Method for coating a mechanical member, and mechanical member thus coated

Abstract

A method for coating a mechanical member provided with at least a support plate and one or more tubular elements attached in through manner to the support plate. The method comprises a first coating step, in which an external surface of the support plate is coated with a first layer of plastic material, and a second coating step in which a terminal portion of the internal surface of the tubular elements is coated with a multi-layer coating. In the second coating step the multi-layer coating is made by depositing in sequence one on top of the other a plurality of layers of plastic material, each of which is deposited partly in correspondence with the terminal portion of the internal surface of the relative tubular element and partly in correspondence with the surface of the first layer of the external surface of the support plate.

Claims

1. A mechanical member provided with at least a support plate and one or more tubular elements attached in through manner to said support plate, in which an external surface of said support plate is coated with a first layer of plastic material, and in which at least a terminal portion of the internal surface of each of said tubular elements, in substantial correspondence with the support plate, is coated with a multi-layer coating which comprises a plurality of layers of plastic material disposed in sequence one on top of the other, each of said layers being deposited partly in correspondence with said terminal portion of the internal surface of the relative tubular element and partly in correspondence with the surface of said first layer of the external surface of said support plate, wherein a first layer of said layers is disposed on the internal surface of each of said tubular elements in a more external position radially with respect to a longitudinal axis of the tubular element and at least a second layer of said layers is disposed internal radially with respect to the axis on said first layer, in which said first layer extends inside said tubular element substantially parallel to said axis for a first length which is from about one to about two times the nominal diameter of said tubular element and said second layer extends inside said tubular element substantially parallel to said axis for a second length which is greater than said first length by a segment which is from about one to about two times the nominal diameter of said tubular element, so as to define a first internal diameter, less than said nominal diameter and substantially constant for the first length of said first layer and at least a second internal diameter, less than said nominal diameter and greater than said first diameter, substantially constant for the segment of the second length beyond which the second layer extends with respect to the first layer.

2. The mechanical member as in claim 1, wherein said segment of said at least one second layer is disposed directly on said internal surface of each of said tubular elements.

3. The mechanical member as in claim 2, wherein at least a third layer of said layers is disposed more internally radially with respect to the axis which extends inside said tubular element substantially parallel to said axis for a third length which is greater than said second length by a segment which is from about one to about two times the nominal diameter of said tubular element so as to define at least a third internal diameter, less than said nominal diameter and greater than said second diameter, substantially constant for the segment of the third length beyond which the third layer extends with respect to the second layer.

4. The mechanical member as in claim 3, wherein said segment of said at least one third layer is disposed directly on said internal surface of each of said tubular elements.

5. The mechanical member as in claim 1, wherein at least a third layer of said layers is disposed more internally radially with respect to the axis which extends inside said tubular element substantially parallel to said axis for a third length which is greater than said second length by a segment which is from about one to about two times the nominal diameter of said tubular element so as to define at least a third internal diameter, less than said nominal diameter and greater than said second diameter, substantially constant for the segment of the third length beyond which the third layer extends with respect to the second layer.

6. The mechanical member as in claim 5, wherein said segment of said at least one third layer is disposed directly on said internal surface of each of said tubular elements.

7. The mechanical member as in claim 1, wherein the first coating layer of the external surface of the support plate comprises a plastic material based on a solventless resin with an epoxy base.

8. The mechanical member as in claim 7, wherein the solventless resin with an epoxy base of the first layer comprises a determinate quantity of inert matter to increase a density of the solventless resin.

9. The mechanical member as in claim 1, wherein each layer of the multi-layer coating of the terminal portion of the internal surface of the tubular elements comprises a plastic material based on a resin with an epoxy base with added amines.

10. The mechanical member as in claim 1, wherein the plastic material comprised within the first coating layer of the external surface of the support plate has an ultimate elongation value higher than an ultimate elongation value of the plastic material in each layer of the multi-layer coating of the terminal portion of the internal surface of the tubular elements.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

(2) FIG. 1 shows a three-dimensional view of part of a mechanical member coated using the method according to the present invention;

(3) FIG. 2 shows an enlarged and sectioned detail of the mechanical member in FIG. 1;

(4) FIG. 3 shows a first operating condition of the method according to the present invention;

(5) FIG. 4 shows a second operating condition of the method according to the present invention;

(6) FIG. 5 shows a third operating condition of the method according to the present invention;

(7) FIG. 6 shows a fourth operating condition of the method according to the present invention;

(8) FIG. 7 shows a fifth operating condition of the method according to the present invention;

(9) FIG. 8 shows a sixth operating condition of the method according to the present invention.

