Measuring cell for a particle size measuring device

Abstract

Measuring cell (1) for a particle size measuring device, wherein the measuring cell (1) defines a sample volume (94) through which a dispersion can be passed in order to generate a diffraction pattern of the dispersed phase contained in the dispersion, wherein the measuring cell (1) defines a measuring cell plane E and has the following: a feed line (32) to introduce the dispersion into the sample volume (94) and a discharge line (34) to discharge the dispersion from the sample volume (94), a first measuring cell assembly (52) comprising a measuring cell base body (42), a first window pane (46) arranged on the measuring cell base body (42), and a first sealing element in the form of a first sealing ring (48) to seal the first window pane (46) on the measuring cell base body (42), a second measuring cell assembly (72) with a closure plate (62) for attaching to the measuring cell base body (42), a second window pane (66) which is arranged on the closure plate (62), and a second sealing element in the form of a second sealing ring (68) to seal the second window pane (66) to the closure plate (62), a disc-shaped third sealing element (90), wherein the disc-shaped third sealing element is designed as a flow disk (90) and defines an inner flow channel (92) and is arranged over a surface between the first and second measuring cell assembly (52, 72) to seal the first and second measuring cell assembly (52, 72) against each other, wherein the flow channel (92) extends between the inlet and outlet (32, 34) in the measuring cell plane E and forms the sample volume (94) between the first and second measuring cell assembly (52, 72).

Description

Field of the invention

[0001] The invention relates to a measuring cell for a particle size measuring device in general and to a wet measuring cell for a laser particle size measuring device in particular. Background of the invention

[0002] A particle size measuring device that operates on the principle of light diffraction uses a bundle of light rays, usually supplied by a laser, to pass through the sample under investigation. Downstream of the sample, the angular intensity distribution generated by scattering from the particle ensemble is recorded by a detector system. Based on the resulting scattering / diffraction pattern, the particle size distribution of the particles in the sample can be determined. Mathematically, the particle size distribution can be described using Mie theory. Mie theory deals with both forward and backward scattering. An important part of Mie theory describes so-called Fraunhofer diffraction, which concerns light diffraction at forward angles. In general, the smaller the particles, the larger the scattering angles, and vice versa. Depending on the setup, particle sizes of up to 1000 µm or even larger can be measured.

[0003] Known particle sizers comprise a light source, typically a laser, and a so-called beam processing unit, which expands the thin, parallel laser beam into a parallel beam with a larger diameter. In early particle sizers, the sample to be examined was examined in a measuring cell in this expanded parallel beam, and the diffraction spectrum generated by the particles was focused onto a detector using a Fourier lens arranged downstream of the sample beam. This technique is referred to as the "conventional technique" according to the standard ISO 13320-1 1999-11-01. Particle size analysis - Laser diffraction methods - Part 1: General principles. EP 0 207 176 B1 by the same applicant describes a particle sizer which reverses the optical conditions compared to the conventional technique. This setup is referred to as a "reverse Fourier setup" (inverse Fourier optics) according to ISO 13320-1:1999(E).In inverse Fourier optics, the Fourier lens is located upstream of the measuring cell so that the sample is illuminated in the convergent light beam.

[0004] Further particle size measuring devices are described in DE 10 2008 064 760 B3 and DE 42 18 638 C2.

[0005] The measuring cell typically has an entrance window through which the light beam enters the measuring cell and an exit window through which the scattered light exits to be detected by the detector system. Some particle sizers can also measure scattered light at backward angles, which exits the measuring cell through the entrance window. The samples are typically present as a dispersion, although depending on the measuring cell and dispersion circuit, either dry or wet dispersed samples can be analyzed.

[0006] For many samples, wet dispersion offers a suitable method of dispersion. The sample material is placed in a closed liquid circuit, or more precisely, a dispersion circuit, containing the measuring cell, and continuously circulated through the dispersion circuit. Laser particle sizers may have a mount for a wet measuring cell. The wet dispersion device is docked to the laser particle sizer as a module and connected to a dispersion inlet and a dispersion outlet on the measuring cell. The measuring cell in the particle sizer operates in a flow-through mode.

[0007] After each measurement, the wet dispersion device and the dispersion circuit, including the measuring cell and any other components in the dispersion circuit, are cleaned—i.e., emptied and rinsed with fresh, particle-free liquid. Nevertheless, it is sometimes necessary to open the measuring cell for thorough cleaning or to remove trapped, possibly oversized particles. On the other hand, the inlet and outlet windows must be well sealed.

[0008] There are wet measuring cells in which the inlet and outlet windows are inserted into seals with complex seal geometries, possibly with thinner wall areas or pockets in the seals. Such seals are complex and expensive to manufacture, may require special molds, can be fragile at connecting bridges due to thin walls, and can be difficult to remove and fiddly reinsert.

[0009] DE 199 13 730 describes a pressure-resistant process window for pipelines.

[0010] General description of the invention It is an object of the invention to provide a measuring cell for a particle size measuring device which, on the one hand, is easy and convenient for the user to open, clean and close again and which, on the other hand, is well sealed.

[0011] A further aspect of the task is to provide a measuring cell for a particle size measuring device which can be produced cost-effectively and, in particular, has simply shaped, stable seals.

[0012] Another aspect of the task is to provide a measuring cell for a particle size measuring device in which the windows and seals can be easily removed and reinserted.

[0013] The object of the invention is achieved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0014] According to one aspect of the invention, a measuring cell for a particle size measuring device, in particular a laser particle size measuring device, is provided. The measuring cell defines a sample volume through which a dispersion can be passed in flow-through operation in order to generate a so-called diffraction pattern of the disperse phase contained in the dispersion by means of light scattering or light diffraction and to record it in the particle size measuring device.

