Differential volumetric dosing device

Abstract

A differential volumetric dosing device for liquids, comprising a cylindrical transfer body (2) extending along a longitudinal axis (X) and having an inlet conduit (8) and an ejection conduit (9) obtained internally to said transfer body (2) with respectively an inlet opening (10) and an outlet opening (11); a cylindrical hollow body (12) disposed coaxially to said transfer body (2), said hollow body (12) being provided on an inner wall thereof with a metering groove (15) alternatively positionable facing the inlet opening (10) or the outlet opening (11) respectively; said transfer body (2) and said hollow body (12) being reciprocally movable along and about the longitudinal axis (X); in which said transfer body (2) comprises at least a first cylindrical portion (6) proximal to said connection end (4) and having a first outer wall (3a) with a first outer diameter (D1), and a second cylindrical portion (7) distal from said connection end (4) and having a second outer wall (3b) with a second outer diameter (D2) different from said first outer diameter (D1), wherein said hollow body (12) is provided with a first sliding portion (13) and a second sliding portion (14) coaxial, adjacent to and communicating with each other, configured and dimensioned to allow said first (6) and said second (7) cylindrical portions to slide within said first sliding portion (13) and said second sliding portion (14), respectively.

Description

[0001] Differential volumetric dosing device

[0002] The present invention relates to a differential volumetric dosing device for liquids. Many industrial sectors require the implementation of precision dosing devices for dosing relatively small quantities of liquids, particularly in the pharmaceutical field.

[0003] In the context of dosing a small amount of liquid, dosing is known to be carried out using devices with a variable-volume chamber formed between the top of a piston and a corresponding cylinder coupled to the piston, where the relative displacement of these determines the dosed volume of the liquid. Thus, the liquid dose is determined as a function of the length of the piston stroke inside the cylindrical chamber and the diameter of the cylindrical chamber.

[0004] The operating principle of the devices described above has the disadvantage of being severely limited in their use for dosing relatively very small amounts of liquid. Normally the stokes of the piston are driven by control members which comprise a chain of mechanical parts to impart the movement to the piston from an actuator. These mechanical parts are linked together with mechanical tolerances that affect the actual stroke of the piston inside the cylinder. When relatively very small amount of liquid needs to be dosed, the respective piston stroke is limited, and these mechanical tolerances make the piston stroke and consequently the liquid dosing inaccurate introducing a measurement error. Thus, the mechanical tolerances of the control members driving the movement of the piston are not negligible.

[0005] To mitigate this problem, for very small dosing and consequently very small strokes, it would be necessary to considerably limit the mechanical tolerances of the control members. This would cause problems due to the greater complexity of these members in order to limit any bending of the mechanical parts. Furthermore, the reduction of the tolerances, which would contribute to the measurement error, would result in greater wear of the components due to greater friction in sliding between them, and a higher cost of the control members due to tighter machining tolerances.

[0006] Such devices include, for example, the one discloses in FR2931939, which is a system that employs a piston coupled to a cylinder and movable therewithin. The movement of the cylinder relative to the piston induces a change in volume of a dosing chamber into which the liquid to be dosed is drawn. A longitudinal groove arranged on the cylinder's inner surface alternately connects the dosing chamber with a suction or discharge conduit arranged on the piston by means of a 180- degree axial rotation of the cylinder.

[0007] According to this configuration, the dosed volume is proportional to the amount of displacement of the cylinder with respect to the piston and the dimension of the diameter of the first one. In this case, liquid dosage is accurate only in the case of fairly long displacements of the cylinder, which is not applicable to the dosing of small quantities of liquid, except with the adoption of a piston with a very small diameter. This latter solution, however, has the disadvantage the piston should have conduits with an extremely reduced diameter, introducing relative drawbacks, such as assembling construction and during the dosage of the liquid due to the fragile construction. Moreover, some materials used to create the piston and / or the cylinder, such as ceramic materials, do not allow the creation of conduits with a very small diameter and / or having considerable length due to the fragility of the material.

