DE20005360U1 - Grinding machine - Google Patents

Description

PATENT ATTORNEY^ ·***·" '*.**«*'

OIPL-PHYS. DR. RER. NAT. JOST LEMPERT D-76207 KARLSRUHE (DURLACH)

PO BOX 410760

DIPL-ING. HARTMUT LASCH TELEPHONE: (0721)9432815 FAX: (0721)9432850

OTEC Präzisionsfinish GmbH Dieselstrasse 12

7 53 34 Straubenhardt-Feldrennach

21 March 2000 17334.2 Le/bu

Grinding machine

The invention relates to a grinding machine, in particular a centrifugal grinding machine for grinding material to be ground by means of grinding bodies with at least one grinding unit with two parts which can be rotated relative to one another about a vertical axis of rotation and which are in the form of a container and a rotary plate located therein.

For example, centrifugal grinding machines are known which consist of a two-part container with a bowl-like, rotatable lower container part forming a base and a stationary cylindrical upper container part.

Such grinding machines are used for the surface treatment of grinding material, for example smaller parts and workpieces, which together with grinding wheels and, if necessary, a liquid processing agent in

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the container. If the lower part is rotated, the workpieces to be treated are moved outwards on the plate until they hit the inner wall of the container, where they are slowed down. The flow of workpieces causes a circular workpiece movement, which results in intensive grinding or polishing.

A particular disadvantage of such centrifugal grinding machines is that the sealing of the annular gap and the guide of the tubes that delimit it have considerable strains that can only be overcome with great effort and corresponding costs. There is a risk that the upper and lower parts, especially the lower part, will heat up considerably as a result of friction if parts of the grinding material and/or additional grinding media get into the gap between the container base and the rotating plate during operation. This results in a relatively short service life of the grinding machine on the one hand, and on the other hand it must be switched off frequently during processing of grinding material in order to avoid overheating of both the grinding machine and the grinding or polishing material.

The invention is based on the object of creating a simply designed and inexpensive centrifugal grinding machine which operates reliably with a low susceptibility to wear and has a long service life.

According to the invention, this object is achieved with a grinding machine, in particular a polishing machine, of the type mentioned at the outset in that the rotary plate has a limited finite vertical distance from the bottom of the container and has a plate edge guided upwards at an opening angle of more than 90° to the horizontal, wherein

The edge of the plate and/or the wall of the container in the area of the edge of the plate are flexible. The opening angle is of course less than 180°:

The plate is also spaced from the bottom of the container. In a highly preferred embodiment, the size of the gap is smaller than the axial distance of the plate from the bottom of the container.

According to a preferred embodiment, the plate edge tapers to a point towards its free peripheral edge. This allows the plate edge to be given a high degree of flexibility, particularly in its outer free edge area.

Another extremely preferred embodiment provides that the plate edge does not touch the container wall when not under load. This ensures that the plate edge only touches the container wall at higher speeds and thus forms a tight seal with it. In a preferred embodiment, the distance is at least 0.1 mm, preferably more than 0.5 mm, but in particular not more than 2 mm. Preferred embodiments are characterized in that the distance of the peripheral edge and also the base plate from the housing wall or the housing base is at least 0.8 mm, but at most 1 mm.

Another extremely preferred embodiment provides that a drive axle of the grinding disc is guided through the bottom of the container in a liquid-tight manner. This achieves the flexibility required for this, particularly in conjunction with the feature of the disc rim tapering to its free edge.

Further preferred embodiments provide that the opening angles (α,β) are 120° to 150°, in particular the opening angles of the plate. 5

In a device according to the invention, it is preferable to work with a grain size of the grinding material of 0.1 to 0.3 mm. The peripheral edge is pressed against the container wall during operation, particularly in its outer edge area, so that the peripheral edge and the wall touch each other. It was found that no increased heating occurs under friction and, in particular, the parts, which are usually made of PU, do not weld together. This may be because fine polishing dust that comes off the polishing grains during work gets between the peripheral wall and the container wall and acts as a lubricant there.

In addition to the choice of a flexible material, the shape of the peripheral edge, in which it is slim in cross-section and tapers from the base area of the plate to the free edge, also contributes to the hollow flexibility of the lip.

