WO2024074603A1

WO2024074603A1 - Sensor block for analyzing a liquid

Info

Publication number: WO2024074603A1
Application number: PCT/EP2023/077545
Authority: WO
Inventors: Manfred SCHNEEBERGER
Original assignee: Liquidtool Systems Ag
Priority date: 2022-10-06
Filing date: 2023-10-05
Publication date: 2024-04-11

Abstract

The invention relates to a measuring chamber (100) for use in an analysis device for analyzing a liquid and to an analysis device for analyzing a liquid, comprising a refractometer which is designed such that the soiling of the optical prism of the refractometer by components of the liquid is reduced and/or the process of cleaning the optical prism is simplified. The measuring chamber (100) comprises a floor (101), a wall (102), and a measuring window (103) which enclose a cavity (104), and a first channel (105) and a second channel (106) pass through the floor (101) and open into the cavity (104), wherein the first channel (105) and the second channel (106) do not contact each other and are arranged at a distance n to each other, and the first channel (105) leads diagonally into the cavity (104) and/or the floor (101) additionally comprises a recess (107) which is connected to the second channel (106) and does not pass through the floor (101).

Description

Sensor block for the analysis of a liquid

The invention relates to a measuring chamber for use in an analysis device for analyzing a liquid, and to an analysis device comprising a refractometer, wherein the measuring chamber and the analysis device are designed such that the contamination of the optical prism of the refractometer by components of the liquid is reduced and/or the cleaning of the optical prism is facilitated.

State of the art

The use of refractometers to analyse liquids has been known for decades. This takes advantage of the fact that the refractive index of a liquid is strongly dependent on the type of liquid or the type and amount of substances dissolved in the liquid. For example, the amount of sugar dissolved in water or the antifreeze content of a cooling liquid can be calculated by determining the refractive index of the respective liquid.

Even in industrial processes, it is necessary to control the exact properties of the liquids used in the process. For this purpose, a sample is either taken and the refractive index is measured, for example, with a hand-held refractometer, or the refractive index is determined directly using an integrated process refractometer.

One application area for process refractometers is monitoring the quality and composition of cooling lubricant emulsions. Cooling lubricant emulsions (CLU emulsions) are often used in the metalworking industry for metal cutting. CLU emulsions are often made from CLU concentrates by stirring them into water. CLU concentrates usually consist of an oil component, buffer component(s), emulsifier(s) and various additives. CLU concentrates are homogeneous liquid products with an oily consistency. When the cooling lubricant emulsion is in use, it is collected and discharged together with chips removed from the machining process. The cooling lubricant emulsion adheres to the discharged chips. Before the cooling lubricant emulsion can be used again, it must be freed of chips and other contaminants. In addition, the fine spraying of the cooling lubricant emulsion at the high pressures used in the machines causes water to evaporate. This causes an enrichment of the active components such as oils, additives and the like in the cooling lubricant emulsion.

To compensate for the discharged cooling lubricant emulsion and the water evaporation, cooling lubricant emulsion of low concentration must be regularly refilled, which is referred to as "refilling". The refill quantity and concentration can be calculated from the current actual and target concentration and the fill level difference in the tank. The current actual concentration can be determined in particular using a refractometer, since the refractive index of the cooling lubricant emulsion depends on the concentration of the active components in the liquid. The refractometer is preferably integrated in the form of a process refractometer directly into an apparatus that conveys and processes the cooling lubricant emulsion.

Conventional process refractometers can be used in equipment, e.g. for preparing cooling lubricant emulsions, and can be integrated into a process control system, but are complex and expensive compared to hand-held refractometers.

From KR 10 2018080835 A, a portable refractometer is known which comprises a prism with an inclined surface onto which a sample of a liquid can be applied. A lens system is arranged on the back of the prism, through which light is projected onto a CCD. The CCD is connected to an evaluation unit which determines the refractive index of the sample from a signal from the CCD.

From WO 2002/088663 an automatic hand-held refractometer is known in which a prism is illuminated by an LED and reflected light is directed to a CCD. The well-known hand-held refractometers are comparatively inexpensive and simple in construction, but cannot be integrated into liquid circuits or liquid tanks.

EP-A 0 337173 describes a device for detecting the alcohol content in fuel by determining the refractive index.

DE 29703860 U1 relates to an arrangement for determining transmitted light refraction in liquids and gases.

US 4,650,323 discloses a device for determining the sugar concentration in a sample liquid by means of light refraction.

US-A 2015/0029496 describes a method for measuring lime deposits by determining the refractive index.

EP 3 963310A1 discloses a device for analyzing a liquid, in particular a cooling lubricant emulsion, in which a refractometer is used to determine the refractive index and at least one further parameter of the cooling lubricant emulsion which is independent of the refractive index.

A common problem with known devices is that the measuring prisms (optical prisms) of the refractometers become dirty with components of the liquids being measured during continuous operation and therefore need to be cleaned regularly. In hand-held refractometers in which individual samples are measured (e.g. on a laboratory scale), this is done regularly by wiping the prism with a soft cloth soaked in a volatile solvent. However, cleaning the optical prisms in processes in which the refractive index is continuously monitored often presents greater difficulties.

Since a portion of the liquid to be analyzed is typically continuously passed through the measuring chamber adjacent to the measuring prism, it is often necessary to interrupt the process in which the liquid is used in order to remove the prism for cleaning purposes. However, interrupting industrial processes is not advisable for economic reasons.

