GB2034375A - Mineral-mining cutter drum - Google Patents

Abstract

A cutting drum for a mining machine comprises a drum body (6) and one or more helical vanes (10, 12, 14) extending around the drum body. Whereas in conventional cutting drums, when viewed in longitudinal section, the vanes extend at right angles to the longitudinal axis of the drum, in accordance with this invention the vanes as a whole or a portion provided by or secured to the vane provides a surface (11, 13, 15, 22) which, when viewed in longitudinal section, extends generally rearwardly, being inclined at an acute angle to the longitudinal axis of the drum, over part only of the spiral channel which is deformed by the rearward face of the vane. This assists rearward movement of the mineral being mined (e.g. coal) towards the face-side conveyor. <IMAGE>

Description

SPECIFICATION Cutting drums for mining machines Cutting drums for mining machines conventionally comprise a hollow cylindrical body adapted to be rotated by drive means about a longitudinal axis and, upon which one or more helical formations (conventionally termed vanes) are provided. Mounted in housings (conventionally termed pick boxes) secured at circumferentially spaced positions around the periphery of the vanes, are cutting tools, conventionally termed "picks".

In the use of the cutting drum, the drum is presented to the face being worked, and is simultaneously rotated about its longitudinal axis, and is traversed across the face. The picks attack the face, and material cut from the face falls into the spiral channel or channels between the vanes, rotation of the drum carrying the material rearwardly from the face, to deposit the material on a conveyor travelling alongside the face.

Such a cutting drum is in common use in the underground mining of coal, in which context the present invention will hereinafter be described. It is however to be appreciated that the invention is not limited to the underground mining of coal.

The rate at which material (such as coal) is cut and removed from the coal face is limited by (inter alia) the size of the cutting drum, its speed of rotation and its rate of traverse of the coal face. It is or course desirable to remove material at as fast a rate as possible, but in attempting to do this, problems are encountered.

One of the problems which is encountered is due to the continued desirability of operating the cutting drums at higher rotational speeds. Additional to imparting to the coal a component of motion in the rearward direction (viz, from the face towards the conveyor) the drum tends to throw the coal outwardly onto the area recently traversed by the cutting drum.

A conventional method of restraining such escape of cut material from the drum is to provide a cowl on the trailing side of the drum. However, the cowl does not contribute in any way to a smooth rearward flow of coal from the face towards the conveyor, and merely bars the radial outward movement of the coal from the spiral channels of the drum.

Additionally, the velocity with which coal is thrown against the cowl is such that a considerable quantity of noise is produced, and considerable breakage of coal into smaller pieces takes place, together with the creation of considerable quantities of dust.

Further, the presence on the cowl decreases the versatility of the drum, particularly at the opposite ends of the run, and necessitates either the use of an additional cutting machine at the ends of the run, or the use of a cowl the position of which on the drum may be adjusted.

With the prime object of overcoming the latter problem, a suggestion has been made in U.K.P.S. 1 176 476 to enclose the spiral channels in a circumferential sense, with a generally frusto conical shield extending across the helical vanes, the shield having radially extending openings facing the seam being cut to allow cut mineral to enter the channels. Whereas this suggestion solves some of the problems associated with the use of a cowl, other problems are created.

In particular, since the picks must lie in a generally cylindrical envelope, the shield cannot extend radially outwardly beyond the pick boxes, or it would interfere with the smooth cutting of the coal. Further, to provide radial openings facing the seam being cut, and to allow the cut coal to enter the spiral channels, (particularly where the cutting drum comprises more than one helical formation) it is necessary for the shield to taper in a reducing diameter extending away from the face being worked. This necessitates that the coal travelling towards the conveyor is ducted through one or more spiral channels which decrease in radial extent, and this consequently subjects the coal in the channel to a considerable tumbling, which tends to break the coal into smaller pieces, again creating quantities of dust.

