Internal Clamping Nut for Axially Compact Gearbox
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Solution Overview
Problem
Conventional gearbox designs are bulky, leading to increased size and weight, with issues such as external clamping nuts adding to axial length, multiple lubricant leak paths, and potential damage during disassembly due to staking operations, which complicates manufacturing and reduces robustness.
Innovation Solution
An axially compact gearbox design featuring a pinion gear with an internal axial bore and a tubular gear stem, where the clamping nut is internally threaded, reducing axial length and eliminating external leak paths, and using bearings between the gear stem and housing to support the pinion and output members, enhancing robustness and manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clamping nut is positioned outside the housing to retain the output member and gear, then the assembly is secure, but the axial length of the gearbox increases
Solution Approach 1:
The clamping nut is repositioned inside the housing and nests within the existing internal space. The output member extends through the axial bore of the pinion gear, allowing the clamping nut to be positioned internally rather than externally, thus securing the assembly while reducing axial length.
Solution Approach 2:
The design moves the clamping nut from an external axial position to an internal radial position within the housing. By utilizing the internal volume of the housing and the axial bore of the pinion gear, the securing function is achieved in a different spatial dimension, reducing the overall axial footprint.
2Reliability
If the clamping nut is positioned outside the housing, then the assembly is secure, but the number of lubricant leak paths increases
Solution Approach 1:
The clamping nut is extracted from the external position and repositioned inside the housing. This removes the external interface between the clamping nut, gear stem, and output flange that created a leak path, thereby eliminating the harmful lubricant leakage while maintaining the securing function internally.
Solution Approach 2:
The design converts the potential harm of having an external clamping nut (which creates leak paths) into a benefit by positioning it internally. The internal positioning eliminates the external leak path while the clamping nut continues to provide secure retention, turning a harmful configuration into a beneficial one.
3Length of moving object
If the gear stem is shortened and splined along its length to reduce axial length, then the gearbox becomes more compact, but the structural complexity increases
Solution Approach 1:
The gear stem is designed to perform multiple functions: it provides structural support, transmits torque through splines along its length, and enables the compact internal arrangement of components. By making the gear stem multi-functional, the design achieves compactness without proportionally increasing complexity, as the same component handles multiple tasks.
Solution Approach 2:
The gear stem is divided into functionally distinct segments: the splined portion for torque transmission and engagement, the portion extending through the output stem, and the end portion for clamping nut retention. This segmentation allows each portion to be optimized for its specific function while contributing to the overall compact design.
4Reliability
If the clamping nut is staked to the gear stem to prevent loosening, then the connection is secure, but the risk of damage during disassembly increases
Solution Approach 1:
The design accepts that the clamping nut may need to be replaced rather than permanently attached. By using a standard threaded connection without staking, the clamping nut can be easily removed and replaced if needed, avoiding the damage risk associated with staking while maintaining sufficient connection security for the application.
Solution Approach 2:
Instead of making the connection permanent through staking (which makes disassembly difficult and damaging), the design uses a reversible threaded connection. This inverts the approach from permanent attachment to temporary, easily removable attachment, reducing damage risk while maintaining connection security during operation.
Data Source
AI summary
A gearbox transmits rotational movement from a driving member to a driven member. The gearbox includes a pinion gear disposed inside a housing. The gear defines an axial bore and rotates in response to rotation of the driving member. An output member extends through the axial bore and engages therewith such that the output member rotates in response to rotation of the gear. The output member extends to a position outside the housing to rotate the driven member. A clamping nut is threadably coupled to the output member and abuts the gear thereby retaining the output member and the gear together. A bearing is disposed radially between the gear and the housing. The bearing rotatably supports the gear and the output member.