Method of manufacture of a drip irrigation hose
A drip irrigation hose of the continuous emitter type in which the outlets from the regulating passage each comprise a single longitudinal slit. 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. The slits are sufficiently long and the film is sufficiently flexible so the water drips from the outlets when the hose is pressurized. The slits are sufficiently short and the film is sufficiently rigid so the outlets close completely when the hose is depressurized. An outlet forming wheel has a knife blade on its periphery. A backing wheel engages the outlet forming 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 nip. A rib forming wheel has around its periphery impressions that define a desired track pattern for the ribs. The outlet forming wheel and the rib forming wheel are mounted on a common shaft to operate in synchronism. A continuous strip of plastic film is directed in a path that reverses direction four times to accommodate these wheels.
1. A method for making drip irrigation hose comprising:
rotating an outlet forming wheel having a knife blade on its periphery;
positioning a backing wheel to engage the outlet forming wheel and establish a nip, the backing wheel having a circumferential slot into which the knife blade fits as the outlet forming wheel rotates;
moving a strip of plastic film through the nip to form single slit outlets repeatedly along the strip as the knife blade rotates;
forming on the strip an elongated flow regulating passage; and
forming inlets to the flow regulating passage that are spaced from the outlets to form a substantial path length from each inlet to a corresponding outlet, wherein the outlets couple the flow regulating passage to the exterior of the hose.
2. The method of claim 1 , wherein the strip of plastic film has first and second margins, and wherein the method further comprises overlapping and sealing the first and second margins to form a tube from the strip of plastic film.
3. The method of claim 2 , wherein the flow regulating passage lies between the overlapping margins.
4. The method of claim 1 , wherein the step of forming a flow regulating passage overlaps and seals margins of the strip between the inlets and the outlets, wherein the outlets couple the flow regulating passage to the exterior of the hose.
5. The method of claim 1 , in which the outlet forming wheel is rotated such that the knife blade forms slits that close completely when the hose is depressurized.
6. The method of claim 5 , in which the strip is flexible, additionally comprising partially wrapping the strip around one of the wheels as the strip moves through the nip.
7. The method of claim 1 , in which the strip is flexible, additionally comprising partially wrapping the strip around one of the wheels as the strip moves through the nip.