(10) To facilitate comprehension, the same reference numbers have been used, where possible, to identify common elements in the drawings that are substantially identical. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF THE INVENTION

(11) With reference to the attached drawings a mechanical member 10 is partially shown, in this case consisting substantially of a tubing plate 11 and a plurality of tubes 12, or bundle of tubes, normally used in fluidic conditioning or heat exchange plants or other.

(12) In particular, the tubing plate 11 has a substantially parallelepiped shape and comprises a plurality of through holes 13 made in a determinate pattern. Each tube 12 is inserted in correspondence with a relative through hole 13, so as to allow a fluid to pass, such as water or other heat-carrying liquid, typically used in such plants.

(13) The tubing plate 11 comprises at least an external surface 15, opposite the side on which the tubes 12 are associated with the holes 13.

(14) The external surface 15 is coated with a coating layer 16 of solvent-less resin with an epoxy base, and in this case also comprising special inert matter which characterizes the density and the resistance both to wear and impact.

(15) The application of this material also confers high insulating qualities to the tubing plate 11.

(16) The coating layer 16 has a thickness comprised between about 2 mm up to more than 10 mm, advantageously between about 3 mm and about 5 mm.

(17) Moreover, the coating layer 16 has a flared mouth 14, in correspondence with each through hole 13.

(18) In this case, the coating layer 16 is conformed so as to also contact the external end surface of each tube 12 associated with the relative through hole 13.

(19) Each tube 12 has a cylindrical internal surface 17, inside which the heat-carrying fluid of the plant is able to flow, in the direction indicated by the arrow F in FIG. 2.

(20) The internal cylindrical surface 17 of each tube 12 is coated at least in correspondence with one of its terminal portions near the through hole 13.

(21) According to the invention, the coating of the internal cylindrical surface 17 also extends continuously on an external surface of the coating layer 16 of the tubing plate 11.

(22) In this way, a substantial surface and structural continuity is defined of the coatings provided for the tubing plate 11 and for the relative tubes 12. Moreover, the coating of the internal cylindrical surface 17 defines a thickening of the tube 12 astride the thickness S of the tubing plate 11, increasing the mechanical resistance in this zone which is subject to phenomena of corrosion by galvanic currents and cavitations deriving from the voracity of the entering flow.

(23) In particular, the internal cylindrical surface provides a multi-layer coating 19, in this case defined by three layers, respectively first 19a, second 19b and third 19c, one on top of the other.

(24) Each of the three layers 19a, 19b and 19c is made with a solvent-less resin with an epoxy base and with added amines.

(25) The resin has particular properties of resistance over time to mineral acids, diluted organic acids, alkalis with a high concentration of solvents and hydrocarbons, and has a field of action PH 1-14.

(26) Each layer 19a, 19b and 19c has a thickness comprised between about 0.15 mm and about 0.25 mm and extends according to different lengths along the tube 12, in order to define a desired configuration.

(27) In FIG. 2, in which a section of the connection zone between tube 12 and tubing plate 11 is shown, for convenience of representation the lengths of the three layers 19a, 19b and 19c are in proportion to each other, but not in proportion with respect to other details shown.

(28) In particular, a first layer 19a is disposed on the internal surface 17 of each of the tubes 12 in a more external position radially with respect to a longitudinal axis X of the tubular element 12 and at least a second layer 19b is disposed internally radially with respect to the axis on the first layer.

(29) The first layer 19a extends inside the tube 12 substantially parallel to the axis X for a first length L1 which is from about one to about two times the nominal diameter D of the tube 12 and the second layer 19b extends inside the tube 12 substantially parallel to the axis X for a second length L2 which is greater than the first length L1 by a segment 119b which is from about one to about two times the nominal diameter D of the tubular element 12, so as to define a first internal diameter D1, less than the nominal diameter D and substantially constant for the first length L1 of the first layer 19a and at least a second internal diameter D2, less than the nominal diameter D and greater than the first diameter D1, substantially constant for the segment 119b of the second length L2 beyond which the second layer 19b extends with respect to the first layer 19a.

(30) In the form of embodiment shown, the segment 119b, the length of which is given by the difference between the lengths L2 and L1, is disposed directly on the internal surface 17 of each of the tubular elements 12.

(31) Moreover, according to one form of embodiment of the present invention, at least a third layer 19c is disposed more internally radially with respect to the axis X and extends inside the tube 12 substantially parallel to the axis X for a third length L3 which is greater than the second length L2 by a segment 119c which is from about one to two times the nominal diameter D of the tube 12, so as to define at least a third internal diameter D3, less than the nominal diameter D and greater than the second diameter D2, substantially constant for the segment 119c of the third length L3 beyond which the third layer 19c extends with respect to the second layer 19b.

