Blind Stitch Sewing Machine Thread Cutter Mechanism
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Solution Overview
Problem
Existing two-thread chainstitch blindstitch sewing machines are unsuitable for vehicle seat covers due to the seam's tendency to dissolve if the thread breaks, and there is a lack of effective thread cutters for two-thread lockstitch blindstitch sewing machines, which are necessary for controlled thread cutting.
Innovation Solution
A two-thread lockstitch blindstitch sewing machine equipped with a thread cutter that includes a thread catcher to grip and cut both the needle and bobbin threads, synchronized with the machine's movement to ensure safe and efficient thread trimming, allowing for controlled thread cutting without stopping the sewing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a thread cutter is added to a two-thread lockstitch blindstitch sewing machine, then controlled thread cutting is enabled, but the device complexity increases
Solution Approach 1:
The thread cutter is integrated into the existing sewing machine structure by nesting it within the throat plate assembly. The cutting device is positioned in the throat plate opening, and the thread catcher is mounted on the needle bar, utilizing existing structural spaces and components rather than adding separate external mechanisms.
Solution Approach 2:
The thread cutting function is merged with the existing threading and stitch formation mechanisms. The thread catcher utilizes the needle bar movement, and the cutting device works in coordination with the gripper and throat plate structures already present in the machine, combining multiple functions into existing components.
2Reliability
If the thread catcher moves synchronously with the gripper, then collision avoidance is ensured, but the control system complexity increases
Solution Approach 1:
The thread catcher executes periodic movement synchronized with the gripper's rotational cycle. The cam mechanism converts the continuous rotational motion into periodic reciprocating motion of the thread catcher, ensuring it moves in and out of the gripper space at the correct intervals without requiring complex electronic control.
Solution Approach 2:
A cam mechanism serves as an intermediary between the gripper's rotational motion and the thread catcher's linear reciprocating motion. The cam profile is designed to coordinate the thread catcher's movement with the gripper's position, using mechanical geometry rather than complex control systems to ensure synchronized operation and collision avoidance.
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
The present invention relates to a blind hem sewing machine, namely a two-thread double lockstitch blind hem sewing machine (1), • which is configured to produce a blind hem stitch that joins together fabrics made of at least two materials, a top material and at least one bottom material, in such a way that the seam is not visible on the top side of the top material, • with a drive motor (7) that oscillates a needle lever (25) about a needle lever axis (26) to which a curved needle (10) is attached, through which the needle thread extends during operation of the blind hem sewing machine, • with a double lockstitch hook (31) that rotates twice with each complete needle stroke from the forward and return travel of the needle lever (25) and which supports a bobbin case (36) in which a supply of bobbin thread is received, preferably wound onto a thread spool (33), • with a fabric bender (12),which intermittently and synchronously with the needle movement lifts the fabric towards the needle lever axis (26), the depth of the needle penetration of the curved needle (10) into the thickness of the upper material being adjustable by adjusting the upper dead position of the fabric flexor (12), • with a fabric feed device (45) which is configured to transport the fabric forward or backward by a selectable stitch length in the seam direction between two stitches, • with a thread lever (75) which specifies the required length of needle thread necessary for each revolution of a needle thread loop around the bobbin case (36), and which retracts this specified thread length for thread tension after each revolution of the needle thread loop, • with a thread tension device (49) for the needle thread, • with a thread tension device (107) for the bobbin thread, and • with a needle plate (28) which has a top and a bottom surface.wherein the material to be sewn and the fabric bender (12) are located essentially on the underside of the needle plate (28), while the gripper (31) and the curved needle (10) are located on the top side of the needle plate (28), wherein it is characterized in that a thread cutter (61) is provided which has a thread catcher (63) which is capable and configured to grasp both the needle thread and the bobbin thread and to feed them to a cutting device (67).