Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B11/00—Equalisation of pulses, e.g. by use of air vessels; Counteracting cavitation
  • F04B11/005—Equalisation of pulses, e.g. by use of air vessels; Counteracting cavitation using two or more pumping pistons
  • F04B11/0058—Equalisation of pulses, e.g. by use of air vessels; Counteracting cavitation using two or more pumping pistons with piston speed control
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
  • F04B1/02—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having two cylinders
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B11/00—Equalisation of pulses, e.g. by use of air vessels; Counteracting cavitation
  • F04B11/0041—Equalisation of pulses, e.g. by use of air vessels; Counteracting cavitation by piston speed control
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B17/00—Pumps characterised by combination with, or adaptation to, specific driving engines or motors
  • F04B17/03—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by electric motors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B23/00—Pumping installations or systems
  • F04B23/04—Combinations of two or more pumps
  • F04B23/06—Combinations of two or more pumps the pumps being all of reciprocating positive-displacement type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/06—Control using electricity
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/20—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by changing the driving speed
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2205/00—Fluid parameters
  • F04B2205/09—Flow through the pump

Definitions

• the present invention relates to a volumetric pump, in particular to a volumetric pump with improved characteristics in terms of flow rate. More in particular, the present invention relates to a volumetric pump that is characterized by the capacity to provide a practically constant flow rate, or at least with fluctuations reduced to a minimum.
• Volumetric pumps are well known machines for compressible fluids whose main characteristic is that of providing the liquid with a volume with variable geometry that is alternatively placed in communication with the suction side during filling and with the delivery side during emptying.
• the pump will simply "displace" the fluid from an environment at lower pressure to an environment at higher pressure.
• the average speed of the fluid inside the pump is generally very low so that the action of the machine is of static type and manifests itself as variation in the pressure of the fluid, unlike constant flow machines; in fact, in these machines the energy exchange is of dynamic type with combined variations of pressure, of kinetic energy and of momentum of the fluid.
• volumetric machines are classified as: reciprocating or plunger volumetric machines, when the moving element, plunger or piston, is provided with reciprocating motion, and rotary volumetric machines when the moving element is provided with rotary motion.
• the attached Figs. 1 and 2 schematically represent two single-acting reciprocating volumetric pumps 1 and 2 arranged with horizontal axis and with disc plunger. Both the pumps 1 and 2 have an inlet section 20 (suction) and an outlet section 30 (delivery). The pumps 1 and 2 also have a volume 12 with variable geometry that is connected through a suction valve 11 to the inlet section 20 and through a delivery valve 10 to the outlet section 30. The volume of the chamber 12 is varied by the stroke of the disc plunger 13. In the pump 1 of Fig. 1, the disc 13 is driven by a connecting rod-crank system 14, while in the pump 2 of Fig. 2 the disc 13 is driven by a brushless servo motor 15 whose rotary motion is converted into linear motion through a planetary roller screw system.
• plunger pumps (an example of which is provided by the pump 3 of Fig. 3) are used, wherein the plunger 16 is totally submerged in the liquid and the seals are external and produced on the fixed part, making them easy to adjust or replace even with the machine running.
• Opening and closing of the suction and delivery valves - generally automatic - can also be controlled by means of external servo-mechanisms; in this case, variation of the pressure in the pipes will depend on the valve opening law. Nonetheless, it must be noted that due to the low compressibility of liquids, opening of the delivery valve must take place more or less instantly upon reversal of the plunger motion.
• the speed of the plunger 13 has a pulsating trend and with the same law it will also vary the flow rate flowing into the suction and delivery pipes. Therefore, the motion of the fluid is not constant but pulsating with a trend similar to the one represented in Fig. 4a) and with intervals of time in which the flow rate delivered by the pump is zero.
• the amplitude of the oscillations can be reduced by increasing the number of effects, i.e., the number of working strokes per crank revolution.
• volumetric pump capable of overcoming the problems related to the single-acting volumetric pumps of known type.
• An object of the present invention is therefore to provide a volumetric pump able to provide a more or less constant flow rate of the fluid.
• a further object of the present invention is to provide a single-acting volumetric pump that is able to provide a more or less constant flow rate of the fluid.
