A double-coating cup

Abstract: The present invention relates to a double-coating cup for coating an optical fibre with two protective layers simultaneously. The cup includes a body provided with an axially extending, frusto-conical boring whose largest diameter is located on the fibre-inlet side, a die holder firmly pressed into the body and having a frusto-conical outer surface which corresponds to the boring, and two die nozzles inserted in the die holder and functioning to apply the two layers of coating material. According to the invention, the body (1) has two first diametrically opposed first coating-material inlet channels (4) spaced at a first axial distance from the inlet side, and two second diametrically opposed second coating-material inlet channels (5) spaced at a second axial distance from the inlet side. The die holder (8) has a frusto-conical boring (10) whose largest diameter lies on the fibre inlet-side, a first cylindrical boring (11) which is a continuation of the conical boring, a first shoulder (12), a second cylindrical boring (13), a second shoulder (14), and a third cylindrical boring (15), wherein the outer surface (9) of the die holder has first ring-shaped slots (17) and first radial borings (18) which connect with the ring-shaped slots (17) and which open into the junction between the frusto-conical boring (10) and the first cylindrical boring (11), and second ring-shaped slots (19) which connect with second radial borings (20) which open into the second cylindrical boring (13). A guide die (21) is inserted into the conical boring (10) of the die holder and includes an outwardly extending part (25) in the end-wall (26) of the die. A first cylindrical die nozzle (27) having a frusto-conical recess (28) is inserted in the first cylindrical boring (11) in a manner such as to form a first coating-material gap or slot (30) between the die nozzle (27) and the guide die (21). A cylindrical intermediate guide die (34) is inserted against the first shoulder (12) and has a frusto-conical outwardly projecting part (37) in the end-wall (38) of the die. A second cylindrical die nozzle (39) having a frusto-conical recess (40) is positioned in the second cylindrical boring (13) and in abutment with the second shoulder (14) in a manner such as to form a second coating-material gap or slot (43) between the die nozzle (39) and the intermediate guide die (34). The die nozzle has distribution channels (44) which connect with the second radial borings (20) and which distribute coating material around the fibre coated with the first coating material and therewith centre the fibre in respective dies.

Description: TECHNICAL FIELD The present invention relates to a double-coating cup for coating an optic fibre with two protective layers simultaneously, said cup comprising a body having a frusto-conical boring formed axially therein, wherein the largest diameter of said boring lies on the inlet side of the fibre, and a die holder which is pressed firmly in the body and has a frusto-conical outer side surface corresponding to said boring, and further comprising two die nozzles inserted in the die holder for the application of said two layers of coating material. BACKGROUND ART Coating cups used to coat an optical fibre with two coating layers simultaneously are known to the art. These coating cups include radially extending slots or frusto-conical borings through which the coating material is applied on to the fibre. The drawback with these known coating cups is that centering of the fibre in the coating material is unreliable. An additional drawback with such known coating cups is that their construction is often complicated, resulting in handling difficulties when carrying out maintenance work and when cleaning the cups, for example. DISCLOSURE OF THE INVENTION The object of the present invention is to avoid the drawbacks associated with earlier known coating cups and to provide a double-coating cup of simple construction which can be readily dismantled for cleaning or like purposes, and to ensure that the two coating layers will be applied onto the fibre with precision such that the fibre will lie fully concentrically in the protective layers, and that coating of the fibre can be effected so that the fibre is centred in the cup-body without risk of wear through contact with the different die nozzles. This object is achieved with a double-coating cup having the characteristic features set forth in the following Claims. Thus, an inventive double-coating cup has the advantage of providing a double-coated fibre of very precise diameter and concentricity. Another advantage is that the cup is of simple construction and can be readily handled and maintained. Other objects of the invention and further advantages afforded by the inventive double-coating cup will be evident from the following description, in which the invention is described in more detail with reference to a preferred exemplifying embodiment thereof and also with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an axial section view of an inventive double-coating cup taken on the line 1-1 in Figures 2 and 3. Figure 2 is a cross-sectional view of the double-coating cup taken on the broken line 2-2 in Figure 1. Figure 3 is another cross-sectional view of the double-coating cup taken on the line 3-3 in Figure 1. BEST MODE FOR CARRYING OUT THE INVENTION The double-coating cup illustrated in Figure 1 includes a body 1 in which there is formed a truncated, conical boring 2 whose largest diameter is located on the inlet side at which a fibre 3 to be coated with two protective layers of coating material is introduced into the cup. The body 1 has two first inlet channels 4, which are diametrically opposed to one another at a first axial distance from said inlet side, and two second inlet channels 5 which are arranged axially spaced from the inlet side and located axially beneath the inlet channels 4. The inlet channels 4 and 5 are connected to pressurized containers containing the two coating materials, by means of nipples and hoses