HK1015465B - Sleeve for optical connector ferrules and method for production thereof - Google Patents

Description

Sleeve for optical connector ferrule and method for manufacturing the same

Technical Field

The present invention relates to a ferrule for holding, aligning and retaining two opposing ferrules used in an optical connector for connecting optical fibers, and a method of manufacturing the same.

Background

Generally, the connecting member of the optical connector is composed of a plurality of ferrules having a sheath type optical fiber connected thereto, the connection is made by surrounding a base optical fiber (base cable) with a sheath and a hollow cylindrical barrel, and the connecting member of the optical connector is adapted to receive and align the opposed ferrules with each other. In particular, unlike electrical connectors, it is desirable that the optical connector ensure precise correspondence between the relative positions of two optical fibers to be connected. It is therefore necessary to fix an optical fibre coincident with the centre of a ferrule whose outer and inner diameters are each finished to a prescribed size to enable insertion of an optical fibre base string, and then to insert a pair of such ferrules into a sleeve from either end of the sleeve until they are relatively tight and the axes of the two optical fibres are centred. As a method for performing such centering, there are known a so-called adjusting method of performing fine adjustment by means of an adjusting mechanism, and a non-adjusting method of aiming at improving the dimensional accuracy of the sleeve and the sleeve. Currently, the dominant approach is non-regulated.

Most of the sleeves that have been widely used so far are made of a ceramic material such as zirconia. For the same reason, sleeves made of ceramic materials such as zirconia have been widely used.

In, for example, published japanese patent application, KOKAI (early publication) No. (hereinafter referred to as "JP- ｃA-") 6-27,348, there is disclosed ｃA ceramic sleeve formed by providing ｃA tubular body with ridges which project at three positions on at least the inner wall surface of the tubular body and extend from one end to the other end of the length of the tubular body. The ridge has an upper surface in the form of a concave circular arc included in a circle centred on the axis of the tubular body, i.e. with a cross section in the form of a concave arc facing the axis of the tubular body. The ridges and the inner wall surface of the tubular body are connected to each other in a gently curved line. The above-mentioned patent document also discloses a method for manufacturing the sleeve. The method comprises the following steps: a step of manufacturing such a ceramic raw material such as zirconia or alumina into a tubular body having the above-described geometry; a step of calcining the obtained tubular body; and a step of polishing the upper surfaces of the ridges on the inner wall surface of the calcined tubular body. When the sleeve is an open sleeve, the method further comprises inserting a slit into the tubular body after the polishing step and extending through the entire longitudinal length of the tubular body.

The ceramic sleeve constructed in the above manner is generally manufactured by: first, a raw material is preliminarily formed into a cylindrical shape by powder extrusion or injection molding, and then subjected to degreasing and sintering treatments, and machining operations to grind the outer surface of the tubular body and to grind the inner wall surface of the tubular body. Therefore, the manufacturing process includes many steps, which inevitably requires a large cost. Moreover, because the raw material is brittle and rigid, the product can create problems such as flaking and the polished surface finish is completely dominated by the grain size of the crystals. Since the ceramic ferrule is relatively rigid and insufficiently resilient, the ridges projecting from the inner wall surface of the ferrule tend to scratch the outer surface of the ferrule, and the ferrule and the ferrules tend to shift so that the optical fibers are not axially aligned when the ferrule and the ferrule are repeatedly attached and detached. Therefore, ceramic materials are not well suited for use as materials for optical connector sleeves that tend to frequently make and break the sleeve.

Further, since the ceramic sleeve inevitably shrinks when sintered after the primary forming, it must be ground to a prescribed size by various methods. When the respective ridges are formed on the inner wall surface of the tubular body to extend longitudinally, the upper surfaces of the respective ridges are ground in ｃA concave arc shape along the axial direction of the tubular body, as disclosed in the above-mentioned JP-A-6-27,348. When these ridges are formed at three positions on the inner wall surface of the tubular body, in fact, not the arc-shaped faces of the ridges, but the opposite side edges of these faces are easily brought into contact with the outer peripheral surfaces of the two sleeves which have been inserted into the sleeve. Thus, when the ridges of the sleeve are of consistent precise dimensions, the sleeve is intended to hold the two sleeves in place in a condition that maintains the opposing side edges (at a total of six locations) in contact with the outer surfaces of the two sleeves. When the ridges have dimensional errors, the contact occurs only at a part of the above-mentioned points even if such errors are small. Therefore, the following may occur: the ridges will cause an increased contact and fixation offset of the points with respect to the two ferrules opposite each other inserted into the sleeve, and therefore the terminal ends of the two optical fibers connected will inevitably be offset so as not to be axially aligned with each other.

Disclosure of Invention

It is therefore an object of the present invention to provide a sleeve for an optical connector ferrule which can properly tighten, align and hold two opposite optical connector ferrules while preventing the above-mentioned problems such as shifting the axial alignment of two optical fibers to be connected and damaging the sleeve by falling-off chips.

Another object of the present invention is to provide a method for efficiently producing a sleeve for an optical fiber ferrule having a predetermined shape, dimensional accuracy and surface finish in a large quantity by a simple process due to the combination of a technique based on a conventional metal mold casting process or molding process and the excellent quality of an amorphous alloy having a glass transition region, and thus eliminating or significantly reducing the processing steps such as grinding, thereby providing a sleeve for an optical connector ferrule having very excellent durability, strength, impact resistance and elasticity required for the sleeve.

