Mixing system and control method

Abstract

The present invention relates to a mixing system for producing a viscous mixture and a method for controlling a mixing system. The mixing system (100; 200) comprises a first pump unit (110) for conveying at least the mixture, a second pump unit (120) for conveying and grinding at least one component of the mixture, and a mixing unit (130; 230) for mixing the components of the mixture, the mixing unit (130; 230) including a mixing container (132; 232). The first pump unit (110), the second pump unit (120) and the mixing unit (130, 230) are connected by a tubing (140) for forming a mixing circuit (MC) in which a fluid circulates in a circulation direction (CD). The system (100; 200) further comprises a hopper unit (150, 150') coupled to the mixing circuit (MC) for supplying at least one component to be mixed with the carrier fluid, and a control unit (CU) for controlling the operation of at least one of the units of the mixing system (100; 200). The method comprises the steps of providing a carrier fluid to the mixing system (100; 200),circulating the carrier fluid in the mixing circuit (MC) at least by the first pump unit (110) and / or the second pump unit (120), adding at least a first component stored in the hopper unit (150; 150'), to the fluid circulating in the mixing circuit (MC) and mixing the circulating carrier fluid and the at least one added component.

Description

[0001] The present invention relates to a mixing system for producing viscous mixtures and a method for controlling a mixing system. The mixing system comprises a first pump unit for conveying at least the mixture, a second pump unit for conveying and grinding at least one component of the mixture, and a mixing unit for mixing the components of the mixture.

[0002] For producing mixtures which include several components, and in particular, viscous mixtures which include a fluid and further components, like powder, the fluid or carrier fluid is usually provided in a container, and said further components are added to said fluid in said container. A stirrer, or the like, mixes the fluid and the added components until the mixture has a predefined consistency. However, in such known mixers, dependent on the kind of the carrier fluid and the added components, lumping can occur, or portions of the added components may adhere on the wall of the mixing container or on elements of the stirrer. Accordingly, the mixture may lack the required quality, e.g. with regard to its consistency or the mixing ratio.

[0003] Thus, it is an object of the present invention, to overcome the above mentioned drawbacks, and to provide a system and a method for producing viscous mixtures, which enable efficient production of viscous mixtures of high quality.

[0004] According to the present invention, there is provided a mixing system for producing a viscous mixture, the system comprises a first pump unit for conveying at least the mixture and grinding at least one component of the mixture, a second pump unit for conveying the mixture, and a mixing unit for mixing the components of the mixture, the mixing unit including a mixing container. The first pump unit, the second pump unit and the mixing unit are connected by a tubing for forming a mixing circuit in which a fluid circulates in a circulation direction. The system further comprises a hopper unit coupled to the mixing circuit for supplying at least one component to be mixed with the carrier fluid, and a control unit for controlling the operation of at least one of the units of the mixing system.

[0005] In this system, the carrier fluid circulates in the mixing circuit, and the at least one component is added to the circulating carrier fluid, whereby an efficient mixing process is established, and lumping may be omitted. The grinding of the added component by the second pump unit further increases the quality of the mixture.

[0006] In an advantage configuration of the mixing system, the first pump unit is arranged downstream the second pump unit, the second pump unit is arranged downstream the mixing unit. Thereby, the second pump unit securely conveys the carrier fluid and the mixture, respectively, through the mixing circuit and into the mixing container, such that a continuous mixing process is guaranteed.

[0007] In order to ensure a safe and reliable material flow in the mixing circuit, a respective kind of Pump may be used. In a preferred embodiment, the second pump unit includes a spindle pump. However, other kinds of pumps may also be used in the first pump unit, like a diaphragm pump or a rotary lobe pump.

[0008] For further increasing the quality of the mixture, and, particularly, for preventing lumping, the first pump unit include a shear pump.

[0009] In a further preferred embodiment of the inventive mixing system, the hopper unit is arranged downstream the second pump unit. The component is thereby added to the circulating carrier fluid before entering the first pump unit in which the carrier fluid and the component are not only conveyed, but the component is also grinded for the first time before reaching the mixing container, and lumping an adhering of the component on elements of the mixing unit may be omitted.

[0010] For supplying the component to be added to the carrier fluid in a defined manner, it is of advantage that the hopper unit is provided with a valve for controlling the supply of the component to the carrier fluid circulating in the mixing circuit.

[0011] The control valve for supplying the component to the carrier fluid may be a shut-off valve that has just an opened position and a closed position. However, dependent on the kind of component and / or the carrier fluid, it may be of advantage that the opening of the control valve may be controlled such that it may be gradually opened and closed, for delivering the component in a defined amount and / or in a defined time period.

[0012] In an advantage embodiment of the inventive mixing system, a vacuum may be generated in the mixing circuit. Such a vacuum supports the absorption of the component to be added into the carrier fluid and the elimination of gas or air bubbles in the mixture.

[0013] Alternatively or additionally to a vacuum in the mixing circuit, an overpressure may be generated in the hopper unit, which improves the feeding of the component to the mixing circuit.

[0014] In a preferred design, a homogenizer unit is coupled to the mixing container of the mixing unit, to enhance the quality of the mixture.

