EP3023638B1

EP3023638B1 - Pumping unit for alimentary liquids

Info

Publication number: EP3023638B1
Application number: EP15003265.4A
Authority: EP
Inventors: Alberto Giordani
Original assignee: Tecnogomma Srl
Current assignee: Tecnogomma Srl
Priority date: 2014-11-17
Filing date: 2015-11-17
Publication date: 2020-01-22
Anticipated expiration: 2035-11-17
Also published as: EP3023638A1; ES2787176T3

Description

The present invention relates to a pumping unit for alimentary liquids, such as for example wines, musts, distilled products, food oils, fruit juices and pulps, and the like.
As is known, single-cylinder or multiple-cylinder volumetric piston pumps are usually used to move alimentary liquids that do not withstand centrifugal motions and tend to emulsify or alter their physical state or their organoleptic characteristics as a consequence of those transfer operations that are not performed delicately.
More particularly, these pumps have one or more chambers that are alternately connected to a suction pipe and to a delivery pipe by means of valves of a different type depending on the liquid to be processed; a piston slides hermetically within each chamber.
The actuation of the pistons is generally performed by link and rod systems or by crank and slotted link mechanisms which, despite being widely used, have some drawbacks that are not negligible and are substantially tied to the pulsed motion of the piston.
The piston speed in fact varies for each stroke from a value equal to zero, when the piston is at one end of the chamber, to a maximum value when the piston is halfway along the stroke, and then the speed returns to zero at the end of the stroke.
The frequent repetition of these working cycles, repetition that is necessary for pumps of the conventional type in order to provide the required flow rates, causes considerable turbulence, which tends to deteriorate the organoleptic characteristics of the transferred liquid, and strong stress on the delivery pipes due to hammer effects.
In addition, one should consider that both in the case of link and rod systems and in the case of crank and slotted link mechanisms, the piston stroke and the flow-rate of the pumps are in practice conditioned by the diameter of the flywheel that actuates the system.
Due to cost and easy handling reasons, the trend is to use flywheels with diameters that do not exceed certain limits and consequently the maximum flow-rates that can be obtained with pumps of the known type are generally relatively low, at least as regards single-cylinder pumps.
It should also be considered that in the pumps currently in use the flywheel is usually actuated by means of chains of gears that transmit to the flywheel the torque generated by the motor.
Consequently, the hydraulic power of known pumps and the maximum pressure of the transferred liquid are limited by the geometric characteristics of the gears and, in particular, by the geometric characteristics of the set of teeth.
It is necessary to stress the fact that the gears contribute to increase the flywheel mass already present in known pumps, making any sudden stop even more difficult.
US6079797 discloses a dual action ball screw pump for a vehicular braking system. The pump body has an axial bore defining a travel chamber and a pressure chamber. An input port and an output port are formed in the pressure chamber. A ball screw is provided in the travel chamber. A piston is connected to the ball screw and slidably extends into the pressure chamber as the ball screw is rotated. The piston divides the pressure chamber into an input chamber having a maximum volume and an output chamber having a maximum volume which is less than the maximum of the input chamber.
EP0309596 discloses a pumping apparatus for delivering liquid at a high pressure, for use in liquid chromatography. The pump has two pistons which reciprocate in two chambers. The output of the first pump chamber is connected via a valve to the input of the second pump chamber. The pistons are driven by ball-screw spindles. The stroke volume displaced by the piston is freely adjustable by corresponding control of the angle by which the shaft of the drive motor is rotated during a stroke cycle. The control circuitry is operative to reduce the stroke volume when the flow rate which can be selected by user at the user interface is reduced, thus leading to reduced pulsations in the outflow of the pumping apparatus.
The aim of the invention is to solve the above described drawbacks, by providing a pumping unit, particularly for alimentary liquids, that is capable of providing a pumping action with flow-rates that are as constant as possible, without entailing the use of oil-pressure controlled systems or of kinematic chains formed by gears in an oil bath.
Within the scope of this aim, a particular object of the invention is to provide a pumping unit that allows to maximize the flow-rate in the presence of an equal diameter of the piston and where said flow-rate can be modified simply and rapidly.
Another object of the invention is to provide a pumping unit which, for an equal flow-rate, entails a lower number of piston strokes, and therefore of reverse motion, so as to minimize shocks and vibrations and to preserve at the best the organoleptic characteristics of the transferred product.
Another object of the invention is to provide a pumping unit in which it is possible to predict accurately even from the beginning, the lifespan of the components used.
A further object of the invention is to provide a pumping unit that avoids the use of the lubricating fluids or lubricants that are normally present in the reduction units that receive the link-and-rod or crank and slotted link systems, and in the pumps operated by oil-pressure controlled cylinders.
In case of failures or malfunctions, these lubricants, normally constituted by reduction unit oil or oil for oil-pressure controlled circuits, may leak and contaminate the place where the pumps are located, the pumps being usually located in environments for processing alimentary liquids.
Another object of the invention is to provide a pumping unit that is capable of reducing the pulses caused by the alternating operation.
Another object of the invention is to provide a pumping unit that has no flywheel mass, has a reduced weight and dimensions, and can be installed easily on a truck that can be towed or is self-propelled in order to facilitate its transfers.
This aim, as well as these and other objects that will become better apparent hereinafter, are achieved by a pumping unit, particularly for alimentary liquids, as claimed in the appended claims.

