FIELD OF THE INVENTION

This invention relates to a scraper winch for scraping broken rock or ore, especially in underground mining operations.

BACKGROUND TO THE INVENTION

Scraper winches are well known and have been used for years.

United States patent number US 2,537.267 A, in the name of Albert G. Gurries and Thomas B. Keesling, entitled "Cable Winch", discloses:

"This invention relates to improvements in cable winches such as are adapted to be mounted on a tractor and driven from the power take-off shaft of the latter; this type of cable winch being commonly known as a power control unit. One object of this invention is to provide a cable winch which includes, in direct unitary relationship with each cable drum, a clutch unit of novel construction and operation; such clutch unit being fluid pressure actuated, preferably hydraulically.

Another object of the present invention is to provide a clutch unit, as in the preceding paragraph, which comprises, in combination with a cable drum rotatably but axially immovably mounted on a driven shaft, a non-flexible clutch disc disposed in concentric cooperative relation to one end head of the cable drum, said one end head of the cable drum being formed exteriorly with a flat radial clutch face, the disc being mounted on and driven by the shaft but axiaily movable there along; a diaphragm plate fixed with said one end head in facing cooperative relation to the clutch disc on the opposite side from said end head but for rotation therewith; a closure member mounted in connection with and covering the diaphragm plate from the outside so as to form a pressure chamber there between; and means to deliver fluid pressure to said chamber whereby to cause the diaphragm plate to deflect axiaily inwardly and to drivingly engage the clutch disc between said diaphragm plate and said clutch face. The closure member is a dome which clears the diaphragm plate, except at its periphery, and thus forms a pressure chamber of substantial capacity, whereby a cushioned clutch action-results, and a nicety of clutch control is accomplished.

An additional object of the invention is to provide a cable winch which incorporates, in rugged, compact and unitary relationship, a pair of cable drums; a fluid pressure actuated clutch unit for each thereof; a fluid pressure actuated brake assembly for each cable drum; a fluid pump to supply the pressure for control of the alcove clutch units and brake assemblies; and a fluid reservoir formed in the main case of the winch and interposed in the fluid pressure control system thereof." United States patent number US 3,373, 972 A in the name of Earl A. Peterson, entitled "Slip Clutch Constant Tension Winch", discloses:

"This invention relates to a slip clutch constant tension winch where the clutch portion of the device slips constantly, but the rate of slippage is variable by the operator to alter the amount of tension on the cable which reels onto or off of the winch drum. An object of my invention is to provide a novel slip clutch constant tension winch in which the clutch is of a type which can be effectively cooled to absorb the heat generated in the clutch due to its slippage. Another object of my invention is to provide a novel constant tension winch device in which the clutch associated therewith is of the constant slip type, and where the cooling medium is a suitable gas or liquid, and also where the tension of the clutch is controlled by a suitable liquid or gas. Still another object of my invention is to provide a novel constant tension winch of the character stated in which the winch and the clutch are arranged in a unit and is. therefore, relatively compact and more effective in operation."

United States patent number US 3.322,397 A in the name of Arthur H. Pillman, entitled: "Scraper Winch", discloses:

"This invention relates to a winch which has a haulage drum and is particularly adapted for use in a mine for hauling scrapers, and in mining operations is usually provided with a pair of similar drums. These winches are well known and are powered with an electric motor driving a worm and worm wheel assembly connected to the driving shaft on which is mounted, one or each side of the driving wheel, a haulage drum. The winches usually are adapted to run at a constant speed, frequently however it is an advantage to vary haulage speeds to suit the work which has to be undertaken, for example the slope may vary from one position to another over which a scraper must work and suitable gears are provided for adjusting the power drive for the haulage drum or drums as required. in a number of cases the haulage drum for a scraper must be changed or repaired and it is a great advantage to be able to remove the drum and replace it on the winch without having to interfere with or remove the hydraulic control gear. The control gear is very liable to damage if exposed to the dust in a mine.

It is an advantage to avoid as far as possible any small pipes or similar fittings on a scraper winch which is in use in a mine, since such fittings not only are in the way when the winch must be repaired or removed, but they are liable to be bent or damaged during the working of the winch. Consequently it is an advantage to have a winch which is compact, easily moved when necessary and with the necessary fittings accessible but without extraneous parts.

It is the object of this invention to provide a winch, specially constructed for use in a mine, for the haulage of a scraper and well adapted to meet the conditions of such usage, such a winch whilst being robust, has a relatively small weight and is able to be moved and mounted without difficulty, also one in which its drum and other parts may be attended to or repaired without the necessity for the removal or interference with its hydraulic system."

