UNDERGROUND MINING VEHICLE

The present invention relates to special purpose vehicles and, more particularly, to underground mining vehicles adapted for working in potentially explosive atmospheres.

BACKGROUND

Explosive or hazardous atmospheres are quite common in industrial processes and in particular in underground coal mines. The presence of an explosive mixture in the ambient air may not pose an immediate risk to personnel but machinery working in the area must be protected to prevent the accidental ignition of the explosive atmosphere. This technique is called explosion protection.

Typically self-propelled explosion protected vehicles for the transporting of personnel and their equipment in coal mines are quite large and cumbersome. Diesel powered vehicles such as the "Driftrunner" made by Specialised Mining. Vehicles and the "PJB" manufactured by P J Berriman, are large vehicles typically weighing over 3,500Kg. A diesel powered skid steer loader manufactured by Dealquip is one of the smallest vehicles available, yet its unladen weight is in excess of 2200Kg and while manoeuvrable,, its single seat low speed and lack of suspension restrict its use as a utility vehicle for the transport of personnel and

their equipment. Alternative battery powered equipment, such as the "EJC" battery powered loader manufactured by Sandvik, are also of a similar size to the diesel vehicles mentioned above. The size and weight of these vehicles has for the most part been a function of the explosion- protected equipment fitted to the vehicles to allow them to operate in an explosive atmosphere.

The increased weight of the explosion-protected equipment has forced designers to build larger machines . These larger machines may be efficient for mining operations or the transport of ore and the like. When used as personnel carriers they are typically designed to carry 6 or more people or payloads in excess of 1,000Kg. Their size and weight make them cumbersome, difficult to manoeuvre, inefficient and expensive to operate when used to transport a few personnel and their equipment.

It is an object of the present invention to address or at least ameliorate some of the above disadvantages. Notes 1. The term "comprising" (and grammatical variations thereof) is used in this specification in the inclusive sense of "having" or "including", and not in the exclusive sense of "consisting only of".

2. The above discussion of the prior art in the Background of the invention, is not an admission that any

information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any country. BRIEF DESCRIPTION OF INVENTION Accordingly, in a first broad form of the invention, there is provided a self-propelled underground mining vehicle for use in coalmines; said mining vehicle characterized in that unladen weight of said mining vehicle is no greater than 2000Kg Preferably, said unladen weight includes weight-reducing components; said weight reducing components including intrinsically safe electrical components. Preferably, said weight reducing components include body panels fabricated from high strength to weight ratio materials; said materials including carbon fibre reinforced polymers.

Preferably, said vehicle is powered by a diesel engine. Preferably, said vehicle is an electrically powered vehicle; said vehicle powered by a battery pack and at least one electric drive motor.

Preferably, said weight reducing components include a water flame trap; said water flame trap having a main body shaped as a pressure vessel. Preferably, said water flame trap is fabricated of high strength to weight ratio materials; said materials

including stainless steel and carbon fibre reinforced polymers.

Preferably, said water flame trap is of a reduced size compared to prior art water flame traps for engines. ¹ of similar capacity; said water flame trap re-supplied with water from a top-up water supply tank.

Preferably, said weight reducing components include an electrically operated shutdown system emergency shutdown system of said diesel engine. Preferably, said weight reducing components include a spring starting mechanism for said diesel engine.

Preferably, said weight reducing components include an hydraulic starting system for said diesel engine.

Preferably, said weight reducing components include a lighting systems of said vehicle comprising Light

Emitting Diode (LED) lights; said LED lights formed of encapsulated clusters of LEDs.

Preferably, flame proof enclosures .for electrical components are limited to a single flame proof enclosure; said single flame proof enclosure enclosing moving components of a main circuit breaker and/or controls of said electrically powered vehicle.

Preferably, all operator inputs for control of said vehicle are through intrinsically safe components. Preferably, said at least one electric drive motor is a non-sparking type of electric drive motor.

