# Patent

## Title
Sewing machine

## Abstract

A sewing machine includes a horizontal hook that is held within an outer hook and an accommodating portion of the outer hook that includes a spiral-shaped columnar portion to which the thread loop captured by the hook point is wound. The sewing machine also includes a chain looper that guide the thread loop induced in spiral shape upward, and an inner hook for chain stitching that is supported by the outer hook that restricting upward movement of the thread loop drawn into the interior of the outer hook.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based on and claims the benefit of priority to Japanese Patent Application No. 2014-159790 filed on Aug. 5, 2014, the contents of which are hereby incorporated by reference in their entirety.
FIELD OF THE INVENTION
The present invention relates to a sewing machine capable of performing chain stitching.
DESCRIPTION OF THE RELATED ART
Sewing machines capable of performing chain stitching are conventionally known. The applicants of the present invention have suggested sewing machines which perform chain stitching using only needle threads in sewing machines which perform lock stitching using needle threads and bobbin threads (see Patent Literature 1, Patent Literature 2 and Patent Literature 3). Such chain stitching differs from cases of lock switching in that one surface is configured similarly to lock switching using a single thread while the other surface on the opposite side is sewn in a shape of a chain. Since such sewing machines capable of performing chain stitching can correspond to use such as basting and seal stitches, they have been suggested as sewing machines which enlarges the available range of sewing machines.
However, all of sewing machines according to the above-mentioned suggestions are sewing machines comprising perpendicular hooks, and the inventions could not be applied to sewing machines comprising horizontal hooks.
Sewing machines capable of performing chain stitching using only needle threads in sewing machines comprising horizontal hooks are disclosed in Patent Literature 4 and Patent Literature 5.
PRIOR ART LITERATURE
Patent Literature
[Patent Literature 1] Japanese Patent Publication No. S45-33108
[Patent Literature 2] Japanese Patent Publication No. S49-18739
[Patent Literature 3] Japanese Patent Publication No. S56-20032
[Patent Literature 4] Japanese Patent Publication No. S56-47787
[Patent Literature 5] Japanese Patent Publication No. H03-66911
SUMMARY OF THE INVENTION
However, according to the techniques of Patent Literature 4 and Patent Literature 5, special structures were required on throat plate sides since thread holding of a single thread was difficult due to their structures, and since preparing operations where complicated since exclusive thread holders and throat plates were required and other factors, the sewing machines could not be used easily.
One or more embodiments of the present invention provide a sewing machine with a simple configuration in which chain stitching can be easily performed even when the sewing machine comprises a horizontal hook.
Embodiment (1): One or more embodiments of the present invention provide a sewing machine comprising a horizontal hook that rotates twice around a vertical center of rotation with respect to a reciprocating direction of a needle when the needle performs a single reciprocating movement in the up and down direction, wherein the horizontal hook comprises an outer hook including a hook point that captures a thread loop of a needle thread and an accommodating portion that is formed to open upwardly, a chain looper that is held within the accommodating portion of the outer hook to be attachable/detachable to and from the outer hook and to move integrally with the outer hook, that includes a spiral-shaped columnar portion to which the thread loop captured by the hook point is wound, and that rotates together with the pulling the thread up and the rotation of the outer hook to guide the thread loop induced in spiral shape upward, and an inner hook for chain stitching that is supported by the outer hook, that forms a thread space upward of the chain looper and that restricts upward movement of the thread loop drawn into the interior of the outer hook.
Embodiment (2): One or more embodiments of the present invention provide the sewing machine of Embodiment (1), wherein the chain looper is held in the accommodating portion of the outer hook at a position concentric with the center of rotation of the outer hook.
Embodiment (3): One or more embodiments of the present invention provide the sewing machine of Embodiment (1), wherein the inner hook for chain stitching further guides a thread loop drawn into the interior of the outer hook out of the thread loop that has been captured by the hook point to the chain looper.
Embodiment (4): One or more embodiments of the present invention provide the sewing machine of Embodiment (1), wherein the accommodating portion of the outer hook is formed such that an inner hook for lock stitching can be mounted instead of the chain looper and the inner hook for chain stitching.
Embodiment (5): One or more embodiments of the present invention provide the sewing machine of Embodiment (1), wherein a thread loop guiding portion for guiding a thread loop is formed on a lower surface of the inner hook for chain stitching.
Embodiment (6): One or more embodiments of the present invention provide the sewing machine of Embodiment (5), wherein the thread loop guiding portion is formed to become narrower towards a downward tip thereof.
