Abstract:
A labyrinth channel for reducing pressure and/or flow rate in a liquid flowing in the channel, the labyrinth channel having a bottom surface and first and second opposing walls and comprising: a first array of spaced apart first baffle teeth that have non-parallel upstream and downstream faces and extend from the first wall towards the second wall to terminate in an end; and a second array of spaced apart second baffle teeth that have non-parallel upstream and downstream faces and extend from the second wall towards the first wall to terminate in an end; wherein baffle teeth in different arrays have a substantially same shape and upstream faces of closest baffle teeth in different arrays are different and/or downstream faces of closest baffle teeth in different arrays are different.

Description:
[0001]    The invention relates to fluid flow control labyrinths and in particular labyrinths that are used to restrict water flow from emitters used in drip irrigation. 
       BACKGROUND OF THE INVENTION 
       [0002]    Irrigation systems that deliver water, often containing plant nutrients, pesticides and/or medications, to plants via networks of irrigation pipes are very well known. In many such irrigation networks, water from an irrigation pipe is delivered to the plants by “emitters” or “drippers”, hereinafter generically referred to as emitters, which are connected to or installed along the length of the pipe. Each emitter comprises at least one inlet or an array of inlets through which water flowing in the pipe enters the emitter and an outlet through which water that enters the emitter exits the emitter. The emitter diverts a relatively small portion of water flowing in the pipe and discharges the diverted water to irrigate plants in a neighborhood of the location of the emitter. 
         [0003]    Generally, to control rate of water discharge by the emitter, the emitter comprises a water flow and pressure reduction channel, a “labyrinth channel” or “labyrinth” through which water that enters the emitter must flow to reach the emitter outlet. The labyrinth channel is a high resistance flow channel along which pressure of water flowing through the emitter drops relatively rapidly with distance along the labyrinth channel from a relatively high water pressure which prevails substantially at or near the emitter inlet to a relatively low discharge pressure, generally a gauge pressure equal to about zero, substantially at or near the emitter outlet. The labyrinth channel generally comprises a tortuous “obstacle” flow path that generates turbulence in water flowing in the labyrinth to reduce water pressure and discharge of water by the emitter. Usually the obstacle path comprises a configuration of baffles that impede and introduce turbulence into water flow. 
         [0004]    U.S. Pat. No. 4,060,200 to Mehouder, the disclosure of which is incorporated herein by reference, describes a labyrinth channel comprising two opposing arrays of equally spaced baffle “teeth” that extend out towards each other from opposite walls of the channel. Each tooth has a cross section perpendicular to the wall substantially in the shape of a truncated isosceles triangle, i.e. the apex of the triangle is “cut off”. The arrays of baffle teeth are substantially mirror images of each other but are displaced relative to each other along the channel by half a repeat period of the baffle teeth, i.e. by half the distance between adjacent baffle teeth. A tooth in one baffle array therefore faces a point in a space, hereinafter a “bay” substantially half way between adjacent baffle teeth in the other array. The tips of two adjacent baffle teeth in one baffle array in the labyrinth and the tip of the tooth in the opposing baffle array that faces the bay formed by the adjacent baffle teeth are substantially coplanar. 
         [0005]    U.S. Pat. No. 5,207,386, the disclosure of which is incorporated herein by reference, also to Mehoudar, describes a labyrinth channel comprising a central “through-flow” flow channel that does not comprise impediments to water flow. The impediment free through-flow channel is flanked on either side by an array of equally spaced, symmetric baffle teeth, similar to the arrays of baffle teeth described in U.S. Pat. No. 4,060,200. As in U.S. Pat. No. 4,060,200, the baffle teeth arrays in U.S. Pat. No. 5,207,386 are displaced relative to each other along the labyrinth channel by half a repeat period of the baffle teeth. 
         [0006]    U.S. Pat. No. 5,207,386 notes that a labyrinth channel comprising a central, impediment free through-flow channel, provides greater reduction in water flow pressure per unit length of the labyrinth than other labyrinth channels. The patent provides a range for the width of the through-flow channel and an optimum for its width relative to dimensions of the baffle teeth. The patent notes that the increased pressure reduction functionality results in a “comparatively low” sensitivity of outflow of water from an emitter to changes in inlet water pressure to the emitter. In addition, the improved pressure reduction functionality enables shorter labyrinth channels to be used to reduce water pressure in emitters, and as a result enables emitters to be produced less expensively. 
