Cylindrical Emitter With Filter And Method For Injecting A Filter Into Such An Emitter

Abstract

The cylindrical emitter (3) with water filter is welded into a pipe (2), the filter develops in the internal concave surface of the emitter and is comprised of a collection channel (4) developing preferably peripherally and to an arc of large magnitude incorporating considerable number of orthogonal openings (5) formed by the side walls (11) of shallow channels (12) that cross perpendicular the collection channel (4) extended to a considerable length front and rear of the openings (5). Every opening (5) cones ponds to a shallow channel (12), the shallow channels are parallel to the flow (14) of the water and are preferably raised over the internal concave surface of the emitter. The flow in the shallow channels (12) feeds continuously the collection channel (4) irrespectible if the surface of the openings (5) is covered or not by foreign particles (15). The openings (5) and the side walls of the filter are formed with the engraving of longitudinal, shallow and preferably radial channels on the cylindrical core of the mold that forms also the internal cylindrical surface of the emitter.

Claims

1. Cylindrical emitter for irrigation welded into a pipe with screen type water filter and meandering path, said filter bearing a collection channel developed at an arc of a large length peripherally on the concave internal surface of the emitter and a plurality of consecutive orthogonal openings with the characteristic that the orthogonal openings are formed between consecutive side walls of a plurality of shallow channels and the side walls of the collection channel said shallow channels crossing perpendicular the collection channel and extending to a considerable length from both sides of it, where the length L of the shallow channels is considerably larger than the width of the collection channel, where every opening corresponds to a shallow channel, where all the shallow channels are parallel to each other having the direction of flow of the water.

2. The cylindrical emitter for irrigation welded into a pipe with water filter according to claim 1, where the cross-section of the shallow channels has trapezoidal form.

3. The cylindrical emitter for irrigation welded into a pipe with water filter according to claim 1, where the side walls of the channels are raised in relation to the internal concave surface of the emitter and open to both ends.

4. The cylindrical emitter for irrigation welded into a pipe with water filter according to claim 3, where the collection channels of the filter are more than one.

5. The cylindrical emitter for irrigation welded into a pipe with water filter according to claim 4, where the length (L) of the shallow channels of the filter is limited.

6. The cylindrical emitter for irrigation welded into a pipe with water filter according to claim 1, where the surface of the filter, develops over the surface or and at the side walls of a part of the emitter of significant width which part is raised in relation to the remaining inner concave surface of the emitter.

7. The cylindrical emitter for irrigation welded into a pipe with water filter according to claim 6, where the side walls of the shallow channels over the openings are cut off.

8. A method for the formation of a filter in a cylindrical emitter according to claim 1, wherein a mold of the cylindrical emitters is comprised of three main parts: two plates, fixable and movable respectively, for engraving the outer cylindrical surface of the emitter, and an internal core that forms the internal concave surface of the emitter, wherein the engraving for the forming of the filter is being done by engravings onto the convex surface of the core.

9. The method for the formation of a filter in a cylindrical emitter according to claim 8, wherein the longitudinal channels which forms the shallow channels are formed by a cutting tool with parallel side walls which is orientated as such as for every channel the engraving to be aligned to the radius of the core which is rotating gradually and as needed before the next engraving process.

10. The method for the formation of a filter in a cylindrical emitter according to claim 8, wherein the longitudinal channels of the core are formed by an engraving tool with a cutting blade or parallel blades and where the core remains still during the engraving process and is engraved by a vertical motion of the engraving tool, where for the next engraving the tool moves as needed in parallel.

Description

DESCRIPTION OF THE DRAWING

[0063] FIG. 1 illustrates in respective cut and spread out form the outer cylindrical surface of the emitter of the present invention with a meandering path of the state of the art.

[0064] FIG. 2 illustrates the longitudinal cross-section of the cylindrical emitter of FIG. 1 welded into the pipe with the side walls of the filter's shallow channels in the internal concave surface of the emitter.

