Apparatus for impregnating fibrous supports with powders

Abstract

The invention relates to a device (100) for impregnating a fibrous or porous support (S) with a powder material (P), comprising: - means (1) for moving the support (S); - means (5) for depositing the powder material (P) on one side of the support (S); - transverse electrodes (4) connected to the terminals of an alternating voltage generator (G1, G2, G3) generating an electric field applied to the path of the moving support (S), characterized in that the generator (G1, G2, G3) generates alternating potentials (u, v, w) with a phase shift of 10° to 180° in pairs, wherein adjacent electrodes (4) are connected to different potentials (u, v, w) alternately along the direction of travel of the support (S).

Description

Technical Field

[0001] This invention relates to the field of impregnating porous support members with powder materials. The support members are, for example, nonwoven and / or agglomerated textiles or porous materials.

[0002] The support is intended to be treated by impregnation with powders having physicochemical properties, such as thermoplastic powders, thermosetting powders, flame-retardant or fire-resistant powders, sterilizing powders, hydrophobic powders, and similar powders. Background Technology

[0003] Document FR3114261 describes an apparatus for impregnating powder into a fibrous or porous support. The apparatus described includes means for moving the support onto which the powder is deposited.

[0004] The powdered support is then conveyed longitudinally between the electrodes connected to the AC voltage generator, with the electrodes on each side of the support connected to one of the terminals of the voltage generator.

[0005] The charged powder is driven by an electric field, perpendicular to the two electrodes, and specifically towards the center of the support. The powder thus impregnates the support.

[0006] With this process, powder with low polarizability is impregnated in a relatively uniform manner; however, in some areas, the powder particles agglomerate due to electrostatic effects, resulting in randomly distributed, essentially point-like, non-uniformity, which may reduce the performance of the obtained product.

[0007] Conversely, in the case of conductive or polarizable powders, electrostatic forces readily generate significant agglomerates, resulting in very significant inhomogeneities by concentrating particles into localized clusters, which are particularly likely to remain primarily on the exterior of the substrate.

[0008] Therefore, there is a need for a device that can provide better powder impregnation by homogenizing the distribution of the powder, especially when the powder is polarizable or exhibits a degree of conductivity. Summary of the Invention

[0009] To address this technical problem, the present invention proposes an apparatus for impregnating fibrous or porous supports using powder materials, the apparatus comprising: - A device for moving the support component. - An apparatus for depositing powder material on one side of a support member. - A transverse electrode, connected to the terminal of an AC voltage generator, thereby generating an electric field applied to the path of the moving support.

[0010] The device according to the invention is characterized in that the generator generates paired AC potentials with phase shifts of 10° to 180°, wherein adjacent electrodes are alternately connected to different potentials in the direction of travel of the support.

[0011] By generating the longitudinal component of the electric field, the phase-shifted potential causes the agglomerates of the powder material to move longitudinally, thereby dispersing them.

[0012] The device according to the invention may also have one or more of the following features.

[0013] The phase shift of the electrode potential can be between 10° and 45°, and more specifically between 15° and 30°.

[0014] This smaller phase shift makes it possible to prevent breakdown between two adjacent electrodes.

[0015] The device may include one or more generators that generate three potentials, and adjacent electrodes are subsequently connected to different potentials of the one or more generators.

[0016] Using a device with three potentials of different phases makes it possible to generate electric fields with complex shapes, thereby allowing for significant agitation of the powder material particles.

[0017] The device may include one or more generators that generate two potentials, and adjacent electrodes are subsequently connected to different potentials of the one or more generators.

[0018] Electrodes connected to different potentials can be located on the same side of the support, while on the other side of the support, there is no facing electrode or a plate electrode at a floating potential.

[0019] Electrodes connected to different potentials can be located on the same side of the support, while a single plate electrode grounded is provided on the other side of the support.

[0020] The electrodes may include a series of pairs of electrodes located on the same side of the support, each pair of electrodes being connected to one of two potentials, while on the other side of the support, a grounded plate electrode is provided.

[0021] Electrodes may include electrodes located on each side of the support, wherein facing electrodes are connected to the same potential among the three potentials, or facing electrodes are connected to pairs of phase-shifted potentials.

[0022] In practice, and more generally, different potentials can be generated by multiple discrete and synchronized generators, or by a single generator with multiple output terminals. Combinations of these two arrangements are also possible.

