Adjustable-mid-span stripper for wire and cable

A tool for removing insulation from mid-span of a conductor cable which includes a frame with first and second jaw members, one of which is slidably mounted on the frame to close and cooperate with the other jaw member to secure cable in the tool for rotation of the frame relative to the cable. A circular ringing knife blade assembly is slidably mounted on the frame for movement toward and away from cable secured in the jaw members and upon extension of the circular knife blade and at least one full rotation of the frame in a first direction relative to the cable, the circular knife blade scores the jacket along a closed cut around the complete periphery of the cable. An insulation stripping assembly includes at least one blade edge for removing the radial thickness of the insulation from the cable. The blade edge is at a constant, fixed cutting angle and is mounted for movement along a straight line toward and away from the cable. An adjustable depth-limiting menas sets the maximum extension of the blade edge. Upon rotation of the tool frame in a second direction opposite the first direction relative to the cable, the blade edge cuts and lifts the insulation from the cable conductor. A second blade edge is mounted adjacent the first blade edge to cut the jacket in a helical direction and helically strip the insulation as the frame is rotated about the cable.

BACKGROUND OF THE INVENTION 
The present invention relates to a tool for stripping insulation from 
electrical wire and cable and, in particular, to a hand tool which 
incorporates a circular ringing knife blade and a separate stripping or 
shaving blade to remove insulation in the mid portion of a span of wire or 
cable of various diameters. 
Among the many known cable insulation shaving or stripping tools are those 
disclosed in U.S. Pat. Nos. 3,204,495, 3,361,015, 3,398,610 and 3,572,189 
to the inventor of the present application. These tools generally utilize 
a pivoting stripping or shaving blade which helically strips the cable 
insulation as the tool is rotated around the cable. The angle of the 
pivotal stripping blade changes with respect to the cable as a function of 
the depth of cut, thereby resulting in varying blade angles for different 
size cables or different depths of cut. Although such tools can be 
utilized in stripping a section of insulation in an intermediate portion 
of the span of the wire or cable, it is desirable to provide a tool which 
is more easily grasped by the user and able to quickly adjust to different 
diameter cables and depth of cut to more effectively strip mid-span cable 
insulation. 
Bearing in mind the deficiencies of the prior art and need for improvement, 
it is therefore an object of the present invention to provide an 
insulation stripping tool for wire and cable which is especially adapted 
for quick and easy removal of a portion of the cable insulation 
intermediate the cable ends. 
It is another object of the present invention to provide a hand-held and 
operated tool for mid-span stripping of wire and cable which permits 
accurate preselection of stripping depth. 
It is a further object of the present invention to provide a mid-span 
insulation stripping tool which provides effective engagement of blade 
cutting edges during operation. 
It is yet another object of the present invention to provide a mid-span 
insulation stripping tool which utilizes a constant, fixed cutting angle 
for the insulation stripping blade. 
It is a further object of the present invention to provide a mid-span 
insulation stripping device which meets the aforementioned objects and is 
usable on wire or cable of varying diameter. 
SUMMARY OF THE INVENTION 
The above and other objects, which will be apparent to those skilled in the 
art, are achieved in the present invention which provides a tool for 
removing insulation from conductor cable which includes a frame with first 
and second jaw members, with at least one of the jaw members being 
slidably mounted on the frame to close and cooperate with the other jaw 
member to secure cable in the tool for rotation of the frame relative to 
the cable. A ringing knife assembly is slidably mounted on the frame for 
movement toward and away from cable secured in the jaw members and 
includes means for releasably securing the ringing knife assembly in a 
fixed position relative to the frame. The ringing knife assembly further 
includes means for extending and retracting a circular knife blade from 
and to the assembly in its fixed position. Upon closure of the jaw members 
about a section of cable, the ringing knife assembly may be secured in a 
fixed position with a circular blade in a retracted position adjacent to 
the cable jacket. Upon extension of the circular knife blade and at least 
one full rotation of the frame in a first direction relative to the cable, 
the circular knife blade scores the jacket along a closed cut around the 
complete periphery of the cable. 
