CA1042665A - Method of coating a glass fiber filament - Google Patents
Method of coating a glass fiber filamentInfo
- Publication number
- CA1042665A CA1042665A CA232,530A CA232530A CA1042665A CA 1042665 A CA1042665 A CA 1042665A CA 232530 A CA232530 A CA 232530A CA 1042665 A CA1042665 A CA 1042665A
- Authority
- CA
- Canada
- Prior art keywords
- plastic
- filament
- cylinder
- core tube
- coating
- 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
- Extrusion Moulding Of Plastics Or The Like (AREA)
Abstract
METHOD OF COATING A GLASS FIBER FILAMENT
ABSTRACT OF THE DISCLOSURE
A method of coating a continuous glass fiber filament with plastic, in which plastic is charged into a vertical closed cylinder having a die opening at its lower end and an axial core tube terminating in the die opening to form an annular orifice. The plastic in liquid form is forced through the orifice by pressurized gas introduced into the upper portion of the cylinder while the glass filament is drawn continuously through the core tube.
ABSTRACT OF THE DISCLOSURE
A method of coating a continuous glass fiber filament with plastic, in which plastic is charged into a vertical closed cylinder having a die opening at its lower end and an axial core tube terminating in the die opening to form an annular orifice. The plastic in liquid form is forced through the orifice by pressurized gas introduced into the upper portion of the cylinder while the glass filament is drawn continuously through the core tube.
Description
~04Z665 This invention relates to a method of coating a continuou~ glaqs fiber filament with plastic.
In the field of gla~q fiber optics it is desirable to coat a continuous gla~s fiber filament with a plastic in order to ~trengthen the-strand. At presont such a coating is applied by feeding the filament from a give-up reel con-tinuously through a re-heating oven and then through liquid plastic. The re-heating step improvQs the adherence of the plastic to the filament. The problem with re-heating the 10" glass filament i8 that the heat cannot be applied uniformly and d~fferential stresses occur. These stresses, added to the tensions created when the filament is drawn from the give-up reel, create strain~ in the filament which affect its oper-ability as an optical device.
Another problem encountered in the known method of coat~ng continuou~ glass fiber filaments is that moisture and dust contaminate the surface of the filament between the time it is drawn and the tim~ it i8 coated. Also, when the glas~
filament is drawn it contains micro-cracks in its surface and if the filame~t i8 left to stand the micro-crack~ enlarge.
The surface conta~ination and the micro-cracks both adver~ely affect the adherence of the plastic coating to the filament which reduces its strength.
It is an object of the pre~ent invention to provide an improved method of coating a continuous gla-qq fiber filament.
In its broadest aspect the invention consi~ts of a method of coating a continuous glaqs fiber fila~nt by the extru~ion of plastic, comprising the ~tep~ of: charging with plastic coating material a closed vertical cylinder having a die aperture in the lower end thereof and an axial core tube , . . .
104'~;5 ter~inating in the die aperture to form an annular orifico, the plastic being liquified to pas~ through the die orifice;
drawing the filament from a source of molten glass coaxial with the core tube, continuouQly through the core tube; and introducing pres~urized ga~ into the upper portion of the cylinder to force the liquified plastic through the annular orifice and onto the filament.
An example embodiment of the invention i8 shown in the accompanying drawing in which:
10, -Pigure 1 i8 a cross-sectional view in elevation of an extruder for use in carrying out the method of the invention.
The e~bodiment shown in the drawing con~ists of an extruder 10 comprising a cylinder 12 which is vertically aligned axially with the outlet orifice of a furnace 13 for producing filaments from molten glas~.
Cylinder 12 ha~ an upper end closure 14 and a lower die clo~ure 16 to form a chamber 18 within the cylinder. Uppex end closure 14 is removably fixed to cylinder 12 by bolts 20 and ha~ a central bore 22 which i8 threaded to accept a boss 24 of a core tube 26 extending axially through the cylinder~
Bore 22 i8 sealed by a threaded nut 28 which bears a~ain~t an 0-ring 30 lying against an annular shoulder 32 in the bore.
Lower die closure 16 is removably fixed to cylinder 12 by bolts 34 and has a contoured aperture 36 into which the free end or nozzle 38 of core tube 26 projects to form an annular orifice 37. Nozzle 38 is removably attached to core tube 26 by set screws 39 and is shaped to act as a valve to ~eat in aperture 36 o~ closure 16 when the core tube i~ moved down~rdly.
A circular pressure plate 40 extends across cha~k~r 18 104;~66S
normal to th~ axi~ of cylinder 12 and ha~ a central aperture 42 through which core tube 26 pxojects. Pressure plate 40 is free to move dpwardly and downwardly in cha~ber 18. A support plate 44 parallel to pressure plate 40 is located adjacent lower die closure 16 with a plurality of large aperture~ 46.
