GRAVIMETRIC DOSING UNIT FOR FLOWABLE BULK MATERIAL

Description

[0001] The present invention relates to a gravimetric dosing unit according to the preamble of claim 1.

[0002] Gravimetric feeders, also known as differential dosing scales, are widely used in many industries for all kinds of free-flowing or pourable materials, i.e., bulk solids, provided they can be conveyed by a gravimetric feeder. The free-flowing materials are placed in a container, from there into a base unit below, and metered out of the feeder by a conveyor located in the base unit. The feeder sits on a scale; therefore, the weight registered by the scale is the gross weight, i.e., the known and constant weight of the feeder components (tare) plus the variable weight of the bulk material currently present in the container and base unit (net weight).

[0003] Thus, during operation of the dosing unit, the scale continuously registers the weight loss of the entire dosing unit, and therefore, due to the constant weight of the dosing unit, the weight loss of the bulk material contained in the dosing unit. This allows the dosing unit's control system to determine the actual mass flow rate of the bulk material dispensed from the weight loss and, in comparison with a predetermined target mass flow rate, to regulate the output conveyor accordingly in order to minimize the difference between the actual and target mass flow rates.

[0004] This can necessitate very precise control of the discharged mass flow, for example in the pharmaceutical industry or when color pigments are to be added in industrial production. Furthermore, the target mass flow can be small, as with the aforementioned color pigments and in drug manufacturing (e.g., a few kilograms per hour), or large, as in plastics manufacturing and mining (e.g., more than 1 ton per hour), where precise dosing may also be required at such high flow rates.

[0005] Precise scales of all kinds are frequently used as weighing instruments, with a resolution over their weighing range of 1:100,000 and more, including those with vibrating string sensors, such as those known under the designation SFT-III, SFT-II-M and SFT-II-L from Coperion K-Tron.

[0006] These scales have a resolution of up to 1:4,000,000, enabling precise dosing even with a container capacity of several hundred kilograms and a throughput of several tons per hour. Using a resolution of, for example, 1:1,000,000, the output mass flow rate of 1 kg / s (3.6 t / h) can still be accurately measured to 1 / 10 g with a container capacity of 100 kg and then used for dosing. For smaller mass flows, the mass flow rate can then be measured to an accuracy of 1 / 100 g or 1 / 1000 g.

[0007] To utilize the precision of the scales for dosing, non-vertical conveyors, i.e., horizontal or inclined ones, are preferred. This allows for better control of the fluid dynamic behavior of the bulk material, as gravity does not act in the conveying direction with horizontal conveyors and thus does not interfere. Longer screw conveyors are well-suited as horizontal conveyors because the actual conveying rate can be varied easily and without delay by adjusting their rotational speed. Furthermore, the distance from the mass flow from the hopper to a collection container located outside the dosing unit can be bridged effectively without any negative impact on the actual mass flow itself.The K4G-L Group brochure, K-Tron Product Information, K4G Continuous Gravimetric Blender shows an arrangement of gravimetric dosing units with different hopper volumes and precision scales that allow highly precise conveying as required at different delivery rates.

[0008] Depending on the bulk materials being conveyed, regular maintenance, especially cleaning of the basic unit of the dosing system, such as the conveyor or screw conveyor, is essential.

[0009] WO 2006 / 010 475 discloses a metering unit comprising a bulk material feeder and a frame for the feeder, which features a short, vertical screw. The feeder is mounted on a plate-shaped extension of the frame, which supports the bulk material container on one side and, via a vertical guide rod attached to it, the feeder's base unit on the other. The base unit is designed to be lowered and rotated along the guide rod, allowing for maintenance without having to completely detach and remove it from the feeder.

[0010] EP 0 486 424 B1 discloses a device for gravimetric metering of bulk materials, comprising at least one metering screw with a drive and an agitator arranged above the metering screw with a separate drive.

[0011] It is further disclosed generally that the arrangement shown for gravimetric dosing can also be placed on a scale, although the method remains unspecified. Moreover, the arrangement shown is not suitable for longer screw conveyors or, in particular, for horizontal screw conveyors.

[0012] The object of the present invention is to further develop a dosing unit with precision scales and a non-vertically, preferably horizontally arranged conveyor in such a way that the basic unit is more easily accessible for maintenance.

[0013] This problem is solved by the characterizing features of claim 1.

