EP3685045B1 - Positive displacement pump with improved cleaning - Google Patents

Description

Technical area

The invention relates to the field of pumps, in particular to volumetric eccentric piston pumps. More particularly, the invention relates to a pump comprising means allowing improved cleaning in place (CIP).

State of the art

In some industrial fields, for example the food industry, the pumps are cleaned without dismantling. An auxiliary pump sends a cleaning liquid which passes through the pump. This process is called Cleaning In Place (CIP).

Positive displacement pumps are among the pumps that can be cleaned by this process. The documents WO9736107 A1 And US1497050A disclose similar positive displacement pumps.

A progressive cavity pump generally comprises a cylinder comprising a suction opening and sharing one end with a discharge zone. At this end, a piston is slidably mounted on the end of a drive shaft and is pressed by pressing means, such as springs, against the cylinder, thus blocking the passage of fluid.

During CIP cleaning, the pressure generated by the auxiliary pump makes it possible to separate the piston from the cylinder and consequently the passage of a flow of cleaning liquid. However, the resistance of the pressing means reduces the distance of this detachment, thus inducing pressure drops in the installation which prevents the passage of the entire cleaning flow through the pump.

This effect is particularly accentuated in volumetric eccentric piston pumps comprising a sleeve surrounding the shaft and formed of bellows whose interior remains at atmospheric pressure. Such a sleeve being subjected externally to the pressure of the cleaning liquid, it then exerts a force in the same direction and the same direction as the pressing means. The combined action of the pressing means and the sleeve on the piston therefore further reduces the separation distance between the cylinder and the piston and thereby increases the pressure drop generated by the pump.

To limit these pressure drops, it is generally necessary to install an external piping network with a valve to divert part of the cleaning flow which is greater than the maximum flow of the pump. This therefore makes installation and cleaning in place complex.

The object of the present invention is to propose a volumetric pump allowing simplified cleaning in place as well as a method for cleaning such a pump.

Description of the invention

• Une tubulure présentant une première extrémité solidaire d'une zone de transmission et une deuxième extrémité se terminant par un cylindre solidaire d'une zone de refoulement, la tubulure comprenant une ouverture d'aspiration et la zone de refoulement comprenant une ouverture de refoulement,
• Un arbre d'entrainement s'étendant entre la zone de transmission et la tubulure avec un bout située au niveau du cylindre, et
• un piston agencé dans la zone de refoulement et monté coulissant au bout de l'arbre en étant plaqué contre le cylindre par des moyens élastiques de manière à bloquer un déplacement de fluide entre la tubulure et la zone de refoulement.

Selon l'invention, la pompe comprend en outre des moyens pour écarter élastiquement le piston du cylindre et le maintenir à une distance prédéterminée de celui-ci.To this end, the subject of the invention is a volumetric eccentric piston pump comprising:

• A pipe having a first end secured to a transmission zone and a second end terminating in a cylinder secured to a discharge zone, the pipe comprising a suction opening and the discharge zone comprising a discharge opening,
• A drive shaft extending between the transmission zone and the manifold with one end located at the level of the cylinder, and
• a piston arranged in the discharge zone and slidably mounted at the end of the shaft while being pressed against the cylinder by elastic means so as to block a movement of fluid between the pipe and the discharge zone.

According to the invention, the pump further comprises means for elastically separating the piston from the cylinder and maintaining it at a predetermined distance therefrom.

By blocking the piston in the off position of the cylinder, the pump behaves like an open valve and there is no longer any need to install a bypass system. The entire cleaning flow can therefore switch from suction to discharge. As a result, the pressure drop becomes very low and CIP cleaning is simplified.

Advantageously, the predetermined distance is between 2 and 10mm.

This distance determined experimentally and by simulations as sufficient distance for the entire cleaning flow to pass through the pump. This variation in distance is a function of the size of the pump.

According to an exemplary embodiment, the pump further comprises a sleeve arranged in the tubing around the shaft. This sleeve comprises at least one metal bellows, which is tightly fixed by first fixing means to the first end of the pipe and by second fixing means to said end of the shaft, so as to prevent the transmission of fluids from the tubing to the shaft.

Advantageously, the means allowing the piston to be moved away from the cylinder are pneumatic means arranged to pressurize the cuff.

In this way, the internal part of the cuff is put under pressure, which makes it possible to take off the piston sufficiently from the cylinder and to keep it at a distance from it.

Advantageously, the pneumatic means comprise a pressurization pot communicating with the sleeve via the zone of transmission, said pressurization pot comprising an oil and is intended to be connected to a source of compressed air.

The pressurization pot makes it possible to completely fill the transmission area, it is also partially filled so that the oil level is in the pressurization pot. Then, by connecting this pressurization pot to a source of compressed air, the resulting pneumatic pressure acts on this oil surface as on a piston.

The volume of oil is therefore transferred from the pressurization pot to the transmission zone and then to the sleeve. The increase in the volume of the cuff makes it possible to lengthen it and thereby to cause the piston to slide so as to move it away from the cylinder. The distance of this gap can be adjusted by adjusting the pressure in the pressurization pot.