Cylinder 12 carries two ports opening into chamber 18: a port 48 located adjacent upper end closure 14 for the introduction of gas, and a port 50 located adjacent lower die closure 16 for the introduction of liquid plastic. An annular 10~ ` band heater 52 circumscribes cylinder 12 between ports 48 and 50.
A level indicator rod projects through a seal 56 in upper end closure 14 and extends into chamber 18 to bear against pressure plate 40. A thermocouple 58 projects through cylinder 12 to chamber 18.
In the operation of the example embodiment, cha~ker 18 is opened by removing bolts 20 and lifting off upper end closure 14 together with core tube 26 and indicator rod 54.
Pressure plate 40 iæ also removed from chamber 18 and the cha~ber i8 charged with a machined billet of ~olid plastic coating material, such a~ nylon or polypropylene, which rest~
against support plate 44. The billet ha~ a central passage to receive core tube 26. Pre~sure plate 40 is then replaced in ch~mber 18 to rest on the billet below ga3 port 48 and upper end clo~ure 16 is replaced on cylinder 12 with core tube 26 extending through pressuro plate 40 and through the billet, and with indicator rod 54 resting on the pressure plate. Gas port 48 i8 connected with a ~ource of inert ga3, ~uch as nitrogon, at constant pressure and liguid plastic port 50 is
In the field of gla~q fiber optics it is desirable to coat a continuous gla~s fiber filament with a plastic in order to ~trengthen the-strand. At presont such a coating is applied by feeding the filament from a give-up reel con-tinuously through a re-heating oven and then through liquid plastic. The re-heating step improvQs the adherence of the plastic to the filament. The problem with re-heating the 10" glass filament i8 that the heat cannot be applied uniformly and d~fferential stresses occur. These stresses, added to the tensions created when the filament is drawn from the give-up reel, create strain~ in the filament which affect its oper-ability as an optical device.
Another problem encountered in the known method of coat~ng continuou~ glass fiber filaments is that moisture and dust contaminate the surface of the filament between the time it is drawn and the tim~ it i8 coated. Also, when the glas~
filament is drawn it contains micro-cracks in its surface and if the filame~t i8 left to stand the micro-crack~ enlarge.
The surface conta~ination and the micro-cracks both adver~ely affect the adherence of the plastic coating to the filament which reduces its strength.
It is an object of the pre~ent invention to provide an improved method of coating a continuous gla-qq fiber filament.
In its broadest aspect the invention consi~ts of a method of coating a continuous glaqs fiber fila~nt by the extru~ion of plastic, comprising the ~tep~ of: charging with plastic coating material a closed vertical cylinder having a die aperture in the lower end thereof and an axial core tube , . . .
104'~;5 ter~inating in the die aperture to form an annular orifico, the plastic being liquified to pas~ through the die orifice;
drawing the filament from a source of molten glass coaxial with the core tube, continuouQly through the core tube; and introducing pres~urized ga~ into the upper portion of the cylinder to force the liquified plastic through the annular orifice and onto the filament.
An example embodiment of the invention i8 shown in the accompanying drawing in which:
10, -Pigure 1 i8 a cross-sectional view in elevation of an extruder for use in carrying out the method of the invention.
The e~bodiment shown in the drawing con~ists of an extruder 10 comprising a cylinder 12 which is vertically aligned axially with the outlet orifice of a furnace 13 for producing filaments from molten glas~.
Cylinder 12 ha~ an upper end closure 14 and a lower die clo~ure 16 to form a chamber 18 within the cylinder. Uppex end closure 14 is removably fixed to cylinder 12 by bolts 20 and ha~ a central bore 22 which i8 threaded to accept a boss 24 of a core tube 26 extending axially through the cylinder~
Bore 22 i8 sealed by a threaded nut 28 which bears a~ain~t an 0-ring 30 lying against an annular shoulder 32 in the bore.
Lower die closure 16 is removably fixed to cylinder 12 by bolts 34 and has a contoured aperture 36 into which the free end or nozzle 38 of core tube 26 projects to form an annular orifice 37. Nozzle 38 is removably attached to core tube 26 by set screws 39 and is shaped to act as a valve to ~eat in aperture 36 o~ closure 16 when the core tube i~ moved down~rdly.
A circular pressure plate 40 extends across cha~k~r 18 104;~66S
normal to th~ axi~ of cylinder 12 and ha~ a central aperture 42 through which core tube 26 pxojects. Pressure plate 40 is free to move dpwardly and downwardly in cha~ber 18. A support plate 44 parallel to pressure plate 40 is located adjacent lower die closure 16 with a plurality of large aperture~ 46.