[0065] FIG. 2.1 illustrates a detail A of FIG. 2.

[0066] FIG. 3 illustrates the cross-section A-A of FIG. 1 & FIG. 2.

[0067] FIG. 4 illustrates the cross-section B-B of the meandering path of the cylindrical emitter of FIG. 1 & FIG. 2 with the sediments of foreign particles at the bottom of the meandering path (lowest point).

[0068] FIG. 5 illustrates the cross-section C-C of the cylindrical emitter of FIG. 3 with parts of the filter at the bottom of the pipe (lowest point) and the sediments of foreign particles.

[0069] FIG. 6 illustrates a cross-section of cylindrical emitter of the present invention where the shallow channels of the filter are not raised in relation to the internal concave surface of the emitter.

[0070] FIG. 7 illustrates a cross-section of a cylindrical emitter where the site walls of the shallow channels of the filter are cut-off at the area of the collection channel, having the capability of bending.

[0071] FIG. 8 illustrates the surface of the flat filter of a linear emitter of the state of the art with the shallow channels of the filter perpendicular to the flow of the water in the pipe, and being submerged in the flat surface of the emitter.

[0072] FIG. 8.1a illustrates the transversal cross-section D-D of the filter of the state of the art of FIG. 8 in the phase where the openings are covered by grains.

[0073] FIG. 8.1b & FIG. 8.1c illustrate the cross-section E-E of the filter of the state of the art of FIG. 8 & FIG. 8.1a with the flow as it is developed in cases of laminar and turbulent flow respectively.

[0074] FIG. 8.1d illustrates the cross-section E-E of the filter of the state of the art of FIG. 8 with the foreign particles covering the entire surface and are developed at continual rows one behind the other along the flow of the water in the pipe.

[0075] FIG. 8.1e illustrates a cross-section Z-Z of the filter of the state of the art of FIG. 8 & FIG. 8.1a in the phase where the flow is divided entering trough the orthogonal openings into the emitter.

[0076] FIG. 8f illustrates the cross-section of an emitter with internal smooth filter of the state of the art occupying an arc of limited length of the internal surface and the opening's side walls being parallel to each other.

[0077] FIG. 8fH illustrates a cross-section of an emitter of the present invention combining the internal smooth filter of an arc of limited length of the state of the art with the shallow channels and the side walls protruding vertically over the collection channel.

[0078] FIG. 9, FIG. 9.1 illustrate transversal cross-sections of a cylindrical emitter of the present invention where the surface of the filter develops and protrudes over the concave or the flat surface respectively of a raised part of considerable width and height.

[0079] FIG. 9.2 illustrates the cross-section D-D of FIG. 9, FIG. 9.1.

[0080] FIG. 9.3 illustrates a cross-section of an emitter of the present invention where the filter develops over an inclined surface.

[0081] FIG. 10 illustrates another variation where both the collection channel of the filter and the shallow channels develop along the flow direction. The design illustrates a view of the internal concave surface of the emitter at the direction Y of FIG. 10a.

[0082] FIG. 10a illustrates the cross-section H-H of FIG. 10.

[0083] FIG. 11 illustrates a cross-section of linear emitter of the present invention where the filter develops over a concave surface of the emitter.

[0084] FIG. 12, 13 illustrate a view and cross-section respectively of a mold for the forming of the filter of the present invention.

[0085] FIG. 14 illustrates a detail of the engraving of the core of FIG. 13.

[0086] FIG. 15 illustrates a detail of a variation of the engraving of the core of FIG. 13.

[0087] FIG. 16 illustrates a variation of FIG. 12,13 where the core consists of two parts.

