Upper decorative stitching device

An upper decorative stitching device is designed to make it possible to precisely transmit the swing movement of a first lever which is capable of swing movements widthwise in a pendulum manner to horizontal reciprocating motion of a second lever, which is provided with a spreader. The device facilitates the operation of switching between an upper decorative stitching and no upper decorative stitching. A connecting rod (9) is provided at both ends with spherical bearings (10, 11) to provide a connection between the first lever (3) and the second lever (8), thereby converting the rotation of the upper shaft into the reciprocal movement of the spreader.

BACKGROUND OF THE INVENTION

The present invention relates to an upper decorative stitching device to be provided mainly on a flat seam stitching machine. Its object is to make it possible to convey precisely the swing movements of the first lever which shows swing movements widthwise in a pendulum style to the horizontal reciprocating motion of the second lever provided with a spreader, to make it possible to reduce the cost of the device by simplifying the structure of the upper decorative stitching device, and also to facilitate the switching operation between the case of the upper decorative stitching and the case of the flat seam stitching.

As an upper decorative stitching device having a first lever which shows swing movements widthwise in a pendulum style in front of the sewing machine by a swing width cam provided on an upper shaft and a second lever having a spreader at the front end which also reciprocates horizontally with the other end of the connecting rod connected to the lower end of the first lever, there is known for example a patent document by the present applicant, i.e. Japanese Patent Publication Number 10-137474. As the upper decorative stitching device is made to connect the spot between the first lever which shows swing movements widthwise in a pendulum style in front of the sewing machine and the second lever which reciprocates horizontally along the needle position with a plate form connecting rod, there were movements up and down caused by the connecting rod at one end and the other end of the swinging step of the first lever, thereby making it difficult to reflect the swing motion of the first lever accurately on the movements of the second lever which should reciprocate horizontally. Moreover, as the upper decorative stitching device is made to change the stitching mode between the upper decorative stitching and the other stitching, e.g., flat seam stitching, by the switching operation of the clutch provided between the upper shaft and the swing width cam, machine construction is complicated which results in elevation of cost.

It is therefore an object of the present invention to provide an upper decorative stitching device capable of precisely conveying the swing movements of the first lever which shows swing movements widthwise in pendulum style to the horizontal reciprocating motion of the second lever, thereby simplifying the structure to obtain cost reduction, and also to make the switching operation between the upper decorative stitching and the flat seam stitching easier.

SUMMARY OF THE INVENTION

To solve the object as described above, the present invention provides an upper decorative stitching device designed to convert the rotation of the upper shaft into the reciprocal movements of the spreader by connecting the spot between the first lever which shows swing movements widthwise in a pendulum style in front of the sewing machine and the second lever which reciprocates horizontally along the needle position with a connecting rod having spherical bearings at both ends by bringing a follower into contact with the swing width cam provided on the upper shaft.

The second feature of the invention is to provide an upper decorative stitching device having a simple structure which permits easier changeover of the stitching mode between the upper decorative stitching and the other mode, e.g., flat seam stitching, by making it possible for a thread guide supporting member having at the lower end a thread guide for feeding upper decorative thread to the spreader to be switched over between the thread feeding position and the non-feeding position.

The third feature of the invention is that the thread guide supporting member is fixed to the front end of the mounting shaft whose front and rear ends are borne by the frame having a second lever, and is forced by coil springs whose front and rear ends are borne by the thread guide cam and the bearings, and, mediated by engagement between a plurality of the recesses and projections disposed on the opposed surfaces of the thread guide cam and the frame, in an ordinary time the thread guide supporting member shall be held perpendicularly to the thread feeding position, and when no upper decorative stitching thread is fed it shall be obviated nearly horizontally to the front right side of the sewing machine and held in a non-feeding position, then engaging the thread guide supporting member displaced to the non-feeding position with the first lever by way of engagement between the recesses and the projections, and separating the first lever from the swing width cam by engaging the thread guide supporting member displaced to the non-feeding position with the first lever to stop the operation of the spreader, thereby expecting to make the changeover operation more rapid and to obtain stability at the changeover position.

The upper decorative stitching device of the present invention is constituted so that the rotation of the upper shaft is precisely converted into the reciprocal movements of the spreader by means of a connecting rod having spherical bearings at both ends between a first lever which shows swing movements widthwise in front of the sewing machine by bringing a follower into contact with a swing width cam provided on an upper shaft and a second lever provided at its front end with a spreader which horizontally reciprocates along the needle position.

A thread guide supporting member having at its lower end a thread guide for feeding an upper decorative stitching thread to a spreader is provided so as to make it possible to be switched over between the thread feeding position and the non-feeding position.

A thread guide supporting member is fixed to the front end of the mounting shaft whose front and rear ends are borne by the frame having the second lever, and is forced by coil springs whose front and rear ends are borne by the thread guide cam and the bearings, and, mediated by engagement between the recess and the projection disposed on the opposed surfaces of the thread guide cam and the frame, in ordinary time the thread guide supporting member shall be held perpendicularly to the thread feeding position, and when upper decorative stitching thread is not fed it shall be obviated nearly horizontally to the front right side of the sewing machine and held in a non-feeding position, and then the thread guide supporting member displaced to the non-feeding position is engaged with the first lever, and the first lever is separated from the swing width cam to stop the operation of the spreader.

DETAILED DESCRIPTION OF THE INVENTION

Next, explanation will be given of embodiments of the present invention in accordance with the accompanying drawings.

