Wrap-around Mechanism For The Stop Motion Means Of A Multi-needle Sewing Machine

Abstract

An automatic stop motion means using, at the beginning of the conventional thread-tensioning section, a separate rotary wrap-around unit for each separate needle thread, each unit comprising a wrap-around wheel mounted on a one-way clutch. All units are mounted on a common shaft which is driven at an adjustably fixed minimum speed. Each wrap-around wheel is normally rotated by its needle thread at a thread-dictated speed which is higher than the adjustably fixed minimum speed of that common shaft. Upon the breakage of a given needle thread, the rotary speed of its wrap-around wheel quickly decreases. When the decreasing rotary speed of the wrap-around wheel equals the fixed speed of said common shaft, which is set to approximate (but not to equal or exceed) the minimum speed of the slowest moving unbroken needle thread, the common shaft will then take over the job of rotating that particular wrap-around wheel. Consequently, the supply end of the broken needle thread continues to be fed into the thread-tensioning section while the withdrawal of that thread from that section decreases and may stop altogether. This action hastens its loss of tension in the thread-tensioning section and correspondingly hastens the operation of the threadtension sensor in shutting down the sewing machine. The foregoing arrangement not only minimizes the frequency of shut-downs, due to overloads on the fastest threads and to false indications of thread breakage on the slowest threads, but also minimizes the "line-out" time, which elapses between thread breakage and shut-down, and thus correspondingly reduces the length of the "line-out" (i.e. the line which is not stitched into the work by the broken thread) and the magnitude of the repair required to correct it.

Description

BACKGROUND OF THE INVENTION

1. Field Of The Invention

This invention relates to an improved means for automatically shutting down a power-driven multi-needle sewing machine.

More particularly, it relates to automatic stop motion means which place and maintain, under tension, a portion of each needle thread, lying between its spool and its needle, and which sense an excessive slackening, loss or reduction of tension in that portion for shut-down purposes.

2. Description Of The Prior Art

In a multi-needle machine, -- of the type used to sew a multiplicity of longitudinally-extending transversely spaced stitch lines into a quilt (or other product) as it is fed forwardly through the machine, -- it is obviously desirable (1) to eliminate (or substantially reduce) the breakage of the fastest threads due to overloads and the shut-downs which result therefrom, and (2) to detect promptly not only the breakage of needle-threads and bobbin-threads but also the development of below-minimum rates of usage of the slowest threads, and to shut down the machine as soon as possible after any such event occurs. Consequently, such machines may be conventionally equipped with stop motion means comprising: means for tensioning an intermediate section of each needle thread, lying between its supply spool and its sewing needle; and means for sensing this tension in order to shut down the machine automatically upon the development of an excessive amount of slack in the thread-tensioning section. Prior U.S. Pats. to Hangartner No. 2,696,608, Kuhn No. 3,009,433, Vossen No. 3,094,855 and Jackson No. 3,529,560 exemplify this conventional prior art practice.

In most, if not all, of the prior art machines, which are equipped with such stop motion means, the individual threads coming from each supply spool are all wrapped around a common roll, located at the beginning of the thread-tensioning section, and are then directed successively through a tension-holding frictional device, which is located at the end of the thread-tensioning section, and a take-up bar, which is located between the thread-tensioning section and the needles and arranged to pull thread from each spool during the upstroke of the needles in order to have a supply of thread available for use by the needles during their ensuing downstroke. The pull of the take-up bar causes the threads to rotate the common wrap-around roll, which is lightly braked to an adjustable degree so as to resist the pull sufficiently to build up a desired degree of tension on the threads in the thread-tensioning section.

