IT201800010289A1 - Mixing head - Google Patents

Description

DESCRIPTION

Attached to a patent application for INDUSTRIAL INVENTION having the title

"Mixing head"

TECHNICAL FIELD

The present invention is part of the food industry sector. In particular, the invention is aimed at a mixing head and finds application for example in the pastry sector to obtain emulsified and aerated creams. Even more particularly, the mixing head according to the present invention finds application in mixing apparatuses operating continuously.

In addition, the invention is aimed at a mixing method that can be implemented in mixing apparatuses operating continuously.

STATE OF THE TECHNIQUE

The known mixing heads are designed to emulsify creams and to aerate them, in order to obtain the desired final specific weight. A cream is fed to the mixing head, possibly adding further ingredients, to be emulsified and aerated also by introducing air or other gas, for example nitrogen. The mixing takes place following the joint action of a suitably configured rotor / stator system. In particular, while the rotor rotates in the stator, the respective series of alternating blades generate a variable meatus within which the cream passes which then undergoes a continuous mixing and an intimate mixing of the components and the gaseous part.

The coupling between rotor and stator provides a dynamic mechanical seal to isolate the mixing chamber. As is known, this gasket comprises a stator portion and a rotor portion kept in mutual contact by a helical spring that wraps the rotating shaft on which the rotor is mounted and which pushes the rotor portion against the stator portion.

Since it is located inside the mixing chamber, the useful life of the gasket depends on the products being processed. In particular, products with a high sugar content strongly stress the gasket which in a short time, generally a month, shows the first leaks and must be replaced.

In fact, during processing, the grain of the sugar is reduced so that the sugar can easily infiltrate between the surfaces in contact. If the temperature in the mixing chamber is such as to dissolve the sugar, the drawbacks caused by this infiltration are limited. But in the event that the temperature of the product drops and / or the process is interrupted, the infiltrated sugar solidifies reducing the performance of the spring and the sealing elements (O-rings) and acting as an abrasive component when the processing.

SUMMARY

In this context, the technical task underlying the present invention is to propose a mixing head, in particular for continuously operating mixing apparatuses, and a mixing method which overcomes at least some of the drawbacks of the prior art mentioned above. In particular, an object of the present invention is to provide a head and a mixing method capable of improving the useful life of the seal interposed between rotor and stator.

A further object of the present invention is to limit friction and to improve the operation of this gasket.

The specified technical task and the specified purposes are substantially achieved by a mixing head and method, comprising the technical characteristics set out in one or more of the appended claims. The dependent claims correspond to further advantageous aspects of the invention.

It should be appreciated that this summary introduces a selection of concepts in simplified form, which will be further developed in the detailed description below.

In particular, in accordance with a first aspect, the present invention is directed to a mixing head suitable to be used for mixing apparatuses operating continuously. The mixing head comprises a rotor / stator system in which a sealing device is interposed between the rotor and the stator having an axially fixed rotor portion and a stator portion maintained in contact with the rotor portion by means of a thrust action operated axially on of it by a pusher.

The Applicant believes that the arrangement of the thrust device so as to make it active on the stator portion improves the useful life of the sealing device interposed between the rotor and the stator, avoiding leaks and infiltrations. In particular, the pusher device is no longer arranged inside the mixing chamber in contact with the substance being processed.

In accordance with a second aspect, the present invention is directed to a mixing method which can be implemented in mixing apparatuses operating continuously. The mixing method provides for providing a mixing chamber comprising a rotor / stator system and introducing a cream to be mixed into the mixing chamber, by rotating the rotor. It is also provided to inject pressurized air into a duct opening to the outside and placed in fluid connection with a sealing device interposed between the rotor and stator and to detect any leaks by measuring the pressure inside said duct and then detecting the variations with respect to the pressure of the injected air.

The Applicant believes that the early detection of any leaks and infiltrations allows the necessary checks and appropriate replacements to be carried out, avoiding damaging further components of the mixing head.

In one or more of the aspects indicated, the present invention may comprise one or more of the following features.

Preferably, an external casing surrounds the mixing chamber which extends along an axis and comprises at least a processing portion. The rotor is arranged inside the processing portion of the mixing chamber and is mounted on a rotating shaft arranged with an axis of rotation coinciding with the axis that crosses the outer casing. The stator is integral with the external casing, has an annular conformation around the axis and wraps the rotor in a radially external position at least in correspondence with the processing portion of the mixing chamber.

The rotor portion of the sealing device wraps around the rotating shaft, is integral with the rotor rotating around the axis and is mounted in a fixed position along the axis itself.

