US3903821A

US3903821A - Cam thread-pulling device for the looper thread of a sewing machine

Info

Publication number: US3903821A
Application number: US452719A
Authority: US
Inventors: Nerino Marforio
Original assignee: Virginio Rimoldi and Co SpA
Current assignee: Virginio Rimoldi and Co SpA
Priority date: 1973-04-13
Filing date: 1974-03-20
Publication date: 1975-09-09
Anticipated expiration: 1992-09-09
Also published as: JPS5041653A; ES425267A1; DE2415991B2; JPS5525879B2; DE2415991C3; DE2415991A1; IT983842B; GB1455633A

Abstract

A thread tensioning device for the looper thread of a sewing machine which includes a cam driven by a rotating shaft, a mounting bracket, a plate member having an elongated opening through which the cam protrudes and means mounting the plate member on the mounting bracket whereby it can be rotated about an axis generally parallel to the axis of the rotating shaft to expose a selected amount of the cam profile.

Description

United States Patent I191 Marforio 51 Sept. 9, 1975 CAM THREAD-PULLING DEVICE FOR THE LOOPER THREAD ()F A SEWING MACHINE [75] Inventor: Nerino Marforio. Milan. Italy [73] Assignec: Virginie Rimoldi & C. S.p.A.. Milan.

Italy 221 Filed: Mar. 20. I974 2| Appl.No.:452,7l9

[30] Foreign Application Priority Data Apr. l3, I973 Ituly r. 22983/73 [52] US. Cl. 112/242 [5 1] Int. Cl. D058 49/00 [58] Field of Search 112/242. 243, 254. 255. l [2/241 [56] References Cited UNITED STATES PATENTS l,(l64,l86 6/[9 3 Wuodwurd l 11/242 l ll8 322 ll/l9l4 Weis ll2/242 X |.234.()94 7/!917 Drumheller. Ill/255 l 4()8 l85 2/1922 Gutchell v r r .7 ll2/242 1866.427 l2/l958 lrmseher Ill/242 FOREIGN PATENTS OR APPLICATIONS 5fi9 7l4 6/1945 United Kingdom l l2/242 S [8675 3/l955 Italy .4 Ill/242 Primm v l;'.\'uminerGeorgc H. Krizmanich [57l ABSTRACT A thread tensioning device for the looper thread of a sewing machine which includes a cum driven by u rotuting shaft a mounting bracket. 11 plate member having an elongated opening through which the cum prutrudes and means mounting the plate member on the mounting bracket whereby it can be rotated about an axis generally parallel to the axis of the rotating shaft to expose a selected amount of the cam profile.

2 Claims, 4 Drawing Figures PATENTEU BIBYS 3,903,821

sumlnrz CAM THREAILPULLING DEVICE FOR THE LOOPER THREAD OF A SEWING MACHINE BACKGROUND OF THE INVENTION The present invention relates to a looper threadpulling device for sewing machines and particularly to such a device. in which the thread is controlled by a cam opcratively driven by a rotating shaft of the machine.

Known devices of this type are provided with a plate having a slit or elongated opening for receiving the cam. the plate which also carries thread-guide means causing the thread to laterally cross the slit and thereby become subject to action of the cam. In known devices of this type. the plate is fixed with screws to the frame of the machine. making it possible to adjust its position in the direction of the axis of the rotating shaft to center the cam perfectly in the slit in the plate.

The cam can be adjusted and fixed in any desired position during the timing operation of the machine components. These thread pulling cams have the following functions:

a. to leave the looper thread slack when the looper is fully to the right of the axis along which the neetile is moving. so that the previously formed loop of the needle thread can be drawn upward:

b. to pull the looper thread when it enters the just formed needle thread loop. that is. when the looper begins its right-to-left travel;

c. to release temporarily the pull on the thread when the looper has already entered the loop and during the last part of the right-to-left movement thereof; and

d. to recover the looper thread when the latter begins its left-toright return stroke by taking up first the slack in the thread and then drawing in further thread from a bobbin.

