Upper feed device for a sewing machine

Abstract: An upper feed arm (33) for a sewing machine has its base end coupled with a longitudinally swinging crank (43) and has an upper feed dog (39) attached at the front end. The mechanism for vertically moving the upper feed arm consists of a clutch mechanism comprising a lever rotatably pivoted on a vertical feed shaft and swinging in cooperation with the main shaft, a abutment disposed on the lever, and a abutment of a collar disposed on the vertical feed shaft, being capable of disconnecting the cooperation of the lever and the vertical feed shaft, and a crank (29) having a roller (31) slidably fitting with a guide disposed parallel to the upper feed arm (33), moving vertically being affixed to the vertical feed shaft. A block (45) is provided below the roller (31) to be engaged with the free end lower surface of the crank and adjustable in the mounting position, thereby preventing the roller from descending more than specified. The upper surface (46) of the block is engaged with the free end lower surface of the crank and inclined.

Description: The present invention relates to an upper feed device for a sewing machine, and more particularly to an upper feed device for a sewing machine for feeding cloth by collaboration of an upper feed dog and a lower feed dog performing ellipsoidal motions in four directions consisting of longitudinal movement and vertical movement. A known upper feed device for sewing machine comprises a crank swinging longitudinally in cooperation with a main shaft, an upper feed arm having the base part pivoted on the crank rotatably in the vertical direction, with an upper feed dog disposed at the free end of the upper feed arm and confronting a lower feed dog, a spring device for pushing down the upper feed arm, and a crank swinging in the vertical direction in cooperation with the main shaft and moving the upper feed arm vertically in engagement with the upper feed arm pushed down by the spring device. In the United States Patent 4,589,364, in the mechanism for moving the upper feed arm vertically, a clutch mechanism comprising the abutment of the collar affixed on the swinging shaft, and the abutment of the lever rotatably supported on the swinging shaft is disposed, and also the roller pivoted on the crank pin of the crank for moving the upper feed arm vertically is fitted in the guide groove formed by the guide disposed below the upper feed arm. In the above devices, on the way of the descent of the upper feed dog toward the bottom dead center, when it is engaged with the cloth on the throat plate and further descent is arrested, the crank pin is separated off the upper feed arm in the former type, or the abutment of the lever is separated from the abutment of the collar in the latter type with the clutch mechanism, and the crank pin separated off the upper feed arm reaches the bottom dead center and pivots reversely and is engaged with the upper feed arm to lift, or the abutment of the lever separated off the abutment of the collar is engaged again to lift the upper feed arm, so that the upper feed dog is ascended above the cloth on the throat plate. In this course, that is, while the upper feed dog is engaged with the cloth on the throat plate, cloth feeding is carried out. Fig. 7 shows the track of the upper feed dog, in which the cloth is fed between point A where the upper feed dog descends and is engaged with the cloth on the throat plate and point B where it is ascended from the cloth on the throat plate. The horizontal line segment AB indicates the cloth feed amount. In Fig. 7, when it is attempted to feed the cloth at the position of line segment CD by lowering the position of the upper feed dog to be engaged with the cloth, the feed efficiency, that is, the cloth feed amount increases, but the engagement with the ascending lower feed dog becomes deeper, and the impulsive cloth gripping force is intensified, and the cloth is damaged with the biting marks of the upper and lower feed dogs. To solve this problem, the Japanese Laid-open Utility Model No. 63-55972 proposes a cam groove in a special shape composed of leaf spring for the guide groove to be engaged with the crank pin in order to reduce the impulsive force, but the fabrication and processing of the cam groove are rather difficult. A further example of an upper feed device in which no mechanism is provided for preventing the ellipsoidal motion of the feed dog descending below a lowermost limit and hence which is susceptible to the above-described problem is described in European Patent Application 326 752. It is hence a primary object of the invention to present an upper feed device for sewing machine capable of enhancing the feed efficiency by the upper feed dog in a simple structure, without damaging the cloth with feed dogs. The upper feed device of the invention is characterized by providing an upper feed arm or an arbitrary member in a mechanism for vertically moving the upper feed arm, with descent arresting means for arresting a motion more than a specific amount to prevent the upper feed dog from descending below a desired position, in which as the upper feed dog moves ellipsoidally in for directions in longitudinal and vertical