Sewing machine

A sewing machine has seam-forming tools, comprising a needle for guiding an upper thread and a looper. The needle is designed as a curved needle which is pivotable about a needle pivot axis. This embodiment is such that a distance of the curved needle from the pivot axis is equal to a radius of a curve of the curved needle about the pivot axis. The looper is designed as a looper which is rotatable about a looper rotational axis and has a lower thread reserve. The looper rotational axis runs parallel to a sewing material support region. The sewing machine can be used to produce a durable seam.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. DE 10 2020 202 270.4, filed Feb. 21, 2020, the content of which is incorporated herein by reference in its entirety as if fully set forth herein.

FIELD OF THE INVENTION

The invention relates to a sewing machine having a curved needle.

BACKGROUND OF THE INVENTION

Sewing machines of this type are known from DE 103 49 127 A1 and DE 10 2011 118 813 B3. DE 1 002 189 A discloses a double machine, operating without a pricker, having a curved eye needle and straight workpiece feed. DE-PS 906 403 discloses a sewing machine for sewing thick fabrics. DE 100 40 807 A1 discloses a blind stitch sewing mechanism. US 2017/0246837 A1 and US 2016/0052465 A1 disclose a method and apparatus for blind stitching of a formed component.

SUMMARY OF THE INVENTION

It is an object of the present invention to further design a sewing machine of the type mentioned above in such a way that a durable seam can be produced.

This object is achieved according to the invention by a sewing machine having seam-forming tools, comprising a needle for guiding an upper thread and a looper,wherein the needle is designed as a curved needle which is pivotable about a needle pivot axis in such a way that a distance of the curved needle from the pivot axis is equal to a radius of a curve of the curved needle about the pivot axis,wherein the looper is designed as a looper which is rotatable about a looper rotational axis and having a lower thread reserve,wherein the looper rotational axis runs parallel to a sewing material support region,wherein an arrangement of the sewing material support region with respect to a movement path of the curved needle is such that the curved needle, during the sewing movement along the movement path, penetrates into sewing material to be sewn from a sewing material side and exits again on the same sewing material side,having a design such that the sewing material is sewn in the form of an abutting-edge sewing using a single-sided double lockstitch.

According to the invention, it has been found that the provision of a lower thread via the looper leads to the possibility of providing, in particular, a lockstitch sewing machine that ensures durable sewing of the sewing material by interlacing the lower thread with the upper thread. The lower thread reserve can be designed as a bobbin case accommodated in or at the looper for a lower thread winding. The sewing material support region is at least one surface portion of the sewing machine that defines a relative position of the sewing material to be sewn to the seam-forming tools of the sewing machine. The spatial orientation of the sewing material relative to the sewing material support region is irrelevant in this context. It is therefore irrelevant whether the sewing material rests on the support region or whether the support region rests on the sewing material from above. The fact that the looper rotational axis runs parallel to the sewing material support region simplifies the assembly of the sewing machine. The sewing material support region is arranged in relation to a movement path of the curved needle in such a way that the curved needle penetrates the sewing material to be sewn from one sewing material side during the sewing movement along the movement path and exits again on the same sewing material side. Such an arrangement makes it possible to sew sewing material in the form of a single-sided double lockstitch. In particular, this enables durable abutting-edge sewing of two pieces of sewing material that have been placed against each other. The entry/exit side of the sewing material can face the looper.

The sewing machine can be designed as a hand sewing machine. A weight of the sewing machine may be less than 5 kg, may be less than 4.5 kg, may be less than 4 kg, may be less than 3.5 kg, may be less than 3 kg, may be less than 2.5 kg, may be less than 2 kg, may be less than 1.5 kg, may be less than 1 kg, and may be even less. Regularly, the hand sewing machine has a weight that is greater than 200 g. Such a hand sewing machine is suitable for sewing bulky sewing material or sewing material that is not transportable for other reasons.

A parallel course of the needle pivot axis to the looper rotational axis leads to a simplification of a drive of the seam-forming tools.

An embodiment comprising a design for sewing material thicknesses greater than 8 mm enables the sewing machine to be used even with comparatively large material thicknesses.

A belt drive for driving the curved needle and the looper can be realized in a compact manner. The belt drive, by means of which the curved needle and the looper are driven simultaneously, enables the seam-forming tools of the sewing machine to be synchronized without any effort.

A needle guide groove arranged helically around the curved needle, over which the upper thread (8) is guided, enables the upper thread to be guided securely along the curved needle without the upper thread being released undesirably from the curved needle. The helical shape of the guide groove may be such that the guide groove completes a quarter to half a revolution about a longitudinal axis of the curved needle along the curved needle. A higher number of revolutions of the helical arrangement of the guide groove is also possible, in particular in the range between 0.25 and 2 revolutions.

