BLASTING CONTAINER

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German Application No. 102024122986.1, filed on Aug. 12, 2024. The entire disclosure of the application referenced above is incorporated herein by reference.

The present invention relates to the processing of bulk goods using blasting processes. Said blasting processes can take place in drum systems, for example. In this respect, a blasting container in the form of a drum with a horizontal or inclined axis is loaded with workpieces. The workpieces are kept in motion and circulated by a rotation of the drum. In this way, the components change their position in the drum. This change in position can be supported by installations in the drum that specifically influence the sliding and slipping movements of the components or, in the case of transverse installation, act in a similar way to drop steps and can thus also cause a turning over of the workpieces.

The components kept in motion in this way are then blasted with blasting medium from nozzles or by means of blasting wheels (turbines) in order to process the surfaces. The movement of the workpieces (sliding, tilting, rotating, falling, turning, etc.) is a prerequisite for ensuring that all the surfaces are reached during the processing and that as uniform as possible a state of the component surfaces is achieved.

The blasting medium comprises particles of a small size with different geometries and size distributions. They impact the component surfaces directly or indirectly as ricochets, but must then also be removed from the component surfaces again. This takes place in a drum system by circulating the parts in the drum. The blasting medium then collects in cavities, recesses and in the lower region of the drum. This has the positive side effect that the parts are thus also protected against damage (part against part or part against drum). However, the workpieces must then also be removed from the drum since otherwise the bulk material would be completely embedded in blasting medium after a short time and a processing of the component surfaces would no longer take place.

To remove blasting medium from the processing space in the drum, the wall of the drum is equipped with openings. These openings have two functions: On the one hand, they are large enough to enable the flowing off of blasting medium and surface abrasion from the processing space. So that the blasting medium can, for example, be processed outside the processing space (separator, sieve, etc.) and can then be fed back to injector nozzles or blasting wheels (turbines). On the other hand, the openings are so small that the bulk material is retained in the drum and cannot enter the blasting medium circuit.

These known blasting containers have proven themselves well for a large number of components since the dimensions of the components differ sufficiently in all orientations (length, width, height, diameter) from the particle diameter of the blasting medium used. Typical blasting medium has similar dimensions in all three spatial directions. In this respect, similar means that these dimensions are of approximately the same order of magnitude, but are not necessarily identical (differing by a factor of less than 10 from one another). In contrast, workpieces can completely or in part regions be rod-shaped, bar-shaped, blade-shaped or even tapering to a point so that their minimum dimension differs greatly from their maximum dimension. However, problems can occur during the blasting if the workpieces to be processed completely reach a dimension, or in individual part regions reach a dimension, of less than approximately 5 to 20 times the dimensions of the blasting particles. Components that are characterized by this description are hereinafter referred to as “pointed components”. Examples of “pointed components” are thin rods, needles, knife blades, cutting blades of scissors or components with protruding or pointed part regions that thus at least locally have geometric properties that can get caught in the openings of the drum and can thus e.g. be damaged. However, if the openings in the wall of the blasting container are reduced to such an extent that the components can no longer remain stuck in the openings, the blasting medium is no longer sufficiently removed from the processing space. An effective and efficient processing with the aim of achieving a largely uniform surface condition is then no longer provided despite the important advantages of the continuous circulation.

It is therefore an object of the present invention to provide a blasting container with which a trouble-free blasting of workpieces (“pointed workpieces”) is possible, the minimum and maximum dimensions of said workpieces deviating greatly from one another at least in part regions.

This object is satisfied by the features of claim 1 and in particular by a blasting container that comprises at least one wall having an inner side and an outer side, wherein the wall is provided with a first and at least one further opening for a discharge of blasting medium. A cover is present at the outer side of the wall above the first opening and above the further opening, with a passage for blasting medium being formed between the cover and the opening covered by said cover.