[0014] Because the dispenser is suspended from the frame above its container and the rail is in turn arranged on the container itself, a complex, double suspension is unnecessary, which on the one hand supports the container and on the other hand the base unit, but as a whole rests on the scale for recording the weight of both, the container and the dispenser.

[0015] Beyond the stated objective, the limiting arrangement according to the features of claim 2 makes it possible to use a simplified, cost-effective suspension that is designed only for stress in the direction of the weight force, but not for stress caused by the forces acting in all directions during maintenance.

[0016] The invention is described in more detail below with reference to the figures.

[0017] It shows: Figures 1a and 1b schematically, an embodiment of the invention is shown. Figures 2a and 2bschematically a further embodiment of the invention, Figures 3a to 3c a view of another embodiment of the invention, 3D figure a three-dimensional partial view of the embodiment according to the Figures 3a up to c, and Figures 4 and 5 A three-dimensional detailed view of two embodiments of the parallel arms of a parallel guide for the container of the dispenser.

[0018] Figure 1aFigure 1 shows a dosing unit 1 according to the invention, comprising a doser 2, which has a funnel-shaped container 3 for bulk material and a base unit 4. The base unit 4, in turn, has a drive 5 and a horizontally oriented conveyor driven by the drive, with a screw conveyor 6, the conveyor terminating in a collector 7, indicated by dashed lines. The drive 5 further comprises a motor 8 and a gearbox 9, to which the conveyor is connected. A control system for the motor 8, and thus for the speed of the screw conveyor 6, is known to those skilled in the art and has been omitted from the figure for the sake of clarity. In the embodiment shown, a transition funnel 10 to a conveying container 11 is also provided, in which the screw conveyor 6, where it runs, is shown with dashed lines.It should be noted that although the screw conveyor 6 is widely used for horizontal conveying, other differently designed, non-vertical suitable conveyors are also known to the expert.

[0019] During operation, bulk material is filled into the container 3, which falls from this via the transfer hopper 10 into the conveying container 11 and is then conveyed to the left into the collector 7 by the screw conveyor 6 running in a conveying pipe 6'.

[0020] A suspension 12 supports the dispenser 2 on its right side via a boom 13 on a scale 14, which in turn rests on a suitably designed support 15 of the frame 16. The suspension 12 carries the dispenser 2 on its left side via a parallel guide 17, which in the illustrated embodiment has an upper parallel arm 18 and a lower parallel arm 19, wherein the parallel arms 18, 19 are provided with end joints 20, 20' and 21, 21' and are thus connected to the frame 16 and the container 3 in such a way that the latter is suspended relative to the frame 16 so as to be movable in the vertical direction.

[0021] This results in a gravimetric dosing unit comprising the frame 16, the dosing unit 2 and the suspension 12, in which the suspension preferably has a parallel guide 17 which is connected on one side to the frame 16 and on the other side to the container 3 of the dosing unit 2, such that the container 3 is suspended vertically movable relative to the frame 16.

[0022] The control unit (omitted above to simplify the figure) can continuously determine the weight of the dispenser 2 in gravimetric operation from the weighing signal of the scale 14 and the geometry of the arrangement shown, thus controlling the motor 8 for precise dosing by the screw conveyor 6. Due to the vertical mobility of the parallel guide 17, the container 3, and therefore the dispenser 2, is free from any influence of the frame in the vertical direction, allowing the scale 14 to determine the actual weight of the dispenser 2. It should be noted that, depending on the scale 14 used, the necessary vertical displacement by the parallel guide 17 may be very small, especially if the scale 14 is designed as a vibrating string balance.Nevertheless, the dosing unit 2 must be decoupled from the frame 16 with respect to vertical forces in a vertical interval corresponding to the scale used, in order to ensure correct weighing and thus precise dosing by the dosing unit 1.

[0023] The figure further shows a rail 25 which is fixed to the container 3 at its inner end region 26 and is arranged to float freely with the other, outer end region 27, but is preferably spring-elastic and deflectable downwards.

[0024] A support structure 28 runs on rail 25, with a running element 29 and a mast 30, from which the base unit 4 is suspended, so that it can be moved back and forth along the length of rail 25, in the Figure 1ato the left towards container 3 in its operating position (i.e. connected to container 3 for gravimetric dosing) and to the right, away from it, in its maintenance position (i.e. detached from container 3 and accessible for maintenance).

