GB2216712A - Mining laser - Google Patents

Abstract

A mining laser has an outer casing 10 with an inner rail 44 occupying part of the length of the casing and supporting a laser tube 56. Alignment of the inner rail 44 and laser tube 56 relative to the casing 10 may be adjusted using an alignment ring 50. Rigid front and rear end caps are fitted into the front and rear ends of the casing as close tolerance fits to improve flame proofing. The alignment ring is fitted into the casing between the front and rear end caps and is connected to the inner rail. A ballast resistor and power supply may be mounted in the using. Preferably the laser has no exposed aluminium or light alloy. <IMAGE>

Description

BACKGROUND TO THE INVENTION THIS invention relates to a mining laser.

Mining lasers are used in a wide variety of applications in underground mines. For instance, a mining laser may be used to generate a beam of laser light which will impinge on a target mounted on a coal cutting machine. If the machine is driven such that the light always impinges on the target, as observed by the driver, it is ensured that the machine follows a straight course. Mining lasers are also used to facilitate such operations as the aligning of conveyor belts, installing of shaft linings, setting out of inclines and so forth.

With increasing safety consciousness in undergound mines, regulations have been promulgated which specify certain flame-proofing requirements for underground electrical equipment, including mining lasers. The mining lasers which are most commonly used in South Africa have an aluminium outer casing and end caps, attached to an inner rail which supports the laser tube and power supply. There is substantial clearance between the outer casing and the end caps. RTV (room temperature vulcanising) rubber and a rubber O-ring are used to seal the outer casing and the ond caps at the ends of the laser. Sealing methods such as the use of RTV rubbor and 0ring are not now recognised as providing permanent flameproof protection.Also the use of aluminium and light alloys is restricted under regulations concerning the usc of such materials in potentially explosive conditions, e.g. "fiery mines11.

SUMMARY OF THE INVENTION According to the invention, there is provided a mining laser which comprises an outer casing, an inner rail occupying part of the length of the casing and supporting a laser tube, rigid front and rear end caps fitted respectively into the front and rear ends of the casing as close tolerance fits, and an alignment ring fitted into the casing at a position between the front and rear end caps, the inner rail being fixed to the front end cap and connected to the alignment ring, the connection between the inner rail and the alignment ring being adjustable to vary the alignment of the inner rail and laser tube relative to the casing.

By the term close tolerance fit" is meant that the spacing between the outer periphery of each of the front and rear caps and the inner surface of the casing is no more than 0,4mm over a longitudinal path of not less than 12,5mm, and further that the spacing between the inner poriphery of the front cap and a lens lodged in an aperture defined by the inner periphery of the front cap is no more than 0,4mm over a longitudinal path of not less than 12,5mm.

In the interests of a compact mining laser, it is proposed to mount a ballast resistor and a power supply for the laser tube rearwardly of the inner rail inside the casing. The ballast resistor and the power supply may be side-by-side with an insulating member between them.

Preferably, there is no exposed aluminium or light alloy in the mining laser of the invention, and any exposed end member is constructed from a metal other than aluminium or light alloy.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a longitudinal cross-sectional view through a first embodiment of a mining laser of the invention; Figure 2 shows a cross-section at the line 2-2 in Figure 1; Figure 3 shows a cross-section at the line 3-3 in Figure 1; Figure 4 shows part of a longitudinal cross-sectional view through a second embodiment of a mining laser of the invention; and Figure 5 shows a cross-section at the line 5-5 in Figure 4.

DESCRIPTION OF EMBODIMENTS In the drawings the numeral 10 refers to an outer casing which is, in this case, a length of accurately honed round cylindrical hydraulic tubing. Fitting into the front end of casing 10 is a front end cap 12 made of brass or bronze.

The front end cap is fixed to the casing by screws 14 and is sealed with respect to the casing by means of an O-ring 16.

Similarly a rear end cap 18, which is made of aluminium, is fitted into the rear end of the casing, and onto this is attached a brass or bonze clamping disc 28.

The rear end cap is fixed to the casing by means of screws 20 and is sealed with respect to the casing by means of an O-ring 22. Both the front and rear end caps are close-tolerance fits in their respective ends of the casing.

By this is meant that the clearance between the periphery of each cap and the inner surface of the casing is no more tan 0,4mm. This low clearance is in accordance with the regulations regarding flameproofing for this kind of equipment. Also, in accordance with regulations, this low tolerancc fit extends over a length of not less than 12,Smm, thus ensuring that should a flamc or an explosion be generated within the casing through any cause whatever, such flamc or explosion will not be capable of setting off an explosion in a potentially explosive surrounding atmosphere.

Cup-shaped rubber bumpers 24 and 26 are fitted externally to the front and rear ends of the casing as illustrated. The clamping disc 28 is situated adjacent to the rear end cap 18 at the rear end of the casing 10 and serves both to lock an incoming cable in place, and also to ensure that the rear end cap is not exposed.

The wires of the cable pass through a plug 32 of RTV rubber, one wirc 34 being connected to the clamping member 28 and the other wire 36 to a threaded brass conductor 38 passing through an insulator 41. Further wires 40 and 42 are connected respectively to the rear cap 18 (which is in electrical contact with the clamping disc 28) and to thc brass conductor 38.

The outer casing 10 accommodates an inner rail 44 of round tubular form. There is a clearance 46 between the outer surface of the inner rail and the inner surface of the outer casing. The front end of the inner rail 44 is fixed rigidly to the front end cap 12 by means of screws 48. The rear end of the inner rail 44 is connected adjustably to an alignment ring 50 by means of nylon screws 52. The alignment ring is made of strong rigid non-conducting material such as Tufnol and is located axially in the casing by means of an o-ring 54.