[0015] The measuring cell has the following features: - A supply line, in particular comprising a supply channel, for introducing the dispersion from a dispersing device into the sample volume and a discharge line, in particular comprising a discharge channel, for discharging the dispersion from the sample volume back into the dispersing device in order to form the dispersion circuit through the measuring cell. - A first measuring cell assembly i) with a measuring cell base body, in particular made of metal, e.g. made of stainless steel, among other things for fastening the measuring cell to a holding device, wherein the measuring cell base body has an inner flat side, ii) with a first window pane, preferably made of glass, which is arranged on the measuring cell base body, and iii) a first sealing element in the form of a first sealing ring made of elastomeric material in order to seal the first window pane to the measuring cell base body in a fluid-tight manner, - A second measuring cell assembly i) with a closure plate for fastening to the measuring cell base body, in particular made of metal, e.g. made of stainless steel, wherein the closure plate has an inner flat side which, in the state mounted on the measuring cell base body, faces the inner flat side of the measuring cell base body, ii) with a second window pane, preferably made of glass, which is arranged on the closure plate, and iii) a second sealing element in the form of a second sealing ring made of elastomeric material in order to seal the second window pane to the closure plate in a fluid-tight manner. - A disc-shaped third sealing element made of elastomeric material, i.e., a third sealing element in the form of a sealing disc made of elastomeric material. A synthetic rubber, in particular a fluoroelastomer or fluororubber (FKM), e.g., Viton®, or a perfluororubber (FFKM), e.g., Kalrez®, can be used as the elastomeric material. Fluoroelastomers have the advantage of high chemical resistance. The third disc-shaped sealing element is located, in particular in a sandwich-like manner, between the first measuring cell assembly and the second measuring cell assembly to seal the first and second measuring cell assemblies from one another and thereby define the sample volume.

[0016] The set of sealing elements is therefore in particular composed of at least three parts, the three parts consisting of the first and second sealing elements, which consist of the first and second sealing rings, respectively, and the disc-shaped third sealing element located therebetween, consisting of the sealing washer. In other words, the first and second sealing rings and the disc-shaped third sealing element in the form of a sealing washer are designed as separate sealing elements.

[0017] This allows the shaping of the first, second and third sealing elements to be simple, which makes sealing elements cost-effective to manufacture and can have a stable shape.

[0018] In particular, the sealing elements can be manufactured without complex and thin-walled transition bridges or other thin-walled components, so that they are easy to remove and reinsert and are also stable and durable.

[0019] The sealing elements can be manufactured from a sheet material in a particularly simple manner and do not need to be individually shaped and manufactured in a special press mold, e.g. hot-formed.

[0020] Preferably, the first and second window panes are secured to the measuring cell base body and the closure plate by the first and second sealing rings, respectively, at least in such a way that the first and second measuring cell assemblies can be handled by the user as first and second structural units. Therefore, the first and second measuring cell assemblies can also be referred to as the first and second measuring cell halves, respectively, whereby "half" is not to be understood in a mathematical sense. The measuring cell plane is defined by the gap between the first and second window panes and preferably runs through the disk-shaped third sealing element.

[0021] The supply line and / or the discharge line are preferably designed as a supply channel or discharge channel in the measuring cell base body or the closure plate, wherein the channels preferably run as bores in the measuring cell base body or in the closure plate.

[0022] The disk-shaped third sealing element defines an inner flow channel and therefore forms a flow disk. The disk-shaped third sealing element has a first and a second flat side and extends flatly or in a sandwich-like manner between the first and second inner sealing surfaces of the first and second measuring cell assemblies, wherein the first and second measuring cell assemblies, wherein the first and second inner sealing surfaces each seal against one of the two opposite flat sides of the sealing disk or flow disk in order to seal the first and second measuring cell assemblies from one another in a fluid-tight manner. The flow channel, in the assembled state, extends between the supply line and the discharge line in the measuring cell plane and forms a part of the sample volume that is visible from the outside in the area between the first and second window panes.

[0023] In other words, the sample volume is limited on the two flat sides parallel to the measuring cell plane by the first and second measuring cell assemblies and on the narrow side by a circumferential inner narrow side of the flow channel in the disc-shaped third sealing element, extending transversely to the measuring plane between the first and second measuring cell assemblies.

[0024] Preferably, the measuring cell base body has a first inner sealing surface and the closure plate has a second inner sealing surface, wherein these first and second inner sealing surfaces face one another and wherein the disc-shaped third sealing element is inserted between the first and second inner sealing surfaces and seals against the first and second inner sealing surfaces. The supply channel and the discharge channel open into a region between the first and second inner sealing surfaces at a first and second end of the flow channel, respectively, the supply channel on one side of the sample volume, either at the top or bottom, and the discharge channel on the opposite side of the sample volume, i.e., at the bottom or top, respectively. The flow channel runs from the opening of the supply channel across the part of the sample volume visible from the outside between the first and second window panes to the opening of the discharge channel.

[0025] This also contributes to simple shaping and production of the sealing elements.

[0026] Preferably, positioning pins project from the first and / or second inner sealing surface of the measuring cell base body or the closure plate, which engage in corresponding openings in the disc-shaped third sealing element when the latter rests against the first or second inner sealing surface, thereby advantageously ensuring exact positioning of the disc-shaped third sealing element when closing the measuring cell and preventing undesired slipping.

[0027] The flow channel is preferably elongated and is delimited on both sides by an inner narrow side, so that in the assembled state the sample volume is delimited parallel to the measuring cell plane by the first and second inner sealing surface of the measuring cell base body or the closure plate, the first and second window panes and the first and second sealing ring, and in the direction perpendicular to the measuring cell plane by the inner narrow side of the flow channel.

[0028] Since the first and second window panes preferably run parallel to each other in the assembled state, the space between the first and second window panes extends two-dimensionally in a disc-shaped manner parallel to the measuring cell plane, and the flow channel through the disc-shaped space runs between the first and second window panes through this space. Since the flow channel is preferably elongated and narrow, a portion, in particular the majority of the disc-shaped space between the first and second window panes, is filled by the disc-shaped third sealing element.

[0029] The first and second window panes are preferably embedded in the first and / or second sealing ring and, with a front side or axial inner side running parallel to the measuring cell plane, seal against the first and second flat sides of the disk-shaped third sealing element, respectively, at least in sections outside (left and right) of the flow channel. In other words, the disk-shaped third sealing element seals flatly against the first and second window panes in the filled space to the left and right of the flow channel.

[0030] In particular, in the assembled state, the first window pane lies flat on only one first flat side of the disk-shaped third sealing element and / or the second window pane lies flat on only one second flat side of the disk-shaped third sealing element opposite the first flat side and the first and / or second window pane are in particular not encompassed on both sides by the disk-shaped third sealing element.

[0031] Preferably, in the assembled state, the first sealing ring rests on the first window pane exclusively on its circumferential narrow side and in particular does not encompass the first window pane on both sides and / or the second sealing ring rests on the second window pane exclusively on its circumferential narrow side and in particular does not encompass the second window pane on both sides.

