CA1044866A - Longitudinally watertight telecommunication cable and manufacture thereof - Google Patents
Longitudinally watertight telecommunication cable and manufacture thereofInfo
- Publication number
- CA1044866A CA1044866A CA230,169A CA230169A CA1044866A CA 1044866 A CA1044866 A CA 1044866A CA 230169 A CA230169 A CA 230169A CA 1044866 A CA1044866 A CA 1044866A
- Authority
- CA
- Canada
- Prior art keywords
- silicone rubber
- conductors
- cable
- multiplicity
- moisture
- 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
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
- H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
- H01B7/285—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/14—Extreme weather resilient electric power supply systems, e.g. strengthening power lines or underground power cables
Abstract
ABSTRACT OF THE DISCLOSURE
In a method of rendering a cable having a core consisting of a plurality of insulated conductors longitudinally watertight a silicone rubber which vulcanizes in air is used between the conductors either throughout the entire length or in blocks. The silicon rubber is introduced into the interstices between the conductors and into the space around the cable core, and the cable core is then provided with a closely fitting sheath. The resulting cable is permanently watertight, and the sealing compound does not flow upon heating and does not attack the conductor insulation.
In a method of rendering a cable having a core consisting of a plurality of insulated conductors longitudinally watertight a silicone rubber which vulcanizes in air is used between the conductors either throughout the entire length or in blocks. The silicon rubber is introduced into the interstices between the conductors and into the space around the cable core, and the cable core is then provided with a closely fitting sheath. The resulting cable is permanently watertight, and the sealing compound does not flow upon heating and does not attack the conductor insulation.
Description
48~
I~Method of manufacturing a longitudinally watertight telecommunication cable, and longitudinally watertight telecommunication cable obtained by this method".
The invention relates ~o a method of manufacturing a longitudinal_ ly watertight telecommunication cable having a core comprising a plurality of conductors each covered with a synthetic insulating material, the inter-stices between the conductors and the space between the core and the sheath being filled with a compound which prevents water from penetrating into the cable core in the direction of length of the cable.
Cables of this type are known. In cables laid in the ground water may penetrate into the cable core through defects of the sheath due to mechan-ical damage. Such defects may be due to subsidence of the ground or to mechan-` ical force. In the core of a cable composed of conductors or bundles of conductors which are twisted together, as generally is the case in telecommuni-cation cables, water which has made its way into the cable may spread in the direction of length thereof through the interstices between the conductors and the space between the core and the sheath. When the conductors are individually insulated with a synthetic resin, the presence of water becomes manifest only after the water has penetrated over a comparatively large dis-tance in that the electric properties of the cable deteriorate, which deterioration can be made good only with great difficulty. Penetration of vater.can be prevented in that highly viscous compounds or a foamed syn-thetic resin are applied throughout the length of the cable or in blocks, i,e. at regular interrals in the direction of length of the cable over a ~given distance. The highly viscous compounds proposed for this purpose usually are paraffin-like substances, petroleum waxes, petroleum jelly and the like. These substances are molten or heated till their viscosity is low and thereafter are pressed into the interstices between the conductors and ; into the space between the core and the sheath. ~fter solidification ~o~
the compounds introduced into the cable form a seal against water. A disad-vantage of these substances is, however, that they become liquid again when the cable temperature rises. This may occur, for example, when the cable wound on a drum is exposed to irradiation by the sun for a long time. By the action of gravity the molten sealing compound tilen flows to the lower parts of the cable on the drum, causing poorly filled interstices or voids to be left in the remaing parts of the cable. This is particularly detri-mental when the sealing compound has been applied in blocks. Another disad-vantage is that the quality of conductor insulations of polyethylene when brought into contact with some paraffin-like substances deteriorates in electrical and mechanical respects in the long run.
When the interstices between the conductors and the space bet-ween the core and the sheath are filled with a foamed synthetic material~ diffi-culties of another nature arise. Foaming is a process which is not readily controllable and which usually starts immediately after the foam-forming mixture has left the container. Foam-forming may have stopped before the interstices between the conductors and the space between the core and the sheath have sufficiently been filled. Another disadvantage is that as a rule a cable in which the core contains a foamed synthetic material as a sealing means will be stiff, which may cause difficulties when the cable is wound on a drum and is laid in the ground.
