GB1573505A

GB1573505A - Pick holder assemblies and pick holding blocks therefor

Info

Publication number: GB1573505A
Application number: GB4290476A
Authority: GB
Original assignee: Padley and Venables Ltd
Current assignee: Padley and Venables Ltd
Priority date: 1977-11-24
Filing date: 1977-11-24
Publication date: 1980-08-28

Description

(54) IMPROVEMENTS IN OR RELATING TO PICK HOLDER ASSEMBLIES AND PICK HOLDING BLOCKS THEREFOR (71) We, PADLEY & VENABLES LIMITED of Callywhite Lane, Dronefield, Sheffield, S18 6XT, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to pick holder assemblies and pick holding blocks for such assemblies and is particularly concerned with the structure and construction of such a holder assembly and holding block for use in the retention of a mineral mining or cutter pick.

According to the present invention there is provided a pick holder assembly comprising a pick holding block having a part circular profiled peripheral portion and a socket for the reception and retention of a pick shank; a carrier having a part circular recess which is substantially complementary to the part circular peripheral portion of the pick holding block, said pick holding block being mounted with its part circular portion within, and in substantially complementary relationship to, the part circular recess of the carrier and said block is being secured to said carrier by welding with the socket of the block at a predetermined orientation relative to the carrier; and wherein the pick holding block has at least one passage extending therethrough through which fluid can be directed from the block in a predetermined direction relative to the socket.

Further according to the present invention there is provided a method of constructing a pick holder assembly which comprises forming a part circular recess in a carrier; mounting in said recess and in substantially complementary relationship therewith a substantially complementary part circular profiled portion of a pick holding block having a socket for the reception of a pick shank; rotating the pick holding block within and relative to the recess to locate the socket at a predetermined orientation relative to the carrier, and welding the pick holding block to the carrier to secure the holding block with its socket at said predetermined orientation.

The present invention was primarily developed to provide a convenient and efficient means whereby several pick holding blocks could be secured, in spaced array, on a cutting head of a cutting machine so that a pick retained in each holding block would project therefrom at a predetermined angle relative to the carrier, in such case the cutting head, and which angle would be determined by the particular design of pick and intended cutting motion. In practice the cutting head usually takes the form of a drum (for example of a coal shearer) which is rotatable about its longitudinal axis and has the pick holding blocks located on the outer surface thereof so that picks retained in the holding blocks project outwardly from the drum at calculated angles of attack.In conventional coal shearer drums the pick holding blocks are helically spaced around the drum, being mounted in the peripheral edge of a helical web or flange which is included as part of the drum and extends radially outwardly relative to the axis of the drum. Such web or flange serves as a screw conveyor for displacing coal or other mineral (which has been cut from the mineral face) axially over the drum during rotation of the latter.

Hitherto pick holding blocks for coal shearer drums have been generally cubic and these have been seated and welded into substantially complementary rectangular recesses provided in the peripheral edge of the web or flange of the drum. In this known manner of construction the amount of relative adjustment available between each cubic pick holding block and the web or flange is negligible so that there is a distinct possibility for a pick holder block to be secured to the web or flange at a position in which its socket (and therefore the pick when retained thereby) is inaccurately orientated relative to the drum. As a consequence of this latter effect, although such an inaccurately mounted pick will probably cut into the mineral face such cutting would be inefficient, shorten the life expectancy of the picks and increase the power requirement of the drum.

By the present invention the web or flange (which together with the remaining portion of the drum is regarded as an example of "a carrier" in accordance with the invention) can be machined with a part cylindrical recess in the peripheral edge thereof and into this recess is fitted a substantially complementary part cylindrical Dick holder block which includes the socket for receiving and retaining a pick shank. With the pick holder block mounted in the part cylindrical recess of, say, the web, the block may be rotated within the recess and relative to the web (by relative rotational sliding movement between the opposed cylindrical surfaces about an axis which is generally perpendicular to the intended direction of cutting) until the socket is accurately positioned in so far as its angular relationship is concerned with respect to the drum.This latter positioning is conveniently achieved by mounting in the pick holder block the pick which it will accommodate in use and rotating such block until the pick presents the required angular relationship relative to the drum (as may be determined by use of an appropriately shaped template). After being position, the pick block may be tack welded to the drum web, the pick removed therefrom and then the block further welded to the web.

