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March, 1961

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An account of further cutter-loaders developed for non-cyclic mining operations is given below.

Double-ended buttock miner

This is one of the most recent machines (Fig. 59) developed by Joy-Sullivan Limited. As the name implies the machine is double-ended, i.e. each end has similar cutting heads incorporated to the main body of the machine which is fitted with crawler tracks. This eliminates flitting and change time. The position of the cutting head can be altered in the vertical plane by hydraulic means to suit conditions. The machine can thus follow the undulations in the seam. Each cutting head consists of two borers rotating in opposite directions and a frame cutter chain that profiles the cut, traversing the bottom, face side and the top. A cross conveyor is incorporated in each head and this loads the coal on the longwall face conveyor. Power for the boring arms and cutter chains is supplied by a 100 h.p. water cooled motor to the leading head through an overload clutch and suitable gearing. A separate 25 h.p. motor powers pumps to furnish hydraulic fluid to the traction motors, the conveyor motors and the head-positioning jacks.

The loop cutters of the heads are adjustable for height of cut. The trailing head can be contracted when not in use. On reaching the stable hole the machine can be pushed over into its new track by hydraulic jacks operated from the machine.

The machine cuts a 5 ft. web and can work in seams 37½ in. to 5 ft. high. It is 18 ft. long, weighs 15 tons, and has been used in Areas 5 and 6 of the East Midlands Division.

Performance has been established at quite a high level in these experiments apart from few teething troubles32. In a 4 ft. 7 in. thick seam, this machine has been proved capable of steady cutting speeds of about 55 yds. per hr., more than twice the rate obtained by the Meco-Moore cutter-loader in similar conditions.

Over a period of 9 weeks, the O.M.S. has averaged 8.6 tons raised and weighed. The size of the R.O.M. product is given below —

It can be said, that from the results so far obtained the machine seems to have a promising future. Further attention to modify the head and rotary arms is being paid with a view to effecting improvements.

The Muschamp coal winner

The Muschamp coal winner (Fig. 60) is one of the most recently developed cutter loaders, it is designed as a conversion unit for the Anderton Shearer drum, and is designed to produce as cheaply as possible a reasonable percentage of large coal. This object is achieved by cutting at both the top and the bottom of the seam with two rotating drums of 12 in. diameter and simultaneously shearing the back of the cut with a narrow-kerf jib and chain The production of fines is thus limited to the actual cutting areas and the main section of the seam is extracted untouched by the cutter picks. The coal is delivered at the rear of the machine on to a loading plough and thence on to the armoured scraper chain conveyor on which the complete machine is situated and along which it traverses the face.

The standard cutting head is bolted on to the machine and no alteration to the machine is necessary. It is pivotally mounted in the position normally occupied by the conventional Anderton Shearer drum and by rotation about its central pivot can be so arranged to cut at different heights of seam without alteration to the cutting head itself. The only adjustment necessary is the raising and lowering of the machine on top of the conveyor so that the lower cutting drum is always working at floor level.

This adjustment of the cutting head is a useful feature when flitting, as it permits the head to be swung to a more or less horizontal position to clear newly-set roof bars and other obstructions.

The cutting head consists of a gearbox coupled on to the cutting unit of the machine and having at each end, projecting at right angles to the gear box, a rotating drum carrying cutter picks. These drums are connected at the face side by a narrow kerf back shearing jib and chain of conventional design.

The loading unit, which is attached to the rear of the machine, comprises a hydraulically driven flighted chain-type gummer operating at floor level and discharging on to the conveyor, a wedging platform designed to break down extra large pieces of coal to manageable proportions, and a plough for diverting the coal on to the conveyor. The plough section is provided with leading and trailing faces and a hinged central partition so that it will deflect the coal in either direction of travel. When flitting, it automatically clears residue coal left at the face in preparation for the next cut.

The Muschamp coal winner is easily adaptable to all makes of Anderton Shearer machines. In general, it is only required to shorten the main output shaft, incorporate a hydraulic pump and valve gear, and substitute a special adaptor unit in place of the standard rope bollards to allow the haulage rope to be led off to both front and rear on the gob side of the conveyor. A fabricated plough is attached to the front of this adaptor section for clearing the face ahead of the machine.

One disadvantage however, is that when operating in friable coal, the block tends to be comminuted by the drum at floor level32. The future application of the machine may well be limited only to hard coals.

