FR2685220A1 - Process for reducing the power absorbed by a stirring rotor and stirring rotor to which it is applied - Google Patents

Abstract

The process according to the invention for stirring a product with the aid of a stirring rotor (8) equipped with blades (11) consists: - in producing a stirring rotor in which at least some of the blades comprise an articulated segment (12) capable of occupying stable and retracted positions, - in actuating the rotation of the stirring rotor in a given direction (f1) to ensure that the product exerts a thrust on the articulated segments of blades, - in stopping rotation of the rotor in the given direction when the thrust exerted on the blade segments reaches a defined value, - and in actuating the rotation of the stirring rotor in the opposite direction (f2), so that the product exerts a thrust on the blade segments causing the latter to occupy their normal stirring position.

Description

METHOD FOR DECREASING THE ABSORBED POWER OF A MOBILE
AGITATOR AND AGITATOR MOBILE USING THE SAME
The present invention relates to the technical field of mixing, stirring, kneading, homogenization, or in general, the stirring of pulverulent, pasty or granular liquid products, in an enclosure or a containment container.

 By stirring or stirring, it is necessary to consider any pure mixing operation between at least two components to be homogenized but, also, any operation aimed at changing the state of one or more basic products or one or more compositions by autoreaction in the face of variations or not in ambient conditions, such as pressure and / or temperature.

 Among the many applications that can be envisaged, it is worth mentioning the manufacture of raw materials, the preparation of industrial products, such as paints, polymers, adhesives, plastics or the manufacture of chemicals of purely and purely industrial character or even food, even pharmaceutical.

 The mixing or stirring of products or compositions of a pulverulent, pasty or liquid nature, is carried out inside containers or vats generally closed and crossed locally by a driven shaft; born in rotation on which is adapted a mobile of agitation composed of a hub fitted with a determined number of blades.

 The power absorbed by a stirring mobile, as described above, is proportional, in particular, to the viscosity of the products to be stirred. Thus, the absorbed power increases when the viscosity of the products to be mixed increases. In certain applications, the viscosity of the product to be brewed changes, generally starting from a maximum viscosity, to result in a reduced viscosity, when the product reaches definitive homogenization or tixotropic conditions. Such a characteristic then requires oversizing the motor member to allow agitation of the product during the start phase of agitation. Furthermore, the blades of the stirring mobile are subjected, during this start-up phase, to intense mechanical forces liable to cause; localized or complete deterioration of the blades.

 The need therefore appears to be able to have a technical means enabling agitation in the general sense of a product by using a given power, even when the viscosity conditions of the product to be stirred change over time.

 The present invention therefore aims to satisfy this need by proposing a process for stirring a product which makes it possible to limit the power absorbed by the stirring mobile, even when the viscosity of the product to be stirred increases.

To achieve this objective, the method according to the invention consists
- to realize a stirring mobile of which at least
some of the blades have an articulated segment
likely to occupy a stable position
corresponding to normal mixing of the product and a
retracted position corresponding to reduced mixing
of the product,
- to control the rotation of the stirring mobile according to a
meaning given to ensure that the product exerts a
thrust on the articulated segments of blades, in view
that they occupy their retracted position,
- to stop the rotation of the mobile in the given direction,
when the thrust exerted on the blade segments and
corresponding to a given viscosity, reaches a
determined value,
- And to control the rotation of the stirring mobile according to
the opposite direction, so that the product exerts a
thrust on the blade segments causing these
last to occupy their normal stirring position.

 Another object of the invention is to propose a stirring mobile comprising a hub driven in rotation and on which blades are mounted, each comprising an articulated segment intended to pivot over an angular range from a normal stable position defined by stubborn.

 Various other characteristics will emerge from the description given below with reference to the appended drawings which show, by way of nonlimiting examples, embodiments of the subject of the invention.

 Fig 1 is a top view showing an embodiment of a stirring mobile according to the invention.

 Fig. 2 is a half-section taken substantially along the lines II-II of FIG. 1.

 Fig. 3 is a half-section in elevation showing another embodiment of a stirring mobile according to the invention.

 Fig. 4 is a partial sectional view taken substantially along lines IV-IV of FIG. 3.

