Volumetric Pump

Abstract

The present invention relates to a volumetric pump that comprises an inlet section and an outlet section. The pump also comprises a first volume with variable geometry that is connected through a first suction valve to said inlet section and through a first delivery valve to said outlet section, and a second volume with variable geometry that is connected through a second suction valve to said inlet section and through a second delivery valve to said outlet section. There are also provided first means for varying the volume of said first volume with variable geometry and second means for varying the volume of said second volume with variable geometry, and 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. Advantageously, said actuator means comprise a servo motor.

Claims

1.-9. (canceled)

10. A volumetric pump comprising: an inlet section; an outlet section; 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; and at least one actuator configured to control operation of said first means for varying the volume of said first volume with variable geometry and for driving of said second means for varying the volume of said second volume with variable geometry, said at least one actuator comprising a servo motor.

11. The volumetric pump of claim 10, wherein the at least one actuator comprises a brushless servo motor.

12. The volumetric pump of claim 11, wherein the at least one actuator comprises a first brushless servo motor for operation of said first means for varying the volume of said first volume with variable geometry and a second brushless servo motor for operation of said second means for varying the volume of said second volume with variable geometry.

13. The volumetric pump of claim 10, wherein said first means for varying the volume of said first volume with variable geometry comprises a first disc plunger and that said second means for varying the volume of said second volume with variable geometry comprises a second disc plunger.

14. The volumetric pump of claim 10, wherein in operating conditions a reduction of the volume of said first volume with variable geometry corresponds to an increase of the volume of said second volume with variable geometry, and an increase of the volume of said first volume with variable geometry corresponds to a reduction of the volume of said second volume with variable geometry.

15. The volumetric pump of claim 10, wherein in operating conditions said first and second means for varying the volume of said first and second volume with variable geometry operate in phase opposition.

16. The volumetric pump of claim 10, wherein in operating conditions the fluid flow rate respectively entering/exiting from said inlet and outlet sections is substantially constant.

17. The volumetric pump of claim 10, wherein the at least one actuator comprises a first actuator and a second actuator, and said first actuator and said second actuator 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; and a slider mounted sliding on said shaft, wherein said slider comprises means for converting said rotary motion into a reciprocating translational motion, 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.

18. The volumetric pump of claim 17, further comprising a control unit configured to: selectively reverse said direction of rotation of said first actuator and said second actuator to implement the respective reciprocating translational motions in phase opposition to each other; and vary according to an acceleration/deceleration curve the respective reciprocating translational motions to obtain a substantially constant flow rate.

19. A method of operating a volumetric pump comprising a first cylinder that is connected through a first suction valve to an inlet section and through a first delivery valve to an outlet section, a second cylinder that is connected through a second suction valve to said inlet section and through a second delivery valve to said outlet section, a first piston functionally inserted in said first cylinder and adapted to move with reciprocating motion to define a first volume with variable geometry, and a second piston functionally inserted in said second cylinder so as to define a second volume with variable geometry, the method comprising: via at least one actuator comprising a servo motor, selectively moving said first piston along said first cylinder to modify said first volume with variable geometry, and via the at least one actuator, selectively moving said second piston to move along said second cylinder to modify said second volume with variable geometry.

20. The method of claim 19, wherein the at least one actuator comprises first and second actuators and each of the first and second actuators comprise a servo motor, a shaft having a rotation axis connected to said servo motor, and a slider mounted on said shaft, the method comprising, for each of the first and second actuators: transmitting to the respective shaft a rotary motion about said rotation axis; and converting said rotary motion into a reciprocating translational motion, so that a first direction of rotation of said shaft corresponds to a first direction of translation of the respective 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.

21. The method of claim 20, further comprising: selectively reversing said direction of rotation of said first and second actuators to implement said reciprocating translational motion of said first and second pistons in phase opposition to each other; and varying according to an acceleration/deceleration curve said reciprocating translational motion of each of said first and second pistons so as to obtain a substantially constant flow rate.

Description

[0032] Further characteristics and advantages of the present invention will be more apparent from the description of the preferred embodiment, illustrated by way of non-limiting example in the accompanying figures, wherein:

[0033] FIG. 1 is a schematic view of a first embodiment of a volumetric pump of known type;

[0034] FIG. 2 is a schematic view of a second embodiment of a volumetric pump of known type;

[0035] FIG. 3 is a schematic view of a third embodiment of a volumetric pump of known type;

[0036] FIG. 4 represents the speed trend of the plunger of the pump of FIG. 1 and of double and triple acting pumps;

[0037] FIG. 5 is a schematic view of a possible embodiment of a volumetric pump according to the present invention;

[0038] FIG. 6 represents the thrust phase trend of two single acting pumps controlled by brushless motors;

[0039] FIG. 7 represents the flow rate trend obtainable with the system of FIG. 6;

[0040] FIG. 8 represents the speed trend of the plungers of the pump of FIG. 5;

[0041] FIG. 9 represents an axonometric (sectional) view of a possible embodiment of a volumetric pump according to the present invention;

[0042] FIG. 10 represents a top view of the embodiment of a volumetric pump of FIG. 9.

