GB1566104A - Electromagnetic waveguides - Google Patents

Electromagnetic waveguides Download PDF

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Publication number
GB1566104A
GB1566104A GB744876A GB744876A GB1566104A GB 1566104 A GB1566104 A GB 1566104A GB 744876 A GB744876 A GB 744876A GB 744876 A GB744876 A GB 744876A GB 1566104 A GB1566104 A GB 1566104A
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GB
United Kingdom
Prior art keywords
waveguide
sleeve
electrically conductive
internal surface
conductive layer
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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
Application number
GB744876A
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Balfour Beatty PLC
Original Assignee
BICC PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by BICC PLC filed Critical BICC PLC
Priority to GB744876A priority Critical patent/GB1566104A/en
Publication of GB1566104A publication Critical patent/GB1566104A/en
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P11/00—Apparatus or processes specially adapted for manufacturing waveguides or resonators, lines, or other devices of the waveguide type
    • H01P11/001—Manufacturing waveguides or transmission lines of the waveguide type
    • H01P11/002—Manufacturing hollow waveguides

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTROMAGNETIC WAVEGUIDES (71) We, BICC LIMITED, a British Company, of 21 Bloomsbury Street, London, WClB 3QN, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to electromagnetic waveguides for use in effecting communication over long distances by conveying microwave signals along waveguides arranged continuously along an appropriate transmission path.
The invention is particularly concerned with substantially rigid electromagnetic waveguides of the kind including a circumferentially continuous electrically conductive metallic layer, and, overlying the internal surface of the electrically conductive laser, a circumferentially continuous layer of electrically insulating material. Electromagnetic waveguides of the aforesaid kind will hereinafter be referred to as "as of the kind described".
It is an object of the present invention to provide an improved method of manufacturing a substantially rigid elongate waveguide of the kind described.
According to the invention in a method of manufacturing a substantially rigid elongate waveguide of the kind described, the internal surface of the electrically conductive layer is lined with a layer of insulating material by applying a coating of hardenable material in a liquid or semiliquid state to the internal surface of the electrically conductive layer, sealing one end of a flexible sleeve of fluid-impermeable electrically insulating material and of a size suitable for forming a lining of the bore of the waveguide to one end of the waveguide, establishing a difference in fluid pressure across the flexible sleeve at said end of the waveguide, drawing the flexible sleeve into the bore of the waveguide in such a way that the sleeve is turned inside out as it travels along the bore and is urged against and adheres to the internal surface of the electrically conductive layer through out the length of the waveguide, and permitting or causing the hardenable material to set.
After the coating of hardenable material has set, preferably the ends of the flexible sleeve are trimmed and the trimmed ends of the sleeve are sealed to the ends of the waveguide.
The pressure differential across the flexible sleeve at the end of the waveguide to which the leading end of the sleeve is sealed is preferably effected by evacuating air and any other fluid from the bore of the waveguide through an outlet at the other end of the waveguide.
The method of the invention is suitable for providing a wrinkle-free smooth lining of plastics insulating material to the internal surface of the electrically conductive metallic layer of a substantially rigid elongate waveguide of the kind described which may be straight or which may be curved in at least one plane. It is especially suitable where it is required to provide such an insulating lining to a waveguide which is so curved in a single plane that opposite end parts of the waveguide are at substantially right angles to one another.
Although the internal surface of the electrically conductive layer may be coated with hardenable material before the flexible sleeve is introduced into the bore of the waveguide, it is preferred to arrange for the coating of hardenable material and the flexible sleeve to be applied to the internal surface of the electrically conductive layer in a single operation. To this end, preferably the internal surface of the sleeve is precoated with hardenable material in a liquid or semi-liquid state, one end of the sleeve is sealed to one end of the bore of the waveguide and, after the bore of the waveguide has been substantially evacuated or a pressure differential has otherwise been established across the sleeve at said end of the waveguide, the sleeve is drawn into the bore of the waveguide, as the sleeve travelling along the bore of the waveguide is turned inside out the coated internal surface of the sleeve being retained against and adhering to the internal surface of the electrically conductive layer.