United States patent number US 3,220, 702 A in the name of Collin C. Cladwell, entitled: "Friction Drives for Devices Such As Scraper Hoists", discloses:

"This invention relates to friction drives for devices such as scraper hoists. Conventionally on the South African gold mines scraper hoist drums are rendered operative by means of a band clutch involving levers and the like. There band clutches have been automated to some extent by replacing human power with hydraulic or pneumatic cylinders. A relatively complex mechanism with a plurality of parts that may break or get damaged is involved. Alternatively, a multi-plate clutch operating on the first motion shaft of the gear reducer is used. This also involves levers acting through a considerable distance which require frequent adjustment.

It has also been proposed (although this is not commonly known) in connection with laboratory printing equipment to connect a wheel in driving relationship to a shaft by sandwiching it between two friction discs rotating with the shaft while the wheel is a running fit on the shaft. In the latter construction a thruster in the form of a spring acting between one disc and the framework of the device provides the sandwiching force. This device is only suitable for small horse powers because of the end thrust exerted on the bearings. In fact the spring is pushing on the shaft in the direction of its length, with its thrust reaction acting on an outside support. In further proposals (which are also not commonly known) spinning drums for catheads were sandwiched between two friction discs, one of which was acted upon by a foot or hand operated linkage reacting on structure that carries the bearings for the cathead shaft. An object of the invention is to provide a friction drive that is suitable for work in the horse power range of scraper hoists, which is hydraulically actuated and in which the actuating mechanism takes up the minimum of space."

Winches are used in underground mining operations to operate scrapers to clean broken rock from the stope face and gullies after a blast. Scrapers are an integral part of the narrow reef mining methods employed on gold and platinum mines, working in the face as well as in strike and dip gullies. There are many different versions of scraper winch machines in everyday use, but models derived from the old Joy-Sullivan design are the most common. This design has two drums and an electric motor in an in line arrangement. The motor drives the pull drum via a gearbox. The change of direction of the pull is done by applying a breaking force via clutch pads onto the surface of drums with the driver positioned directly behind the winch to operate the manual clutch system. The pull force and velocity vary with the effective drum diameter. These parameters are continually changing with the change of the amount of rope wound on the drum. When the rope velocity is the highest, the pull force is the lowest and vice versa.

Scraper winches are powered by low voltage squirrel- cage alternating current electric motors. These machines are purposely designed and built to operate at larger slip angles, due to the variable loading that they experience during the cleaning/ore scraping process. This is in contrast to the relatively stationary operating regimes of conventional motors that are used to power various pump or fan applications. This is illustrated in Figure 1 herebelow, where the conventional motors would ermanently operate at or close to point 1 onthe torque curve.

The winch motors' operating point is, however, dependent on the load, constantly moving between points 1 and 2 on the torque curve. This means that, in extreme situations and for a relatively small amount of slip, the motor torque far exceeds the torque at its full load. This is experienced and interpreted by a winch driver as "the winch having insufficient power to pull the scoop" even when it is jammed somewhere or gets hooked onto an uneven footwall.

Thus, under certain circumstances, scraper winches that are used during face and gulley scraping have the potential to develop much higher pull forces than the rigging system, in particular the rope, can withstand. On the other hand, it was found that the required pull forces measured during actual face and gulley scraping are lower than what the scraper winches can provide. This creates an unsafe situation that has resulted in injuries and fatalities. It is therefore necessary to make an attempt to either limit the winch motor torque and/or use less powerful winch motors. Due to the slow reaction time of conventional motor overload and thermal overload devices, these are not effective methods of torque limiting. This clearly indicates to the need for a variable speed system in scraper winch design. In terms of transportation accidents, recent statistics have shown that scraper systems account for 23% of the accidents in the gold mining sector and 36% of the accidents in the platinum mining sector. 59% of injuries occur during the morning shift with 28% being fatal. This is probably due to the fact that most of the workers are in the stope, transporting material, or travelling to the stope face while the scraper winch is in operation. At the other extreme, 59% of workers are killed during the night shift. This may be due to the fact that there is less supervision on a night shift and that a night shift is primarily a cleaning shift. The average length of rope per drum is 140 meters. This creates a lot of blind situations due to the positioning of the winch driver directly behind the winch. The current products on offer is sold with limited safety covers or none at all as shown in Figure 3 of the drawings attached to this specification. An analysis by the Safety in Mines Research Advisory Committee by Occupation indicates that only five occupations are involved in 98% of the accidents due to the scraper winch system. The analysis also indicates that winch drivers (43.9%) are prone to scraper winch accidents. Surprisingly, 26% of personnel involved in scraper winch accidents are shift bosses and general miners.

