WO2025114111A1 - Pressure-regulated positive displacement pump - Google Patents

Abstract

The present invention relates to a positive displacement pump (100) for viscous material, comprising at least one metering means (19), the at least one metering means (19) comprising a metering piston (3) that is movable in a sleeve (17), the at least one metering means (19) having a pre-compression phase that occurs between an intake phase and a discharge phase, the pre-compression phase being carried out by a stroke C of the metering piston (3), the stroke C making it possible to balance the internal pressures of the positive displacement pump (100) in order to obtain an outlet flow rate that is as high and regular as possible.

Description

Pressure-regulated volumetric pump

[0001] The present invention relates to the field of volumetric pumps used for pumping and extruding viscous materials, for example unvulcanized rubber.

[0002] The manufacture of rubber products requires the ability to extrude products while dosing them quantitatively in a very precise manner. Among the many possible applications, we can cite the development of rubber mixtures, which requires the precise dosing of different basic constituents, or the extrusion of profiles of unvulcanized rubber products intended for the assembly of a final product, for example a tire.

[0003] A volumetric pumping solution is disclosed by document EP0690229B1.

[0004] This solution is obtained by combining an extrusion screw with metering pistons. The rotation of the extrusion screw is synchronized with the rotation of a rotating cam which is used to drive a back and forth movement of the pistons.

[0005] In an intake phase, the extrusion screw fills a compression chamber with viscous material, said viscous material passing through an intake orifice to enter the compression chamber. In a discharge phase, a piston pushes, under pressure, the viscous material present in the compression chamber towards an outlet channel, said viscous material passing through a discharge channel before reaching said outlet channel.

[0006] Closing devices make it possible on the one hand to close the discharge channel during the intake phase, and on the other hand to close the intake orifice during the discharge phase.

[0007] In document EP0690229B1, it is the pistons which, during their alternating movements, open or close the intake ports.

[0008] This type of volumetric pumping solutions with openings and closings of orifices connects different chambers filled with material viscous at different pressures, thus generating sudden variations in pressure of the viscous material when it is pumped.

[0009] The pressure difference between the different chambers is even greater when the extrusion of the viscous material is done through small dies, requiring the viscous material to be strongly compressed in order to get it to the outlet.

[0010] This results in fluctuations in the pressure of the viscous material in the different channels, impacting the regularity and geometric quality of the extruded profiles.

[0011] In particular, the variations in the pressure of the viscous material at the outlet occur when the discharge channel is opened, which places the viscous material present in the outlet channel and having a pressure PI in communication with the viscous material present in the compression chamber and having a pressure P2, the pressure PI being different from the pressure P2.

[0012] When the discharge orifice is opened, the pressures PI and P2 will vary very quickly until an identical equilibrium pressure P is obtained in the outlet channel and in the compression chamber and therefore different from the pressures PI and P2.

[0013] In certain cases, the discharge channel is opened too late, that is to say when the piston has already started its stroke during the discharge phase, causing an increase in pressure P2 to a high value and much higher than the value of pressure PI present in the outlet channel.

[0014] Since the viscous material is often weakly compressible, the rise in pressure P2 is very rapid and constitutes a pressure “peak”. This pressure peak is not only detrimental to the geometric quality of the extruded product, but can also cause premature wear of the mechanical parts of the volumetric pump, or even, in certain extreme cases, breakage of said mechanical parts.

[0015] Furthermore, as is known to those skilled in the art, the higher the pressure, the higher the temperature of the viscous material, causing a degradation of the properties of said viscous material, in particular for materials such as unvulcanized rubber for which a rise in temperature can cause the start of vulcanization, making said material unsuitable for use in downstream processes. [0016] Another consequence of the occurrence of a pressure peak is the limitation of the maximum flow rate achievable by the volumetric pump. It is in fact known to those skilled in the art that the higher the flow rate of a volumetric pump, the higher the internal pressures, causing, as explained previously, a rise in the temperature of the material and an increase in the risk of breakage. The internal pressure being the sum of the pressure linked to the flow rate and the pressure generated by the pressure peak, the higher the pressure peak will be and the more the maximum pressure linked to the flow rate will be limited, and consequently the more the flow rate will be limited.

[0017] In other volumetric pumps, the discharge port opens prematurely, i.e. when the piston has not, or has very little, started its stroke during the discharge phase. In these cases, the pressure in the compression chamber is low and much lower than the pressure in the outlet channel, thus causing a reduction in the PI pressure when the discharge port opens. This reduction in the PI pressure also has an impact on the geometry of the extruded profile.

