Abstract:
A pulsating device has a chamber for receiving liquid entering the device and gas that occupies an initial volume in the chamber. The liquid entering the chamber compresses the gas and decreases the volume occupied by the gas, thereby increasing the pressure in the chamber. A valve is provided to open above a first threshold pressure to begin a pulse of liquid. The valve closes below a second threshold pressure to end the pulse. The pulsating device has an outlet gate that permits liquid in the chamber to exit the chamber when the pressure in the chamber is greater than the pressure outside the chamber.

Description:
TECHNICAL FIELD 
       [0001]    Embodiments of the invention relate to a pulsating device. 
       BACKGROUND 
       [0002]    In such devices, the incoming fluid flow may be of relatively low flow and the ejected pulses may be transformed to be of a relatively high flow. Pulses emitted by pulsating devices can therefore be designed to reach relative large distances in relation to conventional non pulsating devices that would require much higher flow rates in order to reach similar distances. As a result, basing an irrigation system on a pulsating device can reduce some of the expenses associated with such an irrigation system such as for example the energy consumed by the system. 
         [0003]    Israeli patent No. 92886 describes a pulsating device with a chamber and a hollow stem that extends through the chamber to an outlet orifice of the chamber. The device also includes a displaceable valve member that is disposed in the chamber under the outlet orifice. Upon rise of pressure in the chamber the valve can be contracted from a position where it closes to the orifice to a position where it is displaced from the orifice to allow a pulse of water to exit the device. 
       SUMMARY 
       [0004]    The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. 
         [0005]    In an embodiment of the present invention there is provided a pulsating device for transforming a liquid flow entering the device from a liquid source upstream to an intermittent pulsating liquid flow ejected from the device downstream, the device comprising a chamber for receiving the liquid flow entering the device and gas that occupies an initial volume in the chamber, the liquid entering the chamber being adapted to compress the gas and decrease the volume that the gas occupies in the chamber and increase the pressure in the chamber, the device further comprises a valve that is adapted to open above a first threshold pressure Po within the chamber to begin a liquid pulse that exists the chamber and after being opened to close below a second threshold pressure Pc within the chamber to end the liquid pulse exiting the chamber, wherein the device also comprises an outlet gate that communicates between the interior and the exterior of the chamber, and the liquid in the chamber can exit the chamber via the outlet gate when the pressure in the chamber at the outlet gate is above zero. 
         [0006]    Optionally, the device comprises an inlet gate that is formed in the chamber and communicates between the interior and the exterior of the chamber, and air from outside of the chamber can enter the chamber when the pressure in the chamber at the inlet gate is below zero. 
         [0007]    Typically, the pressure of the liquid at the liquid source is greater than the first threshold pressure Po. 
         [0008]    Optionally, the flow rate of each pulse at any point between its beginning and end is greater than the flow rate of liquid entering the chamber via the inlet. 
         [0009]    If desired, relative to a lower end of the chamber at pressure Po the height of liquid in the chamber is Lo and at pressure Pc the height of liquid in the chamber is Lc which is lower than Lo. 
         [0010]    Optionally, relative to a lower end of the chamber at pressure Po the height of liquid in the chamber is Lo and at pressure Pc the height of liquid in the chamber is Lc which is lower than Lo, and the inlet gate communicates with the chamber at a point that is lower than Lc. 
         [0011]    In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed descriptions. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0012]    Exemplary embodiments are illustrated in referenced figures. It is intended that the embodiments and figures disclosed herein are to be considered illustrative, rather than restrictive. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying figures, in which: 
           [0013]      FIG. 1  schematically shows a perspective top view of an embodiment of a pulsating device in accordance with the present invention coupled to an embodiment of a sprinkler in accordance with the present invention; 
           [0014]      FIG. 2  schematically shows a partial cross sectional view of the pulsating device and sprinkler of  FIG. 1 ; and 
           [0015]      FIGS. 3A to 3C  schematically show a partial cross sectional views of the pulsating device and sprinkler of  FIG. 1  during different stages of emitting a pulse. 
       
    
    
