Abstract:
An optical fiber connector plug protecting cap is configured to be mounted to an optical fiber connector plug having a ferrule with an insertion hole into which an optical fiber is inserted and a holding member for holding the ferrule. The optical fiber connector plug protecting cap has a tubular cap member made of a resin material and configured to be fitted to a tip opening of the holding member to cover a tip portion of the ferrule in a non-contacting state, and a strap member having first and second end portions and comprised of an elastic body having a relatively greater flexibility than the cap member. The cap member has a connecting part having a locking hole for locking the first end portion of the strap member. The first end portion of the strap member has an engagement protrusion for engagement with the locking hole in a state in which the first end portion extends through the locking hole. The engagement protrusions of the strap member has a deformable portion configured to be deformed so that the engagement protrusions is locked to an edge portion of the connecting part of the cap member near the locking hole.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical fiber connector plug protecting cap (hereafter, referred to as protecting cap) for protecting a ferrule end face of an optical fiber connector plug. 
     2. Description of the Related Art 
     Hitherto, in case where an optical fiber is fixed to a ferrule attached to an optical fiber connector plug, the optical fiber is bonded/fixed to the optical fiber connector plug by pouring a thermosetting adhesive into the optical fiber connector plug, then inserting the optical fiber whose coating has been peeled over a certain length, and heating/hardening the adhesive by a heater. After the optical fiber has been bonded/fixed, the optical fiber connector plug is used by smoothly polishing a ferrule end face and an optical fiber end face to mirror finish. If the polished faces, of the ferrule and the optical fiber, having been subjected to the polish finish are injured, when the ferrules are oppositely connected each other, an opposed position accuracy is deteriorated, so that a loss becomes large. Therefore, for the purpose of protecting the ferrule end face and the optical fiber end face after the polish finish, there has been known a protecting cap fitting to a tip portion of the optical fiber connector plug and formed by rubber, plastic and the like. 
     As such a protecting cap, there has been proposed a cap  100  with a strap for an FC type optical fiber connector as shown in FIG.  7 A and FIG.  78 . Incidentally, FIG. 7A is a sectional view of the cap with a strap according to the prior art, and FIG. 7B a plan view of the same. 
     In the cap  100  with a strap, a cap portion  101  and a strap portion  102  are integrally molded. The cap portion  101  has an engagement hole  103  engaging with an outer periphery of a plug housing of the FC type optical fiber connector (not shown). The engagement hole  103  has a shape in which its diameter gradually decreases toward a tip of the cap portion  101 . The cap portion  101  is mounted so as to cover the ferrule protruding from a tip of the plug housing. Further, in the strap portion  102  molded integrally with the cap portion  101 , at its tip portion in a side opposite to the cap portion  101  there is provided a passage hole  104  for the purpose of being mounted to an optical fiber cord of the FC type optical fiber connector, so that it is adapted such that the cap portion  101  itself is not disconnected from the optical fiber cord. As a material for the cap  100  with a strap, polyvinyl chloride and rubber have been used. 
     However, with the conventional protecting cap, since the cap portion and the strap portion are integrally molded, the cap portion where a comparatively high hardness is demanded and the strap portion where a flexibility in some extent is demanded become the same material, so that there has been a problem that characteristics of any one of the cap portion and the strap portion are sacrificed. 
     Further, since the conventional cap with a strap is integrally molded in a state having the strap, there is a problem that the number of products obtained in a mold cannot be increased. 
     SUMMARY OF THE INVENTION 
     In view of the forgoing drawbacks in the conventional art, according to the invention, there is provided an optical fiber connector plug protecting cap whose manufacturing time can be remarkably shortened, whose manufacturing cost can be reduced, and in which an optimum material can be selected for both of the cap portion and the strap portion. 
     A 1st mode of the invention solving the problem in the conventional art is an optical fiber connector plug protecting cap adapted to be mounted to an optical fiber connector plug comprising an ferrule to which an optical fiber is insertion-mounted and a holding member for holding the ferrule. The optical fiber connector plug comprises a resin-made cap member fitted to a tip opening of the holding member and covering a tip portion of the ferrule in a non-contacting state, and a strap member consisting of an elastic body relatively having more flexibility than the cap member. The cap member is provided with a lock hole for locking one end portion of the strap member in an insertion state. The one end portion of the strap member is provided with an engagement protrusion engaging with the lock hole in a state that the one end portion has been passed through the lock hole to thereby make it engageable, and that an end portion side from the engagement protrusion of the strap member becomes a pinching portion capable of being pinched in order that the engagement protrusion is locked to an outer edge portion of the lock hole. 
     A 2nd mode of the invention is an optical fiber connector plug protecting cap characterized in that, in the 1st mode, the other end portion of the strap member is provided with a passage hole for passing the optical fiber coated. 
