Note: Descriptions are shown in the official language in which they were submitted.
CA 02239153 1998-10-21
DRIP IRRIGATION HOSE AND METHOD OF ITS MANUFACTURE
Field of the Invention
This invention relates to the field of drip
irrigation and, more particularly, to a turbulent, high
flow drip irrigation hose and method for its manufacture.
Back4round of the Invention
Drip irrigation hose can be classified as having
either discrete emitters or continuous integral emitters.
An example of discrete emitters is shown in U.S. Patent
No. 4,850,531. An example of continuous integral
emitters is shown in U.S. Patent No. 4,247,051.
A design objective of drip irrigation hose is
uniformity of the drip rate from each emitter. Since the
water pressure in a drip irrigation system varies as a
function of elevation of the field, it is customary to
incorporate a pressure regulating mechanism into the
emitters. Turbulent flow is less sensitive to pressure
variation than laminar flow. Accordingly, it has become
common practice for drip irrigation hose to employ a
serpentine flow regulating passage as continuous integral
emitters to promote turbulent flow. An example of such
drip irrigation hose is disclosed in U.S. Patent No.
4,984,739, where a series of staggered, upstream angled
chevrons or weirs form the serpentine passage.
In a typical drip irrigation hose with continuous
integral turbulent flow emitters, the emitters comprise a
flow regulating passage formed by ribs that also seal the
overlapping margins of an elongated bent sheet of plastic
film. The passage is divided by cross ribs to form flow
regulating segments. The bent film forms an elongated
water supply passage having a large diameter. An inlet
is formed from the water supply passage to one end of
each segment of the flow regulating passage. An outlet
is formed from the other end of each segment of the flow
regulating passage to the exterior of the hose. Between
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CA 02239153 2001-07-31
the inlet and outlet., each segment has staggered,
upstream angled chevrons.
Complications can occur when the dimensions of this
type of drip irrigation hose are changed to increase the
flow rate. General.7_y, the flow rate can be increased by
decreasing the length of the segments, increasing the
height of the ribs, or increasing the separation between
the ribs of the flow regulating passage. However, these
measures tend to decrease the reliability and uniformity
of the product and t:o cause the water to squirt out of
the outlets because the line pressure is not fully
dissipated by the flow regulating passage.
Summary of the Invention
The present inventlOrl provides a drip irrigation
hose made from a water impervious material comprising:
an elongated water supply passage having a cross
section;
a longitudinal flow regulating passage having a
cross section smaller than the cross section of the water
supply passage, the flow regulating passage being
disposed along the water supply passage;
a plurality of longitudinally spaced non flow
limiting inlets from the water supply passage to the flow
regulating passage; and
a plurality of longitudinally spaced outlets from
the flow regulating passage to the exterior of the hose,
the outlets being offset from the inlets to provide two
path lengths from each inlet to a respective outlet.
Brief Description of the Drawings
The features of specific embodiments of the best
mode contemplated of carrying out the invention are
illustrated i.n the drawings, in which:
Fig. 1 is a top plan view of a drip irrigation hose
incorporating the principles of the invention with the
outer margin partially cut away;
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CA 02239153 2001-07-31
Fig. 2 is a sectional view taken through plane 2-2
in Fig. 1 illustrat;:ing two inlets to the flow regulating
passage;
Fig. 3 is a sectional view taken through plane 3-3
in Fig. 1 illustrat::ing an outlet from the flow regulating
passage;
Fig. 4 is a schematic block diagram of the method
for manufacturing t:he drip irrigation hose shown in Fig.
l; and
Fig. 5 is a perspective view of apparatus for
performing the bead laying, rib forming, film folding,
and regulating pas~~age forming steps of Fig. 4.
