FR2576644A1 - Dosing syringe and dosing circuit equipped with such a syringe, especially for the agricultural feedstuffs industry - Google Patents

Abstract

A given quantity of liquid is dosed by drawing this liquid up by aspiration from a container by means of a dosing syringe 26. The delivery of the dose controlled by the syringe allows it to be distributed through an appropriate nozzle. In order to facilitate cleaning of the circuit, the front section 34b of the piston of the syringe slides without a seal in the cylinder 32. The resulting leakage is removed by a drainage circuit 60, 54, 64. A retractable stop 66 allows the front section 34b of the piston to be shifted into an intermediate chamber 54, thereby permitting efficient cleaning of the circuit. The valves controlling the circulation of the liquid upstream and downstream of the syringe function by pinching a flexible hose.

Description

 The present invention relates to a syringe for dosing a given quantity of liquid in order to distribute this quantity of liquid in an appropriate use circuit, as well as a dosing circuit using such a syringe.

 In certain industries such as the food industry and in particular dairies, it is necessary to be able to repetitively dose a precise quantity of Liquid. Thus, the industrial manufacture of flavored yogurts requires that a precise and constant dose of flavor be quickly introduced into each yogurt.

 In the present state of technology, this result is obtained by placing a dosing syringe in a line on a pipe connecting a supply tank to a dispensing nozzle and by placing two valves in the pipe, respectively upstream and in downstream of the diversion.

 The operation of such a metering circuit is simple and precise. The valve placed upstream of the bypass being opened while the other valve is closed, the dose which one wishes to distribute is drawn up by the syringe. The valve placed upstream is then closed, then the valve placed downstream is opened to allow distribution. This distribution is obtained by repressing the dose using the syringe. The valves are finally returned to their initial position to allow the distribution of the next dose.

 The weakness of these existing metering circuits concerns their cleaning possibilities. In fact, the industrial use of these circuits leads to frequent changes in the products of which they carry out the dosage. When such a change is made, it is necessary to be able to carry out an easy and effective cleaning of the entire circuit. However, this result cannot be obtained with existing circuits, because part of the liquid which has just been dispensed is trapped by the elastomer seals with which they are in contact both in the syringe or pump stripper, in your valves and in the valves.

 We can consider solving this problem at the dosing syringe by placing an air buffer in the tube, between the syringe and the liquid, which prevents any penetration of the latter into the syringe.

However, if this solution makes it possible to solve the problem posed by cleaning the circuit at the level of the syringe, the quality and the repeatability of the dose are disturbed by the elasticity of the air.

 The present invention specifically relates to a dosing syringe which can be cleaned very easily without affecting the dosing qualities of the circuit, as well as a dosing circuit incorporating such a syringe and in which the conventional valves are replaced by pinching means. flexible hoses.

 To this end and in accordance with the invention, there is provided a dosing syringe comprising a cylinder, a piston capable of sliding in leaktight manner in the cylinder by means of at least one annular seal, to define L inside the cylinder a front chamber provided with an orifice communicating with a use circuit and at least one control chamber capable of being connected to a source of pressurized fluid, characterized in that an annular intermediate chamber is formed in Said cylinder around the piston, between a front part of the latter sliding without seal in the cylinder and a rear part of the piston sliding in the cylinder by means of said seal, means of drainage being provided for circulating a low-flow drainage liquid in said annular chamber, in the direction going from the rear part, towards the front part of the piston.

 According to a preferred embodiment of the invention, the drainage means comprise at least one draining liquid supply pipe opening into said annular chamber near the rear part of the piston and at least one draining drainage pipe in said annular chamber near the front part of the piston.

 In order to further improve the cleaning efficiency of the syringe, means can be provided for bringing the piston into a retracted cleaning position in which the front part of the piston is located in said annular chamber, a cleaning circuit opening into said annular chamber for circulating a washing liquid from said annular chamber to said orifice. This cleaning circuit preferably comprises the supply pipe of the drainage circuit.

 A precise adjustment of the dose can be obtained by equipping the cylinder with an adjustable rear stop for the piston.

