Self-contained lock wire securing tool

A device is disclosed for automatically inserting a ferrule over a safety cable, tensioning the cable and crimping the ferrule onto the safety cable, and cutting off excess cable. The apparatus is used with a safety cable having a ferrule applied to one end and which is placed through a plurality of threaded fasteners in a pattern. A free end is inserted through a ferrule held in the device and gripped by a tension cylinder. Movement of the tension cylinder exerts a predetermined tension on the safety cable. The device then crimps the ferrule onto the safety cable to retain the safety cable in place at the desired tension. The end of the safety cable extending beyond the attached ferrule is automatically cut off to complete the process.

BACKGROUND OF THE INVENTION 
The present invention relates to a tool for applying a ferrule to a lock 
wire passing through a plurality of threaded fasteners to prevent the 
unintentional unthreading of such fasteners. 
In rotating machinery having close tolerances between rotating and 
stationary elements, such as turbines, it is imperative that all objects, 
no matter how small, be kept from contact with the rotating elements of 
the machinery. The presence of any foreign object could result in the 
catastrophic failure of the entire machine. 
Such machinery is inherently complex and requires many nuts, bolts, screws 
and other threaded fasteners to assemble all of its components. Since the 
operation of such machinery may involve very high rotating speeds, which 
may induce vibrations into the machine elements, it is necessary to 
provide some means for preventing the inadvertent unthreading of the 
numerous threaded fasteners. 
It is known to apply lock wires to threaded fasteners to prevent their 
inadverent unthreading. Typically, the lock wire passes through a 
transverse hole in at least two threaded fasteners and is twisted back on 
itself in alternating clockwise and counterclockwise directions between 
the threaded fasteners. The process is duplicated between additional 
threaded fasteners until the entire threaded fastener pattern has been 
wired. Following the required stringing and twisting, the lock wire is cut 
and bent into a certain position. 
While the known lock wire technique has provided satisfactory results, it 
requires a very time consuming and laborious application process. Often 
the final result is unsatisfactory due to variations in the quantity and 
tautness of the twists, and the variations in the tension of the lock 
wire. It has been estimated that annual losses of approximately 
$10,000,000 are incurred just from re-working unacceptable lock wire 
assemblies. 
SUMMARY OF THE INVENTION 
The present invention relates to a device for automatically inserting a 
ferrule over the safety cable, tensioning the wire crimping the ferrule 
onto the safety cable, and cutting off the excess cable. 
The apparatus is used with a safety cable having a ferrule applied to one 
end and which is placed through a plurality of threaded fasteners in the 
pattern. A free end is inserted through a ferrule (held in the apparatus) 
and clamped onto a tension cylinder. Movement of the tension cylinder 
exerts a predetermined tension on the safety cable. The device then crimps 
the ferrule onto the safety cable to retain the safety cable in place at 
the desired tension. The end of the safety cable extending beyond the 
attached ferrule is cut off automatically by the tool to complete the 
process. 
The device eliminates the necessity of hand twisting the lock wire and the 
problems associated with this technique.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A lock wire applied by known techniques is illustrated in FIG. 1 wherein 
threaded fasteners 10, 12 and 14 are engaged with a portion 16 of a 
rotating apparatus (not otherwise shown). The lock wire 18 comprising two 
strands 18a and 18b twisted together at one end are separated such that 
strand 18a passes through a transverse opening in fastener 10 while strand 
18b passes around the exterior of the fastener 10. The strands are twisted 
together on the opposite side of fastener 10 and pass through a transverse 
opening formed in fastener 12. The lock wire 18 continues until the last 
fastener, in this particular instance fastener 14, whereupon one strand 
passes through a transverse opening in the fastener, while the other 
strand passes around and contacts the exterior of the fastener. The 
strands are twisted together on the opposite side of the fastener 14. 
FIG. 2 illustrates a safety cable system applied using the apparatus 
according to the present invention. Threaded fasteners 10, 12 and 14 are 
once again engaged with the machinery portion 16. Lock wire 20 comprises a 
multi strand cable having a ferrule 22 affixed to end 20a. Safety cable 20 
passes through transverse openings formed in the threaded fasteners 10, 12 
and 14 until ferrule 22 bears against one side of fastener 10. At this 
point, ferrule 24 is inserted over the end of cable 20 against the side of 
fastener 14, a tension is applied to the safety cable 20 and the ferrule 
24 is crimped onto the safety cable such that it bears against a side of 
the fastener 14. Safety cable 20 is then automatically trimmed. The 
pre-determined is tension is maintained in safety cable 20 by the contact 
of ferrules 22 and 24 with the sides of the threaded fasteners 10 and 14, 
respectively. 
