Linear Actuator Brake Mechanism for Position Retention
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Solution Overview
Problem
Existing linear actuators face challenges with self-locking spindles being energy-consuming and space-intensive, while non-self-locking spindles lack retention of position when power is interrupted, and traditional brakes are costly, complex, or difficult to calibrate due to ambiguous friction and heat generation.
Innovation Solution
A brake mechanism featuring a cylindrical element with a threaded pin and a nut positioned around it, where a spring compresses the nut against a contact surface to generate brake power, dependent on spring power and friction, allowing for adjustable brake power without direct contact with the worm wheel, thus avoiding heat and noise issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-locking spindle with low thread pitch is used, then position retention when power is interrupted is improved, but energy consumption increases and adjustment speed decreases
Solution Approach 1:
The brake mechanism dynamically engages and disengages based on operational needs. During normal operation, the brake is disengaged allowing free spindle rotation and low energy consumption. When position retention is required (power interruption), the brake automatically engages through spring force, providing self-locking capability without continuous energy input.
Solution Approach 2:
The braking function is extracted as a separate, optional mechanism rather than being inherent to the spindle thread design. This allows the spindle to maintain optimal low thread pitch for speed and efficiency while the additive brake mechanism provides self-locking capability only when needed, eliminating the trade-off between thread pitch and energy consumption.
2Reliability
If a traditional solenoid brake or coil spring parking brake is used, then position retention is improved, but device complexity and space requirements increase
Solution Approach 1:
The brake mechanism is integrated with the existing spindle assembly components. The brake lever utilizes the spindle housing and existing structural elements, merging the braking function with the spindle assembly rather than adding a completely separate parking brake mechanism. This reduces overall device complexity while maintaining position retention capability.
Solution Approach 2:
The brake mechanism is self-actuating through spring force and gravitational action on the brake lever. When power is interrupted, the spring automatically engages the brake without requiring external control systems, solenoids, or complex actuation mechanisms. The system serves itself by using its own structural components (brake lever, spring, contact surface) to achieve position retention.
3Reliability
If a traditional solenoid brake or complex parking brake is used, then position retention is improved, but manufacturing cost increases
Solution Approach 1:
The brake mechanism uses simple, inexpensive components that can be manufactured at low cost: a spring, a brake lever, a contact surface, and a cylindrical element with threaded pin. These basic mechanical elements are far cheaper than solenoid brakes or complex clutch-spring mechanisms, while still providing reliable position retention functionality.
Solution Approach 2:
The brake function is segmented into simple, discrete components (spring, brake lever, contact surface) rather than requiring integrated complex mechanisms. This segmentation allows each component to be manufactured independently using simple processes and assembled easily, reducing overall manufacturing cost while maintaining functionality.
4Reliability
If a spring brake with direct contact on worm wheel is used, then braking function is achieved, but heat generation causes dimensional instability and noise
Solution Approach 1:
The cylindrical element with external threads acts as an intermediary between the spring brake and the worm wheel. The brake contacts this intermediate element rather than the worm wheel directly, preventing heat transfer to the worm wheel and avoiding dimensional instability and noise caused by thermal expansion of the precision gear component.
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 brake mechanism provides effective and adjustable self-locking functionality with reduced energy consumption and space requirements, while being simpler and less expensive, maintaining position retention without heat-induced dimensional instability or noise.
Implementation Method 1
The brake power is generated by the nut rubbing against the contact surface with its one side. The exerted brake power thus depends on the spring power. More spring power results in more brake power. The brake power further depends on the friction between the nut and the contact surface.
Implementation Method 2
a spring compresses the nut against a contact surface to generate brake power, dependent on spring power and friction
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Linear actuator comprising an electric motor (2) which through a transmission (3) drives a spindle unit, where the spindle unit comprises at least one spindle (4) with a spindle nut (5), where the spindle (4) is equipped with a bearing (8). In connection with the spindle unit there is an adjustment element (6), typically tubular. In order to retain the adjustment element (6) in a given position when the power supply for the electric motor (2) is interrupted, a brake (11) comprising a spring (15) and a cylindrical element (12) is provided. The cylindrical element (12) has a threaded pin (12a) on which a nut (13) is arranged, and where the spring (15) is positioned around the cylindrical element (12) between one side of the nut (12) and a stop (14) on the cylindrical element (12) such that the spring (15) presses the nut (13) with its other side against a contact surface (16). The brake power is thus generated by the nut rubbing against the contact surface with its one side. It is thus an alternative brake construction having a simple construction and where the spring only exerts a compressive force. The brake power can be adjusted to the spring power, and the friction between the nut and the contact surface and finally the thread pitch on the nut.