SE2151601A1

SE2151601A1 - Mobile stacking machine

Info

Publication number: SE2151601A1
Application number: SE2151601A
Authority: SE
Inventors: Jon Görgård; Lars Wallberg; Magnus Wallberg
Original assignee: Wallbergs Aakeri I Hennan Ab
Priority date: 2021-12-22
Filing date: 2021-12-22
Publication date: 2023-06-23

Abstract

A mobile stacking machine comprising:- a tracked or wheeled chassis (2);- a platform (5) rotatably mounted to the chassis (2);- a boom structure (20) pivotably connected to the platform;- a conveying arrangement (30) mounted to and carried by the boom structure; and- a feeding unit (40) mounted to the platform and rotatable about a vertical axis of rotation together with the platform.The feeding unit comprises base frame (41) fixed to the platform, a bulk material supporting feed member (42) centrally positioned on the platform and an actuating device for moving the feed member in relation to the base frame. The feed member (42) is configured to receive bulk material that is dropped down onto the feed member from a position above the centre of the platform (5) and move this bulk material to a first belt conveyor (31) of the conveying arrangement.

Description

Mobile stackinq machine FIELD OF THE INVENTION AND PRIOR ART The present invention relates to a mobile stacking machine according to the preamble of claim 1, which is to be used for conveying bulk material, such as crushed stone, into a stockpile.

The stacking machine of the present invention is particularly intended to be used for stockpiling crushed stone at a stone crushing site where stone is crushed into smaller fragments by and thereafter stored in means of a stone crusher large stockpiles or stacks for later use.

A mobile stacking machine according to the preamble of claim 1 is previously known from US 4 664 271 A and WO 2011/151378 A1.

SUMMARY OF THE INVENTION The object of the present invention is to achieve a further development of a mobile stacking machine of the above- mentioned type so as to provide a mobile stacking machine that is improved in at least some aspect.

According to the invention, this object is achieved by means of a mobile stacking machine having the features defined in claim 1.

The mobile stacking machine of the present invention comprises: - a tracked or wheeled chassis; - a platform, which is rotatably mounted to the chassis so as to be rotatable in relation to the chassis about a vertical axis of rotation; - a first actuating device for rotating the platform in relation to the chassis about said vertical axis of rotation; - a liftable and lowerable boom structure having an inner end and an opposite outer end, wherein the boom structure at its inner end is articulately connected to the platform so as to be pivotable in relation to the platform in vertical direction and thereby allow a variation of the elevation of the outer end of the boom structure; - a second actuating device for lifting and lowering the boom structure in relation to the platform; - a conveying arrangement mounted to and carried by the boom structure and comprising one or more belt conveyors for conveying bulk material from the inner end of the boom structure to the outer end thereof; and - a feeding unit mounted to and carried by the platform so as to be rotatable about said vertical axis of rotation together with the platform, wherein the feeding unit comprises a base frame fixed to the platform, a bulk material supporting feed member movably mounted to the base frame and a third actuating device for moving the feed member in relation to the base frame.

The feed member of the feeding unit is centrally positioned on the platform and intersected by said vertical axis or rotation, wherein the feed member has a discharge end facing the boom structure. Furthermore, the feeding unit is upwardly open in order to allow the feed member to receive bulk material that is dropped down onto the feed member from a position above the centre of the platform, wherein the feed member, when subjected to movement under the effect of the third actuating device, is configured to effect a movement of bulk material from the feed member to a first belt conveyor of the conveying arrangement via the discharge end of the feed member. ln this description and the subsequent claims, the expression "liftable and lowerable boom structure" refers to a boom structure which can be pivoted in a vertical plane so as to thereby perform liftings and lowerings of the outer free end of the boom structure. The expression "actuating device for lifting and lowering the boom structure" here refers to the actuating device which is associated with the liftable and lowerable boom structure and which carries out the pivoting thereof in a vertical plane.