Preferably, said vehicle is sized to carry between one and three personnel and their associated equipment. In another broad form of the invention, there is provided a method for producing an underground mining vehicle in which the unladen weight of said vehicle is no greater than 2000Kg; said method including the steps of:

(a) incorporating intrinsically safe electrical components in an electrical system of said vehicle, (b) fabricating body panels of said vehicle from high strength to weight ratio materials; said materials including carbon fibre reinforced polymers .

Preferably, said electrical system includes lighting provided by clusters of LED lights.

Preferably, said electrical system of said vehicle includes one only flame proof enclosure.

Preferably,, said method includes the further step of providing an electrically operated emergency shutdown system for a diesel engine of said vehicle.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of -the present invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is a general plan view of the underground mining vehicle of the present invention showing the principal components of the power train and associated components, Figure 2 is a representation of a preferred form of exhaust gas flame trap for the vehicle of Figure 1,

Figure 3 shows the flame trap in circuit with a supply of water or other isolating fluid,

Figure 4 is a graph showing the relationship between material strength and pressure vessel strength for a given material thickness,

Figure 5 is a graph showing the relationship between pressure vessel diameter and vessel strength for a typical material, Figure 6 shows a side and end view an LED cluster light fitting for use with the vehicle of Figure 1,

Figure 7 is a list of typical components of a pneumatic emergency engine shut-down system of mining vehicles according to prior art, Figure 8 is a table of electrical components typical of a mining vehicle according to the prior art,

Figure 9 is a table of electrical components for use on the vehicle of the present invention,

Figure 10 is a table indicating weight savings due to the various design and equipment choices used in a first preferred embodiment of the invention,

Figure 11 is a schematic layout of the main electrical components of a second preferred embodiment of the present invention,

Figure 12 is a table indicating weight savings due to various design and equipment choices used in a second preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention is directed at a self propelled underground mining vehicle specifically for use in coalmines where potentially explosive gasses may be present. The vehicle of- the present invention is particularly suited for the transport of a small number, typically between one and three personnel, including the operator, and their equipment. This allows for the design of a smaller, lighter vehicle in which significant weight savings are achieved through the use of appropriate technologies to bring the vehicle's unladen mass to under 2000Kg.

To meet the requirements of underground mines, and particularly underground coalmines, the vehicle must be proof against the emission of sparks to allow it to operate in potentially explosive atmospheres. Four principle techniques are utilized in the vehicle of the present invention to meet this requirement , while significantly

reducing it weight. These are, aspects of the engine/motor control system, flame traps, explosion proof enclosure of electrical equipment and/or intrinsically safe electrical components . First preferred Embodiment

With reference now to Figure 1, a preferred embodiment of an underground mining vehicle 10 of the present invention, is powered by a relatively small and light diesel engine 12. Power is transmitted in this instance to the rear wheels 14 by a transmission 16 integral with the rear transaxle 18.

Both the air intake side of the engine 12 and the exhaust outlet side of the engine must be proofed against the emission of sparks. Thus on the intake side, a spark arrestor 20 is fitted between the air filter 22 and the intake manifold 24.

The exhaust gasses emitted by the engine are passed through a water flame trap 26 , to exhaust through outlet 28. Water flame trap .26 both prevents any sparks from reaching the external atmosphere and assists to cool the exhaust gasses. Detailed views of the water flame trap 26 and its installation according to the invention, are shown in Figures 2 and 3.

Typically, known flame traps are designed to fit into the machinery of the vehicle, often formed as cube-like structures with flat surfaces and. sharp corners. This arrangement demands the use of relatively heavy construction materials- For example, a flame trap with an overhaul volume of 125 litres could weigh in excess of 120Kg (without water and fittings) . Also typically, the volume of these flame traps is relatively large so as to carry all of the water required for a reasonable duty cycle within the trap.

As can be seen in Figure 2, the main body 30 of the flame trap 26 of the present invention comprises a cylinder 31 with hemispherical ends 32. This main body shape, which is essentially that of a pressure vessel, allows it to withstand high internal pressures while minimizing the material tensile strength (and therefore the weight) required for the main body 30-.