Additionally, with a frusto-conical taper, as is required in a construction in accordance with U.K.P.S. 1,176,476 coal is thrown radially outwardly against the inner side of the shield against a surface at an angle which tends to throw coal back in a forward direction towards the face being worked. This positively impedes flow of coal towards the conveyor, and decreases significantly the rate at which the cutting drum can operate. Increase in the power applied to the machine, whilst increasing the rate of coal removal marginally, is dissipated in the main in pulverising of the coal, with the creation of noise and dust.

An additional difficulty is that a greater quantity of coal is contained between adjacent vanes at the rear of the drum, than at the front of the drum, and with faster operational speeds difficulty may be encountered in the smooth rearward feed of the band of coal between adjacent vanes and smooth transference thereof onto the conveyor. Although this problem is significantly reduced by a cutting drum of the kind described and illustrated in the Specification of our U.K. Application No.

2000539A (in which the diameter of the drum decreases in the rearward direction, whilst the vanes are maintained at a constant outer diameter) there is still produced a considerable tumbling of the coal, which not only produces considerable quantities of dust (des pite the coal face having been sprayed immediately prior to being attacked by the picks), by also interferes with the smooth transference of the coal onto the conveyor.

It is one of the various objects of this invention to minimise some at least of the problems set out above.

According to this invention there is provided a cutting drum for a mining machine comprising a drum body and one or more vanes extending helically around the drum body from the forward end towards the rearward end, the or each vane being provided with an inclined surface which, when viewed in longitudinal cross section, extends (in a direction from the front towards the back) generally away from the longitudinal axis of the drum, and over part only of the spiral channel which is defined by the rearward face of the vane.

In this manner, not only will a component of rearward motion be imparted to the coal between adjacent vanes by virtue of the helical extension thereof, but an additional component of rearward motion will be imparted to the coal by said inclined surface. Additionally whereas the component of motion imparted by virtue of the helical extension of the vanes is associated with no significant component of motion in a direction radially of the drum, the inclined surface will be effective to convert the radial outward movement of the coal, under the action of centrifugal forces, into a generally rearward movement.

An additional problem encountered in the high speed operation of cutting drums is the tendency of coal which is thrown outwardly of the drum, under the action of centrifugal forces, to strike the underside of the pick boxes which (viewed in the axial direction) are generally wider than the width of the vane portions upon which they are mounted. Such blows, although not necessarily individually being harmful, can over an extended period of working cause failure of the junction between the pick box and the vane, which is usually a welded joint. Such failure can either reduce the efficiency of the cutting drum, or require the cutting drum to be taken out of service.

The latter is a time consuming operation, and necessarily involves the shutting down of the face being worked for a cosiderable period of time.

Whereas to a limited extent the suggestion made in U.K.P.S. 1176476 can be utilised to protect some of the pick boxes, it cannot be used to protect all the pick boxes, particularly those on the side of the drum most remote from the face being worked.

Conversely, in accordance with the present invention, the inclined surface may extend beneath the pick boxes secured to the vane, providing poor protection to all the pick boxes secured to the helical vane over its entire helical extent.

If desired, said surface may be provided by an inclination of the or each vane as a whole at an acute angle to the longitudinal axis of the drum, such angle conveniently lying between 65 and 80 to the longitudinal axis of the drum. Preferably, however said inclined surface is provided at a radially outer section only of the or each vane, the inner section extending, as conventional, in a plane (when viewed in longitudinal section) extending at right angles to the longitudinal axis of the drum.

Such outer section may be afforded by bending of the vane or vanes in a manner such that the radially outer portion is afforded with an inclination additional to the inclination afforded to the vane as a whole by virtue of its helical extension. Preferably however said inclined surface is afforded by a lip portion which extends beneath the pick boxes, affording protection thereto against the action of coal thrown radially outwardly of the drum under the action of centrifugal forces.

Preferably the surface provided by the lip is curved, a radially innermost portion thereof (when viewed in longitudinal cross-section) extending generally at right angles to the longitudinal axis of the drum, and a radially outer portion being inclined at an angle of no more than 45 to the radially inner portion.

