Patent Publication Number: US-11639569-B2

Title: Sewing machine

Description:
TECHNICAL FIELD 
     The present invention relates to a sewing machine used for sewing products made of cloth. 
     BACKGROUND ART 
     This type of sewing machine has feed dogs for feeding cloth on a throat plate pressed by a presser foot. The feed dogs elliptically move by reciprocating in a horizontal direction in a cloth feed direction and in a vertical direction with respect to the upper surface of the throat plate in a sewing process. 
     More specifically, the feed dogs repeat a process in which the feed dogs advance forward in the cloth feed direction when the feed dogs move above the throat plate, retract at a position below the throat plate, and move above the throat plate again. In this case, the forward feed of the cloth by the feed dogs is performed when a needle is in the vicinity of a top dead center position. Therefore, the feed dogs are operated synchronously so as to protrude from the upper surface of the throat plate when the needle is raised. 
     Meanwhile, before a sewing operation is started, the presser foot is raised and cloth is set at an initial position of the sewing operation. At this time, the needle is at the raised position, so that the feed dogs are in a state of protruding from the upper surface of the throat plate. If the cloth is positioned below the needle in this state, the cloth comes in contact with the feed dogs protruding from the upper surface of the throat plate, leading to a possibility of interfering with smooth preparation for the sewing operation. 
     Thus, there has been proposed a feed dog lowering mechanism (refer to, for example, Patent Literature 1 given below) adapted to lower the feed dogs from the upper surface of the throat plate when the presser foot is raised before the sewing operation is begun. 
     The feed dog lowering mechanism disclosed in Patent Literature 1 has an eccentric cam provided on a drive shaft, a lifting and lowering link connected, through a square piece, to a rod extending from the eccentric cam, and a guide member equipped with a guide groove that guides the square piece, and is configured to interlock the rotation of the guide member with a presser operation lever that separates the presser foot above the throat plate. 
     According to the configuration, when the presser foot is raised by operating the presser operation lever, the guide member rotates and the guide groove, which guides the square piece, tilts. The square piece moves along the tilted guide groove, thereby enabling the feed dogs to move to a position below the upper surface of the throat plate (a retracted position). Thus, the feed dog lowering mechanism disclosed in Patent Literature 1 can retract the feed dogs by the simple configuration. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Examined Utility Model Application Publication No. 1-35729 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Meanwhile, feed dogs preferably move a sufficient distance in the state of protruding from the upper surface of a throat plate when moving forward to feed cloth. On the other hand, when the feed dogs switch from forward movement to backward movement, if the feed dogs are positioned above the upper surface of the throat plate even for a short period of time, there is a possibility that the retracting feed dogs will interfere with the forward feed of the cloth. For this reason, the positions of the turn-back points at both ends of a forward path and a return path for the feed dogs to reciprocate in a horizontal direction are set to be slightly below the upper surface of the throat plate. 
     However, if the feed dog lowering mechanism disclosed in the aforesaid Patent Literature 1 is adopted, there is a possibility that the feed dogs in a retracted state are inconveniently positioned above the upper surface of the throat plate due to a setting error of the amount of protrusion of the feed dogs from the upper surface of the throat plate, the dimensional errors of components, or the like. 
     To prevent the problem described above, if the positions of the turn-back points of the feed dogs are set below the upper surface of the throat plate with a relatively large distance, then the amount of protrusion of the feed dogs from the upper surface of the throat plate will be small, leading to a possibility that cloth cannot be sufficiently fed. 
     In view of the above, an object of the present invention is to provide a sewing machine capable of reliably feeding cloth by feed dogs during a sewing operation and positioning the feed dogs sufficiently below the upper surface of a throat plate when the feed dogs are retracted. 
     Solution to Problem 
     To this end, a sewing machine in accordance with the present invention includes: feed dogs which protrude and retract from an upper surface of a throat plate; a presser foot which faces the top of the feed dogs; a drive shaft which transmits the power of a drive source; a horizontal feed drive unit which converts a rotation of the drive shaft into a reciprocating motion in a horizontal direction and transmits the reciprocating motion in the horizontal direction to the feed dogs; a vertical drive unit which converts a rotation of the drive shaft into a reciprocating motion in a vertical direction and transmits the reciprocating motion in a vertical direction to the feed dogs; a vertical travel distance changing part which changes a reciprocating travel distance of the feed dogs in the vertical direction; and a vertical position changing part which moves turn-back points at both ends of a forward path and a return path at the time of horizontal reciprocating travel of the feed dogs to be below the upper surface of the throat plate in the case where the vertical travel distance changing part decreases a vertical travel distance of the feed dogs. 