[0032] In particular, the first and / or second sealing ring and / or the disc-shaped third sealing element do not have any regions with a thinner wall thickness or even pockets into which the first and / or second window pane would be inserted.

[0033] Preferably, the first and / or second sealing ring and / or the disc-shaped third sealing element are punched or cut out of elastomeric sheet material, e.g., laser-cut. The first and / or second sealing ring preferably have a rectangular cross-section.

[0034] In particular, the first and / or second sealing ring and / or the disc-shaped third sealing element are geometrically shaped as generally hollow cylinders, wherein the disc-shaped third sealing element has an irregular cylindrical guide curve. In particular, the first and second flat sides of the disc-shaped third sealing element are thus essentially completely flat, or the disc-shaped third sealing element is essentially completely flat.

[0035] This also contributes to the simplicity of manufacture and stability of the three sealing elements.

[0036] If the first and / or second sealing ring and / or the disc-shaped third sealing element are made of elastomeric plate material, they preferably do not have any shaped elements protruding from the plate plane.

[0037] Preferably, the first and / or second window pane each define a circumferential outer narrow side and are inserted into the first and / or second sealing ring, such that the first or second sealing ring extends annularly around the circumferential outer narrow side of the first or second window pane. The measuring cell base body and / or the closure plate further comprise a first or second window opening, each with a radially circumferential inner annular wall, into which the first or second sealing ring is inserted with the first or second window pane.

[0038] In the assembled state, the first and / or second sealing ring seals with its radially circumferential inner side (inner cylinder jacket) preferably in a fluid-tight manner against the circumferential narrow side of the first or second window pane and seals with its radially outer side (outer cylinder jacket) in a fluid-tight manner against a circumferential inner ring wall of the first or second window opening, in order to insert the first and / or second window pane into the measuring cell base body or the closure plate and to seal it therein with the first or second sealing ring.

[0039] The first and / or second window opening are preferably tapered from the outside in the direction of the sample volume in order to press the radial inner side of the first and / or second sealing ring radially against the circumferential narrow side of the first or second window pane in the mounted state.

[0040] Preferably, the first measuring cell assembly comprises a first fastening ring which is screwed onto the outside of the measuring cell base body and holds the first window pane in the first window opening and / or the second measuring cell assembly comprises a second fastening ring which is screwed onto the outside of the closure plate and holds the second window pane in the second window opening.

[0041] Preferably, the first and second window panes can be held in a clamped manner when the first and second fastening rings are mounted on the first and second measuring cell assemblies, respectively, and the measuring cell is open, i.e. the first and second measuring cell assemblies are separated from one another, so that the first and second measuring cell assemblies, respectively, with the first and second sealing rings and the first and second windows, respectively, can each be handled as a structural unit, but on the other hand, the first and second window panes can be manually pushed out inwards without removing the first and second fastening rings.

[0042] In the area of ​​the window panes, this preferably leads to a sandwich-like structure of the measuring cell with at least 5 layers, namely with the following layers: 1st layer: First fixing ring, 2nd layer: measuring cell body with first sealing ring and first window pane, 3rd layer: sample volume and disc-shaped third sealing element, 4th layer: closure plate with second sealing ring and second window pane, 5th layer: Second fastening ring.

[0043] According to a preferred embodiment, the inner side of the measuring cell base body facing the closure plate together with the first window pane and the first sealing ring surrounding the first window pane form at least in sections a common first flush sealing surface and / or the inner side of the closure plate facing the measuring cell base body together with the second window pane and the second sealing ring surrounding the second window pane form at least in sections a common second flush sealing surface.

[0044] This has the advantage that the first and / or second measuring cell assembly can each seal against a flat side of the sealing disc or flow disc and the two flat sides of the sealing disc or flow disc do not require any special surface shaping, but can simply be flat surfaces.

[0045] In other words, in the assembled state, the flat side of the measuring cell base body, the first sealing ring and the first window pane facing the disc-shaped third sealing element lie flush with one flat flat side of the disc-shaped third sealing element and / or the flat side of the closure plate, the second sealing ring and the second window pane facing the disc-shaped third sealing element lie flush with the other opposite flat flat side of the disc-shaped third sealing element.

[0046] Advantageously, no recesses for the disc-shaped third sealing element need to be milled into the sealing surfaces of the measuring cell base body and / or the closure plate, but the sealing surface of the measuring cell base body and / or the sealing surface of the closure plate simply lie plane-parallel on the disc-shaped third sealing element.

[0047] According to a preferred embodiment, the measuring cell base body and the closure plate each have a mutually facing inner sealing surface, between which the disc-shaped third sealing element is inserted and against which the disc-shaped third sealing element seals on both sides, wherein the inner sealing surface of the measuring cell base body preferably has an integral first sealing bead and / or the inner sealing surface of the closure plate preferably has an integral second sealing bead, wherein the first and / or second sealing bead digs into one of the two opposite flat sides of the disc-shaped third sealing element.

[0048] This can advantageously further improve the sealing effect.

[0049] Preferably, the first and / or second sealing bead runs parallel to the measuring cell plane completely around the first or second sealing ring with the first or second window pane, around the flow channel, and around the area of ​​the openings of the supply line and discharge line.

[0050] Preferably, the measuring cell base body and the closure plate have mutually complementary joint parts or hinge means by means of which the first and second measuring cell assemblies can be folded open and closed in order to close and open the measuring cell.

[0051] For this purpose, the measuring cell base body preferably has at least one slit-shaped hinge pocket on a narrow side and the closure plate has at least one hinge pin, wherein to close the measuring cell the hinge pin is inserted by the user into the slit-shaped hinge pocket in order to pivot the second measuring cell assembly by means of the hinge joint thus formed relative to the first measuring cell assembly when the hinge pin is inserted and to close and open the measuring cell by means of the pivoting movement like a door.

[0052] Preferably, the measuring cell has a quick-clamping mechanism opposite the hinge joint, by means of which the first and second measuring cell assemblies can be clamped against one another with the disc-shaped third sealing element located therebetween, such that the sample volume is sealed fluid-tight by the clamping.

[0053] The quick-release mechanism preferably has a hand wheel and an eccentric lever, which are designed such that, in order to close the measuring cell, the hand wheel is rotated about an axis perpendicular to the measuring cell plane in order to bring a contact and clamping surface of the hand wheel into overlap with the second measuring cell assembly and subsequently the contact surface of the hand wheel is clamped against the second measuring cell assembly by means of the eccentric lever, and which are designed such that, in order to open the measuring cell, the eccentric lever is released and subsequently the hand wheel is rotated about the axis perpendicular to the measuring cell plane until the contact and clamping surface of the hand wheel is rotated out of the overlap with the second measuring cell assembly and releases the closing plate, so that the second measuring cell assembly can be folded away from the first measuring cell assembly.