[0015] A homogenizer unit may be established in various ways. The homogenizer unit may include an outer stirrer extending into the mixing container and / or an inner stirrer, which, in one embodiment, may comprise arms arranged inside the mixing container.

[0016] Generally, a control unit is provided for controlling the mixing system. In an advantage configuration, the control unit is adapted to control the units of the mixing system, preferably, independent from each other. This enables to adapt the mixing process to various parameters, like the kind of the mixture to be produced, or the specifications of the units of the mixing system.

[0017] Further according to the present invention, there is provided a method for controlling a mixing system. The system comprises a first pump unit for conveying at least the mixture and grinding at least one component of the mixture, a second pump unit for conveying the mixture, and a mixing unit for mixing the components of the mixture, with the mixing unit including a mixing container. The first pump unit, the second pump unit and the mixing unit are connected by a tubing for forming a mixing circuit in which a fluid circulates in a circulation direction. The system further comprises a hopper unit coupled to the mixing circuit for supplying a component to be mixed with a carrier fluid, and a control unit for controlling the operation of at least one of the units of the mixing system. The method comprises the steps of providing a carrier fluid to the mixing system, circulating the carrier fluid in the mixing circuit at least by the first pump unit and / or the second pump unit, adding at least a first component stored in the hopper unit, to the fluid circulating in the mixing circuit, and mixing the circulating carrier fluid and the at least one added component.

[0018] The method may further include the step of adding at least one further component to the carrier fluid in the mixing circuit.

[0019] In the inventive method, the at least one further component may be added to the circulating carrier fluid together with the at least one first component or subsequently thereto.

[0020] Further according to the method of the present invention, the at least one further component is supplied via the hopper unit, or is supplied directly into the container of the mixing device, or via a separate supply device.

[0021] The method further includes the step of controlling the opening and closing of the valve of the hopper unit.

[0022] The inventive method may further include the step of controlling the mixing process by controlling the rotational speed of the first and / or the second pump unit.

[0023] The method may further include the step of homogenizing the viscous mixture, in the mixing container of the mixing unit, by a homogenizer coupled to the mixing container of the mixing unit.

[0024] Advantageously, the method includes the step of controlling the speed and / or the operation time of the homogenizer.

[0025] According to the inventive method, the units of the mixing system may be controlled independent from each other. Thereby, various parameters may be taken into account, like the time point of the mixing process, the kind of fluid and the number, the kind or the amount of components to be mixed therewith.

[0026] According to the invention, the control unit is provided with at least one control program for at least one mixture to be produced. It has to be noted, that the control unit may also include more than one program, such that a program corresponding to the mixture to be produced, may be called by an operator.

[0027] The control unit may include a storage device for storing one or more control programs. Moreover, control programs for manufacturing different mixtures may be loaded into the storage device of the control unit. It may also be provided that said loaded programs may be varied, e.g. in accordance with to the mixture to be produced, components thereof or specific production conditions.

[0028] The inventive method thereby provides all advantages explained in conjunction with the inventive mixing system for producing a viscous mixture.

[0029] Further advantages and preferred embodiments of the present invention will be described in the following together with the drawings listed below. The expressions "left", "right', "below" and "above" used in the following description, are referred to the drawings in an alignment such that the reference numbers and the notation of the figures used can be read in normal orientation. Fig. 1:is a perspective view to a first embodiment of a mixing system for producing a viscous mixture according to the present invention; Fig. 2:is a perspective view to the mixing system of Fig. 1, with a mixing container in an opened configuration; Fig. 3:is a perspective view to a second embodiment of a mixing system for producing a viscous mixture according to the present invention; Fig. 4:is a perspective view to a third embodiment of a mixing system for producing a viscous mixture according to the present invention; Fig. 5:is a perspective view to a hopper unit for the mixing system according to the present invention; and Fig. 6:is a cross-sectional view to the T-fitting for connecting the hopper unit to the mixing system;

[0030] Fig. 1 shows a first embodiment of a mixing system 100 for producing a viscous mixture. Mixing system 100 includes a first pump unit 110 for conveying at least the mixture and grinding at least one component of the mixture, a second pump unit 120 for conveying the mixture, and a mixing unit 130 for mixing the components of the mixture. First pump unit 110 has a pump 112 with an inlet 114 and an outlet 116, and a drive device in the form of an electric motor 118. Second pump unit 120 has a pump 122 with an inlet 124 and an outlet 126, and a drive device in the form of an electric motor 128. Mixing unit 130 includes a mixing container 132 with a lid 134, which closes the upper end of mixing container 132. Mixing container 132 is supported by a support frame 133. Lid 134 is provided with an inlet 136 for the carrier fluid or the mixture, respectively, and a fluid inlet 139 for delivering a defined amount of carrier fluid to mixing system 100. In the bottom region of mixing container 132, an outlet 138 is arranged. Mixing container 132 has a substantially cylindrical shape. In the embodiment shown in Fig. 1, mixing unit 130 is provided with a control unit CU, which also controls the other units of mixing system 100.

