Milling head for machining pile heads

Abstract

The invention relates to a milling head (1) which has a rotational axis (x) and is used for machining a pile head (80) of a pile (8) having a pile core (81), a pile casing (82) and a metal reinforcement (83) therebetween, the milling head comprising: a coupling device (13) which can be connected to a drive shaft (2) of a drive device; a central milling cutter (11) which has multiple central bits (111) mounted on the underside of an inner ring plate (112); and a milling cutter ring (12) which has multiple ring bits (121) mounted on the underside of an outer ring plate (122), the central milling cutter (11) and the milling cutter ring (12) being connected to each other and oriented coaxially with the rotational axis (x), the outer ring plate (122) surrounding the inner ring plate (112), separated therefrom by an average circular ring area (kr2). According to the invention, the inner ring plate (112) has at least one transfer opening (1120A, 1120B) which leads from the underside to the upper side of the inner ring plate (112) and is adjoined on the underside by a conveying blade (119A, 119B), which protrudes at least partially into a working region of the central bit (111), and on the upper side by a conveying screw (113A, 113B).

Description

[0001] The invention relates to a milling head for machining pile heads.

[0002] From WO2008135365A1 or also the generic EP 1 990 167 A1, a milling head for machining pile heads of piles is known, which comprise a pile core and a pile casing as well as a metal reinforcement provided between the pile core and the pile casing.

[0003] Concrete piles of this type, which are typically used to support a building on unstable ground, are made of concrete, which can withstand compression, and reinforcing iron, which can withstand tension. The dimensions of the piles are selected according to the building and the ground conditions and can vary widely. Typically, piles with lengths of 5 m - 50 m and diameters of 0.4 m - 2.5 m are used. To construct the piles, boreholes are drilled into the ground into which pipes are inserted. The reinforcing iron is inserted into the pipes and the concrete is poured. Soil material located at the bottom of the pipe is usually displaced upwards and, after the pile is completed, ends up in the head area, which is why it does not have the required strength. Furthermore, the pile or pile head usually does not have the required dimensions.In some cases, the pile head may also be missing coupling elements required for the construction project. Therefore, the pile head is usually reworked and rebuilt to the required dimensions and quality.

[0004] For this purpose, the prefabricated, usually cylindrical pile head is machined using a milling head, typically over a length in the range of 0.5 m - 1.5 m, to remove the defective concrete. The concrete must be removed in such a way that the reinforcing iron, which is typically arranged in a sleeve-like manner coaxial with the pile's axis of rotation, and the intact concrete below the pile head are not damaged. After removing the defective or excess concrete and exposing the reinforcement, it is usually expanded with additional reinforcement and provided with formwork that corresponds to the dimensions of the new pile head to be constructed. The formwork is then filled with concrete and removed after the concrete has hardened.

[0005] Traditionally, when working on pile heads, the pile core was milled out down to the edge of the reinforcing iron. The pile casing was then milled down to the iron reinforcement. This processing was not only usually time-consuming but often also led to damage to the iron reinforcement. Furthermore, particularly when working on the pile casing, the previously intact concrete split off, significantly reducing the available cross-section of the concrete pile and correspondingly increasing the surface pressure transferred from the concrete pile to the structure being built. Such damage to a concrete pile therefore often resulted in considerable consequential damage to the structure built on defective pile heads. To avoid such consequential damage, defective piles and pile heads had to be repaired at great expense and incurring considerable effort.

[0006] When processing pile heads, not only the time factor plays an important role, but also the high-quality completion of the pile heads, which form a key point in the foundation of the structure, e.g. a building or a bridge.

[0007] With the milling head according to WO2008135365A1, which is mounted on a construction vehicle such as an excavator, significant progress has been made in terms of the processing time of a pile head and the quality of the processing. This milling head comprises a coupling device connectable to a drive shaft, a central milling cutter equipped with several central chisels, and a ring milling cutter equipped with several ring chisels, which are firmly coupled to each other and aligned coaxially with the rotation axis of the drive shaft. This milling head enables the simultaneous removal of the pile core and the pile casing without damaging the pile reinforcement located between the central milling cutter and the ring milling cutter.

[0008] Despite the significant improvement achieved in the processing of pile heads with this milling head, the demand remained to develop a milling head that would allow pile heads to be processed even faster and more gently. However, increasing the working speed of a device generally leads to lower quality work results, which is unacceptable given the load-bearing importance of the objects being processed, i.e., the pile heads.

[0009] The present invention is therefore based on the object of creating an improved milling head for machining pile heads.

[0010] The milling head is designed to enable the removal of concrete pile heads with reduced force, increased working speed, and improved work quality. The milling head is designed to penetrate the pile head, pile core, and pile casing more effectively, allowing concrete material to be removed with less effort. The reduced force also reduces the risk of damage to the pile head being processed.

[0011] When machining the pile heads, the concrete should be treated gently, so that accelerated material removal does not result in gaps and cracks in the pile head. At the same time, the load on the milling tools or chisels should be reduced, thus correspondingly reducing the maintenance effort for the milling head.

[0012] The milling head is intended to ensure in particular that no splits occur in the pile casing when machining a pile head, which, depending on the size, would result in correspondingly high repair costs.

[0013] The central drill and milling tools should also be able to be assembled and disassembled in the desired number, so that maintenance requirements are also low in this regard and the milling head can be configured as required with little effort and adapted to the piles to be machined, which can have a diameter of more than 2 m.

[0014] This object is achieved with a milling head having the features specified in claim 1. Advantageous embodiments of the invention are specified in further claims.

[0015] The milling head is used to machine a pile head of a pile, typically a concrete pile, which comprises a pile core, a pile shell and a metal reinforcement that lies between the pile core and the pile shell.

[0016] The milling head, which is rotated about its longitudinal axis or axis of rotation during operation, comprises a coupling device which can be connected to a drive shaft of a drive device, a central milling cutter which has a plurality of central chisels mounted on the underside of an inner ring plate, and preferably a ring milling cutter which has a plurality of ring chisels mounted on the underside of an outer ring plate, which central milling cutter and ring milling cutter are connected to one another in a manner aligned coaxially with the axis of rotation, wherein the outer ring plate encloses the inner ring plate separated therefrom by a central circular ring surface.

[0017] According to the invention, the inner ring plate has at least one transfer opening leading from the underside to the upper side of the inner ring plate, to which a conveyor blade extending at least partially into a working area of ​​the central chisel is connected on the underside and a conveyor spiral is connected on the upper side.