[0054] The measuring cell preferably has one, several or all of the following features: - the supply line and / or the discharge line are designed as holes in the measuring cell base body, - a supply pipe with a connection coupling is included, which is connected to the supply bore, - a discharge pipe with a connecting coupling is included, which is connected to the discharge bore, - the measuring cell is mounted on an elongated base plate, wherein the base plate has in particular a groove or spring guide in order to insert the measuring cell with the base plate into a particle size measuring device, - the measuring cell has an upper handle to turn the measuring cell into a

[0055] particle size measuring device, - the measuring cell has an end plate running transversely to the base plate, which in particular has at least one or two bores through which the supply pipe and / or the discharge pipe extend in order to be able to couple a dispersion hose from the outside.

[0056] The invention also relates to the disc-shaped third sealing element as a replacement or retrofit part for the measuring cell.

[0057] As a replacement or retrofit part for the measuring cell, the disc-shaped third sealing element in the form of a flow disc is characterized by the following features: The flow disc has a thickness in the range between 1 mm and 10 mm, preferably in the range between 2 mm and 6 mm.

[0058] The flow disc is made of a plate made of elastomeric material with a thickness in the range between 1 mm and 10 mm, preferably in the range between 2 mm and 6 mm, and consists only of a piece of this plate made of elastomeric material, and has two flat sides and preferably no shaped elements protruding from the plane of the plate.

[0059] The flow disc is punched or cut out of the plate of elastomeric material.

[0060] The flow disc has a width in the range between 30 mm and 250 mm, preferably in the range between 50 mm and 150 mm, and a length in the range between 50 mm and 300 mm, preferably in the range between 80 mm and 200 mm.

[0061] The flow disc defines a flow channel with a width in the range between 5 mm and 100 mm, preferably in the range between 10 mm and 50 mm, and a length in the range between 30 mm and 250 mm, preferably in the range between 70 mm and 150 mm.

[0062] The flow channel is punched or cut out of the elastomeric material plate and is circumferentially defined by an inner narrow side in the flow disk. In particular, there are no pockets or recesses on the circumferential inner narrow side or on the flow disk for inserting a window pane. Short description of the characters

[0063] They show: Fig. 1 a three-dimensional exploded view of the measuring cell holder with an embodiment of the measuring cell according to the invention, Fig. 2 a three-dimensional exploded view of the measuring cell from Fig. 1, Fig. 3 a three-dimensional individual representation of the flow disk from Fig. 2 from the side of the locking plate, Fig. 4 a three-dimensional individual representation of the flow disk from Fig. 2 from the side of the measuring cell body, Fig. 5 a top view from the right of the measuring cell mounted in the holder, Fig. 6 a horizontal section through the arrangement of Fig. 5 along line FF, Fig. 7 a horizontal section through the arrangement of Fig. 5 along the line GG, Fig. 8 a horizontal section through the arrangement of Fig. 5 along line HH, Fig. 9 an enlarged view of the area around the sample volume Fig. 6, Fig. 10 a vertical section of the arrangement Fig. 5 along line II, Fig. 11 a top view of the measuring cell with measuring cell holder, Fig. 12 a vertical section through the arrangement of Fig. 11 along line CC, Fig. 13 a three-dimensional representation of the unfolded measuring cell without the flow disc, Fig. 14 a three-dimensional view of the measuring cell body, Fig. 15 a top view of the inside of the closure plate. Detailed description of the invention

[0064] Referring to Fig. 1 and Fig. 2, the measuring cell 1 is screwed to a measuring cell holder 16 with a measuring cell base plate 12. The measuring cell base plate 12 has spring projections 14 on its long narrow sides 12a, 12b, which can be inserted into a corresponding groove in a laser particle size measuring device (not shown).

[0065] The measuring cell holder 16 is vertically delimited on the left side by an end plate 18, which is also screwed onto the measuring cell base plate 12. An inlet pipe 22 and an outlet pipe 24 are installed in bores 20 in the end plate 18. The inlet pipe 22 and the outlet pipe 24 are screwed with their respective inner ends 22a, 24a into an inlet channel 32 and an outlet channel 34, respectively, each with a seal 36, in order to establish fluid communication with the sample volume of the measuring cell 1. Hose connection couplings 26 are attached to the outside of the inlet and outlet pipes 22, 24 in order to connect the measuring cell 1 to a dispersing device (not shown) by means of hoses. In the present example, the measuring cell 1 is a wet measuring cell, which is connected to a wet dispersing device. The dispersion is fed into the measuring cell 1 or 2 through the supply channel 32.pumped into the sample volume in the measuring cell 1, flows through the measuring cell 1 and is returned to the wet dispersing device through the discharge channel 34, so that the measuring cell 1 is operated in flow.

[0066] A handle 28 is screwed onto the top of the measuring cell to allow the measuring cell to be removed from the laser particle sizer and reinserted. Alternatively, the side finger grip 29 can be used for this purpose.

[0067] The measuring cell 1 has a measuring cell base body 42, which is screwed onto the measuring cell base plate 12 and through which the supply channel 32 and the discharge channel 34 extend as bores. The measuring cell base body 42 has a central first window opening 44, into which a first window pane 46 with a first sealing ring 48 is inserted. The first window pane 46 and the first sealing ring 48 are secured against falling outward in the first window opening 44 by a first fastening ring 50. For this purpose, the first fastening ring 50 is screwed onto the outer side 42b of the measuring cell base body 42.

[0068] A closure plate 62 forms the counterpart to the measuring cell base body 42. The closure plate 62 has a second window opening 64 into which a second window pane 66 with a second sealing ring 68 is inserted. The second window pane 66 and the second sealing ring 68 are secured against falling outwards by a second fastening ring 70 in the second window opening 64. For this purpose, the second fastening ring 70 is screwed onto the outer side 62b of the closure plate 62. The measuring cell base body 42 and / or the closure plate 62 can be milled from stainless steel, for example. The sealing rings 48, 68 are preferably circular or consist of a circular ring made of elastomer material, for example a fluoroelastomer or fluororubber (FKM). If there are certain requirements for chemical resistance, the first and / or second sealing ring (48, 68) and / or the flow disc 90 can also be made of a perfluoro rubber (FFKM), e.g.Kalrez®, are manufactured or consist of.