[0018] The objects assigned to the invention therefore aim to remedy the aforementioned drawbacks and to propose a volumetric pump capable of limiting variations in internal pressures, thus making it possible to increase the extrusion flow rate while improving the quality and regularity of the extruded profiles.

[0019] The subject of the invention is a volumetric pump for viscous material comprising:

- a body comprising a cylindrical sheath having an axis of revolution UU’, and a feed opening capable of receiving the viscous material,

- a head comprising an outlet channel intended to cause the viscous material to exit from said volumetric pump,

-at least one metering means, comprising an inlet orifice, a compression chamber, a metering piston movable between a bottom dead center and a top dead center, a sleeve and a discharge channel, the at least one metering means being configured to operate according to a first phase called the inlet phase allowing the viscous material to fill the compression chamber of the at least one metering means by passing through said inlet orifice, and according to a second phase called the discharge phase allowing the viscous material to be propelled from the compression chamber compression of the at least one metering means towards the outlet channel by passing through said discharge channel,

- an actuator for driving the metering piston of the at least one metering means, - a feeding means intended to propel the viscous material present in the sheath from the feed opening towards the at least one metering means,

- an intake member intended to open or close the intake orifice to respectively allow or prevent the passage of the viscous material through the intake orifice,

- a discharge member intended to open or close the discharge channel to respectively allow or prevent the passage of the viscous material through the discharge channel, said volumetric pump being characterized in that the at least one metering means is configured to operate according to an intermediate phase called the precompression phase during which the metering piston of said at least one metering means pre-compresses the viscous material in the compression chamber of said at least one metering means, said pre-compression phase occurring between the intake phase and the discharge phase, said pre-compression phase making it possible to pre-compress the viscous material present in said compression chamber to a pressure corresponding to the value of the pressure of the viscous material in the outlet channel.

[0020] Essentially, the volumetric pump according to the invention makes it possible to achieve the regular and smooth extrusion of a profile of viscous material, such as an unvulcanized rubber material. The material inside the volumetric pump does not undergo pressure peaks and the operating pressure of the pump remains regular throughout the operating cycle, making it possible to obtain a regular flow rate and profiles having a constant geometry.

[0021] Limiting pressure peaks by introducing a precompression phase between the intake phase and the discharge phase also makes it possible to reduce the rise in the temperature of the viscous material, thus making it possible to obtain a viscous material at the outlet which always has the desired properties.

[0022] Furthermore, the attenuation of pressure peaks limits the internal pressure of the volumetric pump, thus allowing the pump to operate at higher flow rates. [0023] Advantageously, the attenuation of pressure peaks and the elimination of radial forces on the metering pistons, when said metering pistons are used to close the inlet orifice, also make it possible to reduce wear and the risks of breakage of the mechanical components of the volumetric pump.

[0024] Preferably, the feeding means is a single endless screw which can rotate around the axis UU', the rotation of the endless screw taking place concentrically in the sheath, said endless screw comprising one or more threads intended to shear and propel the viscous material present in the sheath from the feed opening towards the intake member.

[0025] The use of a worm screw makes it possible to obtain a particularly simple, compact, easy-to-implement feeding means capable of operating with a wide variety of viscous materials.

[0026] Still advantageously, the intake member is configured to close the intake orifice before the moment when the metering piston begins the precompression phase.

[0027] The early sealing of the inlet orifice makes it possible to ensure that said inlet orifice is properly sealed at the moment when the corresponding metering piston begins pre-compression. Furthermore, early sealing does not make it necessary to carry out very precise synchronization between the closing of the inlet orifice and the axial position of the metering piston. In particular, it is no longer necessary to carry out very precise positioning of the axial position of said metering piston, as was the case for certain volumetric pumps of the prior art using said metering piston to open or close the inlet orifice.

[0028] The elimination of the very precise axial positioning of said metering piston saves time when assembling the volumetric pump and during maintenance operations in the event of wear of said metering piston. Indeed, for volumetric pumps using the metering piston to close the inlet orifice, wear of the metering piston can cause a modification of the synchronization between the moment of closing of the inlet orifice and the opening of the discharge channel, resulting, in the event late closing of the inlet port, causing irregularities in the output flow of the volumetric pump.

[0029] Preferably, the intake member is a rotary intake valve having the axis of rotation UU' as its axis of rotation, said rotary intake valve comprising at its periphery an alternation of at least one notch and at least one solid zone, said at least one notch being a removal of material carried out over a predetermined angular sector and said at least one notch allowing the viscous material to travel towards the compression chamber when said at least one notch cooperates with the intake orifice corresponding to said compression chamber.

