Sewing machine

A sewing machine comprises: a head portion having a sewing needle driven to vertically reciprocate; a lower shaft having a shuttle connected thereto which is driven to rotate synchronized with the vertical movement of the sewing needle cooperating to form stitches; a table positioned above the lower shaft; a retainer positioned above the table to retain a material for forming stitches thereon; a holding frame placed parallel to the table, the head portion being mounted at a position on the holding frame; and supporting posts adapted to support opposite ends of the holding frame for positioning the holding frame above the table. The sewing machine allows a material to be sewn, which is retained retainer, to be easily mounted or removed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sewing machine with improved structure and constitution, and more particularly to a sewing machine in which a retainer adapted to retain a material to be sewn can move along an X-axis and a Y-axis.

2. Description of the Prior Art

When it is necessary to extend the sewing range of conventional sewing machines, in particular in the Y-axis direction (forward or backward direction), the arm on which the head portion of the sewing machine is installed had to be elongated forward. This causes a problem in that the elongated arm occupies a considerable space.

Moreover, when the arm is elongated, the center of gravity of the sewing machine is positioned at a front portion thereof This makes it difficult to maintain the balance of the sewing machine. Accordingly, there has been a request for a construction capable of reducing the space occupied by the sewing machine while easily maintaining the balance of the sewing machine.

An example of such conventional sewing machines is given inFIG. 1.FIG. 1shows a side elevation view of a conventional sewing machine disclosed in Korean Patent Application No. 1999-0015717, the content of which is incorporated herein for reference (reference numerals presented hereinafter to explainFIG. 1apply toFIG. 1only). Referring toFIG. 1, the conventional sewing machine has a head portion202elongated toward the front side of its body203by means of an arm201. The longer the material to be sewn is in the Y-axis direction (forward or backward direction) as retained on a retainer204atop a table200, the longer the arm201needs to be.

As the arm201becomes longer, the head portion202becomes farther from the body203. This makes the center of gravity of the sewing machine positioned at the front portion thereof Consequently, the body203, having the arm201connected thereto, is subject to additional weight and torsion due to the lengthened arm201. It results in a problem in strength of the machine. Therefore, there has existed a demand for a sewing machine making it possible to minimize or eliminate the length of an aim201for the purpose of avoiding any damage to its body203and, at the same time, to extend the sewing area in the X-axis direction (leftward or rightward direction) and/or Y-axis direction of the sewing machine.

Meanwhile, conventional sewing machines employ single driving motor to drive both a needle and a shuttle race body, as shown inFIG. 2. Referring toFIG. 2, a single driving motor230is adapted to drive an upper shaft210for driving a needle205, as well as a lower shaft220for driving a shuttle race body (not shown in the drawing).

The driving motor230is connected in a line with the upper shaft210. The lower shaft220is positioned below a table200and is parallel to the upper shaft210. A rotation transfer means240, such as a timing belt, is used to enable the single driving motor230to drive both the upper and lower shafts210and220.

Such a simultaneous driving of the upper and lower shafts210and220necessitates the interconnection and coupling of them within the arm201and the body203. When the arm201and the body203need to be removed to extend the sewing area in the Y-axis direction, as mentioned above, the simultaneous driving of the upper and lower shafts210and220cannot be implemented. Therefore, it is necessary to solve such problem and, at the same time, to provide an improved construction accordingly.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a sewing machine having a feeding device which can move a retainer, on which a material to be sewn is retained, in the X-axis or Y-axis direction so that sewing can be performed in an extended sewing area regardless of the position of its head portion.

Another object of the present invention is to provide a sewing machine having an arm lifting device which can move its head portion in the upward or downward direction so that a material to be sewn, which is retained on a retainer, can be easily mounted or removed.

Still another object of the present invention is to provide a sewing machine having an upper shaft driving motor and a lower shaft driving motor for driving its upper and lower shafts, respectively, as a result of having removed its arm and body so that the upper and lower shafts can be driven in accordance with its improved constitution.

In order to accomplish this object, there is provided a sewing machine comprising: a head portion for mounting a needle for sewing thereon; a table for accommodating a material to be sewn thereon; a holding frame for mounting the head portion thereon; and supporting posts for supporting and positioning the holding frame above the table.

According to a feature of the present invention, the holding frame is positioned horizontally in the X-axis direction and the supporting posts are adapted to support the opposite ends of the holding frame vertically.

According to another feature of the present invention, the sewing machine further comprises a retainer for retaining a material to be sewn and an X-axis feeding means for moving the retainer leftward or rightward in the X-axis direction.

According to another feature of the present invention, the X-axis feeding means comprises: an X-axis flame elongated in the leftward and rightward direction; a guide rail installed or formed in the X-axis flame; a holding portion coupled with the guide rail and adapted to move in the leftward or rightward direction while holding the retainer, and an X-axis driving motor for moving the holding portion.

According to another feature of the present invention, the sewing machine further comprises a retainer for retaining a material to be sewn and a Y-axis feeding means for moving the retainer forward or backward in the Y-axis direction.