[0018] The inventive milling head makes it possible to remove segments of the pile core and pile shell simultaneously without damaging the pile reinforcement located in the central circular area. The machining is carried out with high precision, allowing the concrete to be removed even at a distance of just a few centimeters from the reinforcement. The remaining thin concrete sleeve, in which the reinforcement is enclosed, can then be quickly removed using another tool, e.g., a pair of pliers.

[0019] A particularly advantageous feature is that the segments of the pile core and pile shell can be removed by linearly lowering the milling head. Complex tool movements, which are difficult to execute and can lead to damage to the pile head, are eliminated. The pile head can therefore be processed quickly and without causing damage.

[0020] Due to the linear displacement of the milling head and the correspondingly calculable forces acting on the tools, the loads and wear on the milling head are also reduced, which is why maintenance is only necessary at longer intervals.

[0021] The at least one conveyor blade, which extends into the working area of ​​the chisels, allows the milled material removed from the concrete core to be collected and fed through the corresponding transfer opening of the associated conveyor spiral. By removing the milled material, a significant obstacle is removed from the working area of ​​the chisels, allowing the milling head to rotate with reduced resistance and the central chisels to penetrate the pile core with reduced resistance. This increases the effectiveness of the milling tools, while also reducing their load.

[0022] The milling head according to the invention thus achieves a targeted material flow, which reduces the milling process and allows for efficient removal of the pile core and pile casing. Due to the targeted material flow through at least one transfer opening, a large portion of the inner ring plate can otherwise be used for the installation of central chisels. The large mounting surface of the inner ring plate therefore does not impede the material flow. Central chisels can therefore be mounted in the desired number on the underside of the inner ring plate.

[0023] The milled material can be removed particularly efficiently if the inner ring plate is provided with two transfer openings, each connected to a conveyor blade on the underside, extending at least partially into the working area of ​​the central chisel, and to a conveyor spiral on the top. To ensure that the milled material can flow into the conveyor spirals with minimal resistance, it is preferable that each transfer opening be connected to a connecting surface on the top side of the inner ring plate, ensuring a laminar or unobstructed transition from the conveyor blade to the associated conveyor spiral.

[0024] Preferably, the transfer openings, conveyor blades, and central picks are positioned diametrically opposite each other in pairs with respect to the rotation axis and at equal distances from the rotation axis. The conveyor blades, central picks, and ring picks are preferably positioned at the same height in pairs. This ensures that the diametrically opposed tools or picks always act on the pile head in the same way, and disruptive moments or forces caused by asymmetries that could strain the cutter head and its guide are avoided. The cutter head can therefore be optimally guided and operated with minimal effort. Lateral forces acting on the cutter head, which could be detrimental to the installed tools, such as the picks and the preferably provided central drill, are avoided.

[0025] Preferably, the inner ring plate is connected to the underside of a shaft, and the outer ring plate is connected to the underside of an assembly cylinder. The shaft and the assembly cylinder are aligned coaxially with the rotation axis and connected at the top to a coupling plate on which the coupling device is arranged. The assembly cylinder preferably comprises at least one exit window through which the conveyed milled material can be discharged, and at least one assembly window that allows manual access, for example, to the coupling device.

[0026] In a further preferred embodiment, the at least one conveyor spiral or two conveyor spirals, which are preferably rotated by 180° relative to one another, are provided with a side wall in a lower section, which is preferably selected according to the height of the pile heads to be machined. The side wall ensures that the milled material in the lower section cannot escape from the conveyor spirals and can be conveyed out of the remaining area of ​​the pile head which has the reinforcement. Only after the milled material has been conveyed out of this area can it exit laterally in an upper section of the conveyor spiral, which is not provided with a side wall, and be guided away from the milling head via the at least one exit window.The side wall of the conveyor spiral thus ensures the material transport from the inner ring plate to a section of the conveyor spiral where the milled material is laterally removed. The side wall can be integrally formed or welded to the conveyor spiral, which can be made of sheet metal, for example.

[0027] On the underside of the inner ring plate, a central drill is preferably arranged, which is aligned coaxially to the axis of rotation and projects beyond the central chisels and the ring chisels in the milling direction, and therefore penetrates the pile head or the pile core first, thereby performing a guiding or pilot function and ensuring that the central chisels and the ring chisels can follow circular working paths.

[0028] In further preferred embodiments, at least one radial blade is provided on the underside of the inner ring plate, adjoining the central drill, which is preferably aligned at least approximately radially with respect to the axis of rotation. Preferably, the at least one radial blade runs from the central drill to the at least one transfer opening. Therefore, each transfer opening is preferably assigned a radial blade. The at least one radial blade, which is, for example, a straight or curved plate, ensures that milling material exposed by the central drill and radially inner central bits is guided outwards towards the associated transfer opening. The course of the lower edge or front edge of the radial blade, as well as the course of the lower edge or front edge of the conveyor blade, is selected such that contact with the pile core is always avoided.The radial blade is therefore overhanged by the adjacent central chisels in the conveying direction.

[0029] According to the invention, the inner ring plate can advantageously fulfill numerous functions. Mounting openings for accommodating the central chisels and / or the radial blades and / or a receiving opening for accommodating a mounting part or drill chuck, which serves to releasably hold the central drill, can be provided on the underside of the inner ring plate. The drill chuck, for example, includes a locking part by means of which the central drill can be fixed in the drill chuck and released again as needed.

[0030] A receiving opening can be provided on the top side of the inner ring plate to receive the shaft which connects the inner ring plate to the coupling device.

[0031] The connection of the mounting part or drill chuck and the shank to the inner ring plate can be achieved using known mechanical connection techniques, such as a press fit and / or thread. For mounting the central chisels, brackets are preferably provided that are inserted into the mounting holes. The central chisels and the central drill can therefore be advantageously connected to the inner ring plate, allowing maintenance work to be carried out more efficiently. In the event of a defect or necessary maintenance, no welding is required. Instead, the central chisels and the central drill can be easily removed and replaced.

[0032] In further preferred embodiments, it is provided that the central chisels are radially spaced from one another at equal or unequal chisel spacings on circular lines or working circles, wherein the uniform chisel spacing or the different chisel spacings between the working circles preferably lie in a range of 20 mm - 40 mm.