When manufacturing power cables having a small number of conduc-tors of circular cross-section it is known to fill the interstices between, and the space around, the conductors to a circular cross-section with a silicone rubber which is spontaneously vulcanized at room temperature.
The vulcanizing agent is added to the filler material immediately before the application thereof.
A disadvantage of this method is that when the manufacturing process comes to a standstill conduits containing the material are likely
I~Method of manufacturing a longitudinally watertight telecommunication cable, and longitudinally watertight telecommunication cable obtained by this method".
The invention relates ~o a method of manufacturing a longitudinal_ ly watertight telecommunication cable having a core comprising a plurality of conductors each covered with a synthetic insulating material, the inter-stices between the conductors and the space between the core and the sheath being filled with a compound which prevents water from penetrating into the cable core in the direction of length of the cable.
Cables of this type are known. In cables laid in the ground water may penetrate into the cable core through defects of the sheath due to mechan-ical damage. Such defects may be due to subsidence of the ground or to mechan-` ical force. In the core of a cable composed of conductors or bundles of conductors which are twisted together, as generally is the case in telecommuni-cation cables, water which has made its way into the cable may spread in the direction of length thereof through the interstices between the conductors and the space between the core and the sheath. When the conductors are individually insulated with a synthetic resin, the presence of water becomes manifest only after the water has penetrated over a comparatively large dis-tance in that the electric properties of the cable deteriorate, which deterioration can be made good only with great difficulty. Penetration of vater.can be prevented in that highly viscous compounds or a foamed syn-thetic resin are applied throughout the length of the cable or in blocks, i,e. at regular interrals in the direction of length of the cable over a ~given distance. The highly viscous compounds proposed for this purpose usually are paraffin-like substances, petroleum waxes, petroleum jelly and the like. These substances are molten or heated till their viscosity is low and thereafter are pressed into the interstices between the conductors and ; into the space between the core and the sheath. ~fter solidification ~o~
the compounds introduced into the cable form a seal against water. A disad-vantage of these substances is, however, that they become liquid again when the cable temperature rises. This may occur, for example, when the cable wound on a drum is exposed to irradiation by the sun for a long time. By the action of gravity the molten sealing compound tilen flows to the lower parts of the cable on the drum, causing poorly filled interstices or voids to be left in the remaing parts of the cable. This is particularly detri-mental when the sealing compound has been applied in blocks. Another disad-vantage is that the quality of conductor insulations of polyethylene when brought into contact with some paraffin-like substances deteriorates in electrical and mechanical respects in the long run.
When the interstices between the conductors and the space bet-ween the core and the sheath are filled with a foamed synthetic material~ diffi-culties of another nature arise. Foaming is a process which is not readily controllable and which usually starts immediately after the foam-forming mixture has left the container. Foam-forming may have stopped before the interstices between the conductors and the space between the core and the sheath have sufficiently been filled. Another disadvantage is that as a rule a cable in which the core contains a foamed synthetic material as a sealing means will be stiff, which may cause difficulties when the cable is wound on a drum and is laid in the ground.
When manufacturing power cables having a small number of conduc-tors of circular cross-section it is known to fill the interstices between, and the space around, the conductors to a circular cross-section with a silicone rubber which is spontaneously vulcanized at room temperature.
The vulcanizing agent is added to the filler material immediately before the application thereof.
A disadvantage of this method is that when the manufacturing process comes to a standstill conduits containing the material are likely
-2-to become clogged.
For this reason the use of such a spontaneously vulcanized filler material in manufacturing telecommunication cables, in particular when the material is applied in blocks and is intended to prevent penetration of water, gives rise to difficulties.
It is an object of the present invention to provide a method of manufacturing a permanently flexible longitudinally watertight cable in which the sealing compound does not flow upon heating and does not attack the conductor-insulation.
