Machine element or mechanism – Gearing – Plural power paths to and/or from gearing
Patent
1998-07-27
1999-08-17
Wright, Dirk
Machine element or mechanism
Gearing
Plural power paths to and/or from gearing
B29C 4708
Patent
active
059377127
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a geared reduction unit particularly for use with extruders with two worm screws for thermoplastics materials.
In more detail, this reduction unit comprises: to each other and associated with a respective worm screw, and and second output shafts respectively.
Reduction gears of this type must be made so as to enable the output shafts to transmit high torques which are the same as each other.
The arrangement of the two output shafts close together, however, makes it difficult to achieve this result since, for example, the diameter of the gears fixed to these shafts, which constitute the final component of the respective gear trains, must be limited. This dimensional limitation in turn limits the number of teeth or the value of the gear module of these gears which consequently limits the torque which can be transmitted.
The arrangement of the output shafts close together also imposes limits on the dimensions of their bearings which may thus be inadequate to withstand the high radial loads generated as a result of the use of gears with a small number of teeth.
JP-A-01 234 223 discloses a geared reduction unit of the type disclosed at the beginning of the present description, wherein the second output shaft is longer than the first output shaft and is connected to the second gear train by a part which is not alongside the first output shaft.
In order to optimize the performance of this kind of geared reduction unit, the subject of the present invention is a geared reduction unit of the type disclosed in claim 1.
The specific provision of a torsionally resilient portion in the input shaft has the advantage of making the torque transmitted to each output shaft the same, avoiding asymmetrical stresses. Therefore sizes and strength of the gear trains can be reduced with major savings.
At the same time, the different lengths of the two output shafts has the further advantage that the radial bulk of the component of the gear train located on the portion of output shaft not alongside the other output shaft is not subject to limitations which reduce the performance of the reduction unit.
Further advantages and characteristics of the present invention will become clear from the detailed description which follows, given with reference to the appended drawing, provided purely by way of non-limitative example, in which:
FIG. 1 is a schematic plan view of a geared reduction unit according to the invention,
FIG. 2 is a sectional view taken on the line II--II of FIG. 1, and
FIG. 3 is a view corresponding to FIG. 2 showing an alternative embodiment of a reduction unit according a to the invention.
A geared reduction unit, particularly for use in twin-screw extruders for thermoplastics materials, comprises (FIGS. 1 and 2): an input shaft 10, first and second output shafts 12, 14, first and second gear trains 16, 18 for connecting the input shaft 10 to the first output shaft 12 and the second output shaft 14 respectively.
The output shafts 12, 14 are associated with a restive worm screw (not visible in the drawings) and are arranged parallel to and close to each other. The second output shaft 14 is longer than the first output shaft 12 and is connected to the second gear train 18 by a part which is not alongside the first output shaft 12.
To one end of the input shaft 10 is fixed (for example keyed or made integrally) a drive gear 20 which is connected in known manner, not illustrated in the drawings, to a motor for driving the reduction unit.
The first gear train 16 includes a first gear 22 fixed to the first output shaft 12, three second gears 24 in mesh with the first gear 22, a ring gear 26 with internal teeth 28 and external teeth 30 and a third gear 32 fixed to the input shaft 10.
The internal teeth 28 of the ring gear 26 mesh with the second gears 24 while the outer gear 30 meshes with the third gear 32.
The three second gears 24 are arranged symmetrically (see FIG. 2) around the first gear 22 in the same plane which is generally transverse the input shaft 10 and output shafts 12, 14. Alt
REFERENCES:
patent: 4253345 (1981-03-01), Munster
patent: 4261225 (1981-04-01), Zahradnik
patent: 4315440 (1982-02-01), Chszaniecki
patent: 4586219 (1986-05-01), Blach et al.
patent: 4586402 (1986-05-01), Schafer
patent: 4899620 (1990-02-01), Schiffer
patent: 5092189 (1992-03-01), Bonalumi
patent: 5213010 (1993-05-01), Hayafusa et al.
Patent Abstracts of Japan, vol. 13 No. 560 (M-906) Dec. 13, 1989.
F.LLI Maris S.p.A.
Wright Dirk
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