Cylinder 12 carries two ports opening into chamber 18: a port 48 located adjacent upper end closure 14 for the introduction of gas, and a port 50 located adjacent lower die closure 16 for the introduction of liquid plastic. An annular 10~ ` band heater 52 circumscribes cylinder 12 between ports 48 and 50.
A level indicator rod projects through a seal 56 in upper end closure 14 and extends into chamber 18 to bear against pressure plate 40. A thermocouple 58 projects through cylinder 12 to chamber 18.
In the operation of the example embodiment, cha~ker 18 is opened by removing bolts 20 and lifting off upper end closure 14 together with core tube 26 and indicator rod 54.
Pressure plate 40 iæ also removed from chamber 18 and the cha~ber i8 charged with a machined billet of ~olid plastic coating material, such a~ nylon or polypropylene, which rest~
against support plate 44. The billet ha~ a central passage to receive core tube 26. Pre~sure plate 40 is then replaced in ch~mber 18 to rest on the billet below ga3 port 48 and upper end clo~ure 16 is replaced on cylinder 12 with core tube 26 extending through pressuro plate 40 and through the billet, and with indicator rod 54 resting on the pressure plate. Gas port 48 i8 connected with a ~ource of inert ga3, ~uch as nitrogon, at constant pressure and liguid plastic port 50 is
2~
closod by suitable p~ug mean~. Boss ~ is screwed downwardly
closod by suitable p~ug mean~. Boss ~ is screwed downwardly
- 3 -.
.1()42665 in bore 22 to have free end 38 of core tube 26 seat in die aperture 36. Band beater 52, connected to a source of elect-ricity, is switched on to melt the billet of pla~tic within cha~ber 18. The temperature of the pla_tic within chamber 18 is sensed by thermocouple 58.
Extruder 10 iq now ready to coat a cont~nuou_ gla~3 fiber filament 60 which is pulled rom glas~ furnace 13 and pas~ed through core tube 26. Boss 24 of core tube 26 i~
scxewed upwardly t~ un_eat nozzle 38 from die aperture and inert ga~ at constant pressure i8 introduced into chamber 18 through port 48 above pressure plat- 40. The pressurized gas acts against plate 40 to force the liquified plastic out through die aperture 36 around nozzle 38 as strand 60 is pa~sed through core tube 26, producing a plastic coating 6~ on the filament. me thickness of coating 62 is governed by the po_ition of nozzle 38 in die aperture 36, by the gaQ pre~sure and by tho speed of filament 60 which attenuates the coating.
The device of the invention applies a constant pres~ure to the liquid plastic material which produce~ a uni-form extrusion of the plastic onto filamsnt 600 When using a machined billet of plastic, pres~ure plate 40 i~ not nec-e~sary but the plate minimize~ ga~ tracking through the die.
Support plate 44 is optional to seat the billet above lower end clo~ure 16.
If desired, liquid pla~tic may be introduced dir-ectly into chamber 18 instead of using a machined billet of pla~tic. The liquid plastic i_ introduced by connecting port 50 with a suitable ~crew or ram extruder. The use of the device of the prqsent invention in conjunction with a convent-ional screw extruder would s~ooth out the pressure fluctuations 1~)4266S
of such an extruder and provide a smooth coating of plastic on a continuous filament. The leval o~ liquid pla~tic in cham~er 18 using either a,mRchined billet or a conventional extruder i8 sensed by indicator rod 54 which could be employed to provide feedback control for the conventional extruder.
If it is necessary to debydrate the plastic in cha~ber 18 kafore extruding it, a vacuum can be applied to port 48 in the absence o~ pres~ure plate 40.
Because liquid plastic i~ a non-Newtonian fluid, 1~ shear stresses complicate its flow characteris~ic~. The device o the present invention reduces the shear stresses applied to the plastic by conventional extruders and cause~
the material to behave more like a ~ewtonian fluid which i8 more predictable and hence!~more controllable~
By drawing glass fiber filament 60 directly from a molten source through extr~der 10 the ~ filament is coated with plastic kefore the ~urface of the filament can become contaminated or the micro-cracks can become enlarged.
Also, the residual heat of fila~ent 60 can be employed to obtain the required bonding of plastic coating 62 to the filam~nt, Of course extruder 10 mu~t be spaced below glass furnace 13 a distance to allow filament 60 to cool to a temperature which will not degrade plastic coating 62. It will also be appreciated that no lateral stresse~ are imposed on ila~ent 60 before it is coated.
_ 5 _
.1()42665 in bore 22 to have free end 38 of core tube 26 seat in die aperture 36. Band beater 52, connected to a source of elect-ricity, is switched on to melt the billet of pla~tic within cha~ber 18. The temperature of the pla_tic within chamber 18 is sensed by thermocouple 58.