in the appended claims.

Further characteristics and advantages will become better apparent from the description of preferred but not exclusive embodiments of a pumping unit according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic view of a pumping unit;
Figure 2 is a chart of the variations over time of the piston speed in a pump mounted on a pumping unit according to the invention and in a conventional pump;
Figure 3 is a schematic view of a pumping unit according to the invention.

With reference to the cited Figures 1 and 2, a pumping unit, particularly for alimentary liquids, is designated generally by the reference numeral 1.
The pumping unit 1 includes a base, not shown in the figures, which supports a volumetric pump 2 constituted by a body 3 that is preferably but not necessarily made of stainless steel, in which one or more chambers 4 are defined, also known as cylinders, inside which pistons 5, also known as plungers, hermetically slide.
Figure 1 shows a volumetric pump 2 that comprises a single chamber 4 inside which a single double effect piston 5 slides; however, it is evident to the person skilled in the art that the pumping unit according to the present invention can also support pumps having a different number of pistons, or pumps in which the volume variation is given by the motion of elements of another type.
In the specific case, the piston 5 comprises a disk-like body that supports on its edge one or more sealing rings 6 that are appropriately made of synthetic material and/or of natural leather treated with tannin.
The piston 5 is connected to a stem 7 that protrudes from a wall of the body 3 and is able to slide hermetically.
The chamber 4 is connected alternately to a suction pipe 8 and to a delivery pipe 9, which can be connected respectively to a container for liquid to be transferred and to a receiving container.
Conveniently, the connection of the chamber 4 to the pipes is adjusted by suction valves 10a and 10b and by delivery valves 11a and 11b, which cooperate respectively with seats 12a, 12b and 13a, 13b.
The suction valves 10a and 10b and the delivery valves 11a and 11b automatically open and close respectively upon the increase and decrease of the volume of the chamber 4.
In the case being considered, the suction valves 10a and 10b and the delivery valves 11a and 11b are gravity-actuated ball valves, per se already known, which substantially comprise a metallic core coated with a polymeric material that is suitable for food use.
According to a variation that is not shown in the accompanying figures and that is particularly adapted for the transfer of particularly dense liquids, the suction valves 10a and 10b and the delivery valves 11a and 11b substantially comprise ground ball screws made of stainless steel.
In this case, the use of appropriate seats 12a, 12b and 13a, 13b made of steel coated with a polymeric material that is adapted for food use is provided, and in combination therewith it is also provided the use of adapted valve guides, also made of steel coated with a polymeric material that is adapted for food use.
The above already known embodiments, in addition to minimizing the noise of the volumetric pump 2, allow to overcome any sealing problems of the valves caused by scoring or incisions that can be created by small foreign objects.
According to the present invention, the pumping unit 1 is provided with an electromechanical device 14 that is preset to move the piston 5 according to an alternating rectilinear motion.
According to a preferred embodiment, the electromechanical device 14 includes a screw drive means 15 which is operatively connected to the piston 5 and is actuated by an electric motor means 16.
In greater detail, the screw drive means 15 comprises a per se known recirculating ball screw, which is formed by a recirculating ball screw 17 and by a threaded shaft 18.
The recirculating ball screw 17 is coupled to the free end of the stem 7, while the threaded shaft 18 is connected to the electric motor means 16 by means of a flexible coupling 19, with the possibility to turn in both directions of rotation.
In the illustrated example, the electric motor means 16 is arranged substantially in axial alignment with the threaded shaft 18; however, this is merely an example.
According to a constructive variation not shown in the figures, the electric motor means 16 can in fact be mounted in a different position with respect to the threaded shaft 18, using for example reduction units with parallel axes, perpendicular reduction units, or other adequate transmission systems.
Advantageously, the stem 7 is provided with a longitudinal cavity 20 that is substantially cylindrical and is extended at its axis of symmetry.
The longitudinal cavity 20 is conceived to receive part of the threaded shaft 18 during the alternating motion of the piston 5.