DETAILED DESCRIPTION OF THE INVENTION

[0088] FIG. 1, 2, 2.1, 3, 4, 5 illustrate a cylindrical emitter 3 welded into the pipe 2 with a peripheral filter at the water inlet. The water moves in the pipe 2 and enters in the area of the collection channel 4 of the inlet filter through a plurality of openings 5. From the channel 4 and through the path 6, it passes to the meandering path 7, where the water undergoes a predetermined pressure drop. From there it passes through the longitudinal wide zone 7a to one of the peripheral rings 7c1 or 7c2 and finally exits with a low discharge on the soil through the exit hole 8 of the pipe.

[0089] The collection channel 4 of width b includes a large number of consecutive openings 5 of orthogonal cross-section a*b, being developed peripherally onto the internal concave surface of the emitter and onto an arc of considerable length that could cover an angle up to 330°. The filter could be divided in two facing groups of collection channels connected together through an intermediate channel (not drawn).

[0090] The openings 5 are arranged preferably along the large dimension b towards the direction of flow 14 of the water in the pipe being formed by the shallow channels 12, extending to a considerable length L front and back of the collection channel 4. More specifically, the openings 5 are formed between the consecutive side walls 11 of the shallow channels and the collection channel 4 which they cross over it perpendicularly. On every opening 5 of the collection channel 4, corresponds a shallow channel 12, all the channels 12 are parallel to each other, as they are similarly parallel to the flow 14 of the water in the pipe and preferably are raised over the internal concave surface of the emitter 3.

[0091] The local protrusion of the shallow channels 12 causes the minimum reduction of the free cross-sectional of the pipe for two reasons: on one hand is their limited length L since they are so effective that do not require to take over the entire length of the emitter, and on the other hand is their orientation in relation to the direction 14 of flow of the water in the pipe. Supposedly the mean width a of the cross-section of the shallow channel 12 is the same with the width of the side wall 11, then the reduction of the free cross-section is half in relation to the respective of the state of the art where the channels are perpendicular to the flow 14 in the pipe.

[0092] For comparison and in contradiction, FIG. 8 illustrates the shallow channels of WO 2009/104183 that are perpendicular towards the flow 14, are submerged with closed ends internally to the surface of the emitter restricting the flow with their entire frontal surface, as illustrated in cross-section (FIG. 8.1a) perpendicular to the flow 14.

[0093] The sizes of the grains 15 are divided, as already described, in three categories: (a), (b) & (c).

[0094] As far as the sediments are concerned they are categorized as follows:

[0095] 1) Sediments 10 developing along the bottom of the pipe and are caused due to the gravity component. See FIG. 4.

[0096] 2) Sediments that are gathered selectively over the openings 5 of the filter and are caused by the foreign particles 15 that are dragged along from the stream 14a of the main flow 14 of the water that is detached in order to enter into the emitter through the openings 5.

[0097] FIG. 4 illustrates an additional issue of cylindrical emitters (in comparison to the linear ones) the sediment internally to the emitter and more specifically at the bottom of the meandering path 7, obviously from grains of sizes (b) & (c). The meandering path 7 of these emitters is of extremely long length which is developed peripherally with alternating high and low point and continual siphoning (typical case of “U” shaped pipe). See FIG. 1.

[0098] The worst combination happens when a part of the collection channel 4 with the opening 5 is led at the bottom of the pipe 2.

[0099] Furthermore, even in this particular worst case scenario, the sediment 10 is not possible, due to the development of the collection channel 4 onto an arc of considerable length, to cover the terminal openings 5 that are developed diametrically opposite to each other.

[0100] FIG. 5 demonstrates the operational mechanism of the passive self-protection system. The flow at the shallow channels 12 is continuous and feeds continuously the collection channel 4 and the openings 5 even when the surface of the openings 5 and the collection channel 4 is covered by grains of foreign particles, as it is described later on.

[0101] In case where the surface is covered by foreign particles and the flow is disrupted, the shallow channels 12 feed again continuously, not from the surface, but underneath with the aid of a “bypass” through narrow gaps 16 that are created at the bottom of the shallow channels 12 under the grains 15. The mechanism of passive self-protection and the capability of self-cleaning differs considerably and for many reasons from the state of the art.

