Pressure regulated positive displacement pump

Abstract

The present invention relates to a positive displacement pump (100) for viscous materials, comprising at least one metering device (19) including a metering piston (3) movable in a sleeve (17), the at least one metering device (19) having a pre-compression stage occurring between a feeding stage and a conveying stage, the pre-compression stage being implemented by a stroke C of the metering piston (3) such that the internal pressure of the positive displacement pump (100) can be balanced to obtain the highest possible and most regular outlet flow rate.

Description

Technical Field

[0001] This invention relates to the field of positive displacement pumps for pumping and extruding viscous materials (e.g., uncured rubber). Background Technology

[0002] The manufacture of rubber products requires the ability to extrude the product while measuring the quantity of the product with great precision. Among the many envisioned applications, the preparation of rubber compounding (which requires precise measurement of different base components) or the extrusion of molding elements of products made from unvulcanized rubber (intended for assembling final products such as tires) can be mentioned.

[0003] Document EP0690229B1 discloses a positive displacement pumping solution.

[0004] This solution is achieved by combining an extrusion screw with a metering piston. The rotation of the extrusion screw is synchronized with the rotation of a rotating cam, which causes the piston to reciprocate.

[0005] During the feeding stage, the extrusion screw fills the compression chamber with viscous material, which enters the compression chamber through the feed orifice. During the conveying stage, the piston, under pressure, pushes the viscous material present in the compression chamber toward the outlet channel, where it passes through a conveying channel before reaching the outlet channel.

[0006] The sealing device enables the conveying channel to be closed during the feeding phase and the feed orifice to be shut off during the conveying phase.

[0007] In document EP0690229B1, the piston opens or closes the feed orifice during its alternating movement.

[0008] This positive displacement pumping solution, which connects different chambers filled with viscous materials at different pressures by opening and closing orifices, thereby causing abrupt pressure changes in the viscous material while pumping it.

[0009] When viscous materials are extruded through small-sized dies, the pressure difference between different chambers can be even greater, requiring the viscous materials to be compressed significantly in order to be transported to the outlet.

[0010] This causes pressure fluctuations in the viscous material in different channels, thereby affecting the regularity and geometric quality of the extruded molding elements.

[0011] Specifically, the pressure of the viscous material at the outlet changes during the opening of the conveying channel, which connects the viscous material at pressure P1 present in the outlet channel with the viscous material at pressure P2 present in the compression chamber, wherein pressure P1 and pressure P2 are different.

[0012] During the period when the delivery orifice is open, the pressures P1 and P2 change very rapidly until they reach an equilibrium pressure P that is the same in the outlet channel and the compression chamber and is therefore different from the pressures P1 and P2.

[0013] In some cases, the delivery channel opens too late, that is, after the piston has already begun its stroke during the delivery phase, causing the pressure P2 to increase to a much higher value than the current pressure P1 in the outlet channel.

[0014] Because viscous materials are generally poorly compressible, the pressure P2 increases very rapidly and constitutes a pressure "peak". This pressure peak can not only damage the geometry of the extruded product, but may also cause premature wear of the mechanical components of the positive displacement pump, or even, in some extreme cases, breakage of the mechanical components.

[0015] Furthermore, as is known to those skilled in the art, the greater the increase in pressure, the higher the temperature of the viscous material, which leads to a deterioration in the properties of the viscous material, especially for materials such as unvulcanized rubber, where the temperature rise will trigger vulcanization, making the material unsuitable for downstream processes.

[0016] Another consequence of pressure peaks is that they limit the maximum flow rate achievable by a positive displacement pump. Specifically, those skilled in the art know that the higher the flow rate of a positive displacement pump, the higher the internal pressure, which, as mentioned above, leads to increased material temperature and a higher risk of breakage. Since internal pressure is the sum of flow-related pressure and the pressure resulting from pressure peaks, the higher the pressure peak, the more limited the maximum flow-related pressure, and consequently, the more limited the flow rate.

[0017] In other positive displacement pumps, the delivery orifice opens prematurely, either before the piston has begun its stroke or just begun its stroke during the delivery phase. In these cases, the pressure in the compression chamber is low and much lower than the pressure in the outlet channel, resulting in a decrease in pressure P1 during the opening of the delivery orifice. This decrease in pressure P1 also affects the geometry of the extruded forming element. Summary of the Invention

[0018] Therefore, the present invention aims to overcome the above-mentioned defects and provide a positive displacement pump that can limit changes in internal pressure, thereby enabling an increase in extrusion rate while improving the quality and regularity of the extruded molding elements.