[0030] The use of a rotary inlet valve makes it possible to obtain a compact, robust inlet member capable of opening or closing the passage of the viscous material through the inlet orifice independently of the position of the metering piston.

[0031] Still preferably, the discharge member is a rotary discharge valve having as its axis of rotation Taxe UU’, said rotary discharge valve comprising an axial discharge bore, as well as a discharge slot developing perpendicularly to said discharge bore, said discharge bore and said discharge slot constituting a channel through which the viscous material can travel towards the outlet channel when said discharge slot cooperates with the discharge channel.

[0032] The rotary discharge valve is a simple and compact part allowing the flow of viscous material coming from the metering means to be collected and directed towards the outlet channel.

[0033] Preferably, the actuator is a rotary cam comprising at least one thrust cam path, cooperating with a thrust roller to enable each of the metering pistons to be moved in a direction internal to the pump and parallel to axis UU’.

[0034] The use of such a rotating cam makes it possible to actuate the metering pistons with a simple, robust and particularly compact system.

[0035] Advantageously, the rotary cam, the worm screw, the rotary intake valve and the rotary discharge valve are all concentric along axis UU', said valve rotary intake being located at the end of said worm screw and said rotary discharge valve being in contact with said rotary intake valve.

[0036] Such an arrangement makes it possible to obtain a simple and compact volumetric pump with a feed opening close to the outlet channel, allowing the operation of said volumetric pump in a small space.

[0037] Still advantageously, the worm screw, the rotary cam, the rotary intake valve and the rotary discharge valve constitute a single part allowing the synchronization of the different moving mechanical elements of the volumetric pump.

[0038] Such a one-piece configuration makes it possible to avoid having to synchronize the worm screw, the rotary cam (and therefore the metering pistons) and the rotary intake and discharge valves when starting the volumetric pump. The risks of mechanical breakage due to poor synchronization are therefore limited.

[0039] Still advantageously, the metering piston is configured such that its movement between the bottom dead center and the top dead center takes place in an area located at a distance from the intake orifice, thus making it possible to fill the compression chamber with the viscous material from the start of the movement of the metering piston from the top dead center.

[0040] Filling the compression chamber throughout the intake phase makes it possible to obtain, on the one hand, a very short cycle time, since no unnecessary movement of the metering pistons is carried out, and on the other hand, filling the compression chamber with viscous material not containing air bubbles. This absence of air bubbles is beneficial for obtaining a profile with a constant geometry at the outlet of the volumetric pump.

[0041] Preferably, the number of dosing means is greater than or equal to 2 and preferably equal to 4, said dosing means being synchronized to ensure a regular output flow rate.

[0042] The synchronization of several dosing means associated with the balancing of internal pressures thanks to the pre-compression phases ensures excellent regularity of the flow rate and of the extruded profile at the outlet of the volumetric pump. [0043] Other objects, characteristics and advantages of the invention will appear in more detail on reading the detailed description which follows, as well as with the aid of the appended drawings, provided for purely illustrative and non-limiting purposes:

-Figure 1: Axial sectional view of a volumetric pump according to the invention.

-Figure 2: Sectional view along the A-A axis shown in figure 1.

-Figure 3: Partial sectional view along the B-B axis shown in figure 1.

-Figure 4: Axial and partial sectional view of a volumetric pump according to the invention, the piston starting an intake phase from top dead center to bottom dead center. -Figure 5: Axial and partial sectional view of a volumetric pump according to the invention, the piston having reached bottom dead center, at the end of the intake phase.

-Figure 6: Axial and partial sectional view of a volumetric pump according to the invention, the piston being positioned at the end of the pre-compression phase.

-Figure 7: Axial and partial sectional view of a volumetric pump according to the invention, the delivery member starting to open to begin a delivery phase. -Figure 8: Axial and partial sectional view of a volumetric pump according to the invention, the piston performing a delivery phase.

-Figure 9: Axial and partial sectional view of a volumetric pump according to the invention, the piston having reached top dead center, at the end of the delivery phase.

[0044] In the following, for the sake of clarity, the horizontal direction X and the vertical direction Y correspond to the natural orientation of Figures 1 to 9. Similarly, the terms “top”, “bottom”, “lower”, “upper” and their variants should be understood with reference to the vertical direction of the figures.

[0045] The invention relates to a volumetric pump 100 intended to meter and extrude, in the form of a profile, a viscous material, which may be, for example, an unvulcanized rubber material.