The device for applying tension to the safety cable and applying the 
ferrule can be seen best in FIG. 3 and comprises a tension cylinder 26, a 
valve assembly 28 and a tension piston 30 slidably mounted in the tension 
cylinder and having a portion extending exteriorly of the tension cylinder 
26 upon which is mounted wire gripper 32. Outer tube 34 extends generally 
concentrically through the tension cylinder 26 and the tension piston 30, 
and has crimping head 36 attached to its distal end. Fitting 38 attaches 
the valve assembly 28 to a source of pressurized fluid, while valve 
actuator button 40 actuates the valve of the valve assembly 28. 
Although the tool according to the present invention has been successfully 
operated and will be described as using compressed air as the pressurized 
fluid, it is to be understood that other pressurized fluids may be 
utilized without exceeding the scope of this invention. 
A longitudinal cross-sectional view of the tension cylinder 26, the tension 
piston 30, the outer tube 34 and the crimping head 36 is illustrated in 
FIG. 4. As can be seen, tension piston 30 is slidably mounted within 
tension cylinder 26. Tension piston 30 has a piston portion with a first 
face 30a and a second face 30b located on opposite sides, as well as a 
portion which extends exteriorly of the tension cylinder 26. 
Wire gripper 32 is fixedly attached to the exterior end of the tension 
piston 30. As illustrated in FIGS. 6 and 7, wire gripper 32 defines an 
opening 42 which slidably accommodates the end of the tension piston 30. 
The wire gripper 32 may be fixedly attached to the tension piston 30 by 
set screw 44 or similar means. Wire gripper 32 defines a longitudinally 
extending slot 46 passing inwardly from one side and has mounted on its 
rear portion, a gripper plate 48 such that a portion of gripper plate 48 
extends over the rear of the slot 46. An edge 48a of the plate 48 is 
tapered with respect to the sides of the slot 46 such that a safety cable 
inserted into the slot 46 from the open side and urged toward the center 
of the gripper 32 will be gripped by the edge 48a of the plate 48. 
A guide tube 50 is concentrically arranged within the outer tube 34, 
tension cylinder 26 and the tension piston 30, and extends substantially 
from the rear portion of the tension cylinder 26 to the gripping head 36. 
Guide tube 50, which may be formed of brass or similar material, slidingly 
receives crimping piston 52 in its interior. The dimensions of the 
exterior of crimping piston 52 and the interior of guide tube 50 are such 
that crimping piston 52 will readily slide within the guide tube, but will 
not allow the passage of a significant amounts of pressurized air between 
them. It may also be possible to use a seal attached to the crimping 
piston 52 to slidably seal against the inner surface of guide tube 50. 
Guide tube 50 is also concentrically arranged within outer tube 34 so as to 
define an annular space there between. This annular space communicates 
with a first passage 54 defined by the tension cyliner 26 as illustrated 
in FIG. 24. Passageway 54 also provides communication with the interior of 
the tension cylinder 26 such that pressurized air passing through this 
passage 54 will act on first fact 30a of tension piston 30. Since passage 
54 also communicates with the annular space between outer tube 34 and 
guide tube 50, pressurized air will also enter this space and communicate 
with the interior of the guide tube 50 via a plurality of holes 56 formed 
near the cutting head end of guide tube 50. Pressurized air passing 
through passage 54, and the annular space, holes 56 and the interior of 
guide tube 50 will act on a first end 52a of the crimping piston 52. 
Tension cylinder 26 defines a second passage 58 which communicates with the 
interior of tension cylinder 26 such that pressurized air passing through 
passage 58 will act on the second face 30b of tension piston 30. As also 
illustrated in FIG. 4, second passage 58 communicates with the interior of 
the guide tube 50 via slot 64, so that any pressurized fluid within this 
passage will also act on the second end 52b of crimping piston 52. 
FIGS. 8 and 9 illustrate rear and front views of a tension cylinder end 
plate 60, the cross-sectional side view of which is illustrated in FIG. 4. 
FIG. 8 illustrates the rear view end plate 60 (when viewed in the 
direction or arrow 62 in FIG. 4), while FIG. 9 illustrates the opposite or 
front side of the end plate. AS seen in FIG. 9, the front face of end 
plate 60 defines a slot 64 which facilitates communication between the 
passage 58 and the interior of guide tube 50. The front face also defines 
an opening 66 which communicates with passage 54. On the opposite, or 
rear, side of end plate 60, opening 68 communicates with slot 64, while 
opening 66 communicates with slot 70. 