In accordance with this invention, there is provided a method of manufacturing a longitudinally watertight telecommunication cable, which comprises providing an initial multiplicity of longitudinally extending syn-thetic resin-insulated conductors, applying about said initial multiplicity of conductors in longitudinally separated regions first layers of a moisture-vulcanizable silicone rubber, positioning a second multiplicity of longitud-inally extending synthetic resin-insulated conductors about said first con-ductor-silicone rubber combination, applying about said second multiplicity of conductors second layers of a moisture-vulcanizable silicone rubber at the same longitudinally separated regions as the first layers of moisture-vulcanizable silicone rubber, repeating said sequential steps of positioning a multiplicity of longitudinally extending synthetic resin-insulated conduc-tors and applying layers of a moisture-vulcanizable silicone rubber until a cable core having the desired diameter is obtained, and thereafter applying a sheath about said cable core before the silicone rubber has been complete-ly vulcanized.
A silicone rubber which is vulcanized by the action of the moisture in the air is distinguished from a silicone rubber which vulcanizes at ambient temperature in that in the former vulcanization starts only when the rubber is exposed to a moisture-containing atmosphere, whereas in the ~V44~
latter vulcanization starts immediately when the constituents are mixed and is not influenced by the ambient atmoshpere.
Silicone rubbers which vulcanize at ambient temperature by the action of the air moisture are known and commercially available. They usual-ly consist of a mixture of a diorganopolysiloxane, a filler such as silicon dioxide, a substance which causes crosslinking such, for example, as ethyl silicate, and a vulcanisation catalyser. Moisture curing compositions of this kind are described for example in United States Patent No. 3.661.817.
The commercial product may be used as such or mixed with a silicone oil or a rapidly evaporating solvent. The vulcanized~compound is permanently rubber-elastic. It was found that for the purpose concerned the said sili-cone rubbers sufficiently adhere to the commonly used conductor insulations consisting, for example, of polyethylene and polyvinyl chloride, even if the cable is repeatedly bent, but can readily be removed by hand from the conductor insulation.
Another advantage of the said silicone rubbers ~hich vulcanize at ambient temperature by the action of the air moisture is that the process of vulcanisation is comparatively slow. Hence the cable core can be pro-vided with a sheet consisting of an overlappingly wou~d foil before termina-tion of the vulcanizing process, which results in thorough filling of allthe interstices between the conductors and of the space between the core and this sheath. During the process of encasing the cable core in the sheath the compound which has not yet completely vulcanized and is still plastic is pressed into all the spaces between the cable core and the sheath. Under nonmal conditions the moist~re of the air enclosed in the core after the provision of the sheath is sufficient in the vulcanizing process to produce complete vulcanisation of the silicone rubber. When the silicone rubber was applied in blocks it proved possible to build up the blocks from layers. In the case of a core composed of conductors twisted ~_ lV~
together, for example in the form of star-quads or pairs, the said layered provision may be effected in that when a layer of conductors or bundles of conductors is applied around the preceding layer, at the same time a layer is provided of the silicone rubber which vulcanized at ambient temperature by the action of the air moisture. ~fter vulcanization the amounts of silicone rubber provided successively at the same location but at a later instant fo~n a single coherent barrier impenetrable to water. The same applies when the core is built up by twisting together conductor bundles. In this building-up process, during the formation of the cable core the unvulcanized silicone rubber is applied in and round the bundles at locations such that after assembly of the bundles the amounts of silicone rubber will form a single mass in the core at each block location.
Telecommunication cables manufactured by the method according to the invention are permanently flexible and provide no difficulty when being wound on drums or being installed. It was found that during installation the silicone rubber can simply be removed by hand from the conductors.
Example The core of a telephone cable comprising 150 star~quads of conduc-tors which each consist of a copper wire of diameter 0.5 mm coated with an insulating layer of polyethylene 0.32 mm thick was built up by winding on a core consisting of 3 star-quads layers of successively 9, 15, 21, 27, 34 and 41 star-quads~alternately in left and right helices.
Around each layer, except the outermost one, a foil of a linear polyester is wound in an open helix.
On the core and on each successive layer of star_quads silicone rubber which vulcanizes at ambient temperature by the action of the air moisture was provided at regular intervals (of 1 meter) through a length of about 10 cm in an amount such that the interstices between the conductors were completely filled. A material used for this purpose was a product which is marketed under the Silastic (trademark) 738 RTV by Dow Corning Corporation ard which according to the manufacturer is a silicone rubber which vulcanizes at room temperature by the action of the air moisture.
