Bearings – Rotary bearing – Antifriction bearing
Patent
1997-08-08
1998-09-22
Footland, Lenard A.
Bearings
Rotary bearing
Antifriction bearing
384493, F16C 1908
Patent
active
058104836
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a spindle unit with a spindle, a casing, antifriction bearings that are prestressed and support the spindles on two places at a distance from each other in a casing, and a centrifugal regulator, which reduces the prestress on the antifriction bearings as the rotational speed increases, as a result of which the centrifugal regulator is produced as a springy, axially expanding bush with resilient arch-like parts between two compression components and each mass on the arch-like parts.
Such a spindle device is known from DE-U-94 04 249. Such spindle units are used, for example, in machine-tool construction. With such a spindle device the prestress of the spindle antifriction bearings can be reduced during high-speed machining. The spindle units can also be used in similar structural components of various machines. The regulator used in the known construction guarantees the correct coordination of the rotational speed of the spindle and the prestress of the antifriction bearing, which is, practically speaking, congruent to the recommended coordination of the rotational speed of the spindle and the prestress of the antifriction bearing (cf., e.g., the 3700 T catalog: SKF precision bearing, pg. 64, reg. 47150001987-03, printed in the Republic of Germany by Weppert GmbH & Co. KG). In comparison with the traditional constructions with hydraulic control of the prestress of the spindle bearing, as is described, e.g., in the journal Konstruktion (no. 44, p. A20, 1992 for HSC spindles), the spindle unit is constructed in a simpler fashion in accordance with the above German working model.
By virtue of the fact that the variation of the prestress of the spindle bearing is dependent on the displacement of the inner rotating bearing rings, corrosion caused by friction can occur on the outside surface of the spindle; cf., e.g., Tribology Handbook, ed. M. J. Neale, London: Butterworth, 1973, chap. E7. In the case of the known construction named, the regulator with its resilient arch-like parts and the masses arranged on them are located between the bearings for the spindle.
The problem the invention tries to solve is to improve a spindle unit of the type under discussion so that spindle corrosion caused by the displacement of the inner bearing rings with respect to the spindle is avoided, in turn increasing the longevity of the spindle unit.
According to the invention this will be obtained when the regulator is supported by regulator antifriction bearings on its two ends on a casing of the spindle unit; when the regulator does not touch the spindle; when the outer nonrotating rings of the regulator antifriction bearings press against the outer rings of the spindle bearings; and when the regulator is set in rotation with the aid of a springy component, which has a high resistance to rotation and a low resistance to bending, allowing for the axial movement of the regulator with respect to the spindle, as a result of which the springy component is firmly connected to the spindle and regulator.
The regulator consequently acts on the outer ring and is positioned so it can move axially to the spindle. In so doing the danger of a corrosion of the spindle is eliminated because the thrust rings of the regulator displaces the outer nonrotating rings of the spindle bearings while the prestress is being regulated.
The regulator is located, as is usual, between the spindle bearings and requires only a little space. It is, however, also possible to mount the regulator outside the spindle, in which case existing spindle units can be converted. For this purpose the regulator is mounted outside the section on each of whose ends the spindle bearings are located, in which case the outline of the arch of the resilient parts of the regulator has a concave form. With such a construction only minimal changes need to be made in the construction of existing spindle units.
The invention is more clearly illustrated in two working examples with the use of drawings, in which
FIG. 1 represents a longitudinal section through a firs
REFERENCES:
patent: 4859148 (1989-08-01), Hibyan
patent: 4884903 (1989-12-01), Pham et al.
patent: 5388917 (1995-02-01), Hibi et al.
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