In order to achieve the above object, a first aspect of the present invention provides a ferrule for abutting, aligning and retaining two opposing optical connector ferrules, said ferrule being characterized in that it is made of an amorphous alloy, not a ceramic material or a metallic material as in the past. The sleeve for an optical connector ferrule of the present invention is made of an amorphous alloy having at least one glass transition region, preferably one having a temperature width of 30K or more. The substantially amorphous alloy has a composition represented by the general formula and contains at least 50% by volume of an amorphous phase:

X_aM_bAl_c，

wherein X represents one or two elements of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, and a, b and c represent atomic percentages satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35, respectively.

In order to make the optical connector ferrules and the sleeves for abutting, aligning and holding the terminal ends of the two ferrules easily deformable, a second embodiment of the sleeve of the present invention is characterized in that it is made of an amorphous alloy which is more elastically deformable than the material of the optical connector ferrules, i.e., an amorphous alloy having a Young's modulus lower than that of the ferrules by 3-30GPa, so as not to damage the two ferrules or to force the ferrules to increase deflection during repeated mounting and dismounting of the sleeves onto and from the two ferrules.

In order to provide a sleeve having a geometry suitable for abutting, aligning and holding two opposed sleeves and preventing damage to the respective sleeves, a second aspect of the present invention comprises providing a sleeve characterized by a tubular body having three ridges provided at three locations on an inner wall surface thereof, each of the ridges extending in a longitudinal direction of the tubular body from one end thereof to the other end thereof, each of the ridges having an upper surface with an arcuate cross section curved toward an axial direction of the tubular body.

The ferrule of a preferred embodiment of the present invention is characterized in that the tubular body has a slit extending throughout the entire length thereof in the longitudinal direction thereof, thereby elastically holding both optical connector ferrules and preventing them from being displaced even when the ferrule and the ferrule are repeatedly attached and detached.

Another aspect of the invention includes providing various methods for manufacturing sleeves for use with the optical connector ferrules described above.

One of the methods is characterized in that it comprises the following steps: providing a melting vessel having an upper open end; providing a forced cooling mold, wherein the forced cooling mold is provided with at least one mold cavity and is arranged above the melting container; melting an alloy material capable of generating an amorphous alloy in a melting vessel, the amorphous alloy having an amorphous phase volume ratio of at least 50% and at least one glass transition region, the glass transition region having a temperature width greater than or equal to 30K; forcibly transferring the resulting molten alloy into the forced cooling mold; and rapidly solidifying the molten alloy in the forced cooling mold to impart amorphous characteristics to the alloy, thereby obtaining a cast product made of an alloy containing an amorphous phase, wherein the alloy material has a composition represented by the following general formula:

X_aM_bAl_c，

wherein X represents at least one element selected from the group consisting of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, and a, b and c represent those satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35 in atomic percentage, respectively.

In a preferred embodiment of the method, the melting vessel is provided with a molten metal delivery member adapted to forcibly deliver the molten alloy upward, and the forced cooling mold is provided with at least two cavities having the same shape and runners communicating with the cavities, respectively, the runners being provided on an extension of a delivery line of a molten metal delivery member.

Another method is characterized in that it comprises the following steps: providing a vessel for melting an alloy material capable of producing an amorphous alloy containing an amorphous phase in an amount of at least 50% by volume and having a glass transition region having a temperature breadth of greater than or equal to 30K, said vessel being provided with an aperture and capable of retaining a melt of said alloy material; providing a metal mold provided with a sprue and at least one cavity of desired product shape; connecting the hole formed in the container to a sprue of the metal mold; applying pressure to the melt within the vessel via the orifice of the vessel to introduce a predetermined amount of the melt into the mold cavity, thereby filling the mold cavity with the melt; and solidifying the melt in the mold at a cooling rate of 10K/s or more to obtain an article made of an alloy containing an amorphous phase, wherein the alloy material has a composition represented by the following general formula:

X_aM_bAl_c，

wherein X represents at least one element selected from the group consisting of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, and a, b and c represent those satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35 in atomic percentage, respectively.

A further method of the invention is characterized in that it comprises the following steps: heating an amorphous material to a temperature within the supercooled liquid region, the amorphous material having a glass transition region having a temperature width of greater than or equal to 30K, the amorphous material being made of an alloy represented by the following general formula and containing an amorphous phase at least 50% by volume:

X_aM_bAl_c，

wherein X represents at least one element selected from the group consisting of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, a, b and c represent those satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35 in atomic percentage, respectively; adding the resulting hot amorphous material to a vessel maintained at the same temperature; connecting a metal mold provided with a mold cavity with the container, wherein the mold cavity has the shape of the required product; and introducing a predetermined amount of said alloy under pressure into said die by means of the viscous flow of said sub-cooled liquid to form a sleeve.

Other objects, features and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 is a top view of a first embodiment of the sleeve of the present invention;

FIG. 2 is a perspective view of the sleeve shown in FIG. 1;

FIG. 3 is a partial cross-sectional view of one embodiment of the sleeve of the present invention;

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a partial cross-sectional view of another alternative embodiment of the sleeve of the present invention;

FIG. 6 is a fragmentary cross-sectional view schematically illustrating one embodiment of an apparatus to be used in making the sleeve of the present invention;

FIG. 7 is a perspective view of a cast article made by the apparatus shown in FIG. 6; and

fig. 8 is a fragmentary sectional view schematically illustrating another embodiment of an apparatus for use in making the sleeve of the present invention.

