US3683832A

US3683832A - Thread control device for sewing machines

Info

Publication number: US3683832A
Application number: US69556A
Authority: US
Inventors: Edgar Schoij
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1970-09-04
Filing date: 1970-09-04
Publication date: 1972-08-15
Anticipated expiration: 1989-08-15
Also published as: GB1366899A; DE2141669A1; DE2141669B2; FR2107279A5

Abstract

An improved thread control mechanism for sewing machines adapted to minimize breakage and entanglement of the needle thread in a two-thread sewing machine, and which insures the formation of a uniform and desirable line of stitching at high speeds of operation. It is particularly advantageous in connection with a lockstitch sewing machine, which at one stage in a cycle of operation of the machine must subject said thread to a quick take-up action when a loop of the thread has been passed around half of the circumference of a bobbin case. The improved mechanism eliminates the need for a coiled check spring which heretofore has been provided to present an arm in the path of movement of the thread after it leaves a thread tensioning device. By eliminating the need for the check spring, the extent of movement of a thread eyelet at the outer end of a take-up lever is reduced, from the extent that was required in prior constructions involving a check spring. A plurality of cams are provided on a shaft which is rotated at the same speed as the main drive shaft of the sewing machine. These cams act upon different portions of the needle thread as the latter passes through a succession of eyelets provided on certain prongs of rockable members. Normally these members are retained in an active position, but they are shifted to an inactive position upon the lifting of the pressure foot. The thread control means of the present invention exercises the desired control over the needle thread when the machine is used on a variety of types of work which have normally, heretofore, required special adjustments and even changes in the mechanism when variations in the thickness and the nature of the work pieces being dealt with are involved.

Description

United States Patent 3,683,832 1 Aug. 15, 1972 Schoij [54] THREAD CONTROL DEVICE FOR SEWING MACHINES [72] Inventor: Edgar Schoij,Hinsdale,lll. [73] Assignee: Union Special Machine Company,

Chicago, 111.

22 Filed: Sept.4, 1970 211 Appl.No.: 69,556

3,140,682 7/1964 Hale et al. ..l12/242 Primary Examiner-Patrick D. Lawson Attorney-John A. l-lowson 5 7] ABSTRACT An improved thread control mechanism for sewing machines adapted to minimize breakage and entanglement of the needle thread in a twothread sewing machine, and which insures the formation of a uniform and desirable line of stitching at high speeds 31b 3 25b 21 24b an arm in the path of movement of the thread after itleaves a thread tensioning device. By eliminating the need for the check spring, the extent of movement of a thread eyelet at the outer end of a take-up lever is reduced, from the extent that was required in prior constructions involving a check spring. A plurality of cams are provided on a shaft which is rotated at the same speed as the main drive shaft of the sewing machine. These cams act upon different portions of the needle thread as the latter passes through a succession of eyelets provided on certain prongs of rockable members. Normally these members are retained in an active position, but they are shifted to an inactive position upon the lifting of the pressure foot. The thread control means of-the present invention exercises the desired control over the needle thread when the machine is used on a variety of types of work which have normally, heretofore, required special adjustments and even changes in the mechanism when variations in the thickness and the nature of the work pieces being dealt with are involved.

24 Claims, 10 Drawing Figures PATENTEDAUB 1 5 I972 SHEET 2 [IF 6 PATENTEUAUG 1 5 m2 SHEEI 3 [If 6 PATENTEIH I973 3.683.832

sum 5 OF 6 FIG] THREAD CONTROL DEVICE FOR SEWING MACHINES This invention relates to mechanism for controlling the delivery of the desiredamount of thread to the stitch forming mechanism of a high speed sewing machine, and the application of a reasonably high tension to the thread at the time a stitch is being completed to insure the formation of a good stitch. A positively driven cam arrangement is provided for this purpose.

The invention has been developed, and is disclosed herein, in relation to a lockstitch sewing machine which is intended for high speed operation, at speeds of 5,000 to 7,000 R.P.M. or even higher. Heretofore it has been found difficult to control the delivery of the desired amount of thread and to insure uniform stitch formation, with the stitches being soft but firmly gripping the materials being sewn together, without danger of producing puckering of the material, in the operation of the machine at such high speeds.

Certain aspects of the invention are capable of advantageous use in relation to a variety of types of sewing machines, but it has been specifically developed to overcome certain problems encountered in the operation of a lockstitch machine at high speed. Accordingly it is being disclosed herein in relation to such a machine.

One problem presented in connection with the operation of a lockstitch machine at high speeds is that the needle thread mustQat times during each cycle of operation of the machine, be supplied in sufficient amount in the stitch forming region to enable the passage of a loop of said thread around the bobbin case, which revolves at high speed in the region below the throat plate of the machine. It is then necessary to pull the thread upwardly, into engagement with the under surface of the work, with a sufficient tension to bring about the desired stitch formation at the high speed of operation of the machine.