The electric motor means 16 is constituted by a variable-speed electric motor, preferably a brushless motor with a low flywheel mass, the operation of which is controlled by an electronic control device 21 by means of which it is possible to set the operation of the pumping unit 1.
In particular, the electronic control device 21 allows to keep the sliding speed of the piston 5 substantially constant.
Furthermore, the electronic control device 21 allows to associate the time of reverse motion of the piston 5 with the opening/closing time of the suction valves 10a and 10b and of the delivery valves 11a and 11b.
In this regard, it should be considered that since these valves are gravity-actuated, for an equal weight of the balls that in practice constitute the valves, their opening/closing times can be longer or shorter depending on the higher or lower density of the transferred liquid.
From a practical point of view, the electronic control device 21 therefore allows to synchronize the flow-rate gap caused by the pulsed motion of the piston 5 with the rising and falling times of said balls.
Conveniently, in order to reduce the pulses induced by alternating operation, a pulse reduction device is mounted on the pumping unit 1.
In greater detail, the device is constituted by compensation chambers, which are per se known and are not shown in the figures and are arranged on the suction pipe 8 and on the delivery pipe 9.
Advantageously, the compensation chambers are connected to a pair of piston air generators 22, which supply said chambers so that the volume of air sufficient to ensure their effectiveness is maintained inside them.
In the specific case, the piston air generators 22 are constituted by single effect pneumatic cylinders with return spring and one-way valves, which are arranged on the outside, at the dead centers of the axial sliding of the stem 7.
The alternating actuation of the cylinders is performed by a pusher 23 of appropriate shape, which is integral with the stem 7, which upon arriving at the braking steps compresses the air inside the cylinders.
In this manner, the air by passing through the pipes and the one-way valves, is sent to the inner part of each compensation chamber.
After the mechanical compression of the stem of each pneumatic cylinder, the spring returns the stem to its maximum extension, ready for the next maneuver.
Advantageously, the entire pumping unit 1 can be mounted on a truck that can be towed or is self-propelled, not shown in the figures, so as to facilitate its transfers in the various regions of use.
In Figure 3, in which the pumping unit according to the invention is designated generally by the reference numeral 101, the alternating motion of the piston 5 is performed by an electromechanical device 114 that is substantially similar to the preceding one.
More particularly, the electromechanical device 114 includes a slider 115 that slides with a rectilinear motion along a linear guide 116 and is fixed to the base that supports the volumetric pump 2 so as to be substantially aligned with the sliding direction of the piston 5.
The slider 115 is connected kinematically to the stem 7 of the piston 5 and its motion along the linear guide 116 is actuated by a screw drive means 15 which is substantially equivalent to the one already described.
As regards Figure 3, the elements that correspond to the elements that have already been described with reference to Figure 1 have been designated by the same reference numerals.
The operation of the pumping unit according to the present invention is evident from what has been described above.
In particular it is evident that the electromechanical device 14 or 114 allows to guide in the best possible way the piston 5 in its linear alternating motion.
The rotary motion imparted to the threaded shaft 18 by the electric motor means 16 in fact causes the recirculating ball screw 17 to reach alternately the two opposite ends of the threaded shaft 18.
This motion is transmitted, through the stem 7, to the piston 5.
Whereas in the case of the electromechanical device 14 motion transmission is direct, in the case of the electromechanical device 114 it occurs by means of the slider 115 that follows the axial sliding of the piston 5.
During the forward stroke, the piston 5 sucks the liquid from a part of the chamber 4 through the suction valve 10a, while the delivery valve 11a remains closed, and simultaneously compresses the liquid that is present in the opposite part of the chamber 4, sending it through the delivery valve 11b to the delivery pipe 9.
In the reverse stroke, i.e. during return, the liquid is sucked into a part of the chamber 4 through the suction valve 10b, while the liquid contained in the opposite part is sent through the delivery valve 11a to the delivery pipe 9.
The operation of the volumetric pump 2 is different from that of a pump that is actuated in a traditional manner due to greater constancy in the sliding speed of the piston 5 and due to a significant reduction of reverse motion time.
