US3640236A

US3640236A - Thread retainer for sewing machines

Info

Publication number: US3640236A
Application number: US51530A
Authority: US
Inventors: Karl Nicolay
Original assignee: Duerkoppwerke GmbH
Current assignee: Duerkoppwerke GmbH
Priority date: 1969-07-03
Filing date: 1970-07-01
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08
Also published as: DE1933780A1; GB1264736A

Abstract

A double-lockstitch sewing machine, provided with a threadcutting mechanism, has a thread retainer for supplying a predetermined thread length of upper thread at the conclusion of a stitching operation and as a preliminary to a subsequent stitching operation. The retaining arrangement includes a thread brake which is released at the end of the stitching operation and an eye for drawing the released thread from a spool or other supply to provide the desired length.

Description

llnited States Patent Nicolay 5] Feb. 8, 1972 [54] THREAD RETAINER FOR SEWING 2,584,013 1/ 1952 Hagquist ..112/241 MACHINES 2,925,058 2/1960 Conrad ....l12/254 2,976,831 3/1961 Hacklander.. ....112/254 X [721 Km W Bmlefeli Germany 1,273,157 7/1918 De Voe ..112/241 [73] Ass1gnee: guarl'llsrloppwerh Gmbfl, Brelefeld, Ger- FOREGN PATENTS OR APPLICATIONS [22] Filed, July 1 1970 1,128,726 4/1962 Germany ..112/241 i [21] Appl.No.: 51,530 Primary Examiner-Jordan Franklin Assistant Examiner-George H. Krizmanich 301 Foreign Application Priority um Ammeyxal Rm July 3, 1969 Germany ..P 19 33 780.5 [57] ABSTRACT A double-lockstitch sewing machine, provided with a thread- ..ll2/2:6!1b i/92/5X2) cutting mechanism has a thread retainer for supplying a l 58] Field s I 48 254 predetermined thread length of upper thread at the conclusion 252 242/153 of a stitching operation and as a preliminary to a subsequent stitching operation. The retaining arrangement includes a thread brake which is released at the end of the stitching [561 Refer Cited operation and an eye for drawing the released thread from 21 UNITED STATES PATENTS spool or other supply to provide the desired length.

1,048,442 12/ l 912 Blair ..1 12/246 10 Claim, 7 Drawing Figures INVENTOR (ar/ A/ICOL A) marl To ATTORNEY l THREAD RETAINER FOR SEWING MACHINES FIELD OF THE INVENTION My present invention relates to double-lockstitch sewing machines, and more particularly, for an arrangement designed to provide a predetermined length of starting thread for the upper thread of the double-lockstitch sewing machine having a thread-cutting device.

BACKGROUND OF THE INVENTION In a double-lockstitch sewing machine especially, and in commercial and industrial sewing machines of various types, a needle is reciprocated through a stitch plate in the table of the machine and alternately carries an upper thread from a thread supply (e.g., through the stitch plate and into interlocking engagement with a lower thread supplied by a bobbin below the stitch plate.

In a double-lockstitch arrangement with which the system of the present invention is particularly desirable, the lower thread is looped about the looped upper thread as the latter is withdrawn through the fabric by the needle. It is known to provide thread-severing devices in such machines and typical among machines of this general type is that of my US. Pat. No. 3,376,837 issued Apr. 9, 1968. The purpose of the threadsevering device is, of course, to cut loose the stitched article and permit the rapid transformation of the machine for the stitching of another article.