[0008] A further disadvantage in the solutions of the known art is the difficulty or impossibility of replacing a dosing unit in a filling machine, with another one having a different dosing range, since a different piston and / or cylinder size would require special adjustments or additional parts on the machine itself.

[0009] Another drawback of the known solutions is the presence of blind spots in the piston and / or cylinder grooves in which, especially during the first stages of liquid dosing, air bubbles can accumulate and produce dosing errors. An object of the present invention is to provide a dosing device which meets the accuracy requirements for dosing relatively small volumes of liquids while avoiding the drawbacks of the known art mentioned above and at the same time maintaining a good construction simplicity.

[0010] A second object of the present invention is to provide a dosing device having a structure that facilitate the expulsion of air bubbles which may be created during dosing operations.

[0011] A further object of the present invention is to provide a dosing device with easier installation and replacement, and that does not have moving parts connected to pipes or conduits that could hinder movement during dosing operations.

[0012] A further object of the present invention is to provide a dosing device having a connection portion in which all inlet and outlet openings of liquids are arranged adjacent to each other.

[0013] In accordance with the present invention a device of this type is provided according to claim 1 .

[0014] Thus, a solution to this technical problem is proposed by providing a differential volumetric dosing device with a transfer body having at least a first and a second diameter and a hollow body, configured and sized to be reciprocally movable in rotation and translation, wherein the different size of the two diameters and the relative displacement between the transfer body and the hollow body determine the volume of dosed fluid.

[0015] The dependent claims of the present invention outline advantageous embodiments of the invention.

[0016] The invention may be better understood and implemented by reference to the accompanying drawings which illustrate an exemplary and non-limiting form of implementation in which:

[0017] - figure 1 is a schematic side view of a differential volumetric dosing device according to the present invention; - figure 2 is a schematic top view of the differential volumetric dosing device of figure 1 ;

[0018] - figure 3 is a schematic cross-sectional view taken along the line Ill-Ill of figure 1 ;

[0019] - Figures 4a, 4b, 4c and 4d are a schematic view of operating steps of the differential volumetric dosing device according to the present invention along longitudinal section taken along the line IV-IV of figure 2;

[0020] - Figures 5a and 5b are schematic views along section IV of the transfer body and hollow body of the volumetric dosing device of figure 2, respectively.

[0021] With reference to the accompanying figures, a differential volumetric dosing device 1 is generally indicated comprising a transfer body 2 (Fig. 5a) extending along a longitudinal axis X between a connection end 4 and a base end 5 opposed to said connection end 4. Said transfer body 2 having a substantially cylindrical shape and being shaped like a piston. Said transfer body 2 is provided with an inlet conduit 8, through which the liquid enters, and with an ejection conduit 9 from which the liquid exits, both obtained internally to said transfer body 2 and having respectively an inlet opening 10 and an outlet opening 11 on an external side wall 3 of said transfer body 2.

[0022] Preferably, the inlet opening 10 and the outlet opening 11 are both positioned at an equal distance from the connection end 4 of the transfer body 2.

[0023] Furthermore, according to an embodiment the inlet opening 10 and the outlet opening 11 are positioned diametrically opposite to each other. They are thus arranged at an angle of 180° to each other. Alternatively, the inlet opening 10 and the outlet opening 11 can be arranged at a distance of 90° to 270° from each other.

[0024] According to a further alternative embodiment, the inlet opening 10 and the outlet opening 11 may be arranged adjacent to each other.

[0025] Preferably, the inlet opening 10 has a height and a width substantially equal to a height and a width of the outlet opening 11 .

[0026] The differential volumetric dosing device 1 further comprises a hollow body 12 arranged coaxially to the transfer body 2 and operable in translation along the longitudinal axis X and in rotation about the longitudinal axis X (Fig. 4c). The hollow body 12 is also provided on an inner wall with a metering groove 15 which can be positioned alternatively facing the inlet opening 10 (Fig. 4b) or the outlet opening 11 (Fig. 4c) of the inlet 8 and ejection 9 conduits respectively. Said metering groove 15 preferably having a longitudinal development parallel to the longitudinal axis X.