Heretofore it has been considered necessary to pro vide a coiled check spring which has an arm positioned in the path of movement of the thread as it leaves a thread tensioning device and is being delivered toward the eye of the needle. Such a coiled check spring has, however, been found to create further problems in the correct handling of the thread in a high speed stitching operation. Accordingly, the present invention serves to eliminate the need for the provision of a coiled check spring, and it provides a thread tensioning device which is of such character that a proper tension will be applied to the needle thread at the time a stitch is being affixed to the work. This serves to insure the formation of a firm line of stitching without any danger of producing puckering of the work material in the course ofthe stitching operation.

Toward the foregoing end the present invention incorporates a plurality of thread take-up means in the path of movement of the thread, these take-up means being active at the appropriate time during each stitch forming cycle to insure the proper formation of a seam. In this connection, the present invention includes a take-up lever including an eyelet through which the needle thread passes and which is rockable during a certain part of a stitch forming cycle, this take-up lever thereby imparting a take-up action to the thread after it has been passed around to the 6 oclock point of the bobbin case, so as to pull the needle thread thus released up into a position in which it will not become entangled with itself or with other thread. Such a takeup lever has been provided heretofore, as disclosed in the I-Iale et al. US. Pat. No. 3, l40,682 granted July 14, I964. However, in accordance with the present invention it has not been found necessary to impart as great a take-up action to the lever mentioned as was required in accordance with the disclosure of the specified patent.

Through the provision of a plurality of pronged eyelet members along the path of movement of the thread from a source of supply to the needle, and the provision of cam means cooperating with the thread in regions between the eyelets of said members, in accordance with the present invention, it has been found possible to reduce the extent of movement of the eyelet of the take-up lever in the course of the stitching operation. Toward the same end, the present invention eliminates the need for the coiled check spring having an arm in the path of the thread, as shown at 50d in said Hale et al. patent. These aspects of the invention have been found to insure the desired uniform formation of the line of stitching, which has not been possible in the high speed seaming of certain types of work in the past.

With the foregoing features and. advantages of the invention in mind, an illustrative embodiment of the same will now be described in some detail. For this purpose the invention has been illustrated herein and will be described as applied to a lockstitch sewing machine of the character disclosed in said Hale et al. patent. Referring now to the present drawings:

FIG. I is a front elevational view of themachine in question with a portion of the frame broken away in the region of the needle head;

FIG. 2 is-an end elevational view of the machinev as seen from the left of FIG. 1, with a cover plate for the needle head removed;

FIG. 3 is a detail view, in elevation, showing a portion of the upper arm of the frame of the machine with a thread supply source schematically indicated and with certain elements of the thread control means shown;

FIG. 4 is a detail view, in horizontal section through the upper arm of the machine frame, and shows various elements of the thread control means of the present invention;

FIG. 5 is a vertical sectional view taken along the plane S-S of FIG. 3;

FIG. 6 is an elevational view of a part of the upper arm of the frame of the machine with a portion of this broken away to illustrate certain devices within the arm;

FIG. 7 is a detail view in horizontal section through certain adjustable parts of the mechanism shown in FIG. 4;

FIG. 8 is a vertical sectional view along the line 88 of FIG. 4;

FIG. 9 is a detail view, in plan along the line 9-9 of FIG. 5, showing certain elements of thread guiding means; and

FIG. 10 is an exploded perspective view of certain parts incorporated in the machine for imparting a takeup action to the needle thread.

As stated above, the invention hasbeen shown herein as applied to a lockstitch sewing machine of the type disclosed in the I-Iale et al. patent and in certain earlier patents referred to therein. The frame of the machine has a base portion 1 which is provided with a work supporting surface, a vertical standard 2 rising from one end of the base portion, and an overhanging arm 3 extending from the upper portion of the vertical standard in a direction substantially parallel to the base portion 1. The overhanging arm has a head portion 4 in which a vertically reciprocatory needle bar and also a presser bar are mounted. Suitable connections from a power source are provided to a combined hand wheel and pulley 5 secured to the main drive shaft 6 which extend longitudinally of the overhanging arm 3. Within the base portion 1 of the frame there is provided conventional work feeding means and complementary stitch forming means of a well-known character. Thus, as shown in FIG. 2, there is provided a feed dog 7 which is carried by a feed bar that has a downwardly extending portion 8 with suitable connections from a shaft within the work supporting portion of the frame, which shaft is connected in a conventional manner with the main drive shaft 6. The rotary hook 9 is driven by suitable connections from the shaft within the base of the frame and it is driven in synchronization with the reciprocation of the needle bar, but it rotates at twice the speed of the main shaft. The work is held against the top surface of the work supporting portion of the frame by a presser foot 10 which is mounted on a vertically movable presser bar 10a and is adapted for rocking movement to a certain extent as the work is fed through the machine. The presser bar is mounted for sliding movement within a sleeve 10b carried by the needle head of the frame, and it is urged downwardly by a spring 100 within the needle head. The lower end of this spring cooperates with an arm 10d secured to the presser bar. Conventional means are provided for varying the force of the spring 100 in urging the presser foot against the work support and the feed dog 7.