According to another feature of the present invention, the Y-axis feeding means comprises: a moving portion for moving the retainer in the forward or backward direction; and a Y-axis driving motor for moving the moving portion.

According to another feature of the present invention, the sewing machine further comprises a Y-axis feeding means for moving the X-axis feeding means forward or backward in the Y-axis direction.

According to another feature of the present invention, the Y-axis feeding means comprises: a moving portion for moving the X-axis feeding means in the forward or backward direction; and a Y-axis driving motor for moving the moving portion.

According to another feature of the present invention, the moving portion comprises a belt moved by the Y-axis driving motor.

According to another feature of the present invention, the sewing machine further comprises an arm lifting device coupled to the holding frame together with the head portion for moving the head portion upward or downward.

According to another feature of the present invention, the arm lifting device comprises: a guide plate held on the holding frame; and a feeder held on the head portion, wherein the feeder is adapted to move upward or downward in accordance with the guide plate.

According to another feature of the present invention, the arm lifting device is moved upward or downward by hydraulic pressure, pneumatic pressure, or a mechanical structure utilizing the rotation of a screw structure.

According to another feature of the present invention, the sewing machine further comprises: an upper shaft driving motor connected to an upper shaft for driving the sewing needle of the head portion; and a lower shaft driving motor connected to the lower shaft for driving a shuttle race body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3shows a perspective view of a sewing machine according to the present invention. Referring to the drawing, a head portion40is positioned above a table10. The head portion40performs a sewing operation on a material retained on a retainer50.

The table10is a square plate on which the material to be sewn is placed. The table10is provided with guide holes12elongated in the forward and backward director along its opposite sides. The guide holes12are adapted to transmit the movement of a Y-axis feeding means70(FIG. 4), positioned below the table10, to a retainer50, positioned above the table10.

Supporting posts22are formed vertically on the opposite ends of the table10. A holding frame20is supported between the supporting posts22in the horizontal direction. The holding frame20is preferably made of a rectangular steel tube and has a head portion40extending forward from its center portion. An arm lifting device30is preferably provided between the head portion40and the holding frame20to move the head portion40upward or downward.

The sewing machine according to the present invention makes it possible to sew a material in an extended area while the head portion40is held, because the retainer50is adapted to move in the X-axis and Y-axis direction. For this, the holding frame20is positioned horizontally for openness in the forward and backward direction, opposite ends of which being supported by the supporting post22, so that the head portion40is held in a bridge-like fashion.

FIGS. 3 to 5show an arrangement for moving the retainer50in the X-axis or Y-axis direction.

An upper shaft driving motor39is provided behind the holding frame20to drive an upper shaft (not shown) within the head portion40. The upper shaft driving motor39is connected to the upper shaft (not shown), but not to a lower shaft (not shown) for driving a shuttle race body (not shown).

FIG. 4shows a front view of a sewing machine according to the present invention. Referring to the drawing, an X-axis feeding means60is provided above the table10and extends in the X-axis direction. Multiple Y-axis feeding means70are provided below the table10and extend in the Y-axis direction.

The X-axis feeding means60comprises an X-axis frame62elongated in the X-axis direction, a guide rail64installed or formed on the X-axis frame62, and a holding portion66adapted to move leftward or rightward in accordance with the guide rail64. The retainer50, on which a material to be sewn is retained, is coupled to the holding portion66. As the holding portion66can move leftward or rightward, it is possible to sew a material in an extended area in the X-axis direction without any movement of the head portion40.

The Y-axis feeding means70enable movement of the retainer50in the Y-axis direction, that is, in the forward or backward direction. The Y-axis feeding means70extend in the forward and backward direction and have moving portions72adapted to move in the forward or backward direction.

The moving portions72are preferably made of belts72aadapted to move in the forward or backward direction. Holders72bare coupled on top of the belt72aand protrude upward. The holders72bare displaced forward or backward in accordance with the movement of the belts72a.

Each of the Y-axis feeding means70, positioned on opposite sides of the table10, is provided with its own holder72bin parallel orientation. The guide holes12of the table10expose the holders72bupward. The X-axis frame62is connected to the holders72b. When the X-axis feeding means60is not coupled, direct connection could be possible using additional extensions from the retainer50in the leftward and rightward direction.

As the holders72bmove forward or backward in accordance with the movement of the moving portions72—i.e. the belts72a—the retainer60, which is connected to the X-axis frame62, is displace forward or backward accordingly. This makes it possible to sew a material in an extended area in the Y-axis direction without any movement of the head portion40.

A lower shaft driving motor39is positioned below the table10to transmit power to a lower shaft (not shown), which is adapted to drive a shuttle race body (not shown). According to the inventive sewing machine, the upper and lower shafts should each be driven separately because, unlike in the prior art, the head portion40is held in a bridge-like fashion.

More specifically, a prior sewing machine has a body203(FIGS. 1 and 2) positioned in its center portion and a single driving motor230for driving the upper and lower shafts210and220simultaneously. However, the inventive sewing machine has an additional lower shaft driving motor89for separate driving of the shafts. A control unit (not shown) controls the driving operation of the upper and lower shafts38and39.

