Positive-displacement pump for pumping alimentary liquids

Abstract: Reciprocating positive-displacement pump for pumping oenological liquids such as wines, musts, distillates, vinegars and the like, alimentary oils and other alimentary liquids and/or beverages such as fruit juices sand pulp, sugary juices etc., of the kind with a reciprocating piston and with distributing valves provided with rubber-covered balls, comprising a double-­ action fluidodynamic cylinder for actuating the piston, the fluidodynamic cylinder being fed by a central distribution unit which is in turn fed by a source of pressurized fluid.

Description: The present invention relates to a reciprocating positive-displacement pump particularly suitable for the pumping of oenological liquids such as wines, musts, distillates, vinegars and the like, of alimentary oils sand of other alimentary liquids and/or beverages such as fruit juices and pulps, sugary juices, etc. As is known, in order to pump oenological liquids and alimentary liquids in general by means of reciprocating-piston positive-displacement pumps it is necessary to operate so that the liquids undergo the least possible agitation during the pumping operations in order to preserve their organoleptic characteristics, which would in fact be altered and/or compromised by the agitation and the forming of emulsions with air which always occur during turbulent motion. In order to reduce the conditions of turbulence of oenological and alimentary liquids during their decanting from one container to another, the food industry employs single- or two-cylinder positive-displacement piston pumps, the actuation stem whereof is reciprocatingly actuated by a connecting-rod/crank system. In particular, the positive-displacement pumps used are normally of the single- or two-cylinder kind with a distribution provided with ball valves made of alimentary rubber with metallic central cores; in these cases the length of the stroke of the piston is equal to the diameter of the circle traced by the small end of the connecting rod. The reciprocating actuation system with connecting rod and crank has in practice various disadvantages and operative limitations. Said actuation system in fact provides a liquid flow which is pulsating and not constant due to the fact that the speed of the piston (and therefore of the liquid) varies, for each stroke of the piston, from a zero value when the piston is at one end of the cylinder to the maximum value at mid-stroke and then returns to the zero value at the ends of the stroke. The change in the flow-rate of the liquid and therefore in the speed thereof entails considerable turbulence of the liquid and high stresses on the delivery pipes due to water-hammers, with possible wear and/or breakage; the disadvantage is furthermore worsened by the fact that in oenological plants the pipes are normally made of flexible material and are generally not coupled to fixed supports. For an equal diameter and speed of the piston, the liquid flow-rate is furthermore conditioned by the maximum dimension of the piston's stroke, in practice the diameter of the circle defined by the connecting rod's small end, which depends on the diameter of the flywheel used to actuate the piston's stem. Since it is not convenient to use piston and flywheel diameters greater than certain limits due to pump cost and ease-of handling reasons, in practice the maximum obtainable flow-rates are relatively modest. GB-A-2.159.888, GB-A-2.170.869 and FR-A-2.525.288 disclose pumping systems having a piston with a stem coupled to a fluidodynamic cylinder, said cylinder being in turn connected to a distribution unit fed by a source of pressurized fluid and provided with control means associated with the stem of the piston These known pumping systems provide higher and more constant flow rates for a given diameter of the pump's piston, and are also subject to a smaller number of reversal strokes and to a smaller number of speed changes with respect to the systems of the prior art, and therefore they are characterized by lower vibrations. However these known devices provide no means for preventing wearing, scoring or damaging of the internal walls of the cylinder if solid foreign matter enters the cylinder and locates between the cylinder walls and the piston sealing gasket. The aim of the present invention is to overcome the above described disadvantages by providing the oenological industry and the industry of alimentary liquids in general, including dense liquids, with a two stage positive-displacement pump structured and actuated so as to prevent scoring or damage of the internal walls of the pump's cylinder if solid foreign matter is present between said walls and the piston's sealing gaskets. An object of the invention is to provide a pump of the above specified type which is dimensioned so as to allow much higher pump filling coefficients than those obtainable with known positive-displacement pumps and to allow a reduced wear of the inflow and delivery ball valves, thus significantly reducing the noise produced by the system. A further object of the invention is to provide a positive-displacement pump which allows to vary the flow rate in a simple and rapid manner, even without varying the piston's speed. Another object is to provide a pump which can be used and installed in any environmental condition, including immersion in a liquid. Not least object is to provide a decanting pump for the above specified