Since the present invention is primarily concerned with the thread control means which cooperates with the needle thread, this will now be described in detail. As shown in FIG. 3 the thread T to be delivered to the needle is supplied by a suitable source C, from which it is delivered to a thread tensioning device carried by a bracket member B mounted on top of the overhanging arm 3 of the frame. This thread tensioning means is provided with a manually adjustable head 12 which, by turning in one direction or the other, may vary the force of a spring 12a which urges an upper disk 12b downwardly toward a lower disk 120. The thread from the supply is passed between the disks 12b and 120 and is guided for this purpose by

eyelet members

11 and 13 secured to the top of the bracket member B. From the eyelet of member 13 the thread is passed downwardly to the thread control means 21 of the present invention. In the region of the control means 21 the thread is first passed through an eyelet in a prong 14a of an element 14 which is secured to a sleeve 56a that is rockably mounted on a rock shaft 35 (FIG. 4). From this point the thread is passed to and through an eye in a prong 14b of the element 14, and from here successively through openings in

prongs

15c, 15b and 15a of an element 15 which is secured to the rock shaft 35.

From the hole in prong 15a of element 15 the thread is passed downwardly around a hub portion 300 (FIG. 5) of a cam member 30 which is secured by a screw 300 to a rotary shaft 22. After passing through a suitable are around the periphery of hub 300 the thread is passed downwardly and toward the left (FIG. 3) to an eyelet in a vertically adjustable member 16 carried by the needle head of the sewing machine frame. From this point the thread extends upwardly to and through an eyelet in a rockable lever 17 which serves as a thread take-up member. From the latter the thread extends downwardly to and through an eyelet in an element 18 connected with a needle bar bushing 19 which extends downwardly to a certain extent from the needle head. The needle 20a is carried by a needle bar 20 which is reciprocated vertically within the bushing 19 for a suffi-,

cient distance to carry the point of the needle from a lo cation above the work to a position beneath thethroat plate 1a (FIG. 2) of the work support 1. As will be understood, the thread now extends from the last stitch in the work piece, to the eye of the needle, and when the latter starts its upward movement a loop projects from the under side of the work piece and this is then seized by the beak of the rotary hook 9 and is carried by the latter around the thread extending from the bobbin case of the hook to the under side of the work, thus forming a new stitch.

Suitable connections are provided for rocking the take-up lever 17 to alternately pull up the needle thread to complete a stitch and to free the thread to enable a loop of the same to be carried around the bobbin case by the rotary hook 9. The connections for this purpose are of the general character disclosed in the US. Pat. to Covert No. 2,977,9l0 granted Apr. 4, l96l. Such connections are driven by a rotary member secured to the main drive shaft 6 of the machine.

Cooperating with the needle thread in the region in which it passes through the openings in the extensions of

members

14 and 15 are a plurality of

cam elements

30a, 30b, 31a and 31b. As best shown in FIG. 4 the cam elements 300 and 30b are in spaced relation, so that the enlarged portion 30a cooperates with the thread passing between

prongs

15a and 15b, while the enlarged portion 30b of element 30b cooperates with the thread passing between prongs 15b and 156. The two

cam elements

31a and 31b are close together and they are rotated to carry their

enlarged portions

31a and 31b between prongs 14a and 14b of member 14. The purpose of providing the two

cam elements

31a and 31b is to enable variation in the circumferential length of the combined enlarged portions thereof which act upon the thread passing between prongs 14a and 14b. This provides for any adjustment that may be desired to conform with the nature and thickness of the work pieces being dealt with at a particular time.

