Safety Linear Actuator Assembly Retaining Ring Design
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Solution Overview
Problem
Conventional linear actuators face safety hazards due to stress concentration and potential breakage of the lead screw under excessive torsional loads and impacts, leading to accidental displacement and safety risks.
Innovation Solution
A safety linear actuator assembly is designed with a resilient metal retaining ring mounted in a locating groove around the stem of the lead screw, which prevents axial displacement and ensures the lead screw remains within the hollow holder frame, even if the stem breaks, enhancing operational safety and anti-pull strength without occupying external space or requiring mold changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pin is used to hold the cushion ring between two thrust bearings in bearing holders inside the hollow holder frame, then the lead screw is prevented from axial displacement during normal operation, but under excessive torsional load and impact, stress concentration occurs at the pin area causing the lead screw to break and escape, threatening operational safety
Solution Approach 1:
The retaining function is segmented from the pin structure and implemented as a separate resilient metal retaining ring mounted in a locating groove around the stem. This segmentation allows the retaining function to operate independently without creating stress concentration points, as the retaining ring distributes loads evenly around the stem circumference rather than concentrating stress at a single pin location.
Solution Approach 2:
The resilient metal retaining ring provides beforehand cushioning by being pre-installed in the locating groove to prevent lead screw escape before failure can occur. The resilient nature of the ring allows it to absorb impact loads and torsional stresses that would otherwise cause the lead screw to break through the bearing holders and escape from the hollow holder frame.
2Force
If the lead screw is designed to withstand high torsional loads, then the actuator can handle heavy loads, but the lead screw becomes more susceptible to breaking under impact and excessive torsion due to stress concentration
Solution Approach 1:
The resilient metal retaining ring provides beforehand cushioning by being pre-installed in the locating groove to prevent lead screw escape before failure can occur. The resilient nature of the ring allows it to absorb impact loads and torsional stresses that would otherwise cause the lead screw to break through the bearing holders and escape from the hollow holder frame.
Solution Approach 2:
The retaining ring acts as an intermediary safety component between the lead screw and the hollow holder frame. It provides a secondary retention mechanism that mediates the interaction between the lead screw and the housing, preventing direct contact and potential escape even when the primary pin retention fails under excessive loads.
3Reliability
If a brake is added to lock the actuator when stopped, then sudden falling of the retractable tube is prevented, but the device complexity increases
Solution Approach 1:
The safety retention function is extracted from the complex brake system and implemented as a simple resilient metal retaining ring mounted in a locating groove. This extraction provides the essential safety function of preventing lead screw escape without requiring the addition of a brake mechanism, thereby maintaining device simplicity while ensuring operational safety.
Data Source
AI summary
A safety linear actuator assembly includes an actuator including a hollow holder frame, a gear set mounted in hollow holder frame, a driver for rotating gear set and a transmission mechanism that includes a lead screw having a stem located at one end and coupled to gear set and a pin mounted in a pin hole at stem, two bearing holders mounted on stem at two sides of the pin and two thrust bearings mounted on the stem and respectively accommodated in the bearing holders, and a retaining ring mounted in a locating groove at the stem. If the stem breaks accidentally due to that the lead screw bears excessive torsion and impact, the retaining ring will be forced against the respective bearing holders and the hollow holder frame, stopping the lead screw from escaping out of the hollow holder frame and assuring a high level of operational safety.