Abrading – Machine – Tumbling device
Reexamination Certificate
2002-07-31
2004-05-11
Nguyen, George (Department: 3723)
Abrading
Machine
Tumbling device
C451S327000, C451S328000, C451S329000, C451S330000
Reexamination Certificate
active
06733374
ABSTRACT:
BACKGROUND OF THE INVENTION
Device for grinding or polishing workpieces by means of an abrasive, having a container (
2
) and with a rotary disk (
3
) located therein and rotatable relative thereto.
Such devices are known in the form of centrifugal sliding grinding machines, which comprise a two-part container with a shell-shaped, rotatable container lower part forming a bottom and a stationary, cylindrical container upper part.
Such grinding machines are used for the surface machining of grinding articles, e.g. smaller parts and workpieces, which are moved in the container together with the abrasive objects and optionally a liquid process medium. If the lower part is rotated, the workpieces to be treated are moved outwards on the disk until they encounter the inner wall of the container, where they are decelerated. A rotary workpiece movement occurs as a result of the subsequently supplied workpieces and this leads to an intense grinding or polishing action.
It is a disadvantage of such centrifugal sliding grinding machines that the sealing of the annular clearance and the guidance of the faces bounding the same give rise to considerable problems, which can only be overcome with considerable effort and corresponding costs.
There is a danger that the upper and lower parts, particularly the lower part, will be very greatly heated as a result of friction, if parts of the grinding article and/or additionally added abrasive objects during operation enter the gap between the container bottom and the rotary disk. This leads on the one hand to an only relatively short regrind life of the grinding machine and on the other the latter must be frequently switched off during the machining of grinding articles in order to prevent overheating both of the grinding machine and also the grinding or polishing article.
DE 197 28 931 A1 discloses a liquid grinding machine for the liquid working of workpieces. A substantially planar elastic disk is provided, whose radial extension exceeds the radial extension of the surrounding container, so that on inserting the disk in the container its flexible rim or edge is directed upwards and firmly engages on the container wall, the compressive force being reinforced by the centrifugal force during rotation of the disk. The liquid necessary for wet working is introduced into the container below the disk and under the pressure overcoming the aforementioned application forces is forced between the disk rim and container wall into the machining chamber. As a result of considerable technical and constructional effort and expenditure, a penetration of grinding material into the area below the rotary disk is prevented, but in this form is only possible with wet machining.
SUMMARY OF THE INVENTION
The problem of the invention is to provide a simply constructed, inexpensive device for polishing and grinding, whilst avoiding the aforementioned disadvantages, which in the case of limited wear susceptibility functions reliably and has a long regrind life.
According to the invention, in the case of a device of the aforementioned type, this problem is solved in that the rotary disk has an upwardly drawn, elastic disk rim and that the disk rim has a finite spacing from the adjacent inner wall of the container.
The finite spacing or gap, unlike in the case of DE 197 28 931 A1, is constructionally determined by a radial minimum dimension of the rotary disk with respect to the radial inside dimensions of the container and consequently also exists in the inoperative state, particularly without the action of any external forces, such as occur in the prior art as a result of the liquid forced through between the disk and the container wall. Thus, the elastic and in particular flexible disk rim is not in contact with the container wall when the device is in the inoperative state when the disk rim is not burdened by introduced material. The invention deliberately takes into account the fact that the abrasive particles can pass between the disk rim and the container wall, as well as between the disk bottom and the container bottom. This is counteracted by the centrifugal force exerted on such particles by the rotation of the rotary disk and this leads to the particles being directed radially outwards below the disk bottom, which is aided by the elastic and preferably flexible underside of the disk bottom. As a result of this and due to the elastic, flexible design of the disk rim, abrasive particles located between the latter and the container wall are returned to the grinding chamber. A dynamic equilibrium of the material flow occurs and there is always a certain mount of abrasive particles, which form an abrasion-reducing lubricant between the disk rim and the container wall.
According to a preferred development, the disk rim tapers in pointed manner towards its free circumferential edge. As a result the disk rim can be given a high flexibility, particularly in its outer, free edge region.
According to a highly preferred development, the disk rim is inclined outwards and has an inclination to the horizontal of less than 90°, preferably between 30 and 70°. The (inner) opening or aperture angle of the disk rim to the horizontal is consequently between 150 and 110°.
The size of the gap or the finite spacing of the disk rim from the container wall is preferably between 2 and 10% of the disk diameter and therefore, for conventional disk diameters of 15 to 40 cm, generally between 0.4 and 2 mm, preferably between 0.7 and 1 mm.
According to other preferred developments, the bottom of the rotary disk substantially has a constant thickness, the disk rim having a smaller thickness than the disk bottom or the outer circumference (towards the raised disk rim) of the disk bottom tapers.
It can be provided that the disk bottom thickness is between approximately 2 and 8% of its diameter and that the rotary disk thickness is between approximately 5 and 10 mm.
The disk is also spaced from the container bottom. In a preferred development, the vertical spacing is between 1 and 2 mm. The gap width can in particular also be variable, so as to adapt the gap to the granular material used. The adjustability of the gap can be made possible by random known means, e.g. by a washer or the like placed between the container bottom and the disk and as a result a shaft passing through the container bottom for the mounting of the flexible disk can be vertically adjustable and fixed at a random height. Alternatively the container can be vertically adjustable with respect to the disk and can be fixed in a desired height. According to a highly preferred development, the size of the gap between the disk rim and the container wall is smaller than the axial spacing from the disk to the container bottom. This ensures that it is only possible for particles to pass below the rotary disk which are much smaller than the spacing of the rotary disk bottom to the container underside.
According to a highly preferred development, in the transition area from the container bottom to the container wall, an increased spacing is formed with respect to the rotary disk and in particular the circumference of the disk bottom and which is in particular formed by a notch in the passage of the container wall towards the container bottom. This ensures that the rotary disk bottom, which is radially relatively firm, does not strike against the lower area of the container wall as a result of thermal expansion. In the container wall notch it is possible for abrasive material to collect and this consequently guides the returned, loose abrasive particles. As a result of its elasticity and the abrasive particles acting as a lubricant there, a radial thermal expansion in the vicinity of the disk rim is not critical.
It has been found that there is no increased heating under friction and in particular no fusing takes place.
Besides the choice of a flexible material, this is also helped by the shape of the circumferential rim, in that the latter is slender in cross-section and pointed from the bottom area of the disk towards the free edge or lip,
Gegenheimer Helmut
Lutz Helmut
Antonelli Terry Stout & Kraus LLP
Otec Präzisionsfinish GmbH
LandOfFree
Grinding machine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Grinding machine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grinding machine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3238024