Abstract:
The invention relates to an apparatus comprising: a measuring head ( 10 ) having a slot ( 18 ) for receiving a measurement cell ( 26 ) and means ( 28 ) for emitting electromagnetic radiation, and means ( 32, 36 ) for detecting radiation from said emission means ( 28 ) after it has passed through the measurement cell ( 26 ); means ( 16 ) for translatably driving and means ( 12, 14 ) for translatably guiding, allowing the substantially vertical longitudinal movement of the measurement head ( 10 ); at least two recesses ( 44 ) each intended for receiving a measurement cell ( 26 ) and arranged one above the other in a longitudinal direction, the recesses ( 44 ) as well as the driving means ( 16 ) and the guiding means ( 12, 14 ) being configured such that during the translational movement of the measurement head ( 10 ) along the nominal travel thereof each recess is placed inside the slot ( 18 ) of the measurement head ( 10 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus for analyzing phases of multiphase mixtures. 
       BACKGROUND 
       [0002]    Such an analysis apparatus is intended in particular for detecting and measuring incipient phenomena of phase separation, sedimentation in particular into various mixtures. The mixtures concerned are mixtures in which singularities or discontinuities (liquid, solid or gaseous, or a combination) are dispersed in a continuous medium of a different composition and/or state. For example, this concerns emulsions if two or more liquid phases are mixed or suspensions if solid particles are dispersed in a liquid. There are numerous fields of application for such an apparatus. The chemical and para-chemical industries are the main fields, but such devices can be used in any field where it is necessary to analyze the structure and/or stability of a multiphase mixture. 
         [0003]    Document EP-0,760,092 discloses an apparatus for performing an analysis of a sample of a multiphase mixture. The method described therein and the corresponding device allow conducting an optical analysis of a mixture and are ideal for characterizing the stability of a mixture, for example a concentrated liquid dispersion. 
         [0004]    The method described in that document of the prior art consists of emitting a light beam through a sample of the multiphase mixture and measuring the light that is backscattered and potentially transmitted all along the height of the sample. In this manner, it is possible to detect variations in size (coalescence, flocculation) and phase separations (sedimentation, creaming) of the mixture analyzed. 
         [0005]    Systems that use this method currently only permit analysis of a single sample. There are “loaders” of course, which manipulate samples stored in a storage unit, preferably temperature regulated, to bring them one after another to the associated analysis device. The main drawback of this combination of analysis device and loader is related to sample transport. The transport act has some impact, even if carried out carefully, and may for example lead to dispersions in areas where the destabilization phenomenon is more visible and thus mask the phenomenon of interest. Another drawback is the cost of the loader, because it must be precise and carry the samples with very little shaking. In addition, its price increases rapidly with the number of samples to be handled. 
         [0006]    Also known from documents U.S. Pat. No. 6,388,751 and FR-2 453 405 are devices for analyzing a plurality of samples placed in tubes. Several tubes are arranged in a vertical position next to one another and an analysis head moves horizontally in front of each of the tubes in order to obtain a measurement at a given height. These devices are not suitable for phase analysis of a multiphase mixture. 
         [0007]    Document EP-2 144 051 provides a storage rack adapted for an analysis device. The rack is designed to hold tubes each containing a sample and arranged vertically. A reading head is moved on an arm in two horizontal directions, and in one vertical direction. The reading head here has three degrees of freedom. Aside from the complexity of this device, it is difficult to ensure precise positioning of the sample relative to the reading head, and in the case of phase analysis of a multiphase mixture, to obtain repeatability in the measurement results. 
       SUMMARY 
       [0008]    The present invention therefore aims to provide an apparatus for analyzing phases of a multiphase mixture which allows reliable analysis of multiple samples. Advantageously, the analysis apparatus will provide the same analysis result for a sample regardless of its position in the apparatus. Preferably, the cost of this device will be competitive with existing devices. 
         [0009]    To this end, the present invention provides an apparatus for analyzing a phase of multiphase mixtures, comprising:
       a measurement head having on the one hand a recess for receiving a measurement cell containing a mixture to be analyzed, and on the other hand means for emitting electromagnetic radiation and means for detecting electromagnetic radiation coming from said emission means and potentially having entered the measurement cell, and   means for driving and guiding in translation, for moving the measurement head along a nominal path in a direction referred to as a substantially vertical longitudinal direction.       
 
         [0012]    According to the invention, said apparatus further comprises at least two casings each intended for receiving a measurement cell and arranged one above the other in the longitudinal direction, and 
         [0013]    the casings as well as the driving and guiding means are configured such that, during the translational movement of the measurement head along its nominal path, each casing is placed inside the recess of the measurement head. 