An object of the present invention is to provide an analysis device comprising an optical prism for analyzing a liquid, wherein the analysis device is designed such that the contamination of the optical prism by components of the liquid is reduced and/or the cleaning of the optical prism is facilitated.

Disclosure of the invention

It was surprisingly found that with certain designs of the measuring chamber arranged on the optical prism of a refractometer, the contamination rate of the optical prism by components of the liquid can also be significantly reduced during long-term use, and easier cleaning of the optical prism is made possible.

It was also surprisingly found that optical prisms made of soda-lime glass (KNG) are significantly less susceptible to contamination by components of the liquid when continuously monitoring the refractive index of liquids, particularly cooling lubricant emulsions, than optical prisms made of borosilicate crown glass typically used in refractometers (e.g. N-BK7 from Schott). It was also found that optical prisms made of soda-lime glass are significantly easier to clean after continuous use if they are contaminated by components of the liquid than optical prisms made of borosilicate crown glass.

The subject matter of the invention is a measuring chamber for an analysis device for analyzing a liquid, comprising a base, a wall and a measuring window, wherein the base and the wall are made of a solid material and are connected to one another, and the measuring window represents an opening which is designed in such a way that an optical prism can be arranged adjacent to the measuring window in order to close it, wherein the base, the wall and the measuring window enclose a cavity, and wherein a first channel and a second channel penetrate the base and open into the cavity, wherein the first channel and the second channel do not touch one another and are arranged at a distance n from one another, and wherein the first channel is designed to guide a liquid into the cavity and the second channel is designed to guide a liquid out of the cavity, wherein the first channel leads obliquely to the cavity and/or the base additionally comprises a recess on the side of the cavity which is connected to the second channel and does not penetrate the base, wherein the recess does not touch the first channel and takes up part of the distance n. “Slanted” in this context means that the angle between the central axis of the first channel is not perpendicular to the ground, and not parallel to it.

The measuring chamber can be part of a support device for passing a liquid through the measuring chamber, comprising the measuring chamber, a supply line connected to the first channel of the measuring chamber, a discharge line connected to the second channel of the measuring chamber, and optionally a fastening means adapted for fastening and/or aligning an optical prism or a refractometer to the measuring window of the measuring chamber. Accordingly, the measuring chamber is intended for use in a refractometer.

The invention also relates to an analysis device for analyzing a liquid, comprising a measuring chamber with a measuring window and a refractometer arranged adjacent to the measuring chamber, wherein the refractometer comprises an optical prism which is arranged adjacent to the measuring window of the measuring chamber, and wherein the refractometer is set up to determine the refractive index of a liquid which flows through the measuring chamber and flows past the optical prism, wherein at least the part of the optical prism which is arranged at the measuring window, preferably the entire optical prism, consists of soda-lime glass (KNG), and/or the measuring chamber is the measuring chamber according to the invention.

Another subject of the invention is a method for determining the refractive index of a liquid, preferably a cooling lubricant emulsion, comprising the steps: a) passing the liquid through the measuring chamber of the analysis device according to the invention, past the optical prism of the refractometer, preferably by applying a negative pressure; b) measuring the refractive index of the liquid in the measuring chamber with the refractometer; c) optionally passing another liquid through the measuring chamber in order to clean the optical prism.

The use of soda-lime glass as a material in an optical prism of a refractometer, as well as the use of the inventive Measuring chamber to reduce contamination of the optical prism of the refractometer by components of the liquid and/or to facilitate cleaning of the optical prism are also the subject of the invention.

The analysis device according to the invention comprises a measuring chamber with a measuring window and a refractometer arranged adjacent to the measuring chamber. The refractometer comprises an optical prism, as well as a light source on one side of the optical prism, which is directed towards the optical prism, and an evaluation unit on the other side of the optical prism for detecting the light emerging from the optical prism.

The evaluation unit can, for example, comprise a light-sensitive array, e.g. a CCD detector, which transmits a signal to a computer when light hits it, where the refractive index is determined from the signal. The evaluation unit can also comprise a scale and a lens for projecting the light emitted by the optical prism onto the scale, so that a user can read the refractive index. The evaluation unit preferably comprises a light-sensitive array.

It is intended that the measuring chamber is designed to be flowed through by the liquid to be analyzed and that the refractometer is designed to determine the refractive index from the measurement signal. Preferably, the refractive index is continuously monitored.

The functioning of such refractometers is known in principle to the person skilled in the art and is described, for example, in EP-A 3 963310.

In the proposed analysis device, the refractometer is adjacent to a measuring chamber through which the liquid to be analyzed flows. For this purpose, the measuring chamber can be configured to be connected to liquid-carrying lines or the analysis device can have corresponding means to generate a liquid flow through the measuring chamber when the analysis device is at least partially immersed in the liquid to be analyzed. This allows the liquid to be analyzed to be brought into contact with the optical prism of the refractometer for a measurement. It has been found that low contamination rates of the optical prism are achieved if at least the part of the optical prism that is in direct contact with the liquid to be analyzed, and thus at least the part that is arranged at the measuring window of the measuring chamber, is made of soda-lime glass. This makes it possible to keep the contamination rate of the optical prism by components of the liquid to be analyzed low during operation of the analysis device, and easy cleaning of the optical prism is possible. Preferably, the entire optical prism is made of soda-lime glass.

