EP0329864A2

EP0329864A2 - Far infrared drying device

Info

Publication number: EP0329864A2
Application number: EP88202866A
Authority: EP
Inventors: Kenjiro Yoshihara
Original assignee: Yoshihara and Co Ltd
Current assignee: Yoshihara and Co Ltd
Priority date: 1988-02-23
Filing date: 1988-12-13
Publication date: 1989-08-30
Also published as: JPH01128703U; AU590486B2; AU2581388A; EP0329864A3

Abstract

A far infrared drying device comprising a hot air chamber housing (12) having an inner end and an outer end and defining therein a hot air chamber (12a), an electric heater (18) and a blower unit (24) disposed adjacent the inner end of the hot air chamber housing for introducing hot air into the hot air chamber, a radiant heat-resistant plate (16) disposed across the outer end of the hot air chamber housing, and restrictive aperture means (30) provided in at least one of the hot air chamber housing and the radiant heat-resistant plate for discharging the hot air introduced into the hot air chamber therefrom while restricting the amount of the discharged hot air, the radiant heat-resistricted plate having a ceramic layer (31) over its outer surface.

Description

Background of the Invention

The present invention relates to a far infrared drying device, and more particularly, to a far infrared drying device suitable for use as hair driers, food drying machines, cloth drying machines, etc., in which far infrared rays and hot air are combined to effect drying under heating.
At present, electromagnetic waves, not speak of radio waves, are being applied and utilized everywhere. Far infrared rays are one sort of electromagnetic waves, and it is widely known that electromagnetic vibrations in a far infrared range are absorbed by organic substances, living bodies, etc. and hence serve as a heating source. Radiation of far infrared rays is not appreciably absorbed by air, and molecular bond lattice vibrations in the organic substances are resonated at the wavelength of radiation, so that effective heating is achieved with small amount of loss. In addition to specific properties of electromagnetic waves that radiation can be concentrated and dispersed, radiation heating has an advantageous feature that uniform irradiation results in uniform heating as with a beam of light. Thus, if the infrared absorption wavelength of the substance to be heated and dried is known, ideal heating and drying can be performed by fabricating a device which radiates an infrared ray in match with the absorption wavelength.
Further, a shorter wavelength range of infrared rays is absorbed as heat energy with a small absorption rate, whereas a longer wavelength range thereof is absorbed with a larger absorption rate. The heating efficiency is thus more increased in a far infrared range.
Therefore, a relatively low temperature range of the radiator surface less than 400 °C can cause the organic substances to produce heat vibrations and those in uniform amplitude sufficiently.
In the meanwhile, hot-air type drying devices usually manufactured for the purpose of drying under heating require an extremely high temperature of hot air and a large quantity of air drift at a high flow speed, since heat is transmitted through convection. This means that the surface of a substance to be dried is subject to high temperatures for a long period of time and only the surface portion is over-dried due to rapid drift of air, thereby preventing the substance from being uniformly heated and dried. As a result, a problem may arise in the frequent occurence of deformation, degeneration, discoloration, etc.
It is an object of the present invention to solve the foregoing drawback in the conventional drying devices of convection type, and to provide a far infrared drying device in which far infrared rays having desired characteristics as mentioned above are combined with a convection system to effect drying under heating.