With the stacking machine according to the present invention, the discharge end of the conveying arrangement at the outer end of the boom structure can easily be moved upwards and downwards in vertical direction by lifting and lowering of the boom structure in relation to the platform and laterally in horizontal direction by rotation of the platform in relation to the tracked or wheeled chassis. Thus, the layout of the stockpile or stack formed by the stacking machine may easily be modified as desired in order to form a stockpile or stack with an optimal design adapted to the characteristics of the bulk material in question. Furthermore, when so needed, the entire stacking machine may easily be moved to a new position by movement of the tracked or wheeled chassis. the bulk material to be transported upwards along the boom structure by ln the stacking machine of the present invention, the conveying arrangement is delivered to the first belt conveyor of the conveying arrangement by a feed member that is centrally arranged on the platform that carries the boom structure. The feed member is rotatable about a vertical axis of rotation together with the platform and thereby follows the slewing movements of the conveying arrangement when the conveying arrangement and the boom structure are rotated in a horizontal plane together with the platform in order to alter the position of the discharge end of the conveying arrangement. Thus, the feed member and the first belt conveyor remain in the same position in relation to each other during the slewing movements of the conveying arrangement, which facilitates the transfer of bulk material from the feed member to the first belt conveyor. Furthermore, the weight of the bulk material that is dropped down onto the feed member will, as long as this bulk material remains on the feed member, have a stabilizing effect on the stacking machine and counteract a tipping thereof due to the central position of the feed member on the platform.

According to an embodiment of the invention, the feeding unit is a vibratory feeder, wherein the feed member has the form of a trough with an upwardly facing bulk material supporting surface and is resiliently mounted to the base frame, and wherein the third actuating device is configured to vibrate the feed member in relation to the base frame to cause movement of bulk material on the bulk material supporting surface in a direction towards the discharge end of the feed member. ln this case, the bulk material that is dropped down onto the bulk material supporting surface of the feed member is gradually moved towards the first belt conveyor by vibration of the feed member, which prevents a accumulation of bulk material on sudden the conveying arrangement that could cause a tipping of the stacking machine. A vibratory feeder with a feed member in the form of a trough is rather insensitive to the bulk material that is being fed and is very reliable. A vibratory feeder of this type may in a simple manner be given a very robust and durable design, which makes a stacking machine provided with such a feeding unit particularly suited for handling bulk material in the formed of crushed stone. Furthermore, when the bulk material on the feed member is subjected to vibration, there will be a redistribution of differently sized fragments within the bulk material, wherein fragments of smaller size will accumulate in a lower layer at the area closest to the bulk material supporting surface with fragments of larger size resting on top of this layer of small-sized fragments. When the bulk material consists of crushed stone, the layer of small- sized fragments will protect the bulk material supporting surface of the feed member from wear caused by the fragments of larger size.

According to another embodiment of the invention, the feed member is provided with a downwardly inclined guide plate at its discharge end for guiding bulk material from the bulk material supporting surface towards a loading end of the first belt conveyor. The bulk material will slide on the guide plate from the discharge end of the feed member down onto the first belt conveyor, which will make it possible for the above-mentioned layer of small-sized fragments to arrive as a bottom layer on the conveyor belt of the first belt conveyor. Thus, this layer of small- sized fragments may also protect the conveyor belt of the belt conveyor from wear caused by fragments of larger size.

Further advantageous features of the stacking machine according to the present invention will appear from the description following below and the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, a specific description of embodiments of the invention cited as examples follows below. ln the drawings: Fig 1 Fig 2 Fig 3 Fig 4 is a schematic perspective view of a mobile stacking machine according to an embodiment of the present invention, as seen with the boom structure in a fully contracted position, is a schematic planar view from above of the stacking machine of Fig 1, as seen with the boom structure in a fully extended position, is a schematic perspective view of the stacking machine of Fig 1, as seen with the boom structure in a fully contracted position and with the conveyor belts of the conveying arrangement omitted, is a schematic lateral view of the stacking machine of Fig 1, as seen with the boom structure in a lowered and fully contracted position, Fig 5 is a schematic lateral view of the stacking machine of Fig 1, as seen with the boom structure in an elevated and fully extended position, Fig 6 is a cut according to the line Vl-Vl in Fig 5, Figs 7 and 8 are schematic perspective views from different directions of a feeding unit included in the stacking machine of Fig 1, and Fig 9 is a schematic rear view of the feeding unit.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION A mobile stacking machine 1 according to an embodiment of the present invention is illustrated in Figs 1-6. The stacking machine 1 is to be used for conveying bulk material into a stockpile.