     The sewing machine according to the present invention is provided with the vertical position changing part, thus making it possible to move the turn-back points at both ends of the forward path and the return path at the time of the horizontal reciprocating travel of the feed dogs to be below the upper surface of the throat plate. With this arrangement, when the feed dogs are retracted, the turn-back points can be positioned sufficiently below the upper surface of the throat plate by the vertical position changing part. 
     Further, in the sewing machine according to the present invention, the vertical drive unit includes: an eccentric cam which is rotated by the drive shaft; an advancing and retreating arm which is moved forward and backward in the horizontal direction by the eccentric cam; a lifting and lowering link which has a lower end thereof connected to the advancing and retreating arm through a lower connecting shaft and an upper end thereof connected to a feed base which supports the feed dogs through an upper connecting shaft such that the feed dogs can move in the horizontal direction; a square piece provided coaxially with the lower connecting shaft of the lifting and lowering link; a guide member having a guide groove formed therein to linearly guide the square piece; and a rotating shaft which rotatably supports the guide member, the vertical travel distance changing part includes a guide member rotating mechanism which rotates the guide member to change a tilt angle of the guide groove, thereby changing the travel distance of the feed dogs in a state of protrusion from the throat plate, the vertical position changing part is configured by placement in which the rotating shaft of the guide member and the center of a reciprocating travel region of the square piece in the guide groove are shifted away from each other, and the center of the reciprocating travel region of the square piece is positioned, being shifted to be lower than the rotating shaft of the guide member when the guide member is rotated by the guide member rotating mechanism to cause the guide groove to tilt. 
     According to the vertical drive unit having the aforesaid configuration, the rotation of the drive shaft is converted through the eccentric cam into the horizontal advancing and retreating motion of the advancing and retreating arm. The advancing and retreating motion of the advancing and retreating arm causes the square piece to reciprocate along the guide groove of the guide member. The lower end of the lifting and lowering link is connected to the square piece through the lower connecting shaft, and the upper end of the lifting and lowering link is connected to the feed base through the upper connecting shaft. With this arrangement, the lifting and lowering link swings when the square piece reciprocates along the guide groove, and the feed base is moved up and down by the swing of the lifting and lowering link. 
     Regarding the relationship between the inclination of the guide groove and the vertical motion of the feed dogs, the feed dogs move up and down the most when, for example, the guide groove is horizontal. As the guide groove gradually tilts down in the advancing direction of the advancing and retreating arm, the vertical motion of the feed dogs becomes smaller while the horizontal travel distance thereof remains unchanged. In other words, when a tilt is imparted so that the guide groove is tilted down in the advancing direction of the advancing and retreating arm by rotating the guide member, the feed dogs do not move up and down even when the drive shaft rotates (perform only the horizontal reciprocating motion). 
     At this time, in the vertical position changing part, the rotating shaft of the guide member and the center of the reciprocating travel region of the square piece in the guide groove are positioned so as to be shifted away from each other. This shift causes the center of the reciprocating travel region of the square piece to be positioned lower than the rotating shaft of the guide member when the guide groove is in a tilted state. With this arrangement, when the guide groove is tilted, the feed dogs can be reliably retracted below the upper surface of the throat plate by lowering the turn-back points of the feed dogs. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an explanatory diagram illustrating the configuration of an essential section of a sewing machine in an embodiment according to the present invention; 
         FIG.  2    is an explanatory diagram illustrating the configuration of a vertical drive unit; 
         FIG.  3    is an explanatory diagram illustrating the configuration of a guide member; 
         FIG.  4    is an explanatory diagram illustrating the configuration of an essential section of a guide member rotating mechanism; 
         FIG.  5    is an explanatory diagram illustrating a state of an essential section during a sewing operation; 
         FIG.  6    is an explanatory diagram illustrating the state of the essential section at the time of retraction; 
         FIG.  7    is an explanatory diagram illustrating the comparison in configuration between a rotating shaft in the guide member with eccentricity and the same without eccentricity; 
         FIG.  8    is an explanatory diagram illustrating a positional relationship between the trajectory of feed dogs and a throat plate during the sewing operation; 
         FIG.  9    is an explanatory diagram illustrating another positional relationship between the trajectory of the feed dogs and the throat plate during the sewing operation; and 
         FIG.  10    is an explanatory diagram illustrating a positional relationship between the trajectory of the feed dogs during the sewing operation and the feed dogs at the time of the retraction. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described with reference to the accompanying drawings. Although the illustration of the overall configuration is omitted, a sewing machine of the present embodiment is provided with a sewing needle (not illustrated) which vertically reciprocates, a throat plate  1  on which the cloth of clothing or the like is placed, a presser foot  2  which presses the cloth on the throat plate  1 , and feed dogs  3  which protrude and retract from the upper surface of the throat plate  1  to feed the cloth, as illustrated in  FIG.  1   , as the configuration according to the gist of the present invention. 
