Patent Publication Number: US-2007122295-A1

Title: Fluid measurement/division device and process

Description:
FIELD OF THE INVENTION  
      The present invention relates to a fluid measurement/division device and process.  
     BACKGROUND OF THE INVENTION  
      In particular, the device and process of the present invention are usable to divide a fluid flow rate, for example to obtain from an inlet flow two or more outlet flows of equal flow rate, with possible measurement of the flow rate. If only one flow is obtained at the device outlet, the device is used (and operates) as a flow rate measurement device, i.e. it exactly measures the delivered flow rate without effecting any flow rate division.  
     DISCUSSION OF THE RELATED ART  
      Devices of the indicated type are currently formed with at least three cylinders, in each of which a piston is slidably inserted.  
      Each piston is provided with two reduced diameter regions which define two distribution chambers inside the cylinder. Each cylinder also defines two pumping chambers at its ends.  
      The three cylinders are connected together by a plurality of conduits, such that the conduits alternately connect together one or other of the chambers defined between each cylinder and the respective piston.  
      During operation of the traditional device, each of the pistons is in a different operating stage.  
      In particular, while a first piston is in a dosing stage (and dispenses a predetermined quantity of fluid contained in a pumping chamber, forcing it to leave the device), a second piston is in a piloting stage (and causes the fluid to operate the dosing piston).  
      Finally a third piston is in a neutral stage, in which it does not act on the fluid (delivering it to the outside) and is not operated by the fluid; during this stage the piston contained in the cylinder in the neutral stage moves from the piloting position to the dosing position; if this stage were not present, the device would lock because the liquid would not be able to continuously operate the pistons such that they alternate their function by passing from the piloting stage to the dosing stage.  
      However, the described devices of traditional type are large and heavy because of the minimum number of cylinder/piston pairs required for their operation; in this respect, at least three cylinder/piston pairs are required, each of which effects one of the described stages during operation, while the other cylinder/piston pairs effect the others.  
      The traditional devices are also costly to construct because of the large number of components required.  
     SUMMARY OF THE INVENTION  
      The technical aim of the present invention is therefore to provide a fluid measurement/division device and process by which the stated technical drawbacks of the known art are eliminated.  
      Within the scope of this technical aim, an object of the invention is to provide a device of small size and reduced weight; this advantageously enables devices to be constructed which can be handled and installed easily, even in difficultly accessible or narrow positions.  
      Another object of the invention is to provide a device and process which are economical to implement, in particular compared with traditional devices.  
      The technical aim, together with these and other objects are attained according to the present invention by a fluid measurement/division device and process in accordance with the accompanying claims.  
      Advantageously, the device and process of the invention are also usable when the fluid which they are required to handle operates at high or very high pressure (up to and beyond 2000 bar). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Further characteristics and advantages of the invention will be more apparent from the ensuing description of a preferred but non-exclusive embodiment of the fluid measurement/division device and process according to the invention, illustrated by way of non-limiting example in the accompanying drawings, in which:  
       FIGS. 1-4  show a schematic view of the device in four different successive operating stages;  
       FIG. 5  shows a schematic view of a part of an end of a cylinder and of a piston slidable therein, in an embodiment of the device particularly suitable for use with devices operating at high pressure;  
       FIG. 6  shows a schematic upper view of the device of the invention in a different embodiment;  
       FIG. 7  shows a schematic section through line VII-VII of  FIG. 6 ;  
       FIG. 8  shows a lateral side view of the device of  FIG. 6 ;  
       FIG. 9  shows a schematic section of the device of  FIG. 6 ; and  
       FIG. 10  shows a particular of one way valves mounted on the outlet conduits of the device of  FIG. 6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      With reference to said figures, these show a fluid measurement/division device indicated overall by the reference numeral  1 .  
      The device  1  comprises two cylinders  2 ,  3  in which a first and a second piston  4 ,  5  are slidably inserted.  
      Each of the two pistons  4 ,  5  operates alternately as a fluid dosing piston or as a piloting piston for the dosing piston.  
      The dosing piston dispenses fluid to the outside (by its movement), while the piloting piston defines the path for the fluid, which is directed towards the dosing piston to control its movement.  
      Advantageously, the first and second piston  4 ,  5  present reduced diameter regions which, together with the surface of the cylinders  2 ,  3 , define three constant volume distribution chambers  6   a ,  7   a ,  8   a  and two variable volume pumping chambers  9   a ,  10   a  for the first cylinder  2 , and three constant volume distribution chambers  6   b ,  7   b ,  8   b  and two variable volume pumping chambers  9   b ,  10   b  for the second cylinder  3 .  
      The device  1  comprises a plurality of conduits connecting the cylinders  2 ,  3  together and to the outside (for example to interact with a machine), to allow or prohibit hydraulic connection in relation to the position assumed by the first and second piston  4 ,  5 .  
