Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Patent
1998-09-14
2000-04-25
Bucci, David A.
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
744248A, 74441, 74459, F16H 2702, F16H 118
Patent
active
060530650
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is directed to a spindle drive with a spindle and a spindle nut running thereon for the high-precision drive of a linearly movable device.
Spindle drives are employed, for example, in electronic reproduction technology in electronic recording devices for the point-by-point and line-by-line exposing of recording materials, also referred to as output scanners, exposers or recorders.
In an electronic recording device of the flatbed type, the recording material to be exposed is chucked on a linearly movable table or carriage, and the recording element is stationarily arranged. Given a recording device of the inside-drum type, recording material is located in a stationary, cylindrical segment-like holder, and the recording element is mounted on a linearly movable table or carriage. The table or carriage is mechanically rigidly connected to a spindle nut with which the rotary motion of a spindle driven by a motor is converted into a linear motion of the table or carriage.
Required, among other things, in order to achieve a good recording quality, particularly in the rastered exposure of recording materials, is a uniform linear speed of the table or the carriage that is essentially dependent on the quality of the spindle drive. Given recording devices that work in a start/stop mode, the spindle drive must--beyond this--enable a high precision in the positioning of the table or carriage along the spindle. The synchronism and positioning precision should thereby be assured in both directions of the linear motion.
CH-A-344 87 already discloses a two-part spindle nut for a spindle. The spindle nut is composed of two slide nut segments that are guided by a guide member movable in the radial direction relative to the spindle and in anti-tilt fashion.
A uniform linear motion and a high positioning precision cannot be assured in all instances with the known two-part spindle nut. There is the conflict in goal between a spindle nut lying as closely as possible against the spindle that, however, tends to seize at the spindle, and an easily movable spindle nut with an associated slack that disadvantageously deteriorates the uniformity of the linear motion and the positioning precision.
U.S. Pat. No. 2,493,000 discloses that axial sidewall play between slide nut segments and a spindle be eliminated with a spring. The elimination of the sidewall play, however, does not occur dependent on the selectable direction of a linear motion of an element driven by the spindle.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to improve a traditional spindle drive such that a high uniformity of the linear motion of the spindle nut and a high positioning precision along the spindle is achieved in both motion directions of a device driven by the spindle drive.
According to the present invention, a spindle drive is provided having a spindle and a spindle nut running on the spindle for a high-precision drive of a linearly movable device. The spindle nut has a base block connected to the movable device. A bore proceeds axially relative to the spindle for a loose passage of the spindle therethrough. A slide nut segment connects to the base block having a thread supported at the spindle. A further floating slide nut segment has a thread resiliently supported at the spindle and resiliently attached to at least one of the base block and the slide nut segment, but which can have a floating movement relative to the slide nut segment. At least one slide surface is displaceable in an axial direction, said slide surface being arranged between at least one of the slide nut segment and the base block and the further floating slide nut segment. An adjustment mechanism is provided having a spring biased thrust element coupled to the base block with which the resiliently held further floating slide nut segment is displaceable in an axial direction of the spindle relative to the slide nut segment arranged at the base block. The floating base block, the slide nut segment, adjustment mec
REFERENCES:
patent: 2493000 (1950-01-01), Linsley
patent: 4954032 (1990-09-01), Morales
patent: 5303606 (1994-04-01), Kokinda
Bucci David A.
Hansen Colby
Heidelberger Druckmaschinen Aktiengesellschaft
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