FR2812444A1 - Variable solenoid characteristic manufacture process having cylindrical metal tube helical grooves formed with outer mould fusible alloy/resin space added/heated above fusion point forming solenoid. - Google Patents

Abstract

The solenoid manufacture method has a cylindrical metal tube (1) into which helical grooves (2) are formed. A mould (3) is manufactured forming a space between the tube and the outer. A fusible alloy (4) is added in the space and an isolating resin added (7). The alloy is heated just above the fusion point sticking the isolating resin (8) in place.

Description

PROCESS FOR PRODUCING A SOLENOID WITH CHARACTERISTICS

VARIABLES ALONG ITS AXIS

  The present invention relates to a method for producing a

  solenoid, in particular with variable characteristics along its axis.

  To make solenoids with variable pitch and number of strands along their axis, such as solenoids used in electromagnetic wave compression devices, we weld or braze with the main wire of the winding, at the appropriate places, one or more other wires, all isolated from each other after welding. When such solenoids are subjected to high currents, special care must be taken in the welds or solders, which must be free of porosities, inclusions and bonding, which is difficult to achieve and above all to control. Similarly, good quality insulation of the different wires of the winding, using a thin strip of insulating material ("Teflon" for example) is difficult to achieve, and cannot

  be automated. These difficulties result in a high cost of production.

  The subject of the present invention is a method for producing a solenoid, in particular with characteristics (pitch and / or number of conductors and / or section) variable along its axis, a method which is simple and inexpensive to implement , while making it possible to obtain a solenoid

free from all defects.

  The present invention also relates to a solenoid, in particular with variable characteristics along its axis, which is of very good homogeneous quality over its entire length and which can be separated.

  of its support mandrel while retaining its characteristics.

  The process in accordance with the invention consists in taking a metal tube having the diameters and total length of the solenoid to be produced, in machining it over approximately half of its thickness, on its outer face, in order to form there the helical trace of the solenoid, to surround the metal tube thus machined with a mold of cylindrical internal shape coaxial with the tube and with a diameter greater than the external diameter of the metal tube, which is fixedly fixed relative to the mold, to cast a fusible alloy at point of melting advantageously equal to or less than about 100 ° C. in the space between the mold and the metal tube, to machine the inner face of the tube, to heat the fusible alloy to a temperature slightly above its melting point until eliminated all this alloy, and to flow

  an insulating resin on the outside of the winding.

  The present invention will be better understood on reading the

  detailed description of an implementation mode, taken by way of example not

  limiting and illustrated by the appended drawing, in which: * FIGS. 1A to 1F are simplified partial views in section of a solenoid in accordance with the invention at different successive stages of its production, and * FIG. 2 is an external view in perspective and partial of a solenoid as obtained according to the method of the present invention. The present invention is described below with reference to the production of a solenoid for generating high-power electromagnetic pulses, a solenoid whose pitch and / or number of conductors vary from one end to the other of its length. , but it is understood that the invention is not limited to this single application, and that it can be implemented to produce solenoids of other types, such as regular solenoids whose successive turns are contiguous while having to be strongly isolated from each other, or else freestanding solenoids whose winding would not be rigid enough to keep them in shape

  determined after winding if the invention was not applied.

  The first step of the invention consists in machining a metal tube 1 with circular section whose length is equal to or greater than that of the solenoid to be obtained, and whose thickness is substantially equal to the diameter of the metal wire that would be used for wind the solenoid according to the conventional method. It should be noted that the section of the solenoid conductor produced according to the method of the invention is rectangular (or practically rectangular with corners which can be rounded if the machining tool is provided and guided for this purpose), which can need to adapt the thickness of the tube 1 accordingly, so that it has the same characteristics of admissible current density as the conventional conductor with circular section. The first step (FIG. 1A) consists in etching in the outside face of the tube 1 a helical groove 2 whose depth is practically equal to half the thickness of the tube 1. The profile of this groove can be rectangular, as shown on the drawing, but it may have another shape, for example a rectangular bottom which widens progressively at the level of the external face of the cylinder, in order to round the edges of the remaining part. The width of the groove and / or its pitch can

  vary continuously or in jumps.

  In the next step (FIG. 1B), the tube 1 thus etched on the outside is placed inside a mold which is, for example, another metal tube 3, which has a slightly larger internal diameter (by a few millimeters for example ) to the outside diameter, before etching, of the tube 1. The length of the tube 3 is substantially equal to that of the tube 1: it must be at least 10 equal to that of the etched part of the tube 1. The tube 3 is fixed to the support (not shown) of the tube 1, so that they are coaxial with each other. Then, a fusible material 4 is poured into the space between these two tubes. This material 4 advantageously has a melting temperature of less than 100 C. It can be a quaternary alloy, for example an alloy called "CERROBEND", fusible with 99 C; The essential characteristic of the material 4 is that it can be

  easily and completely eliminated after the fourth step described above

  below, while strongly adhering to tubes 1 and 3 until this fourth step (to allow easy and safe execution of the third step described

below).