To alleviate the possibility of the pick holding block from breaking out of the carrier during use and to provide a substantial surface area over which the pick holding block can be welded to the carrier, it is preferred that the substantially complementary part circular profiles have an extent which is greater than one half of the respective circumferences of the notional circles of which they form part. By this latter preference it will be apparent that the pick holding block must be inserted "sideways-on" into the part circular recess, that is to say moved into the recess in a direction which is perpendicular to the plane of the circle of which the recess forms part and which is generally perpendicular to the intended direction of cutting (when mounting the block in a drum web as aforementioned) .

The recess and pick holding block may be, for example, substantially of part cylindrical profile as previously mentioned or of part rusty conical profile. When of substantially part cylindrical profile, the pick holding block may be moved axially along the part cylindrical recess; this is particularly desirable since it may permit the pick holding block to be adjusted axially in the web of a coal shearer drum so that a side face of the pick holding block forms a relatively smooth (within broad tolerances as would be expected bearing in mind the rugged nature of mineral mining machinery); transition surface with the adjacent side face of the web or flange.This substantially smooth transitional positioning of the pick holding block will usually be provided on, what is well known in the art as, the loading side face of the web when the latter is of screw conveyor form as above mentioned. Throughout this specification the loading side face of the web is regarded as that side face over which the mineral slides to be displaced axially over the drum. It is believed that the aforementioned smooth transitional positioning will permit a reduction in the power requirement for driving the drum, will provide smoother running for the drum, will provide improved flow of mineral axially over the drum and will ro- vide less degradation of the mineral and therefore less mineral dust) while the mineral is being screw conveyed from the drum.

Furthermore, by mounting the pick holding block in the web or flange so that the recess in the latter encircles the major extent of the circular portion of the pick holding block and only a relatively minor portion of the pick holding block extends outwardly of the web and radially of the drum, it is believed that there is less likelihood of the pick holding block being damaged by impact on the mineral face, that there will be less degradation of the mineral and that there will be smoother running of the drum in comparison with similar drums having conventionally mounted pick holding blocks.

Still further according to the present invention there is provided a pick holding block for use in a pick holding assembly, said block having a socket for the reception and retention of a pick shank and a part circular profiled peripheral portion which portion is arranged so that, in use of the block, it can be received and secured within, and in substantially complementary relationship to, a substantially part circular recess in a carrier, and wherein the block has extending therethrough at least one passage through which, during use of the block, at least one fluid stream is intended to pass and be directed outwardly of the block at a predetermined direction relative to the socket.

In conventional coal shearer drums it is usual for there to be provided on the web or flange an array of nozzles through which fluid, usually water, is intended to be jetted on to the cutting tips of the picks for dust suppression. Hitherto these nozzles have been mounted on the peripheral edge of the drum web or flange in communication with passages through the wall thickness of the drum which communicate with a high pressure water chamber located within the drum.

Such previously proposed arrangement has the disadvantage that the mounting of the pick holding blocks are completely independent of the mounting of the nozzles associated therewith and it frequently occurs that the water jet is not applied to the respective pick cutting tips; furthermore, the mounting of the nozzles independently of the pick holding blocks results in the nozzles being located on the outer edge of the web or flange at positions remote from, and leading, the pick holding blocks in the intended direction of drum rotation with the effect that the nozzle is extremely vulnerable to damage by mineral impact.By the present invention however one or more nozzles can be fitted to the pick holding block in communication with the fluid passage or passages and the orientation between the or each nozzle and the socket is fixed at a predetermined relationship which relationship is maintained irrespective of any rotational adjustment between the pick holding block and the carrier. In general the picks which will be mounted in the socket of a pick holding block will be of similar sizes and configurations so that their cutting tips will usually be located at approximately the same position with respect to a particular holding block, consequently when this position has been determined the or each nozzle can be fitted to direct its water jet or jets accordingly.Desirably the or each nozzle is located on the pick holding block within a rebate at a position adjacent to the pick socket so that, during use of the block for cutting the presence of a pick in the socket together with the material of the block itself affords a measure of protection against the or each nozzle being damaged.