It was also found that the lowest contamination rates are achieved when the optical prism has no coating on the soda-lime glass surface, at least in the area that is in direct contact with the liquid to be analyzed, i.e. in the area that is arranged at the measuring window of the measuring chamber. Preferably, the entire optical prism has no coatings. Although some such coatings (e.g. hydrophilic coatings) show positive results with other glasses, e.g. borosilicate crown glass, in terms of the contamination rate, such coatings prove to be disadvantageous in the case of soda-lime glass.

Another possibility to reduce the contamination rate of the optical prism is to suitably design the measuring chamber, as described above.

The measuring chamber may comprise the oblique embodiment of the first channel without a recess connected to the second channel, or comprise the recess connected to the second channel without the first channel leading obliquely to the cavity. Alternatively, the measuring chamber may comprise both the oblique embodiment of the first channel and the recess.

If the first channel leads obliquely to the cavity, it is preferably at an angle of between 20° and 70°, preferably between 30° and 65°, more preferably between 35° and 50° to the surface of the base. The second channel is preferably substantially perpendicular to the surface of the base. If the measuring chamber comprises a recess in the base, the first channel can also be substantially perpendicular to the surface of the base. “Substantially vertical” in this context means that the angle of the duct or the ground is between 88° and 92°.

The cross-sections of the channels can have any shape. For example, the channels can have a circular, oval or rectangular cross-section. In the case of rectangular cross-sections, rounded corners are preferred, as these reduce deposits of components of the flowing liquid and flow irregularities.

Circular cross-sections are particularly preferred because they can be produced particularly easily (e.g. by drilling, milling or cutting, in particular drilling). Depending on the throughput of the liquid to be analyzed, the channels can have cross-sectional areas of different sizes. In some embodiments, the first and second channels have cross-sectional areas of equal size, for example in the range from 5 to 30 mm ² , preferably 8 to 25 mm ² , more preferably 10 to 15 mm ² . In some embodiments, the channels have a diameter of 2 to 10 mm, preferably 2.5 to 8 mm, more preferably 3 to 5 mm, more preferably 3.5 to 4.5 mm at the narrowest point, and an aspect ratio (perpendicular to the central axis of the respective channel) of preferably 1:3 to 1:1, more preferably 1:2 to 1:1, more preferably 1:1.5 to 1:1.

The wall is substantially perpendicular to the floor. The cavity, the cross-section of which is defined by the shape of the wall, can also have different cross-sections. For example, the cavity can have a circular, oval or rectangular cross-section. It is also preferred that the cavity has rounded corners. The cavity is particularly preferably designed such that the edge of the cavity in the flow direction of the liquid is flush with the edge of the first channel and the second channel, or extends slightly beyond them, ie the length of the cavity preferably corresponds to the sum of the diameter of the first channel and the second channel and the distance n between the channels in the flow direction, or is at most 10% longer than this sum. For example, the cavity in the flow direction can have a diameter of 6 to 30 mm, preferably 7 to 20 mm, more preferably 8 to 15 mm, more preferably 10 to 12 mm. “In the direction of flow” and “perpendicular to the direction of flow” when describing the dimensions in the measuring chamber refers to the flow direction lateral to the floor and the measuring window (ie not the flow direction through the channels).

Perpendicular to the flow direction of the liquid, the cavity at its widest point preferably has a width that corresponds at least to the diameter of the wider of the two channels perpendicular to the flow direction, and at most twice, more preferably at most 1.8 times, more preferably at most 1.5 times the diameter of the wider of the two channels perpendicular to the flow direction. Preferably, the first channel and the second channel have the same diameter perpendicular to the flow direction. Particularly preferably, the first channel and the second channel have the same cross-section.

The height of the cavity, which is defined by the distance between the bottom and the measuring window, and thus also the height of the wall, is preferably selected at least such that an unhindered flow of the flowing liquid through the cavity remains possible, and at most selected such that a constant exchange of the liquid can take place at the measuring window. The height of the cavity is preferably at least 0.5 mm, more preferably at least 1 mm. Furthermore, the height of the cavity is preferably selected at most such that the product of the height and the width of the cavity at the widest point perpendicular to the flow direction corresponds to the cross-sectional area of the first channel. For example, the height of the cavity can be 1 to 5 mm, preferably 1.5 to 4.5 mm, more preferably 2 to 4 mm. Accordingly, the wall is preferably essentially perpendicular to the measuring window (i.e. the bottom and measuring window are essentially parallel).

Distance n refers to the shortest distance between the edges of the first channel and the second channel that are closest to each other. The distance n between the first channel and the second channel is selected so that the channels do not touch each other. Preferably, the distance n is at least 0.5 mm, more preferably at least 1 mm. Furthermore, the distance n preferably corresponds at most to the diameter of the wider of the two channels and in the flow direction of the liquid. For example, the distance n can be 20 to 100%, preferably 30 to 90%, more preferably 40 to 80% of the diameter of the wider of the two channels in the flow direction of the liquid. For example, the distance n can be in the range of 1 to 10 mm, preferably in the Range of 1.5 to 8 mm, more preferably in the range of 2 to 6 mm, more preferably in the range of 2.5 to 4.5 mm.

