Note: Descriptions are shown in the official language in which they were submitted.
lO~
The invention relates to apparatus intended for repair-
ing industrial rubber goods and particularly to a cable repair
vulcanizing press.
The invention may also be used for heating thermal
setting pipes which envelope damaged portions of flexible cables
and for spot vulcanization of other goods.
It is often necessary to do in situ repairs to flexible
cables intended to feed power to travelling current receivers,
for instance in opencast or underground mining.
Cable repair in mines with a dangerously high concen-
tration of gas or dust places more stringent requirements upon
explosion proofness and fire safety of the cable repair vulcan-
izing presses.
Known in the art are cable repair vulcanizing presses,
wherein moulds are heated with the aid of high-ohmic wire
resistors. Heat from the resistors is transferred through an
electric insulation to the housing bf the cable repair vulcan-
izing press and to mould half sections positioned within
corresponding recesses in the housing.
Main disadvantages of such cable repair vulcanizing
presses are the following:
- A large mass per unit length of the cable to be
repaired, in particular for an explosion-proof model of the cable
repair vulcanizing press. This is explained by the fact that
the housing of the cable repair vulcanizing press is used not
only for accommodating wire resistors but also for exerting
adequate pressure upon the cable being repaired, i.e. the
cable repair vulcanizing press is subjected to considerable
mechanical loads and for this reason it should be made sufficient-
ly strong.
- Low reliability on a_count of a short service life
of the resistors which stems from the oxidation of metal and
--2--
1094279
formation of minute cracks.
- Low heat efficiency which is accounted for by the
fact that in such cable repair vulcanizing presses heat transfers
from a heat source not only to the mould half sections but to
the whole housing of the cable repair vulcanizing press as well.
Difficulty of providing for fire safety and explosion
proofness, which results from the following reasons. The
temperature of heating the mould half sections in vulcanization
reaches 150 to 160C; difference in temperature between the
mould half section and the housing is liable to fluctuate
from 10 to 25C according to gaps which set up large thermal
resistance. Thus, the temperature of the housing under the
mould half sections turns out to be 160 to 185C and in some
cases even higher. In accordance with the acting regulations,
however, the tem~erature of the exterior surface of explosion-
proof shells should not exceed 200C in long-duration operation.
Also, it is to be noted that the temperature control of the
mould half sections of the cable repair vulcanizing press is
often effected with the aid of thermal switch relays which are
lacking in high reliability. Scatter of operational values
or failure in such relays are liable to heat the cable repair
vulcanizing press to temperatures in excess of 200C which is
impermissible in mines with a dangerously high concentration
of gas or dust.
Thus, it is extremely difficult to ensure fire safety
of such cable repair vulcanizing presses.
In addition, the heat Lransfer from the resistor
to the mould half section causes considerably high thermal
resistances and, consequently, when the mould half section is
heated to 150 to 160C the temperature of a high-ohmic resistor
reaches 300 to 400~.
It is extremely difficult to ensure explosion
~)94279
proofness of a heat source heated to such a temperature.
It is not accidental that in many countries the use of
vulcanizing presses incorporating resistance-type heaters in
mines with dangerously high concentration of yas or dust is
prohibited.
In some cases the housing and mould half sections are
made of aluminium alloys which reduces to some extent the
mass of the vulcanizing press. But this measure does not help
in avoiding other disadvantages of the vulcanizing presses
incorporating resistance-type heaters. It should also be noted
that it is not advisable to use aluminium or alloys thereof
for explosion-proof models because a steel object accidentally
dropped onto a shell of aluminium alloys, is liable to cause
sparking and hence the inflammation of methan.
Thus, vulcanizing presses incorporating resistance-type
heaters are characterized by a number of serious disadvantages
which constitute a great impediment to the utilization of the above
vulcanizing presses and in some cases rule out such utilization
at all.
There is known in the art an induction vulcanizing press
as disclosed in U.S.S.R. Inventor's Certificate No. 131005,
comprising two inductors each consisting of three-leg core
and coils placed on each of the legs carrying mould half
sections mounted thereon. The vulcanizing press is provided
with an arrangement adapted to force the mould half sections
against the inductors and is mounted on a specially designed
carriage.
However, the above vulcanizing press is characterized
by a great mass per unit length of a cable to be repaired
which derives from the fact that:
- the vulcanizing press comprises two inductors,
which requires two inputs and complicates the provision for
1094279
explosion proofness.
- the inductor is rather complicated and consists of
three coils and a core, the compression force being transferred
through cores which requires high mechanical strength.