Furthermore, by maintaining the pressure in the pressurization pot, the distance between the cylinder and the piston is also kept substantially fixed. In this way, when the cleaning liquid is circulated between the suction and the discharge, the pressure drop becomes very low.

Advantageously, the pressurization pot comprises restriction means arranged to restrict the passage of fluid from the pot to the transmission zone and vice versa.

By way of example, the restriction means may comprise an oil choke, a controllable solenoid valve.

This restriction of the passage of oil to the transmission and vice versa has the effect of keeping the piston detached from the cylinder during pressure peaks around the bellows likely to be generated during the circulation of the cleaning liquid. Indeed, these restriction means allow a slow movement of oil between the pressurization pot and the transmission zone, thus preventing any abrupt change in the volume of the cuff.

Advantageously, the elastic means fixing the piston to the end of the shaft comprise at least one axial spring. This spring is used to press the piston against the cylinder, in particular during the priming phases. During the pumping phases, the discharge pressure also contributes to pressing the piston against the cylinder.

Such a spring can, for example, be formed from a set of spring washers.

Advantageously, the pump comprises at least one stop arranged to protect the axial spring. In particular, during phases where the transmission zone is pressurized.

The invention also relates to a method for cleaning a pump conforming at least to one of the pumps described above, in which the means making it possible to elastically separate the piston from the cylinder are implemented, then a cleaning fluid is circulated between the suction opening and the discharge opening.

Brief description of figures

• la figure 1 représente une vue en coupe longitudinale d'une pompe selon un exemple de réalisation préféré de l'invention ;
• la figure 2 représente une vue zoomée du bout d'arbre de transmission d'une pompe volumétrique connue ;
• la figure 3 une vue similaire à celle de la figure 2 sur une pompe conforme à un mode de réalisation de l'invention.

The invention will be better understood on reading the description which follows, of exemplary embodiments given by way of non-limiting illustration, the description making reference to the appended drawings, among which:

• there figure 1 represents a view in longitudinal section of a pump according to a preferred embodiment of the invention;
• there figure 2 shows a zoomed view of the transmission shaft end of a known volumetric pump;
• there picture 3 a view similar to that of picture 2 on a pump according to one embodiment of the invention.

detailed description

There figure 1 shows an eccentric piston volumetric pump 1 according to the invention as seen in longitudinal section.

The pump 1 comprises a tube 2 having a first end 21 and a second end 22 as well as a suction opening 23.

The first end 21 is integral with a transmission zone 3 which comprises means of transmission of the pump 1. The second end 22 comprises a cylinder 24 and is integral with a discharge zone 4 which comprises a discharge opening 41.

A drive shaft 5 extends from transmission zone 3 into manifold 2. End 53 of shaft 5 is located at cylinder 24.

As can be seen on the figure 1 , in this embodiment, a sleeve 8 is arranged in the cylinder 2 around the shaft 5. The sleeve 8 comprises a metal bellows in two parts 81, 82, for example steel. The sleeve 8 is tightly fixed by first fixing means 83 to the first end 21 of the pipe 2 and by second fixing means 84 to the end 53 of the shaft. Such a cuff is known per se to those skilled in the art. It is for example described in detail in the document WO97/36107 .

A piston 6 is arranged in the discharge zone 4 and slidably mounted at the end 53 of the shaft 5 and held by an axial spring 7 which presses it against the cylinder 24 so as to block any movement of fluid between the pipe 2 and the discharge area 4.

The second fixing means 84 of the sleeve are also integral with the piston and can therefore slide on the end 53 of the shaft 5 at the same time as the piston.

The operation of such a pump, excluding cleaning, is also known to those skilled in the art.

During CIP cleaning in place, the pump being able to be stopped or rotating, an auxiliary pump, not shown, is connected to the suction opening 23 to send a cleaning liquid intended through the pump and out of the discharge opening 41.

As explained above, with conventional cleaning methods, pressure drops are due to the action of the axial spring 7 and the bellows 8 limiting the displacement of the piston 6 relative to the cylinder 2 under the effect of the pressure of the cleaning fluid.

To solve this problem, the pump 1 according to the invention comprises means for moving the piston 6 away from the cylinder 2 and maintaining it at a predetermined distance from the latter to allow movement of the cleaning fluid between the pipe 2 and the zone of repression 4.

More particularly, the pump according to the invention and as represented by the figure 1 , comprises a pressurization pot 9 communicating with the transmission zone 3.

In known pumps, the transmission is filled with lubricating oil up to a certain level.

The addition of the pressurization pot 9 to the pump 1 makes it possible to completely fill the transmission zone 3 with oil and the oil level rises to a certain level in the pressurization pot 9.

During CIP cleaning of the pump, the pressurization pot 9 is connected to a source of compressed air, not shown. Control means make it possible to control the pneumatic pressure generated by the compressed air which acts on the oil surface as on a piston.