[0031] First pump unit 110, second pump unit 120 and mixing unit 130 are coupled to each other by a tubing 140, forming a mixing circuit MC, in which a carrier fluid, and the mixture respectively, circulates in a circulation direction CD. Tubing 140 has a first tubing portion 142 that couples outlet 116 of pump 112 of first pump unit 110 to inlet 136 of mixing container 132 of mixing unit 130, a second tubing portion 144 that couples outlet 138 of mixing container 132 of mixing unit 130 to inlet 124 of pump 122 of second pump unit 120, and a third tubing portion 146 that couples outlet 126 of pump 122 of second pump unit 120 to inlet 114 of pump 112 of first pump unit 110. Tubing 140 further includes an outlet branch 148 arranged between second tubing portion 144 and to inlet 124 of pump 122 of second pump unit 120. Outlet branch 148 is provided with a shut-off valve for dispensing the mixture from mixing system 100, for further processing. In Figs. 1 and 2, for clarity reasons, only the section of first tubing portion 142 is shown, which extends from outlet 116 of pump 112 vertically upwardly. It has to be understood, that first tubing portion 142 must reach inlet 132 of mixing container 132, to establish mixing circuit MC.

[0032] Mixing system 100 further comprises a hopper unit 150 for supplying at least one component to mixing circuit MC, to be mixed with the carrier fluid. Hopper unit 150, which includes a funnel 152 and a lid 154 for closing the upper end of funnel 152, is coupled to mixing circuit MC by a T-fitting 160 between third tubing portion 146 and inlet 114 of pump 122 of first pump unit 110, such that funnel 152 is arranged vertically above T-fitting 160. Between hopper unit 150 and T-Fitting 160, a control valve 156 is arranged for controlling the supply of the component to mixing circuit MC. Hopper unit 150 and T-fitting 160 will be explained in greater detail in conjunction with Figs. 5 and 6 below.

[0033] As further can be seen in Fig. 1, a hopper unit 150' is arranged close to lid 134 of mixing container 132. Hopper unit 150' is identical to hopper unit 150, but arranged in an alternative position, and replaces hopper unit 150. Alternative hopper unit 150' is coupled to inlet 136 of mixing container 132 via a T-fitting identical to T-fitting 160, with a control valve 156 arranged there between.

[0034] Mixing system 100 further comprises a homogenizer unit 170, which is coupled to mixing container 132 of mixer unit 130. Homogenizer unit 170, in the embodiment shown in Figs. 1 and 2, includes an outer stirrer 172 coupled to lid 134 of mixer unit 130. Outer stirrer 172 includes a drive motor 173 arranged at the outside of lid 134 and, as can be seen in Fig. 2, a stirrer axle 174 extending through lid 134 into mixing container 132. At the free end of stirrer axle 174, a propeller 175 is arranged. Outer stirrer 172 is arranged eccentrically at lid 134 of mixing container 132, such that stirrer axle 174 is positioned in an angle to the central axis of mixing container 132, when lid 134 is closed.

[0035] As further can be seen in Fig. 2, an inner stirrer 176 is provided, with stirrer arms 177 and scraper elements 178. Stirrer arms 177 are wing-shaped and driven by a drive motor (not shown), which is arranged below the bottom of mixing container 132. The drive axle of the drive motor is coaxially aligned with the central axis of mixing container 132, such that stirrer arms 177 rotate about said central axis inside mixing container 132. Scraper elements 178 are also driven by the drive motor of stirrer arms 177. Scraper elements 178 extend longitudinally and at least approximately parallel to the central axis of mixing container 132. Scraper elements 178 are arranged to be in contact with the inner surface of the cylindrical portion of mixing container 132, such that scraper elements 178 slide along said inner surface during their rotational movement.

[0036] During the mixing process, a vacuum is generated in the mixing circuit MC. In order to establish and to maintain said vacuum, a vacuum device 135, such as a vacuum pump, may be coupled to mixing system 100. Vacuum device 135 includes a vacuum pump that is arranged in the housing of control unit CU. In Figs. 1 and 2, the water separator 135a of the vacuum pump is visible, For coupling the vacuum pump of vacuum device 135 to mixing system 100, a connecting vacuum tube 135b is provided, which is connected to the interior of mixing container 132 of mixing unit 130 at the rear side of mixing container 132 in its upper region. A sensor unit (not shown) is connected to mixing circuit MC, for detecting the pressure, and in particular, presence and the amount of the vacuum generated in mixing circuit MC. Said sensor unit is coupled to control unit CU of mixing system 100.

[0037] In order to enhance the supply of the at least one component by hopper unit 150 or alternative hopper unit 150' to the carrier fluid circulating in mixing circuit MC, in hopper unit 150, or in alternative hopper unit 150' respectively, an overpressure is generated, by an overpressure device, like a pressure pump. At lid 154 of hopper unit 150 an overpressure assembly 155 is provided. Overpressure assembly 155 may be designed for coupling a pressure pump thereto, and may include further elements, like a control or shutoff valve or a pressure regulator and a pressure sensor which is also coupled to control unit CU of mixing system 100. However, dependent on the amount of pressure to be generated and thus, the size of the required pump, overpressure assembly 155 may also include a respective pressure pump. Alternatively, pressurized air may be supplied to hopper unit 150 by a pressurized air system already present in the installation location of mixing system 100.

