Abstract
A mold having a first part with a carcass with a molding zone added thereto to provide a mechanical interface between the molding zone and the carcass. Inductors of the mold extend along a longitudinal direction in cavities between the mechanical interface and the molding zone. A cooling device of the mold extends at the mechanical interface between the molding zone and the carcass.
Claims
1. A mold comprising: a first part comprising a carcass with a molding zone added thereto to provide a mechanical interface between the molding zone and the carcass, the mechanical interface comprises an interface sheet made of a heat-conducting material configured to make up for differences in shape between the molding zone and the carcass; inductors extending along a longitudinal direction in cavities between the interface sheet and the molding zone; and wherein the inductors are enclosed in sealed sleeves that can resist a temperature of at least 250? C. to allow a cooling fluid to flow in the cavities around the inductors.
2. The mold according to claim 1, wherein the cooling fluid is water.
3. The mold according to claim 1, wherein the sealed sleeves are made of silica comprising closed porosities.
4. The mold according to claim 1, wherein the sealed sleeves are made of a heat shrinking polytetrafluoroethylene.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention is described below in its preferred embodiments, which are not limitative in any way, and by reference to FIGS. 1 to 6, wherein:
(2) FIG. 1 is a transverse sectional view of a general exemplary embodiment of the mold according to the invention;
(3) FIG. 2 is a transverse sectional view of a part of the mold according to the invention in one embodiment comprising a sheet between the molding zone and the carcass;
(4) FIG. 3 is a transverse sectional view of the first part of a mold according to an embodiment of the invention wherein the cooling device comprises a cavity filled with material capable of changing phases at a given temperature by absorbing latent heat of transformation;
(5) FIG. 4 is a transverse sectional view of a part of the mold according to the invention in an embodiment wherein cooling is achieved by the flow of heat-transfer fluid in the cavities receiving the inductors;
(6) FIG. 5 is a transverse sectional view of an embodiment of a part of the mold according to the invention comprising a device for cooling by transverse injection of gas under pressure into the cavities receiving the inductors, with, in the section SS, the direction of the injectors in a longitudinal section; and
(7) FIG. 6 is a transverse sectional view of an exemplary embodiment of a part of the mold according to the invention comprising two remote and separate induction circuits.
DETAILED DESCRIPTION OF THE EMBODIMENTS
(8) In FIG. 1, according to a first exemplary embodiment, the mold according to the invention comprises a first (101) part and a second (102) part. The description below is provided with the first part (101) as the reference. Those skilled in the art will adapt all the arrangements and embodiments described relating to this first part (101) to the second part of said mold. In this exemplary embodiment, the first part (101) is fixed to a mechanical support (120). Said first part of the mold comprises a carcass (111) fixed to that mechanical support (120) and receives at its distal end of said support (120) a molding zone (112) added to said carcass (111) by mechanical fastening (not shown). Thus, a mechanical interface (115) is created between the carcass and the molding zone. The mold comprises a heating device comprising inductors (132) extending in cavities (131) at the interface (115) between the molding zone (112) and the carcass (111), wherein said cavities are in this exemplary embodiment obtained by grooving the inside of the molding zone. A cooling device (140) represented here schematically also extends at the interface (115).
(9) In FIG. 2 of an exemplary embodiment, the mold according to the invention comprises a sheet (215) between the interface (115) and the cooling device. That sheet in graphite, nickel (Ni) or copper (Cu), which is heat-conducting, is capable of making up for the differences in shape between the molding zone (112) and the carcass (111) at the interface (115), so as to allow uniform contact between the carcass and the molding zone, and thus allow proper heat conduction between the two. The nature of the sheet is selected depending on the temperature to reach during molding. Advantageously, the sheet is brazed at the interface between the molding zone and the carcass, with the mold closed, using the mold heating device for the brazing. Thus the shape adaptation is perfect.
(10) In FIG. 3, according to another exemplary embodiment, the cooling device comprises a cavity (341, 342), which is filled by a material capable of phase transition at a determined temperature, wherein that phase transition is accompanied by the absorption of high latent heat. The phase transition is fusion or vaporization. Said material is water, for example.
(11) In FIG. 4, according to another exemplary embodiment of the mold according to the invention, each inductor (132) is placed in a sealed sleeve (431) that is resistant to high temperature. Depending on the target temperature for inductors, such a sleeve (431) is made of glass or silica, preferably comprising closed porosities to be both sealed and capable of withstanding the thermal shock of cooling. When the temperature of the inductors reached in operation is limited, for example for molding certain plastics, said sleeve is made of heat-shrinking polymer, for example polytetrafluoroethylene (PTFE or Teflon?) for inductor operating temperatures ranging up to 260? C. Thus, the cooling device is made up of the flow of heat-transfer fluid, for example water, in the cavities (131) receiving the inductors, wherein said inductors are insulated from contact with the heat-transfer fluid by their sealed sleeve.
(12) Alternatively, the heat-transfer fluid is a dielectric liquid, for example a dielectric oil. This type of product is available in the market, particularly for cooling transformers. In that case, the electrical insulation of the inductors (132) is not necessary.
(13) In FIG. 5, according to another exemplary embodiment, cooling is carried out by injecting gas in the cavities (131) receiving the inductors (132). To improve the efficiency of the cooling, the gas is injected under pressure of about 80 bars (80.Math.10.sup.5 Pa), by a plurality of conduits (541) distributed longitudinally along the inductors (132). The injection is thus carried out at several points, along the inductors, through injection conduits (542), transversally to said inductors (132).
(14) In section SS of a longitudinal sectional view, the injection conduit (542) is directed so that the direction of the fluid jet in the cavity of the inductor has a component parallel to the longitudinal direction. Thus, by appropriately selecting the injection angle, effective cooling is obtained by a turbulence flow of the gas along the inductor (132).
(15) The temperature gradients present particularly in the carcass, which is fixed to the mechanical support, are liable to lead to distortions of the device or differential deformation stresses. Thus, in an advantageous embodiment, the carcass (111) and the molding zone (112) are made in an iron and nickel alloy comprising 64% iron and 36% nickel, called INVAR, with a low thermal expansion coefficient for temperatures below the Curie temperature of that material, when the material is in the ferromagnetic state, and thus sensitive to induction heating.
(16) In FIG. 6, according to a last embodiment compatible with the previous embodiments, the mold comprises a second series (632) of inductors remote from the first. The first (132) and the second (632) series of inductors are connected to two different generators. Thus, heating is distributed dynamically between the two series of inductors, so as to limit the deformations of the parts of the mold, which deformations are generated by thermal expansion combined with the thermal gradients that occur in the heating and cooling phase.