The recess, if present, preferably occupies 50 to 99%, preferably 60 to 95%, more preferably 70 to 90% of the distance n in the flow direction of the liquid.

The width of the recess preferably corresponds to 20 to 80%, more preferably 30 to 70%, more preferably 45 to 55% of the width of the second channel perpendicular to the flow direction of the liquid. For example, the width of the recess perpendicular to the flow direction of the liquid can be 1 to 6 mm, preferably 1.5 to 3 mm. The depth of the recess (distance from the base of the cavity to the deepest point of the recess) is preferably at least 0.5 mm, more preferably at least 1 mm, more preferably 2 to 6 mm, more preferably 3 to 5 mm. Furthermore, the depth of the recess is chosen at most such that it does not form a continuous channel through the base. The base in the area around the recess is preferably at least 0.5 mm thicker than the depth of the recess, i.e. the remaining thickness of the base below the recess is preferably at least 0.5 mm. In some embodiments, the base in the area around the recess has a thickness of at least 1.5 mm, preferably at least 3 mm, more preferably 4 to 30 mm, more preferably 5 to 20 mm.

The measuring chamber of the analysis device reduces the contamination rate of the optical prism in continuous operation, regardless of the material of the optical prism of the refractometer, and facilitates its subsequent cleaning. It can therefore also be used in analysis devices in which the optical prism is not made of soda-lime glass. Therefore, the measuring chamber as such, as described above, is the subject of the invention. However, it has been found that particularly low contamination rates are achieved when soda-lime glass and the measuring chamber according to the invention are used in combination.

The measuring chamber according to the invention can, for example, be present as part of a carrying device for passing a liquid through the measuring chamber according to the invention. Therefore, a corresponding carrying device is also the subject of the present invention. The carrying device according to the invention comprises the measuring chamber, a supply line connected to the first channel of the measuring chamber, a discharge line connected to the second channel of the measuring chamber, and can further optionally comprise one or more fastening means adapted for fastening and/or aligning an optical prism or a refractometer to the measuring window of the measuring chamber.

Furthermore, this carrying device can have further features, such as a connection for a pump for conveying a liquid through the carrying device, for example a pump for generating a negative pressure on the side of the discharge line or a pump for generating an overpressure on the side of the supply line; connections for pressure valves on the side of the supply line or the discharge line to compensate for the negative pressure or overpressure if necessary (e.g. for cleaning purposes); connections for peripheral devices which, for example, examine certain properties (such as temperature, conductivity, pH value, etc.) of the liquid flowing through; fastenings to align and/or attach pumps or other peripheral devices to the carrying device; viewing windows to enable the user to check the liquid by inspection.

The optional fastening means can be any fastening means that enable alignment and/or fastening of a refractometer to the carrying device. For example, the fastening means can be holes through which the carrying device is screwed to a refractometer using screws. This can form a particularly strong but reversible connection between the carrying device and the refractometer. If the carrying device does not comprise fastening means, the refractometer can be attached to the carrying device using external fastening means such as clamps.

Preferably, the liquid is conveyed through the carrying device by means of a negative pressure on the side of the discharge line. It has been found that by using a negative pressure on the side of the discharge line, the contamination rate can be reduced compared to using a positive pressure on the side of the supply line. At the same time, the use of a negative pressure on the side of the discharge line enables the analysis device according to the invention, in which the carrying device according to the invention is installed, to can be immersed directly in the sample to be analyzed with the supply line without the need for additional connections. Alternatively, the supply line can be connected to a liquid inlet, for example a hose.

Therefore, the discharge line is preferably designed such that it can be connected to a suction device, preferably a pump.

Preferably, the carrying device consists of a block of material from which material has been removed in order to form the features of the measuring chamber, in particular the cavity, the first channel and the second channel and optionally the recess, as well as the other features of the carrying device, in particular the supply line, the discharge line and optionally the fastening means. This has the advantage, among others, that the risk of loss of liquid during transport through the carrying device is reduced, since there are no seams or adhesive points in the block of material that could become leaky.

Preferably, the material is removed from the block of material by milling, cutting and/or drilling to form the features. Particularly preferably, the material is removed by drilling, as this allows the support device to be manufactured with particularly little effort.

The material of the material block and thus of this support device can be any material that can be used for the passage of liquids, in particular cooling lubricant emulsions. The material block preferably consists of a corrosion-resistant metal, particularly preferably stainless steel.

The analysis device according to the invention preferably comprises the carrying device according to the invention for passing a liquid through the measuring chamber and past the optical prism of the refractometer.

The analysis device can be designed to be at least partially immersed in the liquid to be analyzed. In this case, the analysis device is preferably constructed such that the carrying device according to the invention comes into contact with the liquid via the supply line. Preferably, the analysis device also comprises a pump to generate a liquid flow through the measuring chamber, in particular by generating a negative pressure on the side of the discharge line. The pump can additionally be designed to convey the liquid from the discharge line back into the container with the liquid to be analyzed.

If the analysis device is designed to be at least partially immersed in the liquid to be analyzed, floating bodies can be provided, for example, to generate a defined buoyancy in the liquid.

This can, for example, ensure that the analysis device floats on the surface of the liquid and is easy to reach, for example for cleaning or maintenance. In this embodiment, the analysis device can simply be inserted into a container or tank in which the liquid to be analyzed is stored. The analysis device floats freely in the container, so that no anchor points or fastenings are required. Nevertheless, it is of course possible to provide corresponding fastening means on the analysis device.

