NL2010253C2 - Underground fiber optic cable connection box. - Google Patents

Description

Underground fiber optic cable connection box FIELD OF THE INVENTION

The invention relates to the field of fiber optic communication cables, and more specifically to a housing for storing and protecting fiber optic cable connections/splices. In particular, the invention relates to a housing useable to be placed underground.

BACKGROUND OF THE INVENTION

Fiber optic cables, in particular fiber optic cables designed to be buried in the ground, comprise several components intended to protect the optical fibers in the cable. Such components may include an inner tube surrounding the optical fiber(s), and outer tube surrounding the inner tube, and a bundle of protective glass fibers, between the inner tube and the outer tube for providing tensile strength to the cable. In spite of such and other protective measures, cables can become damaged due to unforeseen circumstances, accidents, or deliberate actions. The damage may cause a break in an optical fiber resulting in loss of communication through the optical fiber, which must be repaired. In case an optical fiber in an underground fiber optic cable is broken at a specific location along its length, the corresponding part of the cable should be dug up from the ground to make a (new) connection at said location. This is usually done above ground in a sheltered environment. After the new optical fiber connection has been made, thereby restoring the communication capability of the optical fiber, the connection should be well protected by accommodating the connection in a housing to protect it against liquids, gases and mechanical interference. Subsequently, the housing is buried in the ground, and the repair of the cable thereby is completed.

In addition to the circumstances mentioned above, also for normal installation purposes, optical fiber connections must be provided at locations where the connection is to be buried in the ground, accommodated in a housing. As an example, a fiber optic cable may be installed in the ground to reach a specific location near or at a private or an office building, where it is buried awaiting a later connection to a fiber optic installation in the building. Here, the end of the buried fiber optic cable may be accommodated in a housing buried in the ground, and in a later stage the housing may be dug up to provide a connection between the cable and the fiber optic installation.

Such housing used for one or more connections of fiber optic cables is known from the prior art. The housing may comprise a wall having openings through which fiber optic cables pass into the interior of the housing. The prior art housing has a complex construction which entails high production costs, but which also leads to a relatively long time needed to store the fiber optic cable connection in the housing and close or seal the housing such that the connection is protected against the adverse influences of liquids and gases found in the ground.

In addition, the construction of the prior art housing leaves the cables protruding from the housing at a high risk in a situation where the housing is dug op again from the ground, e.g. for inspection, maintenance, or making new connections between optical fibers. In practice, digging up the housing, at least the final part of such operation, is done by hand using a shovel. The shovel is inserted into the ground downwardly with an edge of the shovel blade being moved essentially parallel to the plane of the shovel blade into the ground in the direction of the expected, yet still invisible location of the housing. If the shovel blade edge hits a fiber optic cable, an increased resistance to the shovel blade movement will alert the person handling the shovel that the housing may be near. Many times, the shovel blade will bend the fiber optic cable to some extent, but will not break the cable, since the cable has a relatively small diameter, and can be moved in the ground by the transverse force exerted by the shovel blade edge, where the local force is spread out over some length of the cable. However, if the shovel is pushed into the ground with too much energy, the shovel blade edge may cut into the cable to an extent that the optical fiber(s) contained therein break. Then, a new repair is necessary.

If the fiber optic cable has been located in the ground through the shovel blade or in another way, the shovel blade may be inserted into the ground at another nearby location so as to probe for the buried housing. Here, the risk of breaking the cable by the shovel blade edge cutting into the cable increases substantially. In particular when the shovel blade edge follows a path quite near to, and substantially parallel to the housing wall where the fiber optic cables enter the housing, the cable is held in position by the resistance of the ground to a movement of the relatively large housing, so that a possibility of bending the cable by the shovel blade edge is limited. Accordingly, the shovel blade edge being moved with sufficient energy may cut deep into the fiber optic cable, or even through the fiber optic cable, thereby creating a discontinuity in the optical fiber(s) of the fiber optic cable, whereby the optical fiber functionality is lost disadvantageously.

SUMMARY OF THE INVENTION

It would be desirable to a housing which reduces the risk of fiber optic cable damage when the housing is dug op from the ground. It would also be desirable to provide a fiber optic cable connection housing of simple construction which can be manufactured at relatively low cost. It would further be desirable to provide a fiber optic cable connection housing which can be closed or sealed easily and reliably, providing optical feedback to the user that the closing or sealing has been performed completely and sufficiently.