Suitable connections are provided from the main drive shaft 6 of the machine for imparting a revolution to each of the

camming elements

30a, 30b, 31a and 31b on each revolution of the main shaft. These connections, as best shown in FIG. 4, involve a helical gear 26 secured to the shaft 22 that cooperates with a helical gear 27 secured to the main drive shaft, which gears have a 1:1 driving ratio. Shaft 22 is joumalled in a sleeve 23 which is carried by a member 24. The latter is formed with a bushing type portion 24a and a flange some adjustment of the angular position of the member 24 within the frame, the flange 24b is provided with slightly elongated openings 24c (FIG. 1) through which the screws 25b extend. The various cams a,30b, 31a and 31b are retained on the shaft 22 by

screws

30e and 316 which cooperate with hub portions 300 and 310 of the

respective members

30 and 31. At the outer end of the shaft 22 there is provided a cap 32 the inner circumferential surface of which engages the cam 31b, and it is firmly retained in position by means of a screw 33 which fits into a threaded opening in the end of shaft 22 (FIG. 5). For retaining the rock shaft 35 against movement in an axial direction it is provided with a I groove in which is placed a C-washer 36 (FIG. 4). This fits into a small depression in the outer face of the front wall 50a of the overhanging arm 3 of the machine frame. Movement of the shaft 35 axially in the opposite direction is prevented by means of a lever 38 which is secured to the shaft by a screw 39 (FIGS. 4 and 6). A washer 37 is fitted onto the shaft 35 within a depression in an intermediate wall 50b of the arm 3 and cooperates with the lever 38 and screw 39 in retaining the shaft 35 against axial movement in said opposite direction.

Rock shaft 35 is urged into the position shown in FIG. 6 by a coil spring 44 which has one or more turnsaround the shaft 35, and has one of its ends engaged with the bottom of overhanging arm 3 and its other end hooked beneath the free end of lever 38. The spring thus urges the free end of said lever against a stop screw or pin 45.

All of the

cams

30a, 30b, 31a and 31b upon rotation with the shaft 22 serve to take-up some length of the needle thread as the outwardly extending portions of these cams move into the passages provided between the prongs of the

members

14 and 15. The extent of the take-up action imparted by the various cams may be varied by selection of cams of different sizes. Also such takeup action can be varied by changing the angular disposition of the

eyelet carrying members

14 and 15 in relation to a horizontal plane extending through the axis of the shaft 35 and a sleeve 56a. This can be accomplished by loosening screws Me and 15e, respectively, and then retighten those screws when the desired position of the

members

14 and 15 has been achieved. With respect to the cam formed by

elements

31a and 31b, the duration and extent of their action upon the thread extending between the prongs 14a and 14b can be varied by changing the relationship of certain parts shown in FIGS. 4, 7, 8 and 10. This involves the provision of a shoulder screw 57 which has an enlarged portion of its stem slidably fitted within an opening 56c provided in lever arm 56b connected with the sleeve 56a. The end of screw 57 has threaded engagement with an opening 58a provided in a washer-like element 58 which surrounds a reduced diameter portion of a stud 59. The opening 580 is off center in relation to the axis of the stud 59, the latter being journalled in an opening 600 provided in a bracket plate 60.

The opening 60a is located adjacent one end of the plate 60, which is of larger dimension than the opposite end of this plate. Adjacent the outer face of the plate 60 there is provided a spring washer 61 which surrounds the stud 59, and outwardly of this there is provided a knurled knob 62 which is secured to the stud by a screw 63. Plate 60 is provided with a suitable opening 60b on its inner face which fits over the end of the rock shaft 35 and is secured thereto by set screws 64. The knob 62 is provided with a radially extending flange which carries markings, such as indicated at 62a, which in conjunction with a mark 66 provided on the outer face of the member 60 gives an indication of the setting of the knob. It is to be noted that the axis of opening 58a in the element 58 is shown in FIG. 10 as being located in the same horizontal plane as the axis of the stud 59. By this arrangement, rotation of the knob 62 will be effective through in one direction or the other from the position shown to bring about the desired position of member 14.

The shaft 35 is adapted to be rocked upon operation of the presser foot lifting mechanism of the sewing machine, which is of the character disclosed in the Covert US. Pat. No. 2,977,910, granted Apr. 4, 1961. This will serve to rock the shaft 35 in a clockwise direction as it is seen in F IG. I and in a counterclockwise direction as it is seen in FIG. 6. As shown in the latter figure the rocking of the lever 40 in a counterclockwise direction about the pivot pin 41 will draw downwardly a pin 42 which has a collar 42a adjustably secured thereto. The downward movement of pin 42 with its collar 42a will cause the latter to engage the arm 38a of member 38 and force iitaway from the stop pin 45. The resulting rocking movement of the lever 38 will, by virtue of its fixed connection with the rock shaft 35 through the action of the screw 39 cause counterclockwise movement of a member 46 that is adjustably connected with the lever 38 by means of a screw 460. Such rocking of the lever 46 will cause upward move ment of a pin 47 that is normally urged downwardly by a spring 48 (FIGS. 5 and 6). Upward movement of the pin 47 will cause its upper end to engage the disk 12b and will lift this against the action of spring 12a to release the frictional holding force from the thread extending between the eyelets l1 and 13. Thus the tension applied to the thread will be released upon the lifting of the presser foot. Also the rocking of the shaft 35 in the clockwise direction in FIG. I will carry the