The internal surface of the flexible sleeve may be pre-coated with liquefied hardenable material by any convenient method but it is preferred to seal one end of the sleeve and to attach to said sealed end a flexible line of a length greater than that of the waveguide to be treated, to anchor the free end of the flexible line to the barrel of a drum and to wind the flexible line on the drum barrel, to introduce a quantity of hardenable material in a liquid or semiliquid state into the open end of the sleeve and to allow it to flow along the sleeve to the sealed end, and to wind the sleeve under tension on to the drum to cause hardenable material to travel along and thoroughly coat the internal surface of the sleeve. Additional hardenable material may be introduced into the sleeve during the winding operation, as and when required.
When the flexible sleeve is being drawn into the bore of the waveguide and the trailing end of the sleeve has been unwound from the drum, the flexible line and the drum to which the line is anchored can be used to control the rate of feed of the sleeve into the waveguide.
In some circumstances it is desirable that the flexible sleeve is urged against the internal surface of the electrically conductive layer at a pressure greater than atmospheric pressure. In this case, preferably the end of the waveguide to which is sealed the leading end of the flexible sleeve, is sealed in such a way as to permit the sleeve to pass into the bore of the waveguide in a fluidtight manner and fluid under superatmospheric pressure is introduced into the bore of the waveguide at said sealed end as, or shortly after, the sleeve is drawn into the bore of the waveguide.
In some circumstances, also, it is desirable that hardening of the coating of hardenable material in a liquid or semi-liquid state be accelerated and, in this case, preferably the fluid under superatmospheric pressure which is introduced into the bore of the waveguide is at such a temperature as to accelerate hardening of said coating. The fluid may be a gas or a liquid.
Where a coating of liquefied hardenable material is applied to the internal surface of the electrically conductive layer before the bore of the waveguide is evacuated or a differential pressure is otherwise established across the flexible sleeve at the end of the waveguide to which the sleeve is sealed, this coating may consist of a liquefied resin only and liquefied hardener for this resin may be pre-coated on the internal surface of the sleeve, the resin and hardener not coming into contact with one another until the sleeve is introduced into the bore of the waveguide.
The flexible sleeve may be of any fluidimpermeable, electrically insulating material, polyethylene currently being preferred. The thickness of the sleeve will depend on the size of the bore of the waveguide and the tensile load that will be applied to the sleeve to draw it into the bore of the waveguide.
The hardenable material is preferably a synthetic adhesive resin, an epoxy resin at present being preferred.
Preferably the electrically conductive metallic layer is formed by applying a metallic coating to an elongate mandrel and to ensure that the metallic coating has a substantially uniform internal dimension thoughout substantially the whole length of the waveguide, preferably the circumferentially continuous electrically conductive metallic coating is manufactured by the method described and claimed in the Complete Specification of our co-pending British Application No. 30798/74 (Serial No.
1520872).
The mandrel is preferably of circular cross-section.
The circumferentially continuous electrically conductive layer may be of sufficient radial thickness to be self-supporting and where it is to be curved in one or more than one plane preferably it is a self-supporting tube of metal or metal alloy, e.g. of copper.
Where the electrically conductive layer is of insufficient thickness to be self-supporting, preferably it is surrounded by a reinforcing wall which may be formed in any convenient manner but preferably which is formed by applying to the external surface of the electrically conductive layer at least one layer of glass fibre or other suitable elongate reinforcing elements bonded with resin.
The invention also includes a substantially rigid electromagnetic waveguide made by the method hereinbefore described.
The invention will be further illustrated by a description, by way of example, of the preferred method of manufacturing a substantially rigid elongate waveguide of the kind described, with reference to the accompanying diagrammatic drawing, in which: Figure 1 is a representation of the method of lining the internal surface of the electrically conductive layer of the waveguide with a layer of insulating material, and Figure 2 is a fragmental side view of the inlet end of the waveguide for a modification of the method shown in Figure 1.
