CA1167531A - Single-sided applicator for microwave heating - Google Patents
Single-sided applicator for microwave heatingInfo
- Publication number
- CA1167531A CA1167531A CA000397968A CA397968A CA1167531A CA 1167531 A CA1167531 A CA 1167531A CA 000397968 A CA000397968 A CA 000397968A CA 397968 A CA397968 A CA 397968A CA 1167531 A CA1167531 A CA 1167531A
- Authority
- CA
- Canada
- Prior art keywords
- applicator
- conductor
- conductors
- edge
- pair
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Constitution Of High-Frequency Heating (AREA)
Abstract
TITLE
SINGLE-SIDED APPLICATOR FOR MICROWAVE HEATING
INVENTORS
Walter Wyslouzil Satish C. Kashyap ABSTRACT OF THE DISCLOSURE
The single-sided applicator for microwave heating has a pair of outer parallel planar conductors and an inner planar conductor centered there between. A pair of metal posts connected between the inner conductor and the outer conductors tune the structure. A coaxial connector is mounted on the applicator, with its ground conductor connected to the outer conductors and its inner conductor connected to the inner planar conductor. The fringing field lines between the inner and outer conductors at one edge are applied to a load.
SINGLE-SIDED APPLICATOR FOR MICROWAVE HEATING
INVENTORS
Walter Wyslouzil Satish C. Kashyap ABSTRACT OF THE DISCLOSURE
The single-sided applicator for microwave heating has a pair of outer parallel planar conductors and an inner planar conductor centered there between. A pair of metal posts connected between the inner conductor and the outer conductors tune the structure. A coaxial connector is mounted on the applicator, with its ground conductor connected to the outer conductors and its inner conductor connected to the inner planar conductor. The fringing field lines between the inner and outer conductors at one edge are applied to a load.
Description
~753~
Background of the Inven~ion _ This inventlon is directed to a microwave heating device and in particular to a microwave applicator capable of heating a layer of material which is accessible from only one side.
A single-sided microwave applicator is particularly applicable to the sealing of cartons by momentarily heating and softening a plastic coating (hot melt) which had been applied to the carton flaps previously9 or by drying a water based adhesive applied to the flaps just prior to sealing.
Conventional heating methods are not suitable because of the long time required for the heat to penetrate the material.
Microwave applicators for this type of application have been described in United States Patent 3~999,02~ which issued on December 21~ 1976 to Goran Boling and in United States Patent 49160,144 which issued on July 3, 197~ to the present inventors Satish C. Kashyap and Walter Wyslouzil. However, these devices are based on the use of waveguide structures which are relatively bulky and awkward to use because the waveguides are not flexible.
Summary of the Invention It is therefore an object of this invention to provide a compact and versatile single-sided microwave applicator that can be fed by flexible coaxial cable.
These and other objects are achieved in an applicator which includes a pair of electrically interconnected coextensive planar conductors mounted substantially in parallel with one another, and an il1ner planar conductor centered in parallel between the pair of conductors whereby field lines may be generated along one edge for application to a load. A pair of meta] posts are connected bet~7een the inner conductor and the pair of coextensive conductors for tuning the applicator.
In accordance with another aspect of the invention, a ~;à753~ -conductive connection plate is mounted between the pair of coexten-sive conductors along the edge opposite to the loading edge o~ the applicator. A coaxial connector is mounted on the connection plate with its ground conductor electrically connected to the connection plate and its inner conductor connected to the inner planar conductor.
Conductlve end plates may also be fi~ed between the coex-tensive planar conductors along their two remaining edges such that only the loading edge of the applicator is open~ In addition, a "window" made of suitable microwave transparent material such as ceramic or "Teflon" [trademark] may be used to cover the open end o~ the applicator.
Many other objects and aspects of the invention will be clear from the detailed description of the drawings.
Brief Description of the Drawings In the drawings:
Figure 1 is a side view of the applicator in accordance with the present invention;
Figure 2 is a cross-section view of the applicator in figure 1;
Figure 3 is a view of the applicator at its loading edge;
and Figure 4 is a second embodiment of the applicator.
Detailed Description The microwave applicator 10 illustrated in figures 1, 2 and 3, consists of two conductive outer plates 11 and 12 which are substantially identical in size and which are connected together at their side by a plate 13, and a conductive inner plate 14 centered between the outer plates 11 and 12 and parallel to them, to form a type of open-circuited stripline. The applicator further includes a coaxial cable c,onnector 15 mounted on plate 13 with the grounded 53:~
outer conductor 16 connected to the plate 13 and the inner conduc-tor 17 connected to the inner plate 14.
When the applicator 10 is energized, an electric field 18 is formed between the inner conductor 14 and the outer conductors 11 and 12, with the fringing field at the open end of the applica-tor 10 being capable of interacting with a layer of material of predetermined thickness. Typically, the thickness of the layer which is heated is a few millimeters, depending on the electrical properties of the material and the dimensions of the applicator.