Embodiment (7): One or more embodiments of the present invention provide the sewing machine of Embodiment (5), wherein the tip of the thread loop guiding portion is disposed proximate of a base of the spiral-shaped columnar portion at which the spiral-shaped columnar portion receives the thread loop.
According to one or more embodiments of the present invention, it is possible to realize a sewing machine with a simple configuration in which chain stitching can be easily performed even when the sewing machine comprises a horizontal hook.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 A view showing an embodiment of the sewing machine according to the present invention.
FIG. 2 An exploded perspective view of a horizontal hook 20.
FIG. 3 A view in which the horizontal hook 20 is seen from above.
FIG. 4 A sectional view at a position of arrow X-X shown in FIG. 3.
FIG. 5 A sectional view at a position of arrow Y-Y shown in FIG. 3.
FIG. 6 A perspective view in which an inner hook for chain stitching 24 is seen from below.
FIG. 7 A sectional view showing a state in which an inner hook for lock stitching 26 is mounted to an accommodating portion 21b of an outer hook 21.
FIG. 8A A view showing a process of performing chain stitching.
FIG. 8B A view showing a process of performing chain stitching.
FIG. 8C A view showing a process of performing chain stitching.
FIG. 8D A view showing a process of performing chain stitching.
FIG. 8E A view showing a process of performing chain stitching.
FIG. 8F A view showing a process of performing chain stitching.
FIG. 8G A view showing a process of performing chain stitching.
FIG. 8H A view showing a process of performing chain stitching.
FIG. 8I A view showing a process of performing chain stitching.
FIG. 8J A view showing a process of performing chain stitching.
FIG. 8K A view showing a process of performing chain stitching.
FIG. 8L A view showing a process of performing chain stitching.
FIG. 8M A view showing a process of performing chain stitching.
FIG. 8N A view showing a process of performing chain stitching.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A best mode for embodying the present invention will now be explained while referring to the drawings and others.
<Embodiment>
FIG. 1 is a view showing an embodiment of the sewing machine according to the present invention.
In this respect, each of the drawings including FIG. 1 indicated hereinafter are schematically illustrated drawings, and sizes and shapes of respective portions are shown in suitably exaggerated form for ease of understanding.
Further, while explanations are made upon indicating specific numerical values, shapes and materials in the following explanations, they may be suitably changed.
The sewing machine 1 according to the present embodiment comprises a needle 10 and a horizontal hook 20.
The needle 10 performs reciprocating movements in the up and down direction (vertical direction) when performing sewing when the sewing machine 1 is correctly set up on a horizontal set up surface.
The horizontal hook 20 is at a position that the needle 10 reaches when it has moved downward in its movable range, and it is set up in an interior of the sewing machine 1 such that it rotates twice around a vertical center of rotation with respect to the reciprocating direction of the needle 10 when the needle 10 performs a single reciprocating movement in the up and down direction.
FIG. 2 is an exploded perspective view of a horizontal hook 20.
FIG. 3 is a view in which the horizontal hook 20 is seen from above.
FIG. 4 is a sectional view at a position of arrow X-X shown in FIG. 3.
FIG. 5 is a sectional view at a position of arrow Y-Y shown in FIG. 3.
The horizontal hook 20 includes an outer hook 21, a magnet 22, a chain looper 23 and an inner hook for chain stitching 24.
The outer hook 21 comprises a hook point 21a, an accommodating portion 21b and a gear portion 21c. In this respect, while the outer hook 21 according to the present embodiment is configured of a plurality of parts for ease of manufacture, these parts might suitably be integrated.
The hook point 21a is provided along an outer peripheral surface of the outer hook 21 and I formed into a shape having a pointed tip for capturing a needle thread loop (thread loop) of the needle thread 30 that passes through the needle 10 (see FIG. 8A and others).
The accommodating portion 21b is formed to open upwardly to accommodate the chain looper 23 and the inner hook for chain stitching 24.
The gear portion 21c is mounted integrally with the outer hook 21 to rotate around a shaft 25 as a center of rotation that projects in a substantially columnar shape downward of the accommodating portion 21b. The gear portion 21c is in mesh with a driving gear that is provided at a driving shaft (not shown). The outer hook 21 rotates in sync with up and down movements of the needle 10 when the gear portion 21c receives driving force from the driving gear.
The magnet 22 is fixed to a lower bottom portion within the accommodating portion 21b by using an adhesive or the like.
The chain looper 23 includes a disk portion 23a and a spiral-shaped columnar portion 23b, and is held within the accommodating portion 21b of the outer hook 21 and at a position concentric with the center of rotation of the outer hook 21 to be attachable/detachable to and from the outer hook 21 and to move integrally with the outer hook 21.
The disk portion 23a is formed at a lower end side of the chain looper 23 to expand in a substantially disk-like shape. The disk portion 23a mates with a shape of the lower bottom portion of the accommodating portion 21b to integrally attach the chain looper 23 with respect to the outer hook 21.