Summary of the Invention

The above object of the present invention is achieved by a far infrared drying device comprising a hot air chamber housing having an inner end and an outer end and defining therein a hot air chamber, an electric heater and a blower unit disposed adjacent the inner end of the hot air chamber housing for introducing hot air into the hot air chamber, a radiant heat-resistant plate disposed across the outer end of the hot air chamber housing, and restrictive aperture means provided in at least one of the hot air chamber housing and the radiant heat-resistant plate for discharging the hot air introduced into the hot air chamber therefrom while restricting the amount of the discharged hot air, the radiant heat-resistant plate having a ceramic layer over its outer surface.
The restrictive aperture means preferably defines the opening ratio in a range of from about 1 to 20 % of the total surface area of the radiant heat-resistant plate.
As one example, the radiant heat-resistant plate is of a perforated heat-resistant plate having a number of holes which constitute the restrictive aperture means. In this case, porous shield means may be disposed close to the inner surface of the perforated heat-resistant plate for regulating the amount and speed of hot air discharged from the hot air chamber through the holes of the perforated heat-resistant plate. The apertures of the porous shield means defines, in combination with the holes of the perforated heat-resistant plate, the opening ratio in a range of from about 1 to 20 % of the total surface area of the radiant heat-resistant plate.
As an alternative example, the hot air chamber housing may be of a perforated housing having a number of holes, the restrictive aperture means being constituted by these holes.
In the far infrared drying device of the present invention thus constructed, the hot air introduced into the hot air chamber by the electric heater and the blower unit is discharged not directly, but restricted by the restrictive aperture means so that most of the hot air is prevented from flowing therethrough to produce a hot air plenum in the hot air chamber. The hot air plenum is utilized as a heat source for heating the radiant heat-resistant plate. In order to prevent the reverse pressure from being applied to the blower unit, a part of the hot air is discharged to the outside through the restrictive aperture means. The radiant heat-resistant plate heated by the hot air conducts heat energy to the ceramic layer on its outer surface, so that the heat energy is radiated from the ceramic layer surface in the form of infrared rays.
Far infrared rays are one sort of electromagnetic waves and hence not principally affected by convection of air (wind). This is based on the assumption that the air must be free of any infrared absorbing substances such as water vapors and dust. However, since it is practically impossible to suppress the occurrence of water vapor during the heating and drying steps of substances, water vapor is desirably purged with air drift for efficient drying. According to the present drying device, a small amount of hot air (dried air) decelerated in the hot air chamber is discharged through the restrictive aperture means to carry out the aim of purging moisture.
The far infrared drying device of the present invention can simply and freely be designed and manufactured by combination of commercial electric appliances easily available, dependent on end uses or scales of the finished products. More specifically, the wavelength of far infrared rays is determined by the surface temperature of the radiator and, in the present invention, by the surface temperature of the outer ceramic layer of the radiant heat-resistant plate. That surface temperature is in turn determined by the temperature of the hot air plenum formed in the hot air chamber. Then, the temperature of the hot air plenum can be varied, regulated and maintained by adjusting any one or combination of operating capacities of the electric heater and the blower unit, the distance between the electric heater and the radiant heat-resistant plate, and the capacity of the hot air chamber. Therefore, it is possible to freely change a temperature of the ceramic layer, i.e., the wavelength of far infrared rays radiated, and hence to produce far infrared rays dependent on respective infrared absorption characteristics specific to various substances to be dried.
By the way, there are nowadays known absorption spectra of organic chemical substances in order of about 200 thousands types, and many of those organic chemical substances are affirmed to have their absorption spectra in ranges of from 3 to 4 microns, from 6 to 7 microns, and from 9 to 12 microns. The radiation wavelength can be determined based on the Wien's displacement law as follows; wavelength = 2898 ÷ (surface temperature of radiator + 273 °C ). In contrast with this, the surface temperature can be determined from the wavelength using the equation of 2898 ÷ wavelength - 273 °C = surface temperature.
It is generally assumed that a wavelength range of from 6 to 7 microns is desired for the industrial field in which heating and drying are mainly intended, except for such functions as melting and cooking or organic substances, and a wavelength range of from 9 to 12 microns is desired for living bodies, etc.
If the wavelength of 7 micron is optimum for heating and drying fishes to produce opened and dried ones without impairing nutritive elements such as protein and vitamin contained therein, it will be required to set a temperature of the ceramic layer of the radiant heat-resistant plate at approximately 141 °C.
In addition, in order to obtain the larger amount of energy at the same wavelength range (i.e., at the same temperature of the radiator) and radiate the heat energy uniformly onto substances to be dried, the possibly large radiation area has to be ensured. According to the present invention, the capacity of the hot air chamber as well as the size and shape of the ceramic layer of the radiant heat-resistant plate can be designed and manufac tured in any ways. Where the capacity of the hot air chamber and the area of the ceramic layer of the radiant heat-resistant layer are increased, it is merely needed to compensate the necessary amount of heat by readjusting the either one or combined capacity of the electric heater and the blower unit.
In the far infrared drying device of the present invention, the opening area of the restrictive aperture means is determined taking into account harmonization between the hot air plenum formed in the hot air chamber to heat the radiant heat-resistant plate and discharge of hot air from the hot air chamber in a small amount necessary enough to purge moisture. From this viewpoint, the opening ratio of the restrictive aperture means is preferably in a range of from about 1 to 20 % of the total surface area of the radiant heat-resistant plate, more preferably in a range of from about 2 to 7 % thereof.
In case the radiant heat-resistant plate is formed of a perforated heat-resistant plate having a number of holes and the restrictive aperture means is constituted by those holes, a small amount of hot air discharged through the holes flows in the same direction as the far infrared rays, thereby making it possible to effect drying under heating while allowing an adequate amount of hot air to directly strike against the substance to be heated.
In an alternative case the porous shield means is disposed close to the inner surface of the perforated heat-resistant plate and the holes of the perforated heat-resistant plate defines, in combination with the apertures of the porous shield means, the opening ratio of the restrictive aperture means, the opening ratio of the perforated heat-resistant plate can be modified by properly selecting the opening ratio of the porous shield means, and hence the opening ratio of the restrictive opening means can easily be adjusted.