In particular, when the grinding machine according to the invention is designed as a liquid grinding machine with a liquid process medium contained in the container, it can be provided in a preferred embodiment that the entire plate is rigid. In a further embodiment, in this case it is provided that the width or thickness of the gap is at least 1/10 mm, whereby it should generally not exceed 2 mm. It has surprisingly been found that in a centrifugal vibratory grinding machine according to the invention with a liquid process medium contained in the container

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Liquid is expelled from the gap between the rotating plate and the base of the stationary container and there is no liquid there. This prevents grinding material, including broken fragments of larger grinding bodies, from getting into this area and thus affecting the bearing of the plate or the drive shaft of the plate that leads out through the base.

The same thing, namely preventing the penetration of abrasive grains or fragments thereof or expelling them from the gap between the rotating plate and the stationary base, can be achieved in a dry-operating centrifugal grinding machine, i.e. a dry grinding machine, by having the plate at least on its underside made of flexible material.

This inventive design of the plate also ensures that if a grinding body or grinding material particle penetrates into the gap, it is only conveyed out again by the relative rotational movement between the plate and the container bottom, but the flexibility of the plate or its underside means that no wear occurs and, in particular, the bearing of the plate is prevented from being impaired.

The invention makes it possible to construct very inexpensive and reliable centrifugal grinding machines, which also allow the use of very fine grinding and/or polishing media.

In a further preferred embodiment, it is particularly provided that a drive axis of the grinding disc is guided in a liquid-tight manner through the bottom of the container.

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The plate or the covering on its underside can, for example, consist of an elastomeric plastic and in particular of rubber, but also of felt, cotton fabric or a usual flexible floor covering, such as PVC flooring or carpet of any kind.

In a preferred embodiment, it is further provided that the plate has a peripheral edge that is pulled upwards. The plate has a flat base over most of its surface, only the edge is pulled up slightly, so that a peripheral edge arranged above the plate is provided on the same.

Even if, particularly in the case of smaller plates, up to about 250 mm in diameter, a grinding seal can be provided between the plate edge and the surrounding pot part, due to the low susceptibility to wear of the centrifugal grinding machine according to the invention associated with the flexible plate, the gap can in particular also be larger than the minimum dimensions of the grinding or polishing body particles, although it remains in the same order of magnitude, in particular it should not be more than twice or three times as large, so that these migrate under the plate when the grinding machine is in operation and, due to the relative movement of the flexible rotating plate with respect to the container bottom, can be released again and transported radially outwards in the direction of the container wall.

For very fine polishing material, such as walnut granulate, the gap should also be very small. For coarser granulate, the width b of the gap is preferably at least 2 mm and most preferably between 3 and 4 mm. The gap width can also be variable in particular in order to

to adapt the gap to the granulate used. The gap can be adjusted using any known means, for example by means of washers or the like that can be inserted between the container base and the plate, by means of which a shaft that passes through the container base for supporting the flexible plate can be adjusted in height and fixed at any height. Alternatively, the container can also be adjusted in height with respect to the plate and fixed at a desired height. 10

A further preferred embodiment is characterized in that a closable outlet is provided below the plate in the bottom of the container.

In a further preferred embodiment, the housing is provided in one piece, with the housing and/or the container being made of plastic in particular. This allows the grinding machine according to the invention to be manufactured economically and thus inexpensively. This is also helped by the fact that the gear is arranged below the plate. In an alternative embodiment, the drive can be designed as a gear motor with an integrated gear, with the motor then being aligned vertically with its axis and a drive shaft emerging from the lower end of the motor and the top of the motor being essentially at the same height as the top of the container.

Due to the design of the grinding units according to the invention, several grinding units can be present in one machine with little design effort, for example to enable the efficient processing of heavier and/or shock-sensitive workpieces that do not allow the joint processing of several workpieces in a single container.

even a very large number of units can be provided, for example more than 30. The plates of the individual containers can either be driven separately or the grinding machine can have a common drive for all units. In the latter case, the plates of the units, each arranged on a shaft, can be connected to the central drive via coupling elements, such as meshing gears, V-belts or the like, wherein the plates of individual containers can preferably be decoupled separately from the central drive, so that while workpieces are being ground in some containers of the grinding machine, the other containers can be cleaned or emptied and loaded with workpieces again, for example. A grinding machine according to the invention can be used in particular for dry polishing jewelry, dental parts, etc.

