JPH059120B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for sewing a skin used in skin-integrated foam molding in which the skin is placed in a mold and then foam-molded. The sewing method of the present invention is used when sewing the outer skin of automobile headrests, seats, etc.

[Prior Art] For example, as a headrest for an automobile, a molded body made of foamed resin is covered with a skin made of leather, resin nonwoven fabric, woven fabric, etc. has been conventionally used. When manufacturing such a headrest, a method has generally been used in which a molded body and a skin are formed separately, and then the molded body is covered with the skin and sewn. However, this method requires a large amount of man-hours and has the disadvantage that the position of the molded body shifts within the skin, resulting in poor appearance quality. Therefore, in recent years, a method has been developed in which a skin formed in a predetermined shape is placed in a mold, and resin is foamed within the skin to integrally mold and integrally join the molded body and the skin. This method is becoming mainstream.

Incidentally, the shape of the epidermis is generally three-dimensional. Therefore, when forming a skin from leather or nonwoven fabric, a sheet-like base material cut into a predetermined shape is aligned with the inner side, sewn with a sewing machine, and then turned over to form a three-dimensional skin.

[Problems to be Solved by the Invention] When sewing using a sewing machine, as shown in FIGS. 7 and 8, by lowering the sewing needle, the upper thread 100 is threaded together with the sewing needle into two stacked bases. The material 401, 402 is inserted from the front surface to the back surface. After the upper thread 100 is entwined with the lower thread 200 placed on the back side, the sewing needle is raised to return the upper thread 100 to the front side. Next, the base material 401,
402 to extend the upper thread 100 and the lower thread 200 to the next sewing position separated by a predetermined interval. Sewing is performed by repeatedly performing this unit sewing. At this time, as shown in FIG. 8, needle holes 301, 302 are bored in the base materials 401, 402. Here upper thread 10
0 is inserted into a thread hole formed in the sewing needle.
Therefore, as shown enlarged in FIG. 9, the base materials 401 and 402 have needle holes 301 and 30 corresponding to the total area of the cross section of the two needle threads 100 and the cross section of the sewing needle.
2 is drilled. Note that once the diameter of the upper thread is determined, the diameter of the thread hole is determined, and the diameter of the sewing needle is the smallest diameter that can have that thread hole while maintaining strength. Therefore, once the diameter of the needle thread is determined, the size of the needle hole is uniquely determined.

When the base material sewn in this way is reversed to form a skin and placed in a mold for integral foam molding, the foamed resin forms at the needle hole 30 as shown in Figure 10.
1,302 and appeared on the surface in some cases. Therefore, it is necessary to seal the seams, which requires a large amount of man-hours. Note that this foamed resin leaks from the base material 401 on the surface side (needle thread side).
There are two types of leakage: leakage from the needle hole 301 of the base material 402 (arrow A) and leakage from the needle hole 302 of the base material 402 on the back side (lower thread side) (arrow B). The needle hole 302 is the bobbin thread 200
It is known that there is more leakage from the needle hole 301 because it is mostly blocked by the needle hole 301.

The object of the present invention is to close the needle hole at the same time as sewing, thereby preventing resin from leaking during molding.

[Means for Solving the Problems] The method of sewing a skin for integrally foamed skin molding of the present invention includes aligning two sheet-like base materials cut into a predetermined shape with their inner sides facing each other, and sewing a first thread on one side and a first thread on the other side. In the outer skin sewing method in which the second thread on the side is sewn while intertwining with each other through the needle hole, a non-breathable tape-shaped seal is attached to at least one surface of two base materials laminated along the inner side. The material is placed and sewn integrally with the base material during sewing,
Due to the tightening stress from the first thread or the second thread due to sewing, the edges of the sealing material located on both sides of the seam are swung toward each other with the seam as the center, so that the two edges of the sealing material are swung toward each other in a substantially clasped shape to cover the seam. are brought into contact with each other.

The greatest feature of the present invention is that the tape-shaped sealing material is sewn together when sewing the base material. The sealing material is sewn only at the center, and the edges on both sides of the seam are able to swing around the seam. Due to the stress acting from the base material and the thread, the respective edges are configured to abut each other in a substantially clasped shape. Note that the term "approximately joined hands" means that the edges on both sides are at least partially in contact with each other in the width direction from the seam to the end, and do not necessarily need to be in full contact with each other in the width direction.

As for the sealing material, it is sufficient that the material and the shape thereof are not particularly limited, as long as they come into contact with each other in a substantially joined-up shape due to the stress acting from the base material and the thread. For example, when a base material having a foam layer such as a slab foam is used, a sealing material such as a film or sheet made of various resins can be used. In this case, since the foam layer of the base material is compressed by the thread, the sewn portion becomes groove-like and a squeezing force is applied. Then, the sealing material is compressed by the thread, and a squeezing force from the base material acts on the sealing material, and a biasing force is generated that biases the edges on both sides of the seam in a direction toward each other, so that the sealing material comes into contact with each other in a substantially clasped shape.