By the provision of a curved surface, the lip performs a "ploughing" operation on the coal in the channel, tending to "turn" the band of coal between adjacent vanes, so that the coal first cut by the drum (being the wet coal by virtue of the spraying of the face being worked with water immediately prior to an attack by cutting picks), and which is located initially radially innermost, will be turned over so that the wet coal adopts an outermost position, assisting in the suppression of dust.

Whereas such an inclined surface may be provided on the or each vane along the whole or a majority of the whole of the helical extension thereof, the provision of such an inclined surface is most advantageous when provided at a rearmost portion of the or each vane, and in particular to that rearmost portion of the or each vane which is "free' '-that is, which is not overlapped in a rearward direction by an adjacent vane (or portion of the vane, if there is only one).

When applied to such portion of the or each vane, the extent and inclination of the said inclined surface may be greater without the incurrence of the problem encountered in a reduction in the size of the opening presented between adjacent vanes, through which opening freshly cut coal falls into the space between said adjacent vanes. Thus, a greater degree of rearward "throw" of the band of the coal may be provided by such an inclined surface over this portion of the or each vane, as distinct from portions of the or each vane which are not "free".

Additionally, the provisions of such an inclined surface on the free end portion of the vane may assist in a lifting of the band of coal from a lowermost position, up and onto the conveyor. This advantage is particularly significant when the height of the conveyor above the floor is greater than (say) 7".

Whereas this invention is particularly suitable for use in a cutting drum of the kind described and illustrated in the specification of our co-pending application number 2000539 A, the invention may be used with considerable advantages in other, conventional cutting drums.

The invention will become more clear from the following description, to be read with reference to the accompanying drawings, of various embodiments thereof.

In the accompanying drawings: Figure 1 is a side elevation of a cutting drum of the general kind illustrated in the drawings of our co-pending application number 2000539 A; Figure 2 is a developed plan view, schematic in form, of the cutting drum illustrated in Fig. 1; Figure 3 is a side elevation of the cutting drum which is the preferred embodiment of this invention; Figures 4, 5, 6, 7 and 8 are longitudinal sectional views, illustrating various formns of execution of this invention.

The cutting drum illustrated in Fig. 1 comprises a generally frusto-conical body 6 in the form of a hollow drum, a front plate 8 at the forward end thereof, and three formations or vanes 10, 1 2, 14 extending helically around the body 6 from the forward to the rearward end thereof. Mounted on the front plate 8, and at spaced positions around the periphery of the vanes 10, 1 2 and 1 4 are pick boxes 16, which carry cutting tools in the form of picks 18.

Fig. 2 is a developed plan view in schematic form, illustrating the relationship between the drum body 6 and the vanes 10, 1 2 and 14. It will be appreciated that, in longitudinal section (that is, in a plane including longitudinal axis of the drum) the vanes will be seen as extending at right angles to the longitudinal axis of the drum, notwithstanding their helical progression around the drum.

Thus, during rotation of the drum, the only component of rearward motion imparted to the bands of coal between adjacent vanes will be by virtue of said helical progression.

In accordance with this invention, the body 6 of the cutting drum is generally frustoconical, comprising a front plate 8 and three helical formations or vanes 10, 12, 14. In accordance with this invention, each of the helical formations 10, 1 2 and 14 is provided with an inclined surface 11, 13, 1 5 respectively, which when viewed in longitudinal cross-section, extends (in a direction from the front towards the back-that is towards the right in Fig. 3) generally away from the longitudinal axis of the drum, and over part only of the spiral channel which is defined by the rearward face of the vane, and the forward face of the immediately following vane.Additionally, the front plate 8 is similarly provided with an inclined surface 9, which when viewed in longitudinal cross-section also extends generally away from the longitudinal axis of the drum, in a similar manner.

Mounted on the front plate 8, and at spaced positions around the periphery of the front plate 8, and around the periphery of the vanes 10, 12 and 14 are pick boxes 16, which carry cutting tools in the form of picks 1 8. During rotation of the drum, and traverse thereof across the face being worked, the picks 1 8 attack the mineral face and pieces of coal fall into the spiral channels between adjacent vanes, and are conveyed, as a band, towards the rearward (right-hand) end of the cutting drum to be deposited on a conveyor (not shown) extending along the face side.