      Advantageously, with reference for example to  FIG. 1 , when the first piston  4  is in the dosing stage and translates to dispense fluid (arrow F 1 ) to pass to the piloting stage, the second piston  5  is in the piloting stage and passes to the dosing stage by passing through a neutral stage.  
      The neutral stage enables operation of the device of the invention to be continuous in that, if it did not exist, the piloting piston would be unable to pass to the dosing stage and the device would lock.  
      As shown in the accompanying figures, the connection conduits comprise: a first conduit  11  to connect a first distribution chamber  6   a  of the first cylinder  2  to a first distribution chamber  6   b  of the second cylinder  3 , a second conduit  12  to connect a second distribution chamber  7   a  of the first cylinder  2  to a second distribution chamber  7   b  of the second cylinder  3 , and a third conduit  13  to connect a third distribution chamber  8   a  of the first cylinder  2  to a third distribution chamber  8   b  of the second cylinder  3 .  
      The connection conduits also comprise a fourth conduit  14  to connect the first pumping chamber  9   a  of the first cylinder  2  to the second distribution chamber  7   b  or to the third distribution chamber  8   b  of the second cylinder  3 , a fifth conduit  15  to connect the second pumping chamber  10   a  of the first cylinder  2  to the first distribution chamber  6   b  or to the second distribution chamber  7   b  of the second cylinder  3 .  
      A sixth conduit  16  is provided to connect the first distribution chamber  6   a  or the second distribution chamber  7   a  of the first cylinder  2  to the first pumping chamber  9   b  of the second cylinder  3 , and a seventh conduit  17  to connect the second distribution chamber  7   a  or the third distribution chamber  8   a  of the first cylinder  2  to the second pumping chamber  10   b  of the second cylinder  3 .  
      Finally, an eighth conduit  18  is provided to connect the first distribution chamber  6   a  of the first cylinder  2  to the outside, a ninth conduit  19  to connect the second distribution chamber  7   a  of the first cylinder  2  to the outside, and a tenth conduit  20  to connect the third distribution chamber  8   a  of the first cylinder  2  to the outside.  
      The device  1  suitably comprises a block  22  defining the first and second cylinder  2 ,  3  and also at least the first, second and third connection conduit  11 ,  12 ,  13 .  
      In a preferred embodiment, shown in  FIGS. 1-4 , the block  22  also defines the fourth, fifth, sixth, seventh, eighth, ninth and tenth connection conduit  14 - 20 .  
      The device advantageously defines a module provided with two cylinders. Several modules can be connected together, but in all cases the cylinders are operationally connected together in pairs.  
      The operation of the fluid measurement/division device of the invention is apparent from that described and illustrated, and is substantially as follows.  
      The fluid enters through the conduit  19  as indicated by the arrow F 2  and is directed into the second chamber  7   b  of the second cylinder (which is in the piloting stage).  
      In the second cylinder  3  the second piston  5  enables the fluid to transit through the fourth conduit  14  to enter the first pumping chamber  9   a  of the first cylinder  2 .  
      This causes the first piston  4  to translate as indicated by the arrow F 3 ; this translation causes the fluid contained in the second pumping chamber  10   a  of the first cylinder to pass through the fifth conduit  15 , to pass through the first chamber  6   b  of the second cylinder and through the first conduit  11 , to be dispensed to the outside through the eighth conduit  18 .  
      The device then assumes the configuration of  FIG. 2 .  
      In this configuration the first cylinder  2  acts as the piloting cylinder, as the fluid enters the first conduit  2  (arrow F 2 ) and is directed into the second pumping chamber  10   b  of the second cylinder  3  (which operates as a dosing cylinder).  
      The second piston  6  then translates as indicated by the arrow F 5 , to dispense the fluid contained in the first pumping chamber  9   b  of the second cylinder  3  (as indicated by the arrow F 1 ) through the sixth conduit  16  and the eighth conduit  18 ; the device then assumes the configuration shown in  FIG. 3 .  
      The fluid continues to enter through the ninth conduit  19  and passes through the second distribution chamber  7   a  of the first cylinder  2  and the second conduit  12  to reach the distribution chamber  7   b  of the second cylinder  3  (which is in the piloting stage), in which the second piston  5  directs the fluid through the conduit  15  (arrow F 6 ) and into the second pumping chamber  10   a  of the first cylinder, this latter translating as indicated by the arrow F 7  to dispense the fluid contained in the first pumping chamber  9   a , as indicated by the arrow F 8  (by passing through the fourth conduit  14 , the third conduit  13  and the tenth conduit  20 ); in this manner the device assumes the configuration of  FIG. 4 .  
      The fluid, which continues to enter the device through the conduit  19  as indicated by the arrow F 2 , enters the second chamber  7   a  of the first cylinder  2  (which operates as a piloting cylinder); in this cylinder the piston directs the fluid into the sixth conduit  16  and then into the first pumping chamber  9   b  of the second cylinder  3  (which operates as a dosing cylinder).  