The stacking machine 1 comprises chassis 2, which is tracked or wheeled in order to allow the stacking machine 1 to be easily moved between different spots at a working site by movement of the chassis along the ground. ln the illustrated embodiment, the chassis 2 is tracked and provided with two track belts 3a, 3b arranged on opposite sides of the chassis. The entire stacking machine 1 is configured to rest against the ground through these track belts 3a, 3b. The track belts 3a, 3b are rotatable by one or more drive motors (not shown) that are mounted to the chassis 2, wherein the stacking machine 1 is moveable on the ground by rotation of the track belts 3a, 3b. The chassis may as an alternative form part of a trailer that is moveable by means of a separate vehicle.

The stacking machine 1 further comprises a platform 5, which is rotatably mounted to the chassis 2 so as to be rotatable in relation to the chassis about a vertical axis of rotation A1, and a liftable and lowerable boom structure 20, which at an inner end 20a is articulately connected to the platform 5 so as to be pivotable in relation to the platform in vertical direction and thereby allow a variation of the elevation of an outer end 20b of the boom structure. ln the illustrated embodiment, the boom structure 20 is articulately connected to the platform 5 through a joint 6, which forms a horizontal pivot axis A2 for the boom structure. The stacking machine 1 is provided with a first actuating device (not shown), for instance in the form of a hydraulic cylinder, for rotating the platform 5 in relation to the chassis 2 about the vertical axis of rotation A1, and a second actuating device 7 for lifting and lowering the boom structure 20 in relation to the platform 5. ln the illustrated embodiment, the second actuating device 7 comprises two hydraulic cylinders 8a, 8b arranged on opposite sides of the boom structure 20, wherein each hydraulic cylinder 8a, 8b is configured to act between the platform 5 and the boom structure 20 in order to pivot the boom structure in relation to the platform by extension and retraction of a piston rod 9 included in the hydraulic cylinder and thereby effect a lifting or lowering of the boom structure 20 in relation to the platform 5. The hydraulic cylinders 8a, 8b are arranged in parallel with each other and are configured to be operated synchronously in order to pivot the boom structure 20 in relation to the platform 5. Each hydraulic cylinder 8a, 8b is at a first end articulately connected to the platform 5 and at an opposite second end articulately connected to the boom structure 20.

The platform 5 is preferably rotatable in relation to the chassis 2 in at least 180° about the vertical axis of rotation A1.

A conveying arrangement 30 is mounted to and carried by the boom structure 20. The conveying arrangement 30 comprises one or more belt conveyors 31, 32 for conveying bulk material from the inner end 20a of the boom structure 20 to the outer end 20b thereof. The boom structure 20 is fixed to the platform 5 at a first end of the platform and one or more counterbalance weights 11 are fixed to the platform at an opposite second end of the platform in order to stabilize the stacking machine 1 and prevent the stacking machine from tipping due to the tipping moment exerted on the stacking machine by the boom structure 20, the conveying arrangement 30 and the bulk material conveyed by the conveying arrangement.

The boom structure may have a fixed length, wherein the conveying arrangement may be formed by one single belt conveyor. However, the boom structure 20 is preferably extensible and provided with one or more longitudinally moveable boom section 22 in order to enable an adjustment of the extension length of the boom structure 20. ln the latter case, the conveying arrangement 30 comprises several belt conveyors 31, 32, wherein a separate belt conveyor 32 is mounted to and carried by each longitudinally moveable boom section 22. ln the extensible, wherein the boom structure 20 comprises a base illustrated embodiment, the boom structure 20 is section 21, through which the boom structure 20 is articulately connected to the platform 5, and a longitudinally moveable boom section 22, which is carried by the base section 21 and displaceable in the longitudinal direction of the base section by 23b for adjustment of the extension length of the boom structure 20. ln means of one or more actuating members 23a, the illustrated example, the boom section 22 is displaceably mounted to the base section 21 through several rollers 24 (see Fig 6), which are rotatably mounted to the boom section 22. A first row with several rollers 24 is arranged on a first side of the boom section 22, wherein the rollers 24 in this first row are received in a first guide track 25a on a first side of the base section 21. A second row with several rollers 24 is arranged on an opposite second side of the boom section 22 in parallel with said first row, wherein the rollers 24 in this second row are received in a second guide track 25b on the other side of the base section 21. However, the boom section 22 may of course also be displaceably mounted to the base section 21 in any other suitable manner. ln the illustrated displaceable in the longitudinal direction of the base section 21 embodiment, the boom section 22 is by means of two actuating members 23a, 23b in the form of hydraulic cylinders arranged on opposite sides of the base 23a, 23b is configured to act between the base section 21 and the boom section 21, wherein each hydraulic cylinder section 22 in order to move the boom section 22 in the longitudinal direction of the base section 21 by extension and 11 retraction of a piston rod 27 included in the hydraulic cylinder and thereby effect an adjustment of the length of the boom structure 20. The hydraulic cylinders 23a, 23b are arranged in parallel with each other and are configured to be operated synchronously in order to displace the boom section 22 in relation to the base section 21. Each hydraulic cylinder 23a, 23b is at a first end connected to the base section 21 and at an opposite second end connected to the boom section 22. The boom section 22 may of course also be displaceable in relation to the base section 21 by means of any other suitable type of actuating member, such as for instance an actuating member in the form of a rack and pinion drive. ln the illustrated embodiment, the conveying arrangement 30 comprises: - a first belt conveyor 31 mounted to and carried by the base section 21 of the boom structure 20; and - a second belt conveyor 32 mounted to and carried by the longitudinally moveable boom section 22 of the boom structure 20, wherein a conveyor belt 33a of the first belt conveyor 31 partly overlaps a conveyor belt 33b of the second belt conveyor 32 to thereby allow bulk material to fall down onto the conveyor belt 33b of the second belt conveyor 33b from the conveyor belt 33a of the first belt conveyor 31 at an outer end 31b of the first belt conveyor.

