Elevator Safety Brake Wedge Coating for Overspeed Rail Grip
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Solution Overview
Problem
Existing safety brake systems for elevator systems face challenges in effectively stopping an elevator car from descending in case of an overspeed condition, especially when the tension member breaks, due to insufficient frictional engagement with the guide rail.
Innovation Solution
A braking mechanism featuring a wedge with a frictional surface coated with polycrystalline blocky diamond material, applied via vacuum brazing with a nickel chromium alloy, providing a high friction coefficient and durable engagement with the guide rail to arrest the elevator car's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional friction materials are used in the safety brake wedge, then the braking mechanism can engage with the guide rail, but the frictional engagement is insufficient to reliably stop the elevator car in overspeed conditions
Solution Approach 1:
The patent applies a coating of polycrystalline blocky diamond material onto the friction surface of the wedge. This composite material combines the metallic substrate with diamond particles, creating a surface with superior friction characteristics and wear resistance, enabling reliable engagement with the guide rail under extreme conditions
Solution Approach 2:
The patent changes the physical and chemical parameters of the friction surface by applying a diamond coating with specific properties (40/50 grit size, thickness greater than 450 microns, diamond coverage greater than 50%). These parameter changes transform the friction surface into one capable of withstanding thermal cycling and providing consistent high-friction engagement
2Duration of action of moving object
If the friction surface undergoes repeated thermal cycling during operation, then the braking mechanism can function during normal operation, but the friction material wears down and loses effectiveness
Solution Approach 1:
The diamond-coated friction surface creates a composite structure where the diamond particles are embedded in a metallic matrix. This composite material exhibits exceptional wear resistance while maintaining friction properties, allowing the braking mechanism to endure repeated thermal cycling and extended service life without significant material loss
Solution Approach 2:
The patent applies a thick layer of diamond material (greater than 450 microns) that is designed to be consumable. Even as the diamond coating wears down during extended service, the thickness ensures the friction surface maintains effectiveness throughout the intended service life of the braking mechanism
3Strength
If the friction surface is made from hard materials to resist wear, then the durability improves, but the coefficient of friction decreases reducing braking effectiveness
Solution Approach 1:
The patent creates a composite friction surface combining diamond particles (for wear resistance) with a metallic binder matrix (for friction). The diamond particles provide hardness and wear resistance, while the metallic matrix maintains adequate coefficient of friction through its inherent friction properties and ability to conform to the guide rail surface
Solution Approach 2:
The diamond coating is applied specifically to the friction surface of the wedge where engagement with the guide rail occurs. This localized application ensures that the hard, wear-resistant diamond material is present only where needed for frictional engagement, while the rest of the wedge structure maintains its original properties
4Reliability
If the diamond coating is applied with high coverage to maximize friction, then the braking effectiveness improves, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent specifies optimal parameters for the diamond coating including 40/50 grit size, thickness greater than 450 microns, and diamond coverage greater than 50% but less than or equal to 76%. These parameter specifications balance braking effectiveness with manufacturability, providing sufficient friction and wear resistance while avoiding excessive manufacturing complexity
Solution Approach 2:
The patent applies the diamond coating during the manufacturing process using vacuum brazing technology, preventing future wear and performance degradation before the braking mechanism enters service. This preliminary protective action eliminates the need for maintenance or replacement during the service life of the braking mechanism
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 ensures reliable and efficient stopping of the elevator car by providing exceptional frictional engagement, minimizing wear, and being resistant to corrosion and thermal cycling, thus addressing the limitations of current safety brake systems.
Implementation Method 1
The friction coating provides a high friction coefficient and durable engagement with the guide rail to arrest the elevator car's movement
Implementation Method 2
The friction coating is secured to the frictional surface via vacuum brazing with a nickel chromium alloy brazing paste
Implementation Method 3
The wedge is movable toward the guide rail and into engagement with the guide rail to slow or stop travel of the elevator car
Data Source
Figure 1
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AI summary
A braking mechanism (24) includes a wedge (42) selectably engageable with a guide rail (20), and a frictional surface (48) defined on the wedge configured for selective engagement with the guide rail in an overspeed condition. The frictional surface includes a friction coating (52) of polycrystalline blocky diamond material. An elevator system (10) includes an elevator car (16), a guide rail (20) along which the elevator car travels, and a braking mechanism (24) located at the elevator car and selectably engageable with the guide rail to slow or stop travel of the elevator car along the guide rail. The braking mechanism includes a wedge (42) having a frictional surface (48) configured for selective engagement with the guide rail in an overspeed condition. The frictional surface includes a friction coating (52) of polycrystalline blocky diamond material.