 Figs. 1 and 2 show an apparatus 1 for stirring, mixing, stirring, kneading or reacting a product or a liquid, pasty or granular pulverulent composition.

The apparatus 1 comprises a tank, a container or an enclosure 2 of various shape traversed for example, at the right of its flat bottom 3, by the output shaft 4 of a drive member 5 of any suitable type. The output shaft 4 crosses the bottom 3 of the tank through sealing means 6 known per se.

 The part of the driving shaft projecting inside the tank 2 supports a stirring mobile 8 comprising, in the example illustrated, a hub 9 fixed in rotation on the driving shaft 4. The mobile stirring 8 comprises blades or vanes 11 extending radially from the hub 9. For example, the stirring wheel 8 is shown provided with six blades 11, but it should be considered that a different number could To be scheduled. Of course, it should be noted that the stirring mobile 8 can be driven in rotation by means of a thrust motor member, not the bottom, but the top or the cover of the tank 2.

According to the invention, some of the blades 11, and in the example described, all the blades 11, are arranged to each comprise, an articulated segment 12 intended to pivot, in the variant embodiment illustrated in FIGS 1 and 2, according to an axe
A substantially parallel to the axis of rotation B of the agitating mobile 8. Each segment 12 of the blade is extended by rings 13 intended to pivot around a shaft 14 which freely traverses a bearing 15 fixed on a radial disc 16 s 'extending substantially perpendicular to the axis B of rotation of the agitation mobile. Each blade segment 12 is capable of pivoting along the axis A over an angular range P delimited, in the example illustrated, by the edges 181, 182 of a notch 19 formed in the disk 16. The edges 181, 182 d 'a notch 19 respectively define a centripetal stop and a centrifugal stop for each corresponding blade engaged in the notch 19. As is clear from FIG. 1, the blades 11 are therefore able to occupy a so-called retracted position, when they are in contact with the centripetal stop 181 and a normal stirring position, when they are in contact with the centrifugal stop 182.

 It should be noted that in the example illustrated, each articulated segment 12 entirely forms the useful surface for stirring a blade. Of course, it could be considered to. constitute a blade 11 comprising a fixed base from which pivots an articulated segment 12.

 The stirring mobile described above makes it possible to implement a stirring process having the following characteristics.

 When the product to be brewed has a viscosity of significant value, it is planned to control by a control circuit 20, the rotation of the motor member 5, so that the stirring mobile 8 rotates in the direction of the arrow f1 . According to this direction of rotation, the blades 11, which are subjected on their centrifugal oriented face 111 to the force exerted by the product to be brewed, are pushed to come to bear on the centripetal stops 181. The stirring mobile 8 then has a useful stirring diameter smaller than that presented when the blades occupy their normal position. Reducing the diameter of the mobile's agitation offers the advantage of being able to agitate the product with a reduced absorbed power compared to that which would be necessary if the blades occupied their normal position. power five in turbulent environment. It therefore appears possible, for example, to ensure the starting of the stirring mobile in this direction f1 in a liquid having a high viscosity, while limiting the power absorbed by the stirring mobile. For example, if the diameter of the turbine is of the order of 1000 mm in normal operation and increases to 850 mm in the retracted position, the power absorbed, for brewing a product of the same viscosity, increases respectively 18.11 to 8.04 Kw.

 The control circuit 20 stops the rotation of the mobile 8, in the direction f1, when the thrust exerted on the blade segments 12 and corresponding to a given viscosity, reaches a determined value. The circuit 20 then drives the motor member 5 to control it in rotation in an opposite direction f2, so that the product exerts a thrust on the centripetal face 112 of the blades driving the latter into contact with their stop 182. The mobile stirring 8 then continues its stirring and stirring operation according to a determined cycle.

 The method according to the invention therefore makes it possible to limit the power absorbed by a stirring mobile while allowing stirring of a product of high viscosity. Such a process thus makes it possible to start a stirring mobile in a product having a high viscosity.

 Figs. 3 and 4 illustrate another alternative embodiment of a stirring mobile enabling the method described above to be implemented.