[0033] During operation or rotation of the milling head around the rotation axis, the central chisels preferably run in pairs, diametrically opposed to each other, in equal working circles that are spaced apart from each other. The radial spacing of the central chisels or working circles in a range of 20 mm - 40 mm ensures particularly efficient removal of the pile core material. At spacings greater than 40 mm, too little material is removed, and at spacings shorter than 20 mm, penetration of the central chisel only occurs under significantly increased force, which is preferably avoided to prevent damage to the pile head and milling head. The chisel spacing is ideally between 25 mm and 35 mm.

[0034] The inner ring plate is preferably offset forward in the milling direction relative to the outer ring plate, so that the central chisels are also offset forward relative to the ring chisels. For example, an axial offset of 10 mm - 25 mm is possible.

[0035] Alternatively or additionally, it is preferably provided that the mounting height of the central chisel changes in the milling direction from working circle to working circle by a height difference which lies in a range of 5 mm - 25 mm and increases in the direction of the rotation axis.

[0036] When operating the milling head, the central drill bit penetrates the pile core first. Then, the central chisels penetrate the pile core in pairs, sequentially and in a stepped manner, so that the pile core is machined from the inside out. The stepped arrangement of the central chisels therefore gradually breaks the surface tension of the pile core. Instead of tearing open the surface of the pile core in one step, the surface tension is broken gradually and thus with reduced force. The milling head according to the invention can therefore be operated efficiently with reduced force or reduced drive torque.

[0037] In a further preferred embodiment, the mounting heights of the ring chisels are also selected to be different in the milling direction. Preferably, the mounting height increases radially outward in steps from ring chisel to ring chisel, or from working circle to working circle of the ring chisels, with a height difference that preferably lies in a range of 5 mm - 25 mm.

[0038] Since the ring cutters located at the outermost edge of the outer ring plate are displaced furthest downwards toward the pile head in the milling direction, the outermost edge of the pile casing is milled first. The pile casing is therefore milled from the outside inward, preventing splitting. The surface tension of the pile casing is thus broken at the outer edge, after which the pile casing is gradually removed inward.

[0039] The central chisels and ring chisels are preferably arranged in at least two spiral rows mounted on the underside of the inner ring plate and the outer ring plate, respectively. The chisel height of the central chisels preferably increases, as described, linearly or non-linearly sequentially from central chisel to central chisel in the direction of the rotation axis or radially inward toward the central drill. In contrast, the chisel height of the ring chisels preferably increases, as described, linearly or non-linearly sequentially from ring chisel to ring chisel radially outward to the edge of the outer ring plate.

[0040] The central drill and the central chisels located at different installation heights and the ring chisels located at different installation heights form, in their engagement area or with the corresponding working circles, a wave shape concentric with the axis of rotation. This wave shape reaches a maximum in the area of ​​the axis of rotation in the milling direction, reaches a minimum in the area of ​​the central annular surface, and increases again towards the outer edge of the outer ring plate in the milling direction. The wave shape ensures optimal engagement of the milling head in the pile head, which can thus be machined efficiently yet gently. The surface tensions in the pile core and pile casing are advantageously broken down, which means that material is removed quickly with reduced energy expenditure and, at the same time, damage such as splitting of the pile casing is avoided.The invention therefore combines these three essential advantages, which are normally mutually exclusive. With reduced energy consumption, material removal is faster and more gentle. It should be noted that the milling process is enhanced, on the one hand, by the disposal of the milled material according to the invention and, on the other hand, by the advantageous arrangement of the central chisels and / or the ring chisels.

[0041] The at least one conveyor blade has a front edge that runs from an inner edge closer to the axis of rotation to an outer edge further away from the axis of rotation. The conveyor blade or blades are arranged and aligned in such a way that contact with the pile head is avoided and the loosened milling material is reliably captured and efficiently transferred to the associated conveyor spiral. The milling material, which is conveyed radially from the inside to the transfer openings to the outside, is caught by the conveyor blades and conveyed upwards to the conveyor spirals. The milling material released by the outer central bits, on the other hand, is first captured on the outside by the conveyor blades and transferred into a material flow that runs inwards and upwards to the conveyor spirals. This prevents milling material from collecting peripherally on the inner ring plate and disrupting the milling process.The rotation of the milling head is hindered. To prevent the material caught by the conveyor blade from being thrown outward by centrifugal forces, the conveyor blades preferably have external blade walls.

[0042] In preferred embodiments, at least one reaming tool, e.g., a chisel, is additionally provided, which grasps material at the periphery of the inner ring plate and deflects it inward. The reaming tool or chisel preferably extends radially outward beyond the inner ring plate by a reaming width, which preferably lies in a range of 5 mm - 40 mm.

[0043] Preferably, the front edge of the conveyor blades is inclined horizontally relative to the diameter of the inner ring plate at a horizontal angle of inclination such that, as the milling head rotates in the working direction, the outer edge of the respective conveyor blade leads and the inner edge lags. The horizontal angle of inclination, which preferably lies in a range of 5° - 25°, ensures that the milled material is grasped peripherally and guided toward the center of the conveyor blade.

[0044] Preferably, the front edge of the conveyor blades is vertically inclined relative to the diameter of the inner ring plate at a vertical angle of inclination such that the inner edge is preferably higher than the outer edge, corresponding to the installation height of the central chisels. The vertical angle of inclination is preferably selected according to the height of the central chisels such that a blade spacing, or a distance from the chisel tips and thus from the surface of the pile core, in the range of 5 mm - 40 mm results between the tips of the central chisels and the front edge of the conveyor blades.

[0045] The conveyor blades are further inclined by a vertical blade inclination angle relative to the axis of rotation, wherein the front edge of the conveyor blades leads during operation of the milling head and the vertical blade inclination angle is preferably in a range between 5° and 85°.

[0046] The at least one radial blade and / or the at least one conveyor blade are preferably each held at least partially in a form-fitting manner in a recess or mounting opening provided in the inner ring plate. In this way, the radial blades and the conveyor blades can be easily assembled and disassembled. However, the at least one radial blade and / or the at least one conveyor blade can also be welded entirely or partially to the inner ring plate, with the radial blade and the conveyor blade preferably resting at least partially flat against a support surface of the inner ring plate.

[0047] The central chisels provided on the central milling machine and the ring chisels provided on the ring milling machine preferably consist of a weldable or form-fitting mount and a chisel element that can be inserted into it and replaced routinely. The mounts are preferably connected to the corresponding mounts or mounting elements of the ring plates by means of form-fitting connections, e.g., dovetail joints. The ring chisels are preferably slightly larger than the central chisels. Furthermore, one of the ring chisels can be connected to the inner ring plate as a reaming chisel.

