AU729332B2 - Overfull sensing of a cable reel - Google Patents

Description

-4.

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT te.

(a I. I. Applicant(s): VALE STATUTORY MINING SERVICES PTY LIMITED A.C.N. 070 483 395 Invention Title: OVERFULL SENSING OF A CABLE REEL The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 OVERFULL SENSING OF A CABLE REEL FIELD OF THE INVENTION This invention relates to overfull sensing of a cable reel and relates particularly but not exclusively to such for use in a mining installation on an electrically operable mobile mining machine.

DESCRIPTION OF PRIOR ART Hitherto, it has been known to use electrically *-.operable mobile machines in mining installations. Such machines may take many forms and one form can be a shuttle -15 car. Another may be a Tamrock loader. Other machines have *been known. Such machines have a cable drum on which, and off which, the electrical cable is wound on and unwound.

As the machine advances or retreats in a mine, the reel is Swound clockwise or anticlockwise which, in turn, either advances out cable or retracts cable by winding it onto or off the drum. The drum is usually driven by a synchronised hydraulic motor system so that the amount of cable laid out or taken in corresponds to the linear movement of the machine in the mine.

A difficulty with such installations is that normally, the cable is intended to be wound in layers one upon each other on the reel. A cable feeding arm is provided on the reel to ensure that as the cable is wound one turn, the next turn of cable lies adjacent the previous turn and after one layer of many turns the situation will be repeated in the next layer. Similarly, when the cable is unwound, the cable is restrained to follow the reverse situation. Unfortunately, such mechanisms do have a problem that sometimes the cable can, in fact, be wound radially outwardly with successive turns of the reel rather than being laid side by side. This, in turn, causes the cable diameter on the drum to exceed what is normally gale/keep/speci/CAP. P08833 3 intended and in some instances, this can cause malfunction.

If malfunction occurs then it is possible that the cable can be severed which, in turn, can cause sparks which in a mine can give rise to dangerous explosive conditions.

Thus, there is a need to provide a means to take the above into account.

OBJECT AND STATEMENT OF THE INVENTION The present invention attempts to overcome the aforementioned problem.

Therefore, according to a first broad aspect of the present invention there may be provided an electrically operable mobile machine for use in a mining installation, 15 said machine having an electric cable reel from which an electric cable for supply of-electrical power to said machine can be wound thereon or unwound thereoff, said reel having a trip bar mounted across the width of the cable reel and operable in response to cable being wound onto said reel to cause the wound diameter of the cable on the reel to exceed a set diameter, to then be deflected by said cable and operate a trip switch to, in turn, permit stopping of further winding.

According to a further broad aspect of the 25 present invention there may be provided an electric cable reel for use with an electrically operable mobile machine, said cable reel being for permitting an electrical power cable to be wound thereon or wound thereoff, said reel having a trip bar mounted across the width of the cable reel and operable in response to cable being wound onto said reelnto cause the wound diameter of the cable on the reel to exceed a set diameter, to then be deflected by said cable and operate a trip switch which will, in turn, be useable for stopping further winding.

Most preferably said trip switch is provided in a pilot circuit in a power supply system of a mining installation, and said pilot circuit has a further switch gale/keep/speci/CAP.P08833 4 which switches off power to said machine.

Most preferably said further switch is provided at a point of supply of power to said cable in a mining installation.

Most preferably said cable has conductors for supply of power to said machine and earth conductors for earth continuity of said pilot circuit and wherein said trip switch is connected in series with one of those earth conductors.

Most preferably said trip bar is mounted so that it is spring biased so that when deflected it deflects .:"against said spring bias and so that when said cable is not exceeding said set diameter, to be urged by said spring bias to a position which is equal to or less than said set 15 diameter relative to said cable reel.

In an alternative embodiment the trip switch is useable to stop operation of an electric motor which provides an electric motor which provides hydraulic fluid .to a hydraulically driven motor which drives the cable reel.

BRIEF DESCRIPTION OF THE DRAWINGS *o *o In order that the invention can be more clearly 25 ascertained an example of a preferred embodiment for use in a mining installation will now be described with reference to the accompanying drawings wherein: Figure 1 is a diagrammatic view of a known mining machine in a mine.

Figure 2 is a plan view of a cable reel according to the example of the present invention.

Figure 3 is a side elevational view of the cable reel shown in Figure 2.