in a manner not shown. On the inlet side, the body is also provided with an externally screw-threaded part 6 for coaction with a holding nut 7 having a central opening 7a for the incoming fibre 3 and for firmly holding the parts of said body 1, in a manner described in more detail here below. A die holder 8 having a frusto-conical outer surface 9, corresponding to the boring 2, is inserted in the body 1. The die holder 8 is provided with a frusto-conical boring 10 which merges with a first cylindrical boring 11. There then follows a first shoulder 12, a second cylindrical boring 13 whose diameter is smaller than the diameter of the boring 11, a second shoulder 14 and a third, still smaller cylindrical boring 15. This latter boring is followed by a frusto- conical outlet boring 16. The outer surface 9 of the die holder 8 has formed therein first ring-shaped slots 17 which lie opposite the coating material entering through the inlet channels 4 and which form material distribution channels, said slots extending roughly through one-quarter of a circle around the die holder, as illustrated clearly on the right of Figure 2. As will also be seen from Figure 2, the slots 17 connect with first radial borings 18 which open into the junction between the frusto-conical boring 10 and the first cylindrical boring 11. The illustrated embodiment includes four radial borings 18 which are mutually spaced at 90° so as to distribute the coating material uniformly around the fibre, as will be described in more detail herebelow. Provided on the die holder 8 opposite the inlet channels 5 are second ring-shaped slots 19 which form distribution channels for the second coating material and which also extend through roughly one-quarter of a circle around the die holder and connect with second radial borings 20, as illustrated in Figure 3, these borings 20 opening into the second cylindrical boring 13. These borings 20 are also four in number and are spaced mutually at 90° in order to uniformly distribute the second coating material. Fitted loosely into the conical boring 10 of the die holder 8 is a fibre-guide die 21. The guide die has an external, frusto-conical surface 22 which corresponds to the shape of the boring 10 and also has a frusto-conical inlet boring 23 which functions to guide the optical fibre into the double-coating cup, this boring 23 merging with a cylindrical guide-boring 24 which opens into a frusto-conical outwardly directed part 25 of the lower end-wall 26 of the guide die. A first cylindrical die 27 is fitted loosely into the first boring 11 of the die holder. The die 27 has a frusto-conical recess 28 which merges with a cylindrical nozzle-boring 29, and which is arranged so as to form a gap 30 between the recess 28 and the outwardly extending part 25 of the guide die. Radial borings 31 in the die open into the recess 28, and therewith into the gap or slot 30, these borings being disposed opposite the first borings 18 in the die holder, as clearly shown in Figure 2. The borings 31 function to distribute the first coating material uniformly in the gap 30 around the incoming fibre 3, causing, at the same time, the fibre to be centered accurately centred in the die and coated uniformly with coating material. As beforementioned, the die or nozzle 27 is fitted loosely into the die holder 8 and his held and centered in said holder by means of screws 32, the tips of which lie in a circular groove 33 provided in the die. Located beneath the first die 27 is a cylindrical intermediate die 34 which is press-fitted into the first boring 11 in abutment with the first shoulder 12. The guide die 34 has a cylindrical boring 35 which merges with a narrower guide-boring 36. This guide-boring opens into a frusto-conical outwardly extending part 37 in the bottom end-wall 38 of the guide die. A second cylindrical die 39 is press-fitted into the second boring 13 of the die holder 8, in abutment with the second shoulder 14. The die has a frusto-conical recess 40 which merges with a cylindrical die-boring 41 and a frusto-conical outlet boring 42. The die 39 is arranged in a manner to form a gap or slot 43 between the outwardly extending part 37 of the intermediate die 34 and the recess 40. Radial borings 44 open into the recess 40, and thus also into the gap 43, in the same manner and for the same reason as that described above with reference to the die 27, as illustrated in Figure 3, so as to distribute the second coating material uniformly around the fibre 3 coated with the first coating material, causing the fibre to be centered in the die and coated uniformly with the second coating material. The full extension of the fibre 3 through the various die borings has not been shown in Figure 1, for the sake of clarity. The Figure does show, however, the manner in which a pair of sealing rings is arranged to prevent the throughflow of coating material between the two die nozzles 27 and 39. Thus, one sealing ring is provided in a groove in the nozzle holder 8, between the ring-shaped slots 17 and 19, and one sealing ring is arranged in a groove in the intermediate guide die 34, against the lower end-wall of the first die nozzle 27. The Figure also shows that the body is provided with a cylindrical, downwardly protruding sleeve which surrounds the exiting fibre coated with said two coating materials. As before mentioned, the coating material used is preferably a UV-curing acrylate, although other materials may be used, of course. The acrylate may be admixed with a UV-hardening paint, so as to incorporate a cable-coding or cable-marking colour in the protective coating. The double-coating cup may also be used to effect a separate colour-coating or colour-marking operation, by drawing a coated fibre once more through the body, the coating material in this case consisting of a paint, preferably a UV-hardening paint, instead of acrylate. It will be understood that the invention is not restricted to the aforedescribed and illustrated embodiment thereof and that modifications can be made within the scope of the following Claims.

