Rotary Hook Noise Reduction via Axial Basket Pressure
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Solution Overview
Problem
Current rotary hooks in lockstitch sewing machines generate significant noise due to play between the rib of the basket and the race of the hook body, which is exacerbated by vibrations and resonance, and existing solutions fail to effectively eliminate this noise without increasing production costs.
Innovation Solution
Applying an axial pressure to the basket to stabilize it within the hook body, either through magnetic means or by creating a vacuum or air jet effect, ensuring the rib leans against a plane surface of the race, thereby reducing vibrations and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If magnetic elements are used to constrain the basket to the hook body, then the structure is simplified and production costs are reduced, but the noise reduction effect is insufficient compared to the sliding coupling type
Solution Approach 1:
The patent replaces the traditional mechanical sliding coupling system with a magnetic field-based constraint system. Magnetic elements are embedded in the hook body and interact with ferromagnetic material in the basket, eliminating the need for physical contact and sliding interfaces. This substitution reduces both manufacturing complexity and noise generation while maintaining effective constraint of the basket.
Solution Approach 2:
The magnetic field acts as an intermediary between the hook body and the basket, providing a non-contact force that constrains the basket's position and motion. This intermediary field allows for precise control of the basket without direct mechanical contact, thereby eliminating sliding friction and associated noise while simplifying the overall structure.
2Object-generated harmful factors
If the rib of the basket and the race of the hook body are made with tighter tolerances to reduce play, then noise is reduced, but production cost increases
Solution Approach 1:
The patent eliminates the mechanical sliding interface between the rib and race by replacing it with a magnetic constraint system. This substitution removes the source of noise generated by play and sliding friction, while avoiding the need for tight tolerances on these components, thereby maintaining low production costs.
Solution Approach 2:
The patent changes the fundamental parameter of constraint from mechanical contact (requiring tight tolerances) to magnetic field interaction. By using magnetic force to constrain the basket, the system achieves precise positioning without requiring tight dimensional tolerances on the rib and race, thus reducing manufacturing costs while eliminating noise.
3Stability of the object's composition
If a C-shaped race with two plane surfaces is used to constrain the basket, then axial and radial translation is prevented, but play exists between the rib and race causing noise
Solution Approach 1:
The patent replaces the C-shaped race mechanical constraint system with a magnetic field-based constraint system. The magnetic elements in the hook body interact with ferromagnetic material in the basket to provide axial and radial constraint without physical contact, eliminating the play and sliding friction that cause noise while maintaining constraint stability.
Solution Approach 2:
The magnetic field serves as an intermediary that provides continuous and precise constraint forces in both axial and radial directions. This intermediary field eliminates the gaps and play inherent in mechanical race-rib interfaces, providing stable constraint without the sliding friction and impact noise associated with mechanical contact.
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 reduces noise levels to below 45 dB, even when the noise would otherwise exceed 68 dB, while being compatible with existing sewing machines and not requiring modifications to stitching members or thread passage areas.
Implementation Method 1
the means suitable to apply said axial pressure on the basket comprise at least one magnetic element
Implementation Method 2
the rib of the basket is made to 'float' in the race of the hook body by means of a cushion of air
Implementation Method 3
convey onto the basket or onto the bobbin case contained therein a jet of compressed air
Data Source
Figure 1
Figure 2~5
Figure 6~9
AI summary
A rotary hook (1) of a lockstitch sewing machine - composed of at least one hook body (2) comprising a cylindrical cavity (11) and a basket (6) free to rotate in the cylindrical cavity (11), to which it is constrained by a rib (14), provided on the outer surface of the basket (6), which engages in a C-shaped race (10), provided in the inner wall of the cylindrical cavity (11) of the hook body (2) and delimited by two plane surfaces parallel to each other and by a cylindrical surface perpendicular to the plane ones, suitable to prevent axial and radial translation of the basket (6) in the cylindrical cavity (11) - further comprises means (23; 25; 27; 29; 32; 35; 36; 37; 39; 31; 42; 43, 44; 16; 21; 121; 221; 20; 200) suitable to apply to the basket (6) an axial pressure to cause the rib (14) of the basket (6) to lean against one of the plane surfaces which delimit the race (10) present in the cylindrical cavity (11) of the hook body (2). Some of the above mentioned means (42; 43; 121; 221; 31; 21; 20; 200) arc carried by the lockstitch sewing machine to which the above mentioned rotary hook (1) belongs.