US2764366A - Thread tensioning device for sewing machines - Google Patents

Description

Se t. 25, 1956 s. J. HAMLETT THREAD TENSIONING DEVICE FOR SEWING MACHINES 2 Sheets-Sheet 1 Filed Jan. 27, 1954 F/GJ INVENTOR.

' 570-Ey J-WA/wm'rr Ev I Arr-0 Nays Sept. 25, 1956 5. J. HAMLETT THREAD TENSIONING DEVICE FOR SEWING MACHINES Filed Jan. 27, 1954 2 Sheets-Sheet 2 INVENTOR. 570mg .J/rflmsrr 7'7'0 NEYS THREAD TENSIONING DEVICE FOR SEWING MACHINES Sidney J. Hamlett, Parma, Ohio, assignor to White Sewing Machine Corporation, Lakewood, Ohio, a corporation of. Delaware Application January 27, 1954, Serial No. 406,473

8 Claims. or. 242-150 This invention relates to sewing machines, more particularly, to means for tensioning the needle thread of a sewing machine. I

The conventional sewing machine comprises a head provided with a reciprocating needle bar having a chuck to hold the needle. The thread employed in the needle is conducted thereto from a spool, or the like, through suitable guides and an oscillating thread take-up member with a thread tensioning means interposed in the thread path'between the needle and thread spool to maintain the thread under proper tension for sewing operations. The tensioning devices heretofore employed have generally included two disks or the like between which the thread passes with the disks resiliently urged together by adjustable spring pressure thereby regulating the ease of movement of the thread therebetween and hence the tension thereof. In addition, an auxiliary or slack take-up spring member, in the form of a comparatively lightweight wire spring, is employed to compensate for the slack introduced in the thread during reciprocations of the needle. force exerted by this spring member is generally determined at the time of assembling the sewing machine head and is not readily changed thereafter. It has been found however that, when sewing on certain materials or when using various attachments or methods for performing special operations, it is highly desirable, and in some cases essential, that the force exerted by the auxiliary or slack take-up spring be readily adjustable by the machine operator. 7

The principal object of the invention is, therefore, to provide an improved thread tensioning means for the needle thread of a sewing machine such that the force exerted by the auxiliary or slack adjusting spring member may be readily calibrated at assembly and thereafter easily varied by the machine operator to the proper predetermined value for the type of sewing operation to be performed and which adjustment of the spring member does not alter the initial calibration.

Another object of the invention is to provide a device of the type defined in the preceding paragraph and wherein the adjusting member is manually actuatable and has a portion readily accessible externally of the sewing machine head for engagement by the finger of an operator, the said portion moving adjacent indicia representative of the sewing operations which may be performed at the tensions of the spring resulting from the indicative positions of the said portion, whereby the proper tension of the said auxiliary spring is obtainable without the need of special tools, skill or gauges.

A more specific object of the invention is to provide an improved adjustable thread tensioning device supported on a plate-like member which is adapted to cover an opening in the head of a sewing machine with a thread tensioning disk and a thread slack compensating spring supported on the inner face of said plate and accessible through a slot in said plate member, the tension of said slack compensating spring being adjustable by The * atent Patented Sept. 25, 1956 means of a manually engageable portion extending externally of the said plate member and movable in an arc thereover adjacent indicia thereon indicative of the resulting tension of said spring.

A still further object of the invention is to provide an improved thread tensioning device, as defined above, which is compact, reliable in operation, and in which both the force exerted 'on the needle thread by the tension disk and the force exerted by the auxiliary or slack compensating spring are separately adjustable to selected predetermined values by manually actuatable members located externally of the device and of the head on which the device ismounted.

The invention further resides in certain novel features of the construction and combination of the parts of the apparatus in which the invention is embodied, and further objects and advantages thereof will be apparent from the following description of the presently preferred embodiment of the invention taken in conjunction with the accompanying drawings forming a part of this application, and in which:

Fig. l is a fragmentary, enlarged, end view of a sewing machine head illustrating theimproved tensioning device in elevation; I V

Fig. 2 is a fragmentary sectional view taken generally horizontally through the portion of the sewing machine head shown in Fig. l with certain portions broken away at different elevations to more clearly illustrate the construction of the tensioning device;

Fig. 3 is a detached elevational view of the interior of the tensioning device per se as seen when removed from the sewing machine head and inverted;