Valve assembly 28 attaches to the end of the tension cylinder 26 and the 
end plate 60, as illustrated in FIG. 3. Valve assembly 28 is shown in 
detail in FIG. 12 and comprises a valve housing defining outlet ports 72 
and 74 which communicate with openings 68 and slot 70 formed in the rear 
or end plate 60, respectively. A generally vertically oriented spool 
assembly 75 is slidably mounted in valve assembly 28, such that 
pressurized fluid inlet port 76, which is attached to a source of 
pressurized air via fitting 38, selectively communicates with either 
outlet port 72 or outlet port 74. Ports 78 and 80 also formed as part of 
the valve housing serve as return vents and may be open to atmospheric 
pressure. 
Valve assembly 75 may comprise a spool valve having lands 82 and 84 
sealingly slidable against the inner surface of opening 86 formed in the 
valve housing. Spring 88 bears against the lower land 84 so as to urge the 
valve assembly 85 upwardly to the position shown in FIG. 12. In this first 
or normal position, the pressurized air inlet 76 communicates with outlet 
port 74 while port 72 is vented through port 78. When the valve assembly 
75 is pushed downwardly via actuator button 40, land 82 will prevent fluid 
communication between inlet port 76 and outlet port 74. This movement will 
also move land 84 downwardly so as to allow communication between the 
inlet port 76 and the outlet port 72. In this downward position, outlet 
port 74 will then be vented through port 80. 
As can be seen in FIGS. 4 and 5, crimping head 36 defines a generally 
triangularly shaped opening 90 which may extend only partially through the 
height of the crimping head 36. Opening 92 extends from the bottom of 
opening 90 to the opposite side of the crimping head 36 to facilitate the 
passage therethrough of the lock wire. 
A crimping punch 94 is operatively associated with the crimping head 36 and 
extends through the crimping head 36 such that an end portion 94a extends 
into the opening 90. An opposite end of the crimping punch 94 extends into 
the interior of the guide tube 50. The crimping punch 94 is readily 
slidable within the guide tube 50 as well as the crimping head 36 such 
that the impact force exerted on the crimping panel 94 by the crimping 
piston 52 will push the crimping punch 94 into a ferrule held in opening 
90 with sufficient force to permanently deform the ferrule and attach it 
to a safety cable. 
The crimping punch 94 also serves as a means to hold a ferrule in the 
opening 90 with sufficient frictional, non-deforming force to enable the 
tool to be manipulated into any position without the ferrule falling out 
of the opening 90. When ferrule 96, illustrated in dotted lines in FIGS. 4 
and 5, is manually inserted into the opening 90, it bears against end 
portion 94a of the crimping punch 94 such that the crimping punch 94 is 
urged slightly attached to the shank of the crimping punch 94 is moved in 
resilient contact with the end of the crimping head 36. Resilient sleeve 
98 resiliently urges crimping punch 94 towards the left, as viewed in 
FIGS. 4 and 5, with sufficient force to hold the ferrule 96 within the 
opening 90, but with a force insufficient to cause any deformation of the 
ferrule. Thus, the ferrule is frictionally retained between the end 94a of 
the crimping punch 94 and the two side walls of the generally triangularly 
shaped opening 90. 
The tool according to the invention also provides means to retain the 
crimping piston 52 in a retracted position displaced away from crimping 
punch 94. This position is generally indicated in FIG. 4 and is toward the 
rear end of the tension cylinder 26. As illustrated in this figure as well 
as in FIG. 10, crimping piston 52 defines an annular groove 52c extending 
around its periphery near second end 52b. Groove 52c is adapted to be 
engaged by a plurality of screw retainers 100 that extend through the wall 
of the rear portion of tension cylinder 26. One of these screw retainers 
is illustrated in FIG. 11 and comprises a threaded shank portion that is 
threadingly engaged with a wall of the tension cylinder 26 and a slotted 
head portion accessible from the exterior of tension cylinder 26 so that 
the radial position of the screw retainer may be readily adjusted merely 
by threading and unthreading its relative to the tension cylinder 26. The 
radial inner end portion of the screw retainer element 100 has a spring 
biased ball 102 that is biased in a radially inward direction, as viewed 
in FIG. 11, but which may be radially displaced in an outward direction. 