The stator portion of the sealing device wraps around the rotating shaft and is mounted smoothly along the axis with respect to the outer casing.

The rotor portion and the stator portion respectively have a rotor annular surface and a stator annular surface arranged transversely to the axis and enveloping the rotating shaft.

The thrust device is active in axial thrust on the stator portion to keep the stator annular surface in contact with the rotor annular surface.

Preferably the thrust device comprises at least one elastic element operatively interposed between the stator portion and the external casing.

Even more preferably, the elastic element is interposed between the stator portion and a stop ring enveloping the rotating shaft and mounted in a fixed position along the axis.

The elastic element preferably has a preload for example equal to 1 mm.

Preferably the thrust device comprises a plurality of elastic elements, preferably helical springs, distributed angularly around the axis and the rotating shaft in order to obtain a uniform distribution of the load. Even more preferably, the elastic elements are interposed between the stator portion and a stop ring enveloping the rotating shaft and mounted in a fixed position along the axis.

The elastic elements preferably have a preload for example equal to 1 mm.

Preferably, a bushing integral with the external casing partially houses the stator portion sliding along the axis. Preferably the stop ring is fixed axially and angularly inside the bushing so as to simplify the assembly of the sealing device.

Preferably, the pusher device is arranged in a housing volume separate from the mixing chamber so as to preserve its structure and mechanical characteristics. The stator annular surface in contact with the rotor annular surface is arranged inside the mixing chamber.

Preferably, the bushing defines the housing volume inside it and comprises sealing gaskets which separate the mixing chamber from the housing volume.

Preferably, the external casing has one or more ducts placed in fluid connection with the sealing device and leading to the outside of the mixing head to detect any leaks. Even more preferably, a lower duct opening into a lower portion of the mixing head and / or an upper duct opening into an upper portion of the mixing head is provided. The lower duct receives by gravity and lets out any leaks that are thus visually highlighted to an operator of the mixing head. The upper duct is connected to a source of compressed air and has a pressure gauge configured to detect pressure differences in the upper duct itself due to leaks and infiltrations.

Preferably the rotor portion comprises a rotor annular body presenting the rotor annular surface and a fixing sleeve fixed to a front surface of the rotor and enveloping the rotating shaft. The fastening sleeve and the rotor annular body are connected to each other for example by means of a tubular body arranged radially external thereto. Preferably a sealing gasket is interposed between the fixing sleeve and the front surface of the rotor in order to avoid infiltrations. Preferably a contact portion of the rotor annular surface and of the stator annular surface has radial dimensions comprised between 89 millimeters and 95 millimeters, preferably 95 millimeters.

Preferably, the rotor annular surface and the stator annular surface have a SiC silicon carbide coating obtained by silicon carbide SiC deposition surface treatment in order to increase its hardness and resistance to mechanical and thermal wear, and therefore improve the estate.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will become clearer from the indicative, and therefore non-limiting, description of a preferred but not exclusive embodiment of a mixing head.

This description will be set forth hereinafter with reference to the accompanying drawings, provided for indicative and, therefore, non-limiting purposes only, in which: - Figure 1 schematically illustrates a sectional view of a mixing head;

Figure 2 schematically illustrates a sectional view of a portion of the mixing head of Figure 1 along the line II-II indicated in Figure 5;

Figure 3 illustrates the enlarged detail III of Figure 2;

Figure 4 illustrates a perspective view of some components of the head of Figure 1 assembled together;

Figure 5 illustrates a front view of the components of Figure 4, with indication of the section planes II-II of Figure 2;

- Figure 6 illustrates a cross-sectional view of the outer casing of the mixing head along the line VI-VI indicated in Figure 1.

DETAILED DESCRIPTION

The present invention is directed to a mixing head.

With reference to the figures, 1 generally indicates a mixing head, preferably suitable for mixing apparatuses operating continuously.

The other numerical references refer to technical characteristics of the invention which, subject to different indications or obvious structural incompatibilities, the technician skilled in the art will be able to apply to all the construction variants described.

Any changes or variants that, in light of the description, are evident to the person skilled in the art must be considered as falling within the scope of protection established by the present invention, according to considerations of technical equivalence.

The mixing head 1 comprises an external casing 2 surrounding at least one mixing chamber 3.

The mixing chamber 3 develops along an "X" axis. As for example illustrated in Figure 3, the mixing chamber 3 has an inlet portion 3a, a processing portion 3b and an outlet portion 3c arranged in sequence along the "X" axis.

The inlet portion 3a preferably has a tapered shape, which narrows away from the processing portion 3b, and is placed in communication with the outside by means of a supply duct, not shown. Preferably, the supply duct is arranged radially with respect to the "X" axis.

