US1529020A - Thread-cutting mechanism for sewing machines - Google Patents

Description

March 10, 1925. r 1,529,020

' ;A. F. FIFIELD THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed Aug. 14, 1922 3 Sheets-Sheet 1 k WITNESSES:

ATTORNEY March 10, 1925. 1,529,020,

A. F. FIFIELD THREAD CUTTING MECHANISM FOR SEWING MACHINES File Aug. 14, 1922 5 Sheets-Sheet 2 WITNESSES: Q INVENTOR z $2.22, mam

March 10; 1925.

A. F. F' IFIE LD THREAD CUTTING MECHANISM FOR SEWING MACHINES 3 Sheets- 5 |NVENTOR Q WITNESSES! ww Z g 1%,

Patented Mar. 10, 1925.

UNITED STATES PATENT OFFICE.

ALBERT F. 'FIFIELD, OI! NEWARK, NEW JERSEY, ASSIGNOR TO THE SINGER MANU- FACTURING COMPANY, OIE ELIZABETH, NEW JERSEY, A CORPORATION OF NEW JERSEY.

, THREAD-CUTTING MECHANISIM FOR SEWIN G'WIACHINES.

.To all whom it may concern}:

Be it known that I, ALBERT F. FIFIELD, a citizen of the United States, residing at Newark, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Thread-Cutting Mechanisms for Sewing Machines, of

which the following is a specificati0n,.reference being had therein tothe accompanying drawings.

v This invention relates to thread-cutting mechanism for sewing machines and has for a particular object to improve the mechanism disclosed in my Patent N 0. 1,447,941 of March 6, 1923. In the device of my said copending application it is found that at high speeds there is some danger of the supply limb of the needle-loop being sheared ofi', together with the work-limb, whereby the thread-end hanging from the needle will be of insufficient length to enable the next sewing operation to be properly started.

Furthenin the device of my said application, the bobbin-thread nipper comprises a spring which presses directly against the needle-loop detaining blade and both the bobbin-thread and the supply limb of the needle loop are caught by the .nipper just before the threads are out. Thus, when the work is removed and the needle-thread end hanging from the needle is thereby pulled out of the-nipper, said needle-thread end will sometimes drag the bobbin-thread end out of the nipper and consequently prevent the bobbin-thread end from beingiheld under control when the initial stitch of the' n'ext sewing operation is formed.

Further, with my prior device, difficulty is occasionally experienced in providing a beginning needle-thread end uniformly long enough to be gripped by the thread-wiper 'below the throat-plate at the beginning ofa sewing operatiombut not so long as tosti'ck out from the finished work.

The present improvement seeks to refine my prior construction and eliminate the sources of the minor difficulties above enumerated to theiend that still greater certainty and uniformity of operation will :be secured and a uniformly satisfactory prod-- not more easily attained.

It is more generally an object of the Application filed. August 14, 1922. Serial no. 581,606.

present invention to provide a sewing machine having thread-severing mechanism of greater simplicity, durability and dependability than has heretofore been attained.

To the accomplishment of the ends in view, the shank of the ledger-blade of my prior construction has been reversed in posi- [1011 so as to lie within the circular path of action of the needle-loop detaining and :severing blade.

passes freely between the nipper-blades and the needle loop detaining blade.

To insure a beginning thread-end of a minimum uniform length, a ledger-blade has been added .to cooperate with a sharpened edge on the thread-wiper to cut off anyexcess needle-thread projecting beyond the wiper. This ledger-blade is formed with astraight, easily sharpened edge and. to insure certainty of action, an additional blade having a thread-guiding edge in clined to the cutting edge of the ledger-blade is associated with the latter to afford, in effect, a V-notch insuring against escape of the needle-thread end from cutting position between the sharpened edge of the thread wiper and its cooperative ledger-blade.

In the accompanying drawings, Fig. 1 is a rear side elevation of a sewing machine embodying the invention. Fig. 2 is a bot tom plan view of the machine. Fig. 3 is a cross-section through the sewing point longitudinallygof the machine bed. Fig. 4

.is a bottom plan view of the throat -plate showing the thread=cutting fand nipping i111- plements carried thereby. n Fig. 5 is view of the thread-cutting and nipping implement looking in the direction of the'iarrow 55, Fig. at. Fig. 6 is'a bottom plan view of the needleeloop detaining and severing "the needle-loop detaining and severing blade to sever the needle and bobbin-threads.

In the preferred embodiment of the invention. as illustrated, 1 represents the machine bed from which rises the standard 2 of the overhanging bracket-arm 3 terminating in the head i in which is journaled to reciprocate the needle-bar 5 carrying the eye-pointed needle 6.

