Leather product and method for producing same

Abstract

The objective of the present invention is to continuously and nicely form a machine stitch by lockstitch with a relatively thick multifilament yarn on the surface of a leather fabric. Provided is a method for producing a leather product comprising: a thread preparation step of preparing a needle thread and a bobbin thread in a sewing machine; a placement step of placing a leather fabric on the needle plate with the back surface of the leather fabric facing upward; and a sewing step of sewing the leather fabric by lockstitch. The thickness of the leather fabric is 2 to 12 millimeters. The needle thread and the bobbin thread are multifilament yarns. The thickness of the needle thread is 1000 to 1800 dtex. The thickness of the bobbin thread is 1600 to 4000 dtex and is greater than that of the needle thread by at least 600 dtex. In the thread preparation step, the tension of the needle thread is adjusted to be 15 to 21 N, and the tension of the bobbin thread is adjusted to be 1 to 2 N.

Description

Leather products and their manufacturing method

[0001] This specification discloses a technique relating to a leather product and a method for manufacturing the same.

[0002] Leather products made by sewing machine stitches onto leather fabric (including natural leather, synthetic leather, and artificial leather) are used for various items that are visible to the human eye, such as automobile interior parts, furniture, bags, etc. Patent Document 1 describes an automobile interior part made by sewing machine stitches onto leather fabric.

[0003] Japanese Patent Application Laid-Open No. 2016-198943

[0004] When sewing leather fabric with a lock stitch using a sewing machine with a relatively thick multifilament thread of about 1600 to 4000 decitex (product count 5 to 0), there is a problem that looseness of the upper and lower threads occurs in places along the stitch, making it difficult to obtain a continuous, attractive seam.

[0005] The technology disclosed in this specification can be realized in the following forms.

[0006] One embodiment of a method for manufacturing a leather product disclosed in this specification is a method for manufacturing a leather product in which a lockstitch sewing machine stitch is sewn into leather fabric. This manufacturing method includes a thread preparation step of preparing an upper thread and a lower thread for a sewing machine, a placement step of placing the leather fabric with the backside facing up on the needle plate of the sewing machine, and a sewing step of using the sewing machine with the upper thread and the lower thread prepared to lockstitch the leather fabric placed on the needle plate to form the sewing machine stitch on the leather fabric. The thickness of the leather fabric is 2 to 12 millimeters. The upper thread and the lower thread are multifilament threads. The thickness of the upper thread is 1000 to 1800 decitex. The thickness of the lower thread is 1600 to 4000 decitex, which is 600 decitex or more thicker than the upper thread. In the thread preparation step, the tension of the upper thread is adjusted to 15 to 21 Newtons, and the tension of the lower thread is adjusted to 1 to 2 Newtons. According to this embodiment of the method for manufacturing leather products, it is possible to form continuous, attractive machine-sewn stitches on the surface of the leather fabric using a relatively thick multifilament thread of 1600 to 4000 decitex.

[0007] A leather product in one embodiment disclosed in this specification is a leather product in which machine-sewn lockstitch stitches are sewn into leather fabric. This leather product includes a first thread that forms the machine stitches on a first surface (front side) of the leather fabric, and a second thread that forms the machine stitches on a second surface (back side) of the leather fabric. The thickness of the leather fabric is 2 to 12 millimeters. The first thread and the second thread are multifilament threads. The thickness of the first thread is 1600 to 4000 decitex, and is 600 decitex or more thicker than the second thread. The thickness of the second thread is 1000 to 1800 decitex. A knot between the first thread and the second thread is located closer to the second surface in the thickness direction of the leather fabric. The leather fabric is leather with urethane foam attached to the back side, and the machine stitches are sewn into the leather and the urethane foam. According to this type of leather product, it is possible to improve the quality of machine-sewn lock stitches using a relatively thick multifilament thread of 1600 to 4000 decitex.

[0008] The technology disclosed in this specification can be realized in various forms other than leather products and their manufacturing methods, such as automobile interior parts, furniture, and bags that use leather products.

[0009] It is a top view showing the leather product of this embodiment. It is a cross-sectional view showing the leather product of this embodiment. It is a process diagram showing a manufacturing method of the leather product. It is a cross-sectional view showing the leather product provided with urethane foam.

[0010] Fig. 1 is a plan view showing a leather product 10 of this embodiment. Fig. 2 is a cross-sectional view showing the leather product 10 of this embodiment. The cross-sectional view of Fig. 2 shows the cross section F2-F2 of Fig. 1.

[0011] The leather product 10 is a product in which a lockstitch sewing machine stitch 200 is sewn onto leather fabric 100. The leather product 10 can be used for various items that are visible to the human eye, such as automobile interior parts, furniture, and bags.