[0027] In accordance with the present invention, the transfer body 2 comprises at least a first cylindrical portion 6 proximal to the connection end 4 and having a first outer wall 3a with a first outer diameter D1 , and a second cylindrical portion 7 distal from the connection end 4 and having a second outer wall 3b with a second outer diameter D2 different from the first outer diameter D1 .

[0028] Furthermore, the first 6 and second 7 cylindrical portions are coaxial to each other.

[0029] Advantageously, the hollow body 12 is provided with a first sliding portion 13 and a second sliding portion 14 coaxial to each other, adjacent and communicating with each other. The first sliding portion 13 and the second sliding portion 14 being hollow portions, configured and dimensioned to allow the first 6 and the second 7 cylindrical portions of the transfer body 2 to slide within the first sliding portion 13 and the second sliding portion 14, respectively.

[0030] In practice, the hollow body 12 accommodates at least partially the transfer body 2 according to a movable coupling in rotation about the longitudinal axis X and in translation along the same longitudinal axis X (Figs. 4a - 4c).

[0031] According to an embodiment, the hollow body 12 is conveniently moved in both rotation and translation by means of external movement means, not shown in the figures, connected through a suitable coupling member 24. Said coupling member 24 is preferably coupled to the hollow body 12 in correspondence of a lower end thereof.

[0032] According to other alternative embodiments, the transfer body 2 could be moved in both rotation and translation by means of external handling means, not shown in the figure.

[0033] In the present description, for simplicity of description, any spatial reference is made by arranging the volumetric dosing device 1 with the longitudinal axis X arranged substantially vertically, as shown in Figures 4a-4d.

[0034] Preferably, the width of said metering groove 15 is substantially identical to the width of said inlet opening 10 and said outlet opening 11 .

[0035] Preferably, when in use, the differential volumetric dosing device 1 has a substantially vertical arrangement in which said connection end 4 of said transfer body 2 is disposed above said base end 5 along the longitudinal axis X.

[0036] Similarly to the first 6 and the second 7 cylindrical portions, the first sliding portion 13 and the second sliding portion 14 of the hollow body 12 have respectively a first sliding diameter D1 ’ and a second sliding diameter D2’. Said first sliding diameter D1 ’ and said second sliding diameter D2’ (measured internally to the hollow body 12) being different from each other and substantially equal, taking in account allowed tolerance for permitting the sliding, to respectively the first outer diameter D1 and the second outer diameter D2 of the transfer body 2.

[0037] In accordance with the example illustrated in the figures, the diameter D1 of the first cylindrical portion 6 is greater than the diameter D2 of the second cylindrical portion 7 of said transfer body 2.

[0038] In accordance with a further aspect of the present invention, said transfer body 2 may further comprise a third cylindrical portion 21 , coaxial to said first 6 and said second 7 cylindrical portions, having a third outer wall 3c having a third diameter D3 smaller than said first D1 and second D2 diameters. According to another aspect of the present invention, said third cylindrical portion 21 is preferably disposed between said first cylindrical portion 6 and said second cylindrical portion 7.

[0039] Preferably on the external side wall 3 of the transfer body 2 between said first cylindrical portion 6 having the diameter D1 and said second cylindrical portion 7 having the diameter D2, is present a first connecting portion 27 having a variable diameter along the longitudinal axis X. Said variable diameter having a dimension varying from a value equal to the diameter D1 to a value equal to the diameter D2.

[0040] It is also preferable that the inner surface of the hollow body 12, between the first sliding portion 13 having the diameter D1 ’ and the second sliding portion 14 having the diameter D2’, is provided with a second connecting portion 28 having a variable diameter along the longitudinal axis X from the value of the diameter D1 ’ to the value of the diameter D2’.

[0041] Said hollow body 12 is preferably provided with a closed end 16 proximal to and facing said base end 5 of said transfer body 2.

[0042] According to an aspect of the present invention, the closed end 16 comprises a bottom wall closing said hollow body 12 and arranged transversely with respect to the longitudinal axis X at one end of said second sliding portion 14.