Mawco cutter loader

This is another recent cutter loader which has been designed and produced by Austin Hoy and Company, in collaboration with the mechanisation department of No. 1 Area, East Midland Division, N.C.B. Underground trials with the prototype have given very successful results. The Mawco cutter unit can be attached to any standard longwall coal cutter equipped with a horizontal drive shaft for disc shearing. This unit produces a larger size of coal than the ordinary disc or drum shearers. The Mawco cutter unit consists of drive sprocket, frame jib, special flexible chain and breaker bar. Fig. 61 shows the Mawco cutter loader in position for flitting. Another view of the machine from the drive-end is shown in Fig. 62.

The adaptation of the disc shearing machine is performed by the removal of the drum from the horizonal drive shaft and its replacement, on a shortened shaft, by a chain drive sprocket to which is fitted, if required, a breaker bar extending as far as necessary into the cut coal. A Hoy side-flexing ball joint type chain, or alternatively, a Hoy dumb-bell flexible chain is driven from the sprocket round a frame jib which has a curved track to bring the pick points into a forward cutting position. Cutting, as with the conventional disc shearer, is carried out in one direction only. Where required the top section of the frame jib may be lowered for flitting, although this has not been found necessary in the trials which have been undertaken. Tests carried out so far show that a cutting speed of the order of 6 ft. 6 in. per min. can be maintained without stalling. The design provides that kervings from the chain are removed and deposited on the conveyor without further degradation, and early indications show a marked increase in +2 in. coal32. Further development work is being carried out in order to determine improvements in chain design and pick lacing with a view to reduction in the in. to 0 size of the product.

On a 200 yd. coal face in the High Hazel seam at Whitwell one of these machines is now achieving about 7 tons per man shift and about half of the total production is of coal more than 2 in. in size. (See Fig. 63.)

CUTTER LOADERS
WEDGING ACTION (Ploughs)

The main work on the development and design of the Plough has been done in Germany. There are many types of ploughs but only those used in British coal fields will be reviewed. Broadly speaking there are two main types of ploughs —

1. Static blade plough

2. Activated blade plough

The static blade plough can be further divided into slow speed and fast speed ploughs. Among the slow speed ploughs which have been used in British coalfields are:

1. Standard plough

2. Cutter plough or Schramhobel

3. Peeler plough

4. Samson stripper

Standard plough

This plough was first introduced in Great Britain at Morrison Busty Colliery in 1947, and later at New Hucknall in 1950. It was only suitable for soft coal and has been superseded by other types of ploughs.

The standard plough is designed to cut and load the coal in both directions. The correct shape and position of the shear blade is of considerable importance. The overall dimension of the standard plough used at the Morrison Busty Colliery was :—

20 ft — length 2 ft. 4 in — width Total weight 2½ tons. 2 ft. — height

The height of the machine depends on seam thickness and is usually ½ to 1/3 of the seam height. The plough is pulled to and fro along the face by means of rope haulage which is capable of exerting a pull of 10 to 12 tons with single rope purchase and twice this amount with double purchase. The plough is held against the face by pressure jacks acting against the structure of the armoured conveyor.

In the Morrison Busty seam on a 75 yd. bordface the plough gave a face O.M.S. of just over 12 tons and a district O.M.S. of about 4 tons. On a 140 yd. end face the O.M.S. was 7.37 tons for the face and just over 3 tons for the district.

Cutter plough or Schramhobel

This plough can be used in harder seams than can the standard plough. It was first introduced in Britain in 1951 at Thrislington Colliery.

Normally the plough is single-ended but a doubleended model is also used38. The plough runs against the side of the conveyor and is constructed in three jointed sections to give flexibility. The plough consists of 4 blades at the front end to pre-cut the coal to a total depth of 10 in. and each blade cuts 2½ in. deeper than the previous one. The pre-cut is 2 in. high. Behind these blades there is a vertical shear blade which is 1 ft. high and cuts above the pre-cut to a depth of 10 in. The bottom section of the coal is removed by another set of three blades which follow a short distance behind the vertical shear blade. The height of the pre-cut from the floor is roughly two thirds of the full height of the plough, The coal is loaded on to the conveyor by plough plate. At the back of the plough there is another plough plate and a cutting blade to clean up the track when the plough is flitting. The normal cutting speed is 18 ft. per min. and the flitting speed 36 ft. per min.