[0102] In case that, large (a), or medium size (b) grains 15 are gathered over a shallow channel 12, due to their arrangement parallel to the flow 14, and the small gaps 16 that are created between the bottom of the channel 12 and the overlying grains which allows an underneath water flow, a continuous and smooth fluid sublayer is created under the grains alongside the shallow channel 12 that permits a continual rolling and sliding of them, causing ultimately their rejection at the open ends of the shallow channel. The grains during their continuous moving and rolling are neither changing any path levels, nor they face any resistance by construction elements (walls or bars) or any recess or sink at the bottom.

[0103] Due to the fact that there is intense and continuous water flow not only in the gap 16 under the grains but over them as well, which is caused exactly on the fact of the parallel arrangement itself in relation to the flow 14, the grains “roll” or “slide” constantly on the shallow channels, pushed from the pressure forces exerted on their frontal surface by the flow at the points of “impact” and zero velocity conditions (Bernoulli principle). This force, in contradiction to the state of the art, is exerted on every single one separately, thus removing and rejecting them one by one from the open ends of the channels 12.

[0104] In case a grain (a) remains partially stuck inside one of the shallow channels 12, the gap 16 between the bottom of the channel and the overlying grain 15 shall remain open for the free passage of the water and shall not be blocked by dust (c), since dust at the channels 12 does not remain still, but moves around constantly along with the flow, until it is completely removed from the emitter.

[0105] In case the cross-section 16, is blocked completely, the pressure force according to the Bernoulli principle will be exerted immediately at its maximum (on the entire frontal surface of the grain) thus removing it. This pressure force, due to the continuous motion, will act upon every single grain separately, and not to a immobilized row (it will not be allocated or weakened).

[0106] An additional advantage as illustrated in the figures is the cross-section of the channels that could be of trapezoidal “Δ” shape with narrower top D.sub.2 in relation to the base D.sub.1. This fact on its own ensures thinner cross-sections (mesh) of filter openings 5 and double security for cylindrical emitter (FIG. 4) since the grain cannot stick and block the inlet into the emitter.

[0107] It is obvious that the gaps 16, due to the trapezoidal cross-section “Δ” of the channels, are way too narrow in comparison to the cross-section b*a of the openings 5 of the filter (see FIG. 2.1 where a=D.sub.2/2).

[0108] In contradiction, rolling, or fluid sublayer for sliding cannot exist in WO 2009/104183 due to the perpendicular arrangement of the shallow channels in the flow, and the gaps 16 that will be initially created will not remain open for long. Additionally the shallow channels could bear for construction and ejection purposes only parallel to each other side walls. For ejection limitations the “Δ” shape cross-section is impossible to be formed in the flat emitter's mold.

[0109] FIG. 8.1b & FIG. 8c of WO 2009/104183 is shown that in the internal of the transversal secondary channels of the state of the art and for the entire width and surface of the emitter 3a, even before the sediments occur, the flow is either passing freely over (laminar) or creates eddy currents (turbulence). Thus the grains in all of the cases are immobilized flattening and diminishing the secondary channels.

[0110] Even if there is an underneath motion of water 14c (see FIG. 8.1a), this might be caused only under the grains that are gathered over the openings 5a (zone Z) and more specifically simultaneously in both inlets left and right of the collection channel 4a and the opening 5a. This motion is perpendicular to the direction of the flow 14, and compresses and immobilizes the gathered grains 15 exactly over the openings 5a. In addition, due to the water motion 14c under the grains 15, a sub pressure is created locally (Bernoulli) and as a result the grains are pressed and held over the emitter and are immobilized even further.

[0111] FIG. 8.1a & FIG. 8.1d, of the state of the art show the grains 15 permanently stuck and arranged in rows on the entire surface of the emitter and along the water flow 14, weakening the pressure force (Bernoulli) which is acting only on the first grain of every row, and more specifically on the part only of the frontal surface that protrudes over the side wall of the channel 12a.