[0038] It has to be noted that also alternative hopper unit 150'is provided with an over pressure assembly 155' coupled to lid 154', which is of identical design like overpressure assembly 155.

[0039] The second embodiment of a mixing system 200 according to Fig. 3 is of similar design as mixing system 100 of Figs. 1 and 2, and in which identical elements are provided with identical reference signs. Mixing system 200 includes a first pump unit 110, a second pump unit 120, a tubing 140, a hopper unit 150 and a homogenizer 170 with an outer stirrer 172 and an inner stirrer 176, from which only one scraper element 178 is visible.

[0040] Mixing system 200 differs from mixing system 100 by mixing unit 230. In Fig. 3, only mixing container 232 and lid 234 of mixing unit 230 are shown. The remaining components of mixing unit 230 are identical to that of mixing unit 130.

[0041] As can be seen in Fig. 3, mixing container 232 has an inlet 236 that is arranged in the upper region of the cylindrical wall of mixing container 232. Accordingly, first tubing portion 142 guides the carrier fluid or the mixture through inlet 236 in said cylindrical wall into mixing container 232.

[0042] Mixing system 200, like mixing system 100 according to Figs 1 and 2, may be provided with hopper unit 150, which is arranged upstream first pump unit 110, and coupled to mixing circuit MC by a T-fitting 160 between third tubing portion 146 and inlet 114 of pump 122 of first pump unit 110.

[0043] However, in the case that an alternative hopper unit 150' is provided in mixing system 200, alternative hopper unit 150' is directly arranged at lid 234, such that the component supplied by said alternative hopper unit 150' is directly suspended into mixing container 232, e.g. by a flange, which enables a fluid connection to mixing container 232.

[0044] Fig. 4 shows a third embodiment of a mixing unit 300, which in general, is of identical design as mixing systems 110 and 200. Accordingly, identical elements are provided with identical reference signs.

[0045] Mixing system 300 includes a first pump unit 110, a second pump unit 120, a hopper unit 150 and a homogenizer 170 with an outer stirrer 172 and an inner stirrer (not visible in Fig. 4),

[0046] Mixing system 300 differs from mixing systems 100 and 200 by mixing unit 330, which includes a cylindrical mixing container 332, which is vertically arranged, with a first inlet 336, a second inlet 337, both arranged in the upper region of cylindrical mixing container 232, an outlet 338 in the bottom of mixing container 232, and a lid 334 that closes the upper end of mixing container 232. Mixing container 332 is further provided with a fluid inlet 339 arranged in the upper region of mixing container 332, for delivering carrier fluid to mixing container 332, and a vacuum port 135c, to which the vacuum pump of vacuum device 135 is connected via vacuum tube 135b (cf. Fig. 1).

[0047] As further can be seen in Fig. 4, Mixing system 300 includes a housing, in which control unit CU and vacuum device 135 are accommodated.

[0048] Mixing system 300 further comprises a tubing 340 with a first tubing portion 342 that couples outlet 116 of pump 112 of first pump unit 110 to first inlet 336 of mixing container 332, a second tubing portion 344 that couples outlet 338 of mixing container 332 to inlet 124 of pump 122 of second pump unit 120, and a third tubing portion 346 that couples outlet 126 of pump 122 of second pump unit 120 to inlet 114 of pump 112 of first pump unit 110. Tubing 340 further includes an outlet branch 348 arranged immediately downstream to outlet 126 of pump 122 of second pump unit 120. Outlet branch 348 is provided with a shut-off valve for dispensing the mixture from mixing system 300, for further processing.

[0049] Tubing 340 is provided with a bypass arrangement 349 formed by a T-fitting 349a arranged in third tubing portion 346, the free or middle branch of which is coupled via a tubing portion 349b to second inlet 337 of mixing container 332, with a shutoff valve 349c arranged between T-fitting 349a and tubing portion 349b. A further shut-off valve 349d is arranged immediately downstream T-fitting 349a, to shut-off third tubing portion 346, in order to activate bypass arrangement 349.

[0050] Tubing 340, first pump unit 110 and second pump unit 120 form mixing circuit MC of mixing unit 300.

[0051] Moreover, immediately upstream inlet 114 of pump 112 of first pump unit 110, a T-fitting 160 is arranged, via which hopper unit 150 is coupled to mixing circuit MC, for delivering a component to be mixed with the carrier fluid to mixing circuit MC. Like in the first and second embodiments of mixing system 100 and 200, also in mixing system 300, a control valve 156 is arranged between T-fitting 160 and hopper unit 150, for controlling the supply of the component to mixing circuit MC. Alternative or additionally, a further hopper unit 150' may be arranged in first tubing portion 342 of tubing 340, downstream first pump unit 110, coupled to mixing circuit MC by a T-fitting 160, with a control valve 156 arranged between T-fitting 160 and hopper unit 150'.

