Upper feed mechanism for sewing machine

Abstract: An upper feed mechanism of a sewing machine, in which the horizontal motion mechanism for moving the upper feed dog (19) back and forth is provided with a double lever mechanism composed of a linear lever (4), a bifurcate lever (6) and a slider (5) slidably mounted on both levers, and a crank lever mechanism (13, 14) for oscillating the levers. When a crank of the crank lever mechanism (13, 14) is at the top dead point or the bottom dead point, the axial lines of the linear lever (4) and the bifurcate lever (6) are matched, and when the slider (5) is moved in this state, the upper dog (19) varies in the feed amount while the front position or rear position is constant. When a rod for coupling the crank and lever of the crank lever mechanism is pivotally mounted on one of the two positions spaced in the peripheral direction with respect ot the lever, the upper feed dog (19) fitted and disposed at the presser foot makes an upper feed motion before the needle drop point, and when it is fitted to the other position, the upper feed dog disposed behind the presser foot makes an upper feed motion behind the needle drop point.

Description: Field of the Invention This invention relates to an upper feed mechanism of a sewing machine, and more particularly to an upper feed mechanism of a sewing machine including an upper feed dog for making upper, lower, back and forth motions by means of a main shaft, and feeding a cloth in cooperation with a lower feed dog. Description of the Prior Art The upper feed mechanism of a sewing machine is available in various types, aside from the type comprising a crank oscillating back and forth by means of a main shaft, an upper feed bar of which base part is rotatably mounted on the crank to oscillate up and down, having an upper feed dog opposing a lower feed dog disposed at a free end of the upper feed bar, a spring device for operating to push down the upper feed bar, and another crank oscillating vertically by means of the main shaft and moving the upper feed bar up and down in cooperation with the spring device, such as the type comprising a crank oscillating back and forth by means of a main shaft, another crank oscillating up and down by means of the main shaft, an upper feed bar of which one end is coupled with the crank for horizontal feed by way of a first link and other end is provided with an upper feed dog opposing a lower feed dog, a second link coupling the middle part of the upper feed bar and the crank for vertical feed, a lever rotatably pivoted on the sewing machine frame, a third link coupling the lever and the pivotal part joining the first link and upper feed bar, and a pressure spring intervening between the lever and the sewing machine frame (the Japanese Laid-open Patent No. 60-227795). Moreover, as for the upper feed dog, a type of feeding upward as being fitted and diposed at the presser foot before the needle location (hereinafter called front upper feed), and a type of feeding upward as being disposed at the rear side of the pressor foot behind the needle drop point (rear upper feed), and the former front upper feed is suited to sewing a thin fabric which is easily deviated or to ruffling, while the latter rear upper feed is suited to sewing denim or other thick and heavy fabric and is capable of feeding the cloth smoothly. The conventional upper feed mechanism of a sewing machine also comprises usually an adjusting device of the upper feed amount within the mechanism for moving the crank for horizontal feed back and forth by means of the main shaft. This adjusting device is, in most cases, composed of an arc-shaped lever, a slider being slidably mounted on this lever and positioned by the operation of an operating mechanism, a crank for oscillating the lever, and a link for coupling the crank and slider, and it is composed so that the pivotal point of the link and crank may be matched with the center of the curvature of the lever, and the upper feed amount is designed to be changed while the rear position is constant in the front upper feed type or the front position is constant in the rear upper feed type. A different version of the upper feed mechanism of a sewing machine comprises, for example, an adjusting mechanism for the vertical motion within a mechanism for moving the crank for vertical feed up and down by means of the main shaft, so that the vertical motion of the upper feed dog may be adjusted depending on the thickness of the fabric or stepped part (the Japanese Laid-open Utility Model No. 58-169862). FR-A-813223, which represents the closest state of the art, discloses a sewing machine having an upper feed dog 15 end lower