Patent Application
20130213957
1. Field of the Invention
The present invention relates to a dielectric heating system of a dielectric material such as a synthetic resin material, more particularly to heating of a thermosetting resin such as an epoxy resin or phenol resin.
2. Description of the Related Art
In molding of a plastic, in general the material is heated to make it plastic and then is injected into a mold etc. to impart a desired shape. For example, in the related art such as shown in
Further, in the related art such as shown in
The present invention, in view of the above problems, provides a dielectric heating system which secures ease of loading and unloading of an object to be heated, prevents leakage of the high frequency wave, and enables a heated object to be efficiently loaded into a later process.
To achieve this, the aspect of the invention of claim 1 provides a dielectric heating system which heats a dielectric object to be heated in a closed space by dielectric heating, the dielectric heating system being provided with a high frequency oscillator, a housing which forms part of a waveguide or a housing which has electrodes at part of the housing wherein the housing is provided with a loading opening and unloading opening, first and second conductive closing members which respectively close the loading opening and the unloading opening from the inner side of the housing, and a first position holding member which holds the object to be heated inside the housing, making the first conductive closing member slide to open the loading opening and charging the object to be heated into the housing and making the second conductive closing member slide to open the unloading opening and unloading the object to outside the housing.
Due to this, it is possible to secure ease of loading and unloading an object to be heated to and from a housing while reliably preventing leakage of the high frequency wave and performing dielectric heating. Furthermore, it is possible to efficiently load a heated object to a processing machine or mold or other later process right after heating.
These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein:
Below, referring to the drawings, embodiments of the present invention will be explained. In the embodiments, parts of the same configuration will be assigned the same reference numerals and explanations will be omitted.
Referring to
The object to be heated 1 is a dielectric material such as a synthetic resin. The heating device of the present invention, not limited to the embodiment, is suitable for heating a thermosetting resin such as an epoxy resin or phenol resin. In the case of the first embodiment, the waveguide 3 is provided, coaxially, with a loading opening 31 and an unloading opening 32. The first and second conductive closing members 12 and 13 respectively close the loading opening 31 and the unloading opening 32 at the time of heating. The first and second conductive closing members 12 and 13 slide by air cylinders or other drive actuators 20 and 21 through the rods 4. The left ends of the rods 4 of
The rods 4 are rod-shaped members of low permittivity and dissipation factor materials (alumina, polytetrafluoroethylene (PTFE), etc.) which are driven from outside of the waveguide 3. Leakage of the microwave from the drive-use rods 4 is reduced by covering the rods 4 by cylindrical conductive materials 8. Further, the metal housings of the drive actuators 20 and 21 are made to closely contact the partition plate 7 for covering and thereby prevent leakage. In the other embodiments as well, a similar configuration is adopted.
When transporting the object to be heated 1 by utilizing gravity, the loading opening 31 is provided at the top of the waveguide 3 and the unloading opening 32 is provided at the bottom. If using suction or discharge of air or rods or other assist, these openings do not necessarily have to be provided above and below each other and can be set coaxially in any direction. In the case of the first embodiment, inside of the waveguide 3 between the loading opening 31 and the unloading opening 32, an immovable first position holding member 14 is set so that its center axis becomes coaxial with the loading opening 31 and unloading opening 32. The loading opening 31, unloading opening 32, and first position holding member 14 are not limited in cross-sections to circular shapes and may also have rectangular shapes. Here, “coaxial” does not indicate coaxial in the strict sense and includes substantially coaxial.
The first position holding member 14 is comprised of a low permittivity and low dissipation factor member (alumina, PTFE, etc.) The same is true for the later explained second and third position holding members as well. The electrodes, waveguide, and conductive closing members 12 and 13 which close the openings are preferably Al or its alloy, Cu or its alloy, etc. Further, as a material with a low permittivity and low dissipation factor compared with the object to be heated 1, polypropylene (PP), PTFE, alumina, glass, etc. are preferable. In particular, for the sliding parts, PTFE, PP, etc. are preferable.
Referring to
After heating, the unloading opening 32 is opened by making the second conductive closing member 13 retract, then the heated object is unloaded and dropped through a chute etc. to be loaded into a processing machine of a later process. In unloading the object, a mechanism may be provided which uses rods, air, or other assist for unloading. Further, the first and second conductive closing members 12 and 13 may be provided outside of the housing, that is, outside of the electrodes and outside of the waveguide. As one example of a processing machine, a transfer molding machine which molds a thermosetting resin (epoxy etc.) etc. may be mentioned. As an illustration of an object to be heated 1, as a part which is obtained by transfer molding etc. of the above-mentioned epoxy resin etc., an IC package etc. may be mentioned, but the invention is not limited to this. The embodiments of the present invention can be applied broadly in general use processing machines. Due to this, it is possible to use fewer component members to realize electrodes or closing or opening of waveguide openings, facilitate the loading and unloading of an object to be heated 1, and suppress leakage of the high frequency wave.
The first and second conductive closing members 12 and 13 are provided to respectively close the loading opening 31 and unloading opening 32 from the inside of the housing. When providing these closing members at the outside of the waveguide, the outside dimensions of the system become larger. To keep the larger size of the facilities and longer operating stroke from causing a drop in productivity and a rise in processing costs as well, it is effective to not provide the parts outside of the waveguide as much as possible and to work to reduce the size. The position holding members which hold the object to be heated and the closing members which close the waveguide openings are set inside of the waveguide, so the outside dimensions of the present embodiment can be made smaller. For this reason, even when making the unloading part of the present embodiment enter inside the processing machine (specifically, between the open mold halves), there is no need to open up the mold wider. Further, as explained later, when the position of a material in a waveguide can be moved, it is possible to reduce the stroke which is required for entry. In this way, it is possible to realize a structure which is designed to heat a material and prevent leakage of a microwave by a small size system.