         [0014]    It is therefore proposed that the samples be arranged on top of one another in a novel manner for the analysis. The longitudinal direction is therefore substantially vertical here. 
         [0015]    To ensure proper guidance of the measurement head, it is proposed that the driving and guiding means comprise a linear ball bearing slide rail. In this embodiment, the linear ball bearing slide rail advantageously is placed at the bottom of the recess of the measurement head. This positioning makes it possible to have a compact structure while providing good guidance. 
         [0016]    For proper positioning of a measurement cell with respect to the measurement head, it is proposed that the apparatus for analyzing phases comprises a support rail having bearing surfaces for receiving an external face of a measurement cell. To improve the precision of this positioning, the bearing surfaces are advantageously arranged in a dihedral angle. 
         [0017]    One embodiment provides that each casing is associated with a cell holder with apertures, this holder being intended for receiving a measurement cell. In this embodiment, the apparatus for analyzing phases may further comprise elastic means which bias each cell contained in a holder toward the bottom of the recess of the measurement head. It is thus possible to guarantee near-perfect positioning of the cell in the apparatus. 
         [0018]    An embodiment which contributes to achieving proper positioning of a measurement cell in the apparatus for measuring phases provides that each casing is associated with an access door mounted so as to pivot about an axis parallel to the longitudinal direction, each door having a face carrying a cell holder arranged such that when in a pivoted position, referred to as the closed position, the cell holder is in place in the corresponding casing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Details and advantages of the invention will be more apparent from the following description, provided with reference to the accompanying drawings in which: 
           [0020]      FIG. 1  is an elevational view of a sample analysis device according to the invention, 
           [0021]      FIG. 2  is a side view of the device of  FIG. 1 , the protective elements having been hidden to expose the device, 
           [0022]      FIG. 3  is a partial cross-sectional view of a sample analysis device along section line III-III of  FIG. 2 , 
           [0023]      FIG. 4  is a partial perspective view illustrating the introduction of samples into a sample analysis device, 
           [0024]      FIG. 5  is a partial perspective view showing sample analysis means, and 
           [0025]      FIG. 6  shows an enlarged perspective view of a sample holder. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]      FIG. 1  illustrates an analysis device adapted to enable analysis of six samples, in particular samples of multiphase mixtures. This embodiment is given by way of non-limiting example, and those skilled in the art will understand from the following description that an analysis device can be provided for measuring a different number of samples. 
         [0027]      FIG. 1  illustrates a possible external appearance of a sample analysis device. This device comprises an inner structure supporting the actual analysis device and an outer casing visible in  FIG. 1 . One will note in this  FIG. 1  the presence of six doors  2  which will be described in more detail below. One of the doors  2  is shown in the open position and in the closed position. 
         [0028]    As one can see in this front view, the doors  2  have an elongated rectangular shape. For the remainder of this description, the following orientation will be used: the longitudinal edges of the doors  2 , corresponding to the long sides of the rectangles, extend horizontally, and the doors are arranged one above the other in a substantially vertical plane. 
         [0029]      FIG. 2  is a side view corresponding to the front view of  FIG. 1  but after removal of the external casing to allow viewing the components inside the analysis device to be described. 
         [0030]    Visible in this figure are a base  4 , and a frame with vertical uprights  6  and crosspieces  8 . The frame serves to support the means for driving and guiding a measurement head  10  in translation. Guidance of said head is provided by a linear ball bearing slide rail which comprises a carriage  12  and a guide rail  14 . The measurement head  10  is driven by means of a lead screw  16  driven in rotation by a motor  17  ( FIG. 2 ) mounted in the base  4 . 
         [0031]      FIG. 3 , which is a sectional view, provides a better understanding of the relative positions of these elements. In the center of this figure is the measurement head  10 . The measurement head  10  corresponds to the movable holder (denoted with a 2 in patent EP-0 760 092B1) and to the elements it carries. This element is adapted in its shape which is generally rectangular and elongated, providing a recess  18  which extends transversely and is relatively wide. Thus, in a top view which also corresponding to the view of  FIG. 3 , the measurement head  10  has a U-shape with a base  20 , a first arm  22 , and a second arm  24 . The recess  18  corresponds to the space between the two arms of the measurement head. It is intended to accommodate a measurement cell  26  containing a multiphase mixture to be analyzed, as illustrated in  FIG. 3 . 
