Machine element or mechanism – Gearing – Pressure distributing
Reexamination Certificate
1999-11-05
2001-10-16
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Gearing
Pressure distributing
C074S424700
Reexamination Certificate
active
06301986
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a gear arrangement, particularly for a double screw extruder, having a drive shaft and at least one driven element.
Gear arrangements of this type are used in the most diverse areas of application, for which reason the following discussion of double screw extruder gears is only exemplary, but should not be taken as limiting in terms of the protection. The optimization problem is more or less common for all gear arrangements, that on the one hand, it should certainly be high-performance and thus, for example, be usable to transfer a large torque, but on the other hand, it should allow for as small an expense as possible.
Thus, expensively designed gear arrangements are already known whose driven shafts are driven via two side shafts, wherein both side shafts are constructed as torsion shafts and are accordingly expensively designed. The two side shafts are driven by the common drive shaft, optionally by the intermediate connection of a reduction gear. A simpler embodiment now consists, for example, in taking away one side shaft and transmitting the driving power only via one side shaft. As is not difficult to recognize, however, only a reduced torque can be transmitted in this case as compared with the embodiment having two side shafts. Finally, an alternative constructive form of a gear arrangement of the type mentioned at the beginning likewise has only one side shaft which, however, for improvement of the torque or driving power transmission, is provided with two teeth meshing areas in alignment with each other, which—relative to the drive direction—are arranged next to each other on the same side shaft or driven shaft and perform a simultaneous power transmission. However, the large spatial requirement necessary here in the axial direction is disadvantageous in this gear variation.
SUMMARY OF THE INVENTION
Taking this as a starting point, an object of the present invention is to further improve gear arrangements of the type mentioned at the beginning, especially in regard to their function and/or their operating behavior.
This object is achieved by the invention in that the driven element is in active connection, at least indirectly, with two intermediate gears driven by the drive shaft and can be driven by them, that the intermediate gears are arranged on axles parallel to each other and act on the same driven element, that the intermediate gears are in engagement with a common distributor gear coupled at least indirectly to the drive shaft and drivable by this distributor gear, and that the distributor gear is mounted in bearings so that it is movable at least indirectly in the radial direction.
The advantage results herein that, by the use of two intermediate gears, two meshing or engagement areas can be made available, and thus despite only one side shaft or torsion shaft driven by the distributor gear, a torque twice as large can be transmitted, compared with the constructive form having only one direct side shaft acting on the driven element and only over one meshing area, and this is done, in addition, at only a slight additional expense. Also, the gear arrangement can operate with a clearly reduced axial construction space compared to the described double meshing of two meshing areas that align with each other.
The special advantage of the gear arrangement presented here, however, lies above all in the fact that the pivotably mounted distributor gear provides that the torque transmission is not disturbed at either of the two intermediate gears, since the distributor gear can be brought into constant contact with the teeth of the intermediate gears by the radially movable, i.e. flexible bearing.
In addition, it is especially advantageous and simple if the radially movable bearing of the distributor gear is made in a pivotable manner and, in particular, via a pivoting element that picks up the distributor gear, and if the pivoting element is itself mounted via a pivoting bearing offset from the distributor gear axle and arranged fixed in the housing. While the distributor gear, which should thus be able to move relative to the two intermediate gears in the radial direction, is arranged to be freely rotatable in the rotational direction, but radially inflexible in the pivoting element, the pivoting element provides for the desired free mobility.
As far as the position of the pivoting bearing is concerned, the axle of the pivot bearing should be positioned relative to the distributor gear such that the plane formed through the axle of the pivot bearing and the axle of the distributor gear runs parallel to the resultant forces of the two tooth meshing normal force planes, so that this plane has a slope toward the plane formed by the axles of the intermediate gears, which corresponds to the drive meshing angle &agr;
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of the resultant forces of the two tooth meshings. This leads, in an especially advantageous way, to a force component acting perpendicularly to the cited resultant forces to press the distributor gear constantly against the load edges of the intermediate gears, such that for small pitch errors or tooth forming errors an active connection interrupted by the errors is immediately restored by the distributor gear being moved a distance away from the contactless meshing by the mentioned force component, until the active connection and thus also the equilibrium of the torque transfer on both intermediate gears is restored.
This automatic adjustment movement for the compensation of any pitch errors occurs of course in the same way for both meshing areas, i.e., relative to both intermediate gears and thus also provides for an equal distribution of the transmitted drive forces independently of which contact is impaired or disturbed by which intermediate gear.
As already mentioned at the beginning, the gear arrangement can be used in the most diverse of application cases. Thus, the driven element can be a pinion that acts together with a driven shaft, i.e., the gear arrangement can be used for a rotating driven movement—at best, without a reversal of the direction of rotation. In the same manner, however, it is also possible to use the invention for linear drives. As far as linear drives are concerned, the uniform distribution of the drive forces and/or the drive torque on both intermediate gears results especially when the drive is used for lifting or lowering, i.e., when the vertically acting weight force on the gear acts independently of the drive direction, such that the force components keep the same direction in the mesh areas independently of the conveying direction. In contrast, in the case of horizontal driving, a change of the drive direction also leads to a reversal of the drive forces, so that the equilibrium ratios can be modified because of the mentioned force component perpendicular to the supporting force. In this case, restoring the optimal equilibrium distribution on both intermediate gears would result only if the position of the pivot bearing of the distributor gear were to be adapted to the new directions of force flow and thus to the new drive meshing angles.
Expediently, the gear arrangement according to the invention thus functions for such applications always with the same drive direction, as is the case, for example, with double screw extruders or with alternating drive directions, if—as for example in lift drives—the force ratios or force directions in the meshes do not change by the reversal of the direction of rotation.
For use in double screw extruders the gear arrangement has two driven shafts, wherein only the first driven shaft can be driven by the two intermediate gears and the distributor gear, but the second driven shaft can be driven directly by the drive shaft, optionally with the intermediate connection of a reduction gear. The gear arrangement can hereby also be used for counter—current extrusion as well as for parallel extrusion.
An advantage of the high-performance, but also very simply designed, gear arrangement consists furthermore in that the gear arrangement housing
Akin Gump Strauss Hauer & Feld L.L.P.
Herrmann Allan D.
P.I.V. Antrieb Werner Reimers GmbH & Co. KG
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