Fig. 4 is a fragmentary, front elevational view of the tensioning device and adjacent portions of a sewing machine head as seen from the right-hand side of Fig. 1;

Fig. 5 is a fragmentary view of a portion of Fig. 2 showing, to an enlarged scale, the device providing for adjustment of the auxiliary or slack compensating spring;

Fig. 6 is a sectional view taken substantially on the line 6-6 of Fig. 5 and looking in the direction indicated by the arrows;

Fig. 7 is an exploded view showing, in detached perspective, the parts of the device for effecting adjustment of the tension of the auxiliary spring; and,

Fig. 8 is a detached, fragmentary, sectional view taken substantially on the line 88 of Fig. 2 further illustrating the adjustment means for the thread tensioning disk.

The sewing machine head lit to which the tensioning device of this invention is shown attached is of conventional construction and hence the details thereof need not be illustrated nor described. It is sufficient to note that such a head comprises the usual reciprocating needle bar 11 and a rod or bar 12 which is adapted to carry the presser foot,-not shown. The latter rod or bar is selectively elevated and lowered by a lever 13 which is pivoted, as at 14, to the machine head and has a cam-shaped portion 15 engageable with a bracket 16 carried by the rod or bar 12.

The forward end of the head 10 is provided with the usual reciprocating thread take-up arm, not shown, which is adapted to reciprocate in a slot 17 provided in the removable end plate 15 of the head. In accordance with this invention, the end plate 18 terminates short of the lower portion of the head thus providing an opening or recess 19 into the head adjacent the lower end of the casting or bracket member 20 which supports and guides the needle bar 11 and presser foot bar 12. This recess or opening 19 is closed by a removable plate member 21 which performs the double function of constituting a portion of the exterior of the sewing machine head and also the supporting member for the thread tensioning device.

As here shown, the plate member 21 is substantially L-shaped' with the longer portion extending horizontally along the lower end face of the head and with the integral shorter portion of the plate member extending along the lower forward port-ion or face of the head. This plate member 21. is removably secured to the head as by means of screws 22 and 23 which pass through the plate member and are received in suitable tapped openings in the head 10. Consequently, the plate member 21, and therefore the entire thread tension mechanism which is mounted therein, may be removed as a unit from a sewing machine head by simply removing the two screws 22 and 23.

The plate member 21 has a pin or stud 24 secured thereto adjacent one end of the member with the pin extending inwardly of the plate member and of the head on which it is mounted. On this stud is loosely supported a thread tensioning disk 25 and this disk is urged into engagement' with the adjacent face of the plate member 21 by an elongated resilient member 26 which is pivotally supported on the inner face of the plate member 21 and adapted to be flexed and/or tilted to vary the force with which the disk 25v engages the inner face of the plate member 21'. As here shown, the member 26 is in the form of a plate spring with an opening in the forward portion to accommodate the pin or stud 24, Which forward portion is spaced from the plate member and the disk 25 by means of a pin or stud 27 secured to the member 26 and engaging the disk 25. The pivotal support for the member 26 is provided by a threaded stud 28 secured to the inner face of the plate member 21. Threaded upon this stud 28 is a shouldered nut member 29 having an axially extending cylindrical'portion or boss freely received in an opening through the plate-like spring 26 as will be apparent inFig. 2.

The end of the member 26 opposite the disk 25 rests upon the forwardly projecting portion of an angularly shaped bracket member 30 which has forwardly projecting side portions to prevent sidewise displacement of the member 26'. The member 30 also has an elongated portion 31 extending at substantially right angles relative to the plate member 26. This portion 31 of the member 3tl is pivoted at 32 to a rotatable member 33 eccentrically of the axis of the latter. The rotatable member 33 is turnably supported in the shorter leg or portion of the plate member 21 and has the part thereof extending exteriorly of the plate member provided with a manually actuatable memberor part in the form of a knob 34. This knob is provided with calibrations or indicia which selectively cooperate with a'stationary arrow or indicium mark 36, see Fig. 4.

The construction thus far described is such that the disk'25 isengaged with the inner face of the plate member 21 under the force exerted by the plate-like spring 26, the valueof which force may be adjusted by turningthe knob 34 to align-one of the calibrations or indicia 35 with the arrow 36. This operates through the eccentric pivot of the bracket 30 on the rotatable member 33 to correspondingly raise or lower the adjacent end of the member 26' thereby altering the force with which the pin 27 engages the disk 25. The extent of this force is initially calibrated byadjustment of the position of the nut-like member 29.

