Segmented Pushrod Shield for Brake Actuator Side Loading
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Solution Overview
Problem
Conventional pushrod dust or stone shields for fluid-operated service brake actuators face challenges with side loading, which compromises their effectiveness and assembly, especially when used with welded clevises, as they lack slits or slices to facilitate fitting over pushrods.
Innovation Solution
A shield configured as an annulus with a radial slit and angular surfaces at the outer end, combined with energy-absorbing lugs and a cover or spring for retention, allows for easier assembly and deformation to absorb lateral pushrod loading, preventing contamination and maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid shield is used with a smooth inner diameter, then the shield provides effective contamination barrier, but the shield cannot accommodate side loading and loses effectiveness
Solution Approach 1:
The shield's inner diameter is segmented into multiple lobes (typically three) that can independently deflect and absorb side loading forces. This segmentation allows the shield to maintain its contamination barrier function while accommodating lateral pushrod movement through the flexible lobe structure.
Solution Approach 2:
The shield transitions from a rigid, fixed-geometry structure to a dynamic, flexible structure with lobes that can deform and adapt to side loading conditions. The flexible material allows the lobes to move and absorb lateral forces while maintaining the seal against contaminants.
2Strength
If a shield without slits is used, then the shield maintains structural integrity, but the shield cannot be assembled over welded clevis pushrods
Solution Approach 1:
The shield incorporates slits that segment the annular structure, allowing it to be expanded and contracted for assembly and disassembly. These slits enable the shield to be fitted over welded clevis pushrods while maintaining overall structural integrity through the flexible lobe design.
Solution Approach 2:
The shield is constructed as a flexible annular element that can deform during assembly. The combination of slits and flexible material allows the shield to be installed over the pushrod assembly and then return to its functional configuration, providing both ease of assembly and structural integrity.
3Reliability
If the shield inner diameter bears the side loading, then the shield provides contamination protection, but the shield and housing structural integrity are compromised
Solution Approach 1:
The flexible lobes act as an intermediary element between the pushrod and the shield's inner diameter. They absorb and dissipate side loading forces through their deformation, preventing these harmful forces from being transmitted to the shield's structural integrity or the housing.
Solution Approach 2:
The shield's flexible lobe structure provides beforehand cushioning by being pre-designed to absorb side loading forces. This cushioning effect protects both the shield and housing from damage before excessive forces can compromise structural integrity.
Data Source
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AI summary
A fluid pressure operable actuator includes a housing (20), with an end wall, and a pushrod (26) projecting through an opening in the end wall for reciprocation upon service pressure application or release. A shield (42), configured as an annulus, is disposed on the pushrod to restrict contamination of an interior chamber of the actuator housing through a gap existing between an edge of the opening and a pushrod outer surface. To facilitate connecting the shield and the pushrod together, the annulus has a slit (60) with an enlarged void (66) at a radially outer end of the slit. This enlarged void engages an outer pushrod surface as the shield and the pushrod are joined.