EXPANSIBLE REEL FOR TESTS ON FILAMENTARY MATERIAL, IN PARTICULAR OPTICAL FIBRES

Abstract: The expansible reel (1) comprises a plurality of rigid structural members (2), parallel to each other and to a central axis of the reel, joined at the ends to supports (3) allowing small radial displacements of the members. Between contiguous rigid members (2) there are placed inflatable members (4) into which compressed air is introduced to space apart the rigid members (2) when an optical fibre wound around the reel (1) is to be submitted to tests under controlled tensile stress conditions (Fig.2).

Description: The present invention relates to supports for filamentary material, and more particularly to an expansible reel for winding up the material and subjecting same to measurements and tests. Preferably the filamentary material is an optical fibre and the following description will refer to this preferred application. When manufacturing optical fibres, it is necessary or desirable, after fibre drawing, to perform tests and measurements on the fibre itself, such as tests of behaviour under tensile-stress conditions, measurements of microbending losses, etc. it is desirable to effect the measurements without removing the fibre from the support on which it has been wound, and hence, if the tests require subjecting the fibre to tensile stresses, the support is to be expansible. A number of expansible and/or collapsible reels used to support skeins of textile yarns are already known: yet said known reels are only designed to allow an easy removal of skeins formed on the reel, or an easy insertion and removal of same to transfer them from one place to another, and do not allow execution of tests where a carefully controlled and uniform tensile stress is to be applied to the wire. A number of examples are described in Austrian Patent No. 127,367, German Patent No. 910,271 and United States Patents Nos. 3,139,242 and 3,166,335. DE-A1-36 05 846 discloses an expandable mandrel in which expansion is obtained by mechanical means. In particular, the operation element is moving in axial direction by an pneumatic operating air skin. A drum for winding up material which is being drawn is also known from European Patent No. 125,609. The drum comprises a cylindrical envelope made of a single piece of an airtight material with a certain degree of resiliency, around which the fibre is wound. The envelope delimits a chamber where the pressure can be varied to allow tests under controlled tensile stress conditions to be made on the fibre. The envelope base must be thicker than the side surface to ensure the envelope indeformability necessary to obtain uniform tensile stresses, which makes the drum difficult to manufacture. The invention provides an expansible reel for winding filamentary material and for carrying out tests and measurements on same, which comprises a plurality of rigid elongated members, parallel to each other and to a central axis of the reel and fastened at the ends to common supports by fastening means allowing radial displacement of said members with respect to such supports. The reel of the invention comprises inflatable members which are located between confronting side faces of said elongated members, extend substantially over the whole length of said side surfaces and are associated at one end with means for connection to a system supplying gas under pressure to vary their internal pressure in a controlled manner, said rigid elongated members being substantially in contact with each other when no gas under pressure is introduced into the inflatable members and being progressively spaced from each other by said inflatable members because of the introduction of gas inside the latter to submit the material wound on the reel to controlled tensile stresses. The invention will become more apparent with reference to the annexed drawings, in which: Fig. 1 is a side view of the reel according to the invention; Fig. 2 is a cross-sectional view according to plane II-II of Fig.1; Fig. 3 is a partial view of a supporting disc; Fig. 4 shows a detail of the fastening of the reel elements to a supporting disc; Fig. 5 is a longitudinal sectional view of a rod and of an associated inflatable member; Fig.6 is a cross sectional view of same, according to plane VI-VI of fig. 5. As shown in Figs. 1 to 3, the reel according to the invention, denoted on the whole by 1, comprises a plurality of elongated structural elements 2 (hereinafter referred to as rods), which are made for instance of light metal, have a substantially trapezoidal section, are arranged parallel to each other around a central axis of the reel and are fastened at their ends to two discs 3. Inflatable members 4 are positioned between contiguous rods, extending along substantially the whole rod length, and are connectable to a compressed air source (not shown), placed outside the reel. To this aim one of the two discs 3 is provided with openings 18 where pipes connectable with the compressed air source are hold, which pipes communicate with the inside of the inflatable members as will be explained hereinafter. Said members 4 can be tubular rubber members, and for the aims of the invention they must reach a diameter of some millimetres in conditions of maximum inflation. The contiguous rods are basically in contact with each other when no air is introduced into members 4 and will become more or less spaced apart upon introduction of compressed air into members 4. Preferably, only every second rod is equipped with the inflatable members, which are associated with both side faces of the rod. Yet inflatable members 4 associated with an only side surface of all rods 2 could be used. Pads 5 with suitable shape and made of suitable material, for instance polyvinylchloride or another hard plastics, tetrafluoroethylene, metal and the like, are fastened to the outer surface of rod 2. The shape and/or the material of the pads can