In order to protect the analysis device from foreign bodies and/or particles which may be contained in the liquid to be analyzed, the analysis device may comprise a filter. If the analysis device is designed to float in the liquid to be analyzed or to be immersed in the liquid to be analyzed, the analysis device may comprise a filter basket which, for example, surrounds the pump and the refractometer of the analysis device and only allows liquid to pass through a filter.

The invention further relates to a method for determining the refractive index of a liquid, preferably a coolant-lubricant emulsion, comprising the steps: a) passing the liquid through the measuring chamber of the analysis device according to the invention, past the optical prism of the refractometer, preferably by applying a negative pressure; b) measuring the refractive index of the liquid in the measuring chamber with the refractometer. The liquid is preferably passed through the first channel into the cavity of the measuring chamber and through the second channel out of the cavity by applying a negative pressure on the side of the second channel. Additionally, the method may include a step of passing another liquid through the measuring chamber to clean the optical prism.

This step can be carried out, for example, with water, optionally containing additives for cleaning, and/or with alcohols, preferably with water without additives or alcohols, more preferably with demineralized water (DE water) or ethanol, more preferably with ethanol.

The method can be used, for example, to determine the quality of a cooling lubricant emulsion. The idea is to introduce a cooling lubricant emulsion as the liquid to be analyzed into the described analysis device, to determine the refractive index of the cooling lubricant emulsion, to determine the concentration of the cooling lubricant emulsion from the refractive index of the cooling lubricant emulsion and, optionally, to examine other quality characteristics of the cooling lubricant emulsion using other connected peripheral devices.

As described above, the use of soda-lime glass as the material of the optical prism of the refractometer is particularly advantageous. Therefore, the use of soda-lime glass as the material in an optical prism of a refractometer when determining the refractive index of a liquid, preferably a cooling lubricant emulsion, in order to reduce contamination of the optical prism by components of the liquid and/or to facilitate cleaning of the optical prism, is also the subject of the invention.

The invention also relates to the use of the measuring chamber according to the invention alone or of a measuring chamber according to the invention in determining the refractive index of a liquid, preferably a cooling lubricant emulsion, by means of a refractometer arranged adjacent to the measuring chamber and comprising an optical prism in order to reduce contamination of the optical prism by components of the liquid and/or to facilitate cleaning of the optical prism. Short description of the characters

Embodiments of the invention are shown in the drawings and explained in more detail in the following description. They show:

FIG. 1 shows a simplified schematic representation of a measuring chamber according to a first embodiment;

FIG. 2 is a simplified schematic representation of the bottom of the

Measuring chamber from FIG. 1 ;

FIG. 3 is a simplified schematic representation of the bottom of a

Measuring chamber according to a second embodiment;

FIG. 4 is a simplified schematic representation of the bottom of a

Measuring chamber according to a third embodiment;

FIG. 5 is a simplified schematic representation of the measuring chamber of FIG. 1, in which the measuring window is closed by an optical prism;

FIG. 6 is a simplified schematic representation of the analysis device according to the invention comprising the measuring chamber from FIG. 1 with an adjacently arranged refractometer;

FIG. 7a shows a detailed schematic representation (cross section) of a carrying device according to the invention according to a first preferred embodiment, comprising a measuring chamber according to a fourth preferred embodiment;

FIG. 7b Oblique view of the carrying device according to FIG. 7a;

FIG. 8a shows a detailed schematic representation (cross section) of a carrying device according to the invention according to a second preferred embodiment, comprising a measuring chamber according to a fifth preferred embodiment. FIG. 8b Oblique view of the carrying device according to FIG. 8a;

FIG. 9a is a schematic representation of a section of a measuring chamber not according to the invention;

FIG. 9b is a schematic representation of a carrying device for passing a liquid through the non-inventive measuring chamber according to FIG. 9a;

In the present description of the embodiments of the invention, identical or similar components are designated by identical reference numerals, whereby a repeated description of these is omitted in individual cases. The figures only represent the subject matter of the invention schematically.

FIG. 1 shows a first embodiment of a measuring chamber 100 according to the invention in a simplified schematic view. The measuring chamber 100 comprises a base 101, a wall 102 and a measuring window 103, wherein the base 101 and the wall 102 are connected to one another and the measuring window 103 represents an opening. The base 101, the wall 102 and the measuring window 103 enclose a cavity 104. A first channel 105 and a second channel 106 penetrate the base 101 and open into the cavity 104. The first channel 105 and the second channel 106 do not touch one another and are arranged at a distance n from one another.

In this first embodiment, the first channel 105 leads obliquely to the cavity 104, and the base 101 additionally comprises a recess 107 which does not penetrate the base 101 and does not touch the first channel 105, but is connected to the second channel 106. Furthermore, in this embodiment, the cavity 104 has an oval-shaped cross-section, and the channels 105 and 106 are cylindrical bores and have an equal cross-sectional area. The arrow 10 indicates the flow direction of the liquid to be analyzed.