Brief Description of the Drawings

Fig. 1 is a sectional view showing a far infrared drying device according to one embodiment of the present invention;
Fig. 2 is an exploded perspective view of the far infrared drying, expecting a body housing;
Fig. 3 is a sectional view of a radiant heat-resistant plate of the far infrared drying device;
Fig. 4 is a sectional view showing the far infrared drying device according to another embodiment of the present invention; and
Fig. 5 is a sectional view of the far infrared drying according to still another embodiment of the present invention.

Detailed Description of the Preferred Embodiments

A few embodiments of the present invention will be described below with reference to Figs. 1 through 5. These figures merely illustrate the embodiments of the present invention by way of example, and should not be construed to limit the invention.
Referring to Figs. 1 and 2, designated at reference numeral 10 is a relatively small, portable far infrared drying device according to one embodiment of the present invention. The illustrated device can be used as a hair drier, for example. The far infrared drying device 10 comprises a hot air chamber housing 12 having an inner end and an outer end and defining therein a hot air chamber 12a, a cylindrical heat reflection housing 14 disposed adjacent the inner end of the hot air chamber housing 12, a radiant perforated heat-resistant plate 16 disposed across the outer end of the hot air chamber housing 12, an electric heater 18 disposed within the heat reflection housing 14, a mount and heat protection plate 20 for mounting thereon the electric heater 18 and shielding heat produced by the electric heater 18, an electric motor 22 and a propeller type blower 24 for introducing air heated by the electric heater 18 as hot air into the hot air chamber 12a, and a body housing 26 for accommodating therein the heat reflection housing 14, the electric heater 18, the mount and heat protection plate 20, the electric motor 22 and the blower 24.
The hot air housing 12 is made of any suitable material resistant to high temperatures, preferably a molding of synthetic resin resistant to high temperature, for example. It is to be noted that if radiation in a range of short wavelengths is required, moldings of a refractory fibrous material or stainless steel will be preferable. The hot air chamber housing 12 is configured such that the outer periphery of the hot air chamber 12a is tapered from the outer end side toward the inner end side to ensure the possibly wide radiation area. The hot air chamber housing 12 is opened at its inner end and has a cylindrical sleeve 12b projecting inward therefrom. The corresponding end of the body housing 26 is axially fitted over the cylindrical sleeve 12b, and the hot air chamber housing 12 is detachably attached to the body housing 26 by means of screws or the like. The hot air chamber housing 12 is also opened at its outer end and has a cylindrical sleeve 12c projecting outward therefrom.
The perforated heat-resistant plate 16 is disposed across the outer end of the hot air chamber housing 12 to close the end opening and has a number of holes 30. The perforated heat-resistant plate 16 is preferably of a thin, disc-like molding of synthetic resin, and has a cylindrical flange 16a axially projecting from the outer periphery thereof. The cylindrical flange 16a is axially fitted over the cylindrical sleeve 12c at the outer end of the hot air chamber housing 12, so that the perforated heat-resistant plate 16 and the hot air chamber housing 12 are fixed together by means of any suitable fastening members such as screws. As an alternative, both the members 12 and 16 may be molded as a one-piece component.
The heat reflection housing 14 is formed of a thin plate such as an aluminium plate, for example, and has a uniform diameter between the opposite open ends thereof, the diameter being slightly smaller than the inner diameter of the body housing 26. The heat reflection housing 14 functions as a heat reflection member for protecting the body housing 26 against a large amount of heat produced by the electric heater 18.
The electric heater 18 is preferably of a coiled heater made of Nichrome wire, which is widely employed as one of household electric appliances, because of its versatility.
The mount and heat protection plate 20 is of a disc-like, aluminium-made punched plate, and provided on one surface facing the electric heater 18 with a plurality of bar-like mount fittings 20a for supporting thereon the electric heater 18 so that it serves, on one hand, to support the electric heater 18. On the other hand, the plate 20 also serves as a heat protection plate which is effective in preventing the large amount of heat produced by the electric heater 18 from being directly transmitted to the electric motor 22. The plate 20 has a diameter fairly smaller than the inner diameter of the body housing 26, and is attached to the body housing 26 such that air flow produced from the propeller type blower 24, which is driven by the electric motor 22 through a motor shaft, can smoothly be introduced into the hot air chamber 12a via the interior of the heat reflection housing 14 and the electric heater 18 without substantial obstruction. Incidentally, the electric heater 18 may be supported on mount fittings secured to the inner wall of the heat reflection housing 14. A sirocco fan may be used as the blower 24.
The body housing 26 is formed of a heat-resistant material and preferably provided with a leg portion 26a for convenience in carrying and gripping. Within the leg portion 26a, there can be incorporated a suitable control unit 26b which enables to switch the electric capacity applied to the electric heater 18 and the electric motor 22 from one to another.
As shown in Fig. 3, each of the holes 30 bored through the radiant heat-resistant plate 16 has a cylindrical shape with a uniform diameter. It is desired that, as shown in Fig. 2, the holes 30 are arranged over the surface of the radiant heat-resistant plate 16 in a uniformly dispersed pattern as a whole. The total area of the holes 30 is substantially smaller than the total surface area of the radiant heat-resistant plate 16 on either one of the inner and outer sides, and the holes 30 constitute restrictive aperture means for discharging the hot air introduced into the hot air chamber 12a therefrom while restricting the amount of the discharged hot air. More practically, the total area of the holes 30 is in a range of from about 1 to 20 %, preferably in a range of from about 2 to 7 % particularly for end use intended in this embodiment. In this case, therefor, a range of from about 93 to 98 % of the total surface area of the radiant heat-resistant plate 16 defines a surface on the inner side of the radiant heat-resistant plate 16, which serves to block out-flow of of the hot air and produce heat radiation to the interior of the hot air chamber, and also defines a surface on the outer side thereof which produces heat radiation onto the substance to be heated and dried. The holes 30 can be arranged over the radiant heat-resistant plate 16 randomly, or in any other suitable patterns or fashions.