Claims: A double-coating cup for applying two protective coatings simultaneously to an optical fibre, said cup comprising a body provided with an axially extending, frusto-conical boring whose largest diameter is located on the fibre-inlet side, a die holder firmly pressed into the body and having a frusto-conical outer surface which corresponds to the boring, and two die nozzles inserted in the die holder and functioning to apply said two layers of coating material, characterized in that the body (1) has two first diametrically opposed first coating-material inlet channels (4) spaced at a first axial distance from the inlet side, and two second diametrically opposed second coating-material inlet channels (5) spaced at a second axial distance from said inlet side; in that the die holder (8) has a frusto-conical boring (10) whose largest diameter lies on the fibre inlet-side, a first cylindrical boring (11) which is a continuation of the conical boring, a first shoulder (12), a second, smaller cylindrical boring (13), a second shoulder (14), and a third, smallest cylindrical boring (15); in that the outer surface (9) of the die holder has first ring-shaped slots (17) located opposite the first inlet channels (4) and first radial borings (18) which connect with said ring-shaped slots (17) and which open into the junction between the frusto-conical boring (10) and the first cylindrical boring (11), and second ring-shaped slots (19) which are located opposite the second inlet channels (15) and which connect with second radial borings (20) which open into the second cylindrical boring (13); in that a guide die (21) having a frusto-conical outer surface (22) is inserted into the conical boring (10) of the die holder and includes a frusto-conical inlet boring (23) which merges with a cylindrical guide boring (24) in a frusto-conical outwardly projecting part (25) in the end-wall (26) of said die; in that a first cylindrical die nozzle (27) having a frusto-conical recess (28) which merges with a cylindrical nozzle boring (29) is inserted in the first cylindrical boring (11) in a manner such as to form a first coating-material gap or slot (30) between the die nozzle (27) and the guide die (21), said die nozzle being provided with distribution channels (31) which connect with the first radial borings (18) and which function to distribute said coating material around the fibre and therewith centre the fibre in the nozzle; in that a cylindrical intermediate guide die (34) provided with a cylindrical boring (35) is positioned against the first shoulder (12) and has a frusto-conical outwardly projecting part (37) in the end-wall (38) of said die; and in that a second cylindrical die nozzle (39) having a frusto-conical recess (40) which merges with a cylindrical nozzle boring (41) is positioned in the second cylindrical boring (13) and in abutment with said second shoulder (14) in a manner such as to form a second coating-material gap or slot (43) between the die nozzle (39) and the intermediate guide die (34), said die nozzle having distribution channels (44) which connect with the second radial borings (20) and which distribute coating material around the fibre coated with said first coating material and therewith centre the fibre in said die nozzle. A cup according to Claim 1, characterized in that the distribution channels (31, 44) in the die nozzles (27, 39) are formed by circumferentially disposed and uniformly spaced radial borings which open into the frusto-conical recesses (28, 40). A cup according to Claim 2, characterized in that the intermediate guide die (34) is provided with an axially disposed sealing ring against the first die nozzle (27); and in that a sealing ring is mounted on the outer surface (9) of the die holder (8) between the first and the second radial borings. A cup according to Claim 3, characterized in that the first die nozzle (27) is loosely fitted into the first cylindrical boring (11) and is firmly held and centered in the die holder by means of screws (32). A cup according to Claim 4, characterized in that the intermediate guide die (34) is press-fitted in the first boring (11); and in that the second die nozzle (39) is press-fitted in the second cylindrical boring (13). A cup according to any one of the preceding Claims, characterized in that the body (1) is provided on the inlet side with a screw thread (6) for coaction with a holding nut (7) provided with an opening (7a) and lying in abutment with the guide die (21).

Inventors: ERICSSON MATS HENRIK, FICKLING PETER RICHARD, SUNDBERG SVEN-ERIK, ERICSSON, MATS HENRIK, FICKLING, PETER RICHARD, SUNDBERG, SVEN-ERIK
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET L M ERICSSON
Application year: 1991
Main classification: C03C25
IPC codes: G02B6, B29C47, C03C25