FR3013814A1 - NEW PROTECTION DEVICE DESIGN FOR COLD INSTALLATION - Google Patents

Abstract

The invention relates to a protection device for a cold production installation, said device comprising a grid (1) intended to cover an orifice (2) for the passage of a refrigerated gas, said grid comprising strands (7a, 7b) forming mesh, said grid (1) of protection defining a surface (S), said gate, passing through the strands (7a, 7b) and wherein a section line (La) of said gate surface by at least one plane (XY) passing through said surface (S) of the grid is of curved and / or angular shape and / or a cross section (Sa) of the strands (7a) of said grid has a curved and / or angular contour. The invention also relates to a cold production installation comprising such a device.

Description

FIELD OF THE INVENTION The present invention relates to the field of cold production, particularly in the field of cryogenics. It relates more particularly to the design of a protective device for a cold production installation. State of the art: In particular in the field of transport and distribution of heat-sensitive products, such as pharmaceuticals and foodstuffs, these grids are necessary to protect the openings of the refrigerant circuit in the container. This is intended to prevent people to intervene in the container accidental injury in contact with the fans of the cold production system. Another function of the grid is to prevent ingestion by the cold production system of pieces of packaging or various waste. The meshes of a protective grid are therefore limited in size to limit these various risks. Moreover, when an exchanger has a cold air blow zone whose temperature is negative, the use of a protective grid can become a source of frost accumulation. Limiting the mesh size favors this phenomenon. Especially during dispensing rounds where the container is frequently opened and is then loaded with moisture, the openings of the protection grids are gradually clogged up, in some cases being completely blocked. Then we lose all or part of the air mixing capacity of the exchangers and, therefore, the cooling capacity of the group.

This phenomenon is particularly critical for cryogenic groups employing a direct or indirect injection of cryogenic gases into the space containing the thermosensitive products. Indeed, the temperature of the gas passing through the grids is much colder than in the case of a mechanical cold production unit. The intensity of the icing phenomenon is therefore stronger. The frost particles then formed are also of a more sticky nature, which accentuates the clogging phenomenon of the grids. The use of materials with poor thermal conductivity has been considered to prevent the accumulation of frost on the strands forming the grid, including flexible materials, to keep small openings. However, most materials having these properties at reasonable economic conditions pose problems of durability and, above all, of compatibility with the agri-food rules concerning hygiene. The objective of the present invention is therefore to be able to use a rigid material, compatible with the agri-food rules while having a good behavior over time, and to obtain a protective grid preventing an accumulation of frost on its strands which can to close openings, even small ones. DESCRIPTION OF THE INVENTION For this purpose, the invention relates to a protection device for a cold production installation, said device comprising a grid intended to cover an orifice for the passage of a refrigerated gas, said grid comprising strands forming stitches. Said protective grid defining a so-called grid surface passing through the strands, a section line of said gate surface by at least one plane passing through said surface of the gate is of curved and / or angular shape and / or a section transverse strands of said grid has a curved contour and / or angular. The curvature of the gate surface, at least in one direction, increases the passage area of the refrigerated gas through the gate relative to the cross sectional area of the main direction of flow through the orifice. Compared to a flat grid, even with openings of similar size, thus increases the surface that the frost that forms from the strands must cover to plug the grid. The accumulation of frost is thus delayed and the clogging of the grid can be avoided if, for example, cycles of use alternate phases in which the flow has a high moisture concentration with others where the Frost can be eliminated. The angular shape provides an approximation of the curvature of the lines, especially if the strands of the grid are made of successive rectilinear segments. Advantageously, the angles used are obtuse and one will avoid the right angles as well as the acute angles sources of accumulation of frost. The notion of curvature, referred to the section of the strands, also has the effect of slowing the progression of the frost. This curvature maximizes the surface tension on the surface of the strands and makes it more difficult to grip the frost. As for the curvature of the grid surface, the progression of frost from the strands to invade the openings is slowed down. Preferably, said section line of the grid always changes direction in the same direction. In other words, the line in the transverse plane is curved with respect to a mean plane resting on the edges of the grid. Advantageously, the gate is configured so that said gate surface is curved in at least one direction of said gate surface. In other words, the previously defined lines are not curved locally around a plane but they are, for example, section lines by planes crossing the grid parallel to each other over the entire extension of the grid, which have the property to be convex by joining the same plane at their ends. In particular, the grid is curved in a cylindrical envelope.