A foil consisting of a linear polyester was overlappingly wound around the cable core and subsequently a sheet was extruded onto the core.
To determine the effect of the sealing, a length of the resulting cable laid horizontally was connected to a vertically arran8ed tube which contained water to a height of t m above the cable. After 6 weeks it was found that the water had penetrated only to the first barrier of silicone rubber.
For this reason the use of such a spontaneously vulcanized filler material in manufacturing telecommunication cables, in particular when the material is applied in blocks and is intended to prevent penetration of water, gives rise to difficulties.
It is an object of the present invention to provide a method of manufacturing a permanently flexible longitudinally watertight cable in which the sealing compound does not flow upon heating and does not attack the conductor-insulation.
In accordance with this invention, there is provided a method of manufacturing a longitudinally watertight telecommunication cable, which comprises providing an initial multiplicity of longitudinally extending syn-thetic resin-insulated conductors, applying about said initial multiplicity of conductors in longitudinally separated regions first layers of a moisture-vulcanizable silicone rubber, positioning a second multiplicity of longitud-inally extending synthetic resin-insulated conductors about said first con-ductor-silicone rubber combination, applying about said second multiplicity of conductors second layers of a moisture-vulcanizable silicone rubber at the same longitudinally separated regions as the first layers of moisture-vulcanizable silicone rubber, repeating said sequential steps of positioning a multiplicity of longitudinally extending synthetic resin-insulated conduc-tors and applying layers of a moisture-vulcanizable silicone rubber until a cable core having the desired diameter is obtained, and thereafter applying a sheath about said cable core before the silicone rubber has been complete-ly vulcanized.
A silicone rubber which is vulcanized by the action of the moisture in the air is distinguished from a silicone rubber which vulcanizes at ambient temperature in that in the former vulcanization starts only when the rubber is exposed to a moisture-containing atmosphere, whereas in the ~V44~
latter vulcanization starts immediately when the constituents are mixed and is not influenced by the ambient atmoshpere.
Silicone rubbers which vulcanize at ambient temperature by the action of the air moisture are known and commercially available. They usual-ly consist of a mixture of a diorganopolysiloxane, a filler such as silicon dioxide, a substance which causes crosslinking such, for example, as ethyl silicate, and a vulcanisation catalyser. Moisture curing compositions of this kind are described for example in United States Patent No. 3.661.817.
The commercial product may be used as such or mixed with a silicone oil or a rapidly evaporating solvent. The vulcanized~compound is permanently rubber-elastic. It was found that for the purpose concerned the said sili-cone rubbers sufficiently adhere to the commonly used conductor insulations consisting, for example, of polyethylene and polyvinyl chloride, even if the cable is repeatedly bent, but can readily be removed by hand from the conductor insulation.
Another advantage of the said silicone rubbers ~hich vulcanize at ambient temperature by the action of the air moisture is that the process of vulcanisation is comparatively slow. Hence the cable core can be pro-vided with a sheet consisting of an overlappingly wou~d foil before termina-tion of the vulcanizing process, which results in thorough filling of allthe interstices between the conductors and of the space between the core and this sheath. During the process of encasing the cable core in the sheath the compound which has not yet completely vulcanized and is still plastic is pressed into all the spaces between the cable core and the sheath. Under nonmal conditions the moist~re of the air enclosed in the core after the provision of the sheath is sufficient in the vulcanizing process to produce complete vulcanisation of the silicone rubber. When the silicone rubber was applied in blocks it proved possible to build up the blocks from layers. In the case of a core composed of conductors twisted ~_ lV~
together, for example in the form of star-quads or pairs, the said layered provision may be effected in that when a layer of conductors or bundles of conductors is applied around the preceding layer, at the same time a layer is provided of the silicone rubber which vulcanized at ambient temperature by the action of the air moisture. ~fter vulcanization the amounts of silicone rubber provided successively at the same location but at a later instant fo~n a single coherent barrier impenetrable to water. The same applies when the core is built up by twisting together conductor bundles. In this building-up process, during the formation of the cable core the unvulcanized silicone rubber is applied in and round the bundles at locations such that after assembly of the bundles the amounts of silicone rubber will form a single mass in the core at each block location.