Detailed Description of the Specific Embodiment
As illustrated in Figs. l, 2 and 3, a drip
irrigation hose 10 is formed from a thin (e.g., 4 to 15
mil) film 12 of flexible water impervious plastic
material bent alone its length
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WO 97/19759 PCT/US95/15481
1 to form an overlapping longitudinal seam between opposing longitudinal
margins, namely an
inner margin 14 and an outer margin I6. Margins 14 and 16 are sealed together
by a
continuous repeating pattern of longitudinally eztending spaced apart ribs 18
and 20 made
of the same or compatible plastic material as film 12. Ribs 18 and 20 and
margins 14 and
16 define a flow regulating passage 22 as described in more detail in the
referenced '05I and
'739 patents. A water supply passage 24 is defined by the remainder of film
I2. At spaced
intervals, rib 18 has a series of interruptions and pillars that form inlets
26 to flow regulating
passage 22. Midway between each pair of inlets 26, an outlet 28 is formed by
one or more
holes in outer margin 16. A series of staggered chevrons 30 are formed along
the inner sides
of ribs 18 and 20 between each of inlets 26 and outlets 28. In each case, the
chevrons are
angled toward inlets 26 to promote turbulent flow along the path length from
each inlet 26
to outlet 28 of flow regulating passage 22. As illustrated in Fig. 1, inlets
26 have a
substantially larger cross sectional area than outlets 28 and the flow
regulating passages. As
a result, inlets 26 are not flow limiting. Thus, the serpentine turbulence
inducing path
lengths are arranged in back to back fashion relative to the outlets in the
sense that the
chevrons angle away from each of outlets 28, so there is parallel flow
throughout the length
of hose 10 from two of inlets 26 to one of outlets 28. The pattern of ribs
illustrated in FIG.
I is repeated continuously along the entire length of hose 10 between
overlapping margins
14 and I6. As a result, outlets 28 are spaced from each other and offset from
inlets 26,
which are also spaced from each other. Since inlets 26 are not flow limiting,
each of inlets
26 feeds two of outlets 28 and each of outlets 28 is fed by two of inlets 26.
As a result, the
flow rate through each outlet 28 is doubled because it is fed by two inlets
and two flow
regulating passages.
In operation when hose 10 is pressurized irt the field, water flows through
supply
passage 24 to inlets 26, passes from inlets 26 through flow regulating passage
22 to outlets
28, and ezits from outlets 28 to the ezterior of hose I0. Two back to back
path lengths are
formed from adjacent pairs of inlets 26 to each outlet 28, thereby doubling
the flow rate for
the dimensions of the flow regulating passage, i.e., path length, rib height
and rib spacing,
vis-a-vis the drip irrigation hose disclosed in the '739 patent. It should be
noted that cross
ribs dividing the flow regulating passage into segments as disclosed in the
'739 patent are not
required in the practice of the invention. Such cross ribs could be provided,
however, if
desired at insets 26 (or outlets 28), effectively dividing each inlet 26 (or
outlet 28) into two
inlets (or outlets) , one for each adjacent segment of the flow regulating
passage.
The method for making the described drip irrigation hose is illustrated in
FIGS. 4 and
5. As represented in FIG. 4 by a block 40, outlets 28 are first formed in film
12, preferably
in the manner disclosed in the '984 patent. Then, as represented by a block 42
inner margin
14 is folded. As represented by a block 44, one or more beads are laid on the
outside surface
of inner margin 14 by one or more extrusion nozzles. As represented by a block
46, a pattern
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W~ 97/19759 PCT/US95/15481
1 of ribs, i.e., ribs 18 and 20, is formed by a molding wheel. As represented
by a block 48,
outer margin 16 is next folded onto inner margin 14 with the formed ribs
therebetween.
Finally, as represented by a block 50, flow regulating passage 22 is finished
by passing inner
margin 14, outer margin 16, and the ribs 18 and 20 through the nip of a form
wheel and a
backing wheel to set precisely the height of ribs 18 and 20. This method is
described in more
detail in the '984 patent.
FIG. 5 illustrates apparatus for performing the steps represented by blocks 44
to 50.
One or more extrusion nozzles 52 deposit one or more continuous longitudinal
beads 54 on
the outside surface of inner margin 14. Film 12 then passes through the nip of
a rotating
molding wheel 56 and a rotating backing wheel 58. Molding wheel 56 has a
pattern of
depressions 60 corresponding to the desired rib pattern on drip irrigation
hose 10, i.e., the
pattern shown in FIG. 1. In the nip of wheels 56 and S8, beads 54 are shaped
by molding
wheel 56 to form the desired brad pattern repeatedly and continuously on film
i2 for the
entire length of hose l 0. Thereafter, external margin 16 of film I2 is folded
by a guide 62
to overlap inner margin 14. As a final step, the overlapped margins of film 12
pass through
the nip of a form wheel 64 and a backing wheel 66. Form wheel 64 has a groove
68 that
depresses the ribs formed by beads 54 to set the rib height at a specified
value that
determines the flow rate of the hose. During the described process, film 12 is
continuously
transported by conventional means not shown. For example, the disclosed wheels
could be
driven or other drive wheels could be provided to transport the film.
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.
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