[0025] Below the outer end region 27 of the rail 25, a second support 31 is located on the frame, on which a support bearing 32 for the outer end region 27 of the rail 25 is arranged. Furthermore, lateral limit stops 33, 33' of a limit arrangement 34 are provided on the second support 31 (see [reference]). Figure 1b ). The limit stop 33' is hidden in the figure by the limit stop 33.

[0026] Figure 1b shows the embodiment of Figure 1aThe base unit 4 has been moved into its maintenance position. Its weight now rests on the outer end section 27 of the rail 25, which, being preferably designed to be vertically spring-elastic to accommodate this weight, has lowered until the end section 27 abuts and rests on the support 32. The outer end section 27 is then simultaneously retracted between the lateral limit stops 33, 33' and is fixed horizontally between them with a predetermined tolerance. This tolerance is defined by the suspension 12: if the base unit 4 is manipulated in the maintenance position, the rail 25 acts as a lever, transmitting all forces generated by the manipulation to the container 3 and from there to the suspension 12, which must absorb these forces. Thus, horizontally acting force components rotate the container 3 about its vertical axis 35.The tolerance in the limiting arrangement 34 allows one permissible rotation and prevents further, impermissible rotation.

[0027] An elaborate reinforcement of the suspension 12 with regard to horizontally acting force components, which rotate the container 3 about its axis 35, is eliminated; conversely, a simplified, cost-effective suspension 12 becomes possible.

[0028] As a result, the outer end region 27 is supported by the frame, meaning that the weight of the base unit 4 is borne by the frame, and the laterally acting forces arising from maintenance are likewise absorbed by the frame 16 via the limit stops 33, 33'. Rotation of the container 3 about its vertical axis 35 is thus prevented or, depending on the design of the limit arrangement 34, limited to a predetermined value. This allows the suspension 12 to be simplified to support only the weight of the metering unit 2, eliminating the need to accommodate horizontally acting forces or moments resulting from maintenance of the base unit 4.

[0029] Thus, the base unit 4 is mounted on the frame 16 in its maintenance position, and in the operating position with a freely suspended rail 27 ( Figure 1a) however, completely decoupled from this, so that the frame 16 cannot exert any forces on it which could distort the weighing of the base unit 4 by the scale 14.

[0030] It is preferable that the rail 25 is designed to be spring-elastic in the vertical direction and that a support bearing 32 is provided on the frame 16, on which the rail 25 rests when spring-elastically deflected downwards, such that the rail 25 rests on the support 32 when the base unit 4 is in the maintenance position, but does not rest on the support 32 when the base unit 4 is in the operating position. Furthermore, a limiting arrangement 34 is preferably provided on the frame 16, which limits rotation of the container 3 relative to the frame 16 about a vertical axis 35. The limiting arrangement (34) preferably has stops (33, 33') connected to the frame (16) which interact with the rail (25).

[0031] It should be noted at this point, however, that the parallel guide 17 and / or the support for the scale can also be designed to be sufficiently robust to absorb all forces acting on the rail during maintenance – in which case the vertically spring-loaded design of the rail and the effort required for a limiting device become unnecessary. The advantage then remains the simple design of the suspension itself, which only acts on the container 3, in conjunction with the rail arranged on the container, which no longer needs to be supported by the frame and thus ensures complete decoupling of the dosing unit from the frame, at least in the direction of the weight force, during gravimetric operation.

[0032] Figure 2aFigure 1 shows a metering unit 40 according to a further embodiment with a modified rail 41, which is designed in multiple parts. A container-side part 42 of the rail 41 is fixed to the container at one end 43 and preferably extends horizontally away from the container 3. A frame-side part 44 of the rail 41, also preferably horizontally oriented, is fixed to the frame 16. Both parts 42, 44 of the rail 41 are aligned with each other, but there is a gap 45 between them, through which the container 3 is decoupled from the frame, but which is designed such that it can be traversed by the running element 29 of the supporting structure 28.

[0033] In the Figure 2aIn the illustrated operating position of the base unit 4, it rests on the inner part 42 of the rail 41 and is connected to the container 3. The scale 14 registers the full weight of the dispenser 2. The gap 45 decouples the inner part 42 from the frame 16, eliminating any forces exerted by the frame that would distort the weight. During operation of the dosing unit, the container is freely movable in the direction of the double arrow 48 due to the changing weight of the dispenser 2. This movement, generated by the scale 14 during the weighing process, is permitted by the suspension 12 or the parallel guide 17 and is – as is also the case in the embodiment according to Figure 1a This is the case when the outer end region 27 of the rail 25 is free-floating.