[0048] The inner and outer diameters of the inner and outer ring plates are preferably precisely adapted to the dimensions of the pile and the position of the reinforcement within the pile, ensuring maximum concrete removal without damaging the reinforcement. The cutter head is therefore provided according to the dimensions of the pile head to be machined, which can have an outer diameter of over 2 m.

[0049] Preferably, central milling cutters and ring milling cutters of any size can be combined with each other or connected to each other via the coupling plate. Furthermore, preferably, outer ring plates of different dimensions and / or equipped with different tools can be releasably connected to the assembly cylinder. Furthermore, preferably, inner ring plates of different dimensions and / or equipped with different tools can be releasably connected to the shaft. In this way, the milling head can be flexibly adapted to the pile heads to be machined.

[0050] The milling head is made of durable material, especially iron and steel. The tool parts that come into contact with the concrete pile are preferably made of hard metal. Typically, the milling tools include receiving openings into which hard metal elements are inserted to process the concrete. The use of plastic parts is possible if they provide the desired strength and, for example, provide the milling head or parts with a certain degree of elasticity.

[0051] The invention is explained in more detail below with reference to the drawings. In the drawings: Fig. 1a shows a sectional view of a milling head 1 according to the invention for machining pile heads 80 with a coupling device 13, with a ring milling cutter 12 having a plurality of ring cutters 12 mounted on the underside of an outer ring plate 122, and with a central milling cutter 11 having an inner ring plate 112, on the underside 112 of which a plurality of central cutters 111 are provided, as well as two conveyor blades 119A, 119B mounted adjacent to transfer openings 1120A, 1120B, through which loosened milling material can be conveyed from the working area of ​​the central cutters 111 to conveyor spirals 113A, 113B; Fig. 1b shows the milling head 1 of Fig. 1a during the processing of a pile head 80, whose pile core 81 and pile casing 82, between which the undamaged iron reinforcement 83 is held in a relatively thin concrete sleeve 88, have already been removed at the height h2; Fig. 2 the milling head 1 of Fig. 1a from below with a view of the inner ring plate 112 equipped with the central chisels 111 and the outer ring plate 122 equipped with the ring chisels 121, which, according to the geometry of the processed pile 8, cover a central circular ring area kr1 corresponding to the pile core 81 and an outer circular ring area kr3 corresponding to the pile casing 82 and delimit a central circular ring area kr2, into which a concrete sleeve 88 with the iron reinforcement 83 remaining after the processing of the pile head 80 can enter; Fig. 3a the inner ring plate 112 of Fig. 2 , which is equipped with two series 111A, 111B of spirally arranged central chisels 111, a central drill 114 and is provided with two transfer openings 1120A, 1120B, to each of which a radial blade 118A, 118B is adjacent on the side and a conveyor blade 119A, 119B is adjacent on the rear side in the direction of rotation, and on the front side of which a reaming chisel 1119A, 1119B is provided; Fig. 3b the inner ring plate 112 of Fig. 3a with the working circles ml of the two series 111A, 111B of central cutters 111 shown, two of which are diametrically opposite each other with respect to the rotational axis x of the milling head 1 or the central drill 114, respectively, are guided along a common working circle ml; Fig. 4 shows a part of the central milling cutter 11 with the inner ring plate 112, the central drill 114, only three mounted central cutters 1112A, 1115B, 1118A, and one of the transfer openings 1120B, adjacent to which the associated radial blade 118B and the associated conveyor blade 119B, which extend into the working area of ​​the central cutter 111, are adjacent; Fig. 5a the inner ring plate 112 of the central drill bit 111, fully equipped with central chisels 111, radial blades 118A, 118B, conveyor blades 119A, 119B, reaming tools 1119A, 1119B and the central drill 114 Fig. 3a in spatial representation; Fig. 5b the inner ring plate 112 of Fig. 5a after removing the central chisel 111 and the conveyor blade 119B as well as the removal of the central drill 114 together with the drill chuck 1143 from a recess 1129 of the inner ring plate 112; Fig. 6a the inner ring plate 112 of Fig. 5a from above with the conveyor spirals 113A, 113B adjoining the upper side of the inner ring plate 112, which rotate 180° relative to each other and circulate the shaft 115 of the central cutter 11 and which are each provided with a spiral wall 1130 in this section, as well as a front view of the transfer opening 1120B, to which the conveyor blade 119B protruding into the working area of ​​the central cutter 111 is connected on the underside and to which the conveyor spiral 113B is connected on the upper side; Fig. 6b the inner ring plate 112 of Fig. 6a with the transfer openings 1120A, 1120B and without the conveyor spirals 113A, 113B, the shaft 115, and the conveyor blade 119B; Fig. 7a shows a central chisel 111 comprising a holder 111F and a chisel element 111M inserted therein; and Fig. 7b shows a ring chisel 121 comprising a holder 121F and a chisel element 121M inserted therein.

[0052] Fig. 1a shows a sectional view of a milling head 1 according to the invention, which, as Fig. 1b shows, is intended for machining pile heads 80 of concrete piles 8.

[0053] The milling head 1 comprises a central milling cutter 11 and a ring milling cutter 12, which are connected to each other at their top by a coupling plate 133 and a counter plate 134 and to a coupling device 13. The coupling device 13 comprises a coupling sleeve 131, into which a drive shaft 2 of a drive device (not shown) can be inserted and locked, for example, by means of a bolt 132. The drive shaft 2 is held, for example, by a construction vehicle, which is capable of rotating the drive shaft 2 about a rotation axis x or about the longitudinal axis of the milling head 1 and of axially displacing it. The milling head 1 can therefore be lowered coaxially onto a pile head 80 in order to machine it, as is Fig. 1b In all embodiments, the milling head 1 is rotated clockwise when viewed from above.

[0054] The ring milling machine 12 comprises an outer ring plate 122, on the underside of which ring chisels 121 are mounted aligned in the direction of rotation or inclined thereto. The upper side of the outer ring plate 122 is connected, for example by means of flange elements and screws or threaded elements, preferably detachably, to the underside of an assembly cylinder 123, the upper side of which is connected, for example by means of flange elements and screws or threaded elements, preferably detachably to the coupling plate 133. The assembly cylinder 123 has a quarter cut through which the view of the central milling machine 11 is exposed. On the underside, the assembly cylinder 123 has exit windows 1231 through which loosened milling material can be guided outwards. On the upper side, the assembly cylinder 123 has assembly windows 1232 which allow intervention in the milling head 1, for example in order to release the central milling machine 11.