The tension of each individual thread in that section (and the speed at which it moves through that section) will vary because such threads are not used or consumed in the sewing operation at the same rate; hence, they are not withdrawn from the thread-tensioning section at the same rate. The most rapidly consumed threads move the fastest and exert the highest pull on the common wrap-around roll. The least rapidly consumed threads move the slowest and exert the lowest pull. Since all threads, fast and slow, enter the thread-tensioning section at the same high speed, which is dictated by the fastest threads, and since they leave that section at different rates ranging from high to low, the tension of the fast threads is high while that of the slow threads is low. As a consequence, it is not uncommon for a given fast thread to be overloaded to its breakage point. Also it is not uncommon for the tension on a given slow thread to drop below a desired minimum. When this drop occurs, it may be falsely sensed by the sensor as a broken thread; hence, the sensor responds by shutting down the machine. This false indication of breakage is highly objectionable. Where the drop is due to the usage of the slowest thread at a rate below the desired minimum, a shut-down is desirable.

SUMMARY OF THE INVENTION

Objects Of The Invention

The principal objects of the present invention are: to eliminate or substantially reduce excessive breakage of the faster threads; to reduce in a substantial measure and possibly eliminate false indications of thread breakage and thereby correspondingly reduce or eliminate accidental shut-downs; and to shut down the machine upon the development of below-minimum rates of usage.

Another important object is to maintain the tension of each needle thread in the thread-tensioning section at a value, which varies in direct proportion to variations in the rate at which that thread is being consumed or used.

Another object is to accomplish the foregoing objectives by a thread-tensioning arrangement which is simple and inexpensive to construct, easy to install, effective in operation and so sturdily constructed that it is not readily damaged or otherwise subject to repair, replacement or other maintenance.

Statement Of The Invention

All of the foregoing objectives can be readily achieved by providing an improved wrap-around mechanism comprising:

A. a group of independent wrap-around wheels, one for each needle thread of a corresponding group of individual threads, each wheel normally being idly rotated by the pull of its needle thread at speeds corresponding to the normal range of rates at which that thread is being used;

B. independent drive means for said wheels, said independent drive means including

1. a common drive shaft for supporting said group of wheels, and

2. means for driving said shaft at a take-over speed slightly below the wheel speed corresponding to the lowest rate of usage in said normal range; and

C. connection means operative, when the usage rate of a given needle thread falls below said normal range of usage rates, to cause said independent drive means to rotate the corresponding wrap-around wheel at said "take-over" speed and thereby take over the job of pulling said given thread from its supply spool and feeding it into its tensioning section.

With this mechanism, each needle thread is positively pulled from its spool at the rate required by its rate of consumption. Thus, when a given needle encounters an increased sewing thickness, an increased amount of thread will be consumed in spanning that thickness. This increases the rate at which that thread is withdrawn from its thread-tensioning section and that rate increase, in turn, causes the corresponding wrap-around wheel to rotate at a correspondingly higher speed. The reverse occurs when the sewing thickness decreases. Since each wrap-around wheel rotates independently of all other wrap-around wheels, the tensioning section of a given slow thread is no longer subjected to the high entering speed of a fast thread and its own slow exit or withdrawal speed. Also, since each wrap-around wheel speeds up and slows down immediately in direct accordance with increases and decreases in the usage of its thread, false indications of breakage are correspondingly eliminated. Now, when the tension of the tensioning-section of a given slow thread drops below the desired minimum, it is due to a below-minimum rate of usage, which makes the ensuing shut-down desirable because the quality of the sewing is always poor in such cases.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiment of the present invention is illustrated in the accompanying drawings wherein:

FIGS. 1-3 are fragmentary diagrammatic top plan, front elevational and side elevational views showing, in a multi-needle sewing machine equipped with an automatic stop motion means constructed in accordance with the teachings of this invention, sewing threads extending from the supply spools to the sewing needles and the associated mechanism for supporting, guiding, tensioning and feeding the threads;

FIG. 4 is an enlarged fragmentary elevational view corresponding to one taken along line 4--4 of FIG. 3 showing the wrap-around means for an individual thread but omitting the thread;

FIG. 5 is a section taken along line 5--5 of FIG. 4; and

FIG. 6 shows a modified wrap-around means.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

Conventional Structure

In FIGS. 1-3, each individual thread travels from a supply spool 10 successively through thread guides 11, 12 and 13, the wrap-around mechanism 14, the "drop wire" 15 of a tension sensor having a stationary contactor bar 16, thread guide 17, a thread-tensioning spring-wire coil 18, a guide bar 19, thread take-up bar 20 and needle 21 on needle bar 22. Except for the wrap-around mechanism 14, the foregoing arrangement is conventional in construction and operation; hence, further description of its structure is not believed to be necessary. It will be understood that its conventional structure may be varied in accordance with the teachings of the prior art.