The processing portion 3b has a substantially cylindrical conformation around the "X" axis.

The outlet portion 3c preferably has a tapered shape, which narrows away from the processing portion 3b, and is placed in communication with the outside through an outlet duct 5 through which the emulsified and aerated cream is sent to subsequent processing. Preferably the outlet duct 5 is arranged coaxial to the "X" axis.

The outer casing 2 has a gap 6 arranged at least partially around the mixing chamber 3. Preferably the gap 6 has an annular shape around the "X" axis. The interspace 6 is suitable for receiving a fluid, for example water, suitable for performing the function of thermal stabilization. The fluid is continuously introduced and extracted into the interspace by means of a circulation system, for example by means of a hydraulic pump. To control the mixing parameters, the fluid is introduced into the interspace 6 at a controlled temperature.

7 indicates a stator integral with the outer casing 2 and laterally delimiting the processing portion 3b of the mixing chamber 3.

The stator 7 has an annular conformation around the "X" axis and preferably defines an internal side wall delimiting the interspace 6. In other words, the interspace 6 is arranged around the stator 7 and in a radially external position to it.

In accordance with a possible embodiment, the stator 7 has a plurality of stator annular mixing portions 8 distributed along the "X" axis at a radially internal surface of the stator 7. Each stator annular mixing portion 8 comprises a plurality of stator blades 9 distributed circumferentially around the axis "X" and extending in a centripetal direction from the radially internal surface of the stator 7. Preferably each stator blade 9 has a radial conformation. The number 10 indicates a rotor arranged inside the processing portion 3b of the mixing chamber 3 and rotating around a rotation axis coinciding with the "X" axis of the mixing chamber 3.

The rotor 10 has a cylindrical shape around the "X" axis and is wound by the stator 7 arranged in a radially external position with respect to it in correspondence with the processing portion 3b of the mixing chamber 3.

In accordance with a possible embodiment, the rotor 10 has a plurality of annular rotor mixing portions 11 distributed along the "X" axis at a radially external surface of the rotor 10.

Each stator annular mixing portion 11 comprises a plurality of rotor blades 12 distributed circumferentially around the "X" axis and extending in a centrifugal direction from the radially outer surface of the rotor 10. Preferably each rotor blade 12 has a radial conformation.

The rotor mixing annular portions 11 are arranged alternating with the stator mixing annular portions 8 along the "X" axis and meshing with them.

The rotor 10 is mounted on a rotating shaft 13, also arranged with a rotation axis coinciding with the "X" axis of the mixing chamber 3. The rotating shaft 13 crosses the outer casing 2.

The rotating shaft 13 can be mounted on bearings 14 housed in a support 15 preferably made as an appendix of the outer casing 2.

Advantageously, the mixing head 1 comprises a sealing device 16 operatively interposed between the rotor 10 and the stator 7, in particular the outer casing 2.

The sealing device 16 comprises a rotor portion 17 operatively associated with the rotor 10 and enveloping the rotating shaft 13. The rotor portion 17 is integral with the rotor 10 in rotation around the "X" axis and is mounted in a fixed position along the axis itself.

In accordance with a possible example of embodiment, the rotor portion 17 comprises an annular rotor body 18 which has an annular rotor surface 19 arranged transversely with respect to the "X" axis and enveloping the rotating shaft 13.

Preferably, the rotor annular surface 19 has a SiC silicon carbide coating obtained by a SiC silicon carbide deposition surface treatment.

Advantageously, SiC Silicon Carbide is a ceramic material having excellent resistance to abrasion, corrosion and thermal shock. Even more advantageously, SiC silicon carbide has excellent thermal conductivity (and therefore low thermal expansion) and extreme resistance to acids and bases.

In addition, SiC Silicon Carbide can be used in the food industry as it is not capable of generating toxicological problems.

Preferably the rotor portion 17 comprises a fixing sleeve 20 fixed to a front surface 10a of the rotor 10 and enveloping the rotating shaft 13. Even more preferably a sealing gasket 20a is interposed between the fixing sleeve 20 and the front surface 10a of the rotor 10. More precisely, the sealing gasket 20a is preferably arranged on a surface of the fixing sleeve 20 orthogonal with respect to the rotation axis "X" of the rotating shaft 13, rather than on a surface parallel to the rotation axis " X ". Even more precisely, the sealing gasket 20a is arranged along the outermost perimeter of the fixing sleeve 20, so as to prevent even the slightest infiltration between the sleeve itself and the surface 10a of the rotor 10. In this way, the sealing gasket 20a arranged in a corresponding housing which accommodates it in a stable manner, advantageously also prevents any deposit of the product being processed inside the housing itself in which it is positioned, preventing the proliferation of bacterial flora.

