IE52949B1 - Modular industrial microwave furnace - Google Patents

Abstract

1. An industrial microwave oven, characterized by comprising at least one module (10) constituted by a metal casing (1) subdivided into three compartments (11, 12, 13) by partitions (14, 15) having openings therein, a plurality of microwave generators (4) arranged in the outer compartments (11, 13) such that the warm air flows directly through said openings (16, 17) in the partitions (14, 15) into the middle compartment (12), said middle compartment (12) forming the microwave applicator oven itself, and a plurality of waveguide means (2) arranged on the metal casing (1) with radiator means (3), the positions of said waveguide and radiator means being distributed so as to couple the maximum microwave energy into the middle compartment (12).

Description

The present invention relates to a modular industrial microwave furnace for the drying or thermal handling of products by microwave energy.

The microwave handling of products is already known.

For that purpose an installation is currently used (Fig.1) which comprises a microwave generator coupled through an insulator and passive transfer means to a microwave applicator in which the product is handled.

Such an installation has the following drawbacks: a) it uses expensive high power generators which require to be protected by means of costly microwave circulators, b) the efficiency is usually very low due to the reflected microwave energy.

SUMMARY OF THE INVENTION The object of the invention is to provide a microwave furnace which has the following advantages: a) efficiency as high as 80% starting from the energy distribution network, b) continuous and discontinuous operation, c) high accuracy and energy adjustment capability d) modular construction, e) low cost construction. - 2 52941) The above object is realized in accordance with this invention by a microwave furnace which comprises at least one module unit consisting in a metal casing subdivided into three adjacent compartments by partitions having each an opening therein, with the outer compartments including a number of small microwave generators, e.g. to 50 low-power magnetrons. These magnetrons are arranged such that the warm air resulting from the cooling of the magnetrons directly flows through said, openings in the partitions into the middle compartment.

A number of waveguides are arranged on top of the casing with microwave radiators located such that interaction between the different magnetrons is avoided, whereby the maximum microwave energy is coupled into the middle compartment forming the microwave applicator section.

The construction according to the invention which includes the microwave generator and applicator in one. sole unit, not only makes use of low cost power units (magnetrons and supply units) but also avoids the need for costly passive transfer means such as circulators which result in a substantial lowering in efficiency. Further, the modular structure according to the invention makes it possible to suit most of the industrial energy utilities in the range from ten to several hundreds of kilowatts. - 3 52949 Other features of the invention will become apparent from the description to follow.

BRIEF DESCRIPTION OF THE DRAWINGS 5 Fig. 1 schematically illustrates a usual microwave installation of the prior art; Fig. 2 is a perspective view of an embodiment of a microwave furnace module according to the invention; Fig. 3 is a schematic sectional view in the embodiment of Fig.2.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT 15 Reference is first made to Fig.1 which exemplifies a prior art industrial microwave installation. The numeral reference 1 denotes the microwave generator which is coupled through an insulator 2 and. passive transfer means such as circulators 3 to the microwave applicator 4 in which is placed the product to be handled.

By contrast with this prior art installation, the invention provides a modular unit as exemplified in Figs.2 et 3. The unit 10 is comprised of a metal casing 1 - 4 52949 subdivided into three compartments 11, 12 and 13 by partitions 14 and 15. The outer compartments 11 and 13 house the power units including a number of microwave generators or magnetrons 4 and the supply transformers 8; the middle compartment 12 constitutes the very applicator in which the product is handled.

The partitions 14 and 15 between the compartments have openings 16 and 17 respectively. The magnetrons 4 are arranged relative to the openings 16 and 17 such that the warm air resulting from the cooling of the magnetrons directly flows into the applicator compartment 12.

The openings 16 and 17 are each provided with a grating 18.

On top of the casing 1 are mounted a number of waveguides 2. The microwave energy from the magnetrons is coupled into the compartment 12 hy means of microwave radiator means 3 which are evenly distributed along each waveguide 2. The position of the waveguides 2 and the radiators 3 is chosen such that the coupling between the magnetrons is negligible. In this way, not only the provision of insulators and circulators is avoided, but also the efficiency is significantly increased. The position and distribution of the radiators 3 over the middle compartment 12 are determined in such a.way that the interaction between the magnetrons is practically avoided. -5 By way of example, a practical design of a 36 kW microwave furnace (18 X 2 magnetrons of 1kW) operating at a frequency of 2450 KHz and intended for drying plsstified paper comprises seventy-two radiators distributed in eighteen rows of four radiators with the rows spaced apart by approximately twenty-five centimeters and the radiators in each row spaced apart by approximately fifteen centimeters.

The outer compartments 11 and 13 are pressurized under variable pressure by separate air fans 9. Thereby the heat from the cooling of the magnetrons as veil as that of the transformers is used in the compartment 12 The exhaust occurs through outlets 5· In the illustrated embodiments there is shown a transport belt 6 made of a flexible and non-absorbing material,e.g. polyethylen, which runs through the compartment 12 for the transportation of the product to be handled. A continuous operation is thereby ensured.

The modular structure as described hereabove eakes it possible installations of any power capability to be realized by simply putting the desired number of module units according to the invention in adjacent relation.

Claims (3)

1. An industrial microwave furnace comprising a metal casing subdivided into three adjacent compartments by 5 partitions having each an opening therein, the outer two compartments each including a number of microwave generators arranged such that the warm air resulting from the cooling of the microwave generators directly flows through said openings in the partitions into the 10 middle one of the adjacent compartments, said middle compartment forming the microwave applicator section, a plurality of waveguides arranged on top of the casing with microwave radiator means evenly distributed along the waveguides, said waveguides and said radiator means 15 being positioned so as to couple the maximum microwave energy into the middle applicator compartment.

2. A microwave furnace as claimed in claim 1, further comprising at least one transport belt arranged for 20 running through the middle compartment for transportation of the product to he handled. -7 529 49

3. An industrial microwave furnace substantially as described herein with reference to figures 2 and 3 of the accompanying drawings.