In constructing a pick holder assembly in which the pick holding block includes one or more fluid passages as aforementioned, after welding of the pick holding block to the carrier. a fluid passage in the holding block is extended through the carrier to permit such passage to communicate with a source of fluid under pressure. Conveniently the extension is achieved by a boring operation using the fluid passage in the holding block as a guide for boring through the carrier. A tubular conduit may then be inserted along the fluid passage in the holding block and its extension through the carrier by which fluid under pressure can be passed to a nozzle fitted on the holding block.From the aforegoing description it will be realised that one or more nozzles can be provided and that the nozzle, or one or more of such nozzles, can provide two or more fluid jets directed outwardly of the holding block in predetermined directions (which jets for example can lead, impinge on, or trail the cutting tip of the pick).

When the carrier is in the form of a rotor drum having a web or flange as above described it is preferred that such web is of saw-tooth profile and that each pick holding block is mounted in its complementary recess at a position substantially corresponding to the notional rebate which would otherwise be formed at a junction between two adjacent teeth in said profile.

One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings in which: Figure 1 is a sketch showing a perspective view of a rotor drum for a conventional coal shearer machine including pick holding blocks to form an assembly in accordance with the invention; Figure 2 is a side elevation of part of the drum shown in Figure 1 and illustrates a pick holding block mounted in a web of the drum to provide a pick holding assembly in accordance with the present invention; Figure 3 is a plan view of the assembly shown in Figure 2; Figure 4 is an end elevation of the pick holding block included in the Figure 2 assembly, and Figure 5 is a section through the pick holding block taken on the line V-V of Figure 2.

The basic structure of the coal shearer drum shown in Figure 1 is conventional in that it includes a hollow cylindrical centre part 1 carrying a co-axial sleeve 2 which is intended to receive and to be keyed for rotation with a drive shaft (not shown). Projecting outwardly from one end of the centre part 1 is a circumferential flange 3. Also extending outwardly from the centre part 1 are three substantially parallel webs 4 which progress helically from the flange 3 to the other end of the centre part 1. Located on the outer peripheral edge of the flange 3 are a circumferentially spaced array of pick holding blocks 5. Also located on the outer peripheral edge of each web 4 is a helically spaced array of pick holding blocks 6 which constitute part of the present invention.For convenience of comparison, the pick holding blocks 5 are of conventional form being substantially cubic shape and welded into substantially complementary rectangular recesses in the edge of the flange 3-in a practical embodiment of the coal shearer drum, the pick holding blocks 5 would be replaced by blocks similar to those shown at As shown in Figures 2 to 4 each pick holding block 6 is of part cylindrical shape, the part cylindrical surface 7 of which is received as a sliding fit within a complementary part cylindrical recess 8 provided by a throughbore in the outer edge of the web 4 to which the holding block 6 is secured by welding.It will be noted that the part cylindrical recess 8 extends for a major circumferential part of the notional circle from which it is formed so that there is substantial area for welding bet ween the opposed cylindrical surfaces of the block 6 and web 4 and that the major part of the holding block 6 (as seen in the side elevation of Figure 2) is located within the body of the web 4.

The holding block 6 includes a socket 9 which opens to a seating 10 provided on a flat face of the block. The socket 9 is intended to receive and retain the shank 11 of a conventional mineral mining pick 12 having a cutting tip 13. When the shank 11 is received in the socket the shoulder formed between the head and shank of the pick is intended to abut against the seating 10. The pick can be retained by conventional means in the holding block 6, for example by a "stud-lock" or similar retaining device which is resiliently mounted in a seating 14 provided in a side wall of the mounting lock.An aperture 15 is bored through the mounting block 6 to communicate with the socket 9 (in the region of the free end of the shank 11 when received in the socket) so that an appropriate tool can be inserted through the aperture 15 for prising the pick from the holding block after release of the retaining device.

Also provided in the holding block 6 is a fluid passage 16 formed by boring through the block from a rebate 17 provided in a side of the block adjacent to the mouth of the socket 9. The passage 16 is enlargened at 16a by counter boring from its end which opens into the rebate 17.