      The fluid entering the chamber  9  of the cylinder  3  causes the piston to translate as indicated by the arrow F 9 , the fluid contained in it then passing through the seventh conduit  17  from which, via the third chamber  8   a  of the first cylinder  2 , the fluid leaves the device through the tenth conduit  20  (as indicated by the arrow F 8 ).  
      The device then returns to the configuration of  FIG. 1  and the cycle recommences.  
      A proximity sensor  26  is provided at each of the two ends of each cylinder  2 ,  3  to sense the movements of the pistons  4 ,  5 ; this enables the dispensed fluid to be measured. A single sensor associated with each cylinder could instead be provided.  
      It should be noted that in the time that passes between the commencement of movement of any one of the pistons and the moment in which it reaches its end-of-travel position, a sort of “neutral stage” occurs. In this respect, during this time interval, which can be varied either by structurally modifying the valve or by modifying the piston movement velocity, that piston not in movement is not piloted and remains at rest in its original position.  
      An embodiment of the device of the invention is described hereinafter with particular reference to  FIG. 5  which is particularly suitable for use in plants with fluids of high or very high pressure (up to and beyond 2000 bar).  
      For high pressure use, traditional proximity sensors are unable to sense when the pistons  4 ,  5  reach the ends of the chamber (because of the large wall thicknesses required to resist such pressures).  
      In this respect, the block  22  defining the cylinders  2 ,  3  is provided at its ends with closure elements  25  associated with proximity sensors comprising a sensing element  26  and a slider or element  27  slidable in a chamber  28 .  
      The slider or element  27  is made of magnetic material and is known to oscillate because it is drawn (arrow F 14 ) by the sensor  26  when the piston  4  is distant from the end of the cylinder  2 , whereas when the piston  4  is brought to the terminal end of the cylinder  2  the slider  27  is drawn towards the piston (arrow F 15 ).  
      In this manner the sensor  26  is able to sense (or count) the strokes undergone by the slider  27 .  
      To enable the piston  4  (preferably made of ferromagnetic material but, in various applications, also of other non-ferromagnetic materials) to draw the slider  27 , the pistons carry magnets  30  embedded in their ends, to cooperate with the corresponding sliders or magnetic elements  27  of the proximity sensors positioned at the cylinder ends.  
      In addition, to limit the negative effect on the magnetic forces caused by the large wall thickness, the pistons present convex ends, the cover elements  25  for the ends of the cylinders  2 ,  3  presenting recessed ends to receive the convex ends of the pistons  4 ,  5 .  
      The present invention also relates to a fluid measurement/division process using the before described device.  
      The process consists of feeding the fluid to the piloting cylinder, in which the piloting piston defines (directing it thereto) that chamber of the dosing cylinder into which the fluid is to be fed.  
      The piloting piston translates to pass to the dosing stage, the dosing piston translating to dispense the fluid and pass to the piloting stage.  
      In passing from the piloting stage to the dosing stage the piloting cylinder passes through a neutral stage.  
      Modifications and variants in addition to those already stated are possible.  
      Particularly,  FIGS. 6-10  show a different embodiment of the device of the invention having the same features as those of the already described embodiment.  
      In addition, the device is provided with one-way valves  35 ,  36  respectively provided at the entrance of the outlet communication conduits  18 ,  20 ; these valves allowing a more stable and homogeneous leaving fluid flow to be achieved.  
      Moreover, as shown in  FIGS. 6, 7 ,  8 , in order to sense or count the number of runs made by the pistons  2 ,  4 , the device is provided with magnets  37  placed at the end of adjustable supports  39  adjacent to every cylinder  2 ,  3  for example constituted by screws engaged in threaded holes of the block of the device.  
      The count of the runs of the pistons in this case is made by measuring the perturbations of the magnetic field generated by such magnets  37 .  
      In addition, in order to eliminate possible instability problems, the pistons  4 ,  5  of the device are asymmetric, so that they are formed with the chambers of one piston staggered one another, in such a way that, in every situation, the piston acting as a piloting piston opens its chambers before the other piston, which acts as dosing piston.  
      Finally, additionally or alternatively to the trick of staggering the chambers, the two pistons  4 ,  5  have different length one with respect to the other and, particularly, one is shorter that the other of about 1 millimetre.  
      It has been found in practice that the fluid measurement/division device and process of the invention are particularly advantageous because the device is extremely compact and lightweight.  
      The fluid measurement/division device and process conceived in this manner are susceptible to numerous modifications and variants, all falling within the scope of the inventive concept; moreover all details can be replaced by technically equivalent elements.  
      In practice the materials used and the dimensions can be chosen at will in accordance with requirements and the state of the art.