[0043] According to further embodiments, the closed end 16 comprises a coupling member 24 coupled to said hollow body 12 to close the bottom of the latter (Fig. 5b).

[0044] Preferably according to said configuration, a sealing member 25 is disposed between said coupling member 24 and said second sliding portion 14 of said hollow body 12. In the described embodiment the sealing member 25 is an elastic 0-ring.

[0045] The main purpose of said closed end 16 is to avoid contamination of the dosed liquid by external agents, as the sealing of the coupling between the hollow body 12 and the transfer body 2 of the volumetric dosing device 1 is within the tolerance limits for the sliding of the hollow body 12 with respect to the transfer body 2, and no further sealing means such as gaskets being present between the two. Similarly, the closed end 16 prevents the environment surrounding the volumetric dosing device 1 from being soiled or contaminated by small amounts of liquid that may leak between the hollow body 12 and the transfer body 2 during dosing operations.

[0046] This creates a variable volume chamber 26 delimited at its upper part by said base end 5 of said transfer body 2 and at its lower part by the closed end 16 of said hollow body 12, while the inner wall of said hollow body 12, in particular said second sliding portion 14, delimits the variable volume chamber 26 laterally (Figs. 4a - 4d). Contrary to the known art, no liquid is present in said variable volume chamber 26.

[0047] According to a further aspect of the present invention, the variable volume chamber 26 is connected to an external controlled environment by means of a compensation conduit 17. Said external controlled environment, not present in the figures, could be a filtration system of the known type. According to said aspect of the present invention, the variable volume chamber 26 draws air from or injects air into said compensation conduit 17 during the movement of the hollow body 12.

[0048] Said compensation conduit 17 is obtained internally to the first cylindrical portion 6 of said transfer body 2.

[0049] Alternatively, said compensating conduit 17 can be formed on said closed end 16 of said hollow body 12. The purpose of said compensation conduit 17 is to compensate variation of pressure in said variable volume chamber 26 caused by the movement of said hollow body 12, during dosing operations.

[0050] Said compensating conduit 17 is thus configured to maintain a substantially equal pressure value between a surface area of said base end 5 and a surface area of said connection end 4 on said transfer body 2. In other words, the compensation conduit 17 maintains a substantially identical pressure value between the inside of said variable volume chamber 26 and the outside of said volumetric dosing device 1. It is thus prevented that positive or negative pressures are created inside the variable volume chamber 26 with respect to the surroundings of the volumetric dosing device 1 which would obstruct the movement of the hollow body 12.

[0051] Conveniently, said compensation conduit 17 is configured to be connected to a filtering circuit, not illustrated in the figure, said filtering circuit being inclusive of a filter and being configured to filter the air that is repeatedly drawn into and expelled from the variable volume chamber 26 during the dosing cycles.

[0052] According to a further configuration, said compensation conduit 17 can be further connected to a recovery circuit, not illustrated in the figure, for recovering any fluid that could have been drawn into the variable volume chamber 26 during operation.

[0053] According to a further aspect of the present invention, said base end 5 corresponds to the lower end of said second cylindrical portion 7 of said transfer body 2, while said connection end 4 correspond to the upper end of said first cylindrical portion 6 of said transfer body 2 with said longitudinal axis X arranged substantially vertically.

[0054] In accordance with another aspect of the present invention, the connection end 4 of said transfer body 2 is provided with a first 18, a second 19 and a third 20 outlet openings of the inlet conduit 8, the ejection conduit 9 and the compensation conduit 17, respectively.

[0055] According to this aspect, moreover, said inlet opening 10 and said outlet opening 11 are provided on said first cylindrical portion 6 of said transfer body 2. Furthermore, according to this configuration, the metering groove 15 preferably extends longitudinally along said first sliding portion 13. According to another aspect of the present invention, said inlet opening 10 and said outlet opening 11 are positioned on the external side wall 3 of said first cylindrical portion 6 closer to said second cylindrical portion 7.

