Friction Brake Actuator for Fast Height Adjustment with Self-Locking
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Solution Overview
Problem
Conventional electromotive height adjustment actuators with self-locking worm gears cannot achieve the required speed and self-locking simultaneously, as reducing the gear ratio eliminates the ability to hold a position without power due to weight forces.
Innovation Solution
Incorporating a sleeve-shaped friction brake with a radial opening on the motor shaft, providing additional frictional torque through static friction when the motor is de-energized, and using a heat-resistant plastic or elastic body design to ensure effective self-locking without significant operational friction loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gear ratio is reduced to increase adjustment speed, then the speed of height adjustment is improved, but the self-locking capability is lost
Solution Approach 1:
A friction brake is introduced as an intermediary component between the motor shaft and the environment. This friction brake acts as a mediator that provides the necessary self-locking function without requiring a high gear ratio, thus enabling both fast adjustment speed and reliable position holding capability.
Solution Approach 2:
The traditional self-locking mechanism based on worm gear geometry is replaced by a friction-based braking system. This substitution allows the use of a lower gear ratio for faster speed while the friction brake independently provides the self-locking function through friction forces.
2Reliability
If a friction brake is added to provide self-locking, then the self-locking capability is improved, but the device complexity increases
Solution Approach 1:
The friction brake is integrated with the motor shaft assembly, combining the braking function with the existing motor structure. This merging approach adds the self-locking capability while minimizing the increase in overall device complexity by reusing the motor shaft as the brake drum.
Solution Approach 2:
The motor shaft serves dual functions: as the rotational drive element during operation and as the brake drum for the friction brake. This multi-functionality reduces the need for separate components and simplifies the overall actuator structure.
3Reliability
If the friction brake is tightly fitted to increase braking torque, then the self-locking capability is improved, but the friction loss during operation increases
Solution Approach 1:
The friction brake is designed with adjustable friction characteristics that can dynamically adapt between operation and braking modes. During motor operation, the friction is minimized to reduce energy loss, while during braking/standstill, the static friction provides strong self-locking capability.
Solution Approach 2:
The friction characteristics are optimized by changing parameters such as the friction material properties, contact pressure, and contact area. These parameter adjustments enable the friction brake to provide sufficient braking torque while minimizing friction losses during motor operation.
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 enables faster height adjustment while maintaining the ability to hold positions securely without power, with minimal friction loss during operation and enhanced braking torque at standstill, ensuring the object remains stationary due to increased static friction.
Implementation Method 1
the friction brake provides an additional frictional torque to prevent the motor shaft from running off... At standstill, the total friction is greater due to the static friction of the friction brake
Implementation Method 2
the friction brake provides an additional frictional torque... the braking torque at standstill is significantly greater than with the sliding friction during operation of the motor
Data Source
AI summary
An electromotive actuator to adjust a height includes an electric motor with a motor shaft, a helical gear assembly operatively connected to the motor shaft, a sleeve-shaped friction brake to act on the motor shaft, and a housing surrounding the electric motor or the helical gear assembly and including a seat of the friction brake. The friction brake includes an opening extending in a radial direction relative to a longitudinal axis of the motor shaft such that the friction brake is attachable to the motor shaft perpendicular to the longitudinal axis.