Method of making fluid-issuing openings through the walls of flexible plastic members, particularly dripper emitters

Described is a method of making fluid-issuing openings through the wall of flexible plastic members, particularly fluid conduits, by forming each opening through a small radius of curvature portion of the conduit wall while the respective wall portion is of curved oblong shape in cross-section, such that during use of the conduit, it assumes a circular shape, thereby increasing the radius of curvature of the wall portion and reducing the cross-sectional area of the outer part of the opening formed therethrough. The method is particularly described for producing linear-source water irrigation emitters which have a smaller sensitivity to clogging, which are easier to clean, and which have a smaller sensitivity to pressure variations in the water supply line.

BACKGROUND OF THE INVENTION 
The present invention relates to a method of making fluid-issuing openings 
through the walls of flexible plastic members, and to fluid conduits 
having a plurality of longitudinally spaced openings through its wall for 
distributing fluid flowing therethrough under pressure. The invention is 
particularly useful in making the drip emitter openings in a water conduit 
used for drip irrigation, and it is therefore described below with respect 
to that application. 
One of the newest and most rapidly developing techniques of irrigation is 
by the use of devices, called drip emitters, which continuously supply a 
slow dribble or trickle of water to the plants. Most of the known systems 
use point-source emitters, i.e. separate drip emitter nozzles or heads 
attached to the water supply pipe. Other systems use linear-source 
emitters, e.g. arrangements wherein the drip emitter openings are formed 
in the water supply pipe itself. These openings, however, must be of very 
small diameter, in the order of 0.5 mm or less, to produce the desired low 
rate of water emission. Such small diameter openings are easily cloggable 
by foreign particles in the water supply, and when clogged, they are 
difficult to clean. Moreover, the rate of water emission through each drip 
emitter opening varies with the water pressure at that particular opening 
so that drip emitters upstream of the line, or at higher elevations, emit 
the water at a higher rate than the emitters downstream of the line, or at 
lower elevations. 
An object of the present invention is to provide a method of making fluid 
openings through the walls of a flexible plastic member, and particularly 
to a method of making drip emitter openings through the wall of a water 
conduit used for drip irrigation, which method produces advantages in one 
or more of the above respects. Another object of the invention is to 
provide flexible plastic members, and particularly drip emitter devices, 
made in accordance with the above method. 
SUMMARY OF THE INVENTION 
According to one aspect of the present invention, there is provided a 
method of making drip emitter openings through the wall of a water conduit 
used for drip irrigation, characterized in forming each opening through a 
small radius of curvature portion of the conduit wall while the respective 
wall portion is of curved oblong shape in cross-section, such that during 
use of the conduit, it assumes a circular shape, thereby increasing the 
radius of curvature of said wall portion and reducing the cross-sectional 
area of the outer part of the opening formed therethrough. 
In some of the preferred embodiments of the invention described below, the 
conduit is normally of substantially circular cross-sectional shape, each 
of the openings being formed while the respective portion of the conduit 
is squeezed to deform some into said curved oblong shape. More 
particularly, each of the openings is produced by first forming a 
longitudinal slit along the outer surface of the respective conduit 
portion, and then forming a hole through the inner surface of the 
respective conduit portion to join with the slit, the hole in the 
undeformed condition of the conduit having a diameter larger than the 
width and smaller than the length of the slit. 
The above preferred method provides a number of advantages which are 
particularly important when used in producing drip emitter irrigation 
devices. First, the fluid openings so produced are less susceptable to 
clogging. This is because the hole portion of the opening may be made of 
larger diameter than in the conventional apertured conduit type of drip 
emitter for the same flow rate, since the slit reduces the rate of flow; 
the slit is also less susceptible to clogging since a particle lodged at 
one point along its length would still permit the passage of the water 
through the remaining length of the slit. Another advantage is that should 
clogging occur, the clogged passageway can usually be cleaned by merely 
squeezing the wall to again cause the intermediate portion having the 
opening to bulge outwardly to again decrease its radius of curvature, 
which opens the passageway and permits the particle to be washed out. 