Figure 4 shows the relationship between pressure vessel diameter and vessel strength. It must be noted that a flame trap needs to be of a sufficient volume to . allow for sufficient water both in volume and depth to prevent .the

•ignition of an explosive atmosphere outside the flame trap.

Thus while this invention seeks to minimise the diameter of the vessel design and provide sufficient volume by a suitable length of the cylindrical shaped portion of the

flame trap body, there is a limitation as to the minimum diameter of the flame trap.

The smaller engine required to drive the smaller and lighter vehicle 10 of the present invention, produces a significantly reduced volume of exhaust gas. The result is a lower volume of potentially explosive gas and a lower level of explosive energy which the flame trap is required to withstand, allowing the gross flame trap weight to be further significantly reduced. This allows the flame trap of the present invention to be preferably fabricated from a high tensile stainless steel, or a carbon fiber reinforced polymer composite material for example.

In its operation, the flame trap main body 30 is partially filled with water and is connected to the exhaust of the diesel engine via a flameproof joint 34. The exhaust gases are then directed internally within the main body 30 to the bottom of the main body where they escape underwater, rising towards the top of the main body 30. From here they exit through the discharge outlet 28.

The main body 30 may be opened via a flame proof joint 36 to allow the flame trap to be cleaned. The joint 36 may be bolted or screwed or similarly fastened but must be flame proof so as to prevent ignition of the atmosphere external

to the flame trap. This joint may be located in different areas of the flame trap .if desired.

The flame trap 26 is fitted with one or more water level sensors 37 which are designed to ensure that the engine can only operate while there is sufficient water in the flame trap. The flame trap 26 is further provided with a method of draining the water from the body via one or more valves 38. This allows the testing of the water, level sensor/s and float valves that may.be fitted to flame trap.

A further reduction in the size and weight of the ^" flame trap of the present invention is achieved by the use of a top-up water header tank 40 (as shown in Figure 3) , connected by water conduit 41 to the inlet 42 of the trap 26. The water header tank 40 is located above the flame trap (as can be seen in Figure -1} and is vented 43 so that it may provide top water to the flame trap. This provides that not all the water for a duty cycle of the vehicle need be accommodated in the flame trap body itself, but may be automatically topped up from a lightly constructed top-up water tank 40 through a one-way valve at fill point 42,

The overall effect of these weight reducing strategies is that the dry weight of the flame trap of the present invention is reduced from the typical figure quoted above of in excess of 120Kg, to 25Kg.

In addition to the flame trap 26, the exhaust emissions are preferably further conditioned by an exhaust gas particulate filter (not shown) such as disclosed in US5,904,042 or US5,272,874. Such particulate filtering systems are designed primarily to improve the exhaust particulate levels and allow personnel to work safely in areas subjected to the vehicle's exhaust fumes.

Another weight impost of known underground mining vehicles is the requirement of flame proofing all of the electrical equipment incorporated in the vehicle. The weight reducing strategies of the present invention firstly include the provision of all lighting by high efficiency light emitting diodes (LEDs) . These diodes are five times more efficient than incandescent bulbs and can be arranged in groups or clusters as shown in Figure 6 to form a complete vehicle light 50. The reduced power required by the LED- lighting allows a reduction in the size of .the alternator- or generator 44 (shown in Figure 1) used to generate the electrical supply to the lighting circuits. The light emitting diodes 52 also produce less heat and are,, in the present invention, made explosion proof by encapsulating the light emitting diodes 52 in a clear casting resin 54. Figure 6 shows a vehicle light 50 comprising a cluster of LEDs 52 encapsulated in clear casting resin 54, Safety is in 'any case also enhanced by

the fact that LEDs are non sparking given that they are solid state devices.

Again with reference to Figure 6, the control system for the LEDs is housed behind the cluster of diodes 52 in a

5. main body 56 which is made of a robust plastic such as PVC or similar. Internally the main body 56 may also use encapsulation or increased safety techniques to explosion protect the electrical circuits in the vehicle, light 50 and the electrical supply cable 58 to the light. This0 combination of materials results in. a vehicle lighting system that is as little as one eighth the weight of flameproof lighting systems.