         [0007]    US Patent Publication 2003/0150940, the disclosure of which is incorporated herein by reference, shows a labyrinth channel comprising two opposing rows of equally spaced baffle “fingers” that extend out towards each other from opposite walls of the channel. The tips of the finger baffles are terraced so that tips of the fingers decrease step-wise in size with height of the fingers off the floor of the channel. The labyrinth channel does not comprise a through-flow channel and tips of fingers in each row extend into spaces between fingers of the other row, i.e. the fingers mesh. All the fingers appear to be tilted at a same angle towards a downstream direction of water flow. 
         [0008]    PCT publication WO 00/01219, the disclosure of which is incorporated herein by reference, describes a “sawblade-shaped zig-zagging” pattern comprised in a fluid flow regulatory channel of an irrigation pipe. The zig-zagging pattern is embossed on a relatively thin web of flexible plastic material. The web is folded over so that longitudinal edges of the web overlap and regions of the overlapping edges are welded to form the irrigation pipe and regulatory channel comprising the zig-zagging pattern. 
       SUMMARY OF THE INVENTION 
       [0009]    An aspect of some embodiments of the invention relates to providing a labyrinth channel that comprises a new configuration of baffles for reducing pressure in a fluid that flows through the channel and/or the fluid flow rate through the channel. 
         [0010]    An aspect of some embodiments of the invention relates to providing a labyrinth channel comprising opposing arrays of baffle teeth that extend toward each other from opposite side walls of the channel and for which upstream and downstream sides of the baffle teeth have different configurations and are not parallel. Baffle teeth in different arrays have a same shape and upstream sides of closest baffle teeth in different arrays have different configurations and/or downstream sides of closes baffle teeth in different arrays have different configurations. A configuration of a side of a baffle tooth refers to a geometrical shape of the side and/or orientation of the side. Hereinafter an upstream or downstream side of a baffle tooth is referred to as a “face” and baffle faces having different configurations are referred to as being different. 
         [0011]    In an embodiment of the invention, each array of baffle teeth in a labyrinth channel comprises baffle teeth, hereinafter “shark-fin baffle teeth”, which have a cross section shape reminiscent of a shark&#39;s dorsal fin. Each shark-fin baffle tooth has an optionally planar “leading-edge face surface” and an optionally planar “trailing-edge face surface”. The leading-edge face surface is more swept back with respect to the side-wall of the channel from which the tooth extends than the trailing-edge face surface. The leading-edge face surface is oriented at an angle with respect to the side wall that is more acute than an angle that the trailing-edge face surface makes with the side wall. 
         [0012]    In an embodiment of the invention, the leading-edge face surfaces of shark-fin baffle teeth in one array and their nearest shark-fin baffle teeth “neighbors” in the other array face in opposite upstream and downstream directions. That is, the leading-edge face surfaces of baffle teeth in the first array and the trailing-edge face surfaces of their nearest baffle teeth neighbors in the other array face in a same upstream or downstream direction. 
         [0013]    Optionally, the shark-fin baffle teeth in a same array are equidistant from each other and are positioned so that the baffle teeth in one array are located opposite the bay regions between adjacent baffle teeth in the other array. Optionally, the baffle teeth in the opposing arrays mesh. Optionally, the tips of two adjacent shark-fin baffle teeth in one baffle array in the labyrinth and the tip of the shark-fin baffle tooth in the opposing baffle array that faces the bay between the two adjacent baffle teeth are substantially coplanar. In some embodiments of the invention, the labyrinth channel comprises a through-flow channel located between the opposing arrays of shark-fin baffles. 