It is clear that in this last phase the cam must recover more or less thread, according to the length of the leftto-right looper stroke. This length varies according to the number of needles and the distance between needles. More precisely. when a certain length of thread has to be taken up for a single-needle sewing machine. the length of thread to be taken up will be greater in a multi-needle machine, because the length of the looper is greater.

In the known art. the takingup of a greater length of thread is effected by adjusting sloted plate toward the shaft carrying the cam to increase the amount of cam projecting over the plate top. increasing in this manner the path of the thread between the two thread guides at the sides of the cam. This type of adjustment is however limited because of the size of the shaft and the cam support below the plate.

Another drawback is. that the vertical movement of the plate causes a slight delay in thread-taking up. so that the cam is no longer in proper condition to avoid a rather violent contact with the thread. Because of these drawbacks it is in most cases necessary to replace the cam with a larger one.

SUMMARY OF THE INVENTION It is the object of the present invention to obviate the above-mentioned trohlcs and to allow the use of a single size of cam independently of the number of needles and the distance between the said needles.

III

The present invention. comprises a device including a cam keyed to a rotating shaft of the sewing machine. a plate overhanging and parallel to the rotating shaft with a slit or elongated opening allowing the cam to penetrate thercthrough. thread guide means to adapt the thread to the cam contour. and means for regulating the section of the cam projecting through the slit of the plate.

DESCRIPTION OF THE DRAWINGS The present invention can best he understood by ref ercnce to the following detailed description of a preferred embodiment thereof given as example. but not limited thereto. and by reference to the accompanying drawings. in which:

FIG. I illustrates a plan view of a front part ofa sew ing machine base comprising the looper thread taking up device according to the present invention;

FIGS. 2. 3 and 4 show a perspective view of the device according to the present invention in three different working positions.

DESCRIPTION OF THE INVENTION The sewing machine chosen to illustrate the present invention is a machine of known type and it comprises. as shown in FIG. I, a base I housing longitudinally a rotating shaft 2 which may be the main shaft of the machinev The base 1 contains also a looper 3 mounted on a support 4 capable of moving along an almost elliptical path formed by the combination of a movement substantially parallel to the axis of main shaft 2 for the taking up and releasing of the needle thread loop. and a movement crosswise thereto. that is. substantially parallel to the direction of feed. The first movement suh stantially parallel to the axis of the main shaft 2 is obtained from the said main shaft by means of transmissions of known type (not shown which transmit an alternating horizontal movement to a drawrod S. The drawrod 5 is as known hinged to a pivot 6 which is an integral part ofthe support 4 of 'thc looper 3. The second movement substantially parallel to the direction of workpiece feed is also transmitted through the main shaft 2 by known transmission means comprising an eccentric (not shown) which engages a connecting rod 7. The free end of rod 7 is pivoted to an arm 8 keyed to shaft 9 of the looper. onto which is clamped a sleeve I0. The base I also includes the lower transport components comprising a multi-claw feed dog I2 fixed to a support 13 hinged to the end 14 between two parallel arms 15 that are fixed to the oscillating transport shaft 16.

Referring now to the drawing. the thread-pulling device for pulling the thread I8 of the looper 3 comprises a cam 19 formed of two equally shaped discs 20, adjacent to and forming an integral part of a hub 21 (FIGS. 2 and 3) the cam I9 is fixed with screws 22 to the main shaft 2. The thread pulling device 17, in addition to the cam I9, comprises a rectangular support 23, rigidly fixed. in overhanding relationship to the shaft 2, to a surface 24 on top of the dividing plate 25 of the base I. The support 23, resting on the surface 24, abuts vertically against the dividing plate 25. The other side of the support 23 is provided with a hole for receiving a threaded pin 28 and a slot (FIG. 4) for receiving the screw 30. Both the threaded pivot 28 and the screw 30 are screwed to a plate 31 on top of the main shaft 2. The axis of the screwed pin 28 is parallel to that of the shaft 2. and lies in essentially a common vertical plane with the axis of shaft 2. The plate 3l comprises in addition an elongated opening or slit 32 through which the cam 19 can pass. The plate 3| has, in addition a first thread guide 33 for leading the thread to disk thread tensioning device 34 of known type, and two further thread guides 35, 36, positioned respectively on opposite sides of the slit 32 so that the thread will run substantially laterally accross the slit. Each of the thread guides 35, 36 is fixed to the plate 31 by means of a screw 37 received in a slot 38 to permit adjustment of the said thread guide with respect to the cam axis. The plate 3! has, in a position located over the slit 32. two