guide members

14 and 15 away from the earns 30 and 31. This, of course, facilitates the removal of a finished work piece and the introduction of a new one. The parts referred to will be restored to the position shown in FIG. 6 through the action of the

springs

44 and 48 when the presser foot is permitted to return into engagement with the work support 1 of the frame. As shown in FIG. 6 the pin 42 is pivotally connected with the presser foot lifting lever 40 by a stud 43 having a screw threaded connection with the lever 40. As shown in FIG. 6, the pin 42 has a sliding engagement within an opening 38b provided in the arm 38a of the lever 38. When the presser foot is permitted to return to its engagement with the work support 1, the spring 44 will again rock the lever 38 in a clockwise direction (FIG. 6) until the arm 38a of the lever engages the stop pin 45. This will enable the spring 48 to urge the pin 47 downwardly and thus cause the disk 12b to be forced downwardly by spring 120 to grip the thread passing between the disks 12b and 120.

It will be understood that when work to be stitched is applied to the work supporting arm 1, the presser foot is lifted under manual control, either by hand or a foot treadle or a knee press, and then restored to its active position after the work has been properly positioned. After the desired line of stitching has been provided on the work piece the presser foot may be lifted again, and this frees the thread so that the work piece may be readily removed from the machine and the thread extending from the needle may be severed.

As shown in FIGS. 2 and 5, there is preferably provided a dust cover 70 to protect against accumulation of any flying dust on the various elements described above which are carried by the shaft 22 externally of the enclosed frame of the machine. This dust cover has a portion of the free end of its cylindrical body fitted onto a slightly reduced diameter portion of the flange 24b of the member 24. A screw 71 may be provided for retaining the cover 70 on the machine, this screw having threaded engagement with a hole 24d provided in the'flange 24b of the member 24. It will be understood that the cylindrical wall of the cover 70 will have openings therein to permit the passage of the thread to and from the various elements described above which cooperate with the thread to impart take-up and pull off actions thereto.

It is believed that the foregoing description of a preferred form of the present invention, as applied to a lock-stitch machine, serves to show how the thread guiding and tensioning means functions to bring about a precise control over the needle thread during high speed operations of the machine. Briefly, the thread from a supply source is first led to a thread tensioning device having thread guiding means for directing the thread toward and away from a pair of thread gripping disks which are urged together under suitable spring force, which may be varied in a conventional manner, so that uniform movement of the thread is assured. From this thread tensioning device, shown at 12 in FIG. 3, the thread is led downwardly to an eyelet of an arm 14a of a member 14 and from here successively through an arm 14b of member 14 and

arms

15c, 15b and 15a of a member 15. In its passage between the various arms mentioned, the thread is subjected to a camming action by a series of

cams

31b, 31a, b, 300. From the eyelet in arm 15a the thread is passed toward the left (FIG. 3) and slightly downwardly to an eyelet l6 and then upwardly to a thread take-up arm 17. From the eyelet in the latter it is passed downwardly to the eye of the needle. The take-up arm 17 swings through a suitable are which imparts to the thread a desired takeup action, after its loop has been passed half-way around the bobbin case of the rotary hook 9. The coordination of the movements of the various elements which apply a pulling force to the thread in the course of a stitch forming operation is such as to prevent the accumulation of any large free loop or length of the thread between the various eyelets through which it is being shifted, and the application of an excessively high tension force to the thread at any time during the operation of the machine is avoided. The

cam elements

30a, 30b, 31a and 31b which contribute to the take-up and pull-off action imparted to the thread, are so synchronized as to avoid any sudden and excessive pull on the thread at any time, so that puckering of the work being stitched is avoided and the desired firmness of the stitch is assured. However, the cam elements 30 do prevent the drawing of thread from the supply during the upward movement of the take-up arm 17 until the latter approaches its upper position. This insures the pulling of the thread out of the hook and up to the underside of the work, after which the locking action on the thread effected by the elements 30 is released and thread which has been drawn from the supply source by pull off earns 31 will be made available for stitch formation.