An insulation stripping assembly on the frame includes at least one blade 
edge for removing the insulation from the cable. The blade edge is at a 
constant, fixed cutting angle and is mounted for movement along a straight 
line toward and away from the cable. An adjustable depth-limiting means 
sets the maximum depth of the blade edge. Upon rotation of the tool frame 
in a second direction, opposite the first direction, relative to the 
cable, the blade edge will lift and cut the insulation jacket from the 
cable to the desired depth set by the depth limiting means. Preferably, a 
spring urges the blade edge toward the cable such that cutting and lifting 
occurs automatically upon rotation in the second direction. A second blade 
edge is mounted adjacent the first blade edge to cut the jacket in a 
helical direction and helically strip the shaved insulation as the frame 
is rotated about the cable. 
The ringing knife assembly may be located adjacent one of the first or 
second jaw members and the insulation jacket shaving assembly may be 
located adjacent the other of the first or second jaw members. Opposed 
first and second handle members may extend outwardly from the first or 
second jaw members, respectively. Releasable locking means or the second 
handle member permits the first and second handle members to be grasped 
and moved toward each other to close and lock the jaw members around the 
cable for scoring and/or shaving the cable insulation. A finger actuated 
lever which is operable while a user is grasping the handle members may be 
provided to move the circular knife blade between retracted and extended 
positions. Upon release of the handle locking means, the handle members 
may be grasped and pulled away from each other to open the jaw members and 
release the cable upon completion of the scoring and/or shaving operations 
.

DETAILED DESCRIPTION OF THE INVENTION 
Reference will be made herein to the preferred embodiment of the mid-span 
cable insulation stripping tool of the present invention as depicted in 
FIGS. 1-12 of the accompanying drawings. Like numeral refer to like 
features of the invention throughout the drawings. 
The preferred hand tool 20 of the present invention includes a "U" or 
"C"-shaped cast alloy frame or body 30 and a pair of opposed handles 22, 
24 for grasping and operating the tool. An elongated shaft 26 connects 
handle 22 to the shaft mounting portion 31 of frame 30. Set screw 33 in 
the shaft mounting portion 31 of frame 30 secures shaft 26 and handle 22. 
An elongated shaft 28 is connected at one end to handle 24 and extends 
through the bore of shaft guide portion 32 of frame 30. The opposite end 
of shaft 28 is secured to an adjustable frame or body member 34 which 
slides along guide member 39 received within channel 37 set in frame 30. 
Set screw 33 in the adjustable frame portion 34 secures shaft 28 and 
handle 24. 
To receive and secure electrical wire or cable 40 (see FIG. 10) there are 
provided opposed jaw faces 36 (integral with frame 30) and 38 (integral 
with adjustable frame member 34). The generally "V"-shaped face of jaw 
member 36 and the generally "U" or "C"-shaped face of jaw member 38 are of 
suitable size to secure various diameters of wire or cable therebetween. 
When the jaw members 36 and 38 close around a wire or cable, as shown in 
FIG. 10, the elongated handles 22, 24 and their respective shafts 26, 28 
are coaxial with a line perpendicular to and extending through the 
longitudinal axis of the wire or cable 40. As used herein, the terms 
"cable" and "wire" are used interchangeably, unless otherwise noted. Cable 
40 consists of a plurality of conductors 46 within an inner insulation 44 
which in turn is surrounded by a semiconductive outer jacket 42. Jacket 42 
and inner insulation 44 make up the insulation to be stripped by tool 20. 
To tightly secure the wire or cable between and within jaw members 36, 38, 
handles 22 and 24 are grasped by the user and pushed toward one another to 
move the respective jaw members together. The position of the adjustable 
frame member 34 ma be fixed relative to frame 30 by a locking mechanism 
shown generally as 78. The locking mechanism consists of a sleeve 83 
extending through the bore of shaft guide 32 and secured by a nut 88 and 
roll pin 89 as shown. Shaft 28 extends through a bore in sleeve 83 and an 
opening in end cap 82 secured to sleeve body 83. A ring member 81 is held 
in position by set screw 87 in cap 82 and includes an integral lever arm 
80 extending downwardly through an opening in cap 82. A cylindrical 
plunger 84 received within bore 85 in frame 30 is urged or biased by 
spring 86 against the lever arm 80 to cock the ring member 81 against 
shaft 28. This arrangement permits shaft 28 to be slid within the bore of 
sleeve 83 to move adjustable frame member 34 and close jaw member 38 
against jaw member 36 when plunger 84 is spring loaded outward against 
lever arm 80, but prevents reverse movement opening jaw member 38. 
However, when lever arm 80 is pushed to compress spring 86, such as by 
grasping handle 24 and pushing with the thumb against lever arm 80, shaft 
28 may easily slide outward to open jaw members 36 and 38 to permit cable 
to be inserted or removed from the tool. 