Referring to Figure 1, the waveguide 1 under manufacture comprises a circumferentially continuous electrically conductive metallic layer 2 and, surrounding the electrically conductive layer, a reinforcing wall 3 of resin bonded glass fibres. In manufacture, the electrically conductive layer 2 is formed on an elongate mandrel (not shown) of circular cross-section having a diameter of 18 mm by electrodeposition and several layers of resin impregnated glass fibres are applied over the electrically conductive layer and hardened to form the reinforcing wall 3. The mandrel is then removed.
The internal surface of a flexible sleeve 5 of polyethylene, having a circumference approximating to the internal circumference of the electrically conductive layer 2 that is to be lined, is pre-coated with epoxy resin in a liquid state by sealing the sleeve at a position spaced from one of its two ends and attaching to this sealed end of the sleeve a flexible line of a length greater than that of the waveguide 1. The free end of the flexible line is anchored to the barrel of a drum 6 and the flexible line is wound to the drum. A quantity of liquefied epoxy resin is then introduced into the open end of the sleeve 5 and is allowed to run down the sleeve to the sealed end where it collects.
The sleeve 5 is now wound on to the barrel of the drum 6 under tension causing liquefied resin to flow along the sleeve and thoroughly coat the internal surface of the sleeve. Preferably, the barrel of the drum 6 has on its circumferential surface a plurality of circumferentially spaced ribs which extend along the length of the barrel and serve to ensure that resin is not squeezed out of the sleeve as it is wound around the drum under tension. Additional liquefied resin may be introduced into the sleeve 5 as and when required as the sleeve is being wound on to the drum 6 until the internal surface of the sleeve is pre-coated with resin throughout the length of the sleeve.
With the waveguide 1 rigidly supported with its axis substantially vertical, the free end of the sleeve 5 is now unwound from the drum 6, is passed around the guide roller 7, and is sealed to the lower end of the waveguide. The barrel of the guide roller 7 has on its peripheral surface a plurality of circumferentially spaced ribs which extend along the length of the barrel and serve to ensure that resin is not squeezed towards the trailing end of the sleeve 5 when the sleeve is drawn around the guide roller under tension. An air-tight cap 8 having an outlet 9 is sealed to the upper end of the waveguide 1, the outlet being connected by a pipe 10 to a vacuum pump (not shown). With a brake applied to the drum 6 to prevent unwinding of the sleeve 5, the vacuum pump is brought into operation and air is drawn out of the waveguide 1. When the waveguide 1 has been substantially evacuated, the brake on the drum 6 is released and the sleeve 5 is drawn smoothly into the waveguide, the sleeve being turned inside out as it travels along the waveguide and the precoated internal surface of the sleeve being urged against and adhering to the internal surface of the electrically conductive metallic layer 2 under atmospheric pressure. During introduction of the trailing end of the flexible sleeve 5 into the bore of the waveguide 1, the flexible line and the drum 6 to which the line is anchored are used to control the rate of feed of the sleeve into the waveguide. When the sleeve 5 has been drawn into the waveguide 1 so that it forms a smooth insulating lining to electrically conductive layer 2 throughout its length, a second vacuum extractor (not shown) connected to the cap 8 is brought into operation to draw off surplus resin that will have accumulated at the upper end of the waveguide. The vacuum in the waveguide 1 is maintained until the resin has set. The vacuum pump is then switched off. the cap 8 is removed and the ends of the sleeeve 5 are trimmed and sealed to the ends of the waveguide.
In a modification of the aforesaid method which is suitable for use when it is desired to accelerate setting of the resin, as will be seen on referring to Figure 2, after the leading end of the sleeve 5 is sealed to the lower end of the waveguide 1, this end of the waveguide is sealed by a sealing cap 12 having a slot 14 which is closed by a pair of flexible rubber flanges 15 and through which the sleeve can pass into the waveguide in substantially fluid-tight engagement with the flanges. The sealing cap 12 also has a pressure inlet 16. In this case, after the waveguide 1 has been evacuated and as the sleeve 5 is drawn into the evacuated waveguide, warm air or other warm fluid under pressure is injected into the inlet 16 to assist in urging the resin-coated polyethylene sleeve against the internal surface of the electrically conductive layer 2 and in setting of the resin.