[0012] The leather fabric 100 of the leather product 10 is a sheet of leather. The leather fabric 100 is in the form of a sheet having a front surface 110 and a back surface 120. The front surface 110 is a first surface that will be the front side that will be visible to the human eye when the leather product 10 is used as a final product. The back surface 120 is the surface opposite to the front surface 110. The back surface 120 is a second surface that will not be visible to the human eye when the leather product 10 is used as a final product.

[0013] In this embodiment, the leather fabric 100 is synthetic leather bonded with urethane foam. In this embodiment, the front surface 110 is formed of synthetic leather, and the back surface 120 is formed of urethane foam. In other embodiments, the leather fabric 100 may be artificial leather or natural leather. In other embodiments, the leather fabric 100 may be leather bonded with a material different from urethane foam (e.g., woven fabric, nonwoven fabric, etc.), or may be leather with no other material bonded to it.

[0014] Figure 4 is a cross-sectional view showing a leather product 10 including a urethane foam 102. The leather fabric 100 in the leather product 10 of Figure 4 includes leather 101 and urethane foam 102. The leather fabric 100 of Figure 4 is formed by bonding the urethane foam 102 to the leather 101. The leather 101 is exposed on the front surface 110 of the leather product 10. The urethane foam 102 is exposed on the back surface 120 of the leather product 10. A sewing machine stitch 200 is sewn into the leather 101 and the urethane foam 102.

[0015] From the viewpoint of forming the sewing stitches 200 continuously and attractively on the surface 110 of the leather material 100, it is preferable that the thickness T of the leather material 100 is 2 mm (millimeters) or more and 12 mm or less.

[0016] The leather fabric 100 has a plurality of needle holes 130 penetrating from the front surface 110 to the back surface 120. The needle holes 130 are formed by a sewing needle (not shown) when sewing machine stitches 200 into the leather fabric 100. The needle holes 130 hold the machine stitches 200.

[0017] The sewing stitch 200 of the leather product 10 is a lock stitch sewn into the leather fabric 100 by a sewing machine (not shown). The sewing stitch 200 includes a front thread 210 and a back thread 220. The front thread 210 is a first thread that constitutes the sewing stitch 200 on the front surface 110 of the leather fabric 100. The back thread 220 is a second thread that constitutes the sewing stitch 200 on the back surface 120 of the leather fabric 100.

[0018] The sewing machine stitch 200 has a knot 230 between the front thread 210 and the back thread 220 in each of the multiple needle holes 130 in the leather fabric 100. The knot 230 is located closer to the back surface 120 in the thickness direction of the leather fabric 100.

[0019] The stitching pitch P of the sewing machine stitches 200, which is also the distance between two adjacent needle holes 130, is a constant interval. From the viewpoint of forming the sewing machine stitches 200 continuously and attractively on the surface 110 of the leather fabric 100, the stitching pitch P is preferably 4.0 mm or more and 6.0 mm or less.

[0020] The surface thread 210 and the back thread 220 of the sewing machine stitch 200 are multifilament threads. In this embodiment, the surface thread 210 and the back thread 220 are multifilament threads made of polyester. In other embodiments, the surface thread 210 and the back thread 220 may be made of nylon or silk, or may be blended yarns or mixed fiber yarns. Furthermore, the material of the surface thread 210 may be different from that of the back thread 220.

[0021] From the viewpoint of forming the sewing machine stitches 200 continuously and attractively on the surface 110 of the leather fabric 100, it is preferable that the thickness of the surface thread 210 is 1600 dtex (decitex) or more and 4000 dtex or less (5 to 0 count in product count), which is 600 dtex or more thicker than the back surface thread 220. Furthermore, it is preferable that the thickness of the back surface thread 220 is 1000 dtex or more and 1800 dtex or less (8 to 5 count in product count).

[0022] 3 is a process diagram showing a manufacturing method of the leather product 10. When manufacturing the leather product 10, the worker first performs the thread preparation process (process P110). In the thread preparation process (process P110), the worker prepares an upper thread and a lower thread for the sewing machine. The worker assembles the multifilament thread that will become the back surface thread 220 into the sewing machine as the upper thread. Depending on the thickness of the upper thread, it is preferable that the size of the sewing machine needle be between 18 and 24 count. The worker assembles the multifilament thread that will become the surface thread 210 into the sewing machine as the lower thread.

[0023] In the thread preparation process (process P110), the worker adjusts the tension of the upper thread to 15 to 21 Newtons. To measure the tension of the upper thread, the worker attaches the upper thread, which is threaded through the sewing machine balance pin at its uppermost position, to a tension gauge. The worker then pulls the upper thread horizontally 100 mm from the sewing machine balance pin to the left side of the sewing machine. The worker then uses the tension gauge to pull the upper thread horizontally at 50 mm per second, and measures the value on the tension gauge at that time as the tension of the upper thread.

