Tool for removing coverings of a coaxial cable

A tool for removing the insulation covering of a coaxial cable. The tool has first and second through holes. The portion having the first through hole will support a cutter member able to adjust the cutting in length of the blade into the outer insulation covering. A scraper member is arranged to scrape-up and cut-off scraps and peel off the insulation covering when the tool is rotated relative to the coaxial cable; the cutter blade cuts in the outer insulation covering in a spiral manner. A certain length of the covering can be removed without doing any damage to an aluminum outer conductor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a tool for removing the protecting and 
insulating covering or coverings of a coaxial cable used in 
telecommunication or power supply for purpose of connecting to a coaxial 
cable connector. 
2. Prior Art Statement 
For removing an outer insulating covering of a coaxial cable in order to 
connect the coaxial cable to a coaxial cable connector, such as disclosed 
in Japanese Patent Application Opened Publication No. 62-271,381, it has 
been a common practice to use a cutter knife in the field. At first a cut 
is made in the outer protection and insulation covering both in 
circumferential and axial directions. Then, the covering is peeled off by 
hand. Also, a particular peeling tool for the removal of covering has been 
used. 
A particular peeling tool for this purpose has the shape of a spanner 
having two jaws. One jaw of which is fixed and provided with a pair of 
rollers. The other jaw is arranged movable and provided with a cutter 
roller. At use, a portion of an outer insulation covering of a coaxial 
cable is placed between the pair of rollers of the fixed jaw. The movable 
jaw is moved forward against the fixed jaw so as to push the cutter roller 
to cut-in at one point of the outer insulation covering of the coaxial 
cable. Then by rotating the spanner shape tool about the coaxial cable 
circumferential cut is made in the outer insulation covering so that it 
can be peeled off. Thereafter, the peeled off portion is removed by using 
cutting pliers and a nipper or like tool. 
However, by using such a conventional cutter knife or peeling tool, it has 
been very difficult to cut off only the outer insulation covering without 
damaging the outer conductor of the coaxial cable. More especially, in 
case of a coaxial cable for CATV purpose, which has the outer conductor 
made of aluminium pipe, if the pipe is damaged even by a very small cut in 
the circumferential direction on the aluminium pipe, it easily tends to 
break by light bending. When it is broken, the transmission 
characteristics will greatly deteriorate and also might cause trouble in 
waterproofing. 
In cutters for use in outer insulation covering of rubber or like soft 
materials, the blade of the cutter can very soon be spoiled so that 
frequent interchange of the cutter blade is required. In case of a cutter 
knife, a supply of cheap cutter blades is rather easy to obtain and use. 
However, in case of a particularly designed cutter tool, the tool itself 
is expensive and the supply of the particular cutter blade is not simple. 
Thus it has a great disadvantage of high and continuous cost. 
Furthermore, for connecting a coaxial cable to a coaxial cable connector, 
it is necessary to expose a core wire or a central conductor over a 
predetermined length and to expose the outer conductor over a 
predetermined length from the base of the exposed central conductor. Thus 
work is necessary to mark a point on the outer insulation covering by 
measuring the required length and thereafter the covering is cut from the 
marked point. 
SUMMARY OF THE INVENTION 
According to the foregoing situation of the prior art technique, a first 
object of the present invention is to obtain a tool for removing the 
covering of a coaxial cable, able to remove the outer insulation covering 
over a certain length without causing any damage to the outer conductor of 
the coaxial cable, at low cost, with an easily exchangeable cutter blade, 
and without need to measure the length of the outer insulation covering to 
be removed. 
Further the second object of the present invention is to realize a tool for 
removing the covering of a coaxial cable which can remove the outer 
insulation covering and the inner insulation covering simultaneously. This 
tool eliminates the need of a two-step covering removal process which had 
been practised conventionally. Namely, the prior technique entails first 
removing the outer insulation covering and then a part of the inner 
insulation covering which is located inside the outer conductor which is 
formed of aluminium pipe. The inner cover is removed by using a particular 
tool designed exclusively for the removal of the inner insulation 
covering. This prior technique is used to fit a coaxial cable to a 
connector of a type disclosed in Japanese Patent Laid Open Application No. 