     The feed dogs  3  are driven by a feed dog drive unit. The feed dog drive unit has a feed rod  4  extending in the horizontal direction, and a feed base  5  which supports the feed rod  4  in a longitudinally movable manner. The feed dogs  3  are integrally provided on the distal end of the feed rod  4 . 
     The feed base  5  has the proximal end thereof connected to a frame (not illustrated) through a swing shaft  6  so as to be vertically swingable. As the feed base  5  swings, the feed dogs  3  at the distal end of the feed rod  4  move in the vertical direction. Further, the feed dog drive unit has a drive shaft  7  which transmits the power of a drive source (not illustrated), a horizontal feed drive unit  8 , and a vertical drive unit  9 . The drive shaft  7  is provided below the feed base  5 . The drive source also drives the sewing needle. 
     The horizontal feed drive unit  8  has a first eccentric cam  10  which is rotated by the drive shaft  7 , a first advancing and retreating arm  11  which is advanced and retreated in the horizontal direction by the first eccentric cam  10 , and an advancing and retreating link  12  which transmits the advancing and retreating motion of the first advancing and retreating arm  11  to the feed rod  4 . The rotation of the drive shaft  7  is converted into a horizontal feed motion by the horizontal feed drive unit  8  configured as described above and the horizontal feed motion is transmitted to the feed dogs  3 . 
     The vertical drive unit  9  is adapted to convert the rotation of the drive shaft  7  into a vertical motion and transmit the vertical motion to the feed dogs  3 , and includes a second eccentric cam  13 , a second advancing and retreating arm  14  which is advanced and retreated in the horizontal direction by the second eccentric cam  13 , and a lifting and lowering link  15  connected to the second advancing and retreating arm  14 , as illustrated in  FIG.  1    and  FIG.  2   . The second eccentric cam  13  corresponds to the eccentric cam in the present invention, and the second advancing and retreating arm  14  corresponds to the advancing and retreating arm in the present invention. 
     The lifting and lowering link  15  has the lower end thereof connected to the second advancing and retreating arm  14  through a lower connecting shaft  16 , and the upper end thereof connected to the feed base  5  through an upper connecting shaft  17 , as illustrated in  FIG.  2   . A square piece  18  is provided at the lower end portion of the lifting and lowering link  15  so as to be coaxial with the lower connecting shaft  16 . 
     The square piece  18  is slidably accommodated in a guide groove  20  formed in a guide member  19 . The guide member  19  is disposed on one side (the right side in  FIG.  2   ) of the drive shaft  7  and directly under the feed base  5 . Because of the position where the guide member  19  is disposed, the lifting and lowering link  15  is connected between the swing shaft  6  in the feed base  5  and the feed dogs  3 . This enables the vertical motion of the lifting and lowering link  15  to be smaller than in the case where the leading end of the feed dogs  3  is lifted and lowered. 
     As illustrated in  FIG.  3   , the guide member  19  has a round body block  22  rotated by a rotating shaft  21  supported by a frame (not illustrated). 
     The guide groove  20  is formed on one surface of the body block  22 . The body block  22  has an extended member  23  extending outward in the radial direction from one portion thereof. A return spring  24  is connected to the extended member  23 . The return spring  24  is installed between the extended member  23  and a frame (not illustrated). 
     Further, the body block  22  is restricted, by a stopper pin  25  corning in contact with the extended member  23 , in counterclockwise rotation in  FIG.  3    from the position at which the guide groove  20  takes a horizontal attitude. The return spring  24  urges the body block  22  in a return direction (the counterclockwise direction) when the body block  22  rotates in the clockwise direction in  FIG.  3   . 
     The simple configuration of the guide member  19  enables the guide member  19  to be installed without any problem even in a relatively narrow space such as directly under the feed base  5 . Consequently, a vertical drive unit  9  has a compact configuration. 