The principal object of the present invention is the
provision of a cable repair vulcanizing press which allows for
the heating of both mould half sections from one inductor.
Another object of the invention is the provision of
a cable repair vulcanizing press having an overheat protection
device adapted to protect the vulcanizing press against over-
heat resulting from a long-duration operation of a magnetic
circuit partially or completely opened.
One more object of the invention is the provision of
a cable repair vulcanizing press which is protected against
overheat resulting from a long duration operation of a maynetic
circuit partially or completely opened to ensure explosion
proofness of such vulcanizing press in mines.
A further object of the invention is the provision
of a cable repair vulcanizing press which ensures the temperature
control of mould half sections in operation.
Yet another object of the invention is the provision
of a cable repair vulcanizing press whose split-mould has a
varying cavity adapted to receive cables to be repaired of
various diameters.
These and other objects are attained in a vulcanizing
press comprising a split mould adapted to receive a cable to
be repaired, and an inductor having a multi-leg core intended
to generate and transmit an alternating magnetic flux to the
split mould, wherein the multi-leg core and the split mould
are mutually arranged so that the separating line of the
split-mould lies in the plane of the magnetic flux passing
in the legs of the multi-leg core.
10~ 79
Such arrangement of the mould half sections ensures
uniform heating thereof from one inductor.
According to one embodiment of the invention, the
multi-leg core has three legs, an induction coil being disposed
on the middle one.
In order to increase the effective length of the split
mould it is expedient that a multi-leg core comprises an uneven
number of legs, but more than three, each even leg carrying an
induction coil connected in combination with other induction
coils into an electric circuit so that the magnetic fluxes of
the cores orientated between said induction coils are deducted.
To prevent prolonged work of the vulcanizing press
with the magnetic circuit thereof being partially or completely
opened, one of the legs conducting an effective magnetic flux
carries an interlocking coil inductively connected to one of
the induction coils to supply a pulse for deenergizing the
vulcanizing press, with the mould half section being removed
or displaced.
To improve the reliability of interlocking the supply
circuit of the vulcanizing press with the mould half section
being removed or displaced the vulcanizing press is provided
with compensating coils arranged between adjacent core legs
and the interlocking coil in perpendicular planes which pass
through the vertical axes of the legs and of the interlocking
coil, said compensating coils being connected to each of the
circuits of the interlocking coil in series and opposing
relationship.
In order to control the temperature of heating of the
split mould by varying the magnetic flux passing therethrough,
it is advisable to mount a shunt consisting of a plurality
of electrical steel sheets and placed parallel to the legs
of the core on the external surfaces of mould half sections.
1094;2~9
According to one embodiment of the invention, the split
mould is provided with an insert made of a material whose
coefficient of heat conduction is sufficient to level off the
temperature of heating of the split mould. A copper insert
conforms to the above requirements most of all.
If desired, a construction with one mould half section
fixed on the legs of the core is possible.
The invention will now be explained in greater detail
with reference to embodiments thereof which are represented
in the accompanying drawings, wherein:
Fig. 1 is a general view of the cable repair
vulcanizing press;
Fig. 2 is a section taken along line II-II in Fig. l;
Fig. 3 is an electric diagram of the interlocking
circuit;
Fig. 4 is an inductor with a partially sectioned
induction coil, according to another em~odiment of the invention;
Fig. 5 is a section taken along line Y-Y in Fig. 4;
Fig. 6 is an electric diagram of the interlocking
circuit of the vulcanizing press, according to another
embodiment of the invention;
Fig. 7 is a diagrammatic representation of the inductor
with the split mould according to one more embodiment of the
invention;
Fig. 8 is a diagrammatic representation of the inductor
with the split mould in position, according to one more
embodiment of the invention;
Fig. 9 is a view of the inductor in axial direction
with the split mould in position according to one more embodiment
of the invention;
Fig. 10 is a mould half section in axial direction
with inserts in position;
109~Z79
Fig. 11 is a view of the mould half section according
to Fig. 10, taken in the direction of arrow A.
Reference is now made to the drawings and in particular
to Figs. 1 and 2 showing a cable repair vulcanizing press
comprising a split mould I consisting of two half sections 2
and 3 and adapted to receive a cable to be repaired, an
inductor having a multi-leg core 4 and an induction coil 5
mounted on one of the legs of the core 4. The inductor is
intended to generate and transmit an alternating magnetic flux
to the split mould.