The method of the present invention has the important advantage that it provides a simple and inexpensive method of applying a layer of insulating material to the internal surface of the electrically conductive layer of a substantially rigid elongate waveguide which may be either straight or curved in one or more than one plane.
WHAT WE CLAIM IS:- 1. A method of manufacturing a substantially rigid elongate waveguide of the kind described, wherein the internal surface of the circumferentially continuous electrically conductive layer is lined with a layer of insulating material by applying a coating
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (18)

**WARNING** start of CLMS field may overlap end of DESC **. Referring to Figure 1, the waveguide 1 under manufacture comprises a circumferentially continuous electrically conductive metallic layer 2 and, surrounding the electrically conductive layer, a reinforcing wall 3 of resin bonded glass fibres. In manufacture, the electrically conductive layer 2 is formed on an elongate mandrel (not shown) of circular cross-section having a diameter of 18 mm by electrodeposition and several layers of resin impregnated glass fibres are applied over the electrically conductive layer and hardened to form the reinforcing wall 3. The mandrel is then removed. The internal surface of a flexible sleeve 5 of polyethylene, having a circumference approximating to the internal circumference of the electrically conductive layer 2 that is to be lined, is pre-coated with epoxy resin in a liquid state by sealing the sleeve at a position spaced from one of its two ends and attaching to this sealed end of the sleeve a flexible line of a length greater than that of the waveguide 1. The free end of the flexible line is anchored to the barrel of a drum 6 and the flexible line is wound to the drum. A quantity of liquefied epoxy resin is then introduced into the open end of the sleeve 5 and is allowed to run down the sleeve to the sealed end where it collects. The sleeve 5 is now wound on to the barrel of the drum 6 under tension causing liquefied resin to flow along the sleeve and thoroughly coat the internal surface of the sleeve. Preferably, the barrel of the drum 6 has on its circumferential surface a plurality of circumferentially spaced ribs which extend along the length of the barrel and serve to ensure that resin is not squeezed out of the sleeve as it is wound around the drum under tension. Additional liquefied resin may be introduced into the sleeve 5 as and when required as the sleeve is being wound on to the drum 6 until the internal surface of the sleeve is pre-coated with resin throughout the length of the sleeve. With the waveguide 1 rigidly supported with its axis substantially vertical, the free end of the sleeve 5 is now unwound from the drum 6, is passed around the guide roller 7, and is sealed to the lower end of the waveguide. The barrel of the guide roller 7 has on its peripheral surface a plurality of circumferentially spaced ribs which extend along the length of the barrel and serve to ensure that resin is not squeezed towards the trailing end of the sleeve 5 when the sleeve is drawn around the guide roller under tension. An air-tight cap 8 having an outlet 9 is sealed to the upper end of the waveguide 1, the outlet being connected by a pipe 10 to a vacuum pump (not shown). With a brake applied to the drum 6 to prevent unwinding of the sleeve 5, the vacuum pump is brought into operation and air is drawn out of the waveguide 1. When the waveguide 1 has been substantially evacuated, the brake on the drum 6 is released and the sleeve 5 is drawn smoothly into the waveguide, the sleeve being turned inside out as it travels along the waveguide and the precoated internal surface of the sleeve being urged against and adhering to the internal surface of the electrically conductive metallic layer 2 under atmospheric pressure. During introduction of the trailing end of the flexible sleeve 5 into the bore of the waveguide 1, the flexible line and the drum 6 to which the line is anchored are used to control the rate of feed of the sleeve into the waveguide. When the sleeve 5 has been drawn into the waveguide 1 so that it forms a smooth insulating lining to electrically conductive layer 2 throughout its length, a second vacuum extractor (not shown) connected to the cap 8 is brought into operation to draw off surplus resin that will have accumulated at the upper end of the waveguide. The vacuum in the waveguide 1 is maintained until the resin has set. The vacuum pump is then switched off. the cap 8 is removed and the ends of the sleeeve 5 are trimmed and sealed to the ends of the