Flow control devices particularly useful for drip irrigation

Fluid flow control devices are described particularly useful as drip irrigation emitters provided with flow regulation to reduce their pressure-sensitivity, thereby enabling them to be used in long lines and in undulating terrain. The disclosed devices include a first flexible plastic strip bonded on one surface to a second plastic strip along bond lines defining a pressure-dropping passageway. A third plastic surface is bonded to the opposite surface of the first flexible plastic strip along bond lines defining therewith a static pressure chamber in which the first flexible plastic serves as a common wall with the chamber and the passageway for at least part of the length of the passageway. Thus variations in the velocity of the fluid through the pressure-dropping passageway causes the common wall to be flexed to vary the cross-sectional area of the passageway and thereby to regulate the fluid flow therethrough. Both linear-source emitters and point-source emitters are described.

RELATED APPLICATIONS 
This application is related to my copending application Ser. No. 715,550 
filed Aug. 18, 1976 titled "Fluid Flow Control Devices Particularly Useful 
in Drip Irrigation". 
BACKGROUND OF THE INVENTION 
The invention relates to fluid flow control devices. The invention is 
particularly useful in producing drip irrigation emitters, and is 
therefore described below with respect to this application. 
One of the newest and most rapidly developing techniques for irrigating 
plants is by drip irrigation, in which emitters connected to water 
conduits are used for supplying a continuous, slow trickle of water to the 
plants. Most of the known systems use individual emitters, known as 
point-source emitters, individually coupled to the water conduits at 
longitudinally spaced points. Also known are linear-source emitters in 
which the water conduit itself is provided with a plurality of emitter 
openings spaced longitudinally of the conduit. 
My above-cited application Ser. No. 715,550 discloses fluid flow control 
devices particularly useful as drip irrigation emitters of the type 
including a flexible plastic strip bonded on one surface to a second 
plastic surface along bond lines defining therebetween a pressure-dropping 
passageway having an inlet at one end for receiving pressurized fluid from 
a conduit, and an outlet at the opposite end for outletting the fluid at a 
low flow rate. 
SUMMARY OF THE PRESENT INVENTION 
The present invention is directed to fluid flow control devices of the 
foregoing type to provide flow regulation of the fluid outputted by the 
device. 
According to the present invention, there is provided a fluid flow control 
device particularly useful as a drip irrigation emitter comprising a first 
flexible plastic strip bonded on one surface to a second plastic surface 
along bond lines defining therewith a pressure-dropping passageway having 
an inlet at one end for receiving pressurized fluid from a conduit and an 
outlet at the opposite end for outletting the fluid, characterized in that 
the device includes a further plastic surface, bonded to the opposite 
surface of the first flexible plastic strip along bond lines defining 
therewith a static pressure chamber in which the first flexible plastic 
strip serves as a common wall with said chamber and said passageway, the 
static pressure chamber having an inlet at one end for receiving 
pressurized fluid from the conduit, whereby variations in the velocity of 
the fluid through said passageway causes said common wall to be flexed to 
vary the cross-sectional area of the passageway and thereby to regulate 
the fluid flow therethrough. 
It will thus be seen that the present invention regulates fluid flow by 
utilizing the "Bernoulli effect", namely, the phenomenon of internal 
pressure reduction with increased stream velocity in a fluid. Thus, the 
flexible common wall is subjected, on one face, to the inlet pressure from 
the static pressure chamber, and on the opposite face to the internal 
pressure of the fluid within the passageway which internal pressure varies 
with fluid velocity. Accordingly, if the fluid flow increases, the 
internal pressure in the passageway drops, thereby causing the pressure on 
the opposite face of the flexible common wall, namely that of the static 
pressure chamber, to deflect the common wall such as to reduce the 
cross-sectional area of the passageway and thereby to reduce the fluid 
flow. 
According to the preferred embodiments of the invention described in the 
present application, the second plastic surface is a second flexible 
plastic strip bonded to one face of the first flexible plastic strip and 
forming said pressure-dropping passageway therewith; and the further 
plastic surface is a third flexible plastic strip bonded to the opposite 
face of the first strip and forming the static pressure chamber therewith. 