The length of thread that is pulled from the supply source during each cycle of operation of the machine may be varied to create a tight or loose stitch. Such variation may be brought about by changing or adjusting the various cam elements used, or it can be brought about by adjusting the angular position of the

members

14 and 15 to place the eyelets in the

projections

14a, 14b, and 15a, 15b and 15c in a location such as shown in FIGS. 1 and 4 which will enable the cam elements to exert the necessary pulling and locking action on the thread, at the time it is needed. In connection with the thread control mechanism shown and described herein, it is believed to be clear that the

cam elements

31a and 31b serve to pull off most of the desired amount of thread from the supply cone C in the course of a stitching operation, while the take-up 17 pulls off the remaining necessary thread as it reaches the top of its stroke at the end of the stitch forming cycle. The

cam elements

30a and 30b serve to apply the desired high tension to the thread during a predetermined period of the stitch forming cycle. This results from the location of the elements mentioned in relation to the path of movement of the thread from its source to the stitch forming region.

The operation of the various thread controlling and tensioning means involved in this invention is so synchronized with the operation of the stitch forming elements as to avoid the presence of any length of free thread which may become entangled and form a knot in itself, as it might do if allowed to form a hanging loop. Also the invention insures applying the thread, to the work being stitched, in a uniform manner and without causing puckering or other objectionable effects, regardless of the speed of operation of the machine. This is partly achieved by the action of the take-up lever 17 which, for example, will quickly pull up thread from the rotary hook after a loop of the thread, which is passed around the bobbin case, has reached the 6 oclock point. The desired application of the thread to the work in forming a stitch, and the pulling of thread from the supply source to be available for the next stitch, is brought about by the action of the various cam elements that have been described. It has been found that the mechanism of the present invention serves to apply the stitching to the work in the desired form, regardless of the thickness and other characteristics of the work, and at all speeds at which the machine is operated. The

various cam elements

30 and 31 cooperate with the

members

14 and 15 in such manner as to bring about this result, without the need for a check spring, such as that designated 50d in the above-mentioned Hale et al. patent. The absence of any need for such a spring in the present construction reduces the distance through which it is necessary to swing the eye of member 17. This in addition to its primary function, was previously required to compensate for the movement of the thread engaging portion of the check spring.

While the invention has been described in considerable detail in relation to the illustrative embodiment, it will be understood that various modifications may be made within the scope of the appended claims. Such modifications may encompass adaptation of certain features of the invention to sewing machines of types other than the one herein disclosed.

What is claimed is:

1. Sewing apparatus comprising a machine having a reciprocatory needle bar carrying a needle, cooperating stitch forming means, a main drive shaft, connections from said shaft for reciprocating said needle bar and driving said cooperating stitch forming means, a thread supply means, means for controlling the delivery of thread from said supply means to said needle comprising a control shaft rotated in synchronism with said drive shaft, clamping means operated by said control shaft for gripping the thread and looking it against movement to prevent additional thread being delivered from the supply to the needle from the time the thread begins to be pulled up by the cooperating stitch forming means until the time that the stitch is set.

2. In sewing apparatus as set forth in claim 1, wherein said clamping means for locking the thread in position comprises cam means rotated by the control shaft in timed relation to the cooperating stitch forming means.

3. In sewing apparatus as set forth in claim 1, wherein there are means also operated by said control shaft positioned between the clamping means and the thread supply for pulling off a predetermined amount of thread from the supply during the period in which the thread is gripped by the clamping means.

4. Sewing apparatus comprising a machine having a reciprocatory needle bar carrying a needle, cooperating stitch forming means, a main drive shaft, connections from said shaft for reciprocating said needle bar and driving said cooperating stitch forming means, a thread supply means, means for controlling the delivery of thread from said supply means to said needle comprising a control shaft rotated in synchronism with said drive shaft, a plurality of cam elements rotated by said control shaft, thread guiding means adapted to retain different portions of said thread in the paths of movement of said cam elements. there being only a rockable eyelet carrying arm and stationary eyelet means in the path of movement of the thread from the region of said cam elements to the eye of said needle.

5. Sewing apparatus comprising a machine having a reciprocatory needle bar carrying a needle, cooperating stitch forming means, a main drive shaft, connections from said shaft for reciprocating said needle bar and driving said cooperating stitch forming means, a thread supply means, means for controlling the delivery of thread from said supply means to said needle comprising a control shaft rotated in synchronism with said drive shaft, a plurality of cam elements rotated by said control shaft, thread guiding means adapted to retain different portions of said thread in the paths of movement of said cam elements, certain of said cam elements being arranged to cooperate with spaced apart portions of the thread, and other of said cam elements being arranged to cooperate with a single portion of I said thread in spaced relation to the first mentioned portions of the thread.

6. In sewing apparatus as set forth in claim 5, said other of said cam elements involving relatively adjustable members adapted to vary the duration of activity of said cam elements upon a cycle of operation of the machine.

.7. In sewing apparatus as set forth in claim 6, said certain of said cam elements having a duration of activity upon a cycle of operation of the machine that is longer than the combined duration of the activity of said other of said cam elements.