         [0014]    There is therefore provided in accordance with an embodiment of the invention, a labyrinth channel for reducing pressure and/or flow rate in a liquid flowing in the channel, the labyrinth channel having a bottom surface and first and second opposing walls and comprising: a first array of spaced apart first baffle teeth that have non-parallel upstream and downstream faces and extend from the first wall towards the second wall to terminate in an end; a second array of spaced apart second baffle teeth that have non-parallel upstream and downstream faces and extend from the second wall towards the first wall to terminate in an end; wherein baffle teeth in different arrays have a substantially same shape and upstream faces of closest baffle teeth in different arrays are different and/or downstream faces of closest baffle teeth in different arrays are different. 
         [0015]    Optionally, ends of the first teeth are contiguous with or intersect a same first surface that follows a contour of the labyrinth flow channel. Optionally, ends of the second teeth are contiguous with or intersect a same second surface that follows a contour of the labyrinth flow channel. Optionally, the first and second surfaces that follow the channel contour are coincident. Alternatively, the first and second surfaces that follow the channel contour are parallel and displaced one from the other. 
         [0016]    In some embodiments of the invention, each tooth has a planar trailing-edge surface that makes an external angle β with the wall from which the tooth extends. Optionally, β has a value less than or equal to 100°. Alternatively or additionally, β optionally has a value greater than or equal to 80°. Optionally, β has a value substantially equal to 90°. 
         [0017]    In some embodiments of the invention, each tooth has a planar leading-edge surface that makes an included angle α with the trailing edge surface. Optionally, α has a value less than or equal to 45°. Additionally or alternatively, α optionally has a value greater than or equal to 15°. 
         [0018]    In some embodiments of the invention, the value of α is the same for all baffle teeth. In some embodiments of the invention, the value of β is the same for all baffle teeth. 
         [0019]    In some embodiments of the invention, one of the leading-edge and trailing-edge face surfaces of a tooth is an upstream face of the tooth. Optionally, if the upstream face of a first tooth is a leading-edge surface of the tooth, the downstream face of the nearest second tooth is the leading-edge surface of the second tooth. 
         [0020]    In some embodiments of the invention, the upstream and downstream faces of a first baffle tooth are respectively parallel with the downstream and upstream faces of a nearest second baffle tooth. Optionally, a distance between the upstream face of a first baffle tooth and a nearest downstream face of a second baffle tooth is equal to a same distance “A” between the downstream face of the first baffle tooth and the nearest upstream face of a second baffle tooth. Optionally, A is less than or equal to 3 mm. Additionally or alternatively, A is greater than or equal to 0.3 mm. 
         [0021]    In some embodiments of the invention, ends of the first and second teeth are located a same distance B from the respective walls from which they extend. Optionally, the channel has a width greater than 2 B. Alternatively, the channel has a width optionally less than 2 B. Optionally, the channel has a width substantially equal to about 2 B. In some embodiments of the invention, B is greater than A. 
         [0022]    In some embodiments of the invention, the leading-edge and trailing-edge face surfaces intersect a common surface at different locations of the common surface to define an end surface of the tooth. Optionally, the common surface is planar. Optionally, the intersections of the leading and trailing edge surfaces are different parallel straight lines. 
         [0023]    In some embodiments of the invention, the labyrinth channel or portion thereof is straight. In some embodiments of the invention, the labyrinth channel or a portion thereof is circular. In some embodiments of the invention, the bottom surface of the labyrinth channel or portion thereof is substantially a circularly cylindrical surface. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0024]    Non-limiting examples of embodiments of the present invention are described below with reference to figures attached hereto. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same symbol in all the figures in which they appear. Dimensions of components and features shown in the figures are chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. 
