Patent Publication Number: US-10767293-B1

Title: Sewing-thread pre-stress device for a sewing machine

Description:
BACKGROUND 
     Field of the Invention 
     The present invention relates to a related component of a sewing machine, and more particularly to a sewing-thread pre-stress device for a sewing machine. 
     Related Prior Art 
     A sewing machine is usually equipped with a sewing-thread-prestress supply device which provides a suitable pre-stress for the sewing thread so that the sewing thread can maintain proper tension for subsequent sewing operations. The sewing-thread pre-stress device of the sewing machine is shown in  FIG. 11  and comprises: a base  70 , a sponge  81 , an abutting member  82  and a top cover  83 . 
     The base  70  has at least one groove  71 . 
     The sponge  81  is disposed in the groove  71 . 
     The abutting member  82  is disposed on the sponge  81 , so that the sponge  81  is pressed against one surface of the abutting member  82 . 
     The top cover  83  is disposed on the abutting member  82 , and a thread space  84  is formed between the top cover  83  and the abutting member  82  for allowing a sewing thread  90  to be inserted therethrough. One surface of the top cover  83  facing the abutting member  82  is provided with two protruding portions  831  which press against another surface of the abutting member  82  opposite to the surface of the abutting member  82  facing the sponge  81 . 
     Thereby, when the sewing thread  90  is inserted in the thread space  84 , the sponge  81  provides an upward force pushing the abutting member  82  to move toward the top cover  83 , thereby clamping tight the sewing thread  90  inserted in the thread space  84  to provide the sewing thread  90  a proper tension. 
     However, the aforementioned sponge  81  is prone to fatigue and deterioration after being used for a period of time, resulting in failure to provide an appropriate pressing force and further resulting in failing to provide a proper tension. 
     In addition, the protruding portions  831  of the top cover  83  are likely to interfering with the extending of the sewing thread  90 , and there is also a risk of pressing the sewing thread  90 . 
     Furthermore, if the size of the protruding portions  831  of the top cover  83  is too large, the width of the thread space  84  may be too wide, which may result in failure to provide the sewing thread  90  with proper tension. On the other hand, if the size of the protruding portions  831  of the top cover  83  is too small, there is a possibility that the protruding portions  831  recover due to the restoring force of the metal, thereby failing to produce a corresponding effect. 
     In order to overcome the above many defects, a sewing thread pre-stress device for a sewing machine is required. 
     The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
     SUMMARY 
     One objective of the present invention is to provide a sewing-thread pre-stress device for a sewing machine which is capable of providing the sewing thread an appropriate tension. 
     Another objective of the present invention is to extend the life of the product to avoid fatigue of the sewing-thread supply device. 
     To achieve the above objectives, a sewing-thread pre-stress device for a sewing machine in accordance with the present invention comprises: 
     a sewing-thread support including at least one accommodating groove which has a groove bottom; 
     a pre-stress supply member made of an elastic material, provided in the accommodating groove, and having a folding portion disposed at the groove bottom, and two extension portions each having one end connected to two sides of the folding portion; 
     an abutting member disposed on the pre-stress supply member, and the two abutting portions abut against the abutting member; and 
     a top cover disposed on the abutting member and fixed to the sewing-thread support, so that a thread space is defined between the top cover and the abutting member for allowing a sewing thread to be inserted therethrough. 
     As can be seen from the foregoing, each embodiment of the sewing-thread pre-stress device for a sewing machine in accordance with the present invention mainly provides proper elasticity by the pre-stress supply member, since the pre-stress supply member is made of an elastic material and generally V-shaped, the amount of change in the elastic force is relatively small, the sewing thread of different diameters can be inserted into the thread space. When the thicker sewing thread is inserted into the thread space, it does not provide excessive abutting force, so that the sewing thread pressure is moderate, avoiding the problem that the knitted fabric wrinkles if the sewing thread pressure is excessively large or the sewing thread gets knotted if the sewing thread pressure is too small. 
     In addition, the pre-stress supply member is made of an elastic material, which can also effectively prevent the sewing-thread pre-stress supply device from elasticity fatigue. 