[0046] As visible in Figure 1, the volumetric pump 100 according to the invention comprises a body 1, a head 2, at least one metering means 19, an actuator 13, a feeding means 22, an intake member 4 and a delivery member 5.

[0047] The body 1 comprises a sheath 9, of cylindrical shape having as its axis of revolution an axis UU', and a feed opening 6 capable of receiving the viscous material which may be in different forms, such as for example, strips, granules, blocks. Depending on the presentation of the viscous material entering the volumetric pump 100, the geometric shape of the feed opening 6 will be adapted accordingly. For example, if the viscous material is in the form of a rectangular strip, the feed opening 6 will comprise a rectangular-shaped orifice having dimensions slightly larger than the dimensions of the strip of viscous material to be metered.

[0048] The head 2, positioned in the extension of the body 1, comprises an outlet channel 7 intended to cause the viscous material to exit the volumetric pump 100. In certain embodiments not shown, the outlet channel 7 can cooperate with other channels located downstream of said outlet channel 7, said channels making it possible, for example, to cause the viscous material to exit laterally and not axially. In other embodiments not shown, the outlet channel 7 can cooperate with a die making it possible to extrude the viscous material according to a predetermined profile.

[0049] As illustrated in Figure 1, the at least one metering means 19 comprises an inlet orifice 12, a compression chamber 16, a metering piston 3, movable between a bottom dead center and a top dead center, a sleeve 17 and a discharge channel 10.

[0050] As shown in Figures 1 and 2, the intake orifice 12 is capable of placing the intake member 4 in communication with the compression chamber 16, thus allowing the viscous material to travel from the jacket 9 to said compression chamber 16. The intake orifice 12 may, for example, be in the form of a rectangular slot.

[0051] As shown in Figures 1 and 2, the discharge channel 10 is capable of placing the discharge member 5 in communication with the compression chamber 16, thus allowing the viscous material to travel from said compression chamber 16 to the outlet channel 7. The discharge channel 10 may, for example, be in the form of a cylindrical bore made in the head 2.

[0052] Advantageously, the discharge channel 10 can also be oblong in shape with the smallest dimension of the oblong section oriented along the height of said head 2, thus making it possible to increase the passage section of the viscous material without increasing the height of the head 2. It is known that this increase in the passage section will make it possible to reduce the pressure necessary to move the viscous material into the discharge channel 10, thus allowing a greater flow rate without increasing the temperature.

[0053] In certain embodiments not shown, the outlet channel 7 cooperates with other channels located downstream of said outlet channel 7, said downstream channels being able to advantageously be oblong in shape with the smallest dimension of the oblong section directed appropriately so as not to increase the dimensions of the volumetric pump 100. As explained previously, the oblong shape of said downstream channels makes it possible to increase the flow rate of the volumetric pump 100 without increasing the internal pressure or the temperature of the material.

[0054] As can be seen in Figure 1 and Figures 4 to 9, the metering piston 3 slides alternately in a corresponding sleeve 17 between a bottom dead center (BDC) and a top dead center (TDC).

[0055] As shown in Figure 1, the actuator 13 makes it possible to actuate the metering piston 3 of the at least one metering means 19 in an alternating back and forth movement.

[0056] In certain embodiments and as can be seen in FIG. 1, the actuator 13 is a rotary cam 18, comprising at least one thrust cam path 18a, cooperating with a thrust roller 14 to enable each of the metering pistons 3 to be moved in a direction inside the pump and parallel to the axis UU’. In these embodiments, the movement in the direction outside the pump and parallel to the axis UU’ is generated by the pressure of the viscous material entering the compression chamber 16.

[0057] In certain embodiments, a second return cam path 18b cooperates with a return roller 15, making it possible to set the metering piston 3 in motion, in a direction external to the pump and always parallel to the axis UU’.

[0058] As is known to those skilled in the art, other actuators may be used to move the metering piston 3, such as, for example, hydraulic or pneumatic cylinders, or electromechanical actuators. [0059] Looking at Figure 1 and Figures 4 to 9, it is visible that the compression chamber 16 is delimited by the walls of the jacket 17, by the metering piston 3, by the head 2, and by the delivery member 5.

[0060] The volume of the compression chamber 16 is therefore variable depending on the position of the metering piston 3 in the sleeve 17. The volume of the compression chamber 16 is minimum when the metering piston 3 is at top dead center and it is maximum when the metering piston 3 is at bottom dead center.

[0061] The force-feeding means 22 is intended to propel the viscous material present in the sheath 9 from the feed opening 6 towards the at least one metering means 19, the path of the viscous material being represented by arrows visible in FIG. 1.

