US2292257A - Needle-bar mechanism for sewing machines - Google Patents

Description

Q 4, EQ2@ F. F. ZEHER REEDLEBAR MECHNISM FUR SEWING MACHINES 2 'sheetsheet -1 Fwede E Zenker Patented Aug. 4, 1942 NEEDLE-BAR MECHANISM FOR SEWING MACHINES Frederick F. Zeier, Fairfield, Conn., assigner to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application January 3, 1940, Serial No. 312,230

6 Claims. (C1. 112-206) In practice, it has been found that in known i machines having a needle-feed, wherein the usual needle-bar frame is hung at its upper end upon a stationary fulcrum-stud to vibrate in the line of feed, the needle becomes heated when stitching heavy fabrics with a relatively long stich at high speed. This heating is caused by the fact that the needle enters the fabric at an angle and at a point located at one side of a vertical line passing through the axis of the needle-bar y frame fulcrum-stud and, during the feeding stroke, swings in an arc to a )point located on the opposite side of said vertical line where it emerges `from the fabric at an angle. This swinging lateral movement of the blade of the needle while in the `fabric causes the needle- .puncture to be spread adjacent the upper and lower surfaces of the fabric, and this spreading of the needle-puncture by the needle creates a pressure on the blade of the needle which increases materially the friction between the needle and the fabric. This increased friction generates heat in the needle and, at high speeds of operation, is suflicient to render the needle unfit for continued sewing.

The primary object of the present invention is the provision in a sewing machine of a shifting fulcrum-support for the needle-bar frame designed so that the needle enters and emerges from the -fabric in a direction substantially perpendicular to the surfaces of the fabric being stitched.

With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

Referring to the drawings, Fig. l is a front end elevation of the head of a sewing machine em- -bodying the invention.

Fig. 2 is a vertical section of the sewing machine head together with a portion of the bracket-arm.

Fig. 3 is an enlarged perspective view of the needle-bar-frame shifting fulcrum and actuating mechanism therefor.

Fig. 4 is an enlarged fragmentary View of the needle and fabric of a prior machine showing, in full lines, the position of the needle just after it `penetrates thev fabric and, in dotted lines, the position of the needle immediately before it iS withdrawn from the fabric. f

Fig. 5 is a view similar to Fig. 4 showing the relation between the needle and the fabric in a sewing machine fitted with the present improvement.

Referring more in detail to the accompanying drawings, one embodiment of the invention is shown as applied to a sewing machine having a bracket-arm I terminating in a head 2 overhanging a work-support, shown only as line 3 in Figs. 1 and 2. Journaled in a conventional Torrington needle-bearing 4 fixed in a wal-1 5 of the bracket-arm I is a rotary main-shaft 6 having secured at its outer end, preferably by a setscrew l, the usual counterbalanced needle-bar crank 8. Fixed in the free end of the crank 8 is a second needle-bearing 9 in which is journaled a crank-pin I8 fastened in one end of a link II pivoted at its other end upon a pin I2 integral with a split collar I3 clamped upon a needle-bar I4. At its lower end the needle-bar I4 carries the usual needle I5.

The needle-bar I4, see Figs. 2 and 3, is journaled for endwise reciprocation in spaced 4bearings provided in the lugs I6 and Il integral with a vibratory frame I8 having an offset head I9 pivotally hung on a fulcrum-.pin 2,3 formed upon the lower end of a crank-arm 2 I. The frame I8 is formed with the offset head to enable the needle-bar I4 to be readily inserted in the .bearing lugs I6 and II. Threaded into the end of the fulcrum-pin 28 is a cap-screw 22 which prevents the offset head. I9 of the frame I8 from shifting lengthwise of the fulcrum-pin 20. The crank-arm 2l is preferably formed integral with a short stub-shaft .23 journaled for oscillation in a bearing 24 provided in the top of the machinehead 2 rearwardly of the vertical plane containing the longitudinal axis of the main-shaft B. Clamped by means of a screw 25 upon the inner end of the stud-shaft 23 is the split upper end of a rock-lever 28 provided at its lower end with a `pin 21 connected by a pitman 28 to an eccentric 29 preferably cut upon the rear portion of the counterbalanced needle-bar crank 8.