Various practical forms for manufacturing a cutting drum in accordance with this invention will now be described, with reference to the schematic drawings which constitute Figs. 4 to 8. It is to be appreciated that these drawings are to be considered in conjunction with known technology in the art of manufacturing cutting drums for underground mining machines.

In the construction shown in Fig. 4, said surface 22a is provided by a helical member 21 of somewhat triangular cross-section secured by a welding operation to the rearwardly-facing surface 24 of each vane (which surface 24, when viewed in longitudinal section, extends at right angles to the longitudinal axis of the cutting drum). Although the surface 22a shown in Fig. 4 is curved, and the angle between the longitudinal axis of the cutting drum and tangents to said surface decreass from 90 to about 30 , if desired, said surface 22a may be straight, extending at about 45 to the longitudinal axis.

In the construction illustrated in Fig. 5, each vane is cut along a helical line a short distance into its radially outermst portion, and an axially outer portion is deformed so as to present a surface 22bwhich is inclined at an acute angle of about 45 to the longitudinal axis, the space between the deformed and undeformed portions of the vane being infilled with brazing material.

In the construction illustrated in Fig. 6, each vane as a whole is inclined, when viewed in longitudinal section, to the longitudinal axis of the cutting drum, at an angle between 65 and 80 (being, as shown, preferably at about 75 ) to said longitudinal axis.

Thus, the outwardly-facing surface as a whole affords an inclined surface 22c.

In the construction illustrated in Fig. 7, each vane is prefabricated from two vane sections 10a, 10b, one of which (when viewed in longitudinal section) extends at right angles to the longitudinal axis of the drum, the other of which being at a radially outer portion inclined at an acute angle to the longitudinal axis of the drum to present a rearwardly-facing inclined surface 22d. In the construction illustrated in Fig. 7, the section 10a may be of smaller thickness than the conventional vane (being reduced, compared with the vane thickness shown in Fig. 4, from 50mm. to 30mm., and being, as conventional, of mild steel) and the section lOb may be of 10mm. thickness, being of a higher grade steel such as stainless steel.In this manner, the reduction in the space between adjacent vanes occasioned by the use of the present invention may be lessened.

In Fig. 8, a construction is shown in which a radially outer portion of each vane is deformed to afford surface 22ewhich is inclined at about 75 to the longitudinal axis of the cutting drum.

By the provision of such a rearwardly4acing inclined surface as is shown in Figs. 2 to 8, during rotation of the cutting drum a greater rearward impetus is provided to the coal between adjacent vanes, assisting movement of the coal away from the face being worked towards the conveyor. Additionally, said inclined surface may function in a manner somewhat akin to the action of a plough, turning the band of coal over during its progression towards the conveyor. In this manner, coal first cut from the face, being the wet coal in view of the spraying of the face immediately prior to an attack by the picks with water, will adopt a radially outer position, assisting in the suppression of dust.

Further, in the portions of the band of coal adjacent to the floor, said inclined surface will assist in "lifting" the coal from the floor level, and depositing the coal on the conveyor belt.

Whereas the invention is illustrated in the accompanying drawings in use as part of a cutting drum, the body of which is tapered, the invention may be used with simiiar advantage in conventional cutting drums, such as those the body of which is of constant diameter.

Additionally, whereas the invention may take the form of the provision of an inclined surface on the whole of the helical vane or vanes, the invention may take the form of the provision of such a surface on a portion only of the or each vane. In particular, such an inclined surface may be provided only at a rearmost portion of the or each vane, and in particular that rearmost portion of the or each vane which is "free"-that is, which is not overlapped in a rearward direction, by an adjacent vane (or a portion of the vane, if there is only one). The "free" rearmost portions of the vanes 10, 1 2 and 14 are indicated in Fig. 2 by the letters a, b and c. It will be appreciated that these portions of the vane are responsible in the main for lifting coal from the floor level onto the conveyor belt.