A variant may be made with a grid configured so that it is on all the planes rotating about an axis passing through the surface of the grid that the section lines are curved by joining the same plane at their ends. In particular, the grid is convex in a spherical envelope. Preferably, whatever the variants considered, the surface of the grid is convex in the sense that said section line of the grid is curved with respect to a mean plane resting on the edge of the grid. In a particular embodiment, the radius of curvature of said surface along said direction is substantially constant.

Advantageously, said direction of curvature corresponds to the direction in which said surface of the grid has its smallest dimension. This configuration allows a large bending, ie a small radius of curvature, which increases the passage area of the grid without giving it an exaggerated size in the direction perpendicular to the orifice it must cover. Advantageously, said grid is curved in the opposite direction to that where a ventilation means is intended to be placed relative to said grid. In other words, the further one gets away from the edges of the grid, the more the distance to the ventilation means increases.

This makes it possible, in particular, to allow meshes of larger size in the center of the grid, thus to limit their occultation by icing. Preferably, the strands delimiting at least one of said meshes are curved in line with said mesh. In particular, the cross section of said strands may be circular. Said device may also include a cover defining an orifice for passing the refrigerated gas.

Preferably, access openings to the orifice being present between the grid and the cover, their maximum size is that of the maximum mesh size of the grid. Indeed, the grid may, for example, be slightly offset relative to the orifice, leaving then lateral openings. The attachment means of the grid or the means attached to the cover, for example, can form separations and advantageously limit the size of each opening, taken individually, below the maximum mesh size of the grid. The invention also relates to a cold production installation comprising a protection device as described above. Said installation may comprise a heat exchanger intended for the refrigeration of said gas, and a means for ventilating the refrigerated gas towards said orifice. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood and other details, features and advantages of the present invention will become more clearly apparent from the following description, with reference to the accompanying drawings, in which: FIG. perspective of a first protection device according to the invention. Figures 2a and 2b schematically show a perspective view of the geometry of two variants of a grid for the device of Figure 1.

Figures 3a and 3b show schematically the cross section of one of the strands forming the grid of a device according to two embodiments of the invention. Figures 4a and 4b show schematically, seen in projection in two perpendicular directions, a second protection device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION With reference to FIG. 1, the invention relates to a protection device for a cold production installation. It comprises a protective grid 1 placed in front of a passage opening 2, here blowing, a refrigerated gas, for example air. A refrigerated gas production system 3, not detailed, is located under this blowing orifice. The refrigerated gas produced is in particular sucked by a ventilation device 4 and directed towards the orifice 2 by a cover 5 which also serves as protection of the ventilation device 4. In the example presented, the ventilation device is a wheel centrifugal blowing 4 which sucks the gas through a central cavity and delivers it to the periphery. The cover 5 here has a flat shape with a first semi-cylindrical portion 5a, whose function is to collect a portion of the gas blown by the ventilation wheel, and a second portion 5b, substantially parallelepipedic, acting as a conduit between the wheel of 4 and the orifice 2. The average direction of the flow imposed by the cover 5 follows, in the example of Figure 1, that of an X axis perpendicular to the Y axis of the ventilation wheel 4 and parallel to the side walls of the duct formed by the part 5b of the hood. The X axis is oriented in the figure in the flow direction of the gas.