According to a preferred embodiment of the invention, the valves of the metering circuit are formed in a valve system comprising a fixed cylinder in which slides a primary piston forming with the cylinder a rear control chamber capable of being connected to a source of pressurized fluid, the front face of this primary piston comprising a first compression part, a secondary piston movable along the axis of the primary piston in a part integral with the fixed cylinder, the rear face of which comprises a mobile anvil placed opposite of the first compression part and the front face of which comprises a second compression part, a fixed anvil secured to said fixed part and placed between the second compression part and the movable anvil, first elastic means interposed between said fixed part and the secondary piston to urge the second compression part in abutment against the fixed anvil and second elastic means interposed between the fixed cylinder and the primary piston to separate the first compression part from the movable anvil, flexible parts of the pipe placed respectively upstream and downstream of said branch being so killed between the first compression part and the movable anvil and between the fixed anvil and
The second compression piece.

A preferred embodiment of the invention will now be described, by way of nonlimiting example, with reference to the attached drawings in which:
FIG. 1 is a view schematically illustrating an aroma dosing circuit for the distribution of these aromas in yogurts,
FIG. 2 is a view in longitudinal section on a larger scale of the dosing syringe equipping the circuit of FIG. 1,
FIG. 3 is a top view, in longitudinal section, of the valve system fitted to the circuit of FIG. 1, and
FIG. 4 is a side view in partial section of the valve system shown in FIG. 3.

 In known manner, the distribution and metering circuit shown in solid lines in FIG. 1 comprises one or more pipes 10 each connecting a reservoir 12 containing an aroma 14 to a dispensing nozzle 16. Pots 18 resting on an animated tray 20 with a step-by-step advance movement shown diagrammatically by the arrow F in FIG. 1, scroll below the nozzles 16 in order to receive the dose of aroma intended for them.

 The actual metering is carried out by placing a tube 24 on each pipe 10, the end of which is connected to a dosing syringe 26. This system is completed by a set of two valves 28 and 30 placed respectively upstream and downstream of the bypass formed by tube 24.

 The syringe 26 is used to draw the desired dose of aroma from the reservoir 12 through the tube 24.

For this purpose, the valves 28 and 30 must be respectively open and closed as illustrated in Figure 1.

The dose is then isolated by closing the valve 28, then discharged using the syringe 26 to the jar 18 which is located below the nozzle 16, after opening the valve 30.

 According to the invention, the dosing syringe 26 is produced in the manner which will now be described with reference to FIG. 2.

 The dosing syringe 26 comprises a body or cylinder 32 comprising a stepped bore 35 in which a stepped piston 340 is slidably received. The tube 24 is tightly connected to an orifice 33 extending the bore 5 at the front end of the cylinder 32 ( on the left in FIG. 2) The tube 24 thus communicates with a front chamber 36 formed in the bore 35, at the front of the piston 34.

In its rear part (on the right in FIG. 2), the piston 34 comprises a part 34a of larger diameter sliding in leaktight manner, by means of a seal 37, in a part of larger diameter 35a of The bore 35. At the front and at the rear of the part 35a, the piston 34 slides in leaktight manner
the bore 35 by means of two seals 38, 39 mounted in the cylinder 32. There is thus defined on either side of the part 34a of the piston a front control chamber 40 and a rear control chamber 42. Ports 44 and 46 opening respectively into chambers 40 and 42 make it possible to connect these chambers alternately, by conduits 48 and 50, either to a source of compressed air 52 or to the atmosphere. The movement of the piston 34 inside the cylinder 32 is thus pneumatically controlled in one or the other direction.

According to the invention, the front part 34b, of smaller diameter, of the piston 34 slides with a very small clearance in the corresponding part 35b of
the bore 35 without any seal being placed between these surfaces. The quality of the surface finish guaranteeing the weakness of the clearance at this level can in particular be obtained by running in.

Still according to the invention, the part of the bore 35 located between the front part 35b and
the part carrying the seal 38 has a diameter substantially larger than the corresponding part of the piston 34. Thus, inside the cylinder 32 and around the piston 34 an intermediate annu
laire 54. This intermediate chamber 54 is used in normal operation to continuously sweep and drain the slight leaks of liquid which may occur from the front chamber 36 to this intermediate chamber 54 as a result of the absence of a gasket. sealing between part 34b of the piston and part 35b of the bore.