As shown in Fig. 3, the radiant heat-resistant plate 16 has a ceramic layer 31 formed over its outer surface and the cylindrical inner surface of the respective holes bored therethrough. Preferably, the ceramic layer 31 is formed by mixing siliceous minute particles with silicon paint and then applying the mixture to the above surfaces by baking painting.
In the far infrared drying device thus constructed, the hot air introduced into the hot air chamber 12a by the electric heater 18 and the blower unit, comprising the electric motor 22 and the blower 24, is discharged not directly, but restricted such that most of the air flow is prevented from flowing to the outside by the inner surface of the radiant heat-resistant plate 16, for example, the foregoing non-perforated portion of 93 to 98 %, to produce a hot air plenum in the hot air chamber 12a. The temperature of the hot air plenum becomes higher as the holes 30 as the restrictive aperture means give a stricter restriction to the air flow passing therethrough, i.e., as the opening ratio of the holes 30 is smaller. The hot air plenum is utilized as a heat source for heating the radiant heat-resistant plate 16. The heated radiant heat-resistant plate 16 transmits the heat energy to the ceramic layer 31 on its outer surface, so that far infrared rays are radiated from the surface of the ceramic layer 31 in the form of heat energy.
In order to prevent the reverse pressure from being applied to the blower unit, a part of the hot air introduced into the hot air chamber 12a is discharged to the outside through the holes 30 of the radiant heat-resistant plate 16 in the same direction as the far infrared rays.
In this manner, both far infrared rays and a small amount of hot air are radiated and discharged from the radiant heat-resistant plate 16 in the same direction, so that the substance to be heated and dried, which is positioned in front of the radiant heat-resistant plate 16, is dried under heating by the action of both the far infrared rays and the hot air, with an adequate amount of hot air being kept discharged to strike against the substance surface. As a result, the substance to be heated and dried can uniformly and sufficiently be dried under heating up to the interior thereof, while the adequate amount of hot air serves to eliminate the infrared absorbing matters, such as water vapors and dust, produced by the substance to be heated and dried, thereby ensuring it to offer positive heating and drying action with the far infrared rays. In case of hair driers, the adequate amount of hot air also serves to give a human body with warmness in soft touch, provide a tender striking of the hot air against hair, and hence offer a comfortable feeling in usage.
According to this embodiment, therefore, it becomes possible to effect optimum drying under heating dependent on the end use by combination of the far infrared rays and the adequate amount of hot air.
In the foregoing embodiment, the holes 30 are bored through the radiant heat-resistant plate 16. However, the holes 30 can be bored in place other than the radiant heat-resistant plate 16, because they are basically to constitute the restrictive aperture means as mentioned above. For example, the holes 30 may be bored through the hot air chamber housing 12. Fig. 4 shows such a modified embodiment in which the identical members as those in Fig. 1 are designated at the same reference numerals. In this modified embodiment, the opening ratio of the holes 30 is likewise defined in a range of from about 1 to 20 % of the total surface area of the radiant heat-resistant plate 16 with a view of constituting the restrictive aperture means.
Fig. 5 shows still another embodiment of the present invention. In Fig. 5, the identical members as those in Fig. 1 are designated at the same reference numerals. This embodiment illustrates a large-scaled far infrared drying machine 40 for industrious use. A hot air chamber housing 12 and a radiant heat-resistant plate 16 are both disposed within a drying chamber 41 built of fireproof bricks. The members 12 and 16 have a rectangular shape, also as viewed from front, in matching with the drying chamber 41, A heat reflection housing 14, electric heater 18, heat protection plate 20, electric motor 22, and blower 24 are all disposed outside the drying chamber 41, and The outlet end of the heat reflection housing 14 is connected through a duct 41 to the hot air chamber housing 12 within the drying chamber 41.
Within the hot air chamber housing 12, there is disposed porous shield means 43 close to the inner surface of a perforated heat-resistant plate 16 for regulating the amount and speed of hot air discharged from a hot air chamber 12a through holes 30 of the perforated heat-resistant plate 16. The porous shield means 43 can be formed of a glass fiber fabric, for example, and its opening ratio can freely be set by selecting the desired mesh size of the fabric. In this embodiment, the holes 30 of the perforated heat-resistant plate 16 and the apertures of the porous shield means 43 jointly constitute restrictive aperture means. The sum of opening ratios of the above holes and apertures defines the foregoing preferable opening ratio in a range of from about 1 to 20 % of the total surface area of the radiant heat-resistant plate 16.
In this embodiment, the opening ratio of the holes 30 of the radiant heat-resistant plate 16 can be modified by properly selecting the opening ratio of the porous shield means 43, i.e., mesh size of the glass fiber fabric. Thus, the opening ratio of the restrictive aperture means is adjusted easily.
Although the present invention has been described as being applied to a drying device, the invention is also applicable to other uses in which heating resulted from combination of far infrared rays and hot air is utilized. By way of example, the present invention can be used for a heating system.
As described above, according to the present invention, since far infrared rays and hot air are combined to effect drying under heating, it becomes possible to uniformly heat and dry up to the interior of the substance to be heated and dried. It is also possible to solve the problem of frequent occurrence of deformation, degeneration and discoloration, which has been experienced in the convection type.