feed dog 38. In this document, the upper feed dog 15 is oscillated by oscillation generated by an eccentric 18 on the main shaft 17 of the sewing machine and transmitted through an eccentric rod 19, a first lever arm 20 on a rocking shaft 21, a second lever arm 24, a short rod 25 and a feed dog supporter 13. The feed amount of the feed dog 15 can be adjusted by changing a connecting point of the eccentric rod 19 on the first lever arm 20. GB-A-208968 relates to improvements in sewing machine feed mechanism and discloses adjustment of feed amount as follows. Angular adjustment between the actuator lever 19 and the cam 26 is possible since the actuator 19 is provided with an arcuate slot 42 to receive a set screw 43 which enters into a tapped socket of the cam structure 26. Owing to this angular adjustment while the amplitude of the swinging motion of the cam structure does not change, the location of its camming portions relative to the feed lever 24 may be varied, and therefore the extent of the feed may vary without variations of the amplitude of motion of the actuator 19 and the cam device 26. DE-C-381326 describes a sewing machine having an upper feed dog 18 and a lower feed dog 14. This document discloses a sewing machine having two rocking shafts (40, 41): one of the shafts 41 is inserted in another shaft 40, and each shaft has arms (39, 65) to connect to feed dogs (14, 18). The feed amount of the feed dog can be adjusted by changing connecting points of a guide rod 48 on a driving arm 45 and a driven arm 44. This invention is intended to exchange the upper feed dog for front upper feed and the upper feed dog for rear upper feed depending on the application so as to use the front upper feed and rear upper feed separately, but in the conventional upper feed mechanism if only the upper feed dogs were exchanged, the upper feed dog might collide the presser foot when the upper feed amount was changed. In other words, in the sewing machine of front upper feed, if the upper feed dog is merely changed in position to behind the needle drop point, the rear position is constant and the upper feed amount changes, and therefore if the upper feed amount is increased, the upper feed dog may collide against the presser foot if moved to the front side. In the sewing machine of rear upper feed type, similarly, when the upper feed amount is increased while the front position is constant and the upper feed amount is changed, the upper feed dog may collide the presser foot upon completion of the cloth feed. SUMMARY OF THE INVENTION It is hence a primary object of this invention to solve the above-discussed problems, and provide an upper feed mechanism of a sewing machine capable of easily changing the mode of upper feed depending on the sewing condition when sewing a fabric. To achieve the above object, this invention provides an upper feed mechanism of a sewing machine comprising: an upper feed bar having an upper feed dog mounted to one end thereof and having an adjustable oscillating range; horizontal and vertical oscillating motion mechanisms coupled to the upper feed bar for moving the upper feed bar back and forth and up and down respectively by means of the main shaft so that said motions result in a feeding movement of said upper feed dog, and said oscillating range being adjustable by provision of a crank rotated and driven by the main shaft and a lever pivoted oscillatably, a rod for coupling the crank and the lever thereby oscillating the lever, a transmission mechanism for transmitting the lever oscillation to the upper feed bar, said transmission mechanism including: an upper feed amount adjusting device; said adjusting device being capable of adjusting the upper feed amount without moving the upper feed dog characterised in that an upper feed dog is provided in dependence on whether front upper feed is employed or whether rear upper feed is employed, and further characterised in that said lever can be arranged in a first position in relation to the rod when front upper feed is required and in a second position when rear upper feed is required, so that when the upper feed amount is changed, the rear position of adjustment is unchanged when front upper feed is employed, and the front position of adjustment is unchanged when rear upper feed is employed. In this mechanism, by changing over the linking position of the rod to the lever, the front upper feed and rear upper feed can be selectively used, and the upper feed amount may be varied while the front position is constant or the rear position is constant. Typical examples of the adjusting device of upper feed amount used in this upper feed mechanism include a mechanism composed of a linear crank, a