These peculiarities are clearly highlighted in the chart of Figure 2, in which the variations over time of the speed of the piston 5, represented with a solid line 50, are compared with those of the piston of a traditional single-cylinder pump of the traditional type, shown in dashes 60.
Reduction of reverse motion time is furthermore facilitated by the absence of flywheel mass and by the management of the electric motor means 16 that is performed by the electronic control device 21 which, as already highlighted previously, allows to synchronize the reverse motion time of the piston 5 with the opening/closing time of the suction valves 10a 10b and of the delivery valves 11a and 11b.
Another advantageous characteristic of the present pumping unit is constituted by the fact that the electromechanical device 14 or 114 allows to use also pistons/chambers that have a longer stroke and a large bore.
This allows to reduce the number of strokes per minute even to one quarter in the volumetric pump 2 with respect to a pump of the traditional type, with a consequent reduction of wear and more delicate transfer, to the full advantage of the organoleptic characteristics, which are better preserved, of the transferred product.
Furthermore, the long stroke of the piston 5, which by way of example is four times longer than that of conventional pumps, gives the volumetric pump 2 a very large liquid priming and vacuum capacity, greatly facilitating the suction of liquids even in underground tanks.
Another advantageous characteristic of the present pumping unit is constituted by the fact that the electromechanical device 14 or 114 allows to exert forces and strokes that are not available in traditional pumps which, subjected to intense operating pressures, are overloaded to the point of damaging the gears of the reduction unit and the systems for transferring rotary motion into linear motion.
Another advantageous characteristic of the present pumping unit is constituted by the fact that the electromechanical device 14 or 114 lacks radio transmissions of motion, with consequent reduced wear of the rolling element; however, this does not hinder the possibility of different motion transmissions.
Moreover, it should be considered that the electromechanical device 14 or 114 has a very high efficiency, since it uses systems with rolling motions preferably along balls or rollers.
The electromechanical device 14 or 114, by using preferably brushless motors with a low flywheel mass with electronic position and speed control, allows the present pumping unit to have a constant torque from zero to the maximum rotary speed of the threaded shaft 18, with the consequent possibility to vary the flow-rate of the volumetric pump 2 from zero to the maximum flow-rate at the maximum operating pressure.
These electronic controls, which are an integral part of the present pumping unit, furthermore allow to interface the machine with external electric/electronic control systems, for example for the supply of refrigeration and/or heating circuits.
A further advantage of the invention resides in that the present pumping unit can be used as a dosage pump; by using an electronic management of the motion of the piston inside the chamber, it is in fact easy to program the exact quantity of cycles in order to dose or mix the transferred liquids in addition to being able to detect, with good approximation, the pumped quantity thereof and the actual partial and/or total operating times; therefore, it also acts as a litre-counter.
Another advantage of the invention resides in the fact that the present pumping unit can be used to supply filtering systems requiring for example pumps with a small flow-rate with high pumping pressures and self-controlled constant pressures.
Another advantage of the invention resides in that the motion of the piston is started according to a progressive acceleration ramp until the set speed is reached; this leads to a great advantage during the final filling of tanks and/or of other containers.
Once the almost complete filling of the vessel has been reached, in order to complete total topping-up, the operator, after stopping the pump, must in fact restart it to complete the filling; the fact that the piston speed can vary without discontinuities between two limiting values evidently facilitates this operation, in particular with respect to pumps of the traditional type, which in general merely have the possibility to use two different operating speeds.
Moreover, it should be considered that starting process according to an acceleration ramp is advantageous also for the flexible hoses used for transfer.
It has been demonstrated, therefore, that the pumping unit, particularly for alimentary liquids, according to the invention, fully achieves the intended aim and objects.
The pumping unit, particularly for alimentary liquids, thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with other technically equivalent elements.
In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.