[0112] FIG. 8f illustrates a cross-section of an emitter 3f with an internal smooth filter of the state of the art that occupies a short length of the arc and the side walls of the openings 5s are parallel to each other. It is clear that sliding and rolling in this case cannot occur.

[0113] Rolling & sliding cannot occur neither in case where the filter with openings develops over a smooth surface, even though that the collection channel of the openings is aligned towards the direction of the flow, (i.e. WO 2010048063 A1) irrespectable of how high this might be, since the fluid sublayer under the grains in this case is completely missing, and the grains “stick” and are sacked and held on the surface of the filter as they lay directly over the openings 5a and are entering into them. The same occurs and at EP 0501114 & U.S. Pat. No. 5,609,303 despite the fact that the collection channel which is not raised is developing on an arc.

[0114] In FIG. 5 the flow 14a that is being detached from the main flow 14 in order to enter into the opening 5, drags along some grains. More specifically, grains of dimensions (b) & (c) in case of clean openings 5, and only (c) ones in case of the covering of the openings by other grains. The grains due to the continuous flow and motion are driven continuously away from the area of the filter and from there towards the end of the pipe 2, where they are gathered and are finally removed in predetermined time intervals through a seldom opening of the ends of the pipe 2 before irrigation starts.

[0115] It is obvious that the stream 14a detached from the flow 14 in order to enter into the opening 5 and the emitter, will follow the direction of the water flow 14 in the pipe. Opposite flow to 14a (flow line 14b in FIG. 5) at the same time and together with the flow 14a, cannot exist (in order to trap permanently the grains 15 over the openings 5 and over the emitter “pressing” them simultaneously from both front and back as in state of the art). As far as the sub pressure is concerned, created under the grains by the underneath passing current 14a, it cannot hold them on the openings 5 since the shallow channel 12 a) has the direction of main flow 14, b) there is a permanent smooth fluid sublayer, c) the motion of grains is continuous and d) a reverse flow 14b is impossible.

[0116] The above is in contradiction to the technologies of the state of the art, WO 2009/104183, FIG. 8.1a.

[0117] In addition, the orientation of the shallow channels 12 being aligned to the direction of flow 14, seeing that it is not reducing considerably the free cross-section of the pipe at the area of the emitter, allows the channels 12 to become even deeper by increasing the height H of the side walls 11 ensuring deeper orthogonal or trapezoidal cross-section for the “underneath” passing by of the water in case that the surface of the filter is fully covered by grains.

[0118] FIG. 2.1 shows the trapezoidal “A” shaped cross-section with the top-opening D.sub.2 being narrower in comparison to the bottom D.sub.1 one, due to the convergence of the side walls 11. The relation holds: D.sub.2/D.sub.1≦1.

[0119] FIG. 6 illustrates a cross-section of the emitter 3d of the present invention where the shallow channels 12d are not raised beyond the internal concave surface of the emitter and the side walls 11d are developed within the internal concave surface. The trapezoidal cross-section “L” of the openings 5d is obvious.

[0120] FIG. 7 illustrates another variation of a cross-section of a cylindrical emitter 3c where the side walls 11c of the shallow channels 12c are, either cut-off, or connected with very thin joining parts 19 with the opposite peripheral side walls of the collection channel 4c. The cutting off of the side walls could be at any point inside the collection channel 4c, while the new gaps formed, are the same or narrower compared to the already narrow mean dimension “a” of the main openings 5c.

[0121] With this variation the capability of the bending of the free parts of the side walls 11c of the shallow channels 12c is achieved and is caused automatically in the area of the collection channel 4c, due to the higher hydraulic pressure exerted over the collection channel 4c in case of total covering or clogging of the openings 5c (“filter cake”). At the same time along with the bending a partial or instantaneous rearrangement of the grains is caused and gabs between them are formed, reinstating the water flow in the emitter.