[0019] The subject of this invention is a positive displacement pump for viscous materials, comprising: - The main body includes a cylindrical shell and a supply port, the cylindrical shell having an axis UU' serving as the axis of rotation, and the supply port being capable of receiving viscous materials. - A head, which includes an outlet channel designed for discharging viscous material from the positive displacement pump. - At least one metering device comprising a feed orifice, a compression chamber, a metering piston movable between a bottom dead center and a top dead center, a sleeve, and a conveying channel, said at least one metering device being configured to operate in the first stage, referred to as the feeding stage, to allow viscous material to fill the compression chamber of said at least one metering device by passing through said feed orifice, and to operate in the second stage, referred to as the conveying stage, to advance the viscous material from the compression chamber of said at least one metering device through said conveying channel to said outlet channel. - An actuator for moving the metering piston of the at least one metering device. - A feeding device designed to advance viscous material present in the cylinder from the supply port to the at least one metering device. - A feeding component designed to open or close the feed orifice to allow or prevent viscous material from passing through the feed orifice, respectively. - A conveying component designed to open or close the conveying channel to allow or prevent viscous materials from passing through it, respectively. The positive displacement pump is characterized in that the at least one metering device is configured to operate in an intermediate stage called a pre-compression stage, during which the metering piston of the at least one metering device pre-compresses the viscous material in the compression chamber of the at least one metering device, the pre-compression stage occurring between the feeding stage and the conveying stage, the pre-compression stage enabling the viscous material present in the compression chamber to be pre-compressed to a pressure corresponding to the pressure of the viscous material in the outlet channel.

[0020] Essentially, the positive displacement pump according to the invention enables the regular and non-aggressive extrusion of molding elements of viscous materials (e.g., uncured rubber materials). The material within the positive displacement pump does not experience any pressure peaks, and the pump's operating pressure remains stable throughout the entire operating cycle, thereby enabling regular flow rates and molding elements with constant geometry.

[0021] Introducing a pre-compression stage between the feeding and conveying stages to limit pressure peaks also reduces the temperature rise of viscous materials, thus enabling the production of viscous materials that still retain the desired properties at the outlet.

[0022] In addition, reducing the peak pressure can limit the internal pressure of the positive displacement pump, thus enabling the pump to operate at much higher flow rates.

[0023] Advantageously, when the metering piston is used to close the feed orifice, reducing the pressure peak and eliminating the radial load on the metering piston also makes it possible to reduce the risk of wear and breakage of the mechanical components of the positive displacement pump.

[0024] Preferably, the feeding device is a single worm gear rotatable about an axis UU', the worm gear rotating concentrically within the cylinder, the worm gear including one or more threads designed to shear viscous material present in the cylinder and to advance the viscous material from the feed port to the feed member.

[0025] The use of a worm gear makes it possible to obtain a particularly simple, compact, easy-to-use feeding device that can operate on a wide variety of viscous materials.

[0026] Furthermore, the feed assembly is configured to close the feed orifice before the metering piston begins the pre-compression phase.

[0027] The anticipated closure of the feed orifice ensures that it closes appropriately at the moment the corresponding metering piston begins pre-compression. Furthermore, this anticipated closure eliminates the need for highly precise synchronization between the closure of the feed orifice and the axial position of the metering piston. In particular, the highly precise positioning of the metering piston's axial position, as is required in some prior art positive displacement pumps where the metering piston is used to open or close the feed orifice, is no longer necessary.

[0028] Eliminating the need for highly precise axial positioning of the metering piston allows for time savings during the assembly of the positive displacement pump and in maintenance operations when the metering piston is worn. Specifically, for positive displacement pumps that use a metering piston to close the inlet orifice, wear of the metering piston causes a change in the synchronization between the inlet orifice closure time and the delivery channel opening time. As a result, when the inlet orifice closes later, the outlet flow rate of the positive displacement pump becomes irregular.

[0029] Preferably, the feeding member is a rotary feed plug having an axis UU' as the axis of rotation. The rotary feed plug includes at least one alternating notch and at least one solid region around its periphery. The at least one notch is created by removing material in a predetermined angular sector, and when the at least one notch mates with a feed orifice corresponding to a compression chamber, the at least one notch allows viscous material to travel into the compression chamber.

[0030] The use of a rotary feed plug enables a compact and robust feed mechanism that can open and close the passage of viscous materials through the feed orifice independently of the position of the metering piston.