Claims

(1) A far infrared drying device comprising a hot air chamber housing (12) having an inner end and an outer end and defining therein a hot air chamber (12a), an electric heater (18) and a blower unit (24) disposed adjacent the inner end of said hot air chamber housing for introducing hot air into said hot air chamber, a radiant heat-resistant plate (16) disposed across the outer end of said hot air chamber housing, and restrictive aperture means (30) provided in at least one of said hot air chamber housing and said radiant heat-resistant plate for discharging the hot air introduced into said hot air chamber therefrom while restricting the amount of the discharged hot air, said radiant heat-resistant plate having a ceramic layer (31) over its outer surface.
(2) A far infrared drying device according to claim 1, wherein said restrictive aperture means (30) defines the opening portion in a range of from about 1 to 20 % of the total surface area of said radiant heat-resistant plate (16).
(3) A far infrared drying device according to claim 1, wherein said radiant heat-resistant plate is of a perforated heat-resistant plate (16) having a number of holes (30), and said restrictive aperture means is constituted by those holes (30).
(4) A far infrared drying device according to claim 3, wherein porous shield means (43) is disposed close to the inner surface of said perforated heat-resistant plate (16) for regulating the amount and speed of hot air discharged from said hot air chamber (12a) through the holes (30) of said perforated heat-resistant plate, the holes of said perforated heat-resistant plate and the apertures of said porous shield means jointly defining the opening portion in a range of from about 1 to 20 % of the total surface area of the radiant heat-resistant plate.
(5) A far infrared drying device according to claim 3, wherein said hot air chamber housing is of a perforated housing (12) having a number of holes (30), and said restrictive aperture means is constituted by those holes (30).