bifurcate lever and a slider mounted on the crank and also fitted to the bifurcate lever in which the oscillation of the crank is transmitted to the bifurcate lever through the slider to oscillate the bifurcate lever, and a mechanism of crank lever composed of an arc-shaped crank, a lever, and a rod for coupling the lever and the slider mounted on the crank in which the operation lever for sliding the slider along the crank can turn about the center of the curvature of the crank if it is located within its oscillation range, for example, in the middle position. The lever oscillating amount can be varied, without moving the lever, by moving the slider in the state where the axial line of the linear crank and the axial line of the bifurcate lever are matched in the former mechanism, or by moving the slider along the crank by turning the operation lever when the crank is located in the middle position of the oscillation range in the latter mechanism. In other words, without moving the upper feed dog which cooperates with the lever, the upper feed amount which is the amount of motion of the upper feed dog may be varied. It is desired that the above slider motion be operated from outside the sewing machine by means of operation lever, dial or the like. Accordingly, the upper feed amount may be adjusted while sewing. To operate the slider from outside the sewing machine, an operation shaft is usually provided, and an actuation lever is affixed to this shaft, while the operation lever or dial if affixed to the shaft end of the operation shaft projecting to outside the sewing machine. The adjusting device of the upper feed amount and the changeover means of the oscillating range as described above are similarly provided in the vertical motion mechanism, so that the vertical motion of the upper feed dog may be adjusted while the top dead point is constant or the bottom dead point is constant. When adjusting the vertical motion while the bottom dead point is constant, an upper feed dog of which bottom dead point is matched on the throat plate is generally used, and when adjusting the vertical motion while the top dead point is constant, an upper feed dog of which top dead point is located above the throat plate is employed. By providing the vertical motion mechanism with the adjusting device and changeover means as described above, it is possible to set range of vertical motion of the upper feed dog in the optimum conditions depending on the thickness and kind of fabric, presence or absence of stepped part or its degree. Such adjusting device and changeover means may be installed either in the horizontal motion mecahnism or in the vertical motion mechanism, or in both of them. When intended to operate the sliders from outside by installing the adjusting device and changeover means in both mechanisms and also furnishing each of the both mechanisms with oepration shafts, it is desired to build in a double shaft structure by fabricating one of the two operation shafts in a hollow tube to be externally fitted on the other shaft. By incorporating the operation shafts into one piece, the structure is simplified, and the space for installation is saved. By the same reason, when installing the crank for horizontal feed into the horizontal motion mechanism and the crank for vertical feed into the vertical motion mechanism, the oscillation shafts to which the cranks are affixed should be preferably built in a double shaft structure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevation showing a part of an upper feed mechanism of a sewing machine of this invention in a sectional view; Fig. 2 is an exploded perspective view of the upper feed mechanism shown in Fig. 1; Fig. 3 is a other side elevation of the sewing machine; Fig. 4 is an operation diagram for front upper feed; and Fig. 5 is an operation diagram for rear upper feed. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to Fig. 2, a tubular shaft 12 is rotatably fitted to one side of an oscillating shaft 11 to make up a double shaft structure, and a crank 13 for horizontal feed is affixed to one end of the tubular shaft 12, and a crank 14 for vertical feed is affixed to the shaft end of the oscillating shaft 11 projecting from the crank 13, and one end of a lever 16 of which other end is pivotally mounted on the middle part of an upper feed bar 15 is coupled to the crank 13 for horizontal feed, while its middle part is coupled to the crank 14 for vertical feed by means of a link 17. On the upper feed bar 15, an upper feed dog 19 for front upper feed or an upper feed dog for rear upper feed is detachably mounted at a free end of the upper feed, and a base end of the upper feed bar is coupled to