An embodiment of the invention is explained in more detail below with reference to the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A sewing machine1, of which drive and stitch-forming components are shown inFIG.1and upper-thread guide components are shown inFIG.2, serves for abutting-edge sewing of two pieces2,3of sewing material4placed end to end. The sewing machine1as a whole is designed as a hand sewing machine, i.e. it is not permanently installed for stationary operation and can be held in the hand by an operator during the sewing process. In particular, the sewing machine1can be designed without supply lines which are connected to an external supply unit.

The two pieces2,3of the sewing material4butt against each other via an abutting edge5. The sewing machine1is designed to sew sewing material4having a material thickness D which is greater than 8 mm. The sewing material4can have a material thickness in the range between 10 mm and 25 mm, for example.

Seam-forming tools6of the sewing machine1include a needle7for guiding an upper thread8(cf. alsoFIG.2) and a looper9.

The needle7is designed as a curved needle. The curved needle7can be pivoted about a needle pivot axis10. A distance A between the curved needle7and the needle pivot axis10is equal to a radius r of a curve of the curved needle7about the needle pivot axis10.

A stitch plate12belongs to a sewing material support region11, which specifies a position of the sewing material4relative to the seam-forming tools6upon abutting-edge sewing.

The sewing material support region11is arranged in relation to a movement path13of the curved needle7, which is indicated by a dashed line inFIG.1, in such a way that during the sewing movement along the movement path13, the curved needle7penetrates into the sewing material4to be sewn from a sewing material side14, which points upward inFIGS.1and2, and exits again on the same sewing material side14. This entry/exit sewing material side14faces the looper9. The curved needle does not come out of the sewing material4on the sewing material side opposite this entry/exit sewing material side14.

The looper9is rotatable about a looper rotational axis15and has a lower thread reserve in the form of a bobbin case16. The stitch plate12has a case stop piece17for preventing rotation of the bobbin case about the looper rotational axis15.

The looper rotational axis15runs parallel to the needle pivot axis10. Both axes10,15run horizontally and perpendicularly to the drawing plane inFIGS.1and2.

The looper rotational axis15runs parallel to the sewing material support region11.

A belt drive18having a drive motor19, which may be an electric motor having a battery supply, and a belt20are used to drive the curved needle7and the looper9. The belt20is driven via a drive shaft21of the drive motor19and runs over a main shaft22, a thread lever eccentric23, a tension roller24and a looper shaft which runs along the looper rotational axis15.

Via a further eccentric25, the main shaft22is pivotally connected to a swing lever26, which in turn is eccentrically pivotally connected to a needle drive shaft28via a needle drive wheel27. Via a further belt29, the needle drive wheel27is connected to a needle shaft which runs along the needle pivot axis10. The shafts21,22and28again run parallel to the needle pivot axis10and to the looper rotational axis15. The belt drive with the belts20,29is designed in such a way that the looper9rotates twice during a movement period of the curved needle7. Via the swing lever26and the further belt29, an oscillating drive of the curved needle7about the needle pivot axis10is achieved, which is synchronized with the rotation of the looper9about the looper rotational axis15. The sewing machine1generates a double lockstitch in the sewing material4via the seam-forming tools7,9and the belt drive18for abutting-edge sewing and thus for durably joining the two pieces2,3of the sewing material4.

The tension roller24is pretensioned against the belt20by a tensioning spring and provides sufficient tension to the belt20. The belt29may also have a tension roller not shown in the drawing.

The movement of the curved needle along the movement path13is guided by a frame-fixed curve guide30. The curved needle7is connected to the needle shaft by a needle holder31.

A thread lever32of the sewing machine is driven via the thread lever eccentric23. The thread lever32has a thread lever arm33.

FIG.2additionally shows upper thread guide components of the sewing machine1. The upper thread8is fed via an upper thread reserve in the form of a thread reel34. From there, the upper thread8first runs over a thread pre-tensioning unit35and a thread deflection eyelet36. From there, the upper thread8runs over a thread lever eyelet37and another thread deflection eyelet38to a guide groove39, which is arranged helically in a jacket wall of the curved needle7. At this free end, the curved needle7has an eye40.

A plane of the movement path13, which runs parallel to the drawing plane ofFIG.1, is offset perpendicularly to the drawing plane ofFIG.1with respect to a movement path of a looper tip41of the looper, so that the looper tip41can run past a needle tip of the curved needle7when gripping an upper thread loop upon stitch formation. The needle tip of the curved needle7having the eye40passes through a stitch hole42in the stitch plate12.

As far as possible, the seam-forming tools6and the upper thread guide components are accommodated in a housing43of the sewing machine1(cf.FIG.2).