This scan is obtained by performing a ciPcu
lation of water at very low flow rate between a water inlet orifice 56 opening into the chamber 54 near the rear end thereof and a drainage orifice 58 opening into the chamber 54 near the front end of it. The water sweeping through the intermediate chamber 54 is introduced into the orifice 56 by a supply pipe 60 communicating with a water tank 62. A drainage pipe 64 is connected to the orifice 58 to reject the sewer l sweeping water and the liquid drained by this water.

 In order to ensure that the leakage authorized by the clearance formed between the parts 34b and 35b takes place from the front chamber 36 towards the intermediate chamber 54 and not vice versa, the circulation of the water takes place at a very low flow rate, obtained practically by gravity flow.

 Thanks to the arrangements which have just been described, the controlled leakage of the liquid which is carried out The metering and sweeping of this leakage with water, avoids any presence of the liquid to be metered at the joint 38, which eliminates any problem. of cleaning. In addition, the quality and repeatability of the dose are excellent since the leakage is very low and practically identical with each injection, these being made at regular intervals.

 In order to allow fine adjustment of the dispensed dose, the rear end of the cylinder 32 (on the right in FIG. 2) carries a stop 66 adjustable by a micrometric screw 68. The rear end of the piston 34 comes to bear on this stop 66 at the end of the suction period, when compressed air is admitted into the chamber 40, the chamber 42 being connected to the atmosphere.

This position is shown in broken lines in Xla Figure 2 and designated by the reference MAUX.

According to an interesting aspect of the dosing syringe 26 shown in FIG. 2, there is also a cleaning position allowing the piston 34 to be moved back beyond the rear position defined by the stop 66. To this end, the stop 66 as well as
The micrometric screw 68 are mounted on a tilting plate 70 articulated on the body of the cylinder 32 by an axis 72, the plate 70 being normally held in position by a tilting rod 74 fitted with a nut 76.

 After tilting of the plate 70 (arrow F1 in FIG. 2) allowed by loosening the nut 76, the pressurization of the chamber 40 has the effect of bringing the part of larger diameter 34a of the piston into abutment against the rear end of chamber 42.

This position, shown in dashed lines in Figure 2 is designated by the reference NETT. The front part 34b of the piston 34 is then completely disengaged from the part 35b of the bore and is located entirely inside the intermediate chamber 54. The passage between the latter and the front chamber 36 is thus largely open. A solution of pressurized rinsing liquid injected by the chamber 54 thus makes it possible to quickly and simply clean the entire circuit.

Preferably, the rinsing liquid is conveyed into the chamber 54 by the supply pipe 60 serving to bring the sweeping water into normal operation. The rinsing liquid is evacuated through the drainage pipe 64
As illustrated in FIG. 2, the dosing syringe 26 further comprises at least one orifice 80 passing radially through the body of the cylinder 32 to open into the front chamber 36. In the circuit shown, this orifice 80 has the main function of allowing ttre the priming of the circuit by connecting your chamber 36 to a vacuum chamber 82, by a pipe 78. This orifice 80 or another similar orifice can also be used to introduce additives such as ferment into the chamber 36.This orifice 80 is then connected to a positive injection and external dosing device by means of a valve or a valve preventing the return of the injected additives.

 In another alternative embodiment shown in dashed lines in FIG. 1, the part of the pipe 10 located upstream of your syringe is connected directly to the orifice 80, while the part of the pipe 10 located downstream is connected directly to the orifice 33. The tube 24 is then removed. When several orifices similar to the orifice 80 are provided, and when these orifices are used to introduce additives, this variant makes it possible to premix these additives Fs with the liquid in the chamber 36 during the suction controlled by the syringe . The mixing is continued during the delivery. In the application to the production of flavored yogurts, an efficient mixing of the milk and flavor is thus ensured by sucking the milk through port 33 and sucking the flavor through port 80 .

 In addition to the dosing syringe which has just been described with reference to FIG. 2, the metering circuit represented in FIG. 1 comprises a valve system 84 comprising the valves 28, 30 and operating by crushing the pipe 103 To this end, the pipe 10 is produced in the form of a flexible pipe at least at the level of the system 84. The valve system 84 will now be described in detail with reference to FIGS. 3 and 4.