[0122] FIG. 8fH illustrates the cross-section of an emitter 3.sub.H of the present invention where the internal (smooth) filter of short and limited arc of the state of the art (see FIG. 8f) is combined with the shallow channels 12.sub.H and the side walls 11.sub.H. The common arrangement is being raised vertically over the collection channel 4.sub.H as an extension of the thin straight bars of the filter of the state of the art protruding internally to the emitter. In this case the side walls 11.sub.H of the openings 5.sub.H are preferably parallel to each other and of greater depth H.

[0123] FIG. 9, FIG. 9.1, FIG. 9.2, illustrate variations in cross-sections of cylindrical emitter 3b where the surface of the filter develops over the concave (FIG. 9) or the flat (FIG. 9.1) surface of a part 20 of considerable width that is significantly raised beyond the rest of the concave surface of the emitter, and the shallow channels 12c and their side walls 11b have the direction of the water flow in the pipe and are also preferably extended beyond the raised part 20. The shallow channels 12b could be formed also on the inclined side surface of the raised part 20 while the side walls 11b extending to a considerable length on the concave internal surface of the emitter, could be parallel to each other or radially arranged.

[0124] The raised parts of considerable width internally to the cylindrical emitters are a characteristic of the special emitter of self-compensating water discharge (Pressure Compensated, or PC) since in the internal of these raised parts are placed the elastic membranes and the system of the self-compensation. Raised parts are also present to the emitters of WO 2010048063 A1.

[0125] FIG. 9.3 illustrates a cross-section of an emitter 3i of the present invention where the filter 5i develops both to the flat-horizontal as well as to the inclined surface, while the side walls 11i that may extend to a considerable length over the concave internal surface of the emitter, could be parallel to each other or even converging (radially).

[0126] FIG. 10, FIG. 10a illustrate another variation where the collection channel 4f (inside of an orthogonal outline of dashed lines) of the filter develops not peripherally, but along the direction of the main flow 14 and parallel to the shallow channels 12f with the protruding in this case side walls 11f. In FIG. 10 a view of the internal concave surface of the emitter 3f at the direction Y of FIG. 10a is shown, while FIG. 10a is the cross-section H-H of the FIG. 10.

[0127] At specific intervals could be optionally thin transversal bars 31f crossed and joined with the side walls 11f. The grid that is formed from the bars 31f and the side walls 11f ensures a controlled elasticity and bending of the extended side walls 11f. This elasticity and bending allows in case of total covering and clogging of the openings 5f (cross-section: a*b), partial or instantaneous passage, reinstating the water flow similar to the case of FIG. 7, due to the higher hydraulic pressure caused automatically in case of clogging. Alongside with the bending there could be a sideward motion of two consecutive side walls 11f under the pressure of the overlying foreign particles (due to them being stuck) expanding momentarily the small dimension “a” of the surface of the cross-section of the opening 5f of the grid, disturbing the continuity of the layer (“filter cake”) of the foreign particles, reinstating the flow.

[0128] FIG. 11 illustrates another variation of a cross-section of linear emitter 3g of the present invention where the filter develops over the concave surface 21 of the linear emitter and the shallow channels 12 have the direction of the water flow in the pipe.

[0129] FIG. 12,13 illustrate in a plan view and cross-section M-M respectively a mold for the formation of a new filter. The mold of cylindrical emitters is comprised in general from three main parts: the two plates 40a & 40b, fix and movable respectively, where it is engraved the outer cylindrical surface of the emitter 3, and the internal core 41 that forms the internal concave surface. The pictures illustrate the plates open and the core 41 at closing position but parallel shifted (for illustration purposes). For the closing and the injection, the movable plate is moving towards the center and direction Mc covering the core 41. For the opening and ejection, the core is pulled (axial motion in the direction Co) and afterwards or even simultaneously the movable plate 40b is opened and the part is ejected.

