Spaced apart, transverse ribs 42 and 43 extend longitudinally through the seam to :onne t the margins of strip 38, forming a seal and a flow regulating passage 44 therebetween. A water supply passage 45, having a much larger cross-section area then flow regulating passage 4- is defined by the remainder of strip 3S. Longitudinally spaced apart slits 46 in the portion of strip 33 between supply passage 45 and flow regulating passage 44 serve as inlets to flow regulating passage 44. Longitudinally spaced apart slits 47, formed in the exterior margin of strip 38, serve as outlets from the hose. Slits 47 are displaced from the respective slits 46 to provide a substantial path length from each inlet to a respective outlet. Preferably, cross ribs 48 are employed to divide the flow regulating passage into segments, such that slit 46 is at one end of the segment and a slit 47 is at the other end of a segment. Alternatively, the inlets could be formed by interruptions in rib ~2 as illustrated in FIGS.5 and 6 of the '051 patent and as illustrated in the '739 patent. The shape of ribs 42, 43 and 48 are determined by the track pattern on wheel 22 (FIG.2). Preferably, chevrons are formed on the adjacent interior surfaces of ribs 42 and 43 to create turbulent flow in the flow regulating passage as illustrated in the '739 patent.

By controlling the length of the slits and the flexibility of the film, water drips from the outlets when the hose is pressurized without clogging when the hose is depressurized. Typically, the line pressure of the water used for crop irrigation ranges from about 4 psig to 14 psig. Slits 47 are sufficiently long and strip 38 is sufficiently flexible so the water drips from the outlets when the hose is pressurized, rather than squirting. The effective area of the outlets remains small because the material on both sides of die slits remain in the same plane, rather than buckling. If the slits are too short or the strip is too rigid, the material on either side of the slits does not move sufficiently to make a large hole when the hose is pressurized and water squirts out the hose and erodes the soil. Slits 47 are sufficient short and strip 38 is sufficiently rigid so the outlets close completely when the hose is depressurized. If the slits are too long or die strip is too flexible, the slits do not close when the hose is depressurized. Typically, the slits are about 1/4 inch for a 4 mil film thickness and the slits are about 3/8 inch for a 15 mil film thickness. Thus, if the slits are much shorter than about 1/4 inch for a 4 mil film thickness or if the film is much thicker than about 4 mil for a slit length of about 1/4 inch, the water may squirt from the outlets. Similarly, if the slits are much longer than about 3/8 inch for a 1 mil film thickness or if the film is much thinner than about 15 mil for a slit length of about 3/8 inch, the outlets may not close after die hose is depressurized.

The described embodiment of the invention is only considered to be preferred and illustrative of the inventive concept; the scope of the invention is not to be restricted to such embodiments . Various and numerous other arrangements may be devised by one skilled in the art without departing from the spirit and scope of this invention.

Claims (6)

117,428/3

1. Apparatus for making drip irrigation hose comprising: an outlet port forming wheel (20) having a knife blade (3D) on its periphery; means (26) for wrapping a continuous moving sh ip of plastic film around the wheel lo form slit outlets repeatedly in one margin of the strip with the knife blade; means (22) for forming a desired (rack pattern repeatedly on one margin of the film in predetermined relationship with (he knife blade formed outlets; means ( 1 6) for overlapping the margins of the film to form a water supply passage; means ( 1 ) for sealing the overlapping margins (o form therebetween a flow regulating passage through the track patterns to the outlets; anil means for repeatedly forming inlets ( 1 0) from the water supply passage to the flow regulating passage so a track pattern lies between each inlet and outlet.

2. The apparatus of claim 1 , in which the pattern forming means comprises a (rack pattern forming wheel, means for wrapping the strip of plastic film around the track pattern forming wheel to form the (rack patterns, and means for coupling (he track pattern forming wheel to the outlet port forming wheel to operate in synchronism therewith.

3. Hie apparatus of claim 2, in which the coupling means comprises a shaft connected between the wheels.

4. Λ method for making drip irrigation hose comprising the steps of: repeatedly forming slit outlets ( 10) in one margin of a cont inuous moving strip of plastic film with a kni fe blade; repeatedly forming a desired track pattern ( 14) on one margin of the film in predetermined relationship with (he outlets; overlapping the margins of the film ( 16) to form a water supply passage; sealing the overlapping margins ( 1 8) to form therebetween a flow regulating passage through the track patterns lo the outlets; and repeatedly forming inlets from the water supply passage lo (he flow regulating passage so a track pattern lies between each inlet and outlet.

5. The method of claim , in which the step of forming sl it outlets comprises wrapping the str ip of plaslic film around a wheel having a knife blade on its periphery to form a slit outlet each time the wheel rotates,

6. The method of claim 5, in which the step of forming a desired (rack pattern comprises depositing one or more molten plastic beads on the one margin of (he film, wrapping (he strip of plastic film around a (rack pattern forming wheel lo form a (rack pattern in the one or more molten beads each time the (rack pattern forming wheel rotates, and coupling (he (rack pattern forming wheel to the outlet port forming wheel lo operate in synchronism therewith. For the Applicant, Saiaford T. Colb & Co. C:°24592