Multi-needle quilting machines are conventionally used in the manufacture of a variety of products such as mattress pads, bedspreads and quilted outer and inner wear clothing material. The material fed into the machine often consists of a layer of cloth on each side of a layer of batting. This sandwich is stitched or quilted into various designs. For the sake of simplicity, we shall assume in the present case that a multi-needle machine is being used to sew the material together along straight, parallel stitch lines.

In such use, there are times when a needle thread breaks, causing the corresponding portion of that line of stitching to be omitted. Some machines not equipped with stop motion means corresponding to sensor 15 and indicator bar 16, continue to operate until the operator of the machine observes the broken thread condition. He then stops the machine, rethreads the broken thread and reinstitutes the operation of the machine. This operator does not attempt to sew in the "line out", i.e. the line of omitted stitching, which usually is not less than a yard long and may run several yards long, depending on the alertness of the operator. Such "line outs" are sewn in later, usually on a single needle machine by a special "line out" operator, who hand-guides each line of stitching. In operations having from 40 to 60 thread-breaks per machine per shift, repairing "line outs" is an expensive and time-consuming operation.

In machines conventionally provided with stop motion means, such means will automatically stop the machine not only when a needle thread breaks but also when a bobbin thread breaks. This reduces the length of each "line out". As a consequence, a "line out" resulting from a broken needle thread normally measures from 3 inches to 9 inches long. Those resulting from a broken bobbin thread are normally twice as long, usually ranging from 6 inches to 18 inches in length.

The present invention does not eliminate thread breaks or "line outs". For all practical purposes, it eliminates machine shut-downs due to overloads on the fast threads and those occasioned by false indications of slow thread breakage.

Inventive Structures/FIGS. 3-5 and 6

Broadly speaking, the wrap-around mechanism 14 of our invention centers upon the use of a multiplicity of independent wrap-around wheels, one for each thread, each wheel normally being idly rotated by its thread in direct accordance with its rate of usage, and, when that rate of usage decreases below a predetermined minimum, an independent drive means becomes operative to rotate the wheel at a fixed thread-pulling speed which is slightly lower than the wheel speed corresponding to said predetermined minimum rate of usage.

More specifically, the wrap-around mechanism 14 of our invention comprises: a series of independent wrap-around wheels 24, one for each sewing thread; a common shaft 25 for supporting said series; a series of one-way clutches 26, one for each wrap-around wheel 24, each clutch cooperating with its wheel to form a wrap-around unit and functioning to mount its wrap-around wheel on said common shaft 25 for shaft-driven rotary movement at a selected or fixed predetermined minimum speed under broken-thread conditions; means for spacing the wrap-around wheels; means for braking the wrap-around wheels for thread-tensioning purposes; and suitable means for driving said shaft 25 at said fixed predetermined minimum speed.

Obviously, any of various ways of spacing and braking the wrap-around wheels may be employed. Preferably, each should be designed to permit ready adjustment. In FIGS. 4-5 of the preferred embodiment, the spacing means comprises a suitable number of shaft-encircling washers 28 between adjacent wrap-around wheels while the braking means comprises a suitable number of shaft-encircling springs 30, one for a group of wrap-around wheels 24. The washers 28 may be varied in thickness or number for adjustment purposes. Each spring 30 is slightly compressed between a fixed shaft-encircling collar or bearing standard 31 and the adjacent end of its group of wrap-around wheels. By compressing a group of wrap-around units and washers together, each spring provides the slight braking action required to produce a slight degree of tension in the tensioning section of each individual thread associated with that group of units and washers.