[0055] The central milling cutter 11 comprises an inner ring plate 112, on the underside of which central chisels 111 are mounted aligned in the direction of rotation or inclined thereto. Coaxially aligned with the rotation axis x, a central drill 114 is provided on the underside of the inner ring plate 112, which projects downwards beyond the central chisels 111 and the ring chisels 121 in the milling direction. The inner ring plate 112 further has two transfer openings 1020A, 1020B (see Fig. 3a ), which are diametrically opposite one another with respect to the axis of rotation x, and to which a radial blade 118A, 118B and a conveyor blade 119A, 119B are each assigned.

[0056] At the top, a conveyor spiral 113A, 113B each connects to the transfer openings 1020A, 1020B. The conveyor spirals 113A, 113B, which enclose a shaft 115 at the top, are preferably formed from solid sheet metal. The underside of the shaft 115 is connected to the inner ring plate 112 and is held at the top, preferably releasably, by a connecting device 14. The shaft 115 is connected to the coupling device 13 in a force-fitting and / or form-fitting manner by means of the connecting device 14. The connecting device 14 preferably comprises clamping devices distributed along the circumference of the shaft 115, which allow the shaft 115 to be clamped to the counter plate 134. The connecting device 14 thus allows the shaft 115 and thus the central milling cutter 11 to be released from the milling head 1. The central milling cutter 11 can therefore be removed, serviced and reinserted or replaced by a central milling cutter 11 having different characteristics.

[0057] Fig. 1b shows the milling head 1 of Fig. 1a during the processing of a pile head 80 of a pile 8, shown in section, which has a height h1 and a diameter d. The pile core 81 and the pile casing 82, between which the undamaged iron reinforcement 83 is held in a relatively thin concrete sleeve 88, have already been removed from top to bottom over a height difference h2. The loosened milled material was captured by the conveyor blades 119A, 119B and fed through the transfer openings 1220A, 1220B to the conveyor spirals 113A, 113B, where it is lifted and carried away via the pile head 80 or the remaining concrete sleeve 88. Within the pile head 80, the milled material is held laterally by a spiral wall 1130, which is peripherally formed or welded to the conveyor spirals 113A, 113B. The milled material is therefore lifted above the pile head 80 and only then discharged outwards to the outlet openings 1231 of the assembly cylinder 123 under the influence of centrifugal force.

[0058] Fig. 1b further shows that the central chisels 111 and the ring chisels 121 are at different heights and thus engage the pile head 80 at different depths. At least the central chisels 111 located close to the central drill 114 are all lower in the milling direction than the ring chisels 121. The central chisels 111 and the ring chisels 121 are also mounted on the inner ring plate 112 and the outer ring plate 122 at different heights in the milling direction. The mounting height of the central chisels 111 increases radially in the direction of the rotation axis x, preferably from central chisel 111 to central chisel 111. The mounting height of the ring chisels 121 increases radially outwards, preferably from ring chisel 121 to ring chisel 121. A linear or non-linear increase can be provided. The central drill 114 itself, which performs a guiding or pilot function, projects downwards beyond the central chisel 111.

[0059] Fig. 1b shows a cross-section through the pile head 8 with the symmetrical course of the milling line dl, which, depending on the arrangement of the central drill 114, the central chisel 111 and the ring chisel 121, has a maximum in the area of ​​the rotation axis and is interrupted and has a minimum in the area of ​​the concrete sleeve 88 or in the area of ​​the central circular ring surface kr2 and subsequently increases again outwards in the milling direction. When machining the pile head 8, a corresponding wave shape running concentrically to the rotation axis x results on its surface. This wave shape ensures that the central milling cutter 11 and the ring milling cutters 12 optimally engage the pile head 80 and dissolve the pile core 81 from the inside out and the pile casing 82 from the outside in.This gradual processing of the pile head 80 allows the surface tension in the pile core 81 and the surface tension in the pile shell 82 to be advantageously resolved without causing damage to the pile head 80.

[0060] After completing the processing of the pile head 80, the milling head 1 is raised again. The remaining concrete sleeve 88, which still surrounds and protects the iron reinforcement 83, is then removed with minimal effort using additional tools, such as milling cutters and clamps.

[0061] Fig. 2 shows the milling head 1 from below, looking at the inner ring plate 112 equipped with the central chisels 111 and the outer ring plate 122 equipped with the ring chisels 121, which, according to the geometry of the processed pile 8, cover a central circular ring area kr1 corresponding to the pile core 81 and an outer circular ring area kr3 corresponding to the pile casing 82, and delimit a central circular ring area kr2 into which a concrete sleeve 88 with the iron reinforcement 83 remaining after the processing of the pile head 80 can enter. A part of the central circular ring area kr2 is shown hatched.

[0062] The outer ring plate 122 has an outer diameter d122o and an inner diameter d122i. The inner ring plate 112 has an outer diameter d112.

[0063] On the outer ring plate 122, three series 121A, 121B, 121C of twelve spirally arranged ring cutters 121 and 1211, 1212, ..., 12112 are arranged, each offset by 120°. Three ring cutters 121 each follow the same working circle ml (only one working circle ml is shown). The mounting height of the ring cutters 121 preferably increases continuously from the inside to the outside, from the first ring cutter 1211 to the last ring cutter 12112 or from one working circle ml to the next. Therefore, the outermost ring cutters 12112 are the highest in the milling direction and therefore first engage the outer edge of the pile casing 82. In this way, the pile casing 82 is machined from the outside to the inside, thus avoiding damaging chipping. The increase in the mounting height of the ring chisels 121 is preferably in a range of 5 mm - 25 mm. For example, the increase in the mounting height of the first ring chisels 1211, 1212, ...close to 5 mm and the increase in the mounting height of the last ring chisels ..., 12111, 12112 close to 25 mm.

[0064] On the inner ring plate 112, which is Fig. 3a As shown larger, two series 111A, 111B of eight spirally arranged central chisels 111 and 1111, 1112, ..., 1118 are each arranged offset by 180°.