     In addition, the rotating shaft  21  is provided such that the center thereof is eccentric with respect to the center of the round body block  22 . The relationship among the eccentric rotating shaft  21 , the tilt of the guide groove  20  caused by the rotation of the guide member  19 , and the reciprocating travel region of the square piece  18  creates the configuration for obtaining the function as the vertical position changing part in the present invention. This configuration will be described in detail later. 
     As illustrated in  FIG.  4   , the guide member  19  is rotated by operating a presser operation lever  26 . The presser operation lever  26  is adapted to be raised and lowered to lift and lower the presser foot  2  (refer to  FIG.  1   ). The presser operation lever  26  and the presser foot  2  are connected with each other through a link mechanism (not illustrated) for making the up and down movement of the presser foot  2  follow the up and down operation of the presser operation lever  26 . 
     More specifically, in a state in which the presser operation lever  26  is down, the presser foot  2  is in a state of pressure-contact with cloth on the feed dogs  3 , and in a state in which the presser operation lever  26  is up, the presser foot  2  is in a state of being separated from the cloth on the feed dogs  3 . 
     Further, as illustrated in  FIG.  4   , the guide member  19  is connected to the presser operation lever  26  through a rotating link  27 . The rotating link  27  has a first link part  28  which follows the up and down movement of the presser operation lever  26 , a transmission shaft  29  which converts the vertical motion of the first link part  28  into rotation and transmits the rotation, and a second link part  30  which transmits the rotation of the transmission shaft  29  to the extended member  23  of the guide member  19 . The rotating link  27  is the guide member rotating mechanism in the present invention and constitutes, together with the presser operation lever  26 , the vertical travel distance changing part in the present invention. 
     When the presser operation lever  26  is positioned at the lower end of the operation range thereof, the guide groove  20  of the guide member  19  is set to be horizontal (or substantially horizontal) by the first link part  28 , the transmission shaft  29 , and the second link part  30 . Further, a function of the vertical travel distance changing part makes it possible to adjust the tilt angle of the guide groove  20  of the guide member  19  according to the operation angle of the presser operation lever  26 . 
     As illustrated in  FIG.  5   , when the guide groove  20  of the guide member  19  is horizontal, the direction in which the square piece  18  reciprocates becomes the horizontal direction along the guide groove  20 , so that the feed base  5  is lifted up and pulled down by the lifting and lowering link  15  as the square piece  18  reciprocates. Consequently, the vertical travel distance of the feed dogs  3  reaches a maximum and the feed dogs  3  move, drawing an elliptical trajectory, to feed the cloth by the advancing motion when protruding upward above the upper surface of the throat plate  1 . 
     When the presser operation lever  26  is raised, the first link part  28  moves along the longitudinal direction thereof, and the second link part  30  rotates the guide member  19  against the biasing of the return spring  24  as the transmission shaft  29  rotates. This causes the guide groove  20  of the guide member  19  to tilt. The tilt of the guide groove  20  at this time will be a tilt that causes gradual movement down in a direction in which the second advancing and retreating arm  14  pushes out (rightward in the drawing). 
     As illustrated in  FIG.  6   , when the guide groove  20  of the guide member  19  tilts, the upper end of the lifting and lowering link  15  does not vertically move even when the square piece  18  reciprocates along the guide groove  20  in the tilted state. Consequently, the feed dogs  3  operate, drawing a linear trajectory in the horizontal direction, without a vertical motion. At this time, the feed dogs  3  are positioned below the upper surface of the throat plate  1 , so that the feed dogs  3  do not interfere with the setting of cloth above the feed dogs  3  to prepare for a sewing operation. 
     Further, as described above, the rotating shaft  21  is provided such that the center thereof is eccentric with respect to the center of the round body block  22 , thus making it possible to reliably retract the feed dogs  3  below the upper surface of the throat plate  1 . 
     This will be described in detail by comparison with a case where the center of the rotating shaft  21  is not eccentric with respect to the center of the body block  22 . 
     In  FIG.  7   , a configuration OM without eccentricity is illustrated as a reference example on the left side in the drawing, and a configuration NM with eccentricity, which is the present embodiment, is illustrated on the right side in the drawing. 
     The square piece  18  reciprocates along the guide groove  20 . At this time, the longitudinal dimension of the guide groove  20  can be reduced by making the longitudinal center of the guide groove  20  and a center S 1  of a reciprocating travel region W of the square piece  18  coincide with each other, and the body block  22  can be consequently made compact. Further, in this case, the center of the body block  22  and the longitudinal center of the guide groove  20  coincide with each other. 