[0062] As illustrated in Figure 1, in a preferred embodiment, the feeding means 22 is a single endless screw 8 that can rotate around the axis UU', the rotation of the endless screw 8 taking place concentrically in the sheath 9, said endless screw 8 comprising one or more threads intended to shear and propel the viscous material present in the sheath 9 from the feed opening 6 towards the intake member 4.

[0063] In other embodiments, other feeding means may be used to propel the viscous material from the feed opening 6 to the intake member 4, such as, for example, “syringe” systems or gear pumps.

[0064] The intake member 4 is intended to open or close the intake orifice 12 to respectively allow or prevent the passage of the viscous material through the intake orifice 12.

[0065] When the intake member 4 is in the open position, the flow of the viscous material through the intake orifice 12 takes place from the sheath 9 towards the compression chamber 16.

[0066] In a preferred embodiment and as can be seen in Figures 1 and 2, the intake member 4 is a rotary intake valve 40 having the axis of rotation UU' as its axis of rotation, said rotary intake valve 40 comprising at its periphery an alternation of at least one notch 20 and at least one solid zone 23, said at least one notch 20 being a removal of material carried out over a predetermined angular sector and said at least one notch 20 allowing the viscous material to travel towards the compression chamber 16 when said at least one notch 20 cooperates with the inlet orifice 12 corresponding to said compression chamber 16.

[0067] Preferably, and as shown in figures 3 to 6, the notch 20 is not made over the entire height of the rotary intake valve 40.

[0068] Advantageously, the remainder of the periphery of the rotary intake valve 40, comprising the solid zone 23, cooperates with the sheath 9 to close the intake orifice 12 and prevent any passage of viscous material towards the corresponding compression chamber 16.

[0069] Thus, during its rotation, the rotary intake valve 40 will open or close the intake orifice 12 alternately.

[0070] In a preferred embodiment, the body 1 comprises a circular bore concentric with the axis UU’ and having a diameter enabling it to serve as a rotational guide bearing for the rotary intake valve 40.

[0071] The discharge member 5 is intended to open or close the discharge channel 10 to respectively allow or prevent the passage of the viscous material through the discharge channel 10.

[0072] When the discharge member 5 is in the open position, the flow of the viscous material through the discharge channel 10 takes place from the compression chamber 16 towards the outlet channel 7.

[0073] In a preferred embodiment, and as can be seen in Figure 1 and Figures 3 to 8, the discharge member 5 is a rotary discharge valve 50 having the axis of rotation UU' as its axis of rotation, said rotary discharge valve 50 comprising an axial discharge bore 11, as well as a discharge slot 21 extending perpendicularly to said discharge bore 11, said discharge bore 11 and said discharge slot 21 constituting a channel through which the viscous material can travel towards the outlet channel 7 when said discharge slot

21 cooperates with the discharge channel 10. [0074] When the discharge slot 21 no longer cooperates with the discharge channel 10, the rotary discharge valve 50 cooperates with the head 2 to close the discharge channel 10 and prevent any passage of the viscous material towards the outlet channel 7.

[0075] Thus, during its rotation, the rotary discharge valve 50 will open or close the discharge channel 10 alternately.

[0076] In a preferred embodiment, the head 2 comprises a circular bore concentric with the axis UU’ and having a diameter enabling it to serve as a rotational guide bearing for the rotary discharge valve 50.

[0077] In a preferred embodiment, the rotary cam 13, the worm screw 8, the rotary intake slide 40 and the rotary discharge slide 50 are all concentric along the axis UU', said rotary intake slide 40 being located at the end of said worm screw 8 and said rotary discharge slide 50 being in contact with said rotary intake slide 40.

[0078] Advantageously, the worm screw 8, the rotary cam 13, the rotary intake valve 40 and the rotary discharge valve 50 constitute a single part allowing the synchronization of the different moving mechanical elements of the volumetric pump 100.

[0079] As can be seen in Figure 3, the at least one metering means 19 is configured to operate according to a first phase called the intake phase allowing the viscous material to fill the compression chamber 16 of the at least one metering means 19 by passing through said intake orifice 12.

[0080] During each admission phase of said at least one metering means 19: - the admission orifice 4 of said at least one metering means 19 is open, - the discharge orifice 5 of said at least one metering means 19 is closed, - the metering piston 3 of said at least one metering means 19 performs a stroke between a top dead center and a bottom dead center.