[0065] How Fig. 3b shows, two diametrically opposed central chisels 111 each follow the same working circle ml. The installation height of the central chisels 111 preferably increases continuously from the first central chisel 1111 to the last central chisel 1108 radially from the outside to the inside, which is why the central chisels 1108 closest to the rotation axis x are the highest in the milling direction and therefore penetrate the center of the pile core 81 first after the central drill 114. In this way, the pile core 81 is machined from the inside to the outside, whereby the machining of the pile core 81 can be carried out more quickly.

[0066] For example, the increase in the mounting height of the first ring chisels 1111, 1112, ... is close to 5 mm and the increase in the mounting height of the last ring chisels ..., 1107, 1108 is close to 25 mm.

[0067] The central chisels 111 are arranged in pairs, each with equal or unequal chisel spacings ma, radially offset from one another, and each defines a working circle ml when rotating. The difference in the radii of the working circles ml corresponds to the respective chisel spacing. The uniform chisel spacing ma or the different chisel spacings ma are preferably in a range of 20 mm - 40 mm. With this arrangement of the central chisels, the material is removed optimally. The working circles ml are thus offset from one another radially and also vertically.

[0068] The inner ring plate 112 also has two transfer openings 1120A, 1120B, which are diametrically opposed to each other with respect to the rotation axis x, through which the loosened milled material can be removed. For the removal of the milled material, a conveyor blade 119A, 119B is provided adjacent to the trailing edge of each of the transfer openings 1120A, 1120B. These blades extend partially into the area of ​​the respective transfer opening 1120A, 1120B and partially into the working area of ​​the central chisel 111. At the front, the conveyor blades 119A, 119B have a front edge 119B, which runs from an inner edge to an outer edge of the conveyor blades 119A, 119B. The conveyor blades 119A, 119B therefore first engage with the front edge 1193 in the exposed milled material in order to carry it away upwards via the conveyor blades 119A, 119B.

[0069] Fig. 3a shows that the front edge 1193 is inclined horizontally relative to the diameter d112 of the inner ring plate 112 by a horizontal inclination angle a1 such that, upon rotation of the milling head 1 in the working direction, the outer edge 1192 of the respective conveyor blade 119A; 119B leads and the inner edge 1191 lags. The milled material is therefore first captured on the outside of the front edge 1193 and displaced inward toward the associated transfer opening 1120A, 1120B. The displacement of the milled material results in a favorable material flow, which relieves the load on the conveyor blades 119A, 119B. The horizontal inclination angle or lead angle a1 is preferably in a range of 0° - 25°.

[0070] Each of the transfer openings 1120A, 1120B is also assigned a radial vane 118A, 118B, which conveys the milling material exposed by the central drill 114 and the internal central chisels 111 outward to the transfer openings 1120A, 1120B. The radial vanes 118A, 118B can be simple plates, which are preferably held in a form-fitting manner by the inner ring plate 112 and are preferably aligned radially or inclined toward the associated transfer opening 1120A, 1120B.

[0071] Fig. 3b further shows that a reaming chisel 1119A, 1119B is mounted on the leading edge of each of the transfer openings 1120A, 1120B, which projects outward beyond the inner ring plate 112 by a clearance width b, which preferably lies in a range of 5 mm - 40 mm. The reaming chisels 1119A, 1119B capture concrete fragments that have not yet been loosened and could damage the conveyor blades 119A, 119B, as well as the outer milled material, and convey it radially inward so that it can be captured by the conveyor blades 119A, 119B. The reaming chisels 1119A, 1119B are preferably identical to the ring chisels 121, which are preferably larger than the central chisel 111.

[0072] In order to ensure that the milled material can be well captured peripherally, the conveyor blades 119A, 119B can also project radially outwards beyond the inner ring plate 112 by up to 35 mm.

[0073] Fig. 3b further shows that the inner ring plate 112 has mounting openings 1128 on the underside into which the central chisels 111 or holders for the central chisels 111 are inserted.

[0074] Fig. 4 shows a portion of the central milling cutter 11 with the inner ring plate 112, the central drill 114, only three mounted central chisels 1112A, 1115B, 1118A, and one of the transfer openings 1120B, adjacent to which the associated radial blade 118B and the associated conveyor blade 119B extend into the working area of ​​the central chisel 111. The penetration depth is shown for each of these tools; for the central drill 114 the penetration depth t0, for the central chisels 1112A, 1115B, 1118A the penetration depths t1, t2, t3, for the inner edge 1181 and the outer edge 1182 of the radial blade 118B the penetration depths t1181, t1182 and for the inner edge 1191 and the outer edge 1192 of the conveyor blade 119B the penetration depths t1191, 1192.

[0075] The front edge 1183 of the radial blade 118B extends from the inner edge 1181 to the outer edge 1182, or from the penetration depth t1181 to the penetration depth t1182, with a descending outward inclination. The front edge 1193 of the conveyor blade 119B extends from the inner edge 1191 to the outer edge 1192, or from the penetration depth t1191 to the penetration depth t1182, with a descending outward inclination.

[0076] The front edge 1193 of the conveyor blade 119B is inclined vertically relative to the diameter d112 of the inner ring plate 112, preferably by a vertical angle of inclination a2, such that the inner edge 1191 is preferably higher than the outer edge 1192 in the conveying direction, corresponding to the course of the mounting heights of the central chisels 111. The conveyor blade 119B can therefore not come into contact with the surface of the pile head 80 or the pile core 81.

[0077] Preferably, a blade spacing a3 is provided between the front edge 1193 of the conveyor blade 119 and the working circles ml of the central chisel 111 or the tips of the central chisel 111, which is in a range of preferably 5 mm - 40 mm.

[0078] Fig. 4 further shows that the central drill 114, which comprises a milling tool or drilling tool 1141 and a tool shank 1142, is held in a mounting part or drill chuck 1143 and fixed by means of a locking part 11431, e.g. by a bolt.

[0079] Fig. 5a shows the inner ring plate 112 of the central cutter 111; radial blades 118A, 118B; conveyor blades 119A, 119B; reaming tools 1119A, 1119B; and the central drill 114, fully equipped Fig. 3a in spatial representation. A series of central chisels 111 is marked with the corresponding serial numbers 1111, 1112, ..., 1108. Furthermore, a view of the conveyor blade 119B through the transfer opening 1120B is shown on the right.