be different depending on the tests to be made. For instance, if only tensile stress tests are to be made, pads with convex and smooth surface can be used such as the pad denoted by 5a in Fig. 2, which extends over the whole width of the side surface of the corresponding rod and gives the reel a cylindrical surface basically without sharp corners. To measure microbending losses, the surface of the pads can present a certain roughness, as shown for pad 5b; said roughness can be obtained by applying a coating of emery cloth or paper on pads like pads 5a or by making the whole pad of a material whose surface can be conveniently machined. If the fibre is to be subjected to higher strains, as demanded e.g. for adhesion tests of the primary coating, pads with an irregular surface like pad 5c could be used, which pad has a smaller width than the rod and presents two longitudinal ribs at the edges. The pads can be fastened to the rods in any suitable way, for instance by screws. Rods 2 ought to be connected to discs 3 so as to allow small radial displacements (some millimetres) of the rods during the reel expansion, and to this aim discs 3 present slots where the head of a screw 6 or the like is fitted. For instance, as shown in Fig. 4, screws 6 acting as spacers can be used. Those screws have a portion protruding outside discs 3 where a groove 6a is realized which can be engaged by an end of a resilient member 21 (Fig. 3), for instance a spring, whose other end is gripped to pins or the like protruding from the discs. Thus unwanted movements of rods 2 are avoided. Discs 3 have a central recess 19 (Fig. 3) allowing the reel to be coupled to mechanisms rotating the reel for winding up the fibres. Besides, the two discs 3 are linked by a rigid axial member 20 (Fig. 2), e.g. a tube, which prevents deformations of reel 1 which would be otherwise possible owing to loose connection among the rods 2 and the discs. With reference to Figs. 5 and 6, which relate to the case in which the inflatable members are associated with every second rod, the side faces of rods 2 present at the ends two recesses 8, 9 of different width wherein the end portions of the inflatable members 4 are hold and closed. To this aim the end portions of the inflatable members are folded on themselves and the folded portion is pressed against the bottom of recesses 8, 9 by metal tangs secured e. g. by screws 11. The wider recess 8 provides moreover the seat for a screw rivet 13 whose head is introduced into the inflatable member 4. Rivet 13 presents an axial through hole 14 and is associated with a washer 15 which keeps the tube wall compressed against the bottom of the recess. Seats 12 form the end portion of ducts 16 provided inside the rod 2 and communicating on the one side with the interior of inflatable member 4, through the axial bore of rivet 13, and on the other side with a duct 17 which ends on the internal surface of rod 2. Duct 17 is connected, through suitable connectors, to the corresponding opening 18 (Fig. 3) on disc 3. In case all rods 2 are equipped with an inflatable member 4, recesses 8, 9 will be provided on a single side face of the rods and a single duct 16 will be present ending on the inside rod surface. The way of using the reel according to the invention is as follows. Before and during fibre winding, members 4 are kept deflated and rods 2 are kept blocked and basically in contact with each other by the springs engaging grooves 6a of screws 6. The fibre winding is performed with the usual techniques, so as to avoid overlapping of contiguous loops. The tensile stress applied to the fibre wound up in these conditions is practically null. To carry out the measurements, pressure air is introduced into members 4, which are inflated and shift rods 2 outwards, thereby causing an increase in the reel diameter. Hence the fibre wound undergoes a certain strain, which depends on the pressure within the inflatable members. Just as an indication, the pressure applied to inflatable members could range from 0 to 5 Atm. Obviously, the system supplying the compressed air comprises adjustment valves and control instruments allowing the introduction of strictly controlled pressure variations. During the tests, resilient members 21 can be removed or kept in place, according the type of tests. As mentioned, tensile stress tests, microbending loss measurements, adherence tests of the first coating or any other test wherein the fibre is to undergo a tensile stress can be performed. Depending on the tests to be performed, the most suitable pads 5 are to be mounted onto the rods prior to the winding. In addition, the fibre could be covered by a band wound on the reel, of which the surface in contact with the fibre presents a sinuous trend, for instance complementary to that given by pads 5c to the external surface of reel 1, or presents a desired roughness spectrum. The reel with the wound fibre can be used to make measurements both in open air and with the fibre immersed in a liquid, e.g. water, at ambient temperature or at different temperatures, or yet to make measurements inside furnaces, autoclaves, etc. Obviously these types of tests will require the use of convenient materials for rods 2. If the fibre is wound on the reel while members 4 are slightly inflated, deflation thereof makes it possible to transfer the fibre as a skein to a convenient container. In this case the diameter of discs 3 should not exceed the diameter of the reel under rest conditions. It is clear that what described has been given only by way of non limiting example and that variations and modifications are possible without going out of the scope of the invention as defined in the following claims. More particularly, even though reference was mainly made to optical fibres, the invention can be used to make tests on wires of whatever material, wherein behaviour under controlled tensile stress condition is to be investigated.