The conveyor belt 33a of the first belt conveyor 31 extends in an endless loop along the base section 21 of the boom structure 20, wherein this conveyor belt 33a extends over a driving drum 34a, which is rotatably mounted to the base section 21 at the outer 12 end 31b of the first belt conveyor 31, and over a tail drum 35a (see Fig 2), which is rotatably mounted to the base section 21 at the inner end 31a of the first belt conveyor. The driving drum 34a is driven in rotation by means of at least one drive motor 36a mounted to the base section 21. ln the illustrated embodiment, the driving drum 34a is driven in rotation by means of two synchronously operated drive motors 36a, which are mounted to the base section 21 on opposite sides of the driving drum 34a.

The conveyor belt 33b of the second belt conveyor 32 extends in an endless loop along the displaceable boom section 22 of the boom structure 20, wherein this conveyor belt 33b extends over a driving drum 34b, which is rotatably mounted to the boom section 22 at the outer end 32b of the second belt conveyor 31b, and over a tail drum 35b (see Fig 5), which is rotatably mounted to the boom section 22 at the inner end 32a of the second belt conveyor. The driving drum 34b is driven in rotation by means of at least one drive motor 36b mounted to the boom section 22. ln the illustrated embodiment, the driving drum 34b is driven in rotation by means of two synchronously operated drive motors 36b, which are mounted to the boom section 22 on opposite sides of the driving drum 34b. ln the illustrated embodiment, each belt conveyor 31, 32 is provided with several sets 37 of support rollers for supporting an upper part of the associated conveyor belt 33a, 33b, wherein these support roller sets 37 are distributed in the longitudinal direction of the belt conveyor 31, 32 between the tail drum 35a, 35b and the driving drum 34a, 34b of the belt conveyor. Each support roller set 37 comprises three or more rotatable support 13 rollers 38, which are arranged in series with each other transversally to the longitudinal direction of the associated belt conveyor 31, 32 and which are inclined in relation to each other in order to form a V-shaped or U-shaped support for the upper 33b of the associated belt conveyor 31, 32. ln the illustrated example, each support roller part of the conveyor belt 33a, set 37 comprises four support rollers 38 arranged in series with each other.

The stacking machine 1 further comprises a feeding unit 40, which is mounted to and carried by the platform 5 so as to be rotatable about the above-mentioned vertical axis of rotation A1 together with the platform. The feeding unit 40 comprises: - a base frame 41, which is fixed to the platform 5; - a bulk material supporting feed member 42, which is movably mounted to the base frame 41 and centrally positioned on the platform 5, wherein the feed member 42 is arranged in such a position on the platform 5 that it is intersected by the vertical axis or rotation A1; and - an actuating device 43 for moving the feed member 42 in relation to the base frame 41.