motions, the lower portion of the ellipsoidal track is cut off at a desired height by the descent arresting means so as to form a nearly horizontal line. According to the upper feed device of the invention, aside from improvement of the feed efficiency, since the upper feed dog is not lowered from a specified height if the feed efficiency is raised, increase of the feed damages caused by increase of the gripping force of the upper and lower feed dogs on the cloth may be prevented. If the upper feed is not sufficient due to ascent of the descent position of the upper feed dog, the upper feed dog affixed on the upper feed arm may be adjusted in the vertical position. As a result, without changing the descent position of the upper feed dog, or by freely adjusting the descent position, the lower portion of the ellipsoidal track may be cut to a desired height. In a preferred embodiment, the descent arresting means is composed of a pin placed sideways below the upper feed arm, and it arrests on the way of descent of the upper feed arm coming down along with the downward rotation of the crank. In this case, it is desired to adjust the vertical position of the pin, so that the height of the descent position of the upper feed dog is adjusted, thereby varying the feed efficiency. The descent arresting means in a preferred embodiment in the upper feed device having a clutch mechanism disposed in the vertical motion mechanism of the upper feed dog is composed of a block installed below the roller pivoted on the crank pin. This block preferably has the upper surface engaged with the roller and inclined longitudinally. This longitudinal position is designed to be adjustably. The descent arresting means in other preferred embodiment is composed of stopper piece supported on the sewing machine frame by a rod, so as to engage with the abutment of the collar composing the clutch mechanism affixed on the swinging shaft or the stopping means disposed on the swinging shaft. In this case, too, preferably it is designed to adjust the position of the stopper piece by varying the mounting position of the rod. Specific embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which:- Fig. 1 is a perspective view of an conventional upper feed device for sewing machine. Fig. 2 is a side view of parts of an upper feed device for sewing machine embodying the invention. Fig. 3 is a motion diagram of upper feed dog of upper feed device for sewing machine embodying the invention. Fig. 4 is a perspective view in other embodiment of upper feed device for sewing machine embodying the invention. Fig. 5 is an exploded perspective view of a mechanism for moving the upper feed arm vertically of the upper feed device shown in Fig. 4. Fig. 6 is a sectional view of the upper feed device shown in Fig. 4. Fig. 7 is a motion diagram of a conventional upper feed dog. In the upper feed device shown in Fig. 1, swinging of a crank 15 affixed on an upper knife shaft 13 for moving an upper knife 11 vertically is transmitted to a bifurcate lever 19 rotatably supported on a vertical feed shaft 17 through a slider crank mechanism, and the vertical feed shaft 17 is oscillated through a clutch mechanism 27 consisting of a abutment 21 at the boss part of the bifurcate lever 19 and a abutment 25 of a collar 23 affixed on the vertical feed shaft 17, thereby vertically oscillating a crank 29 affixed on the shaft end. In the crank 29, a roller 31 pivoted on the crank pin slidably fits in a guide groove 37 formed by an upper feed arm 33 and a guide 35 disposed parallel at its lower side, and by its swinging the upper feed arm 33 is moved vertically in collaboration with a spring device 41 for pushing down the upper feed arm, and at its front end an upper feed dog 39 is installed so as to be adjusted in the position by a screw 40 driven into the upper feed arm 33 through a slot (not shown) in the lengthwise direction. In this way, the upper feed dog 39 moves vertically by the swinging of the crank 29, and its longitudinal motion is effected by the longitudinal swinging of the crank 43 pivoting the upper feed arm 33. In thus composed upper feed device, below the roller 31 pivoted on the crank pin, as shown in Fig. 2, a block 45 as descent arresting means is mounted on a felt 49 of a bed 47 of sewing machine. When the crank 29 descends, the block 45 is engaged with the free end lower surface of the crank 29, thereby preventing further descent of the roller 31, that is, the crank 29. When lowering is arrested, the abutment 21 of the clutch mechanism 27 is released from the abutment 25. The block 45 responsible for defining of lowering of the roller 31 has its upper surface 46 as the plane of action inclined downward at the front, and it is designed to be adjusted longitudinally in the mounting position by a screw 53 driven into a sewing machine frame (not shown) within a range of a slot 51 in the lengthwise direction, so that the lowering limit of swinging of the crank 29 may be freely adjusted by the adjustment of the longitudinal position. In the foregoing embodiment, the block 45 has the upper surface as the plane of action inclined downward at the front and is engaged with the free end lower surface of the crank 29, but the upper surface