         [0032]    Technically, measurement head  10  is a measurement head with the characteristics of the measurement head described in EP-0 760 092 but of a shape adapted to the environment described herein. Thus, measurement head  10  comprises means for emitting electromagnetic radiation toward the measurement cell  26  and means for detecting electromagnetic radiation backscattered by a mixture located within the measurement cell  26 . Advantageously and as illustrated in  FIG. 3 , it further comprises means for detecting electromagnetic radiation transmitted by the mixture in the measurement cell  26 . 
         [0033]    The means for emitting electromagnetic radiation comprise, for example, a diode  28  which emits in the near infrared. In the embodiment of  FIG. 3 , the diode  28  is carried by the first arm  22  of the measurement device. As a non-limiting illustration, the diode  28  emits rays having a wavelength of 880 nm (880 10 −9  m). The radiation emitted by the diode  28  first passes through a rectilinear slit  30  so that the mixture in the measurement cell  26  is irradiated along a horizontal plane. 
         [0034]    Electromagnetic radiation backscattered by the mixture contained in the measurement cell can be detected by a photodiode  32 . In the illustrative case of  FIG. 3 , the photodiode  32  is carried by the first arm  22  of the measurement cell and is located near the emission diode  28 . It receives the backscattered radiation after the latter has passed through a slit  34 . 
         [0035]    Electromagnetic radiation transmitted through the mixture contained in the measurement cell can be detected by a photodiode  36 . In the illustrative case of  FIG. 3 , the photodiode  36  is carried by the second arm  24  of the measurement cell and is directly facing diode  28  in the emission direction of said diode  28 . 
         [0036]    Reference is made here to the description in patent EP-0 760 092B1, particularly columns 4 and 5, concerning further details of an embodiment of a measurement head which can be used in the present invention. Of course, this is an example of a preferred embodiment and the numerical values given are not limiting. 
         [0037]    To obtain a measurement, a measurement cell  26  is placed within the recess  18  of the measurement head. The measurement cell should be properly positioned relative to the emission diode  28 , to the photodiode  32  for detecting scattered radiation, and to the photodiode  36  for detecting transmitted radiation.  FIGS. 2 to 5  propose a non-limiting example arrangement which allows proper mechanical positioning of the measurement cell  26  with respect to the measurement head  10 . A support rail  38  extends vertically as a backbone of the device. It provides a face, called the front face, which a measurement cell  26  abuts against when carrying out a measurement. This front face is oriented towards the opening of the recess  18  of the measurement head  10 . On the opposite side, in other words facing the bottom of the recess  18 , the support rail  38  supports the guide rail  14 . The latter cooperates with a carriage  12  which is slidable, by means of ball bearings, on the guide rail  14 . The carriage  12  carries the measurement head  10  and is arranged at the bottom of the recess  18  of this measurement head. The lead screw  16  passes through the base  20  of the measurement head  10  and thus drives the measurement head  10  in translation along the support rail  38  via the carriage  12  on one side and the guide rail  14  on the other. 
         [0038]    The following description relates to measurement cells  26  which each have the general shape of a right circular cylindrical tube (in the region where analysis of a mixture is to be carried out), but other measurement cell shapes could be considered, such as a tubular cylinder of square cross-section. These measurement cells  26  are arranged one above the other and in the extension of one another. The longitudinal axes corresponding to these measurement cells (longitudinal axis defined by the cylindrical shape) are all vertical—and thus parallel to the support rail  38 . 
         [0039]    The support rail  38  has, on its front face, bearing studs  40  which each have a bearing face  42 . The studs  40  are arranged in two vertical columns, the bearing faces  42  of studs in the same column all being coplanar. The bearing faces  42  of the studs  40  of the two columns define a dihedral angle adapted to the dimensions of a measurement cell  26 . Preferably, the bearing faces  42  are defined such that when a measurement cell  26  bears against two studs in two separate columns, the bearing faces  42  are tangent to the external surface of the measurement cell. Preferably (as suggested by  FIG. 4 ), a measurement cell  10  bears against four studs  40  (two in each column of studs) during phase analysis of a mixture. 
         [0040]    To position a measurement cell  26  against the support rail  38 , said cell is placed in a sample holder  44  (such as the one illustrated in  FIG. 6 ) attached to one side, referred to as the inner side, of a door  2  mentioned above with reference to  FIG. 1  and also shown in  FIGS. 3 and 4 . 
         [0041]    Each door  2  has the general shape of an elongated rectangle. It has two long horizontal edges and two (short) transverse edges. One transverse edge is mounted so as to pivot via a hinge  46 , directly or indirectly, on a vertical upright  6 . The pivot axis of each door  2  is a vertical axis, so that movement of the door  2  occurs in a horizontal plane. 