[0130] FIG. 14 illustrates a detail of a variation of the engraving of the core. The engravings for the forming of the new filter, i.e. the side walls 11 creating the openings 5, are being done by engravings (47, 47a) onto the convex surface of the core. The core is comprised from the slightly conical main part that forms the concave surface of the emitter and is located in the center, and from the cylindrical parts 42 & 43 at both ends for its supporting by the pulling.

[0131] The engraving of the shallow channels 45 creating the side walls of the channels of the filter, is being done by cutting tool/blade 48 with parallel side walls which is always orientated so that at every step/pitch to be aligned to the radius of the core. The cylindrical core during its engraving is rotated preferably constantly and at specific angle α° each time corresponding to the pitch of the peripheral openings of the filter, and is engraved with the vertical motion of the cutting tool, gradually and radially, to the entire, or at a large arc of the periphery of the emitter.

[0132] With this configuration the shallow channel 12 that is formed by the injection, presents a trapezoidal shape “Δ” and is narrower at its external surface, with the opening 5 to achieve two stage filtration, and the filter to become even more thinner and more effective. This configuration limits drastically the partial penetration of foreign particles in the shallow channel 12 maintaining the opening 16 open.

[0133] The core may bear at the end of its conical part an also conical shaped surface 47a where there may also exist engravings for a second arrangement of a collection channel 4 and new openings 5. These engravings over the surface 47a create the side walls 11d of the channels of the filter that are developed internally of the emitter 3d and are not protruding internally, as described in the FIG. 6.

[0134] FIG. 15 illustrates a detail of another variation of the engraving of the core 41a where the channels 46 of the core that forms the side walls of the filter, have all of them parallel walls to each other. The core remains still and is engraved with vertical motion of the characteristic tool where, if it is single, it moves one step at a time, or if it is multiple with one and only vertical motion.

[0135] FIG. 16 illustrates another variation where the core is dividable and is comprised by two parts 41b & 41c.

[0136] In general a vast number of variations and combinations are possible since, due to the axial pulling of the core 41, all of the forms “Δ” are ejectable as long as they are developed straight and parallel to the direction of the pulling. It should be noted that the linear emitters of the state of the art do not have a core, and for this reason “Δ” forms are impossible to be ejected.

[0137] The surface of the concave filter, is obviously larger in comparison to the corresponding surface of the flat filter, regardless of it either developing into a linear (i.e. FIG. 11), or developing into a cylindrical emitter (i.e. FIG. 9).

[0138] This of course holds under the prerequisite that the filters of the linear as well as that of the cylindrical ones which are compared have both the same width B.

[0139] The correlation between the surfaces of filters that could be developed at these particular surfaces corresponds exactly to the relation between the arc and the chord of a circle, where the length E of the arc is always larger than the chord B that it corresponds to.

[0140] Thus the concave filter is more advantageous, since the larger the available surface for the development of the collection channel 4 (and the filter by extension) into a small emitter, the better the result of the filtration and the life span of the emitter.

[0141] In addition, the development of the filter into a concave surface allows for a larger cross-section for the water to pass-through from the pipe, on either a linear or cylindrical emitter.

[0142] It is obvious that the new filter of the cylindrical emitter illustrates undeniable abilities not only of passive self-protection but passive self-cleaning as well since the motion of the water through the shallow channels is continuous independently if they are clean or covered by sediments.

[0143] The cylindrical emitter in general requires special attention due to: a) the heavy construction of both the emitter itself as well the dripline pipe which is extruded with thick wall thickness, since it is intended usually for multi-seasonal uses, b) the special and critical issues with the internal sediments in the meandering path. It is mandatory for certain precautions and safety measures to be considered, because it is not prudent to have to abandon early a thick and heavy pipe intended to operate for many years just because the emitters or their filter are clogged and decommissioned earlier.

[0144] The meandering paths of the figures are indicative and for illustration purposes only while in some case the shallow channels extend only towards one side (front or back) of the collection channel 4.