applications which is structured and dimensioned so that it can be easily installed, together with the piston actuation devices, on a towable or self-propelled trolley to facilitate its movement. This aim, these objects and others which will become apparent from the following description are achieved by a two-stage positive-displacement pump with a reciprocatingly slidable piston and with ball-valve distribution, particularly for pumping oenological liquids and alimentary liquids in general, including dense liquids, according to the accompanying claims. Further structural and functional characteristics of the pump according to the invention will become apparent from the following detailed description, given with reference to the accompanying drawings, which are provided merely by way of non-limitative example, wherein: figure 1 is a schematic view of a two-stage positive-displacement pump executed according to the invention; figure 2 is a sectional view of a seat for a sealing valve, made of elastically resilient material, such as rubber or the like, and with a metallic core, to reduce the noise produced by the pump and extend the useful life of said seat. figure 3 is the time diagram of the variations of the speed of the piston of a reciprocating double-action pump, actuated by means of known connecting-rod/crank systems, and figure 4 is the time diagram of the variations of the speed of the piston of a reciprocating double-action pump executed according to the invention. With reference to the above described figures, and in particular to figure 1, the pump according to the invention is constituted by a hollow body 1 made of stainless steel, inside which a piston 2 sealingly slides and is peripherally provided with an appropriate gasket 3. The piston 2 has a stem 4 which protrudes from a front wall 1a and is sealingly slidable on said wall. The cylindrical sliding chamber of the piston 2 is connected, at its opposite ends, to two longitudinal ducts 5-5a through openings 6 in which known ball valves, made of alimentary rubber with metallic core, indicated by 7-7a and 8-8a in figure 1, are arranged. The pair of valves 7-7a constitutes the inlet valves, since said valves can open toward the inside of the cylinder 1a, whereas the opposite one 8-8a constitutes the delivery valves, since these valves can be opened toward the outside of said cylinder. The longitudinal duct 5 is connected, by means of a tube 9, to the container of the liquid to be decanted, whereas the opposite one 5a is connected to a tube 10 for delivering the pumped liquid to a decanting container. The stem 4 of the pump's piston 2 is coaxially rigidly associated with the stem 4a of another piston 11 which is mounted sealingly slidable within a cylindrical body 12 and is actuated in both directions by pressurized fluid, substantially pressurized oil, which is alternately fed, through the end inlets 13-13a, by a known oleodynamic control unit 14. Said control unit is provided with an oil tank and with an equally known related oil-air or oil-water heat exchanger. The pressurized oil is fed to the control unit 14 by a variable-flow rate positive-displacement pump 15 actuated by an electric motor 16 (or by an internal-combustion engine). According to a first embodiment, the alternating reversal of the flow of pressurized oil in the oleodynamic cylinder 12 is performed by the control unit 14 upon an actuation imparted by a cam-like element or the like which is rigidly associated with the stem 4 of the pump and movable so as to make contact with two limit switches 18-18a. Said limit switches are constituted by position sensors associated with hydraulic, electric or other known shunting valves which, upon every impact with said cam 17, transmit a signal to the control unit 14, which reverses the oleodynamic flow inside the cylinder 12. According to another embodiment, the alternated reversal of the pump's piston can be provided by means of a distributing valve which can deflect the flow in the oleodynamic cylinder 12 every time the maximum preset pressure is reached in the pump. With this system, the movement of the pump's piston can reverse during the stroke if there is any foreign matter in the cylinder. In the practical execution, the assembly formed by the positive-displacement pump 1, by the oleodynamic cylinder 12 and by the associated limit switches, by the control unit and by the positive-displacement pump 15 with associated motor can be easily mounted on a towable or self-propelled trailer in order to facilitate its movement in the various areas of utilization. If a plurality of pumps is mounted in battery, it is necessary to install the limit switches 18-18a on the pump in order to adjust the offset of the deliveries. According to the invention, in order to minimize the noise produced by the decanting pump 1 and extend the useful life of the valve seats, the seats 19 (figure 2) of said valves are made of rubber with a metal core 20 and are provided with holes 21 for fixing, by means of screws or the like 22, to the body of the pump 1. By means of this solution, the possible presence of foreign solid matter, such as for example the matter found in grape crushes, cannot cause damage to the valve seats, whereas if said seats were made of steel they would be subjected to scoring or incisions which would compromise the seal of the valves. The operation of the above described two-stage positive-displacement pump is the conventional one, i.e. that