[0031] Preferably, the conveying component is a rotary conveying plug, which has an axis UU' as the axis of rotation. The rotary conveying plug includes an axial conveying hole and a conveying groove extending perpendicular to the conveying hole. When the conveying groove is engaged with the conveying channel, the conveying hole and the conveying groove form a channel through which viscous materials can travel to the outlet channel.

[0032] A rotary conveyor plug is a simple and compact component that enables the collection of viscous material streams from a metering device and the delivery of these viscous material streams to an outlet channel.

[0033] Preferably, the actuator is a rotary cam including at least one thrust cam path, which cooperates with a thrust roller to enable each metering piston to move along the pump and in a direction parallel to the axis UU'.

[0034] Using this rotary cam enables the movement of the metering piston through a simple, robust, and particularly compact system.

[0035] Advantageously, the rotary cam, worm, rotary feed plug, and rotary conveyor plug are all coaxial with axis UU', the rotary feed plug is located at the end of the worm, and the rotary conveyor plug is in contact with the rotary feed plug.

[0036] This arrangement enables the creation of a simple and compact positive displacement pump with its inlet located close to the outlet channel, allowing the positive displacement pump to operate in a small space.

[0037] Furthermore, the worm gear, rotary cam, rotary feed plug, and rotary delivery plug are integrated into a single component, thereby enabling the different moving mechanical components of the positive displacement pump to be synchronized.

[0038] This integrated configuration eliminates the need for synchronization of the worm gear, rotary cam (and therefore the metering piston), rotary feed plug, and rotary delivery plug during positive displacement pump startup. Therefore, the risk of mechanical breakage due to poor synchronization is limited.

[0039] Furthermore, the metering piston is configured such that its movement between the bottom dead center and the top dead center occurs in an area located at a certain distance from the feed orifice, so that once the metering piston begins to move from the top dead center, the viscous material can be filled into the compression chamber.

[0040] Filling the compression chamber throughout the feeding phase enables very short cycle times by preventing unnecessary movement of the metering piston, and also allows for the filling of the compression chamber with bubble-free, viscous material. This bubble-free process facilitates the production of molded elements with constant geometry at the outlet of the positive displacement pump.

[0041] Preferably, the number of metering devices should be greater than or equal to 2, preferably equal to 4, and the metering devices should be synchronized to ensure a regular outlet flow rate.

[0042] The synchronization of multiple metering devices, working together to balance the internal pressure through the pre-compression stage, ensures excellent flow regularity at the outlet of the positive displacement pump and excellent regularity of the extruded molding elements. Attached Figure Description

[0043] Other objects, features, and advantages of the invention will become apparent in more detail from the following detailed description and with reference to the accompanying drawings, which are provided by way of non-limiting illustration only, wherein: - Figure 1 Axial cross-sectional view of the positive displacement pump according to the present invention.

[0044] - Figure 2 Along Figure 1 The cross-sectional view of axis AA is shown.

[0045] - Figure 3 Along Figure 1 The diagram shows a partial cross-sectional view of axis BB.

[0046] - Figure 4 According to a partial axial cross-sectional view of the positive displacement pump of the present invention, the piston begins the feeding stage from the top dead center to the bottom dead center.

[0047] - Figure 5 According to a partial axial cross-sectional view of the positive displacement pump of the present invention, the piston has reached the bottom dead center at the end of the feeding stage.

[0048] - Figure 6 According to the present invention, a partial axial cross-sectional view of the positive displacement pump shows the piston at the end of the pre-compression stage.

[0049] - Figure 7 According to a partial axial cross-sectional view of the positive displacement pump of the present invention, the conveying member begins to open to begin the conveying phase.

[0050] - Figure 8 According to a partial axial cross-sectional view of the positive displacement pump of the present invention, the piston performs the delivery stage.

[0051] - Figure 9 According to a partial axial cross-sectional view of the positive displacement pump of the present invention, the piston has reached the top dead center at the end of the delivery phase. Detailed Implementation

[0052] In the following text, for clarity, the horizontal direction X and the vertical direction Y correspond to... Figures 1 to 9The natural orientation. Similarly, the terms "top," "bottom," "lower," "upper," and their variant forms should be understood with reference to the vertical direction in the diagram.

[0053] The present invention relates to a positive displacement pump 100, which is intended for metering and extruding viscous materials in the form of molding elements, said viscous materials being, for example, unvulcanized rubber materials.

