GB2268940A

GB2268940A - Sewing machine

Info

Publication number: GB2268940A
Application number: GB9213316A
Authority: GB
Inventors: Shun Pui Chiu
Original assignee: Ngai Keung Metal and Plastic Manufactory Ltd
Current assignee: Ngai Keung Metal and Plastic Manufactory Ltd
Priority date: 1992-06-23
Filing date: 1992-06-23
Publication date: 1994-01-26
Anticipated expiration: 2012-06-23
Also published as: CN1036410C; GB2268940B; CN1082640A; GB9213316D0

Abstract

Work is fed in a sewing machine by means, which may be the needle (29) or presser foot (37) acting on the workpiece from above. As shown the needle bar (25) is pivotable as well as axially movable and a drive crank engaging a follower (33) on the needle bar displaces the latter pivotally to feed the workpiece, the needle bar being returned by spring bias. To form chain stitches a looper (46) is pivoted by the needle and returns under spring bias to seize the loop. The needle and presser foot may be provided in a module. The sewing machine may be a hand-held machine. The needle may also have lateral motion for zig-zag stitching. <IMAGE>

Description

SEWING MACHINE The present invention relates to a sewing machine.

According to a first aspect of the invention, there is provided a sewing machine which comprises a body having an upper part and a lower part providing therebetween a sewing region through which a piece of article to be sewn is to pass, a sewing mechanism including a needle and a pressfoot and supported by the upper body part, a drive mechanism within the body for driving the sewing mechanism, a platform including a needle hole provided by the lower body part, against which platform a said piece of article is to be held by the press-foot when the sewing mechanism performs sewing operation with the needle passing through the press-foot into and out of the needle hole, and moving means provided above the platform in the sewing region and arranged to be driven by the drive mechanism to move a said piece of article during sewing operation.

Preferably, the moving means is arranged to be driven by the drive mechanism to move at least rearwards in order to advance a said piece of article during sewing operation.

More preferably, the moving means is arranged to be driven by the drive mechanism to operate in a reciprocating manner per advancement of a said piece of article during sewing operation.

In a specific construction, the drive mechanism includes a crank member for driving the moving means.

It is preferred that the moving means forms part of the sewing mechanism.

In a preferred embodiment, the moving means is provided by the needle of the sewing mechanism.

In another preferred embodiment, the moving means is provided by the press-foot of the sewing mechanism.

Preferably, the needle or the press-foot providing the moving means is supported for axial and pivotal movement.

In a specific arrangement, the sewing mechanism includes a follower member fixed relative to the needle or the pressfoot of the moving means and providing a substantially horizontally-extending passage with which the crank member engages for drive transmission, said passage having a closed end against which the crank member is to bear in order to pivot the said needle or press-foot.

The sewing machine may further comprise a thread looping member located within the lower body part and directly below the needle hole of the platform for temporarily retaining a loop of thread just brought through the needle hole by the needle.

Preferably, the thread looping member is pivotably supported for movement between a retaining position for retaining a said loop of thread and a releasing position for subsequently releasing the said loop of thread.

Advantageously, the thread looping member is resiliently biassed towards the retaining position and is arranged to be moved from the retaining position to the releasing position by the needle passing through the needle hole of the platform.

The thread looping member may comprise a hook formation for retaining a said thread loop.

It is preferred that the sewing mechanism is in the form of a module removable from the body of the sewing machine.

According to a second aspect of the invention, there is provided a sewing machine which comprises a body having an upper part and a lower part providing therebetween a sewing region through which a piece of article to be sewn is to pass, a sewing mechanism including a needle and a pressfoot and supported by the upper body part, a drive mechanism within the body for driving the sewing mechanism, a platform including a needle hole provided by the lower body part, against which platform a said piece of article is to be held by the press-foot when the sewing mechanism performs sewing operation with the needle passing through the press-foot into and out of the needle hole, and a thread looper provided underneath the needle hole and supported for movement between a thread-retaining position for temporarily retaining a portion of a thread brought down by the needle and a thread-releasing position for subsequently releasing a said thread portion in order to form a stitch in a said piece of article during sewing operation, said thread looper being movable by the needle through engagement therewith.

Preferably, the thread looper is resiliently biassed by a spring towards the thread-retaining position.

It is preferred that the thread looper is rotatably supported for said movement.

More particularly, the thread looper comprises a hook formation for retaining a said thread portion.

In a preferred embodiment, the thread looper includes an inclined surface on the hook formation against which at a small angle the needle bears when initially engaging the thread looper.

