Track Pin Bushing Retention via Cold Expansion
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Solution Overview
Problem
Current track chain designs face issues with pin and bushing retention, leading to 'walking' of bushings under load, which can cause weld cracking and track pad failure, and result in costly maintenance due to loose pins or bushings falling out of the track chain members.
Innovation Solution
A retention device comprising a fastener with a threaded portion and a tubular spacer is used to secure the track pin and bushing within the track chain member, along with bushing retention shelves in the lugs to prevent axial movement and egress, combined with a hydraulic pressing mechanism for installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring pin bushing is expanded and welded within the bore of a track pad, then the bushing is retained in place, but weld cracking and track pad failure occur due to imperfections and high tensile residual stresses
Solution Approach 1:
The invention extracts the welding process from the bushing installation method, replacing it with a cold expansion process. The bushing is expanded within the bore using a expansion tool, creating a interference fit without welding. This eliminates weld cracking and residual stresses while maintaining reliable bushing retention.
Solution Approach 2:
The invention replaces the thermal welding process with a mechanical expansion process. Instead of welding the bushing to the track pad, the bushing is mechanically expanded within the bore to create a secure interference fit, eliminating the harmful thermal effects of welding.
2Reliability
If the bushing is welded into place, then retention is achieved, but high tensile residual stresses cause weld cracking
Solution Approach 1:
The invention removes the welding process entirely from the bushing installation. The bushing is retained through cold expansion creating an interference fit, which eliminates weld cracking and high tensile residual stresses associated with welding.
Solution Approach 2:
The invention substitutes the thermal welding mechanism with a mechanical expansion mechanism. The bushing is expanded within the bore using a expansion tool, creating retention through interference fit without the harmful thermal effects that cause cracking.
3Ease of operation
If no retention device is used, then the track chain can rotate freely, but the pin or bushing falls out under load
Solution Approach 1:
The invention applies preliminary action by expanding the bushing within the bore before the track chain is installed. This pre-expansion creates an interference fit that prevents the bushing from falling out under load, while still allowing free rotation during operation.
Solution Approach 2:
The invention changes the dimensional parameter of the bushing by expanding it within the bore. This expansion creates an interference fit that provides retention, while the bushing remains free to rotate during normal operation.
4Reliability
If the bushing is pressed fit into place, then retention is achieved, but the bushing walks axially out of the bore under load
Solution Approach 1:
The invention extracts the pressing fit method and replaces it with cold expansion. The bushing is expanded within the bore to create an interference fit, which prevents axial movement while maintaining retention, eliminating the walking problem associated with press fits.
Solution Approach 2:
The invention substitutes the pressing fit mechanism with a cold expansion mechanism. The bushing is expanded within the bore using a expansion tool, creating an interference fit that prevents axial movement while maintaining secure retention.
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 effectively prevents bushing 'walking' and pin egress, enhancing the stability and longevity of track chain assemblies by maintaining proper tension and reducing maintenance costs through secure retention of track pins and bushings.
Implementation Method 1
a tubular spacer defining a thru-hole configured to receive the fastener may also be provided that is configured to abut the bushing or the track pin, being spaced away from bushing or track pin a minimum distance of 10 mm or less
Implementation Method 2
combined with a hydraulic pressing mechanism for installation
Implementation Method 3
A retention device for retaining a track pin or track bushing in the bore of a track chain member is provided according to an embodiment of the present disclosure. The pin retention device comprises a fastener defining a longitudinal axis, a first end and a second end along the longitudinal axis, a head at the first end and a threaded portion at the second end
Data Source
AI summary
A track chain member includes a shoe member, and a first rail member extending from the shoe member. The first rail member includes a first lug defining a first bore defining a first longitudinal axis and including a first bushing retention shelf disposed in the first bore, as well as a second lug including a second bushing retention shelf disposed in the second bore. A third lug extends in a direction opposite that of the first lug and second lug and is disposed axially between the first lug and the second lug.