It will be understood from the above description that as the main-shaft 6 is rotated, the crank-arm 2| and hence the fulcrum-pin 20 is swung about the axis of the stub-shaft 23 in an arc, the length of Whichv is determined by the eccentricity of the eccentric 29. While I lhave illustrated the eccentric 29 as having a fixed eccentricity, it is obvious that an adjustable eccentric may be substituted therefor, whereby the arc of movement of the fulcrum-pin 20 can 'be controlled to conform with the stitch-length.

As described in detail in my copending application above referred to, the frame E8 is vibrated in the line of feed in timed relation with the upper feeding mechanism and the lower feeding mechanism (not shown) of the machine so that the needle I will assist in advancing the material uniformly past the stitching mechanism. Inasrnuch as the mechanism for vibrating the frame I8 is fully disclosed in my copending application Serial No. 267,958, only such reference will now be made to the saine as will enable one to understand the functioning of the present Vinvention. It will be observed in Figs. 1 and 2 that the frame I8 has journaled in it a presser-bar 36 and a feed-bar 3i carrying at their lower ends a presser-foot 32 and a feed-dog 33, respectively. The presser-bar 35 and the feed-bar 3l are alternately raised and lowered in effecting a feeding action by mechanism fully described in my copending application and therefore will not be further described in this application.

Vibratory movement of the frame I8 in the line of feed is accomplished by a link 34 connected at one end to a lug 35 formed on the frame I8 and at its other end to the lower end of a depending rock-lever 35 secured upon the outer end of a rock-shaft 3l journaled in suitable bosses 33 cast upon the rear of the machine-head 2. Clamped upon the inner end of the rock-shaft 3l, see Fig. 2, is the split lower end of an upstanding rock-lever 39 connected at its upper end by a relatively short pitman 40 to an adjustable eccentric II secured upon the main-shaft 8. The adjustable eccentric 4I, the constructive features of which are disclosed in the United States Patent to W. Myers, No. 2,128,081, issued Aug. 23, 1938, is provided so that the amplitude of vibration of the needle in the line of feed can be made to conform with the length of stitch to which the lower feeding mechanism is adjusted.

Referring to Figs. 2 and 3, it will be observed that the eccentric 4I imparts to the lower end of the needle-bar frame I3 vibrations about the fulcrum-pin 2t in the line of feed, and that the eccentric 29 imparts to the fulcrum-pin 20 oscillations about the longitudinal axis of the stubshaft 23. The eccentrics 29 and 4I are relatively timed so that the lower end of the needle-bar frame I8 and the fulcrum-pin 2t therefor move in the same direction at the same time. This simultaneous movement of the frame I8 and the pin 20 maintains the needle-bar frame substantially vertical, so that during the work-penetrating stroke the longitudinal axis of the needle I5 is disposed perpendicular to the upper surface S of the fabric F, as shown in Fig. 5. The position of the needle I5 illustrated in Fig. 5 is the same during the withdrawal stroke of the needle. It will be appreciated that the friction between the fabric F and the needle I5 is at a minimum when the conditions, as shown in Fig. 5, are approached.

Fig. 4 exemplines the condition which existed in machines prior to the present invention. When, as in previous machines, the sewing machine is fitted with a stationary fulcrum-stud,

instead of a shifting fulcrum-pin as in the presing the feeding stroke, the needle I5 moves from the full line position into the dotted line position. It can be clearly seen that this lateral movement of the blade of the needle I5 spreads the needle-puncture in the fabric adjacent the upper and lower surfaces thereof, and that this spreading action increases the pressure between the needle and the fabric. Obviously, this increased pressure generates excessive heat when the needle is withdrawn from the fabric.

From the above description, it will be understood that I have provided a novel shifting fulcrum-support for the usual needle-bar-frame which is constructed and actuated so that the friction between the reciprocating needle and the fabric being stitched will be reduced to a minimum. It will be seen also that I have provided a novel floating fulcrum-support Which is extremely simple in construction and which is compact and contained entirely within the head of the machine-frame. The parts or elements of the floating fulcrum-support have been proportioned and arranged so that they may be operated at a high rate of speed without setting up prohibitive vibrations.

While various parts of the mechanism cooperating with the characteristic fetures of this improvement have been shown and described somewhat in detail herein, it is evident that the specific construction and arrangement of such parts are not material to the invention and also that the construction and arrangement of parts of the shifting fulcrum-support may be considerably Varied Within the scope of the invention.