of a double-action pump according to intake and discharge cycles performed by the piston 2 which, during the leftward stroke in figure 1, sucks the liquid in through the valve 7, whereas the opposite one 8 remains pressed in its seat and simultaneously compresses the liquid present in the opposite part, sending it through the valve 8a to the delivery duct; in the reverse rightward stroke, the liquid is again sucked in through the valve 7a and the liquid contained in the part of the cylinder which is opposite to the preceding one is sent, through the valve 8, to the delivery duct. Analyzing the operation of the pump, the adoption of a reciprocating actuation of the piston 2 by means of a fluidodynamic cylinder with an equal stroke allows to achieve a sliding of the piston 2 which is as constant as possible and therefore to achieve very short motion reversal times; said reversal is also facilitated by the small masses in motion and by the absence of a flywheel and of the associated connecting-rod systems. In practice, the adoption of a fluidodynamic cylinder allows to maintain high precision in the cycles and speed of the piston even when the speed of the motor fluctuates or when the temperature of the oil of the oleodynamic circuit varies. Since the cylinder 1a of the pump can furthermore be longer, for example 2.5 times longer or more, than the cylinder of current pumps actuated by crank systems, a greater intake capacity and therefore a greater volumetric efficiency are achieved; with this solution, the number of stroke reversals of the piston 2 is also smaller, for an equal flow-rate with known pumps, so that the ball valves, by working less, have a longer useful life. The variation of the flow rate of the pump according to the invention is achieved by varying the number of cycles thereof consequent to the variation in the flow-rate of the pump of the oleodynamic circuit, by means of an adapted external regulator which can be positioned even remotely from the variable-flow-rate oleodynamic pump. Said regulators can also be mounted in batteries, with no limitations of number, in order to control the flow-rate in a programmable manner. With said system it is in fact possible to "preset" various flow-rates, as many as the number of regulators, which are selected by means of a simple electric, hydraulic or similar "ON-OFF" signal. By adopting a pump according to the present invention it is therefore possible to achieve a flow-rate which can vary from zero to a maximum value or various "freely presettable" flow-rates. If the limit switches are moved in order to vary the flow-rate, the speed of the piston remains constant, but the pump is less efficient. With respect to pumps actuated by connecting-rod/crank systems, the solution according to the present invention offers the advantage of allowing to provide a number of cycles which is normally comprised between 30-35 per minute as opposed to a number of cycles equal to 70-75 per minute normally adopted in known pumps. In conventional piston and double-action pumps, the variations of the piston's speed in the course of time, as illustrated by the diagram of figure 3, furthermore entail pulsating flow pumpings which can vary from zero to a maximum value and back to zero, between which there are extensive regions 23 with no flow rate which must be compensated in order to try and even out said flow as much as possible. In the case of oleodynamic-cylinder actuation, according to the invention, the variation of the piston's movement speed in the course of time, as illustrated in figure 4, entails pumping actions with a substantially constant flow-rate, with small regions 24 to be compensated. Another advantage of the present invention is furthermore that it allows flow-rate variations by varying only the stroke of the piston 2, not its speed, by moving the limit switches 18-18a. A further advantage offered by the oleodynamic actuation system is constituted by the possibility of rotating the two mutually rigidly associated stems 4-4a and the respective pistons 2 and 11 about their common axis by means of the contact of the cam 17 with a rotating shaft provided with axial grooves adapted to impart to said cam 17, and therefore to the stems 4-4a, a slight rotation upon every stroke of the pistons, in order to avoid the forming of longitudinal scores on the surface of the cylinder, thus uniformly distributing its wear. Said oleodynamic central distribution unit can be furthermore provided with a device which reverses the flow according to the maximum pressure of the actuation fluid in relation to the "preset" maximum operating pressure of the oleodynamic pump. Another advantage of the present invention is that the pump and the associated oleodynamic cylinder can be installed in different rooms which may even be distant from those in which the remaining parts of the machine, such as the oleodynamic pump and the related control unit and motor, are installed. This fact allows to use the pump below deck, in the case of tanker ships, or in rooms with lack of air or presence of liquids, gases or vapors. The pump according to the invention can finally be coupled to other identical ones to form multiple-cylinder pumping stations. It is obvious that all modifications sand variations with structurally and functionally equivalent characteristics which are within the inventive concept defined by the accompanying claims are within the scope of the protection of the present invention.