[0080] Fig. 5b shows the inner ring plate 112 of Fig. 5a after removing the central chisel 111 and the conveyor blade 119B, as well as removing the central drill 114 together with the drill chuck 1143 from a recess 1129 of the inner ring plate 112. Also visible are recesses 1123 on the underside of the inner ring plate 112, which serve to accommodate the radial blades 118A, 118B. Also remaining is the housing 121F of the reaming chisel 1119B.

[0081] In order to realize the mounting heights or for the mutual vertical displacement of the central chisels 111, the underside of the inner ring plate 112 is provided with ring-shaped steps S1, S2, S3, S4, S5, which preferably correspond to the working circles ml.

[0082] Fig. 6a shows the inner ring plate 112 of Fig. 5a from above with the conveyor spirals 113A, 113B, which adjoin the upper side of the inner ring plate 112 and are offset by 180°, which encircle the shaft 115 of the central milling cutter 11 and which are each provided with a spiral wall 1130 in this section. The transfer opening 1120B, to which the conveyor blade 119B, which projects into the working area of ​​the central chisel 111, is connected at the bottom, and to which the conveyor spiral 113B is connected at the top. The inner ring plate 112 has a transfer surface 1125A, 1125B for each of the transfer openings 1020A, 1020B, via which the milled material is conveyed from the conveyor blade 119A, 119B to the associated conveyor spiral 113A, 113B. It is possible to completely cover this transfer surface 1125A, 1125B by the conveyor blade 119A, 119B. The conveyor blade 119A, 119B can therefore, for example,welded to the front at the lower end of the transfer surface 1125A, 1125B or attached to the corresponding transfer surface 1125A, 1125B, if necessary screwed on.

[0083] The conveyor blade 119B, which adjoins or extends further from the underside of the transfer opening 1120B, is inclined by a blade inclination angle a4 relative to the rotation axis x and forms an inclined plane. The blade inclination angle a4, at which the conveyor blade 119B is inclined with the front edge 119B forward below the transfer opening 1120B, is preferably in a range of 5° - 85°. Preferably, a vertical orientation of the conveyor blade 119B, in which the milled material is pushed forward and barely displaced upward, is avoided. The blade inclination angle a4, which in the illustrated embodiment is approximately 45°, is therefore selected such that the milled material can reach the transfer opening 1120B and further to the conveyor spiral 113B via the conveyor blade 119B. To prevent the conveyed milled material from escaping to the outside, the conveyor blade 119B has an outer wall 1195.

[0084] The transfer surface 1125B is preferably shaped such that a preferably laminar transition without obstacles results between the conveyor blade 119B at the entrance of the conveyor spiral 113B.

[0085] Fig. 6b shows the inner ring plate 112 of Fig. 6a without the conveyor spirals 113A, 113B, the shaft 115, and the conveyor blade 119B. After removing the conveyor blade 119B, a connection space with a connection surface 1127 is exposed at the lower edge of the transfer surface 1125B or on the underside of the transfer opening 1120B, in which the conveyor blade 119B is fastened, e.g., screwed and / or welded. Likewise, the connection surfaces 1126A, 1126B of the conveyor spirals 113A, 113B are exposed. These connection surfaces extend to an edge or a stop 11261 that is flush with the upper edge of the associated conveyor spiral 113A, 113B, so that the milled material can enter the conveyor spiral 113A, 113B unhindered.

[0086] Fig. 7a shows a central chisel 111 comprising a holder 111F and a chisel element 111M inserted therein.

[0087] Fig. 7b shows a ring chisel 121 comprising a holder 121F and a chisel element 121M inserted therein. The ring chisel 121 is also used as a reaming chisel in the present embodiment, as Fig. 6b shows. List of reference symbols

[0088] 1 Milling head 11 Central milling cutter 111, 1111, ..., 1118 Central pick 111A, 111BC Central pick groups 111F Pick holder 111MMitch or tool 1119A, 1119BRemoval tool, reaming pick 112 Inner ring plate 1120A, 1120B Transfer openings 1123 Mounting openings for the radial blades 1124 Receiving opening for the shaft 115 1125A, 1125B Transfer surfaces of the transfer openings 1126A, 1126B Connecting surface for the conveyor spirals 1127 Connecting surfaces for the conveyor blades 1128 Mounting openings for central pick 111 1129 Receiving opening for the mounting part 1143 113A, 113B Conveyor spirals 1130 Spiral wall 114 Central drill 1141 Milling tool, carbide cutting edges 1142 Tool shank 1143 Mounting part, drill chuck 11431 Locking part 115 Shaft 118A, 118BRadial vanes 1181 Inner edge of the radial vanes 1182 Outer edge of the radial vanes 1183 Front edge of the radial vanes 119A,119BFeeling blade 1191Inner edge of the conveying blades 1192Outer edge of the conveying blades 1193Front edge of the conveying blades 1195Outer wall of the conveying blades 12Ring milling cutter 121; 1211, ..., 12112 Ring pick 121A, ..., 121CRing pick groups 121F Pick holder 121M Pick or tool 122Outer ring plate 123Assembly cylinder 1231Exit window 1232Access mounting window 13Coupling device 131Coupling sleeve 132Coupling means, coupling bolt 133Coupling plate 134Counter plate 14Connecting device 2Drive shaft 8Pile 81Pile core 82Pile casing 83Metal reinforcement 88Concrete sleeve a1Horizontal inclination angle of the front edge a2Vertical inclination angle of the front edge a3Blade spacing a4Blade inclination angle bClearance width dPile diameter d112Outer diameter of inner ring plate d122iInner diameter of outer ring plate d122oOuter diameter of outer ring plate dlMilling line along the pile diameter h1Pile height h2Pile head height kr1,central annular area kr2middle annular area kr3outer annular area machisel spacing mlchisel lines, working circles S1, ..., S5steps on the inner ring plate 112 t0penetration depth of the central drill t1penetration depth of the central chisel 1118A t2penetration depth of the central chisel 1115B t3penetration depth of the central chisel 1112A t1181penetration depth of the inner edge of the radial blade t1182penetration depth of the outer edge of the radial blade t1191penetration depth of the inner edge of the conveyor blade t1192penetration depth of the outer edge of the conveyor blade,

Claims

1. Milling head (1) having a rotation axis (x) for machining a pile head (80) of a pile (8) that comprises a pile core (81), a pile jacket (82) and a metal armouring (83) interposed therebetween, with a coupling device (13), which is connectable to a drive shaft (2) of a driving device, with a central milling cutter (11), which comprises a plurality of central chisels (111) mounted on a lower side of an inner ring plate (112), characterised in that the inner ring plate (112) comprises at least one transfer opening (1120A, 1120B) leading from the lower side to the upper side of the inner ring plate (112), which at least one transfer opening (1120A, 1120B) is adjoined on the lower side by a conveyor shovel (119A, 119B) projecting at least partially into a working area of the central chisels (111) and which at least one transfer opening (1120A, 1120B) is adjoined on the upper side by a conveyor spiral (113A, 113B).