waveguide. In a modification of the aforesaid method which is suitable for use when it is desired to accelerate setting of the resin, as will be seen on referring to Figure 2, after the leading end of the sleeve 5 is sealed to the lower end of the waveguide 1, this end of the waveguide is sealed by a sealing cap 12 having a slot 14 which is closed by a pair of flexible rubber flanges 15 and through which the sleeve can pass into the waveguide in substantially fluid-tight engagement with the flanges. The sealing cap 12 also has a pressure inlet 16. In this case, after the waveguide 1 has been evacuated and as the sleeve 5 is drawn into the evacuated waveguide, warm air or other warm fluid under pressure is injected into the inlet 16 to assist in urging the resin-coated polyethylene sleeve against the internal surface of the electrically conductive layer 2 and in setting of the resin. The method of the present invention has the important advantage that it provides a simple and inexpensive method of applying a layer of insulating material to the internal surface of the electrically conductive layer of a substantially rigid elongate waveguide which may be either straight or curved in one or more than one plane. WHAT WE CLAIM IS:-
1. A method of manufacturing a substantially rigid elongate waveguide of the kind described, wherein the internal surface of the circumferentially continuous electrically conductive layer is lined with a layer of insulating material by applying a coating
of hardenable material in a liquid or semiliquid state to the internal surface of the electrically conductive layer, sealing one end of a flexible sleeve of fluid-impermeable electrically insulating material and of a size suitable for forming a lining of the bore of the waveguide to one end of the waveguide, establishing a difference in fluid pressure across the flexible sleeve at said end of the waveguide, drawing the flexible sleeve into the bore of the waveguide in such a way that the sleeve is turned inside out as it travels along the bore and is urged against and adheres to the internal surface of the electrically conductive layer throughout the length of the waveguide, and permitting or causing the hardenable material to set.
2. A method of manufacturing a substantially rigid elongate waveguide of the kind described, wherein the intemal surface of the circumferentially continuous electrically conductive layer is lined with a layer of insulating material by applying a coating of hardenable material in a liquid or semi; liquid state to the internal surface of the electrically conductive layer, sealing one end of a flexible sleeve of fluid-impermeable electrically insulating material and of a size suitable for forming a lining of the bore of the waveguide to one end of the waveguide, establishing a difference in fluid pressure across the flexible sleeve at said end of the waveguide by evacuating air and any other fluid from the bore of the waveguide through an outlet at the other end of the waveguide, drawing the flexible sleeve into the bore of the waveguide in such a way that the sleeve is turned inside out as it travels along the bore and is urged against and adheres to the internal surface of the electrically conductive layer throughout the length of the waveguide, and permitting or causing the hardenable material to set.
3. A method as claimed in Claim 1 or 2, wherein the circumferentially continuous electrically conductive layer is a self-supporting tube of metal or metal alloy.
4. A method of manufacturing a substantially rigid elongate waveguide of the kind described, which method comprises forming a circumferentially continuous electrically conductive layer on an elongate mandrel; forming a reinforcing wall around the electrically conductive layer; removing the elongate mandrel; and lining the internal surface of the electrically conductive layer with a layer of insulating material by applying a coating of hardenable material in a liquid or semi-liquid state to the internal surface of the electrically conductive layer, sealing one end of a flexible sleeve of fluidimpermeable electrically insulating material and of a size suitable for forming a lining of the bore of the waveguide to one end of the waveguide, establishing a difference in fluid pressure across the flexible sleeve at said end of the waveguide, drawing the flexible sleeve into the bore of the waveguide in such a way that the sleeve is turned inside out as it travels along the bore and is urged against and adheres to the internal surface of the electrically conductive layer throughout the length of the waveguide, and permitting or causing the hardenable material to set.