[0052] Mixing system 300 is further provided with a first pressure sensor PS1 for sensing the pressure at inlet 124 of pump 122 of second pump unit 120, and a second pressure sensor PS2 for sensing the pressure at outlet 126 of pump 122. First pressure sensor PS1 is arranged in second tubing portion 344 that couples outlet 338 of mixing container 332 to inlet 124 of pump 122 Second pressure sensor PS2 is arranged in the t-fitting that forms outlet branch 348, and that couples outlet 126 of pump 122 of first pump unit 120 to T-fitting 349a of bypass arrangement 349. In addition to first and second pressure sensors PS1, PS2, a third pressure sensor PS3 is provided at outlet 116 of pump 112 of first pump unit 110, for sensing the pressure in mixing circuit MC at outlet 116. Third pressure sensor PS3 may detect an overpressure in mixing circuit MC. Moreover, third pressure sensor PS3 may indicate pump 112 of first pump unit 110 being clogged or running dry or a blockage in first tubing portion 342 between outlet 116 of pump 112 and first inlet 336 of mixing container 332, when measuring a pressure value that is below a predetermined pressure value or below the pressure values detected by first and second pressure sensors PS1, PS2.

[0053] Hopper unit 150 and hopper unit 150' are of identical design. Accordingly, in conjunction with Fig. 5, only hopper unit 150 will be explained in detail.

[0054] Hopper unit 150 comprises funnel 152 and lid 154 with overpressure assembly 155 arranged on lid 154. Moreover, at lid 154, a filler neck FN is arranged for filling the component to be mixed to the carrier fluid into funnel 152, and an inspection window IW for a visible inspection of funnel 152. At the bottom of funnel 152, a screw connector SC is arranged, for coupling control valve 156 to funnel 152 and further to mixing circuit MC. Hopper unit 150, when arranged upstream first pump unit 110, is provided with mounting posts MP extending vertically downwards from funnel 152, for mounting hopper unit 150 to the mounting plane or mounting level of mixing system 100.

[0055] In the embodiment of mixing system 300 shown in Fig. 4, hopper unit 150, 150', a level sensor LS is arranged at the lower end of the funnel of hopper unit 150, 150', for detecting the filling level of hopper unit 150, 150'.

[0056] Even if not shown, also lid 154 of hopper unit 150 of mixing system 300 includes overpressure assembly 155, and may further include a filler neck FN and an inspection window IW. Furthermore, funnel 152 of hopper unit 150 may have a conical shape as shown in Fig. 4 or a pyramid shape as shown in Fig. 5.

[0057] Furthermore, overpressure assembly 155 may be provided with a compressed air meter (not shown), that is arranged in the compressed air tube which connects hopper unit 150, 150' to the compressed air source. Said compressed air meter determines or counts the amount of compressed air delivered to hopper unit 150, 150', and may be used for detecting the air consumption, and to control the process of delivering the component to be mixed in mixing unit 300. An increasing air consumption indicates that the component is sucked into mixing circuit MC. In the case the air consumption is zero, one hand, shut-off valve 156 may be closed, and on the other hand, the nozzle for introducing the component into mixing circuit MC may be clogged. Dependent on the time point of the process, a respective signal may be sent to control unit CU and / or to an operator, indicating a possible failure.

[0058] Hopper unit 150 is coupled to mixing circuit by T-fitting 160 shown in detail in Fig. 5, which is a cross sectional view to T-fitting 160 in a plain extending centrally through the branches of T-fitting 160.

[0059] As shown in Fig. 6, T-fitting 160 has a first branch 161, a second branch 162 and a third branch 163. First branch 161, which is the inlet branch for the fluid, the carrier fluid or the mixture, circulating in mixing circuit MC in circulating direction CD, and second branch 162, which is the outlet branch for the circulating fluid, are arranged coaxially to each other. Third branch 163, or the supply branch, is arranged between the first branch or inlet branch 161 and the second branch or outlet branch 162, and extends vertically to circulation direction CD.

[0060] The third branch or supply branch 163 is provided with a supply tube 164, which extends into T-fitting 160. Supply tube 164 has a first, straight portion 164a arranged coaxially in supply branch 163, and a second, straight portion 164b arranged in T-fitting 160 and coaxially to inlet branch 161 and outlet branch 162. A third, curved portion 164c connects first and second portions 164a und 164b to each other. Supply tube 164 is connected with the free end of supply branch 163, such that the component to be mixed with the carrier fluid is supplied from funnel 152 of hopper unit 150 via supply tube 164 to mixing circuit MC. Supply tube 160 acts like a ventury nozzle in T-fitting 160. That means, by the fluid passing supply tube 164, and in particular second portion 164b of supply tube 164, a ventury effect is generated, such that the component is sucked out of supply tube 164 by the fluid streaming along second portion 164b of supply tube 164.

[0061] For producing a viscous mixture, like a viscous gel, in mixing system 100, a carrier fluid is filled into mixing circuit MC. The carrier fluid may be water or any other desired fluid, according to the mixture to be produced. A respective amount of said carrier fluid is directly filled into mixing container 132 of mixing unit 130. The component to be mixed with the carrier fluid, like a gel-forming powder, is filled into funnel 132 of hopper unit 130. A vacuum is generated in mixing circuit MC by activating vacuum device 135 with a vacuum pump coupled via vacuum tube 135b to mixing container 132 of mixing unit 130. The position of connecting branch 135 above the fluid level in mixing container 132 ensures that during the generation of a vacuum no fluid is sucked out of mixing circuit MC by the vacuum device. Moreover, an overpressure is generated in funnel 152 by the overpressure device coupled to lid 134 of hopper unit 130. The amount of the vacuum and the overpressure generated in mixing circuit MC and hopper unit 150 is detected by respective sensor units and the result is transmitted to control unit CU of mixing system 100, via which the vacuum device and the overpressure device are controlled, such that control unit CU may activate or stop the vacuum device and the overpressure device until a desired amount of vacuum and pressure is reached.

