Ball Screw Seal Guide Part Phase Alignment
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Solution Overview
Problem
Conventional ball screw device seals face challenges with precise mounting and phase alignment, leading to potential damage and lubrication leakage due to non-circular inner peripheral shapes and reliance on operator precision.
Innovation Solution
The introduction of a guide part on the seal member, which is either projecting or recessed, helps align the seal member with the threaded shaft's rolling groove and land parts, facilitating accurate phase matching and reducing frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tightening margin of the seal member with respect to the threaded shaft is formed to be large, then it is possible to absorb an error in shape accuracy and a mounting error and restrain generation of gap, but contact pressure of the seal member to the threaded shaft becomes high at the same time
Solution Approach 1:
The seal member is divided into multiple sealing lips (first sealing lip and second sealing lip) with different functions. The first sealing lip contacts the rolling groove portion while the second sealing lip contacts the land portion, allowing each lip to be optimized for its specific contact region and distribute the sealing function across multiple contact points rather than relying on a single high-pressure contact zone
Solution Approach 2:
Different portions of the seal member are given different properties: the first sealing lip is designed with specific curvature radius to match the rolling groove curvature, while the second sealing lip is designed to match the land portion geometry. This local optimization allows each region to provide appropriate sealing pressure without requiring uniformly high contact pressure across the entire seal member
2Reliability
If the shape of the inner peripheral surface of the seal member is made into a non-circular shape, then it is possible to improve sealability by conforming to the threaded shaft cross-section, but operations of arranging the seal member in the nut and matching a phase with that of a threaded shaft are extremely time-consuming
Solution Approach 1:
The seal member incorporates asymmetric guide protrusions on its outer periphery that correspond to asymmetric guide grooves in the nut. This asymmetric feature pattern provides unique phase alignment references that guide the operator to the correct mounting position, eliminating the need for complex phase matching operations while maintaining the non-circular inner peripheral shape needed for sealing
Solution Approach 2:
The guide protrusions and guide grooves are pre-formed during manufacturing with fixed geometric relationships to the inner peripheral sealing surface. This preliminary establishment of alignment features ensures that when the seal member is installed, the phase alignment is automatically achieved through the guide features, eliminating time-consuming post-manufacturing adjustment operations
3Reliability
If a non-circular shape of the seal member is used, then it is possible to improve sealability, but mounting error and mounting failure of the seal member happen due to difficulty in ascertaining the non-circular shape
Solution Approach 1:
The guide protrusions and guide grooves provide visual and tactile cues through their geometric form. The asymmetric pattern of these guide features creates a unique 'key-lock' configuration that is easily recognizable during mounting, allowing operators to quickly identify the correct orientation and position without needing to understand complex non-circular geometry, thereby reducing mounting errors
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3D
AI summary
There is provided a seal for a ball screw device, which is able to restrain damage to a seal member and grease leakage. In order to do so, a guide part (50), which has a project or a recessed part in an axis direction of a threaded shaft (10), is provided in an outer peripheral edge part of a seal member (40) provided in a nut (20) of a ball screw device (1), in a portion corresponding to an inner peripheral edge part that is in sliding contact with a rolling groove (11) of the threaded shaft (10) or a land part (12) between the rolling grooves (11, 11).