The spiral-shaped columnar portion 23b projects upwardly from the disk portion 23a in a substantially columnar shape, and a spiral shape is formed on an outer peripheral surface thereof. A needle thread loop (thread loop) captured by the hook point 21a is wound to the spiral-shaped columnar portion 23b. The chain looper 23 rotates together with pulling the thread up and the rotation of the outer hook 21, and the needle thread loop induced by the spiral shape of the spiral-shaped columnar portion 23b is guided upward together with the rotation of the outer hook 21.
The inner hook for chain stitching 24 is located further upward of the chain looper 23, and is supported by a wall-like portion that forms an outer periphery of the outer hook 21.
The inner hook for chain stitching 24 is formed to have a substantially disk-like shape to substantially cover an aperture of the accommodating portion 21b, and includes a first thread guiding portion 24a, a first cam surface 24b, a second thread guiding portion 24c, a protruding portion 24d, a second cam surface 24e and a thread space 24f. 
The first thread guiding portion 24a has a small protruding shape in form of a hook projecting towards the thread space 24f side. The first thread guiding portion 24a assists reliable guidance of a thread located inside of the outer hook 21 out of the needle thread loop captured by the hook point 21a to downside of the hook point 21a. 
FIG. 6 is a perspective view in which the inner hook for chain stitching 24 is seen from below.
The first cam surface 24b projects downward from the inner hook for chain stitching 24 and has an annular shape of which a portion corresponding to the thread space 24f is cut off. The first cam surface 24b functions as a thread loop guiding portion which guides the needle thread loop (thread loop) guided downside by the first thread guiding portion 24a to form a needle thread loop (thread loop) that is larger than a diameter of the chain looper 23 and further guides it to a predetermined position of the spiral-shaped columnar portion 23b of the chain looper 23. The first can surface 24b is formed to become narrower towards a downward tip thereof. Further, the tip of the first cam surface 24b is disposed proximate of a starting position of the spiral shape at which the spiral-shaped columnar portion 23b receives the thread loop, namely, proximate of a base 23c of the spiral-shaped columnar portion 23b. Since the first cam surface 24b that functions as a thread loop guiding portion is disposed in this manner, it is possible to reliably wind the needle thread loop (thread loop) to the spiral-shaped columnar portion 23b. 
The second thread guiding portion 24c is a surface that is warped in a substantially arc-like shape that projects upward of the inner hook for chain stitching 24. The second thread guiding portion 24c guides the thread upside of the needle thread loop captured by the hook point 21a to reliably pass an upper portion of the chain looper 23.
The protruding portion 24d is formed to slightly project to the outer peripheral side beyond the accommodating portion 21b. The protruding portion 24d assists stabilization of a phase at which the hook point 21a releases the needle thread loop to be of constant phase.
The second cam surface 24e is a cam surface formed close to an outer periphery upward of the inner hook for chain stitching 24 and is disposed at a position on a substantially opposite side of the second thread guiding portion 24c. The second cam surface 24e guides the needle thread loop that is released by the hook point 21a to a predetermined position of the spiral-shaped columnar portion 23b of the chain looper 23.
The thread space 24f is formed to have a shape in which an outer peripheral portion of the inner hook for chain stitching 24 is partially removed. The thread space 24f is provided such that the thread can fall off to upward of the chain looper 23.
With the above configuration, the inner hook for chain stitching 24 restricts upward movement of the needle thread loop that has been drawn into the interior of the outer hook 21.
Here, the inner hook for chain stitching 24 is formed, for instance, by means of a ferromagnetic body such as steel or the like, and its position is maintained by the magnetic force of the magnet 22 so that it does not come off the outer hook 21.
The accommodating portion 21b of the outer hook 21b is formed such that an inner hook for lock stitching 26 can be mounted instead of the chain looper 23 and the inner hook for chain stitching 24.
FIG. 7 is a sectional view showing a state in which the inner hook for lock stitching 26 is mounted to the accommodating portion 21b of the outer hook 21.
It is possible to attach a bobbin 27 reeled with the bottom thread to the inner hook for lock stitching 26, and by assuming this state, the sewing machine 1 according to the present embodiment can perform usual lock stitching.
Next, operations when performing chain stitching using the sewing machine 1 according to the present embodiment will be explained.
First, preparations for chain stitching will be explained.
When the inner hook for lock stitching 26 is disposed in the outer hook 21, the inner hook for lock stitching 26 is taken out from the outer hook 21.
Next, the chain looper 23 is inserted into the accommodating portion 21b within the outer hook 21, and the chain looper 23 is integrally attached to the outer hook 21.
Then, the inner hook for chain stitching 24 is mounted onto an upper portion (rib portion) on an outer periphery of the outer hook 21 on an upper portion of the chain looper 23 to fix a throat plate (not shown) to the main body of the sewing machine.
Further, when the needle 10 is not threaded yet, the needle 10 is threaded.
In this manner, preparations for chain stitching are completed.
Next, chain stitching operations will be explained.