More preferably, the thread looper further includes a second inclined surface against which the needle strikes to so move the thread looper.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an embodiment of a sewing machine in accordance with the invention; Figure 2- is a perspective view of a drive mechanism of the sewing machine of Figure 1; Figure 3 is a perspective view of a sewing mechanism of the sewing machine of Figure 1; Figures 4A and 4B are side views showing the sewing mechanism of Figure 3, with a press foot thereof in lowered and raised relative positions, respectively; Figures 5A and 5B are partially broken perspective view showing the manner in which the drive mechanism of Figure 2 drives the sewing mechanism of Figure 3 in two different driving conditions;; Figures 6A to 6F are side views showing a sequence of driving conditions of the drive mechanism of Figure 2 acting upon the sewing mechanism of Figure 3; Figures 7A and 7B illustrate the locus of a needle of the sewing mechanism of Figure 3 acting under the driving operation of the drive mechanism of Figure 2; upon a word piece; Figure 8 is a perspective view of a thread looping mechanism of the sewing machine of Figure 1, which is arranged to co-operate with the needle of the sewing mechanism of Figure 3; Figures 9A to 9F are side views showing a sequence of operating conditions of the drive mechanism of Figure 2, the sewing mechanism of Figure 3 and the thread looping mechanism of Figure 8 in co-operation; and Figures lOA to 10K illustrate a sequence of operating conditions of the needle of the sewing mechanism of Figure 3 and the thread looping mechanism of Figure 8 in cooperation upon a thread.

Referring firstly to Figures 1 to 3 of the drawings, there is shown a sewing machine 10 embodying the invention, which sewing machine 10 includes a body 11 formed by a base 12 and a sewing head 13. The base 12 is in the form of a box providing thereon a sewing platform surface 14 in which a needle hole 43 is formed. The sewing head 13 has an inverted L-shape which extends upwards at one end 13A from one end of the base 12 and then sideways towards the opposite end of the base 12, terminating with a free end 13B above the base 12, thereby forming therebetween a sewing region.

The sewing machine 10 further comprises a drive mechanism 15 and a sewing mechanism 16 located at opposite ends 13A and 13B of the sewing head 13, respectively.

As best shown in Figure 2, the drive mechanism 15 is formed by a driving shaft 17 having opposite ends 17A and 17B, and an electric motor 18 which is in drive engagement with the shaft end 17A through a drive output pinion 19, a speed reduction gearwheel-and-pinion 20 and a crown gearwheel 21 mounted fast on the shaft end 17A. A hand-wheel 53 is provided at the extremity of the shaft end 17A, exposed outside the sewing head 13, for manual rotation of the shaft 17. The shaft end 17B extends to the sewing mechanism 16 and engages therewith by means of a radiallyextending crank arm 22 having at its free end an axiallyextending stud 23.

As best shown in Figure 3, the sewing mechanism 16 has an upright cubical casing 24 and further includes a needle assembly 25 and a press-foot assembly 26. The needle assembly 25 is formed by a needle trunk 27, a cross-bar 28 moulded integrally and lying across the trunk 27, and a sewing needle 29 extending from the bottom end of the trunk 27. The trunk 27 is vertically slidably journalled through the casing 24, with the cross-bar 28 exposed outside the casing 24 through a generally rectangular opening 30 provided on one side 24A of the casing 24 facing the drive mechanism 15. The cross-bar 28 has a co-extending groove 31 also facing the drive mechanism 15, which groove 31 has a closed end 32 and an open end 33 reaching short of the corresponding end of the cross-bar 28 which projects forwards out of the top body port end 13B to act as a thread lever 34.As is shown, the groove 31 extends for generally the same length as the width of the casing 24 on the open-side 24A.

Referring also to Figures 4A and 4B, the press-foot assembly 26 is formed by a press-foot trunk 35, an integral rod 36 co-axially extending from the top end of the trunk 35, and a press-foot 37 provided at the bottom end of the trunk 35. The trunk 35 and the rod 36 are vertically slidably journalled through the casing 24, and is resiliently biassed downwards by a coil spring 38 disposed on the rod 26 within the casing 24 and co-acting between the trunk 35 and the top wall of the casing 24. The pressfoot assembly 26 further includes a generally L-shaped lever 39 for lifting up the press-foot 37. The lever 39 has an inner end at which a lateral stud 40 is provided hinged within a blind hole 41 formed in an adjacent side of the trunk 35, whereby the lever 39 is pivotably engaged with the trunk 35.The other end of the lever 39 is exposed on the rear side of the sewing head end 13B for user's pivotal movement between a downward position in which the press-foot 37 is lowered onto the sewing platform 14 (Figure 4A) and an upward position in which the pressfoot 37 is lifted therefrom (Figure 4B).