parallel arms

39, 40 so adjusted as to enter exactly between the two disks 20, the said arms carrying the thread 18 controlled by the thread guides 35, 36.

With particular reference to H65. 2. 3. 4, we shall now describe the operation of the thread pulling device 17 during the looper thread take-up phase. when the looper begins its left-to-right return stroke to take up thread slack. The cam I) initially contacts the thread [8 between the two thread guides 35. 36 (FIG. 2), then begins to draw in the looper thread by making it run in the track between the two parallel arms 39, 40 (H6. 3). Once the entire slack of the looper thread has been taken up. the cam draws in further thread from a bobbin (not shown). The thread taking-up action of the cam stops after partial rotation there. The interval of time for thread takingup obviously does not only depend on the contour of the cam, but also upon the relative position of the two thread guides 35, 36 and that of the two

parallel arms

39, 40 with respect to the cam. To increase the length of thread to be taken up from the looper as a function of the number of needles and as a function of the distance between the needles without having to change the moment in which thread taking-up begins and without having to replace the cam, it is sufficient to loosen the screw and rotate the plate 3] in downward direction around the threaded pin 28. Then the plate 31 is again securely fastened to the support 23 by tightening the screw 30, thus precluding any rotation of the plate during operation of the sewing machine. The downward rotation of the plate increases the time interval the cam remains in contact with the thread and therefore increases the length of thread taken up, without however changing the time moment in which the said interval begins. This is essentially due to the fact that the rotation of the plate does not substantially change the position of the thread guides 35. 36, which are approximately in line with the threaded pin 28. The rotation of the plate increases the cam section projecting through the slit 32, thereby increasing the length of thread running through the track between the two

parallel arms

39, 40. Obviously. modifications and variations can be made to this insertion, for example, the slot 29 could be made on the plate 31 instead of on the support 23; in addition, the various components can be replaced by other, technically equivalent ones without departing from the scope of the invention.

I claim:

I. A cam thread pulling device for the looper thread of a sewing machine comprising a cam operatively driven by a rotating shaft, a support bracket mounted on the sewing machine adjacent said cam, a plate member including means defining an elongated opening therein through which said cam can extend and including thread guiding means thereon to direct thread in a direction substantially laterally across said elongated opening. means securing said plate member to said support bracket for adjustable rotation about an axis sub stantially parallel to the axis of the rotating shaft to expose a selected amount of said cam beyond the surface of said plate member and thereby provide for the take up of different lengths of thread, and means contacting said plate member and said support bracket to secure them together in a selected position where no rotation of said plate member will occur during operation of the sewing machine.

2. A device according to claim I, wherein the said means providing the axis of rotation for said plate member has its axis parallel to the axis of said rotating shaft and both axes lie in a common vertical plane.

Claims

1. A cam thread pulling device for the looper thread of a sewing machine comprising a cam operatively driven by a rotating shaft, a support bracket mounted on the sewing machine adjacent said cam, a plate member including means defining an elongated opening therein through which said cam can extend and including thread guiding means thereon to direct thread in a direction substantially laterally across said elongated opening, means securing said plate member to said support bracket for adjustable rotation about an axis substantially parallel to the axis of the rotating shaft to expose a selected amount of said cam beyond the surface of said plate member and thereby provide for the take up of different lengths of thread, and means contacting said plate member and said support bracket to secure them together in a selected position where no rotation of said plate member will occur during operation of the sewing machine.

2. A device according to claim 1, wherein the said means providing the axis of rotation for said plate member has its axis parallel to the axis of said rotating shaft and both axes lie in a common vertical plane.