[0081] In Figure 4, an arrow has been added to clearly show the path of the viscous material in the volumetric pump 100 during the intake phase. [0082] At the end of the intake phase and as shown in FIG. 5, the metering piston 3 reaches the bottom dead center, the intake member 4 closes while the delivery member 5 remains closed.

[0083] As illustrated in Figure 7, the at least one metering means 19 is configured to operate according to a second phase called the discharge phase making it possible to propel the viscous material from the compression chamber 16 of the at least one metering means 19 towards the outlet channel 7 by passing through said discharge channel 10.

[0084] During each delivery phase of the at least one metering means 19: - the inlet orifice 4 of said at least one metering means 19 is closed, - the delivery channel 5 of said at least one metering means 19 is open, - the metering piston 3 of said at least one metering means 19 performs a stroke between a bottom dead center and a top dead center.

[0085] As for figure 4, an arrow has been added to figure 8 to clearly show the path of the viscous material in the volumetric pump 100 during the discharge phase.

[0086] At the end of the delivery phase and as shown in FIG. 9, the metering piston 3 reaches top dead center, the intake member 4 remaining closed, while the delivery member 5 closes.

[0087] According to the invention, and as can be seen in Figure 6, the at least one metering means 19 is configured to operate according to an intermediate phase called the precompression phase during which the metering piston 3 of said at least one metering means 19 pre-compresses the viscous material in the compression chamber 16 of said at least one metering means 19, said pre-compression phase occurring between the intake phase and the discharge phase, said pre-compression phase making it possible to pre-compress the viscous material present in said compression chamber 16 to a pressure corresponding to the value of the pressure of the viscous material in the outlet channel 7.

[0088] As shown in Figure 6, during each pre-compression phase of said at least one metering means 19:

- the inlet orifice 4 of said at least one metering means 19 is closed, - the discharge channel 5 of said at least one dosing means 19 is closed,

-the metering piston 3 of said at least one metering means 19 performs a stroke C between the bottom dead center and an intermediate point allowing the pre-compression of the viscous material in the compression chamber 16 of said at least one metering means 19.

[0089] Thanks to the use of the intake member 4, it is thus possible to completely decouple the stroke of the metering piston 3 and the phases of opening or closing of the intake orifice 12.

[0090] This decoupling makes it possible to freely choose the stroke C carried out by the metering piston 3 during the pre-compression phase, the closure being carried out independently by the rotation of the intake member 4.

[0091] When it is necessary to carry out precise dosing with the volumetric pump 100 of the invention, the different admission, pre-compression and discharge phases are carried out successively a predetermined number of times in order to obtain the desired quantity of viscous material.

[0092] Advantageously, the intake member 4 is configured to close the intake orifice 12 before the moment when the metering piston 3 begins the precompression phase.

[0093] In the preferred embodiment in which the intake member 4 is a rotary intake valve 40, the anticipation of the closing of the intake orifice 12 is achieved by synchronizing and shaping the rotary intake valve 40 so that the notch 20 is sufficiently distant from the intake orifice 12 at the moment when the metering piston 3 begins pre-compression, the distance from said notch 20 making it unlikely that the viscous material will travel towards said notch 20, thus making it possible to improve the sealing of the closure of the intake member 4 and consequently the metering quality of the volumetric pump 100.

[0094] As can be seen in Figure 7, when the metering piston 3 has completed its precompression, the delivery member 5 begins to open the delivery channel 10 and the delivery phase can begin. [0095] The opening of the discharge channel 10 will bring the viscous material present in the corresponding compression chamber 16 into contact with the viscous material present in the outlet channel 7.

[0096] Given that the pre-compression phase makes it possible to obtain a pressure for the viscous material present in the compression chamber 16 equivalent to the pressure of the viscous material present in the outlet channel 7, no pressure variation occurs either for the pressure in the compression chamber 16 or for the pressure in the outlet channel 7, thus making it possible to maintain an extruded profile having constant geometric characteristics and of good quality.

[0097] In addition, the mechanical components of the volumetric pump 100 do not undergo any shock or any sudden variation in stress, thus making it possible to preserve the reliability of the volumetric pump 100 and to improve its service life.

[0098] Advantageously and as shown in Figures 3 to 8, the metering piston 3 is configured such that its movement between the bottom dead center and the top dead center takes place in an area located at a distance from the intake orifice 12, thus making it possible to fill the compression chamber 16 with the viscous material from the start of the movement of the metering piston 3 from the top dead center, that is to say from the start of the intake phase.

[0099] By zone located at a distance from the intake orifice 12 it is necessary to understand that the metering piston 3 never comes to block the intake orifice 12 during its alternating movement between the bottom dead center and the top dead center.

