Fastener

There is provided a fastener which can be brought into firm engagement with a mounting hole without being affected by a change in thickness of a member in which the mounting hole is provided or a larger or smaller inside diameter of the mounting hole. This fastener 1 includes a pin 10, a metal plate spring member 30 and a grommet 50. The plate spring member 30 has a base portion 31 and a pair of elastic engagement pieces 35, 35 which are opened in their free state and which are closed when pressed against their elastic restoring force. The elastic engagement pieces 35 have engagement shoulder portions 37 which are brought into engagement with the mounting hole, and distal ends thereof are folded to constitute folded portions 40. The folded portions 40 are offset widthwise from each other, and engagement projecting pieces 43 are formed on inner sides thereof. Abutment pieces 45 are formed on the folded portions 40 in positions lying closer to the base portion 31 with which a distal end portion 15 of the pin 10 is brought into abutment to impart a driving force thereto. Abutment portions 45a are formed on the abutment pieces 45 which convert the driving force applied along an inserting direction of the pin 10 into a driving force applied widthwise outwards of the abutment pieces 45.

TECHNICAL FIELD

The present invention relates to a fastener, for example, which is inserted into a mounting hole formed in a body panel of a motor vehicle to be fixed therein.

BACKGROUND ART

For example, a fastener is used in mounting a mounting-subject member such as a trim board on a mount-base member such as a body panel of a motor vehicle.

As a conventional fastener of this type, Patent Document 1 discloses a clip including a synthetic-resin pin, a metal plate spring member which receives the pin to fix a mounting-subject member to a mount-base member securely and a synthetic-resin grommet. The plate spring member is made up of a receiving portion having a through hole for the pin and a pair of leg portions. The pair of leg portions are folded back inwards at ends thereof so as to be expanded in accordance with an insertion of the pin between the leg portions. The grommet has a main body portion, which accommodates the plate spring member. At an upper end of the main body portion, an expandable portion, which is configured to follow an expansion of the leg portions, is formed.

Then, the pair of leg portions of the plate spring member are expanded by inserting the pin through the through hole in the plate spring member, inserting the clip through mounting holes formed in the mounting-subject member and the mount-base member with the plate spring member fitted in the main body portion of the grommet, and press fitting the pin. Then, the expandable portion of the main body portion of the grommet is expanded to be brought into engagement with circumferential edges of the mounting holes, whereby both the members are fixedly held together via the clip.

RELATED ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In the clip of Patent Document 1, since the pair of leg portions of the spring member are expanded by pushing in the pin, the leg portions of the spring member cannot be expanded wider than an outside diameter of the pin, and an expandable width of the pair of leg portions is constant. As a result, an expandable width of the expandable portion of the grommet which is expanded by the pair of leg portions is also constant.

Because of this, in case the thickness of the mounting-subject member such as a trim board is reduced with time in a fixed state using the clip, a gap may be produced between the circumferential surfaces of the mounting holes and the clip, and the clip may be loosened.

In addition, in the clip, since the expandable width of the expandable portion of the grommet is determined by the outside diameter of the pin, in case the inside diameter of the mounting hole is larger than its standard size or the thickness of the mounting-subject member is thinner than its standard thickness due to dimensional errors, for example, the clip may be loosened relative to the mounting hole.

Consequently, an object of the invention is to provide a fastener which can be brought into secure engagement with a mounting hole without being affected by a change in thickness of a member in which the mounting hole is provided or irregularity in inside diameter of the mounting hole.

Means for Solving the Problem

With a view to attaining the object, the invention provides a fastener having a pin and a metal plate spring member which receives the pin and adapted to be fixed in a mounting hole, wherein the plate spring member has a base portion adapted to be brought into an engagement with a front side of the mounting hole and having an insertion hole through which the pin is inserted and a pair of elastic engagement pieces engageable with each other by being pressed against their elastic restoring force to be closed, the pair of elastic engagement pieces having engagement shoulder portions formed at axially intermediate positions thereof to engage with a circumferential edge of a back side of the mounting hole with the elastic restoring force when expanded and to pass through the mounting hole when contracted, and the pin has a head portion and a shaft portion extended from the head portion, the shaft portion releasing an engagement of the pair of elastic engagement pieces to allow them to be expanded by being inserted into between the pair of elastic engagement pieces in a closed state and restricting the pair of elastic engagement pieces from contracting inwards by being disposed between the pair of engagement pieces in an opened state.

In the invention, preferably, respective distal ends of the pair of elastic engagement pieces are folded inwards to constitute folded portions, the folded portions are offset widthwise from each other, and an engagement projecting piece is formed on one or both inner sides of the folded portions which are adjacent widthwise to each other, whereby when the elastic engagement pieces are closed, one of the engagement projecting pieces is brought into engagement with the other inner side or the other engagement projecting piece so as to hold the elastic engagement pieces in the closed state. Preferably, abutment pieces are formed on the folded portions in positions lying closer to proximal portions thereof than the engagement projecting pieces with which a distal end portion of the pin is brought into abutment to thereby apply a driving force thereto when the pin is inserted with the elastic engagement pieces in the closed state, and abutment portions are formed individually on the abutment pieces which convert the driving force exerted in the inserting direction of the pin into a driving force exerted widthwise outwards of the abutment pieces, whereby when inserted between the elastic engagement pieces in the closed state, the shaft portion of the pin is brought into abutment with the abutment pieces at a distal end portion thereof.

In the invention, preferably, the respective abutment pieces of the folded portions are folded so that distal end portions thereof approach back surface sides of the elastic engagement pieces. Preferably, Inner sides of the abutment pieces which lie adjacent widthwise to each other are caused to slope widthwise outwards so that the inner sides extend apart from each other towards distal ends thereof, the sloping inner sides constituting the abutment portions, and the distal end portion of the shaft portion of the pin has a tapered shape to be brought into abutment with the sloping inner sides of the abutment pieces when the pin is driven.

In the invention, preferably, a constricted portion is formed in the shaft portion of the pin in which the folded portions of the plate spring member fit when the pin is driven until the head portion of the pin is brought into engagement with a circumferential edge of the insertion hole in the plate spring member.

In the invention, preferably, in the base portion of the plate spring member, a pair of narrow portions are formed on an outer circumference of the insertion hole between the pair of elastic engagement pieces to face each other, so that the base portion is bendable at the pair of narrow portions to deflect the pair of elastic engagement pieces.

In the invention, preferably, the narrow portions formed in the base portion of the plate spring member are disposed at both side portions of the base portion which lie at right angles to the deflecting direction of the pair of elastic engagement pieces in positions which lie eccentric towards widthwise portions of the elastic engagement pieces where the folded portions are not formed when the base portion is viewed in an axial direction.

In the invention, preferably, expanded portions are formed on the shaft portion of the pin which are brought into abutment with portions of the pair of elastic engagement pieces which lie closer to proximal portions than the engagement shoulder portions but are not brought into abutment with portions which lie closer to distal ends than the engagement shoulder portions when the shaft portion of the pin is disposed between the pair of elastic engagement pieces.

In the invention, preferably, the fastener further has a grommet in addition to the pin and the plate spring member, and the grommet has a base portion adapted to be brought into engagement with a circumferential edge of the front side of the mounting hole and a leg portion which extends from a back surface side of the base portion, an insertion opening is provided in the base portion through which the pair of elastic engagement pieces of the plate spring member and the shaft portion of the pin are inserted, a holding unit is provided between the base portion and the shaft portion of the pin which temporarily holds the pin which is inserted into the plate spring member through the insertion hole in a position where no driving force is applied to the abutment pieces, and disengagement prevention claws are provided on the pair of elastic engagement pieces of the plate spring member in positions which lie closer to the proximal portions than the engagement shoulder portions which are brought into engagement with a circumferential edge of a back side of the insertion opening in the base portion, whereby by the disengagement prevention claws being brought into engagement with the circumferential edge of the back side of the insertion opening in the base portion, the plate spring member is held in the grommet, and the pin is temporarily held in the grommet by the holding unit in that state.

In the invention, preferably, provided on the shaft portion of the pin are a temporary holding portion which temporarily holds the pin in the grommet in a position where no driving force is applied to the abutment pieces of the plate spring member and a fixing portion which fixed the pin in the grommet when the pin is driven until the head portion thereof is brought into engagement with the circumferential edge of the insertion hole in the plate spring member.

In an aspect of the invention, preferably, the leg portion of the grommet has a pair of leg portions which are disposed in a direction which is at right angles to the deflecting direction of the pair of elastic engagement pieces of the plate spring member held in the grommet.

In another aspect of the invention, preferably, the leg portion of the grommet has a pair of leg portions which are disposed in the deflecting direction of the pair of elastic engagement pieces and outside of the pair of elastic engagement pieces.

In the other aspect of the invention, more preferably, the pair of leg portions of the grommet are connected together at distal ends thereof and tapered towards the distal ends.

In the other aspect of the invention, preferably, a guide leg portion having a engagement groove extending along an axial direction is formed in a position lying at right angles to the pair of leg portions, and a pair of projecting portions are formed on the shaft portion of the pin which are brought into engagement with an inner circumference of the engagement groove at both end portions when the pin is driven until the head portion of the pin is brought into engagement with the circumferential edge of the insertion hole in the plate spring member.

Advantage of the Invention

According to the invention, by pressing the pair of elastic engagement pieces which are opened in their free state so as to be closed inwards against their elastic restoring force and bringing them into engagement with each other in that state, the engagement shoulder portions are prevented from being caught at the mounting hole or the elastic engagement pieces are prevented from being pressed strongly against the inner circumference of the mounting hole when the engagement shoulder portions pass through the mounting hole, whereby the inserting resistance is reduced, enabling the plate spring member to be inserted into the mounting hole smoothly.

Then, after the pair of elastic engagement pieces are inserted into the mounting hole and the base portion of the plate spring member is brought into engagement with the front side of the mounting hole, the shaft portion of the pin which is inserted from the insertion hole in the base portion is driven thereinto, whereby the engagement of the elastic engagement pieces is released, and the elastic engagement pieces are expanded by their elastic restoring force, and the engagement shoulder portions are then brought into engagement with the circumferential edge of the back side of the mounting hole, whereby the fastener can be fixed in the mounting hole.

As this occurs, since the elastic engagement pieces of the plate spring member are brought into engagement with the circumferential edge of the back side of the mounting hole with the elastic restoring force, even in the event that the thickness of the member in which the mounting hole is formed changes or the inside diameter of the mounting hole is larger or smaller than its standard dimension, the pair of elastic engagement pieces are expanded or contracted diametrically so as to keep the engagement shoulder portions in engagement with the circumferential edge of the back side of the mounting portions, thereby mounting the fastener in the mounting hole without any looseness.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of a fastener according to the invention will be described by reference to the drawings. As shown inFIGS. 1,8A and8B, this fastener1is used, for example, to mount a mounting-subject member4such as a trim board on a mount-base member2such as a body panel via the fastener1by being inserted and fixed in a mounting hole3formed in the mount-base member2.

As shown inFIG. 1, the fastener1in this embodiment has a pin10, a metal plate spring member30which receives the pin10and a grommet50which holds both the pin10and the plate spring member30.

Firstly, referring toFIGS. 2A to 3Cand6to10C, the plate spring member30will be described. This plate spring member30is formed of a single metal plate and has a base portion31and a pair of elastic engagement pieces35,35which extend from the base portion31and which are left open in their free state and are closed when pressed against their elastic restoring force to be brought into engagement with each other.

As shown inFIG. 3C, the base portion31has a circular shape as a whole, and a circular insertion hole31ais formed in a center thereof for the pin10to be inserted therethrough. A pair of notches31b,31bare formed in an inner circumference of the insertion hole31ain positions which intersect the pair of elastic engagement pieces35,35at right angles. A pair of narrow portions31c,31care formed in facing positions on an outer circumference of the insertion hole31ain the base portion31by the notches31b, whereby the base portion31is bendable at the pair of narrow portions31c,31cto deflect the pair of elastic engagement pieces35,35(refer toFIG. 2B).

Strip-shaped pieces of a predetermined width protrude from both side portions of the base portion31which lie at right angles to the notches31b,31b, and these strip-shaped pieces are then folded back inwards, so as to form bent portions33,33which are each bent into a substantially U-shape as viewed from side. Respective proximal end portions of the elastic engagement pieces35are connected to the bent portions33,33. The U-shaped bent portions33function to increase the elastic restoring force of the elastic engagement pieces35,35which are connected thereto.

The proximal end portions of the pair of elastic engagement pieces35,35extend from the U-shaped bent portions33so as to rise at a predetermined angle with respect to the base portion31, and disengagement prevention claws36,36are cut to rise outwards in both widthwise sides of the proximal end portions. The disengagement prevention claws36,36are brought into engagement with a circumferential edge of a back side of an insertion opening53in the grommet50, which will be described later, so as to prevent the disengagement of the plate spring member30(refer toFIGS. 7A to 9B).

Axially intermediate portions of both the elastic engagement portions35,35are bent obliquely outwards so as to be spaced away from each other to thereby constitute engagement shoulder portions37which are brought into engagement with a circumferential edge of a back side of the mounting hole3when the elastic engagement pieces35,35are opened and which pass through the mounting hole3when the elastic engagement pieces35,35are closed. The engagement shoulder portion37has a circular arc shape with a convexly curved surface oriented radially outwards so as to match the circular mounting hole3(refer toFIGS. 2A,2B,3B,3C).

Respective distal end portions of the elastic engagement pieces35,35are folded inwards so as to constitute folded portions40,40, and further, as shown inFIGS. 3B,3C, the folded portions40,40are formed so as to be offset from each other in a width direction thereof, so that both the folded portions40,40are prevented from interfering with each other when the pair of elastic engagement pieces35,35are made to approach each other to thereby be closed.

Engagement projecting pieces43,43are provided on inner sides of the folded portions40which lie adjacent to each other in the width direction so as to project towards the other adjacent folded portion40. Each engagement projecting piece43is formed in a position where it is superposed on the other engagement projecting piece43when the elastic engagement pieces35,35are closed. Then, when the elastic engagement pieces35,35are closed, as shown inFIG. 2B, the engagement projecting pieces43,43are brought into engagement with each other so as to hold the elastic engagement pieces35,35in the closed state.

Note that the engagement projecting piece43may be formed only on one of the folded portions40. In this case, when the elastic engagement pieces35,35are closed, the engagement projecting piece43on the one folded portion40is brought into engagement with a back surface of the inner side of the other folded portion40(an opposite side to a facing surface of the one folded portion40), whereby the elastic engagement pieces35,35are closed.

An abutment portion45is formed on each folded portion40at a portion thereof which extends further towards the base portion31than the engagement projecting piece43(at distal end portion of the folded portion40) to receive a driving force from a distal end portion15(which will be described later) of the pin10through an abutment therewith when the pin10is inserted while the elastic engagement pieces35,35are closed. In the case of this embodiment, the abutment piece45is formed to be bent into a “collapsed V-shape” as viewed from a side thereof so that a distal end portion of the folded portion40is directed towards a back surface of the elastic engagement piece35from which the folded portion40extends.

An abutment portion is formed on each abutment piece45which changes the direction of the driving force from the inserting direction of the pin10to a widthwise outward direction of the abutment piece45. In this embodiment, the inner sides of the abutment pieces45which lie adjacent widthwise to each other are each made into a sloping inner side which extends widthwise outwards while gradually sloping towards the base portion31of the plate spring member30, and this sloping inner side constitutes the abutment portion45a(refer toFIGS. 2A and 2Band10A to10C). These abutment portions45a,45aare designed to be brought into abutment with an outer circumferential surface of the conical-shaped distal end portion15of the pin10while the elastic engagement pieces35,35are closed (refer toFIG. 6).

Next, referring toFIGS. 4A to 4Cand6to9B, the pin10, which is received in the above-described plate spring member30, will be described. This pin10has a circular head portion11and a shaft portion13which extends a predetermined length from a center of one surface of the head portion11, which is inserted into between the elastic engagement pieces35,35which are closed to release the engagement of the elastic engagement pieces35,35and to expand them, and which is then disposed between the elastic engagement pieces35,35which are opened to restrict them from contracting inwards. A distal end portion of this shaft portion13has a taper shape so as to be brought into abutment with the sloping inner sides of the abutment pieces45when the pin is driven into the plate spring member30. The shaft portion13of this embodiment has a substantially cylindrical shape and the distal end portion15thereof has a substantially conical shape. Then, as shown inFIG. 6, the distal end portion15of the shaft portion13is designed to be brought into abutment with the respective abutment portions45a, which are each formed into a sloping surface, of the abutment pieces45of the elastic engagement pieces35,35in a closed state.

Guide ribs17,17of a predetermined height extend along an axial direction at a proximal portion of the shaft portion13at two circumferentially-opposed locations. These guide ribs17,17fit individually in slits56(which will be described later) in the grommet50when the pin10is driven into the grommet50so as to guide driving of the pin10. A constricted portion19is formed in a position of the shaft portion13which lies closer to the proximal portion than the distal end portion15in which the folded portions40of the plate spring member30fit when the pin is driven into the plate spring member30until the head portion11of the pin10is brought into engagement with a circumferential edge of the insertion hole31ain the plate spring member30. An inner surface of a distal end portion of the constricted portion19is formed into a reversely tapered surface19awhich diametrically gradually expands towards the distal end portion15, whereas an inner surface of a proximal end portion is formed into a tapered surface19bwhich diametrically gradually contracts towards the distal end portion15.

Plate-shaped pieces21,21are provided on an inner circumferential surface of the constricted portion19in positions which are aligned with the guide ribs17,17so as to project therefrom. A deflectable piece25is provided to connect to a distal end of the guide rib17and a distal end of the plate-shaped piece21via a cutout hole23so as to bridge them while being allowed to be deflected. An engagement projecting portion25ais provided at a proximal end portion of the deflectable piece25, while an engagement claw portion25bis provided at a distal end portion thereof.

The engagement projecting portion25aand the engagement claw portion25bare disposed so as to be brought into engagement with an upper edge portion and a lower edge portion of a base portion51of the grommet50, respectively, as shown inFIG. 7B, when the pin10is driven halfway downwards into the grommet50so as to hold the pin10securely against while preventing the disengagement of the pin10from the grommet50. As this occurs, the pin10is temporarily held in a position where the pin10does not apply a driving force to the abutment pieces45of the plate spring member30. Namely, in this embodiment, the engagement projecting piece25aand the engagement claw portion25bof the pin10and the base portion51of the grommet50constitute the holding unit of the invention.

Portions on an outer circumferential surface of the shaft portion13which face inner surfaces of the deflectable pieces25are cut to flat planes which intersect the projecting direction of the guide ribs17at right angles to thereby be formed into pressing surfaces27(refer toFIGS. 4A to 4C).

Next, the grommet50which holds the pin10and the plate spring member30will be described by reference toFIGS. 1,5A,5B. This grommet50has the base portion51having a disk shape and a pair of leg portions55,55which extend from a rear surface side of the base portion51. An annular wall52projects from an outer circumference of an upper end of the base portion51, and a circular insertion opening53is formed in a center of the base portion51through which the shaft portion13of the pin10and the elastic engagement pieces35of the plate spring member30are inserted. Fitting recess portions54of a predetermined width are formed in an upper surface of the base portion51so as to extend through the center of the insertion opening53, in which the bent portions33,33of the plate spring member30are fitted to thereby prevent the rotation of the plate spring member30relative to the grommet50.

As shown inFIG. 1, the pair of leg portions55are disposed in a direction which intersects at right angles the deflecting direction of the pair of elastic engagement pieces35,35of the plate spring member30which is held in the grommet50. A slit56is formed in each leg portion55so as to extend along the extending direction of the leg portion55. Each leg portion55is made up of guide pieces57,57which result by dividing the leg portion55into two via the slit56. A projecting portion58is provided on an inner side of each guide piece57so as to project inwards, and an outer circumference of a distal end of the guide piece57is shaped so as to be constricted gradually towards the distal end.

Next, a using method of the above-described fastener1will be described.

As has been described heretofore, in a free state in which no external force is applied thereto, the pair of elastic guide pieces of the plate spring member30which makes up the fastener1are spaced away from each other to thereby be opened (refer toFIG. 2A). From this state, the pair of elastic engagement pieces35,35are pressed inwards against their restoring force so that both the elastic engagement pieces35,35are closed.

As this occurs, since the respective engagement projecting pieces43,43of the folded portions40are aligned with each other, one engagement projecting piece43is brought into engagement with the rear surface side of the other engagement projecting piece43(the opposite side to the facing surface of the one engagement projecting piece43) by causing both the elastic engagement pieces35,35to approach each other while offsetting the folded portions40,40to be spaced away widthwise from each other, whereby the elastic engagement pieces35,35can be held in the closed state (refer toFIG. 2B). When the engagement projecting piece43is formed only on one of the folded portions40, the pair of elastic engagement pieces35,35can be held in the closed state by bringing the engagement projecting piece43on the one folded portion40into engagement with the rear surface of the inner side of the other folded portion40(the opposite side to the facing surface of the one folded portion40).

In this embodiment, in the base portion31of the plate spring member30, the pair of narrow portions31c,31are formed on the outer circumference of the insertion hole31abetween the pair of elastic projecting pieces35,35to face each other. As a result, since the base portion31is bendable at the pair of narrow portions31c,31cas shown inFIG. 2Bwhen the elastic engagement pieces35,35are deflected, the elastic engagement pieces35,35are allowed to be deflected easily, whereby not only can the workability in bringing the elastic engagement pieces35,35into engagement with each other be increased, but also a releasing action can be performed smoothly when the engagement between the elastic engagement pieces35,35is released by driving the pin10into therebetween.

Next, the bent portions33,33of the plate spring member30are aligned with the fitting recess portions54,54of the grommet50, and the elastic engagement pieces35,35of the plate spring member30are driven into the insertion opening53in the grommet50. Then, the elastic engagement pieces35,35in the closed state are inserted between the leg portions55,55of the grommet50. When the plate spring member30is driven into the grommet50completely, the U-shaped bent portions33,33fit in the fitting recess portions54,54so as to prevent the rotation of the bent portions33,33relative to the grommet50, and as shown inFIG. 6, the disengagement prevention claws36,36provided on the elastic engagement piece35are brought into engagement with the circumferential edge of the rear surface of the insertion opening53, whereby the plate spring member30is held in the grommet50.

In this state, when the plate spring member30is held in the grommet50, the pair of leg portions55,55of the grommet50are disposed on both the sides of the pair of elastic engagement pieces35,35, as a result, since the pin10is restricted from moving in the direction which intersects the deflecting direction of the elastic engagement pieces35at right angles, the distal end portion15of the pin10can be surely pressed against the abutment pieces45,45of the plate spring member30.

Next, the pin10is temporarily held in the grommet50. Namely, the guide ribs17,17of the pin10are aligned with the slits56,56of the grommet50and the notches31b,31bof the plate spring member30, and the pin is driven halfway downwards into the grommet50through the insertion opening53in the grommet50. As a result, the engagement projecting pieces25aand engagement claw portions25bare brought into engagement with the upper and lower edge portions of the base portion51, whereby the pin10is held in the grommet50while being prevented from being disengaged therefrom (refer toFIG. 7B). As this occurs, as shown inFIGS. 6 and 7A, the distal end portion15of the pin10holds the elastic engagement pieces35,35in the closed state without applying any driving force to the abutment pieces45.

In this embodiment, as described above, by driving the elastic engagement pieces35,35in the closed state through the insertion opening53in the grommet50, the plate spring member30can be held in the grommet50while being prevented from being disengaged therefrom, and by driving the pin10into the plate spring member30and the grommet50through the insertion hole31ain the plate spring member10and the insertion opening53in the grommet50, the pin10can be held in the grommet50in the position where the elastic engagement pieces35are not opened by the holding unit (the engagement projecting portions25aand the engagement claw portions25bof the pin10and the base portion51of the grommet50). In this way, since the fastener1includes not only the pin10and the plate spring member30but also the grommet50which holds both the pin10and the plate spring member30, the plate spring member30and the pin10can be assembled together in advance, thereby enhancing the workability in fixing the fastener1in the mounting hole3.

Then, a mounting hole5in the mounting-subject member4is aligned with the mounting hole3in the mount-base member2(refer to (FIGS. 7A and 7B), and a distal end portion of the assembled fastener1is inserted from the mounting hole5. Then, the base portion51of the grommet50is brought into abutment with a circumferential edge of a front side of the mounting hole5, and the distal end portions of the elastic engagement pieces35of the plate spring member30and the leg portions55of the grommet50are caused to project from the mounting hole3.

In this embodiment, since the pair of leg portions55,55of the grommet50constitute insertion guides when the fastener1is inserted into the mounting hole5and the mounting hole3, the insertion capability of the fastener1can be enhanced. Further, since each leg portion55is made up of the guide pieces57,57which result from dividing the leg portion into two and is hence highly flexible, the insertion resistance can be reduced while maintaining the guiding performance of the fastener1.

In this embodiment, by closing the pair of elastic engagement pieces35,35which are left open in their free state against their elastic restoring force and bring the elastic engagement pieces35,35into engagement with each other in the closed state, the engagement shoulder portions37are prevented from being caught by the mounting hole3when the engagement shoulder portions pass through the mounting hole3, and the elastic engagement pieces35are prevented from being driven through the mounting hole3while being pressed strongly against the inner circumference of the mounting hole, whereby the fastener1can be inserted through the mounting hole1smoothly while reducing the insertion resistance.

Then, the pin10is driven into the plate spring member30to open the pair of elastic engagement pieces35,35in the closed state. In this embodiment, since the respective abutment portions45aof the abutment pieces45are each formed into the sloping surface and the distal end portion15of the shaft portion13of the pin10is formed into the conical shape, when the pin10is driven into the plate spring member30, the conical distal end portion15of the pin10is brought into abutment with the abutment portions45aof the abutment pieces45which constitute the inner sides thereof, whereby the pin10is driven into the plate spring member30while the abutment portions45aof the abutment pieces45and the conical surface of the distal end portion15of the pin10are brought into sliding contact with each other.

As this occurs, the driving force F1(refer toFIG. 6) for driving the pin10is converted into a driving force which drives the abutment pieces45widthwise outwards by the abutment portions45aof the abutment pieces45. To describe this in greater detail by reference toFIGS. 6 and 10Ato10C, as shown inFIG. 6, the abutment pieces45,45of the plate spring member30which are bent at a predetermined angle strike against an outer circumference of the conical distal end portion15of the pin10. Then, when the pin10is driven further, the conical distal end portion15are driven between the abutment portions45aprovided on the abutment pieces45as the sloping surfaces while brought into sliding contact therewith, whereby the driving force F1is converted into driving forces F2, F2which drive the abutment pieces45widthwise outwards, as shown inFIG. 10A.

As a result, as shown inFIG. 10B, the engagement between the engagement projecting pieces43,43is released, whereby the engagement projecting pieces43,43are expanded by the elastic restoring force (refer to arrows in the figure) itself. Then, as shown inFIG. 10B, the pin10enters between the elastic engagement pieces35,35.

As a result, as shown inFIG. 8A, the respective engagement shoulders37,37of the elastic engagement pieces35are brought into engagement with the circumferential edge of the rear side of the mounting hole3in the mount-base member2, and the base portion51of the grommet50is brought into the circumferential edge of the front side of the mounting hole5in the mounting-subject member4, whereby the mount-base member2and the mounting-subject member4are held by the engagement shoulders37,37and the base portion51, thereby mounting the mounting-subject member4on the mount-base member2. As this occurs, since the shaft portion13of the pin10is disposed between the pair of elastic engagement pieces35,35, the elastic engagement pieces35,35are restricted from being deflected inwards, whereby the disengagement of the plate spring member30from the mounting hole3is prevented.

In this embodiment, by driving the shaft portion13of the pin10towards the bent portions40of the elastic engagement pieces35, as described above, the distal end portion15is brought into abutment with the abutment pieces45of the folded portions40to thereby apply the driving force to the abutment pieces45of the folded portions40. Then, the driving force is converted into the driving forces which drives the abutment pieces45widthwise outwards by the abutment portions45a, whereby the pair of elastic engagement pieces35,35can be offset widthwise from each other so as to release the engagement therebetween. Therefore, the engagement of the pair of elastic engagement pieces35,35in the closed state can be released smoothly by the simple operation of driving the pin10, thereby enhancing the workability in mounting the fastener1.

When the pin10is driven into the grommet50, the pressing surfaces27provided on the shaft portion13are brought into abutment with the projecting portions58of the guide pieces57, whereby both the leg portions55,55are forced to be expanded from inside, thereby further enhancing the disengagement prevention force.

In this embodiment, the constricted portion19is formed in the shaft portion13of the pin10in which the folded portions40of the plate spring member30fit when the head portion11of the pin10is pushed in until the head portion11is brought into engagement with the circumferential edge of the insertion hole31in the plate spring member30. Namely, since the folded portions40are allowed to fit in the constricted portion19, as shown inFIG. 8A, by bent corner portions of the flexed portions40being brought into engagement with the reversely tapered surface19aand the abutment pieces45of the folded portions40being brought into engagement with the tapered surface19bin such a state that the fastener1is fixed in the mounting holes, the disengagement of the pin10from the plate spring member30can be surely prevented.

Since the pair of elastic engagement pieces35,35of the plate spring member30which makes up the fastener1are expanded in their free state and are brought into engagement with the circumferential edge of the back side of the mounting hole by their restoring force, even in the event that the thickness of the mount-base member2in which the mounting hole3is formed changes or the inside diameter of the mounting hole3is larger or smaller than its standard dimension, the pair of elastic engagement pieces35,35are flexible enough to be opened or closed elastically so as to expand or reduce a space therebetween to maintain the engagement shoulder portions37,37in such a state that the engagement shoulder portions37,37are surely kept in press contact with the circumferential edge of the back side of the mounting hole3for engagement, as a result, the fastener1can be fixed firmly in the mounting hole3without any looseness.

In this embodiment, the respective abutment portions45aof the abutment pieces45are formed into the sloping inner sides and the distal end portion15of the shaft portion13of the pin10is formed into the tapered shape (here, the conical shape). Because of this, when the pin10is driven into the plate spring member30from the insertion hole31therein with the pair of elastic engagement pieces35,35inserted in the mounting holes3,5, since the conical distal end portion15slides along the abutment portions45aconfigured as the sloping surfaces while in contact therewith, the driving force F1driving the pin10(refer toFIG. 6) can be converted into the driving forces F2which drive the abutment pieces45widthwise outwards (refer toFIG. 10A) with good efficiency, whereby the releasing work of the engagement between the pair of elastic engagement pieces35,35can be performed quickly.

When removing the mounting-subject member4from the mount-base member2, as shown inFIGS. 8A,8B, a distal end of a tool such as a screwdriver with a flattened tip is inserted into between the annular wall52of the grommet50and the head portion11of the pin10to prize an outer circumferential edge of the head portion11to lift up the pin10so as to remove the folded portions40of the plate spring member30from the constricted portion19in the pin10(refer toFIG. 9A). Then, the pair of elastic engagement pieces35,35become expandable/contractible again, and thereafter, by lifting up the pin10, the fastener1can be removed so that the mounting-subject member4can be removed from the mount-base member2(refer toFIGS. 9A,9B).

Although the fastener1of the embodiment is made up of the pin1, the plate spring member30and the grommet50, the fastener1may be made up of the pin10and the plate spring member30. As this occurs, the U-shaped bent portions33of the plate spring member30are brought into direct abutment with the circumferential edge of the mounting hole in the mounting-subject member.

FIGS. 11 to 18show another embodiment of a fastener of the invention. Like reference numerals will be given to portions which are substantially like to those described in the embodiment above and the description thereof will be omitted herein.

As shown inFIG. 11, a fastener1aof this embodiment has a pin10a, a plate spring member30aand a grommet50aas with the embodiment above. Hereinafter, the members10a,30a,50awill be described mainly on portions thereof which differ from the corresponding members10,30,50of the embodiment above.

The plate spring member30ashown inFIGS. 12A to 13Bhas a base portion31in which a slit-like insertion hole31ais formed. A pair of notches31b,31bare formed in a direction which is at right angles to the forming direction of the insertion hole31a. A pair of narrow portions31c,31care formed in an outer circumference of the insertion hole31ain the base portion31so as to be situated between a pair of elastic engagement pieces35,35and in positions which face each other.

As shown inFIG. 13A, the narrow portions31c,31care disposed at both end portions of a direction (refer to a line C) which intersects a deflecting direction (refer to arrows B) of the pair of elastic engagement pieces35,35of the base portion31at right angles. When the base portion31is viewed in an axial direction, the narrow portions31c,31care formed in positions which are eccentric towards widthwise portions of the elastic engagement pieces35,35where folded portions40are not formed. Namely, in the figure, the upper narrow portion31cis formed in the position which is eccentric towards the widthwise portion of the left-hand side elastic engagement piece35where no folded portion40is formed, while the lower narrow portion31cis formed eccentric towards the widthwise portion of the right-hand side elastic engagement piece35where no folded portion is formed.

The insertion hole31apasses through a widthwise center of U-shaped bent portions33to extends as far as just before engagement shoulder portions37, whereby proximal portions of the elastic engagement pieces35are cut out. Disengagement prevention claws36are formed in a widthwise center of the proximal portions of the elastic engagement pieces35via the cutout portions so as to rise obliquely outwards.

Triangular plate-shaped projecting pieces are provided on inner sides of the folded portions40,40formed at respective distal end portions of the elastic engagement pieces35which lie adjacent widthwise to each other so as to project towards the other adjacent folded portion40(refer toFIGS. 12B,13A,15). A side of the projecting piece which lies to face a proximal portion of the plate spring member30ais formed into an abutment piece45with which a distal end portion15a(which will be described later) of the pin10ais brought into abutment to thereby apply a driving force, while a side of the projecting piece which lies to face a distal end portion is formed into an engagement projecting piece43which holds the elastic engagement pieces in a closed state.

In the pin10ashown inFIG. 14A, plate-shaped expanded portions14are disposed at a proximal portion of the shaft portion13which are wider than the distal end portion of the shaft portion13. The expanded portions14extend towards a distal end of the shaft portion a length which enables the expanded portions14to be brought into abutment with portions of the elastic engagement pieces35,35which lie closer to proximal portions than engagement shoulder portions37thereof and which prohibits the expanded portions14from being brought into abutment with portions of the elastic engagement pieces35,35which lie closer to distal end portions than the engagement shoulder portions37thereof when the shaft portion13is disposed between the elastic engagement pieces35,35(refer toFIG. 17).

Deflectable wall portions18,18are formed on both side portions of the shaft portion13which lie at right angles to the expanded portions14so as to be deflected via voids18a. Fixing projecting portions18b,18bare formed on the deflectable wall portions18so that a side of the fixing projecting portion which faces the distal end of the shaft portion is tapered and a side which faces the proximal end portion has a stepped portion formed thereon. This fixing projecting portion18bis designed to be brought into engagement with an inner circumference of an engagement groove59ain the grommet50a, which will be described later, at a proximal end portion thereof when the pin10ais driven into the plate spring member30auntil a head portion11is brought into engagement with a circumferential edge of the insertion hole31a(refer toFIG. 18). Namely, the fixing projecting portion18constitutes a fixing portion which fixes the pin in the grommet and has the projecting portion which is brought into engagement with the inner circumference of the engagement groove59a.

The distal end portion15aof the shaft portion13is formed into a triangular plate-like shape and has a tapered shape in which both sides of the distal end portion15abecome wider gradually towards the head portion11. Bridge-shaped deflectable pieces25,25are connected to sides of a proximal end of the distal end portion15aand respective distal ends of the expanded portions14,14, and an engagement projecting portion25aand an engagement claw portion25bare formed on each deflectable piece25. The engagement projecting portions25aand the engagement claw portions25bare brought into engagement with upper and lower edge portions of the base portion51of the grommet50awhen the pin10ais driven into the grommet50a(refer toFIG. 15), whereby the pin10ais temporarily held in a position where the pin10adoes not apply a driving force to the abutment pieces45. Namely, the engagement projecting portions25aand the engagement claw portions25bconstitute a temporary holding portion in this embodiment.

In the grommet50ashown inFIGS. 14A and 14B, a quadrangular inserting opening53a(refer toFIGS. 15,16) is formed in a center of the base portion51, and a pair of leg portions55a,55aare provided to extend from both facing side edges of a back side of the insertion opening53awhich are disposed in the deflecting direction of the pair of elastic engagement pieces35,35and outside of the same elastic engagement pieces35,35(refer toFIGS. 11,16,17). The leg portions55a,55aare connected to each other at distal ends thereof into a shape which tapers towards the distal ends (here, into a substantially V-shape). An elongated groove55bis formed in a widthwise center of each leg portion55aso as to extend in the extending direction of the leg portion55a. This elongated groove55bfacilitates the deflection of the leg portion55awhen the leg portion55ais pressed from inside by the elastic engagement piece35and constitutes a portion which a disengagement prevention claw36enters when the plate spring member30ais held in the grommet50a.

A pair of guide leg portions59,59are provided to extend from both side edges of the insertion opening53ain the base portion51which are at right angles to the leg portions55a,55a. The guide leg portions59,59are disposed in positions which are at right angles to the deflecting direction of the elastic engagement pieces35and which lie between the pair of elastic engagement pieces35,35. An engagement groove59ais formed in each guide leg portion59so as to extend in an axial direction thereof (in a direction in which the guide leg portion59extends). Then, when the pin10ais driven into the plate spring member30auntil the head portion11is brought into engagement with a circumferential edge of the insertion hole31a, the pairs of projecting portions (the fixing projecting portions18b, the engagement projecting portions25a) are brought into engagement with inner circumferences of the engagement grooves59aat both end portions thereof (refer toFIG. 18).

Next, a using method of the fastener1aof this embodiment will be described.

Since a basic using method is similar to that of the embodiment described first, characteristic portions will mainly be described. Firstly, the pair of elastic engagement pieces35,35which are spaced apart from each other in their free state (refer toFIG. 12B) in which no external force is applied thereto are pressed inwards to be deflected against their elastic restoring force.

In this embodiment, the narrow portions31c,31cprovided in the base portion31are disposed at both the side portions of the base portion31which lie at right angles to the deflecting direction of the elastic engagement pieces35, and when the base portion31is viewed in the axial direction, the narrow portions31c,31care formed in the positions which are eccentric towards the widthwise portions of the elastic engagement pieces35,35where the folded portions40are not formed (refer toFIG. 13A). Because of this, when the pair of elastic engagement pieces35, are deflected inwards, the base portion31is bent about a line L inFIG. 13A, and the one engagement projecting piece43and the other engagement projecting piece43move so as to approach each other widthwise as is indicated by arrows D.

As a result, although the pair of engagement projecting pieces43would otherwise be caused to approach each other to thereby be superposed on each other, the engagement projecting pieces43are brought into engagement with each other while being expanded widthwise, and therefore, even in the engaged state shown inFIG. 13B, a biasing force is produced by which the engagement projecting pieces43are caused to approach each other widthwise, whereby the engagement projecting pieces43are brought into engagement with each other while pressing against each other widthwise. Thus, the engagement of the engagement biasing pieces43is made more difficult to be released, whereby a risk can be eliminated that the engagement between the elastic engagement pieces35,35is released during transportation.

Thereafter, the pair of elastic engagement pieces35,35are aligned with the pair of leg portions55a,55aof the grommet50aand the plate spring member30ais driven into the inserting opening53ain the grommet50, whereby the pair of disengagement prevention claws36,36enter the elongated grooves55b,55bof the corresponding leg portions55aand the disengagement prevention claws36,36are brought into engagement with the circumferential edge of the back side of the insertion opening53a(refer toFIG. 16), whereby the plate spring member30acan be held in the grommet50a.

Next, the pin10ais driven into the plate spring member30ato a predetermined depth with the plate-shaped expanded portions14of the pin10aaligned with both the sides of the slit-shaped insertion hole31ain the plate spring member30aand the pair of deflectable wall portions18,18of the pin10aaligned with the pair of notches31b,31bin the plate spring member30a, whereby as shown inFIG. 15, the engagement projecting portions25aand the engagement claw portions25bare brought into engagement with the upper and lower edge portions of the base portion51, and the pin10ais held in the grommet50awhile being prevented from being disengaged therefrom. In this state, the tapered sides of the distal end portion15aof the pin10aare brought into engagement with the abutment portions45a,45aof the abutment pieces45.