As is well known in the art, these retaining elements may be radially 
positioned within the tension cylinder 26 such that the end with the ball 
102 extends through the guide tube 50 into the interior of the guide tube 
50. When balls 102 engage groove 52c, the crimping piston 52 is retained 
in its retracted position. As will be described in more detail 
hereinafter, the fluid pressure acting on the rear portion 52b will 
initially be insufficient to overcome the retaining force exerted on 
crimping piston 52 by the screw retainer 100. However, when the pressure 
acting on end 52b reaches a predetermined value, it overcomes the 
retaining force and forces the crimping piston 52 along guide tube 50 into 
contact with the crimping punch 94 with sufficient force to deform the 
ferrule 96 and lock it onto the lock wire. 
The operation of the tool will now be described with particular reference 
to FIGS. 13, 14 and 15. As illustrated in FIG. 13, when valve element 75 
is in its normal position, inlet port 76, which is connected to a source 
of pressurized fluid 104 communicates with outlet port 74. This applies 
pressurized air to passage 54 through slot 70 and opening 66 such that the 
pressurized fluid acts on side 30a of tension piston 30, thereby urging 
the tension piston 30 toward the left as viewed in FIGS. 13 and 4 until 
tension piston 30 reaches an extreme position. The fluid pressure also 
acts on the first end 52a of the crimping piston 52 to urge it toward the 
right, as viewed in FIGS. 4 and 13 with sufficient force such that groove 
52c will be engaged by the balls 102 of the locking elements 100. The air 
within the interior of guide tube 50 on the opposite side of piston 52 as 
well as in tension cylinder 26 on the opposite side of tension piston 30 
will be vented to atmosphere via passage 58, slot 64, opening 68 and valve 
ports 72 and 78. 
When tension cylinder 30 reaches its most extreme extended position and 
crimping piston 52 is retained in its retracted position, as illustrated 
in FIG. 4, the tool is ready for use. A ferrule is manually inserted into 
opening 90 and, as previously discussed, is retained therein by frictional 
contact with crimping punch 94. The tool may be manipulated such that lock 
wire 20 passes through the ferrule, retained in opening 90, and opening 
92, as illustrated in FIG. 15. After the safety cable 20 has been inserted 
through the ferrule and the opening 92, the distal end is placed into and 
gripped by wire gripper 32. The tool is then positioned such that the 
gripping head 36 is against the side of the fastener 14 and valve actuator 
button 40 is manually depressed. This moves the lands 82 and 84 to the 
positions shown in FIG. 14. Thus, pressurized air inlet 76 now 
communicates with passage 58 through valve outlet port 72 opening 68 and 
slot 64. The pressurized air acts on face 30b of tension piston 30 to urge 
it toward the light as viewed in FIGS. 4 and 14. 
Pressurized air also acts on the second end 52b of crimping piston 52. 
However, the retaining elements 100 are now engaged with the groove 52c 
and prevent any movement of crimping piston 52. Movement of tension piston 
30 continues until the wire 20 has been tensioned to a predetermined 
amount. At this time movement of the tension piston 30 ceases thereby 
causing the pressure acting on end 52b of the crimping piston 52 to 
increase. This increase in pressure subjects the crimping piston 52 to 
forces sufficient to overcome the retaining elements 100, thereby urging 
crimping piston 52 rapidly toward the left, as illustrated in FIGS. 4 and 
14 through guide tube 50 and into contact with the crimping punch 94. The 
impact between the crimping piston 52 and the crimping punch 94 is such 
that crimping punch 94 deforms the ferrule 96 and locks it onto the lock 
wire 20. 
Once the crimping operation has been completed, the push button 40 is 
released thereby returning the lands 82 and 84 to their positions shown in 
FIG. 13. This allows the pressurized air to return the crimping piston 52 
to its retracted position and to also move the tension piston 30 to its 
initial, extended position. The safety cable extending between the opening 
92 and the wire gripper 32 may then be cut off and the tool removed. The 
frictional force exerted on the ferrule by the crimping punch 94 is 
insufficient to dislodge it from the safety cable after it has been 
crimped. Once the tool had been removed, the tension piston 30 and the 
crimping piston 52 are in their positions ready for a subsequent crimping 
operation. 
While the wire gripper 32 has been shown to be oriented such that it grips 
a wire after having passed through the ferrule, it should be understood 
that both the wire gripper 32 as well as the tension piston 30 may be 
rotated about the longitudinal axis of the tool so as to achieve any 
desired orientation of the wire gripper. Then length and size of the 
crimping head and the outer tube may be made to any dimension so as to 
facilitate the application of ferrules and lock wires to positions that 
were heretofore rendered inaccessible by known lock wire techniques. 
The foregoing description is provided for illustrative purposes only and 
should not be construed as in any way limited this invention, the scope of 
which is defined solely by the appended claims.