5. A method as claimed in Claim 4, wherein the pressure differential across the flexible sleeve at the end of the waveguide to which the leading end of the sleeve is sealed is effected by evacuating air and any other fluid from the bore of the waveguide through an outlet at the other end of the waveguide.
6. A method as claimed in any one of the preceding Claims, wherein the internal surface of the flexible sleeve is pre-coated with hardenable material in a liquid or semi-liquid state, one end of the sleeve is sealed to one end of the waveguide and, after the waveguide has been substantially evacuated or a pressure differential has otherwise been established across the sleeve at said end of the waveguide, the sleeve is drawn into the waveguide, as the sleeve travelling along the waveguide is turned inside out the coated internal surface of the sleeve being retained against and adhering to the internal surface of the electrically conductive layer.
7. A method as claimed in Claim 6, wherein the internal surface of the flexible sleeve is pre-coated with liquefied adhesive material by sealing one end of the -sleeve and attaching to said sealed end a flexible line of a length greater than that of the waveguide to be treated, anchoring the free end of the flexible line to the barrrel of a drum and winding the flexible line on to the drum barrel, introducing a quantity of hardenable material in a liquid or semi-liquid state into the open end of the sleeve and allowing it to flow along the sleeve to the sealed end, and winding the sleeve under tension on to the drum to cause hardenable material to travel along and thoroughly coat the internal surface of the sleeve.
8. A method as claimed in Claim 7, wherein additional liquefied hardenable material is introduced into the sleeve during the winding operation, as and when required.
9. A method as claimed in any one of the preceding Claims, wherein the end of the waveguide to which is sealed the leading end of the flexible sleevc, is sealed in such a way as to permit the sleeve to pass into the waveguide in a fluid-tight manner and fluid under superatmospheric pressure is introduced into the waveguide at said sealed end as, or shortly after, the sleeve is drawn into the waveguide.
10. A method as claimed in Claim 9, wherein the fluid under superatmospheric pressure which is introduced into the bore of the waveguide is at such a temperature as to accelerate hardening of the coating of hardenable material.
11. A method as claimed in any one of the preceding Claims in which a coating of liquefied hardenable material is applied to the internal surface of the electrically conductive layer before the waveguide is evacuated or a differential pressure is otherwise established across the flexible sleeve at the end of the waveguide to which the sleeve is sealed, wherein said coating consists of a liquefied resin and liquefied hardener for this resin is precoated on the internal surface of the sleeve, the resin and hardener not coming into contact with one another until the sleeve is introduced into the waveguide.
12. A method as claimed in any one of the preceding Claims, wherein the waveguide is substantially straight and, during lining of the internal surface of the electrically conductive layer with a layer of insulating material, the waveguide is rigidly supported with its axis substantially vertical.
13. A method as claimed in any one of Claims 1 to 11, wherein the waveguide is curved in one or more than one plane.
14. A method as claimed in any one of the preceding Claims, wherein the ends of the flexible sleeve are trimmed and the trimmed ends of the sleeve are sealed to the ends of the waveguide.
15. A method as claimed in any one of the preceding Claims, wherein the flexible sleeve is of plastics material.
16. A method as claimed in any one of the preceding Claims, wherein the hardenable material is a synthetic resin.
17. A method of manufacturing a substantially rigid elongate waveguide substantially as hereinbefore described with reference to the accompanying drawings.
18. A substantially rigid elongate waveguide which has been made by the method claimed in any one of the preceding Claims.
GB744876A 1977-05-25 1977-05-25 Electromagnetic waveguides Expired GB1566104A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB744876A GB1566104A (en) 1977-05-25 1977-05-25 Electromagnetic waveguides

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB744876A GB1566104A (en) 1977-05-25 1977-05-25 Electromagnetic waveguides

Publications (1)

Publication Number Publication Date
GB1566104A true GB1566104A (en) 1980-04-30

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB744876A Expired GB1566104A (en) 1977-05-25 1977-05-25 Electromagnetic waveguides

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PCNP Patent ceased through non-payment of renewal fee