The invention is explained in detail below using a preferred embodiment with reference to the drawing.

Fig. 1 shows a container of an inventive

Centrifugal vibratory grinding machine;

Fig. 2 shows another embodiment of a grinding machine according to the invention;

Fig. 3 shows a further embodiment of a grinding machine according to the invention in side view;

Fig. 4 the essential parts of the sliding machine

according to Figure 3 in vertical section; and 25

Fig. 5 an enlarged view of the area

the peripheral edge of the turntable.

The grinding unit 1 of a centrifugal grinding machine in the form of a disc centrifugal machine shown in Fig. 1 has a container 2 with a rotating disc 3. If the disc is rigid, the work is carried out with liquid in the container.

In principle, the plate - for wet and dry processing - can be made of a flexible material, e.g. rubber. The plate is driven by a shaft 3a. The shaft 3b passes through a container base 2a, preferably in a liquid-tight manner, and is rotatably mounted on it via bearings 4. The plate 3 is spaced from the container base 2a, forming a gap 5, the gap width b being approximately 3 mm for dry processing, for example. The plate 3 and/or the container 2 can be arranged so that the height is adjustable, e.g. by varying the gap width b.

When the grinding machine is in operation, the comparatively wide gap 5 allows small particles of the grinding material or in particular the grinding bodies to get between the plate 3 and the container base 2a, whereby these are conveyed back towards the container wall 2b due to the rotating flexible plate 3 without any significant wear of the container base 2a or plate 3 occurring. Furthermore, the flexible plate 3 largely prevents the generation of frictional heat, as grinding bodies that get under the plate 3 are not crushed, but are conveyed radially outwards.

A grinding machine according to the invention has in particular several, e.g. more than 30 units, which enable a rational

nal separate processing of relatively heavy (e.g. heavier than 10 g) and/or shock-sensitive workpieces. The diameter D of the container 2 can be, for example, approximately 4-5 cm.
5

Figure 2 shows another embodiment of a grinding machine according to the invention, which is structurally simple and can therefore be manufactured at low cost and offered inexpensively, so that it can also be used in the private sector for polishing private pieces of jewelry.

The grinding machine 1 in Figure 2 has a one-piece housing 2', which is preferably made of plastic, so that the container 2 in particular is also made of plastic. A plate 3 is arranged in the container 2. In this design, the plate 3 has a peripheral edge 3a that is drawn diagonally upwards, the outer wall of which follows the contour of the container in this area, so that a finite gap 5 is formed radially between the plate 3 or its peripheral edge 3a and the container 2 or the container wall 2b, which has essentially the same dimensions over its entire height. The upwardly drawn plate edge 3a creates a bowl-shaped receptacle for the material to be ground.

The drive shaft 3b for the plate 3 passes through the container bottom 2b. This is coupled to a drive shaft 12a of a gear 12, which is centered by a centering ring 12b. In the embodiment shown, the drive 11 is designed as a gear motor 14, in which the motor 13 and gear 12 are integrated with one another. Accordingly, not only the gear 12 but also the drive motor 13 is arranged below the container 2 in a foot 2c 5 of the housing 2'. The gear motor 14 is connected via

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Screw connections 16 are attached to the housing 2 ¹ , more precisely to the container bottom 2b.

Figures 3 and 4 show a further embodiment of the invention, in which the grinding machine according to the invention is also structurally simple and can therefore be manufactured inexpensively.

In this embodiment, the housing 2' has a foot 2c, which is not formed in one piece with the container 2. Rather, the container 2 is fixed to the foot 2c in a manner to be explained below. In any case, in this embodiment, as shown in particular in Figure 3, a motor 13 is arranged to the side of the container 2 and the foot 2c in such a way that the output shaft of the motor 13 (not shown itself) exits downwards from the motor 13. The gear 12 is also arranged below the motor 13, and the drive 11 can also be designed as a geared motor 14. The top of the motor 13 is essentially at the same height as the top edge of the container 2. A protective wall 16 is provided between the container 2 and the motor 13, which is preferably partially curved, in particular semi-curved, around the container 2. Alternatively, the wall region facing the motor 13 can be raised relative to the wall region of the container 2 facing away from the motor 13 in order to produce such a protective wall effect.