For each (coal) mining pick 12, the angle of attack which it presents to the (coal) face during use of the shearer machine is predominantly determined by the orientation and positioning of the pick holding blocks 6 in the webs 4. Consequently the angular relationship between the socket 11 and the web 4 for each pick holding block should be fixed with reasonable accuracy for efficient (coal) cutting. In general the coal picks 12 used on a particular shearer drum will be of the same size and configuration so that when determining the onentation of the pick holding block 6 on the drum the angle a (Figure 2) which should be formed (to provide efficient cutting characteristics) between the longitudinal axis of the socket 9 and a plane which includes the axis of the rotor drum 1 and extends through the cutting tip 13 can be determined with reasonable accuracy.From a knowledge of this angle a, after the pick holding block 6 has been located in the recess 8 of its web 4, the holding block 6 may be rotated within the recess 8 (with the pick retained in the socket 9) about an axis which is generally perpendicular to the intended direction of cutting and until the socket 9 is positioned in the required angular relationship to the drum. This latter positioning is conveniently effected by use of a template mounted on the edge of the web 4. After rotationally positioning the holding block 6 the latter may be tack welded to the web 4 prior to the pick 12 being removed from the socket and the holding block fully welded to the web 4 across the opposed cylindrical surfaces (as indicated at 8a in Figure 3).

When the holding block 6 is welded to the web 4 in its operational position, the longitudinal axis of the socket 9 is located in a plane which is substantially at right angles to the axis of rotation of the drum so that the said axis of the socket is off-set at an acute angle from the loingitudinal direction of the adjacent part length of the outer edge of the helical web 4 (as will be seen from Figure 3).

The off-settin of the socket 9 (and thereby of the pick 12 is achieved by appropriately off-setting the cylindrical recess 8 so that the axis of such recess extends other than substantially normally to the wall of the web 4 (usually the axes of the recesses 8 will extend approximately parallel to the axis of the drum). The off-setting of the recess 8 in this manner alleviates the requirement for a pick holding block of substantial thickness in the direction of the axis of the cylinder from which its surface 7 is formed.

Since the part cylindrical recess 8 encloses the major portion of the part cylindrical surface 7 on the holding block, it will be apparent that the holding block must be inserted sideways on into the recess 8, that is to say in a direction perpendicular to the plane of the notional circle which partly lies in the surface 8 and along an axis which is generally perpendicular to the intended direction of cutting. However, this sideways on positioning of the holding block 6 is convenient since it permits the holding block to be moved into the web 4 until one of the side faces of the holding block is relatively smooth with the adjacent side face of the web 4.The helical webs of the rotor drum serve as screw conveyors whereby, during use of the coal shearer in which the drum is rotated in the direction of arrow X (Figures 1 to 3), the cut coal is displaced over the surface of the drum between the helical webs and in so doing moves over the loading side faces 18 of the webs 4. To alleviate the degradation of coal during its movement by the screw conveyors it is desirable that the loading side faces 18 should be substantially smooth. Consequently the pick holding blocks 6 are positioned in the webs 4 prior to their welding thereto so that their side faces present relatively smooth transition surfaces with the loading side faces 18 of the respective webs 4; this is particularly shown in Figure 3 where a chamfered side face 19 of the block 6 provides a substantially smooth continuation of the loading side face 18.

In addition to alleviating the degradation of coal (and thereby the creation of coal dust) as the coal flows over the loading side faces 18, it is believed that the smooth transitional surfaces formed between the webs 4 and the side faces of the pick holding blocks will create less resistance to rotation of the drum and reduce the likelihood of the holding blocks from breaking out of the webs.

During coal cutting it is desirable that water is sprayed on to the coal face in the region of the cutting tips 13 to suppress emission of coal dust. For this purpose the hollow centre part 1 of the drum is formed as a chamber within which is retained high pressure water. In conventional drums the high pressure water is passed through passages in the webs 4 or flange 3 to emerge as jets through nozzles (shown at 20 on flange 3) which are mounted directly on the outer edges of the flange and webs. The effectiveness therefore of the water jets in known constructions is somewhat restricted by the accuracy with which the pick blocks 5 are welded on to the drum and it frequently occurs in conventional structures that the water jets are directed by the nozzles 20 to relatively ineffective positions which may be considerably remote from the cutting tips of the picks.In addition, the location of the nozzles 20 on the edges of the flange and webs remote from the holding blocks 5 render them vulnerable to damage during coal cutting. By a further aspect of the present invention, water jet nozzles 21 are mounted on the pick holding blocks 6 and more particularly within the counter bore 1 6a of the rebate 17. By this arrangemen+ the fluid passage 16 and bore 1 6a may be accurately located in the block 6 so that the nozzle 21 when fitted thereto directs its water jet directly at or towards the cutting tip 13 and this positioning of the nozzle is fixed irrespective of any inaccuracy which may occur during fitting of the holding block 6 to the drum.It will be noted from Figures 1 to 3 that the nozzle 21, by being located in the rebate 17, is substantially sheltered from damage by the material of the block and also by the head of the pick when fitted thereto.