[0023] The device for moving the support member may include: - A circulating annular conveyor having an outer surface including recesses, wherein a device for depositing powder deposits powder into the recesses of the outer surface. - A device for pressing the support member is configured to press the support member (S) against the outer surface of the annular conveyor (1) in which the recess is filled with the powder material (P). - The circular conveyor passes over the electrode during its cyclic movement, where the support is pressed against the outer surface of its recess containing powder.

[0024] If the support is a linear strip, thin strip, or narrow strip, the device may include a tubular constraint member through which the support to be treated or impregnated passes, and powder is also dispensed into the tubular constraint member, with electrodes located at the constraint member between the inlet of the support and powder and the outlet of the impregnated support.

[0025] Specifically, the electrodes may have a potential with a shifted phase, having an increasing phase shift in the direction of travel of the support, so as to drive the powder material to move along the direction of travel of the support by changing the electric field.

[0026] Alternatively, the electrodes may have a potential with a shifted phase, having a decreasing phase shift in the direction of travel of the support, so as to drive the powder material to move in the opposite direction of travel of the support by changing the electric field.

[0027] The present invention also relates to a method for impregnating a fibrous or porous support with a powder material by applying an electric field, comprising the following steps: -Moving support components, - Deposit powder material on the surface of the moving support component.

[0028] The method is characterized by further comprising the following steps: - A support with powdered material is conveyed at the electrodes of a generator that generates paired AC potentials with phase shifts of 10° to 180°, wherein adjacent electrodes are alternately connected to different potentials in the direction of travel of the support. Attached Figure Description

[0029] The invention will be clearly understood by reading the following description, the details of which are given by way of example only and illustrated in conjunction with the accompanying drawings, in which the same reference numerals refer to the same elements:

[0030] [ Figure 1 [Illustrated side view of an embodiment of the impregnation apparatus according to the present invention]

[0031] [ Figure 2 ]yes Figure 1 A longitudinal cross-sectional view of the device's electrodes and the electric field vectors at different times during the oscillation period.

[0032] [ Figure 3 [A] is a schematic side view of an alternative embodiment of the impregnation apparatus.

[0033] [ Figure 4 [This is a partial perspective view of a third embodiment of an impregnation apparatus for narrow or linear supports.]

[0034] [ Figure 5 ]、

[0035] [ Figure 6 ]、

[0036] [ Figure 7 ]、

[0037] [ Figure 8 ]and

[0038] [ Figure 9 ]yes Figure 1 , Figure 3 and Figure 4 A schematic diagram of the different electrode components of the impregnation equipment.

[0039] The specific embodiments shown are given as illustrative and non-limiting examples. Some elements are shown schematically and are not drawn to scale. In particular, powder particles are shown as individually visible to facilitate better understanding, but their actual size may be on the micrometer or even nanometer scale, making them invisible to the naked eye. Detailed Implementation

[0040] Figure 1 This is a schematic side view of an apparatus 100 for impregnating a fibrous or porous support S according to a first embodiment of the present invention.

[0041] The impregnation apparatus 100 includes a device 1 for moving the support S, which in this case is a longitudinal conveyor that moves the support along the longitudinal axis in a predetermined direction of travel (indicated by the arrow).

[0042] Specifically, the support S can be an open-cell foam, a mesh or fabric of woven or nonwoven fibers. A conveyor, for example, can remove the support S from the drum and transport it at the outlet to a winding machine that readjusts it back into the drum.

[0043] Impregnation equipment 100 includes means 5 for depositing powder material or powder P, such as a spreader, metering device, dispenser, or grid through which particles of powder P pass.

[0044] exist Figure 1In the example shown, powder P is deposited by gravity through dispenser 5, which distributes powder P by gravity, possibly accompanied by mechanical agitation of dispenser 5 to move the powder. Deposition occurs accordingly on the upper surface of support S.

[0045] However, powder P can also be deposited on the lower surface, for example by means of a blower or by depositing powder on a conveyor 1 and then covering it with a support S.

[0046] The support member S coated with powder P then passes under the constraint conveyor 3 along the travel direction, which covers the powder P and is used to spatially constrain the powder.

[0047] The support S then passes under the transverse electrodes 4 (three in this case), and these transverse electrodes are connected to AC high voltage generators G1, G2, and G3, which generate three phase-shifted potentials u, v, and w, each powering one of the electrodes 4.

[0048] These electrodes 4 are formed, for example, as thin metal strips deposited on a dielectric support.

[0049] Generators G1, G2, and G3 specifically generate potentials of several thousand volts or even tens of thousands of volts.