[0069] When the first window pane 46 with the first sealing ring 48 is inserted into the measuring cell base body 42 and secured with the first fastening ring 50, the first window pane 46 and the first sealing ring 48 are clamped in the first window opening 44 and these parts together form a first measuring cell assembly 52, which represents a first structural unit that can be handled by the user. In the same way, the closure plate 62 with the second window pane 66 inserted into the second window opening 64, the second sealing ring 68 and the screwed-on second fastening ring 70 form a second measuring cell assembly 72, which also represents a second structural unit that can be handled by the user. The radially circumferential outer sides 48c, 68c of the first and second sealing rings 48, 68 rest against a radially circumferential inner annular wall 44a, 64a of the first and second measuring cell windows 44, 64.

[0070] The inside of the measuring cell base body 42 forms a first inner sealing surface 42a and the inside of the closure plate 62 forms a second inner sealing surface 62a, between which a disk-shaped third sealing element 90 in the form of a sealing disk with a flow channel 92 is inserted.

[0071] Referring to the Fig. 3 and Fig. 4, the sealing disc forms a flow disc 90 with the flow channel 92. The flow disc 90 is laser-cut from a plate made of elastomeric material, e.g., fluororubber (FKM) or perfluororubber (FFKM), e.g., from a Viton® or Kalrez® plate, and is essentially in the form of a flat plate with two flat, flat sides 90a, 90b, which form the sealing surfaces of the flow disc 90. Cut out inside the flow disc 90 is the flow channel 92, which extends laterally to the measuring cell plane E in the flow disc 90.

[0072] In other words, the first and second measuring cell assemblies 52, 72 form two mutually corresponding, joinable measuring cell halves, which are sealed against each other by means of the flow disk 90 as an intermediate sealing disk, whereby “halves” is not to be understood mathematically.

[0073] The flow channel 92 has a substantially elongated shape and is circumferentially delimited by an inner narrow side 92a. When the measuring cell 1 is assembled, the first and second measuring cell assemblies 52, 72 are put together with the flow disk 90 inserted between them and clamped against one another so that the flow channel 92 defines the sample volume 94 in the measuring cell. In the assembled state, the sample volume 94 is delimited parallel to the measuring cell plane E on one side by the first window pane 46 or by the first measuring cell assembly 52 and on the other side by the second window pane 66 or by the second measuring cell assembly 72. In the measuring cell plane E, the sample volume 94 is delimited by the circumferential inner narrow side or annular wall 92a, so that an elongated, extended sample volume 94 is delimited on all sides for the dispersion to pass through.

[0074] Referring to the Fig. 7 and Fig. 8, the supply channel 32 and the discharge channel 34 open at the mouth 33, 35 into a lower end 92b and an upper end 92c of the flow channel 92, respectively. The first and second measuring cell assemblies 52, 72, when joined together, together with the flow channel 92 of the flow disk 90 extending from the mouth 33 to the mouth 35, therefore define the sample volume 94 within the measuring cell 1.

[0075] How best in Fig. 9 and Fig. 10, the window pane 46 with the first sealing ring 48 runs flush with the sealing surface 42a of the measuring cell base body 42, so that a generally first flat inner sealing surface 52a of the first measuring cell assembly 52 is created. In the same way, the second window pane 66 with the second sealing ring 68 runs flush with the sealing surface 62a of the closure plate 62, so that here too a substantially second flat inner sealing surface 72a of the second measuring cell assembly 72 is created. The flow disk 90 is therefore sandwiched between the first and second measuring cell assemblies 52, 72 and seals flatly on both sides against their first and second flat inner sealing surfaces 52a, 72a.

[0076] How best in Fig. 10, the first and second measuring cell assemblies 52, 72 with the flow disk 90 clamped therebetween form a sandwich-like five-layer arrangement seen from left to right consisting of i) the first fastening ring 50, ii) the central region 42c of the measuring cell base body 42, thinned out in this example, with a plane-parallel inserted first window disk 46 and a circumferential first sealing ring 48, iii) the flow disk 90, iv) the closure plate 62 with a plane-parallel inserted second window disk 66 and a circumferential second sealing ring 68 and v) the second fastening ring 70.

[0077] How best in Fig. 9, the two sealing rings 48, 68, designed as three separate sealing elements, and the flow disk 90 located therebetween seal against each other at least in some areas, namely in particular in the areas to the sides (left and right) of the flow channel 92. In particular, the first and second sealing rings 48, 68 seal with their respective inner axial end faces 48a, 68a against the two flat sides 90a and 90b of the flow disk 90, respectively, and are plane-parallel to the inner sides 46a, 66a of the two window panes 46, 66 and the inner sealing surfaces 42a, 62a of the measuring cell base body 42 and the closure plate 62.

[0078] The flow channel 92 therefore runs transversely in the measuring cell plane E between the two window panes 46, 66 and up to a lower and upper end 92b, 92c, into which the supply channel 32 and the discharge channel 34 respectively open.

[0079] Both the first and second sealing rings 48, 68 and the flow disk 90 are simply punched or laser-cut from an elastomeric sheet material, for example, from a flat fluororubber or perfluororubber sheet (e.g., Viton® or Kalrez®). Therefore, the sealing elements 48, 68, 90 preferably have a (very flat) cylindrical shape in the mathematically geometric sense. In particular, the flow disk 90 has the shape of a simple disk with certain openings, but does not have a three-dimensional shape deviating from a cylindrical shape, so that the flow disk can be manufactured (without individual hot forming) from a simple sheet material by punching or cutting. The first and second sealing rings 48, 68 preferably have a rectangular cross-section ( Fig. 9, Fig. 10). A custom (hot) press mold for producing the sealing elements is therefore not necessary. Furthermore, the measuring cell base body 42 and / or closure plate 62 do not require any (ring) grooves for inserting the sealing rings, although such grooves should not be categorically excluded.

[0080] The thickness of the flow disk 90 is 4 mm, and the thickness of the first and second sealing rings 48, 68, as well as the first and second window panes 46, 66, is also 4 mm. Due to the flat shape of the sealing concept, the thickness of the flow disk 90 defines the thickness of the sample volume 94, which in this example is also 4 mm. In this example, the flow disk has a height of 128.5 mm and a width of 70 mm.