The water flow passage to the nozzle 21 from the water chamber within the drum is preferably formed after welding of the block 6 to the web 4. The passage 16 (prior to fitting of the nozzle 21) conveniently serves as a guide for a drill which is used to bore an extension passage 22 through the web 4 and to communicate with the water chamber in the drum. Into this extension passage 22 and fluid passage 16 may be inserted and secured a tube (not shown) to the outer end of which is fitted the nozzle 21 received in the counter bore 16a.

From Figure 2 it will be apparent that the nozzle 21 precedes the socket 9 and thereby the pick in the intended direction of rotation of the drum (indicated by arrow X).

It will be seen from Figure 1 that each of the webs 4 is of substantially saw-tooth profile and that the recesses 7 are each located at a position corresponding to the notional rebate which would otherwise be formed between two adjacent teeth on a web. This arrangement is desirable since it permits adequate clearance to be provided for the cutting tips 13 of the picks and also permits a relatively smooth transition surface to be provided, after welding, between the cylindrical surface 7 of the pick holding block and the immediately trailing outer edge of the web 4. Such a smooth transition surface is believed desirable to alleviate the degradation of coal after cutting and to permit smooth running of the drum with a consequential reduction in its power requirement.

As an alternative to mineral mining, the present invention may be applied to a pick holder assembly for use in a road planing machine whereby the surface layer of mineral such as concrete or granite chippings embedded in bitument is broken or cut.

WHAT WE CLAIM IS: 1. A pick holder assembly comprising a pick holding block having a part circular profiled peripheral portion and a socket for the reception and retention of a pick shank; a carrier having a part circular recess which is substantially complementary to the part circular peripheral portion of the pick holding block, said pick holding block being mounted with its part circular portion within, and in substantially complementary relationship to, the part circular recess of the carrier, and said block being secured to said carrier by welding with the socket of the block at a predetermined orientation relative to the carrier; and wherein the pick holding block has at least one passage extending therethrough through which fluid can be directed from the block in a predetermined direction relative to the socket.

2. An assembly as claimed in claim 1 wherein the substantially complementary part circular recess and profiled portion of the holding block co-operate over an extent which is greater than one half of the respective circumferences of the notional circles of which they form part.

3. An assembly as claimed in either claim 1 or claim 2 in which the part circular profiled portion of the holding block and the part circular recess have substantially complementary and co-axial part cylindrical profiles.

4. An assembly as claimed in any one of the preceding claims in which the or at least one passage extends through the pick holding block to communicate with fluid passage means in the carrier from which fluid passage means at least one stream of fluid can be directed from the holding block in the predetermined direction relative to the socket.