 As illustrated in these figures, the system 84 comprises a fixed cylinder 86 in which a primary piston 88 slides. A control chamber 90 formed between the rear end of the piston 88 (left in FIG. 3) and the bottom of the cylinder 86 communicates alternatively with a source of compressed air or with the headlight through an orifice 92. The piston 88 is normally held in its rear position shown in FIG. 3 under the action of a compression spring 94 interposed between the piston 86 and the piston 88, when the chamber 90 is connected to the atmosphere.

 The front end or piston 88 carries a support piece 96 constituted by a cylindrical rod oriented radially relative to the axis of the piston. The ends of the rod 96 slide in guide grooves 99 parallel to the axis of the piston 88 and formed in a part 98 integral with the fixed cylinder 86.

 A secondary piston 100 is mounted coaxially with the piston 88 and in the extension of the latter, on the side of its front end. The secondary piston 100 carries at its rear end a movable anvil 102 oriented radially with respect to the axis of the piston 88 and located opposite the rod 96. The ends of the anvil 102 are also slidably received in the grooves 99 of part 98.

 At its front end, the secondary piston 100 carries a support piece 104 constituted by a cylindrical rod oriented radially with respect to the axis of the piston 100 and the ends of which are also received in the grooves 99 of the piece 98. A spring of compression 106 interposed between the front end of the secondary piston 100 (on the right in FIGS. 3 and 4) and the bottom of the part 98 normally maintains the rod 104 in abutment against fixed anvils 108 integral with the part 98.

 As illustrated in particular in Figure 3, each valve system 84 is associated with two flexible pipes 10 of the circuit described above with reference to Figure 1. The part of these pipes located upstream of the bypass constituted by the tube 24 passes between the rod 96 and the movable anvil 102, while the part of these pipes located downstream of the bypass passes between the fixed anvil 108 and the movable rod 104. As can be seen, the two tubes 10 are arranged symmetrically relative to the common axis of pistons 88 and 100.

The dimensioning of the various parts constituting the valve system 84 is such that in the absence of pressure in the chamber 90 (position shown in Figures 3 and 4), the spacing between the rod 96 and the anvil 102 corresponds to the external diameter of the uncompressed pipes 10, while the space formed between
The anvil 108 and the rod 104 is slightly less than
The thickness of the compressed pipes. Thus, in the rest position, the valves 28 are open and the valves 30 closed. This position allows the aspiration of a dose of aroma by the dosing syringe 26.

 When compressed air is admitted into the chamber 90, this has the effect, first of all, of moving the primary piston 88 forwards (stroke C1 in FIG. 4) thus pinching the pipes 10 between the rod 96 and The anvil 102, upstream of the bypass formed by the tube 24. At this time, the valves 28 and 30 are closed simultaneously.

 In a second step (stroke C2 in Figure 4), the primary piston 88 drives the secondary piston 100 in its forward movement (to the right considering Figures 3 and 4). The rod 104 then moves away from the fixed anvil 108, which has the effect of opening the pipes 10 downstream of the branch formed by the tube 24. Simultaneously, the pipes 10 remain closed upstream of this branch since they remain pinched between the rod 96 and the anvil 102. This position makes it possible to repress the dose of aroma using the syringe 26, to distribute it in the corresponding pot 18.

 When the pressure is released in the chamber 90, the pistons 100 and 88 return to the positions shown in FIGS. 3 and 4, under the combined action of the springs 106 and 94.

 Of course, the invention is not limited to the embodiment which has just been described by way of example, but covers all its variants. In particular, the valve system 84 could control the flow in a single pipe 10 or on the contrary in more than two pipes. In addition, it is recalled that the dosing syringe according to the invention, as well as the corresponding dosing circuit, are not limited to the particular support described and relate to all the technical fields in which a precise and repetitive dosing problem occurs. pose. Finally, the relative arrangement of the different components shown in Figure 1 can be changed. Thus, it is possible to place the reservoir 12 in the upper part, the valve system 84 being pivoted by 900 relative to FIG. 1. The suction is then carried out by the lower branch, while the upper branch provides the backflow. This produces a natural purge of air that can enter the circuit and the priming thereof by the orifice 80 can be avoided.