The cross section of the orifice 2 with respect to the mean direction X of the flow, along the walls of the part 5b of the cover, here has the shape of a flattened rectangle, whose short side corresponds to the direction of the Y axis of the wheel 4. However, it may be advantageous to extend hood walls to laterally border the grid 2. As is illustrated in Figure 1, the extension of the hood walls parallel to the Y direction of the The axis of the wheel by plates 6 forms a portion of disk. The orifice 2 can then be seen as having a curved shape, in particular towards the outside of the cover, and more particularly a cylindrical shape of axis oriented in the direction Z, orthogonal to the direction Y of the axis of the wheel of ventilation. The orifice 2 has its largest dimension in this direction Z. In the example presented, this orifice surface 2 corresponds to a half-cylinder starting tangentially to the walls of the cap perpendicular to the direction Y and having for radius However, it is possible to envisage variants with a larger radius of curvature and not starting with a zero angle at the walls, for example by giving the side plates 6. the shape of disk portions with a smaller angular sector. Referring to Figure 1, the grid 1 is formed of strands 7a oriented in one direction and intersecting strands 7b oriented in a second direction to form meshes passing the flow. The strands are wire-shaped along a central line, with a thickness determined by a substantially constant cross-section. The directions of the strands 7a and 7b may be orthogonal, as in Figure 1 where the strands 7b are oriented in the Z direction corresponding to one of the sides of the orifice. However, variants where these directions are not orthogonal and / or inclined oriented are possible. The series of strands 7a and 7b define a set of meshes juxtaposed. In this way, it is possible to define a grid surface S resting on said strands or, more precisely, on central lines of the strands, for example with mesh-by-mesh interpolations. The meshes form the passage openings of the flow through this grid surface. In the example illustrated in FIG. 1, the surface of the grid 1 follows the surface of the orifice 2. With reference to FIG. 2a, the central lines La of the strands 7a thus have a curved shape in their extension direction , corresponding to arcs of circle. If the grid surface S is cut along a plane XY perpendicular to the direction Z and thus crossing the surface S of the grid, in particular a plane containing the central line La of a strand 7a, the section line of the surface S of grid by this plane is thus curved with for radius of curvature that of the cylinder defining the surface of the grid. In the example presented, for any XY plane crossing the grid, this line is an arc of a circle joining a plane YZ on which the strands 7a rest. The fact that the line of the section is curved is also true for any plane crossing the grid surface S even if it is not perpendicular to the direction Z.30 The curvature of a strand 7a creates a curved path between two corners of a mesh along the strand 7a, which makes it more difficult to advance the frost, especially when it starts at the two corners of a mesh to invade the mesh from the strand 7a.

Advantageously, it will avoid the presence of right or acute angle, accelerating the start of frost, following the strands 7a, either on the grid or the connection with the walls or walls 5a perpendicular to the Y direction.

Furthermore, the surface S of the gate being curved preferably outwardly relative to the blower wheel 4, the meshes are removed from this wheel by the geometry of the grid which allows, if desired, to enlarge. The path to be traveled by the frost is created at the corners of the mesh along the strands 7a and 7b is larger, which delays or limit its extension.

In a variant embodiment, with reference to FIG. 2b, the circular arc formed by each central line La of a strand 7a corresponds to a succession of rectilinear segments between each intersection with the central lines Lb of the strands 7b going into the other direction. The shape of the central line of the strand along this time is angular with obtuse angles between two successive segments. The line of intersection of the surface S with a plane crossing this surface, perpendicular or inclined with respect to the direction Z, retains this property. Advantageously, it will always avoid the formation of right angles along the strand 7a. In this variant also, we can extend the path to follow between two corners of a mesh by the size of the mesh. According to another variant of the invention, the grid may be slightly offset relative to the orifice. For example, it can rely on a grid surface S corresponding to a cylinder of the same axis as the side plates 6 but with a slightly larger radius. This creates openings between the grid 1 and the edge of the orifice 2. The important thing in this case is that the size of these openings remains smaller than that of the mesh of the grid, so as not to destroy the protective effect provided. by the grid. It should be noted, in this regard, that the side plates 6 shown in Figure 1 have the function of plugging an opening whose size does not meet the specifications corresponding to that of the mesh of the grid 1. A way to achieve the The invention therefore comprises, for example, bulging grids in front of a plane orifice made in a hood modified by the presence of plates 6, whether or not attached, plugging the lateral openings where the grid 1 stops. Said plates may be solid or themselves meshed. According to another aspect of the invention, which may be combined with the preceding, the strands 7a and 7b may have a curved or angular section, particularly with obtuse angles. With reference to FIG. 3a, the cross-section Sa of a strand 7a around its central line La may be circular, or generally, have a finite radius of curvature over most of its periphery. This curved shape, with reference to FIG. 3b, can be approximated, as for the central lines 7a of the strands, by an angular line Sa 'where the angles a' between successive segments are preferably obtuse. This characteristic creates a radius of curvature effect in the transverse direction of a strand 7a-7b, similarly to the longitudinal curvature of the strand 7a. With this effect, the surface tension is maximized on the strands 7a and 7b, making it more difficult to form the frost and especially the attachment of frost on the strand. Its progression between two corners of a stitch along the strands 7a and 7b is thus made more difficult to prevent it from invading the stitch then. The invention may also be realized, with reference to FIGS. 4a and 4b, in front of an orifice 2 'of substantially square or circular shape. In the example shown, the fan 4 'blows or draws air along its axis of rotation X', aligned with the direction perpendicular to the orifice 2 '. In this case, the portion of the hood 5 'between the fan and the orifice acts as a duct. The orifice is formed on the downstream face 5'c of the cover, substantially flat and perpendicular to the axis X '. In a first variant embodiment, the grid 1 'is curved, formed by two series of strands 7'a and 7'b forming a star mesh. The central lines of the strands 7'b form a series of curves centered around an axis X 'passing through the center of the orifice 2', oriented from the fan 4 'to the orifice 2', and located in successive planes Y'Z 'perpendicular to this axis X'. In possible variants, these curves can be approximated by successive line segments between each mesh.

