Machine element or mechanism – Gearing – Directly cooperating gears
Reexamination Certificate
1998-04-07
2001-02-13
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
Directly cooperating gears
Reexamination Certificate
active
06186020
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for converting rotary motion into axial motion, in accordance.
2. The Prior Art
Such a device is known from DE 25 02 052 C2.
A similar device is described in DE 36 29 281 A1. However, in that document, differing from the abovementioned device, the planet rollers have a threaded groove as profiling. Threaded groove profiling of this type rules out any slip between the planet rollers and the thread of the thrust element.
A device for converting rotary motion into axial motion is known from U.S. Pat. No. 3,861,221, in which device a threaded rod acts on planet rollers mounted in a planet carrier. In this case, the threaded rod and the planet wheels have threads that are matched to one another. The thrust element is displaced axially by a hollow wheel that is supported axially on this thrust element and in which the planet rollers roll.
Proceeding from the device according to DE 25 02 052 C2, the invention is concerned with the problem of providing a device of the generic type that is of more simple construction and functions with less friction.
SUMMARY OF THE INVENTION
This problem is solved by a design of such a device according to the defining features of patent claim
1
.
The invention is primarily based on the idea of mounting the planet rollers in a carrier which is driven by a shaft which is firmly connected to this carrier, and of profiling said planet rollers in such a way that slip-free transmission of the rotary motion into axial motion of the thrust element is ensured.
As a result, in the case of the solution according to the invention, slip therefore cannot occur. This results from the following. The carrier rotates without slip. The axles of the planet rollers rotate therewith, likewise without slip. As a result, the drive grooves of the planet rollers—even if they were to slip in an intrinsically undesired manner in the thread of the thrust element—are always definitely assigned in the axial direction to the thread of the thrust element.
The drive grooves of the planet rollers must be grooves which are located separately alongside one another, are each closed in the circumferencial direction, and have no pitch, in order to avoid stresses if any—intrinsically undesirable—slip should occur between a planet roller and the thrust element driven thereby. With regard to possible slip between a planet roller and thrust element, it should be noted once more that such slip does not as a result signify any slip between the rotary drive of the carrier and the thrust element.
Rather, the only significance of any—intrinsically unintentional—slip between a planet roller and the thrust element is that, during the occurrence of such slip between the relevant planet roller and the thrust element, sliding friction occurs instead of rolling friction, which occurs when there is no slip. Were such slip not possible, as is the case, for example, of the prior art mentioned in the device according to the specification DE 26 29 281 A1 acknowledged at the beginning as the prior art, then jamming of the force-transmitting parts may occur. Such designs which rule out slip between plant wheels and thrust element cannot be used functionally reliably in practice.
Expedient refinements of the device according to the invention are indicated by the subclaims.
A particular advantage of the invention, is that no toothed parts have to be used. Such a device is extremely well suited for applications having relatively low transmission ratios and high desired displacement speeds of the thrust element.
Primarily, according to the invention, the thrust element is to be designed as a tube which engages over the planet rollers and the drive device of the planet roller carrier. However, it is also possible to design the thrust element as a rod enclosed by the planet rollers. In this case the carrier as a whole, that is to say also in its drive region, must be implemented to be hollow at the center, just like the drive device, in order to be able to ensure free movement of the thrust element designed as a rod.
In the case of the device according to the invention, it should be emphasized as particularly advantageous that the thrust element can be moved out over a distance over which previously no guide element needs to be present. In this way, the thrust element operates in accordance with the principle of free advance, comparable with the principle of bridge building being carried out with free advance, or with moving a piston out of a hydraulic cylinder.
REFERENCES:
patent: 3861221 (1975-01-01), Stanley
patent: 4337671 (1982-07-01), Ulf
patent: 4576057 (1986-03-01), Saari
patent: 4964314 (1990-10-01), Wilkes
patent: 5501117 (1996-03-01), Mensing et al.
patent: 25 02 052 (1975-10-01), None
patent: 36 29 281 (1988-03-01), None
patent: 85 30 837 (1988-09-01), None
patent: 1540855 (1968-08-01), None
Collard & Roe P.C.
Marmor Charles A
Parekh Ankur
Wittenstein GmbH & Co.
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