[0062] To start the mixing process, after a predefined amount of carrier fluid is supplied to mixing container 132, first and second pump units 110, 120 are activated, such that the carrier fluid circulates in mixing circuit MC in circulation direction CD. The circulation speed of the carrier fluid may be adjusted by controlling the speed of pumps 112 and / or 122 of first and second pump units 110, 120. Thereafter, controlled by control unit CU of mixing system 100, control valve 156 of hopper unit 150 is opened. Thereby, the component stored in funnel 152, is supplied to mixing circuit MC. Control unit CU may open control valve 156 in a manner that the component is supplied in a desired time, at once or in portions of desired amount. The carrier fluid passing supply tube 164 in T-fitting 160, generates a ventury effect, such that the component is sucked into mixing circuit MC.

[0063] After the component in hopper unit 150 is completely or partially supplied to mixing circuit MC, control valve 156 is closed by control unit CU, and first and second pump units 110, 120 circulate the mixture in mixing circuit MC for a desired time, e.g. according to a program stored in control unit CU of mixing system 100. Pump 122 of second pump unit 120 is preferably a feed pump for ensuring the desired circulation speed or volume flow of the carrier fluid or the mixture in mixing circuit MC is established or maintained. Pump 122 may be a spiral pump, which is suited for feeding viscous fluids, like gel. Pump 112 of first pump unit 110 is preferably a shear pump for grinding or shredding possible clumps of the component, such that lumping is prevented and the mixture has a uniform consistency and the required viscosity, since the complete component is mixed into the carrier fluid.

[0064] At the same time of the operation of first and second pump units 110, 120, or after a desired time period, homogenizing unit 170 is activated. According to the program for producing the mixture, which is stored in control unit CU, outer stirrer 172 and inner stirrer 176 are activated at the same time or subsequently. Inner stirrer 176, and particularly scraper elements 178 of inner stirrer 176, prevent the component from adhering at the inner surface of mixing container 132 of mixing unit 130, whereby lumping is prevented and the mixture has a uniform consistency and the required viscosity. Outer stirrer 172 with propeller 175, enhances the mixing of the component with the carrier fluid during the mixing process.

[0065] After the mixing of the component with the carrier fluid is completed, it is possible to mix a further component to the mixture. The further component may be filled into funnel 152 of hopper unit 150, which is empty, since the first component has already been supplied to mixing circuit MC. An overpressure is generated in hopper unit 150, and the further component may be supplied to the mixture in mixing circuit MC by opening control valve 156 of hopper unit 150 controlled by control unit CU of mixing system 100.

[0066] In a homogenizing step, which may be executed after the one or more components have been mixed with the carrier fluid, outer and inner stirrer 172, 176 are activated or stopped at the same time or subsequently, according to the selected program for producing the specific mixture. The homogenising step enhances the consistency of the mixture and possible gas or air bubbles in the mixture are removed. During the homogenizing step, first and second pump units 110, 120 may be deactivated.

[0067] During the production process, it is possible to vary the speed of the components, like the rotational speed of pumps 112, 122 of first and second pump units 110, 120, and / or of outer and inner stirrer 172, 176 of homogenizing unit 170.

[0068] Generally, one or more specific programs for producing specific mixtures may be loaded into control unit CU of mixing system 100. The specific program corresponding to the mixture to be produced, may be selected and executed automatically.

[0069] However, it is possible to an operator selects a program stored in control unit CU, and varies parameters of said program, e.g. in adaption to specific conditions, varied requirements to the mixture to be produced, specific characteristics of the components or environmental conditions.

[0070] It further possible to an operator to set the operating parameters of the units of mixing system 100 manually, independent from each other and without using a preselected program.

[0071] The process for producing a mixture in mixing system 200 is similar to the process explained in conjunction with mixing system 100. A carrier fluid is filled into mixing container 132 of mixing unit 130, and circulates in mixing circuit MC fed by first and second pump units 110, 120. In contrast to mixing system 100, where the circulating fluid enters mixing container 132 via lid 134, in mixing system 200, the circulating fluid is fed into mixing container 232 via the cylindric wall of mixing container 232, in its upper region.

[0072] Furthermore, in mixing system 200, when hopper unit 150' is arranged at lid 234 of mixing unit 230, the component to be mixed into the carrier fluid directly falls into the carrier fluid in mixing container 232.

[0073] Also in the production process executed in mixing system 200, the production process and the units of mixing system 200 may be controlled as described in conjunction with mixing system 100.