[0024] In the thread preparation process (process P110), the operator adjusts the tension of the bobbin thread to 1 to 2 Newtons. To measure the tension of the bobbin thread, the operator attaches the bobbin thread pulled from the bobbin onto the needle plate to a tension gauge. Then, the operator pulls the bobbin thread horizontally from above the needle plate toward the back of the sewing machine by 100 mm. The operator then uses the tension gauge to pull the bobbin thread horizontally at 50 mm per second, and measures the value on the tension gauge at that time as the tension of the bobbin thread.

[0025] After performing the thread preparation process (process P110), the worker performs the placement process (process P120). In the placement process (process P120), the worker places the leather fabric 100 on the needle plate of the sewing machine with the back surface 120 of the leather fabric 100 facing up. In other words, the worker places the leather fabric 100 on the needle plate of the sewing machine with the front surface 110 of the leather fabric 100 facing the needle plate.

[0026] After the placing step (step P120), the worker performs the sewing step (step P130). In the sewing step (step P130), the worker uses a sewing machine with an upper thread and a lower thread prepared to lock stitch the leather fabric 100 placed on the needle plate, thereby forming sewing machine stitches 200 on the leather fabric 100. In this way, the leather product 10 is completed.

[0027] The applicant conducted an evaluation test of forming machine stitches on leather fabric. The conditions of the evaluation test were as follows: <Leather fabric> Various leather fabrics with a thickness of 2 mm to 12 mm (including natural leather, synthetic leather, and artificial leather) <Sewing thread> Various product numbers of Toyobo Ester Sewing Thread G manufactured by FTC Co., Ltd. <Sewing machine> Industrial sewing machine LU2-4410-B1T-BF-CS manufactured by JUKI Corporation

[0028] The results of this evaluation test showed that when a leather product 10 is manufactured under the conditions of the manufacturing method shown in Figure 3, the sewing machine stitches 200 can be formed continuously and attractively on the surface 110 of the leather fabric 100. In the leather product 10 obtained in this manner, due to the relationship between the tension of the upper thread and the lower thread during sewing, the knot 230 between the surface thread 210 and the back surface thread 220 is located closer to the back surface 120 than the center of the leather fabric 100 in the thickness direction.

[0029] According to the manufacturing method of the leather product 10 in the embodiment described above, it is possible to form a continuous and attractive lock-stitch sewing stitch 200 using a relatively thick multifilament thread of 1600 to 4000 decitex on the surface 110 of the leather fabric 100. Furthermore, according to the leather product 10 of this embodiment, it is possible to improve the quality of the lock-stitch sewing stitch 200 using a relatively thick multifilament thread of 1600 to 4000 decitex.

[0030] The technology disclosed in this specification is not limited to the above-described embodiments, examples, and modifications, and can be realized in various configurations without departing from the spirit thereof. For example, among the technical features of the above-described embodiments, examples, and modifications, those corresponding to the technical features of each form described in the Summary of the Invention section can be appropriately replaced and combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, technical features not described as essential in this specification can be appropriately deleted.

[0031] 10... Leather product 100... Leather fabric 101... Leather 102... Urethane foam 110... Surface 120... Back surface 130... Pinhole 200... Sewing machine stitch 210... Surface thread 220... Back thread 230... Knot

Claims

1. A method for manufacturing a leather product in which a sewing machine stitch is sewn into leather fabric by a lock stitch, comprising: a thread preparation step of preparing an upper thread and a lower thread for a sewing machine; a placement step of placing the leather fabric on the needle plate of the sewing machine with the back side of the leather fabric facing up; and a sewing step of forming the sewing machine stitch on the leather fabric by lock stitching the leather fabric placed on the needle plate using the sewing machine with the upper thread and the lower thread prepared, wherein the thickness of the leather fabric is 2 to 12 mm, the upper thread and the lower thread are multifilament threads, the thickness of the upper thread is 1000 to 1800 decitex, and the thickness of the lower thread is 1600 to 4000 decitex, which is at least 600 decitex thicker than the upper thread, In the thread preparing step, the tension of the upper thread is adjusted to 15 to 21 Newtons, and the tension of the lower thread is adjusted to 1 to 2 Newtons.

2. A leather product having machine stitches sewn into leather fabric by lock stitching, comprising: a first thread that constitutes the machine stitches on a first surface of the leather fabric, and a second thread that constitutes the machine stitches on a second surface of the leather fabric, the thickness of the leather fabric is 2 to 12 millimeters, the first thread and the second thread are multifilament threads, the thickness of the first thread is 1600 to 4000 decitex and is 600 decitex or more thicker than the second thread, the thickness of the second thread is 1000 to 1800 decitex, a knot of the first thread and the second thread is located closer to the second surface in the thickness direction of the leather fabric, the leather fabric is leather with urethane foam attached to the back side, and the machine stitches are sewn into the leather and the urethane foam.

Images