[0034] In the maintenance position, the support structure 28 with the running element 29 rests on the outer part 44 of the rail 41, which is rigidly connected to the frame and is therefore supported by the frame 16, whereby manipulation forces acting on the base unit cannot be transferred to the container 3 because of the gap 45, so that its suspension is in turn protected from the corresponding stress and can be designed, in simplified terms, only for the weight forces of the gravimetric operation.

[0035] It is preferably the case that the rail 41 is formed in multiple parts, wherein a container-side part 42 is connected to the container 3 and a frame-side part 44 is connected to the frame 16, and wherein the parts 42, 44 of the rail 41 are aligned with each other in a manner that allows movement relative to each other, such that the supporting structure 28 can be moved over a gap 45 between the aligned ends.

[0036] Figure 2bshows a view of rail 41 from above, in another, opposite Figure 2a modified embodiment. A section of the container 3, to which the inner part 42 of the rail 41 is attached, and a section of the frame 16, to which the outer part 44 of the rail 41 is attached, are visible. Both parts 42, 44 are aligned, with the gap 45 formed between the opposing and oppositely shaped ends 46, 47 of parts 42, 44. In the embodiment shown, rectangular recesses 46 are provided on part 42, into which rectangular projections 47 of part 44 extend. This design allows the container-side part 42 to move relative to the frame-side part 44 in the direction of the double arrow 48 ( Figure 2a ) can move freely (the container 3 is therefore decoupled from the frame) although the space 45 is designed in such a way that it can be easily driven over by the supporting structure 28 or the running element 29.

[0037] Furthermore, this embodiment has the advantage that rotation of the container 3 in the suspension 12 is limited, e.g., even when the base unit 4 is released from its operating position, since the interacting recesses 46 and projections 47 then abut each other laterally. The projections 47 and recesses 46 therefore constitute lateral stops of a limiting arrangement 49 and act analogously to the stops 33, 33' according to [reference]. Figure 1a and b.

[0038] It should be noted that the person skilled in the art can design the space 45 or the pairing of projections / recesses as they see fit in the specific case in order to achieve the effect according to the invention in accordance with the specific design of the suspension 12 and the drive 28.

[0039] It is further preferably the case that the limiting arrangement 32 has lateral, cooperating stops at the aligned ends of the rail 41, preferably interlocking projections 47 and recesses 46.

[0040] The Figures 3a to c show a dosing unit 50 in a side view ( Figure 3a ), a view from below ( Figure 3b ) and a three-dimensional section from obliquely below onto the rail 51 and the limiting arrangement 52 of the dosing unit 50 ( Figure 3c In each figure, a coordinate system 53 shows the height h, length I and width b of the dosing unit 50. 3D figure The rail 75 with the limiting arrangement 52 of the dosing unit 50 is shown in more detail in the form of an exploded view.

[0041] Figure 3aFigure 50 shows a metering unit 50 in a side view, with a cylindrical container 54 for bulk material of a metering unit 55, which has a connection nozzle 56 for refilling bulk material, a transition hopper 57 and a conveying container 58 (in which a horizontal screw conveyor, not visible, runs), wherein a conveying pipe 59, through which the screw conveyor extends, opens from the conveying container 58 to the left into a vertical transition pipe 60, from which the metered bulk material is discharged downwards. A motor 61 drives the screw conveyor, with the gearbox 62 (see Figure 50) being the transmission mechanism. Figure 3b ) between him and the screw conveyor (which is connected to gearbox 9 of Figure 1a(corresponds) is concealed by an outer vertical support 63 of the frame 64 of the metering unit 50. In the embodiment shown, the motor 61, the gearbox 62, the transition hopper 57, the feed hopper 58, the feed pipe 59 and the transition pipe 60 form the basic unit 73 of the metering unit 55.

[0042] The outer vertical beam 63 conceals a second outer vertical beam 63' located behind it; likewise, an inner vertical beam 65 of the frame 64 conceals an inner vertical beam 65' located behind it. The vertical beams 63, 63', 65, 65' stand on a base plate 66 and support, among other things, an outer and upper crossbeam 67, which is in Figure 3a Although concealed by the outer vertical beam 63, it is shown with a dashed line for clarity. The crossbeam 67 has an inverted U-shape in cross-section and is in Figure 3b Visible from below.