8. Sewing apparatus comprising a machine having a main drive shaft, a plurality of thread carrying elements arranged to cooperate to form stitches, connections from said shaft for operating said elements, means for controlling delivery of thread to one of said elements in a predetermined amount to insure its firm and uniform application to a work piece being stitched, said means comprising a device for applying a main tension to said thread in its path of movement from a supply source, means providing a plurality of stationary eyelets through which the thread is passed from said device, a plurality of cams arranged for rotation in the region of said eyelets, each of said cams having an outwardly extending portion adapted to engage the thread and apply a force thereto, whereby a stitch is applied to the work piece under a desired force.

9. In sewing apparatus as set forth in claim-8, certain of said cams being adapted to pull thread from said supply source through said device for applying a main tension to said thread.

10. In sewing apparatus as set forth in claim 9, said device for applying a main tension to said thread comprising a pair of disks, a spring urging one of said disks toward the other, and adjustable means for varying the force, of said spring. r

11. In sewing apparatus as set forth in claim 8, said cams being carried by a shaft which is rotated at the same speed as themain drive shaft of the machine.

12. In sewing apparatus as set forth in claim 8, certain of said cams being adapted to pull thread from said supply source through said device for applying a main tension to said thread, and other" of said cams being adapted to apply a further tension to said thread and to deliver successive portions thereof to said one of said thread carrying elements.

13. In sewing apparatus as set forth in claim 8, said thread carrying elements comprising a reciprocatory needle and a rotary hook, said means for controlling delivery of thread serving to control the thread delivery to said needle and serving to supply the amount of thread needed to form a loop around the rotary hook and to then pull up said loop to the underside of the work being stitched.

14. In sewing apparatus as set forth in claim 13, said means for controlling delivery of thread to said needle including a rockable arm having an eyelet therein through which the thread is passed toward said needle, said arm serving to alternately provide and then takeup a certain length of thread that is sufiicient to enable said hook to carry a loop of thread around a bobbin case within said rotary hook.

15. In sewing apparatus as set forth in claim 14, certain of said cams being adapted to pull thread from a supply source to make it available to form a stitch.

16. In sewing apparatus as set forth in claim 8, a presser foot which is spring urged downwardly against the work being stitched, manually operable means for lifting said presser foot, and connections from said manually operable means for shifting said normally stationary eyelets away from said cams when the presser foot is lifted.

17. In sewing apparatus'asset forth in claim 16, said lifting of the presser foot being arranged to release the main tension applied to the thread by said device 18. Sewing apparatus comprising a sewing machine having thread carrying stitch forming elements and means for controlling the delivery of thread to at least one of said stitch forming elements from a supply, said thread controlling means comprising first and second means for applying variable tension to the thread, thread pull-off means, thread take-up means, said first thread tension applying means being adapted to apply a predetermined, constant, tension to the thread throughout a part of a stitch forming cycle, said second thread tension applying means being adapted to apply a considerably higher tension to the thread through one portion of the stitch forming cycle and completely releasing this higher tension during the remaining portion of the stitch forming cycle, said second tension applying means being located between said one of the stitch forming elements and said first tension applying means in the path of delivery of the thread, said thread pull-off means being adapted to pull off one portion of the amount of thread that is needed for forming a stitch, during the period when said second thread tension applying means applies said high tension, said thread pull-off means being located between said first and second tension applying means in the path of delivery of the thread, said thread take-up means being adapted to pull off from a supply the remaining portion of the thread needed for forming a stitch, during the period in the cycle when said higher tension is released, 5

and said second tension applying means and said pulloff means being adapted to engage the thread in successive order with the second tension applying means first and the pull-off means later.

19. In sewing apparatus as set forth in claim 18, said second tension applying means and said pull-ofi means being arranged to disengage the thread simultaneously.

20. In sewing apparatus as set forth in claim 18, said second tension applying means and said pulloff means each comprising cam means involving at least one cam, said cam means being mounted for rotation on a common shaft driven by the main drive shaft.

21. in sewing apparatus as set forth in claim 20, said cams being formed with outwardly extending portions arranged to engage the thread.

22. In sewing apparatus as set forth in claim 21, said outwardly extending portions of said cams being of a larger peripheral length on the tension applying cam means than on the pull-off cam means.

23. A method of controlling the delivery of thread to the needle of a sewing machine having a thread carryl fffi, bliicit %%n;s2;%h%3sslaisigzit needle to carry its thread through the work into cooperation with the rotary loop taker, pulling the needle thread up from the loop taker after it has been passed around the thread carried by thelatter, applying a high tension force to the needle thread as it is being pulled from a loop taker, releasing said high tension when the needle thread has been pulled up to the work piece and the stitch is set.

