GB2307700A

GB2307700A - Thread cutter for a chainstitch sewing machine

Info

Publication number: GB2307700A
Application number: GB9524683A
Authority: GB
Inventors: Fei-Lung Ku
Original assignee: KU FEI LUNG
Current assignee: KU FEI LUNG
Priority date: 1995-12-02
Filing date: 1995-12-02
Publication date: 1997-06-04
Anticipated expiration: 2015-12-02
Also published as: GB2307700B; GB9524683D0

Abstract

A thread cutter for a chainstitch sewing machine has a cutter arm (2) received in a recess (12) in a base plate and pivotable at one end about a fulcrum (21), the arm (2) carrying a cutter (4) and trapper (3) at its other end, and a thread-catching arm formed with a notch (51) drivingly engaged by a swinging arm (7) and with slots (52) engaging guide elements (521) on the cutter arm so as to be guidingly displaceable relative to the latter, the catching arm being connected to a rod (6) formed with thread-catching hooks (63) and the swinging arm (7) having a projection (74) which engages in a curved guide slot (22) in the cutter arm (2).

Description

THREAD CUTTER FOR A CHAINSTITCH.SEWING MACHINE BACKGROUND OF THE INVENTION A known conventional thread cutter for a chainstitch sewing nachine, as shown in FIG. 6, disclosed in an U.S. Patent, No. 4,098,209, including a diving unit (not shown in the drawing), a swing arm 90 which has a front head 901 at one end polished to be smooth and of which the other end is moved by the driving unit to swing clockwise through a proper ange and then swing back to perform a round of thread cutting action. At the beginning of the action, the front head 901 of the swing arm 90 fits in a notch 921 of a hook rod arm 92. As the swing arm 90 is moved to swing, the front head 901 moves down in the notch 921 so that the hook rod arm 92 is pushed down, guided by a screw 923 in a slot 922, moving down slantingly.During downward movement of the hook rod arm 92, it touches a high point 931 of the cutter arm 93, forcing the cutter arm 93 to also move along with the hook rod arm 94 slantingly.

During continuous forward movement of the swing arm 90, the hook rod arm 92 moves forward straight, guided by the slot 922 sliding along the screw 923, and then a hook rod 94 fixed with the hook rod arm 92 moves to let its front hook 941 and its rear hook 942 hook related threads, the hook rod arm then further moves forward, but the cutter arm 93 is to be stopped by means of the screw 933 blocking an upper end of the slot 932.

So the cutter 95 fixed on the front end of the cutter arm 93 does not advance.

Next, the swing arm 90 is moved to swing back, retreating the hook rod arm 92, letting the hook rod 94 pass by the cutter 95 to cut the threads. Then the hook rod arm 92 is moved back to its original position, and the cutter arm 93 is moved back by a spring 934 lengthened, with the high point 931 not pushed by the hook rod arm 92. The thread cutter just described has the swing arm 90 directly moving the hook rod arm 92 forward and backward, and the cutter arm 93 is moved indirectly by means of the high point 931 being pushed by the hook rod arm 92 forward and being retreated by the spring 934. Therefore, the cutter arm is indirectly moved back and forth by the swing arm, which gives rise to complicated structure of the conventional cutter, in addition to disorder, and wear and tear of connecting spots such as the high point 931 and the spring 934.

SUMMARY OF THE INVENTION The object of this invention is to offer a thread cutter for a chainstitch sewing machine, having a swing arm directly moving a hook rod arm and a cutter arm to move forth and back in order to get rid of inconsistent movement of these components possibly caused by a long period of use.

The main feature of the present invention is a cutter arm having its rear end pivotally fixed on a base plate, a cutter fixed on a front end of the cutter arm, a pincher fixed under the front end of the cutter arm, a hook rod arm pivotally connected on the cutter arm and movable back and forth, a hook rod connected with the front end of the hook rod arm, the swing arm having a front head fitting in a notch in a rear end of the hook rod arm, a sliding element fixed under the swing arm being fitted in a guide slot of the cutter arm, and the swing arm being moved by a driving means to swing to let its front head move directly the hook rod arm and the cutter arm for cutting threads.

BRIEF DESCRIPTION OF DRAWINGS The invention will be better understood by reference to the accompanying drawings, wherein: FIG. 1 is an exploded view of a thread cutter for a chainstitch sewing machine in the sresent invention; FIG. 2 is a view showing a working a thread cutter for a chainstitch sewing machine in the present invention; FIG. 3 is a view showing a portion of a thread cutter for a chainstitch sewing machine in the present invention; FIG. 4 is a cross-sectional view of a thread cutter for a chainstitch sewing machine in the present invention; and, FIG. 5 is a top view of a known conventional thread cutter for a chainstitch sewing machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A thread cutter for a chainstitch sewing machine, as shown in FIGS. 1 - 3, includes a base plate 1, a cutter arm 2, a pincher 3, a cutter 4, a hook rod arm 5, a hook rod 6, a swing arm 7 and a fixing element 8 as main components combined together.