[0081] How best in Fig. 9, 10 and 13-15, the measuring cell base body 42 and the closure plate 62 each have an annular or completely closed first and second sealing bead 54, 74, which run around the respective inner sealing surfaces 42a, 62a of the measuring cell base body 42 and the closure plate 62. The first and second sealing bead 54, 74 each have a substantially elongated shape with a circular bulge in the region of the two window panes 46, 66. The first and second sealing bead 54, 74 runs completely closed on the outside around the associated window opening 44, 64, and thus around the associated window pane 46, 66 and the associated sealing ring 48, 68. Furthermore, the first sealing bead 54 runs at the upper and lower ends around the openings 33, 35 of the supply and discharge channels 32, 34.

[0082] How best to Fig. 9 and Fig. 10, the first and second sealing bead 54, 74 dig into the respective flat side 90a, 90b of the flow disk 90, completely closed all the way around all other openings or sealing interfaces, so that an effective seal can be achieved between the first and second measuring cell assemblies 52, 72 and the flow disk 90 located therebetween.

[0083] Referring to the Fig. 13, the user hangs the second measuring cell assembly 72 as a second structural unit, like a door leaf, on the first measuring cell assembly 52 as a first structural unit. For this purpose, the closure plate 62 has a hinge section 75. A hinge pin 76 is inserted into the hinge section 75 in the closure plate 62 ( Fig. 2) and the measuring cell base body 42 has two hinge slots or hinge pockets 56a, 56b at its rear end, which accommodate the hinge pin 76. The upper hinge pocket 56b is closed with a plate 58, allowing the user to thread the hinge pin 76 diagonally from below into the upper hinge pocket 56b and then insert the lower portion of the hinge pin 76 laterally into the lower hinge pocket 56a. This is particularly convenient to handle. The entire second assembly 72, comprising the closure plate 62, the window pane 66 inserted therein, the circumferential ring seal 68, and the fastening ring 70, can then be pivoted open and closed as a unit, like a door leaf. When the flow disk 90 is placed on the inner sealing surface 42a of the measuring cell base body 42 and rests against the sealing bead 54, the user pivots the second measuring cell assembly 72 against the flow disk 90 and thus closes the sample volume 94.In order to achieve a fluid-tight closure, the first and second measuring cell assemblies 52, 72 with the flow disk 90 in between are clamped against each other with a quick-clamping mechanism 102.

[0084] The quick-clamping mechanism 102 comprises an asymmetric hand wheel 104, which is rotated with a contact and clamping surface 106 from the outside against a corresponding contact and clamping surface 108 of the second measuring cell assembly 72, in this example the second fastening ring 70. Subsequently, the eccentric lever 110 is tightened to achieve a secure clamping of the first and second measuring cell assemblies 52, 72 against the flow disk 90 located therebetween. In the clamped state, as best shown in Fig. 9, the two sealing beads 54, 74 are inserted into the flow disk 90, in a ring-shaped manner, among other things, outside the two sealing rings 48, 68, whereby an effective and reliable fluid-tight sealing of the measuring cell can be achieved.

[0085] To open it, for example to clean the measuring cell 1, the user opens the eccentric lever 110, turns the hand wheel 104 out of communication with the closure plate 62 or the second fastening ring 70 attached thereto, and can then open the measuring cell 1 again by pivoting the second measuring cell assembly 72 away from the first measuring cell assembly 52 and the flow disk 90. ​​The user can then easily remove the flow disk 90 from the sealing surface 42a, which is flat except for the sealing bead 54. To secure the flow disk 90 against falling when opening and closing the measuring cell 1 and to position it precisely, four positioning pins 112 are formed on the inside of the measuring cell base body in this example, which engage in corresponding openings 114 in the flow disk 90.Nevertheless, the flow disk 90 can be very easily removed from the measuring cell base body 42 by the user, which is due, among other things, to the generally flat, layered sealing construction with the three separate sealing elements 48, 68, 90 and to the fact that the flow disk merely rests flat on the generally flat inner surface of the first measuring cell assembly 52 and, in particular, does not have to be inserted into special openings, grooves, or the like in the measuring cell base body 42. In other words, the flow disk 90 preferably merely rests flatly on the one hand against the essentially flat inner side of the measuring cell base body 42 or the first measuring cell assembly 52 and, on the other hand, against the essentially flat inner side of the closure plate 62 or the second measuring cell assembly 52.

[0086] Referring to the Fig. 9 and Fig.10, the first and second window openings 44, 64 in the measuring cell base body 42 and in the closure plate 62 are tapered in the direction of the flow disk 90, so that the radially circumferential annular walls 44a, 64a of the first and second measuring cell windows 44, 64 are conical. As a result, the first and second sealing rings 48, 68, with their radially circumferential inner narrow sides 48d, 68d, are pressed radially from the outside against the radially circumferential outer narrow sides 46c, 66c of the first and second window panes 46, 66, respectively, which can improve the sealing effect. Furthermore, when the fastening rings 50, 70 are screwed on, the window panes 46, 66 are held clamped in the associated window openings 44, 64 by means of the sealing rings 48, 68, so that they cannot easily fall out. The clamping effect can also be improved by tapering the window openings 44, 64.Nevertheless, when the measuring cell is open, the user can simply push the window panes 46, 66 outwards without having to fiddle with the sealing rings 48, 68 and without having to unscrew the fastening rings 50, 70. To do this, the user only needs to press against the respective window pane 46, 66 with their finger from the outside when the measuring cell 1 is open, and the respective window pane 46, 66 falls out of the corresponding window opening 44, 64, since the window panes 46, 66 are only fastened from the outside with the fastening rings 50, 70 and are otherwise clamped in the corresponding window opening 44, 64 by means of the sealing rings 48, 68. The sealing rings 48, 68 can then be pulled inwards out of the corresponding window opening 44, 64 just as easily, provided they do not fall out when the window panes are pushed out.

[0087] In summary, the presented three-part sealing set consisting of the two sealing rings 48, 68 and the flat flow disc 90 provides a sealing concept that is easy to manufacture, user-friendly and yet efficient.

[0088] It will be apparent to those skilled in the art that the embodiments described above are to be understood as examples, and that the invention is not limited to them, but can be varied in many ways without departing from the scope of the claims. Furthermore, it is clear that the features, regardless of whether they are disclosed in the description, the claims, the figures, or otherwise, also individually define essential components of the invention, even if they are described together with other features.

