GB1588729A

GB1588729A - Cable repair vulcanizing press

Info

Publication number: GB1588729A
Application number: GB4710777A
Authority: GB
Original assignee: KOMMUNAR GOR METAL I
Current assignee: KOMMUNAR GOR METAL I
Priority date: 1977-11-11
Filing date: 1977-11-11
Publication date: 1981-04-29

Description

(54) CABLE REPAIR VULCANIZING PRESS (71) We, KOMMUNARSKY GORNO-METALLURGICHESKY INSTITUT - of Voroshilovgradskoi oblasti, Prospekt Lenina 16, Kommunarsk, Union of the Soviet Socialist Republics, a corporation organised and existing under the laws of the Union of Soviet Socialist Republics, do hereby declare the invention, -for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a cable repair vulcanizing press e.g. for heating thermosetting pipes which envelope damaged portions of flexible cables and for spot vulcanization of other items.

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 concentration of gas or dust places stringent requirements upon explosion-proofness and fire safety of cable repair vulcanizing 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 electrical insulation to the housing of the cable repair vulcanizing press and to mould halves positioned within corresponding recesses in the housing.

Main disadvantages of such cable repair vulcanizing presses are the following: -A large mass of the press per unit length of the cable to be repaired, in particular for an explosion-proof 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 sufficiently strong.

-Low reliability on account of a short service life of the resistors which stems from the oxidation of metal and formation of minute cracks.

-Low heat efficiency, which is accounted for by the fact that in such cable repair vulcanizing presses heat is transferred from a heat source not only to the mould halves 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 halves in vulcanization reaches 150 to 1600C; difference in temperature between the mould halves and the housing is liable to fluctuate from 10 to 25"C according to gaps which set up large thermal resistance. Thus, the temperature of the housing under the mould halves turns out to be 1600C to 1850C and in some cases even higher. In accordance with safety regulations, however, the temperature of the exterior surface of explosion-proof shells should not exceed 200"C in longduration operation.Also, it is to be noted that the temperature control of the mould halves of the cable repair vulcanizing press is often effected with the aid of thermal switch relays which are of insufficiently high reliability. Scatter of operational values or failure in such relays is liable to heat the cable repair vulcanizing press to temperature in excess of 200"C, 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 transfer from the resistor to a mould half causes considerably high thermal resistances and, consequently, when a mould half is heated to 150 to 1600C the temperature of a high-ohmic resistor reaches 300 to 4000. It is extremely difficult to ensure explosion proofness of a heat source heated to such a temperature.

It is no accident that in many countries the use of vulcanizing presses incorporating resistance-type heaters in mines with dangerously high concentration of gas or dust is prohibited.

In some cases the housing and the mould halves 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 explosionproof presses, because a steel object accidentally dropped onto a shell of aluminium alloy is liable to cause sparking and hence ignition of methane.

Thus, vulcanizing presses incorporating resistance-type heaters are characterized by a number of series disadvantages which constitute a great impediment to the utilization of such vulcanizing presses and in some cases rule out such utilization altogether.

An induction vulcanizing press disclosed in U.S.S.R. Inventor's Certificate No.

131005, comprises two inductors, each consisting of a three-leg core and coils placed on each of the legs, carrying mould halves mounted thereon. The vulcanizing press is provided with an arrangement adapted to force the mould halves against the inductors and is mounted on a specially designed carriage. However, this vulcanizing press is characterised by a great mass of the press per unit length of 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 explosionproofness; -the inductor is rather complicated and consists of three coils and a core, the compression force being transferred through the core, which requires high mechanical strength.

The present invention provides a cable repair vulcanizing press comprising a longitudinally split ferromagnetic mould for receiving a cable to be repaired, and an inductor having a multi-leg core and intended to generate and transmit an alternating magnetic flux to the split mould in order to heat the mould, the core and the split mould being mutually arranged so that the plane of separation of the split mould lies in the plane of the magnetic flux passing, in use, in the legs of the core.

The invention will be described further, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a general view of a cable repair vulcanizing press; Figure 2 is a section taken along line II - II in Figure 1; Figure 3 is a diagram of the interlocking electrical circuit; Figure 4 shows an inductor with a partially sectioned induction coil; Figure 5 is a section taken along line V-V in Figure 4; Figure 6 is a diagram of an alternative interlocking circuit of the vulcanizing press; Figure 7 is a diagrammatic representation of an inductor with a split mould, according to another embodiment; Figure 8 is a diagrammatic representation of an inductor with a split mould in position, according to another embodiment; Figure 9 shows an inductor viewed in the axial direction, with the split mould in position, according to another embodiment;; Figure 10 shows a mould half viewed in the axial direction with inserts in position; and Figure 11 is a view of the mould half shown in Figure 10 taken in the direction of arrow A.

The cable repair vulcanizing press illustrated in Figures 1 and 2 comprises a split mould 1 consisting of two halves 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.