Furthermore, in the case of a base material that does not have a foam layer, the sealing material itself can be formed from an elastic body such as various foams, vinyl chloride resin sheets, rubber sheets, and the like. Among these, it is desirable to use a foamed elastic body that has a large difference in volume between the compressed state and the uncompressed state, and therefore has a large squeezing force.
In this case, the sealing material itself is compressed by the thread and the base material to generate a squeezing force, and the edges on both sides abut approximately in the shape of palms together around the seam. In addition, in order to prevent the foamed resin from permeating the sealing material and coming out from the seams during molding, it is desirable to use a non-breathable sealing material. As such foamed elastic bodies, those made of closed cells such as PP foam and PE foam are known.

If the length from the seam to the edge of the sealing material is too long or too short, it may be difficult to contact the sealing material in a substantially clasped manner. Generally, a length of 10 to 30 mm is preferred. Further, the appropriate thickness is 0.5 to 5 mm.

Although the sealing material can be provided only on one side of the two base materials aligned on the inner surface, it is preferable to provide it on both sides, one side and the other side. This results in 2
The needle holes formed in the sheet of base material can be plugged from both sides, making sealing treatments and the like unnecessary. However, when sewing with a sewing machine, it is difficult to visually check the back side of the lower thread side while sewing, and the sealing material may be misaligned. Therefore, it is desirable to sew using a bobbin thread whose major diameter is at least 1.2 times the diameter of the needle thread. Here, the long axis of the bobbin thread refers to the longest diameter of the cross section of the bobbin thread, and if the cross section is oval, it is the long axis, and if the cross section is circular, it is the diameter. As a result, the needle hole on the back side is closed with two upper threads and one lower thread, and leakage of the foamed resin can be prevented, so that sealing treatment on the back side can be made unnecessary. Note that if the long axis of the lower thread is thinner than 1.2 times the diameter of the upper thread, it will be difficult to completely close the needle hole, resulting in a gap and leakage. More preferably, it is 1.75 to 2.5 times. 2.5
Even if the thickness is doubled or more, the effect will be saturated and the number of turns on the bobbin will decrease, which is not preferable because the number of times the bobbin must be replaced will be extremely increased.

The sewing method of the present invention can be performed using a sewing machine in a conventional manner. Also, the first thread and the second thread
The material of the thread is not particularly limited either, and threads made of the same material as conventional threads can be used.

[Operations and Effects of the Invention] In the sewing method of the present invention, a tape-shaped sealing material is arranged on at least one surface of two base materials laminated to match the inner surface, and is integrally attached to the base materials during sewing. Sewn. At this time, the squeezing force from the thread acts on both sides of the seam of the sealing material, and a biasing force is generated that biases the sealing material itself or the base material toward the sealing material in a direction toward each other. As a result, the sealing material comes into contact with the seams in a substantially clasped shape so as to cover the seams.

The obtained skin body is inverted and placed in a mold, and a foamed resin is injected to perform integral foam molding of the skin. At this time, when the foamed resin reaches the sealing material,
The foamed resin also tries to invade between the edges of both sides that are in contact with each other in a substantially joined-up shape. However, the pressure of foaming acts on the entire sealing material, and a force that presses the edges of both sides, which are in contact with each other in a substantially clasped shape, toward each other also acts.
Therefore, since the sealing material maintains a state in which the two palms are in contact with each other, the foamed resin is prevented from entering between the edges on both sides, and the foamed resin is prevented from reaching the needle hole. It is assumed that.

Further, if a sealing material made of an elastic body is used, the sealing material is compressed by sewing. However, since no compressive force is applied to the needle hole, the compressed portion swells into the needle hole and acts to block the needle hole, thereby further preventing leakage of the foamed resin from the needle hole.

Therefore, when integral foam molding is performed using the skin formed by the sewing method of the present invention, leakage of the foamed resin from the sewn portion can be prevented. In other words, the needle hole can be closed simply by sewing in the same manner as in the past, without the need for sealing the seams, thereby reducing the number of man-hours and cost.

[Example] Hereinafter, this will be explained in detail using examples.

Example 1 In this example, the present invention was applied to the case of forming the skin of the headrest of an automobile seat.

First, as shown in the cross-sectional view in FIG. 2, a felt layer 11 and a polyurethane slab foam layer 12 are
A sheet-like base material is prepared in which a polyurethane film 13 and a polyurethane film 13 are integrally laminated with adhesive. Then, this base material is cut into a plurality of sheets constituting the developed shape of the headrest.

