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For removing the insulation, the following tools may be used as auxiliary means:
- Cable strippers
- Automatic deinsulating tongs
- Thermal deinsulating device
- Deinsulating fixtures
Removing the sheath insulation
- Cutting the rubber sheath in between the cores until it can be taken hold of by hand.
- Ripping the rubber sheath apart up to the given measure.
- Cutting the sheath insulation carefully all around.
Figure 6 Stripping of a light
rubber hose cable
1 notching the rubber coating between the cores,
2
thearing the rubber sheath apart,
3 cutting off the sheath insulation
carefully
Make sure that the core insulation is not cut when removing the sheath insulation!
Removing the core insulation
- By the cable stripper
. Cutting off one half of the insulation by a longitudinal cut by the knife (stripping off).
. Cutting off the second half by a longitudinal cut, too.
Figure 7 Stripping the core
insulation by the electrician's knife
Pay attention to the correct handling of the knife, because the fine-wire conductor might be damaged by a wrong touch of the knife and break in the course of further working.
- By the deinsulating tongs
. With movable deinsulating edges, these are adapted to the cross-section of the conductor.
. The conductor is put into the pair of jaws of the deinsulating tongs and the tongs are actuated.
Figure 8 Stripping the core
insulation off with the help of the wire strippers
1 clamping jaw,
2 stripping jaw
Figure 9 Wire strippers
1 cutting edge for various diameters,
2 clamping
jaw,
3 conductor
Do only use the cutting edge assigned to the cross-section of the conductor and marked accordingly. Conductor cross-sections exceeding 6 mm2 are deinsulated by the cable stripper.
By the thermal deinsulating device
- Switching the device on.
- Cleaning the resistance wire curl.
- Selection of temperature. (Core insulation must only melt, not burn.)
- Removing the core insulation by the deinsulating handle of the device.
- Switching the device off and pulling the plug after use.
The core insulation of heat-proof silicone and rubber-covered cables is not removed by thermal deinsulating devices due to their heat resistance and the strong smell that would develop.Make sure that the ends of the conductors are always cleanly deinsulated. The conductor must neither show rests of the insulation nor indentations.
Removal of yarn wrappings from cables
- Cutting the yarn wrapping open.
- Prevent the yarn wrapping from undoing by ligaturing.
- Cutting the yarn wrapping open and removing it.
- Proceed as described above.
Why must mobile cables get a special treatment before being connected?
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What operations have to be done before the cable is connected?
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For
- cleaning the conductor
- tinning the conductor
- soldering on of cable eyes
- pressing on of cable eyes
the handbook of "Making Permanent Joints" should be used.
After cleaning - also of the internal layers - the end of the conductor must be accurately retwisted clockwisely.Tinning of cables and the use of sweating thimbles has to be avoided to the farest possible extent.
These methods should be applied only in special cases, for instance if and when eyes must be bent or pressing cable thimbles cannot be used.
Figure 10 Tinning of a
conductor
Figure 11 Soldering of a cable
eye
1 fire-resistant wrapping,
2 tin-base
solder,
3 nozzle of the sounder,
4 cable eye
Figure 12 Cable eye soldered
on
1 plastic hose or tape
Figure 13 Pressing inserts for
V-shaped grooving or hexagonal pressing
Figure 14 Putting a shaped
conductor into the cable eye
1 binding for aerial line
Figure 15 Cable eye before and
after the pressing operation
Figure 16 Making the V-shaped
grooving at the top and bottom side of the cable eye
1 top pressing insert,
2 bottom side pressing
insert,
3 V-shaped grooving (left: D-shape, right: C-shape of the
cable eye)
Bending of eyes
- Twisting of the cleaned appropriately prepared core.
- Bending the eye with the help of an arbor or round-nose pliers. or
- Dividing the conductor and twisting it separately.
- Putting it around an arbor from both sides and joining the two ends by twisting them together.
When bending eyes, make sure that the internal diameter of the eye is 0.1 to 0.2 mm greater than the diameter of the locking screw or bolt.
Figure 17 Bending of eyes
1 twisting of the cleaned conductor,
2 eye bent
over an arbor,
3 completed eyes after the conductor having been
divided up and twisted separately
After this, the end of the conductor and the eye are tinned by soldering iron tin bath.
- If the twisted conductors are tinned first, they have to be shaped to an eye by round-nose pliers afterwards.
When tinned in a tin bath, the prepared and flux-coated end of the conductor is dipped into the fluid tin to approximately 3/4 of its lengths.
The process of tin-coating is completed, if and when the end of the conductor and the eye have a uniform, tin-covered surface.
Putting on of conductor end sleeves and contact eyes
- If not other forms are required, this technique should be preferred.
- It can be used with cross-sections up to 16 mm2.
What are the advantages of this technique compared with tin-coating?
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Sequence of operations for working conductor end sleeves
- The wires are stripped.- The wide end of the sleeve is shoved on the blank end of the conductor.
- The end of the conductor together with the conductor end sleeve is put into the clamping fixture.
- Clamping by fastening the clamping screw by the required contact pressure.
Special fields of use of conductor end sleeves
- At terminal points with two cables, one conductor end sleeve of the appropriate size can be drawn over the two wires.- Circuit bridges which must not be broken when being disconnected can be twisted and provided with a conductor end sleeve.
- Conductor of less than 0.75 mm2 in cross-section are stripped over such length that they can be folded up two or three times and then put into a conductor end sleeve of a corresponding size.
- Size conductor end sleeves and contact eyes are not marked, attention must be payed that the conductor cross-sections and the end sleeves are fitting together.
Assignment of conductor end sleeves to the conductor cross-sections
(Cross-sections indicated in mm2, main dimensions and length in mm)
|
Conductor |
Conductor |
Main dimension |
Length | |
| |
|
Internal diameter |
External diameter | |
|
0.5 |
1.3 |
1.3 |
1.8 |
12 |
|
0.75 |
1.3 |
1.3 |
1.8 |
12 |
|
1.0 |
1.5 |
1.5 |
2.2 |
12 |
|
1.5 |
1.8 |
1.8 |
2.6 |
12 |
|
2.5 |
2.2 |
2.2 |
3.4 |
12 |
|
4.0 |
2.9 |
2.9 |
4.1 |
12 |
|
6.0 |
3.5 |
3.5 |
4.8 |
16 |
|
10.0 |
4.4 |
4.4 |
5.7 |
16 |
|
16.0 |
.5.5 |
5.5 |
6.8 |
16 |
Sequence of operations with the use of contact eyes
- Stripping the wire.
- Prebending the stripped conductor over an arbor.
- Pressing the contact eye on the prepared conductor.
Figure 18 Prebending of the
conductor over an arbor
1 arbor, 2 contact eye
- Putting the conductor with the contact eye in the mould of the pressing device or in the pressing pliers.
The conductor must be placed into the slot of the contact eye and in the slot of the matrix of the pressing device.
- Pressing on by pressing device or pressing pliers.
Figure 19 Principle of the
pressing-on of contact eyes
1 punch, 2 conductor, 3 contact eye, 4 matrix, 5 contact eye with conductor after having been pressed in the matrix
Figure 20 Pressing-on of
contact eyes by the pressing tongs
1 completed contact eye
All individual wires of the flexible conductor must be held by the sleeve or by the eye.
Why should to cables, which shall be connected to mobile equipment, preferably conductor end sleeves and contact eyes be attached or cable eyes be pressed on?
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