     These together with other objects of the invention, along with the various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an assembly perspective view of the present invention; 
         FIG. 2  is an exploded view of a first embodiment of the present invention; 
         FIG. 3A  is another exploded view of the first embodiment of the present invention; 
         FIG. 3B  is another exploded view of the first embodiment of the present invention; 
         FIG. 4  is a cross-sectional view showing the first embodiment of the present invention; 
         FIG. 5  is a cross-sectional view showing another angle of the first embodiment of the present invention; 
         FIG. 6  is an exploded view of a second embodiment of the present invention; 
         FIG. 7  is an exploded view of a third embodiment of the present invention; 
         FIG. 8  is an exploded view of a fourth embodiment of the present invention; 
         FIG. 9  is a cross-sectional view showing a fifth embodiment of the present invention; 
         FIG. 10  is a cross-sectional view of a preferred embodiment of the present invention; and 
         FIG. 11  is a cross-sectional view of a conventional sewing-thread pre-stress device for a sewing machine. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will be clearer from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention. 
     Referring to  FIGS. 1-10 , a sewing-thread pre-stress device for a sewing machine in accordance with the present invention comprises: a sewing-thread support  10 , a pre-stress supply member  20 , an abutting member  30 , and a top cover  40 . 
     The sewing-thread support  10  has at least one accommodating groove  11  which has a groove bottom  12 . Preferably, the sewing-thread support  10  defines a plurality of accommodating grooves  11  along a longitudinal direction X. Each of the accommodating grooves  11  is a rectangular groove, and has a first side  11 A along the longitudinal direction X. A direction perpendicular to the longitudinal direction X is defined as a transverse direction Y. Each of the accommodating grooves  11  has a second side  11 B along the transverse direction Y. 
     In one embodiment, the sewing-thread support  10  is an independent structure and mounted at a predetermined position on the sewing machine. 
     In another embodiment, the sewing-thread support  10  is part of the sewing machine. 
     The pre-stress supply member  20 , which is made of an elastic material, that is, a material that conforms to Hooke&#39;s law, is provided in the accommodating groove  11 , and has a folding portion  21  disposed at the groove bottom  12 , and two extension portions  22  each having one end connected to the two sides of the folding portion  21 . An angle is formed between the two extension portions  22 , so that the pre-stress supply member  20  is substantially V-shaped. Another end of each of the extension portions  22  opposite to the folding portion  21  has an abutting portion  23 . Preferably, the abutting portion  23  extends in a direction perpendicular to the extending direction of the extension portions  22 . 
     In a preferred embodiment, a limiting groove  13  is formed at the groove bottom  12  and located at a central position along the first side  11 A of each of the accommodating grooves  11 . The limiting groove  13  is an elongated groove and extends along the transverse direction Y, and the folding portion  21  is disposed in the limiting groove  13 . 
     Preferably, the abutting portions  23  extend along the transverse direction Y. 
     Preferably, the extending direction of the extension portions  22  has a component of the longitudinal direction X. 
     Preferably, the angle is less than 180 degrees. 
     The abutting member  30  is disposed on the pre-stress supply member  20 , and the two abutting portions  23  abut against the abutting member  30  to enable force to be transmitted between the abutting member  30  and the pre-stress supply member  20 . The abutting member  30  can be a rectangular sheet member. In the preferred embodiment, the abutting member  30  has a first lateral portion  31 , a top portion  32  and a second lateral portion  33  which are connected to one another. The top portion  32  has two opposite edges connected to the first and second lateral portions  31 ,  33  respectively. The first and second lateral portions  31 ,  33  are connected to the top portion  32  at an approximately right angle, so that the abutting member  30  is U-shaped at cross section, and the two abutting portions  23  are abutted against the top portion  32 . 
     The top cover  40  is disposed on the abutting member  30 , fixed to the sewing-thread support  10 , and has a cover portion  41  and a locking portion  42 . The locking portion  42  is fixed to the sewing-thread support  10  to prevent the top cover  40  from moving and tilting. The cover portion  41  is located on another surface of the abutting member  30  opposite to one surface thereof facing the pre-stress supply member  20 . In other words, the cover portion  41  covers the abutting member  30  to define a thread space  50  between the top cover  40  and the abutting member  30 , and the width of the thread space  50  can be controlled by the displacement of the abutting member  30 . The thread space  50  allows the sewing thread L to be inserted therethrough, and the sewing thread L is inserted through the thread space  50  along the transverse direction Y. 