[00100] Such a configuration is made possible thanks to the use of the intake member 4 which makes it possible to close or open the intake orifice 12 during the different operating phases of the volumetric pump 100.

[00101] In certain embodiments, the number of metering means 19 is greater than or equal to 2 and preferably equal to 4 as shown in FIGS. 2 and 3, said metering means 19 being synchronized to ensure a regular output flow rate.

[00102] In certain embodiments with several dosing means 19, each of said dosing means 19 operates according to the three phases previously described. [00103] In certain embodiments with several metering means 19, at least two of said metering means 19 can be synchronized to carry out at the same time the same phases among the admission, discharge and pre-compression phases.

[00104] In certain embodiments with several dosing means 19, the different phases of the different dosing means 19 are carried out so as to ensure a continuous output flow.

[00105] By way of example, a volumetric pump 100 may comprise the worm screw 8, the rotary intake valve 40, the rotary discharge valve 50 and three metering means 19 driven simultaneously by the rotary cam 18. At a time t, the first metering means 19 may carry out an intake phase, the second metering means 19 may carry out a pre-compression phase and the third metering means 19 may carry out a discharge phase.

[00106] In this example, the rotary intake valve 40 is shaped and synchronized for, at time t:

- open the inlet orifice 12 corresponding to the first dosing means 19, - close the inlet orifices 12 corresponding to the second and third dosing means 19.

[00107] Still in the same example, the rotary discharge valve 50 is shaped and synchronized for, always at the same time t:

- close the discharge channel 10 corresponding to the first and second dosing means 19,

- open the discharge channel 10 corresponding to the third dosing means 19.

[00108] Generally speaking, during operation of the volumetric pump 100, the intake 4 and discharge 5 members respectively are shaped and synchronized to open or close the different intake orifices 12 and the different discharge channels 10 in relation to the phases carried out by the different metering means 19 of a volumetric pump 100.

[00109] In the embodiments where several metering means 19 carry out, at the same time, one of the phases among the admission, discharge and pre-compression phases, the admission 4 and discharge 5 members are shaped and synchronized to open or close the inlet ports 12 and the discharge channels 10 of the different dosing means 19 according to the phases being carried out.

[00110] The stroke C can be determined by carrying out tests with a volumetric pump 100 equipped with pressure sensors arranged both in the compression chamber 16 and in the outlet channel 7. In particular, these tests make it possible to compare the pressures in the compression chamber 16 and in the outlet channel 7 at the time of opening of the delivery member 5 at the end of the pre-compression phase. In the event of a pressure difference, the stroke C is adapted accordingly.

[00111] Tests were carried out to compare the flow rate values and the outlet temperatures of a volumetric piston pump inside which the pressures are not balanced by a pre-compression phase and a volumetric pump 100 according to the invention.

[00112] For these tests, the same unvulcanized rubber was extruded by the piston pump having no pre-compression phase and by the pump of the invention. The Mooney viscosity ML 1+4 at 100°C of the unvulcanized rubber extruded during the comparative tests is 70 UM (Mooney unit). The Mooney, also known as viscosity or plasticity, characterizes, in a known manner, solid substances. An oscillating consistometer as described in the ASTM D1646 standard (1999) is used. This plasticity measurement is carried out according to the following principle: the sample analyzed in its raw state (i.e., before curing) is molded (formed) in a cylindrical enclosure heated to a given temperature (e.g., 35°C or 100°C). After one minute of preheating, the rotor rotates within the test piece at 2 revolutions/minute and the torque needed to maintain this movement is measured for 4 minutes of rotation. The Mooney viscosity (ML 1 + 4) is expressed in "Mooney units" (with 1 MU = 0.83 Nm) and corresponds to the value obtained at the end of the 4 minutes.

[00113] Table 1 below summarizes, in base 100, the results obtained. [Table 1]

[00114] As illustrated in Table 1, the volumetric pump 100 of the invention makes it possible, for the same unvulcanized rubber material, to reduce the temperature of said unvulcanized rubber at the outlet.

[00115] At the same time, the output flow rate can be significantly increased, without risk of deterioration of the quality of the material or without risk of breakage or premature wear of the volumetric pump 100.