The top three causes of injuries to winch drivers are due to

• Struck by ropes

• Struck by snatchblock

• Entanglement

In summary, the traditional winch is operated by hand via mechanical clutches. The operation is potentially dangerous and requires both a driver and a signaler to assist in blind situations. It is noisy and is a fixed speed drive system designed many years ago. These winches utilize wearing clutch bands which require frequent changing. This in the face of mine operators being faced with rising costs as well as health and safety issues. They need to reduce costs and improve productivity to ensure viability.

The pressure in the mining industry to achieve safety performance levels equivalent to current international benchmarks for underground metalliferous mines, the pressure on the national power grid and the pressure on production costs due to volatile gold and platinum markets, established the need for safer, energy efficient and cost effective mining equipment.

Traditionally, the scraping of ore and moving of it to the ore pass, is done using a double drum scraper winch using a single electric motor. This winch design has two drums and the single electric motor in an in-line configuration. The motor is started direct-on-line and drives via gearboxes (primary and planetary). The change of direction between pull and retrieve is achieved by applying a braking force via clutch bands acting on the planetary ring gear.

The winch motor operating point varies considerably and is dependent on the load - scraper fill, type of ore, incline, pull/retrieve, as well as the operator experience and feel.

• Reports produced in the past suggest that the motor is around 35% oversized for safe scraping pull. This means that the efficiency is far lower than optimal.

• The motor runs during the entire period in which the winch has been switched on.

• Due to the cyclic nature of the operation, the motor is often operating on low load and on no-load with resulting low power factor. This obviously affects the mine power supply overall power factor with negative implications on kW demand.

• The nature of the clutching operation causes energy loss to friction, especially if the correct forged material is not used on the ring gears. With reference to the prior art winch 13 shown in the attached figure 3, the flanges 25 as well as a cover plate 26 of its drums 16 and 17 are worn down by the rope. After some use, the flanges become thin and sharp at their circumferences posing a danger to mine workers.

The external motor 18 or the prior art winch is exposed, protruding form a side of the winch. Not only does the motor 18 get in the way, but dust frequently enters its housing, reducing its effectiveness and longevity.

Clutch handles 14 and 15 are operated from behind the winch resulting in the operator not always having a clear view of the scraping operations (blind spots) and being in harm's way in case of a breakage such as a breakage of a rope of the winch.

OBJECT OF THE INVENTION

It is an object of this invention to provide a scraper winch which, at least partially, alleviates some of the abovementioned difficulties.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a scraper winch comprising a support frame having two drums mounted therein, each drum having its own variable speed drive for rotating the drums about their axes.

A further feature of the invention provides for the winch to have a remote control unit to enable an operator to control the winch from a remote location. There is provided for the winch to have guide rollers to guide its ropes onto and from the drums, as the drums rotate.

There is still further provided for the drives to be electric motors located at least partially inside the drums. Preferably, the motors including their bearings, are located inside the drums.

A yet further feature provides for regenerative braking between drums. There is provided for a remote control of the winch to be attached to a control unit with a length of cable.

An air passage including air filters is defined through the support frame. Preferably, an air vent opening is located on top of the frame and two air vent exits on the side and/or at the bottom of the frame.

These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the invention is described below by way of example only and with reference to the accompanying drawings in which :

Figure 1 shows a cross section of a mine working with a scraper winch depicted in the mine working; Figure 2 shows a perspective view of a scraper for use with the scraper winch;

Figure 3 shows a perspective view of a prior art scraper winch;

Figure 4 shows a front perspective view of a scraper winch in accordance with the invention;

Figure 5 shows a front view of the scraper winch of Figure 4; and

Figure 6 shows a cross-sectional front view of the scraper winch of figures 4 and 5.

DETAILED DESCRIPTION OF THE DRAWINGS With reference to the drawings, an underground mine working is generally indicated by reference numeral 1 .

A scraper winch is installed on a scraper winch support 4. The scraper winch drives a rope 5 which is connected to a scraper 6. Ends of the rope 5 wind onto drums of the scraper winch.

The rope 5 runs from a return drum through a snatch block 7 attached at a remote end of the mine working and back to a rear end of the scraper 6. The snatch block 7 is attached with an anchor 8 to a mine wall such as a footwall 3 of the mine working. The scraper rest on the footwall 3, and is used to scrape ore on the surface 12 of the footwall, in the direction of the winch, as is described below.