FIG. 8A to FIG. 8N are views showing processes of performing chain stitching.
First, a needle thread loop generated below the throat plate through up and down movements of the needle 10 is captured by the outer hook 21 to draw it to downward of the inner hook for chain stitching 24.
More specifically, the hook point 21a of the outer hook 21 captures the needle thread by means of the descended needle 10 (FIG. 8A). This process is identical to that for performing lock stitching. A thread positioned inside of the horizontal hook 20 out of the captured needle thread loop is sorted to downside of the hook point 21a while a thread positioned outside of the horizontal hook 20 is sorted to upside of the hook point 21a and is drawn by the hook point 21a (FIG. 8B, FIG. 8C).
Next, the needle thread loop is wound to the spiral-shaped columnar portion 23b of the chain loop 23 for holding the needle thread loop. Namely, a thread upside of the needle thread loop that has been drawn by the hook point 21a passes the upside of the chain looper 23 while a downside thread is guided by the first cam surface 24b of the inner hook for chain stitching 24 and is caught at a downward portion (proximate of the base 23c) of the spiral-shaped columnar portion 23b of the chain looper 23 (FIG. 8C, FIG. 8D).
Thereafter, when the hook point 21a of the outer hook 21 rotates up to a certain phase, the needle thread loop that had been hooked at the hook point 21a comes off the hook point 21a since the needle thread is pulled down by a take-up lever, and the needle thread loop is wound to a downward portion (proximate of the base 23c) of the spiral-shaped columnar portion 23b of the chain looper 23 (FIG. 8D, FIG. 8E).
The needle thread loop wound to the spiral-shaped columnar portion 23b of the chain looper 23 follows the spiral-shaped columnar portion 23b accompanying the rotation of the outer hook 21, namely, the rotation of the chain looper 23 and moves upward of the spiral-shaped columnar portion 23b (FIG. 8F, FIG. 8G).
Next, the next descending needle 10 is made to progress into a loop constituted of the held needle thread loop and a cloth fed stitch. More specifically, the repeatedly descended needle 10 passes through the previous stitch and the needle thread loop formed by being caught at the chain looper 23, and the hook point 21a of the outer hook 21 captures the needle thread of the descended needle 10. Prior or after the capture, the spiral-shaped columnar portion 23b of the chain looper 23 releases the needle thread loop that had been wound thereto (FIG. 8H, FIG. 8I, and FIG. 8J).
Then, the released needle thread loop is tightened by the action of the hook point 21a of the outer hook 21 dragging out a needle thread loop of the next stitch and by tightening with the take-up lever which is started at a slightly later phase so as to complete a chain stitch (chain stitch).
More specifically, a needle thread loop that is generated by an ascent of the needle 10 is captured and drawn by the outer hook 21 (FIG. 8K).
At the time of pulling the thread up by means of the take-up lever after capturing of the needle thread, the needle thread loop is guided by the spiral-shaped columnar portion 23b of the chain looper 23 to be induced upward (FIG. 8L).
The needle thread loop that has moved upward of the chain looper 23 is pulled upward through a clearance between the chain looper and the inner hook for chain stitching 24 to form a seam (FIG. 8M).
When the needle topmost point has been reached in the state of FIG. 8M, the process returns to the state of FIG. 8E after assuming the state shown in FIG. 8N, and by repeating sewing movements, the sewing machine 1 continues chain stitching.
As explained so far, according to the present embodiment, since the chain looper 23 and the inner hook for chain stitching 24 are provided inside the outer hook 21 in the sewing machine 1, it is possible to realize chain stitching with a simple structure even if the sewing machine is comprised with a horizontal hook.
Further, it is possible to easily switch between lock stitching and chain stitching in the sewing machine 1 by merely exchanging small parts to easily perform chain stitching, and the application range of the sewing machine 1 comprised with a horizontal hook is remarkably improved.
Moreover, since the inner hook for chain stitching 24 is disposed on the upper portion of the chain looper 23 in the sewing machine 1, unmanaged or irregular movements of the needle thread loop captured by the outer hook 21 can be restricted so that chain stitch seams can be reliably formed.
<Modified Embodiment>
The present invention is not limited to the above-described embodiment but may be variously modified and changed which are also included in the scope of the present invention.
For instance, the present embodiment has been explained based on a configuration in which the magnet 22 is fixed to the outer hook 21. The present invention is not limited to this, and it is also possible to provide the magnet at the chain looper 23 or to provide the magnet on the inner hook for chain stitching 24 side.
Further, the present embodiment has been explained based on an example in which the position of the inner hook for chain stitching 24 is held using magnetic force of the magnet 22. The present invention is not limited to this, and it is also possible to hold the inner hook for chain stitching without using magnetic force.
In this respect, while the embodiment and the modified embodiment can be used upon suitably combining them, detailed explanations will be omitted. The present invention is not to be limited by the above explained respective embodiments.
EXPLANATION OF THE REFERENCE NUMBERS