Figure 4 is a schematic block circuit diagram showing interconnection of a trip switch associated with said cable reel into a pilot circuit in a power supply for the mining machine of figure 1.

galelkeeplspeci/CAP. P08833 5 DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring firstly to Figure 1 there is shown a mine installation having a mine 1 and a mining machine 3 therein working at a mining face 5. The machine 3 has drive wheels 7 which are rotated by suitable electric motor means (not shown). Power for the electric motor means and for other controls and apparatus associated with the mining machine 3 is supplied via a trailing cable 9. The cable 9 is wound onto or off a cable reel 11 and suitable control means are provided to ensure that the reel 11 is rotated in unison with the driving of the drive wheel 7 so that the cable length which is wound out or wound back approximates the linear movement of the machine 3. The cable 9 passes 15 to an explosion protected distribution box 13 at a point of power supply to the mine 1. The distribution box 13 may be within the mine or it may be external of the mine. It is known to utilise a pilot circuit as part of the power distribution system to ensure that at all times there is continuity of earth conductor(s) throughout the length of the cable 9 and associated connectors. The pilot circuit has not been shown in Figure 1. In the event of non continuity of the earth conductor(s), the pilot circuit *o o* operates to disconnect power to the machine 3 at the 25 distribution box 13.

The above system represents prior art.

Referring now to Figures 2 and 3 there is shown a cable reel 11 mounted for axial rotation within a frame Motor means is provided with the reel 11 to cause it to rotate clockwise or anticlockwise so that cable 9 can be wound onto or off the drum 11. The motor means has not been shown as this is considered prior art. The cable 9 is guided onto and off the drum by a cable laying arm 17 which is caused to traverse backwards and forwards across the axial length of the drum to lay the cable 9 side-by-side in each turn. In this way when each layer is completed, the cable can be wound in successive layers one upon the other.

gale/keep/speci/CAP.P08833 6 The arm 17 is supposed to prohibit the cable 9 from being wound directly radially outwardly with each successive turn. Unfortunately, this does not always occur and the cable 9 can be wound directly over the top of itself without forming a layer across the axial length of the reel 11. This can cause sufficient cable build-up to, in some instances, either jam the cable 9 within the frame 15 or to cause the cable 9 to rupture. Because sparks can be generated on rupture of the cable 9, this can cause a dangerous explosive situation in mining environments and is to be avoided.

Mounted to the frame 15 is a cable trip bar 19.

4 The trip bar 19 is carried by two spring loaded arms 21 one near each end of the trip bar 19. The arms 21 have 15 spring means 23 associated therewith which spring bias the trip bar 19 to a position adjacent a set diameter for cable on the reel 11. Thus, it can be seen that the trip bar 19 s spring biased and the arms 21 are such that the trip bar 19 can be deflected when it is engaged by the outer sheath of a cable 9. The arms 21 are, in turn, supported on a bracket 25 which, in turn, is attached to a mounting arm 27. The mounting arm 27 is, in turn, fastened to the frame 15. Typically, the arms 21 are directed radially relative *o to the central axis of the reel 11. The trip bar 19 25 therefore is mounted across the width of the cable reel and is operable to be deflected in response to cable being wound onto said reel, which causes the wound diameter of the cable 9 on the reel 11 to exceed a set diameter. A trip switch 29 (shown only in Figure 2) can then be operated as the trip bar 19 is deflected and used to switch off power to the machine.

The provision of the trip bar 19 in association with the trip switch 29 therefore provides a simple and economic means for avoiding a dangerous situation which could occur if the cable reel 11 becomes overfull with cable 9.

The trip bar 19 and the trip switch 29 may be gale/keep/speci/CAP.PO8833 7 provided as a unit mounted on the bracket 25 and mounting arm 27 for retro-fitting to existing mining machines.

Alternatively, it can be supplied as an integral part of a new machine.

Referring now to Figure 4 there is shown a schematic electrical block circuit diagram of a typical installation. The mining machine 3 is shown as a block on the right hand side of Figure 4, and the distribution box 13 is shown on the left hand side of Figure 4. Three phase power is supplied to the distribution box and passes through solenoid operated switch means 31 to the cable 9.

The solenoid operated switch means 31 can, in turn, be operated by other switching control means either at the distribution box 13 or at some other location. The three .15 phase power is therefore passed along the cable 9, through plug and socket connectors 33 at the machine 3, and through a slip ring 35 to an explosion protected machine junction box 37. The three phase power then passes through terminations 39 to the electric motor within the machine 3 and to other electrical circuitry within the machine 3. A 0 to pilot circuit is formed for the power distribution by at least one conductor 41 which forms part of the cable 9.

Desirably, however, there are individual conductors 41 for each phase conductor in cable 9. The pilot circuit is an 9 25 earth continuity detection circuit and has a trip relay 43 within the distribution box 13 which can, in turn, cause tripping of the three phase power supply solenoid operated switch means 31 in the event of discontinuity in the earth conductors of the individual power conductors in cable 9.

