Planetary gear transmission systems or components – Planet periphery surrounds axis of interacting gear – Particular gear tooth
Patent
1996-02-27
1998-01-06
Marmor, Charles A.
Planetary gear transmission systems or components
Planet periphery surrounds axis of interacting gear
Particular gear tooth
475162, 475904, 74462, F16H 132
Patent
active
057048657
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an eccentric gear of the type that includes first and second cooperating gear rings. One of the gear rings has a certain number of internal straight cogs and the other has a smaller number of external, equally straight cogs. At least one gear ring has a conical form with a large end and a small end, while the second gear ring has a smaller pitch diameter than the first one and is eccentrically mounted in bearings relative to the first one in order to roll off upon the internal cogs of the latter, and with the axes of symmetry of each respective gear ring forming an angle with each other.
An example of the field of use for eccentric gears of the type described relates to their use as distribution rollers in printing machines--more particularly as distribution rollers with a built-in mechanism for realizing an axial, reciprocal motion of the roller at the same time as it rotates with high speed. Another field of use is where they are used are reduction gears where silent running is important. For medical applications, controlling of curtains, awnings, electrical domestic appliances and the like, planetary gears of plastic material are often used. These often have a high noise level, which is inconvenient.
2. Prior Art
In WO-A-9306999, a device is disclosed according to which a slightly shaped conical gear ring rolls against a cylindrical internal gear ring. The conical eccentric gear ring, which is eccentrically mounted in bearings, has one or more fewer cogs than the cylindrical gear ring and in this way a slow change of the angular interposition between the gear rings is attained. This change of angular interposition is transferred to a cam element and a cam roll which thus effects an axial displacement of a distribution roller in which the mechanism is located.
In U.S. Pat. No. 5,030,184, a gear correction method is described which makes it possible to produce an eccentric gear in which the two gear rings have cogs numbers that differ from each other by one or several cogs.
According to the constructional arrangement of the cogs in the gear of WO-A-9306999, a cross-section is laid through the slightly conical, eccentrically arranged gear ring in a position around the middle of the axial extension of the gear ring. In this position. the cogs are intercorrected by the calculation and correction process described in said U.S. Pat. No. 5,030,184. In this load, the conical, external gear ring operates in a manner so that its abutment against the cylindrical, internal gear ring becomes optimal. Thus, the resulting cog contact is optimal only in a section at a point of half the axial extension of the conical, eccentric gear ring. In theory, in an unloaded state (of the gear) only two pairs of cogs are in contact in this axial section, i.e., one pair in each loading direction. At the time of loading of the gear, several pairs of cogs will come in contact with each other due to cog distorsion. Normally, 3 to 5 pairs of cogs will be loaded in each loading direction. In each axial section, being other than the optimal middle section of the conical gear ring, a cog abutment is obtained that differs from the possible optimal one in this section.
Objects and Characteristics of the Invention
In order to obtain optimal load transfer of the cog pairs, which are in contact with each other in the unloaded state of the gear, it is desirable that the cog contact in each axial cross-section be optimal. This is achieved by turning the blank of the slightly conical gear ring with a certain cone point angle determined according to the method as described hereinafter. From this blank, the conical gear ring is manufactured with a certain cog cone angle, determined by the method as described hereinafter.
According to the present invention, an eccentric gear is obtained whose straight cogs in the conical gear ring have a helical line of contact against the internal, straight cogs of the cylindrical gear ring. This helical line of contact makes the gear run smoothly
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Kwon Peter T.
Marmor Charles A.
Scandrive I Hallstahammar AB
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