The single-ended Schramhobel was installed on a 160 yd. face in a 3 ft. seam. Compressed-air pushers for the armoured conveyor were installed at 10 yd. intervals. The plough was pulled by a 50 h.p. hauler situated in the tail gate. The hauler was a clifton wheel with three turns of rope around it. The slack rope is taken up by a compressed-air hauler. The plough is flitted back from the tail gate by means of a 15 h.p. electric hauler situated in the main gate.

The face is supported by I m. long G.H.H. link bars and Schwartz friction props. Three yard wide strip packs are made with 14 yd. wastes. There is a dummy road in the centre of the face with a 3-yd. pack on either side. Timbering was based on a prop free front system with staggered bars.

The coal was worked two shifts a day. Stone work was carried out during the night shift.

The following manpower was used:—

Five cuts of 10 in. were obtained each day giving an O.M.S. of 43 tons.

The Schramhobel can negotiate faults. At Thrislington Colliery in a 3 ft. seam an O.M.S. of 6.2 tons was attained.

A recently modified form of this type of plough, called Hard Coal Hobel, with pre-cutting kerving bits which are adjustable in height can be seen in Fig. 64.

Peeler plough

This plough was designed by a British Mining Engineer and depends on making an undercut leaving the top coal to fall on to the armoured conveyor. During its early trial at Llanhorsan Colliery in South Wales, the plough did not show much promise.

Later on, in a number of installations in the Scottish coalfield this kind of plough with some modifications was used with considerable success10

Pulsed infusion shotfiring was tried in one instance to soften the top 12 in. of coal prior to ploughing so that this would fall as the plough extracted the comparatively soft lower portion of the seam.

Samson stripper

The Samson stripper has been developed and designed by Mayor and Coulson Limited, and the prototype was working in 1945. The machine can work in medium hard coal. It works on the wedging principle and is self-propelled (Fig. 65). The machine fixes itself between the roof and floor by means of a hydraulic jack which is capable of exerting a pressure of 100 tons. A horizontal hydraulic cylinder pushes the plough unit forward into the coal. When the vertical jack is retracted the machine is brought forward up to the ploughing head by reversing the direction of pressure in the horizontal cylinders. The cutting of coal and the moving of the central hydraulic jack forward comprise one cycle. The stripper progresses along the face in strips. Each strip may be anything up to 2ft. 7 in. It is thus a slow speed static blade plough. It is a double-ended machine with similar cutting heads at each end. Each head consists of four vertical shearing blades. Any one of these blades can be arranged to be some 18 in. in advance of the other blades. This arrangement provides facilities for removing any soft band of coal in advance of the other blades which are in contact with harder coal.

Just at the base of the cutting head there is a horizontal blade which prepares a level floor for the operation of the stripper. Another horizontal cutting blade may be fitted at roof level of the machine.

A 30 h.p. squirrel cage motor (1 hr. rated) provides power to the hydraulic pumps and is mounted in the centre of the machine.

The stripper works in conjunction with an armoured snaking conveyor. (See Fig. 66.)

Although the machine has given good results its application is limited by the requirements of a strong roof and floor. The machine requires stable holes at each end of the face. The first production model was introduced in 1948. This machine has been used in an American mine with some success.

Installation at Brackley Colliery.

Brackley Colliery is situated in No. 1 Area of the N.C.B., North Western Division.

The Samson stripper was installed on a single unit face lying at a depth of 1,400 ft.46. The face was advancing along a dip of 1 in 6. the line of face being on bord. The seam was 4 ft. 11 in. thick with two dirt bands near the upper part of the seam. Seven inches of coal were left at the top to form the roof. The seam is overlain by layers of soft weak bind and it is underlain by a friable coal 1 ft. thick beneath which is a band of warrant. The face was 140 yd. long and was served by three gates, the lower (left hand side) one houses the roadway conveyor.

The coal-getting operation consisted of pre-cutting the face with an A.B. Fifteen coalcutter mounted on an armoured conveyor and fitted with a straight jib. The stripper followed the cutter (starting from another gate) taking a 2 ft. web of coal. One strip is completed in a total time of 2½ hr. The machine is then prepared for the next strip in the reverse direction. During this time the snaking of the conveyor is completed and the coal cutting machine is flitted back to the other end to make a second cut. The second cut takes about 1hr. and by the time the coalcutter reaches the other end of the stable the stripper, the roof supports and the conveyor are in position ready for the commencement of the return trip. To pass the stripper the jib of the coal cutter is swung over the conveyor. As soon as the stripper is clear of the stable bole, work commences on moving forward the tail end of the conveyor, the roof supports and the conveyor.