The needle 6 cooperates with a loop-taker 7 which is preferably in the torm of a rotary hook operating to give the needle-loop half twist in casting it about the usual bobbin in the thread-case 8, thereby juxtapos ing the bobbin-thread and the work-limb of the needle-loop, as explained in my said copending application. and enabling the needle and bobbin threads to be cut together at a point close to the work by means of a needle loop detaining and severingblade having but one cutting edge. The roi'ary hook 7 is mounted on the shat't 9 which at its rearward end is geared at 10 to the shaft 11 extending vertically within the standard 2 and at its upper end geared at 12 to the main-shaft 13.

The main-shaft 13 is connected as usual to drive the ueedle bar 5 and the, teed-cam '14 which latter operates through the usual connections to move the work-clamp 15 back and forth over the bed 1 and thus determine the placing of the stitches. the present machine is intended for sewing on buttons. the work-clamp 15 is of the usual button holding type disclosed. for example. in the patent to C. M. Horton. No. 667,676. of December 19, 1905.

The present machine is equipped with a stop-motion device. constructed substantially in accordance with the disclosure of my said patent and including the stop-motion lever 16 which carries the belt-shifter 17 adjacent the tight and loose pulleys 18. 19. respectively. on the main-shaft 13. The lever 16. as shown in full lines in Fig". 1. is instopping position. It may be tilted about its pivot 17 to dotted line position to start the machine. Atthe end of the sewing operation the lever 16 is automatically released and springs to full line or stopping position. whereupon a vertically spring pressed plunger 20 carried by said lever engages a notch in a stopping cam 21 on the mainshatt 13. The lever 16 is so mounted that it may partake of a sidewise. overthrow movement under the action of the stopping cam 21 in coming to rest. This overthrow movement is balanced by the usual butler spring (not shown) and brings the mainshaft 13 to rest without destructive shock. The present stop-motion device preferably has incorporated therewith a braking device permitting" high speed operation. as disclosed in my said patent. The present improvement. however. is not concerned with the mechanism of the braking device and a description of the latter is therefore deemed unnecessary. In so far as the present improvement is concerned the stop-motion lever 16 is constructed and operated substantially in accordance with the disclosure of said Horton patent.

Mounted below the bed 1 is the usual thread-cutter operating slide-bar 22 which in the present instance is connected at its rear end by means of a link 23 to a lever 2 pivoted at 25 to the bed 1. The lever 25 is connected by a link 26 to an auxiliary slidebar 2'? which at the end of the sewing operation is given the usual two-stage movement; the first stage of such movement being given by the cam-operated lever 28 and the second stage by the overthrow of the stopmotion lever which is transmitted to the slide-bar 27 through the usual bellcranklever 29. This mechanism for imparting: to a threadu'utter operating slide-bar a two stage univement is old in the art and is disclosed in said Horton patent.

The in'ipleinents ot the. present threadcutting; mechanism are mounted on the usual throat-plate 30 from the under side of which projects the pivot-post 31 for the threadcutter lever-arm 32. The lever-arm 32 is connected to the slidebar 22 by means of the link 353. The lever-arm 32 has mounted thereon a needle-loop detaining blade S t. similar in shape and function to that dis closed in in said patent. Such blade has at its outer edge an upstanding lip trans verse to the plane oi the blade 34 and having its inner forward edge 36 sharpened as shown in Figs. -'land 6. The projection 33 is opcrutively received in the circular clearance groove 3T in the throat-plate.

The cutting edge 36 of the blade 3 i co operates with the ledger-blade 36 which. together with its shank 39, is disposed within the circle of operation 0. Fig. 6. (ii the cutting lip 35. By sharpening the inner torward edge 36 of the lip 35. instead ot the outer edge. and by disposinc the ledgerblade 38 within, rather than outside ot. the circular path oi. movement of the cutting lip it will be seen upon referring to Fig.

I 3 that the cutting edge 36 is set inwardli.

from the outer edge 40 of the loop-detaining blade 34. thereby overcoming the possibility of the supply or lower limb s of the needlcloop getting" in the path of the cutting blade.

The needle-loop detainingblade 34: has its shank 41 (Fig. 7) oftset below the plane ot the blade 34 proper. The shank 41 is secured to the carrier arm 32 by means of the screw 12 which also serves to secure a pair of bobbin-thread nipper-blades 43. it in a position spaced below the needle-loop detaining blade 34. The blade 43 is preferably made relatively stilt and the blade 44-. springy. The ends of these blades are oppositely curved to form a mouth 45. Fig. 1, which catches the bobbin-thread b. and

of the carnier l'evel" 32.