         [0042]    The inner face of each door  2  comprises a sample holder  44  where a measurement cell  26  placed in the sample holder  44  is oriented vertically and can abut against the studs  40  of the support rail  38 . As indicated above, it is arranged so that a measurement cell  26  abuts against four studs  40 . The sample holder  44  has apertures, so as to allow a measurement cell  26  to abut against the corresponding studs  40  and not form an obstacle to the travel of electromagnetic radiation emitted by the transmission means toward the detection means (photodiode  32  and/or photodiode  36 ) when the measurement cell  26  is in abutment against the corresponding studs  40  and the measurement head  10  is positioned relative to the measurement cell  26  for performing an analysis of the mixture contained in said measurement cell. 
         [0043]    Each door  2  has a closure system for maintaining a measurement cell  26 , inserted into its sample holder  44 , in abutment against the support rail  38 . For this purpose, a hook  48  referred to as a “push-pull” hook is provided near the transverse edge opposite the hinge  46 , which cooperates with a hook catch  50  attached to the structure of the device. The hook catch  50  is, for example, mounted on a double-bent member  52  mounted on a vertical upright  6 . The closure system comprising the hook  48  and hook catch  50  is preferably provided with a spring to ensure proper positioning of the measurement cell  26  during analysis by eliminating any play due to manufacturing tolerances. 
         [0044]    As shown in particular in  FIG. 4 , a measurement cell  26  has a circular body  54  and a cap  56  that is generally rectangular (in a top view). By offsetting the cap  56  relative to the body  54 , a keyway system is achieved by creating in the sample holder  44  a casing  58  of appropriate shape for the cap  56 . 
         [0045]    A door  2  is opened in order to position a measurement cell  26  in the device. The measurement cell  26  is inserted into the corresponding sample holder  44 . The cap  56  of the measurement cell enters its casing  58 , thereby pre-positioning the cell. The door  2  can then be closed. The measurement cell  26  rests against the corresponding studs  40 . To ensure good repeatable orientation (angular position relative to the axis of symmetry of the body  54  of the measurement cell  26 ), a reference pin  60  is provided on the support rail  38  such that the cap  56  of the measurement call rests against this pin. In addition, when the cap  56  is resting against the reference pin  60 , it is arranged that the body  54  of the measurement cell  26  is only in contact with the sample holder  44  where it rests on the bottom. Thus, the sample holder  44  cannot affect the position of the measurement cell  26  in the device. 
         [0046]    The device described above allows positioning up to six samples simultaneously, one above the other. Analysis can be performed once the samples are in place (between one and six samples). By moving the measurement head  10  along the support rail  38 , the measurement head  10  passes successively in front of each of the samples placed in the device and thus obtains a series of measurements. Regarding the measurements performed on a sample, we refer again here to patent EP-0 760 092B1, particularly columns 6 and 7 of the description and the method claims in that document. 
         [0047]    In the device described above, to perform analyses of six samples (alternative embodiments may provide a device that can house a number of samples not equal to six, either more or less) with a single measurement head, each sample, arranged in a measurement cell, is positioned accurately and reproducibly each time relative to the measurement head. 
         [0048]    The device described above provides a path of about 700 mm for a measurement head (for six samples), which can be adapted according to the samples and the number of samples. Precision guidance is provided by the use of a guide rail, preferably a ball bearing slide rail, and by its cooperation with a lead screw to drive the measurement head in translation. 
         [0049]    For better positioning of the measurement cell, it is proposed in the above description to have the measurement cell bear against two dihedrals at specific points. This bearing is as localized as possible. In addition, the tube position (angular position relative to its axis of symmetry) is indexed by the abutment of a cap of a specific shape against a reference pin. 
         [0050]    With these arrangements, it is possible to achieve excellent performance. Regardless of the operator, a measurement cell will always be similarly positioned in the analysis device. In addition, the measurement cell can be manipulated while maintaining the bottle vertically, without affecting the sample it contains. With such a device, regardless of whether the sample is positioned within the apparatus at a lower, intermediate, or upper “level”, the result of the analysis performed with the measurement head will be the same. The position of the sample in the apparatus therefore has no influence on the measurement obtained. 
         [0051]    The mechanical structure proposed provides excellent guidance of the measurement head for the entire length of its travel. The guidance system proposed here comprises a limited number of parts for positioning the measurement cell relative to the measurement head. 
         [0052]    The invention is not limited to the preferred embodiments described above by way of non-limiting examples. It also relates to variants within the reach of the skilled person, within the scope of the following claims.