Claims: An expansible reel for winding filamentary material and for carrying out tests and measurements on same, which comprises a plurality of rigid elongated members (2), parallel to each other and to a central axis of the reel and fastened at the ends to common supports (3) by fastening means (6, 7) allowing radial displacement of said members with respect to such supports (3), characterized by inflatable members (4), which are located between confronting side faces of said elongated members (2), extend substantially over the whole length of said side surfaces and are associated at one end with means (13, 14, 16, 17, 18) for connection to a system supplying gas under pressure to vary their internal pressure in a controlled manner, said rigid elongated members (2) being substantially in contact with each other when no gas under pressure is introduced into the inflatable members (4) and being progressively spaced from each other by said inflatable members (4) because of the introduction of gas inside the latter to submit the material wound on the reel to controlled tensile stresses. A reel as claimed in claim 1, characterized in that said inflatable members (4) are tubular members closed at the ends, the end portions of each of said tubular members being compressed against the side surface of the respective rigid member (2) by a tongue (10) fastened to said side surface. A reel as claimed in claim 1 or 2, characterized in that pads (5, 5a, 5b, 5c) are associated with the outer surface of each rigid member (2), which pads are interchangeable to form a surface with predetermined physical characteristics whereupon the material is wound. A reel as claimed in claim 3, characterized in that said pads (5a) have a smooth and rounded external surface, with width basically equal to that of the rigid member. A reel as claimed in claim 3, characterized in that said pads (5b) have an external surface machined so as to present a predetermined roughness spectrum or covered with a material having a predetermined roughness spectrum. A reel as claimed in claim 3, characterized in that said pads (5c) have an outside surface machined thus as to present successions of recesses and protrusions, with variable bending radius. A reel as claimed in any of claims 1 to 6, characterized in that the means (13, 14, 16, 17, 18) for connection with the compressed gas supply system comprise a screw rivet (13) which is located within the respective inflatable member (4) and engages a seat (12), provided in the end portion of the rigid member and forming an end portion of a duct (16) obtained in said end part of the rigid member, said rivet presenting an axial through hole (14) communicating at one end with the inflatable member (4) and at the other end with said seat (12). A reel as claimed in any of claims 1 to 7, characterized in that an inflatable member (4) is associated with each of the two side faces of alternate rigid members (2). A reel as claimed in claims 7 and 8, characterized in that the seats (12) of the screw rivets (13) associated with each of the inflatable members (4) of a same rigid member form the end portions of corresponding ducts (16) which at the other end communicate with a common duct (17) which extends up to the internal face of the rigid member (2) and is connected with an opening (18) on one of said supports, which opening is connectable to the compressed gas supply system, in parallel with the openings (18) associated with all rigid members (2) equipped with inflatable members (4). A reel as claimed in claim 7, characterized in that each rigid member (2) is associated with an inflatable member (4), and in that said duct (16) communicating with the inside of the inflatable element (4) extends to the internal face of the rigid member (2) and is connected to an opening (18) on one of said supports, which is connectable to the compressed gas supply system, in parallel with the openings (18) associated with all the rigid members (2). A reel as claimed in any of claims 1 to 10, characterized in that the means (6) for fastening the rigid members (2) to the supports (3) pass through slots (7) in each support (3) and present each, in a portion protruding from the support (3), a groove (6a) which can be engaged by an end of an amovable member (21) apt to resiliently connect the end of the rigid member (2) to a central zone of the support. A reel as claimed in any preceding claim, characterized in that said filamentary material is an optical fibre.

Inventors: COCITO, GIUSEPPE
Applicants: SIP SOCIETA ITALIANA PER L'ESERCIZIO DELLE TELECOMUNICAZIONI P.A.
Application year: 1989
Main classification: B65H75
IPC codes: G01N3, G01M11, B65H75