one end of a lever 21 of which middle part is pivoted on a machine frame 20 by means of a link 22. The lever 21, as specifically shown in Fig. 1, is pressed at one end by a coil spring 23 which is installed so as to adjust the spring pressure on the machine frame 20, and is thrust so as to rotate in the counterclockwise direction in the drawing, and a stopper pin 25 provided in the machine frame 20 across a pivot 24 in order to adjust the amount of projection is designed to define the counterclockwise motion of the lever 21. In this constitution, the upper feed dog 19 makes an ellipsoidal motion combining the horizontal motion and vertical motion by the oscillating motions of the cranks 13 and 14 for horizontal feed and vertical feed. At the other end of the tubular shaft 12 and at a proper position of the oscillating shaft 11, the horizontal motion mechanism and the vertical motion mechanism furnished with the oscillating amount adjusting device and the changeover mechanism of oscillating range are respectively coupled. That is, at the other end of the tubular shaft 12, a bifurcate lever 6 is affixed, and a square piece 27 fitted with the bifurcate lever 6 is rotatably mounted on a slider 5 which is attached to a linear lever 4 pivotally supported on a fixed shaft 28 which is supported parallel to the oscillating shaft 11. An arc-shaped groove 31 of which a center of curvature is located on a straight line passing through an axis shaftline of the oscillating shaft 11 is formed in a upper part of a guide piece 32. The slider 5 rotatably supports a square piece 33 fitted to the arc-shaped groove 31 of the guide piece 32 of which a bifurcate part in the lower side part is fitted to the oscillating shaft 11. To the guide piece 32 for fitting the square piece 33 in the arc-shaped groove 31 formed at one side of the guide piece, an actuation lever 35 affixed to an operation shaft 34 supported rotatably on the machine frame parallel to the fixed shaft 28 is pivotally mounted at a position corresponding to the groove middle part on the opposite side, and the guide piece 32 straddling over the oscillating shaft 11 is moved up and down by the vertical motion of the actuation lever 35, and accordingly the slider 5 moves up and down, so that the bifurcate lever 6 coupled with the lever 4 is changed in the amount of oscillation. Numeral 36 is an operation lever affixed to the projection end of the operation shaft 34 projecting from the sewing machine frame, and it is thrust so as to turn upward always in the clockwise direction in the drawing by a spiral spring 43, and it is designed so that the operation lever 36 may be fixed on a mounting plate 37 by pinching the mounting plate from both sides by means of a holder 39 linked to the operation lever 36 through an arc-shaped groove 38 of the mounting plate 37 mounted on the sewing machine frame, and the operation lever itself. The mounting plate 37 has an arc-shaped groove 40 disposed outside the arc-shaped groove 38, so that a pair of stopper screws 41 fixed at a proper position being slidably fitted to the groove 40 may be fixed at a position adjusted by pinching the operation lever 36 above and below from both sides. On the mounting plate 37, furthermore, the outside of the arc-shaped groove 40 is formed in an arc shape, and graduations 42 to indicate the upper feed amount are provided along the edge. The lever 4 has also a one-body lever 2 projecting radially, and this lever has an arc-shaped groove 44 formed about the fixed shaft 28, and its lower end of a rod 3 is coupled with an eccentric crank 1 while the upper end of the rod 3 is coupled with the position of an upper end or lower end of the arc-shaped groove 44 by means of a pin 45 fixed to the lever 2 through the arc-shaped groove 44. Here, the pin 45 fixed to the lower end or upper end of the arc-shaped groove 44 is positioned on the line crossing through the centre of rotation of the eccentric crank 1 in the state where the axial line of the lever 4 and the axial line of the bifurcate lever 6 are matched. A distance between the lower end and upper end of the arc-shaped groove is twice the eccentric amount of the eccentric crank. The horizontal motion mechanism is thus composed, and in the state where the upper end of the rod 3 is pivotally mounted on the lower end of the arc-shaped groove (point A in Fig. 4) by means of a pin 45, the eccentric crank 1 rotates a half turn in the clockwise direction from the bottom dead point a as shown in Fig. 4, and when reaching the top dead point b, the lever 4 and the bifurcate lever 6 rotates from the solid line position up to the single-dot chain line position. In consequence, when the eccentric crank 1 