     In a preferred embodiment, the top cover  40  has a limiting portion  43  formed on each of two lateral surfaces  411  of the cover portion  41  adjacent to one end thereof. Each of the limiting portions  43  has two limiting bodies  431  extending along a height direction Z, respectively. A thread hole  51  is formed between the two limiting bodies  431  and communicates with the thread space  50 , and the thread holes  51  are aligned to each other, so that the sewing thread L is restricted to insert in the thread space  50  only through the two thread holes  51  to limit the position of the sewing thread L in the longitudinal direction X, and as a result, the sewing thread L won&#39;t arbitrarily swing and interfere with the extension of the sewing thread  90 , and the risk of pressing the sewing thread  90  can be effectively avoided. 
     Preferably, the sewing-thread support  10 , the pre-stress supply member  20 , the abutting member  30  and the top cover  40  are stacked along the height direction Z which is perpendicular to the transverse direction Y and the longitudinal direction X. Since the top cover  40  is fixed, moving the abutting member  30  along the height direction Z can control the width of the thread space  50 . 
     In another embodiment, as shown in  FIG. 3B , the difference of this embodiment from previous embodiment is that the abutting portions  23  are disposed on the groove bottom  12 , and the folding portion  21  abuts against the abutting member  30 . 
     In the first embodiment of the present invention, as shown in  FIG. 3A , the pre-stress supply member  20  is a V-shaped elastic piece of a folded type, the folding portion  21  is located at a position where the elastic piece is folded, the two extension portions  22  are two sides of the elastic piece extending in different directions, and the two abutting portions  23  are two end edges of the elastic piece. 
     In the second embodiment of the present invention, as shown  FIG. 6 , the pre-stress supply member  20  is a torsion spring which is generally V-shaped, the folding portion  21  is a coil portion of the torsion spring, the extension portions  22  are two arms extending from the coil portion, and the two abutting portions  23  are respectively connected to the folding ends of the arms. 
     In a third embodiment of the present invention, as shown in  FIG. 7 , the pre-stress supply member  20  is a bent iron wire, which is generally V-shaped, and the folding portion  21  is where the bent iron wire is folded. 
     In a fourth embodiment of the present invention, as shown in  FIG. 8 , the pre-stress supply member  20  is a V-shaped elastic piece of a folded structure, the folding portion  21  is located at a position where the elastic piece is folded, and the extension portions  22  are two sides of the elastic piece extending in different directions. The extension portions  22  are provided with a plurality of indentations  221  to reduce the weight of the pre-stress supply member  20  and control the elastic force of the pre-stress supply member  20 , and the two abutting portions  23  are two end edges of the elastic piece, respectively. 
     In a fifth embodiment of the present invention, as shown in  FIG. 9 , another pre-stress supply member  60  is provided, which is made of an elastic material, that is, a material complying with Hooke&#39;s law. The pre-stress supply member  60  is disposed in the accommodating groove  11  and has a first pushing portion  61 , a turning portion  62  and a second pushing portion  63  which are connected to one another. An extending direction of the first pushing portion  61  is parallel to that of the second pushing portion  63 . The first pushing portion  61  and the turning portion  62  define an angle therebetween, and the second pushing portion  63  and the turning portion  62  define an angle therebetween, so that the first pushing portion  61 , the turning portion  62  and the second pushing portion  63  form a Z-shape in cross section. The first pushing portion  61  is disposed on the groove bottom  12 , and the second pushing portion  63  abuts against the top portion  32 , so that a margin of compression and restoring is provided between the first pushing portion  61  and the turning portion  62 , and between the second pushing portion  63  and the turning portion  62 , thereby providing the sewing thread a pre-stress. 
     As can be seen from the foregoing, each embodiment of the sewing-thread pre-stress device for a sewing machine in accordance with the present invention mainly provides proper elasticity by the pre-stress supply member  20 , since the pre-stress supply member  20  is made of an elastic material and generally V-shaped, the amount of change in the elastic force is relatively small, the sewing thread L of different diameters can be inserted into the thread space  50 . When the thicker sewing thread L is inserted into the thread space  50 , it does not provide excessive abutting force, so that the sewing thread pressure is moderate, avoiding the problem that the knitted fabric wrinkles if the sewing thread pressure is excessively large or the sewing thread gets knotted if the sewing thread pressure is too small. 
     Furthermore, in each embodiment of the sewing-thread pre-stress device for a sewing machine of the present invention, the extension portions  22  on both sides of the pre-stress supply member  20  are extended evenly, so that the elastic force is evenly distributed over two sides of the abutting member  30  along the longitudinal direction X, and with the abutting portions  23 , the force can be evenly distributed at both sides of the abutting member  30  along the transverse direction Y, thereby effectively achieving the effect of averaging the supplied force. 
     While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.