62-271,381, in which a reinforcement sleeve is interposed in the outer 
conductor. 
For achieving the above mentioned first object, the inventive tool for 
removing the covering of a coaxial cable for connecting the coaxial cable 
to a coaxial cable connector, is characterized in that it comprises; 
a bottom portion provided with a first through hole having an inner 
diameter slightly larger than the outer diameter of the coaxial cable, 
a top portion provided with a second through hole having an inner diameter 
slightly larger than the outer diameter of core wire of the coaxial cable 
and to be coupled with said bottom portion with the intervention of spacer 
members having a height corresponding to a length of the outer insulation 
covering of the coaxial cable to be removed, 
a cutter accommodating recess provided in said bottom portion at a position 
adjacent to an end of the outlet of the first through hole and bottom 
surface to form a certain angle against a plane normally intersecting with 
an axial line of the first through hole and extending substantially in a 
radial direction of the bottom portion, 
a cutter member being arranged freely slidable in said cutter accommodating 
recess with its cutting edge facing against said first through hole, and 
having a cutter blade being able to be positioned and clamped thereat 
against the end surface of the outer insulation covering of the coaxial 
cable of which the cutting end is inserted into the first through hole so 
as to cut into the outer insulation covering at an inclined angle while 
leaving a very thin thickness thereof, 
a scraping surface member for scraping off the rest of the thickness of the 
outer insulation covering being cut in a spiral shape by said cutter edge 
when the tool is rotated relative to the coaxial cable. 
Furthermore, in order to achieve above mentioned second object, the 
inventive tool for removing covering of a coaxial cable and for connecting 
the coaxial cable to a coaxial cable connector, is characterized in that 
it comprises; 
a bottom portion provided with a first through hole having its inner 
diameter slightly larger than the outer diameter of the coaxial cable, 
a top portion to be coupled with said bottom portion with the intervention 
of spacer members having a height corresponding to the length of the outer 
insulation covering to be removed, the top portion being so arranged to 
support and guide a drill member having a drill axis provided at its 
center with a second through hole having an inner diameter slightly larger 
than the outer diameter of the core wire of the coaxial cable, the drill 
axis having an outer diameter slightly smaller than the inner diameter of 
the outer conductor of the coaxial cable and having a drill blade length 
corresponding to said length of the outer insulation covering to be 
removed, and the drill axis being aligned coaxially with said first 
through hole in a space formed by the spacer members and to freely slide 
in the aligned condition, 
a cutter accommodating recess provided in said bottom portion at a position 
adjacent to an end of the outlet of the first through hole and the bottom 
surface to form a certain angle against a plane normally intersecting with 
an axial line of the first through hole and extending substantially in a 
radial direction of the bottom portion, 
a cutter member being arranged freely slidable in said cutter accommodating 
recess with its cutting edge facing against said first through hole, and 
having a cutter blade being able to be positioned and clamped thereat 
against the end surface of the outer insulation covering of the coaxial 
cable of which the cutting end is inserted into the first through hole so 
as to cut in the outer insulation covering at an inclined angle while 
leaving a very thin thickness thereof, 
a scraping surface member for scraping off the rest of the thickness of the 
outer insulation covering being cut in a spiral shape by said cutter edge 
when the tool is rotated relative to the coaxial cable. 
