Orbital disk grinder

Details Orbital disk grinder Orbital disk grinder

1993-10-08

1996-03-05

Rose, Robert A.

Abrading

Frame or mount

Portable abrader

451344, 451294, B24B 2303

Patent

active

054962072

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to an orbital disk grinder.
More particularly, it relates to an orbital disk grinder which has a housing accommodating a motor which moves a grinding disk via an output shaft while gyrating in a circular orbit and simultaneously rotating about its axis.
Orbital disk grinders of the generic type have been freely available on the market for many years. If they are lifted off the workpiece with the motor still running, these grinders have the disadvantage that in the fine processing stage i.e. whilst the grinding disk rotates about its axis, simply due to the bearing friction, at approx. 200 min.sup.-1, resulting from the friction between the output shaft and the eccentric journal, the grinding plate accelerates to the idling speed of the output shaft, which is up to 13,000 r.p.m. This speed increase can result in so much material being removed when the grinding disk is applied to the workpiece, that irreparable damage to the workpiece surface occurs.
A further development of the orbital disk grinder of this type, in accordance with EP-PS 320 599, features an electromagnetic brake located between the grinding plate and the orbital disk grinder housing, which is intended to prevent a speed increase in the grinding disk. This electromagnetic brake is very effective, but has the disadvantage that additional braking energy is required in order to compensate for the acceleration energy. This results in wasted energy. Furthermore, greater design requirements are involved for the electromagnetic braking device, with the mass and volume of the orbital disk grinder increasing considerably.
From U.S. Pat. No. A 5,018,314, an orbital disk grinder is known which, based on the orbital disk grinder of this type, is intended to prevent the acceleration of the grinding disk by mechanical means. In this case too, the acceleration energy is "destroyed".


SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an orbital disk grinder, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an orbital disk grinder in which speed control means is provided for setting the speed of the grinding disk preferably low when a normal force acting on a working surface is low and high when the normal force acting on the working surface is high, wherein the normal force acting on the grinding disk serves as a setting variable of a motor speed control.
When the orbital disk grinder is designed in accordance with the present invention, it has the advantage that by restricting the energy which is supplied to the motor, the acceleration effect does not even arise in the first place. This has the advantage that energy is saved, reductions in noise and vibration when idling are achieved, service life is increased, and the weight and volume of the orbital disk grinder are kept low.
The novel features which are considered characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional side view of an embodiment example of the orbital disk grinder,
FIG. 2 shows an enlarged section of a further embodiment example of an orbital disk grinder in the area of the control mechanism, and
FIG. 3 shows the embodiment example of FIG. 2 in the second switching position possible.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

The orbital disk grinder 1 shown in part cross-section in FIG. 1, comprises a housing 3 with a handle 5, in which an on-/off switch 7 and a electrical connection cable 9 are located. Arranged in the interior of the housing 3 is a motor 11 with a commuta

REFERENCES:
patent: 5018314 (1991-05-01), Fushiya et al.
patent: 5317838 (1994-06-01), Bourner

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