       [0016]    It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated within the figures to indicate like elements. 
       DETAILED DESCRIPTION 
       [0017]    Attention is first drawn to  FIG. 1 . A pulsating device  10  in accordance with an embodiment of the present invention is adapted to transform an incoming liquid flow from a liquid source upstream (not shown) to an outgoing liquid pulse that is ejected downstream. The liquid may be water that may contain substances used in agricultural applications in which the device is used such as plant nutrients, pesticides and/or medications; and the liquid source upstream may optionally be a pipe such as an irrigation pipe. 
         [0018]    It is noted that references to pressure made herein are all expressed in terms of deviation from the atmospheric pressure that exists in the environment outside of the device which is defined as “zero”. Also it is noted that directional terms appearing throughout the specification and claims, e.g. “forward”, “rear”, “up”, “down” etc., (and derivatives thereof) are for illustrative purposes only, and are not intended to limit the scope of the appended claims. Finally it is noted that the directional terms “down”, “below” and “lower” (and derivatives thereof) all define identical directions. 
         [0019]    Attention is additionally drawn to  FIG. 2 . The pulsating device  10  has a body  12 , an emitting portion  14  in an optional form of a sprinkler and a valve  16  that is located therebetween. The body  12  has an inner chamber  18 , an inlet  20  and an outlet  22 . The inlet  20  leads liquid into the chamber  18  from the liquid source upstream. The outlet  22  is located at an orifice at a lower end of a hollow pipe section  24  of the body  12 . The pipe section  24  extends up to above the upper end of the body  12  and provides a passage for liquid exiting the chamber  18  via the outlet  22 . 
         [0020]    Attention is additionally drawn to  FIGS. 3A to 3C . When first starting to use the pulsating device  10  the inner chamber  18  of the device  10  can be substantially empty of liquid and full with a gas  26  such as air ( FIG. 2 ). When irrigation starts liquid enters the chamber  18  via the inlet  20  and starts to fill the chamber  18 . The liquid entering the chamber  18  compresses the gas  26  and decrease the volume that the gas  26  occupies in the chamber  18  and thereby increases the pressure in the chamber  18 . As long as the pressure at the liquid source is greater than the pressure in the chamber  18 , the level of liquid in the chamber  18  and accordingly the pressure in the chamber  18  rises and the gas  26  remains trapped at an upper portion of the chamber  18 . The valve  16  which is exposed to the chamber  18  via the pipe section  24  will allow the pressure in the chamber  18  to rise until it reaches a first threshold pressure Po which is the pressure at which the valve  16  opens. The level of the liquid just before the valve  16  opens and as measured from a lower end of the chamber  18  is Lo ( FIG. 3A ), and the pressure in the chamber  18  will rise to Po only if the pressure at the liquid source is greater than Po. 
         [0021]    The valve  16  that opens at pressure Po in the chamber  18  begins a pulse of liquid that starts to exit the chamber  18  and pipe section  24  towards the emitting portion  14  where it is emitted to the outside environment. As liquid exits the chamber  18  the pressure in the chamber  18  drops, the gas  26  that is trapped at the upper portion of the chamber  18  expands and the level of liquid in the chamber  18  decreases ( FIG. 3B ). The pulse continues until the pressure in the chamber  18  drops and reaches a second threshold pressure Pc where the valve  16  closes and ends the pulse. The second threshold pressure Pc is lower than the first threshold pressure Po and the level of the liquid just before the valve  16  closes and as measured from a lower end of the chamber  18  is Lc which is lower than Lo ( FIG. 3C ). 
         [0022]    As long as the device  10  remains in liquid communication with the pressurized liquid source upstream, the termination of a given pulse will be followed by a subsequent rise of pressure in the chamber  18  ( FIG. 3A ) which will lead to a subsequent pulse that is released from the chamber  18  and emitted from the device  10  to the outside environment ( FIG. 3B ) until the pressure drops and the pulse stops ( FIG. 3C ). In some cases, to ensure that the device  10  forms pulses it is preferable to configure the device  10  such that the flow rate of each pulse being emitted from the chamber  18 , at any point between its beginning and end, is greater than the flow rate of liquid entering the chamber  18  via the inlet  20 . This reduces the possibility of the formation of an equilibrium in the chamber  18  between the liquid entering the chamber and the liquid exiting it, that may stop the formation of the pulses exiting the chamber  18 . 
         [0023]    In an embodiment of the present invention it is also possible to configure the inlet  20  to the chamber  18  to be of a regulated type. Such a regulated inlet can ensure that the flow rate of liquid entering the chamber  18  is substantially constant and independent of the pressure differences that are formed between the liquid pressure at the liquid source upstream and the liquid pressure in the chamber  18  that varies during the formation of the pulses. By configuring the liquid flow entering the chamber to a substantially constant rate it is easier to avoid reaching the above mentioned equilibrium between the liquid entering the chamber and the liquid exiting it, that may stop the formation of the pulses. 
         [0024]    During experiments with a pulsating device  10  generally similar to that described above, it was observed by the inventor of the present invention that over time at least some of the substances of the gas  26  that is trapped in the chamber  18  may in some cases dissolve into the liquid that it contacts in the chamber  18 . This may lead to a drop in the amount of gas  26  that is present in the chamber  18  in gas form and as a result to a decline in the performance of the pulsating device  10 . Therefore, in an embodiment of the present invention the pulsating device  10  is equipped with an outlet gate  28  that is adapted to allow liquid in the chamber  18  to seep out of the chamber  18  when the pressure in the chamber  18  at the outlet gate  28  is above “zero”. And, optionally the pulsating device  10  is also equipped with an inlet gate  30  that is located above the outlet gate  28  and is adapted to allow air to seep into the chamber  18  when the pressure in the chamber  18  at the inlet gate  30  is below “zero”. 
         [0025]    In embodiments of the pulsating device  10  that include the outlet gate  28 , each time the pulsating device  10  is turned off and put to rest between irrigation cycles the chamber  18  can be emptied from its liquid via the outlet gate  28 . In embodiments that include also the inlet gate  30  new air can enter the chamber  18  via the inlet gate  30  when it is emptied. When a new irrigation cycle starts by for example renewing the supply of pressurized liquid that enters the chamber  18  via the inlet  20 , liquid will again start to fill the chamber  18  and the pulsating sequence will resume. 
         [0026]    During a pulsing sequence when the pressure in the chamber  18  varies between the first threshold pressure Po and the second threshold pressure Pc; a small amount of liquid will constantly seep out of the chamber  18  via the outlet gate  28 . When irrigation stops, liquid will continue to seep out of the outlet gate  28  as long as there is liquid in the chamber  18  above the outlet gate  28  that forms a pressure greater than “zero” within the chamber  18  at the outlet gate  28 . During the emptying of the chamber  18  from liquid the pressure in the gas  26  above the liquid drops to “zero” and then continues to drop to below “zero”. When the level of liquid in the chamber  18  reaches a position below the inlet gate  30  and when the pressure above the liquid is below “zero” then the inlet gate  30  will allow air from outside of the chamber  18  to seep into the chamber  18  and “charge” the chamber  18  with new air in gas state. 
         [0027]    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. 
         [0028]    Although the present embodiments have been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the scope of the invention as hereinafter claimed.