Replaceable Wear Pad with Embedded Polygonal Nuts
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Solution Overview
Problem
Existing wear pad apparatus for crawler tracks of construction machines face issues with rivet nuts that can rotate under high torque, leading to insufficient pretension between the base plate and wear pad, and deformation under high pretension, resulting in loosening and the need for frequent retightening.
Innovation Solution
A replaceable wear pad apparatus featuring elongated reinforcing elements with polygonal cross-section sockets and nuts embedded in molded wear pad material, along with integral bearing collars and hollow caps, allowing for high pretension without requiring frequent retightening and providing a cost-effective and durable solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rivet nuts are used in the wear pad apparatus, then the production cost is reduced and ease of manufacture is improved, but the nuts can rotate under high torque and deform under high pretension, leading to loosening and requiring frequent retightening
Solution Approach 1:
The patent introduces a preliminary locking mechanism feature on the rivet nut that prevents rotation before the fastening operation begins. The locking feature engages with a corresponding structure in the reinforcing element, ensuring that the nut cannot rotate during torque application, thus maintaining reliability while keeping the rivet nut manufacturing approach
Solution Approach 2:
The patent employs an asymmetric locking feature design where the locking protrusion on the nut does not have a matching feature on the opposing side, preventing the nut from rotating in either direction. This asymmetric engagement ensures the nut remains fixed during high torque application while maintaining the cost-effective rivet nut construction
2Strength
If high pretension is applied to achieve secure fastening, then the connection strength is improved, but the rivet nuts deform and cannot maintain the desired pretension
Solution Approach 1:
The locking mechanism is pre-configured on the rivet nut to engage with the reinforcing element before high pretension is applied. This preliminary engagement prevents the nut from deforming or rotating during the high pretension phase, allowing the full strength benefit of high pretension to be realized while maintaining reliability
3Ease of manufacture
If the wear pad is made replaceable for cost savings, then the manufacturing cost is reduced, but the fastening means may loosen during operation requiring retightening
Solution Approach 1:
The locking feature on the rivet nut is designed to prevent loosening during the wear pad's operational life. By preventing rotation and maintaining pretension throughout the service period, the fastening system eliminates the need for retightening operations, reducing maintenance time while preserving the cost benefits of replaceable wear pads
Data Source
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AI summary
A replaceable wear pad apparatus (12) for a crawler track (10) of a construction machine includes an elongated reinforcing element (34,36) having first and second sides. The reinforcing element includes first and second holes (80,82) disposed therethrough and includes first and second polygonal cross section sockets defined (84,86) therein on the first side of the reinforcing element co-axial with the first and second holes (80,82), respectively, each socket (84,86) including a socket floor (88) and multiple sides (90,92,94,96,98,100). First and second polygonal cross section nuts (104,106) are received in the first and second sockets, each nut having a threaded bore (108) co-axial with one of the holes (80,82). A wear pad (32)is molded from a wear pad material, the reinforcing element (34,36) and the nuts (104,106) being embedded in the molded wear pad material so that the wear pad material holds the nuts (104,106) in place within the sockets (84,86).