Patent Description:
In some technical domains, such as metallurgy, measuring devices are used for measuring a parameter of a distant element, such as a steel sheet produced by a mill or a hot strip mill. For instance, the measuring device may be a pyrometer intended for measuring the temperature of a steel sheet. When the distant element is located in an environment comprising dust particles and/or water droplets, at least the optical part of the measuring device needs to be protected, otherwise it becomes "polluted" and therefore the parameter measurements are erroneous.

To prevent the dust particles and/or the water droplets to reach the optical part, and notably its lens, this optical part may be fixed in an end part of a hollow body and a pressurized gas may be injected, with an angle typically equal to <NUM>° and in the direction of the distant element, into the internal space delimited by this hollow body, through an inlet defined in an intermediate part.

However, despite the pressurized fluid, some dust particles and/or some water droplets still enter the hollow body and reach the optical part. Therefore the parameter measurements become rapidly erroneous, which may be questionable when they are used for permanently controlling a process, such as cooling a steel sheet at a given temperature before coiling it. In such a situation, quality defects appear on the steel sheet and maintenance operations must be done continuously, almost each day, for cleaning the optical part in order to get reliable measurements These maintenance operations are very complex and may induce damages on the optical fiber and/or lens of the measuring device (for instance a pyrometer), which are costly.

To improve the situation, it has been proposed to set a grid inside the hollow body before the optical part. But, such a solution cannot be used when the measuring device comprises a laser producing a light beam aiming at a precise area of the distant element. The holes of the grid become gradually obstructed, which prevents obtaining the parameter measurements.

It has been also proposed to add one or two shutters to the hollow body and to set the shutters in an open position each time a measure must be done. But, such a solution introduces a lot of complexity and fragility (due to the mechanical parts and control means) and increases the cost and bulkiness.

In the <CIT> it has been proposed a device made with an intermediate part comprising an inlet of pressurized gas in connection with circumferential holes through which the pressurized gas is blown in the direction to the distant element, thus protecting the optical part of the measuring device located upstream to the intermediate part. While such a device is simple to manufacture and more efficient than most other devices, some particles are still able to come inside and water may condense inside the device thus impairing measurement to be performed.

<CIT> discloses a device for preserving the transparency of optical elements, when such elements are used in a contaminating atmosphere.

An objective of the invention is to improve the situation without introducing complexity and fragility while avoiding the particles and dust to come inside the device.

To this end, the invention relates notably to a device according to claim <NUM>.

The device of the invention may also comprise the following optional characteristics considered separately or according to all possible technical combinations:.

The invention also relates to a method for making a device as above introduced, said method being an additive manufacturing method.

The invention also relates to a computer assisted design file which comprises digital information for the implementation of the method as above introduced when loaded onto a machine.

The invention finally relates to a mill arranged for producing a metal sheet defining a distant element, wherein said mill comprises at least one protecting device as above introduced, facing said metal sheet.

Other characteristics and advantages of the invention will emerge clearly from the description of it that is given below by way of an indication and which is in no way restrictive, with reference to the appended figures in which:.

The invention concerns essentially a protecting device <NUM> intended for protecting means O for measuring a parameter of a distant element <NUM>.

In the following description it will be considered as an example that the distant element <NUM> is a steel sheet produced by a mill 2a, and more precisely by a hot strip mill. But the invention is not limited to this type of distant element. Indeed, it concerns any type of element or piece located in a difficult environment, for instance comprising dust particles and/or water droplets and having a parameter that has to be measured by a measuring means, periodically or occasionally. So, such an element may be part of a device, apparatus or system that is different from a mill. Another example may be a coke oven.

Moreover, it will be considered in the following description, as an example, that the parameter to be measured is the temperature. So, the measuring mean to be considered is a temperature measuring mean, such as a pyrometer O. It will be considered in the following description, as an example, that the protecting device <NUM> according to the invention belongs to the hot strip mill 2a, and therefore is installed permanently near the distant element <NUM>. But the protecting device <NUM> could be external to the hot strip mill and brought near the distant element <NUM> when a parameter measurement must be performed.

An example of embodiment of a protecting device <NUM> according to the invention is illustrated in <FIG>. As mentioned above, in this non-limiting example the protecting device <NUM> belongs to a hot strip mill 2a that produces an element <NUM>, which is a steel sheet whose temperature must be periodically measured in order to get a targeted temperature before coiling. For instance, and as illustrated in <FIG>, the hot strip mill 2a comprises spraying means <NUM> intended for spraying water on top of the steel sheet <NUM> for cooling it as a function of its temperature measured by at least one protecting device <NUM> located under this steel sheet <NUM>.