To better address one or more of these concerns, in a first aspect of the invention a housing for fiber optic cables is provided, comprising: a base part having a bottom wall, the bottom wall having a first side and a second side opposite the first side, wherein the base part comprises bushings for allowing fiber optic cables to pass; and a casing part having an interior and an opening configured to be closed by the base part, wherein the first side of the bottom wall of the base part is configured to face the interior of the casing part, wherein the base part further comprises a protecting structure, the protecting structure extending at the second side of the base part, and having a height from the second side of the bottom wall greater than the height of the bushings from the second side of the bottom wall.

With such fiber optic cable housing, buried in the ground, the cables protruding from the bottom wall of the base part have a predetermined length which is protected by the protecting structure against a shovel blade edge or similar tool approaching the housing in a plane substantially parallel to the plane of the bottom wall of the base part. This predetermined cable length is defined by the difference between the height or maximum height of the protecting structure and the height of the bushings from the second side of the bottom wall. Thus, when a transverse force is exerted on the cables, it can only be exerted at least at a distance from the point of exit of the cables from the bushings, and not directly adjacent to this point of exit. Consequently, the cables may yield over some distance before the force would exceed a limit for damaging the cables. This yielding may be sufficient to alert a person exerting the force that the fiber optic cable housing is about to be found, and to cause the person to decrease the force. Accordingly, the cables are protected against such damage.

In an embodiment of the fiber optic cable housing, the protecting structure comprises a sidewall of the base part, the side wall extending from an edge of the bottom wall of the base part. In some embodiments, the side wall extends from the whole edge of the bottom wall of the base part. In other embodiments, the side wall may comprises at least two side wall portions each extending from part of the edge of the bottom wall of the base part. For example, when the bottom wall has a circular circumference, the side wall may be ring shaped, thereby protecting the housing from all sides against a sharp object, like a shovel blade edge, moving substantially parallel to the bottom wall of the base part. A similar protection can be obtained when the side wall is discontinuous, i.e. when the side wall is comprised of spaced side wall portions.

In an embodiment of the fiber optic cable housing, the protecting structure comprises a protecting element extending at the second side of the base part between diametrically opposing sections of the bottom wall of the base part. One or more than one protecting element may be provided. In case of more than one protecting element, the different protecting elements may cross, where they have a part in common. In some of such embodiments, the protecting element has a cross shape when projected on the second side of the base part. If the base part comprises a side wall and a protecting element, the protecting element may extend between diametrically opposing sections of the sidewall of the base part. In some embodiments, the height of the protecting element from the second side of the bottom wall is greater than the height of the side wall.

In an embodiment of the fiber optic cable housing, the protecting element comprises a wall or a bracket. The protecting element may be substantially C-shaped, U-shaped or V-shaped, where the ends of the protecting element are located at the diametrically opposing sections of the bottom wall of the base part. The C-shaped, U-shaped or V-shaped may function to guide an object moving substantially in the plane of the bottom wall of the base part away from the bottom wall due to the particular shape.

In an embodiment of the fiber optic cable housing, the base part and the casing part are securely engageable by rotating the base part and the casing part relative to one another. For this purpose, at least a portion of the casing part engaging the base part and/or at least a portion of the base part engaging the casing part may have a substantially circular cross-section. To facilitate rotating the base part and the casing part relative to each other, in an embodiment of the fiber optic cable housing the casing part further comprises a plurality of gripping elements extending in a direction away from the opening of the casing part. The gripping elements provide a grip for a user on the casing part. If the base part comprises a side wall, the side wall may also comprise a plurality of gripping elements extending at right angles to the bottom wall of the base part, to provide a grip for a user on the base part. Furthermore, if the base part comprises a protecting element, the protecting element may provide a grip for the user while rotating the base part and the casing part relative to each other.

In an embodiment of the fiber optic cable housing, a portion of the casing part adjacent the opening of the casing part has a cylindrical shape, wherein said portion of the casing part has at least one substantially L-shaped groove, wherein the groove has a first part extending from the edge of the opening, and a second part linking up to the first part and extending substantially at right angles to the first part, and wherein the base part has at least one pin configured to be inserted into the first part of the groove, and to be moved into the second part of the groove by rotating the base part and the casing part relative to one another. The combination of the groove, which may be through the casing part wall from the inside to the outside, and the pin serve to provide a bayonet type mechanism for engaging the base part and the casing part by rotation. With the groove and the pin being visible from the outside of the housing, it can be positively visibly established by a user whether or not the engagement of the base part and the casing part is completed. Upon completion, the pin will be located at a predetermined position in the second part of the groove. The housing may comprise more than one groove/pin combination. In some embodiments, the housing comprises two diametrically opposed groove/pin combinations. The groove/pin combination may be applied also in other housings comprising a base part, and a casing part having an interior and an opening configured to be closed by the base part.