The engagement between the drive mechanism 15 and the sewing mechanism 16 is best illustrated in Figures 5A and 5B, in that the crank stud 23 of the drive mechanism 15 is slidably engaged within the groove 31 of the cross-bar 28 of the sewing mechanism 16. Upon rotation of the driving shaft 17, the crank arm 22 and hence the stud 23 rotate, thereby setting the needle assembly 25 into a reciprocating motion generally in a vertical direction relative to the casing 24. In each cycle of rotation, the crank stud 23 will hit the closed end 32 of the groove 31 for a certain period of time (Figure 5B), thereby pivoting the entire sewing assembly 25 momentarily backwards.The needle trunk 27 is resiliently biassed forwards by a spring 42 into a vertical normal sewing position (Figure 5A). It will be appreciated that the spring 42 serves to return the sewing needle 29 to the vertical position as soon as the crank stud 23 rotates away from the groove closed end 32.

Figures 6A to 6F illustrate the operation in one cycle and relative position of the needle assembly 25 and the driving crank arm 22 and stud 23 which rotate anti-clockwise as shown by arrow A. In Figure 6A, the crank stud 23 and hence the needle assembly 25 are in the uppermost position.

Upon rotation of the crank stud 23, the needle assembly 25 is moved downwards, as shown in Figure 6B, during which movement the crank stud 23 in free to travel along within the open end 33 of the groove 31 of the cross-bar 28.

Figure 6C shows the lowermost position of the needle assembly 25 brought to by the crank stud 23. The needle assembly 25 starts to be moved upwards as the crank stud 23 rotates upwards from its lowermost position. When the crank stud 23 hits the closed end 32 of the cross-bar groove 31, the needle assembly 25 will no longer only be moved upwards but also pivoted rearwards about the point where the needle trunk 27 intercepts the top wall of the casing 24, as shown in Figure 6D, against the action of the spring 42 (not shown). Figure 6E shows the rearmost position of the crank stud 23 and hence that of the needle assembly 25.As soon as the crank stud 23 rotates further upwards past this rearmost position, the needle assembly 25 will return under the action of the spring 42 to the original vertical position, as shown by the phantom lines of Figure 6F, which is equivalent to the position as shown in Figure 6A.

It is understood that the needle 29 is driven to move on a vertical plane or in two dimensions, namely along a z-axis (vertically up and down) as well as along a y-axis (back and forth).

In use, the press-foot 37 is lowered down onto a work-piece 44 (a piece of article to be sewn) for holding it against the platform 14 for sewing operation to be performed.

Figure 7A shows the locus of movement of the sewing needle 29 in each cycle of sewing operation upon the work-piece 44. As is shown in Figures 6A to 6F, the needle 29 passes below the press-foot 37 and hence through the work-piece 44 into the base 12 for at least the entire period when the crank arm 22 and stud 23 turn below the foremost position and before reaching the rearmost position (Figures 6B to 6E), during which the needle 29 is momentarily pivoted backwards upon upward withdrawal (Figures 6D and 6E) thereby advancing the work-piece 44 for one step (one stitch pitch) while still in engagement therewith. The pressing force of the press-foot 37 on the work-piece 44 is pre-adjusted so as not to be too large to hinder such workpiece feeding. Figure 7B shows the needle locus in a sequence of sewing cycles. It will be appreciated that the just described cycle of operation repeats so as to perform a continuous sewing/stitching operation.

In a slightly modified embodiment, the stitching pitch may be user-adjustable by providing means for changing the position along the cross-bar 28 at which the groove 31 is closed or otherwise blocked.

The sewing machine 10 embodying the invention is designed to perform chain stitching, and further includes a thread looping mechanism 45, as shown in Figure 8, provided underneath the sewing platform 14. The looping mechanism 45 is provided by a thread looper 46 having an integral shaft 47, and a base support 48 rotatably supporting the looper 46 about its shaft 47. The looper 46 is positioned directly below the needle hole 43 in the sewing platform 14, and is resiliently biassed clockwise, as indicated by arrow B, by a coil spring 49 disposed on one end of the shaft 47. The thread looper 46 has a first inclined surface 50A, a second inclined surface 50B and an integral hook 52.