[0054] As in Figure 1 As can be seen, the positive displacement pump 100 according to the present invention includes a main body 1, a head 2, at least one metering device 19, an actuator 13, a feeding device 22, a feeding component 4, and a conveying component 5.

[0055] The main body 1 includes a cylindrical shell 9 and a supply port 6. The cylindrical shell 9 has an axis UU' serving as the axis of rotation. The supply port 6 is capable of receiving viscous materials in various forms (e.g., strips, granules, lumps). Depending on the form of the viscous material entering the positive displacement pump 100, the geometry of the supply port 6 will be adjusted accordingly. For example, if the viscous material is in the form of rectangular strips, the supply port 6 will include a rectangular orifice, the size of which is slightly larger than the size of the strip-shaped viscous material to be metered.

[0056] The head 2, located in the continuation of the body 1, includes an outlet channel 7 designed for discharging viscous material from the positive displacement pump 100. In some embodiments (not shown), the outlet channel 7 may cooperate with other channels located downstream of the outlet channel 7, which allow, for example, viscous material to be discharged laterally rather than axially. In other embodiments (not shown), the outlet channel 7 may cooperate with a die to extrude viscous material having a predetermined profile.

[0057] like Figure 1 As shown, at least one metering device 19 includes a feed inlet 12, a compression chamber 16, a metering piston 3 that can move between the lower dead center and the upper dead center, a sleeve 17, and a conveying channel 10.

[0058] like Figure 1 and Figure 2 As shown, the feed port 12 allows the feed member 4 to communicate with the compression chamber 16, thereby enabling viscous material to travel from the sleeve 9 into the compression chamber 16. The feed port 12 can be, for example, in the form of a rectangular slot.

[0059] like Figure 1 and Figure 2 As shown, the conveying channel 10 enables the conveying member 5 to communicate with the compression chamber 16, thereby allowing viscous material to travel from the compression chamber 16 to the outlet channel 7. The conveying channel 10 can be, for example, in the form of a cylindrical orifice formed in the head 2.

[0060] Advantageously, the conveying channel 10 can also have an elongated shape, the minimum dimension of which is oriented along the height of the head 2, thereby increasing the flow cross-section of the viscous material without further increasing the height of the head 2. It is known that this increase in flow cross-section makes it possible to reduce the pressure required to convey viscous material through the conveying channel 10, thereby enabling a greater flow rate without increasing the temperature.

[0061] In some embodiments not shown, the outlet channel 7 cooperates with other channels located downstream of the outlet channel 7. These downstream channels are advantageously elongated in shape, the minimum dimensions of the elongated segments of which are suitably oriented to avoid increasing the size of the positive displacement pump 100. As described above, the elongated shape of the downstream channels allows for an increase in the flow rate of the positive displacement pump 100 without increasing the internal pressure or temperature of the material.

[0062] As in Figure 1 and Figures 4 to 9 As can be seen, the metering piston 3 slides back and forth between the bottom dead center (BDC) and the top dead center (TDC) in the corresponding sleeve 17.

[0063] like Figure 1 As shown, the actuator 13 enables the metering piston 3 of at least one metering device 19 to reciprocate.

[0064] In some implementation schemes, such as in Figure 1 As can be seen, the actuator 13 is a rotary cam 18 including at least one thrust cam path 18a, which cooperates with the thrust roller 14 to enable each of the metering pistons 3 to move along the pump interior and parallel to the axis UU'. In these embodiments, the movement along the pump exterior and parallel to the axis UU' is generated by the pressure of the viscous material entering the compression chamber 16.

[0065] In some implementations, the second return cam path 18b cooperates with the return roller 15, enabling the metering piston 3 to move along the outside of the pump while still parallel to the axis UU'.

[0066] As is known to those skilled in the art, other actuators can be used to move the metering piston 3, such as hydraulic cylinders or pneumatic cylinders, or electromechanical actuators.

[0067] Will Figure 1 and Figures 4 to 9 Taking this into account, it is clear that the compression chamber 16 is defined by the wall of the sleeve 17, the metering piston 3, the head 2, and the conveying component 5.

[0068] Therefore, the volume of the compression chamber 16 can vary depending on the position of the metering piston 3 in the sleeve 17. The volume of the compression chamber 16 is smallest when the metering piston 3 is at top dead center, and largest when the metering piston 3 is at bottom dead center.

[0069] The feeding device 22 is designed to advance viscous material present in the cylinder 9 from the supply port 6 to at least one metering device 19, the conveying of which is achieved by... Figure 1 As shown by the arrow in the image.