Furthermore, the product (s) delivered using the dosing circuit according to the invention can be distributed in containers, as described above, but also in columns of
Liquid under slight overpressure.

Claims (10)

 1. Dosing syringe comprising a cylinder (32), a piston (34) capable of sliding in leaktight manner in the cylinder by means of at least one annular seal (37, 38, 39), to define Inside the cylinder a front chamber (36) provided with an orifice (33) communicating with a useful circuit (10, 24) and at least one rear control chamber (40, 42) capable of being connected to a source of pressurized fluid (52), characterized in that a annular intermediate chamber (54) is formed in said cylinder 532) around the piston (34), between a front part (34b) of the latter sliding without seal in the cylinder and a rear part (34a) of the piston sliding in the cylinder (32) through said seal (37, 38, 39), drainage means (60, 62 , 64) being provided to circulate a low-flow drainage liquid in said annular chamber (54), in the direction going from the rear part, towards the par front tie of the piston.  2 metering syringe according to claim 1, characterized in that the drainage means comprise at least one supply pipe (60) for drainage liquid opening into said annular chamber (54) near the rear part (34a) of the piston and at least one drainage pipe (64) opening into said annular chamber near the front part (34b) of the piston.  3. Dosing syringe according to any one of claims 1 and 2, characterized in that means (66 to 76) are provided for bringing the piston (34) into a retracted cleaning position (NETT) in which the front part ( 34b) of the piston is located in said annular chamber (54), a cleaning circuit (60) opening into said annular chamber for circulating a washing liquid from said annular chamber towards said orifice (33).  4. Dosing syringe according to claims 2 and 3, characterized in that the cleaning circuit comprises said supply pipe (60).  5. Dosing syringe according to any one of claims 1 to 4, characterized in that the cylinder (32) has an adjustable rear stop (66) for said piston (34).  6. Dosing circuit comprising at least one pipe (10) connecting a reservoir (12) for supplying liquid (14) to a nozzle (16) for dispensing said liquid, a dosing syringe (26) communicating through at least one orifice (33) with said pipe, and two valves (28, 30) placed on said pipe respectively upstream and downstream of this orifice, characterized in that said dosing syringe (26) is produced according to any one of the preceding claims, said pipe (10) being made of a flexible material at least at the level of said valves (28, 30), the latter comprising means (96, 102, 104, 108) for pinching the pipe in order to close it.  7. Metering circuit according to claim 6, characterized in that said valves (28, 30) are formed in a valve system (84) comprising a fixed cylinder (86) in which slides a primary piston (88) forming with the cylinder a control chamber (90) capable of being connected to a source of pressurized fluid, the front face of said primary piston comprising a first compression part (96), a secondary piston (100) movable along the axis of the primary piston in a part (98) integral with the fixed cylinder, the rear face of which comprises a movable anvil (102) placed opposite the first compression part and the front face of which comprises a second compression part (104), a fixed anvil (108 ) integral with said fixed part (98) and placed between the second compression part and the movable anvil, first elastic means (106) interposed between said fixed part and the secondary piston to urge the second compression part (104) con support the fixed anvil (108) and second elastic means (94) interposed between the fixed cylinder (86) and the primary piston (88) in order to separate the first compression part (96) from the movable anvil (102), flexible parts of at least one pipe (10) placed respectively upstream and downstream of the orifice (33) of the dosing syringe being located between the first compression part (96) and the movable anvil (102) and between the fixed anvil (108) and the second compression part (104).  8. Metering circuit according to claim 7, characterized in that it comprises at least two independent pipes (10), the flexible parts of which are placed between the same compression parts (96, 104) and the same anvils (102, 108 ), symmetrically with respect to the common axis of the primary (88) and secondary (100) pistons.  9. Dosing circuit according to any one of claims 6 to 8, characterized in that said orifice (33) of the dosing syringe (26) communicates with said pipe (10) via a tube (24) placed in bypass on the latter.  10. Dosing circuit according to any one of claims 6 to 8, characterized in that the dosing syringe (26) has at least two orifices (33, 80) opening into the front chamber (36), part of said pipe ( 10) placed upstream of said syringe being connected to one (80) of said orifices and a part of said pipe (10) placed downstream of said syringe being connected to the other orifice (33).