As illustrated in <FIG>, a device <NUM> according to the invention comprises a protection piece <NUM> extending longitudinally from a first extremity <NUM> to an opposite free second extremity <NUM> intended for facing the steel sheet <NUM>, and a coaxial measuring means piece <NUM> extending longitudinally from a first extremity 7a wherein an optical element of a measuring means O (here a pyrometer) is located, to an opposite second extremity 7b. The protection piece <NUM> and the measuring means piece <NUM> are coaxially coupled one to the other, for example by screwing thanks to internal and external threads respectively located at the first extremity <NUM> of the protection piece <NUM> and at the second extremity 7b of the measuring means piece <NUM>. Both measuring means piece <NUM> and protection piece <NUM> comprise a hollow body <NUM>,<NUM> delimiting an internal space <NUM>,<NUM> in continued communication and have a circular (transversal) cross-section.

The protection piece <NUM> comprises a pressurized gas inlet <NUM> in fluidic communication via a channel 12a (<FIG>) with a gas diffusion space <NUM> arranged in the thickness of the upper part <NUM> of the cylindrical wall of the hollow body <NUM>. The gas diffusion space <NUM> is in fluidic communication with the gas projection means <NUM> located at the free extremity <NUM> of the protection piece <NUM> along an active part of the periphery <NUM> of said free extremity <NUM> and more precisely along a curvilinear canal <NUM> (<FIG> and <FIG>) located in the thickness of said active part of the periphery <NUM>. The gas projection means <NUM> will be more detailed in reference to <FIG> and <FIG>.

As illustrated on <FIG> and <FIG>, the free extremity of the upper part <NUM> of the cylindrical wall of the hollow body <NUM> comprising the pressurized gas inlet <NUM>, the gas diffusion space <NUM> and the gas projection means <NUM> is bevelled then forming a first bevelled edge <NUM>. The free extremity of the opposite longitudinal lower part <NUM> is reversely bevelled then forming a reverse fulfilled bevelled edge <NUM>. The first <NUM> and second <NUM> bevelled edges are respectfully configured on both upper and lower sides of the median longitudinal plane P of the protection piece <NUM> (<FIG>).

Therefore, the free extremity <NUM> of the protection piece <NUM> is divided into a first bevelled edge <NUM> in the thickness of which the gas projection means <NUM> are located, and a second edge <NUM> configured in reverse bevel, the gas projection means <NUM> being therefore located opposite to said reverse bevelled edge <NUM>. Preferably and as illustrated on <FIG> et <FIG>, the second bevelled extremity <NUM> is longitudinally longer than the first bevelled extremity <NUM>.

According to the invention, the gas projection means <NUM> located along a curvilinear canal <NUM> are configured to project an inclined pressurized gas curtain <NUM> delimiting a protected internal space <NUM> inside the hollow body <NUM> of the protection piece <NUM>. For this purpose, the gas projection means <NUM> are configured to project an inclined pressurized gas curtain <NUM> with an angle α to the longitudinal axis X-X' of said device <NUM> greater than <NUM>° and less than <NUM>°. Preferably, in the configuration illustrated on <FIG> and <FIG> such angle is greater than or equal to <NUM>° and less than <NUM>°. Most preferably, the gas projection means <NUM> and the reverse bevelled edge <NUM> are both configured to project the pressurized gas curtain <NUM> tangentially to the reverse bevelled edge <NUM>, and especially tangentially to the external border <NUM> (<FIG>) of said reverse bevelled edge <NUM>.

Such a gas projection direction allows to close the free extremity <NUM> of the protection piece <NUM> with a continued curtain of pressurized gas <NUM>, therefore avoiding particles and dust to come inside the device and to reach the lens of the optical device. Preferably, the pressurized gas is tangent to the external border <NUM> of said reverse bevelled edge <NUM> for avoiding any disturbance of the gas flow curtain that could allow particles, dirtiness and dust to come inside the device. Projected gas may be air on any other suitable gas such as inert gas.

