Machine element or mechanism – Elements – Gear casings
Reexamination Certificate
1998-08-03
2001-01-30
Bucci, David A. (Department: 3682)
Machine element or mechanism
Elements
Gear casings
C074S6650GA
Reexamination Certificate
active
06178851
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority of Patent Application Ser. No. 297 13 785.9, filed in Germany on Aug. 2, 1997, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a gear for twin-screw extruders with a first output shaft, driven by a drive shaft in particular via a reduction gear, and a second output shaft, driven by the first output shaft via two side shafts, arranged on both sides, wherein the shafts are arranged axis parallel and inside a joint gearbox case. There exist various designs for gearbox cases known in the technology. For example, there exists a gearbox case consisting of four gearbox case parts which are attached to each other via horizontal junction planes. The center junction plane extends exactly through the axes of the two drive shafts, while the upper and lower junction planes extend through the axes of the side shafts and parallel to the center junction plane. Owing to the arrangement of the gear train between the two output shafts and the side shafts in the form of a rectangle with the gear shaft axes positioned at its corner points, it is possible to have a continuous adjustment of the spacing between the side-by-side arranged output shafts may be adjusted continuous.
Such gearboxes, which are divided into four parts, result in a drawback, in that when the axial spacing between the two output shafts is changed, the spacing between the two side shafts is changed as well because the length of the gear train remains the same. As a result, the side shafts creep from the associated separating joint, which requires the adaptation and displacement of the separating joints that extend through the axes for the side shafts. This in turn, means that each new axial spacing between the output shafts requires the adaptation of all four gearbox parts that adjoin the side shafts, so that a complete separate gearbox case must be provided even for the slightest difference in the axial spacing.
Based on the foregoing, it is the object of the present invention to provide a gear for twin-screw extruders of the aforementioned type, which gear permits a continuous change in the axial spacing while the gearbox case parts remain unchanged and which is accordingly simplified considerably with respect to the variant variety of these parts.
SUMMARY OF THE INVENTION
The above object is solved in accordance with the present invention in that the gearbox case is divided along a vertical junction plane into two gearbox case halves, and that the junction plane extends between the axes of the two output shafts. The vertical separation of the gearbox case by a plane that is parallel to the shaft axes has the advantage that the gear can be assembled or disassembled easily by swinging open the gearbox case. This is preferably done by disengaging one of the output shafts from the side shafts during the opening of the gearbox case, thereby making all shafts freely accessible, even though they are still held securely inside their rolling bearing seats.
With this form of divided gearbox case, the junction plane no longer extends through the shaft axes and thus also cannot divide the rolling bearing seats into halves. As a result of the optimum accessibility of the shafts or rolling bearing seats when the gearbox case is opened up, it is possible to produce the rolling bearings seats independent of the respective position in the gearbox case, but only after the gearbox case halves have been produced by drilling the rolling bearing seats in the gearbox case. The individual shafts are then installed by inserting them or fitting them in and the bearings are subsequently pressed in, that is to say once again without having to consider the axial spacing of output shafts and side shafts for the form of the gearbox case parts or when positioning the junction plane.
It is conceivable that rolling bearing seats can theoretically be produced in this way for state of the technology horizontal separating joints. However, using this gear assembly method does not accomplish the desired result because of the problems associated with the joining and assembling of a divided horizontal gearbox case in that the side shafts, for example, are no longer accessible once the output shafts have been installed. Rather, with a horizontal division of the gearbox case, this requires all shaft axes to be positioned in each case exactly in the associated junction plane, since the poured-in rolling bearing seats become accessible only then and the inserting of the bearings or the shafts is made possible.
To be sure, gearboxes with a vertical junction plane are known from the state of the technology. However, this vertical junction plane extends perpendicular to the axes for the output or side shafts, wherein up to four gearbox case parts are arranged one after another. This design also has the additional significant disadvantage that in order to open the gearbox case, the shafts and their bearings must first be removed from the rolling bearing seats, thereby making access to the gear very difficult and complicated. The initial installation of the gear is correspondingly complicated.
All these disadvantages of the state of the technology are avoided for the gear according to the invention as a result of the favorable arrangement of the junction plane. Owing to the fact that the rolling bearing seats are not positioned in the gearbox case until later on, in a precise adaptation to the respective application case, the axial spacing of the output shafts can be changed continuously over a larger range, without requiring a new gearbox case or individual new gearbox case parts. Thus, the essential advantage of this design is that any axial spacing desired by the client can be realized over a wider range and that despite the varied axial spacing, only the two equal gearbox case halves are necessary for this. In other words, it is not necessary to provide new, separate gearbox case parts for different axial spacings, but only to provide new bores in the complete gearbox case.
Also, the same gear train consisting of the same gearing parts can be used, even for varied axial spacings. Neither the side shafts, nor the output shafts are fixed exactly in their position relative to the junction plane. Consequently, these shafts can have a nearly optional arrangement inside the gearbox case while the rectangular drive train is maintained. The position of the rolling bearing seats is in turn adapted to this and they are subsequently drilled into the gearbox case. In other words, the present invention makes it possible to use the same gear train with all its individual parts for many different application cases since the position of the rolling bearing seats is independent of the junction plane.
On the whole, this leads to a strong decrease in the parts variety and a corresponding increase in the lot sizes for the individual parts and thus to considerable cost-savings on the whole.
Furthermore, the spectrum of axial spacings required by the market can also be supplied without interruption by the present invention for a specific rotational moment range in that the axial spacings for various gear sizes overlap. In addition, if a gear for a large machine requiring only a low rotational moment is required, it is possible to use a gear with smaller gear size for which the maximum rotational moment of the output shaft corresponds to the required rotational moment and which has a larger axial spacing that is adapted to the large machine, thereby leading to a corresponding cost reduction.
Another advantage of the present invention is that only two casting patterns are therefore still required for a complete gearbox case and this for a plurality of axial drive shaft spacings, whereas the state of the technology required four new patterns for each individual desired axial spacing. The gear according to the invention with the vertical junction plane also makes it possible to integrate the reducing section into the gearbox case so that a sep
Aumueller Marion
Berky Alfred
Koch Guido
Thiel Lothar
Bucci David A.
Kim Chong H.
Kinberg Robert
P.I.V. Antrieb Werner Reimers GmbH & Co. KG
Spencer George H.
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