[0070] like Figure 1 As shown, in a preferred embodiment, the feeding device 22 is a single worm 8 rotatable about an axis UU', the worm 8 rotating concentrically within the cylinder 9, the worm 8 including one or more threads designed to shear viscous material present in the cylinder 9 and to advance the viscous material from the supply port 6 to the feed member 4.

[0071] In a further embodiment, other feeding devices can be used to advance the viscous material from the feed port 6 to the feed member 4, such as a syringe system or a gear pump.

[0072] The feed member 4 is designed to open or close the feed orifice 12 to allow or prevent viscous materials from passing through the feed orifice 12, respectively.

[0073] When the feeding component 4 is in the open position, the viscous material flows from the cylinder 9 to the compression chamber 16 through the feed port 12.

[0074] In a preferred embodiment, such as in Figure 1 and Figure 2 As can be seen, the feeding member 4 is a rotary feed plug 40, which has an axis UU' as the axis of rotation. The rotary feed plug 40 includes at least one alternating notch 20 and at least one solid region 23 around its periphery. The at least one notch 20 is generated by removing material in a predetermined angular sector, and when the at least one notch 20 mates with the feed port 12 corresponding to the compression chamber 16, the at least one notch 20 allows viscous material to travel into the compression chamber 16.

[0075] Preferably, such as from Figures 3 to 6 It is evident that the notch 20 is not formed over the entire height of the rotary feed plug 40.

[0076] Advantageously, the remainder of the periphery of the rotary feed plug 40 (including the solid area 23) mates with the cylinder 9 to seal the feed orifice 12 and prevent any sticky material from entering the corresponding compression chamber 16.

[0077] Therefore, the rotary feed plug 40 will alternately open or close the feed orifice 12 when rotating.

[0078] In a preferred embodiment, the body 1 includes a circular hole coaxial with the axis UU', the diameter of which allows it to be used as a rotational guide support for the rotary feed plug 40.

[0079] The conveying component 5 is designed to open or close the conveying channel 10 to allow or prevent viscous materials from passing through the conveying channel 10, respectively.

[0080] When the conveying component 5 is in the open position, the viscous material flows from the compression chamber 16 to the outlet channel 7 through the conveying channel 10.

[0081] In a preferred embodiment, such as in Figure 1 and Figures 3 to 8 As can be seen, the conveying component 5 is a rotary conveying plug 50. The rotary conveying plug 50 has an axis UU' as the axis of rotation. The rotary conveying plug 50 includes an axial conveying hole 11 and a conveying groove 21 extending perpendicular to the conveying hole 11. When the conveying groove 21 is engaged with the conveying channel 10, the conveying hole 11 and the conveying groove 21 form a channel through which viscous materials can travel to the outlet channel 7.

[0082] When the conveying trough 21 is no longer engaged with the conveying channel 10, the rotary conveying plug 50 engages with the head 2 to close the conveying channel 10 and prevent any sticky material from reaching the outlet channel 7.

[0083] Therefore, the rotary conveyor plug 50 will alternately open or close the conveyor channel 10 when it rotates.

[0084] In a preferred embodiment, the head 2 includes a circular hole coaxial with the axis UU', the diameter of which allows it to be used as a rotational guide support for the rotary delivery plug 50.

[0085] In a preferred embodiment, the rotary cam 13, the worm 8, the rotary feed plug 40, and the rotary conveyor plug 50 are all coaxial with the axis UU'. The rotary feed plug 40 is located at the end of the worm 8, and the rotary conveyor plug 50 is in contact with the rotary feed plug 40.

[0086] Advantageously, the worm gear 8, the rotary cam 13, the rotary feed plug 40, and the rotary delivery plug 50 constitute the same component, thereby enabling the different moving mechanical components of the positive displacement pump 100 to be synchronized.

[0087] As in Figure 3As can be seen, at least one metering device 19 is configured to operate in a first stage, known as the feeding stage, allowing viscous material to fill the compression chamber 16 of at least one metering device 19 by passing through the feed orifice 12.

[0088] During each feeding stage of the at least one metering device 19: - The feed port 4 of the at least one metering device 19 is open. - The conveying port 5 of the at least one metering device 19 is closed. - The metering piston 3 of the at least one metering device 19 performs a stroke between the top dead center and the bottom dead center.

[0089] exist Figure 4 Arrows have been added to clearly show the conveying of viscous material by positive displacement pump 100 during the feeding phase.