Detailed Description

According to one aspect of the invention, the sleeve is made of an amorphous alloy that can abut, align and hold two opposing optical connector ferrules. The amorphous alloy exhibits lower hardness and higher elasticity than ceramic materials, exhibits higher tensile strength and higher flexural strength, and is superior to ceramic materials in terms of durability, impact resistance, surface finish, and the like, and therefore constitutes an optimum material for the sleeve itself, which can tightly abut against two opposing optical connector ferrules while they are aligned without axial displacement and can hold them absolutely reliably. The sleeve, which has been made of an amorphous alloy having those characteristics described above, is such that: the ridges having a semicircular cross section are formed on the inner wall surface of the sleeve, so that the outer surface of each sleeve is not easily damaged, or the gap is not easily increased after the sleeves are repeatedly coupled to or detached from the sleeve, thereby enabling stable coupling between the respective opposite sleeves.

Further, the amorphous alloy has high precision casting ability and workability, and therefore, a sleeve having a smooth surface that can faithfully reproduce the contour of a mold cavity can be manufactured by means of a metal mold casting method or a molding method. For ceramic sleeves, after sintering, the sleeve made of ceramic material must be ground to a predetermined size by all means, since once sintered after primary shaping, the sleeve shrinks as described above. In sharp contrast, a sleeve made of an amorphous alloy can omit the step of adjusting the size or adjusting the surface roughness, or can omit such a lengthy step that: since the sleeve does not require a sintering step, the resultant sleeve can be prevented from shrinking due to sintering. Therefore, a sleeve having a prescribed size, satisfying dimensional accuracy and surface quality can be manufactured by a simple process having mass productivity.

The material used for the sleeve of the present invention is not limited to a particular material, but may be any material that can produce an article formed substantially of an amorphous alloy. Among other materials consistent with this description, amorphous alloys of Zr-TM-Al and Hf-TM-Al (TM: Transition metal) having a large temperature difference between the glass Transition temperature (Tg) and the crystallization temperature (Tx) exhibit high strength and high corrosion resistance, and have a wide supercooled liquid range (glass Transition range) of not less than 30K, Δ ═ Tx-Tg, and in the case of using the Zr-TM-Al amorphous alloy, have an extremely wide supercooled liquid range of not less than 60K. In the above temperature range, these amorphous alloys have very good workability because they exhibit viscous flow even at a low pressure of not more than several tens MPa. As indicated by the fact that: they can be made to provide an amorphous bulk material by means of a casting method, using a cooling rate of the order of a few tens of K/s, and are therefore characterized by being simple and very stable to manufacture. The aforementioned amorphous alloys of Zr-TM-Al and Hf-TM-Al are disclosed in U.S. Pat. No.5,032,196 issued to Masumoto et Al, 7, 16, 1991, the contents of which are incorporated herein by reference. After further investigation on the use of these alloys, the present inventors ascertained that: by casting with a metal mold starting from a molten state and by molding processing using viscous flow returning to a glass transition range, these alloys can produce amorphous materials and can reproduce the shape and size of the cavity of a metal mold with high fidelity, and, owing to the promotion of the physical properties of the alloys, will be suitable for optical connector ferrules and sleeves for connecting the optical connector ferrules.

The amorphous alloys of Zr-TM-Al and Hf-Tm-Al used in the present invention have a very large range of Δ Tx, although it may vary depending on the composition of the alloy and the method of determination. For example, Zr₆₀Al₁₅Co_2.5Ni₇₅Cu₁₅The alloys (Tg: 652K, Tx: 768K) have an extremely wide range of Δ X up to 116K. It also provides very good oxidation resistance and is very difficult to oxidize even when it is heated to a high temperature of Tg in air. From room temperature to around Tg, the Vickers hardness (Hv) of the alloy at each temperature is 460(DPN), the tensile strength is 1,600MPa, and the bending strength can reach 3,000 MPa. The thermal expansion coefficient alpha of the alloy is only 1 multiplied by 10 from the room temperature to the vicinity of Tg^-5As large as the value of/K, the Young's modulus is 91GPa, and the elastic limit in a compressed state exceeds 4-5%. Moreover, the toughness of the alloy is high, so that the pendulum impact value falls between 6 and 7J/cm²Within the range of (1). While this alloy exhibits extremely high strength properties as described above, it has a flow pressure that can be reduced to around 10MPa when the alloy is heated to its glass transition range. Therefore, this alloy is characterized in that: the processing is very convenient, and tiny parts and high-precision parts with complex shapes can be manufactured only by low pressure. Moreover, due to the properties of the so-called glass (amorphous) substance, this alloy is characterized in that: the formed (deformed) article produced has an extremely smooth surface and there is substantially no possibility of forming a step which would occur when a slip band appears on the surface during deformation of the crystalline alloy.

Generally, the amorphous alloy starts to crystallize by heating the amorphous alloy to its glassy state and holding it for a long period of time. In contrast, the aforementioned alloys having a wide range Δ Tx can enjoy a stable amorphous phase and avoid any crystallization for a duration of up to 2 hours when maintained at a suitably selected temperature within the Δ Tx range. Thus, users of these alloys do not have to feel anxious about crystallization during standard molding processes.

The aforementioned alloys can fully exhibit these characteristics during the transition from the molten state to the solid state. Generally, production of amorphous alloys requires rapid cooling. By comparison, bulk materials having a single amorphous phase can be produced from an alloy in the molten state by cooling at a rate of about 10K/s. The solid bulk material so formed also has a very smooth surface. The alloy has transferability, and thus can be faithfully reproduced even when the surface of a metal mold is scratched in the order of micrometers by polishing.

Therefore, when the above-described alloy is used as a sleeve material, the metal mold used to produce a formed product only needs to have a mold surface capable of achieving the surface quality required for the sleeve, because the product thus produced can faithfully reproduce the surface quality of the metal mold. Therefore, in the conventional metal mold casting method, these alloys can allow the step of adjusting the size and surface roughness of the molded article to be omitted.