Next, align the two adjacent base materials 1 and 1' in the unfolded shape so that the felt layers 11 of each are facing each other, and then add a layer of 0.6 mm thick and 15 mm wide to the base material 1 side.
A tape 4 made of PP foam having a foam density of 0.035 g/cm ³ is overlapped, and the sewn portion is sewn using a sewing machine as shown in FIG. At this time, upper thread 2 and lower thread 3
The same polyester thread with a diameter of 0.35 mm was used. The maximum diameter of the sewing machine needle is 0.95mm, and the diameter of the thread hole is 0.4mm.
mm. Then, at the first sewing position, insert the sewing machine needle with the upper thread 2 inserted into the thread hole from the base material 1 toward the base material 1', and insert the upper thread 2 into the bobbin thread 3 placed on the base material 1' side. After intertwining, the sewing machine needle was pulled out from the base material 1, and then unit sewing was repeatedly performed in which the upper thread 2 and the lower thread 3 were extended from the sewing position to the next sewing position separated by a predetermined interval. The sewing pitch is 4mm.

The remaining base materials were sewn in the same manner, and after sealing the seam of the base material 1' where the bobbin thread 3 was exposed, the seam was turned over at the sewn portion to obtain a skin. Base material 1 from which needle thread 2 is exposed
is in the same condition as it was sewn. For comparison, sewing was performed in the same manner except that tape 4 was not used, and a skin was similarly sealed only on the base material 1' side.

Each of these skins was placed in a mold, and after the molds were clamped, foamed urethane resin was injected and foamed to perform integral foam molding of the skin. After molding, the mold was opened, the molded product was taken out, and the seam portion of the skin was observed. As a result, foamed resin leaked from the seams in the case where tape 4 was not used, but no leakage of foamed resin was observed from the skin sewn by the sewing method of the example.

In this case, the tape 4 is compressed by the needle thread 2 and the base material 1. At this time, an urging force is generated on both sides of the seam of the tape 4 due to the squeezing force of the needle thread 2, which urges the tape 4 to move closer to each other, as shown in FIG. The two hands touch each other in a clasped manner. Further, since no compressive force is applied to the needle hole, the compressed portion bulges into the needle hole and blocks the needle hole. It is thought that these effects prevented the foamed resin from leaking from the needle holes on the base material 1 side.

Example 2 This example is the same as Example 1 except that the diameter of the bobbin thread 3 is different. In other words, upper thread 2 has a diameter
Using 0.35mm polyester thread, bobbin thread 3 has a diameter
A 0.6 mm polyester thread was used. The maximum diameter of the sewing machine needle is 0.95 mm, and the diameter of the thread hole is 0.4 mm.

This skin was not subjected to sealing treatment as in Example 1, and the skin was integrally foam-molded as it was. In this skin, the needle holes on the base material 1' side were closed by the upper thread 2 and lower thread 3, so no leakage of the foamed resin occurred even without sealing treatment.

That is, in the outer skin sewn in this example, the fourth
As shown in the figure and FIG. 5, the needle hole 10 on the side of the base material 1' was closed by the upper thread 2 and the lower thread 3, and it is considered that this prevented leakage of the foamed resin. In this example, a bobbin thread 3 having a perfectly circular cross-section was used, but the same effect can be obtained by using a bobbin thread 3' having an elliptical cross-section and a major axis (a) of 1 mm or more, as shown in FIG. is obtained.

That is, according to the sewing method of Example 2,
Since needle holes on both sides formed in two base materials can be closed at the same time as sewing, the number of man-hours can be further reduced compared to the method of Example 1.

[Brief explanation of the drawing]

Figures 1 to 3 relate to a sewing method according to an embodiment of the present invention, in which Figure 1 is an explanatory diagram showing the sewing state, Figure 2 is a sectional view of the base material, and Figure 3 is a diagram of the molded body. It is a sectional view of the main part. 4 to 6 relate to the sewing method of the second embodiment; FIG. 4 is a sectional view of the needle hole portion of the sewn skin; FIG. The figure is a sectional view corresponding to FIG. 4 showing another aspect of the bobbin thread. Figures 7 to 10 relate to the conventional sewing method; Figure 7 is an explanatory diagram showing the relationship between upper thread and lower thread during sewing; Figure 8 is a sectional view of the needle hole of the sewn skin; Figure 9 is a sectional view taken along line B-B in Figure 8.
Figure 0 is a sectional view of the main part of the molded body. 1, 1'...Base material, 2... Upper thread, 3... Lower thread,
4... Tape (sealing material), 10... Needle hole.

Claims (1)

[Claims] 1. Two sheet-like base materials cut into a predetermined shape are sewn by aligning the two sheet-like base materials with their center sides facing each other and intertwining the first thread on one side and the second thread on the other side with each other through the needle hole. In the outer skin sewing method, a non-breathable tape-shaped sealing material is disposed on at least one surface of the two base materials laminated to match the inner surface, and is integrally attached to the base material during the sewing. The sealing material is sewn, and a pair of edges of the sealing material located on both sides of the seam are swung toward each other in a direction centered on the seam due to tightening stress from the first thread or the second thread due to sewing. A method for sewing an outer skin for integral foam molding, characterized in that the outer skin is brought into contact with each other in a substantially joined shape so as to cover the seam.