           [0025]      FIG. 1A  schematically shows a perspective view of an irrigation pipe having an optionally internally mounted emitter comprising a labyrinth channel, in accordance with an embodiment of the invention; 
           [0026]      FIG. 1B  schematically shows an enlarged view of a portion of the emitter shown in  FIG. 1A ; 
           [0027]      FIG. 1C  schematically shows a plan view of the emitter shown in  FIG. 1A ; 
           [0028]      FIG. 1D  schematically shows an enlarged view of a portion of the plan view shown in  FIG. 1C  greatly enlarged; 
           [0029]      FIGS. 2A and 2B  schematically show perspective and plan views of a circular labyrinth in accordance with an embodiment of the invention; 
           [0030]      FIGS. 3A and 3B  schematically show perspective and side views of a cylindrical labyrinth in accordance with an embodiment of the invention; and 
           [0031]      FIG. 4  schematically shows a plan view of a portion of a labyrinth similar to the labyrinth shown in  FIG. 1B  and  FIG. 1D , in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0032]      FIG. 1A  schematically shows a perspective view of a portion of an irrigation pipe  20  having an internally mounted emitter  30  comprising a labyrinth channel  40 , in accordance with an embodiment of the invention. An enlarged view of a portion of emitter  30  is shown in  FIG. 1B . The enlarged portion of emitter  30  that is shown in  FIG. 1B  is indicated by an ellipse  31  in  FIG. 1A .  FIG. 1C  schematically shows a plan view of emitter  30  and a portion, indicated by ellipse  33 , of emitter  30  in  FIG. 1C  is shown greatly enlarged in  FIG. 1D . Emitter  30  is optionally formed from a plastic and is bonded to an inside surface  22  of irrigation pipe  20  using any of various methods, such as thermal or ultrasound welding, known in the art. After bonding to surface  22 , the portion of the surface to which it is bonded optionally forms a wall, or “roof” of the emitter that delimits labyrinth channel  40 . In  FIGS. 1B-1D  surfaces of emitter  30  that are bonded to inside surface  22  of pipe  20  are shown shaded. Irrigation pipe  20  is formed with outlet orifices  21  from which fluid that emitter  30  diverts from fluid flowing in the pipe is discharged. 
         [0033]    Emitter  30  is optionally formed having a plurality of inlet apertures  32  optionally located along an upper edge surface of the emitter which is bonded to inside surface  22  of irrigation pipe  20 . Optionally, emitter  30  is formed with additional inlet apertures (not shown) on a bottom surface of the emitter, which surface is not seen in the perspectives of  FIGS. 1A-1D . 
         [0034]    Water in irrigation pipe  20  enters emitter  30  through inlet apertures  32  at a relatively high inlet pressure equal to the water pressure in the irrigation pipe at the location of the emitter and flows into an optionally circumferential inlet channel  34 . Water entering the emitter through inlet apertures  32  is schematically indicated for some of the apertures by bold dashed arrows  24 . In inlet channel  34  the water flows in an optionally counterclockwise direction indicated by bold dashed arrows  25  until it reaches and enters an inlet portal  36  of labyrinth channel  40 . The inlet portal, labyrinth channel  40  and water flow in the labyrinth channel are most clearly shown in  FIGS. 1C and 1D . 
         [0035]    Water that enters labyrinth inlet portal  36  flows generally in an optionally clockwise direction indicated by arrows  27  through labyrinth channel  40  until it reaches a labyrinth outlet portal  37  from which it exits the labyrinth and empties into a discharge reservoir  39 . Because of the presence and configuration of baffle teeth arrays  45  and  46 , labyrinth channel  40  is characterized by a relatively high resistance to water flow per unit length of the labyrinth. As a result, pressure of water that entered the channel at the relatively high inlet pressure drops rapidly per unit length of the labyrinth as the water flows through the labyrinth and the water flows into a discharge reservoir  39  at a relatively low flow rate and gauge pressure, optionally substantially equal to about zero. Water in discharge reservoir  39  drips out of irrigation pipe  20  via discharge apertures  21  that communicate with discharge reservoir  39  at a relatively low “drip” flow rate. Water discharging from the discharge apertures is indicated by dashed arrows  29  in  FIG. 1A . 
         [0036]    Labyrinth channel  40  optionally comprises an outer wall  41  and an inner wall  42  that extend from a channel floor and define a perimeter of the channel and two channel sections  40   a  and  40   b . Labyrinth channel  40  is lined with opposing arrays  45  and  46  of baffle teeth in accordance with an embodiment of the invention. Array  45  comprises optionally shark-fin baffle teeth  47  that extend from outer wall  41  towards inner wall  42  and array  46  comprises optionally shark-fin baffle teeth  48  that extend from inner wall  42  towards outer wall  41 . Optionally, baffle teeth  47  and  48  have similar shapes and may be transformed one into the other by rotation and/or translation. Each pair of adjacent baffle teeth  47  delineate a bay  51  between them and each pair of adjacent baffle teeth  48  delineate a bay  52  between them. Optionally, the baffle teeth are equally spaced one from the other in their respective arrays by a same distance. Details of shark-fin baffle teeth  47  and  48  are most clearly shown in  FIGS. 1B and 1D . 