According to the invention, the multi-leg core 4 and
the split mould I are mutually arranged to that the separating
line of the split mould lies in the plane of the magnetic flux
passing in the legs of the core 4. From the standpoint of
operation requirements, the most suitable is a vertical
arrangement of the legs in the core 4. With such arrangement,
the magnetic flux generated in the legs is oriented in a vertical
plane and, hence, the separating line of the split mould also
lies in the vertical plane, as is illustrated in Fig. 1.
According to an embodiment of the invention illustrated
in Figs. 1 and 2 the cable repair vulcanizing press comprises
a three-leg core 4, such as a laminated core, having an induction
coil 5 mounted on the middle leg of the core 4. The inductor
is placed within a housing 6 whose inner space is confined
by a cover 7 made of an insulating material. The housing 6
of the vulcanizing press is welded of sheet steel or cast of
light alloys. The ends of the legs of the core 4 extend through
the cover to the outside; these ends carry detachable half
sections 2 and 3 of the split mould I. Both half sections 2 and
3 are forced together by joining stirrups 8. The half sections
2 and 3 are made of a magnetically soft steel. The joining
stirrups 8 are passed between the legs of the core 4. As a result,
--8--
~0~ ~79
the half sections of the split mould I do not impart the
compression force to the core 4.
To ensure the explosion proofness of the vulcanizing
press, the interior space of the housing 6 is filled with
powdered quartz (for the sake of simplicity not shown), the
thickness of powdered quartz layer being selected in accordance
with the acting regulations for the manufacture of explosion-
proof equipment. The core 4 is manufactured by stamping
electrical steel sheets.
However, it will be clear for those skilled in the art
that the core can be manufactured from U-shaped sections, which
makes it possible to use cold-rolled strips and to decrease
the mass of the core.
In order to prevent long-duration operation of the
vulcanizing press having its magnetic circuit partially or
completely opened, i.e. having its split mould removed or out of
position, in this embodiment provision is made of an interlocking
coil 9 mounted on the extreme leg of the core 4. The interlocking
coil 9 is inductively connected to the induction coil 5 and to
an interlocking unit 10 mounted within the housing 6. Fig. 3
illustrates the electric diagram of the interlocking unit 10
comprising diodes II for rectifying the current, a thyristor 12
connected in parallel with a "start" button of a switch 13, and
a resistor 14.
The coil 5 is connected to a starting mechanism 15 by
means of a connector whose half section 16 is secured on the
housing 6.
It should be noted that the arrangement of the inter-
locking coil 9 along the height of the leg has an appreciable
effect upon the value of the electromotive force induced in said
coil 9 with the magnetic circuit being either closed or opened;
the higher is disposed the interlocking coil 9 on the leg of the
~0~4Z79
core 4, the less are the values of stray fluxes flowing there-
through.
When manufacturing general-purpose vulcanizing presses,
the interlocking coils are arranged as high as possible, as
is illustrated in Fig. 2. The mould half sections being in
position, the effective magnetic flux flows through the inter-
locking coil 9 inducing therein an electromotive force
sufficient for opening the thyristor.
When manufacturing explosion-proof vulcanizing
presses, however, it is necessary to place the interlocking
coil into the powdered quartz at the depth of, say, 14 to 16 mm.
With such an arrangement of the interlocking coil and with the
split mould being removed the stray magnetic flux which is
commesurable with the operation magnetic flux flows through the
core and the coil. This being the case, the electromotive
force induced in the interlocking coil 9 is liable to cause
a current sufficiently strong for opening the thyristor 12
and shunting the "start" button. Thus, the reliability of the
interlocking unit decreases.
As is shown in Figs. 4, 5 the interlocking coil 9 is
arranged on the core carrying the induction coil, which is
dictated by the specific requirement that the conductors of
the interlocking coil 9 should be insulated from the housing
6 without increasing the dimensions thereof. In order to in-
crease the reliability of the interlocking unit in the explosion-
proof model of the vulcanizing press, there are placed
compensating coils 17 between the legs of the core 4 in per-
pendicular planes passing through the axes of the legs and of
the interlocking coil 9. The compensating coils 17 are
connected in series and opened relationship with respect to
the interlocking coil 9 in the circuit of the interlocking unit
(Fig. 6). The number of turns W17 of the compensating coil 17
--10--
10~4279
with respect to the number of turns Wg of the interlocking coil
9 is selected so that with the magnetic circuit being opened,
the electromotive force of the interlocking coil 9, determined
from the formula Eg = -Wg dt~g and the electromotive force
of the compensating coil 17, determined from the formula E17 =
W d ~g are equal, where ~g - is a stray flux flowing
through the interlocking coil and ~ is a stray flux flowing
~17
through the compensating coil.