Having thus set forth the nature of the invention what I claim herein is:

1. A sewing machine having, in combination, a bracket-arm terminating in a head, a mainshaft journaled in said bracket-arm, a frame supported on said head and adapted to be vibrated in the line cf feed, a needle-bar journaled for endwise reciprocatory movements in said frame, a needle carried by said needle-bar, connections for vibrating said frame to effect a feeding of the work, a stub-shaft journaled in said head above the level of said main-shaft, means fixed to said stub-Shaft and providing a fulcrum for said frame, and means operatively connecting said stub-shaft to said main-shaft for shifting the fulcrum of said frame so that the needle penetrates and emerges from the fabric in a direction substantially perpendicular to the surface of the fabric.

2. A sewing machine having, in combination, a bracket-arm terminating in a head, a mainshaft journaled in said bracket-arm, a frame supported on said head and adapted to bevibrated in the line of feed, a needle-bar journaled for endwise reciprocatory movements in said frame, a needle carried by said needle-bar, connections for vibrating said frame to effect a feeding of the work, a stub-shaft journaled in said head above the level of said main-shaft, a crank-arm fixed to said stub-shaft and providing at its free end a fulcrum for said frame, and means within the confines of said head for actuating said stub-shaftv to shift the fulcrum of said frame so that the needle penetrates and emerges from the fabric in a direction substantially perpendicular to the surface of the fabric.

3. A sewing machine having, in combination, a bracket-arm terminating in a head, a mainshaft journaled in said bracket-arm, a frame supported on said head and adapted to be vibrated in the line of feed, a needle-bar journaled for endwise reciprocatory movements in said frame, a needle carried by said needle-bar, connections for Vibrating said frame to effect a feeding of the work, a stub-shaft journaled in said head above the level of said main-shaft, means fixed to said stub-shaft and providing a fulcrum for said frame, and means for actuating said stub-shaft to shift the fulcrum of said frame so that the needle penetrates and emerges from the fabric in a direction substantially perpendicular to the surface of the fabric, said last-named means including a rock-lever fixed to said stubshaft, and a pitman connected at one end to said rock-lever and at its other end to means on said main-shaft for actuation thereby.

4. A sewing machine having, in combination, a machine frame including a bracket-arm terminating in a head, a shaft journaled in said bracket-arm and extending into said head, a vibratory frame sustained upon said head and adapted to be vibrated in the line of feed, a needle-bar journaled for endwise reciprocatory movements in said vibratory frame, a needle carried by said needle-bar, means including a crank secured to that portion of the shaft within said head for reciprocating said needle-bar, connections for Vibrating said vibratory frame to effect a feeding of the work, an oscillatable fulcrumpin located in the upper portion of said head for supporting said vibratory frame, and means within the confines of said head for oscillating said fulcrum-pin, said means deriving its actuations from an eccentric located adjacent said crank on said shaft.

5. A sewing machine having, in combination, a bracket-arm terminating in a head, a mainshaft journaled in said bracket-arm, a frame having an offset upper end sustained by said head and adapted to be vibrated, a needle-bar journaled for endwise reciprocatory movements in said frame, a needle carried by said needlebar, connections for vibrating said frame, a stubshaft journaled in said head above the level 0f and rearwardly of the axis of the main-shaft, means fixed to said stub-shaft and providing a fulcrum for the offset upper end of said frame, and means within the confines of said head operatively connecting said stub-shaft to said main-shaft for shifting the fulcrum of said frame so that the needle penetrates and emerges from the fabric in a direction substantially perpendicular to the surface of the fabric.

6. A sewing machine having, in combination, a machine frame including a bracket-arm terminating in a head, a wall separating said bracketarm from said head, a shaft journaled in said bracket-arm and extending into said head, a vibratory frame sustained upon said head and adapted to be vibrated in the line of feed, a needle-bar journaled for endwise reciprocatory movements in said vibratory frame, a needle carried by said needle-bar, means including a needle-bar actuating crank secured to thatV portion of the shaft within said head for reciprocating said needle-bar, connections for Vibrating said vibratory frame to effect a feeding of the work, a. stub-shaft journaled in said head, a crank-arm fixed to said stub-shaft and providing a fulcrum for said vibratory frame, a rocklever secured to said stub-shaft, and a pitman secured at one end to said rock-lever and at its other end to an actuating eccentric on said mainshaft, said eccentric being fast on said mainshaft between said needle-bar actuating crank and the wall separating said bracket-arm from said head.

FREDERICK F. ZEIER.

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