Further, fluid openings formed in conduits in accordance with this method 
tend to produce some regulation in the rate of water flow, as an increase 
in pressure at the location of the opening causes the radius of curvature 
of that conduit portion to increase, and thereby the sides of the slit to 
abut each other with greater force, which reduces the fluid flow through 
the opening. 
According to a still further aspect of the invention, there are provided 
drip irrigation devices comprising a fluid conduit having a plurality of 
drip emitter openings each made in accordance with the above method. 
While it is preferred that the conduit wall normally be of circular shape 
and be squeezed to deform same into the oblong shape at the time the 
openings are formed, as discussed above, it is contemplated that the 
conduit wall may normally (i.e. when undeformed) be of the curved oblong 
shape and be formed into a circular shape by the water pressure during 
use. The latter arrangement also provides some of the advantages of easy 
cleaning and self-regulation described above with respect to the preferred 
embodiments, even though it is more susceptible to clogging. 
Further, while the invention is preferably applied to providing the drip 
emitter openings in linear-source water irrigation emitters, other 
applications of some of the features of the invention will be apparent, 
such as in dispensing tooth-paste, glue, and the like through an opening 
in a plastic cap. According to a further aspect of the invention, 
therefore, there is provided a method of making a fluid opening through 
the wall of a flexible plastic member, comprising: squeezing opposed 
portions of the plastic member wall towards each other to deform the 
member and to cause an intermediate portion of its wall between the 
squeezed portions to bulge outwardly; forming a slit in the outer surface 
of the outwardly bulged wall portion; forming a hole through the inner 
surface of the bulged wall portion to join with the slit, the hole in the 
undeformed condition of the plastic member having a diameter larger than 
the width and smaller than the length of the slit; and releasing the 
plastic member to permit it to return to its indeformed condition. 
Further features and advantages of the invention will be apparent from the 
description below.

DESCRIPTION OF SEVERAL PREFERRED EMBODIMENTS 
The drip irrigation device illustrated in FIG. 1 is of the linear-source 
emitter type. It includes a water conduit 2 connected to a water supply 
line 4 via a pressure-regular 6, the water conduit 2 being formed with 
drip-emitting openings 8 longitudinally spaced along its length and each 
of a sufficiently small diameter so as to produce a slow dribble or 
trickle of water therethrough. As indicated earlier, the conventional 
techniques for producing the drip emitter openings 8 result in openings 
which are easily clogged, which are difficult to clean, and which produce 
non-uniform outputs according to variations in the water pressure at the 
particular location of the opening in the conduit. The present invention 
enables the apertured-conduit type of drip irrigation devices to be 
constructed providing advantages in some or all of the above respects. 
FIGS. 2a-2d illustrate the main steps in making each of the fluid openings 
8 in the drip emitter device of FIG. 1. Thus, FIG. 2a illustrates the 
normal (undeformed) condition of a section of the conduit 2 where an 
opening 8 is to be produced. As shown in FIG. 2b, opposed portions 10, 12 
of this section are squeezed towards each other to deform the conduit to a 
curved oblong or elliptical shape wherein intermediate portions 14, 15 of 
its wall between the squeezed portions 10, 12 bulges outwardly. A slit 16 
is formed in the outer surface of one (or both) of the outwardly bulged 
wall portions (this being shown in portion 14), and then a hole 18 is 
formed through the inner surface of the bulged portion to join with slit 
16. 
FIG. 2c is an enlarged view illustrating the configuration of the opening 8 
when so formed and while the conduit is still in its deformed squeezed 
condition, and FIG. 2d illustrates the shape of opening 8 after the 
conduit has been released and permitted to return to its normal undeformed 
condition. 
It will be appreciated that when the conduit is deformed as shown in FIGS. 