FIG. 1is a partial cutaway front view of the upper decorative stitching device according to the present invention,FIG. 2is a partial cutaway side view of the device, andFIG. 3is a partial cutaway plan view showing mainly the driving portion of the spreader.

In the drawings showing the embodiments, reference numeral1designates an upper shaft which repeats reciprocal semi-rotation along with the driving of the sewing machine, a swing width cam2is fixed to the upper shaft1, a first lever3which moves in a swinging motion widthwise in front of the sewing machine along with the rotation of the upper shaft1, a frame6is formed on the right side in the illustration rearward of the elevating position of the needle bar7, a bell crank type second lever8, borne on the reverse surface of the frame6, is provided in a freely swinging manner in a horizontal direction, and a connecting rod9is a means of connecting the lower end part3′ of the first lever3with the one side arm8′ of the second lever8to convert the swinging movement of the first lever3into the horizontal reciprocal movement.

The connecting rod9connects the lower end part3′ of the first lever3with the one side arm81of the second lever8mediated by the spherical bearings10,11provided at both ends, by which it converts the swinging movements of the lower end part31of the first lever3into the horizontal reciprocal movement of the second lever8as precisely as possible. The reference mark (a) inFIG. 3denotes a stroke of the connecting rod9.

The reference numeral12denotes a spreader provided with its base end part fixed to the front end of the other arm8″ (left-hand in the figure) of the second lever8. The spreader12is angled downwardly as shown inFIG. 2, so as to reciprocate along the outside of the needle position13as shown inFIG. 3.

A thread guide14provided at the right side in front of the needle position13, is provided at the lower end of the thread guide supporting member17which is fixed to the front end of the mounting shaft16whose front and rear parts are borne by the bearing15which is erected on the frame6, and, biased by a coil type spring19which is set between the thread guide cam18fixed to the mounting shaft16and the operator side bearing15, it is placed at an ordinary time in a feeding position of upper decorative thread (solid line position in illustration).

On the confronting surfaces between the rear end part of the thread guide cam18(left side inFIG. 2) and the frame6, there are provided a recess20which continues for about 90 degrees along the rotation direction on the thread guide cam18side and a projection21provided on the frame6in a position corresponding to the recess20, and, by engagement between the recess20and the projection21, the thread guide supporting member17is held in a perpendicular state at an end of the recess20in order to hold the thread guide14in a feeding position of the upper decorative thread.

In the case of the flat stitch and the over-lock stitch in which no upper decorative stitch thread is fed, when a rotary operation is made by 90 degrees in the arrow marked direction inFIG. 1with a switching operation knob22provided on the lateral side of the thread guide supporting member17, the projection21on the frame6side is engaged with the other end of the recess20on the thread guide cam18side to hold the thread guide14in the obviating position shown by the dashed line in the same figure.

Both side ends of the recess20are formed optionally in a deeper style, so that they can be engaged by the projection to stop in a manner of click motion. Needless to say, engagement and release between the recess20and the projection21are elastically performed against the bines of the spring19which forces the thread guide cam18and the thread guide supporting member17on the mounting shaft16.

As will be clear from the foregoing description, in this embodiment the switching means S of the thread guide14comprise the recess20on the thread guide cam18side, the projection21on the frame6side, the switching operation knob22on the lateral side of the thread guide supporting member17, and the spring19for biasing the thread guide cam18.

The thread guide supporting member17displaced to the obviating position in the manner as stated above causes the lateral side switching operation knob22to come into pressure contact with the lateral side of the first lever3, as shown in the dashed lines inFIG. 1. By this pressure contact of the switching operation knob22, the first lever3is displaced beyond the range of swing motion to separate the engagement between the follower4and the swing width cam2as shown inFIG. 1, whereby the connecting rod9and the second lever8are stopped from operating and driving of the spreader12is stopped.

Furthermore, when the thread guide supporting member17is reinstated to the position illustrated in solid line by operating the switching operation knob22, the follower4comes into contact with the swing width cam2by traction of the spring5to reinstate the device simply to the upper decorative stitching state.

In the drawings, the element indicated by the numeral23denotes a return spring of the second lever8,24denotes a thread guide,25denotes a fulcrum shaft of the first lever3positioned at the front upper part of the sewing machine, and26denotes a fulcrum shaft of the second lever8.

The upper decorative stitching device according to the present invention is highly useful in the case of partly changing over the sewing method in the course of sewing a piece of garment such as for example for upper decorative stitching a neck portion or a sleeve of a pajama, and flat stitching or over-lock stitching a bottom portion.

Needless to say, the fixing positions, respective sizes, etc. of the first lever, second lever, connecting rod for connecting the two levers and the spreader are not limited to the style of the disclosed embodiment but their designs may be optionally modified in line with the purport of the present invention.

DESCRIPTION OF THE NUMERALS USED

1Upper shaft2Swing with cam3First lever (3′ denotes the lower end part)4Follower5Spring6Frame7Needle bar8Second lever (8′ depicts a one-side arm and8″ the other side arm)9Connecting rod (‘a’ denotes a stroke of the connecting rod)10Spherical bearing11Spherical bearing12Spreader13Needle position14Thread guide15Bearing16Mounting shaft17Thread guide supporting member18Thread guide cam19Spring20Recess21Projection22Knob for switching operationS Switching means23Return spring for second lever24Thread guide25Fulcrum shaft for first lever26Fulcrum shaft for second lever