The aforementioned characteristics of the amorphous alloy having high tensile strength and high bending strength include: it can simultaneously have relatively low hardness, high tensile strength, high bending strength, relatively low Young's modulus, high elastic limit, high impact resistance, fine surface smoothness, and high precision castability or workability, making these alloys suitable for use as materials for sleeves of optical connector ferrules. These alloys can be molded in large quantities even by conventional molding methods.

As mentioned above, of the formula X_aM_bAl_cThe amorphous alloys expressed, even when they contain an element such as Ti, C, B, Ge or Bi in a proportion of not more than 5% by atom, have the same properties as those mentioned aboveThe same features as described above.

The advantages resulting from the use of these alloys in the sleeve will be described in more detail below.

The first advantage is that: high-precision formed products can be produced in large quantities. The inner diameter of the sleeve, which grips an optical connector ferrule directly, or the diameter of a circle passing through the points of contact with the ferrule at the upper ends of its ridges, is required to be as close as possible to the outer diameter of the ferrule. The shaped articles obtained so far by means of injection, degreasing and sintering of a ceramic material do not satisfy the dimensional accuracy and surface quality of the sleeve. Thus, it is customary to produce a molded article of a size that can be worked and then finish it by means of a complicated polishing process that includes: performing metal wire polishing (wire 1 lapping) by using diamond grinding slurry to perform grinding finish on the inner diameter; and grinding and finishing the outer diameter. In the present invention, in the casting process as well as in the viscous flow forming (glass forming) process, a formed product can be produced in large quantities using a suitably prepared metal mold without the need for finish polishing or additional, simple finishing treatment. The method of the present invention can efficiently produce sleeves having satisfactory through-hole roughness and through-hole inner surface roundness. Thus, most of the lengthy manufacturing process using a ceramic material can be eliminated.

A second advantage includes the mechanical properties of the sleeve, such as strength and roughness. The sleeve must not be rigid, scratched or split because of the need to frequently and repeatedly attach and detach the optical connector ferrule from the sleeve. The hardness, strength and roughness of the above mentioned alloys are sufficient to eliminate the various defects mentioned above.

According to the present invention, as described above, by using amorphous alloys having a wide glass transition region, such as Zr-TM-Al and Hf-TM-Al amorphous alloys, it is possible to manufacture a sleeve satisfying the dimensional accuracy and surface quality required for a sleeve for an optical connector ferrule with a low cost and high productivity by means of a metal mold casting method or a molding method. Moreover, since the amorphous alloy used in the present invention has excellent strength, roughness and corrosion resistance, the sleeve made of such amorphous alloy has a long service life and is easily free from abrasion, deformation, chipping, or other similar defects.

The amorphous alloy having the above characteristics can be advantageously used for a ferrule, other parts of an optical connector, precision parts of a micro motor, and a sleeve.

In a further embodiment of the invention, the sleeve is made of an amorphous alloy which is more susceptible to elastic deformation than the optical connector sleeve material, i.e. an amorphous alloy having a Young's modulus which is about 3-30GPa, preferably 5-15GPa, lower than that of the sleeve. By selecting such a special material, the sleeve can more easily hold the opposed sleeves stably and center their axes without subjecting the sleeves to damage or increased deflection (backlash), even when the sleeves are repeatedly attached to and detached from the sleeve.

As a material for the sleeve, ceramics or metals may be used. Among other materials, an amorphous alloy, particularly having the general formula X_aM_bAl_cAn amorphous alloy having the composition shown and containing an amorphous phase at a volume ratio of at least 50% has been proved: its mechanical properties, castability and processability are particularly desirable, as described above. By using such an amorphous alloy, the sleeve can be produced in large quantities by a metal mold casting method or a molding method (glass forming) without requiring finish polishing or an additional simple finishing treatment. The use of amorphous alloys can efficiently produce ferrules with satisfactory roundness of the cross-section of the tiny fiber insertion holes and smoothness of the inner surfaces of the holes. PC polishing, which is typically performed on the front end of a ferrule to impart a convex spherical surface to ensure intimate contact of the glass fibers, is no longer necessary. Final polishing after the optical connector is set in placeThus, the method is adopted. Therefore, the lengthy manufacturing process using the metallic material and the ceramic material can be greatly shortened. The same comments apply to the overlap between the ferrule outer diameter and the ferrule outer diameter axis and the ferrule micro-fiber receptacle axis.

In a second aspect of the invention, the sleeve is given a geometry such that: adapted to hold the two opposing cannulae with their axes aligned with each other without causing damage to the cannulae.

Next, the shape of the sleeve of the present invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2 illustrate a preferred embodiment of the sleeve of the present invention; fig. 1 is a plan view of the sleeve, and fig. 2 is a perspective view thereof.

The sleeve 1 comprises a tubular body 2, ridges (elongated protrusions) 3 which are protruded from the inner wall surface of the tubular body 2 at three positions extending longitudinally from one end to the other end of the tubular body, and an elongated slit 4 in the wall surface of the tubular body 2 throughout the entire length thereof in the longitudinal direction.