[0056] According to a further aspect of the present invention, the metering groove 15 extends longitudinally parallel to the longitudinal axis X for a section of the inner wall of said hollow body 12 from a first end 23 closer to said second connecting portion 28, to a second end 22 farther away from said second connecting portion 28.

[0057] Preferably said hollow body 12 is configured to be moved with respect to said transfer body 2 along the longitudinal axis X for a stroke C from a stroke initial position, wherein said first end 23 is disposed closer to one of said inlet opening 10 or said outlet opening 11 of said transfer body 2 (Fig. 4a), to an end position, wherein said second end 22 is disposed closer to one between said inlet opening 10 or said outlet opening 11 (Fig. 4b).

[0058] Preferably, said metering groove 15 has a length shorter than the length of said second cylindrical portion 7 of said transfer body 2. Preferably, said metering groove 15 extends for a length less than the sum of the lengths of said second cylindrical portion 7 and said third cylindrical portion 21.

[0059] In accordance with another aspect of the present invention, said inlet conduit 8 and said ejection conduit 9, extend along respective axes which are divergent one to the other at least in their section in proximity of respective inlet opening 10 and outlet opening 11 (Fig. 5a).

[0060] According to an alternative embodiment, said inlet conduit 8 and said ejection conduit 9 extend along respective axes which form an acute angle with respect to the longitudinal axis X, at least in proximity of the respective inlet opening 10 and outlet opening 11 .

[0061] According to a further aspect of the present invention, the volumetric dosing device 1 has a dosing volume equivalent to an annular chamber having an outer diameter equal to the diameter D1 , an inner diameter equal to the diameter D2 and a height equal to the stroke C. In practice, this annular chamber has a crosssection equivalent to the difference between a circular cross-section having diameter D1 and a circular cross-section having diameter D2.

[0062] According to a further aspect of the present invention, said second cylindrical portion 7 is provided with a cavity 30 communicating with said compensation conduit 17. Preferably, said cavity 30 extends between said compensation conduit 17 and said base end 5.

[0063] According to an aspect of the present invention, said first cylindrical portion 6 of said transfer body 2 is positioned adjacent to said connection end 4 along the longitudinal axis X, while said second cylindrical portion 7 is positioned adjacent to said base end 5. Thus, said first cylindrical portion 6 is positioned above said second cylindrical portion 7 along the longitudinal axis X when said volumetric dosing device 1 is in use.

[0064] Alternatively, said first cylindrical portion 6 of said transfer body 2 is positioned adjacent with respect to said base end 5, while said second cylindrical portion 7 is positioned adjacent to said connection end 4. Thus, according to this configuration, said first cylindrical portion 6 is positioned below said second cylindrical portion 7 along the longitudinal axis X.

Claims

CLAIMS1 . A differential volumetric dosing device for liquids comprising:- a transfer body (2) extending along a longitudinal axis (X) between a connection end (4) and a base end (5) opposed to said connection end (4), and having an inlet conduit (8) and an ejection conduit (9), said inlet conduit (8) and said ejection conduit (9) being obtained internally to said transfer body (2) with, respectively, an inlet opening (10) and an outlet opening (11 ) on an external side wall (3) of said transfer body (2);- a hollow body (12) arranged coaxially and around said transfer body (2), said hollow body (12) being provided on an inner wall thereof with a metering groove (15) alternatively positionable facing the inlet opening (10) or the outlet opening (11 ) of said inlet (8) and ejection (9) conduits respectively; said transfer body (2) and said hollow body (12) being reciprocally movable along and about the longitudinal axis (X); said dosing device being characterized in that said transfer body (2) comprises at least a first cylindrical portion (6) proximal to said connection end (4) and having a first outer wall (3a) with a first outer diameter (D1 ), and a second cylindrical portion (7), distal from said connection end (4), having a second outer wall (3b) with a second outer diameter (D2), different from said first outer diameter (D1 ), in which said first (6) and second (7) cylindrical portions are coaxial to one another, and in that said hollow body (12) is provided with a first sliding portion (13) and a second sliding portion (14) coaxial, adjacent and communicating to one another, and configured and dimensioned to allow said first (6) and said second (7) cylindrical portions of said transfer body (2) to slide within said first sliding portion (13) and said second sliding portion (14), respectively.