     A 3rd mode of the invention is an optical fiber connector pug protecting cap characterized in that, in the 1st or 2nd mode, at a side opposite to the end portion side of the engagement protrusion of the strap member there is provided an abutting portion which abuts against the outer edge portion of the lock hole. 
     A 4th mode of the invention is an optical fiber connector plug protecting cap characterized in that, in any of the 1st-3rd modes, the lock hole is provided in an end portion of the cap member at a side opposite to an insertion side of the ferrule. 
     A 5th mode of the invention is an optical fiber connector plug protecting cap characterized in that, in the 4th mode, the lock hole is formed in a protrusion portion whose cross-section is smaller than that of the cap member. 
     A 6th mode of the invention is an optical fiber connector plug protecting cap characterized in that, in any of the 1st-5th modes, at least one surface of the pinching portion is provided with a slip prevention portion. 
     A 7th mode of the invention is an optical fiber connector plug protecting cap characterized in that, in any of the 1st-6th modes, a thin-walled portion is provided between the pinching portion and the engagement protrusion. 
     An 8th mode of the invention is an optical fiber connector plug protecting cap characterized in that, in any of the 1st-7th modes, the strap member consists of elastomer or rubber. 
     A 9th mode of the invention is an optical fiber connector plug protecting cap characterized in that, in any of the 1st-8th modes, the optical fiber connector plug is any of an FC type, an SC type, an LC type and an MU type. 
     In the invention, since the protecting cap is divided into the cap member and the strap member, an optimum material can be used for each of the cap member and the strap member. Further, it can be use only as the cap member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a partial sectional view of an optical fiber connector plug to which a protecting cap according to an embodiment 1 of the invention is mounted; 
     FIG. 1B is a main portion enlarged view of the same; 
     FIG. 2A is a side view of the protecting cap according to the embodiment 1 of the invention; 
     FIG. 2B is a plan view of the same; 
     FIG. 3A is a plan view of a cap member according to the embodiment 1 of the invention; 
     FIG. 3B is a sectional view of the same; 
     FIG. 4A is a side view of a strap member according to the embodiment 1 of the invention; 
     FIG. 4B is a plan view of the same; 
     FIG. 5A is a main portion enlarged side view of the strap member according to the embodiment  1  of the invention; 
     FIG. 5B is a main portion enlarged plan view of the same; 
     FIG. 5C is another main portion enlarged plan view of the same; 
     FIG. 6A is a main portion enlarged side view of the strap member according to other embodiment of the invention; 
     FIG. 6B is a main portion enlarged plan view of the same; 
     FIG. 7A is a sectional view of a cap with strap according to the prior art; and 
     FIG. 7B is a plan view of the same. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereunder, the invention is described on the in detail on the basis of embodiments. 
     First, a structure of an optical fiber connector plug to which a protecting cap of their invention is mounted is described. Incidentally, FIG. 1A is a partial sectional view of an optical fiber connector plug to which the protecting cap of the invention is mounted, and FIG. 1B a main portion enlarged view of the same. 
     (Embodiment 1) 
     As shown in FIG. 1A, an optical fiber connector plug is an SC type optical fiber connector plug  10 . The SC type optical fiber connector plug  10  comprises an SC type plug housing  20  fitted to an SC type optical connector adapter (not shown), and an Sc type plug frame  30  fitted into the SC type plug housing  20 . As further described below in detail, a protecting cap  40  of the invention is fitted to a tip opening of the SC type optical fiber connector plug  10 . 
     As shown in FIG. 1B, within the SC type plug frame  30  there are held a ferrule  33  consisting of a collar member  32  and a ferrule cylindrical body  31  for holding an optical fiber, and a compression spring  34  held on an outer periphery of a rear end portion of the collar member  32 . 
     Such an SC type plug frame assembly is assembled by inserting in order the ferrule  33  in which the optical fiber is held in the SC type plug frame  30 , and the compression spring  34 . And, after the assembly, the SC type plug frame  30  has a ferrule insertion hole  35  penetrating through in a longitudinal direction. The ferrule  33  protrudes in the ferrule insertion hole  35 . Additionally, the SC type optical fiber connector plug  10  is obtained by inserting this SC type plug frame assembly into the SC type plug housing  20 . 
     The protecting cap  40  is fitted into the ferrule insertion hole  35  of the SC type optical fiber connector plug  10 , thereby protecting a tip of the ferrule  33  is a non-contacting state. 
     Hereunder, the protecting cap  40  fitted to the SC type optical fiber connector plug  10  is described in detail. Incidentally, FIG. 2A is a side view of the protecting cap according to this embodiment, and FIG. 2B a plan view of the same. Further, FIG. 3A is a plan view of the cap member according to this embodiment, and FIG. 3B is a sectional view of the same. FIG. 4A is a side view of a strap member according to this embodiment, and FIG. 4B a plan view of the same. 