Claims: Positive-displacement pump (1) for pumping oenological liquids in particular, and alimentary liquids in general, comprising at least one reciprocating double-action piston (2) with distribution with automatic valves (7, 7a, 8, 8a) and a device for the reciprocating movement of said piston, said device comprising a fluidodynamic cylinder (12) provided with a plunger, said plunger being associated with a stem (4) of the piston (2) of the pump (1), said fluidodynamic cylinder being fed by a fluidodynamic distribution control unit (14), said distribution control unit being in turn fed by a source of pressurized fluid, said control unit being adapted to reverse the pressurized fluid inside said fluidodynamic cylinder (12) at the opposite ends of said fluidodynamic cylinder by means of control means partially rigidly associated with said stem (4) of said piston of the pump and structured so as to transmit to said control unit the commands for the deviation of the fluid, characterized in that at least said stem (4) of the pump is rotatable about its own axis to prevent the formation of scores on the inner surface of the cylinder of the pump due to extraneous matter sucked in together with the pumped liquid. Pump according to claim 1, wherein said control means are constituted by a cam element (17) rigidly associated with said stem (4) of the piston and by two position sensors (18, 18a) associated with valves, said sensors (18, 18a) being arranged at an adjustable distance with respect to one another and to said cam element in order to allow variations of the reciprocating strokes of the piston (2) of the pump (1) and of the stroke of the fluidodynamic cylinder (12) and consequently allow variations of the flow-rate of the pump. Pump according to claim 1, wherein it comprises flow-rate selectors adapted to vary the flow-rate of the oleodynamic feed circuit between said source of pressurized fluid and said fluidodynamic cylinder (12), said regulators being possibly arranged remotely from said source of pressurized fluid and being grouped in a battery to preset various flow-rate according to the number of said selectors. Pump according to claim 1, wherein said plunger (11) has a stem (4a) which is coaxial to the stem (4) of said piston (2) of the pump (1) so that said plunger (11) and said piston (2) have substantially equal strokes. Pump according to claim 1, wherein said control means are constituted by an automatic distribution unit adapted to reverse the direction of the fluid in the fluidodynamic cylinder (12) every time a preset maximum pressure is reached in the pump. Pump according to claim 1, wherein said pump (1) has automatic ball valves (7, 7a; 8, 8a) having balls made of rubber and seats made of alimentary rubber, said seats having an inner metallic core (20) and screw means (21) for coupling to the body of the pump (1). Pump according to the preceding claims, characterized in that it can be installed, together with said fluidodynamic cylinder and said distribution control unit, on a towable or self-propelled trolley, as well as below or above deck on tanker ships for transporting alimentary liquids in general, as well as in other enclosed places short of and/or lacking air, or in the presence of dangerous vapors and/or gases and the like. Pump according to the preceding claims, characterized in that it can be coupled with other identical pumps to form multiple-cylinder pumping stations for particular applications.

Inventors: GIORDANI ALBERTO, GIORDANI, ALBERTO
Applicants: GIORDANI ALBERTO, GIORDANI, ALBERTO
Application year: 1989
Main classification: F04B9
IPC codes: F04B9, F04B15, F04B53