Claims

A pumping unit for alimentary liquids, comprising a volumetric pump (2) provided with at least one chamber (4) inside which a piston (5) slides hermetically; said chamber (4) is connected alternately to a suction pipe (8) and to a delivery pipe (9) by means of automatic valves (10a, 10b, 11a, 11b); said pumping unit (1) further comprising an electromechanical device (114) for the alternating motion of said piston (5); said electromechanical device (114) being substantially constituted by a screw drive means (15) operatively connected to said piston (5) and actuated by an electric motor means (16); said pumping unit (1) being characterized in that said electromechanical device (114) comprises at least one slider (115) that can slide on at least one linear guide (116); said slider (115) being associated with said screw drive means (15) so as to interact with said piston (5).
The pumping unit according to claim 1, characterized in that said screw drive means (15) comprises at least one recirculating ball screw (17) and a threaded shaft (18); said threaded shaft (18) being turned by said electric motor means (16); said recirculating ball screw (17) being associated with a stem (7) that is connected to said piston (5).
The pumping unit according to claim 2, characterized in that said stem (7) comprises a substantially cylindrical longitudinal cavity (20) adapted to receive at least a portion of said threaded shaft (18), during the alternating motion of said piston (5).
The pumping unit according to one or more of the preceding claims, characterized in that said electric motor means (16) comprises at least one variable-speed electric motor.
The pumping unit according to one or more of the preceding claims, characterized in that said electric motor means (16) comprises an electronic control device (21) for controlling said electric motor.
The pumping unit according to claim 5, characterized in that said electronic control device (21) comprises a system for synchronizing the reverse motion time of said piston (5) with the opening/closing time of said valves (10a, 10b, 11a, 11b).
The pumping unit according to one or more of the preceding claims, characterized in that said valves (10a, 10b, 11a, 11b) are gravity-actuated ball valves constituted by a metallic core coated with polymeric material suitable for food use.
The pumping unit according to one or more of the preceding claims, characterized in that the said sealing seats (12a, 12b, 13a, 13b) of said valves (10a, 10b, 11a, 11b) comprise a metallic core associated with the body (3) of said volumetric pump (2); said core being coated with polymeric material suitable for food use.
The pumping unit according to one or more of the preceding claims, characterized in that it comprises a pulse reduction device which comprises at least one compensation chamber that can be connected to the delivery pipe (9), or the suction pipe (8), of said volumetric pump (2); said compensation chamber being fed by at least one piston air generator (22) that can be operated by the axial sliding of said stem (7) during the alternating motion of said piston (5).