Bearings – Linear bearing – Recirculating
Reexamination Certificate
1999-12-14
2001-05-08
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
C384S055000, C384S057000, C384S059000
Reexamination Certificate
active
06227708
ABSTRACT:
The invention relates to a guiding frame with a carrier provided with a fastening groove and carrying at least one substantially rectangular guiding rail disposed parallel to the carrier and secured in a fastening groove and on which rests a guiding bearing that guides a sliding part.
The carrier used in such guiding frames is comprised of a hollow shape of square or rectangular cross section, made, for example, of an aluminum alloy. The outer circumference of the carrier comprises undercut fastening grooves, so-called T-grooves. These fastening grooves can be used to fasten parts to the carrier to create machine frames, area installations or the like. It is generally known to fasten to a carrier a guiding rail on which a guiding bearing is able to move in the longitudinal direction of the rail and supports a part that is to be adjusted longitudinally, for example a slide plate, which, for example, must be precisely positioned for a machining task. Tilting, for example, of the slide plate would cause a workpiece or tool to be inaccurately positioned and the results of the machining done in that position to be inaccurate. It is also generally known to fasten to such carriers two mutually parallel guiding rails on which rest guiding bearings of longitudinally movable slides. A guiding bearing of the one guiding rail is rigidly connected to a guiding bearing of the other guiding rail by means of a slide plate or the like. The guiding bearings are roller bearings whose rollers run on the guiding rails. Such guiding frames are suitable for slides with small to medium-sized loads. However, they are less well suited for high-precision positioning tasks, for example for tool or workpiece carriages. Highly accurate positioning must be achieved if correspondingly accurate machining operations are to be performed on workpieces. For this purpose, it is generally known to use shaft-mounted spherical sleeves or guiding rails of round cross section. However, this requires that the hollow-section pieces or other fastening means into which the spherical sleeves are built have special profile sections.
Known from DE-A 31 32 869 is a guiding frame with a carrier that carries two substantially rectangular guiding rails disposed parallel to the carrier and attached thereto, and on which rests a guiding bearing that guides a sliding part. This bearing is a roller bearing with an external roller cage.
In contradistinction to the prior art, the task underlying the invention is to improve a guiding frame having the features cited in the preamble in such a way that it can be used for high-precision positioning tasks even of heavy loads, in particular tool and/or workpiece carriages.
This task is accomplished by the fact that the substantially rectangular guiding rail is supported via a rounded portion on the supporting edges of the carrier that delimit the undercut fastening groove or on an intermediate bearing that bridges the undercut fastening groove.
It is of importance for the invention, first, that the guiding frame is equipped with a substantially rectangular guiding rail. This can be attached to the top outer wall of the carrier in a conventional manner. The attachment is made, for example, by screwing with the aid of the undercut fastening grooves. However, rectangular guiding rails have the considerable disadvantage of sensitivity to torsion. Especially when two or more mutually parallel guiding rails are present, guiding rails that have become twisted during manufacture or on attachment to the carrier will attempt to impart a corresponding twist to the slide or its guiding bearing during the travel thereof. Depending on the degree of twist of the guiding rails, jamming can occur that prevents the movement of the slide. Jamming that affects system tolerances can also result. All parts of the system are subject to tolerances. This applies in particular to the carrier and/or any parts of the slide, especially if they are made of hollow extruded sections. The carrier and the hollow-section sliding parts are often configured with a slight concavity of the surfaces between their edges, for example in order to improve the desired firm seat of the front end of a hollow section against such a concave surface abutted by said front end. Such concavities are extremely small, but can still cause angular deviations of the sliding parts and/or the guiding bearings, resulting in jamming. The mounting of the carrier inside the guiding frame can also cause twist and/or angular deviations, which entail a corresponding risk of jamming. The risk of jamming is especially great when the guiding frame has to be manufactured to very close tolerances in order to achieve the desired positioning accuracy.
It can be advantageous to configure the guiding frame so that two or more mutually parallel guiding rails are present, each of which comprises a guiding bearing, and which are rigidly connected to one other, and at least one of which is attached via a rounded portion to least one carrier. It is of further considerable importance for the invention that at least one guiding rail is supported via a rounded portion. The rounded portion makes it possible to correct the seat of the guiding rail on the carrier. This correction is made by means of the slide during the mounting of the guiding rail on the carrier, in such a way that the slide can be moved on the guiding frame with permissible resistance to movement.
A very simple embodiment of the guiding rail is created if said guiding rail can be supported by its areas comprising rounded portions on the supporting edges forming the fastening groove. All that is needed in this case is to configure the guiding rail with a rounded portion, a production task of limited complexity. The guiding rail can be supported on the carrier not only directly but indirectly, via an intermediate bearing. This intermediate bearing bridges the fastening groove, thus resting on the planar outer surface of the carrier. On its side proximate the guiding rail it is implemented so as to be rounded and permits the required torsion-sensitive mounting of the guiding rail.
The guiding frame can be configured so that the guiding rail comprises a circular rounded portion in the region of the supporting edges. The positionability of the guiding rail on the carrier is then ideal and is independent of the torsion angle. Production is also simplified.
To reduce the surface pressure between the carrier and the guiding rail, the guiding frame can be realized so that the radii of the supporting edges are increased in comparison to other edge radii of the carrier.
The surface pressure between the supporting edges of the carrier and the guiding rail is reduced to an especially large extent if the supporting edges are implemented as concave. In both of the foregoing cases the cost and work of production are slight, since both the increase in the edge radii and the concave implementation of the supporting edges can be effected simultaneously with the manufacture of the carrier by extrusion, if carriers made of extruded aluminum alloy, for example, are used.
The guiding frame can be improved in that the guiding rail rests on a circularly cylindrical rounded portion in a corresponding circularly cylindrical rounded recess in the intermediate bearing. The guiding rail is accordingly of one piece and can be hingedly supported in the correspondingly rounded recess in the intermediate bearing. Comparatively great relative torsion can occur between the guiding rail and the intermediate bearing or the carrier. The supporting surfaces between the guiding rail and the intermediate bearing that come into play during such torsion are large and the specific surface pressures are therefore low. Depending on stability requirements, the intermediate bearing can be configured with a correspondingly large area, including on its side proximate the carrier.
If it is necessary to avoid a rounded configuration for the side of the guiding rail proximate the carrier, the guiding frame can be implemented so that the guiding rail is planar o
Pies Gerrit
Rixen Wolfgang
Hannon Thomas R.
Pandiscio & Pandiscio
LandOfFree
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