• Yet another object of the present invention is to provide a volumetric pump that is simple to manufacture at competitive costs.
• a volumetric pump comprising an inlet section and an outlet section, and which is characterized by comprising a first volume with variable geometry connected through a first suction valve to said inlet section and through a first delivery valve to said outlet section, a second volume with variable geometry connected through a second suction valve to said inlet section and through a second delivery valve to said outlet section, first means for varying the volume of said first volume with variable geometry, second means for varying the volume of said second volume with variable geometry, actuator means of said first means for varying the volume of said first volume with variable geometry and of said second means for varying the volume of said second volume with variable geometry, said actuator means comprising a servo motor.
• the system with two independently controlled volumes with variable geometry makes it possible to guarantee a constant flow rate of the fluid as better described below, while the use of the servo motor, in particular a brushless servo motor, has considerable advantages from the point of view of performances compared to conventional drives.
• Fig. 1 is a schematic view of a first embodiment of a volumetric pump of known type
• Fig. 2 is a schematic view of a second embodiment of a volumetric pump of known type
• Fig. 3 is a schematic view of a third embodiment of a volumetric pump of known type
• Fig. 4 represents the speed trend of the plunger of the pump of Fig. 1 and of double and triple acting pumps;
• Fig. 5 is a schematic view of a possible embodiment of a volumetric pump according to the present invention.
• Fig. 6 represents the thrust phase trend of two single acting pumps controlled by brushless motors
• Fig. 7 represents the flow rate trend obtainable with the system of Fig. 6;
• Fig. 8 represents the speed trend of the plungers of the pump of Fig. 5;
• Fig. 9 represents an axonometric (sectional) view of a possible embodiment of a volumetric pump according to the present invention.
• Fig. 10 represents a top view of the embodiment of a volumetric pump of Fig. 9.
• a volumetric pump according to the present invention designated with the reference number 5, comprises - in its most general embodiment - an inlet section 53 and an outlet section 54.
• the body of the pump then splits into two branches 61 and 62.
• a first of these branches for example the branch 61, there is positioned a first volume with variable geometry 511 connected through a first suction valve 611 to said inlet section 53 and through a first delivery valve 612 to said outlet section 54.
• the branch 62 there is positioned a second volume with variable geometry 521 connected through a second suction valve 621 to said inlet section 53 and through a second delivery valve 622 to said outlet section 54.
• the pump 5 also comprises first means 51 for varying the volume of said first volume with variable geometry 511 and second means 52 for varying the volume of said second volume with variable geometry 521.
• first means 51 for varying the volume of said first volume with variable geometry 511 comprise a first disc plunger and the second means 52 for varying the volume of said second volume with variable geometry 521 comprise a second disc plunger.
• other plunger or piston means or equivalent systems could also be used.
• actuator means 510, 520 of said first means 51 for varying the volume of said first volume with variable geometry 511 and of said second means 52 for varying the volume of said second volume with variable geometry 521 said actuator means 510, 520 comprising a servo motor that is advantageously a brushless servo motor.
• said actuator means could comprise a first brushless servo motor 510 for operation of said first means 51 for varying the volume of said first volume with variable geometry 511 and a second brushless servo motor 520 for driving said second means 52 for varying the volume of said second volume with variable geometry 521.
• a reduction of the speed of the plunger acting on the first volume with variable geometry 511 corresponds to an increase of the speed of the plunger acting on said second volume with variable geometry 521
• an increase of the speed of the plunger acting on the first volume with variable geometry 511 corresponds to a reduction of the speed of the plunger acting on said second volume with variable geometry 521.
• a reduction of the volume of said first volume with variable geometry 511 corresponds to an increase of the volume of said second volume with variable geometry 521
• an increase of the volume of said first volume with variable geometry 511 corresponds to a reduction of the volume of said second volume with variable geometry 521
• said first 51 and second 52 means for varying the volume of said first 511 and second 521 volume with variable geometry substantially operate in phase opposition.
• the volumetric pump 5 advantageously comprises an inlet section 53 and an outlet section 54.
• the pump 5 further comprises a first cylinder 511 that is connected through a first suction valve 611 to said inlet section 53 and through a first delivery valve 612 to said outlet section 54, and a second cylinder 521 that is connected through a second suction valve 621 to said inlet section 53 and through a second delivery valve 622 to said outlet section 54.