To use the inventive tool for removing the covering of the coaxial cable, 
at first the end of the coaxial cable is cut altogether including the 
outer insulation covering, outer conductor and the inner insulation 
covering. This end is termed the "base end". The center conductor is 
arranged to project over a predetermined length. Then the whole of the 
coaxial cable having the thus treated base end is inserted into the first 
through hole of the bottom portion. At this time, the downwardly facing 
leading edge of the inclined cutter blade of the cutter member will cover 
a part of the thickness of the outer insulation covering and thus prevent 
further passage. By rotating the tool while pushing it towards the coaxial 
cable in a direction to cut into the outer insulation covering, the 
cutting edge of the cutter blade will cut the covering along a spiral line 
while leaving a very thin thickness of the covering at the periphery of 
the outer conductor and the scraping member will scrape up the cut-off 
scrap and automatically peel off the outer insulation covering. In the 
meanwhile the core wire will proceed and penetrate into the second through 
hole in the top portion. By further rotating the tool while pushing 
against the coaxial cable, the base end of the coaxial cable will abut 
against the lower surface of the top portion facing against the bottom 
portion and further stroke is prevented. At this condition if the tool is 
rotated relatively one more turn, the spiral cut of the outer insulation 
covering will be clearly cut off from the covering. By the interval 
between the top portion and bottom portion separated by the spacer 
members, the outer conductor will be exposed by a certain predetermined 
length without having any damage by the cutter on it. 
In a modified embodiment of the present invention, in which the inner 
insulation covering is also removed, at first the outer insulation 
covering, the outer conductor and the inner insulation covering are cut 
together and the core wire or the inner conductor is arranged to extend 
over a certain length from the base end. This base end of the coaxial 
cable is inserted into the first through hole of the bottom portion and 
the downwardly facing leading edge of the cutter blade will cover a part 
of thickness of the outer insulation covering and prevent further 
penetration into the through hole. In this condition, the drill member is 
shifted up relative to the top portion to separate the top of the drill 
axis from the opposite end of the first through hole. Thus the core wire 
extends in the space formed by the spacer members. 
Then at first to insert the top end of the core wire into the second 
through hole provided at the center of the drill axis and the drill axis 
is shifted down against the first through hole until it reaches the 
extremity of movement. By this, all the preparation works to remove the 
outer insulation covering and the inner insulation covering simultaneously 
have been completed. By rotating and pushing the tool relative to the 
coaxial cable, while removing the outer insulation covering as explained 
above, the drill axis will proceed and cut into the inner insulation 
covering and remove the inner insulation covering. The core wire will 
proceed into the second through hole provided in the center of the drill 
axis and the coaxial cable will proceed upwardly until the exposed base 
end of the outer conductor of the cable will abut against the lower 
surface of the top portion. From this condition, by rotating the tool one 
turn more relative to the coaxial cable, a spiral form peeled off scrap 
portion will clearly be cut and separate from the outer insulation 
covering and also the removal of the inner insulation covering from inside 
of the outer conductor is finished. Thus the coaxial cable with covering 
removed may be withdrawn from the tool and a reinforcement sleeve is put 
inside the outer conductor and a known coaxial cable connector as has been 
disclosed in Japanese Patent Application Opened Publication No. 62-271,381 
is mounted on this coaxial cable. By the presence of the reinforcement 
sleeve, the soft cylinder shaped outer conductor made of aluminium will 
not be deformed and it ma sufficiently bear the clamping force of the 
connector. 
In a preferred embodiment of the present invention, the above mentioned 
spacer members or spacer means are formed of a pair of projections 
radially and oppositely arranged on either the bottom portion or the top 
portion. 
Further in a preferred embodiment of the present invention, the cutter 
member may be formed to have a clamping member in a form of engaging 
member to engage the cutter blade by fitting in the cutter accommodating 
recess. 
Also in a preferred embodiment of the present invention, the cutter member 
may have a stopper to provide adjusting of the cutting-in length of the 
cutting edge of the cutter blade into the outer insulation covering of the 
coaxial cable. 
In a further preferred embodiment of the present invention, the spacer 
members are formed as a pair of projections integrally formed with the top 
portion and the engaging block may be formed integrally with one of the 
projections. 
In a very convenient embodiment of the present invention, the spacer 
members are formed in the shape of a pair of projections integrally formed 
with the top portion and a complementary recess with the engaging block 
projecting from the top surface of the bottom portion formed in one of the 
pair of projections to mate with it. 
Also in a convenient embodiment of the present invention, the scraping 
surface member may be provided in the cutter accommodating recess. 