         [0037]    Each shark-fin baffle tooth  47  and  48  has a swept back leading-edge face surface  61  and a trailing-edge surface  62 . In a given baffle tooth  47  or  48  the trailing-edge surface  62  makes an external angle β ( FIG. 1D ) with the wall  41  or  42  respectively from which it extends and an internal “included” tooth angle α with the leading-edge face surface  61  of the given baffle tooth. Angle α is optionally between 15° and 45° and angle β is optionally between 80° to 100° and preferably substantially equal to 90°. In accordance with an embodiment of the invention, as shown in  FIGS. 1A-1D , an upstream face of a baffle tooth in one array is parallel to the downstream face of its nearest neighbor in the opposing array. Leading and trailing-edge face surfaces  61  and  62  of a given baffle tooth  47  or  48  intersect a relatively narrow optionally rectangular, planar end surface  64  ( FIG. 1B ) of the tooth. Optionally, end surfaces  64  of teeth in opposing baffle teeth arrays  45  and  46  are substantially coplanar and lie substantially on or intersect a same plane schematically indicted in  FIGS. 1B and 1D  by a dashed line  50 . (It is noted that if a labyrinth such as labyrinth  40  is produced by injection molding, dies for producing the labyrinth may in some instances require that surfaces of features of the labyrinth, such as face and end surfaces  61 ,  62  and  64  of baffle teeth  47  and  48  be slightly angled at a release angle. The release angle allows satisfactory release of the labyrinth from the die that produces it after production. In  FIG. 1D  a die release angle would result in surfaces  61 ,  62  and  64  being slightly tilted away from the normal to the plane of the figure. End surfaces  64  would then intersect the planar surface indicated by numeral  50  at the release angle and not lie completely on the surface.) 
         [0038]    In accordance with an embodiment of the invention, an upstream face of a baffle tooth in one array is different, i.e. has a different configuration, respectively from the upstream face of its nearest neighbors in the opposing array and/or a downstream face of a baffle tooth in one array is different from the downstream face of its nearest neighbors in the opposing array. Optionally, in section  40   a  of labyrinth  40 , leading-edge face surfaces  61  of each baffle tooth  47  in array  45  faces upstream and leading-edge face surfaces  61  of its nearest baffle teeth neighbors  48  in array  46  face downstream. Optionally, in section  40   b  of labyrinth  40 , leading-edge faces  61  of each baffle tooth  47  face downstream while the leading-edge face surfaces of its nearest opposing neighbors face upstream. It is noted that whereas in labyrinth  40 , baffle teeth in different sections, i.e.  40   a  and  40   b , of the array are shown facing opposite upstream and downstream directions, a labyrinth in accordance with an embodiment of the invention, similar to labyrinth  40 , may have baffle teeth in a same array in different sections of the labyrinth face a same direction. 
         [0039]    Dimensions of features of labyrinth channel  40  are labeled in  FIG. 1D . The labyrinth channel has a depth “D”, schematically indicated by a circle with a cross inside to indicate a direction perpendicular to the plane of the figure and width “W”. Baffle teeth  47  extend from their associated wall  41  into the channel a distance “B 1 ” and baffle teeth  48  extends from their associated wall  42  into the channel a distance “B 2 ”. As a result, bays  51  and  52  have a depth respectively equal to B 1  and B 2 . Optionally, as indicated in  FIG. 1D , end surfaces  64  of baffle teeth  47  and  48  are substantially coplanar so that W=B 1 +B 2 . Optionally B 1  is equal to B 2 . A leading-edge face surface  61  of a baffle tooth  47  and a nearest leading-edge face surface  61  of a baffle tooth  48  are separated by a distance “A 1 ”. A trailing-edge face surface  62  of a baffle tooth  47  and a nearest trailing-edge face surface  61  of a baffle tooth  48  are separated by a distance “A 2 ”. Optionally, A 1 =A 2 . Optionally, distance between an end surface  64  of a given baffle tooth  47 ,  48  and the opposing wall  42 ,  41  towards which the given tooth extends, is respectively larger than A 1  or A 2  and preferably at least equal to B 2  or B 1  respectively. End surfaces  64  have a width “e” and baffle teeth  47  and  48  in a same array  45  and  46  respectively are separated by a distance “L”. For the exemplary embodiment of the invention shown in  FIGS. 1A-1D , for which an upstream face of a baffle tooth in one array is parallel to the downstream face of its nearest neighbor in the opposing array, L=A 1 /cos α+A 2 /sin β+2 e. 
