Patent Application
20150090167
The present invention relates to a cloth feeding mechanism of a sewing machine, and particularly to a direct drive cloth feeding mechanism of a sewing machine.
In a conventional sewing machine, to meet sewing requirements, processes of sewing forward or sewing in reverse are frequently performed. Such processes are also commonly known as forward stitch and backstitch. The above sewing machine generally uses a single power source for controlling the change of direction of a structure to meet the requirements of forward stitch and backstitch. In a conventional backstitch transmission mechanism, a lever is manually moved to actuate a transmission element, a cloth feeding teeth member is driven by rotation of a transmission shaft, and a fabric is then forwarded or reversed by a rough surface of the cloth feeding teeth member, so as to backstitch the fabric. However, the above operation not only is time consuming, an operator also needs to constantly press the lever. As such, the operator may be further burdened in a way that work efficiency of the operator is lowered to fail in meeting economical considerations.
Therefore, the technique of incorporating connecting rods with an electromagnet is proposed for driving the backstitch transmission mechanism to achieve automatic backstitch. In the above structure, a plurality of connecting rods are coupled with and driven by the electromagnet, and the transmission element is controlled by the connecting rods. Although automatic backstitch is achieved through controlling the connecting rods with the electromagnet, such mechanism for controlling the cloth feeding teeth member to perform forward stitch and backstitch is rather complicated. Further, due to loosening or poor assembly of the connecting rods between the electromagnet and the transmission element, incorrect transmission may be generated. In addition, the above indirect driving mechanism through the connecting rods and the electromagnet is incapable of precisely controlling a rotation angle of the transmission element, such that precise movement of the cloth feeding teeth member may not be controlled precisely neither.
Therefore the primary object of the present invention is to overcome the problem of insufficient transmission precision in a backstitch structure of a conventional sewing machine.
To achieve the above object, a direct drive cloth feeding mechanism of a sewing machine is provided. The direct drive cloth feeding mechanism includes a cloth feeding structure, a vertical driving structure and a direction adjustment structure. The cloth feeding structure includes a swing shaft, and a cloth feeding teeth member pivotally disposed on the swing shaft and driven by the swing shaft to perform a horizontal reciprocal movement. The vertical driving structure includes an eccentric shaft connected to the cloth feeding teeth member and driven by a driving motor to drive the cloth feeding teeth member to perform a vertical reciprocal movement, and an eccentric cam disposed on the eccentric shaft and driven by the eccentric shaft to rotate. The direction adjustment structure includes a stepping motor, and an adjustment portion driven by the stepping motor. The adjustment portion includes a rotating shaft pivotally connected to the stepping motor and driven by the stepping motor to rotate and switch between a first position and a second position, a track portion disposed in the rotating shaft, a sliding block disposed in the track portion, and a linkage rod pivotally connected to the swing shaft and the eccentric cam and having one end connected to the sliding block. The linkage rod is driven by the eccentric cam to perform a first swinging displacement and a second swinging displacement when the rotating shaft is at the first position and the second position respectively, such that the sliding block is driven to slide back-and-forth in the track portion. The cloth feeding teeth member performs a forward feeding process when the linkage rod performs the first swinging displacement, and performs a reverse feeding process when the linkage rod performs the second swinging displacement.
In one embodiment, the eccentric shaft includes a main shaft penetrating through the eccentric cam and driven by the driving motor to rotate, a connecting portion pivotally connected to the cloth feeding teeth member, and an auxiliary shaft eccentrically disposed at one end of the main shaft, connected to the connecting portion and driven by the main shaft to allow the cloth feeding teeth member to perform the vertical reciprocal movement.
Through the stepping motor of the present invention, the rotating shaft of the adjustment portion is directly driven to rotate and switch between the first position and the second position, so as to further change movement of the linkage rod to perform the first swinging displacement and the second swinging displacement. Further, the linkage rod changes the position of the cloth feeding teeth member for performing the horizontal reciprocal movement through different swinging displacement. By incorporating the above horizontal reciprocal movement with the vertical reciprocal movement provided by the eccentric shaft, the cloth feeding teeth member can perform forward and reverse feeding processes. Compared to a cloth feeding mechanism of a conventional sewing machine, in which a plurality of connecting rods are connected to control the rotating shaft, the present invention offers simpler operations. In the present invention, the rotating shaft is directly driven by the stepping motor, so that the rotation angle of the rotating shaft can be precisely controlled to enhance adjustment precision, and the sewing quality of the sewing machine can also be improved.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
Since the stepping motor 31 is capable of precisely controlling the rotation angle of the rotating shaft 321, by adjusting the rotation angle of the rotating shaft 321, the displacement of the sliding block 324 sliding back-and-forth in the track portion 322 may be further adjusted. As the rotation angle of the rotating shaft 321 gets larger, i.e., as the inclined angle of the track portion 322 gets larger, the displacement of the sliding block 324 sliding back-and-forth in the track portion 322 becomes shorter to increase a cloth feeding speed of the cloth feeding teeth member 12. Under a same sewing speed, a stitch length sewn by a sewing needle (not shown) on the cloth becomes smaller. On the contrary, as the rotation angle of the rotating shaft 321 gets smaller, i.e., as the inclined angle of the track portion 322 gets smaller, the displacement of the sliding block 324 sliding back-and-forth in the track portion 322 becomes longer to reduce the cloth feeding speed of the cloth feeding teeth member 12. Under the same sewing speed, the stitch length sewn by the sewing needle of the sewing machine 100 on the cloth becomes larger. Therefore, with the stepping motor 31, the present invention is capable of controlling the stitch length of the sewing machine 100, and offers a simpler operation compared to a conventional sewing machine that can only adjust the stitch length through a button.
The stepping motor 31 of the present invention is further capable of driving the rotating shaft 321 to rotate to a third position A3 that is between the first position A1 and the second position A2. More specifically, the third position A3 is an original point. When the rotating shaft 321 is located at the third position A3, movement of the linkage rod 323 driven by the eccentric cam 22 are counteracted with movement of the linkage rod 323 driven by the sliding block 324 sliding in the track portion 322. As such, the linkage rod 323 does not drive the swing shaft 11 to rotate, in a way that the cloth feeding teeth member 12 remains at a still state. Hence, the stepping motor 31 may freely control the rotating shaft 321 to switch among the first position A1, the second position A2 and the third position A3, so as to control the cloth feeding teeth member 12 to perform the forward, reverse and still feeding processes.
Through the stepping motor 31 of the present invention, the rotating shaft 321 of the adjustment portion 32 is directly driven to rotate and switch between the first position A1 and the second position A2, so as to further change movement of the linkage rod 323 to perform the first swinging displacement and the second swinging displacement. Further, the linkage rod 323 changes the position of the cloth feeding teeth member 12 for performing the horizontal reciprocal movement through different swinging displacement. By incorporating the above horizontal reciprocal movement with the vertical reciprocal movement provided by the eccentric shaft 21, the cloth feeding teeth member 12 can perform forward and reverse feeding processes. Compared to a cloth feeding mechanism of a conventional sewing machine, in which a plurality of connecting rods are connected to control the rotating shaft, the present invention offers simpler operations. In the present invention, the rotating shaft 321 is directly driven by the stepping motor 31, so that the rotation angle of the rotating shaft 321 can be precisely controlled to enhance adjustment precision, and the sewing quality of the sewing machine 100 can also be improved.