This calibration is normally effected at the factory andisnot thereafterdisturbed during the normal'operation of the machine;

Thethread' which is employed with the needle of the sewingmachine is conducted over the outer face of the end of the head 10 inthe usual manner and is introduced between the plate member 21" and the disk 25 through an arcuate; slot 37 provided in the plate member21 adjacent a portion of the disk 25, as will be evident from Fig. 1. The thread is guided and assisted in this movement by an arcuate wire-like member 38 which has a configuration the member 38 secured to the plate member 21 along one surface of an outwardly projecting boss 39. The slot 37 is formed in a manner well understood in the art to provide a somewhat pointed portion of the plate member 21 and guide member 38 adjacent the lower portion of the slot so that the thread may be easily hooked over this portion of the member 38 and pulled arcuately around in the slot to receive a portion of the thread between the plate member 21 and the disk 25 with this portion of the thread issuing from the interior of the plate 21 adjacent the upper end of the slot 37.

The aforementioned outstanding boss 3 of the plate member 21 has the wall adjacent the slot 37 removed and extending through the opening thus provided is the' elongated portion 40 of the auxiliary or slack compensating spring 41. This spring is formed of wire and has the outer end formed as a loop 42, see Figs. 1, 3 and 7, into which the thread is passed as it is introduced into the slot 37. This is due to the fact that the loop 42 does not have the parallel portions tightly engaged and hence when the thread is introduced in the slot 37, as mentioned heretofore, the portion 40 of the spring member 41 is deflected upwardly and the thread slips between the said parallel portions of the loop 42 entering therein whereupon the spring member 41 descends to its initial position as will be readily apparent.

The initial position of the outer end or loop portion 42 of the spring member 431 is determined by a stop or abutment 43 secured to the inner face of the plate mem ber 21 and upon which the elongated portion 40 of the spring member normally rests. The inner end portion of the spring member 41 is in the form of a spiral coil 44 disposed concentric with a pin or stud 45 secured to the inner face of the plate member 21 substantially centrally of the aforementioned boss 39. The inner end 46 of the spiral portion 44 of the spring is directed at substantially right angles to the plane of the spiral and this portion 46 is received in an opening or slot 4-7 provided in an annular member 42% that is rotatably supported upon the pin or stud 45. Also rotatabl'y supported on this pin or stud is an adjusting member, generally designated 49, which has its inner end 59 provided with an opening turnably received on the stud 45 with the spiral portion 44 of the spring 41 disposed between the member 48 and the member 49. The member 49 has an elongated portion or arm 51 extending through a slot 52 along the upper edge of the boss 39 so that the outer end of the arm portion of the adjusting member 49 extends exteriorly of the plate member 21 and is movable in an arc thereover as will be apparent from Fig. 1. This arm portion 51 of the member 49 may be provided with an annularly offset flange such as 53 to facilitate engagement and actuation by the finger of an operator.

The members 418 and 49 are adapted to be disposed in a predetermined angular relationship at assembly to provide an initial predetermined tension of the spring member 41 which tension may thereafter be readily manually varied by simply moving the arm portion 51 For thepurpose of the initial calibration, one of the members 48, 49 is provided with a projection and the other of the members with a plurality of recesses for selectively receiving that projection. As here shown, this is achieved by providing the periphery of the member 48 with a plurality of notches or recesses 54 in which a projection 55 on the member 49 is engageable. This projection is preferably formed as an integral part or lug on the member 4-9 which is turned inwardly towards the member 48 as will be apparent from Fig. 2.

The parts of the auxiliary spring tension adjusting mechanism are held in adjusted position and prevented from accidental displacement by having their turning movement, as a unit, frictionally' restrained. This is achieved in the preferred embodiment by providing an annular dished spring member 56 which is supported on' the stud 45 betweenthe plate mem'ber 21 and the-mem ber 48, the assembly being retained in position by slidably compressing the spring 56 and maintaining the parts in this relationship with the projection 55 engaging the selected notch 54 by a suitable retaining means provided on the stud 45. As here shown, this retaining means is in the nature of a split collar 57, the bifurcated POIUOIIS of which are engaged in horizontally extending grooves or shoulders on the stud 45.