In order to avoid damage to the sleeves, it is required that each ridge 3 has an arcuate upper surface projecting in the axial direction of the tubular body 2 and may be, for example, substantially semicircular, substantially semi-elliptical, triangular with a rounded upper end, etc. in cross section. It is preferred to assume that the cross-section of each ridge 3 is substantially semicircular in shape, as shown in figure 1. By providing such ridges on the inner wall surface of the tubular body 2 at three locations and extending longitudinally, the sleeve 1 can hold two sleeves therein and clamp the two sleeves at three points of contact with the three ridges of the outer wall surface of the two sleeves. Thus, the ferrule 1 can hold the ferrules in abutment stably with the axes of the ferrules (and the optical fibers connected thereto) aligned with each other without causing damage to the ferrules. As each ridge has a sharp upper end, the ridge has a disadvantage in that, due to the contact points: this will concentrate the load on each upper end and tend to cause damage to the outer surface of the casing. When the ridges are provided on the inner wall surface of the sleeve at four or more positions, the ridges will tend to offset the contact and fixing points of the respective opposing ferrules inserted into the sleeve and tend to spread the axes of the connected optical fibers away.

The ridges are preferably arranged in three places, equally spaced, on the inner wall surface of the tubular body 2, but a slight deviation of said regular spacing is also possible. Although the height of the ridges 3 is merely to enable the ridges 3 to securely hold the two sleeves, it is generally preferred that the height of the ridges be about 0.1-1.0mm (if the cross-section of the ridges is semicircular, the radius is about 0.1-1.0 mm). Although the ridges 3 are preferably continuously raised, they may also extend discontinuously along the entire length of the tubular body, depending on the requirements of the respective application.

As described above, the sleeve 1 has the slit 4 formed in the wall surface thereof longitudinally throughout the entire length thereof. The present invention achieves the above-described effects even if an unfinished precision sleeve has such a slit, because an amorphous alloy such as the above-described material is used, and the effects are brought about by the formation of the above-described ridges. However, the provision of the slits 4 is advantageous in that it enhances the elasticity of the sleeve 1 and enables the sleeve to securely and elastically grip each of the opposed sleeves and to align their axes with each other even if there is a more or less deviation in dimensional accuracy, and also to repeatedly attach and detach both sleeves to and from the sleeve without increasing the offset when the sleeves are in the holding state.

As for the mechanical properties of the material of the sleeve 1 itself, the sleeve 1 preferably has a young's modulus in the range of about 90-99GPa and an elastic limit in the range of about 1% to several%. The sleeve of the present invention is made of an amorphous alloy, a material that is in sharp contrast to conventional ceramic materials such as zirconia, which lacks almost elasticity. The advantage of this sleeve is therefore its elastic properties, which fully allow repeated connection and disconnection of the two sleeves to and from it.

Figures 3 and 4 show one way of using the sleeve 1 of the present invention in an optical connector. The sleeve 1 assumes the use of two sleeves 10 each of which is of one-piece construction, each sleeve including a capillary portion 11 and a flange portion 12.

Specifically, this ferrule 10 is constituted by a capillary portion 11 formed along its axis with a through hole 13 for inserting an optical fiber 17 (or a base string of an optical fiber coated with a plastic film) having a small diameter, and a flange portion 12 formed along its axis with a through hole 14 for inserting a sheath type optical fiber 16 (an optical fiber coated with a sheath 18) having a large diameter. The small-diameter through hole 13 and the large-diameter through hole 14 are connected to each other by a tapered portion 15.

The connection of the optical fiber to the ferrule 10 having such a structure is accomplished by: stripping the front end of the jacketed optical fiber 16 having the jacket 18 to expose the optical fiber 17 for a predetermined length; applying an adhesive to the bare optical fiber and the front end of the jacketed optical fiber; inserting the bare optical fiber 17 into the small-diameter through hole 13 in the ferrule 10 from the flange portion side of the ferrule 10; and the front end portions of the optical fiber 17 and the sheath optical fiber 16 are fixed by the adhesive in the through holes 13 and 14 of the ferrule 10.

The connection of a pair of optical fibres 17, 17 is done by: the ferrules 10, 10 into which the optical fibers have been inserted and connected are passed through both ends of the sleeve 1, respectively, so that the ferrules are inserted into the sleeve 1, and then the ends of the ferrules 10, 10 are abutted against each other. Therefore, the leading end portions of the optical fibers 17, 17 can be brought into contact with each other and connected in a state in which: their axes are mutually aligned.

The circle 5 (fig. 1) passing through the upper ends of the three ridges 3 at the three locations of the sleeve 1 has a diameter slightly smaller than the outer diameter of the capillary portion 11 of the sleeve 10. Therefore, when the ferrules 10, 10 are inserted into the sleeve 1 through both ends of the sleeve 1, respectively, the sleeve 1 is slightly pushed to be opened and finally the capillary portions 11, 11 can be held in an elastically clamped state.

Fig. 5 shows another way of using the sleeve 1 of the invention in Optical connectors (Optical connectors). A ferrule 10a uses a capillary portion 11a and a flange portion 12a as separate members.

Specifically, this ferrule 10a is constituted by the capillary portion 11a and the flange portion 12a, the capillary portion 11a being formed along its axis with a through hole 13a for inserting an optical fiber 17, the diameter of the through hole 13a being a small diameter, the flange portion 12a being formed along its axis with a through hole 14a for inserting a sheath optical fiber 16, the diameter of the through hole 14a being a large diameter. It is assembled by fixing the end of the capillary 11a, which is enclosed in a tapered hole 15a, in the front end hole portion 19 of the flange 12a by means of a tight fit or an adhesive. The small-diameter through hole 13a in the capillary 11a and the large-diameter through hole 14a in the flange 12a are connected by the intermediary of a tapered hole portion 15 a.

The method used to connect the optical fibre to the ferrule 10 and the manner in which the sleeve 1 and the two ferrules 10a, 10a are assembled is the same as that of the embodiment shown in figures 3 and 4.