The drive means indicated in FIG. 3 includes a readily adjustable speed change mechanism 32, having input and output connections 33 and 34. The input connection preferably is driven from the main drive shaft (not shown) of a multi-needle sewing machine (not shown). The output connection 34 is connected to drive the common shaft 25.

Each one-way clutch 26 may be of any suitable construction, the construction indicated being of the wedge-roller type wherein a roller 36, located between the wheel 24 and shaft 25, connects those parts together by a wedging action when the speed of the wheel 24 decreases to the point where it tends to fall below the speed of the shaft. When the speed of the wheel 24 in one direction initially exceeds the speed of the shaft in the same direction, the roller 36 becomes unwedged and thus disconnects the wheel from the shaft. So long as the wheel speed exceeds the shaft speed, the roller 36 remains unwedged.

Operation Of Inventive Structure

In the present case, the usage of each individual thread, from its supply spool or cone to its needle under unbroken thread conditions, is the same as in any conventional multi-needle sewing machine. The present invention takes over only when there is a malfunction in the sewing caused by needle thread breakage or bobbin thread breakage or by an excessive loss in tension of a given thread.

Accordingly, the operation of a multi-needle sewing machine, constructed in accordance with the present invention, is identical to that of machines conventionally provided with stop motion means except that each of our wrap-around wheels 24 is free to rotate at the speed which its particular rate of thread usage dictates; hence, the tension placed and maintained on the thread-tensioning section of each individual thread is determined by and varies in direct accordance with the rate at which that thread is used or consumed. For a given sewing operation, we may assume that the tension on each thread individually, and of all threads collectively, will normally be within an operative range having more or less known minimum and maximum values corresponding to the amount of thread required by the smallest and largest stitches. Consequently, the speed change mechanism 32 is adjusted to drive the common shaft 25 at a rotational speed slightly below the slowest usage rate of the slowest unbroken thread.

It will be understood that each needle thread preferably extends 360.degree. or more around the periphery of its wrap-around wheel and that it rotates its wrap-around wheel 24, independently of the rotation of all the other wheels, at a rate determined by its own usage rate. The tension and the load on the fastest intact needle thread will be the product of its own fast usage rate alone. This eliminates thread-breakage overloads which occur on the fastest thread of a group when that thread has to drive a common wrap-up roll for all members of the group.

Similarly, the tension on the slowest intact needle thread will be the product of its own slow usage rate. This eliminates the development, on the slowest intact thread in a group, of a tension which is the product of its own slow usage rate and the much faster usage rate of the fastest thread in that same group; hence, it correspondingly eliminates the loss of tension on the slower unbroken threads which give rise to false indications of thread breakage.

Now, if the speed of the wrap-around wheel for the slowest intact thread of a group decreases to the point where the tension, in the tensioning section of that slow thread, drops below the desired minimum, such drop will necessarily be due to a below-minimum rate of usage. The below-minimum tension in this case results in the operation of the stop motion means, which shuts down the sewing machine. This shut-down is desirable because the quality of sewing is always poor where the machine is not using enough thread.

Obviously, if any needle thread breaks, there will be a rapid loss of tension in its intermediate tensioned section. Likewise, if the bobbin thread for any needle thread breaks, there will be a rapid loss of tension in the intermediate tension section of its needle thread but, in this case, the speed of such loss may be cut in half. In each case, the "drop wire" 15 is quickly lowered into contact with the stationary contactor bar 16 causing the stop motion means to shut down the operation of the machine. The lowered position of the "drop wire" 15 enables the operator to locate the break quickly and thus minimize the loss of time involved in rethreading the broken thread and reinstituting the operation of the machine.

The common portion of the wrap-around mechanisms shown in FIGS. 4-5 and in FIG. 6 comprises: a group of independent thread-driven wrap-around wheels 24; a common drive shaft 25 for supporting said wheels, said shaft being rotated in one direction at a suitable "take-over" speed; a one-way clutch 26 mounting each wheel 24 on shaft 25 for said shaft-driven rotary movement at said take-over speed, and for said thread-driven rotary movement at said higher thread usage speeds; a shaft-encircling spring 30; and a fixed shaft-encircling collar 31.

