EP0260252A1

EP0260252A1 - A device for following the product concentration of products having milk as raw material or fluids containing said products

Info

Publication number: EP0260252A1
Application number: EP85902544A
Authority: EP
Inventors: Harri Kopola; Risto MYLLYLÄ
Original assignee: HT-AUTOMAATIO Oy
Current assignee: HT-AUTOMAATIO Oy
Priority date: 1983-10-28
Filing date: 1985-04-26
Publication date: 1988-03-23
Also published as: FI70087C; FI70087B; FI833955A; WO1986006483A1; DK624886D0; DK624886A; FI833955A0

Abstract

Un dispositif surveille la concentration de produits à base de lait comme matière première et de fluides contenant ces produits par un procédé de réflexion. Le dispositif convient particulièrement pour surveiller la concentration de lait dans le courant de produit ou dans l'eau de lavage de tuyauteries de produits laitiers, spécialement pour fournir les informations d'interface requises pour la régulation du processus. Le dispositif comprend un élément détecteur (3) couplé à une partie (2) de transmission de lumière d'un tuyau (1) contenant ce produit. L'élément détecteur comprend un émetteur (4) et un récepteur (5) de lumière, et une partie électronique (6, 7) de commande de la fonction de l'émetteur de lumière (4) et de traitement des signaux reçus par le récepteur de lumière (5). L'émetteur de lumière (4) est placé avec avantage de façon à former un angle d'approx. 30-50o, de préférence de 40-45o par rapport au récepteur de lumière (5).A device monitors the concentration of raw milk products and fluids containing these products by a reflective process. The device is particularly suitable for monitoring the concentration of milk in the product stream or in dairy pipe wash water, especially to provide the interface information required for process control. The device comprises a sensor element (3) coupled to a light transmission part (2) of a pipe (1) containing this product. The detector element comprises a light emitter (4) and a light receiver (5), and an electronic part (6, 7) for controlling the function of the light emitter (4) and for processing the signals received by the light receiver (5). The light emitter (4) is advantageously placed so as to form an angle of approx. 30-50o, preferably 40-45o relative to the light receiver (5).

Description

A device for following the product concentration of products having milk as raw material or fluids containing said products

This invention relates to a device for following the product concentration of products having milk as raw material or fluids containing said products by means of a reflection method. The invention is particularly adapted for following the milk concentration in the product flow or washing water of dairy pipe line systems and especially to give the required interface information for the process control.

It is known to measure milk concentration in the washing water of dairy pipe line systems as an optical transmission measurement. Thereby the measuring is based on the absorption of light between an emitter and a receiver, which depends on the turbidity of the product. A mixture of milk and water is, however, so turbid and the absorption of light, consequently, so great that it is practically possible to measure milk concentrations of 0...1...2 % only by means of said transmission method.

In the identification of the quality of the fluid, also a capacitive measuring method can be used. Further, the quality or concentration of a product can be determined on the basis of the variation in the conductivity of the product. In these methods, a detector immersed in the product is usually used, which can "cause problems particularly in connection with food stuff products and conditions varying widely at different stages of the process.

So the object of the present invention is to develope a device operating by means of a reflection method, by means of which device product concentration and variations thereof in particular can be followed accurately and within a wide range of variation without the device being in any contact at all with the product. This has been carried out by means of a device according to the invention, which is characterized in that the device comprises a detector element intended to be fitted in connection with a light transmitting portion of a pipe containing said product, said detector element comprising a light emitter and a light receiver, and an electronics portion for controlling the function of the light emitter and for treating signals received by the light receiver.

The device according to the invention can be attached to form a part of a process pipe line system as a unit of its own similarly to the other measuring devices mentioned above, but, on account of the measuring method thereof and the structure of its detector element, it is also adapted to be attached in connection with the sight glass of already existing process pipe line systems without changing the structure of the system in any way.

In the following the structure and the operation of the device according to the invention will be described in more detail with reference to the attached drawings, wherein

Figure 1 is a cross-section.of a device according to the invention, when fitted as a unit of its own, Figure 2 is a section of the device of Figure 1 along the line II-II in Figure 1, and

Figure 3 is a block diagram of the function of an electronic portion of the device.

Figures 1 and 2 show cross-sections of a measuring device according to the invention when fitted as a unitof its own to form a part of a process pipe line system. The measuring unit is formed by a process pipe portion 1 comprising a T-branch, in which the measuring device itself is fitted. A glass tube 2 of a round cross-section is positioned inside said pipe portion 1, the product to be analysed flowing in said glass tube. A detector element 3 of the measuring device is positioned against the surface of the glass tube 2 inside the T-branch of the pipe portion 1, said detector element comprising a light emitter 4, for which purpose a diode emitting infrared light is particularly suitable, and a light receiver 5, for which purpose a conventional photodiode can be used. Printed circuit boards 6 and 7 are positioned above the detector 3 in the T-branch, in which boards electronics required for controlling the light emitter 4 and for treating signals received by the light receiver 5 is gathered, the function of said electronics being described more closely in connection with Figure 3. A spring element 10 is fitted above said printed circuit boards 6 and 7, which element presses the detector element 3 tightly against the glass tube 2 when the open end of the T-branch is closed by means of a cover 8. Power supply to the measuring device and the outside communication take place by means of a cable 9.