5. An assembly as claimed in any one of the preceding claims wherein the or at least

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. surfaces formed between the webs 4 and the side faces of the pick holding blocks will create less resistance to rotation of the drum and reduce the likelihood of the holding blocks from breaking out of the webs. During coal cutting it is desirable that water is sprayed on to the coal face in the region of the cutting tips 13 to suppress emission of coal dust. For this purpose the hollow centre part 1 of the drum is formed as a chamber within which is retained high pressure water. In conventional drums the high pressure water is passed through passages in the webs 4 or flange 3 to emerge as jets through nozzles (shown at 20 on flange 3) which are mounted directly on the outer edges of the flange and webs. The effectiveness therefore of the water jets in known constructions is somewhat restricted by the accuracy with which the pick blocks 5 are welded on to the drum and it frequently occurs in conventional structures that the water jets are directed by the nozzles 20 to relatively ineffective positions which may be considerably remote from the cutting tips of the picks.In addition, the location of the nozzles 20 on the edges of the flange and webs remote from the holding blocks 5 render them vulnerable to damage during coal cutting. By a further aspect of the present invention, water jet nozzles 21 are mounted on the pick holding blocks 6 and more particularly within the counter bore 1 6a of the rebate 17. By this arrangemen+ the fluid passage 16 and bore 1 6a may be accurately located in the block 6 so that the nozzle 21 when fitted thereto directs its water jet directly at or towards the cutting tip 13 and this positioning of the nozzle is fixed irrespective of any inaccuracy which may occur during fitting of the holding block 6 to the drum.It will be noted from Figures 1 to 3 that the nozzle 21, by being located in the rebate 17, is substantially sheltered from damage by the material of the block and also by the head of the pick when fitted thereto. The water flow passage to the nozzle 21 from the water chamber within the drum is preferably formed after welding of the block 6 to the web 4. The passage 16 (prior to fitting of the nozzle 21) conveniently serves as a guide for a drill which is used to bore an extension passage 22 through the web 4 and to communicate with the water chamber in the drum. Into this extension passage 22 and fluid passage 16 may be inserted and secured a tube (not shown) to the outer end of which is fitted the nozzle 21 received in the counter bore 16a. From Figure 2 it will be apparent that the nozzle 21 precedes the socket 9 and thereby the pick in the intended direction of rotation of the drum (indicated by arrow X). It will be seen from Figure 1 that each of the webs 4 is of substantially saw-tooth profile and that the recesses 7 are each located at a position corresponding to the notional rebate which would otherwise be formed between two adjacent teeth on a web. This arrangement is desirable since it permits adequate clearance to be provided for the cutting tips 13 of the picks and also permits a relatively smooth transition surface to be provided, after welding, between the cylindrical surface 7 of the pick holding block and the immediately trailing outer edge of the web 4. Such a smooth transition surface is believed desirable to alleviate the degradation of coal after cutting and to permit smooth running of the drum with a consequential reduction in its power requirement. As an alternative to mineral mining, the present invention may be applied to a pick holder assembly for use in a road planing machine whereby the surface layer of mineral such as concrete or granite chippings embedded in bitument is broken or cut. WHAT WE CLAIM IS:

1. A pick holder assembly comprising a pick holding block having a part circular profiled peripheral portion and a socket for the reception and retention of a pick shank; a carrier having a part circular recess which is substantially complementary to the part circular peripheral portion of the pick holding block, said pick holding block being mounted with its part circular portion within, and in substantially complementary relationship to, the part circular recess of the carrier, and said block being secured to said carrier by welding with the socket of the block at a predetermined orientation relative to the carrier; and wherein the pick holding block has at least one passage extending therethrough through which fluid can be directed from the block in a predetermined direction relative to the socket.

one fluid passage in the holding block communicates with a nozzle carried by said block and through which nozzle fluid is intended to be directed in the predetermined direction relative to the socket.

6. An assembly as claimed in claim 5 wherein the or a passage through the holding block communicates with a passage in the carrier and said passages house a continuous tube through which fluid is intended to pass from the carrier and through the holding block to said nozzle.

7. An assembly as claimed in any one of the preceding claims in which the carrier is a cutting head of a cutting machine and a plurality of said holding blocks are secured by welding in spaced array in respective part circular recesses in the cutting head with the respective sockets of said holding blocks at predetermined orientations relative to the cutting head.

8. An assembly as claimed in claim 7 in which the cutting head is in the form of a drum which is rotatable about its longitudinal axis and has the pick holding blocks located on the outer surface thereof.

9. An assembly as claimed in claim 8 wherein the drum includes a helical web or flange which extends radially outwardly relative to the axis of the drum and at least some of the holding blocks are helically spaced around the drum in the peripheral edge of said web or flange.

10. An assembly as claimed in any one of claims 7 to 9 wherein the cutting head is hollow and provides a fluid reservoir with which the fluid passage or passages in one or more of the holding blocks communicate.

11. An assembly as claimed in either claim 8 or claim 9 or claim 10 when appendant to either claim 8 or claim 9 wherein at least one fluid passage in at least one holding block is located to direct fluid outwardly from the block at a position on the block which precedes the socket in the intended direction of rotation of the drum.