The feed member 42 has a discharge end 42a facing the boom structure 20. The feeding unit 40 is upwardly open to thereby allow bulk material to be dropped onto the feed member 42 from a position above the centre of the platform 5. When the feed member 42 is subjected to movement in relation to the base frame 41 under the effect of the actuating device 43, the feed member 42 is configured to effect a movement of bulk material from the feed member 42 to the first belt conveyor 31 of the 14 conveying arrangement 30 via the discharge end 42a of the feed member 42. Thus, the actuating device 43 is configured to move the feed member 42 in such a manner that bulk material received on the feed member 42 will be gradually moved towards the discharge end 42a of the feed member and further on onto the first belt conveyor 31. The discharge end 42a of the feed member 42 is located above the inner end 31a of the first belt conveyor 31 to thereby allow bulk material to slide and/or fall down onto the conveyor belt 33a of the first belt conveyor 31 from the discharge end 42a of the feed member.

The feeding unit may be designed as a short belt conveyor with a feed member in the form of a robust conveyor belt. However, the feeding unit 40 is preferably designed as a vibratory feeder. ln the illustrated embodiment, the feeding unit 40 is a vibratory feeder with a feed member 42 in the form of a trough, which has an upwardly facing bulk material supporting surface 44 and is resiliently mounted to the base frame 41. ln this case, the actuating device 43 is configured to vibrate the feed member 42 in relation to the base frame 41 to cause movement of bulk material on the bulk material supporting surface 44 in a direction towards the discharge end 42a of the feed member 42.

The bulk material supporting surface 44 is planar and may be horizontally positioned or slightly inclined downwards towards the discharge end 42a.

The feed member 42 rests on the base frame 41 via several resilient support elements 45, which are interposed between the base frame 41 and the feed member 42. One or more resilient support elements 45 are with advantage arranged between the base frame 41 and the feed member 42 at each corner of the feed member 42. The resilient support elements 45 may for instance have the form of compression spring, preferably he|ica| compression springs, wherein each compression spring 45 is fitted between an upwardly facing shoulder 46a on the base frame 41 and an opposite downwardly facing shoulder 46b on the feed member 42. The resilient support elements 45 may as an alternative have the form of blocks of elastomeric material. ln Figs 7 and 8, some of the resilient support elements 45 are shown at a distance from the associated shoulders 46b on the feed member 42. However, in reality the shoulders 46b on the feed member 42 are in direct contact with the associated resilient support elements 45. ln the illustrated embodiment, the actuating device 43 of the feeding unit 40 comprises two vibration producing actuators 47a, 47b, which are fixed to and carried by the feed member 42, wherein each vibration producing actuator 47a, 47b comprises a drive motor 48 having a rotary output shaft and at least one weight eccentrically secured to and rotated by the output shaft. The drive motor 48 of each vibration producing actuator 47a, 47b may be provided with two output shafts that extend from the drive motor in opposite directions, wherein each output shaft carries a weight that is eccentrically secured to and rotated by the output shaﬁ. instance be operated in the manner described in US 6 041 915 A or US 5 265 730 A.

The vibration producing actuators 47a, 47b may for 16 The actuating device 43 of the feeding unit 40 may as an alternative comprise one or more vibration producing actuators that are fixed to the base frame 41 and configured to vibrate the feed member 42 via a motion transferring mechanism provided between the vibration producing actuators and the feed member 42.

The feed member 42 downwardly inc|ined guide plate 49 at its discharge end 42a for is with advantage provided with a guiding bulk material from the bulk material supporting surface 44 towards the loading end of the first belt conveyor 31. ln the illustrated embodiment, such a guide plate 49 is fixed to the feed member 42 in order to vibrate together with the feed member.

The feeding unit 40 may further comprise an infeed hopper 50, which is arranged above the bulk material supporting surface 44 on the feed member 42 and configured to guide falling bulk material towards the bulk material supporting surface 44. ln the illustrated embodiment, an infeed hopper 50 is fixed to the base frame 41 of the feeding unit 40, wherein this infeed hopper 50 is formed by two opposite side walls 51a, 51b and a rear end wall 52 arranged between the two side walls at the rear ends thereof.

