Fiber optic cable sheath removal tool

A cutting tool (10) for making precise circumferential and longitudinal cuts in an fiber optic cable (12) includes a rotary-driven cutting wheel (18) that extends partially into the top of a housing (24) having an open bottom. The housing receives a pair of upper and lower cable guides that have opposed longitudinal and transverse channels (36 and 42) and 38 and 44) for retaining the cable in a longitudinal and transverse relationship, respectively with the cutting wheel. A cable lock guide (48) attaches to the bottom of the housing to maintain the guides in a fixed relationship while an adjustment mechanism (52) extends through the guide lock to displace the guides (and the cable retained therebetween) towards the cutting wheel to control the depth of cut. By placing the cable in the longitudinal channels in the guides, the tool can make a longitudinal cut when displaced along the axis of the cable. By placing the cable in the transverse channels in the guides, the tool can make a circumferential cut when rotated about the cable axis.

TECHNICAL FIELD 
This invention relates to a technique for removing the protective layers 
(e.g., the sheath) of a fiber optic cable to facilitate a repair. 
BACKGROUND ART 
Presently, many telecommunications carriers, such as AT&T, use fiber optic 
cables to carry optically formatted telecommunications traffic between 
facilities. A typical fiber optic cable comprises one or more individual 
optical fibers surrounded by a buffer tube that is enclosed by metal 
jacket covered by a plastic sheath. To repair one of more damaged fibers, 
a technician must remove a portion of the plastic sheath, the metal jacket 
and the buffer tube to expose the damaged fiber(s) without causing injury 
to any undamaged fibers. Heretofore, a technician manually exposed the 
damaged fiber(s) using a knife or saw, often a slow and dangerous 
operation. Indeed, technician, despite exercising extreme care, some times 
would slip with the knife or saw, causing injury as well as possibly 
damaging one or more undamaged fibers. 
U.S. Pat. No. 5,457,877, issued in the name of Patrick McDermott, and 
originally assigned to AT&T, discloses an apparatus for cutting through 
the sheath of a fiber optic cable of the type described above to avoid the 
difficulties associated with sheath removal by hand. The McDermott tool 
comprises a rotary-driven cut-off wheel enclosed within a guide box so 
that a portion of the wheel extends beyond the top of the guide box. The 
box has an upwardly extending end wall in spaced-apart parallelism with 
the cut-off wheel. The end wall has a generally "U"-shaped notch in its 
upper edge for seating the cable. By rotating the cable relative to the 
cut-off wheel, an operator can make a circumferential cut into the cable 
sheath. Thereafter, the operator removes the cable from the notch and 
places it in abutment with the end wall to make a cut in the sheath along 
the longitudinal cable axis. 
While the McDermott tool avoids the dangers associated with sheath removal 
by and, the tool does not generally possess the precision needed for 
removing the protective layers of an active fiber optic cable without 
damaging the signal-carrying fibers. Moreover, the McDermott tool does not 
readily accomplish removal of long longitudinal portions of the cable 
sheath. 
Thus, there is a need for a technique for removing the sheath of a fiber 
optic cable or the like which overcomes the aforementioned disadvantages 
of the prior art. 
BRIEF SUMMARY OF THE INVENTION 
Briefly, in accordance with a preferred embodiment, the present invention 
discloses a tool for cutting the protective layers (e.g., the sheath) of a 
fiber optic cable or the like. The tool includes a rotary-driven cutting 
wheel that partially extends into an opening in the top of a housing 
having an open bottom for receiving an upper and lower cable guides mated 
one above the other to circumscribe the cable. The cable guides have 
opposed longitudinal channels that run the length of the guides parallel 
the face of the cutting wheel for retaining the cable to facilitate a 
longitudinal sheath cut by the cutting wheel. The guides also have opposed 
transverse channels running the width of the guides perpendicular to, and, 
and intersecting with, the longitudinal channels, for seating the cable 
perpendicular to the face of the cutting wheel to facilitate a 
circumferential sheath cut. A cable guide lock releasably attaches to 
bottom of the housing to retain the upper and lower cable guides within 
the housing to hold the cable in a fixed relationship with the cutting 
wheel. An adjusting mechanism extends through the cable guide lock to 
displace the upper and lower cable guides, and the cable circumscribed 
thereby, towards the cutting wheel to control the depth of cut of the 
cutting wheel into the cable. 