In initially assembling the auxiliary tensioning device, the spring member 56 is first placed on the stud 45 after which the member 48 may be placed thereon and the spring 4-1 superposed upon the latter with the end 46 received in the slot 47. The member 49 is then placed on the stud with the ing or projection 55 engaging one of the notches 54 of the member 48. Consequently, the loop portion 42 of the spring member 41 is held against the stop. 43 with a predetermined force the value of which may be adjusted by rotating the member 48 relative to the member 49 and re-engagin-gthe adjacent notch 54 with the lug 55. The parts are then held in this predetermined adjustment by deflecting the spring 56 and placing the split collar 57 upon the stud 45. Thereafter arcuate turning movement of the member 49 correspondingly turns the member 48 through the positive interconnection of the lug 55 and the notch 54 thereby winding or unwinding the spiral portion 44 of the spring 41 and correspondingly varying the force with which the outer end of the spring acts upon the thread engaged therewith.

The force or tension required to be exerted upon the thread by the auxiliary spring member 41 for proper operation under different sewing conditions is determined for a given initial calibrated tension of this spring and the outer face of the plate member 21 is provided with spaced indicia 58, see Fig. 1, at the locations of the arm 51 which result in the proper tension of the spring 41 for the corresponding sewing operations. In the illustrated embodiment, the mechanism has been calibrated to provide four predetermined tensions of the spring member 41 and these are designated, reading from right to left, Z, S, and M. The position designated Z provides the minimum force or tension of the spring member 41 and has been found to provide the proper action when employing the sewing machine with a zigzag attachment. The position of the member 49 when the arm is cooperating with the indicia S has been found to provide the proper tension for the spring member 41 for standard sewing operations. The position of the adjusting arm 51 in alignment with the indicia designated provides the tension of the auxiliary spring 41 which gives best results with attachments for making buttonholes, ruifling, hemstitching and the like, while the position of the arm member 51 when cooperating with the indicia marked M provides the maximum tension of the spring member 41 and which has been found desirable for certain special types of stitching such as those which use more than two threads; While four positions have been marked and specifically described with respect to the adjustment of the spring member 41, it will be evident that the tension of the spring member is varied for each increment of movement of the arm member 51 and hence the tension of the member can have values intermediate those which have been specifically marked and described.

It will be observed that the mechanism comprising the tensioning device of this invention is extremely compact and for this purpose the plate member 26 has an opening 59 intermediate its ends to accommodate the inner end of the stud 45 for the auxiliary spring mechanism so that there will be no interference of the parts when the member 26 is moved to effect adjustment of the tension provided by the disk 25. It will also be observed that the plate-like spring member 26 has the portion adjacent the disk deflected so that it is parallel to, but not coplanar with, the main part of the member. This provides a space between the back of the disk member 25 and the adjacent surface of the plate-like spring member 26 to actuate the tension releasing mechanism customarily provided for operation in conjunction with elevation of the presser foot.

In this device, tension release is effected by having the lower end of a finger-like member 60 extend between the plate spring 26 and the disk 25, the upper I between the adjacent portions of the members 6% and 62. The construction is such that When the lever 13 is raised, thereby raising the presser foot rod 12, the'pin 63 engages the bracket on the member 62. This member acts through the screw 64 to rock the member 60 thereby pulling the adjacent end of the spring member 26 inwardly of the head and releasing the tension upon the thread which passes between the plate 21 and the disk 25.

It is believed that. the construction of the preferred embodiment of this invention will now be readily apparent together with the operation thereof. However, by way of review, it is desired to point out that the device, when assembled and installed upon a sewing machine head, is employed by pulling a portion of the thread into the slot 37 from the lower part thereof so that this portion of the thread, passing inwardly through the slot, deflects the spring 41 upwardly so that the thread not only passes between the plate 21 and the disk 25 but is also received in the loop 42 of the spring and the thread emerges from the upper portion of the slot 37. As soon as the thread has entered the loop 42, the spring 41 will again urge this portion to its lower position against the stop 43, the tension exerted upon the thread by the plate 25 being determined by the adjusted position of the knob 34 while the force of the spring 4-1 is determined by the setting or position of the arm portion 51. The disposing of the thread through the other guides and needle of the machine may then be completed and the sewing operations begun.