The fixing sleeve 20 and the rotor annular body 18 are connected to each other for example by means of a tubular body 21 arranged radially external thereto.

The sealing device 16 comprises a stator portion 22 operatively associated with the stator 7 and enveloping the rotating shaft 13. The stator portion 22 is slidably mounted along the "X" axis, ie in the axial direction, with respect to the external casing 2 on which is mounted.

The stator portion 22 has a stator annular surface 23 arranged transversely with respect to the "X" axis and enveloping the rotating shaft 13. Preferably the stator annular surface 23 has a coating of Silicon Carbide SiC obtained by surface treatment of deposition of Carbide di SiC silicon.

Reference 24 generally indicates a thrust device active on the stator portion 22 in axial thrust to keep the stator annular surface 23 in contact with the rotor annular surface 19.

The stator annular surface 23 in contact with the rotor annular surface 19 are arranged inside the mixing chamber 3. The pusher 24 is arranged in a housing volume "V" separated from the mixing chamber 3.

A contact portion of the rotor annular surface 19 and of the stator annular surface 23 has radial dimensions of between 81 millimeters and 87 millimeters, preferably 87 millimeters, so as to have a smaller friction surface and therefore a reduction in the heat generated.

The thrust device 24 can comprise at least one elastic element operatively interposed between the stator portion and the external casing. Preferably the thrust device comprises a plurality of elastic elements 25, preferably helical springs, distributed angularly around the "X" axis and the rotating shaft 13.

The springs preferably have a preload for example equal to 1mm and work in thrust to keep the stator annular surface 23 in contact with the rotor annular surface 19 and guarantee sealing.

Preferably the elastic elements 25 are axially interposed between the stator portion 22 and a stop ring 26 enveloping the rotating shaft 13 and mounted in a fixed position along the "X" axis.

For example, a bushing 27 may be provided, integral with the outer casing 2, inside which the stator portion 22 slides axially with respect to the bush itself is partially housed.

In addition, the bush 27 houses the stop ring 26 which is axially and angularly fixed inside the bush itself.

For example, the stop ring 26 is angularly fixed inside the bushing 27 by means of shape couplings consisting of radial protrusions 28 and seats 29 suitable for receiving the radial protrusions and extending in an axial direction. The shape coupling avoids off-axis slippage and keeps the stop ring 26 centered.

For example, the stop ring 26 is axially fixed inside the bush 27 by means of a fixing pin 30 is inserted radially between the bush 27 and the stop ring 26. In this way the stop ring is axially locked at least in the opposite direction to the stator portion 22.

Preferably, the bushing 27 defines the housing volume "V" inside it and comprises sealing gaskets 31 which separate the mixing chamber 3 from the housing volume "V".

In accordance with a possible embodiment which may not include the sealing device 16 and the thrust device 24 in the previously described embodiments, the external casing 2 can have one or more ducts 32 placed in fluid connection with the device sealing, and in particular with the coupling between the rotor annular surface 19 and the stator annular surface 23, and leading to the outside of the mixing head.

Preferably, as better illustrated in Figure 6, at least one lower duct 33 opening into a lower portion of the mixing head and / or an upper duct 34 opening into an upper portion of the mixing head is provided.

The lower duct 33 receives by gravity and lets out any leaks that are thus visually highlighted to an operator of the mixing head.

The upper duct 34 is connected to a source 35 of compressed air and has a pressure gauge 36 configured to detect pressure differences in the upper duct 34 itself due to leaks and infiltrations.

In addition to the above, in general the components of the mixing head have rounded edges so as to improve the hygiene of the mixing head itself.

In use, the mixing head 1 allows to implement a mixing method in which the cream to be mixed is introduced into the mixing chamber 3 and the rotor 10 is rotated.

The mixing takes place continuously, emulsifying and aerating the cream as a result of the rotor / stator interaction and possibly further introducing a gas, for example nitrogen, into the inlet portion of the mixing chamber. The mixed cream then proceeds out of the mixing chamber.

During mixing, pressurized air is injected into the upper duct 34 and the pressure inside the upper duct 34 is measured, thus detecting the variations (generally increasing) with respect to the pressure of the injected air which indicate leaks from the mixing chamber 3.

A visual or audible alarm system can be operatively associated with the pressure gauge 36 to highlight possible leaks.