Referring now to Figures 9A to 9F which illustrate the operation and the relative position of the needle assembly 25, the crank arm 22 and stud 23 and the thread looper 46, in a sequence corresponding to that shown in Figures 6A to 6F. Initially, the sewing needle 29 comes down through the hole 43 firstly bearing at a small angle against the looper first inclined surface 50A towards the looper second inclined surface 50B (Figures 9A and 9B) and then passes the looper first inclined surface 50A and subsequently strikes the looper second inclined surface 50B, thereby rotating the thread looper 46 anticlockwise as shown by arrow C in Figure 9C until reaching its lowermost position.

As soon as the needle 29 moves upwards, the thread looper 46 is gradually released and then returned to its original rest position (Figure 9A) by the spring 49 when it is no longer engaged by the needle 29. From Figures 9D to 9F, the thread looper 46 remains in the rest position, whilst the needle assembly 25 is momentarily pivoted rearwards by the crank arm 22 and stud 23 in identical manner as described with reference to Figures 6D to 6F.

The operation of the thread looper 46 is best illustrated in sequence in Figures 10A to 10K, in co-operation with the needle 29 carrying a thread 51. The needle 29 comes down with the thread 51 through the hole 43, rotating the thread looper 46, as shown in Figures 10A and 10B. When the thread looper 46 is gradually released by the needle 29 moving upwards from its lowermost position of Figure 10B, it engages the thread 51 with the integral hook 52 (Figure lOC) and retains a loop 51A of the thread 51 upon returning to its original rest position (Figure lOD). Figure 10E shows the next downward movement of the needle 29 which carries a subsequent portion of the thread 51 and passes it through the retained thread loop 51A while bearing against at a small angle past the looper first inclined surface 50A.The bearing against the looper first inclined surface 50A ensures that the needle 29 will not miss the thread loop 51A as the inclined surface 50A is provided on the part of the hook 52 of the thread looper 46 passing through the retained thread loop 51A.

As soon as the needle 29 reaches its lowermost position, the previously retained thread loop 51A is released, as shown in Figure lOF. Upon the needle 29 leaving its lowermost position, the thread looper 46 hooks to retain a second loop 51B of the thread 51, as shown in Figures lOG and 10H, said second thread loop 51B eventually locking the first thread loop 51A. Through the second thread loop 51B the needle 29 next comes down past in like manner to introduce a third loop 51C of the thread 51 (Figure 10I) and in the further following cycle a fourth thread loop 51D passing through the third thread loop 51C (Figure 10J), and so forth with one thread loop locking the preceding one.

Eventually, chain stitches are formed in the work-piece 44, as shown in Figure 10K.

It will be appreciated that the needle mechanism 25 and more particularly the needle 29 serves to stitch as well as to advance/feed the work-piece 44 step-by-step in a selfsynchronised manner. In fact, such synchronism is inherent as the needle 29 serves to provide the two related operations which will otherwise have to be provided the former by the needle and the latter by a separate feed-dog mechanism driven in synchronism by the same drive mechanism, as in prior art sewing machines.

In the absence of such feed-dog mechanism and the associated drive transmission system, the construction and manufacture of the drive mechanism 10 can be made much simpler. More importantly, the base and sewing head 12 and 13 of the sewing machine 10 can simply be joined together, without catering for any drive transmission engagement therebetween as the drive mechanism 15 is completely contained within the sewing head 13.

It will also be appreciated that the sewing mechanism 16 of the subject sewing machine 10 is made as a separate module which is much more convenient to be handled during manufactory and assembling. The installation of the sewing module is relatively simple, requiring mere engagement between the cross-bar 28 and the crank stud 23.

It is envisaged that in a different embodiment, the pressfoot assembly of the sewing mechanism may be constructed to move momentarily backwards and forwards for feeding a workpiece in place of the needle assembly.

It is also envisaged that the sewing machine according to the present invention may take the form of a hand-held sewing machine.

In a more advanced embodiment, the needle or the press-foot assembly of the sewing mechanism may be arranged to be moved by the drive mechanism not only backwards and forwards for feeding a work-piece but also laterally to either side for making a zig-zag or intermittent zig-zag stitching or stitching a pattern. In such a sewing machine, the needle assembly may be driven to move in three spatial or x-y-z directions or coordinates. The sewing machine may have separate cam drive mechanisms for controlling movement of the needle assembly in x- and ydirect ions and a separate drive mechanism for moving the needle assembly up and down to stitch. The sewing machine may comprise memory means for storing control instructions including at least directional data designating the direction of movement of the needle assembly. The sewing machine may be programmable, namely further including means for reading instructions and for transforming the stored instructions into electrical signals for operating the said drive mechanisms.