The illustrated stacking machine 1 is particularly intended to be used at a stone crushing site for producing stockpiles of bulk material in the form of crushed stone. ln this case, crushed stone produced by a stone crusher may for instance be conveyed from the stone crusher to the stacking machine 1 by means of a belt conveyor, which is positioned with its discharge end above the 17 feed member 42 of the stacking machine to allow crushed stone to be dropped down from the belt conveyor onto the bulk material supporting surface 44 of the feed member. The feed member 42 is continuously vibrated in order to gradually move the crushed stone on the bulk material supporting surface 44 towards the discharge end 42a of the feed member. When the crushed stone reaches the inclined guide plate 49 at the discharge end 42a of the feed member, the crushed stone will move along the guide plate 49 under the effect of gravity and fall down from the guide plate 49 onto the conveyor belt 33a of the first belt conveyor 31. At the discharge end of the first belt conveyor 31, the crushed stone will fall down from the conveyor belt 33a of the first belt conveyor 31 onto the belt conveyor 33b of the second belt conveyor 32. When reaching the discharge end of the second belt conveyor 32, the crushed stone will fall down onto the stockpile that is being formed. ln order to produce a stockpile that extends in an arc-shaped path along the ground, the platform 5 is rotated in relation to the chassis 2 about the vertical axis of rotation A1 during the stockpiling operation to thereby move the discharge end 30a of the conveying arrangement 30 in the desired arc-shaped path. During the stockpiling operation, the boom structure 20 may also be pivoted in relation to the platform 5 in order to adjust the elevation of the discharge end 30a of the conveying arrangement 30 as desired in dependence on the prevailing height of the stockpile that is being formed. The extension length of the boom structure 20 may remain fixed during a stockpiling operation, but may also be adjusted as desired during a stockpiling operation by movement of the displaceable boom section 22 in relation to the base section 21 of the boom structure. 18 When the belt conveyors 31, 32 are started after a standstill, the second belt conveyor 32 is preferably started before the first belt conveyor 31 to thereby prevent tipping of the stacking machine 1 due to an excessive accumulation of bulk material on the second belt conveyor 32. For the same reason, the conveyor belt 33b of the second belt conveyor 32 is preferably driven at higher speed than the conveyor belt 33a of the first belt conveyor 31.

The invention is of course not in any way restricted to the embodiments described above. On the contrary, many possibilities to modifications thereof will be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention such as defined in the appended claims.

