Drive Unit Overload Protection via Shear Pin Breaking Point

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Solution Overview

Problem

Existing drive units for ring gears lack optimal overload protection, leading to potential tooth fracture and significant capital losses when torque flows from the ring gear to the pinion during transmission blockages.

Innovation Solution

A drive unit design with mechanical overload protection arranged between the gear and pinion, featuring a predetermined breaking point in the output shaft, which ensures that the overload protection is triggered before tooth fracture occurs, protecting the teeth from excessive torque and allowing for precise and cost-effective implementation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If overload protection is arranged between the engine and transmission, then the torque flow from the drive motor is limited, but the teeth of the gear rim are not protected against tooth force fracture when torque flows from the gear rim to the pinion

Engineering Contradiction:

Improveoverload protectionVSAvoidtooth strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent inverts the conventional arrangement of overload protection by placing it between the transmission and pinion rather than between the engine and transmission. This reversal allows the overload protection to effectively protect the gear rim teeth from tooth force fracture when torque flows from the gear rim to the pinion during transmission blockages, while still limiting torque flow from the drive motor.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The overload protection device acts as an intermediary element positioned between the transmission and pinion. It mediates the torque flow by providing a predetermined breaking point that fails at a defined torque threshold, thereby protecting the expensive gear rim teeth from excessive forces while allowing normal operation below this threshold.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If transmission components are dimensioned larger to prevent tooth fracture, then the system becomes more robust, but the cost and complexity increase

Engineering Contradiction:

Improvetooth strengthVSAvoidtransmission component dimensions

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent applies the principle of using a cheaper, sacrificial component (the overload protection device with predetermined breaking point) that is designed to fail before the expensive gear rim teeth. This disposable-like approach protects the valuable transmission components from damage while keeping the overall system cost-effective.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The overload protection device provides beforehand cushioning by being positioned to absorb or fail first under excessive torque conditions. This prior protection mechanism prevents tooth fracture before it can occur, allowing the transmission components to be dimensioned optimally without excessive oversizing for safety margins.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Manufacturing precision

If quality assurance monitoring is increased for transmission components, then the manufacturing precision improves, but the assembly process becomes more complex and time-consuming

Engineering Contradiction:

Improvequality assurance monitoringVSAvoidassembly process

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent extracts the quality assurance burden from the transmission components by introducing a separate overload protection device. This extraction allows the transmission components to be manufactured with standard quality controls while the overload protection device provides the additional safety layer, simplifying the overall manufacturing and assembly process.

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution provides reliable protection against tooth fracture, reduces capital losses, and allows for smaller transmission component dimensions, as well as simplified quality assurance and assembly processes, while maintaining the system's integrity and oil-tightness.

Implementation Method 1

the overload protection is designed as a predetermined breaking point. Such a predetermined breaking point enables extremely cost-effective overload protection. The predetermined breaking point is indeed destroyed when the overload protection is triggered.

Methodology Applied

Scientific EffectFracture Mechanics: Fracture Mechanics

Data Source

PatentEP2280191B2Drive unit with overload protection for driving a crown gear, set comprising a plurality of such drive units and device comprising such a drive unit

Publication Date: 2017.03.15 LIEBHERR COMPONENTS BIBERACH GMBH

AI summary

The drive unit has a motor (3) i.e. hydraulic motor, a transmission (4) and a drive shaft on which a pinion (6) is arranged for driving the gear ring. A mechanical overload protection unit e.g. slip clutch or disengaging clutch, is arranged between the transmission and the pinion. The overload protection unit is designed as a predetermined breaking point (20) of an output shaft. A common housing (10) i.e. oil-tight housing, is provided for the transmission, the overload protection unit and a main bearing (9) of the output shaft. The predetermined breaking point is realized by shear pins. Independent claims are also included for the following: (1) a set of drive units for common drive of a gear ring (2) a device comprising a gear ring.