The blasting container can generally be of any design, but is in particular configured as a blasting drum that can be rotated about an axis of rotation, wherein the wall forms a circumferential wall of the blasting drum. A rear wall of the blasting container can be closed, wherein either no wall can be provided at the side disposed opposite the rear wall, or a wall having an opening or a wall having a closable opening can be provided. However, only the workpieces are supposed to be fed through these openings into the blasting container and discharged therefrom. The wall of the blasting container can either be formed as a completely curved circumferential wall or from part regions that are planar or also curved. The blasting container does not also have to have a circular cross-section, but can be formed as a polygon in cross-section. It can be advantageous if not only a first and a further opening are present for the discharge of blasting medium, but if a large number of such openings are provided in the wall. These openings can have a circular cross-section, for example. Ovals, “smileys”, triangles, rectangles, squares or slit-like structures are likewise possible.

According to the invention, a cover is located above both the first and the further opening at the outer side of the wall of the blasting container. However, the cover does not completely close the opening, but is arranged such that a passage for blasting medium is formed between the cover and the opening covered by said cover. The cover is therefore attached spaced apart from the outer side of the wall of the blasting container so that blasting medium can first exit through the opening in the wall and then through the passage between the cover and the wall. It is hereby ensured, on the one hand, that the blasting medium can flow off easily via sufficiently large openings to guarantee the function of the blasting system. On the other hand, pointed workpieces are also kept movable within the blasting container, i.e. the workpieces can neither exit from the blasting container nor jam in the openings of the wall.

It is understood that, in accordance with the invention, it is harmless if there are additional openings without a cover in the wall of the blasting container, as long as said openings are sufficiently small to prevent workpieces from getting stuck or jammed.

The openings in the wall can generally be of any design in the plan view, for example, round, triangular or polygonal.

Advantageous embodiments of the invention are described in the description, in the drawing and in the dependent claims.

According to a first advantageous embodiment, the cover can completely cover the opening associated with it, with the area of the cover in particular being able to be larger than that of the opening.

According to a further advantageous embodiment, the cover can be planar at least in the region of the opening. The geometry of the outer contour of the opening and the cover can also be the same. For example, both the opening and the cover can have a circular outer contour, wherein the diameter of the cover is, however, selected to be larger than the diameter of the opening.

According to a further advantageous embodiment, the cover can have margins that are curved in the direction of the wall or the wall can have opening margins that are curved in the direction of the cover. Due to such bends or curved part regions, narrower gaps and labyrinths can also be formed that prevent workpieces from leaving the processing space while still allowing the blasting medium to flow off unhindered.

According to a further advantageous embodiment, the cover can be provided with elevations at its side facing the opening in order to prevent the workpieces from jamming or wedging. The cover can, for example, be designed as a basically planar but structured, embossed or also corrugated metal sheet. It is also possible to provide the cover with concave or convex elevations or recesses. In this respect, shell-like or cup-like structures are also possible.

According to a further advantageous embodiment, the cover can be fastened to the wall, for example releasably or non-releasably. For example, screws or also welded connections can be used for this purpose. The cover can be fastened above its associated opening, for example, with the aid of webs or spacers.

According to a further advantageous embodiment, the wall of the blasting container can also be double-walled, with the wall having the openings for the discharge of the blasting medium being an inner wall that is surrounded by an outer container wall and that is provided with the covers. If this outer wall is likewise provided with openings for a discharge of blasting medium, said blasting medium can flow off unhindered. These openings are preferably arranged offset from the openings of the inner wall. In this respect, the openings in the outer wall can be formed by punching out part regions, wherein the part regions can be bent over and used as spacers. For example, web-like sections of the outer wall can be punched out, bent over and soldered or welded to the outer side of the inner wall so that the outer wall is fastened spaced apart from the inner wall.

It can also be advantageous to round off the margins and corners of the openings to prevent the components from jamming. An outer margin of the covers can be bent towards the outer side of the wall to reduce the passage between the wall and the cover.