FIG. 6 schematically illustrates one embodiment of an apparatus and method for manufacturing the sleeve of the present invention by means of a metal mold casting technique.

A forced cooling mold 20 is a split mold composed of an upper mold 21 and a lower mold 26. The upper die 21 has a pair of cavities 22a and 22b formed therein and adapted to define the outside dimensions of a sleeve. Inside these cavities 22a and 22b, there are formed, respectively, cores 25a, 25b for determining the internal dimensions of the sleeve. These mold cavities 22a and 22b are communicated with each other through a runner 23 so that the molten metal can flow into the mold cavities 22a and 22b through the front ends of the circumferential portions 24a and 24b of the runner which are spaced apart by a predetermined distance so as to surround the mold cavities 22a and 22b in half. On the other hand, a sprue (through hole) 27 communicating with the above-mentioned runner 23 is formed at an appropriate position of the lower die 26. Below the sprue 27, a recess 28 is formed in a shape conforming to that of a cylindrical raw material accommodating portion or crucible 32 which itself constitutes an upper portion of the melting vessel 30.

When necessary, the cores 25a, 25b may be integrally formed in the lower mold 26. Although the forced cooling mold 20 may be made of a material such as copper, a copper alloy, cemented carbide, or super heat-resistant stainless steel, it is preferably made of a material such as copper or a copper alloy having a large heat capacity and a large thermal conductivity to increase the cooling rate of the molten alloy injected into the mold cavities 22a and 22 b. The upper die 21 may be provided therein with a flow passage through which a cooling medium such as cooling water or cooling gas can flow.

In an upper portion of a main body 31 of the melting vessel 30, the vessel 30 is provided with a cylindrical raw material accommodating portion 32 and is disposed directly below a sprue 27 of a lower die 26 so as to enable vertical movement of the vessel 30 up and down. In the raw material accommodating hole 33 of the raw material accommodating portion 32, a molten metal conveying member or plunger 34 having a diameter almost the same as that of the raw material accommodating hole 33 is slidably disposed. The molten metal delivery member 34 is vertically movable by a hydraulic (or pneumatic) cylinder plunger 35, not shown. An induction coil 36 as a heat source is provided so as to surround the raw material accommodating portion 32 of the melting vessel 30. As for the heat source, any appropriate method such as heating by means of resistance may be employed in addition to the high-frequency induction heating. The material of the raw material containing portion 32 and the material of the molten metal delivery member 34 are preferably both heat-resistant materials, such as ceramics or metal materials coated with heat-resistant films.

Incidentally, in order to prevent the molten alloy from forming an oxide film, it is preferable to arrange the apparatus entirely in a vacuum, or in an inert gas atmosphere such as argon, so as to establish a flow of inert gas at least between the lower mold 26 and the upper portion of the raw material containing portion 32 of the melting container 30.

The production of the sleeve according to the invention is carried out in such a way that: first, the melting vessel 30 is set in a state of being separated downward from the forced cooling mold 20, and then the empty space above the molten metal delivery member 34, which is located inside the raw material containing portion 32, is filled with the alloy raw material a having a composition capable of generating the above-described amorphous alloy. The alloy raw material a to be used may be in any one of forms such as a rod shape, a pellet shape, and a fine particle shape.

Next, the induction coil 36 is excited to rapidly heat the alloy raw material a. After confirming that the alloy raw material a has been melted by detecting the temperature of the molten metal, the induction coil 36 is demagnetized and the melting vessel 30 is raised until its upper end is inserted into the recess 28 of the lower die 26. The hydraulic cylinder is then actuated to complete the rapid raising of the molten metal delivery member 34 by the plunger 35 and the injection of molten metal through the sprue 27 of the mold 20. The injected molten metal is introduced forward into the mold cavities 22a, 22b through the runners 23, 24a, 24b while being compressed and rapidly solidified therein. In this case, by appropriately setting factors such as the injection temperature, the injection speed, and the like, a cooling rate exceeding 103K/s can be obtained. Then, the melting container 30 is lowered, and the upper mold 21 and the lower mold 26 are separated to take out the product.

In fig. 7, the shape of a cast product produced by the above method is shown. By cutting the runner sections 42a and 42b from the sleeve sections 41a and 41b of a cast product 40 and grinding the cut surfaces of the sleeve sections left after cutting, sleeves 1 can be obtained which have a smooth surface faithfully reproducing the mold cavity surface as shown in fig. 1 and 2.

The above-described high-pressure die casting method can provide a casting pressure of about 100MPa and an injection speed of about several m/s, and has the following advantages.

(1) Filling the mold with molten metal can be accomplished in a matter of milliseconds and such rapid filling can greatly enhance the quenching action.

(2) The high close contact of the molten metal with the mold increases the cooling rate and also enables precise molding of the molten metal.

(3) Such disadvantages as shrinkage cavities which may occur during shrinkage of the cast product due to solidification can be reduced.

(4) The method can manufacture a shaped article with a complex shape.

(5) The method can smoothly cast a high-viscosity molten metal.

Fig. 8 schematically shows another constructional embodiment of the device for manufacturing the sleeve of the invention and another embodiment of the method for manufacturing the sleeve of the invention.

In fig. 8, reference numeral 60 shows a vessel for melting an alloy material which can produce an amorphous alloy as described above and can hold the produced melt therein. Below such a container 60 is provided a split metal mold 50 having a cavity 52a, 52b having the shape of a desired product. The container 60 may be heated by any known heating method (not shown), such as high-frequency induction heating and resistance heating.