[0043] The crossbeam 67 serves as a support for a scale 68, on which the container 67 rests via a vertical support element 69 provided with a boom 69' (which corresponds to the boom 13 of Figure 1a (corresponds) supports. The support element 69 is part of the suspension 80.

[0044] On the opposite, inner side of the dosing unit 50, a vertical frame section 70 of the suspension 80 is visible, on which an upper parallel arm 71 and a lower parallel arm 72 are arranged. These, in turn, support the container 54 so as to be vertically displaceable, insofar as this is necessary due to the movement of the scale 68 during the weighing process. A control unit 74 is arranged on the dosing unit 50 itself and controls the dosing process, which is generally known to those skilled in the art, in a conventional manner.

[0045] Figure 3bThe figure shows the dosing unit 50 from below, with the scale 68 obscured by the crossbeam 67. The trapezoidal contour of the frame 64 is visible, with one narrow side at the location of the transition tube 60 and the wide side on the outside, where the control unit is also located. This arrangement allows a group of six dosing units 50 to be arranged in a hexagon around a common collector, which is not shown in the figure.

[0046] Further evidence shows a second section 81 of another embodiment of a rail 75 ( Figure 3c and 3d ) and a second side section 98 of a correspondingly designed limiting carrier 95 ( Figures 3c and 3d ) a limiting arrangement 52, which limits a rotation of the container 54 about its vertical axis 35.

[0047] Figure 3cFigure 1 shows a section of the dosing unit 50 in a three-dimensional view, obliquely from below, with a view of the rail 75 projecting from the container 54, which is surrounded by a protective sheath 76 arranged on the crossbeam 67. As mentioned above, the crossbeam 67 has an inverted U-shape in cross-section and is arranged with its closed side facing upwards on the vertical supports 63, 63'. It supports the scale 68, which in turn supports the vertical support element 69 and thus the container 54 via the support arm 69' (see also Figure 6). Figure 3a ).

[0048] A downward-running support section 77 of the support element 69 terminates in a horizontally oriented connecting plate 78, to which a mounting head 79 of the rail 75 is attached, thus fixing the rail 75 to the support element 69 (and therefore to the container 54). The rail 75 is in 3D figure still shown in detail.

[0049] In the illustrated embodiment, the rail 75 has a first section 82 extending away from the container 54 and a second section 81 adjoining and angled towards the first. Furthermore, in the illustrated embodiment, the rail 75 is designed as a double rail, with two laterally adjacent single rails 85 and 86, which are spaced apart from each other and thus form a gap through which the mast 87 projects, on which the base unit 73 (see also Fig 3a ) is suspended.

[0050] The support structure 83 for the base unit 73 has, in addition to the mast 87, a running element designed as a lower 85 and an upper sliding disc 86. When the clamping discs or sliding discs 88 and 89 are clamped against each other, they fix the base unit 73 to the rail 75 in which Figure 3cin their operating position. If the sliding discs 88, 89 are separated from each other, the base unit 73 can be moved along the gap between the individual rails 85, 86 via the mast 87.

[0051] The base unit 73 is moved into the maintenance position by loosening a clamping ring 90, which connects the transition hopper 58 to the container 54, via its clamping screw 91, so that it hangs in the rail 75 supported only by its support structure 83. The base unit 73, with the sliding discs 88, 89 detached, can then be pulled away from the container 54 until the screw conveyor is withdrawn from the transition tube 60. This is generally the case when the support structure 83, or the mast 87, is located in an outer area of ​​the first section 82 of the rail 75. There, the base unit 73 can be rotated counterclockwise about the axis of the mast 87 and simultaneously pushed along the second section 81 until the screw conveyor lies parallel to, and outside of, the crossbeam 67.One advantage of this design of the rail 75 is that the base unit 73 does not have to be pulled away from the container 54 in a straight line over the entire length of the screw conveyor, which saves space and allows for tighter space conditions in the specific line from the point of view of maintenance.

[0052] Preferably, the support structure 83 is designed such that it allows rotation of the base unit 73 relative to the rail 75. In the illustrated embodiment, this is easily possible because, with the sliding discs 88, 89 detached from each other, the mast 87 can be rotated at any time in the gap between the individual rails 85, 86, corresponding to the position of the screw conveyor. More preferably, the support structure 83 has a mast 87 projecting between the individual rails 85, 86 and, even more preferably, a disc 89 resting on the individual rails 85, 86, which is designed as a sliding disc.