Claims

[1] Measuring cell (1) for a particle size measuring device, wherein the measuring cell (1) defines a sample volume (94) through which a dispersion can be passed in order to generate a diffraction pattern of the disperse phase contained in the dispersion, wherein the measuring cell (1) defines a measuring cell plane E and has the following: a supply line (32) to introduce the dispersion into the sample volume (94) and a discharge line (34) to discharge the dispersion from the sample volume (94), a first measuring cell assembly (52) with a measuring cell base body (42), a first window pane (46) arranged on the measuring cell base body (42), and a first sealing element in the form of a first sealing ring (48) for sealing the first window pane (46) to the measuring cell base body (42), a second measuring cell assembly (72) with a closure plate (62) for fastening to the measuring cell base body (42), a second window pane (66) which is arranged on the closure plate (62), and a second sealing element in the form of a second sealing ring (68) for sealing the second window pane (66) to the closure plate (62), a disc-shaped third sealing element (90), wherein the disk-shaped third sealing element is designed as a flow disk (90) and defines an inner flow channel (92) and is arranged flat between the first and second measuring cell assemblies (52, 72) in order to seal the first and second measuring cell assemblies (52, 72) from one another, wherein the flow channel (92) extends between the supply line and the discharge line (32, 34) in the measuring cell plane E and forms the sample volume (94) between the first and second measuring cell assemblies (52, 72). [2] Measuring cell (1) according to claim 1, wherein the measuring cell base body (42) has a first inner sealing surface (42a) and the closure plate (62) has a second inner sealing surface (62a), wherein the first and second inner sealing surfaces (42a, 62a) face each other and wherein the disc-shaped third sealing element (90) is inserted between the first and second inner sealing surfaces (42a, 62a) and seals against the first and second inner sealing surfaces (42a, 62a), wherein the supply line (32) and the discharge line (34) open into a region between the first and second inner sealing surfaces (42a, 62a) at a first and second end (92b, 92c) of the flow channel (92), respectively, the supply line (32) on one side of the sample volume (94) and the discharge line (34) on the opposite side of the sample volume (94), and wherein the flow channel (92) runs from the mouth (33) of the supply line (32) via the part of the sample volume (94) visible from the outside between the first and second window panes (46, 66) to the mouth (35) of the discharge line (34). [3] Measuring cell (1) according to claim 2, wherein positioning pins (112) project from the first and / or second inner sealing surface (42a, 62a) and engage in corresponding openings (114) in the disc-shaped third sealing element (90) when the latter rests against the first or second inner sealing surface (42a, 62a). [4] Measuring cell (1) according to one of the preceding claims, wherein the disk-shaped third sealing element is designed as a flow disk (90) and defines an inner flow channel (92), wherein the flow channel (92) is delimited by an inner narrow side (92a) and in the assembled state the visible part of the sample volume (94) is delimited parallel to the measuring cell plane E by the first and second window panes (46, 66) and in the direction perpendicular to the measuring cell plane E by the inner narrow side (92a). [5] Measuring cell (1) according to one of the preceding claims, wherein the disk-shaped third sealing element is designed as a flow disk (90) and defines an inner flow channel (92) and, in the assembled state, the first and second window panes (46, 66) run parallel to one another and the space between the first and second window panes (46, 66) extends two-dimensionally in a disk shape parallel to the measuring cell plane E and the flow channel (92) runs through the disk-shaped space between the first and second window panes (46, 66), and wherein a part of the disk-shaped space between the first and second window panes (46, 66) is filled by the disk-shaped third sealing element (90). [6] Measuring cell (1) according to one of the preceding claims, wherein the first and / or second sealing ring (48, 68) each seals with an end face (48a, 68a) at least in sections against the disc-shaped third sealing element (90). [7] Measuring cell (1) according to one of the preceding claims, wherein in the assembled state the first window pane (46) lies flat on only a first flat side (90a) of the disk-shaped third sealing element (90) and / or wherein the second window pane (66) lies flat on only a second flat side (90b) of the disk-shaped third sealing element (90) opposite the first flat side and the first and / or second window pane (46, 66) are in particular not encompassed by the disk-shaped third sealing element (90). [8] Measuring cell (1) according to one of the preceding claims, wherein in the assembled state the first sealing ring (48) rests on the first window pane (46) only on its circumferential narrow side (46c) and in particular does not engage around the first window pane (46) and / or wherein the second sealing ring (68) rests on the second window pane (66) only on its circumferential narrow side (66c) and in particular does not engage around the second window pane (66). [9] Measuring cell (1) according to one of the preceding claims, wherein the first and / or second sealing ring (48, 68) has a square cross-section. [10] Measuring cell (1) according to one of the preceding claims, wherein the first and / or second sealing ring (48, 68) and / or the disc-shaped third sealing element (90) have a shape that can be produced by punching or cutting out of an elastomeric plate material. [11] Measuring cell (1) according to one of the preceding claims, wherein the first and / or second sealing ring (48, 68) and / or the disc-shaped third sealing element (90) are made of elastomeric plate material and do not have any shaped elements protruding from the plate plane. [12] Measuring cell (1) according to one of the preceding claims, wherein the first and / or second window pane (46, 66) each define a circumferential outer narrow side (46c, 66c) and the first and / or second sealing ring (48, 68) is arranged in a ring-shaped manner around the circumferential outer narrow side (46c, 66c) of the first or second window pane (46, 66), and wherein the measuring cell base body (42) and / or the closure plate (62) have a first or second window opening (44, 64), each with a radially circumferential inner annular wall (44a, 64a), into which the first or second window pane (46, 66) with the first or second circumferential sealing ring (48, 68) is inserted. [13] Measuring cell (1) according to claim 12, wherein the first and / or second sealing ring (48, 68) seals with its radially circumferential inner side (48d, 68d) against the circumferential narrow side (46c, 66c) of the first or second window pane (46, 66) and seals with its radial outer side (48c, 68c) against a circumferential inner annular wall (44a, 64a) of the first or second window opening (44, 64) in order to insert the first and / or second window pane (46, 66) into the measuring cell base body (42) or the closure plate (62) and to seal it therein with the first or second sealing ring (48, 68). [14] Measuring cell (1) according to claim 13, wherein the first and / or second window opening (44, 64) are tapered from the outside in the direction of the sample volume in order to press the radial inner side (48d, 68d) of the first and / or second sealing ring (48, 68) radially against the circumferential