In a second embodiment which is shown in
As shown in
The operation of the second embodiment of the present invention becomes as follows. When an object to be heated 1 is loaded into the loading opening 31, the object to be heated 1 is held in position by the first position holding member 14 and the second position holding member 15. The first conductive closing member 12 and the third position holding member 14′, which are formed integrally each other, are made to advance to close the loading opening 31. At this time, the taper surface which is provided at the first position holding member 14 and the taper surface which is provided at the third position holding member 14′ are connected by a wedge action (first wedge connection). For this reason, after the object to be heated 1 is loaded into the loading opening 31, the first conductive closing member 12 can be pushed against and close the loading opening 31.
Before loading the object to be heated 1 in the loading opening 31, the second conductive closing member 13 and the second position holding member 15 which are joined integrally each other, are already advanced, so the taper surface which is provided at the first position holding member 14 and the taper surface which is provided at the second position holding member 15 are connected by a wedge action (second wedge connection). The second conductive closing member 13 is pushed against and closes the unloading opening 32. After the first and second conductive closing members 12 and 13 are closed, a high frequency wave is applied to heat the object to be heated. After this, the unloading opening 32 is opened by making the second conductive closing member 13, and the second position holding member 15 which are joined integrally each other, retract and the heated object is unloaded. In this embodiment, the first position holding member 14 is fastened to the waveguide 3 and is immovable and is provided with both the first and second wedge connections. (Note that even with just one of the first and second wedge connections, the leakage is reduced by that amount, so this is effective.)
In this way, when the taper surfaces are connected by a wedge action, leakage of an electrical wave can be prevented. If an electromagnetic wave leaks, electric power which can be used for heating the material is lost. This power loss ends up resulting in a longer heating time. Further, inside the waveguide, due to the effects of the microwave, a potential distribution is formed. This potential distribution acts on both the first and second conductive closing members 12 and 13. If the first and second conductive closing members 12 and 13 are pushed by the first and second wedge connections against the inside walls of the waveguide, there will no longer be any clearance at the interface between these and the inside walls of the waveguide and there will also no longer be a potential difference with the waveguide. In general, at locations where a potential difference is formed, a discharge phenomenon (sparks) occurs and the input power is greatly consumed, so the material heating time is greatly prolonged. Further, if the discharge phenomenon is large, the first and second conductive closing members 12 and 13 and the waveguide are liable to melt bond. According to the ANSI standard, it is known that the power density of the leaking electromagnetic waves has to be kept down to 5 mW/cm2 or less (for reducing effect on human body).
In third and fourth embodiments, the first position holding member 14 moves the object to be heated 1 from the loading part position (IN) of the loading opening 31 to the unloading part position (OUT) of the unloading opening 32. The first conductive closing member 12 is set at the first position holding member 14 and slides integrally with the first position holding member 14. In the fourth embodiment of
The action and effect of the third and fourth embodiments are as follows: The loading opening 31 is closed by making the first conductive closing member 12 and the first position holding member 14 which are integrally joined each other, advance to make the object to be heated move from the IN position to the OUT position and to close the opening. Further, a high frequency wave is applied to heat the object to be heated. The unloading opening 32 is opened by making the second conductive closing member 13 retract and to unload the heated object 1. In the fourth embodiment, the second conductive closing member 13 and the second position holding member 15 which are joined integrally each other, are made to retract to open the opening and unload the heated object 1. The merits of this structure are that, in addition to the merits of the first embodiment, by providing the loading part IN (loading opening 31) and the unloading part OUT (unloading opening 32) at different positions, the distance of movement to the processing machine can be shortened (for example, the distance of movement between the loading position of the object to be heated and the loading position of the heated object at the processing machine etc.).
Further, inside the waveguide, in the same way as there are antinodes and nodes in vibration, there are strong spots and weak spots in the field intensity. For this reason, the point of the ability to move the first position holding member 14, so that the object to be heated 1 can be held at any position inside of the waveguide (for example, a position with the highest field intensity), is also one of the important advantageous effects of the invention. Further, by moving the first position holding member 14, in accordance with the target temperature of heating of the object to be heated 1, it is possible to suitably adjust the strength position of the field intensity inside of the waveguide at the time of heating. In the case of the first and second embodiments as well, the loading opening 31 and unloading opening 32 should be set at positions of the highest field intensity.
In a fifth embodiment which is shown in
If, in this way, the first and second conductive closing members 12, 13 are kept from directly sliding against the wall surface of the inside of the waveguide, it is possible to prevent wear due to direct sliding from causing clearances to be formed. Further, it is possible to prevent dust from wear from being caught up and causing abnormal wear of the sliding parts (promoting wear, which promoted wear ends up causing larger clearances to be formed). Furthermore, it is possible to prevent dust from wear caused by sliding from being mixed in with the material and causing problems in quality.
The projecting sliding parts 16-1, 16-2, 17-1, and 17-2 are supported at the wall surface inside of the waveguide by two points (
Referring to
The first conductive closing member 12 and first position holding member 14 are made to advance through the loading opening 31 to close it. At this time, the second conductive closing member 13 and the second position holding member 15 may be simultaneously made to advance. The taper surface 34 which is provided at the first position holding member 14, and the taper surface 33 which is provided at the second position holding member 15, mate whereupon the first and second conductive closing members 12 and 13 are pushed by the waveguide 3 and closed. The high frequency wave is applied to head the object to be heated 1. The second conductive closing member 13 and the second position holding member 15 are made to retract to open the opening, then the heated object to be heated 1 is unloaded and is transported by a chute etc. to a later process.
While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-036015 | Feb 2012 | JP | national |