FIG. 5shows a side elevation view of a sewing machine according to the present invention. Referring to the drawing, each of the X-axis feeding means60has an X-axis feeding motor68and the Y-axis feeding means70extend in the forward and backward direction along the side.

The X-axis feeding means60is positioned above the table10and is connected to the retainer50. The Y-axis feeding means70is positioned below the table10and is connected to the X-axis feeding means60through the guide hole12. Reference numeral42denotes a needle.

FIG. 6shows a top view illustrating an X-axis feeding means and Y-axis feeding means according to the present invention. Referring to the drawing, the X-axis feeding means60has an X-axis driving motor68provided on a side thereof for driving movement in the leftward or rightward direction The Y-axis feeding means70have a Y-axis driving motor74for driving movement in the forward or backward direction.

The X-axis driving motor68rotates a driving pulley68bcoupled to a driving shaft68awhich faces forward. This rotation moves a belt69leftward or rightward, which is wound around the driving pulley68b. As the belt69is moved, a holding portion66connected thereto is moved accordingly. As a result, the retainer50, which is coupled to the holding portion66, is displaced A following pulley (not shown), which is provided on an end opposite from the end on which the driving pulley68bis provided, winds the belt69.

The Y-axis driving motor74is connected, via driving shafts74a, to the rear portions of the Y-axis feeding means70, which extend in the forward and backward direction along opposite sides of the table. As the Y-axis driving motor74is rotated, the belts72awhich are wound around driving pulleys (not shown) are moved forward or backward accordingly.

Holders72bare coupled on top of the belts72aand protrude upward. The holders72bmove the X-axis feeding means60horizontally forward or backward in accordance with the movement of the belts72a. The belts72aare wound around driving pulleys (not shown) at their rear portions, as well as around following pulleys (not shown) at their front portions.

FIG. 7shows an exploded perspective view of an arm lifting device according to the present invention. Referring to the drawing, a guide plate32, which is fixedly coupled to the holding frame20, engages a feeder34, which is fixedly coupled to the head portion40, within the arm lifting device30.

The guide plate32is in the shape of a bar elongated in the upward and downward direction and is hollow in its center portion, as in the case of a rail used in the railway. The feeder34has rear ends defining a narrowed space between them so that the guide plate32can be fitted from above or below into the space. The hollow portion of the guide plate32is fitted with the rear ends of the feeder34. As a result, the feeder34can slide upward or downward relative to the guide plate32, but cannot move laterally, i.e., in the forward or backward directions.

Movement of the arm lifting device30in the upward or downward direction can be realized, for example, by means of a pneumatic or hydraulic cylinder or via a mechanical structure, such as the rotation of a screw structure, but the means for movement is not limited thereby.

More specifically, the arm lifting device30is supported by the holding frame20and the head portion40is connected to the arm lifting device30. A control box (not shown) controls the upward and downward movement through a structure using a pneumatic or hydraulic cylinder or a mechanical structure using a screw.

FIGS. 8aand8bshow side sectional views illustrating a head portion lowered and lifted respectively by an arm lifting device according to the present invention. Referring to the drawing, the feeder34, which is integrated and moved together with the head portion40, is displaced upward or downward in accordance with the guide plate32, which is integrated to the holding frame20.

When the arm lifting device30applies pneumatic pressure through an upper pneumatic pressure opening (not shown), the lifting plate36within the arm lifting device30is pushed down from above and lowered accordingly. This makes the feeder34descend along the guide plate32and, as a result, the head portion40is moved downward.

When the head portion40is to be moved upward, on the other hand, pneumatic pressure is discharged through a lower pneumatic pressure opening (not shown). The lifting plate36within the arm lifting device30is then lifted. This makes the feeder34ascend along the guide plate32and, as a result, the head portion40is moved upward.

If the head portion40has finished its operation, the arm lifting device30lifts the head portion40to facilitate removal of the sewn material. If another material is placed in position to be sewn, the head portion40is lowered for sewing so that the needle42can approach the material.

This behavior makes it possible to use the retainer50in the sewing machine more efficiently and to sew thicker materials, although only materials the thicknesses of which are below a determined value can be sewn with prior sewing machines.

The present invention eliminates any coupling portion between an arm and a bed, as used in prior sewing machines. Instead, the inventive sewing machine has a holding frame supported by support posts, a head portion mounted on the holding frame, and a means for driving its upper shaft separately. Due to an arch-shaped arrangement positioned on its center portion without any structure for connecting upper and lower portions, sewing area is substantially increased in the Y-axis direction. Accordingly, it is possible to sew materials with unlimited length, such as a long cloth, without any interruption.

In addition, the retainer can be lifted when sewing is started or finished and the head portion can be moved up and down. This makes it possible to easily place and remove the material to be sewn and to process materials with various thicknesses, although only thin materials can be sewn with conventional sewing machines.

The inventive sewing machine separately drives its upper and lower shafts using separate driving motors. This avoids any overloading to single motor adapted to drive upper and lower shafts simultaneously via, for example, a timing belt.