2b and 2c, the outer surface or skin of the conduit is under tension, 
whereas its inner surface or skin is under compression. Accordingly, when 
the outer surface is slit, as shown at 16, the outer edges of the slit 
diverge to produce the V-shaped section of the slit 16 shown in FIGS. 2b 
and 2c. Hole 18 is then formed through the V-shaped slit 16, preferably 
from the outer to the inner direction. Now when the conduit is released 
and permitted to return to its normal undeformed condition as illustrated 
in FIG. 2d, the outer surface of the conduit wall contracts and closes 
slit 16. The upper portion of hole 18 also tends to close, thereby 
producing the curved or conical juncture 20 between the upper end of hole 
18 and the lower end of slit 16. 
In FIG. 2d, slit 16 is formed of a depth less than the thickness of the 
bulged wall portion 14 so as to terminate short of its inner surface. 
Also, the diameter of hole 18 is considerably less than the length of the 
slit 16, and is considerably larger than the width of the slit in the 
normal undeformed condition of the conduit wall, as shown in FIG. 2d. 
It will thus be seen that in use, the conduit 2 will assume the circular 
cross-sectional shape of FIGS. 2a and 2d, wherein slit 16 closes but is 
not sealed, so that it permits a slow dribble of water to issue through it 
from the interior of the conduit via its respective hold 18. Because of 
the resistance to the fluid flow imposed by the slit portion 16 of the 
opening 8, the hole portion 18 of the opening may be of larger diameter 
than what would normally be required in the conventional drip emitters to 
produce the desired slow rate of emission. Accordingly, the hole portion 
18 of the opening is less susceptible to clogging than in the conventional 
devices. The slit portion 16 of the opening is also less susceptible to 
clogging since a particle lodged in one portion of its length will have 
little effect on the passage of the water through the remaining portion of 
its length. 
The openings 8 formed as described above may also be easily cleaned by 
merely again squeezing the opposed portions 10, 12 of the conduit adjacent 
to the respective opening to cause the intermediate portion 14 to bulge 
outwardly, thereby opening slit 16 and the upper end of hole 18 (as shown 
in FIG. 2b), whereupon any particles lodged in the hole or slit will 
usually be washed out. This procedure may be repeated one or more times 
until the particle is washed out. 
Further, the openings 8 made according to the method described above will 
also produce some flow regulation tending to maintain the rate of water 
output more constant than conventional holes with variations in the water 
pressure at the respective openings. This is because a higher water 
pressure within the conduit at any particular location will tend to cause 
the conduit to assume a more perfectly circular cross-section which causes 
the edges of slit 16 at that location to be pressed against each other 
with greater force, thereby decreasing the flow through the slit. 
The above method of forming the openings 8 may be implemented very easily 
in the apparatus presently used for producing the drip emitter openings in 
plastic water conduits. The present procedures use laser beams or piercing 
pins for forming the openings. The above described method may be 
implemented by merely including rollers and a slitting blade at the 
piercing station, the roller being effective to squeeze the conduit and 
hold some squeezed as the blade effects the slit and the laser beam or pin 
pierces the hold. 
FIG. 2e illustrates the hole 18 portion of the opening 8 as being formed 
along an axis 30 which constitutes a radial line through the wall of 
conduit 2. 
FIG. 3 illustrates a variation wherein the hole portion 38 of the opening 
is formed along an axis 32 which is at an oblique angle to the radial line 
30 through the conduit wall, the hole portion 38 being formed through the 
inner surface of the conduit and joining with the slit portion 36 of the 
opening as described above. 
FIG. 4 illustrates a still further variation wherein the hole portion 48 of 
the opening is formed eccentrically with respect to the slit portion 46. 
FIG. 4a illustrates the provision of two holes 48a, 48b, each passing 
through one face of the slit 46. It will be appreciated that FIGS. 4 and 
4a illustrate the squeezed or deformed condition of the conduit wall, 
corresponding to the condition illustrated in FIG. 2c. 
FIGS. 5a and 5b illustrate a still further variation, wherein the conduit 
wall 52 includes a protuberance on its outer surface, in the form of a 
longitudinally extending rib 54, in which the openings 55 (FIG. 5b) are 
produced. Thus, each opening would include a longitudinal slit 56 formed 
in the outer surface of rib 54 and a hole 58 formed through the inner 
surface of the conduit to join with slit 56. The provision of the rib 50 
provides an increased contacting surface between the sides of the slits 
56. 