rotates a half turn from the top dead point b to the bottom dead point a, the lever 4 and bifurcate lever 6 turn to the solid line position. Thus, by the rotation of the eccentric crank 1, the bifurcate lever 6 oscillates between the left dead point indicated by solid line and the right dead point indicated by single-dot chain line, and the upper feed bar cooperating therewith moves horizontally while the rear position is constant, and when the upper feed dog for front upper feed is provided, the upper feed dog moves back and forth before the needle drop point P while the rear position is constant. When the upper end of the rod 3 is coupled with the upper end of the arc-shaped groove 44 (point B in Fig. 5), since the interval of A and B is set twice the eccentric amount of the crank on the straight line passing through the center of rotation of the eccentric crank 1, that is, the length between a and b, the eccentric crank 1 begins to rotate from the top dead point b, reversely to the case mentioned above, by changeover to the point B side. And then it reaches the bottom dead point a. As a result, the lever 2 and the bifurcate lever 6 turn reversely to the above case, that is, the bifurcate lever 6 turns in the counterclockwise direction, from the solid line position to the double-dot chain line position. When the eccentric crank 1 rotates a half turn from the bottom dead point a to the top dead point b, the levers 4 and 6 return to the solid line position. In this way, by the rotation of the eccentric crank 1, the bifurcate lever 6 oscillates between the right dead point indicated by solid line and the left dead point indicated by double-dot chain line, and the upper feed bar cooperating therewith moves horizontally while the front position is constant, and when the upper feed dog for rear upper feed is provided, the upper feed dog moves back and forth behind, the needle drop point P. The upper feed amount is adjusted by adjusting the position of the slider 5 by controlling the operation lever 36. For example, when the slider 5 is moved toward the free end of the lever 4, the oscillating amount of the bifurcate lever 6 increases, and to the contrary when moved toward the pivot of the lever 4, the oscillating amount of the bifurcate lever 6 decreases. As shown in Figs. 4, 5, if the slider 5 is moved toward the lever 4 in the matched state of the axial lines of the lever 4 and bifurcate lever 6, the bifurcate lever 6 does not move, and when the position of the slider 5 is changed in the state shown in Fig. 4, the bifurcate lever 6 always oscillates by changing the oscillating amount in the rightward direction, with the left dead point located at the solid line position. When the position of slider 5 is changed in the state shown in Fig. 5, on the other hand, even if the oscillating amount is changed in the leftward direction, the right dead point remains located at the solid line position. Thus, even if the upper feed amount is changed, the upper feed dog 19 does not collide against the presser foot because the rear position is unchanged in the front upper feed and the front position is unchanged in the rear upper feed. In the horizontal motion mechanism described herein, points A and B are located on the straight line passing through the center of rotation of the eccentric crank 1, and their interval is set same as the length between a and b, so that the oscillating range may be evenly distributed to right and left, but this is not limitative, and these points may not be necessarily located on the straight line passing through the center of rotation, and their interval may be somewhat longer than or shorter than the length between a and b. If different, however, it is necessary to determine the length of the component on the straight line shorter than the length between a and b (because it is not possible to change over if set longer than the length between a and b). In this case, by changeover between A and B, part of the oscillating range is overlapped. Points A and B may be also, preferably, set in the same length from the center of oscillation o, and may be positioned on a same circumference or on different circumferences. If different, the right and left amplitudes (oscillating amounts) of the bifurcate lever 6 will be different. Regarding the vertical motion mechanism coupled to the oscillating shaft 11, an actuation lever 51 is affixed to a tubular shaft and the tubular shaft is fitted to the operation shaft 34 making up a double shaft structure together with the operation shaft 34, and an operation lever 53 affixed to the tubular shaft 52 for turning the actuation lever 51 is attached to a support plate 54 by means of a headed pin 56 