Due to structural elements (pins, elevations, half shells) on the cover and/or chamfered or rounded edges or margins, simple labyrinth-like structures can be produced by means of which the blasting medium can flow off safely. Components cannot enter or become wedged here. The circulation of the components in the blasting container furthermore leads to components not remaining permanently in a cluster, but instead repeatedly separating from one another.

According to a further advantageous embodiment, the wall can be formed in the region of a recess in the container wall by an insert that is inserted into the recess, with the insert having the openings and with at least one cover being fastened to an outer side of the insert. A modular design hereby results since different inserts having different openings can be inserted into the blasting container as required. The insert can be designed as flush with the rest of the container wall in the region of the inner wall of the container. The insert can also be provided with sieves or perforated metal sheets that allow a passage of liquid. The insert can, for example, be L-shaped so that it extends in the region of the container wall, on the one hand, and in the region of a container base, on the other hand. The front side of the insert can form the inner wall of the container in the region of the recess, wherein, at the rear side of the insert, there can be holding webs between which a cover is mounted.

According to a further aspect, the present invention relates to a method for blasting workpieces with blasting medium in a blasting container of the kind described above, wherein the maximum clear width of the openings in the container wall is W_max and the maximum dimension of the workpieces is L_max, wherein the maximum clear width of the openings is selected such that L_max is greater than W_max. The size of the openings can hereby be optimized, wherein it is ensured for this purpose that the maximum clear width of the opening is greater than the maximum dimension of the workpieces so that they cannot fall through the opening if they lie planar above the opening. A penetration of the opening in the case of a perpendicular impact of the workpieces is likewise prevented by the cover. The maximum clear width W_max of the opening can be, for example, the diameter of a round opening in a perforated metal sheet or the diagonal of a rectangular opening.

According to a further advantageous embodiment, the maximum dimension of the blasting medium is S_max, and the minimum clear width of the passage is in the range from 3 S_max to 5 S_max. With this dimensioning, it is ensured that the blasting medium can sufficiently exit from the blasting container.

A further problem can arise if the workpieces impact the opening of the wall at a shallow angle. In this case, the workpieces can dip into the opening at least with a part section, wherein they can then, however, abut the cover with their front end.

To prevent a workpiece from completely passing through the opening in this case, the product of the maximum clear width D_max of the passage and the maximum clear width of the opening W_max, divided by the minimum dimension L_min of the workpieces, can be selected to be smaller than the maximum dimension of the workpieces L_max. In this case, the size of the passage and the size of the opening are selected in dependence on the minimum and the maximum dimension of the workpieces so that even on a flat entry of a pointed workpiece into the space between the opening and the cover, a part of the workpiece still projects from the opening so that it does not dip completely into the opening, but moves out of the opening again on a rotation of the blasting container.

The method according to the invention takes into account the fundamental dimensional differences between the blasting medium and the workpieces. While the dimensions of the particles of the blasting medium are of the same order of magnitude in all spatial directions (e.g. μm or mm), the measurements of the dimensions of the workpieces or of individual elements on the workpieces differ by multiple orders of magnitude from one another. Examples in this regard are components with pointed elements such as needles with a length of 50 mm and a diameter of 0.5 mm, in which the length and the diameter are in a ratio of 100:1.

According to a further aspect of the present invention, it also relates to a blasting system comprising a blasting container of the kind described above and a blasting device for applying blasting medium to workpieces located in the blasting container. The blasting device can, for example, comprise a blasting nozzle or a blasting wheel. Furthermore, the blasting system can have a rotation drive for the blasting container.

The present invention will be described in the following purely by way of example with reference to advantageous embodiments and to the drawing. There are shown:

FIG. 1 a part section through the wall of a blasting container;

FIGS. 2a) to h) highly schematized sections through a wall, similar to the representation in FIG. 1;

FIG. 3 a workpiece extending partly through an opening of the wall;

FIG. 4 a perspective view of a blasting container;

FIG. 5 a partly sectioned view of an insert for the blasting container of FIG. 4; and

FIG. 6 to FIG. 8 representations of components of the insert.