A circular or ringing knife blade assembly 50 is slidably mounted in frame 
30 adjacent to jaw member 36 to score the periphery of insulation on cable 
secured within the jaw members. The ringing knife assembly 50 is shown in 
more detail in FIGS. 5-8 and includes an assembly housing 56 having a pair 
of integral straight flanges 60 which are slidingly received within 
corresponding slots 35 in frame 30 for movement of the assembly 50 toward 
and away from the cable. A flat cover plate 58 is secured by screws 49 
over the housing 56 and includes a visible mark or indicia 71 which may be 
used in conjunction with indicia 70 on frame 30 to locate or relocate the 
relative position of the ringing knife blade assembly 50 with respect to 
the frame (see FIG. 10). 
Circular knife blade 52 is secured by a screw button 57 and washer 53 to a 
threaded opening 69 in a holder member 65 which slides within the interior 
space between housing 56, housing side walls 63 and cover plate 58. 
Circular knife blade 52 is located in a plane perpendicular to the 
longitudinal axis of cable held within the tool jaw members and is 
provided to score the cable insulation jacket around the periphery of the 
cable as the tool is rotated relative to the cable. 
A knob 72 having a threaded shaft received within a correspondingly 
threaded opening in frame 30 may be tightened to bear against pin 73, 
which in turn bears against the ramped indentation 55 in circular knife 
blade assembly 50 to secure the housing 56 in a fixed position relative to 
frame 30. 
When ringing knife blade assembly housing 56 is secured in a fixed position 
on frame 30 by knob 72, the position of circular knife blade 52 mounted on 
knife holder member 65 may be further adjusted toward and away from cable 
secured within the tool 20. A cam arrangement is provided to extend and 
retract the circular knife 52 relative to housing 56. A rotatable roller 
64 is mounted by shaft 66 to the end of the holder member 65 opposite that 
of the circular knife 52. A spring 59 in the interior portion 68 of holder 
65 acts against a roll pin 67 mounted in housing 56 to urge or bias the 
holder and circular knife blade into a retracted position such that roller 
64 contacts lever handle 54. Lever 54 is rotatably mounted to housing 56 
on offset shaft 62 and includes a cam surface 61 which bears against 
roller 64. Cam surface 61 is configured so that holder member 65 and knife 
blade 52 are in the extreme retracted position when lever 54 is in the 
extreme upward position as shown in FIG. 5 (corresponding to the extreme 
downward position as shown in FIGS. 1, 3 and 10). When lever 54 is rotated 
180.degree. so that the detent portion 61a of cam surface 61 engages 
roller 64, holder 65 and circular knife blade 52 are pushed against the 
bias of spring 59 to the extreme extended position toward the cable 
secured in the tool. An elongated opening 58a in cover plate 58 permits 
movement of the knife blade screw 57 and circular knife blade 52 between 
the retracted and the extended positions. 
To provide the actual stripping of insulation from the cable secured in 
tool 20, there is provided insulation stripping assembly 90 mounted on 
adjustable frame member 34 adjacent to jaw face 38. As shown in FIG. 9 
with screws 95 and cover plate 94 removed, and in FIGS. 11a, 11b and 12, 
the insulation stripping assembly includes a cutting knife 100 having a 
first cutting edge 110 parallel to the longitudinal axis of the cable as 
secured in a tool, and a second cutting edge 108 along a radial line 
extending from the cable secured in the tool. Knife 100 is slidingly 
received within a channel 98 in adjustable frame member 34 and includes a 
pair of leg members 102 extending in a direction away from the cable 
position. Between leg members 102 a spring 97 bears against a pin 96 set 
in adjustable frame 34 (FIG. 12) to urge or bias knife 100 in the 
direction of the cable position. A rod 93 threaded into the bore of a 
collar 101 disposed at the end of legs 102 is adjustable toward and away 
from the cable position to adjust and limit the movement of knife 100 
toward cable received in jaw members 36, 38. An adjusting knob 92 set at 
the far end of threaded rod 93 permits the user to adjust the movement and 
position of knife 100 by comparing the position of the back edge 106 of 
the axial cutting edge against indicia 104 marked on adjusting frame 
member 34. A set screw 105 in end collar 101 permits the user to fix the 
thread rod 93 and consequently the limit of travel of knife 100 at a fixed 
position. 