Claims

Claims 1. Volumetric pump (100) for viscous material comprising: - a body (1) comprising a cylindrical sheath (9) having an axis of revolution UU’, and a feed opening (6) capable of receiving the viscous material, - a head (2) comprising an outlet channel (7) intended to cause the viscous material to exit from said volumetric pump (100), -at least one metering means (19) comprising an inlet orifice (12), a compression chamber (16), a metering piston (3) movable between a bottom dead center and a top dead center, a sleeve (17) and a discharge channel (10), the at least one metering means (19) being configured to operate according to a first phase called the inlet phase allowing the viscous material to fill the compression chamber (16) of the at least one metering means (19) by passing through said inlet orifice (12), and according to a second phase called the discharge phase allowing the viscous material to be propelled from the compression chamber (16) of the at least one metering means (19) towards the outlet channel (7) by passing through said discharge channel (10), -an actuator (13) allowing the metering piston (3) of the at least one metering means (19) to be driven, - a feeding means (22) intended to propel the viscous material present in the sheath (9) from the feed opening (6) towards the at least one dosing means (19), - an intake member (4) intended to open or close the intake orifice (12) to respectively allow or prevent the passage of the viscous material through the intake orifice (12), - a discharge member (5) intended to open or close the discharge channel (10) to respectively allow or prevent the passage of the viscous material through the discharge channel (10), said volumetric pump being characterized in that the at least one metering means (19) is configured to operate according to an intermediate phase called the precompression phase during which the metering piston (3) of said at least one metering means (19) pre-compresses the viscous material in the compression chamber (16) of said at least one metering means (19), said pre-compression phase occurring between the intake phase and the discharge phase, said pre-compression phase making it possible to pre-compress the viscous material present in said compression chamber (16) to a pressure corresponding to the value of the pressure of the viscous material in the outlet channel (7). 2. Volumetric pump (100) for viscous material according to claim 1, in which the feeding means (22) is a single worm screw (8) movable in rotation around the axis UU', the rotation of the worm screw (8) taking place concentrically in the sheath (9), said worm screw (8) comprising one or more threads intended to shear and propel the viscous material present in the sheath (9) from the feed opening (6) towards the intake member (4). 3. Volumetric pump (100) for viscous material according to claim 1 or 2, in which the intake member (4) is configured to close the intake orifice (12) before the moment when the metering piston (3) begins the pre-compression phase. 4. Volumetric pump (100) for viscous material according to any one of claims 1 to 3 wherein the intake member (4) is a rotary intake valve (40) having as its axis of rotation the axis UU', said rotary intake valve (40) comprising at the periphery an alternation of at least one notch (20) and at least one solid zone (23), said at least one notch (20) being a removal of material carried out on a predetermined angular sector and said at least one notch (20) allowing the viscous material to travel towards the compression chamber (16) when said at least one notch (20) cooperates with the intake orifice (12) corresponding to said compression chamber (16). 5. Volumetric pump (100) for viscous material according to any one of claims 1 to 4 in which the discharge member (5) is a rotary discharge plug (50) having as its axis of rotation the axis UU', said rotary discharge plug (50) comprising an axial discharge bore (11), as well as a discharge slot (21) developing perpendicularly to said discharge bore (11), said discharge bore (11) and said discharge slot (21) constituting a channel through which the viscous material can travel towards the outlet channel (7) when said discharge slot (21) cooperates with the discharge channel (10). 6. Volumetric pump (100) for viscous material according to any one of claims 1 to 5 in which the actuator (13) is a rotary cam (18) comprising at least one thrust cam path (18a), cooperating with a thrust roller (14) to enable each of the metering pistons (3) to be set in motion, in a direction internal to the pump and parallel to the axis UU'. 7. Volumetric pump (100) for viscous material according to claim 6 wherein the rotary cam (13), the worm screw (8), the inlet rotary plug (40) and the discharge rotary plug (50) are all concentric along the axis UU', said inlet rotary plug (40) being located at the end of said worm screw (8) and said discharge rotary plug (50) being in contact with said inlet rotary plug (40). 8. Volumetric pump (100) for viscous material according to claim 7 in which the worm screw (8), the rotary cam (13), the rotary intake valve (40) and the rotary discharge valve (50) constitute a single part allowing the synchronization of the different moving mechanical elements of the volumetric pump (100). 9. Volumetric pump (100) for viscous material according to any one of claims 1 to 8 wherein the metering piston (3) is configured such that its movement between the bottom dead center and the top dead center takes place in an area located at a distance from the inlet orifice (12), thus making it possible to fill the compression chamber (16) with the viscous material from the start of the movement of said metering piston (3) from the top dead center. 10. Volumetric pump (100) for viscous material according to any one of claims 1 to 9 in which the number of metering means (19) is greater than or equal to 2 and preferably equal to 4, said dosing means (19) being synchronized to ensure a regular output flow rate.