The stable at the mother gate is 12 yd. long and the tail gate stable is 10 yd. long. Each stable is made 6 ft. in advance of the face line.

Manpower at the face :—

The machine was taking two strips per shift. The face length was extended to 180 yd. giving a face O.M.S. of 125 cwt. compared to 66 cwt. by a hand loaded face in the same seam.

Rapid ploughs

Although some of the slow ploughs were found to work satisfactorily they have certain disadvantages. They are bulky and heavy and the output is limited by their slow speed. Deep cuts are thus a necessity. To overcome this, experiments were progressing in Germany to develop rapid ploughs. The most popular of the rapid ploughs is the Loebbehobel and its conversion unit Anbauhobel.

The Loebbehobel is capable of working in seams 1 ft. 8 in. to 7 ft. in thickness and can produce, load and deliver to a gate conveyor from 1.5 to 5 tons per min. or 500 to 1,500 tons per shift. This plough makes a shallow cut of 2 in. to 6 in. deep and the cutting speed is 72.5 ft. per min. The cutting unit is driven by the same motor which drives the armoured conveyor. Different types of cutting bits can be fitted to the Loebbehobel to suit different conditions.

The equipment consists mainly of the Westfalia P.F.i Panzer conveyor which uses special drive units. The cutting element runs on guide tubes which are bolted to the structure. The returning hobel chain travels inside these guide tubes. Spill plates are bolted to the goaf side of the conveyor. Tests have proved48 that the double chain Panzer conveyor of this type requires 0. 1 h.p. per ft. of length for 100 t.p.h. of production. A typical layout for a Loebbehobel face is given in Fig. 67.

In cases where coal is too hard the plough can he used to load the prepared coal after cutting and firing. It has operated in seams having gradients from 1 in 12 against the load to 1 in 2¼ in favour of the load. The plough requires stable holes at each end of the face.

Installation at Britannia Colliery.

The first installation of the Loebbehobel or "fast plough" in South Wales was made in 1952 at Britannia Colliery in a 180 yd. long single unit face where average seam thickness was 3 ft. 3 in.50. The cleatline was 45 deg. to the face-line. The plough was capable of operating in either direction and took between a 2 in. and 6 in. slice of coal over the lower 15 in. of the face, the upper section falling after each passing.

The plough was hauled across the face by means of a 7/8 in. mild-steel traction chain which has a breaking strength of 50 tons. The plough was pulled along the face at a speed of 72.5 ft. per min. Two safety shear pins were coupled to the driving wheel to ensure that the maximum pull on the plough was within 20 tons.

Signalling buttons and telephones were positioned every 40 ft. and 60 ft. respectively along the face so that the man responsible for driving the conveyor and plough could be kept informed of all happenings.

Pneumatic rams, held by staker props at one end, were attached to the conveyor structure at 20 ft. intervals and pushed the conveyor and plough up to the face with a pressure of approximately 26,000 lb.

Stables at each end of the face were formed by a team of men who used pneumatic picks to get the coal.

The face was supported by G.H.H. extendible roof bars and Dowty props with a prop-free-front system. Waste was pneumatically stowed to minimise the subsidence effect and to improve the ventilation.

Make-up of the actual plough team operating over three shifts is given below:—

The five day week output was 2,368 tons for an advance of 37 ft. giving a team O.M.S. of 8.2 tons. One main disadvantage of the Loebbehobel is that it requires expensive equipment and can only be installed with its special driving head which is part of the face conveyor. It is thus not possible to use this on faces conventionally worked but using an armoured conveyor. A modification was made to the drive unit of the Loebbehobel and this has become known as the Anbauhobel. The cutting head in the Anbauhobel is the same as that in the Loebbehobel, the difference being that it uses a separate motor for driving the plough. The drive head of the plough or the return end can be fixed to the face conveyor in any position along the face. This makes the system very flexible in negotiating faults. Fig. 68 shows an Anbauhobel mounted on a Panzer conveyor.

(To be continued)

Drawings and Photographs accompanying the article