US2844114A

US2844114A - Stitch adjusting device for sewing machines

Info

Publication number: US2844114A
Application number: US608915A
Authority: US
Inventors: Benink Christiaan Jose Marinus; Wenz Herbert
Original assignee: GM Pfaff AG
Current assignee: GM Pfaff AG
Priority date: 1955-09-12
Filing date: 1956-09-10
Publication date: 1958-07-22
Anticipated expiration: 1975-07-22
Also published as: CH343216A; DE1027970B; GB812298A; FR1155837A; FR72257E; GB867805A

Description

July 22, 1958 c. J. M. BENINK ET Al. 2,844,114

STITCH ADJUS'IINC DEVICE FCR SEWING MACHINES Filed Sept. 10, 1956 3 Sheets-Sheet l Fig. 1

Iii: x

July 22, 1958 l c. JQM. BENINK ET AL 2,844,114

sIIIcEADJusTING DEvIcE FOR SEWING MACHINES Filed sept. 1o, 195e s sheets-sheet 2 l/VVENTOBS STITCH ADJUSIING DEVICE FOR SEWING MACHINES Filed sept. 1o; 195e A C. J. M. BENlNK ET AL July 22, 195.8

3 Sheets-Sheet 3 United States -Patent f g 2,844,114 ce Patented Julyzz, 195s sTrrcH ADJUsTlNG nEvIcE Fon SEWING MAcHlNEs Christiaan Joseph Marinus Benink and Herbert Wenz,

Kaiserslautern, Pfalz, Germany, assignors to G. M. Pfaff A.G., Kaiserslautern, Pfalz, Western Germany The invention relates to sewing machines and particu-s larly to the mechanism for adjustingthe length `of the stitches produced by the machine. Y i

More in particular, the invention relates to a stitch length adjusting mechanism for sewing machines provided with a contact lever which, by swinging between` two curved edges which define the limits of an aperturek in a rotatable disk, provides'for the same stitch length for the forward and the back stitch.

The invention is based on a mechanism having a contact lever which by reciprocating between two curved edges which dene the limits of a cavity in a turnable disk provides for the same length of the forward stitch and the back stitch, in particular by the coaxial arrangement ofthe disk with the stitch'setting shaft andby continuous curves which are in nonsymmetric relationship', the radial distances of which from the axis of rotation of said disk relative to av central neutral line are inversely related to each other. At the same time, the contact edges provide an accurately operating device which is directly and continuously adjustable in accordance with the markings, which requires merely a single, brief, readily executed setting operation to enable sewing immediately in accordance with the adjusted stitch in both directions.

Suitably a stop which is secured to the contact leve and which projects into the aperture of the disk is spring biased and continuously engages one of the two curved edges.

The swinging movement of the contact lever is effected by an adjustment member, which is secured upon the stitch setting shaft, into the track of operation of which extends a pin which is mounted upon the contact lever.

The stitch setting shaft is subject to the tension of a spring which holds the arm in inoperative position when the handle is released.

It is an object of the invention to provide a stitch adjusting mechanism which is simple to operate and which is made of components which are easily produced.

It is a further object of the invention to provide a stitch adjusting mechanism which requires particularly little space and which is simple to operate by virtue of the fact that the disk is mounted upon a hollow shaft which is journalled in the wall of the housing and which, in turn, receives the stitch setting shaft.

Other objects and advantages of the invention will become apparent when reference is had to the following description of an embodiment of the invention which is illustrated in the accompanying drawings in which:

Fig. 1 shows a front view of a sewing machine which is provided with the new stitch adjusting mechanism;

Fig. 2 is a cross-section of the machine taken through the mechanism along line II-II of Fig. 1;

Fig. 2a is a cross section taken from the right hand side of Fig. 2 showing the shaft, cams and connecting bars;

Fig. 3 is a partial sectional view taken along line III--III in Fig. 2, and

Fig. 4 is a partialA sectional -view taken along line IV-IV in Fig. 3. Y t

Fig. 1 illustrates the sewing machine which consists ofL the base plate 1, standard 2,arm 3 and head 4. The arm shaft or main shaft 5 is rotatably journalled inthe arm of the machine in the usual manner and carries the.'` balance wheel 6 at the end which projectsv from the standard 2'. The mainshaft furthermore supports thevstitch setting cam 7 (Fig. 2) which is in operative engagement with rthe bifurcated cam follower vbar 8, the end of which is joined to the crank 9, which in turn is clamped onto," the feeder advancing shaft 11 journalled in bearing lugs 10 (only one of which is'shown). `i n A sliding member 13 is pivotally fastened to the cam'j` follower bar 8 by meansof pivot bolt 12 and is received in the stitch settling guide 14. The latter is rotatably journalled by means of shaftY screw 15 and guide sleeve.' 16 in the standard 2 whichhasarecess 17 forthat pur-V pose. The guide 14 isprovided with an arm ,18 ,toY which the draw bar 20 ispivotally connected by'means. of shoulder screw 19. ,v

The lug 21 ofthe base plate 1 pivotally'supports thefeeder lift shaft ,22' which is connected in the usual4` manner by way of crank 23 and cam bar 24-to thev lifting cam (not shown) which is mounted von-the arin `shaft 5.