' When themachine is' sewing, the carrier-- lever 32 and blades 34, 43 and 44 occupy a retracted position indicated in dotted lines;

in Fig. 4. As the sewing-operationis nearing completion the usual thread-cutter operatmg;camsgroove 46 in the teed-wheel 14" acting through the lever 28, imparts to the slide-rod 22 its first stage. of movement which causes the needle-loop detaining blade 34 to be projected into the last needleloop as the latter is being passed around the bobbin by the rotary hook 7. After the take-up has acted, the last needle-loop is thus detained below the work in a spread condition by the blade 34. The inner edge of the blade 34 also catches the bobbinthread I) and directs said thread into the mouth of the nipper 43, 44, at the same time serving to pull off enough bobbinthread to insure the interlocking of the latter with the needle-thread when the initial stitch of the next sewing operation is formed. The supply limb of the needle-loop passes freely between the loop-detaining blade 34 and the upper-blades 43, 44, while the work-limb 'w of the needle-loop and the bobbin-thread b extend in juxtaposed relation above the blade 34 directly in the path of the cutting lip 35, and between the latter and the ledger-blade 38, as shown in Fig. 3. Theoverthrow motion of the stop-lever 16, in bringing the main-shaft 15 to rest, operates in the usual manner to impart the second stage of movement to the slide-bar 22 which transmits to the blade 34 a cutting impulse carrying the lip 35 into shearing engagement with the ledger-blade 38 and thereby severing the bobbin-thread Z) and the work-limb 'w of the needle-loop close to the work.

Mounted on the carrier-lever 32 is a thread-wiper or gripper 47 of usual hooked form which is adapted to nip the beginning end of the needle-thread against the under side of the throat-plate 30. In the present instance the edge 48 of the thread-gripper is sharpened for cooperation with the sharpened straight edge 49 of a ledger-blade 50 secured to the throat-plate 30, to cut off any excess of needle-thread sticking out beyond the gripper and thus insure a needle-thread end of a uniform minimum length, i. e., no longer than is essential to the secure holding of such thread-end by the gripper 47 during the formation of the initial stitches. A second blade 51 having a thread-guiding point 52 underlying the cutting edge 49 and directed at an angle to the latter is provided "for catching the needle-thread end and directing it to the cutting edge 49 of the ledgerblade 50. The finger 52 together with the cutting edge 49 forms a. V-notch insuring against escape 3of=the thread. This construct'ion:has an advantage over a single ledgerblarle formed with a V-notchin =that the straight cutting edge 49 may be separated tromnthe finger' 52' and easily sharpened on a-n ordinary grinding wheel.

l'la-ving thus-set fortluthe nature otthe invention; what I claim: herein is:

1. I n ausewing'maclri ne, the combination with a throat-plate, of a needle-loop detaining blade mounted below the throat-plate to swing about an axis transverse to the plane of the throat-plate, said blade having a blunt outer curved edge and a portion extending toward said throat-plate, said portion having a cutting edge disposed inwardly from said outer edge.

2. In a sewing machine, the combination with a throat-plate, of a needle-loop detaining blade mounted below the throat-plate to swing about an axis transverse to the plane of the throat-plate, said blade having a blunt outer curved edge and a cutting edge disposed inwardly from said outer edge, and a ledger-blade mounted inwardly from said cutting edge and cooperating with the latter to sever the thread. i

3. In a sewing machine, the combination with a throatplate, of a needle-loop detaining blade mounted below said throat-plate on an axis transverse to the plane of the throat plate, and a bobbin-thread nipper mounted in spaced relation with and below said needle-loop detaining blade.

4. In a sewing machine, the combination with throat-plate, of a carrier mounted on the under side of said throat-plate, a needle-loop detaining blade mounted on said carrier, and a bobbin-thread nipping device also mounted on said carrier in spaced relation with said needle-loop detaining blade so as not to nip the thread of the needle-loop.

5. A thread-cutting mechanism for sewing machines comprising, a flattened needleloop detaining blade pivoted transversely of the planes of its faces and having a curved outer edge and a cutting lip disposed at said outer edge and at an angle to the faces of said blade, said lip having a cutting edge disposed inwardly from the outer edge of said blade.

6. In a sewing machine, the combination with a threadwiper in the form of a hook adapted to grip the beginning end of the needle-thread below the work and having adjacent its hooked extremity a rearwardly directed cutting edge, of a ledger-blade having a straight sharpened edge, and a second blade detachable from said ledger-blade and formed with a thread-guiding edge disposed at an angle to said ledger-blade and forming therewith a V-notch, substantially as and for the purposes specified.

7. The combination With stitch-forming mechanism including a reciprocating needle, a bobbin and a rotary hook adapted to give the needle-loop a half twist in casting it about the bobbin and juxtapose the bobbinthread and the Work-limb of the needle-loop, of a needle-loop detaining and severing blade having a bobbin-thread pull-off edge, a pair of bobbin-thread nipper-blades spaced from said blade and adapted to seize only the bobbin-thread While permitting the 10 needle-loop to pass freely between the needleloop detaining blade and the nipper-blades, and means for severing the juxtaposed threads.

In testimony whereof, I have signed my 15 name to this specification.

ADBERT F. FIFIELD.

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