The configuration of the metal mold 50 is substantially the same as the mold 20 shown in fig. 6 mentioned above, except that the vertical positional relationship is reversed. Specifically, the upper die 56 is formed in an upper portion of a sprue (through-hole) 57 of a recess 58 for accommodating a lower end portion of the container 60, the upper die 56 corresponding to the lower die 26 shown in fig. 6. Meanwhile, the lower die 51 is the same as the upper die 21 shown in fig. 6 except that the cavities 52a, 52b, the runners 53, 54a, 54b, and the cores 55a, 55b are reversed in shape and arrangement from those shown in fig. 6. Such a metal mold 50 may have cavities 55a, 55b integrally formed with an upper mold 56, as necessary.

The manufacturing process of the sleeve is as follows: connecting a small hole 61 formed in the bottom of the container 60 to the sprue 57 of the metal mold 50; applying pressure to the molten alloy A ' in the vessel 60 by means of an inert gas, thereby pushing the molten alloy A ' from the small hole 61 in the bottom of the vessel 60 through the runners 53, 54a and 54b and onwards into the mould cavities 52a, 52b until they are filled to the maximum with molten alloy A '; the molten alloy is solidified at a cooling rate preferably exceeding 10K/s to obtain a sleeve substantially made of an amorphous alloy.

By the above manufacturing method, a sleeve having a dimensional accuracy L in the range of + -0.0005 to + -0.001 mm and a surface accuracy in the range of 0.2 to 0.4 μm can be manufactured.

The above-described method makes it possible to manufacture two cast products by one step using a metal mold provided with a pair of mold cavities. Of course, three or more cast products may also be manufactured using one metal mold in which three or more cavities are provided.

In addition to the alloy casting methods described above, extrusion molding may also be used to manufacture the sleeve. Since the above-mentioned amorphous alloy has a large supercooled liquid region Δ Tx, by heating such amorphous alloy material to a temperature within the supercooled region; adding said heated material to a vessel maintained at the same temperature; connecting said container to a metal mold of said mold cavity having the shape of the desired article; by pressing a predetermined amount of heated alloy into the die cavity by means of the viscous flow of the supercooled liquid and molding the alloy, a sleeve having a prescribed shape can be obtained.

The invention will now be described in more detail with reference to working examples which clearly demonstrate the efficacy of the invention.

Example 1:

by using the apparatus shown in fig. 6, and employing the following manufacturing conditions: an injection temperature of 1273K, an injection speed of 1m/s, a casting pressure of 1MPa, and a packing time of 100 msec, it was possible to manufacture a sleeve made of an amorphous alloy having Zr₆₀Al₁₀Ni₁₀Cu₁₅Composition, shape as shown in fig. 1 and 2, inner diameter of 2.5mm, outer diameter of 3.1mm, and radius of curvature of ridge of 0.3 mm.

The resulting sleeve is an article having excellent surface smoothness and faithfully reproducing the contour of the metal mold cavity. It has been found that it has a Young's modulus of 80GPa, a flexural strength of 2,970MPa, a Vickers hardness of 400(DPN), and a coefficient of thermal expansion alpha of 0.95X 10^-5/K。

By the same method, a sleeve made of an amorphous alloy having a capillary portion and a flange portion integrally formed as shown in fig. 3 can be manufactured. The sleeve has Zr₆₀Al₁₅Co_2.5Ni₇₅Cu₁₅And its Young's modulus is 91 GPa. When two optical fibers are connected at each end to two ferrules manufactured as described above and the ferrules are mounted in the ferrule through both ends of the ferrule, respectively, the two optical fibers can be stably connected without shifting the axial alignment of the two optical fibers.

Example 2:

including Zr₆₀Al₁₅Co₂₅Ni_7.5Cu₁₅The various alloys listed in the tables below and included herein were made by melting the relevant constituent metals. They were placed in a quartz crucible and completely melted by high-frequency induction heating. The melt was passed through a molten bath at 2Kgf/cm²Was injected into a copper mold having a cylindrical cavity with a diameter of 2mm and a length of 30mm through a fine hole formed in the lower portion of the crucible under a gas pressure of (1) and was maintained at room temperature to obtain a bar-shaped specimen for measuring mechanical properties. The results of this determination are shown in the table below.

Watch (A)

Alloys therefor	Tensile strength (MPa)	Bending strength (MPa)	10-5Kalpha (Room temperature-Tg)	E(GPa)	Hardness Hv	Tg(K)	Tx(K)
								Zr67Cu33Zr65Al7.5Cu27.5Zr65Al7.5Ni10Cu17.5Zr60Al15Co2.5Ni7.5Cu15	1,8801,4501,4801,590	3,5202,7102,7702,970	0.80.80.91.0	99939291	540420430460	603622630652	669732736768

As is clear from the above table, the amorphous alloy material produced exhibits such properties: the flexural strength values were much better than the locally stabilized zirconia (about 1,000MPa) previously used as the sleeve material, with a young's modulus value of about 1/2 and a hardness value of about 1/3, indicating that these alloy materials all have the necessary properties for use as the sleeve material.

Example 3:

a metal mold for a sleeve shown in fig. 6 was connected to a metal extruder, and a sleeve was manufactured by using the same alloy as in example 1. For the extrusion, amorphous blanks prepared beforehand by casting, respectively, of 25mm diameter and 40mm length, made of the same alloy, were used. Each billet is preheated to 730K and the container of the extruder and the entrance portion and the molding portion of the metal mold are also heated to 730K. The hot billet is added to the container of the extruder and then injected into the metal mold. And cooling the metal mold. Then, the formed article is taken out of the mold, and the inlet portion is removed and inspected. It was found that the appearance, dimensional accuracy, surface roughness, and the like of the formed article were almost equal to those of the sleeve obtained in example 1.