The volume of oil is therefore transferred from the pressurization pot to the transmission zone and then to the cuff. The increase in the volume of the cuff makes it possible to lengthen it and make the piston slide to move it away from the cylinder. The distance of this gap can be adjusted by adjusting the level of pressure in the pressurization pot.

Furthermore, by maintaining the pressure in the pressurization pot, the distance between the cylinder and the piston is also kept substantially fixed.

Thus, the cleaning liquid can pass entirely from the suction to the discharge with a reduced pressure drop.

The sufficient distance is dependent on the size of the pump. It is preferably between 2 and 10 mm.

In addition, the pressurization pot 9 comprises restriction means 91 making it possible to control the displacement of oil between the pressurization pot 9 and the transmission zone.

In the example of the figure 1 , the restriction means 91 comprise an oil restrictor.

In variants not shown, the restriction means 91 may be different, for example a controllable solenoid valve.

The oil passage control keeps the piston detached from the cylinder during pressure peaks around the bellows likely to be generated during the circulation of the cleaning liquid.

THE figures 2 and 3 represent a zoom on the end 53 of shaft 5 respectively in a known pump and in an improved pump according to the invention.

As seen on the figures 2, 3 the second fixing means 84, 84', is integral with the piston 6, the axial spring 71 acts on the end 840, 840' of the second fixing means 84, 84' to press the piston 6 against the cylinder 24.

In the case of the figure 2 , when the volume of the sleeve 8 increases, the piston 6 and the second fastening means 84' slide so that the piston 6 moves away from the cylinder 24. Under the effect of the pressure which increases in the sleeve, the end 840' crushes the coils of the spring, or the washers in the case of spring washers, and can therefore cause them to break.

To protect the spring 71 from breaking, the pump shown in picture 3 provides an abutment composed of two parts 72, 73, secured respectively to the end 840 of the second fixing means 84 and to the end 53 of the shaft 5. Thus, when the two parts 72, 73 of the abutment are in contact, the piston movement is stopped and the pressure on the spring does not increase.

The invention is obviously not limited to the examples illustrated. In variants not shown, the pump may not include a cuff. The means for moving the piston 6 away from the cylinder 2 and maintaining it at a predetermined distance can be different, for example, from controlled mechanical means.

The invention also relates to a method for cleaning a pump 1 according to the invention comprising at least some of the characteristics described above, in which the means making it possible to elastically separate the piston 6 from the cylinder 24 are implemented, then a cleaning fluid is circulated between the suction opening 23 and the discharge opening 41.

Claims (10)

1. An eccentric piston positive displacement pump (1) comprising:

   - a pipe (2) having a first end (21) secured to a transmission area (3) and a second end (22) ending in a cylinder (24) secured to a discharge area (4), the pipe (2) comprising a suction port (23) and the discharge area comprising a discharge port (41),

   - a drive shaft (5) extending between the transmission area and the pipe with one end (53) situated at the cylinder (24),

   - a piston (6) arranged in the discharge area (4) and mounted to slide at the end (53) of the shaft (5) and being pressed against the cylinder (24) by elastic means (7) so as to prevent fluid from moving between a pipe (2) and the discharge area (4),

   characterized in that the pump (1) further comprises means (8, 9) for moving the piston elastically away from the cylinder (24) and keeping it at a predetermined distance from same.
2. The pump (1) as claimed in claim 1, in which said predetermined distance is between 2 mm and 10 mm.
3. The pump (1) as claimed in either one of claims 1 or 2, further comprising a sleeve (8) arranged in the pipe (2) around the shaft (5) and comprising at least one metal bellows (81, 82), the sleeve (8) is sealingly fixed by first fixing means (83) to the first end (21) of the pipe (2) and by second fixing means (84) to said end (53) of the shaft, in such a manner as to prevent the transmission of fluids from the pipe (2) toward the shaft (5).
4. The pump (1) as claimed in claim 3, in which the means for moving the piston (6) away from the cylinder (24) are pneumatic means (9) adapted to pressurize the sleeve (8).
5. The pump (1) as claimed in claim 4, in which the pneumatic means comprise a pressurization pot (9) communicating with the sleeve via the transmission area (3), said pressurization pot (9) contains an oil and is intended to be connected to a source of compressed air.
6. The pump (1) as claimed in claim 5, in which the pressurization pot (9) comprises restriction means (91) adapted to restrict the passage of fluid from the pot to the transmission area and vice versa.
7. The pump (1) as claimed in claim 6, in which the restriction means (91) comprise an oil flow reducing valve.
8. The pump (1) as claimed in any one of claims 1 to 7 in which the elastic means fixing the piston (6) to the end (53) of the shaft (5) comprise at least one axial spring (71).
9. The pump (1) as claimed in claim 8, comprising at least one abutment (72, 73) adapted to protect the axial spring.
10. A method of cleaning a pump as claimed in any one of claims 1 to 9 in which the means for elastically moving the piston (6) away from the cylinder (24) are used and a cleaning fluid is then circulated between the suction port (23) and the discharge port (41).

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