With reference to FIG. 4b, the strands 7'a form, seen in the direction X 'perpendicular to the orifice, a series of spokes supported in the center on a substantially circular mesh and joining the periphery of the surface occupied by the wire rack. Referring to Figure 4a, seen in a plane perpendicular to the orifice passing through the corresponding radius, each strand 7'a has a curved or angular profile away from the orifice in the opposite direction to that of the fan. Thus, the surface of the grid, for any plane passing through this axis X ', has a convex section, substantially based on the trace of a common plane Y'Z' at the base of the grid 1 '.

The strands 7'b and 7'a may further have a circular cross section or simply curved or angular with obtuse angles. This arrangement gives a convex shape to the surface occupied by the grid. Other provisions of the strands are conceivable. For example, it is possible to cross mesh 7'a and 7'b strands on a curved surface. A substantially square or circular opening has substantially the same dimension in all directions. Bending the surface of the grid may cause it to be excessively displaced from the orifice. It is always possible to make a flat grid plugging the orifice 2 'according to the invention by making both strands 7'a and strands 7'b with a curved or angular section with obtuse angles.

Claims (12)

REVENDICATIONS1. Protective device for a cold production plant, said device comprising a grid (1) intended to cover an orifice (2) for the passage of a refrigerated gas, said grid comprising strands (7a, 7b) forming meshes, said protection grid (1) defining a so-called grid surface (S) passing through the strands (7a, 7b), characterized by the implementation of one or each of the following measures: a section line ( La) of said gate surface by at least one plane (XY) passing through said surface (S) of the gate is of curved and / or angular shape; a cross-section (Sa) of the strands (7a) of said grid has a curved and / or angular contour. 2. Device according to the preceding claim wherein said section line (La) of the grid (1) always rotates in the same direction, within the plane passing through said surface. (2: said section line (La) of the grid (1) is convex) (3: The area delimited by said section line (La) of the grid (1) and the segment joining its two ends is convex). 3. Device according to the preceding claim configured so that said surface (S) gate (1) is curved in at least one direction (Y) of said gate surface. 4. Device according to the preceding claim wherein the radius of curvature of said surface (S) along said direction (Y) is substantially constant. 5. Device according to the preceding claim wherein said direction of curvature (Y) corresponds to the direction in which said surface of the gate has its smallest dimension. 6. Device according to any one of the preceding claims wherein the strands (7a, 7b) delimiting at least one of said meshes are curved in line with said mesh. 7. Device according to the preceding claim wherein the cross section (Sa) of said strands (7a) is circular. 8. Device according to any one of the preceding claims comprising a cover (5, 5 ') defining said orifice (2, 2') for passing the refrigerated gas. 9. Device according to the preceding claim wherein, access openings to the orifice (2 ') being present between the grid (1') and the hood (5'c), their maximum size is that of the maximum size. mesh of the grid (1 '). 10. Cold production plant comprising a protective device according to any one of claims 1 to 10. 11. Installation according to the preceding claim in combination with claim 3 wherein said grid (1) is curved towards a direction (X) corresponding to the outside of the installation relative to the orifice (2). 12. Installation according to one of claims 10 or 11 comprising a heat exchanger (3) for cooling said gas, and a means (4) for ventilating the refrigerated gas towards said orifice.