Telecommunication cables manufactured by the method according to the invention are permanently flexible and provide no difficulty when being wound on drums or being installed. It was found that during installation the silicone rubber can simply be removed by hand from the conductors.
Example The core of a telephone cable comprising 150 star~quads of conduc-tors which each consist of a copper wire of diameter 0.5 mm coated with an insulating layer of polyethylene 0.32 mm thick was built up by winding on a core consisting of 3 star-quads layers of successively 9, 15, 21, 27, 34 and 41 star-quads~alternately in left and right helices.
Around each layer, except the outermost one, a foil of a linear polyester is wound in an open helix.
On the core and on each successive layer of star_quads silicone rubber which vulcanizes at ambient temperature by the action of the air moisture was provided at regular intervals (of 1 meter) through a length of about 10 cm in an amount such that the interstices between the conductors were completely filled. A material used for this purpose was a product which is marketed under the Silastic (trademark) 738 RTV by Dow Corning Corporation ard which according to the manufacturer is a silicone rubber which vulcanizes at room temperature by the action of the air moisture.
A foil consisting of a linear polyester was overlappingly wound around the cable core and subsequently a sheet was extruded onto the core.
To determine the effect of the sealing, a length of the resulting cable laid horizontally was connected to a vertically arran8ed tube which contained water to a height of t m above the cable. After 6 weeks it was found that the water had penetrated only to the first barrier of silicone rubber.
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of manufacturing a longitudinally watertight tele-communication cable, which comprises providing an initial multiplicity of longitudinally extending synthetic resin-insulated conductors, applying about said initial multiplicity of conductors in longitudinally separated regions first layers of a moisture-vulcanizable silicone rubber, positioning a second multiplicity of longitudinally extending synthetic resin-insulated conductors about said first conductor-silicone rubber combination, applying about said second multiplicity of conductors second layers of a moisture-vulcanizable silicone rubber at the same longitudinally separated regions as the first layers of moisture-vulcanizable silicone rubber, repeating said sequential steps of positioning a multiplicity of longitudinally extending synthetic resin-insulated conductors and applying layers of a moisture-vulcanizable silicone rubber until a cable core having the desired diameter is obtained, and thereafter applying a sheath about said cable core before the silicone rubber has been completely vulcanized.
2. A method according to claim 1, which includes winding a foil of a linear polyester about at least one of said conductor-silicone rubber combinations in an open helix prior to positioning a next multiplicity of said conductors about said combination.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7408740A NL7408740A (en) | 1974-06-28 | 1974-06-28 | PROCESS FOR THE MANUFACTURE OF A LONG WATERPROOF CABLE AND LONG WATERPROOF CABLE OBTAINED ACCORDING TO THIS PROCESS. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1044866A true CA1044866A (en) | 1978-12-26 |
Family
ID=19821645
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA230,169A Expired CA1044866A (en) | 1974-06-28 | 1975-06-25 | Longitudinally watertight telecommunication cable and manufacture thereof |
Country Status (19)
| Country | Link |
|---|---|
| JP (1) | JPS5118879A (en) |
| AT (1) | AT346943B (en) |
| AU (1) | AU500770B2 (en) |
| BE (1) | BE830690A (en) |