Several linear-source emitter embodiments of the invention are described 
below wherein the device further includes a conduit formed of flexible 
plastic material, the first, second and third plastic strips constituting 
the lapped ends in a seam of the conduit bonded by said bond lines, the 
bond lines having a gap providing communication between the interior of 
the conduit and the inlets of the pressure-dropping passageway and the 
static pressure chamber formed in said seam. 
Point-source emitter embodiments of the invention are also described 
wherein the device includes a connector attached to the device at the 
inlets of the pressure-dropping passageway and static pressure chamber for 
connecting both to a conduit. 
The first, second and third flexible plastic strips may all be made of the 
same material heat-bondable to each other. 
However, the invention may also advantageously be used wherein the second 
and third flexible plastic strips are made of the same material, and the 
first flexible plastic strip is made of a different material which 
produces a strong bond with the material of the second and third flexible 
plastic strips. This feature enables strong inexpensive materials to be 
used for the second and third strips, and to be strongly bonded by the use 
of a material for the first strip which produces both a strong bond with 
the latter materials, and also a very flexible or pliable common wall 
between the static chamber and the pressure-dropping passageway. 
Further features and advantages of the invention will be apparent from the 
description below.

DESCRIPTION OF SEVERAL PREFERRED EMBODIMENTS 
The device in FIG. 1 is a linear-source emitter made by bonding, in the 
manner described in the above-cited copending patent application, two end 
strips 312, 313 (FIGS. 1a-1c) of a flexible plastic sheet along bond lines 
314, 316, to define a conduit 300 and a seam including a pressure-dropping 
passageway 318 having an inlet 320 and an outlet 322. In this case, 
however, an additional strip 311 of flexible plastic sheet material is 
inserted between the two end strips 312, 313 before they are bonded 
together by the plastic-welding dies. Thus, when the dies are applied, the 
inner face of strip 312 is bonded to one face of strip 311 along the bond 
lines 314, 316, and the inner face of strip 313 is bonded to the opposite 
face of strip 311 along the same bond lines. 
Accordingly, the intermediate strip 311 (hereinafter sometimes referred to 
as the first strip) is bonded to one face to strip 312 (hereinafter 
sometimes referred to as the second strip) along bond lines 314, 316, 
forming with the latter strip the pressure-dropping passageway 318, which 
passageway has an inlet 320 (FIG. 1a) communicating with the interior of 
conduit 300, and an outlet 322 (FIG. 1c). 
The intermediate or first strip 311 is also bonded, on its opposite face, 
to strip 313 (hereinafter sometimes referred to as the third strip) along 
the same bond lines 314, 316, forming a chamber 330 having, at one end, an 
inlet 322 (FIG. 1a) communicating with the interior of conduit 300, but 
closed at its opposite end by bond line 316, as shown in FIG. 1c. Chamber 
330 thus acts as a static pressure chamber having an internal pressure 
equal to the pressure within conduit 300 at the location of the particular 
drip emitter element 301, 302. 
The intermediate strip 311 serves as a common wall between the static 
pressure chamber 330 and the passageway 318 for the complete length of the 
latter passageway. This common wall, being of flexible plastic material, 
will be deflected to decrease or increase the cross-section area of 
passageway 318 according to the pressure differential on its opposite 
faces. The pressure on the chamber 313 side of wall 311 is constant, and 
depends on the pressure of the fluid at that particular location within 
conduit 300, which pressure is transmitted to chamber 330 via inlet gap 
332. On the other hand, the pressure on the passageway 318 side of the 
wall 311 varies with variations in the velocity of the fluid flowing 
through the passageway in accordance with the "Bernoulli effect". Thus, an 
increase in the flow rate causes a reduction in the passageway pressure 
and thereby a deflection of the common wall 311 into the passageway, 
restricting its cross-sectional area and reducing the flow rate of the 
fluid therethrough. Accordingly, the output of each of the drip emitter 
elements 301, 302, etc. along the conduit will remain substantially 
constant notwithstanding variations in the pressure of the water within 
the conduit at the particular location of the emitter element. 