Some typical dimensions in inches for operation at 2~50 ~z are indicated in figures 2 and 4. Vther ISM frequencies such as 915 MHz may of course also be used. In that case, the applicator could be larger for deeper penetration. The inner conductor 14 must be narrower than the outer conductors 11 and 12, however the edges of the conductors 11, 12 and 14 would normally be even at the open end of the applicator 10 to allow the field to interact with the product.
In order to couple the microwave power efficiently into ~he material to be heated and to avoid power reflection to the source, a tuning structure is incorporated into the applicator 10.
The tuning structure consists of two metal posts 19 and 20 posi-tioned between the inner conductor 14 and the outer conductors 11 and 12, respectivelyO If the posts are of appropriate size and located at an appropriate positLon, the applicator is matched satisfactorily over the entire ISM band of 50 M~lz. This implies that tuning is not critical so that a variety of materials can be treated without the need for rematching the applicator. It also implies that manufacturing tolerances are not very stringent.
The device is typically operated at peak power levels up to 800 watts, with the average power limited to about 300 watts by 7~3~
the power handling capability of the coaxial cable.
A sealing operation can be completed in, typically, second.
The applicator 40 shown in figure 4 is similar to appli-cator 10 in figures 1 to 3 in all respects except that it further includes end plates 41 and 42 connected to the grounded outer plates 11 and 12. ~nd plates 41 and 42 affect the field somewhat, which may require a different positioning of the tuning posts 19 and 20. ~owever, plates 41 and 42 enhance the mechanical strength of the applicator 40 and also help to reduce any energy leakage since the applicator is totally enclosed except for the open end.
In addition, this opening may be covered by a microwave transparent material such as a ceramic or Teflon [trademark], which will exclude vapours or foreign materials from entering the applicator.
Many modifications in ~he above described embodiments of the invention can be carried out without departing from the scope thereof and, therefore, the scope of ~:he present invention is intended to be limited only by the appended claims.
Background of the Inven~ion _ This inventlon is directed to a microwave heating device and in particular to a microwave applicator capable of heating a layer of material which is accessible from only one side.
A single-sided microwave applicator is particularly applicable to the sealing of cartons by momentarily heating and softening a plastic coating (hot melt) which had been applied to the carton flaps previously9 or by drying a water based adhesive applied to the flaps just prior to sealing.
Conventional heating methods are not suitable because of the long time required for the heat to penetrate the material.
Microwave applicators for this type of application have been described in United States Patent 3~999,02~ which issued on December 21~ 1976 to Goran Boling and in United States Patent 49160,144 which issued on July 3, 197~ to the present inventors Satish C. Kashyap and Walter Wyslouzil. However, these devices are based on the use of waveguide structures which are relatively bulky and awkward to use because the waveguides are not flexible.
Summary of the Invention It is therefore an object of this invention to provide a compact and versatile single-sided microwave applicator that can be fed by flexible coaxial cable.
These and other objects are achieved in an applicator which includes a pair of electrically interconnected coextensive planar conductors mounted substantially in parallel with one another, and an il1ner planar conductor centered in parallel between the pair of conductors whereby field lines may be generated along one edge for application to a load. A pair of meta] posts are connected bet~7een the inner conductor and the pair of coextensive conductors for tuning the applicator.
In accordance with another aspect of the invention, a ~;à753~ -conductive connection plate is mounted between the pair of coexten-sive conductors along the edge opposite to the loading edge o~ the applicator. A coaxial connector is mounted on the connection plate with its ground conductor electrically connected to the connection plate and its inner conductor connected to the inner planar conductor.
Conductlve end plates may also be fi~ed between the coex-tensive planar conductors along their two remaining edges such that only the loading edge of the applicator is open~ In addition, a "window" made of suitable microwave transparent material such as ceramic or "Teflon" [trademark] may be used to cover the open end o~ the applicator.
Many other objects and aspects of the invention will be clear from the detailed description of the drawings.
Brief Description of the Drawings In the drawings:
Figure 1 is a side view of the applicator in accordance with the present invention;
Figure 2 is a cross-section view of the applicator in figure 1;
Figure 3 is a view of the applicator at its loading edge;
and Figure 4 is a second embodiment of the applicator.
Detailed Description The microwave applicator 10 illustrated in figures 1, 2 and 3, consists of two conductive outer plates 11 and 12 which are substantially identical in size and which are connected together at their side by a plate 13, and a conductive inner plate 14 centered between the outer plates 11 and 12 and parallel to them, to form a type of open-circuited stripline. The applicator further includes a coaxial cable c,onnector 15 mounted on plate 13 with the grounded 53:~
outer conductor 16 connected to the plate 13 and the inner conduc-tor 17 connected to the inner plate 14.
When the applicator 10 is energized, an electric field 18 is formed between the inner conductor 14 and the outer conductors 11 and 12, with the fringing field at the open end of the applica-tor 10 being capable of interacting with a layer of material of predetermined thickness. Typically, the thickness of the layer which is heated is a few millimeters, depending on the electrical properties of the material and the dimensions of the applicator.