Below the plate, a closable opening 15 is also provided in the container bottom 2b, through which any grinding material that may have gotten under the plate 3 can be removed.

From Figure 4 it can be seen that a U-shaped bracket 17 is provided in the base 2c of the housing 2', which

en legs on the base 2c of the housing. It supports the container 2 with its web. A drive shaft 3b for the plate 3 leads through the base 2b and the web of the bracket 17 into the gear 12, which extends from its parts directly under the motor 13 to the middle under the container 2, in which appropriate intermediate gears or other types of gear design such as toothed belts etc. are provided.

Figure 5 shows a detailed representation of the upwardly drawn peripheral edge 3a of the rotary plate 3, which can be rotated about the axis A in the container 2. In the embodiment shown, at least the peripheral edge 3a consists of a flexible material with a shock hardness of 50 to 95°. The rotary plate itself or its base 3b can consist of the same material or a different material. Additionally or alternatively, the container wall 2b can also be designed to be flexible or elastic in the area of the peripheral edge 3a.

The peripheral edge 3a tapers from the base area 3b of the plate 3 to its free edge 3c. The opening angle α of the peripheral edge 3a to the base 3b is approximately 150° in the illustrated embodiment. The angle ß between the underside 3d of the base and the outside 3e of the peripheral edge 3a is accordingly approximately 130°. The values for both angles α, ß are preferably between 110° and 150°.

When the rotary plate 3 is unloaded, i.e. when it is neither rotating and centrifugal forces are exerted on the peripheral edge 3a nor the peripheral edge 3a is loaded by filled material, the peripheral edge 3a does not touch the inner wall 2b of the container 2, particularly in the edge area 3c,

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but rather has a finite distance or gap 5 in the order of magnitude of most preferably 0.8 to 1 mm. There is also a gap 5a or finite distance between the underside 3d of the turntable 3 and the upper wall 2c of the base 2a of the container 2.

When operating the disc grinding machine according to the invention, in particular when working in the dry process, the free edge 3c of the peripheral edge 3a is pressed against the wall 2b of the container 2 by the centrifugal force and the grinding material and grinding material filled in the container, so that the entry of grinding material into the gaps 5, 6 is largely prevented. Due to the flexibility of the peripheral edge 3a in particular (or the wall 2b), any abrasive grains that have nevertheless entered can be pressed out of the gap again by the centrifugal forces acting on them as a result of the movement of the turntable. Surprisingly, despite the contact of the peripheral edge 3a with the wall 2b of the container, there is no excessive heating of the disc and in particular of the peripheral edge 3a, which is usually made of PU, and in particular no welding to the peripheral wall due to heating. This may be due to the fact that grinding dust or powder formed by the removal of material from the abrasive grains enters the gap 5 between the peripheral edge 3a, in particular in the area of the edge 3c and the container wall 2a, where it creates a lubricating effect.

Claims (30)