FIG. 1 shows in a highly schematic and purely exemplary manner a section through a wall 10 of a blasting container that serves to blast workpieces with a blasting medium. The blasting container can in particular be configured as a blasting drum composed of metal that is open at one side, wherein the wall 10 can have a circular or polygonal contour. The wall 10 has an inner side 12 directed into the interior of the blasting container and an outer side 14 pointing in the opposite direction. Furthermore, the wall 10 has a plurality of openings 16 that are provided for an exit of blasting medium from the interior of the container. Only a first opening is shown in FIG. 1. However, it is understood that the wall 10 has a plurality of such openings 16.

As FIG. 1 further illustrates, a cover 18 is arranged at the outer side 14 of the wall 10 above the opening 16, but is spaced apart from the wall 10 so that a passage 20 for blasting medium is formed between the cover 18 and the opening 16 covered by said cover 18. In this respect, the cover 18 completely covers the opening 16 and the area of the cover 18 is furthermore larger than the area of the opening 16. In the embodiment example shown, the cover 18 is planar in the region of the opening and also beyond.

The geometry of the outer contour of the opening 16 and the cover 18 can in principle be arbitrary, wherein both outer contours can also be the same, for example, circular, oval, triangular, polygonal or irregular.

In the embodiment example shown in FIG. 1, the cover 18 is fastened to the outer side 14 of the wall 10 via spacers 22. The fastening can generally take place using screws, rivets, a single-piece connection or also a bonded connection.

According to a further embodiment, not shown, the cover 18 can also be part of an outer wall that has further openings for a discharge of blasting medium between the covers and offset from the openings 16 of the wall 10.

FIG. 2 shows different design options of the cover 18 and the marginal regions of the opening 16 in a highly schematic and simplified manner.

In the embodiment shown in FIG. 2a), the margin of the cover 18 is bent over downwardly in the direction of the outer side 14 of the wall 10. This is likewise the case in the embodiment according to FIG. 2b), wherein, in this embodiment, the margin of the opening 16 is additionally bent over in the direction of the cover 18 to form a kind of labyrinth seal through which blasting medium can indeed exit to a sufficient degree, but no workpieces can move outwardly.

In the embodiment according to FIG. 2c), the margin of the opening 16 is likewise bent over towards the outer side. However, in this embodiment example, the cover 18 is configured as a planar element.

In the embodiment according to FIG. 2d), similar to the variant according to FIG. 2b), the margin of the opening 16 is bent over in the direction of the cover 18 and the margin of the cover 18 is bent over in the direction of the wall 10. However, the margins in this embodiment are obliquely angled, whereas the margins in the embodiment according to FIG. 2b) are uniformly curved.

FIG. 2e) shows a variant in which the cover 18 is provided with elevations in the form of ribs or pins 24, which are located above the opening 16, at its side facing the opening 16.

In the embodiment variant shown in FIG. 2f), the wall 10 is planar in the region of the opening 16. However, a convex dome 26 is provided at the cover 18 in the region of the opening 16.

In the embodiment according to FIG. 2g), the wall 10 is again planar in the region of the opening 16. However, the cover 18 has the shape of a corrugated metal sheet.

Finally, in the embodiment according to FIG. 2h), a plurality of pins 28 are attached to the cover 18 and are located above the opening 16. Otherwise, the cover 18 and the wall 10 are planar.

FIG. 3 purely schematically shows a workpiece 30 that extends partly through the opening 16 in the wall 10 and that contacts the cover 18 with its one end (the left one in FIG. 3). In FIG. 3, the maximum clear width of the opening 16 is designated as W_max. In the embodiment example shown, the maximum dimension L_max of the workpiece 30 extends in the longitudinal direction and the minimum dimension L_min of the workpiece 30 extends perpendicular thereto and also in the drawing plane. It is therefore a rod-shaped or pin-shaped workpiece, for example, scissors, parts of scissors, surgical instruments or the like.

