Abrading – Machine – Tumbling device
Reexamination Certificate
1998-02-18
2001-10-02
Morgan, Eileen P. (Department: 3723)
Abrading
Machine
Tumbling device
C451S327000, C451S328000
Reexamination Certificate
active
06296556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a centrifugal slide grinder with a shell-like rotary receptacle bottom part and a stationary essentially cylindrical receptacle top part.
2. Description of the Prior Art
Centrifugal slide grinders are used for surface machining especially of smaller parts and workpieces which are moved together with the grinding wheels and optionally with a liquid process agent. As DE 44 28 817 C2 shows, a known centrifugal slide grinder has a top-opening, and shell-like bottom part which is rotary-driven around a vertical axis. Above the bottom part there is a stationary cylindrical receptacle top part which rests with its lower edge on the upper edge of the bottom part with the interposition of a seal. When the bottom part is caused to rotate the workpieces to be machined are forced radially to the outside in the bottom part until they meet the inner wall of the stationary receptacle top part which causes a braking action to be applied to the work pieces. Radially peripheral workpiece motion which causes intensive grinding arises by workpieces following from upstream.
The transition area between the upper edge of the turning bottom part and the lower edge of the stationary receptacle top part is very susceptible to wear. Attempts have therefore been made to make the seal which acts between these two parts as a slip ring seal, the slip ring located on the bottom part and/or on the receptacle top part consisting of ceramic. In this way the wear which occurs in the seal can be reduced, however ceramic rings of a larger diameter are very expensive and the additional problem arises that the diameter of the ceramic rings and thus the diameter of the receptacle top part is limited by production technology to a maximum roughly 50 cm, so that a centrifugal slide grinder of this type in its volume and also in its performance is subject to serious limitations. Attempts have been made to form a ceramic ring from several ceramic ring segments, in doing so however problems occurred with regard to sealing.
In DE-P9 44 28 817 the seal which acts between the two parts is formed by a hardened steel ring on the bottom part and a felt ring on the receptacle upper part. By means of screws the desired contact pressure is established between the soft ring seal of felt or nonwoven material and the steel ring. If the felt ring is worn for example by the working of fine grinding media into the felt, on the contact surface between the two annular seals a gap forms which can no longer be equalized by the felt seal. This and the wear due to friction on the contact surfaces between the receptacle upper and bottom part then leads to the fact that extremely small parts can no longer be machined.
In known centrifugal slide grinders with slip ring seals in which the parts of the receptacle bottom part and top part which form the seals are pressed elastically against one another, lubrication takes place by means of a lubricating fluid which can penetrate to the interior of the receptacle part.
In many grinding processes it is desirable or necessary to ensure absolute dryness within the grinder, which is not the case in known grinders which operate with a fluid.
SUMMARY OF THE INVENTION
The invention is a centrifugal slide grinder which operates reliably, which has long service life, but which also enables absolutely dry grinding.
The invention provides a centrifugal slide grinder which has the receptacle bottom and top part provided each with a ceramic part on their opposing faces.
The hard ceramic parts which are made preferably annular, therefore made as rings, ensure that even when the receptacle upper part is tilted relative to the receptacle bottom part no welding of the bordering surfaces of the receptacle bottom part and top part takes place which permanently ensures uniform rotation capacity of the upper part relative to the lower part. In one preferred embodiment between the ceramic parts a finite gap is present. The size of the gap is generally such that it is in the particle size range or somewhat less, so that particles cannot penetrate through the gap from the interior of the grinder to the outside. The configuration of the ceramic rings on the lower receptacle top part and the upper face of the receptacle bottom part ensures that when a very small abrasive particle penetrates into the gap, by which the aforementioned tilting can occur, simply the relative rotary motion between the top and bottom part pulverizes the particle, and the aforementioned damage cannot occur, as would take place for example when using metal.
In another preferred embodiment the gap be adjustable. In this way the gap width can be matched to the size of the abrasive particles used. Here other preferred embodiments provide for the gap having a size from 0.05 to 0.5 mm and especially the gap having a size of roughly 0.3 mm, of course it being necessary to watch that the gap is not larger than the (minimum) dimensions of the abrasive particles.
The adjustability of the gap can be achieved in different ways, for example by washers or the like. One highly preferred embodiment has the gap being adjustable using set screws, especially the set screws being located on the periphery of the receptacle upper part and a support part bearing the latter.
In another preferred embodiment the inner wall of the receptacle upper part tapers radially conically to the inside in its lower end section. This results in the receptacle upper part over most of its height having a relatively large diameter which decreases as a result of the conical configuration of the lower end region to the lower edge with a clearly smaller diameter. Since the diameter of the lower edge determines the necessary size or diameter of the seal, in the centrifugal slide grinder of the invention one-piece slip rings of ceramic can be used, although the receptacle upper part has a relatively large volume and thus high output. In known centrifugal slide grinders the workpieces to be machined, especially in the presence of legs sensitive to buckling, etc., can be damaged or bent in the grinding process; this is due to the fact that the workpieces in the transition from the rotating bottom part to the stationary receptacle top part are strongly braked and at the same time experience deflection from the inner wall of the bottom part which runs obliquely upward at a angle of roughly 30 to 45 degrees to the essentially vertical inner wall of the receptacle upper part. Since the lower section of the receptacle upper part tapers conically to the inside according to the embodiment just described, its inner wall runs at an angle relative to the vertical. The inner wall of the bottom part also runs obliquely to the vertical. By means of the corresponding configuration the angle between the two inner walls of the bottom part and the receptacle upper part can be kept small so that the load resulting from the deflection of the workpieces to be machined is low. In one preferred embodiment the inner walls of the receptacle upper part and bottom part are flush in the area of the gap. The inner wall of the bottom part therefore passes smoothly into the inner wall of the receptacle upper part. In this way there is no unevenness in the transition area as is present by tilting or unwinding in the prior art.
For the configuration and especially the alignment of the contact surfaces between the lower edge of the receptacle upper part and the upper edge of the bottom part various alternatives are conceivable. In one possible embodiment it is provided that the gap is aligned at an angle which deviates clearly from a right angle to the inner walls of the receptacle upper part and bottom part, especially the gap being aligned essentially horizontally or vertically to the axis of rotation. In this way axial motion of the receptacle upper part or bottom part acts uniformly on the contact surface.
Alternatively it can be provided that the gap is aligned at an angle to the inner walls of the receptacle upper part and bottom part. The outer p
Antonelli Terry Stout & Kraus LLP
Morgan Eileen P.
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