In a further convenient embodiment of the present invention, the scraping 
surface member is formed integrally with the engaging block. 
Throughout the explanation of this specification, terms like "top", 
"bottom", "upper" or "lower" had been used. However, it should be 
understood that this is just used for providing an easy understanding of 
the invention to explain in a relative positions that the tool is used for 
a coaxial cable with its base end surface facing upwardly and to abut the 
tool at the end surface. The tool can be used in any direction like 
horizontal direction or even upside down and the term top, upper or the 
like will not mean an exact physical positions.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The invention will now be explained in detail by referring to the 
accompanying drawings. 
FIG. 1 shows, in perspective view, a preferred embodiment of the inventive 
tool 1 for removing the outer insulation covering of a coaxial cable. 
According to the present invention, the tool is formed from a generally 
cylindrical lower portion or bottom portion 2 and a generally cylindrical 
upper portion or top portion 3 coupled by bolts 16 having head with a 
hexagonal hole and coupled with intermediately positioned spacer members 
(13). The bottom portion 2 is provided with a first through hole 5 having 
an inner diameter only slightly larger than the outer diameter of the 
coaxial cable at its center for passing through the coaxial cable. The top 
portion 3 is provided with a second through hole 7 at its center for 
passing through the center conductor or core wire 6 of the coaxial cable 
4. These portions can be made of aluminium or hard plastic materials. 
At the upper end surface of the bottom portion 2 facing against the top 
portion, a cutter recess or cutter accommodating recess 8 is provided for 
housing a cutter member. This cutter housing recess 8 is provided in a 
manner that the bottom surface of the same will have a small angle with a 
plane crossing normally against the axial line of the first through hole 
5. In the illustrated embodiment, the cutter member comprises a cutter 
blade 9 having its cutting edge extending toward the first through hole 5 
and arranged freely adjustable to slide on the bottom surface of the 
cutter recess 8, a clamping member in the form of an engaging block 10 to 
engage the cutter blade 9 and fit in the recess 8, a scraping member 11 to 
scrape up the removed scrap portion of the outer insulation covering of 
the coaxial cable, and a stopper member in the form of a screw 12 for 
adjusting the cutting-in length of the cutting end of the cutter blade to 
cut into the outer insulating covering of the coaxial cable. 
In the illustrated embodiment, the engaging block 10 clamps the cutter 
blade 9 and couples the block 10 to the bottom portion 2 by mating a bolt 
10a having a hexagonal hole head into an inclined bolt hole provided 
between the engaging block 10 and the bottom portion 2. The cutter blade 9 
can be moved against the coaxial cable 4 with its cutting edge inserted 
into the first through hole 5 to cut into the outer insulation covering 4a 
from the base end surface thereof and by leaving a very thin thickness of 
the covering 4a, for instance 0.1 mm, and this position is adjusted by a 
stopper 12 and clamped at the adjusted position. 
The scraping member 11 can also be provided at other location than to 
provide it on the engaging block 10, for instance in the cutter housing 
recess 8. 
In the embodiment generally shown in FIG. 1 or FIG. 3, the spacer members 
are formed of a pair of projections 13 integrally formed of the top 
portion 3 at radially opposite locations. The height of these spacer 
members are arranged to correspond to the necessary length of the outer 
conductor to connect the cable to a coaxial cable connector. These 
projections can be provided on the bottom portion 2 instead of the top 
portion 3. It is also possible to provide a complementary shaped recess to 
couple with the engaging block 10 on one of the projections 13 or to form 
the engaging block integrally with the projections 13. 
After setting and clamping the cutter blade 9 on the bottom portion 2, the 
top portion 3 can be assembled together by aligning the screw bolt holes 
14 of the bottom portion 2 and the bolt passing holes 15 of the top 
portion 3 and thereafter inserting bolts 16 having hexagonal hole head 
into holes 15 and 14 and fixed by screwing. In order to realize an easy 
alignment between the first through hole 5 and the second through hole 7, 
a ring shape projection may be provided on the end surface of the bottom 
portion 2 facing against the top portion 3 so that the inner surfaces of 
the projections 13 is coupled to the outer peripheral surface of the ring 
shape projection 17. 