Some typical dimensions in inches for operation at 2~50 ~z are indicated in figures 2 and 4. Vther ISM frequencies such as 915 MHz may of course also be used. In that case, the applicator could be larger for deeper penetration. The inner conductor 14 must be narrower than the outer conductors 11 and 12, however the edges of the conductors 11, 12 and 14 would normally be even at the open end of the applicator 10 to allow the field to interact with the product.
In order to couple the microwave power efficiently into ~he material to be heated and to avoid power reflection to the source, a tuning structure is incorporated into the applicator 10.
The tuning structure consists of two metal posts 19 and 20 posi-tioned between the inner conductor 14 and the outer conductors 11 and 12, respectivelyO If the posts are of appropriate size and located at an appropriate positLon, the applicator is matched satisfactorily over the entire ISM band of 50 M~lz. This implies that tuning is not critical so that a variety of materials can be treated without the need for rematching the applicator. It also implies that manufacturing tolerances are not very stringent.
The device is typically operated at peak power levels up to 800 watts, with the average power limited to about 300 watts by 7~3~
the power handling capability of the coaxial cable.
A sealing operation can be completed in, typically, second.
The applicator 40 shown in figure 4 is similar to appli-cator 10 in figures 1 to 3 in all respects except that it further includes end plates 41 and 42 connected to the grounded outer plates 11 and 12. ~nd plates 41 and 42 affect the field somewhat, which may require a different positioning of the tuning posts 19 and 20. ~owever, plates 41 and 42 enhance the mechanical strength of the applicator 40 and also help to reduce any energy leakage since the applicator is totally enclosed except for the open end.
In addition, this opening may be covered by a microwave transparent material such as a ceramic or Teflon [trademark], which will exclude vapours or foreign materials from entering the applicator.
Many modifications in ~he above described embodiments of the invention can be carried out without departing from the scope thereof and, therefore, the scope of ~:he present invention is intended to be limited only by the appended claims.
Claims (6)
1. A single-sided microwave applicator comprising:
- a pair of electrically-interconnected, coextensive planar conductors substantially in parallel with one another forming four applicator edges;
- an inner planar conductor centered in parallel between the pair of conductors whereby field lines may be generated along a first edge of the applicator for application to a load;
- a pair of metal posts fixed between the inner conductor and the pair of coextensive conductors for matching the applicator to a predetermined load; and - means mounted at a second edge of the applicator for connecting the applicator to a microwave power transmission line.
- a pair of electrically-interconnected, coextensive planar conductors substantially in parallel with one another forming four applicator edges;
- an inner planar conductor centered in parallel between the pair of conductors whereby field lines may be generated along a first edge of the applicator for application to a load;
- a pair of metal posts fixed between the inner conductor and the pair of coextensive conductors for matching the applicator to a predetermined load; and - means mounted at a second edge of the applicator for connecting the applicator to a microwave power transmission line.
2. An applicator as claimed in claim 1 which further includes:
- a conductive connection plate connecting the pair of coextensive conductors along an edge of the applicator opposite to the first edge.
- a conductive connection plate connecting the pair of coextensive conductors along an edge of the applicator opposite to the first edge.
3. An applicator as claimed in claim 2 wherein the connecting means includes a coaxial connector having an outer ground conductor and an inner conductor, and mounted on the conductive connection plate, the ground conductor being electrically connected to the connection plate and the inner conductor being connected to the inner planar conductor.
4, An applicator as claimed in claim 1 wherein the edge of the inner planar conductor and the coextensive conductors are substantially even at the first edge of the applicator.
5. An applicator as claimed in claims 1, 3 or 4 which further includes conductive end plates fixed between the coextensive planar conductors along third and fourth edges of the applicator.
6. An applicator as claimed in claims 1, 3 or 4 which further includes conductive end plates fixed between the coextensive planar conductors along third and fourth edges of the applicator to form an enclosed structure with an opening at the first edge of the applicator, and a microwave transparent layer covering the opening.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US26459981A | 1981-05-18 | 1981-05-18 | |
| US264,599 | 1981-05-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1167531A true CA1167531A (en) | 1984-05-15 |
Family
ID=23006786
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000397968A Expired CA1167531A (en) | 1981-05-18 | 1982-03-09 | Single-sided applicator for microwave heating |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1167531A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115278971A (en) * | 2022-09-07 | 2022-11-01 | 四川大学 | Microwave heating assembly and microwave heating device |
-
1982
- 1982-03-09 CA CA000397968A patent/CA1167531A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115278971A (en) * | 2022-09-07 | 2022-11-01 | 四川大学 | Microwave heating assembly and microwave heating device |
| CN115278971B (en) * | 2022-09-07 | 2023-03-31 | 四川大学 | Microwave heating assembly and microwave heating device |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |