TONGUE FOR A SEATBELT DEVICE AND FABRICATION METHOD THEREOF

Abstract

A tongue for a seatbelt device includes: a metal core at which an insertion portion is formed continuously from a metal core base portion; a molded portion formed by the metal core base portion of the metal core being covered with a synthetic resin material; a webbing pass-through portion, one end of which opens along the thickness direction of the metal core base portion in one face of the molded portion, and another end of which opens in an end portion of the molded portion at a side opposite to the insertion portion; and a groove portion formed between the metal core base portion and the webbing pass-through portion, the groove portion opening in the end portion of the molded portion at the side opposite to the insertion portion and opening in an inner periphery face of the webbing pass-through portion.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese Patent Application No. 2012-127505 filed Jun. 4, 2012, the disclosure of which is incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a tongue for a seatbelt device that is applicable to a seatbelt of a vehicle, and to a fabrication method of the tongue.

2. Related Art

In a tongue for a seat belt device that is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2007-76635 (referred to as a “tongue plate” in the publication of JP-A No. 2007-76635), a webbing pass-through portion (referred to as a “pass-through hole” in the publication of JP-A No. 2007-76635) through which a webbing can pass is formed. One end of this webbing pass-through portion opens at one thickness direction side of a molded portion, and the other end opens at an opposite side of the molded portion from a side at which an insertion portion is provided (of a region referred to as a “tongue plate core” in the publication of JP-A No. 2007-76635, the insertion portion is a portion to which molding is not applied).

In this structure, when the molded portion is being molded, the other end side of the webbing pass-through portion relative to an intermediate portion (i.e., the side that opens at the opposite side of the molded portion from the side at which the insertion portion is provided) is an undercut. Here, the undercut region is molded using a slide die in a resin-molding die. However, when the tongue plate core is placed on an upper face of the slide die, the tongue plate core is exposed at the inside of the webbing pass-through portion or the like. For molding to be applied to the tongue plate core between the slide die and the tongue plate core, the tongue plate core must be retained from the opposite side thereof from the side at which the slide die is disposed. Therefore, there is an opening in a face of the molded portion at the opposite side thereof from the one end of the webbing pass-through portion, and this opening must be covered up with a cover that is structured as a separate body or the like.

SUMMARY

The present invention provides a tongue for a seat belt device and a fabrication method thereof, the tongue including a webbing pass-through portion of which one end opens at one thickness direction side of a molded portion and the other end opens at the opposite side of the molded portion from a side at which an insertion portion is provided, and the molded portion being moldable without an unnecessary opening that must be covered with a separate member being formed.

A first aspect of the present invention includes: a metal core at which an insertion portion is formed continuously from a metal core base portion in which a penetrating hole through which a webbing passes is formed, the insertion portion being insertable into a buckle, and the penetrating hole penetrating in a thickness direction of the metal core base portion; a molded portion that is formed by the metal core base portion of the metal core being covered with a synthetic resin material at surroundings of the penetrating hole; a webbing pass-through portion through which the webbing passes, one end of the webbing pass-through portion opening along the thickness direction of the metal core base portion in one face of the molded portion, another end of the webbing pass-through portion opening in an end portion of the molded portion at a side opposite to the insertion portion, and the webbing passing through the inside of the penetrating hole at a penetration direction intermediate portion of the webbing pass-through portion; and a groove portion formed between the metal core base portion and the webbing pass-through portion, the groove portion opening in the end portion of the molded portion at the side opposite to the insertion portion and opening in an inner periphery face of the webbing pass-through portion.

In the first aspect of the present invention, the insertion portion of the metal core is inserted into the buckle. In this state, if the webbing is wrapped round the body of an occupant sitting on the seat, the webbing is in a state of application to the body of the occupant and the body of the occupant is restrained by the webbing.

Further in the first aspect, the one end of the webbing pass-through portion through which the webbing passes opens in the one face along the thickness direction of the metal core base portion of the molded portion, while the other end of the webbing pass-through portion opens in the end portion at the side opposite to the insertion portion. Therefore, for example, if the seatbelt device is specified such that the other face with respect to the thickness direction of the metal core base portion of the molded portion is oriented to the vehicle width direction middle side of the webbing pass-through portion in a state in which the seatbelt device is not being used, the opening through which the webbing passes is not visible if the tongue for a seatbelt device is viewed from the vehicle width direction middle side. Thus, the appearance is good.

Meanwhile, the groove portion is formed in the molded portion of the first aspect of the present invention, between the metal core base portion and the webbing pass-through portion. The groove portion opens at the end portion of the molded portion at the side opposite to the insertion portion, and opens at an inner periphery face of the webbing pass-through portion. This groove portion is formed by, for example, when the molded portion is being formed on the metal core base portion, a protrusion corresponding to the groove portion being provided at a slide die that is for forming the other end side of the webbing pass-through portion relative to the penetration direction intermediate portion of the webbing pass-through portion. Therefore, due to the metal core base portion being supported by the protrusion on the slide die when the molded portion is being formed, the molded portion may be formed excellently. Moreover, the webbing pass-through portion side of the metal core base portion, sideward of the groove portion, is covered with the synthetic resin material. Therefore, the metal core does not come into contact with the webbing passing through the webbing pass-through portion.

A method for fabricating a tongue for a seatbelt device according to a second aspect of the present invention includes: covering a metal core base portion of a metal core with a synthetic resin material and forming a molded portion, at which metal core an insertion portion is formed continuously from the metal core base portion, the insertion portion being insertable into a buckle, and a penetrating hole through which a webbing passes being formed in the metal core base portion, the penetrating hole penetrating in a thickness direction of the metal core base portion; during the forming of the molded portion, forming a webbing pass-through portion through which the webbing passes, by causing a core to enter the penetrating hole from one thickness direction side of the metal core base portion and providing a slide die at the other thickness direction side of the metal core base portion, one end of the webbing pass-through portion opening in one face of the molded portion at the one thickness direction side of the metal core base portion and another end of the webbing pass-through portion opening in an end portion of the molded portion at a side opposite to the insertion portion; and, during the forming of the molded portion, supporting the metal core base portion with a protrusion that protrudes from a surface at the metal core base portion side of the slide die, and forming a groove portion that opens in the end portion of the molded portion at the side opposite to the insertion portion.

In the second aspect of the present invention, the metal core base portion structuring the metal core is mold-formed with the synthetic resin material in a state in which the core is inserted into the penetrating hole formed in the metal core base portion from the one thickness direction side of the metal core base portion and in which the slide die is disposed at the other thickness direction side of the metal core base portion. Hence, the metal core base portion is covered by the molded portion. Moreover, the webbing pass-through portion is formed in the molded portion by this mold-forming with the one end opening in the surface of the molded portion at the one thickness direction side of the metal core base portion, an intermediate portion passing through the penetrating hole in the metal core base portion, and the other end opening at the side opposite to the insertion portion of the metal core.

If the tongue for a seatbelt device in which this webbing pass-through portion is formed is specified, for example, such that the other face with respect to the thickness direction of the metal core base portion of the molded portion is oriented to the vehicle width direction middle side of the webbing pass-through portion in the state in which the seatbelt device is not being used, the opening through which the webbing passes is not visible if the tongue for a seatbelt device is viewed from the vehicle width direction middle side. Thus, the appearance is good.

The protrusion protrudes from the surface of the metal core base portion side of the slide die, and the metal core base portion is supported by this protrusion. Therefore, unintended displacement of the metal core during the mold-forming may be suppressed, and excellent molding is possible. In addition, because this protrusion supports the metal core base portion, a gap is formed between the slide die and the metal core base portion.

Therefore, the groove portion is formed in correspondence with the protrusion in the molded portion that is formed. The groove portion opens at the end portion of the molded portion at the side opposite to the insertion portion of the metal core, and opens at the webbing pass-through portion side of the molded portion. Sideward of the groove portion, the synthetic resin material constituting the molded portion is charged into the gap between the metal core base portion and the webbing pass-through portion. Therefore, the surface at the webbing pass-through portion side of the core metal base portion sideward of the groove portion is covered by the molded portion. Consequently, the metal core does not come into contact with the webbing passing through the webbing pass-through portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary Embodiments of the present invention will be described in detail based on the following figures, wherein:

FIG. 1 is a front view, from a vehicle forward side, schematically showing the structure of a seatbelt device employing a tongue for a seatbelt device in accordance with an exemplary embodiment of the present invention.

FIG. 2 is a perspective view of the tongue for a seatbelt device in accordance with the exemplary embodiment of the present invention.

FIG. 3 is a side view of the tongue for a seatbelt device in accordance with the exemplary embodiment of the present invention.

FIG. 4 is a plan view of the tongue for a seatbelt device in accordance with the exemplary embodiment of the present invention.

FIG. 5 is a sectional diagram of the tongue for a seatbelt device, taken along line 5-5 in FIG. 4.

FIG. 6 is a sectional diagram of the tongue for a seatbelt device, taken along line 6-6 in FIG. 4.

FIG. 7 is a sectional diagram, corresponding with FIG. 5, showing a state in which a metal core is set in a die for molding a molded portion and a synthetic resin material is charged therein.

FIG. 8 is a sectional diagram, corresponding with FIG. 6, showing the state in which the metal core is set in the die for molding the molded portion and the synthetic resin material is charged therein.

FIG. 9 is a sectional diagram, corresponding with FIG. 8, showing a variant example.

FIG. 10 is a sectional diagram, corresponding with FIG. 8, showing another variant example.

DETAILED DESCRIPTION

—Structure of the Present Exemplary Embodiment—

FIG. 1 shows, in a front view, schematics of the overall structure of a seatbelt device 12 that employs a tongue for a seatbelt device 10 (hereinafter referred to simply as the “tongue 10”) according to an exemplary embodiment of the present invention.

As is shown in FIG. 1, the seatbelt device 12 is equipped with a webbing winding device 14, which serves as a webbing accommodation unit. The webbing winding device 14 is fixed to a vehicle body structuring a vehicle, at the lower end side of a center pillar of the vehicle. A spool, which is not shown in the drawings, is rotatably provided in the webbing winding device 14 to be turnable about an axis whose axial direction is in, for example, a front-and-rear direction of the vehicle. A length direction proximal end side of a webbing 16, which is formed in a long, narrow belt shape with flexibility, is anchored to the spool.

The length direction proximal end side of the webbing 16 is accommodated in a state of being wound round an outer periphery portion of the spool. A distal end side of the webbing 16 with respect to the spool is drawn out in the vehicle upward direction along the center pillar, passes through a shoulder anchor 18 which is provided at a vicinity of an upper end portion of the center pillar, and is folded back to the vehicle downward direction. A distal end of the webbing 16 that is folded back to the vehicle downward direction is anchored at an anchor 22, which is fixed to the vehicle body sideward of a vehicle seat 20.

The present exemplary embodiment has a structure in which the webbing winding device 14 and the anchor 22 are fixed to the vehicle body side. However, structures are possible in which the webbing winding device 14 is incorporated in a seatback 24 structuring the seat 20, and structures are possible in which the webbing winding device 14 is provided rearward of the seatback 24. Structures are also possible in which the anchor 22 is mounted to a member structuring a framework of the seat 20 or the like, rather than the vehicle body.

The tongue 10 according to the present exemplary embodiment is provided between the distal end of the webbing 16 (the portion that is anchored at the anchor 22) and the shoulder anchor 18. A buckle 26 corresponds with the tongue 10. The buckle 26 is fixed to a member that structures the vehicle body, the framework of the seat 20 or the like, at the opposite side of the seat 20 from the positions at which the webbing winding device 14 and the anchor 22 are disposed.

As is described in detail herebelow, the tongue 10 can be attached to the buckle 26. An occupant 30 sitting on a seat cushion 28 of the seat 20 unwinds the webbing 16 from the spool of the webbing winding device 14 and, in a state in which the webbing 16 is wrapped round the body of the occupant 30 from forward thereof, attaches the tongue 10 to the buckle 26, producing a state of application of the webbing 16 to the body of the occupant 30. In this state, the webbing 16 between the tongue 10 and the anchor 22 serves as a lap webbing 32 and restrains the pelvis area of the occupant 30 from forward thereof, and the webbing 16 between the shoulder anchor 18 and the tongue 10 serves as a shoulder webbing 34 and restrains the shoulder area and chest area or the like of the occupant 30 from forward thereof.

The seatbelt device 12 of the present exemplary embodiment is structured for use at a single-person seat 20, for example, a driver's seat or assistant driver's seat of a vehicle, but the present invention may be employed at a bench seat for plural people that is used at, for example, the rear seat of a vehicle or the like. When the present invention is employed at a bench seat, the webbing winding device 14, the anchor 22 and the like are provided at one seat width direction side relative to a sitting position of the occupant 30, and the buckle 26 is provided at the other side.

—Structure of the Tongue 10—

FIG. 2 shows schematics of the structure of the tongue 10 in a perspective view, FIG. 3 shows the tongue 10 in a side view, and FIG. 4 shows the tongue 10 in a plan view.

As shown in FIG. 2 and FIG. 3, the tongue 10 is provided with a metal core 42. The metal core 42 is formed by stamping of a metal plate followed by bending and forming. The metal core 42 is provided with an insertion portion 44. When the tongue 10 is attached to the buckle 26, the insertion portion 44 is inserted into the buckle 26 through an opening formed in the buckle 26. A through-hole 46 is formed in the insertion portion 44. When the insertion portion 44 is inserted into the buckle 26, a latch provided at the buckle 26 enters into the through-hole 46. If the insertion portion 44 acts to disengage from the buckle 26, the latch interferes with an inner periphery portion of the through-hole 46 and movement of the insertion portion 44 in the direction of disengagement from the buckle 26 is restricted. Thus, the tongue 10 is in a state of attachment to the buckle 26.

As shown in FIG. 5, a proximal end side of the metal core 42 relative to the insertion portion 44 (i.e., the opposite side of the tongue 10 from the direction of insertion when the tongue 10 is inserted into the buckle 26) serves as a metal core base 48. The metal core base portion 48 is provided with an angled plate portion 50. The angled plate portion 50 is formed in a plate shape whose thickness dimension is substantially equal to the thickness dimension of the insertion portion 44. However, the angled plate portion 50 is angled relative to the insertion portion 44 so as to displace to one side in the thickness direction of the metal core 42 as the proximal end side of the metal core 42 is approached from the insertion portion 44.

A flat plate portion 52 is formed continuously from the angled plate portion 50 at the opposite side thereof from the side at which the insertion portion 44 is provided. The flat plate portion 52 is formed in a plate shape whose thickness dimension is substantially equal to the thickness dimensions of the insertion portion 44 and the angled plate portion 50, and extends substantially in parallel with the insertion portion 44 from an end portion of the angled plate portion 50 at the opposite side thereof from the side at which the insertion portion 44 is provided. In other words, the metal core 42 is overall inflected in a crank shape with respect to the direction from the proximal end side to the distal end side (that is, the orientation when the insertion portion 44 is inserted into the buckle 26).

A penetrating hole 54 is formed in the angled plate portion 50 of the metal core base portion 48. The penetrating hole 54 penetrates in the thickness direction of the flat plate portion 52. An opening dimension of the penetrating hole 54 in a direction that is orthogonal to both the insertion direction and the thickness direction of the insertion portion 44 (hereinafter, this direction is referred to where appropriate as the “tongue width direction”) is set to be larger than a width dimension of the aforementioned webbing 16.

A molded portion 60 is formed at the metal core base portion 48. The molded portion 60 is formed by mold-forming, which is described below. The molded portion 60 covers the metal core base portion 48, including inner periphery portions of the penetrating hole 54. As shown in FIG. 5, a portion of the molded portion 60 that covers the inner periphery portion of the penetrating hole 54 serves as a webbing pass-through portion 62. The webbing 16 can pass through the inner side of the webbing pass-through portion 62. As is also shown in FIG. 5, one opening end 64 of the webbing pass-through portion 62 (corresponding to “one end of the webbing pass-through portion” in the claims) opens in a face of the molded portion 60 at one thickness direction side of the flat plate portion 52. Correspondingly, another opening end 66 of the webbing pass-through portion 62 (corresponding to “another end of the webbing pass-through portion” in the claims) is disposed at the other thickness direction side of the molded portion 60 relative to the flat plate portion 52 of the metal core base portion 48, and opens in an end portion at the opposite side of the molded portion 60 from the side thereof at which the insertion portion 44 is provided.

Accordingly, the webbing 16 that is drawn out from the spool of the webbing winding device 14 and folded back at the shoulder anchor 18 is inserted into the webbing pass-through portion 62 through the opening end 66, the webbing 16 emerges through the opening end 64 of the webbing pass-through portion 62, and the distal end side of the webbing 16 is anchored at the anchor 22.

Now, as shown in FIG. 4, a pair of groove portions 72 are formed in the molded portion 60. These groove portions 72 are formed next to one another in the tongue width direction between a region at the opening end 66 side of the webbing pass-through portion 62 and the flat plate portion 52 of the metal core base portion 48. As shown in FIG. 4 and FIG. 6, the groove portions 72 open in an inner periphery face of the webbing pass-through portion 62 at the opening end 66 side of the webbing pass-through portion 62, and open at the opposite side of the molded portion 60 from the side thereof at which the insertion portion 44 is provided.

—Method of Molding the Molded Portion 60—

Next, a method of molding the molded portion 60 is described.

As shown in FIG. 7 and FIG. 8, a die 90 is used for molding the molded portion 60. The die 90 includes a lower die 92 and an upper die 94. A close-fitting portion is formed in both the lower die 92 and the upper die 94. The insertion portion 44 of the metal core 42 fits into the close-fitting portion. Because of the insertion portion 44 of the metal core 42 being fitted into the close-fitting portion, the insertion portion 44 is not covered with a synthetic resin material that constitutes the molded portion 60.

A cavity 98 corresponding with the metal core base portion 48 is formed in each of the lower die 92 and the upper die 94. The molded portion 60 is formed by the synthetic resin material being charged into the cavity 98.

A slide hole 102 is formed in the upper die 94. An upper end of the slide hole 102 opens in an upper face of the upper die 94 (a face opposite to the side thereof at which the lower die 92 is disposed), and the lower end of the slide hole 102 opens in the cavity 98 at the lower die 92 side of the upper die 94. An opening shape of the slide hole 102 becomes gradually larger from the lower end side toward the upper end side. A slide die 100 is fitted into the inside of the slide hole 102.

In the state in which the slide die 100 is fitted into the slide hole 102, a distal end of the slide die 100 protrudes to inside the cavity 98 from the lower end of the slide hole 102. The distal end side of the slide die 100 protruding to the inside of the cavity 98 enters into the penetrating hole 54 of the metal core base portion 48. In accordance with the distal end side of this slide die 100, the inner periphery portion of the penetrating hole 54 is covered by the molded portion 60, and the webbing pass-through portion 62 is formed with the opening end 64 opening in the molded portion 60 at the one thickness direction side of the flat plate portion 52.

The slide die 100 is slidable toward the upper end side of the slide hole 102 (that is, upward and rightward in FIG. 7 and FIG. 8). Thus, the opening end 64 side of the webbing pass-through portion 62, which is an undercut, may be formed.

A slide die 112 is also provided inside the die 90. A distal end side of the slide die 112 is interposed between the cavity 98 of the lower die 92 and the metal core base portion 48. The distal end abuts against the distal end of the above-described slide die 100. When the synthetic resin material is charged into the die 90, the synthetic resin material is not charged into the region of the slide die 112. Thus, a region of the webbing pass-through portion 62 at the other thickness direction side of the flat plate portion 52 relative to the metal core base portion 48 is formed, and this region connects with the region of the webbing pass-through portion 62 that is formed by the distal end of the above-described slide die 100. The slide die 112 is slidable toward the opening end 66 side of the webbing pass-through portion 62 (that is, leftward in FIG. 7 and FIG. 8). Thus, the opening end 66 side of the webbing pass-through portion 62, which is an undercut, may be formed.

As shown in FIG. 8, a pair of protrusions 114 are formed at a face of the slide die 112 at the side thereof opposing the flat plate portion 52. These protrusions 114 are formed in block shapes, and the protrusions 114 touch against the flat plate portion 52 in a region in which the slide die 112 opposes the flat plate portion 52. Hence, the aforementioned groove portions 72 are formed. A structure in which the flat plate portion 52 is exposed in the groove portions 72 (i.e., a structure in which the flat plate portion 52 is not covered with the synthetic resin material at the inner sides of the groove portions 72) is possible, and a structure in which the synthetic resin material enters in between the protrusions 114 and the flat plate portion 52 and some or all of the flat plate portion 52 at the inner sides of the groove portions 72 is covered with the synthetic resin material is also possible.

—Operation and Effects of the Present Exemplary Embodiment—

In the tongue 10 in which the molded portion 60 is molded as described above, the groove portions 72 are formed between the flat plate portion 52 of the metal core base portion 48 and the webbing pass-through portion 62. According to this structure, the protrusions 114 that are formed at the slide die 112 for forming the groove portions 72 abut against the flat plate portion 52 of the metal core base portion 48 from the lower die 92 side thereof, and the protrusions 114 may support the metal core base portion 48 when the molded portion 60 is being molded. Thus, the metal core 42 may be kept stable when the molded portion 60 is being molded, and the molded portion 60 may be molded with high quality.