(32) In the form of embodiment shown, the segment 119c, the length of which is given by the difference between the lengths L3 and L2, is disposed directly on the internal surface 17 of each of the tubes 12.

(33) The reduction in diameter, with respect to the nominal diameter D of the tube 12, in correspondence with the first layer 19a and the segments 119b and 119c, is given by the sum of the thicknesses of the layers 19a, 19b, 19c which on each occasion radially overlap along the tube 12, thus defining the diameters D1, D2, D3. Therefore the diameter D1 in correspondence with the entrance zone of the fluid, the direction of the flow of which is shown by the arrow F in FIG. 2, and astride the tubing plate 11, the thickness of which is shown by the letter S, is smaller because the thickness of the multi-layer coating 19, given by the sum of the thicknesses of all the layers 19a, 19b, 19c, is greater. The diameter D2 is greater than the diameter D1 because, in correspondence with the segment 119b, there are only two layers overlapping radially, 19b and 19c, the sum of their thicknesses determining the diameter D2. The diameter D3 is, in its turn, greater than the diameter D2, because in correspondence with the segment 119c only the layer 19c is provided, the thickness of which determines the diameter D3.

(34) In some forms of embodiment, the first layer 19a extends inside the tube 12 for a length L1 comprised between about 50 mm and about 100 mm, the second layer 19b is disposed above the first layer 19a and extends for a length L2 comprised between about 150 mm and about 200 mm, while the third layer 19c is disposed above the second layer 19b and extends for a length L3 comprised between about 250 mm and about 300 mm. In general, each layer 19a, 19b and 19c extends for a relative length L1, L2 and L3, such that they overlap by at least about 20 mm above the layer 19a, 19b below.

(35) In this way, a usable passage section is defined inside the tube 12, which section is tapered off toward the exit of the tube, in order to promote the fluidic conditions of use.

(36) The method according to the present invention to coat the mechanical member 10 as described heretofore is as follows, and refers to the operating sequence shown schematically in FIGS. 3 to 8.

(37) Initially, the inside of the tubes 12 are washed and finished, so as to prepare at least the internal cylindrical surface 17 for coating.

(38) Advantageously, both the tubing plate 11, and the tubes 12 are subjected, before coating, to a surface treatment which both performs a surface cleaning of impurities and also produces a desired surface roughness of the material, in order to promote the grip of the coating material. In some forms of embodiment, the roughness which is made on the tubing plate 11 is in the range of about 80 microns, while the roughness made inside the tube 12 is in the range of about 20-25 microns.

(39) With reference to FIG. 3, inside the end of the tubes 12, on the side where the connection with the through holes 13 of the tubing plate 11 occurs, a plurality of caps 20 are disposed, for example made of non-stick material.

(40) Each cap 20 has a flared conformation so as to define, subsequently, the flared mouth 14 of the coating layer 16 in correspondence with the through holes 13 of the tubing plate 11.

(41) A layer of primer 21, or other similar compound, is subsequently deposited on the external surface 15 of the tubing plate 11, which improves the adhesive conditions of the coating layer 16 which is subsequently deposited.

(42) The layer of primer 21 is deposited so as to completely recover the tubing plate 11 and all the interstices between cap 20 and cap 20.

(43) Once the catalysis of the layer of primer 21 has occurred, the plastic material that makes up the coating layer 16 is applied, for example by spatula.

(44) Once the plastic material of the coating layer 16 has dried, the coating layer 16 is smoothed, taking away any excess material in order to uncover the heads of the caps 20 below.

(45) Subsequently, the caps 20 are removed and the mechanical member 10 is cleaned of any working residues and/or surplus material used for the coating of the external surface 15 of the tubing plate 11.

(46) Advantageously, a layer of epoxy resin is applied on top of the coating layer as protection.

(47) As shown in sequence in FIGS. 6, 7 and 8, the three layers 19a, 19b and 19c are deposited one on top of the other, in order to define the multi-layer coating 19, as described above.

(48) Each layer 19a, 19b and 19c is advantageously applied by means of a spray gun with a radial spray, so as to form a uniform protective layer on the corresponding portion of the internal cylindrical surface 17.

(49) It is clear that modifications and/or additions of steps or parts may be made to the mechanical member 10 as described heretofore, without departing from the field and scope of the present invention.

(50) For example, it comes within the field of the present invention to provide that the multi-layer coating 19 can consist of a number of layers other than three, for example two, four or more, depending on the operating conditions of the mechanical member 10 and/or other determinate factors.

(51) It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of method for coating a mechanical member and mechanical member thus coated, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.