[0050] The phase shift of the electrodes 4 is typically in the range of 10° to 180°. As the powder passes under the electrodes 4, it is agitated by electrostatic forces and penetrates into the support S, thereby impregnating the support S with a controllable gradient in its thickness direction, and even achieving a uniform distribution of the powder P across the entire thickness of the support S.

[0051] The phase shift between electrodes 4 induces an electric field component parallel to the support, which causes the powder P to move longitudinally. This leads to the breakdown of agglomerated powder P clusters, which, when the powder is polarizable or sufficiently conductive, may form through electrostatic attraction of the powder P particles. This phenomenon is associated with the generation of traveling waves rather than standing waves in the impregnation zone.

[0052] However, a large phase shift (e.g., 120° or 180° for a three-phase or inverting generator) will generate a transverse electric field between the electrodes that is higher than the longitudinal electric field allowed for impregnation. The amplification factor of the electric field can be √3 or √2, which may cause arcing breakdown between adjacent electrodes 4, and thus lead to excessive horizontal sweeping or even failure of the impregnation device 100.

[0053] Therefore, for two or three phase shift potentials u, v, w, the phase shift is advantageously maintained at about 10° to 45°, and especially 15° to 30°.

[0054] The example discussed in this case involves two or three phase-shifted potentials; however, other embodiments with four or more mutually phase-shifted potentials are of course also possible.

[0055] These smaller phase shift ranges result in a sufficiently large longitudinal component to prevent the formation of agglomerates, while reducing the transverse voltage, thereby enabling a smaller gap between electrodes 4 at the same applied voltage.

[0056] Figure 1 The embodiment shown illustrates a second set of identical electrodes 4 facing the first set of three electrodes 4, but this second set of electrodes is connected to potentials u, v, w in a different manner. Specifically, along the direction of travel of the support, the top electrode 4 is connected sequentially to the first potential u, then to the second potential v, and finally to the third potential w.

[0057] Following the same convention, the bottom electrode 4 is connected in sequence to the third potential w, then to the first potential u, and finally to the second potential v.

[0058] This arrangement generates a composite electric field with a longitudinal component, which originates from the phase shift between the electrodes 4 located on the same side and from the phase shift between the electrodes 4 facing each other.

[0059] Figure 2 It shows Figure 1 The electrodes 4 of the immersion device and the electric fields oriented at different times within the same period of the AC potentials u, v, w between the electrodes 4.

[0060] Electrode 4 (not all reference numerals are shown in the figure) is shown with an oval cross-section, with six electrodes on each side of the central space through which the support S (not shown) passes.

[0061] The electric field is represented by an arrow, the orientation of which corresponds to the direction of the electric field, and the length of which corresponds to the strength of the electric field.

[0062] It can be seen that the paired facing electrodes 4 generate alternating strong and weak electric fields, with the electric field being mainly transverse at the center of the space between the facing electrodes 4.

[0063] At the edge of the space between the facing electrodes, a tilted electric field is observed, and therefore has a non-zero longitudinal component.

[0064] These electric fields are induced between adjacent phase-shifting electrodes 4 on the same plane, and the induced transverse electric field is used to disperse the agglomerated powder P.

[0065] Figure 3 An alternative embodiment of the impregnation apparatus according to the present invention is shown.

[0066] In this embodiment, the means for moving the support S includes a circular conveyor that moves in a cycle, such as a hollow roller around which the support S is wound.

[0067] The surface of conveyor 1 includes a reduced-size recess (in) Figure 3 (Not visible in the middle), the deposition device 5 deposits powder P in the recess.

[0068] The support member S is pressed against the outer surface of the conveyor 1 by a clamping device, which may be a special structure for inserting the support member or a device for tensioning the support member, for example by means of a reel that supplies the support member S and winds the support member at the outlet of the impregnation equipment 100.

[0069] During its cycle, the conveyor 1 passes the support S, which is pressed against its outer surface coated with powder P, over the electrode 4.

[0070] In this case, three electrodes 4 are shown, arranged inside the cylinder forming the conveyor 1. Each of them is connected to one of the potentials u, v, and w, and faces the plate electrode 40 with a floating potential.

[0071] Figure 4 A third embodiment of the impregnation apparatus 100 is shown, which is applicable to a support S in the form of a strip or a line.

[0072] The device 1 for moving the support S includes, for example, two spools that form the source of the untreated support S and adjust it once the support S has been impregnated.