The base plate 1 has a plurality of location holes 11 spaced apart in the peripheral edge for screws 111 to lock the base plate 1 on the table of a sewing machine, a recess 12 in an upper surface, a threaded hole 121 near an rear end of the recess 12, and another threaded hole 13 near an upper edge of the base plate 1.

The cutter arm 2 is provided with a hole 21 at the rear end for a screw 212 and a washer 211 to pass through and engage the threaded hole 121 of the base plate 1 to secure the cutter arm 2 in its position, and at the rear end close to one side a guide slot 22 shaped slightly arcuate and having a gap 221 forming an angle from the arcuate portion of the guide slot 22; and there are several threaded holes 23, 24, holes 25, 26 opened on the cutter arm 2 and a protruding plate 27 provided on one side of the mediate portion.

The pincher 3 is shaped flat, having two holes 31, 31 in a rear end portion for screws 32, 32 to pass through the holes 25, 25 and 31, 31 to engage threaded holes 331, 331 of a locking member 33 so as to be fixed under the front end of the cutter arm 2; furthermore a thin pincher 34 is provided and positioned between the pincher 3 and the cutter arm 2.

The cutter 4 has a slot 41 in a rear portion for a screw 42 to pass through and via a hole 431 of a cushion 43 to engage the threaded hole 24 of the cutter arm 2, being fixed on the front end the cutter arm 2.

The hook rod arm 5 is elongated, having a notch 51 in a rear end, two slots 52 spaced apart in line in an intermediate portion for two screws 522, 522 and two washers 521, 521 respectively pass through to engage the threaded holes 23, 23, fixing the hook rod arm 5 on the cutter arm 2, and two threaded holes 53, 53 in a front end section.

The hook rod 6 is elongated, having a front hook 63 and a rear hook 64 spaced in line in a front end portion, and two holes 61, 61 in a rear end portion for screws 62, 62 to pass through to engage the threaded holes 53, 53 of the hook rod arm 5 so as to fix the hook rod 6 on the front end of the hook rod arm 5.

The swing arm 7 has a through hole 71 on the mediate portion for a screw 721 combined with a nut 72 to pass through and be fixed with the threaded hole 13 of the base plate 1 and at the front end a front head 73 which is positioned inside the notch 51 of the hook rod arm 5, and behind the front head 73 a sliding element 74 to be positioned in the guide slot 22 of the cutter arm 2; and there is a driving element (not shown in the drawing) connected with the other end of the swing arm 7 to drive the swing arm 7 to swing by means of the screw 721 acting as a fulcrum, thus the front head 73 can move forward and backward through a certain distance.

The fixing element 8 is fixed with clipping plate 83 and connected with one end of a spring 84 by means of a threaded hole 81 thereof and a screw 82; and a protruding plate 85 protruding from one side of the fixing element 8 is provided and positioned near the protruding plate 27 of the cutter arm 2; a fixing plate 86 of the fixing element 8 has holes 87 for the fixing element 8 to be fixed in its position.

In operating, referring to FIG. 2, the swing arm 7 is moved to swing by the driving means, permitting the slide ring 77 to move from its original position wherein the sliding element 74 is located in the gap 221 end of the guide slot 22 of the cutter arm 2 to the front of the gap 221 in the beginning of movement of the swing arm 7. Then the cutter arm 2 is moved from its original tilting condition to an upright position by means of the screw 212 acting as a fulcrum. And simultaneously, the hook rod arm 5 is also moved to lie straight by the cutter arm 2.

Next, the swing arm 7 is continuously swung to change its angle to force the sliding element 74 move to the front end of the guide slot 22, with the cutter arm 2 not moving at all. On the contrary, the hook rod arm 5 is moved to slide forward, pushed by the front head 73 in the notch 51, letting the front end of the slot 52 touching the screw 522 moved to separate from the screw 522 and then the rear end of the slot 52 contacting the screw 522 to be stopped there. Then the forward movement of the hook rod arm 5 also moves the hook rod 6 forward to hook the related threads with the front hook 63 and the rear hook 64.

Furthermore, the swing arm 7 is swung to retreat back, pulling the hook rod arm 5 and the hook rod 6 back to their original position. During retreating movement of the hook rod 6, the front and the rear hook 63 and 64 thereof pass by the blade of the cutter 4 in close contact with the cutter 4 so that the cutter 4 will cut off the threads hooked by the hooks 63 and 64. Finally, in the course of time, the swing arm 7 returns back to its original position* with the cutter arm 2 and the hook rod arm 5 also recovering their slanting position, finishing one round of thread cutting action.

As can be understood from the above description, the swing arm in the present invention directly moves the hook rod arm and the cutter arm, improving indirect movement of the swing arm as described in the known conventional thread cutter for a chainstitch sewing machine.