FIGS. 6a and 6b illustrate a still further variation, wherein the conduit 
62 is provided with a protuberance, again in the form of a longitudinally 
extending rib 64, but in this case, it is formed on the inner surface of 
the conduit wall. The procedure for making the opening 65 is otherwise the 
same as described above, wherein the sides of the conduit 62 are squeezed 
towards each other to cause the portion containing the rib 64 to bulge 
outwardly, at which time the slit 66 is formed followed by the formation 
of the hole 68. 
FIGS. 7a and 7b illustrate a variation of FIGS. 6a and 6b, in that no hole 
(comparable to hole 68 in FIG. 6b) is formed through the inner rib 74 of 
the conduit 72 of FIGS. 7a and 7b, but rather a portion 79 of the rib 74 
is removed on one side of its slit 76. 
FIGS. 8a and 8b illustrate a further possible variation of the invention. 
Whereas in the above-described embodiments, the conduit is normally (i.e. 
when undeformed) of circular cross-section, and is squeezed to produce the 
curved oblong shape at the time the openings are formed, in the embodiment 
of FIGS. 8a, 8b the conduit 82 is normally (i.e., in its undeformed 
condition) in the curved oblong shape (as shown in FIG. 8a) when the fluid 
openings 88 are formed. For purposes of example, these openings are shown 
as including the hole portion and not the slit, although of course the 
slit could also be included. When the conduit is put into use, the high 
water pressure within the conduit causes it to assume the circular shape, 
as shown in FIG. 8b, thereby increasing the radius of curvature of the 
portion of the conduit wall in which the openings 88 are formed and 
thereby reducing the cross-sectional area of the outer part of the 
openings 88. 
It will be seen that in the embodiment of FIGS. 8a, 8b, the greater the 
water pressure within the conduit at the portion thereof through which the 
respective opening 88 is formed, the more circular in shape that portion 
of the conduit assumes, and the greater will be the reduction in the 
cross-sectional area of the outer part of the respective opening 88. 
Accordingly, the arrangement of FIGS. 8a and 8b also effects some flow 
regulation with variations in pressure. Although this arrangement is more 
susceptible to clogging than the arrangements including the slit, it 
facilitates the cleaning of the openings by merely squeezing the portion 
of the conduit back to the shape illustrated in FIG. 8a, thereby enlarging 
the opening 88 and permitting clogging particle to be washed therethrough. 
Instead of making the conduit of substantially uniform wall thickness, it 
will be appreciated that the longitudinally extending strip 84 of small 
radius-of-curvature, through which the openings 88 are formed, may be of 
substantially greater thickness than the remainder of the conduit wall 82. 
Thus, the weight and manufacturing cost of the conduit would be minimized 
by having it constituted mainly of a thin wall section, sufficient to 
support the pressure of the fluid within the conduit, whereas regulation 
is still produced by providing the strip (84) with sufficient thickness to 
permit constriction of the openings (88) when the conduit is pressurized. 
Such a construction may be produced by extruding the conduit with a 
non-uniform thickness; or by first extruding a separate strip (84) in the 
shape illustrated and then bonding same to plastic sheet material forming 
the remaining, smaller-thickness conduit wall. 
It will be appreciated that the illustration of conventional holes for the 
fluid emiter openings in FIGS. 8a, 8b is purely for purposes of example, 
and that other shaped holes (e.g. the slit-and-hole configuration of the 
earlier described figures) could also be used. 
While the invention has been described with respect to the formation of 
drip emitter openings in a water irrigation conduit, this being a 
preferred embodiment, it will be appreciated that the invention could also 
be used in other applications such as the formation of openings in 
toothpaste or glue dispensers. 
Also, while in the above-described embodiments, the slit (e.g. 16), when 
included, preferably terminates short of the inner surface of the conduit, 
it will be appreciated that it, or a part thereof (e.g. the center part), 
can pass completely through the conduit wall. 
Further variations, modifications and applications of the invention will be 
apparent.