[0073] Between the two spools 1, a strip-shaped or linear vertical tensioning section forming a support member S passes through a tubular constraint member 7, the support member S passes through the tubular constraint member 7, and the device 5 for deposition also dispenses powder P into the tubular constraint member 7.

[0074] Electrode 4 is located at the tubular constraint member 7, and in this case, specifically includes three electrodes 4 located on one side of the constraint member 7, which are connected from bottom to top to the first potential u, the second potential v and the third potential w, respectively.

[0075] By using this configuration of electrode 4 and a phase-shifted potential with an increasing phase from the first potential u to the third potential w, the powder P particles move in the opposite direction to the travel direction of the support S. When the powder is poured into the restraining member 7, this movement of the powder P is oriented upward, and thus the amount of powder lost falling at the lower outlet of the restraining member 7 can be reduced.

[0076] Conversely, if it is necessary to avoid the accumulation of powder P at the deposition device 5 or at the device inlet, the constraint member 7, the electrode 4 and their connections at different potentials u, v, w can be reversed so that the phase shift helps to advance the powder P along the travel direction of the support member S.

[0077] Therefore, the phase shift between potentials u, v, w enables the powder P to move backward or forward relative to the support S.

[0078] exist Figure 4 The electrode 4 facing these electrodes is a single grounded plate electrode 40.

[0079] The different electrode 4 and plate electrode 40 configurations shown in the above figures are interchangeable.

[0080] Figures 5 to 9 The electrode 4 and, where applicable, various possible configurations of the plate electrode 40 are illustrated.

[0081] exist Figure 5 In this structure, electrodes 4 are in the form of metal plates embedded in dielectric 41. There are three of them. Figure 5 The middle element is located at the top and is connected to one of the potentials u, v, and w.

[0082] Facing these three electrodes 4 are plate electrodes 40 that are not connected to any potential (including ground) and are therefore at a floating potential.

[0083] Considering that powder P is deposited on the support S from above, electrode 4 is therefore located on the side where the powder P is deposited.

[0084] The floating potential of the plate electrode 40 reduces the electric field as it approaches the plate electrode 40. This results in an electric field gradient across the thickness of the support S, which can controllably limit the penetration depth of the powder P into the support S.

[0085] This arrangement corresponds to Figure 3 The situation.

[0086] The opposite arrangement is also possible, in which the plate electrode 40 is located on the upper side and the three electrodes 4 are located on the lower side (or the powder P is deposited below the support S).

[0087] Figure 6 and Figure 5 They are basically the same, but the difference is that plate electrode 40 is grounded.

[0088] By grounding the plate electrode 40, the electric field remains relatively uniform and thus maintains a high standard until the portion near the plate electrode 40, where the electric field rapidly cancels out.

[0089] This results in a relatively uniform and strong electric field across the possible entire thickness of the support S, especially if the support has a small thickness, without the need to arrange and connect multiple facing electrodes.

[0090] This arrangement corresponds to Figure 4 The layout within.

[0091] Similarly, the opposite arrangement is also possible, in which the plate electrode 40 is located on the upper side and the three electrodes 4 are located on the lower side (or the powder P is deposited below the support S).

[0092] Figure 7 An arrangement with two sets of electrodes 4 is shown, which are located on each side of the channel of the support S.

[0093] The facing electrode 4 is connected to the same potential, from left to right: the first potential u, the second potential v, and the third potential w.

[0094] Figure 8 yes Figure 7 In the variant arrangement, specifically, the facing electrodes 4 are not connected to the same potential. Figure 8 The set of electrodes 4 located at the top are connected from left to right to the first potential u, the second potential v, and the third potential w, respectively.

[0095] exist Figure 8 A set of electrodes 4 located at the bottom are connected from left to right to the third potential w, the first potential u, and the second potential v, respectively.

[0096] This arrangement specifically corresponds to Figure 1 This situation allows for the acquisition of... Figure 2 The complex electric field described in detail is used to disperse agglomerates of powder P.

[0097] Figure 9 Another embodiment with two potentials u and v is shown. Electrode 4 comprises a series of pairs of electrodes 4, each pair of electrodes being connected to one of the potentials u and v, and all located on the same side of the support S. A grounded plate electrode 40 is arranged on the other side of the support S.

[0098] The series of phase shifts at the two potentials u and v produce significant agitation of the powder particles P during the passage of the support S covered with powder P.

[0099] An embodiment including a series of paired electrodes 4 on each side of the support S is also possible, with the facing electrodes 4 being able to be connected to the same potential u, v or phase-shifted potential u, v.