| BR (1) | BR7503980A (en) |
| CA (1) | CA1044866A (en) |
| CH (1) | CH594963A5 (en) |
| DE (1) | DE2525934A1 (en) |
| DK (1) | DK141185B (en) |
| ES (1) | ES438881A1 (en) |
| FI (1) | FI59499C (en) |
| FR (1) | FR2276672A1 (en) |
| GB (1) | GB1505544A (en) |
| IE (1) | IE41389B1 (en) |
| IT (1) | IT1036369B (en) |
| NL (1) | NL7408740A (en) |
| NO (1) | NO752287L (en) |
| SE (1) | SE414354B (en) |
| ZA (1) | ZA753736B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7705840A (en) * | 1977-05-27 | 1978-11-29 | Nkf Groep Bv | LONG WATERPROOF CABLE AND SLEEVE CONNECTION. |
| DE2808438A1 (en) * | 1978-02-27 | 1979-09-06 | Kabel Metallwerke Ghh | Longitudinal moisture ingress sealing of power cables - consists of rubber inserts extending along about two per cent of cable length |
| DE2908454C2 (en) * | 1979-03-05 | 1986-11-27 | kabelmetal electro GmbH, 3000 Hannover | Moisture-proof power cable with a closed metal jacket and process for its production |
| DE3304715A1 (en) * | 1983-02-11 | 1984-08-16 | kabelmetal electro GmbH, 3000 Hannover | Process for manufacturing longitudinally watertight cables and lines |
| DE3630918A1 (en) * | 1986-09-11 | 1988-03-24 | Kabelmetal Electro Gmbh | Longitudinally water-tight transmission line for electrical power cables |
| JPH0733305Y2 (en) * | 1988-07-22 | 1995-07-31 | 住友電気工業株式会社 | Running water prevention cable for underwater suspension |
| JPH04309742A (en) * | 1991-04-09 | 1992-11-02 | Mitsubishi Electric Corp | Ventilating device |
| JPH04309740A (en) * | 1991-04-09 | 1992-11-02 | Mitsubishi Electric Corp | Ventilating device |
-
1974
- 1974-06-28 NL NL7408740A patent/NL7408740A/en not_active Application Discontinuation
-
1975
- 1975-06-10 ZA ZA3736A patent/ZA753736B/en unknown
- 1975-06-11 DE DE19752525934 patent/DE2525934A1/en active Pending
- 1975-06-20 GB GB26331/75A patent/GB1505544A/en not_active Expired
- 1975-06-24 JP JP50077068A patent/JPS5118879A/en active Granted
- 1975-06-25 AT AT487775A patent/AT346943B/en not_active IP Right Cessation
- 1975-06-25 FI FI751884A patent/FI59499C/en not_active IP Right Cessation
- 1975-06-25 IT IT68633/75A patent/IT1036369B/en active
- 1975-06-25 IE IE1415/75A patent/IE41389B1/en unknown
- 1975-06-25 NO NO752287A patent/NO752287L/no unknown
- 1975-06-25 CH CH826875A patent/CH594963A5/xx not_active IP Right Cessation
- 1975-06-25 BR BR5120/75D patent/BR7503980A/en unknown
- 1975-06-25 SE SE7507272A patent/SE414354B/en unknown
- 1975-06-25 AU AU82434/75A patent/AU500770B2/en not_active Expired
- 1975-06-25 CA CA230,169A patent/CA1044866A/en not_active Expired
- 1975-06-25 DK DK289575AA patent/DK141185B/en unknown
- 1975-06-26 BE BE157725A patent/BE830690A/en unknown
- 1975-06-26 ES ES438881A patent/ES438881A1/en not_active Expired
- 1975-06-27 FR FR7520278A patent/FR2276672A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| AU8243475A (en) | 1977-01-06 |
| ZA753736B (en) | 1977-01-26 |
| FI59499C (en) | 1981-08-10 |
| BR7503980A (en) | 1976-06-29 |
| AU500770B2 (en) | 1979-05-31 |
| FI59499B (en) | 1981-04-30 |
| NO752287L (en) | 1975-12-30 |
| FR2276672A1 (en) | 1976-01-23 |
| ATA487775A (en) | 1977-07-15 |
| DE2525934A1 (en) | 1976-01-15 |
| BE830690A (en) | 1975-12-29 |
| AT346943B (en) | 1978-12-11 |
| DK141185B (en) | 1980-01-28 |
| SE414354B (en) | 1980-07-21 |
| DK141185C (en) | 1980-07-07 |
| IE41389L (en) | 1975-12-28 |
| FI751884A (en) | 1975-12-29 |
| IT1036369B (en) | 1979-10-30 |
| JPS5725933B2 (en) | 1982-06-01 |
| IE41389B1 (en) | 1979-12-19 |
| DK289575A (en) | 1975-12-29 |
| JPS5118879A (en) | 1976-02-14 |
| CH594963A5 (en) | 1978-01-31 |
| NL7408740A (en) | 1975-12-30 |
| GB1505544A (en) | 1978-03-30 |
| ES438881A1 (en) | 1977-01-16 |
| SE7507272L (en) | 1975-12-29 |
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