narrow side (46c, 66c) of the first or second window pane (46, 66) in the assembled state. [15] Measuring cell (1) according to one of claims 12-14, wherein the first measuring cell assembly (52) comprises a first fastening ring (50) which is fastened to an outer side (42b) of the measuring cell base body (42) and holds the first window pane (46) in the first window opening (44) and / or wherein the second measuring cell assembly (72) comprises a second fastening ring (70) which is fastened to an outer side (62b) of the closure plate (62) and holds the second window pane (66) in the second window opening (64). [16] Measuring cell (1) according to one of the preceding claims, wherein the inner side (42a) of the measuring cell base body (42) facing the closure plate (62) together with the first window pane (46) and the first sealing ring (48) surrounding the first window pane (46) form at least in sections a common first flush sealing surface and / or wherein the inner side (62a) of the closure plate (62) facing the measuring cell base body (42) together with the second window pane (66) and the second sealing ring (68) surrounding the second window pane (66) form, at least in sections, a common second flush sealing surface. [17] Measuring cell (1) according to one of the preceding claims, wherein the measuring cell base body (42) and the closure plate (62) each have a mutually facing inner sealing surface (42a, 62a), between which the disc-shaped third sealing element (90) is inserted and against which the disc-shaped third sealing element (90) seals on both sides, wherein the inner sealing surface (42a) of the measuring cell base body (42) has a first sealing bead (54) and / or the inner sealing surface (62a) of the closure plate (62) has a second sealing bead (74), wherein the first and / or second sealing bead (54, 74) digs into one of the two opposite flat sides (90a, 90b) of the disc-shaped third sealing element (90). [18] Measuring cell (1) according to claim 17, wherein the disk-shaped third sealing element is designed as a flow disk (90) and defines an inner flow channel (92) and the first and / or second sealing bead (54, 74) runs parallel to the measuring cell plane E completely around the first or second sealing ring (48, 68) with the first or second window pane (46, 66), around the flow channel (92), and around the area of ​​the openings (33, 35) of the supply line (32) and discharge line (34). [19] Measuring cell (1) according to one of the preceding claims, wherein the measuring cell base body (42) and the closure plate (62) have mutually complementary hinge parts (56a, 56b, 76) by means of which the first and second measuring cell assemblies (52, 72) can be opened and closed in order to close and open the measuring cell (1). [20] Measuring cell (1) according to claim 19, wherein the measuring cell base body (42) has at least one slot-shaped hinge pocket (56a, 56b) on a narrow side and the closure plate (62) has at least one hinge pin (76) and the hinge pin (76) can be inserted into the slot-shaped hinge pocket (56a, 56b) by the user in order to be able to pivot the second measuring cell assembly (72) by means of the hinge joint thus formed relative to the first measuring cell assembly (52) and thereby to close and open the measuring cell (1). [21] Measuring cell (1) according to one of the preceding claims, wherein the measuring cell (1) has a clamping mechanism (102) by means of which the first and second measuring cell assemblies (52, 72) with the disc-shaped third sealing element (90) lying therebetween can be clamped against one another in such a way that the sample volume (94) is sealed in a fluid-tight manner by the clamping. [22] Measuring cell (1) according to claim 21, wherein the clamping mechanism (102) comprises a hand-operated rotary wheel (104) and an eccentric lever (110), which are designed such that, in order to close the measuring cell (1), the hand-operated rotary wheel (104) is rotated about an axis perpendicular to the measuring cell plane E in order to bring a contact and clamping surface (106) of the hand-operated rotary wheel (104) into overlap with the second measuring cell assembly (72) and subsequently the contact and clamping surface (106) of the hand-operated rotary wheel (104) is clamped against the second measuring cell assembly (72) by means of the eccentric lever (110), and which are designed such that, in order to open the measuring cell (1), the eccentric lever (110) is released and subsequently the hand-operated rotary wheel (104) is rotated about the axis perpendicular to the measuring cell plane E until the contact and clamping surface (106) of the hand wheel (104) is rotated out of the overlap with the second measuring cell assembly (72) and releases the second measuring cell assembly (72),so that the second measuring cell assembly (72) can be folded away from the first measuring cell assembly (52). [23] Measuring cell (1) for a particle size measuring device, wherein the measuring cell (1) defines a sample volume (94) through which a dispersion can be passed in order to generate a diffraction pattern of the disperse phase contained in the dispersion, wherein the measuring cell (1) defines a measuring cell plane E and has the following: a supply line (32) to introduce the dispersion into the sample volume (94) and a discharge line (34) to discharge the dispersion from the sample volume (94), a first measuring cell assembly (52) with a measuring cell base body (42), a first window pane (46) arranged on the measuring cell base body (42), and a first sealing element in the form of a first sealing ring (48) for sealing the first window pane (46) to the measuring cell base body (42), a second measuring cell assembly (72) with a closure plate (62) for fastening to the measuring cell base body (42), a second window pane (66) which is arranged on the closure plate (62), and a second sealing element in the form of a second sealing ring (68) for sealing the second window pane (66) to the closure plate (62), a disc-shaped third sealing element (90), wherein the measuring cell (1) is fastened to an elongated base plate (12), wherein the base plate (12) forms part of a tongue or groove guide (14), and / or the measuring cell has a handle (28) for inserting the measuring cell (1) into a particle size measuring device. [24] Flow disc (90) prepared as a replacement or retrofit part for the measuring cell (1) according to one of the preceding claims, wherein the flow disc (90) has a thickness in the range between 1 mm and 10 mm, preferably in the range between 2 mm and 6 mm, wherein the flow disc (90) is made of a plate of elastomeric material with a thickness in the range between 1 mm and 10 mm, preferably in the range between 2 mm and 6 mm, and consists only of a piece of the plate of elastomeric material and has two flat sides (90a, 90b), wherein the flow disc (90) is punched or cut out of the plate of elastomeric material, wherein the flow disc (90) has a width in the range between 30 mm and 250 mm, preferably in the range between 50 mm and 150 mm, and a length in the range between 50 mm and 300 mm, preferably in the range between 80 mm and 200 mm; wherein the flow disc (90) defines a flow channel (92) with a width in the range between 5 mm and 100 mm, preferably in the range between 10 mm and 50 mm, and a length in the range between 30 mm and 250 mm, preferably in the range between 70 mm and 150 mm, and wherein the flow channel (92) is punched or cut out of the plate of elastomeric material and is circumferentially delimited by an inner narrow side (92a) in the flow disc (90). [25] Particle size measuring device with the measuring cell (1) according to one of claims 1-23.

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