A second part of the rope 5 then extends from a front end of the scraper 6 back to the winch where it is wound on the pull or scraping drum.

In use, the scraper is returned to the far or remote end of the mine working proximate the snatch block by winding the rope onto the retrieve drum. This necessitates an unwinding of the rope form the pull drum to allow the scraper to be pulled to the far end of the mine working. This operation is now reversed to pull the scraper 6 over the surface 12 and scrape any ore thereof closer to the winch. In other words, the pull drum is engaged to wind the rope onto itself thus necessitating the rope to be wound off the return drum.

The scraper is pulled into a loading chute 10 from where the ore falls into a car 1 1 , immediately below the chute 10. The car then conveys the ore away from the mine working.

The scraper 19 typically has upright, parallel side walls 22, 23 an upper front nudge bar 24 and a rear inclined wall 21 so that the inclined wall 21 extends upward and rearward from an open bottom 20 of the scraper 19. Figures 4 to 6 show a winch 2 in accordance with this invention. The winch 2 has an outer frame which forms a partially open housing of the winch.

The frame has two foot beams 35 on which it is supported.

Two co-axially disposed drums 30 and 31 are mounted inside the frame. The drums have flanges 32 to support a rope 5 wound thereon.

Drum 30 is mounted on an axle 33 and drum 31 is mounted on its own axle 34.

A remote control unit 28 is connected to a control unit of the winch through a cable 27.

A fan cover 29 having air vents is mounted over an extraction fan 40.

A roof of the frame has air inlet vents 44 therein.

Air vents are also located in a rear wall of the frame. Another air exit vent 43 is located in a floor of the frame.

Pairs of upright rollers 37 are mounted in front of each drum substantially aligned, but defining a slightly narrower opening than the flanges of each drum.

Horizontal rollers 38 are located in front, towards a lower and of each drum to support the weight of the rope thereon, if the rope is slack enough to rest thereon. Within each drum is an electric motor 41 and 42. These motors are variable speed motors and they rotate about their axes 33 and 34.

An inlet fan 39 sucks air through the inlets 44 and in the general direction of the arrows towards fan 40 and out through the vents of cover 29 as well as out of the vent 43 and the vents in the rear wall.

The winch 2 described herein incorporates a totally new approach using two motors that are optimally sized for their respective duties, i.e. one for pull and one for retrieve.

• These motors are designed to work at their optimum efficiency point, the efficiency of the motor/drive system is pegged through the operating range.

• The motors do not run all the time. Only starting when required.

• The motor speed is controlled by variable frequency drives, which means they can ramp up and down with no high starting currents.

• The retrieve motor can run faster than the pull motor to return the empty scraper faster and increasing operating efficiency.

• There are no clutches, thus energy is not wasted on friction losses.

• When one motor is under power the other motor is being pulled along due to the continuous rope system and acts as a generator. This power being generated is fed back into the system.

The applicant estimates that a saving in energy using the winch described herein would be in the order of 40%. • Since the operator can operate the winch from a remote position, there is no need for him to have an assistant to signal.

• There are no clutch bands to wear out, thus avoiding downtime and expenses in transporting and replacing worn bands.

· The roller guide system prevents drum cheek or flange wear, which reduces downtime to have winches transported to surface for drum replacement.

• The retrieve motor can be speeded up to ensure a quicker return for the next pull, effectively reducing cleaning time

• The operator is not directly behind the winch, and removed from a dangerous area.

• Visibility of the scraping path due to the remote operation increases.

• Properly designed and fitted rope guards ensure that finger and hand accidents can be reduced.

• Roller guide system assists with rope guidance.

· Reduction in downtime

• Reduction in costs of transporting spares and hauling winches out for overhaul.

• The motors are protected within the winch and thus not subjected to damage such as on the traditional winch.

· The motors include a sealed for life bearing system which means zero maintenance.

The winch utilises regenerative braking, the efficiency of the motor/drive system is pegged through the operating range thus reducing energy costs. It is envisaged that the winch described herein will fill a gap in the market for a winch that the driver would operate from a remote, safe position, without the need for a signaler. The winch is quieter, faster, lighter and more compact, and is programmable to increase speeds and record operations and faults. It utilizes regenerative braking, the efficiency of the motor/drive system is pegged through the operating range, thus reducing energy costs.

It will be appreciated by those skilled in the art that the invention is not limited to the precise details as described herein. Many embodiments are possible without departing from the scope of the invention.

BREDENKAMP ATTORNEYS AGENTS/ATTORNEYS FOR THE APPLICANT