Strip 312 is of shorter width than the two strips 311 and 313. Strip 311 is 
first continuously bonded along its outer edge to strip 313 to produce 
bond line 316 (FIGS. 1a-1c), and is then bonded to strip 312 along upper 
bond line 314 having the inlet gaps 320 and along the lower bond line 316 
having gaps 336. Thus, the passageway 318 between strips 312 and 311 will 
be open (FIG. 1c) to permit the emission of the water, whereas the 
corresponding end of chamber 330 between strips 311 and 313 will be closed 
to provide the static pressure chamber for effecting the flow regulation 
through outlet 322 of the passageway 318. 
Preferably, strip 311 includes an opening 338 (FIG. 1a) at the inlet ends 
320 332 of the passageway 318 and chamber 330, respectively, to assure 
that the water from conduit 300 will enter both the passageway and the 
chamber. 
FIG. 2, which is a fragmentary view corresponding to FIG. 1c, illustrates a 
variation wherein, instead of including opening 338 in strip 311, the 
latter is folded or lapped at its inner edge, as shown at 311a, to provide 
a thickened edge which assures the communication between conduit 300, 
passageway 318, and chamber 330. 
FIG. 3 illustrates a slight variation. Instead of using the above-described 
two-step bonding process to produce the open outlet 322 in passageway 318 
and the closed end of the static pressure chamber 330, the three strips 
are bonded at one time, but a ridge 340 is provided in bond line 316, the 
ridge being below the lower edge of strip 212 so that it closes the end of 
the static chamber between strips 311 and 313, but leaves open the end of 
the passageway between strips 311 and 312. 
FIG. 4 illustrates a further variation wherein the intermediate strip (311 
in the FIG. 1 emnbodiment) does not extend for the complete length of the 
seam, but rather is provided only at the outlet end of the passageway 318, 
as shown at 351. Its upper edge 351' is below the upper edge of the last 
two transverse bond lines 345' defining the outlet end of the 
pressure-dropping passageway 318, and its lower edge 351" is below the 
outlet end section 346' of the outer bond line 346. Thus, a static 
pressure chamber 330' is formed only co-extensive with the last leg of the 
pressure-dropping passageway 318, this chamber being opened to the conduit 
300 at its inner end, and being closed at its outer end by bond line 346'. 
Obviously, strip 351 could extend for two or more of the end legs in the 
passageway. 
FIG. 5 illustrates a still further variation, wherein the drip emitters 
301' (only one being shown) are formed with pressure-dropping passageways 
318' having two (or more) legs or loops between the bonded seam strip 
312', and the intermediate strip 311'. As in the above described 
embodiments, the bond lines are applied so as to form the gap defining the 
passageway inlet 320' (FIG. 5a) communicating with the interior of conduit 
300, and the passageway outlet 322' (FIG. 5b). It will be appreciated that 
the static pressure chamber 330' produced between strips 311' and 313' 
will be co-extensive with the fluid passageway 318', as in FIGS. 1-3, 
chamber 330' being open at the inlet 332' (FIG. 5a) end to provide 
communication with the interior of conduit 300, and being closed at the 
opposite end (FIG. 5b). 
FIGS. 6, 6a and 6b show how the invention could also be advantageously used 
in producing point-source emitters individually attached to the conduit by 
connectors. Thus, each emitter is formed of three flexible plastic strips, 
namely the two outer strips 362, 363, and the inner strip 361, bonded 
together along bond lines 364, 366 to define the pressure-dropping 
passageway 368 between strips 361, 362 and the static pressure chamber 373 
between strips 361 and 363. A connector 375 is inserted into the inlet end 
of the emitter and includes a bore 376 to provide communication between 
the conduit into which the drip emitter is inserted and the inlet end of 
the pressure-reducing passageway 368, as well as the inlet end of the 
static pressure chamber 373. The opposite end of the emitter is 
constructed as described above with respect to FIG. 1, to open the outlet 
and 322' of the passageway 368 and to close the corresponding end of the 
static pressure chamber 373. 
The device illustrated in FIG. 7 (and its sectional views FIGS. 7a, 7b, 7c) 
is similar to that of FIG. 3, except that instead of one bond line (340) 
applied between the first plastic strip (311) and third plastic strip 
(313), there are provided two spaced bond lines 440, 441 which define a 
passageway 442 providing communication between the outlet end of one 
static chamber (430a) between the strips 411, 413, and the inlet end of 
the next static chamber (430b). 
FIGS. 8 and 9 (including their respective sectional views FIGS. 8a-8c and 
9a) illustrate a still further variation wherein two static chambers are 
formed, one on each side of the pressure-dropping passageway. 