[0053] In 3D figureThe diagram shows, in the style of an exploded view, the rail 75 and a limiting support 95, which encompasses the rail 75 in its assembled state, as shown in the Figure 3c is shown.

[0054] In addition to the connecting plate 78, with which the rail 75 is attached to the downwardly extending support section 77, and thus to the container 54 (see Figure 3c ), it further has a first limiting cam 100 which projects outwards at the end of its first section 82, and a second limiting cam 101 which, in the embodiment shown, projects away from the end face of the second section 81.

[0055] Both limiting cams 100,101 each have a rectangular outline, a bottom surface 102, 103, an opposite top surface which is hidden in the figure by the bottom surfaces 102,103, an end face 104,105 and a left side 106,107 and right side 108,109, with a left shoulder area 110,111 and a right shoulder area 112,113 adjoining the left 106,107 and right side.

[0056] The limiting beam 95 has a mounting section 96, which is fixed to the cross member 67 of the frame 64, as well as a first side section 97 and a second side section 98, in which a first limiting opening 114 and a second limiting opening 115 are provided. The limiting openings 114, 115 are formed by inner 116, 117 and outer limiting edges 118, 119, as well as lower 120, 121 and upper limiting edges 122, 123. Furthermore, a recess 124 is provided in the mounting section 96, which allows the passage of the first section 82 of the rail 75.

[0057] In its assembled state, the rail 75 lies in the limiting beam 95 such that the limiting cam 100 projects through the limiting opening 114 and the limiting cam 101 through the limiting opening 115, but without the shoulder areas 110, 112 and 111, 113, nor with the left 106, 107 or right sides 108, 109, nor with the undersides 102, 103 or the opposite upper sides, making contact with the corresponding limiting edges of the limiting openings 114, 115. At the same time, the first section 82 of the rail 75 projects through the recess 124, so that the assembly section 78 lies behind the assembly section 96 and behind the crossbeam 67, where it is fixed to the vertical beam section 77.

[0058] In other words, the limiting cams 100, 101 of the rail 75 protrude freely and without striking through the limiting openings 114, 115 as long as no forces act on the rail 75, i.e., the base unit 73 is in its operating position and is not subject to any unwanted force, as is also the case in Fig. 3c is shown.

[0059] The situation is different if the base unit 73 is moved outwards from the operating position along the first section 82 of the rail 75: then the vertically elastic rail 75 lowers downwards (principle according to Figure 1a ), until the undersides 102, 103 of their limiting cams 100, 101 abut the lower limiting edges 120, 121 of the limiting openings 114, 115, whereby the limiting beam 95 and, via this, the crossbeam 67 take over the weight of the base unit 73 - the rail 75 is then coupled to the frame 64 via the weight force of the base unit 73.

[0060] The situation is also different if a horizontal force is exerted on the base unit 73, which threatens to twist the container 54 about its axis 35: the rail 75 then strikes the corresponding edges of the limiting opening 114,115 with the left 110,111 or right 112 shoulder areas, so that this force is in turn absorbed by the limiting support 95 or the frame 64 and thus the suspension 80 of the metering unit 50 is only stressed to the intended extent.

[0061] Analogously for all other forces acting on the base unit: if the rail 75 shifts in any direction as a result, it strikes the corresponding edges 116 to 123 of the openings 114, 115 with the limiting cams 100, 101, so that these forces are introduced via the limiting beam 95, thus into the crossbeam 67, i.e. the frame 64, and cannot excessively stress the suspension 80.

[0062] It follows that the gap between the limiting cams 100, 101 and the limiting openings 114, 115 is dimensioned only so large that the suspension 80 can withstand movement of the rail 75 until the limiting cams 100, 101 contact the limiting openings 114, 115 without damage. It follows that preferably the limiting arrangement (34) has a limiting carrier 95 fixed relative to the frame 64, with openings 114, 115, the edges 116 to 123 of which form limiting stops for limiting cams 100, 101 provided on the rail 75.