The maximum clear width D_max of the passage 20 is likewise shown in FIG. 3. The maximum dimension L_max of the workpiece 30 is greater than the maximum clear width W_max of the opening 16.

Furthermore, it can be advantageous if the maximum clear width of the passage 20 is approximately 3 to 5 times as large as the maximum dimension S_max (not shown in the Figure) of the blasting medium. It is hereby ensured that the blasting medium can flow through the passage 20 with a sufficient flow rate.

FIG. 3 further illustrates that there is a critical length for the workpiece 30 (shown as a dashed line in FIG. 3) at which the workpiece 30 could fall completely into the gap between the wall 10 and the cover 18 and could thus exit from the blasting container. However, it has been found that this does not occur if the maximum dimension L_max of the workpieces 30 is greater than or equal to the product of the maximum clear width D_max of the passage 20 and the maximum clear width W_max of the opening 16, divided by the minimum dimension L_min of the workpiece 30. It can be advantageous here if the maximum dimension L_max of the workpieces is selected to be somewhat larger, for example 10-15% larger, in order to reliably prevent a jamming of the workpieces in the position shown in FIG. 3.

A blasting container of the kind described above can be used in a blasting system that is provided with a blasting device for applying blasting medium to workpieces located in the blasting container. For this purpose, a rotation drive can be provided for the blasting container in order to rotate it during the blasting. The blasting container can be provided with an inlet opening and an outlet opening that can be optionally closable.

FIG. 4 shows a perspective view of an embodiment example of such a blasting container 50 whose circumferential wall 10 in turn has an inner side 12 and an outer side 14. In the embodiment example shown, the circumferential wall is not purely circular cylindrical, but is composed of different planar segments that extend in the circumferential direction and also in the radial direction. In the embodiment example shown, the segments of the circumferential wall that are oriented in the circumferential direction are provided with rectangular recesses into each of which an insert 52 is inserted that forms the wall in the region of the recesses.

The insert 52 with its individual components is shown in more detail in FIGS. 6 to 8. As is in particular illustrated in FIG. 7, the insert 52 has a plate 54, for example a rectangular plate, that is provided with a plurality of rectangular openings 16 arranged parallel next to one another. In the region of the recess, the front side or inner side of the plates 54 thus forms the wall 10. Rear webs 56 are fastened to the rear side of the plate 54 at both sides of each opening 16, wherein, between a respective two adjacent webs, a rectangular cover 18 is fastened whose two outer ends are obliquely angled (cf. in this respect also FIG. 5). This arrangement approximately corresponds to that of FIG. 2a). In this respect, the arrangement is such that a respective passage 20 (cf. in this respect FIG. 5) for blasting medium is formed between each cover 18 and the opening 16 covered by it in the region of the angled ends of the cover 18.

For an assembly of the insert 52, the plate 54 prepared in this way is fastened to an L-shaped support 58. A spacer 60 provided with flow openings can furthermore be arranged between the support 58 and the plate 54.

The shorter leg of the support 58 can be occupied by a cover plate 62. Said cover plate 62 can also be designed as a sieve plate, wherein corresponding recesses, into which the shorter leg of the insert 52 is inserted in a flush manner, are provided in the base of the container 50.

FIG. 5 shows a partly sectioned side view of the insert of FIG. 4 and FIG. 8. As can be seen, the cover 18, which is trapezoidal in cross-section, is fastened to the web 56 at both sides, wherein the passages 20 are formed between the plate 54 and the cover 18 in the region of the opening 16.

The container wall 12 can, in particular in the region of its radially extending segments, contain passage openings 51 for blasting fluids (e.g. gases, usually air or liquids, usually water) that either enter the drum from two-substance nozzles (gas/blasting medium or water/blasting medium) or are taken along as air from the environment, e.g. by blasting medium exiting at a high speed from blasting wheels. These blasting fluids accumulate on the surfaces and have to be discharged from the drum in order not to adversely influence the blasting process.