The multi-leg core 4 and the split mould 1 are mutually arranged so that the plane of separation 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, a vertical arrangement of the legs in the core 4 is preferable. With such an arrangement, the magnetic flux generated in the legs is oriented in a vertical plane and, hence, the plane of separating of the split mould also lies in the vertical plane, as is illustrated in Figure 1.

In the press illustrated in Figures 1 and 2 the three-leg core 4, a laminated core, has the 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 alloy. The ends of the legs of the core 4 extend through the cover 7 to the outside; these ends carry the halves 2 and 3 of the split mould 1. The halves 2 and 3 are forced together by joining stirrups 8. The halves 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, the halves of the split mould 1 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 being selected in accordance with safety regulations for the manufacture of explosion-proof equipment.

The core 4 is manufactured by stamping .:lectrical 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, provision is made of an interlocking coil 9 mounted on the extreme leg of the core 4. The coil 9 is inductively connected to the induction coil 5 and to an interlocking unit 10 mounted within the housing 6. Figure 3 illustrates the interlocking unit 10, comprising diodes 11 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 plug-and-, socket connector, one member 16 of which is secured on the housing 6.

It should be noted that the position of the interlocking coil 9 along the height of the leg has an appreciable effect upon the value of the electromotive force induced in the coil 9 with the magnetic circuit being either closed or opened; the higher the coil 9 is disposed on the leg of the core 4, the lower are the values of stray fluxes flowing therethrough.

In a general-purpose vulcanizing press, the interlocking coil is arranged as high as possible, as is illustrated in Figure 2. The mould halves being in position, the effective magnetic flux flows through the interlocking coil 9, including 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, when the split mould is removed, the stray magnetic flux which flows through the core and the coil may be commensurate with the operation magentic flux. 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.

In the alternative arrangement shown in Figures 4 and 5, the interlocking coil 9 is arranged on the core leg carrying the induction coil 5, 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 increase the reliability of the interlocking unit in the explosionproof vulcanizing press, compensating coils 17 are placed between the legs of the core 4 in perpendicular planes passing through the axes of the legs and of the interlocking coil 9. The compensating coils 17 are connected in series and opposed relationship with respect to the interlocking coil 9 in the circuit of the interlocking unit (Figure 6).The number of turns Wc of the compensating coil 17 with respect to the number of turns Wi of the interlocking coil 9 is selected so that, with the magnetic circuit being opened, the electromotive force Eo of the interlocking coil 9, determined from the formula Ei = - Wi.d < fti/dt, equals the electromotive force Ec of the compensating coil 17, determined from the formula Ec = - Wc.dc/dt, where f i is the stray flux flowing through the interlocking coil and 4)c is the stray flux flowing through the compensating coil.

According to another embodiment (Figure 7) the multi-leg core comprises an uneven number of legs, but more than three, each even leg carrying an induction coil 5.

The induction coils 5 are connected into circuit so that the magnetic fluxes of the core legs disposed between the induction are deducted (being of opposite sense).

With such a construction the mass of the core can be decreased as compared to inductors composed of three-leg cores. This being the case, the cross-section of the legs wherein the magnetic fluxes are deducted is capable of being comparatively small.

Inasmuch as the temperature in mines situated in temperate climatic zones varies only slightly, the working capacity of the vulcanizing press can be ensured by providing an appropriate number of turns in the induction coil. However, it is extremely difficult to ensure a given temperature of heating of the split mould in mines situated in climatic zones which are characterized by sharp temperature changes and in open cast mining.

To control the temperature of heating of the split mould, the vulcanizing press may be provided with an electromagnetic shunt 19 composed of a plurality of electric steel sheets adjacent the mould halves, as is illustrated in Figures 8 and 9. 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 flus is divided into two fluxes, namely: a flux passing through the magnetic shunt and a flux passing through the split mould 1. The value of the magnetic flux through the split mould 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 perpendicular to the axis of the induction coil 5, the value of the magnetic flux passing through the split mould changes.

The electromagnetic shunt is arranged either on the external surfaces of the mould halves, as illustrated in Fig. 9, or between the legs of the core 4, as is illustrated in Fig.

8.

Each half of the split mould 1 may be provided with one or more inserts 18 made of a material whose coefficient of heat conduction suffices to level off the temperature of heating of the split mould around the perimeter and lengthwise thereof. Figs. 10 and 11 illustrate the construction of split inserts 18 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 difference crosssection. This being the case, there is no need to provide a great number of split moulds of different size for use with the vulcanizing press.

The above-described vulcanizing press is designed for repairing various cables: ranging from low voltage cables designed for electric wirings to power cables used in excavators, in which cables voltage reaches 35 kV. The vulcanizing press may be either stationary or portable.

Hereinafter there is given a description of the main operation in 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, it is placed between the mould halves 2 and 3, which are then forced together by means of the stirrups 8. By means of a connector member the vulcanizing press is connected to the mains.

