Centrifugal Overspeed Governor with Dual-Stage Spring System
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Solution Overview
Problem
Conventional overspeed governors with centrifugally operated brakes face difficulty in adjusting the detection of electrical and mechanical switching speeds due to the proportional and quadratic increase of centrifugal force with rotational speed, making it challenging to set the trigger points accurately.
Innovation Solution
An overspeed governor design featuring a sheave with an eccentric piece and two centrifugal weights, utilizing a spring system with distinct spring constants for non-linear and discontinuous spring characteristics, allowing for independent adjustment of the trigger points by incorporating a first spring constant up to the electrical switching speed and a second spring constant greater than the first, which increases more strongly at higher deflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single spring constant is used in the centrifugal overspeed governor, then the device structure is simple, but the adjustment of electrical and mechanical switching speeds becomes difficult and imprecise
Solution Approach 1:
The spring system is segmented into multiple springs with different spring constants (first spring constant and second spring constant) that act at different deflection ranges. This segmentation allows independent adjustment of the electrical switching speed (using the first spring constant) and mechanical switching speed (using the second spring constant), resolving the contradiction between structural simplicity and detection precision.
Solution Approach 2:
Different parts of the spring system have different local properties - the first spring has a first spring constant optimized for low-speed operation up to the electrical switching point, while the second spring has a second spring constant optimized for high-speed operation from the electrical switching point. This local differentiation enables precise control of switching speeds while maintaining overall system simplicity.
2Device complexity
If the spring force increases linearly with deflection, then the spring system is simple, but the sensitivity of switching speed detection increases uncontrollably at high speeds
Solution Approach 1:
The spring system transitions from a static single spring constant to a dynamic multi-stage spring constant system. At low deflections (below electrical switching speed), only the first spring with the first spring constant is active. At high deflections (above electrical switching speed), the second spring with the second spring constant engages, changing the overall spring characteristic. This dynamic adaptation prevents uncontrollable sensitivity increase while maintaining simple linear characteristics within each stage.
3Measurement precision
If a non-linear spring characteristic is used to control sensitivity, then switching speed detection becomes possible, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of using a complex non-linear spring, the system segments the spring characteristic into multiple linear segments using separate springs. The first spring provides a first linear characteristic up to the electrical switching speed, and the second spring provides a second linear characteristic from the electrical switching speed. This segmentation achieves the required detection capability while keeping each spring simple and manufacturable.
Solution Approach 2:
The system changes the spring constant parameter at a specific deflection point (electrical switching speed). Below this point, the first spring constant applies; above this point, the second spring constant applies. This parameter change approach achieves variable sensitivity without requiring complex non-linear spring geometry, maintaining manufacturing simplicity while enabling precise switching speed detection.
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
This design enables easy adjustment of the trigger points for both electrical and mechanical switching speeds, providing high spring forces at high speeds and simplifying the detection process, while using commercially available springs and maintaining a compact design.
Implementation Method 1
The eccentric piece is pivotally mounted on the first centrifugal weight and pivotally mounted on the second centrifugal weight, wherein the first and second centrifugal weights pivot the eccentric piece in response to a centrifugal force-induced displacement of the first and second centrifugal weights.
Implementation Method 2
The brake comprises a reset unit with a spring system which pulls the centrifugal weights towards their undeflected position with the spring force provided by the spring system.
Data Source
AI summary
The invention relates to an overspeed governor for a lifting gear comprising a sheave driven by a overspeed governor cable and a brake for braking the sheave, wherein the brake comprises at least one eccentric piece, mounted on the sheave in a pivoting manner, wherein the eccentric piece is mounted on a first centrifugal weight in a pivoting manner and mounted on a second centrifugal weight in a pivoting manner, wherein, in the event of a displacement of the first and second centrifugal weights due to centrifugal force, the first and the second centrifugal weights pivot the eccentric piece, the brake comprising a reset unit having a spring system which pulls the centrifugal weights in the direction of the undeflected position thereof, wherein the spring system has a first spring constant up to a switching speed, the spring system has a second spring constant from the electric switching speed of the sheave and the second spring constant is greater than the first spring constant.