In accordance ,withthe invention the machine'is provided on'the front side of the standard 2. with a molded1 conformation 25 which 'is provided with a bore26` in'. which a bearing sleeve 27 is securely'mounted. A hollow switching shaft 28 Ais Arotatablyreceiigled in sleeve '27 andJ presents at` its end 'which projects 'from the'standard 2 a kn'ob 29 and has at its other end which extends into the standard 2 secured to it a socket 31 having a disk 32 by means of a screw 30.' The disk 32 is provided with a recess 33 presenting outer and inner

curved edges

34 and 35, respectively, as related to the axis of rotation.

A disk 36 having a crimped border is secured by means of screws 37 in bores 38 in standard 2 between the operating knob 29 and the conformation 25 on the standard 2. The disk 36 and the knob 29 are provided with markings for settings (not shown in the drawing). Bores 39 in knob 29 serve for the insertion of screws 37 and are covered by a countersunk disk 40.

A crank shaped supporting arm 41` is provided on bearing sleeve 27 and is secured against turning by screws 42 (Fig. 4). The supporting arm 41 extends through an aperture 43 in the wall into the interior of the standard 2. A bolt 44 is provided at the free end of arm 41 which supports a contact lever 46 having a hub 45 and which is held in place by a lock ring 47. Lever 46' presents an abutment or follower in the form of a stud 48 (Fig. 3) which extends into the recess 33 of disk 32.

The free end 49 of lever 46 extends at an angle and is pivotally connected to the draw bar 20 by means of a collar screw 50. 4 l

The stitch setting guide 14 (Fig. 2) has still a further arm 51 which is provided With a bore 52 which is en- ,gaged by one end of a spring 53, the iother end of which is secured to a strap 54 which is hooked to an opening 55 in a recess 56 lof the standard. The spring 53 tends to bias the stitch setting guide 14 in such a manner that the stud 48 on the lever 46 engages the curved edge 34 for the forward stitch on the disk 32.

A pin 57 is secured to the offset end 49 of lever 46 which extends into the plane' of rotation of a setting member 59 which is secured to a member 60 (Fig. 2). The latter is held in place by means of a screw 61 upon a stitch setting shaft 62 which is journalled in the hollow switching shaft 28. The free end of the shaft 62 is provided with a knob The setting member 59 is biased by a spring 64 (Figs. 3

:and 4) which 'is hooked atone end into a 'bore 65 of a second lever arm 66 and at the other end into a groove 67 in stud 44 whereby it isV turned counterclockwise to such an extent (as seen in Fig. 3) that its third lever arm 68 engages the reduced studend 69. y

The desired stitch length is set by rotating the switching knob 29 which causes the stud 48 to slide along the outer arcuated edge 34, because the contact lever 46 is pulled upwardly by spring 53 by way of draw bar 20 and Stitchsetting guide V14. The outer curved edge 34 is formed in a manner that the distance from the point of rotation of the disk 32 increases continuously when the disk is turned clockwise. Suitableforming of curved edge 34 permits of predetermining the increase of the stitch length in relation .to the angle of rotation to be the same or as otherwise desired. t

For setting the corresponding back stitch of the same size, knob 63 is turned clockwise (as see in Fig. 3) against the action `of spring 64 until lever 46 is pressedvdownwardly by the arm 58 of the .setting member 59 until the stud 48 engages `the curved back stitch edge 35. The curved edgev 35 is inversely related to the curved forward stitch edge 34 withreference to a neutral circle which is concentric With respect to the axis of rotation of the disk 32. Releasing manipulator knob 63 results in return of setting member 59 under the pressure of spring 64 to its initial position, while stud 48 is again brought into engagement with the forward stitch edge 34.

What is claimed is:

l. Stitch adjusting mechanism for sewing machines of the type comprising a main shaft including cam means, a feeder advancing shaft and a feeder raising shaft, follower bars operatively connecting said advancing shaft and said raising shaft, respectively, to said main shaft, a stitch setting guide connected to said follower bar for said advancing shaft and a draw bar operatively connecting said guide and said stitch adjusting mechanism, said mechanism including setting shaft extending through the housing of the sewing machine a contact lever connected to said draw bar having a follower member, a disk concentric With said setting shaft extending in a plane perpendicularly to said shaft and presentingan aperture receiving said follower member for guiding said draw bar, said aperture being defined by a pair of curved edges extending in said plane at radial distances from the axis of rotation of said disk in inverse relationship to one another and relative to a concentric neutral arc.

2. Stitch adjusting mechanism in accordance with claim l, wherein said disk is secured to a sleeve journalled in the wall of said machine housing and said setting shaftis received in said sleeve.

3. Stitch adjusting mechanism as set forth in claim 2 including a spring biasing said contact lever against one of said curved edges and extending between said housing and said setting guide, and a setting member secured to said stitch setting shaft having an arm operatively engaging said Contact lever by way of a stud provided on said contact lever.

4. Stitch adjusting mechanism in accordance with claim 3 wherein said stitch setting shaft is provided with a turning knob and is spring biased by means of a return spring adapted to maintain said arm in inoperative position upon release of said knob.

References Cited in the le of this patent UNITED STATES PATENTS