In an embodiment of the fiber optic cable housing, the second part of the groove comprises a movable lip defining a one way passage for the pin, locking the pin in an end position of the pin in the second part of the groove. The lip provides visible proof of (a) the pin being positioned sufficiently far into the second part of the groove, and (b) the pin being locked against inadvertent opening of the housing. Once the pin is locked in the second part of the groove by the lip, the housing can only be opened by deliberately using a tool to push the lip aside, thereby providing a path for the pin of the base part to leave the groove through the second part and the first part of the groove.

In an embodiment of the fiber optic cable housing, the casing part comprises a raised edge part bridging the first part of the groove. Since the first part of the groove interrupts the edge of the casing part, a structural strength of the corresponding portion of the casing part may be restored by the raised edge part. The raised edge part connects the sides of the groove to each other.

In an embodiment, the fiber optic cable housing comprises at least one storage tray for storing fiber optic cable connections, and routing and storing an excess fiber optic cable length. The storage tray is advantageously mounted on the base part at the first side thereof.

In an embodiment of the fiber optic cable housing, the storage tray comprises at least one clamping element for clamping a plurality of protecting fibers included in the fiber optic cable. When stripping the fiber optic cable(s), the protecting fibers between the inner tube and the outer tube of the cable are exposed. The clamping element may comprises a screw having a screw head, and being configured to be screwed into a bush. The protecting fibers may be wound around the screw, and clamped between the screw head and the bush.

These and other aspects of the invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 depicts an exploded view in perspective of components of a housing, including a base part, a casing part, a pushing element and a storage tray in an embodiment of the present invention.

Figure 2 depicts a different view in perspective of the embodiments of the base part and the pushing element of Figure 1.

Figure 3 depicts in a sub-assembly in perspective view of the base part, the pushing element and the storage tray of Figure 1, on an enlarged scale, and two cables secured in bushings of the base part.

Figure 4 depicts the housing of Figure 1 in perspective view, and in assembled form, with fiber optic cables mounted.

Figure 5 depicts the assembled housing of Figure 4 as seen from another perspective. DETAILED DESCRIPTION OF EMBODIMENTS

Figures 1 and 2 depict components of a housing 1 comprising a base part 2, a casing part 4, a sealing ring or O-ring 6, a pushing element 8, pushing element mounting screw 10, sealing sleeves 12, a storage tray 14, a tray mounting screw 16, and clamping screws 18a, 18b.

The base part 2 comprises a circle-shaped bottom wall 20 having a first side 20a and a second side 20b, a cylinder-shaped side wall 22, a protecting element 24 shaped as a wall having a rounded edge facing away from the second side 20b of the bottom wall 20, two bushings 26a, 26b each defining a passage for a fiber optic cable, a bush 28, and two radially outwardly extending pins 29 provided on the outer circumference of the side wall 22. In Figures 1 and 2, only one pin 29 is visible. The pin 29 not visible is located at a diametrically opposed position on the side wall 22. Figure 2 shows a pushing element screw hole 100 and a storage tray screw hole 140 in bush 28. The base part 2 may be molded integrally from a plastic material.

The casing part 4 has an interior and one opening 40 which can be closed by the base part 2, when the casing part 4 is assembled with the base part 2. Before such assembly, the sealing ring 6 may be placed in a substantially cylinder-shaped portion 4a of the casing part 4 against a shoulder 42. After assembly, the sealing ring 6 seals the connection between the base part 2 and the casing part 4. The casing part 4, in particular the portion 4a thereof, is provided with two grooves 44 each having a first groove part 44a and a second groove part 44b. The groove 44 is configured to interact with the pin 29 of the base part 2. The first groove part 44a extends at right angles to an edge of the opening 40, whereas the second groove part 44b extends at a small angle to the edge of the opening 40. The groove 44 extends through the wall of the casing part 4. The width of the groove 44 is slightly greater than a diameter of the pin 29 of the base part. At least one of the grooves 44 comprises a lip 46 extending in the second groove part 44b. The lip 46 is made from a flexible and elastic material, or may be mounted flexibly and elastically in the second groove part 44b. The lip 46 and an opposite side wall of the groove 44 delimit a tapering area, such that the pin 29, moving through the second groove part 44b, pushes the lip 46 aside until the pin 29 passes an end of the lip 46, following which the lip 46 - through its elastic properties - snaps back to its original position, thereby locking the pin 29 in an end position thereof, and preventing the pin 29 to move in an opposite direction. Raised edge portions 48 bridge the first groove parts 44a to support parts of the portion 4a of the casing part 4 next to the second groove parts 44b. On the outer surface, the casing part 4 is provided with gripping elements, in particular ribs, 49 to provide a grip for a user on the casing part 4. The casing part 4 may be molded integrally from a plastic material.

