Machine element or mechanism – Mechanical movements – Reciprocating to reciprocating
Reexamination Certificate
1998-11-25
2001-12-11
Olszewski, Robert P. (Department: 3652)
Machine element or mechanism
Mechanical movements
Reciprocating to reciprocating
C074S089100, C074S09900A, C187S268000
Reexamination Certificate
active
06327925
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a linear drive unit.
REVIEW OF THE RELATED TECHNOLOGY
Known linear drive units, such as sliding nuts and roller nuts, are usually driven by means of electric motors either directly or via a cogwheel and/or belt drive. This kind of drive unit has its shortcomings. One is that the electric motor must be mounted in direct proximity to the linear drive unit. Also, it has proven particularly disadvantageous that in order to determine the respective current position of a linear drive unit, electrically operated measuring systems such as encoders or gages are usually needed, with the aid of which information can be obtained regarding the actual position of the motor, the gear, or the linear drive unit itself. This is noted in German patent DE 195 25 454 A1.
Still another disadvantage is that known linear drive units can generally not be used whenever specific requirements regarding the surrounding environment prohibit the use of electrical or metallic components, as these can impact or interfere, to varying degrees, with electrical or magnetic fields.
SUMMARY OF THE INVENTION
The present invention has an object, among others, to overcome deficiencies in the prior art such as noted above.
It is, therefore, a particular object of the present invention to improve a linear drive unit so that any required positioning of the drive unit can be performed and ensured reliably without additional expenditure.
In accordance with a first preferred embodiment of the present invention, a linear drive unit has a threaded rod and, in combing (meshing) engagement with the threaded rod, a threaded nut forming a unit with a cog ring having a number of equally spaced cogs projecting in a radial direction from its outer circumference. The threaded nut, furthermore, preferably has two assigned connecting links, which are guided inside a housing of the linear drive unit in a direction parallel to the axis of the threaded rod. The connecting links can be driven back and forth in the axial direction.
During each oscillating movement of one of the connecting link (i.e., a movement from one end position designated as the starting position, to the other end position of the one connecting link, and back again into its starting position), the one connecting link acts upon the cogs projecting from the cog ring, with the result that the force exerted via the cogs is converted, in increments, into a rotary motion of the threaded nut, thereby causing a linear shifting of the threaded rod.
In accordance with a second preferred embodiment of a linear drive unit in accordance with the present invention, the threaded rod, in contrast to the above-described embodiment, has forms a unit with a cog ring having a number of equally spaced cogs that project in a radial direction, analogously to the cogs projecting from the threaded nut of the first embodiment. As in the first embodiment the rod is in meshing engagement with a threaded nut.
In the second embodiment an oscillating movement occurs in one of the connecting links, which is moved to and fro in the axial direction, as in the first embodiment. During this oscillating movement the connecting link acts upon the cogs that project from the threaded rod so that the threaded rod, which is installed so that it can rotate within the housing, is driven into an incremental rotation, causing the threaded nut to perform a linear movement in proportion to the pitch of its thread.
In an advantageous embodiment of the invention, depending on the desired direction of the linear movement, one or the other of preferably two connecting links may by driven, for example, via hydraulically or pneumatically activated pistons. The connecting links may also be driven via ball screws, cam disks, or cam mechanisms or, if the impact on electrical or magnetic fields is not an issue, via lifting magnets.
An exact definition of the linear drive unit can be established via the number of lifting strokes when the connecting links, which are guided parallel to the axis of the threaded rod, are operated with this type of drive (for example via hydraulically or pneumatically actuated pistons that cause the connecting links to be moved from their starting position into one end position and back again into the starting position).
The design of the linear drive unit according to the present invention thus permits an operation during which no position measurements need to be performed, because the position of the actuator designed in the form of a linear drive unit according to the invention is immediately and directly related to the number of movement increments which have been performed, each of which, as specified above, corresponds to one to-and-fro movement of the last activated connecting link from its last known position, which may be determined or measured according to a known and customary method, for example via a reference marking.
The reference marking and monitoring of the number of oscillating strokes may be in the form of light barriers, for example, which are activated through light conductors. In this way the new position reached in relation to the known starting position can be verified, and optionally also determined directly at the linear drive unit, without requiring any additional, relatively complex electronic components.
That is, the amount of axial translation is proportional to the number of oscillating strokes, so counting the number of strokes gives the exact location of the rod within the mechanical precision of the threads, backlash, etc.
If the linear drive unit is to be used in metrology, for example as a positioning unit, and in order to not only prevent but exclude from the outset any impact on or interference with electrical or magnetic fields, then all components of the linear drive unit according to the invention are preferably manufactured from materials such as polyamide, polyvinyl chloride (PVC), polyoxymethylene (POM), or the like, the use of which guarantees that no electrical or magnetic fields are impacted, let alone disrupted in any way. In other words, the reliable functioning of the linear drive unit according to the present invention is ensured even though absolutely no metallic components are used.
REFERENCES:
patent: 3968861 (1976-07-01), Kernen
patent: 4089624 (1978-05-01), Nichols et al.
patent: 4534234 (1985-08-01), Cosenza
patent: 4718291 (1988-01-01), Wood et al.
patent: 4753122 (1988-06-01), Nishikawa et al.
patent: 4919236 (1990-04-01), Karlsson et al.
patent: 5127281 (1992-07-01), Yanawgisawa
patent: 5339704 (1994-08-01), Linberg
patent: 5906136 (1999-05-01), Yabe et al.
patent: 4105090 (1991-08-01), None
patent: 4336596 (1995-05-01), None
patent: 19525454 (1997-01-01), None
patent: 586326 (1994-03-01), None
patent: 1620743 (1991-01-01), None
Gombert Bernd
Willberg Bertram
Browdy and Neimark
Chin Paul T.
Deutsches Zentrum fur Luft-und Raumfahrt e.V.
Olszewski Robert P.
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