According to another embodiment of the invention (Fig.
7) the multi-leg core comprises an uneven number of legs, but`
more than three, each even leg carrying an induetion coil 5.
The induction coils 5 are connected into circuit so that the
magnetie fluxes of the cores disposed between the induction
eoils are deducted. With such a construction of the core the
mass thereof ean be deereased due to a lesser number of the core
legs as compared to inductors eomposed of three-leg eores.
This being the case, the eross-seetion of the legs, wherein
the magnetie fluxes are deducted is liable to be comparatively
small.
Inasmueh as the temperature in mines situated in
temperate elimatie zones varies only slightly, the working
eapaeity of the vuleanizing press in ease of modest drop in
ambient temperature ean be provided by means of seleeting a
proper number of turns in the induetion eoil.
However, it is. extremely diffieult to provide for a
temperature of heating of the split mould in mines situated in
elimatie zones whieh are eharaeterized by sharp temperature
drop and in open east mining.
To eontrol the temperature of heating of the split
mould, the vuleanizing press is provided with an electromagnetie
shunt 19 composed of a plurality of eleetrie steel sheets
established on the externalsurfaces of the mould half seetions,
--11--
4Z79
as is illustrated in Figs. 8, 9 according to an alternative
embodiment of the invention. The shunt 19 permits the temperature
of the split mould to be controlled by varying the magnetic
flux, since in this case the effective magnetic flux is divided
into two fluxes, namely: a flux flowing through the magnetic
shunt and a flux flowing through the split mould I. The value
of the magnetic flux flowing through the split mould I can be
selected by varying the position of the electromagnetic shunt 19
with respect to the core 4. When the electromagnetic shunt 19
moves with respect to the core 4 in the plane which is perpen-
dicular to the axis of the induction coil 5, the value of the
magnetic flux flowing through the split mould changes.
The electromagnetic shunt is alternatively arranged on
the external surfaces of the mould half sections, as is
illustrated in Fig. 9 or between the legs of the core 8, as is
illustrated in Fig. 8.
According to an alternative embodiment of the invention
the split mould I is provided with an insert 18 made of a mat-
erial whose coefficient of heat conduction suffices to level off
the temperature of heating of the split mould around the
perimeter and lengthwise thereof. Fig. 10 illustrates the con-
struction of split inserts made of copper and intended both for
levelling off the temperature and for repairing cables of
various cross-section, which is achieved by means of removing or
installing a necessary number of inserts of different cross-
section. This being the case, the necessity of completing the
vulcanizing press with a great number of the split moulds is
excluded.
The above described vulcanizing press is designed for
repairing various-function cables: from low voltage cables
designed for electric wirings to power cables used in excavators,
in which cables voltage reaches 35 kv. The vulcanizing press
-12-
10'~ 1Z79
may be manufactured either stationary or portable.
Herein after there is given a description of main
operations while utilizing the vulcanizing press in those
cases when only the cable shell is damaged, the insulations
of the conductors being intact.
After the damaged portion of the cable has been
prepared for vulcanization, the same is put into the mould half
sections 2 and 3 which are forced together by stirrups 8. By
means of a connector half section the vulcanizing press is
connected to the mains.
Now the "start" button of a switch 13 in the distant
control circuit is pressed. In the coil 5, there passes a
current which creates an alternating magnetic flux in the core 4
and the split mould I. With the split mould I properly
installed in the interlocking coil 9, there is induced an
electromotive force, and current passes which is sufficient
for opening the thyristor 12 and for shunting the "start" button.
If the magnetic circuit is opened, the current value in the
circuit of the coil 9 is not sufficient for opening the thyristor
12. In this case, after releasing the "start" button, the coil
is not energized since the button has not been shunted by the
thyristor.
It is to be noted that the mass of the split mould is
comparatively small and therefore the time of heating thereof
up to a predetermined temperature does not take much time.
As the unvulcanized rubber is being heated the mould
half sections are forced together by means of stirrups. The
damaged section vulcanized, the vulcanizing press is switched
off with the aid of the "stop" button, the mould half sections
2 and 3 are opened and the cable is ready for operation.
If there is no need for the cable to be put into
operation at once, the vulcanizing press is switched off but the
-13-
~094279
split mould is not taken off. In this case the quality of
vulcanization improves due to slowly proceeding processes of
polymerization.
The above described vulcanizing press has the following
advantages:
- small mass per unit length;
- reliability, long service life;
- small time constant for heating and, hence, high heat
efficiency, low consumption of electric power;
- contactless transmission of power, which provides for
higher explosion proofness.
-14-