Extruder 10 iq now ready to coat a cont~nuou_ gla~3 fiber filament 60 which is pulled rom glas~ furnace 13 and pas~ed through core tube 26. Boss 24 of core tube 26 i~
scxewed upwardly t~ un_eat nozzle 38 from die aperture and inert ga~ at constant pressure i8 introduced into chamber 18 through port 48 above pressure plat- 40. The pressurized gas acts against plate 40 to force the liquified plastic out through die aperture 36 around nozzle 38 as strand 60 is pa~sed through core tube 26, producing a plastic coating 6~ on the filament. me thickness of coating 62 is governed by the po_ition of nozzle 38 in die aperture 36, by the gaQ pre~sure and by tho speed of filament 60 which attenuates the coating.
The device of the invention applies a constant pres~ure to the liquid plastic material which produce~ a uni-form extrusion of the plastic onto filamsnt 600 When using a machined billet of plastic, pres~ure plate 40 i~ not nec-e~sary but the plate minimize~ ga~ tracking through the die.
Support plate 44 is optional to seat the billet above lower end clo~ure 16.
If desired, liquid pla~tic may be introduced dir-ectly into chamber 18 instead of using a machined billet of pla~tic. The liquid plastic i_ introduced by connecting port 50 with a suitable ~crew or ram extruder. The use of the device of the prqsent invention in conjunction with a convent-ional screw extruder would s~ooth out the pressure fluctuations 1~)4266S
of such an extruder and provide a smooth coating of plastic on a continuous filament. The leval o~ liquid pla~tic in cham~er 18 using either a,mRchined billet or a conventional extruder i8 sensed by indicator rod 54 which could be employed to provide feedback control for the conventional extruder.
If it is necessary to debydrate the plastic in cha~ber 18 kafore extruding it, a vacuum can be applied to port 48 in the absence o~ pres~ure plate 40.
Because liquid plastic i~ a non-Newtonian fluid, 1~ shear stresses complicate its flow characteris~ic~. The device o the present invention reduces the shear stresses applied to the plastic by conventional extruders and cause~
the material to behave more like a ~ewtonian fluid which i8 more predictable and hence!~more controllable~
By drawing glass fiber filament 60 directly from a molten source through extr~der 10 the ~ filament is coated with plastic kefore the ~urface of the filament can become contaminated or the micro-cracks can become enlarged.
Also, the residual heat of fila~ent 60 can be employed to obtain the required bonding of plastic coating 62 to the filam~nt, Of course extruder 10 mu~t be spaced below glass furnace 13 a distance to allow filament 60 to cool to a temperature which will not degrade plastic coating 62. It will also be appreciated that no lateral stresse~ are imposed on ila~ent 60 before it is coated.
_ 5 _
Claims (5)
1. A method of coating a continuous glass fiber fila-ment by the extrusion of plastic, comprising the steps of:
charging with plastic coating material a closed vertical cylinder having a die aperture in the lower end thereof and an axial core tube terminating in the die aper-ture to form an annular orifice, the plastic being liquified to pass through the die orifice;
drawing the filament, from a source of molten glass coaxial with the core tube, continuously through the core tube;
and introducing pressurized gas into the upper portion of the cylinder to force the liquified plastic through the annular orifice and onto the filament.
charging with plastic coating material a closed vertical cylinder having a die aperture in the lower end thereof and an axial core tube terminating in the die aper-ture to form an annular orifice, the plastic being liquified to pass through the die orifice;
drawing the filament, from a source of molten glass coaxial with the core tube, continuously through the core tube;
and introducing pressurized gas into the upper portion of the cylinder to force the liquified plastic through the annular orifice and onto the filament.
2. A method as claimed in claim 1 in which the cylinder is charged with a billet of solid plastic and the plastic is liquified in situ.
3. A method as claimed in claim 1 in which the plastic is charged into the cylinder in liquid form adjacent the die aperture.
4. A method as claimed in claim 1 in which the plastic is nylon.
5. A method as claimed in claim 1 in which the plastic is polypropylene.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA232,530A CA1042665A (en) | 1975-07-30 | 1975-07-30 | Method of coating a glass fiber filament |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA232,530A CA1042665A (en) | 1975-07-30 | 1975-07-30 | Method of coating a glass fiber filament |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042665A true CA1042665A (en) | 1978-11-21 |
Family
ID=4103739
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA232,530A Expired CA1042665A (en) | 1975-07-30 | 1975-07-30 | Method of coating a glass fiber filament |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1042665A (en) |
-
1975
- 1975-07-30 CA CA232,530A patent/CA1042665A/en not_active Expired
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