When it is desired to efiect a different type of sewing, as for example one employing an attachment as contrasted with standard sewing, the force exerted by the auxiliary spring 41 is readily varied to the proper value by simply engaging a finger with the portion or arm 51 and moving the latter to the proper location indicated by the indicia 58. The tension to be exerted by the disk 25 likewise is readily adjusted by turning the knob 34 to bring the proper one of the indicia 35 into alignment with the arrow or mark 36. Consequently, not only the tension exerted upon the thread by the tension disk 25 but also the tension of the auxiliary or slack compensating spring 41 are readily adjustable without the need of special tools, gauges, or the like and without the need of disassembling or even partially disassembling the apparatus. Moreover, the value of the force exerted by the spring 41 for-each adjusted position thereof can be accurately predetermined at assembly and this initial calibration retained throughout repeated rocking or turning of the arm 51 to vary the force since the members 48 and 49 are positively retained in their calibrated angular relationship after assembly regardless of the rotative position of the entire assembly.

Attention is also directed to the fact that the tensioning mechanism of this device is entirely supported upon and carried by plate-like member 21 so that it may be placed or removed as a unit by means of the two screws 22 and 23. In this regard, it should also be noted that the finger member 60 of the tension releasing mechanism is readily engaged and disengaged with the plate spring 26 so that the tensioning mechanism may be readily placed and removed without need of dismantling any part of the presser foot elevating apparatus or the conneetions to effect release of the spring tension afforded by the plate spring 26. It will now be apparent that the device here illustrated and described is not only compact but also provides an attractive appearance since the mounting or supporting plate for the entire tensioning mechanism also serves as a portion of the cover of the head.

It will be evident that variations can be made in the specific details of the construction and in the mode of mounting the several parts of the mechanism by those skilled in the art and, hence, the invention is not to be considered as limited to the exact details of construction here illustrated and described except as required by the spirit and scope of the appended claims.

Having thus described the invention, 1 claim:

1. In a thread tensioner for a sewing machine head, a pair of members both supported for frictionally restrained turning movement about a common axis, a spring having a portion spirally coiled about said axis with the inner end of the spring connected to one of said members and the other end of said spring extending to a position wherein it can engage the thread employed in sewing, a fixed stop against which the said other end portion of the spring is urged by the coiled portion thereof, means operatively interconnecting said members in different rotative positions relative to each other thereby providing a selected initial tension of said spring against said stop for a selected position of said other member, and a manually engageable portion on one of said members movable for adjustment of the position of the members and the winding of the spirally wound portion of the spring to thereby vary the tension of said spring.

2. In a thread tensioner for a sewing machine head, a pair of members both supported for frictionally restrained turning movement about a common axis, a spring having a portion spirally coiled about said axis with the inner end of the spring connected to one of said members and the other end of said spring extending to a position to engage the thread employed in sewing, a fixed stop against which the said other end portion of the spring is urged by the coiled portion thereof, a projection provided on one of said members selectively engageable in one of a plurality of recesses in the other of said members to provide a selected initial tension of said spring against said stop for a selected position of said other member, and a manually engageable portion on one of said members movable for adjustment of the position of the members and the winding of the spirally wound portion of the spring to thereby vary the tension of said spring.

3. In a thread tensioning device for sewing machines, a plate member having an opening therein, a pin rigidly mounted on said plate member, a pair of members rotatably supported on said pin and frictionally restrained from said rotation, a spring having a portion spirally coiled about said pin with the inner end of the spring connected to one of said pair of members and the other end of said spring extending outwardly through said opening in said plate member and provided with a loop through which thread is passed, a fixed stop against which the said other end portion of the spring is urged by the coiled portion thereof, means operatively interconnecting said pair of members in different rotative positions relative to each other thereby providing a selected initial tension of said spring against said step for a selected position of said other member, and a manually engageable portion on one of said members of the pair of members movable to adjust the position of said members and the winding of the spirally wound portion of the spring and the tension of the spring.

4. In a thread tensioning device for sewing machines,- a plate'member having spaced openings therein, a pin rigidly mounted on said plate member, a pair of members rotatably supported on said pin and frictionally restrained from said rotation, a spring having a portion spirally coiled about said pin with the inner end of the spring connected to one of said pair of members and the other end of said spring extending outwardly through one of said openings in said plate member and provided with a loop through which thread is passed, a fixed stop against which the said other end portion of the spring is urged by the coiled portion thereof, a projection provided on one of said pair of members and selectively engageable in one of a plurality of recesses in the other of said pair of members to provide a selected initial tension of said spring against said stop for a selected position of said other member, and an arm on the said other of the pair of members extending through the other of said openings in said plate member and having a manually engageable portion for movement to vary the position of said pair of members and the tension of the spring.