     As shown in FIG.  2 A and FIG. 2B, the protecting cap  40  of this embodiment is composed of a resin-made cap member  41  fitted to the ferrule insertion hole  35  of the SC type plug frame  30  and covering the ferrule  33  in the non-contacting state, and of a strap member  42  which consists of an elastic body relatively having more flexibility than the cap member  41  and which is locked to the cap member  41  in a state that its tip is protruded by a predetermined amount. 
     As shown in FIG.  3 A and FIG. 3B, the cap member  41  is provided with an engagement hole  43  covering, in the non-contacting state, the ferrule  33  which has an outer diameter fitting into the ferrule insertion hole  35  that is a tip opening of the SC type optical fiber connector plug  10  and which, in a state that it is fitted in the ferrule insertion hole  35 , protrudes into the ferrule insertion hole  35 . 
     The engagement hole  43  has an inner diameter larger than the outer diameter of the ferrule  33  in order that, in a state that the cap member  41  is fitted into the ferrule insertion hole  35 , it is held in a state non-contacting with the ferrule  33 , and it has a sufficient depth. 
     Further, an outer peripheral face of the cap member  41  becomes a taper portion  44  for fitting the cap member  41  into the ferrule insertion hole  35  at a constant position. 
     The taper portion  44  is provided on an outer peripheral face of the cap member  41  contacting with an opening edge portion of the ferrule insertion hole  35  such that its outer diameter gradually increases toward a direction opposite to a side, of the cap member  41 , at which the ferrule  33  is inserted. 
     In this manner, since the cap member  41  is fitted inside the ferrule insertion hole  35  in a state not contacting with the ferrule  33 , the ferrule  33  can be surely protected. 
     Further, the cap member  41  has, at its side opposite to a side at which it is fitted inside the ferrule insertion hole  35 , a convex portion  45  whose cross-section is smaller than that of the cap member  41 . 
     The convex portion  45  is provided with a lock hole  46  penetrating in a direction approximately perpendicular to a direction along which the ferrule  33  engages inside the engagement hole  43  of the cap member  41 . The lock hole  46  has an approximately rectangular sectional shape through which a tip portion of a strap member  42  can be inserted. Further, as described in detail below, the lock hole  46  is designed to lock the strap member  42 . 
     Further, an end portion at an engagement hole  43  side of the cap member  41  is beveled at a predetermined angle. By this construction, the cap member  41  can be easily fitted into the ferrule insertion hole  35 . Of construction, it is understood, however, that the beveling of the end portion of the cap member  41  can be omitted if desired. 
     As to a material used for the cap member  41 , it is not limited especially so long as it is a thermoplastic or thermosetting resin material capable of being manufactured by injection molding. For example polyamide or polypropylene can be used as the material for the cap member  4 . 
     Further, as shown in FIG.  4 A and FIG. 4B, the strap member  42  locked to the cap member  41  is a long, band-shaped member having a predetermined thickness, an insertion portion  47  capable of being inserted through the lock hole  46  at its tip portion side, and a passage portion  48  for passing the optical fiber cord at its base end portion side. 
     As shown in FIG.  5 A and FIG. 5B, the insertion portion  47  is provided with an engagement protrusion  49  protruding in a thickness direction of the strap member  42 . Incidentally, FIG. 5A is a main portion enlarged side view of the strap member according to this embodiment, and FIG. 5B a main portion enlarged plan view of the same. 
     The engagement protrusion  49  is provided at a predetermined position from a tip of the insertion portion  47 , and has a slant portion  50  having a slant face whose thickness gradually increases from the tip portion of the strap member  42  toward the base end portion side and which has a predetermined angle, and a vertical portion  51  having a face approximately perpendicular to a thickness direction of the insertion portion  47 . The engagement protrusion  49  has a shape adapted for insertion into the lock hole  46  of the cap member  41 . The vertical portion  51  of the engagement protrusion  49  abuts against an outer edge portion of the lock hole  46  in an inserted state so that the insertion portion  47  cannot be disengaged easily from the lock hole  46  of the cap member  41 . 
     Further, a tip portion side of the insertion portion  47  from the engagement protrusion  49  becomes a pinching portion  52 . The pinching portion  52  is one for pulling the insertion portion  47  by pinching its tip when the insertion portion  47  is inserted through the lock hole  46  and the engagement protrusion  49  is passed through the engagement hole  46 . That is, by pulling the pinching portion  52  in a direction along which the insertion portion  47  comes out from the lock hole  46 , the engagement protrusion  49  can be easily passed through the engagement hole  46 . 