Now the "start" button of the switch 13 in the remote 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 1. If the split mould 1 is properly installed an electromotive force is induced in the interlocking coil 9 and current passes which is sufficient for opening the thyristor 12 and for shunting the "start" button. Conversely 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 heating it up to a predetermined temperature does not take much time.As the rubber is being heated and vulcanized the mould halves are forced together by means of the stirrups 8.

The damaged section having been vulcanized, the vulcanizing press is switched off with the aid of the "stop" button, the mould halves 2 and 3 are separated 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 split mould is not dismantled. In this case the quality of vulcanization is improved owing to slowly proceeding processes of polymerization.

The above-described vulcanizing press has the following advantages: - small mass per unit length of mould; - reliability, long service life; - small time constant for heating and, hence, high heat efficiency, low consumption of electric power; - contactless transmission of power, which enhances explosion-proofness.

WHAT WE CLAIM IS: 1. A cable repair vulcanizing press comprising a longitudinally split ferromagnetic mould for receiving a cable to be repaired, and an inductor having a multileg core and intended to generate and transmit an alternating magnetic flux to the split mould in order to heat the mould, the core and the split mould being mutually arranged so that the plane of separation of the split mould lies in the plane of the magnetic flux passing, in use, in the legs of the core.

2. A press as claimed in Claim 1, wherein the core comprises an uneven number of legs, the or each even leg carrying an induction coil.

3. A press as claimed in Claim 2, wherein the core comprises more than three legs, the induction coils being arranged so that the magnetic fluxes due to them have opposite senses in the or each leg disposed between the induction coils.

4. A press as claimed in Claim 2, wherein, on one of the legs through which an effective magnetic flux passes in use there is disposed an interlocking coil which supplies a signal for deenergizing the press if the split mould is removed or displaced.

5. A press as claimed in Claim 4, wherein between the legs of core, in perpendicularly disposed planes which pass throught the vertical axes of the legs and of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. to be controlled by varying the magnetic flux, since in this case the effective magnetic flus is divided into two fluxes, namely: a flux passing through the magnetic shunt and a flux passing through the split mould 1. The value of the magnetic flux through the split mould 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 perpendicular to the axis of the induction coil 5, the value of the magnetic flux passing through the split mould changes. The electromagnetic shunt is arranged either on the external surfaces of the mould halves, as illustrated in Fig. 9, or between the legs of the core 4, as is illustrated in Fig. 8. Each half of the split mould 1 may be provided with one or more inserts 18 made of a material whose coefficient of heat conduction suffices to level off the temperature of heating of the split mould around the perimeter and lengthwise thereof. Figs. 10 and 11 illustrate the construction of split inserts 18 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 difference crosssection. This being the case, there is no need to provide a great number of split moulds of different size for use with the vulcanizing press. The above-described vulcanizing press is designed for repairing various cables: ranging from low voltage cables designed for electric wirings to power cables used in excavators, in which cables voltage reaches 35 kV. The vulcanizing press may be either stationary or portable. Hereinafter there is given a description of the main operation in 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, it is placed between the mould halves 2 and 3, which are then forced together by means of the stirrups 8. By means of a connector member the vulcanizing press is connected to the mains. Now the "start" button of the switch 13 in the remote 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 1. If the split mould 1 is properly installed an electromotive force is induced in the interlocking coil 9 and current passes which is sufficient for opening the thyristor 12 and for shunting the "start" button. Conversely 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 heating it up to a predetermined temperature does not take much time.As the rubber is being heated and vulcanized the mould halves are forced together by means of the stirrups 8. The damaged section having been vulcanized, the vulcanizing press is switched off with the aid of the "stop" button, the mould halves 2 and 3 are separated 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 split mould is not dismantled. In this case the quality of vulcanization is improved owing to slowly proceeding processes of polymerization. The above-described vulcanizing press has the following advantages: - small mass per unit length of mould; - reliability, long service life; - small time constant for heating and, hence, high heat efficiency, low consumption of electric power; - contactless transmission of power, which enhances explosion-proofness. WHAT WE CLAIM IS:

1. A cable repair vulcanizing press comprising a longitudinally split ferromagnetic mould for receiving a cable to be repaired, and an inductor having a multileg core and intended to generate and transmit an alternating magnetic flux to the split mould in order to heat the mould, the core and the split mould being mutually arranged so that the plane of separation of the split mould lies in the plane of the magnetic flux passing, in use, in the legs of the core.

the interlocking coil, there are arranged compensating coils connected in series and opposed relationship with the interlocking coil.

6. A press as claimed in Claim 1 including an electromagnetic shunt consisting of a plurality of sheets placed parallel to the legs of the core adjacent the external surfaces of the mould halves.

7. A press as claimed in Claim 1, wherein the split mould is provided with inserts made of a material whose coefficient of heat conduction is higher than that of the split mould.

8. A press as claimed in Claim 7, wherein the inserts are made of copper.

9. A press as claimed in Claim 1, wherein one of the mould halves is fixed on the legs of the core.

10. A cable repair vulcanizing press substantially as described herein with reference to, and as shown in, the accompanying drawings.