Additionally, whereas the extent of the rearwardly inclined surface on portions of the vane which are not "free" is limited by the need to provide sufficient space between adjacent vanes in the axial direction (to allow coal cut from the face to fall into the channels between adjacent vanes) this limitation does not apply to the "free" rearmost portions of the vanes, and over these sections, the extent of the rearwardly facing inclined surface may be increased.

Thus, in a highly advantageous utilisation of this invention, over the initial sections of the vanes an inclined surface is provided which is relatively small in axial extent, and over the remainder, "free" sections of the vanes, an inclined surface which is greater in axial extent may be provided.

It will additionally be appreciated that in the constructions illustrated in Figs. 4, 5 and 7 said inclined surface is so arranged as to provide protection to the underside of the pick boxes 16, to minimise the likelihood of damage being caused to the pick boxes by pieces of coal being thrown there against and a centrifugal force is created by rotation of the cutting drum.

Claims (14)

1. A cutting drum comprising a drum body and one or more vanes extending helically around the drum body from the forward end towards the rearward end, the or each vane being provided with an inclined surface which, when viewed in longitudinal crosssection, extends (in a direction from the front towards the back) generally away from the longitudinal axis of the drum, and over part only of the spiral channel which is defined by the rearward face of the vane.

2. A cutting drum according to claim 1 wherein the or each vane as a whole is inclined at an acute angle to the longitudinal axis of the drum, when viewed in longitudinal cross-section, to provide said inclined surface.

3. A cutting drum according to claim 2 wherein said inclined surface lies between 65 and 80 to the longitudinal axis of the drum.

4. A cutting drum according to claim 1 wherein said inclined surface is provided at a radially outer section only of the or each vane, the inner section of the vane (when viewed in longitudinal cross-section) extending in a plane extending at right angles to the longitudinal axis of the drum.

5. A cutting drum according to claim 4 wherein the radially outer section of the vane is deformed and extends at an inclination which is less than 65 to the longitudinal axis of the drum to provide said inclined surface.

6. A cutting drum according to claim 5 wherein the angle of inclination is greater than 45 .

7. A cutting drum according to claim 4 wherein the inclined surface is curved, and is provided by a deformation of the radially outer section of the vane.

8. P cutting drum according to any one of the preceding claims wherein said inclined surface is afforded by a circumferential lip portion which is secured to the vane.

9. A cutting drum according to claim 8 wherein the lip is afforded by a separate member secured to a radially outer portion of the vane.

10. A cutting drum according to one of claims 8 and 9 wherein the lip portion extends beneath some at least of the pick boxes secured to the vane.

11. A cutting drum according to any one of claims 8, 9 and 10 wherein the inclined surface provided by the lip portion, when viewed in longitudinal cross-section, is curved.

1 2. A cutting drum according to any one of the preceding claims wherein the said inclined surface is provided over the whole or a majority of the whole of the helical extension of the or each vane.

1 3. A cutting drum according to any one of claims 1 to 10 wherein said inclined surface is provided at a rearmost portion only of the or each vane.

14. A cutting drum according to claim 1 3 wherein said inclined surface is provided at a "free" portion (as hereinbefore described) only of the or each vane.

1 5. A cutting drum according to any one of claims 1 to 11 wherein the said inclined surface extends over a forward most region of the or each vane, which vane provides, or has secured thereto a portion which provides, a further inclined surface which when viewed in longitudinal section extends generally rearwardly, being inclined at an acute angle to the longitudinal axis of the drum and of greater axial extent than the first said inclined surface.

1 6. A cutting drum according to any one of the preceding claims wherein the drum body is tapered, increasing in diameter from one end to the other.

1 7. A cutting drum according to claim 1 5 wherein the diameter of the drum body de creases in the rearward direction, in periphery of the or each helical vane being located in a cylindrical surface of constant diameter.

1 8. A cutting drum constructed and ar ranged substantially as hereinbefore described with reference to Figs. 3, 4, 5, 6, 7 or 8 of the accompanying drawings.