[0074] The process for producing a mixture in mixing system 300 is similar to the process explained in conjunction with mixing system 100. After a predefined amount of carrier fluid is supplied to mixing container 332, first and second pump units 110, 120 are activated, such that the carrier fluid circulates in mixing circuit MC in circulation direction CD. Thereafter, control valve 156 of hopper unit 150 is opened, for supplying the component stored in funnel 152 to mixing circuit MC. After the component in hopper unit 150 is completely or partially supplied to mixing circuit MC, control valve 156 is closed by control unit CU, and first and second pump units 110, 120 circulate the mixture in mixing circuit MC for a desired time, e.g. according to a program stored in control unit CU of mixing system 300.

[0075] In this situation, bypass arrangement 349 is deactivated. That means, shut-off valve 349c is closed and shut-off valve 349d is opened, such that the carrier fluid or the mixture, respectively, fed by first and second pump units 110, 120, circulates through first, second and third tubing portions 342, 344, 346 and mixing container 332. Thereby, the carrier fluid and the component are mixed together and the component is grinded by pump 112 of first pump unit 110.

[0076] After a predetermined time, e.g. dependent on the selected program or the product to be produced, bypass arrangement 349 is activated by opening shut-off valve 349c and closing shut-off valve 349d, and deactivating first pump unit 110. Accordingly, the mixture, fed by second pump unit 120 only, circulates via T-fitting 349a and tubing portion 349b of bypass arrangement 349 into mixing container 332, and second tubing portion 344 of tubing 340 to second pump unit 120. This constitution, in which only one pump unit is used for circulating the mixture, the intrusion of air bubbles into the mixture is reduced, whereby the quality of the mixture is enhanced.

[0077] Thereafter, homogenizing unit 170 is activated. According to the selected program for producing the mixture, outer stirrer 172 and inner stirrer 176 are activated at the same time or subsequently.

[0078] Also in the third embodiment of mixing unit 300, it is possible to mix a further component to the mixture. The further component may be filled into funnel 152 of hopper unit 150, which is empty, since the first component has already been supplied to mixing circuit MC. An overpressure is generated in hopper unit 150, and the further component may be supplied to the mixture in mixing circuit MC by opening control valve 156 of hopper unit 150 controlled by control unit CU of mixing system 100.

[0079] It has to be understood, that, for mixing a further component to the mixture, bypass arrangement 349 is deactivated and first pump unit is activated, at least until the further component has been grinded and mixed with the carrier fluid.

[0080] For controlling first and second pump units 110, 120 in mixing system 300, pressure date delivered by first and second pressure sensors PS1, PS2 are used. Based on the sensor date, first and second pump units 110, 120 may be adjusted such that a defined pressure value is set in mixing circuit MC, whereby the fluid flow is optimized.

[0081] The one or more components of the mixture may be lactic acid and / or potassium sorbate, which act as preservative substances, and a gel-forming substance. Such a gel may be used in the production of sausages, where said gel forms the casing for the sausage meat. The carrier fluid in this case is water, and the gel-forming component has an amount of approximately 8%. However, depending on the area of application, other carrier fluids and components as well as other amounts of components may be selected.

[0082] The overpressure in hopper unit 150 may be selected dependent on the desired application. The overpressure, in a specific case where a gel used in the production of sausages is produced, may have an amount of 0,5 bar or less.

[0083] Furthermore, during the mixing process, a vacuum of approximately 10% to maximal 20 % is adjusted, which means that the pressure in mixing circuit MC is 100 mbar to 200 mbar below the normal pressure (1013 mbar). During the production process, the value of the pressure in the vacuum may be varied. During the mixing process, the vacuum may be maintained on a constant low level, whereas the homogenising step is executed in a high vacuum of 85% to 95%, with corresponds to a pressure volume between 850 mbar and 950 mbar below normal pressure, which supports the removal of air bubbles in the mixture.

[0084] Outlet branch 148; 348 of tubing 140; 340 may directly be coupled to a production apparatus, e.g. for processing the mixture just produced, like an apparatus for producing sausages, a packaging apparatus for packaging the mixture, or a cooling apparatus for cooling the mixture just produced prior processing or packaging.

[0085] It has to be noted that mixing unit 100; 200; 300 usually includes only one of hopper units 150 or 150'. However, it is also possible mixing unit 100 includes both hoppers 150 and 150', e.g. for supplying two different components to the carrier fluid.

[0086] Pump 122 of second pump unit 110 has been described as being a spindle pump, which is suited for feeding viscous substances. However, other pumps may be used in second pump unit 120, like a diaphragm pump or a rotary lobe pump, which are also suited for feeding viscous substances.

[0087] Control unit CU, even if it controls mixing system 100, has been described as being a part of mixing unit 130. It is also possible that a separate control unit is provide, for controlling mixing system 100, but which is not part of one of the units of mixing system 100.Reference signs