     As illustrated in  FIG.  7   , in the configuration NM of the present embodiment, the center of the rotating shaft  21  is set eccentric with respect to the center of the body block  22 , thereby causing the center S 1  of the reciprocating travel region W of the square piece  18  to be shifted to the lowering side of the guide groove  20  so as to tilt farther than a center S 2  of the rotating shaft  21 . 
     In the state in which the cloth is fed during a sewing operation, the feed dogs  3  move on the elliptical trajectory, moving above the upper surface of the throat plate  1  to feed the cloth and moving below the upper surface of the throat plate  1  to go back to the return position thereof. At this time, the feed dogs  3  move, drawing an elliptical trajectory R with respect to the throat plate  1  as indicated by the relationship between the trajectory of the feed dogs  3  and the throat plate  1  in  FIG.  8   . 
     Further, the turn-back points P at both ends of the forward path and the return path of the reciprocating travel of the feed dogs  3  in the horizontal direction are set to be very slightly below the upper surface of the throat plate  1 . The trajectory of the feed dogs  3  in the retracted state becomes a linear trajectory that connects both turn-back points P. In the configuration OM without eccentricity illustrated as a reference example in  FIG.  7   , the center S 1  of the reciprocating travel region W of the square piece  18  and the center S 2  of the rotating shaft  21  coincide with each other, so that the positions of the turn-back points P of the feed dogs  3  during a sewing operation (a state in which cloth feed is being performed) and the turn-back points P of the feed dogs  3  in the retracted state due to the tilt of the guide groove  20  do not change. 
     Here; if it is assumed that the turn-back points P of the feed dogs  3  are undesirably positioned slightly above the upper surface of the throat plate  1  as illustrated in  FIG.  9    due to an error of the height adjustment of the feed dogs  3  or a dimensional error of a component, then the feed dogs  3  will protrude above the upper surface of the throat plate  1  even when the feed dogs  3  are in the retracted state, preventing smooth setting of cloth under a sewing needle in the case of the configuration OM without eccentricity illustrated in  FIG.  7   . 
     In contrast, according to the configuration NM with eccentricity of the present embodiment illustrated in  FIG.  7   , the center S 1  of the reciprocating travel region W of the square piece  18  is shifted to the lowering side of the tilted guide groove  20  with respect to the center S 2  of the rotating shaft  21 , thus generating a lowering allowance L (exaggerated for convenience of explanation) between the lower connecting shaft  16  and the upper connecting shaft  17  of the lifting and lowering link  15 . 
     Consequently, turn-back points Pa of the feed dogs  3  in the retracted state can be positioned below the turn-back points P of the feed dogs  3  during a sewing operation as illustrated in  FIG.  10    simply by rotating the guide member  19  by the rotating shaft  21  with eccentricity so as to tilt the guide groove  20 . Thus, cloth can be smoothly set under a sewing needle when preparing for a sewing operation or the like. 
     In the present embodiment, the function as the vertical position changing part in the present invention is obtained by setting the center of the rotating shaft  21  of the guide member  19  to be eccentric with respect to the center of the round body block  22  of the guide member  19 . The function as the vertical position changing part can be obtained by the position of the center S 1  of the reciprocating travel region W of the square piece  18  being shifted more to the lowering side than the rotating shaft  21  of the guide member  19  when the guide groove  20  tilts. 
     Further, the present embodiment is configured such that the guide groove  20  becomes horizontal when the presser operation lever  26  is positioned at the lower end, however, the present invention is not limited thereto. More specifically, the configuration may alternatively be such that the guide groove  20  becomes horizontal when the presser operation lever  26  is positioned at the upper end. In addition, the angle of the guide groove  20  during a sewing operation is not limited to horizontal, and can be set appropriately according to the dimensions of parts or the like. 
     DESCRIPTION OF REFERENCE NUMERALS 
       1  . . . throat plate;  2  . . . presser foot;  3  . . . feed dogs;  5  . . . feed base;  7  . . . drive shaft;  8  . . . horizontal feed drive unit;  9  . . . vertical drive unit;  13  . . . second eccentric cam (eccentric cam);  14  . . . second advancing and retreating arm (advancing and retreating arm);  15  . . . lifting and lowering link;  16  . . . lower connecting shaft;  17  . . . upper connecting shaft;  18  . . . square piece;  19  . . . guide member;  20  . . . guide groove;  21  . . . rotating shaft;  26  . . . presser operation lever (vertical travel distance changing part);  27  . . . rotating link (guide member rotating mechanism); P, Pa . . . turn-back point; W . . . reciprocating travel region; and S 2  . . . center of reciprocating travel region.