     Additionally, at a base end portion side from the engagement protrusion  49  of the insertion portion  47 , there is provided an abutment portion  53  having an abutting face  54  mutually opposing to the vertical portion  51  of the engagement protrusion  49  with a predetermined spacing. The abutment portion  53  abuts against an outer end portion of the lock hole  46  by passing the insertion portion  47  through the lock hole  46  and pulling the pinching portion  52 , thereby regulating an excessive insertion of the strap member  42 . By this construction, after the engagement protrusion  49  has been passed by pulling the pinching portion  52 , the abutting face  54  abuts against the outer end portion of the lock hole  46 , so that the tip of the strap member  42  is prevented from being excessively pulled out from the lock hole  46 . 
     In this manner, by providing the engagement protrusion  49  and the portion  53 , it becomes possible to simply pass the insertion portion  47  through the lock hole  46 , and the insertion portion  47  can be comparatively easily locked to the lock hole  46 . 
     On the other hand, as shown in FIG. 5C, the passage portion  48  at the base end portion side of the strap member  42  has a shape protruding to both sides in a width direction. The passage portion  48  has a passage hole  55  penetrating in a thickness direction of the strap member  42 . The passage hole  55  is an elongated hole extending along a longitudinal direction of the strap member  42 . 
     After the optical fiber cord has been passed through the passage hole  55 , the insertion portion  47  at a side opposite to the passage portion  48  is locked to the cap member  41 . By this, even if the cap member  41  fitted to the ferrule insertion hole  35  is separated, the cap member  41  can be prevented from being lost because the optical fiber cord has been passed through the passage hole  55 . 
     The material selected for the strap member,  42  it is not limited so long as it is a material which is comparatively flexible in comparison with the cap member  41  and which is capable of being injection-molded for example rubber and a thermoplastic elastomer can be used for the strap member  42 . Preferably, polyurethane, amide-based elastometers and the like are used because they have excellent in flexibility. 
     (Other Embodiments) 
     In the above, the embodiment 1 of the invention has been described, but the protecting cap is not limited to one mentioned above. 
     In the embodiment 1 mentioned above, the engagement protrusion  49  is provided so as to protrude in the thickness direction of the insertion portion  47 , but it is not limited to this especially, and it may be provided so as to protrude to both sides in a width direction of the insertion portion  47 . Further, also the butting portion  53  may be provided so as to similarly protrude to both sides in the width direction of the insertion portion  47 . 
     Further, as shown in FIG.  6 A and FIG. 6B, the pinching portion  52  passed through the engagement hole  46  by pulling the tip of the insertion portion  47  may be provided with a slip prevention portion  56  on at least one surface of the pinching portion  52 . Incidentally, FIG. 6A is a main portion enlarged side view of the strap member according to this other embodiment, and FIG. 6B a main portion enlarged plan view of the same. 
     The slip prevention portion  56  is formed by being made into a concave/convex form such as a striped pattern simultaneously with when the strap member  42  is formed by the injection molding. Incidentally, the slip prevention portion  56  may be formed by a blast working for instance after the strap member  42  has been injection-molded. In this manner, by providing the slip prevention portion  56  in the pinching portion  52 , a slip occurring when passing the insertion portion  47  provided with the engagement protrusion  49  through the lock hole  46  of the cap member  41  can be prevented. 
     Additionally, in order to cut out the pinching portion  52  protruding from the cap member  41  after the strap member  42  has been locked to the lock hole  46 , a thin-walled portion where a thickness of the strap member  42  has been reduced be provided between the pinching portion  52  and the engagement protrusion  49 . In this manner, by providing the thin-walled portion  57  in the chipping portion  52 , the excess chipping portion  52  can be easily cut out, so that a beautiful spectacle can be improved. Of course, it is needless to say that, even in case where there is no thin-walled portion  57 , the strap member  42  may be used with the chipping portion  52  being cut. 
     Additionally, in the embodiment 1 mentioned above there has been exemplified and described the SC type optical fiber connector plug  10  as the optical fiber connector plug to which the protecting cap  40  is mounted, but it is not limited to this especially. The protecting cap  40  of the invention may be mounted to such an optical fiber connector plug as FC type, LC type and MU type for instance. Incidentally, the LC type optical fiber connector plug is a type in which the ferrule is directly mounted to the plug housing without using the plug frame. Therefore, in this case, the protecting cap can protect the end face of the ferrule by the fact that it fits to a tip opening portion of the plug housing. 
     According to the invention, since the protecting cap is divided into the cap member and the strap member, an optimum material can be selected in compliance with a used mode of each of them. That is, since the cap member protects the end face of the ferrule in the non-contacting state, a comparatively hard material can be selected for it. Further, since the strap member is elastically deformed, a comparatively flexible material allowing an elastic deformation can be selected for it. Additionally, since each of them can be formed by the injection molding, a manufacturing time can be shortened and a manufacturing cost can be reduced. Of course, as to the protecting cap of the invention, it is possible to use only the cap member in compliance with a use.