Abrading – Precision device or process - or with condition responsive... – Computer controlled
Patent
1995-09-14
1997-11-18
Rose, Robert A.
Abrading
Precision device or process - or with condition responsive...
Computer controlled
451343, 74573R, 73468, B24B 4900
Patent
active
056881606
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for the dynamic balancing of a body rotating about a longitudinal axis with respect to a support, including: an assembly fixed to and rotating with said body, the assembly comprising at least one mass, the position of which is adjustable, and at least one electric motor connected to adjust the reaction of the mass; control means for controlling the naster; power supply means; and a between the assembly and both the control means and the power supply means.
In particular, the invention relates to an apparatus for dynamically balancing the grinding wheel of a grinding machine.
BACKGROUND ART
Undesired vibrations are generally present in a grinding machine, and are generated by out-of-balance conditions of the grinding wheel due to various possible reasons depending on the wheel itself, such as: shape and/or constitution defects (inhomogeneity of the materials, concentricity errors between the external abrading surface and the internal centering hole, etc.), inaccurate mechanical coupling to the rotating spindle (hence causing the wheel center of gravity to be spaced apart from the rotation axis), and, in general, deteriorations due to wear and/or splintering during the machining operations of workpieces. These vibrations may cause inaccuracies in the characteristics of the machined workpieces, such as roundness errors (ovality and lobing), and introduce loads and stresses that may damage the machine tool. Known balancing are coupled to the grinding wheel and comprise movable masses driven by electric motors that adjust the position of the masses, in the course of the wheel rotation, along radial or, more often, angular paths in order to compensate the previously mentioned out-of-balance conditions. The driving motors are also part of the apparatus, rotate along with it and the wheel, and are fed by a fixed external power source, through an electric coupling, including sliding contacts such as, for example, slip rings and sliding brushes.
The characteristics (like frequency, amplitude, and/or other) of the vibrations generated by an out-of-balance condition of a rotating body are picked up by processing the signals provided by an appropriate sensor, and displayed, or are further processed in a proper unit (that also comprises the previously mentioned power supply source) for sending "balancing" signals to the motors, in order to properly drive the movable masses, by means of an electric coupling including the same, or different slip rings.
A balancing apparatus which has the previously mentioned features is shown and described in patent U.S. Pat. No. 3,698,263. In such apparatus, the motors for driving the masses are manually controlled by an operator on the basis of the vibration parameters that are displayed by an instrument. A problem of the known apparatuses is represented by the wear that the brushes undergo when they remain in contact with the relevant slip rings in the course of the grinding wheel rotations, and by the subsequent need to frequently perform maintenance and replacement operations.
In other known apparatuses, in order to overcome the inconveniences caused by the sliding contacts, there is a battery in the rotating part, means that enable the "wireless" recharge of the battery, and means for providing control signals for the displacement of the masses. An apparatus of this type is described in patent application DE-A-3743432, wherein the recharge of the battery occurs in the course of the rotation along with the wheel, by means of a "dynamo" charging generator, comprising a stator that is stationary with respect to the wheel and an idle rotor.
The control signals are optically transmitted from a stationary part to the rotating assembly, thus driving the displacement of the balancing masses.
It should be realized, however, that the layout dimensions may cause a problem as the space available may not always be sufficient to accomodate the insertion of the battery. Furthermore, no information regarding the charge of the battery
REFERENCES:
patent: 5240358 (1993-08-01), Hackett et al.
patent: 5540615 (1996-07-01), Murtuza
patent: 5549019 (1996-08-01), Cattani
Malpezzi Domenico
Pozzetti Mario
MARPOSS Societa' per Azioni
Nguyen George
Rose Robert A.
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