The inner rail supports a laser plasma tube 56, mounted with RTV rubber in a central position inside the inner rail.

The laser tube is aimed at a rear or inner lens 58 supported by a mount 60 of aluminium. The mount 60 is in turn supported by an aluminium guide 62 relative to which it is axially movable for focussing purposes. Laser light passing through the rear lens 58 impinges on a front lens 64 locked in position between the front cnd cap 12 and a locking ring 66 which engages the front end cap 12 in threaded fashion. A gasket 68 is located between the front lens 64 and the locking ring 66.

The wires 40 and 42 convey current to a power supply unit 70 located just behind the inner rail 44. Side-by-side in the casing 10 with the unit 70 is a ballast resistor 72. The side-by-side location of the unit 70 and ballast resistor 72 shortens the overall length of the laser. In use of the laser, the ballast resistor will get extremely hot and it is contained in a heat sink 75 to convey the heat to the outer casing 10. The heat sink is in turn isolated from the unit 70 by an insulator 73 (see also Figure 2). One wire 74 from the ballast resistor 72 is connected to the anode contact at the rear end of the laser tube 56. The other wire 76 from the unit 70 is connected to the inner rail, with another wire 78 connecting the inner rail to the negative contact at the front end of the laser tube.

Referring~now to Figure 4, a second embodiment of a mining laser is shown, which mainly differs from the first embodiment in the sealing arrangement of the end portions.

In order to prevent any unauthorised underground tampering with the interior portion of the mining laser, there are provided grub screws 82, the heads of which are covered with a brass screw cover 84. The grub screws 82 lock the front end cap 12 outwardly against the casing 10, by locating in holes in the walls of the casing 10. The annular brass screw cover 84 engages the front end cap in threaded fashion, and can only be unscrewed by means of a special tool which engages with circular diametrically opposed aporturcs 86. The grub screws 82 in turn may only be removed by means of a special, L-shaped allen key.

The rear end cap 18 is secured in position with studs 88 which retain the rear end cap 18 against the casing 10 by locating in holes in the walls of the casing 10. An aluminium stud retaining ring 90 abuts the head of each stud, and locks each stud in position. The retaining ring 90 nests in the rear end seal, and is held in position by a brass clamping disc 92, shown in cross section in Figure 5, the inner periphery of which defines cavities 94 for locating screws (not shown) which fix the end cover 18 to the clamping disc 92.

The aluminium locking ring 66 doubles as an anchor for the front end of the inner rail 44, which is fixed rigidly to the rear portion of the locking ring 66 by means of screws 48.

A major advantage of the illustrated embodiments is their flame-proof construction. As indicated earlier, the close-tolerance fit between and front end caps 12 and 18 and the outer casing 10, as well as the close tolerance fit between the lens 64 and the front end cap 12, satisfies the regulations regarding flame-proof clearances. Also the use of a steel outer casing, a brass or bronze front ond cap and brass or bronze clamping disc ensures that no aluminium or light alloy is exposed, thus eliminating any danger of sparking due to possible violent contact with rusty steel or the like.

It will be appreciated that the rigid fixture of the front end of the inner rail 44 to the front end cap 12, and the close fit of the front end cap 12 in the casing 10 means that there is no facility for adjustment of the inner rail relative to the casing at the front end of the casing, Such adjustment as is necessary to get the lascr beam correctly aligned relative to the casing is provided for in the present embodiment by the nylon screws 52, the alignment ring 50 and flat surfaces 80 with slots 81, formed on the rear outer end of the inner rail 44 (see also Figure 3).

Adjustmcnt can be effected by slightly loosening one of the four nylon screws 52 and correspondingly tightening the screw diametrically opposite to it. By suitablo relative adjustment of the four screws, fine axial orientation of the laser beam relative to the outer casing may be effected.

The steps required to efect such adjustmcnt are:1. Checking the amount of mis-alignment of the laser spot, at say 100 metres, by rotating the laser in special V blocks (not shown) 2. Removing the inner rail and adjusting the movement of the laser spot to half the amount of the original mis-alignmcnt.

3. Re-inserting the inner rail and rechecking the alignment.

By repeating this procedure, near perfect alignment can cventually be achieved.

Claims (6)

CLAIMS;

1.

A mining laser which comprises an outer casing, an inner rail occupying part of the length of the casing and supporting a laser tube, rigid front and roar end caps fitted respectively into the front and rear ends of the casing as close tolerance fits, and an alignment ring fitted into the casing at a position between the front and rear ends caps, the inner rail being fixed to the front end cap and connected to the alignment ring, the connection between the inner rail and the alignment ring being adjustable to vary the alignment of the inner rail and laser tube relative to the casing.

2.

A mining laser according to claim 1, in which a ballast resistor and a power supply for the laser tube are mounted rearwardly of the inner rail inside the casing.

3.

A mining laser according to either Claim 1 or Claim 2, in which the ballast resistor and the power supply y are side-by-side with an insulating member between them.

4.

A mining laser according to any one of Claims 1 to 3 in which there is no exposed aluminium or light alloy.

5.

A mining laser according to any one of Claims 1 to 3 in which any exposed end mcmber is constructed from a metal other than aluminium or light alloy.

6.

A mining laser substantially as herein described with reference to Figures 1 to 3 or to Figures 4 and 5 of the accompanying drawings.