[0090] At the end of the feeding stage, such as Figure 5 As shown, the metering piston 3 reaches the lower dead center, and the feeding component 4 closes while the conveying component 5 remains closed.

[0091] like Figure 7 As shown, at least one metering device 19 is configured to operate in a second stage, referred to as the conveying stage, to advance viscous material from the compression chamber 16 of the at least one metering device 19 through the conveying channel 10 to the outlet channel 7.

[0092] During each delivery phase of at least one metering device 19: - The feed port 4 of the at least one metering device 19 is closed. - The conveying channel 5 of the at least one metering device 19 is open. - The metering piston 3 of the at least one metering device 19 performs a stroke between the bottom dead center and the top dead center.

[0093] as Figure 4 , already Figure 8 Arrows are added to clearly show the conveying of viscous material by positive displacement pump 100 during the conveying phase.

[0094] At the end of the transport phase, such as Figure 9 As shown, when the metering piston 3 reaches the top dead center, the feeding component 4 remains closed, and the conveying component 5 is closed at the same time.

[0095] According to the present invention, as in Figure 6As can be seen, at least one metering device 19 is configured to operate in an intermediate stage called a pre-compression stage, during which the metering piston 3 of the at least one metering device 19 pre-compresses the viscous material in the compression chamber 16 of the at least one metering device 19. The pre-compression stage occurs between the feeding stage and the conveying stage, and the pre-compression stage enables the viscous material present in the compression chamber 16 to be pre-compressed to a pressure corresponding to the pressure of the viscous material in the outlet channel 7.

[0096] like Figure 6 As shown, during each pre-compression stage of the at least one metering device 19: - The feed port 4 of the at least one metering device 19 is closed. - The conveying channel 5 of the at least one metering device 19 is closed. - The metering piston 3 of the at least one metering device 19 performs a stroke C between the bottom dead center and the midpoint, thereby enabling the pre-compression of the viscous material in the compression chamber 16 of the at least one metering device 19.

[0097] Because of the use of the feed component 4, the stroke of the metering piston 3 can be completely separated from the opening or closing phase of the feed orifice 12.

[0098] This separation allows for free selection of the stroke C performed by the metering piston 3 during the pre-compression stage, and independent closure is achieved by the rotation of the feed member 4.

[0099] When precise metering is required using the positive displacement pump 100 according to the invention, various feeding stages, pre-compression stages and conveying stages are performed sequentially in a predetermined number of times to obtain the required amount of viscous material.

[0100] Advantageously, the feed member 4 is configured to close the feed orifice 12 before the metering piston 3 begins the pre-compression phase.

[0101] In a preferred embodiment where the feed member 4 is a rotary feed plug 40, the feed orifice 12 is pre-closed by synchronizing and adjusting the rotary feed plug 40 as follows: the notch 20 is far enough from the feed orifice 12 when the metering piston 3 begins pre-compression, and the distance of the notch 20 makes it impossible to feed viscous material toward the notch 20, thereby improving the tightness of the closure of the feed member 4 and thus improving the metering quality of the positive displacement pump 100.

[0102] As in Figure 7 As can be seen, when the metering piston 3 has completed pre-compression, the conveying component 5 begins to open the conveying channel 10, thereby enabling the conveying stage to begin.

[0103] Opening the conveying channel 10 allows the viscous material present in the corresponding compression chamber 16 to come into contact with the viscous material present in the outlet channel 7.

[0104] Since the pre-compression stage enables the pressure of the viscous material in the compression chamber 16 to be equal to the pressure of the viscous material in the outlet channel 7, neither the pressure in the compression chamber 16 nor the pressure in the outlet channel 7 will change, thereby maintaining the extruded molding element with constant and high-quality geometric characteristics.

[0105] Furthermore, the mechanical components of the positive displacement pump 100 are not subjected to any impact or abrupt stress changes, thereby maintaining the reliability of the positive displacement pump 100 and improving its service life.

[0106] Advantageously, such as from Figures 3 to 8 It is evident that the metering piston 3 is configured such that its movement between the bottom dead center and the top dead center occurs in an area located at a certain distance from the feed orifice 12, thereby enabling the filling of the compression chamber 16 with viscous material once the metering piston 3 begins to move from the top dead center, i.e., from the beginning of the feeding stage.

[0107] The area located at a certain distance from the feed orifice 12 should be understood as meaning that the metering piston 3 will never close the feed orifice 12 during the process of moving back and forth between the bottom dead center and the top dead center.