 In this example, each blade II has a fixed foot 21 extending radially and inclined from the hub 9. Each foot 21 has at least one, and in the example illustrated, two joints 22 for a segment or a heel 23 able to pivot along a radial axis C substantially perpendicular to the axis of rotation B of the stirring mobile. Each segment 23, which is oriented towards the bottom of the tank, is capable of occupying a position defined by a stop 24 carried by the segment 23 and intended to come to bear on the fixed foot 21. When the segments 23 are in contact with the stops 24, the blades occupy a maximum unfolded position corresponding to a normal stirring position. If the stirring mobile 8 is controlled to rotate in the direction f1, the upper surface 231 of the segments are subjected to the thrust of the product, so that the segments 23 are raised according to the arrow f3. In the example illustrated, the retracted position of the segment 23 is not precisely defined by a fixed stop, but it could, of course, be considered a stop to determine this position. The articulated segment is therefore raised more or less according to the speed of rotation and in relation to the force applied to the segment. When the motor member 5 rotates the mobile in the direction f2, the liquid pushes on the lower surface 232 tending to bring the segments 23 to bear on the stops 24.

 The invention is not limited to the examples described and shown, since various modifications can be made without departing from its scope.

Claims (10)

 1 - Method of brewing a product using a stirring mobile (8) equipped with blades (11), characterized in that it consists  - to realize a stirring mobile of which at least  some of the blades have a segment  articulated (12, 23) capable of occupying a position  stable corresponding to normal mixing of the product  and a retracted position corresponding to a  reduced mixing of the product,  - to control the rotation of the stirring mobile according to  a given meaning (f1) to ensure that the product  pushes on the articulated segments of  blades, so that they occupy their position  retracted,  - to stop the rotation of the mobile in the given direction,  when the thrust exerted on the blade segments  and corresponding to a given viscosity reaches a  determined value,  - and to control the rotation of the stirring mobile  in the opposite direction (f2), so that the product  pushes on blade segments  training them to occupy their position  normal agitation.  2 - Method according to claim 1, characterized in that it consists in controlling the rotation of the stirring mobile (8)  - in a given direction (f1) to ensure pivoting  centripetal of the blade segments, so that these  the latter occupy a retracted position,  - And in the opposite direction (f2) to ensure the centrifugal pivoting of the blade segments, so that the latter occupy a normal stirring position.  3 - Method according to claim 1 or 2, characterized in that the blade segments (12) occupy a stable position in the retracted position.  4 - Method according to claim 1, characterized in that it consists in controlling the rotation of the stirring mobile  - in a given direction (f1) to ensure the lifting of  blade segments (23), so that the latter  occupy a retracted position,  - and in an opposite direction (f2) to ensure the  lowering of the blade segments, so that these  the latter occupy a normal brewing position.  5 - Stirring mobile ensuring the implementation of the method according to one of claims 1 to 4, characterized in that it comprises a hub (9) driven in rotation and on which are mounted blades (11) each comprising an articulated segment (12, 23) intended to pivot on an angular range (P) from a normal stable position defined by a stop (182, 24).  6 - Stirring mobile according to claim 5, characterized in that each segment (12) of the blades is articulated along a pivot axis (A) which is parallel to the axis (B) of rotation of the shaft, so that each segment has a centripetal oriented face (112) and a centrifugal oriented face (111).  7 - Agitation mobile according to claim 5, characterized in that each articulated segment (12) of blades pivots on a given angular range, defined by a centrifugal stop (182) defining the normal stable position and by a centripetal stop (181 ).  8 - Agitation mobile according to claim 6 or 7, characterized in that the segments (12) of blades are articulated around axes (A) of pivoting angularly spaced in a regular manner and carried by a disc (16) extending perpendicular to the rotary drive shaft, the disc (16) comprising, in relation to each articulated segment, a notch (19) having a given angular opening defining the range of pivoting of the segment between the centripetal stops ( 181) and centrifugal (182).  9 - Agitation mobile according to claim 5, characterized in that each segment (23) of the blade is articulated around a radial axis (c) substantially perpendicular to the axis (A) of rotation of the shaft to allow Lifting or lowering the blade segments.  10 - Brewing apparatus, characterized in that it comprises  - a stirring mobile (8) conforming to one of the  claims 5 to 9 driven in rotation by a  motor member (5) and mounted inside a  container (3),  - And a control circuit (20) able to control the  rotation of the drive member (5) in both directions  of rotation in relation to the viscosity presented by  the product to be brewed.