    1 sewing machine
    10 needle
    20 horizontal hook
    21 outer hook
    21a hook point
    21b accommodating portion
    21c gear portion
    22 magnet
    23 chain looper
    23a disk portion
    23b spiral-shaped columnar portion
    23c base of spiral-shaped columnar portion 23b 
    24 inner hook for chain stitching
    24a first thread guiding portion
    24b first cam surface
    24c second thread guiding portion
    24d protruding portion
    24e second cam portion
    24f thread space
    25 shaft
    26 inner hook for lock stitching
    27 bobbin
    30 needle thread

## Claims

1. A sewing machine comprising:
a driving structure that reciprocates a needle; and
a horizontal hook that rotates twice around a vertical axis of rotation when the needle performs a single reciprocating movement,
wherein the vertical axis of rotation of the horizontal hook is parallel to a reciprocating direction of the needle, and perpendicular to a horizontal set up surface of the sewing machine; and
wherein the horizontal hook comprises
an outer hook including a hook point that captures a thread loop of a needle thread and an accommodating portion that is formed to open upwardly,
a chain looper that is held within the accommodating portion of the outer hook to be attachable/detachable to and from the outer hook and to move integrally with the outer hook, that includes a spiral-shaped columnar portion to which the thread loop captured by the hook point is wound, and that rotates together with the pulling the thread up and the rotation of the outer hook to guide the thread loop induced in spiral shape upward, and
an inner hook for chain stitching that is supported by the outer hook, that forms a thread space upward of the chain looper and that restricts upward movement of the thread loop drawn into the interior of the outer hook.

2. The sewing machine according to claim 1, wherein the chain looper is held in the accommodating portion of the outer hook at a position concentric with the center of rotation of the outer hook.

3. The sewing machine according to claim 1, wherein the inner hook for chain stitching further guides a thread loop drawn into the interior of the outer hook out of the thread loop that has been captured by the hook point to the chain looper.

4. The sewing machine according to claim 1, wherein the accommodating portion of the outer hook is formed such that the chain looper and the inner hook are detachably attached to the sewing machine.

5. The sewing machine according to claim 1, wherein a thread loop guiding portion for guiding a thread loop is formed on a lower surface of the inner hook for chain stitching.

6. The sewing machine according to claim 5, wherein the thread loop guiding portion is formed to become narrower towards a downward tip thereof.

7. The sewing machine according to claim 5, wherein the tip of the thread loop guiding portion is disposed proximate of a base of the spiral-shaped columnar portion at which the spiral-shaped columnar portion receives the thread loop.