The invention has been given by way of example only, and various other modifications of and/or alterations to the described embodiments may be made by persons skilled in the art without departing from the scope of the invention as specified in the appended claims.

Claims

1. A sewing machine which comprises a body having an upper part and a lower part providing therebetween a sewing region through which a piece of article to be sewn is to pass, a sewing mechanism including a needle and a pressfoot and supported by the upper body part, a drive mechanism within the body for driving the sewing mechanism, a platform including a needle hole provided by the lower body part, against which platform a said piece of article is to be held by the press-foot when the sewing mechanism performs sewing operation with the needle passing through the press-foot into and out of the needle hole, and moving means provided above the platform in the sewing region and arranged to be driven by the drive mechanism to move a said piece of article during sewing operation.

2. A sewing machine as claimed in claim 1, wherein the moving means is arranged to be driven by the drive mechanism to move at least rearwards in order to advance a said piece of article during sewing operation.

3. A sewing machine as claimed in claim 2, wherein the moving means is arranged to be driven by the drive mechanism to operate in a reciprocating manner per advancement of a said piece of article during sewing operation.

4. A sewing machine as claimed in claim 3, wherein the drive mechanism includes a crank member for driving the moving means.

5. A sewing machine as claimed in any one of claim 1 to claim 4, wherein the moving means forms part of the sewing mechanism.

6. A sewing machine as claimed in claim 5, wherein the moving means is provided by the needle of the sewing mechanism.

7. A sewing machine as claimed in claim 5,' wherein the moving means is provided by the press-foot of the sewing mechanism.

8. A sewing machine as claimed in claim 6 or claim 7, wherein the needle or the press-foot providing the moving means is supported for axial and pivotal movement.

9. A sewing machine as claimed in claim 8 when dependent upon claim 4, wherein the sewing mechanism includes a follower member fixed relative to the needle or the pressfoot of the moving means and providing a substantially horizontally-extending passage with which the crank member engages for drive transmission, said passage having a closed end against which the crank member is to bear in order to pivot the said needle or press-foot.

10. A sewing machine as claimed in any one of the preceding claims, further comprising a thread looping member located within the lower body part and directly below the needle hole of the platform for temporarily O retaining a loop of thread just brought through the needle hole by the needle.

11. A sewing machine as claimed in claim 10, wherein the thread looping member is pivotably supported for movement between a retaining position for retaining a said loop of thread and a releasing position for subsequently releasing the said loop of thread.

12. A sewing machine as claimed in claim 11, wherein the thread looping member is resiliently biassed towards the retaining position and is arranged to be moved from the retaining position to the releasing position by the needle passing through the needle hole of the platform.

13. A sewing machine as claimed in any one of claim 10 to claim 12, wherein the thread looping member comprises a hook formation for retaining a said thread loop.

14. A sewing machine as claimed in any one of the preceding claims, wherein the sewing mechanism is in the form of a module removable from the body of the sewing machine.

15. A sewing machine which comprises a body having an upper part and a lower part providing therebetween a sewing region through which a piece of article to be sewn is to pass, a sewing mechanism including a needle and a pressfoot and supported by the upper body part, a drive mechanism within the body for driving the sewing mechanism, a platform including a needle hole provided by the lower body part, against which platform a said piece of article is to be held by the press-foot when the sewing mechanism performs sewing operation with the needle passing through the press-foot into and out of the needle hole, and a thread looper provided underneath the needle hole and supported for movement between a thread-retaining position for temporarily retaining a portion of a thread brought down by the needle and a thread-releasing position for subsequently releasing a said thread portion in order to form a stitch in a said piece of article during sewing operation, said thread looper being movable by the needle through engagement therewith.

16. A sewing machine as claimed in claim 15, wherein the thread looper is resiliently biassed by a spring towards the thread-retaining position.

17. A sewing machine as claimed in claim 15 or claim 16, wherein the thread looper is rotatably supported for said movement.

18. A sewing machine as claimed in any one of claim 15 to claim 17, wherein the thread looper comprises a hook formation for retaining a said thread portion.

19. A sewing machine as claimed in claim 18, wherein the thread looper includes an inclined surface on the hook formation against which at a small angle the needle bears when initially engaging the thread looper.

20. A sewing machine as claimed in claim 19, wherein the thread looper further includes a second inclined surface against which the needle strikes to so move the thread looper.

21. A sewing machine substantially as hereinbefore described with reference to Figures 1 to 10 of the accompanying drawings.