The use of LED lighting systems together with solid state electronic control and intrinsically safe components avoids5 the use of flame proof enclosures and significantly reduces the capacity requirements for the on-board power generation by generator or alternator 44. Figures 8 and 9 give a comparison between the weights of electrical components of a typical explosion proof raining vehicle of the prior art0 and of the vehicle of the present invention.

Traditionally, compressed air has been used on mining vehicles for a variety of functions, including engine starting and emergency shut-down. The emergency shut-down function alone requires a large number of components as

shown in Figure 7, amounting to a considerable weight impost of some 56Kg on the vehicle. The vehicle of the present embodiment of the invention incorporates intrinsically safe electrical sensors to monitor temperature, pressure and level of the engine. These sensors together with the shutdown valve used on the vehicle amount to 5Kg with, the whole occupying a volume of only 2 litres compared with the 200 litres of the traditional arrangement. This reduced volume amounts to a significant overall weight saving of approximately 20Kg as well as requiring less mounting space and associated equipment .

In the present preferred embodiment of the invention, the vehicle is equipped with either a spring or an hydraulic starting system for the diesel engine. This eliminates the air compressor and air tanks required for compressed air starting and emergency shutdown systems typically used on mining vehicles. By way of example, a preferred spring starting system by Kineteco weighs approximately 4Kg whereas equivalent air starters and their valving weigh between 11 and 18Kg, thus a weight saving in the present vehicle of at least 7Kg, An hydraulic starting system has a similar weight as that of an air starter, but still avoids the use of the air components of Figure 7 and still provides a weight advantage.

Yet another area in which the present invention has been able to make considerable weight reductions is in the use of body panels, fuel and water tanks formed of light-weight polymer composite material, instead of the typically used steel fabricated panels and tanks.

Figure 10 shows some of the principle areas of weight savings for this embodiment of the invention.

Second Preferred Embodiment

In a second preferred embodiment of an underground mining vehicle according to the invention, the unladen vehicle mass is again limited to no more than 2000Kg. In many respects, the vehicle chassis, body panels and passenger and load configuration are similar or the same as that of the first preferred embodiment described above, but in this instance the vehicle is propelled by means of an electric power source coupled to at least one electric drive motor. With reference to Figure 11, the battery or battery pack 70 employed in this embodiment of the vehicle, comprises high power density to weight ratio designs, such as Nickel Iron, Nickel Metal Hydride or Lithium Ion, The battery pack is housed in a battery compartment 71 made from, a high strength to weight ratio material resistant to battery acid, such as carbon fibre composites or stainless steel.

The power supplied by the battery pack 70 is carried by cables to a main circuit breaker flame proof enclosure 72. Flame proof enclosures are heavy and in this preferred embodiment the number and size of the flame proof enclosures are minimised. The main circuit breaker enclosure 72 is in fact, the only flame proof enclosure used on the mining vehicle of this embodiment. The main circuit breaker enclosure 72 contains moving components capable of producing arcing and sparking, thus requiring that a flame proof enclosure be used to house these components..

The electrical current passes from the main circuit breaker enclosure 72 to the main control enclosure 74. This main control enclosure 74 is not flame proof but is required to provide mechanical protection for the control components it contains and is thus manufactured from high strength to weight ratio material. These components are all solid state and are either encapsulated or emersed to provide explosion protection of the electrical circuits to the external atmosphere.

The main control enclosure 74 supplies the electric motor or electric motors 76 and, depending on the operator inputs, will drive the motor forwards, reverse, slow or fast. The electric motor or motors 76 are in the preferred embodiment of the non sparking type having a high power to

weight ratio. These motors are lighter than flame proof motors of the same output.

In this preferred embodiment, operator control inputs 78 are intrinsically safe and therefore not capable o£ generating a spark that could ignite the external explosive atmosphere. These intrinsically safe circuits thus do not require any explosion proof enclosures , again helping to minimise the weight of the underground mining vehicle.

The above describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.