Claims

1.Claims 1. A mobile stacking machine for conveying bulk material, such as crushed stone, into a stockpile, the stacking machine (1) comprising: - a tracked or wheeled chassis (2); - a platform (5), which is rotatably mounted to the chassis (2) so as to be rotatable in relation to the chassis about a vertical axis of rotation (A1); - a first actuating device for rotating the platform (5) in relation to the chassis (2) about said vertical axis of rotation (A1); - a liftable and lowerable boom structure (20) having an inner end (20a) and an opposite outer end (20b), wherein the boom structure (20) at its inner end (20a) is articulately connected to the platform (5) so as to be pivotable in relation to the platform in vertical direction and thereby allow a variation of the elevation of the outer end (20b) of the boom structure; - a second actuating device (7) for lifting and lowering the boom structure (20) in relation to the platform (5); and - a conveying arrangement (30) mounted to and carried by the boom structure (20) and comprising one or more belt conveyors (31, 32) for conveying bulk material from the inner end (20a) of the boom structure (20) to the outer end (20b) thereof, characterized in: - that the stacking machine (1) comprises a feeding unit (40) mounted to and carried by the platform (5) so as to be rotatable about said vertical axis of rotation (A1) together with the platform, wherein the feeding unit (40) comprises a base frame (41) fixed to the platform (5), a bulk material supporting _ A mobile _ A mobile feed member (42) movably mounted to the base frame (41) and a third actuating device (43) for moving the feed member (42) in relation to the base frame (41); - that the feed member (42) is centrally positioned on the platform (5) and intersected by said vertical axis or rotation (A1), wherein the feed member (42) has a discharge end (42a) facing the boom structure (20); and - that the feeding unit (40) is upwardly open in order to allow the feed member (42) to receive bulk material that is dropped down onto the feed member from a position above the centre of the platform (5), wherein the feed member (42), when subjected to movement under the effect of the third actuating device (43), is configured to effect a movement of bulk material from the feed member (42) to a first belt conveyor (31) of the conveying arrangement (30) via the discharge end (42a) of the feed member (42). stacking machine according to claim 1, characterized in that the feeding unit (40) is a vibratory feeder, wherein the feed member (42) has the form of a trough with an upwardly facing bulk material supporting surface (44) and is resiliently mounted to the base frame (41), and wherein the third actuating device (43) is configured to vibrate the feed member (42) in relation to the base frame (41) to cause movement of bulk material on the bulk material supporting surface (44) in a direction towards the discharge end (42a) of the feed member (42). stacking machine according to claim 2, characterized in that the feed member (42) is provided with a _ A mobiledownwardly inclined guide plate (49) at its discharge end (42a) supporting surface (44) towards a loading end of the first belt for guiding bulk material from the bulk material conveyor (31). .A mobile stacking machine according to claim 2 or 3, characterized in that the feeding unit (40) comprises several resilient support elements (45) interposed between the base frame (41) and the feed member (42), wherein the feed member (42) rests on the base frame (41) via these resilient support elements (45). stacking machine according to claim 4, characterized in that each resilient support element (45) has the form of a compression spring, preferably a helical compression spring, and is fitted between an upwardly facing shoulder (46a) on the base frame (41) and an opposite downwardly facing shoulder (46b) on the feed member (42). _ A mobile stacking machine according to any of claims 2-5, characterized in that the third (43) comprises two vibration producing actuators (47a, 47b), which actuating device are fixed to and carried by the feed member (42). A mobile stacking machine according to claim 6, characterized in that each vibration producing actuator (47a, 47b) comprises a drive motor (48) having a rotary output shaft and at least one weight eccentrically secured to the output shaﬁ.8. A mobile stacking machine according to any of claims 2-7, characterized in that the feeding unit (40) comprises an infeed hopper (50), which is arranged above the bulk material supporting surface (44) on the feed member (42) and configured to guide falling bulk material towards the bulk material supporting surface (44). 9. A mobile stacking machine according to any of claims 1-8, characterized in that the boom structure (20) is fixed to the platform (5) at a first end of the platform, wherein one or more counterbalance weights (11) are fixed to the platform at an opposite second end of the platform. A mobile stacking machine according to any of claims 1-9, characterized in: - that the boom structure (20) is extensible, wherein the boom structure (20) comprises a base section (21), through which the boom structure (20) is articulately connected to the platform (5), and a longitudinally moveable boom section (22) which is carried by the base section (21) and displaceable in the longitudinal direction of the base section by means of one or more actuating members (23a, 23b) for adjustment of the extension length of the boom structure (20); - that said first belt conveyor (31) is mounted to and carried by said base section (21); and - that the conveying arrangement (30) comprises a second belt conveyor (32) mounted to and carried by said longitudinally moveable boom section (22), wherein the first belt conveyor (31) partly overlaps the second belt conveyor (32) to allowbulk material to fall down onto the second belt conveyor (32) from a discharge end of the first belt conveyor (31). A mobile stacking machine according to claim 10, characterized in that the longitudinally moveable boom section (22) is displaceable in the longitudinal direction of the base section (21) by means of two actuating members (23a, 23b) in the form of hydraulic cylinders arranged on opposite sides of the base section (21). A mobile stacking machine according to any of claims 1-11, characterized in that the second actuating device (7) comprises two hydraulic cylinders (8a, 8b) arranged on opposite sides of the boom structure (20), each one of these hydraulic cylinders (8a, 8b) being configured to act between the platform (5) and the boom structure (20) in order to pivot the boom structure (20) in relation to the platform (5) and thereby effect a lifting or lowering of the boom structure (20) in relation to the platform (5). A mobile stacking machine according to any of claims 1-12, characterized in that each belt conveyor (31, 32) comprises: - a conveyor belt (33a, 33b) that extends in an endless loop over a rotatable driving drum (34a, 34b) at an outer end (31b, 32b) of the belt conveyor and over a rotatable tail drum (35a, 35b) at an inner end (31a, 32a) of the belt conveyor, and - several sets (37) of support rollers for supporting an upper part of the conveyor belt (33a, 33b), these support roller sets (37) being distributed in the longitudinal direction of the belt conveyor (31, 32) between the tail drum (35a, 35b) and thedriving drum (34a, 34b), wherein each support roller set (37) comprises three or more support rollers (38), which are arranged in series with each other transversally to the longitudinal direction of the belt conveyor (31, 32) and which are inclined in relation to each other in order to form a V- shaped or U-shaped support for the upper part of the conveyor belt (33a, 33b).