A technician makes a longitudinal sheath cut by placing the cable in the 
longitudinal channels of the upper and lower cable guides and then placing 
the guides (with the cable circumscribed thereby) into the housing before 
attaching the cable guide lock to the housing. Next, the technician 
manipulates the adjusting member to displace the cable guides, and hence, 
the cable, to establish the depth of cut by the wheel. Lastly, the 
technician displaces the tool relative to the cable along its longitudinal 
axis. To make a circumferential sheath cut, the technician places the 
cable in the transverse channels of the upper and lower cable guides and 
then places the guides (with the cable circumscribed thereby) into the 
housing before attaching the cable guide lock to the housing. Next, the 
technician manipulates the adjusting mechanism to displace the cable 
guides, and hence, the cable, to establish the depth of cut of the wheel. 
Lastly, the technician rotates the tool relative to the cable about its 
circumference. For both longitudinal and circumferential sheath cuts, the 
cable guides maintain the cable in a fixed relationship with the cutting 
wheel, thus assuring a precision cut.

DETAILED DESCRIPTION 
FIGS. 1-4 depict an improved tool 10 in accordance with the invention for 
making both circumferential and longitudinal cuts in a cable 12 (see FIGS. 
3 and 4) to facilitate removal of one or more protective layers (e.g., the 
sheath) of the cable. For purposes of discussion, a circumferential cut is 
a cut made in to the cable about its circumference at a substantially 
constant radius. A longitudinal sheath cut is a cut made into the cable 
along its longitudinal axis. 
The tool 10 comprises a motor 14 powered by a rechargeable energy source 
17, such as a rechargeable battery pack. As best seen in FIG. 1, the motor 
14 drives a shaft 16 that carries a cutting wheel 18 attached to the motor 
shaft by a threaded fastener 20. The cutting wheel 18 generally comprises 
a carbide disc, as shown, or a saw blade (not shown), capable of cutting 
through the protective layers (e.g., the sheath) of the cable 12 of FIGS. 
3 and 4. 
Still referring to FIG. 1, the motor 14 mounts a flange 21 having an 
opening 22 through which the motor shaft 16 extends. The flange 21 is 
integral with, and extends upwardly from one of the opposed sides 23a and 
23b of a housing 24 having opposed ends 25a and 25b. The housing 24 has an 
open bottom and an open top, the later enclosed by a removable cover 26. 
The housing sides 23a and 23b have opposed openings 27a and 27b, 
respectively, aligned parallel to the shaft 16. The openings 27a and 27b 
are sized large enough to receive the cable 12 (see FIGS. 3 and 4) to 
permit the cutting wheel 18 to make a circumferential cut in the cable as 
described hereinafter with respect to FIG. 3. 
The ends 25a and 25b of the housing 24 have opposed openings 28a and 28b, 
respectively, in aligned registration with each other perpendicular to the 
axis of the shaft 16. The end openings 28a and 28b each have a generally 
horizontal top and two parallel sides, the sides terminating with the open 
bottom of the housing 24 for receiving an upper cable guide 30. The upper 
cable guide 30 is generally parallelepiped in shape and has a slot 35 in 
its top for receiving the lower portion of the cutting wheel 18 when the 
cable guide is received in the bottom of the housing 24 as seen in FIG. 2. 
As seen in FIG. 1, a generally half-rounded longitudinal channel 36 runs 
the length of the bottom of the upper cable guide 30. A half-rounded 
transverse channel 38 runs the width of the bottom of the upper guide 
cable 30 perpendicular to, and intersecting with, the channel 36. The 
upper cable guide 30 mates with the top of a complementary lower cable 
guide 40 having longitudinal and transverse channels 42 and 44. The 
channels 42 and 44 run along the length and width, respectively, of the 
top of the lower cable guide 40 in aligned registration with the channels 
36 and 38, respectively, in the upper cable guide 30. In this way, the 
upper and lower cable guides 30 and 40 circumscribe the cable 12 when the 
cable is seated in the longitudinal cable guide channels 36 and 42 or when 
the cable is seated in the transverse cable guide channels 38 and 44. 
To assure a precise sheath cut, the longitudinal channels 36 and 42 and the 
transverse channels 38 and 44 are sized for a particular diameter cable 
12. Thus, different size cables, require separate pairs of upper and lower 
cable guides 30 and 40, with the appropriately sized longitudinal and 
transverse channels 36 and 42, and 38 and 44, respectively. Ideally, a 
single pair of upper and lower cable guides 30 and 40 enables both 
circumferential and longitudinal sheath cuts in a particular diameter 
cable. However, in some instances, separate pairs of upper and lower cable 
guides members 30 and 40 may be necessary for circumferential and 
longitudinal sheath cuts in the same cable 12. 