The top portion, bottom portion and the spacer members can be formed 
integrally by using plastic resin. 
In FIG. 4a, when the coaxial cable is to be handled to remove the outer 
insulation covering to connect to a coaxial cable connector, the core wire 
6 is exposed for a certain length required for connector connection from 
the base end portion where the outer insulation covering 4a, outer 
conductor 4b and inner insulation covering 4c are cut together and 
arranged in one surface as can be seen from FIG. 4a. After arranging the 
cable end in the above condition, the coaxial cable 4 may be inserted from 
the bottom end of the first through hole 5 of the bottom portion 2, 
leading edge of the cutter blade 9 arranged at inclined direction and 
facing to down side will hit a part of thickness of the outer insulation 
covering 4a to prevent its further passage. If the tool is mutually 
rotated relative to the coaxial cable 4 in a direction that the down side 
faced leading edge of the cutter blade 9 will cut in the outer insulation 
covering from the base end and pushing the tool against the coaxial cable 
in the axial direction, the cutting edge of the cutter blade 9 will cut in 
the outer insulation covering 4a in spiral-wise fashion while leaving a 
very thin portion of its thickness. At the same time of the said spiral 
cut, the scraper or scraping surface member 11 will successively scrape up 
the cutting scrap of the outer insulation covering from the cut off end of 
the covering and peel it off continuously. During the above process, the 
core wire 6 will enter and pass through the second through hole 7 of the 
top portion 3. By further rotating and pushing the tool, the base end 
portion of the cable will abut against the bottom surface of the top 
portion 3. Thus further movement is prevented. At this condition by 
mutually rotating the tool against the coaxial cable by one turn, the 
peeled off scrap portion connected in spiral form is very easily and 
clearly cut from the outer insulation covering 4a. By the mutual interval 
between the top portion 3 and bottom portion 2, provided by the spacer 
members 13, the outer conductor 4b can be exposed without damaged by the 
cutter blade and project over a predetermined length. 
FIG. 5 shows in a perspective view like FIG. 1, a preferred embodiment of 
the tool for removing coverings of the coaxial cable according to the 
present invention. This embodiment is able to remove the inner insulation 
covering simultaneously with the removal of the outer insulation covering. 
In case of this embodiment, the top portion 3 is arranged to support a 
drill member 18 being freely slidable in the axial direction. This drill 
member 18 comprises a drill axis supporting portion 20 supporting a drill 
axis 19 projecting downwardly and guide bars 21 being guided by guide 
holes 15a provided in the top portion 3 and guide holes 15b provided in 
the bottom portion 2 in alignment therewith in a manner freely slidable. 
The top portion 3 is provided with a through hole 22 for passing through 
the drill axis 19. It is preferred to arrange the through hole 22 for the 
drill axis facing against the top end of the drill groove being widened 
radially outwardly so as to escape the drill cut scrap coming up along the 
drill grooves upwardly at the time of drilling. 
It is obvious that many modifications can be considered for supporting and 
guiding the drill axis supporting portion against top portion 3 and bottom 
portion 2 freely slidable other than the above mentioned guide bar and 
guide hole construction. 
The cutter blade of the drill axis 19 is arranged over a length 
substantially equal with the height of the space provided by the spacer 
members 13. At the center of the drill axis, a core wire through hole 23 
is provided for passing through the core wire 6 of the coaxial cable. In 
order to prevent the drill member 18 from detaching from the top portion 3 
and possible loss, it is better to provide a stopper 16A projecting 
radially in the guide hole 15a of the top portion 3 and to provide a 
stopper guide groove 16B at side surface of at least one of the guide bars 
21 of the drill member 18 mating with this guide hole 15a so that lower 
end of the guide groove 16B restricts the upper limit of the pulling up 
stroke of the drill member 18. However, it is also possible not to provide 
such a stopper 16A so that the drill member 18 can be separated from the 
top portion 3. It is preferred to provide serrations around the side 
surfaces of the drill axis supporting portion 20 for allowing easy grip of 
the same when the portion is rotated relative to the top portion 3. 