5. in a thread tensioning device for sewing machines, a plate member having a pair of openings therein, a pin rigidly mounted on said plate member, a pair of members rotatably supported on said pin, a spring having a portion spirally coiled about said pin between said pair of members with the inner end of the spring connected to one of said pair of members and the other end of said spring extending outwardly through one of said openings in said plate member and provided with a loop through which thread is passed, a fixed stop against which the said other end portion of the spring is urged by the coiled portion thereof, a projection provided on one of said pair of members and selectively engageable in one of a plurality of recesses in the other of said pair of members to provide a selected initial tension of said spring, means providing a frictional force on said members to retain them in an adjusted position until positively moved therefrom, and an arm on the said other of the pair of members extending through the other of said openings in said plate member and having a manually engageable portion movable in an arc to vary the position of said pair of members and the tension of the spring.

6. In a thread tensioning device for sewing machines, a plate member having a pair of openings therein, a pin rigidly mounted on said plate member, a spring having a portion spirally coiled about said pin and an elongated portion extending outwardly therefrom through one of said openings in said plate member with the outer end of said elongated portion provided with a loop through which thread is passed, a member rotatably supported on said pin and having an opening therein adapted to receive the inner end of said spring for movement of the latter with the former, a fixed stop against which the said elongated portion of the spring is urged by the coiled portion thereof, an adjusting member rotatably supported on said pin, a projection provided on one of the said members supported on said pin and selectively engageable in one of a plurality of recesses in the other of those members to provide a selected initial tension of said spring, means providing a frictional force on said members to retain them in an adjusted position until positively moved therefrom, and an arm on said adjusting member extending through the other of said openings in said plate member and having a manually engageable portion moving over a portion of the outer surface of said plate member substantially parallel therewith to vary the tension-of the spring.

7.- In a thread tensioning device for sewing machines, a plate member having a pair of openings therein, a pin rigidly mounted on said plate member, an annular spring" disposed about said pin adjacent the base thereof and engaging said plate member, an annular member resting upon said spring with said pin passing therethrough, a wire spring member having a spirally coiled portion disposed about said pin with the inner end of the last-mentioned spring member connected to said annular member, the outer end of said Wire spring member extending outwardly of said plate member through one of said openings in the latter and provided with a loop adapted to engage the sewing thread, a fixed stop on said plate member for the said outer end of the wire spring member, a spring adjusting member rotatably supported on said pin with a portion thereof selectively engageable with one of a plurality of spaced recesses in the said annular member to provide an initial tension of said wire spring member for a selected position of said adjusting member, means for retaining the said adjusting member on said pin, and an arm on said adjusting member extending through the other of said openings in said plate member and having a manually engageable portion moving in an are over a portion of the outer surface of said plate member substantially parallel therewith to vary the tension of said wire spring member.

8. In a thread tensioning device for sewing machines, a plate member having a pair of openings therein, a pin rigidly mounted on said plate member, an annular spring disposed about said pin adjacent the base thereof and engaging said plate member, an annular member resting upon said spring with said pin passing therethrough, a wire spring member having a spirally coiled portion disposed about said pin with the inner end of the lastmentioned spring member connected to said annular member, the outer end of said wire spring member extending outwardly of said plate member through one of said openings in the latter and provided with a loop adapted to engage the sewing thread, a fixed stop on said plate member for the said cuter end of the wire spring member, a spring adjusting member rotatably supported on said pin with a portion thereof directed towards and engageable with one of a plurality of spaced recesses on the periphery of said annular member to provide an initial tension of said wire spring member for a selected position of said adjusting member, means for retaining the said adjusting member on said pin, an arm on said adjust- 1- member extending through the other of said openings in said plate member and having a manually engageable portion moving in an arc over a portion of the outer surface of said plate member substantially parallel therewith to vary the tension of said wire spring member, and indicia said outer surface of the plate member cooperating with the said arm of the adjusting member for indicating the type of sewing for which the wire spring member is adjusted.

References Cited in the file of this patent UNITED STATES PATENTS 386,380 Dial July 17, 1888 2,51%,703 Marsac Aug. 15, 1950 2,609,772 'Casas-Robert Sept. 9, 1952 FOREIGN PATENTS 370,672 Italy Apr. 26, 1939 414,717 Italy Aug. 24, 1946

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