Thus, as shown particularly in FIGS. 8a-8c, the device includes a fourth 
plastic strip 514 adjacent to, and joined continuously along, the bottom 
of the second plastic strip 512. The first plastic strip 511 is also 
joined continuously along the bottom of the third plastic strip 514. This 
arrangement may be conveniently provided by folding over the two lapped 
ends of the plastic strip used for making the conduit 500 and the seam, so 
that one folded end defines the two adjacent plastic strips 512, 514, and 
the other folded end defines the two adjacent plastic strips 511, 514. Now 
if all four plastic strips are bonded along the upper bond lines 515 
provided with the inlet gaps 520, and the lower bond lines 516 provided 
with the outlet gaps 522, it will be seen that: a pressure-dropping 
passageway 518 is formed between plastic strips 511 and 512; one static 
chamber 530a is formed on one side of the passageway 518 between strips 
512 and 514; and a second static chamber 530b is formed on the other side 
of passageway 518 between strips 511 and 513. To assure communication 
between the inlets of the two static chambers and the pressure-dropping 
passageway, the inner strips 511 and 512 are preferably formed with 
openings 538a and 538b (FIG. 8a), respectively, near their inlet ends. 
FIGS. 9, 9a illustrate a modification in the device of FIG. 8 wherein the 
pressure-dropping passageway is a short single-leg one rather than a 
meandering or multiple-leg one. Thus, the transverse bond lines 617a, 617b 
define a converging single-leg passageway 618 between the two inner strips 
611, 612, which strips are provided with openings 628, 638b near the inlet 
to apply the inlet pressure to the two static chambers on opposite side of 
the passageway. It will be appreciated that water does not enter the seam 
between the passageways 618 by virtue of the longitudinal bond lines 614, 
616 which are provided with gaps only at the transverse bond lines 617a, 
617b. 
It will also be appreciated that the same four-strip double-static-chamber 
arrangement can be used in the point-source emitter, e.g. of FIG. 6. 
FIG. 10 illustrates a further variation particularly useful in the 
point-source emitter construction. The device of FIG. 10 is similar to 
that of FIG. 6 in that it includes the three plastic strips 761, 762, 763 
bonded together along bond lines defining a pressure-dropping passageway 
768 between strips 761 and 762, and a static pressure chamber 773 between 
strips 761 and 761. However, in this construction, the inlet end of the 
static chamber 773 communicates with passageway 768 via an opening 780 
formed in the inner strip 761. The inlet end 720 and the outlet end 722 of 
passageway 768 are open, whereas the two ends of the static chamber 773 
are closed. Accordingly, the pressure in the static chamber will be 
determined by the location of opening 780 in the middle strip 761. Since 
the pressure in the static chamber is a factor determining the degree 
passageway 768 will be varied with pressure, the output rate of the 
emitter can be fixed by merely providing the middle strip 761 with the 
opening 780 at the appropriate location. This substantially simplified the 
production of emitters for different flow rates. 
It will be appreciated that the foregoing feature of FIG. 10 could also be 
used in the linear-source emitter constructions and in the 
double-static-chamber constructions described above. It will also be 
appreciated that the double-static chamber constructions could use four 
separate strips, the two inner strips being continuously bonded at their 
lower edges to their respective outer strips, with the upper edges of the 
inner strips being formed with the folded ends as shown at 311a in FIG. 2 
to assure communication between the interior of the conduit, the 
passageway, and the two static chambers on opposite sides of the 
passageway. 
Examples of flexible plastic strip material that could be used are 
polythylene, polylvinyl chloride, chlorinated polyethylene, polyvinylidene 
chloride, and various blends thereof. The intermediate strips should be 
very pliable and could be selected of a material strongly bondable to the 
outer strips; examples of such materials include polyvinylidene chloride 
for the inner strip and polyethylene, PVC, or nylon-reinforced PVC for the 
outer strips. The strip materials preferably would be in the form of 
sheets as described above, but could be originally in the form of thin 
tubular extrusions subsequently bonded along one edge to form the seam, 
with the intermediate strips being inserted into the tubular extrusion 
before the bonding step. 
Many other variations and applications of the invention will be apparent.