[0108] This configuration is made possible by the use of the feed member 4, which allows the feed port 12 to be closed or opened during different operating phases of the positive displacement pump 100.

[0109] In some embodiments, the number of metering devices 19 is greater than or equal to 2, preferably equal to 4, such as Figure 2 and Figure 3 As shown, the metering device 19 is synchronized to ensure a regular outlet flow rate.

[0110] In some embodiments having multiple metering devices 19, each of the metering devices 19 operates in the three stages described above.

[0111] In some embodiments having multiple metering devices 19, at least two of the metering devices 19 can be synchronized to simultaneously perform the same stages of the feeding stage, conveying stage, and pre-compression stage.

[0112] In some embodiments with multiple metering devices 19, different metering devices 19 implement different stages to ensure continuous outlet flow.

[0113] For example, the positive displacement pump 100 may include a worm gear 8, a rotary feed plug 40, a rotary conveyor plug 50, and three metering devices 19, which are operated simultaneously by a rotating cam 18. At time t, the first metering device 19 may perform the feeding stage, the second metering device 19 may perform the pre-compression stage, and the third metering device 19 may perform the conveying stage.

[0114] In this embodiment, the rotary feed plug 40 is adjusted and synchronized such that at time t: - Open the feed port 12 corresponding to the first metering device 19. - Close the feed port 12 corresponding to the second and third metering devices 19.

[0115] Continuing in the same embodiment, the rotary feed plug 50 is adjusted and synchronized so that it again reaches the same time t: - Close the conveying channel 10 corresponding to the first and second metering devices 19. - Open the conveying channel 10 corresponding to the third metering device 19.

[0116] Normally, during the operation of the positive displacement pump 100, the feed component 4 and the conveying component 5 are adjusted and synchronized respectively so as to open or close different feed orifices 12 and different conveying channels 10 according to the different metering devices 19 of the positive displacement pump 100.

[0117] In an implementation scheme in which multiple metering devices 19 simultaneously perform one of the feeding, conveying, and pre-compression stages, the feeding component 4 and the conveying component 5 are adjusted and synchronized to open or close the feed orifices 12 and conveying channels 10 of different metering devices 19 according to the currently implemented stage.

[0118] The stroke C can be determined by testing a positive displacement pump 100 equipped with pressure sensors located in both the compression chamber 16 and the outlet channel 7. Specifically, these tests allow for a comparison of the pressure in the compression chamber 16 and the pressure in the outlet channel 7 at the time the delivery member 5 opens at the end of the pre-compression phase. If a pressure difference exists, the stroke C is thus adjusted.

[0119] Tests were conducted to compare the flow rates and outlet temperatures of a piston-type positive displacement pump (whose internal pressure was not balanced through a pre-compression stage) and a positive displacement pump 100 according to the invention.

[0120] For these tests, the same uncured rubber was extruded using a piston pump without a pre-compression stage and a pump according to the invention. The uncured rubber extruded in the comparative test had a Mooney viscosity ML 1+4 of 70 MU (Mountie units) at 100°C. The Mooney index (also known as viscosity or plasticity index) is well-known for characterizing solid substances. An oscillating consistency meter is used as described in standard ASTM D1646 (1999). This plasticity measurement is performed based on the principle that the sample to be analyzed in its untreated state (i.e., before curing) is molded (shaped) in a cylindrical chamber heated to a given temperature (e.g., 35°C or 100°C). After one minute of preheating, a rotor rotates within the test specimen at 2 rpm, and the working torque used to maintain this motion is measured for 4 minutes of rotation. The Mooney viscosity (ML 1+4) is expressed in "Mountie units" (1 MU = 0.83 Nm) and corresponds to the value obtained at the end of 4 minutes.

[0121] Table 1 below summarizes the results obtained with a base of 100.

[0122] Table 1 As shown in Table 1, for the same unvulcanized rubber material, the positive displacement pump 100 according to the present invention enables the temperature of the unvulcanized rubber at the outlet to be reduced.

[0123] At the same time, the outflow rate can be increased significantly without any risk of material quality degradation or the risk of breakage or premature wear of the positive displacement pump 100.