FIG. 2 shows the bottom 101 of the first embodiment of the measuring chamber 100 for clarity, with the outline of the wall 102 being drawn in without showing the wall 102 itself. The arrow 10 indicates the flow direction of the liquid to be analyzed. FIG. 3 shows the bottom 101 of a second embodiment of the measuring chamber 100, with the outline of the wall 102 drawn in, similar to FIG. 2. The second embodiment differs from the first embodiment in that the first channel 105 leads perpendicularly to the cavity 104. The arrow 10 indicates the flow direction of the liquid to be analyzed.

FIG. 4 shows the bottom 101 of a third measuring chamber 100, with the outline of the wall 102 drawn in, similar to FIG. 2. The third embodiment differs from the first embodiment in that the bottom does not include a recess. In addition, the wall 102 has a rectangular outline, and the first channel 105 and the second channel 106 have a rectangular cross-sectional area. The arrow 10 indicates the flow direction of the liquid to be analyzed.

FIG. 5 shows the positioning of an optical prism 302 on the measuring window 103 of the measuring chamber according to the first embodiment.

FIG. 6 shows the arrangement according to FIG. 5, wherein in addition to the measuring chamber 100 and the prism 302, a light source 303 and an evaluation unit 304 of a refractometer 301 are also shown. The combination of the refractometer 301 and the measuring chamber 100 forms an embodiment of the analysis device 300 according to the invention. An approximate beam path of the light emitted by the light source 303 is shown.

FIG. 7a shows the cross section of a carrying device 200 according to the invention according to a first preferred embodiment, comprising a measuring camera 100 according to a fourth preferred embodiment. FIG. 7b shows an oblique view of the carrying device 200 according to FIG. 7a. The arrow 10 indicates the flow direction of the liquid to be analyzed.

The support device 200 comprises a measuring chamber 100 in which the outline of the wall 102 and thus the cross section of the cavity 104 has an oval shape with flattened sides, and the first channel 105 and the second channel 106 have a round cross section. Furthermore, the bottom 101 of the measuring chamber 100 comprises a recess 107. The support device 200 also comprises a supply line 201 connected to the first channel 105 and a discharge line 202 connected to the second channel 106, as well as a plurality of fastening means 203 in the form of profiles and holes, by means of which a refractometer with complementary fastening means can be aligned and fastened to the support device 200.

The supply line also has a further connection 204, through which, for example, a temperature sensor can be passed in order to measure the temperature of the liquid flowing through in order to determine the refractive index. The support device (200) can be made, for example, from a stainless steel block by removing material from the block by drilling and milling (profiles). The pointed ends of the supply line 201 and the discharge line 202 shown are due to the shape of the drill used. Alternative materials for the support device can be, for example, plastics that are insoluble in the cooling lubricant emulsion used, or corrosion-resistant metals and alloys.

FIG. 8a shows the cross section of a carrying device 200 according to the invention according to a second preferred embodiment, comprising a measuring chamber 100 according to a fifth preferred embodiment. FIG. 8b shows an oblique view of the carrying device 200 according to FIG. 8a. The arrow 10 indicates the flow direction of the liquid to be analyzed.

The support device 200 comprises a measuring chamber 100 in which the outline of the wall 102 and thus the cross section of the cavity 104 has a rectangular shape with rounded corners, and the first channel 105 and the second channel 106 have a rectangular cross section with rounded corners. Furthermore, the first channel 105 leads obliquely to the cavity 104 (not shown).

This support device 200 also comprises a supply line 201 connected to the first channel 105 and a discharge line 202 connected to the second channel 106, as well as a plurality of fastening means 203 in the form of profiles and holes, by means of which a refractometer with complementary fastening means can be aligned and fastened to the support device 200. The supply line also has a further connection 204 through which, for example, a temperature sensor can be passed in order to measure the temperature of the liquid flowing through in order to determine the refractive index. The support device can be made from a stainless steel block by removing material from the block by drilling, cutting (laser) and milling. The pointed ends of the supply line 201 and the discharge line 202 shown are due to the shape of the drill used.

The fastening means 203, the measuring chamber 100 and the connector 204 can be arranged at the same distances as the corresponding features of the support device 200 according to FIGS. 7a and 7b, and the support device 200 according to FIGS. 8a and 8b can have the same dimensions as the support device 200 according to FIGS. 7a and 7b, so that both can be connected to the same refractometers and can be interchanged if necessary.

FIG. 9a shows a section of a non-inventive measuring chamber 100 and FIG. 9b shows a section of a support device 200 for passing a liquid through it. The non-inventive support device 200 differs from the inventive support device 200 according to FIGS. 7a and 7b essentially in that no recess 107 is provided in the base 101 of the measuring chamber. The arrow 10 indicates the flow direction of the liquid to be analyzed.

The examples, figures and claims illustrate the invention.

Examples

The degree of contamination of the optical prisms was examined by optically examining the prisms in daylight. For this purpose, the prisms were removed from the refractometer using tweezers. The contamination was classified into three categories:

Clean: No cloudiness, deposits, or streaks visible on the surface in contact with the liquid; Slightly contaminated: streaks visible, maximum 20% of the surface contaminated with white opacities;

Contaminated: Streaks strongly visible, more than 20% of the surface contaminated with white opacities.

A series of tests was carried out in which 9 different commercially available cooling-lubricating emulsions were conveyed through industrial machines over a period of approximately 2.5 months, and in which sensor blocks according to the invention (analysis devices) and sensor blocks not according to the invention were used to measure the refractive index. Measurements of the refractive index were carried out hourly, with the sensor blocks not being cleaned between measurements. During each measurement, a sensor block was flowed through with cooling-lubricating emulsion for 22 seconds by applying a negative pressure. After the entire test period had elapsed, the conveying was stopped, the prisms were removed from the refractometers and their degree of contamination was assessed.