One of the problems in high-speed commercial and industrial sewing machines and, in general, sewing machines using upper and lower threads, is that irregularities occur in the commencement of the sewing operation, especially with fast starts. One of the irregularities or nonuniformities derives from the fact that, even where manual or automatic devices are provided for severing the upper thread at the conclusion of a prior stitching operation, the length of the upper thread which remains is nonuniform. Should this length be excessively long, it remains on the fabric and is unsightly. Should it be too short, the thread may be withdrawn through the eye of the needle and rethreading of the machine will be required. Furthermore, the cutting device does not always position the thread in a reproducible manner and may, on the one hand, permit the free thread end to overlie the pressor foot or, on the other hand, cause the free thread end to be clamped between the presser foot and the stitch plate. If the thread is clamped, there is little danger that loose stitches will be formed, although an undesirable thread portion may overlie the fabric. However, when the thread merely overlies the presser foot in an undefined manner, a slow movement of the needle may withdraw the thread from the needle eye as noted above.

It has already been indicated that the cutting devices for the upper and lower threads may be actuated manually or with the aid of servo devices, the cutting systems being operated as soon as the previously stitched goods are drawn along the table to a distance sufficient to provide the satisfactory length of free end for upper and lower threads. Upon removal of the previously stitched goods from the machine, the withdrawn length of the lower thread remains beneath the stitch plate while the upper thread is drawn with the fabric through the stitch hole in the stitch plate.

The withdrawal of the upper thread through thestitch plate to avoid some of the disadvantages mentioned earlier has been proposed, these systems using a wiper or swinging member passing beneath the presser foot. Here again the position of the thread on the upper side of the stitch plate is well defined and can be either above or below the presser foot and either lies loosely or is clamped. One of the prior art proposals to limit the disadvantages of earlier systems has been to use the wiper to place the thread invariably upon the upper side of the presser foot. In this case, the free end of the upper thread is engaged by the gripper finger during the initial formation of a stitch and is drawn beneath the surface of the fabric to the underside thereof. This system has the disadvantage that loose or nonlocked stitches can develop initially, especially for rapid starts ofthe stitching operation. Increasing the length of the free end is not always a solution since excessively long free ends are drawn from the needle eye with slow start modes of stitching.

OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invention to provide a thread-retaining system or thread-control system for the upper thread of a sewing machine wherein the aforementioned disadvantages can be avoided.

A more specific object of this invention-is to provide a thread-control system for a double-lockstitch sewing machine provided with thread-severing means for the upper and lower threads, which provides the desired length of free thread end at the conclusion of a stitching operation so that the subsequent stitching operation may commence without loose stitches,'l,oss of thread from the needle eye or excessively long strands atthe ends of a thread seam.

Another object of this invention is to provide, in a sewing machine of the character described, a thread-control arrangement which will insure uniform and reproducible starts of a stitchingiseam regardless of the rate at which sewing is begun and independently of the degree to which the fabric is moved following the prior stitching operation.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with my present invention by providing a thread brake for the upper thread of the sewing machine, lever means mounted on the arm thereof, and an actuating system including a member for releasing the thread brake and a second member cooperating with the first member for drawing out the desired length of thread ofa supply prior to the severing step. The thread brake, according to the present invention, may be of the double-disk type in which one disk is spring loaded against another, the thread being frictionally engaged between these disks. In this system, the lever for releasing the thread brake advantageously includes a finger receivable between the disks for spreading them apart and relieving pressure upon the thread.

According to another feature of this invention, the threaddrawing'means includes an eye or loop engaging the thread between a pair of fixed eyes for withdrawing the thread from its normal position linearly spanning these eyes.

The two levers according to the invention may be coupled with a single actuator, preferably provided with lost-motion means in order to operate the thread brake lever first and the loop-forming lever subsequently. Alternatively electromechanic or pneumatic levers may be provided for controlling the levers, programming means being employed to operate the levers in the proper sequence.