         [0040]    By way of a numerical example, optionally, A 1  and A 2  satisfy a relationship 3 mm≧A 1 , A 2 ≧0.3 mm and A 1 =A 2 =A. Optionally B 1 =B 2 =B and A and B satisfy a relationship of 2 A≧B≧A. Optionally, 2 A≧D≧0.5 A and 0≧e≧0.25 A. 
         [0041]    The inventors have performed theoretical studies of the efficiency of a labyrinth channel in accordance with an embodiment of the invention that is similar to labyrinth channel  40  and has dimensions similar to those noted above. The studies indicate that per unit length, a labyrinth channel in accordance with an embodiment of the invention provides resistance to fluid flow that is greater than that provided by prior art labyrinth channels having similar dimensions. In particular, the studies indicate that the turbulence or “head loss” coefficient “K” for a single baffle tooth in a labyrinth in accordance with an embodiment of the invention may be as much as 16% greater than that of prior baffle teeth in prior art labyrinths having similar dimensions. 
         [0042]    As a result of the improved resistance to fluid flow per unit length, a labyrinth configuration in accordance with an embodiment of the invention provides greater design latitude in tailoring a labyrinth to a given desired range in pressure drop between an inlet and an outlet of the labyrinth and/or flow rates through the labyrinth than conventional labyrinth configurations. 
         [0043]    For example, for a given desired or anticipated pressure drop, a labyrinth in accordance with an embodiment of the invention can generally be made shorter than a conventional labyrinth. An emitter comprising a shorter labyrinth, is generally less expensive to make and less prone to clogging by particulate matter in fluids discharged by the emitter than an emitter comprising a longer labyrinth. Alternatively, for a given pressure drop, and a same length, a labyrinth in accordance with an embodiment of the invention can be made wider than a conventional labyrinth. A wider labyrinth is usually less prone to trapping particulate matter and clogging than a narrower labyrinth and can be particularly advantageous for use in environments for which fluids discharged by an emitter comprising the labyrinth are expected to be unusually adulterated by particulate matter. Additionally, for a same length, width and operating pressure range drop, a labyrinth in accordance with an embodiment of the invention may advantageously be used to provide a lower fluid flow rate than a conventional labyrinth. For example, for a same pressure operating range of an irrigation emitter, and same length and width of a labyrinth in the emitter, an emitter comprising a labyrinth in accordance with an embodiment of the invention may provide a lower drip rate than a conventional emitter. 
         [0044]    It is noted that whereas in the exemplary embodiment of the invention shown in  FIGS. 1A-1D , labyrinth channel  40  comprises straight sections, the invention is not limited to straight labyrinths. A labyrinth in accordance with an embodiment of the invention may, for example be curvilinear, elliptical, circular or cylindrical and is not limited to planar labyrinths. 
         [0045]      FIGS. 2A and 2B  schematically show perspective and plan views of a circular emitter labyrinth channel  100 , in accordance with an embodiment of the invention. In the figures only features of the emitter that are germane to labyrinth channel  100  are shown. Water optionally enters labyrinth channel  100  through an inlet portal  101  and empties into a discharge reservoir  102  via an outlet portal  103 . Water flow is indicted by dashed arrows  104 . 