may be inclined downward at the rear side or be curved, or may be engaged with the collar affixed on the crank, upper feed arm or vertical feed shaft. The device is thus composed, and the upper feed dog for making four ellipsoidal motions consisting of longitudinal move and vertical move is arrested in the descending motion, as shown in Fig. 3, as the free end lower surface of the crank 29 is engaged with the block 45, and then moves nearly in a horizontal track, and its feed action section EF is nearly same in length as the total motion mount GH in the longitudinal direction of the upper feed dog 35, so that the cloth may be fed at a high feed efficiency. What is more, if the feed efficiency is raised, the upper feed dog 35 does not descend below a specified height, and engagement with the lower feed dog 55 does not become deeper, so that the cloth may not be damaged. In the upper feed device shown in Fig. 4 and Fig. 5, swinging of a knife lever 63 affixed on an upper knife shaft 61 is transmitted to a lever 69 rotatably supported on a vertical feed shaft 67 through a rod 65, and the lever 69 transmits its swinging to the vertical feed shaft 67 through a clutch mechanism 71, thereby swinging the crank 73 affixed at its shaft end. The clutch mechanism 71 comprises, as shown in Fig. 5, an adjusting screw 75 driven in the lever 69, abutment 79 of a collar 77 affixed to the vertical feed shaft 67 by screw 68, and C-spring 81 coupling the lever 69 and collar 77 and pressing the projected end of the adjusting screw 75 to the abutment 79 of the collar 77. When the lever 69 is rotated downward resisting the action of the spring 81 in the state that the collar 77 is stopped still, the adjusting screw 75 is separated from the abutment 79. The spring force of the spring 81 can be adjusted by driving the adjusting screw 75 and varying its projecting extent. The crank 73 rotatably pivots a guide 85 having a guide groove 84 slidably engaged with a upper feed arm 83. The upper feed arm 83 is moved vertically by swinging of the crank 73. An upper feed dog 87 is attached to the front end of the upper feed arm 83 so as to be adjustable in the position by a screw 88 driven into the upper feed arm 83 through a slot 86 in the lengthwise direction. A collar 89 is affixed to the vertical feed shaft 67 through a screw 90 as shown in Fig. 6. A rod 93 supported on the sewing machine frame 91 adjustably in the mounting position engages with a abutment 97 of the collar 89 to prevent the collar 89, that is, the crank 73 from rotating more than specified, so that the upper feed dog 87 may not descend below a specified height. The abutment 97 of the collar 89 composing the descent arresting means together with the lower end of the rod may be replaced by the abutment 79 of the collar 77, or the collar 77 or a member mounted on the vertical feed shaft may be used. The vertical motion of the upper feed dog 87 is effected in this way, and its longitudinal move is effected by the longitudinal swinging of the crank 99 pivoting the upper feed arm 83.

Claims: An upper feed device for a sewing machine, said upper feed device comprising: an upper feed arm (33,83) having a base end and a front end; an upper feed dog (39,87) attached to said front end; a longitudinally swinging crank (43,99) linked to said base end; a vertical motion mechanism comprising: a crank (29,73) swinging vertically in cooperation with a main shaft and linking said upper feed arm (33,83); said upper feed device being characterized in that: said vertical motion mechanism further comprises: means (27,71) for disconnecting the cooperation between the main shaft and said vertically swinging crank (29,73); and, a descent arresting means (45,93) for preventing the upper feed dog from descending below a desired position. An upper feed device according to claim 1, wherein the descent arresting means is a block (45) installed below the upper feed arm (33) or below a vertically moving member of the members composing the vertical motion mechanism. An upper feed device according to claim 2, wherein the block (45) is inclined or curved on an upper surface as the plane of action, and the mounting position is adjustable. An upper feed device according to claim 1, wherein the descent arresting means includes a stopper mounted on an end of a rod (93) which is supported on a sewing machine frame, the stopper being disposed within a movable range of a part (89) moving vertically, said part (89) being affixed on to a member (67) composing the vertical motion mechanism or a vertically moving member of the members composing the vertical motion mechanism. An upper feed device according to claim 4, wherein the rod (93) is supported on a sewing machine frame adjustably in position. An upper feed device according to claim 1, wherein the upper feed dog (39) is affixed on the upper feed arm (33) adjustably in height.

Inventors: HIKIGUCHI SYOZO, KASUDA TAKASHI, KEIICHI AOKI, NOGUCHI KAZUO, SETO YOJI, TERANISHI AKIRA, HIKIGUCHI, SYOZO, KASUDA, TAKASHI, KEIICHI, AOKI, NOGUCHI, KAZUO, SETO, YOJI, TERANISHI, AKIRA
Applicants: PEGASUS SEWING MACHINE MFG CO, PEGASUS SEWING MACHINE MFG. CO., LTD.
Application year: 1991
Main classification: D05B27
IPC codes: D05B27, D05B29