According to another feature of this invention, at least one of the levers is provided with an adjustable fulcrum for regulation of its stroke and therefore the timing relationship of levers.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description reference being made to the accompanying drawing in which:

FIG. 1 is a diagrammatic side elevational view of the arm of a double-locksn'tch sewing machine according to the invention with the cover plate removed;

FIG. Zis a view similar to FIG. 1 showing the parts of the mechanism of the present invention in another position;

FIG. 3- is a detail view of the adjustment means of the system of FIGS. 1 and 2 in another position;

FIG. 4 'is a view similar to FIG. 1 or FIG. 2 illustrating another system for actuating the levers of the present invention;

FIG. is a view similar to FIG. 4 showing still another actuating means;

FIG. 6 is a diagrammatic view of the means for operating the control member of system of FIGS. 1 and 2; and

FIG. 7 is a detail view of a thread brake which may be used with the system of the present invention.

SPECIFIC DESCRIPTION In FIGS. 1 and 2 of the drawing, the arm of the doublelockstitch sewing machine is represented at l and is provided in the stitching head of this arm, with a slot 2 in which the thread-feed lever 3 is vertically reciprocable in the usual manner.

To the right of the slot 2, there is provided a fixed threadguide eye 4 which is mounted by screws 4a upon a support plate T, carrying the mechanism of the present invention. The thread guide 4 has a leg 4b provided with an aperture 4c through which the thread 7 extends. Below the thread-feed lever 3, I provide a double-eye arrangement generally represented at 5 and fixed to the head. The double-eye arrangement comprises a bracket 5 having an upper eye 5b and a lower eye 50 between which the loop 17a of a wiper 17 is receivable. The fixed eye 5a of the thread-guide bracket 5 are horizontally staggered so that the thread 7 normally forms a thread line in passing through this eye but may be deflected from the straight line as shown in FIG. 2.

At the upper end of the arm 1, there is provided still another bracket 6 provided with thread-guide eyes 6a through which the thread 7 is passed and which serves as a direction-changing device affording some friction to the path of the thread through the system. The thread 7, of course, derives from a supply spool not illustrated.

From the fixed eyes 6a of the bracket 6, the thread 7 is looped around the thread brake 8 and then passes through the eye 4b, 4c, the thread-feed lever 3 and the eyes 5b and 5a to the needle. The upper thread-cutting arrangement is not seen in FIGS. 1 and 2 but is diagrammatically represented at 30 in FIG. 6, and may be of any conventional construction.

The actuating bar 9 (FIGS. 1, 2 and 6) of the actuating means, which may be connected to the upper thread cutter 30 (for severing the thread) by a lost-motion connection 31 formed by a slot 32 in the bar 9 and a pin 33 engageable by the left-hand end of this slot in the extreme right-hand position of the bar 9, is pivotally connected at 34 to a bellcrank lever 35 whose fulcrum 36 to the post of the sewing machine arm is located in the region of the stitch-setting mechanism. The bellcrank lever 35 is coupled with rod 37 at a pivot 38, the rod being, in turn, actuatable by a pedal 39. When the machine operator treads upon the pedal 39, the bellcrank lever 35 swings in a clockwise sense to draw the actuating member 9 to the right. A spring represented diagrammatically at 40 resists this displacement and returns the bar 9 into its left-hand position.

The actuating bar 9 is guided along the lateral flank of the arm 1 by means not shown and carries a pair of adjustable pins 10 which slide in a slot 11a of a lost-motion arm 11. The slot 11a defines with the pins an adjustable lost-motion d corresponding to the stroke of the bar 9 prior to the displacement of member 11. Member 11 is connected with the thread brake lever 14, the latter being swingable in a fulcrum 14a on the plate T. The connection is formed by a slot 12 extending generally vertically in the lever 11 and receiving a pin 13 of the lever 14. The foot 14b of lever 14 is generally wedge shaped (FIG. 7) and is receivable between the disk 8a and 8b of the thread brake to spread these disks apart against the spring 8c and permit the thread 7 to be drawn frictionlessly through this thread brake.

At a fixed location on the arm of the machine, there is provided an eccentric fulcrum 15 which is rotatable as shown in FIGS. 1 and 3 to adjust the actual fulcrum point of the lever 16 (loop-forming lever). The swinging lever 16, in turn, carries a pin 16a which is received in the lost-motion slot 90 of the bar 9 at its lower end, the swinging lever 16 carries the loop former 17.