Claims (14)

CLAIMS 1. Mixing head (1) for continuously operating mixing apparatuses comprising: an external casing (2) surrounding a mixing chamber (3) which extends along an axis (X) and comprising at least one processing portion (3b); a rotor (10) arranged inside the processing portion (3b) of the mixing chamber (3) and mounted on a rotating shaft (13) which crosses said outer casing (2) and is arranged with a rotation axis coinciding with said axis (X); a stator (7) integral with the external casing (2), having an annular shape around said axis (X) and enveloping the rotor (10) in a radially external position at least in correspondence with the processing portion (3b) of the chamber mixing (3); a sealing device (16) comprising: - a rotor portion (17) operatively associated with the rotor (10) and enveloping said rotating shaft (13), in which said rotor portion (17) is integral with the rotor (10) in rotation around the axis (X) and is mounted in a fixed position along the axis (X), - a stator portion (22) operatively associated with the stator (7) and enveloping said rotating shaft (13), in which said stator portion (22) is slidably mounted along the axis (X) with respect to the outer casing (2), wherein said rotor portion (17) and said stator portion (22) have respectively an annular rotor surface (19) and an annular stator surface (23) arranged transversely with respect to said axis (X) and enveloping said rotating shaft (13), a thrust device (24) active on the stator portion (22) in axial thrust to keep said stator annular surface (23) in contact with said rotor annular surface (19). 2. Mixing head according to claim 1, wherein said thrust device (24) comprises at least one elastic element (25) operatively interposed between the stator portion (22) and the outer casing (2). Mixing head according to claim 1 or 2, wherein said thrust device (24) comprises a plurality of elastic elements (25), preferably helical springs, angularly distributed around the axis (X) and the rotating shaft ( 13). 4. Mixing head according to claim 2 or 3, wherein said at least one elastic element (25) is axially interposed between said stator portion (22) and a stop ring (26) enveloping said rotating shaft (13) and mounted in fixed position along the (X) axis. 5. Mixing head according to claim 5, comprising a bushing (27) integral with the outer casing (2), in which said bushing (27) partially houses said stator portion (22) sliding along the axis (X), said stop ring (26) being fixed axially and angularly inside said bush (27). Mixing head according to one or more of the preceding claims, wherein said thrust device (24) is arranged in a housing volume (V) separated from the mixing chamber (3), said annular stator surface (23) in contact with said rotor annular surface (19) being arranged inside said mixing chamber (3). 7. Mixing head according to claims 5 and 6, wherein said bushing (27) defines inside it said housing volume (V) and comprises sealing gaskets (31) which separate the mixing chamber (3) from the volume of housing (V). 8. Mixing head according to claim 6 or 7, wherein said outer casing (2) has one or more ducts placed in fluid connection with said housing volume (V) and leading to the outside of the mixing head (1) . Mixing head according to claim 8, wherein said outer casing (2) has a lower duct (33) opening into a lower portion of the mixing head (1) and / or an upper duct (34) opening into a portion top of the mixing head connected to a source (35) of compressed air and having a pressure gauge (36) configured to detect pressure differences in the upper conduit (34). Mixing head according to one or more of the preceding claims, wherein said rotor portion (17) comprises a rotor annular body (18) having said rotor annular surface (19) and a fixing sleeve (20) fixed to a front surface (10a) of the rotor (10) and enveloping said rotating shaft (13), said fixing sleeve (20) and said rotor annular body (18) being connected together for example by means of a tubular body (21) arranged radially external to them . 11. Mixing head according to claim 10, wherein a sealing gasket (20a) is interposed between the fixing sleeve (20) and the front surface (10a) of the rotor (10). Mixing head according to one or more of the preceding claims, wherein a contact portion of the rotor annular surface (19) and the stator annular surface (23) has radial dimensions ranging from 81 millimeters to 87 millimeters, preferably 87 millimeters. 13. Mixing head according to one or more of the preceding claims, wherein the rotor annular surface (19) and the stator annular surface (23) have a silicon carbide SiC coating obtained by deposition surface treatment of silicon carbide SiC. 14. Mixing method feasible in continuously operating mixing apparatuses comprising: - providing a mixing chamber (3) comprising a rotor / stator system in which the rotor (10) rotates around an axis (X) with respect to the stator (7) and in which an upper duct (34) is placed in connection with fluid with a seal interposed between said rotor (10) and said stator (7) and flows outwards; - introduce a cream to be mixed into the mixing chamber (3) and rotate the rotor (10); - injecting pressurized air into said upper duct (34); - by measuring the pressure inside said upper duct (34) and detecting variations with respect to the pressure of the injected air to detect leaks from the mixing chamber (3).