The synthetic resin material is charged between the slide die 112 and the flat plate portion 52 of the metal core base portion 48 and forms the molded portion 60 at both tongue width direction sides of the protrusions 114. Therefore, the webbing 16 may be prevented from abutting against the metal core base portion 48 at the inside of the webbing pass-through portion 62.

Furthermore, the metal core base portion 48 may be completely covered with the molded portion 60 even with the webbing 16 being prevented from abutting against the metal core base portion 48. Therefore, there is no need to form an opening or the like in the molded portion 60 at the other thickness direction side of the metal core base portion 48 in order to separately provide a structure for supporting the metal core 42, a member for closing off such an opening is unnecessary, and costs may be reduced.

The present exemplary embodiment has a structure in which a pair (that is, two) of the protrusions 114 are formed at the slide die 112. However, it is sufficient that these protrusions 114 be a structure that can support the metal core base portion 48 in a state in which a main body portion of the slide die 112 (a portion excluding the protrusions 114) is separated from the flat plate portion 52, and the protrusions 114 are in no way limited in regard to number. There may be one of the protrusions 114, or there may be three or more.

The present exemplary embodiment has a structure in which the flat plate portion 52 (the metal core 42) is supported from the lower die 92 side thereof by the protrusions 114 formed at the slide die 112. As shown in FIG. 9, a structure is possible in which a support piece 116, which serves as an upper side retention body, extends from the slide die 112 toward a face of the flat plate portion 52 at the opposite side thereof from the side at which the protrusions 114 are disposed, and the metal core 42 is retained such that the flat plate portion 52 is sandwiched by the support piece 116 and the protrusions 114.

Further, instead of the support piece 116 extending from the slide die 112 as shown in FIG. 9, as shown in FIG. 10, a structure is possible in which one or a plural number of retention pins 118, which serve as the upper side retention body, is/are formed in the cavity 98 at the upper die 94, toward the flat plate portion 52 side and toward the lower die 92 side. The metal core 42 is retained such that the flat plate portion 52 is sandwiched by the retention pins 118 and the protrusions 114.

Claims

1. A tongue for a seatbelt device, comprising:

a metal core at which an insertion portion is formed continuously from a metal core base portion in which a penetrating hole through which a webbing passes is formed, the insertion portion being insertable into a buckle, and the penetrating hole penetrating in a thickness direction of the metal core base portion;

a molded portion that is formed by the metal core base portion of the metal core being covered with a synthetic resin material at surroundings of the penetrating hole;

a webbing pass-through portion through which the webbing passes, one end of the webbing pass-through portion opening along the thickness direction of the metal core base portion in one face of the molded portion, another end of the webbing pass-through portion opening in an end portion of the molded portion at a side opposite to the insertion portion, and the webbing passing through the inside of the penetrating hole at a penetration direction intermediate portion of the webbing pass-through portion; and

a groove portion formed between the metal core base portion and the webbing pass-through portion, the groove portion opening in the end portion of the molded portion at the side opposite to the insertion portion and opening in an inner periphery face of the webbing pass-through portion.

2. A method for fabricating a tongue for a seatbelt device, comprising:

covering a metal core base portion of a metal core with a synthetic resin material and forming a molded portion, at which metal core an insertion portion is formed continuously from the metal core base portion, the insertion portion being insertable into a buckle, and a penetrating hole through which a webbing passes being formed in the metal core base portion, the penetrating hole penetrating in a thickness direction of the metal core base portion;

during the forming of the molded portion, forming a webbing pass-through portion through which the webbing passes, by causing a core to enter the penetrating hole from one thickness direction side of the metal core base portion and providing a slide die at the other thickness direction side of the metal core base portion, one end of the webbing pass-through portion opening in one face of the molded portion at the one thickness direction side of the metal core base portion and another end of the webbing pass-through portion opening in an end portion of the molded portion at a side opposite to the insertion portion; and,

during the forming of the molded portion, supporting the metal core base portion with a protrusion that protrudes from a surface at the metal core base portion side of the slide die, and forming a groove portion that opens in the end portion of the molded portion at the side opposite to the insertion portion.