[0043] With reference to the accompanying FIG. 5, a volumetric pump according to the present invention, designated with the reference number 5, comprisesin its most general embodimentan inlet section 53 and an outlet section 54.

[0044] From the inlet section 53, the body of the pump then splits into two branches 61 and 62. In 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.

[0045] In the second branch, for example 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.

[0046] The pump 5 according to the present model 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.

[0047] For example, the 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. However, other plunger or piston means or equivalent systems could also be used.

[0048] There are also provided 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.

[0049] Although a single servo motor could be used to control the first 51 and second 52 means for varying the volumes with variable geometry 511 and 521for example through appropriate mechanisms that allow synchronized drive thereof according to the chosen law of motionit is preferable for said actuator means to 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.

[0050] In fact, considering that the flow rate Q is a function of the speed v.sub.i according to the law:

Q=(.Math.r.sup.2).Math.v.sub.i

it is in fact possible to control, through the two brushless servo motors 510 and 520, the speed of the first 51 and second 52 means for varying the volumes, overlapping the thrust phases as schematized in FIG. 6 (in which the part of the graph with the continuous line relates to the thrust phase of one of the means for varying the volume, while the part of the graph with the dashed line relates to the thrust phase of the other means for varying the volume).

[0051] In particular, considering only the delivery phases (FIG. 6), 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, and 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.

[0052] In practice, in operating conditions 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, and 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.

[0053] In other words, with reference to FIGS. 6, 7 and 8, by making the deceleration phase of one of the brushless motors coincide with the start of the acceleration phase of the second, the sum of the speeds and the fluid flow rate displaced will remain constant (FIG. 7).

[0054] It can be said that, in operating conditions (FIG. 8), 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.

[0055] As they are not connected to the connecting rod-crank mechanism, it is simple to set the suction phase with independent speed and accelerations to those of the delivery phase by decelerating or accelerating the plunger at will to obtain the synchronism described above. Moreover, as the system can be monitored instantaneously, it is possible to offset any delays due to pressure drops during motor operation, restoring the perfect synchronism of the two plungers required to obtain linearity of the flow rate.

[0056] In practice, 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.

[0057] Moreover, there are advantageously provided 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, and 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 and 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.

[0058] Advantageously, said first and second actuator unit 510 and 520 each comprise: [0059] a servo motor; [0060] 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; [0061] a slider mounted sliding on said shaft, wherein 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.

[0062] Advantageously, 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.

[0063] Preferably, there is also provided a control unit adapted to control said first and second actuator unit, wherein said control unit is adapted to: [0064] selectively reverse said direction of rotation of said first and second actuator unit to implement said reciprocating translational motion of said first and second piston in phase opposition to each other; [0065] vary according to an acceleration/deceleration curve said reciprocating translational motion of each of said first and second piston so as to obtain a substantially constant flow rate.

[0066] 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 (suctionrepresented by the arrows 81 and 82) and an outlet section (deliveryrepresented by the arrows 83 and 84), where the flow of liquid is appropriately guided by the specific valves.

[0067] 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.

[0068] Displacement of the piston, obtained as described, 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.

[0069] 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.

[0070] Precise and prompt variation translates into an analogous behavior of the flow rate of the pump; it is therefore possible to manage two pumps so as to obtain the sum of the two flow rates with a constant value varying number of revolutions and direction of motion of the two single units.

[0071] It should be noted that it is possible to produce a constant flow rate with only two pumping units, a situation that cannot be obtained by the pumps with more than one pumping unit currently available on the market.

[0072] From the point of view of construction, as is known, in connecting rod-crank mechanisms 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. In the system with planetary rollers that can be used in the pumps of the present invention, 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.

[0073] 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. In fact, based on speed, pumps are classified as: [0074] slow pumps: Vm=0.30.8 [m/s] [0075] normal pumps: Vm=0.81.2 [m/s] [0076] fast pumps: Vm=1.22.4 [m/s].

[0077] 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.

[0078] In practice, it has been seen how the volumetric pump according to the present invention allows the set objects to be achieved. With the 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.

[0079] On the basis of the description provided, other characteristics, modifications or improvements are possible and evident to a person skilled in the art. These characteristics, modifications and improvements should therefore be considered a part of the present utility model. In practice, the materials used, the dimensions and contingent shapes can be any according to requirements and to the state of the art.