In the embodiment shown two conductors form part of the pilot circuit. One is the earth conductors 41 of the power supply conductors 9, and the other is cable Cable 41 passes into the machine 3 through the plug and socket connector 33 and through slip ring 47. It then passes through the slip ring 47 to the junction box 37. The trip switch 29 is, in turn, connected in series with conductor 41 within the junction box 37 and is gale/keep/speci/CAP.PO8833 8 therefore provided in series in the trip circuit.

Conductor 41 then passes through a diode 49 to earth.

Conductor 45 provides a return conductor path for the pilot circuit and passes through slip ring 49 into the junction box 37 and then to earth via a semi-conductor diode device (not shown). The conductor 45 is also connected to earth at the distribution box 13.

The above schematic block circuit diagram shows that power is supplied through the cable 9 which may be some two to three hundred metres in length and onto the cable reel 11. It also shows that the trip bar 19 will operate within the pilot circuit to cause the relay 43 to operate to, in turn, cause the solenoid operated switch means 31 of the three phase power to operate to, in turn, 15 cut-off power to the machine 3 in the event of an over diameter of the cable 9 on the reel 11. When the machine 3 stops the problem can be investigated and rectified without .the likelihood of a dangerous situation occurring within the mine.

Modifications may be made to the invention as would be apparent to persons skilled in the art of mining machines and/or control circuits therefor.

For example, instead of the trip switch operating e* in the continuity circuit, the trip switch could be useable 25 to drop-out contacts of an electric motor which drives a hydraulic pump for supplying hydraulic fluid to the hydraulic motor of the cable reel 11. Thus, on stopping the electric motor which drives that pump, the cable reel will stop rotating. Most mine machines include many hydraulic circuits and many electric motors for providing hydraulic fluid to those hydraulic circuits. Electric interlock means are provided such that if hydraulic pressure is reduced in one or more of the hydraulic circuits then switch means can be operated to switch off all other electrical motors including the traction motor for drive wheels 7. Thus, by operating the trip switch to stop the supply of hydraulic fluid to the hydraulic motor gale/keep/speci/CAP.PO8833 9 which drives the cable reel 11, the cable reel 11 will stop rotating and the electrical interlock circuitry will also operate to then stop traction drive to the drive wheels 7 by disconnecting power to the machine.

These and other modifications may be made without departing from the ambit of the invention the nature of which is to be determined from the aforegoing description.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australian or in any other country.

H:\janel\Keep\speci\81875-98.doc 23/11/00

Claims (9)

1. An electric cable reel for use with an electrically operable mobile machine, said cable reel being for permitting an electrical power cable to be wound thereon or wound thereoff, said reel having a trip bar mounted across the width of the cable reel and operable in response to cable being wound onto said reel exceeding a set diameter, to then be deflected by said cable and operate a trip switch which will, in turn, be useable for stopping further winding.

2. An electric cable reel as claimed in claim 1 wherein said trip switch is provided in a pilot circuit in a power supply system of a mining installation, and said pilot circuit has a further switch which switches off power to said machine in response to tripping of said trip switch.

3. An electric cable reel as claimed in claim 1 or *claim 2 wherein said further switch is provided at a point of supply of power to said cable in a mining installation.

4. An electric cable reel as claimed in any one of othe preceding claims wherein said cable has conductors for supply of power to said machine and earth conductor means for earth continuity of said pilot circuit and wherein said trip switch is connected in series with said earth 25 conductor means.

5. An electric cable reel as claimed in any one of the preceding claims wherein said trip bar is mounted so that it is spring biased so that when deflected it deflects against said spring bias and so that when said cable is not exceeding said set diameter, to be urged by said spring bias to a position which is equal to or less than said set diameter relative to said cable reel.

6. An electric cable reel as claimed in any one of claims 1 to 4 wherein the trip switch is useable to stop operation of an electric motor which provides an electric motor which provides hydraulic fluid to a hydraulically S driven motor which drives the cable reel. HX\janel\Keep\Speci\81875-98.doc 23/11/00 11

7. An electrically operable mobile machine for use in a mining installation, said machine having an electric cable reel from which an electric cable for supply of electrical power to said machine can be wound thereon or unwound thereoff, said reel having a trip bar mounted across the width of the cable reel and operable in response to cable being wound onto said reel to exceeding a set diameter, to then be deflected by said cable and operate a trip switch to, in turn, permit stopping of further winding.

8. An electric cable reel for use with an electrically operable mobile machine substantially as herein described with reference to the accompanying drawings. 15

9. An electrically operable mobile machine for use in a mining installation substantially as herein described with reference to the accompanying drawings. Dated.this 25TH day of AUGUST 1998 *o VALE STATUTORY MINING SERVICES PTY LTD By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent 25 Attorneys of Australia gale/keep/speci/CAP.P08833