2. Volumetric dosing device (1 ) as in claim 1 , wherein said hollow body (12) has a closed end (16) proximal to and facing said base end (5) of said transfer body (2), and wherein said transfer body (2) is provided with a compensationconduit (17) obtained internally to the first cylindrical portion (6).

3. Volumetric dosing device (1 ) as in claim 2, wherein said connection end (4) is provided with a first (18), a second (19) and a third (20) openings of said inlet conduit (8), said ejection conduit (9) and said compensation conduit (17) respectively.

4. Volumetric dosing device (1 ) as in claim 2 or 3, wherein at least said second cylindrical portion (7) is provided with a cavity (30) communicating with the compensation conduit (17).

5. Volumetric dosing device (1 ) as in any of the preceding claims, wherein said connection end (4) is arranged at an upper end of said first cylindrical portion (6), while said base end (5) is arranged at a lower end of said second cylindrical portion (7) of said transfer body (2), with said longitudinal axis (X) arranged substantially vertically.

6. Volumetric dosing device (1 ) as in any of the preceding claims, wherein said outer diameter (D1 ) of said first cylindrical portion (6) is greater than said second outer diameter (D2) of said second cylindrical portion (7).

7. Volumetric dosing device (1 ) as in claim 6, wherein said inlet opening (10) and said outlet opening (11 ) are arranged in said first cylindrical portion (6) of said transfer body (2).

8. Volumetric dosing device (1 ) as in claim 6 or 7, wherein said metering groove (15) extends parallel to said longitudinal axis (X) along said first sliding portion (13) of said hollow body (12).

9. Volumetric dosing device (1 ) as in any of the preceding claims, wherein said transfer body (2) further comprises a third cylindrical portion (21 ) coaxial to said first (6) and said second (7) cylindrical portions, said third cylindrical portion (21 ) having a third outer wall (3c) having a third outer diameter (D3) smaller than said first (D1 ) and second (D2) diameters, said third cylindrical portion (21 ) being interposed between said first cylindrical portion (6) and said second cylindricalportion (7).

10. Volumetric dosing device (1 ) as in any of the preceding claims, wherein said metering groove (15) extends parallel to the longitudinal axis (X) for a section of the inner wall of said hollow body (12) from a first end (23) closer to a connecting portion (28) between said first sliding portion (13) and said second sliding portion (14), to a second end (22) farther away said second connecting portion (28), and wherein said hollow body (12) is configured to be moved with respect to said transfer body (2) along the longitudinal axis (X) for a stroke (C) from a stroke initial position wherein said first end (23) is positioned closer to with one of said inlet opening (10) or said outlet opening (11 ) of said transfer body (2), to an end position wherein said second end (22) is positioned in correspondence with one of said inlet opening (10) or said outlet opening (11 ).

11. Volumetric dosing device (1 ) as in any of the preceding claims, wherein said inlet opening (10) and said outlet opening (11 ) are positioned on the first outer wall (3a) of said first cylindrical portion (6) in a section closer to said second cylindrical portion (7).

12. Volumetric dosing device (1 ) as in any of the claims 2 - 11 , wherein said closed end (16) comprises a coupling member (24) coupled to said hollow body (12) to close the bottom part of the latter.

13. Volumetric dosing device (1 ) as in claim 12, wherein said closed end (16) further comprises a sealing member (25) disposed between said coupling member (24) and said second sliding portion (14) of said hollow body (12).

14. Volumetric dosing device (1 ) as in any of the preceding claims, wherein said inlet opening (10) and said outlet opening (11 ) are both positioned at an equal distance from said connection end (4) of said transfer body (2).

15. Volumetric dosing device (1 ) as in any of the preceding claims, wherein said inlet conduit (8) and said ejection conduit (9) extend along a respective axis which are divergent one to the other at least in their section in proximity of therespective inlet (10) and outlet (11) openings.

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