• a first piston 51 functionally inserted in said first cylinder and adapted to move with reciprocating motion so as to define a first volume with variable geometry 511
• a second piston 52 functionally inserted in said second cylinder so as to define a second volume with variable geometry 521
• a first actuator unit 510 of said first piston 51 adapted to selectively move said first piston along said first cylinder to modify said first volume with variable geometry 511
• a second actuator unit 520 of said second piston 52 adapted to selectively move said second piston along said second cylinder to modify said second volume with variable geometry 521.
• said first and second actuator unit 510 and 520 each comprise:
• a servo motor - a shaft, having a rotation axis connected to said servo motor, wherein said servo motor transmits to said shaft a rotary motion about said rotation axis;
• said slider comprises means for converting said rotary motion into a reciprocating translational motion according to said longitudinal axis, so that a first direction of rotation of said shaft corresponds to a first direction of translation of said slider along said shaft, and a second direction of rotation of said shaft, opposite said first direction, corresponds to a second direction of translation of said slider along said shaft.
• said slider is connected in one piece with said or first and second cylinder so that the translation of said slider according to said first and second direction of translation causes the variation of said first and second volume with variable geometry.
• control unit adapted to control said first and second actuator unit, wherein said control unit is adapted to:
• Figs. 9 and 10 schematically represent sectional views of a volumetric pump 5 with two pumping units of volumetric type 151 and 152, with single-acting reciprocating drive, arranged with horizontal axis with piston in the form of a cylinder.
• the two pumps have an inlet section (suction - represented by the arrows 81 and 82) and an outlet section (delivery - represented by the arrows 83 and 84), where the flow of liquid is appropriately guided by the specific valves.
• a brushless servo motor 510 provides the rotary motion to the corresponding screw 71 (the screw operated by the servo motor 520 and the corresponding screw thread not visible) and is converted into linear motion through a system of planetary rollers belonging to the screw thread 73 (the screw connected to the piston 75 operated by the servo motor 520 and the corresponding screw thread not visible).
• the screw thread 73 translates and generates the stroke of the piston (not visible as inserted in the corresponding cylinder 74) to which it is connected.
• Rotation of the screw 71 generates, according to the direction, a translation of the piston in one direction or the other.
• Displacement of the piston produces a reciprocating rectilinear motion and consequently the pumping action.
• the first important characteristic consists in obtaining the reciprocating rectilinear motion, operating only with reversal of motion, produced by the brushless motor that is particularly suitable to produce said movement.
• the second great advantage consists in the fact that the brushless motor is capable of modifying its rotation speed proportionally, following precise instructions provided by the electronic drive.
• the stroke C and bore D are linked to each other by a characteristic parameter of each pump, which is the C/D ratio.
• the stroke/bore ratio is generally between 1.2 for short stroke pumps and 2 for long stroke pumps.
• ratios greater than 2 it is possible also to use ratios greater than 2 and this means an increase of the duration of the delivery phase and consequently higher outputs obtainable with the pumps according to the present model.
• a further parameter to be considered to reduce pressure drops in the pipes and in the valves is the average speed of the plunger "Vm".
• Vm the average speed of the plunger
• Vm 1.2 ⁇ 2.4 [m/s].
• Brushless motors are able to provide angular accelerations such as to allow, ideally, the desired speed Vm to be reached almost instantaneously. For correct sizing of the pump it must nonetheless be considered that these accelerations would produce high pressure drops in the system (quadratic proportionality) and high stresses on the mechanical members.
• volumetric pump according to the present invention allows the set objects to be achieved.
• volumetric pump according to the present invention it is in fact possible to have a substantially constant fluid flow rate; moreover, the use of a brushless servo motor allows continuous and precise control of plunger movement, guaranteeing constant flow rate in any condition.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Reciprocating Pumps (AREA)
• Details Of Reciprocating Pumps (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (2)

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• 2017
  • 2017-11-14 US US16/348,169 patent/US20190264679A1/en not_active Abandoned
  • 2017-11-14 EP EP17805135.5A patent/EP3538762A1/de active Pending
  • 2017-11-14 WO PCT/EP2017/079131 patent/WO2018087376A1/en active Application Filing
  • 2017-11-14 CN CN201780070176.6A patent/CN109952432A/zh active Pending

Patent Citations (3)

Non-Patent Citations (1)

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