Stripping of a width of cable insulation jacket around the periphery of the 
cable is accomplished by the axial direction cutting edge 110. The angle 
of axial edge wall 109 permits smooth and easy lifting and removal of the 
entire thickness of the insulation from the cable conductor so that the 
stripping of the jacket may proceed in a helical manner (for example, as 
shown in FIG. 1 of U.S. Pat. No. 3,572,189, the disclosure of which is 
hereby incorporated by reference). Radial direction cutting edge 108 is 
angled to advance the entire knife 100 in an axial direction as cutting 
edge 110 strips the insulation jacket. An angled edge wall 107 provides 
relief for the portion of the cut made by edge 108. As seen best in FIGS. 
11a and 11b, there is provided an angled relief edge 111 along the side 
edge of front face 112 to insure smooth helical cutting movement as knife 
100 engages the cable insulation. 
The preferred embodiment of tool 20 as shown is set up for operation by 
initially adjusting the final cutting positions of both the circular 
ringing knife 52 and the shaving or stripping knife 100. Where a sample 
cable is available, thumbscrew 72 is loosened and the circular knife 
assembly 50 is slid in an outward direction along tool frame channels 35 
away from jaw members 36 and 38 to clear circular knife 52 from 
interference with the cable. The tool jaw members are fully opened by 
depressing locking lever arm 80 and pulling on both handles 22, 24 to move 
jaw members 36, 38 apart. The sample cable is then placed between the jaw 
members 36, 38 and opposing pressure is placed on handles 22, 24 to move 
the jaw members together and close them fully about the cable sample, as 
shown in FIG. 10. Circular knife lever 54 is then moved upward to a locked 
position such that detent 61a on the cam surface engages roller 64. In 
this position, the circular knife is in a fully extended position relative 
to the ringing knife assembly 50. The entire ringing knife assembly 50 is 
moved toward the cable so that the edge of knife 52 is below the surface 
of the jacket 42, and insulation 44, and at a desired distance away from 
conductor 46, for example, about 1/16 of an inch. The position of the 
ringing knife assembly 50 relative to frame 30 is then locked in a fixed 
position by tightening thumb screw 72 downward. Finally, the circular 
knife 52 is retracted by moving the circular knife lever 54 180.degree. 
into a fully retracted position. 
The position of stripping blade 100 is set by turning the adjusting 
thumbscrew 92 to raise or lower the blade to the proper insulation cutting 
depth, preferably so that the cutting edge 11 is below the level of the 
cable insulation but spaced away from the largest diameter of the 
conductors, for example, 1/32 in. The cable may be rotated within the jaws 
36, 38 to insure that the cutting edge does not hit the conductors 46. The 
depth adjustment of knife 100 should be adjusted if necessary. 
Where no sample of cable is available but the dimensions of the insulation 
are known, shaving or stripping knife 100 should be set to a desired depth 
using indicia 104 on adjustable frame member 34. For example, for 0.250 
in. thick insulation, a setting of 0.200 in. will effectively strip the 
cable insulation without nicking the conductor. To set the blade, use 
thumb screw 92 and indicia 104 to set the depth of cut of edge 110 to 
0.200 in. below the face of jaw member 38. 
The ringing knife assembly may also be set up without a sample cable but 
with known dimensions. After the thumbscrew 72 has been loosened and the 
ringing knife assembly 50 has been fully retracted away from the jaw 
members, the cable to be cut is set within the jaws of the tool as 
described above by pushing the handles 22, 24 toward each other. The 
circular knife adjustment lever 54 is then moved to the locked position 
(cam detent 61a engaging roller 64) and the entire assembly 50 is moved 
toward the cable until the edge of circular blade 52 touches the surface 
of the cable. At this point, the assembly is locked in position by 
tightening thumbscrew 72. Circular knife blade 52 is then retracted by 
moving lever 54 180.degree. to a fully retracted position. Thumbscrew 72 
is then loosened to permit the entire circular knife assembly 50 to be 
moved a desired distance toward the cable slightly less than the thickness 
of the cable insulation. For example, if the cable insulation is 0.250 in. 
thick, the circular knife assembly 50 would be moved using indicia 70, 71 
a distance of 0.200 in. toward the cable. The entire circular knife 
assembly 50 is then locked in place by tightening thumbscrew 72. 