Although specific embodiments and working examples have been disclosed above, the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (17)

1. A ferrule for holding, aligning and retaining two opposing optical connector ferrules, wherein said ferrule is formed from a substantially amorphous alloy having an amorphous phase volume fraction of at least 50% and having at least one glass transition region having a temperature breadth of greater than or equal to 30K, wherein said substantially amorphous alloy has a composition represented by the general formula:

X_aM_bAl_c，

wherein X represents at least one element selected from the group consisting of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, and a, b and c represent those satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35 in atomic percentage, respectively.

2. The sleeve of claim 1 wherein the glass transition region has a temperature breadth of greater than or equal to 60K.

3. A sleeve according to claim 1, which is made of an amorphous alloy having a young's modulus lower than that of the sleeve by 3 to 30 Gpa.

4. A sleeve according to any one of claims 1 to 3, comprising a tubular body and three ridges provided on the inner wall surface of the tubular body, respectively, each of said ridges extending in the longitudinal direction of said tubular body from one end thereof to the other end thereof and having an upper surface with an arcuate cross section, said upper surface being curved toward the axial direction of the tubular body.

5. A sleeve as claimed in claim 4, wherein said tubular body has a slit extending longitudinally therethrough for the entire length thereof.

6. A sleeve as claimed in claim 4, wherein each said ridge has a semi-circular cross-section.

7. A sleeve as claimed in claim 4, wherein each said ridge has a semi-elliptical cross-section.

8. A sleeve as claimed in claim 4, wherein each said ridge has a triangular cross-section with a rounded upper end.

9. A sleeve as claimed in claim 4, wherein each said ridge extends continuously or discontinuously over the entire length of said tubular body.

10. A sleeve as claimed in claim 4, wherein each ridge has a height of from 0.1 to 1.0 mm.

11. A method for manufacturing a sleeve for optical connector ferrules according to claim 1, comprising the steps of:

providing a melting vessel having an upper open end;

providing a forced cooling mold, wherein the forced cooling mold is provided with at least one mold cavity and is arranged above the melting container;

melting an alloy material capable of generating an amorphous alloy in a melting vessel, the amorphous alloy having an amorphous phase volume ratio of at least 50% and at least one glass transition region, the glass transition region having a temperature width greater than or equal to 30K;

forcibly transferring the resulting molten alloy into the forced cooling mold; and

rapidly solidifying said molten alloy in said forced cooling mold to impart amorphous characteristics to the alloy and thereby obtain a cast article made of an alloy containing an amorphous phase, wherein said alloy material has a composition represented by the general formula:

X_aM_bAl_c，

wherein X represents at least one element selected from the group consisting of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, and a, b and c represent those satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35 in atomic percentage, respectively.

12. A method according to claim 11, wherein said melting vessel has a molten metal delivery member disposed within said vessel and adapted to forcibly deliver said molten alloy upwardly, and said forced cooling mold is provided with at least two cavities of the same shape and with runners communicating with said cavities, said runners being disposed on an extension of a delivery line of a molten metal delivery member.

13. The method according to claim 12, wherein the molten metal delivery member is caused to forcibly deliver the molten alloy in the melting vessel into the cavities of the forced cooling mold while applying pressure to the molten alloy filled in the cavities of the forced cooling mold.

14. The method of claim 11, wherein the forced cooling mold is a water cooled mold or a gas cooled mold.

15. The method of claim 11, wherein the step of melting the alloy material in the melting vessel is performed in a vacuum or under an inert gas atmosphere.

16. A method for manufacturing a sleeve for optical connector ferrules according to claim 1, comprising the steps of:

providing a vessel for melting an alloy material capable of producing an amorphous alloy containing an amorphous phase in an amount of at least 50% by volume and having a glass transition region having a temperature breadth of greater than or equal to 30K, said vessel being provided with an aperture and capable of retaining a melt of said alloy material;

providing a metal mold provided with a sprue and at least one cavity of desired product shape;

connecting the hole formed in the container to a sprue of the metal mold;

applying pressure to the melt within the vessel via the orifice of the vessel to introduce a predetermined amount of the melt into the mold cavity, thereby filling the mold cavity with the melt; and

solidifying the melt in the mold at a cooling rate of 10K/s or more to obtain an article made of an alloy containing an amorphous phase, wherein the alloy material has a composition represented by the following general formula:

X_aM_bAl_c，

wherein X represents at least one element selected from the group consisting of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, and a, b and c represent those satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35 in atomic percentage, respectively.

17. A method for manufacturing a sleeve for optical connector ferrules according to claim 1, comprising the steps of:

heating an amorphous material to a temperature within the supercooled liquid region, the amorphous material having a glass transition region having a temperature width of greater than or equal to 30K, the amorphous material being made of an alloy represented by the following general formula and containing an amorphous phase at least 50% by volume:

X_aM_bAl_c

wherein X represents at least one element selected from the group consisting of Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni and Cu, a, b and c represent those satisfying 25. ltoreq. a.ltoreq.85, 5. ltoreq. b.ltoreq.70, and 0. ltoreq. c.ltoreq.35 in atomic percentage, respectively;

adding the resulting hot amorphous material to a vessel maintained at the same temperature;

connecting a metal mold provided with a mold cavity with the container, wherein the mold cavity has the shape of the required product; and

introducing a predetermined amount of said alloy under pressure into said die by means of the viscous flow of said sub-cooled liquid to form a sleeve.