Pick Assembly Interference Fit Prevents Shaft Rotation
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Solution Overview
Problem
Existing pick assemblies for pavement milling and mining experience short working life and uneven wear, particularly in fine milling applications, due to rotational movement within holders, leading to inefficient processing and frequent tool replacement.
Innovation Solution
A pick assembly design featuring a holder body, strike body with a super-hard polycrystalline diamond (PCD) tip, and a base body with a spring sleeve and O-ring or quad-ring interference member, preventing rotational movement of the shaft within the base bore through frictional interference, ensuring secure attachment and extended tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pick is allowed to rotate within the holder during impact, then wear occurs evenly around the pick and the impact tip can be angled to cause rotation, but the working life is reduced due to frequent tool replacement
Solution Approach 1:
The patent inverts the conventional approach by preventing rotation of the pick within the holder instead of allowing it. The interference member creates a non-rotating connection, which surprisingly extends working life by maintaining consistent groove profiles and reducing wear that would otherwise occur from rotational movement.
Solution Approach 2:
The patent changes the rotational parameter from free rotation to constrained non-rotation by introducing the interference member with specific dimensional tolerances. This parameter change from rotational freedom to rotational constraint is what extends the working life while maintaining processing effectiveness.
2Reliability
If a non-rotating connection is implemented using interference fit, then rotation is prevented and working life is extended, but the combined radial margin of interference must be precisely controlled at 10 to 200 microns
Solution Approach 1:
The patent specifies a precise parameter range for the radial margin of interference (10 to 200 microns) to achieve the optimal balance between preventing rotation and allowing for manufacturing tolerances. This parameter control enables non-rotational attachment while maintaining feasibility in manufacturing.
Solution Approach 2:
The interference member is designed to be compressible, allowing it to dynamically adjust to manufacturing variations while maintaining the non-rotating connection. The compressibility provides a buffer that accommodates dimensional variations without requiring extremely tight tolerances on all components.
3Ease of manufacture
If the interference member is made compressible to allow assembly, then the pick can be press fit into the holder, but the interference member must be compressed sufficiently to prevent free rotation
Solution Approach 1:
The interference member is designed with compressibility, allowing it to be dynamically compressed during assembly to facilitate press fitting, and then maintain its compressed state during operation to prevent rotation. This dynamic property enables both ease of assembly and reliable rotation prevention.
Solution Approach 2:
The compressible interference member acts as a cushioning element that absorbs the stresses of assembly and operation. It is compressed beforehand during assembly to allow the pick to be press fit, and this pre-compression helps maintain the non-rotating connection during use while accommodating thermal and mechanical variations.
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 significantly extends the working life of pick assemblies by preventing rotation and reducing wear, maintaining consistent groove profiles and surface roughness, and reducing the need for frequent tool replacements, while enhancing the processing efficiency and consistency of pavement texturing and mining operations.
Implementation Method 1
frictional interference between the shaft, interference assembly and base bore preventing rotation of the shaft within the base bore in use
Implementation Method 2
A protective spring sleeve may be disposed around the shank both for protection and to allow the high impact resistant pick to be press fit into a holder while still allowing the pick to rotate
Data Source
Figure 1~2B
Figure 2C~2D
Figure 3
AI summary
A pick assembly comprising a holder body, a strike body, a base body attachable to a drive mechanism, and an interference assembly comprising at least one interference member. The holder body comprises a head portion and a shaft depending from the head portion. The strike body comprises a super-hard strike tip. The head portion and the strike body are cooperatively configured such that the strike body can be attached to the head portion, the strike tip being exposed for striking a body to be degraded when in use. The base body comprises a base bore. The base bore, shaft and interference assembly are cooperatively configured such that the shaft can be secured within the base bore, the interference member disposed between the shaft and the bore. Frictional interference between the shaft, interference assembly and base bore is sufficient to prevent rotation of the shaft within the base bore in use.