Abrading – Machine – Rotary reciprocating tool
Reexamination Certificate
2000-01-18
2001-08-14
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary reciprocating tool
C451S350000
Reexamination Certificate
active
06273799
ABSTRACT:
The invention concerns: a polishing head for plate materials in granite, hard stone or ceramic, with abrasive segments having continuous tangential oscillating motion, that is, a rotating head which, by means of segments of abrasive material which are made to come into tangential contact with their slow oscillating motion, grinds and polishes the surface of the tile or slab of particularly hard natural or artificial material.
Prior art comprises various types of head with abrasive grinding segments with oscillating motion to grind and/or polish plate materials. The head described in patent EP 0437831 B1 is particularly relevant, in that the abrasive segments are made to oscillate on oscillating radial shafts driven by a pin each coupled, by means of a cylinder that slides in a radial direction, to a ring having vertical eccentric rotary motion with respect to the axis of the head; the said ring is made to rotate by a first eccentric, driven by a pair of gears with internal teeth, in which the crown gear is connected rigidly to the casing of the head and the pinion, also mounted on a second eccentric able to rotate freely with respect to the axis of the head, drives the said first eccentric by means of a pin attached to it, which slides in a radial groove; the eccentric rotation of the ring is controlled by a plurality of pins mounted on eccentric planetary gears with eccentricity equal to that of the said first eccentric; the second eccentric is coupled with anti-rotational joint to the structure of the machine on which the head is mounted, to provide a reaction to the motion transmitted to the said internal mechanisms.
The eccentricity of the said second eccentric is small with respect to the eccentricity of the first eccentric to lower the speed of oscillation and to achieve a slower dressing of the grinder; the eccentricity of the first eccentric is larger, sized in relation to the required dimensions, to obtain wider oscillation arcs and to avoid long segment-holder arms with consequently large vertical dimensions.
However, this solution, whilst constituting a valid improvement on previous mechanisms with cams and/or rollers, does not provide a grinding/polishing action which is reliable over a period of time, especially as regards high volumes of ceramic materials, for which all the quality control checks are employed, including the reflectivity of the polished surfaces.
These controls have shown that the said head does not provide a perfectly polished surface, but one which is polished in a discontinuous manner, with a veined finish, to the point where the materials thus machined are not acceptable.
Furthermore, the head moves the grinding segments with singular points discontinuity that occur once every 1
of the complete forwards and backwards stroke, that is, once for every rotation of the head, where n is the number of revolutions performed by the head to achieve one complete oscillation: this causes the dressing of the grinder to be momentarily stopped, thereby causing the cutting capacity of the abrasive segments to become discontinuous, due to the sliding motion of the contact line without the required slow dressing motion.
Such prior art may be subject to considerable improvement with a view to overcoming the previously mentioned drawbacks.
From the foregoing emerges the need to resolve the technical problem of finding a new configuration of the mechanism for controlling the motion which enables the oscillating motion of the grinding segments to be continuous.
The invention resolves the said technical problem by adopting a polishing head for plate materials in granite, hard stone or ceramic with grinding segments having continuous tangential oscillating motion comprising: abrasive segments made to oscillate on radial shafts each driven by means of a pin coupled, by means of a cylinder which may slide in a radial direction, to a ring having vertical eccentric rotary motion; the said ring coupled with rotatory motion to a first eccentric driven by gears with internal teeth, with the crown gear fixed to the housing of the head and the pinion coupled with rotatory motion to the second eccentric, in turn coupled with anti-rotational joint to the structure of the machine onto which the head is mounted; a plurality of pins mounted on eccentric planetary gears, with eccentricity equal to that of the said first eccentric, and coupled with rotational motion to the said ring and to the body of the head; means for connecting the said pinion to the said first eccentric; characterised in that there are: constituting the said means for connection, another pair of crown and pinion gears, in which the first crown gear is rigidly connected to the second pinion in turn coupled with rotatory motion to the said second eccentric; the first pinion connected rigidly to the said first eccentric concentrically with respect to the axis of the head; the second crown gear rigidly connected to the housing concentrically with the axis of the head.
The advantages obtained with this invention are: with the two-stage reducing crown and pinion gears a low dressing speed of the abrasive is achieved, as the eccentricity of the said second eccentric is made to be small to obtain a low transmission ratio, made even more so by the two-stage reduction, without being limited by the high value required for the first eccentric; the dressing speed is constant throughout the oscillation stroke of the abrasive segment-holder arm, in that the motion does not have singular points of discontinuity, except at the ends of the strokes, and the abrasive grinding segments always has a new cutting edge parallel to the previous one at every point during the oscillation, thereby achieving a completely tangential cut. Also, the meshing arc between the crown gears and their respective pinions is very long and there are a large number of meshing teeth; the resulting tangential force transmitted on each tooth is therefore relatively low thereby considerably reducing wear; furthermore, the uniform distribution of the load prevents the teeth of the crown gear or pinion from being damaged should the grinding segments be subjected to shocks as a result of possible fracturing of the material during machining. Also, all the segments are in contact with the surface being machined, with the exception of the one close to the end of its stroke: with this segment the inversion of the oscillation direction may occur when not in contact with the surface being machined, as contact is guaranteed for m−1 segments, thereby avoiding the so called “pump” effect. Finally, the abrasive grinding segments are constructed without the addition of side areas of the cylindrical surface to avoid the said “pump” effect, thereby making the regeneration of the abrasive more economical and enabling it to be used completely.
REFERENCES:
patent: 4965965 (1990-10-01), Wallin et al.
patent: 5161331 (1992-11-01), Zambon
patent: 3601636 (1987-07-01), None
patent: 437831A (1991-07-01), None
patent: 7127657 (1982-08-01), None
Pedrini S.p.A.
Rose Robert A.
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