[0088] CDcirculation direction CUcontrol unit MCmixing circuit FNfiller neck IWinspection window SCscrew connector MPmounting post PS1first pressure sensor PS2second pressure sensor PS3third pressure sensor LSlevel sensor 100 / 200 / 300mixing system 110first pump unit 112pump 114inlet 116outlet 118drive device 120second pump unit 122pump 124inlet 126outlet 128drive device 130 / 230 / 330mixing unit 132 / 232 / 332mixing container 133support frame 134 / 234 / 334lid 135vacuum device 135awater separator 135bvacuum tube 135cvacuum port 136 / 236inlet 336first inlet 337second inlet 338outlet 339fluid inlet 138outlet 140 / 340tubing 142 / 342first tubing portion 144 / 344second tubing portion 146 / 346third tubing portion 148 / 348outlet branch 150 / 150'hopper unit / alternative hopper unit 152funnel 154lid 155overpressure assembly 156control valve 160T-fitting 161inlet branch 162outlet branch 163supply branch 164supply tube 164afirst portion 164bsecond portion 164cthird portion 170homogenizer unit 172outer stirrer 173drive motor 174stirrer axle 175propeller 176inner stirrer 177stirrer arms 178scraper elements 349bypass arrangement 349aT-fitting 249btubing portion 349cshut-off valve 349dshut-off

Claims

1. A mixing system (100; 200; 300) for producing a viscous mixture, the system (100; 200; 300) comprising a first pump unit (110) for conveying at least the mixture and grinding at least one component of the mixture, a second pump unit (120) for conveying the mixture, and a mixing unit (130; 230; 330) for mixing the components of the mixture, the mixing unit (130; 230, 330) including a mixing container (132; 232, 332), the first pump unit (110), the second pump unit (120) and the mixing unit (130, 230; 330) are connected by a tubing (140; 340) for forming a mixing circuit (MC) in which a fluid circulates in a circulation direction (CD), the system (100; 200; 300) further comprising a hopper unit (150, 150') coupled to the mixing circuit (MC) for supplying at least one component to be mixed with the carrier fluid, and a control unit (CU) for controlling the operation of at least one of the units of the mixing system (100; 200; 300).

2. The mixing system (100; 200; 300) according to claim 1, wherein the first pump unit (110) is arranged downstream the second pump unit (120), the second pump unit (120) is arranged downstream the mixing unit (130; 230; 330).

3. The mixing system (100; 200; 300) according to claims 1 or 2, wherein the first pump unit (110) includes a shear pump and / or wherein the second pump unit (120) includes a spindle pump.

4. The mixing system (100; 200; 300) according to any of claims 1 to 3, wherein the hopper unit (150) is arranged downstream the second pump unit (120).

5. The mixing system (100; 200; 300) according to any of claims 1 to 4, wherein the hopper unit (150) is provided with a valve (156) for controlling the supply of the component to the carrier fluid circulating in the mixing circuit (MC).

6. The mixing system (100; 200; 300) according to any of claims 1 to 5, wherein in the mixing circuit (MC), a vacuum is generated, and / or wherein in the hopper unit (150; 150'), an overpressure is generated.

7. The mixing system (100; 200; 300) according to any of claims 1 to 6, wherein a homogenizer unit (170) is coupled to the mixing container (132; 232; 332) of the mixing unit (130; 230; 330).

8. A method for controlling a mixing system (100; 200; 300), the mixing system (100; 200; 300) comprising a first pump unit (110) for conveying at least the mixture and grinding at least one component of the mixture, a second pump unit (120) for conveying the mixture, and a mixing unit (130, 230; 330) for mixing the components of the mixture, the mixing unit (130; 230; 330) including a mixing container (132; 232; 332), the first pump unit (110), the second pump unit (120) and the mixing unit (130; 230, 330) are connected by a tubing (140; 340) for forming a mixing circuit (MC) in which a fluid circulates in a circulation direction (CD), the system (100; 200; 300) further comprising a hopper unit (150; 150') coupled to the mixing circuit (MC) for supplying a component to be mixed with a carrier fluid, and a control unit (CU) for controlling the operation of at least one of the units of the mixing system (100; 200; 300), the method comprises the steps of: - providing a carrier fluid to the mixing system (100; 200; 300); - circulating the carrier fluid in the mixing circuit (MC) at least by the first pump unit (110) and / or the second pump unit (120); - adding at least a first component stored in the hopper unit (150; 150'), to the fluid circulating in the mixing circuit (MC); and - mixing the circulating carrier fluid and the at least one added component.

9. The method according to claim 8, further including the step of adding at least one further component to the carrier fluid in the mixing circuit (MC), wherein the at least one further component is preferably added to the circulating carrier fluid together with the at least one first component or subsequently thereto.

10. The method according to claims 8 or 9, wherein the at least one further component is supplied via the hopper unit (150; 150'), or is supplied directly into the mixing container (132; 232; 332) of the mixing unit (130; 230; 330), or via a separate supply device.

11. The method according to any of claims 8 to 10, further including the step of controlling the opening and closing of the valve (156) of the hopper unit (150; 150').

12. The method of any of claims 8 to 11, further including the step of controlling the mixing process by controlling the rotational speed of the first and / or the second pump unit (110,120).

13. The method according to any of claims 8 to 12, further including the step of homogenizing the viscous mixture, in the mixing container (132; 232; 332) of the mixing unit (130; 230; 330), by a homogenizer (170) coupled to the mixing container (132; 232; 332) of the mixing unit (130; 230; 330).

14. The method according to claim 13, further including the step of controlling the speed and / or the operation time of the homogenizer (170).

15. The method according to any of claims 8 to 14, wherein the control unit (CU) is provided with at least one control program for at least one mixture to be produced.

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