         [0046]    Labyrinth channel  100  comprises an inner array  110  of optionally shark-fin baffle teeth  112  and an opposing outer array  111  of shark-fin baffle teeth  113 . Shark-fin baffle teeth  112  and  113  have leading-edge face surfaces  116  ( FIG. 2B ) and trailing-edge face surfaces  118  and ends  117 . Optionally, ends  117  lie substantially on or intersect a same circularly cylindrical surface indicated by a dashed line  121 . By way of example, leading-edge surfaces  116  of baffle teeth  113  in array  111  face upstream while leading-edge surfaces  116  of baffle teeth  112  in array  110  face downstream. It is noted that in labyrinth channel  100  all the baffle teeth in a same array, optionally as shown in  FIGS. 2A and 2B , face a same direction. 
         [0047]      FIGS. 3A and 3B  schematically show perspective and plan views of a cylindrical emitter labyrinth channel  140 , in accordance with an embodiment of the invention. Only features of the emitter that are germane to labyrinth channel  140  are shown. Water optionally enters labyrinth channel  140  through an inlet portal  141  and empties into a discharge reservoir, not shown, via an outlet portal  142 . Water flow is indicted in  FIG. 3B  by dashed arrows  144 . 
         [0048]    Labyrinth channel  140  comprises an upper array  150  of optionally shark-fin baffle teeth  152  and an opposing lower array  151  of shark-fin baffle teeth  153 . Shark-fin baffle teeth  152  and  153  have leading-edge face surfaces  156 , trailing edge face surfaces  158  and ends  157 . Optionally ends  157  are substantially coplanar and lie substantially on or intersect a same plane schematically indicted by a dashed line  221 . By way of example, leading-edge surfaces  156  of baffle teeth  152  face downstream while leading edge surfaces  156  of baffle teeth  153  face upstream. 
         [0049]    It is noted that in the above embodiments of the invention, ends of baffle teeth in different opposing arrays of baffle teeth comprised in a labyrinth are indicated as being contiguous with a same surface, a “contour surface”, that follows a contour of the labyrinth. For example, the ends of baffle teeth in opposing arrays of labyrinth  40  and  140  ( FIGS. 1B ,  1 D,  3 A,  3 B) are indicated as lying in or intersecting a same plane while baffle teeth in opposing arrays of labyrinth  100  lie on or intersect a same circularly cylindrical surface ( FIGS. 2A ,  2 B). In some embodiments of the invention, ends of baffle teeth in different opposing arrays are not contiguous with a same contour surface. In some embodiments of the invention, ends of baffle teeth in a same array of opposing arrays of baffle teeth in a labyrinth are contiguous with a same contour surface while ends of baffle teeth in different arrays are contiguous with different parallel contour surfaces. 
         [0050]    By way of example,  FIG. 4  schematically shows a plan view of a portion of a labyrinth  200  similar to labyrinth  40  shown in  FIG. 1B  and  FIG. 1D . However, whereas in labyrinth  40 , ends  64  of opposing baffle teeth  47  and  48  are substantially contiguous with a same plane  50 , in labyrinth  200  ends  64  of baffle teeth  47  are coplanar with a plane  201  while ends  64  of opposing baffle teeth  48  are coplanar with a different plane  202  parallel to plane  201  but displaced from plane  201  by a distance “d”. 
         [0051]    It is further noted that whereas in the above discussion it is indicted that a labyrinth may be produced by injection molding, a labyrinth in accordance with an embodiment of the invention is not limited to production by injection molding but may of course be produced using any suitable method known in the art. For example a labyrinth in accordance with an embodiment of the invention may be produced by embossing on a suitable plastic material. In addition a “roof” of a labyrinth in accordance with an embodiment of the invention is not necessarily provided by a wall of an irrigation pipe with which it is used but may be provided in part or completely by a component that is not a part of the wall. It is also noted that a labyrinth in accordance with an embodiment of the invention is not limited to being used with emitters that are internally mounted to an irrigation pipe, but may of course be comprised in emitters that are coupled externally to an irrigation pipe or inline between portions of an irrigation pipe. In the description and claims of the present application, each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb. 
         [0052]    The invention has been described with reference to embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the described invention and embodiments of the invention comprising different combinations of features than those noted in the described embodiments will occur to persons of the art. The scope of the invention is limited only by the following claims.