Once the circular knife 52 and stripping knife 100 have been set up 
according to either of the above procedures, tool 20 is then ready for 
operation. After insuring that ringing knife 52 is in a fully retracted 
position (as shown in FIGS. 5 and 10 for example), the tool is placed on 
the desired mid-span portion of the cable to be stripped by placing the 
jaws 36, 38 around the cable and pushing the handles 22, 24 toward each 
other until the cable is fully seated and secure within the closed jaw 
members. In the orientation shown in FIGS. 1 and 10, the tool should then 
be rotated in a clockwise direction around the cable while applying 
moderate pressure on lever 54 to move circular knife 52 toward and into 
fully extended position. This pressure on lever 54 moves the circular 
knife 52 edge into cutting engagement with the cable insulation jacket to 
create the ringing effect of a closed cut around the complete periphery of 
the cable. Rotation of the tool should continue while the pressure is 
applied on lever 54 until the circular knife 52 is in a fully extended 
position with the cam detent 61a engaged with roller 64. After the ringing 
or circular knife 52 is locked into its fully extended position cutting 
into the cable insulation, the tool should continue to be rotated 
clockwise one additional complete rotation to make sure all of the 
insulation material has been scored and cut by the knife 52. Preferably, 
the tool will make at least two complete revolutions before the knife is 
in the fully extended position to avoid forcing knife 52 to quickly enter 
the insulation and possibly damaging the tool. 
To commence the mid-span shaving or stripping of the cable insulation 
(without removing the cable from the tool), the direction of tool rotation 
is reversed to turn in a counterclockwise direction as shown in FIGS. 1 
and 10. The biasing action of spring 97 then forces the cutting edges of 
shaving or stripping knife 100 into the cable insulation. As the tool is 
rotated in the counter clockwise direction, cutting edges 108 and 110 will 
bite into the cable insulation and reach the depth limit set by thumbscrew 
92 (usually in 1/2 revolution or less). At this point, cutting edge 110 
has served its purpose and essentially no longer provides a cutting 
function. Lifting surface 109 urges the insulation away from the conductor 
46 so that it may be completely cut by edge 108. The thickness of 
insulation removed is generally greater than the depth of cut of edge 110 
set by thumb screw 92 due to the lifting action of surface 109. As the 
tool is rotated about the cable, it will also be advanced along the axial 
direction of the cable to helically strip the insulation. The depth of 
stripping of cable insulation should be checked during rotation and, if 
adjustment is necessary, thumbscrew 92 should be turned to change the 
limiting depth of cut of knife 100. 
In an alternative use, the tool may be used to shave insulation from the 
cable, i.e., remove only a portion of the thickness of the insulation to a 
given diameter. In such use, the stripping knife 100 would be set by 
thumbscrew 92 so that the blade would be higher (a lesser depth of cut) 
and edge 110 would continue to cut during counterclockwise rotation of the 
tool without the full lifting action of surface 109 to leave a shaved 
insulation surface. 
To terminate the insulation shaving or stripping action, the tool should be 
held back during rotation so that forward axial movement along the cable 
is stopped. Upon a further complete rotation, the mid-span stripping will 
be completed. The tool is then removed from the cable by depressing the 
locking lever 80 while pulling on both handles 22, 24 to open the jaw 
members sufficiently to remove the cable. 
The preferred embodiment of the present invention also provides for 
simplified replacement of the circular knife 52 and stripping knife 100. 
In the case of the replacement of the circular knife 52, all that is 
necessary is that screw button 57 is unscrewed to remove the old blade and 
insert the new blade. To change stripping knife 100, it is merely 
necessary to unscrew screws 95 so that cover plate 94 can be removed from 
the shaving or stripping knife assembly 90. The old stripping knife 100 
and spring 97 are removed and thumbscrew 92 is fully backed off toward the 
right as seen in FIG. 9. The new stripping knife 100 is then inserted in 
channel 98 in the fully extended position and a new spring 97 is inserted 
between legs 102. The cover plate 94 is then refitted and the blade 100 is 
adjusted to the desired position using thumbscrew 92. 
Although the invention has been described herein in use to strip a mid-span 
portion of a wire or cable, it can also be used to strip the end portion 
of a cable, without use of the circular knife 52. 
Thus, the present invention provides a useful tool for shaving or stripping 
a desired depth and length of cable insulation in fulfillment of the 
objects listed above. While the invention has been described with 
reference to specific embodiments, it will be recognized by those skilled 
in the art that variations are possible without departing from the spirit 
and scope of the invention, and that it is intended to cover all changes 
and modifications of the invention disclosed herein for the purposes of 
illustration which do not constitute departure from the spirit and scope 
of the invention.