To constraint such gas direction, the gas projection means <NUM> comprise a curvilinear canal <NUM> (<FIG> and <FIG>) which is located in the thickness of the bevelled edge <NUM>. The curvilinear canal <NUM> extends transversally along all the bevelled edge <NUM> and is longitudinally inclined (<FIG>) in direction to the reverse bevelled edge <NUM>. In this example, the curvilinear canal <NUM> (and the resulting pressurized gas curtain <NUM>) is longitudinally inclined with an angle α of around <NUM>° while the angle β of the first bevelled edge <NUM> is around <NUM>° and the angle λ of the reverse bevelled angle <NUM> is around <NUM>°. The respective values of these angles α, β, λ are adapted to the structural configuration of the free extremity <NUM> of the protection piece <NUM> and especially to the tilt and the length of the bevelled edge <NUM> so as to get the gas curtain <NUM> tangent to the reverse bevelled edge <NUM> and preferably to the external border <NUM>. Such values have also to be considered in conjunction with the pyrometer orientation relative to the steel sheet. In this example, the pyrometer is located on the floor and oriented <NUM>° pointing the steel sheet.

The velocity of the gas curtain <NUM> also contributes to avoid particles to come inside the device. This velocity is preferably comprised between <NUM> to <NUM>. Such a velocity is adjusted according to the velocity of the entering gas flow at the inlet <NUM> and to the respective thicknesses of the inlet <NUM>, the channel 12a, the gas diffusion space <NUM> and the curvilinear canal <NUM>. In this example and in reference with <FIG>, the thickness T1 of the channel <NUM> is around <NUM> millimeters, the thickness T2 of the gas diffusion space <NUM> is around <NUM> millimeters, and the thickness T3 of the curvilinear canal <NUM> is around <NUM> millimeters. The entrance velocity at the gas inlet <NUM> is <NUM>. s-<NUM>, the gas velocity in the gas diffusion space <NUM> is comprised between <NUM> and <NUM>. s-<NUM>, and the gas velocity at the exit of the curvilinear canal <NUM> is <NUM>. s-<NUM> falling up at about <NUM>-<NUM>. s-<NUM> at the reverse bevelled edge <NUM>.

According to the invention, the protection device <NUM> including the protection piece <NUM> and the measuring piece <NUM> may be produced by implementing an additive manufacturing method in three dimensions. One means here by "additive manufacturing method" a three-dimensional printing process. Such an additive manufacturing method allows to consolidate every element in a single part, which guarantees the tightness.

This additive manufacturing method may be operated with a three-dimensional (or 3D) printer, or by selective laser sintering with metal powder as raw material, or by a binder jetting method also starting with a metal powder, or else by a laser cladding technology with metal wire as raw material, for instance. The selective laser sintering is interesting in the present case because it does not require an important post-process and gives more accuracy.

For instance, the metal powder may be a powder of stainless steel <NUM> which allows resisting to high temperature and humidity conditions. But it could be another metal supporting the high temperature (typically <NUM>) and the humidity conditions. Also for instance, it is possible to use a selective laser sintering machine such as an EOS M280 ® made by EOS GmbH (Electro Optical Systems GmbH).

In order to make the device <NUM> according to the invention with a 3D printer, it is necessary to create a computer assisted design file comprising digital information defining all the geometrical features of this device <NUM> and allowing implementation of the method describe above, and then to load this computer assisted design file into a machine.

Claim 1:
Device for protecting a means for measuring a parameter of a distant element (2a), said device (<NUM>) comprising a measuring means piece (<NUM>) able to comprise at least an optical element (O), and a protection piece (<NUM>) for protecting said optical element (O), wherein said protection piece (<NUM>) comprises a hollow body (<NUM>) and extends longitudinally from a first extremity (<NUM>) coupled to the measuring means piece (<NUM>), to a second extremity (<NUM>) intended for facing said element (2a), wherein said protection piece (<NUM>) further comprises an inlet (<NUM>) of pressurized gas in fluidic communication with gas projection means (<NUM>) which are located along an active part of the periphery (<NUM>) of the second extremity (<NUM>) and configured to project an inclined pressurized gas curtain (<NUM>) delimiting a protected internal space (<NUM>) inside of the protection piece (<NUM>), wherein the hollow body (<NUM>) has a circular cross-section, characterized in that the second extremity (<NUM>) of the hollow body (<NUM>) is divided into a first bevelled edge (<NUM>) in the thickness of which said gas projection means (<NUM>) are located, and an opposite reverse bevelled edge (<NUM>), and and in that the gas projection means (<NUM>) are configured to project an inclined pressurized gas curtain (<NUM>) in the direction of said reverse bevelled edge (<NUM>).