The most essential portion of the measuring device is positioned in the detector 3. It is manufactured of a non-transparent PVC-plastic as a disc-like element, the lower surface of which is provided with a through-like shape in a manner corresponding to the arching of the glass tube 2. So the light emitter 4 and the light receiver 5 are brought tightly against the surface of the glass tube 2. It is essential with respect to the function of the detector element that the light emitter 4 is positioned at an angle of approx. 30-50 , preferably 40-45 , with respect to the light receiver 5 and as near it as possible, but in such a manner, however, that a wall is left between the emitter and the receiver, which wall prevents a direct light communication therebetween. By arranging the light emitter and the light receiver in this way, most of the reflections caused by the glass tube 2 are avoided, especially when the light receiver is perpendicular to the surface of the glass tube 2 and the light receiver consequently receives a signal which is reflected mainly from the product. If desired, it^'is also possible,as is generally known, to further reduce the interfacial reflections by positioning a suitable polarizer in front of the light source. The reason for the emitter and the receiver being positioned as near each other as possible is that the product to be measured, i.e. milk products, has a great turbidity, wherefore the depth of penetration of the light signal from the emitter is usually below 5 mm. By means of a measuring device according to the invention, a resolution of at least approx. 1 % is obtained when the milk concentration of the product to be measured is below 50 %, and a resolution of approx. 5 % when the milk concentration of the product exceeds 80 %.

Figure 3 illustrates schematically the function of the measuring device according to the invention. When a measurement is carried out, a light pulse is emitted by the light emitter 4 and he radiation caused by said pulse through reflection from the product behind the glass tube 2 is observed by means of the light receiver 6. The pulsing of the emitter 4 and the synchronous detection 12 of the signal received are controlled by synchronizing electronics 11. Said synchronizing electronics also controls sample taking from the received background light (when the emitter is dark) . This procedure enables the use of the device tube simultaneously as sight glass as well, for the background sample taking eliminates errors in the measuring result caused by ambient background light coming into the tube through sight glass holes. In a reference portion 13, the signal detected is compared to reference values preset in a portion 15 for setting a reference value. Said reference portion.13 sends,on the basis of the comparison, a digital ON/OFF data into an optoisolator acting as a connection part 14. The function and the structure described above are adapted for use when the device operates as an interface detector, by means of which the interface occuring in product changes or between the product and the washing water is controlled. Through minor changes of the electronics portion, which are obvious to a person skilled in the art, the device is, however, suitable for measuring an absolute product concentration, too.

As already mentioned before, the measuring device according to the invention is adapted to be attached also in connection with the sight glass of already existing process pipe line systems, whereby only the portion of the device corresponding to the T-branch is required, which portion is positioned against the sight glass of the pipe by means of a suitable fastening element, such as e.g. a metal collar. The dimensions of the T-branch as well as those of the detector element must thereby be adjusted according to the dimensions of the sight glass.

It is obvious to one skilled in the art that the different embodiments and structural forms of the invention are not restricted to the afore-described example, but they can vary considerably ithin the scope of .the attached claims. So, for instance, the light transmitting connection from the detector element to the product can be some other than a glass tube, such as e.g. a transparent plastic tube or an optic fibre as well.

Claims

Claims:

1. Device for following the product concentration of products having milk as raw material or fluids containing said products by means of a reflection method, which device comprises a detector element (3) intended to be fitted in connection with a light transmitting portion (2) of a pipe containing said product, said detector element comprising a light emitter (4) and a light receiver (5), and an electronics portion (6, 7) for controlling the function of the light emitter (4) and for treating signals received by the light receiver (5) , c h a r a c t e r i z e d in that said detector element (3) is formed of a non- ransparent material, in which the light emitter (4) and the light receiver (5) are embedded at a distance from each other, whereby a wall preventing direct light communication is provided between the light emitter (4) and the light receiver (5).

2. Device according to claim 1, c h a r a c t e r¬ i z e d in that said light emitter (4) is fitted in the detector element (3) at an angle of approx. 30-50°, preferably 40-45 with respect to the light receiver (5).

3.Device according to claim 1 or 2, c h a r a c t e r i z e d in that said detector element (3) is a plate, whereby that surface of said plate which is brought against the light transmitting portion (2) is partly concaved into an arched shape correspond¬ ing to the arching of the light transmitting portion.