2. Milling head (1) according to claim 1, characterised in that a ring milling cutter (12) is provided, which comprises a plurality of ring chisels (121) mounted on an lower side of an outer ring plate (122), which central milling cutter (11) and ring milling cutter (12) are connected to each other coaxially aligned with the rotation axis (x), wherein the outer ring plate (122) surrounds the inner ring plate (112) separated thereof by a middle circular ring area (kr2).

3. Milling head (1) according to claim 1 or 2, characterised in that the inner ring plate (112) comprises two transfer openings (1120A, 1120B), each of which is adjoined on the lower side by a conveyor shovel (119A; 119B) projecting at least partially into the working area of the central chisels (111) and each of which is adjoined on the upper side by a conveyor spiral (113A; 113B).

4. Milling head (1) according to claim 1, 2 or 3, characterised in that the transfer openings (1120A, 1120B) and the conveyor shovels (119A, 119B) and the central chisels (111) lie diametrically opposite each other in pairs with respect to the rotation axis (x) and at equal distances from the rotation axis (x).

5. Milling head (1) according to one of the claims 1 - 4, characterised in that the inner ring plate (112) is connected to a lower side of a shaft (115) and that the outer ring plate (122) is connected to a lower side of a mounting cylinder (123), and that the shaft (115) and the mounting cylinder (123) are aligned coaxially to the rotation axis (x) and are connected at their upper side to a coupling plate (133) on which the coupling device (13) is arranged.

6. Milling head (1) according to one of the claims 1 - 5, characterised in that the at least one conveyor spiral (113A; 113B) or two conveyor spirals (113A; 113B), which are preferably turned 180° relative to each other, is provided with a side wall (1130) in a lower section, which is preferably selected according to the height of the pile heads (80) to be machined.

7. Milling head (1) according to one of the claims 1 - 6, characterised in that a central drill unit (114) is arranged on the lower side of the inner ring plate (112), which is aligned coaxially to the rotation axis (x) and projects beyond the central chisels (111) and the ring chisels (121) in the milling direction, and that at least one radial shovel (118A, 118B) is provided on the lower side of the inner ring plate (112), which shovel (118A, 118B) adjoins the central drill unit (114) and is preferably aligned radially with respect to the rotation axis (x).

8. Milling head (1) according to one of the claims 1 - 7, characterised in that the central drill unit (114) is releasably held in a mounting part or drill chuck which is inserted into a receiving aperture (1129) on the lower side of the inner ring plate (112).

9. Milling head (1) according to one of the claims 1 - 8, characterised in that the central chisels (111) are each radially offset from one another at equal or unequal chisel spacings (ma) and define work circles (ml) during rotation, wherein the uniform chisel spacing (ma) or the different chisel spacings (ma) or the radial spacings of the work circles (ml) of the central chisels (111) preferably lie in a range of 20 mm - 40 mm.

10. Milling head (1) according to one of the claims 1 - 9, characterised in that the central chisels (111) are each radially spaced at equal or unequal chisel distances (ma) on work circles (ml), wherein the mounting height of the central chisels (111) in the milling direction changes from one work circle (ml) to the next work circle (ml) by a height difference which preferably lies in a range of 5 mm - 25 mm, and increases in the direction of the rotation axis (x).

11. Milling head (1) according to one of the claims 1 - 10, characterised in that the ring chisels (121) are each radially offset from one another at equal or unequal chisel spacings and define work circles (ml) during rotation, wherein the mounting height of the ring chisels (121) increases radially outwards in the milling direction from one work circle (ml) to the next work circle (ml) by a height difference which preferably lies in a range of 5 mm - 25 mm.

12. Milling head (1) according to one of the claims 1 - 11, characterised in that the central drill unit (114) and the central chisels (111) and ring chisels (121) which lie at different mounting heights form in their engagement area or with their working circles (ml) a waveform which runs concentrically to the rotation axis (x), which has a maximum in the region of the rotation axis (x) in the milling direction, which has a minimum in the region of the central circular ring area (kr2) and which rises again towards the outer edge of the outer ring plate (122) in the milling direction.

13. Milling head (1) according to one of the claims 1 - 12, characterised in that the at least one conveyor shovel (119A, 119B) has a front edge (1193) which extends from an inner edge (1191) lying closer to the rotation axis (x) to an outer edge (1192) lying farther away from the rotation axis (x), which front edge (1193) is inclined horizontally relative to the diameter (d112) of the inner ring plate (112) by a horizontal inclination angle (a1) in such a way that, during the rotation of the milling head (1) in the working direction, the outer edge (1192) precedes and the inner edge (1191) follows behind.

14. Milling head (1) according to one of the claims 1 - 13, characterised in that the at least one conveyor shovel (119A, 119B) has a front edge (1193) which extends from an inner edge (1191) lying closer to the rotation axis (x) to an outer edge (1192) lying farther away from the rotation axis (x), which front edge (1193) is inclined vertically relative to the diameter (d112) of the inner ring plate (112) by a vertical inclination angle (a2) in such a way that, preferably in accordance with the course of the mounting height of the central chisels (111), the inner edge (1191) lies higher than the outer edge (1192).

15. Milling head (1) according to one of the claims 1 - 14, characterised in that the at least one conveyor shovel (119A, 119B) has a front edge (1193) which extends from an inner edge (1191) lying closer to the rotation axis (x) to an outer edge (1192) lying farther away from the rotation axis (x), which front edge (1193) is set back over the entire length by a shovel spacing (a3) in the range of preferably 5 mm - 40 mm in the milling direction relative to the working circles (ml) of the central chisels (111).

16. Milling head (1) according to one of the claims 1 - 15, characterised in that the at least one conveyor shovel (119A, 119B) is inclined by a vertical inclination angle of the shovel (a4) relative to the rotation axis (x), wherein the front edge (1193) of the conveyor shovel (119A, 119B) is leading and the inclination angle of the shovel (a4) is in a range of preferably 5°-85°.

Images