The modified portion of the FIG. 6 wrap-around mechanism resides in the use of a 2nd series of one-way clutches 38 in place of the groups of washers 28 used in FIGS. 4-5. Each clutch 38 is mounted on shaft 25 but reversely arranged relative to the one-way clutches 26. Each of the 2nd series clutches, except the opposite end clutches 38, is thus sandwiched between and in end-to-end frictional engagement with the clutches 26 of two adjacent wrap-around units. However, while each interposed clutch 38 can rotate bodily with the shaft in said one direction, it cannot rotate faster than the shaft or free wheel in the said one direction. As a consequence, the interposed clutch 38 prevents a fast thread wrap-around unit from driving a slow thread wrap-around unit in said one direction through the frictional connections existing between them. The one-way clutches 26 of the one series can free wheel in one direction at all speeds higher than the speed of shaft 25. The one-way clutches 38 of the 2nd series cannot free wheel in said one direction at or above the speed of the shaft 25.

This modified arrangement insures the rotation of all slow thread wheels in said one direction freely and independently of the rotation of the faster wheels in the same direction. Stated otherwise, it insures the free wheeling of all slow thread wheels in said one direction at all above-shaft speeds, between the high speed of the fastest wheel 24 and the lower speed of the common take-over shaft 25, and thereby prevents a fast thread wheel from rotating the adjacent reversely arranged clutch 38 through the frictional connections existing between them.

Claims

Having described our invention, we claim:

1. In a multi-needle sewing machine of the type wherein each needle thread, extending from its spool forwardly to its needle, has an intermediate section under a tension which corresponds to its rate of usage and wherein each thread not only extends around a rotary wrap-around unit at the beginning of its intermediate section but also has the magnitude of its tension sensed by a sensor which operates a stop motion mechanism when the sensed tension falls below a value corresponding to the lowest rate of usage desired, an improved wrap-around mechanism comprising:

A. a group of independent wrap-around wheels, one for each needle thread of a corresponding group of individual threads, each wheel normally being idly rotated in one direction by the pull of its needle thread at speeds corresponding to the normal range of rates at which that thread is being used;

B. independent drive means for said wheels; and

C. means for connecting the independent drive means to a given wheel when the usage rate of the needle thread for that given wheel falls below said normal range of usage rates, said connection means being operative, when said independent drive means is connected to said given wheel, to cause said independent drive means to rotate the corresponding wrap-around wheel in said one direction at a "take-over" speed slightly lower than the slowest wheel speed, which corresponds to the lowest usage rate in said normal range, and thereby take over the job of pulling said given thread from its supply spool and feeding it forwardly through its tensioning section.

2. The improved wrap-around mechanism of claim 1 including:

A. means to provide each individual wheel with the braking action required to insure the production of requisite tension in the tensioning section of the individual thread associated with that particular wheel.

3. The improved wrap-around mechanism of claim 1 wherein:

A. said independent drive means includes

1. a common drive shaft for supporting said group of wheels, and

2. means for driving said shaft in said one direction at said take-over speed; and

B. said connection means includes one series of one-way clutches, one for each wrap-around wheel,

1. each clutch mounting its wrap-around wheel on said common shaft

a. for said shaft-driven rotary movement in said one direction at said take-over speed, and

b. for said thread-dictated free wheeling rotary movement in said one direction at said higher speeds.

4. The improved wrap-around mechanism of claim 3 including:

A. a 2nd series of one-way clutches mounted on said common drive shaft, one interposed between and frictionally connected with each pair of adjacent wrap-around wheels,

1. each interposed 2nd series clutch being reversely arranged, relative to the clutches of said one series which free wheel in said one direction, so that said interposed clutch cannot free wheel in said one direction and thereby permit a fast thread wheel to drive a slow thread wheel in said one direction through the frictional connection existing between them.