[0063] Figure 4 shows a view obliquely from above of an embodiment for a parallel arm 71 of the dosing unit 50 ( Figure 3a), which consists of an elastically deformable material such as sheet metal, has a rectangular body 120 and, in the area of ​​its four corners, connecting tongues projecting from it, parallel aligned, acting as leaf springs 121, 121', 122, 122', which are provided at their ends with a hole 123 for a screw, so that they can be attached to the frame 64, to a vertical frame section 70, or to a suitably designed transition piece 140 on the container 54 (see Figure 3aThe leaf springs 121, 121' are bolted to the frame section 70 and the leaf springs 122, 122' to the transition piece 140. Due to their dimensions, the leaf springs 121, 121', 122, 122' act as joints for the parallel arm 71, allowing the required vertical movement of the container 54 to function properly. As mentioned, the dimensions depend on the type of scale used and can easily be appropriately determined by a person skilled in the art. In the case of a vibrating string balance, the necessary vertical travel of the container 54 is in the range of a fraction of a millimeter, but is nevertheless essential to prevent upward bearing forces of the frame section 70 from distorting the weight measured by the scale 68.

[0064] The parallel arm 71 further has stiffening areas 125,125' laterally angled between the leaf springs 121,122 and between the leaf springs 121',122', which stiffen the parallel arm 71 in a defined manner between the respective leaf springs, so that its body 120 acts as a stiff lever which is attached to the frame and to the container 54 via the joints formed by the leaf springs 121,121', 122,122'.

[0065] The lower parallel arm 72 ( Figure 3a ) is formed in the same way as the upper parallel arm 71.

[0066] It turns out that the parallel arms (18,19,71,72) preferably have joints designed as leaf springs 121,121', 122,122'.

[0067] Figure 5Figure 6 shows another embodiment of a parallel arm 130, which is fundamentally identical in design to the parallel arm 71, 72, but has a recess 132 in its body 131 that extends across its entire width to the beveled stiffening sections 133, 133', such that the body 131 is divided into two parallel strips 134, 135 running across the width of the parallel arm 130, which are connected to each other via the beveled sections 133, 133'. The sections of the beveled sections 133, 133', which are delineated by dashed lines in Figure 6 and lie between the strips 134, 135, now act as vertically oriented leaf springs 136, 136', which allow a relative displacement of the strips 134, 135 in the horizontal plane according to the double arrows shown.

[0068] Thus, the parallel arm 130 enables not only the vertical movement required according to the scale 68, but also a lateral displacement of the container 54, as becomes necessary, for example, when the vertical frame section 70 and the container axis 35 (p. Figure 3a ) are not exactly parallel, but slightly interlocked. This will be less of a case with a 50 metering unit according to the Figures 3a to d This is especially necessary when the container rests on two scales instead of one, so that the support points of the two scales and the parallel guide form a three-point support. In this case, the support points of the two scales cannot be exactly at the same height, meaning the container is slightly inclined relative to the vertical and therefore also slightly inclined relative to the parallel guide. The parallel arm 130 is then able to accommodate a slight lateral deviation of the container section it supports.

[0069] Again, the lateral deviation is usually in the millimeter range, but this must be accepted depending on the type of scale used: If the parallel guide were to keep the container perfectly vertical, one of the two scales would be subjected to a heavier load, the other to a lighter load, since the scales are not at exactly the same height in their initial position. The scale with the heavier load might then operate above its intended operating range, which can lead to undesirable hysteresis in the measurement signal, distorting the measurement result and reducing the dosing accuracy.

[0070] It follows that preferably a parallel arm 18,19,71,72 further has at least one horizontally acting joint, which is preferably designed as a leaf spring 136,136', more preferably in the case of a gravimetric dosing unit in which two scales are provided.

[0071] It should be noted at this point that the container can also be arranged on three scales, in which case a parallel guide is omitted, but a rail 25, 75 according to the invention is provided, preferably with a limiting arrangement 34, 52. It should also be noted that the suspension preferably has a ball bearing which interacts with an associated scale to transmit the weight to be weighed. The scale has a spherically shaped surface at its upper end, where the weight is to be received, which corresponds to a slightly wider, oppositely shaped spherical or elliptical cavity in, for example, a cantilever 13, 69' ( Figure 1a , 3a ) interacts and thus allows a slight lateral displacement of the boom relative to the scale without affecting the precise weight measurement.

[0072] In its entirety, the invention provides for all embodiments a gravimetric dosing unit for bulk materials, comprising a doser with a container for the bulk material to be dosed and a base unit with a horizontally arranged conveyor for the bulk material, wherein the container and base unit are detachable from each other for maintenance, with a frame on which at least one scale is arranged, on which the doser is supported operationally by means of a suspension, such that the dosing unit is designed for gravimetric dosing, wherein the suspension is connected to the container of the doser and supports it above the container, the container itself is provided with a rail projecting away from it, and wherein the base unit has a support structure running on the rail, such that it can be moved back and forth between an operating position and a maintenance position.