FIG. 5a shows a situation where the drill member 18 is pulled upwardly to 
the extremity from the top portion 3. At this condition, the coaxial cable 
4 may be inserted from bottom end of the first through hole 5 of the 
bottom portion 2. The base end face of the outer insulation covering 4a is 
stopped by the cutter blade 9. But the core wire 6 of the coaxial cable 
will extend from the top end of the first through hole 5 into a spacer 
bound by the spacer member (13). Then the drill member 18 is pushed 
against the top portion 3 while allowing the top end of the core wire 6 to 
enter into the core wire through hole 23 up to the position as shown in 
FIG. 5B. In this condition, the drill axis supporting portion 20 abuts 
against the upper surface of the top portion 3. By this all the 
preparation work of removing the insulation coverings have been completed. 
Under this condition, by relatively rotating the whole tool 1 and by 
pushing it against the coaxial cable 4, the outer insulation covering is 
peeled off as has been explained above. At the same time, the drill axis 
19 will cut into the inner insulation covering 4c at the inside of the 
outer conductor 4b. The cutting off of the scrap of the covering will be 
brought out along the spiral form drill groove of the drill axis 19. The 
core wire 6 will proceed into the second through hole at the center of the 
drill axis 19 i.e. into the through hole 23 for passing the core wire and 
the tool 1 may be forwarded with respect to the coaxial cable until the 
top end of the exposed outer conductor 4b will abut against the bottom 
surface of the top portion 3. By further rotating once the tool 1 relative 
to the coaxial cable, the spirally connected peeled off scrap portion will 
be cut clear from the outer insulation covering 4a and also the removal of 
the inner insulation covering 4c inside the outer conductor 4b is 
completed. The coaxial cable peeled off the covering may be withdrawn from 
the tool 1. A reinforcing sleeve, known per se, from for instance Japanese 
Patent Application Opened No. 62-271,381, having the outer diameter 
slightly less than the inner diameter of the outer conductor 4b and the 
length substantially equal to that of the exposed outer conductor 4b may 
be inserted into the outer conductor 4b and the coaxial cable connector is 
mounted in a known matter also disclosed in the above patent publication. 
In a preferred embodiment of the present invention, a marker member 25 
having marker projection 24 as shown in FIG. 6 slightly projecting 
radially inside into the first through hole 5 by spring bias may be 
provided in the bottom portion 2. By means of this marker projection 24, 
the outside surface of the coaxial cable, from which the insulation 
covering is to be removed can be marked clearly. This mark is put at a 
location for confirming a complete clamping of the connector mounted on 
the end of the cable when the connector is mounted. The connector is for 
instance disclosed in the above mentioned Japanese Patent Application 
Publication No. 62-271,381. The marker member may also be provided in a 
slit 26 in the bottom portion 2 so as to make its axial position 
adjustable. The location thereof may be fixed by a clamping element 27 and 
a clamping screw 28 so as to fit various kind of connectors and afford to 
confirm secure mounting of the same. 
By using the tool for removing the covering of the coaxial cable according 
to the present invention, the cutting edge of the cutter blade will never 
reach the outer conductor so that the outer conductor is not damaged at 
all and perfectly free from damages. Moreover, for the cutter blade, cheap 
and easily obtainable cutter knife, segment breaking-off type sold in the 
market can be used. Therefore advantages of very cheap operating cost and 
easy exchange of the cutter blade can be obtained. The outer insulation 
covering can be removed for a certain length without the need of measuring 
the length of the outer insulation covering to be removed. 
In accordance with the further embodiment of the inventive tool for 
removing the covering of the coaxial cable provided with the drill member, 
the insulation coverings at outside and inside of the outer conductor can 
be removed simultaneously by the cutter blade and by the drill axis 
respectively.