For cleaning, sensor blocks according to the invention and sensor blocks not according to the invention were used as described above to measure the refractive index. After the tests were completed, the sensor block was emptied but not cleaned further and taken out of service for 2 weeks so that the remains of the cooling-lubricating emulsion could dry on the optical prism. After drying, all prisms could be classified as contaminated. Cleaning was carried out by rinsing the prism with ethanol or with the respective cooling-lubricating emulsion under increased pressure.

The cooling-lubricating emulsions used were:

Vasco 6000 (Blaser Swisslube AG);

Rinatol P90 (Ess + Müller AG);

B-Cool MC660 (Blaser Swisslube AG);

Zubora 65H Ultra (Zeller+Gmelin GmbH & Co. KG);

Zubora 67H Extra (Zeller+Gmelin GmbH & Co. KG);

B-Cool MC610 (Blaser Swisslube AG);

Zubora 67H Ultra (Zeller+Gmelin GmbH & Co. KG);

Swisscool 3500 (Motorex AG); Vasco 7000 (Blaser Swisslube AG).

The sensor blocks used included support devices for passing a liquid through the measuring chamber, as shown in FIGS. 7a and 7b, as shown in FIGS. 8a and 8b, and for comparison purposes support devices as shown in FIG. 9b. The prism material used was soda-lime glass (uncoated) and N-BK7 borosilicate crown glass (Schott AG) coated with a standard glass coating (Glasskote SC 100; Total Specialties USA Inc.). Borosilicate crown glass without a coating showed contamination within a few days and was therefore not used for the tests.

Comparison example 1

150 sensor blocks comprising a refractometer containing an optical prism made of N-BK7 borosilicate crown glass, coated with Glasskote SC100, and further comprising the non-inventive carrying device, as shown in FIG. 9b, were operated with the cooling-lubricating emulsions listed above. After completion of the test series, 57 prisms showed severe contamination and were therefore classified as contaminated. The remaining prisms can be classified as slightly contaminated. The ratio of clean, slightly contaminated and contaminated prisms corresponds to 0% : 62% : 38%.

Cleaning after the cooling-lubricating emulsion has dried, as described above, with ethanol or with cooling-lubricating emulsion (increased pressure) is not successful and must therefore be carried out with cleaning agents.

Example 1

14 sensor blocks comprising a refractometer containing an optical prism made of N-BK7 borosilicate crown glass, coated with Glasskote SC100, and further comprising the carrying device according to the invention, as shown in FIGS. 7 and 7a, were operated with the cooling lubricant emulsions listed above. After completion of the test series, 2 prisms showed severe contamination and were therefore classified as contaminated. 1 prism could be classified as slightly contaminated. The remaining 11 prisms remained clean. The ratio of clean, slightly contaminated and contaminated prisms is 79% : 7% : 14%.

Cleaning after the cooling lubricant emulsion has dried, as described above, is successful with ethanol. A cleaning agent is not required.

Example 2

14 sensor blocks comprising a refractometer containing an optical prism made of N-BK7 borosilicate crown glass, coated with Glasskote SC100, and further comprising the carrying device according to the invention, as shown in FIGS. 8 and 8a, were operated with the cooling-lubricating emulsions listed above. After completion of the test series, 2 prisms showed severe contamination and were therefore classified as contaminated. 1 prism could be classified as slightly contaminated. The remaining 11 prisms remained clean. The ratio of clean, slightly contaminated and contaminated prisms also corresponds to 79% : 7% : 14% in this setup.

Example 3

15 sensor blocks comprising a refractometer containing an optical prism made of uncoated soda-lime glass, and further comprising the carrying device according to the invention, as shown in FIGS. 7 and 7a, were operated with the cooling-lubricating emulsions listed above. After completion of the test series, none of the prisms showed severe contamination. Even slight contamination could not be detected in any of the prisms. The ratio of clean, slightly contaminated and contaminated prisms corresponds to 100% : 0% : 0%.

Cleaning after the cooling lubricant emulsion has dried, as described above, is successful with ethanol, but can also be done with the cooling lubricant emulsion used if it is pumped through the sensor block under increased pressure. A cleaning agent is not required. Example 4

15 sensor blocks comprising a refractometer containing an optical prism made of uncoated soda-lime glass, and further comprising the carrying device according to the invention, as shown in FIGS. 8a and 8b, were operated with the cooling-lubricating emulsions listed above. After completion of the test series, none of the prisms showed severe contamination. Light contamination was found in one prism. The ratio of clean, slightly contaminated and contaminated prisms corresponds to 93% : 7% : 0%.

Cleaning after the cooling lubricant emulsion has dried, as described above, is successful with ethanol, but can also be done with the cooling lubricant emulsion used if it is pumped through the sensor block under increased pressure. A cleaning agent is not required.