As best seen in FIG. 1, a cable guide lock 48 mounts to the bottom of the 
housing 24 to retain the upper and lower cable guides 30 and 40 within the 
housing, thereby maintaining the cable 12, when circumscribed by the 
guides, in a fixed position relative to the cutting wheel 18. In the 
illustrated embodiment of FIG. 1, a plurality of threaded fasteners 50--50 
extend upward through the cable guide lock 48 for receipt in corresponding 
threaded passages (not shown) in the bottom of the housing 24. When the 
threaded fasteners 50--50 fully engage the housing 24, the cable guide 
lock 48 restrains the upper and lower cable guides 30 and 40 against 
lateral movement, yet permits the guides to enjoy a small degree of 
vertical movement. Rather than make the cable guide lock 48 completely 
detachable from the housing 24 as seen in FIG. 1, the cable guide lock 
could be hinged at one of its sides or ends to the housing. A single 
fastener 50 or a pair of such fasteners would then secure the cable guide 
lock 48 to the housing 24. Alternatively, the cable guide lock 48 could 
include a pair of raised, spaced-apart lips (not shown) for engaging 
corresponding channels (not shown) in the housing 24 to retain the cable 
guide lock to the housing. 
An adjusting mechanism 52, comprised knurled knob at the lower end of a 
shaft threaded vertically through the cable guide lock 48, serves to 
vertically displace the upper and lower cables guides 30 and 40 towards 
the cutting wheel 18 of FIG. 1. By manipulating the adjusting mechanism 
52, a technician can effectively control the depth to which the cutting 
wheel 18 extends through the slot 35 of the upper cable guide 30 of FIG. 1 
and into the cable. The more the technician threads the adjusting 
mechanism 52 into the cable guide lock 48, the deeper the cutting wheel 18 
cuts into the cable 12. 
Referring to FIG. 3, a technician operates the tool 10 to make a 
circumferential sheath cut by first placing the cable 12 in the transverse 
channels 38 and 44 (see FIG. 1) of the lower and upper cable guides 30 and 
40, respectively. Next, the technician places the upper and lower cable 
guides 30 and 40 (with the cable 12 circumscribed thereby) into the bottom 
of the housing 24 so that the cutting wheel 18 extends into the slot 35 in 
the upper cable guide with the motor shaft 18 of FIG. 1 parallel to the 
longitudinal cable axis. Thereafter, the operator secures the cable guide 
lock 48 to the bottom of the housing 24 and then manipulates the adjusting 
mechanism 52 to assure the proper cutting depth. Finally, the operator 
rotates the tool 10 relative to the cable 12 about the circumference of 
the cable to effect a circumferential sheath cut. 
Referring to FIG. 4, a technician effects a longitudinal sheath cut by 
first placing the cable 12 in the longitudinal channels 36 and 42 (see 
FIG. 1) of the upper and lower cable guides 30 and 40, respectively. Next, 
the technician places the upper and lower cable guides 30 and 40 (with the 
cable 12 circumscribed thereby) into the bottom of the housing 24 so that 
the cutting wheel 18 (see FIG. 1) extends into the slot 35 (see FIG. 1) in 
the upper cable guide 30 with the face of the cutting wheel parallel to 
the longitudinal cable axis. Thereafter, the operator secures the cable 
guide lock 48 to the bottom of the housing 24 and then manipulates the 
adjusting mechanism 52 to assure the proper cutting depth. Finally, the 
operator displaces the tool 10 relative to the cable 12 in a direction 
parallel to the longitudinal cable axis. 
The foregoing discloses a tool 10 for accomplishing both longitudinal and 
circumferential sheath cuts in a fiber optic cable 12 with improved safety 
and precision. 
It is to be understood that the above-described embodiments are merely 
illustrative of the principles of the invention. Various modifications and 
changes may be made thereto by those skilled in the art that will embody 
the principles of the invention and fall within the spirit and scope 
thereof. For example, while the tool 10 has been described with respect to 
making circumferential and longitudinal sheath cuts in the fiber optic 
cable, the tool can easily be employed to make sheath cuts in other types 
of cable, and in cylindrical objects generally.