Claims

1. A positive displacement pump (100) for viscous materials, comprising: - The main body (1) includes a cylindrical body (9) and a supply port (6), the cylindrical body (9) having an axis UU' as the axis of rotation, and the supply port (6) being capable of receiving viscous materials. - Head (2), which includes an outlet channel (7) designed for discharging viscous material from the positive displacement pump (100). - At least one metering device (19) comprising a feed orifice (12), a compression chamber (16), a metering piston (3) movable between a lower dead center and a top dead center, a sleeve (17), and a conveying channel (10), the at least one metering device (19) being configured to operate in a first stage, referred to as the feeding stage, to allow viscous material to fill the compression chamber (16) of the at least one metering device (19) through the feed orifice (12), and in a second stage, referred to as the conveying stage, to advance the viscous material from the compression chamber (16) of the at least one metering device (19) through the conveying channel (10) to the outlet channel (7). - Actuator (13) for moving the metering piston (3) of the at least one metering device (19), - A feeding device (22) designed to advance viscous material present in the cylinder (9) from the supply port (6) to the at least one metering device (19). - Feeding component (4), which is designed to open or close the feed orifice (12) to allow or prevent viscous material from passing through the feed orifice (12), respectively. - A conveying component (5) designed to open or close the conveying channel (10) to allow or prevent viscous material from passing through the conveying channel (10), respectively. The positive displacement pump is characterized in that the at least one metering device (19) is configured to operate in an intermediate stage called a pre-compression stage, during which the metering piston (3) of the at least one metering device (19) pre-compresses the viscous material in the compression chamber (16) of the at least one metering device (19), the pre-compression stage occurring between the feeding stage and the conveying stage, the pre-compression stage enabling the viscous material present in the compression chamber (16) to be pre-compressed to a pressure corresponding to the pressure of the viscous material in the outlet channel (7).

2. The positive displacement pump (100) for viscous materials according to claim 1, wherein, The feeding device (22) is a single worm (8) capable of rotating about axis UU', the worm (8) rotating concentrically in the cylinder (9), the worm (8) including one or more threads, the one or more threads being designed to shear viscous material present in the cylinder (9) and advance the viscous material from the supply port (6) to the feed member (4).

3. The positive displacement pump (100) for viscous materials according to claim 1 or 2, wherein, The feed member (4) is configured to close the feed orifice (12) before the metering piston (3) begins the pre-compression phase.

4. The positive displacement pump (100) for viscous materials according to any one of claims 1 to 3, wherein, The feeding member (4) is a rotary feed plug (40) having an axis UU' as the axis of rotation. The rotary feed plug (40) includes at least one alternating notch (20) and at least one solid region (23) around its periphery. The at least one notch (20) is created by removing material in a predetermined angular sector, and when the at least one notch (20) mates with the feed port (12) corresponding to the compression chamber (16), the at least one notch (20) allows viscous material to travel into the compression chamber (16).

5. The positive displacement pump (100) for viscous materials according to any one of claims 1 to 4, wherein, The conveying component (5) is a rotary conveying plug (50), which has an axis UU' as the axis of rotation. The rotary conveying plug (50) includes an axial conveying hole (11) and a conveying groove (21) extending perpendicular to the conveying hole (11). When the conveying groove (21) is engaged with the conveying channel (10), the conveying hole (11) and the conveying groove (21) constitute a channel that allows viscous materials to travel to the outlet channel (7).

6. The positive displacement pump (100) for viscous materials according to any one of claims 1 to 5, wherein, The actuator (13) is a rotary cam (18) including at least one thrust cam path (18a) that cooperates with a thrust roller (14) to enable each of the metering pistons (3) to move along the pump and in a direction parallel to the axis UU'.

7. The positive displacement pump (100) for viscous materials according to claim 6, wherein, The rotary cam (13), the worm (8), the rotary feed plug (40) and the rotary conveyor plug (50) are all coaxial with the axis UU'. The rotary feed plug (40) is located at the end of the worm (8), and the rotary conveyor plug (50) is in contact with the rotary feed plug (40).

8. The positive displacement pump (100) for viscous materials according to claim 7, wherein, The worm gear (8), the rotary cam (13), the rotary feed plug (40), and the rotary delivery plug (50) constitute the same component, thereby enabling the different moving mechanical components of the positive displacement pump (100) to move synchronously.

9. The positive displacement pump (100) for viscous materials 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 occurs in an area located at a certain distance from the feed orifice (12), so that once the metering piston (3) begins to move from the top dead center, it can fill the compression chamber (16) with viscous material.

10. The positive displacement pump (100) for viscous materials according to any one of claims 1 to 9, wherein, The number of metering devices (19) is greater than or equal to 2, preferably equal to 4, and the metering devices (19) are synchronized to ensure a regular outlet flow.

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