The loop-forming wiper 17 is fixed to a setscrew 18 which is bored to receive the wire from which the member 17 is bent.

In operation, the actuation of the rod 9 by a movement thereof to the right, upon conclusion of a stitching seam, results initially in displacement of the lever 14 in the counterclockwise sense to spread the disks of the thread brake 8 and permit the thread 7 to be freely drawn thereto. Shortly thereafter, the further displacement of member 9 swings the lever 16 to the right (counterclockwise about the fulcrum 15), to draw its movable eye 17 to the right (FIG. 2) and provide an additional thread supply between the thread feed lever 3 and the needle. The limiting positions of the levers 14 and 16, just prior to thread cutofi, is shown in FIG. 2. A slight additional displacement of member 9 suffices to actuate the upper thread cutter 30 (FIG. 6).

In FIG. 4, the lever [14 and the lever 116 each are provided with a pneumatic cylinder 114' and 116', the pistons of which are biased into the opposite or rest positions of the levers by springs diagrammatically represented at 114" and 116" respectively. A programmer P pneumatically actuates the cylinder 114 slightly ahead of the cylinder 116' and then triggers a pneumatic cylinder coupled with the thread cutter 130 which is shown diagrammatically. The

levers

114 and 116 perform precisely the same functions as the levers 14 and 16 previously described. Operation of the programmer P can be triggered by a switch or valve controlled by the operator or by automatic means.

In FIG. 5, the

levers

214 and 216 are shown to be displaceable against the force of springs 214" and 216" by electromechanical means, i.e., solenoids 214' and 216' controlled by an electrical programmer P.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

1. A thread-control mechanism for a sewing machine having an arm overhanging a stitch plate, a needle reciprocable on said arm, a reciprocable thread-feed member reciprocable on said arm and feed means for advancing a sewing thread in succession through said thread-feed member and said needle, said thread-control mechanism comprising a thread brake on said arm forming part of said feed means and engageable with a sewing thread fed through said thread feed member and needle for retarding passage thereof to said needle, a brake-control lever engageable with said thread brake and swingably mounted on said arm for releasing the thread, a loop-forming lever swingably mounted on said arm and forming part of said feed means for engaging thread between said thread-feed member and said needle for forming a thread loop, and actuating means forming part of said feed means for sequentially operating said brake-control lever and said loop-forming lever.

2. The mechanism defined in claim 1 wherein said sewing machine has an upper thread cutter for severing said thread, said actuating means being operatively connected with said cutter for operating same upon the formation of said loop.

3. The mechanism defined in claim 2, further comprising means for adjusting the stroke of at least one of said levers.

4. The mechanism defined in claim 2, further comprising spring means yieldably resistant to displacement of at least one of said levers by said actuating means.

5. The mechanism defined in claim 4 wherein said means includes at least one pneumatic cylinder.

6. The mechanism defined in claim 4 wherein said actuating means includes at least one electromagnet.

7. The mechanism defined in claim 4 wherein said actuating means includes a bar mounted in said arm and shiftable longitudinally thereof and lost-motion means connecting said bar with said loop-forming lever.

l actuating lever being provided with a movable eye received between said fixed arms.

10. The mechanism defined in claim 9, wherein said thread brake has a spring-biased disk, said brake-control lever engaging said disk.

I0! l 1F

Claims

5. The mechanism defined in claim 4 wherein said actuating means includes at least one pneumatic cylinder.

8. The mechanism defined in claim 7 wherein said loop-forming lever is provided with an eccentric fulcrum rotatable to shift the fulcrum axis on said arm.

9. The mechanism defined in claim 8, further comprising a pair of vertically spaced fixed thread-guiding eyes between said thread-feed member and said needle, said loop-forming lever being provided with a movable eye received between said fixed arms.