fixed through an arc-shaped groove 55, and the structure is same as that of the horizontal motion mechanism except that graduations 57 to indicate the vertical stroke are provided in the arc-shaped edge of the support plate 54. Therefore, the same reference numbers as in the horizontal motion mechanism refer to the identical structure. In this mechanism, when the main shaft 1 rotates, the oscillating shaft 11 oscillates, and the crank 14 for upper feed oscillates up and down, the upper feed bar 15 and the upper feed dog 19 move up and down. The vertical stroke can be adjusted by operating the operation lever 52 to move the slider 5 along the lever 4, but the moving range differs between when the connecting point of the rod 3 and the lever 2 is positioned at the lower end of the arc-shaped groove 44 and when it is positioned at the upper end. In other words, when positioned at the lower end, it moves downward while the upper position is constant, and when positioned at the upper end, it moves upward while the lower position is constant. In the above embodiment, an application of this invention is explained by presenting an example of upper feed mechanism comprising the crank 13 for horizontal feed, the crank 14 for vertical feed, the first lever 16 of which one end is linked to the crank 13 for horizontal feed, middle part to the crank 14 for vertical feed through the link 17, and other end to the upper feed bar, the second lever 21 rotatably pivoted to the machine frame and linked to the upper feed bar through the link 22, the spring 23 engaged with the second lever 21 across the pivot, and the stopper pin 25, and it may be similarly applied to the upper feed mechanism of the type of moving horizontally by coupling the base end of the upper feed bar to the crank for horizontal feed, and feeding vertically by means of the crank for vertical feed and the spring for pushing down the upper feed bar, and also to other conventional upper feed mechanisms.

Claims: An upper feed mechanism of a sewing machine comprising: an upper feed bar (15) having an upper feed dog (19) mounted to one end thereof and having an adjustable oscillating range; horizontal and vertical oscillating motion mechanisms coupled to the upper feed bar (15) for moving the upper feed bar (15) back and forth and up and down respectively by means of the main shaft so that said motions result in a feeding movement of said upper feed dog (19), and said oscillating range being adjustable by provision of a crank (1) rotated and driven by the main shaft and a lever (2) pivoted oscillatably, a rod (3) for coupling the crank (1) and the lever (2) thereby oscillating the lever (2), a transmission mechanism (4, 5, 6, 27) for transmitting the lever (2) oscillation to the upper feed bar (15), said transmission mechanism including: an upper feed amount adjusting device, (4, 5, 6); said adjusting device being capable of adjusting the upper feed amount without moving the upper feed dog (19) characterised in that an upper feed dog (19) is provided in dependence on whether front upper feed is employed or whether rear upper feed is employed, and further characterised in that said lever (2) can be arranged in a first position (A) in relation to the rod (3) when front upper feed is required and in a second position (B) when rear upper feed is required, so that when the upper feed amount is changed, the rear position of adjustment is unchanged when front upper feed is employed, and the front position of adjustment is unchanged when rear upper feed is employed. An upper feed mechanism according to claim 1, wherein said horizontal motion mechanism comprises: said changeover mechanism (1,2,3), said transmission mechanism (4,5,6,27), and said upper feed amount adjusting device (4,5,6); wherein the rod (3) may be changed over and linked to the first position when the upper feed dog (19) is for front upper feed and to the second position when the upper feed dog (19 is for rear upper feed. An upper feed mechanism according to claim 1 wherein said vertical motion mechanism comprises: said changeover mechanism (1,2,3), said transmission mechanism (4,5,6,27), and said upper feed amount adjusting device (4,5,6); wherein by linking the rod (3) to the first position (A) the upper feed dog (19) moves downward while the upper position is constant and by changing over and linking the rod (3) to the second position (B) the upper feed dog (19) moves upward while the lower position is constant.

Inventors: KASUDA TAKASHI, KASUDA, TAKASHI, KASUDA, TAKASHI C/O PEGASUS SEWING
Applicants: PEGASUS SEWING MACHINE MFG CO, PEGASUS SEWING MACHINE MFG. CO., LTD.
Application year: 1988
Main classification: D05B27
IPC codes: D05B27