12. An assembly as claimed in claim 11 when appendant to claim 5 wherein the or a nozzle is located in a rebate in the holding block and said rebate is positioned adjacent to the socket so that the nozzle precedes the socket in the intended direction of rotation of the drum.

13. An assembly as claimed in claim 9 or any one of claims 10 to 12 when appendant to claim 9 in which the helical web or flange is intended to provide, during use of the assembly and rotation of the drum, a screw conveyor for axially displacing over the drum mineral which has been cut from a mineral face and wherein the pick holding blocks are located in the web or flange so that the loading side (as herein defined) of the web or flange forms a relatively smooth transition surface with the holding blocks to mineral flow along the loading side of the web or flange.

14. An assembly as claimed in claim 9 or in any one of claims 10 to 13 when appendant to claim 9 wherein the web or flange is of substantially saw tooth profile and each pick holding block is mounted in its complementary part circular recess at a position substantially corresponding to the notional rebate which would othenvise be formed at a junction between two adjacent teeth in said profile.

15. A pick holder assembly as claimed in claim 1 and substantially as herein described with reference to the accompanying illustrative drawings.

16. The combination of a pick holder assembly as claimed in any one of the preceding claims and at least one pick in which the shank of the or each pick is removably secured in a respective socket of a holding block.

17. The combination as claimed in claim 16 wherein the or a fluid passage in at least one pick holding block is located to direct a stream of fluid at or towards a cutting tip of the pick in the socket of that holding block.

18. A method of constructing a pick holder assembly which comprises forming a part circular recess in a carrier; mounting in said recess and in substantially complementary relationship therewith a substantially complementary part circular profiled portion of a pick holding block having a socket for the reception of a pick shank; rotating the pick holding block within and relative to the recess to locate the socket at a predetermined orientation relative to the carrier, and welding the pick holding block to the carrier to secure the holding block with its socket at said predetermined orientation.

19. A method as claimed in claim 18 which comprises inserting the shank of a pick in the socket of the holding block; rotating the holding block within the recess to locate the pick at a predetermined orientation relative to the carrier; tack welding the holding block to the carrier while the pick is in said predetermined orientation relative to the carrier; removing the pick from the holding block and further welding the holding block to the carrier.

20. A method as claimed in either claim 18 or claim 19 in which the pick holding block has extending therethrough at least one passage through which fluid is intended to be directed at a predetermined orientation relative to the socket and which method comprises, subsequent to welding the pick holding block to the carrier, using said passage as a guide for a boring operation by which said passage is extended through the carrier to communicate with fluid passage means in the carrier.

21. A method as claimed in claim 20 which comprises locating a continuous tube in said passage through the holding block and the extension passage formed in the carrier, and locating on the holding block and in communication with said tube a nozzle for directing fluid which passes through said tube in a predetermined direction relative to the socket.

22. A method as claimed in any one of claims 18 to 21 in which the carrier comprises an axially rotatable drum which includes a radially outwardly extending helical flange or web in the peripheral edge of which the pick holding block is mounted, said flange or web having a loading side face (as herein defined) and which method comprises adjusting the pick holding block in its recess prior to said welding to locate the pick holding block so that it forms, with the loading side face of the web or flange, a relatively smooth transition surface to the flow of mineral along said loading side face.

23. A method of constructing a pick holder assembly as claimed in claim 18 and substantially as herein described.

24. A pick holder assembly when constructed by the method as claimed in any one of the preceding claims 18 to. 23.

25. A pick holding block for use in a pick holding assembly. said block having a socket for the reception and retention of a pick shank and a part circular profiled peripheral portion which portion is arranged so that, in use of the block, it can be received and secured within, and in substantially complementary relationship to, a substantially part circular recess in a carrier, and wherein the block has extending therethrough at least one passage through which, during use of the block at least one fluid stream is intended to pass and be directed outwardly of the block at a predetermined direction relative to the socket.

26. A pick holding block as claimed in claim 25 in which the or at least one said passage extends through the pick block to open therefrom at a position adjacent to the mouth of the socket.

27. A pick holding block as claimed in claim 26 wherein the said opening of the passage is located in a rebate in the pick block adjacent to the mouth of the socket.