In this embodiment, the temporary holding portion (the engagement projecting portions25aand the engagement claw portions25b) and the fixing portion (the fixing projecting portions18b) are provided on the shaft portion13of the pin10a, whereby the pin alone can be temporarily held in the grommet50a. Therefore, the necessity can be obviated of providing a construction to prevent the disengagement of the pin10aon the plate spring member30a, the rigidity, spring properties and elastic restoring force of the plate spring member30acan be ensured strongly.

Thereafter, the assembled fastener1is inserted into the mounting holes5,3of the mounting-subject member4and the mount-base member2, respectively.

In this embodiment, as this occurs, since the leg portions50awhich are connected together at the distal ends thereof and the guide leg portions59constitute guides, the grommet50acan be inserted smoothly without being caught at the mounting holes5,3.

Then, after the base portion51is brought into abutment with the circumferential edge of the front side of the mounting hole5, the pin10ais driven into the grommet50a. Then, the engagement of the abutment pieces45,45is released by the triangular plate-shaped distal end portion15a, and the pair of elastic engagement pieces35,35are opened, whereby the leg portions55a,55aof the grommet50aare forced to be expanded by the engagement shoulder portions37,37from inside thereof. As a result, the engagement shoulder portions37,37of the elastic engagement pieces35are brought into indirect engagement with the circumferential edge of the back side of the mounting hole3via the leg portions55a,55a, whereby the mounting-subject member4can be mounted on the mounting base2via the fastener1a(refer toFIG. 17). In addition, in this embodiment, since the distal end portion15aof the pin10ahas the triangular plate shape and is brought into abutment with the abutment portions45a,45aof the abutment pieces45,45at both the sides thereof, the driving force from the pin10ais allowed to be exerted on the abutment portions45a,45aefficiently without being dispersed, thereby smoothly releasing the engagement of the elastic engagement pieces35,35.

When the pin10ais driven into the grommet50auntil the head portion11of the pin10ais brought into engagement with the circumferential edge of the insertion hole31ain the plate spring member30, as shown inFIG. 18, the fixing projecting portions18bare brought into engagement with the inner circumferences of the engagement grooves59aat the proximal ends thereof, and the engagement projecting portions25aare brought into engagement with the inner circumferences of the engagement grooves59aat the distal ends thereof. Further, the engagement claw portions25bare brought into engagement with the circumferential edges of distal end faces of the guide leg portions59, whereby the pin10ais fixed in the grommet50a.

In this embodiment, as described above, when the pin10ais driven into the grommet50auntil the head portion11of the pin10ais brought into engagement with the circumferential edge of the insertion hole31ain the plate spring member30a, the pairs of projecting portions (the fixing projecting portions18band the engagement projecting portions25a) formed on the shaft portion13of the pin10aare brought into engagement with the inner circumferences of the engagement grooves59ain the guide legs59,59with an appropriate clicking sensation felt. Therefore, it can be grasped more clearly that the pin mounting work in the grommet50ais completed.

In this embodiment, since the leg portions55a,55aof the grommet50aare disposed outwards of the elastic engagement pieces35,35, the elastic engagement pieces35of the plate spring member30aare not brought into direct engagement with the mounting hole3but are brought into indirect engagement with the mounting hole3via the leg portions55a(refer toFIG. 17). In this way, since the metal plate spring member30ais prevented from being brought into direct engagement with the mounting hole3, the generation of rust in the plate spring member30acan be prevented, and the generation of abnormal noise can be suppressed when or after the fastener1ais fixed in the mounting hole3. In addition, in the case of the member in which the mounting hole3is formed being made of a metal, the generation of rust at the circumferential edge of the mounting hole can also be prevented.

In this embodiment, by providing the expanded portions14having the shape described above on the shaft portion13of the pin10a, when the shaft portion13of the pin10ais disposed between the elastic engagement pieces35,35, since the expanded portions14are brought into engagement with the portions on the elastic engagement pieces35,35which lie closer to the proximal portions thereof than the engagement shoulder portions37, the elastic engagement pieces35,35can be restricted from being closed inwards at the proximal portions, as a result, the mounting strength of the fastener can be enhanced, and the looseness thereof can be prevented. On the other hand, since the expanded portions14are not brought into engagement with the engagement shoulder portions37of the elastic engagement pieces35and hence, the elastic engagement pieces35can be deflected, the fastener can deal with a change in thickness of the member in which the mounting hole is formed more flexibly, thereby surely mounting the fastener without any looseness.

When removing the mounting-subject member4from the mount-base member2, the pin10ais prized to be lifted upwards, and the pairs of the projecting portions18b,25aare released from the engagement with the inner circumferences of the engagement grooves59ain the guide leg portions59, whereby the expanded portions14of the pin10aare removed from between the elastic engagement pieces35,35, the pin10abeing returned to its temporarily held state shown inFIGS. 15,16. Then, the expanded portions14are disengaged, and the pair of elastic engagement pieces35,35become expandable/contractible again. Therefore, the mounting-subject member4can be removed from the mount-base member2by removing the fastener1afrom the mounting holes3,5.

In this embodiment, as this occurs, since the pair of leg portions55a,55aof the grommet50aare connected to each other at the distal ends thereof to thereby be tapered towards the distal ends, when the fastener1ais reinserted into the mounting hole after it has been removed from the mounting hole, the fastener1acan be driven into the mounting hole as it is so as to be fixed therein without closing the pair of elastic engagement pieces35,35to bring the engagement projecting pieces43into engagement with each other, thereby enhancing the workability.

DESCRIPTION OF REFERENCE NUMERALS