List of reference symbols

100 measuring chamber

101 Floor

102 Wall

103 measuring windows

104 Cavity

105 first channel

106 second channel

107 Recess

200 Carrying device

201 Supply line

202 Discharge line

203, Fasteners

204 additional connections;

300 Analysis device

301 Refractometer

302 optical prism

303 Light source

304 Evaluation unit

Claims

Patent claims

1. Measuring chamber (100) for an analysis device for analyzing a liquid, comprising a base (101), a wall (102) and a measuring window (103), wherein the base (101) and the wall (102) are connected to one another, and the measuring window (103) represents an opening which is designed such that an optical prism can be arranged adjacent to the measuring window (103) in order to close it, wherein the base (101), the wall (102) and the measuring window (103) enclose a cavity (104), and wherein a first channel (105) and a second channel (106) penetrate the base (101) and open into the cavity (104), wherein the first channel (105) and the second channel (106) do not touch one another and are arranged at a distance n from one another, and wherein the first channel (105) is designed to introduce a liquid into the cavity (104) to conduct, and the second channel (106) is arranged to conduct a liquid out of the cavity (104), characterized in that the first channel (105) leads obliquely to the cavity (104) and/or the base (101) additionally comprises a recess (107) on the side of the cavity (104) which is connected to the second channel (106) and does not penetrate the base (101), wherein the recess (107) does not touch the first channel (105) and occupies part of the distance n, preferably 50 to 99% of the distance n, and preferably has a width which corresponds to 30 to 80% of the width of the second channel (106).

2. Measuring chamber (100) according to claim 1, wherein the first channel (105) is at an angle between 20° and 70° to the surface of the bottom (101) and the second channel is substantially perpendicular to the surface of the bottom.

3. Measuring chamber (100) according to claim 1, wherein the first channel (105) is substantially perpendicular to the surface of the bottom (101), the second Channel (105) is substantially perpendicular to the surface of the base (101), and the base (101) comprises the recess (107). Carrying device (200) for passing a liquid through a measuring chamber, comprising the measuring chamber (100) according to one of claims 1 to 3, a supply line (201) connected to the first channel (105) of the measuring chamber (100), a discharge line (202) connected to the second channel (106) of the measuring chamber (100), and optionally one or more fastening means (203) designed for fastening and/or aligning an optical prism or a refractometer to the measuring window (103) of the measuring chamber (100). Carrying device (200) according to claim 4, wherein the discharge line (202) is designed such that it can be connected to a suction device, preferably a pump. Support device (200) according to claim 4 or 5, wherein the support device consists of a block of material from which material has been removed, preferably by milling, cutting and/or drilling, more preferably by drilling, to form the features of the measuring chamber (100) and the support device (200), in particular the cavity (104), the first channel (105), the second channel (106), the supply line (201), the discharge line (202), and optionally the recess (107) and/or the fastening means (203). Analysis device (300) for analyzing a liquid, comprising a measuring chamber (100) with a measuring window (103) and a refractometer (301) arranged adjacent to the measuring chamber, wherein the refractometer (301) comprises an optical prism (302) which is arranged adjacent to the measuring window (103) of the measuring chamber (100), and wherein the refractometer (301) is designed to determine the refractive index of a liquid which flows through the measuring chamber (100) and flows past the optical prism (302), characterized in that at least the part of the optical prism (302) which is arranged at the measuring window (103), preferably the entire optical prism (302), consists of soda-lime glass, and/or wherein the Measuring chamber (100) is a measuring chamber (100) according to one of claims 1 to 3. Analysis device (300) according to claim 7, wherein the measuring chamber (100) is a measuring chamber (100) according to one of claims 1 to 3 and the optical prism (302) consists of soda-lime glass. Analysis device (300) according to claim 7 or 8, wherein at least the part of the optical prism (302) arranged on the measuring window (103), preferably the entire optical prism (302), has no coating. Analysis device (300) according to one of claims 7 to 9, wherein the analysis device (300) comprises the carrying device (200) according to one of claims 4 to 6. Analysis device (300) according to one of claims 7 to 10, further comprising a suction device which is configured to convey a liquid through the measuring chamber by negative pressure. Method for determining a refractive index of a liquid, preferably a cooling lubricant emulsion, comprising the steps: a) passing the liquid through the measuring chamber (100) of the analysis device (300) according to one of claims 7 to 11, past the optical prism (302) of the refractometer (301), preferably by applying a negative pressure; b) measuring the refractive index of the liquid in the measuring chamber (100) with the refractometer (301); c) optionally passing another liquid through the measuring chamber (100) in order to clean the optical prism (302). Method according to claim 12, wherein the analysis device (300) comprises the measuring chamber (100) according to one of claims 1 to 3, and wherein the liquid is guided through the first channel (105) into the cavity (104) of the measuring chamber (100) and through the second channel (106) out of the cavity (104) by applying a negative pressure on the side of the second channel (106). Use of soda-lime glass as a material in an optical prism (302) of a refractometer (301) when determining the refractive index of a liquid, preferably a cooling-lubricating emulsion, in order to reduce contamination of the optical prism (302) by components of the liquid and/or to facilitate cleaning of the optical prism (302). Use of a measuring chamber (100) according to one of claims 1 to 3, or a carrying device (200) according to one of claims 4 to 6, when determining the refractive index of a liquid, preferably a cooling-lubricating emulsion, by means of a refractometer (301) arranged adjacent to the measuring chamber (100) and comprising an optical prism (302), in order to reduce contamination of the optical prism (302) by components of the liquid and/or to facilitate cleaning of the optical prism (302).