While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A thread cutter for a chainstitch sewing machine comprising: a base plate nearly shaped square, having a plurality of location holes spaced apart in a peripheral edge for screws to lock said base plate on a table of a sewing machine, and a threaded hole in one side; a cutter arm shaped elongate, having two threaded holes and two holes behind said threaded holes spaced in a front portion; a pincher being flat and having two holes in a rear portion for screws to pass through and also through said holes of said cutter arm to engage a threaded hole of a locking member, said pincher thus being fixed on a front end of said cutter arm, a thin pincher being positiioned between the cutter arm and the pincher; a hook rod arm having two threaded holes in a front portion; a hook rod shaped elongate end having two holes in a rear end for a screw to pass through to engage said threaded hole of said hook rod arm and to fix said hook rod on said front end of said rod arm, and a front hook and a rear hook behind said front hook in a front end portion of said hook rod; a swing arm shaped elongate and having a hole in an intermediate portion for a screw and a washer to pass through to engage said threaded hole of said base plate so as to fix said swing arm thereon, a rear end connected with a driving means so that said swing arm can be moved by said driving means to swing with said screw as a fulcrum, moving a front head through an angle; and characterized by: said base plate having a recess in its upper surface, for said cutter arm to lie therein, a theaded hole in a rear portion of said recess for a screw to engage so as to pivotally fix said cutter arm; said cutter arm having a hole for a screw and a washer to pass through to engage said threaded hole of said base plate, a guide slot having a slightly curved section and a gap which is its bent rear end section, a protruding plate and two holes in an intermediate portion; said hook rod arm having a notch in a rear end, two slots provided in line in an intermediate portion, a screw and a washer provided respectively to pass through and engage said threaded hole of said cutter arm so as to fix said hook rod arm on said cutter arm; said swing arm having its front head fitting in said notch of said hook rod arm, a sliding element hehind said front head to be positioned inside and slide along the guide slot of the cutter arm; and said fixing element being fixed with a clipping plate and with one end of a spring by means of a screw and having a plurality of holes on a fixing plate for it to be fixed in its position and having a protruding plate.

Amendments to the claims have been filed as follows CLAIMS 1. A thread cutter for a chainstitch sewing machine comprising: a base plate having a plurality of location holes spaced apart in a peripheral edge for receiving screws to lock said base plate on a table of a sewing machine, and a threaded hole in one side; an elongate cutter arm having a first set of holes comprising first and second threaded holes and a second set of holes consisting of two holes spaced behind said first set, the sets of holes being positioned in a front portion of the cutter arm;; a flat pincher having a third set of holes consisting of two holes in a rear portion thereof, screws passing through the second and third set of holes to engage threaded holes of a locking member, said pincher thus being fixed on the front end of said cutter arm, a second pincher being positioned between the cutter arm and the first pincher; a cutter being fixed to said cutter arm by a screw passing through said first hole of the first set of holes; a hook rod arm having a fourth set of holes consisting of two threaded holes in a front portion thereof;; an elongate hook rod having a fifth set of holes consisting of two holes in a rear end thereof, screws engagingly passing through the fourth and fifth sets of holes to fix said hook rod on said front end of said hook rod arm, the hook rod further having in a front end portion thereof a front hook and a rear hook behind said front hook; an elongate swing arm having a hole in an intermediate portion thereof, a screw and a washer passing through the hole of the swing arm and engaging said threaded hole of said base plate so as pivotally to mount said swing arm thereon, a rear end of the swing arm being connected with a driving means so that said swing arm can be moved by said driving means to swing with said screw as a fulcrum, moving a front head of the swing arm through an angle; and characterised by: said cutter arm lying in a recess in the upper surface of the base plate, a screw passing through a washer, a threaded hole in a rear portion of said recess and a hole in the cutter arm pivotally to mount said cutter arm on the base plate; said cutter arm having a guide slot having a curved front section and a rear end section that is angled away from the front section, the cutter arm having a protruding plate portion and a seventh set of holes consisting of two threaded holes being provided in an intermediate portion of the cutter arm;; said hook rod arm having a notch in a rear end thereof and two slots provided in line in an intermediate portion thereof, two screws passing through a respective washer engaging in a respective one of the holes of said seventh set and a respective slot of the hook rod arm so as to allow said hook rod arm to slide on said cutter arm; said swing arm having its front head fitting in said notch of said hook rod arm, a sliding element of the swing arm being positioned behind said front head and received inside the guide slot of the cutter arm for sliding along the guide slot, wherein, in use, the cutter arm and hook rod arm are moved relative to the base plate when the swing arm is moved by the driving means; and a fixing element fixed relative to the base plate and having a clipping plate mounted thereon, the clipping plate engaging the plate protruding from the cutter arm during movement of the cutter arm relative to the base plate, one end of a spring being fixed to the fixing element by means of a screw, and the other end of the spring being fixed to the cutter arm, the fixing element having a fixing plate provided with a plurality of holes for fixing the element in position relative to the base plate.