1. Grinding machine, in particular a centrifugal grinding machine for grinding material to be ground by means of grinding bodies, with at least one grinding unit ( 1 ) with two parts which can be rotated relative to one another about a vertical axis of rotation (A) and which are in the form of a container ( 2 ) and a rotary plate ( 3 ) located therein, characterized in that the rotary plate ( 3 ) has a limited finite vertical distance from the bottom ( 2a ) of the container ( 2 ) and has a plate edge ( 3a ) which is guided upwards at an opening angle of greater than 90° to the horizontal, the plate edge and/or wall ( 2b ) of the container ( 2 ) being flexible in the region of the plate edge ( 3a ). 2. Device according to claim 1, characterized in that the plate edge ( 3 a) tapers to a point towards its free peripheral edge ( 3 c). 3. Device according to claim 1 or 2, characterized in that the plate edge ( 3 a) does not touch the container wall ( 2 b) in the unloaded state. 4. Grinding machine according to one of claims 1 to 3, characterized in that the width (b) of the gap ( 5 ) is at least 1/10 mm. 5. Device according to one of the preceding claims, characterized in that the distance from the plate bottom ( 3 b) to the container bottom ( 2 c) and/or between the plate edge ( 3 a) and the container wall ( 2 a) is at least 0.5 mm. 6. Device according to claim 5, characterized in that the distance from the plate bottom ( 3 b) to the container bottom ( 2 c) and/or between the plate edge ( 3 a) and the container wall ( 2 a) is at least 0.8 mm. 7. Device according to one of the preceding claims, characterized in that the distance from the plate bottom ( 3 b) to the container bottom ( 2 c) and/or between the plate edge ( 3 a) and the container wall ( 2 a) is at most 2 mm. 8. Device according to claim 7, characterized in that the distance from the plate bottom ( 3 b) to the container bottom ( 2 c) and/or between the plate edge ( 3 a) and the container wall ( 2 a) is at most 1 mm. 9. Device according to one of the preceding claims, characterized in that the opening angles (α, β) of the plate are 110 to 160°. 10. Device according to claim 9, characterized in that the opening angles (α, β) of the plate ( 3 ) are 120 to 150°. 11. Device according to one of the preceding claims, characterized in that the flexible regions of the plate ( 3 , 3a ), in particular of the plate edge ( 3a ) and/or the container wall ( 2a ) consist of or are lined with material with a Shore hardness of 50 to 95°. 12. Grinding machine according to one of claims 1 to 11, characterized in that a drive axis of the grinding disc ( 3 ) is guided in a liquid-tight manner through the bottom of the container ( 2 ). 13. Grinding machine according to one of claims 1 to 12, characterized in that the plate is rigid. 14. Grinding machine according to one of claims 1 to 13, characterized in that the plate ( 3 ) has flexible material at least on its underside. 15. Grinding machine according to one of claims 1 to 14 or 13, characterized in that the plate ( 3 ) consists essentially of yielding, in particular flexible material. 16. Grinding machine according to one of claims 1 to 15, characterized in that the underside of a rigid support of the plate ( 3 ) is covered with flexible material. 17. Grinding machine according to one of claims 1 to 16, characterized in that the flexible plate material is an elastomeric plastic. 18. Grinding machine according to one of claims 1 to 17, characterized in that the plate material is made of rubber. 19. Grinding machine according to one of claims 1 to 18, characterized in that the flexible material is felt, cotton fabric or flexible floor covering material. 20. Grinding machine according to one of the preceding claims, characterized in that the size (a) of the gap ( 5 ) is smaller than the axial distance (b) of the plate ( 3 ) from the container bottom ( 2a ). 21. Grinding machine according to one of the preceding claims, characterized by a one-piece housing ( 2 '). 22. Device according to one of the preceding claims, characterized in that a housing ( 2 ') and/or the container ( 2 ) consists of plastic. 23. Device according to one of claims 1 to 22, characterized in that a drive motor for the turntable ( 3 ) is arranged underneath it. 24. Device according to one of claims 1 to 22, characterized in that a drive ( 11 ) for the plate ( 3 ) has a gear ( 12 ) between the drive motor ( 13 ) and the plate ( 3 ). 25. Device according to claim 24, characterized in that the gear ( 12 ) is arranged below the plate ( 3 ). 26. Device according to claim 24 or 25, characterized in that the drive ( 11 ) is designed as a geared motor ( 14 ) with integrated gear ( 12 ). 27. Device according to claim 25 or 26, characterized in that the gear motor ( 14 ) or the motor ( 13 ) is arranged below the container ( 2 ) in a foot ( 2c ) of the housing ( 2 '). 28. Device according to one of claims 24 to 27, characterized in that the drive motor ( 13 ) is arranged laterally of the container ( 2 ). 29. Device according to claim 28, characterized in that the top of the motor ( 13 ) is substantially at the same height as the top of the container ( 2 ). 30. Device according to one of the preceding claims, characterized in that a closable outlet ( 15 ) is provided below the plate ( 3 ) in the bottom ( 2a ) of the container ( 2 ).