The pushing element 8 comprises a pushing element base 80 having a central hole 82 for the pushing element mounting screw 10 whereby the pushing element 8 can be mounted on the first side 20a of the base part 2 by screwing the pushing element mounting screw 10 in the pushing element screw hole 100. The pushing element 8 further comprises compression bushes 84 configured to be inserted into the passages of the bushings 26a, 26b of the base part 2 to compress the sealing sleeves 12 mounted in the passages of the bushings 26a, 26b, so as to provide a liquid tight and gas tight sealing between an inner wall of each bushing 26a, 26b and a fiber optic cable. The pushing element 8 may be molded integrally from a plastic material.

The storage tray 14 comprises a mounting support 142 supporting a tray part 144. The storage tray may be mounted on the first side 20a of the bottom wall 20 of the base part 2 by screwing the mounting support 142 by the tray mounting screw 16 into the storage tray screw hole 140 of the bottom wall 20 of the base part 2. To keep the storage tray 14 in position when mounted on the bottom wall 20 of the base part 2, the bottom wall 20 is provided with a support rib structure 25 extending around part of the storage tray 14 abutting the bottom wall 20. The tray part 144 comprises a storage space 146 for storing excess length of fiber optic cable, and clamps 148 for clamping splices protecting connections between optical fibers.

The tray part 144 further comprises two bushes 150a, 150b having holes for the clamping screws 18a, 18b. The storage tray 14 may be molded integrally from a plastic material.

As can be understood from Figure 3, protective fibers, i.e. fibers that provide tensile strength, of a fiber optic cable 300a guided through bushing 26a can be wound around the clamping screw 18a and clamped between a head of the clamping screw 18a and the bush 150a. Similarly, protective fibers of a fiber optic cable 300b guided through bushing 26b can be wound around the clamping screw 18b and clamped between a head of the clamping screw 18b and the bush 150b. Such clamping will resist pulling forces exerted on the fiber optic cables 300a, 300b relative to the base part 2. It is noted here that the pushing element 8, when screwed in position, will cause the sealing sleeves 12 to expand and clamp the fiber optic cables in the bushings 26a, 26b, thereby assisting in resisting pulling forces exerted on the fiber optic cables 300a, 300b relative to the base part 2.

It is noted that in the situation of Figure 3, the protecting element 24 may be mounted in a support, such as clamped between the jaws of a bench-vice, when performing operations to connect optical fibers of the fiber optic cables 300a, 300b. Furthermore, the protecting element 24 may be used to handle the base part 2, such as to fix it or rotate it when connecting the base part (in fact: the sub-assembly shown in Figure 3) to the casing part 4.

Figures 4 and 5 illustrate a height of the side wall 22, a height of the bushings 26a, 26b, and a height of the protecting element 24, all from the second side 20b of the bottom wall 20 of the base part 2. As can be seen, the height of the protecting element 24 is greater than the height of the side wall 22, and greater than the height of the bushings 26a, 26b. As can be further seen, the height of the side wall is greater than the height of the bushings 26a, 26b. Accordingly, any object, whether sharp or blunt, moving substantially parallel to the plane of the bottom wall 20 of the base part 2, may come into contact with at least one fiber optic cable 300a, 300b at a distance from the point where the fiber optic cable 300a, 300b emerges from the corresponding bushing 26a, 26b, respectively. This allows the fiber optic cable 300a, 300b to yield (bend) over some distance without becoming directly damaged by the object, which would most likely happen if the height of the bushings 26a, 26b were greater than any of the protecting structures. If the object moves substantially parallel to the plane of the bottom wall 20 of the base part 2, and also not at right angles to the plane of the protecting element 24, it may be deflected by the rounded edge of the protecting element 24.

