Abrading – Machine – Rotary tool
Reexamination Certificate
1999-07-07
2001-03-27
Young, Lee (Department: 3729)
Abrading
Machine
Rotary tool
C451S359000, C451S290000, C451S548000, C451S342000
Reexamination Certificate
active
06206766
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a U.S. national application of international application Serial No. PCT/DE98/00484 filed Feb. 17, 1998, which claims priority to German Serial Nos. 197 19 971.2 and 297 15 683.7 filed May 13, 1997 and Sep. 1, 1997, respectively.
The invention relates to a grinding wheel for machining metal-circular saw blades at relatively high rotational speeds, such grinding wheels having machining areas which contain hard materials, such as for example diamond or cubic boron nitride, which can be used to achieve high material-removal rates.
DE 296 08 590 has disclosed grinding wheels for machining metal circular-saw blades, in which the centering and alignment on a drive shaft of a grinding machine is intended to be improved by designing the diameter of the tool-mounting bore which is formed in the grinding wheel to widen on one side.
However, grinding wheels whose machining areas contain cubic boron nitride or diamond abrasive particles allow very high material-removal rates to be achieved if the cutting rate and therefore the rotational speed of the grinding wheel are set to be correspondingly higher. These increased rotational speeds lead to the centering, which the design of the tool-mounting bore is supposed to improve, deteriorating as a result of the increasing centrifugal forces.
Furthermore, this leads to true running problems arising, and in particular to the vibrations, which are transmitted into the machining area by the true running problems, causing high levels of wear in the machining area as a result of increased abrasion of the hard materials, so that the grinding wheels have to be dressed or replaced more frequently.
Therefore, the object of the invention is to improve grinding wheels in such a manner that the centering can be improved, in particular at relatively high rotational speeds, and consequently true running problems can be avoided.
According to the invention, this object is achieved by means of the features of claim
1
. Advantageous configurations and refinements of the invention are given by using the features mentioned in the subordinate claims.
The grinding wheels according to the invention differ from the grinding wheels which have customarily been used hitherto in particular in that a contour, in which at least one centering element can engage in a form-fitting manner, is provided in the base body of the grinding wheel, at least on one side, in the radially outer region of the tool-mounting bore, which may be of conventional design or may be designed as disclosed by DE 296 08 590. During grinding, the grinding wheel and at least one centering element are held in a force-fitting manner on the tool spindle of the grinding machine. For this purpose, a conventional screw connection, for example, may be used, although it is also possible to employ hydraulically or pneumatically actuable piston-cylinder units or a spring force, these options being suitable in particular for automatic operation.
It is particularly advantageous for the contour to be formed on both sides of the base body of the grinding wheel, and to maintain symmetrical conditions.
The only factor which needs to be taken into account during contouring is that a bearing surface for the centering element(s) is to be present on at least one side, on which bearing surface a surface, which is directed towards the axis of rotation of the grinding wheel, of the centering element(s) is supported, and the centering action can be improved at relatively high rotational speeds as a result of the centrifugal forces.
There are a number of possible designs for the contour(s). A circular groove may be formed on one or both sides of the base body of the grinding wheel, in which groove corresponding webs on the centering element(s) engage in a form-fitting manner and virtually without play when the grinding wheel is attached to the drive spindle of the grinding machine. It is advantageous if those areas of the centering element(s) which engage in the grooves and are of web-like design are convex, at least on their internal diameter, so that they do not bear against the corresponding surface of the groove over the entire area, thus facilitating insertion.
Another possible design of the contour(s) consists in forming a flange-like widening, which projects beyond the normal thickness of the base body of the grinding wheel and on which there is at least one radially outer bearing surface for the centering element (s), on which bearing surface the centering element(s) can be supported. Advantageously, the bearing surface(s) is/are inclined with respect to the axis of rotation.
The contour may also, however, be a web which runs in a circle and may, if appropriate, be symmetrically divided into individual segments by means of apertures. In this case, the centering element(s) is/are in each case supported against the radially outer surface of the web.
The possible examples for the design of the contours may be improved by forming bearing surfaces which are bevelled on at least one side and on which the corresponding bearing surfaces on the centering element(s) are supported. Bevelled surfaces have the advantage, on the one hand, of providing larger bearing surfaces and, on the other hand, of facilitating the introduction or fitting together of the centering elements when the grinding wheel is being attached to the grinding machine, and if necessary alignment errors can be compensated for during introduction, thus reducing the wear on the centering elements and the base body of the grinding wheel.
The possible designs of the contours which have been described thus far can be achieved relatively easily by machining operations for the case of the grooves and the flange-like design, but it is also possible to provide the base body of the grinding wheel with the desired shape by means of known casting processes.
Furthermore, it is also possible to achieve the improvement in the centering for the grinding wheels in question by designing the contours in the form of apertures or recesses through or in the base body of the grinding wheel, or by additionally providing such recesses or apertures. In this case, at least two apertures or recesses which are arranged symmetrically opposite one another in the radial direction on one axis are required, in order to compensate for the centrifugal forces which arise and to avoid undesirable imbalances.
The recesses or apertures may advantageously be improved if they are designed to widen conically outwards, in order, as is already the case for the bevelled design of certain surface areas of the grooves, flanges or webs, to improve in particular the insertion of the centering elements.
It is advantageous for one of the corresponding centering elements to be provided in a stationary position on the flange of the drive spindle of the grinding machine, while on the other side of the grinding wheel an additional centering element, which is preferably of corresponding design, is held in a force-fitting manner in the contour and the tool-mounting bore of the grinding wheel. The second centering element may in this case be a separate component which can be held in a force-fitting manner towards the flange of the drive spindle of the grinding machine.
If the grinding wheel is attached to the drive spindle by means of a screw connection, it is advantageous to join the screw and the centering element together, thus facilitating handling. It is particularly advantageous if the connection is designed in such a way that the screw can rotate independently of the movement of the centering element, i.e. in such a manner that the centering element is prevented from rotating with the screw.
If, on the other hand, a piston-cylinder arrangement is selected, the centering element may be part of the piston or of the cylinder, depending on which of the two elements is used to attach the grinding wheel to the drive spindle.
In addition to the improved centering action at high rotational speeds, which is improved by the improved support for the grinding whee
August Heinr. Schmidt GmbH & Co. KG Maschinenfabrik
Barnes & Thornburg
Trinh Minh
Young Lee
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