24. A method as set forth in claim 23 in which thread is drawn from the needle thread supply source during the application of a high tension thereto, said thread so drawn being stored outside of the area in which said thread is affected by the application of said high tension, and adding the thread so drawn from the needle thread supply when said high tension is released, and thereafter drawing further thread from said supply in preparation for the next stitch-forming cycle.

Claims

1. Sewing apparatus comprising a machine having a reciprocatory needle bar carrying a needle, cooperating stitch forming means, a main drive shaft, connections from said shaft for reciprocating said needle bar and driving said cooperating stitch forming means, a thread supply means, means for controlling the delivery of thread from said supply means to said needle comprising a control shaft rotated in synchronism with said drive shaft, clamping means operated by said control shaft for gripping the thread and locking it against movement to prevent additional thread being delivered from the supply to the needle from the time the thread begins to be pulled up by the cooperating stitch forming means until the time that the stitch is set.

5. Sewing apparatus comprising a machine having a reciprocatory needle bar carrying a needle, cooperating stitch forming means, a main drive shaft, connections from said shaft for reciprocating said needle bar and driving said cooperating stitch forming means, a thread supply means, means for controlling the delivery of thread from said supply means to said needle comprising a control shaft rotated in synchronism with said drive shaft, a plurality of cam elements rotated by said control shaft, thread guiding means adapted to retain different portions of said thread in the paths of movement of said cam elements, certain of said cam elements being arranged to cooperate with spaced apart portions of the thread, and other of said cam elements being arranged to cooperate with a single portion of said thread in spaced relation to the first mentioned portions of the thread.

7. In sewing apparatus as set forth in claim 6, said certain of said cam elements having a duration of activity upon a cycle of operation of the machine that is longer than the combined duration of the activity of said other of said cam elements.

9. In sewing apparatus as set forth in claim 8, certain of said cams being adapted to pull thread from said supply source through said device for applying a main tension to said thread.

10. In sewing apparatus as set forth in claim 9, said device for applying a main tension to said thread comprising a pair of disks, a spring urging one of said disks toward the other, and adjustable means for varying the force of said spring.

12. In sewing apparatus as set forth in claim 8, certain of said cams being adapted to pull thread from said supply source through said device for applying a main tension to said thread, and other of said cams being adapted to apply a further tension to said thread and to deliVer successive portions thereof to said one of said thread carrying elements.

14. In sewing apparatus as set forth in claim 13, said means for controlling delivery of thread to said needle including a rockable arm having an eyelet therein through which the thread is passed toward said needle, said arm serving to alternately provide and then take-up a certain length of thread that is sufficient to enable said hook to carry a loop of thread around a bobbin case within said rotary hook.

17. In sewing apparatus as set forth in claim 16, said lifting of the presser foot being arranged to release the main tension applied to the thread by said device

18. Sewing apparatus comprising a sewing machine having thread carrying stitch forming elements and means for controlling the delivery of thread to at least one of said stitch forming elements from a supply, said thread controlling means comprising first and second means for applying variable tension to the thread, thread pull-off means, thread take-up means, said first thread tension applying means being adapted to apply a predetermined, constant, tension to the thread throughout a part of a stitch forming cycle, said second thread tension applying means being adapted to apply a considerably higher tension to the thread through one portion of the stitch forming cycle and completely releasing this higher tension during the remaining portion of the stitch forming cycle, said second tension applying means being located between said one of the stitch forming elements and said first tension applying means in the path of delivery of the thread, said thread pull-off means being adapted to pull off one portion of the amount of thread that is needed for forming a stitch, during the period when said second thread tension applying means applies said high tension, said thread pull-off means being located between said first and second tension applying means in the path of delivery of the thread, said thread take-up means being adapted to pull off from a supply the remaining portion of the thread needed for forming a stitch, during the period in the cycle when said higher tension is released, and said second tension applying means and said pull-off means being adapted to engage the thread in successive order with the second tension applying means first and the pull-off means later.

19. In sewing apparatus as set forth in claim 18, said second tension applying means and said pull-off means being arranged to disengage the thread simultaneously.

20. In sewing apparatus as set forth in claim 18, said second tension applying means and said pull-off means each comprising cam means involving at least one cam, said cam means being mounted for rotation on a common shaft driven by the main drive shaft.

23. A method of contRolling the delivery of thread to the needle of a sewing machine having a thread carrying needle and a cooperating thread carrying rotary loop taker, which comprises the steps of causing the needle to carry its thread through the work into cooperation with the rotary loop taker, pulling the needle thread up from the loop taker after it has been passed around the thread carried by the latter, applying a high tension force to the needle thread as it is being pulled from a loop taker, releasing said high tension when the needle thread has been pulled up to the work piece and the stitch is set.