Claims

1. Gravimetric dosing unit for bulk materials, with at least one weighing device (14,68), with a suspension (12) and with a dosing device (2,55) which has a container (3,54) for the bulk material to be dosed and a base unit (4,73) which has a conveyor for the bulk material that is not arranged vertically, whereby the container (3,54) and base unit (4,73) being detachable from one another for maintenance purposes, and with a frame (16,64) on which the at least one weighing device (14,68) is arranged, on which in turn the dosing device (2,55) is operatively supported via the suspension (12) in such a way that the dosing unit (1,50) is designed for gravimetric dosing, characterised in that the suspension (12) is connected to the container (3,54) of the dosing unit (2,55) and supports it via its container (2,54), the container (2,54) in turn is provided with a rail (25,75) projecting away from it, and that the base unit (4,73) has a support structure (28,83) running on the rail (25,75) in such a way that it can be moved back and forth between an operating position and a maintenance position.

2. Gravimetric dosing unit according to claim 1, wherein a limiting arrangement (34) is provided on the frame (16), which limits the rotation of the container (3) relative to the frame (16) about a vertical axis.

3. Gravimetric dosing unit according to claim 1, wherein the limiting arrangement (34) has stops (33,33') connected to the frame (16) which interact with the rail (25).

4. Gravimetric dosing unit according to claim 1, wherein the rail (25) is designed to be spring-elastic in the vertical direction and a support (32) is provided on the frame (16) on which the rail (25) rests when deflected downwards in a spring-elastic manner, such that the rail (25) rests on the support (32) when the base unit (4) is in the maintenance position, but does not rest on the support (32) when the base unit (4) is in the operating position.

5. Gravimetric dosing unit according to claim 1, wherein the rail (41) is designed in multiple parts, wherein a container-side part (42) is connected to the container (3) and a frame-side part (44) is connected to the frame (16), and wherein the parts (42,44) of the rail (41) are aligned with each other in a relatively movable manner such that the supporting structure (28) can be moved via a gap (45) between the aligned ends.

6. Gravimetric dosing unit according to claim 5 or 1, wherein the limiting arrangement (34) has lateral stops cooperating with each other at aligned ends of the rail (41), preferably alternately interlocking projections (47) or teeth (46).

7. Gravimetric dosing unit according to claim 1, wherein the rail (75) has a section (82) extending away from the container (54) and a second section (81) adjoining it and angled relative to the first section.

8. Gravimetric dosing unit according to claim 1, wherein the rail is designed as a double rail with two individual rails running side by side, which are arranged at a distance from each other.

9. Gravimetric dosing unit according to claim 1, wherein the suspension (12) has a parallel guide (17) with parallel arms (18,19,71,72) connected on one side to the frame (16) and on the other side to the container (3) in such a way that the container (3) is suspended so as to be vertically movable relative to the frame (16).

10. Gravimetric dosing unit according to claim 1, wherein the limiting arrangement (34) comprises a limiting carrier (95) fixed relative to the frame, with openings (114,115) whose edges (116 to 123) form limiting stops for limiting cams (104,105) provided on the rail (75).

11. Gravimetric dosing unit according to claim 9, wherein the parallel arms (18,19,71,72) have joints designed as leaf springs (121,121',122,122').

12. Gravimetric dosing unit according to claim 9, wherein a parallel arm (18,19,71,72) further comprises at least one horizontally acting joint, which is preferably designed as a leaf spring (136,136').

13. Gravimetric dosing unit according to claim 1, wherein the support structure (83) is designed in such a way that it allows the base unit (73) to rotate relative to the rail (75).

14. Gravimetric dosing unit according to claims 8 and 12, wherein the supporting structure (83) comprises a mast (87) passing between the individual rails (85,86) and, further preferably, a sliding disc (89) resting on the individual rails (85,86).

15. Gravimetric dosing unit according to claim 1, wherein two weighing devices are provided.

16. Gravimetric dosing unit according to claim 1, wherein three weighing devices are provided.

17. Gravimetric dosing unit according to claim 1, wherein the suspension has a ball support which interacts with an associated weighing device to transmit the weight to be weighed.