It is noted that the protecting element 24 is shaped as a wall extending from the second side 20b of the bottom wall 20 of the base part 2. Alternatively, the protecting element 24 could be substantially C-shaped, U-shaped or V-shaped, having ends which are located at diametrically opposing sections of the bottom wall 20 of the base part 2. As an example, a U-shape is indicated in Figure 5 by a dash-dotted line, where there is no material in a region indicated by arrow 24a delimited by the dash-dotted line and the bottom wall 20 of the base part 2.

Figures 4 and 5 further illustrate the pins 29 in their end position in the second groove part 44b, and the locking thereof by the (free end of the) lip 46 against a movement in a direction of arrow 400. The locked position of the pin 29 in the groove 44 is clearly and easily visible on the housing 1, and guarantees a user that the housing 1 is properly closed.

In the embodiment shown in the Figures, the housing 1, in particular its base part 2, comprises two bushings 26a, 26b. In other embodiments, a housing having appropriate dimensions may comprise more than two bushings to allow more than two cables entering/exiting the housing.

As explained above, a housing for fiber optic cables has a casing part and a base part having a bottom wall. The bottom wall has a first side and a second side opposite the first side. The base part comprises bushings for allowing fiberoptic cables to pass. The casing part has an interior and an opening configured to be closed by the base part, wherein the first side of the bottom wall of the base part is configured to face the interior of the casing part.

The base part further comprises a protecting structure extending at the second side of the base part, and having a height from the second side of the bottom wall greater than a height of the bushings from the second side of the bottom wall. The protecting structure may be a sidewall of the base part, or a protecting element extending between diametrically opposing sections of the bottom wall of the base part.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms "a" or "an", as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims (17)

A fiber optic cable housing, comprising: a base part with a bottom wall, the bottom wall having a first side and a second side opposite the first side, the base part comprising cuffs for transmitting fiber optic cables; and a housing part with an interior and an opening configured to be closed by the base part, the first side of the bottom wall of the base part being configured to face the interior of the housing part, the base part further having a protective structure wherein the protective structure extends on the second side of the base member and has a height from the second side of the bottom wall that is greater than a height of the cuffs from the second side of the bottom wall. The fiber optic cable housing of claim 1, wherein the protective structure comprises a side wall of the base member, the side wall extending from an edge of the bottom wall of the base member. The fiber optic cable housing of claim 1 or 2, wherein the protective structure comprises a protective element that extends between diametrically opposed sections of the bottom wall of the base member. The fiber optic cable housing of claim 3, wherein the protective element comprises a wall. The fiber optic cable housing according to claim 3 or 4, wherein the protective element comprises a bracket. Optical fiber cable housing according to claim 3, 4 or 5, wherein the protective element has a cross shape when projected onto the second side of the base part. The fiber optic cable housing according to any of claims 3-6, wherein the height of the protective element is greater than the height of the side wall and greater than the height of the cuffs. The optical fiber cable housing according to claim 7, wherein the protective element is substantially C-shaped, U-shaped or V-shaped. The fiber optic cable housing according to claim 7 or 8, wherein the protective element has a rounded edge. 10. Optical fiber cable housing according to any of claims 3-9, wherein the protective element, viewed when projected onto the second side of the bottom wall of the base part, extends between the cuffs. 11. Optical fiber cable housing according to one or more of the preceding claims, wherein the base part and the housing part can be fixedly coupled to each other by rotating the base part and the housing part relative to each other. 12. Optical fiber cable housing according to one or more of the preceding claims, wherein the housing part further comprises a plurality of gripping elements which extend in a direction away from the opening of the housing part. An optical fiber cable housing according to claim 11 or 12, wherein a portion of the housing portion adjacent the opening of the housing portion has a cylindrical shape, said portion of the housing portion having at least a substantially L-shaped groove, the groove has a first part that extends from the edge of the opening, and a second part that is connected to the first part and extends substantially perpendicular to the first part, and wherein the base part has at least one pin that is configured to be introduced into the first portion of the groove, and moved into the second portion of the groove by rotating the base member and the housing member relative to each other. The fiber optic cable housing of claim 13, wherein the second part of the groove comprises a movable lip that defines a one-way passage for the pin, and locks the pin in an end position of the pin in the second part of the groove. Optical fiber cable housing according to claim 13 or 14, wherein the housing part comprises a raised edge part that bridges the first part of the groove. Optical fiber cable housing according to one or more of the preceding claims, comprising at least one storage bin for storing optical fiber cable connections, and routing and storing an excessive optical fiber cable length. The fiber optic cable housing according to claim 16, wherein the storage bin comprises at least one clamping element for clamping a plurality of protective fibers forming part of the fiber optic cable.