  In the third step (FIG. 1C), a helical groove 5 is engraved in the inner face of the tube 1 which is the exact image of the groove 2 relative to a circular cylindrical surface 6 (the trace of which is visible in FIG. 1B) coaxial with the tube 1, passing through the bottom of the groove 2. If the depth of the groove 2 and equal to half the thickness of the tube 1, that of the groove 5 is equal to it,

  and there should no longer be any material from the tube 1 at the bottom of the groove 5, that is

  say that the engraving of the groove 5 must make the material 4 appear at the bottom of this groove. Of course, if, for reasons of machining convenience or mechanical strength of the tube 1, the depth of the groove 2 was greater or smaller than the half thickness of the tube 1, the depth of the groove 5 would be

  decreased or increased accordingly.

  In the fourth step (FIG. 1 D), an insulating resin 7 is poured onto the inside face of the tube 1, so that it perfectly fills the groove 5 and covers the inside face of the remaining part of the tube 1 with a thickness sufficient to form a rigid support tube capable of subsequently supporting the conductive part of the solenoid before it is placed on a solid support mandrel, if such a mandrel is provided, or else to form a self-supporting support otherwise. In the first case, the thickness of the insulating resin layer 7 covering the internal face of the tube 1 may be less than in the second case, and is a function of the outside diameter of the solenoid support mandrel. In all cases, this thickness of the insulating resin layer 7 is a function of the qualities

  mechanics of this resin and the length of the solenoid.

  Then, as soon as the resin 7 is hardened, the fusible alloy 4 is melted, for example by immersing it in boiling water if this

  alloy has, as mentioned above, a melting temperature of 990C.

  Of course, if the material 4 has another composition, and if it melts at a temperature above 100 ° C., an appropriate process is used to melt and eliminate it, without damaging either the solenoid remaining after the external etching and inside of the tube 1, neither the resin 7. The structure shown in FIG. 1 is then obtained. Finally, as shown in FIG. 1F, a layer of resin 8 is poured onto the outside of the solenoid, perfectly filling the groove 2 released by the elimination of the material 4. The thickness of the layer 8 above the outer face of the solenoid can be substantially the same as that of the layer 7 under the inner face of the solenoid. Of course, the layers 7 and 8 are formed in a manner known per se so as not to contain any air bubble which would be detrimental to the high voltage withstand of the solenoid. As shown in the drawing, layers 7 and 8 extend axially from the solenoid and meet beyond the ends

  1A and 1B of this solenoid, in order to coat it completely.

  FIG. 2 shows an example of a solenoid produced according to the method of the invention, the layers 7 and 8 not being shown for clarity of the drawing. One sees there clearly the successive changes of section of the solenoid, that is to say, in the present case, that at different successive points it has "branches" from which one or more "secondary" conductors leave. It is important to note that these branches do not result from welding of "secondary" conductors to a main conductor, as is the case for the prior art, but from a simple machining of a homogeneous tube, and what is

  "branches" are therefore perfectly homogeneous.

Claims (9)

  1. Method for producing a solenoid, characterized in that it consists in taking a cylindrical metal tube (1) having the diameters and total length of the solenoid to be produced, in machining it over approximately half of its thickness, on its outer face, to form the helical trace (2) of the solenoid there, to surround the metal tube thus machined with a mold (3) of coaxial cylindrical interior shape of the type and with a diameter greater than the outside diameter of the metal tube , which is held fixedly relative to the mold, to pour a fusible alloy (4) into the space between the mold and the metal tube, to machine (5) the inner face of the first machining on the rest of the thickness of the tube, pouring an insulating resin (7) on the inner face of the tube, heating the fusible alloy to a temperature slightly above its melting point until all this alloy is eliminated,   and pouring an insulating resin (8) on the outer face of the winding.   2. Method according to claim 1, characterized in that   The fusible alloy has a melting point equal to or less than 100 C.   3. Method according to claim 2, characterized in that   the alloy is a quaternary alloy called "CERROBEND".   4. Method according to one of the preceding claims,   characterized by the fact that the solenoid has variable characteristics along of its axis.   5. Solenoid characterized in that it is in the form of a homogeneous ribbon in one piece, cylindrically wound and embedded in a resin (7, 8).   6. Solenoid according to claim 5, characterized in that it   has variable characteristics along its axis.   7. Solenoid according to claim 6, characterized in that   its pitch is variable along its axis.   8. Solenoid according to claim 6 or 7, characterized in that   that its section is variable along its axis.   9. Solenoid according to one of claims 6 to 8, characterized by   the fact that it includes, at different successive points, branches.