[0100] More generally, when powder P is polarizable or has sufficient conductivity, the use of multiple electrodes 4 with phase shift potentials makes it possible to greatly reduce the inhomogeneities associated with agglomerates of powder P.

Claims

1. An apparatus (100) for impregnating a fibrous or porous support (S) with a powder material (P), the apparatus (100) comprising: - A device (1) for moving the support (S). - An apparatus (5) for depositing the powder material (P) on one side of the support (S). - The transverse electrode (4) is connected to the terminals of the AC voltage generator (G1, G2, G3) to generate an electric field applied to the path of the moving support (S). The generator (G1, G2, G3) generates pairs of AC potentials (u, v, w) with phase shifts of 10° to 180°, wherein, in the direction of travel of the support (S), adjacent electrodes (4) are alternately connected to different potentials (u, v, w).

2. The device according to claim 1, characterized in that, The phase shift between the potentials (u, v, w) of the electrodes (4) is between 10° and 45°, and more particularly between 15° and 30°.

3. The device according to claim 1 or 2, characterized in that, The device includes one or more generators (G1, G2, G3) that generate three potentials (u, v, w), and adjacent electrodes (4) are each connected to different potentials of the one or more generators.

4. The device according to claim 1 or 2, characterized in that, The device includes one or more generators (G1, G2, G3) that generate two potentials (u, v), and adjacent electrodes (4) are each connected to different potentials of the one or more generators (G1, G2, G3).

5. The device according to any one of claims 1 to 4, characterized in that, The electrodes (4) connected to the different potentials (u, v, w) are located on the same side of the support (S), and on the other side of the support (S), the device does not include the facing electrode (4) or includes a plate electrode (40) with a floating potential.

6. The device according to any one of claims 1 to 4, characterized in that, The electrode (4) connected to the potential (u, v, w) is located on the same side of the support (S), and on the other side of the support (S), the device includes a single grounded plate electrode (40).

7. The device according to claim 1 or 2, characterized in that, The electrode (4) includes a series of pairs of electrodes (4) located on the same side of the support (S), each pair of electrodes being connected to one of two potentials (u, v).

8. The device according to any one of claims 1 to 4, characterized in that, The electrodes (4) are arranged on each side of the support (S), wherein facing electrodes (4) are connected to the same potential (u, v, w), or facing electrodes (4) are connected to pairs of phase-shifted potentials (u, v, w).

9. The device according to any one of claims 1 to 8, characterized in that, The device (1) for moving the support (S) includes: - A circular conveyor (1) that moves in a loop, the circular conveyor (1) having an outer surface including a recess, wherein the device (5) for depositing the powder material (P) deposits the powder material (P) in the recess of the outer surface. - A device for pressing the support member, which is configured to press the support member (S) against the outer surface of the annular conveyor (1), wherein the recess is filled with the powder material (P). - The annular conveyor (1) passes over the electrode (4) during its cyclic movement, wherein the support (S) presses against the outer surface of its recess containing the powder material (P).

10. The device according to any one of claims 1 to 8, characterized in that, The support member (S) is a linear strip or thin strip, and the device includes a tubular constraint member (7) through which the support member (S) to be impregnated passes, and the powder material (P) is also dispensed into the tubular constraint member (7). The electrode (4) is located at the constraint member (7) between the inlet of the support member and the powder material (P) and the outlet of the impregnated support member (S).

11. The device according to any one of claims 1 to 10, characterized in that, The electrode (4) has a phase-shifted potential (u, v, w) with an increasing phase shift in the direction of travel of the support (S) to drive the powder material (P) in the direction of travel of the support (S) by changing the electric field.

12. The device according to any one of claims 1 to 10, characterized in that, The electrode (4) has a phase-shifted potential (u, v, w) with a decreasing phase shift in the direction of travel of the support (S) to drive the powder material (P) in a direction opposite to the direction of travel of the support (S) by changing the electric field.

13. A method for impregnating a fibrous or porous support (S) with a powder material (P) by applying an electric field, the method comprising the steps of: -Move the support member (S); - Deposit powder material (P) onto the surface of a moving support (S); The method is characterized by further comprising the following steps: - The support (S) with the powder material (P) is conveyed at the electrode (4) of the generator (G1, G2, G3) that generates a pair of AC potentials (u, v, w) with phase shifts of 10° to 180°, wherein, in the direction of travel of the support (S), adjacent electrodes (4) are alternately connected to different potentials (u, v, w).

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