Method for forming a headrest

A method for forming a headrest, which involves pre-assembling an incomplete headrest unit including a trim cover assembly having an opening therein and a headrest frame having been placed via the opening within the trim cover assembly, and a foaming process for subjecting such incomplete headrest unit to a foaming by injecting a liquid base foaming material into the interior of trim cover assembly and curing that foaming material, so as to produce a final headrest. In the method, an injection nozzle device is utilized, which has an entrapping or catching element provided at the nozzle portion thereof. Prior to the foaming process, the nozzle portion of injection nozzle device is inserted via the opening into the interior of trim cover assembly in a first direction, and then drawn in a second direction opposite to the first direction, thereby causing the opening to be closed positively by the catching element, to prevent leakage of the liquid base foaming material from the opening. Further, at least one extension may be formed at the opening, which extends continuously from the trim cover assembly into the interior of the latter, so that such at least one extension may be caught by the catching element for the purpose of positively closing the opening against the leakage of liquid base foaming material therethrough.

BACKGROUND OF INVENTION
 1. Field of the Invention
 The present invention relates to a method for forming a headrest adapted
 for use on an automotive seat, and more particularly to the method of this
 kind wherein the headrest is formed by injecting a liquid foaming base
 material into the interior of a preformed three-dimensional trim cover
 assembly having a predetermined headrest outer shape and then subjecting
 both liquid foaming base material and trim cover assembly to foaming
 integrally together.
 2. Description of Prior Art
 According to a typical known foaming process for producing a headrest, a
 three-dimensional trim cover assembly of a predetermined headrest shape is
 firstly provided by sewing together required separate cover sections, with
 an opening defined therein, then a generally U-shaped headrest frame
 having a pair of headrest stay portions is inserted through the opening
 into the interior of the trim cover assembly, and thereafter, a liquid
 base foaming material is injected and cured in the trim cover assembly, so
 as to produce a foamed resultant headrest with the pair of headrest stay
 portions projecting therefrom.
 This foaming process has encountered the problem that the liquid base
 foaming material is leaked through the opening to the outside of trim
 cover assembly, leaving an objectionable spot thereon. Conventionally, in
 an attempt to prevent the leakage of liquid base foaming material, typical
 solution is for example found in the Japanese Granted Patent Pub. No.
 6-45149 and Japanese Laid-Open Patent Pub. No. 7-31759, wherein a pair of
 extensions are formed in the portion of trim cover assembly corresponding
 to that opening such as to extend inwardly from the opening into the trim
 cover assembly, and a flattened tubular film piece is fitted between the
 pair of extensions, so that an injection nozzle can be inserted through
 the flattened tubular piece into the interior of trim cover assembly, and,
 during the foaming process, the liquid base foaming material being
 injected from the nozzle is prevented by those two extensions and film
 from the opening in question.
 However, such conventional method requires cutting of an externally exposed
 part of the film which projects outwards from the opening, subsequent to
 the foaming process, thus resulting in a troublesome labor on the part of
 worker and also in the high likelihood of a cut, tear or undesired damage
 being given to the trim cover assembly when the worker cuts off the film.
 SUMMARY OF THE INVENTION
 In view of the above-stated drawbacks, it is therefore a primary purpose of
 the present invention to provide an improved method for forming a headrest
 which eliminates the foregoing various troubles and effectively prevents a
 liquid base foaming material against leakage from the opening of trim
 cover assembly during a foaming process.
 In order to achieve such purpose, in accordance with the present invention,
 there is basically provided the steps of:
 pre-assembling an incomplete headrest unit comprising a three-dimensional
 trim cover assembly of a predetermined headrest configuration, which has
 an opening formed therein and an extension means extending therefrom via
 said opening into an interior of the three-dimensional trim cover assembly
 and a headrest frame means having a stay portion, wherein the headrest
 frame means has been inserted via the opening into and placed in the
 interior of three-dimensional trim cover assembly, with the stay portion
 projecting outwardly therefrom;
 providing an injection nozzle means having a catching means for catching
 the extension means associated with the three-dimensional trim cover
 assembly;
 inserting the injection nozzle means through the opening in a first
 direction toward the interior of three-dimensional trim cover assembly,
 while locating the catching means at the extension means therewithin;
 drawing the injection nozzle means in a second direction opposite to such
 first direction, to thereby catch the extension means;
 drawing further the injection nozzle means in such second direction,
 thereby causing the opening to be closed positively by the extension means
 and catching means
 thereafter, injecting a liquid base foaming material through the injection
 nozzle means into the interior of trim cover assembly;
 curing the liquid base foaming material to form a foam padding integrally
 with the interior of trim cover assembly and headrest frame means; and
 thereafter, removing the injection nozzle means from the trim cover
 assembly, whereby the headrest is formed.
 Accordingly, a positive closing of the opening is attained via the catching
 means to insure avoiding creation of any loosen point or clearance at the
 opening through which the liquid base foaming material will invade or will
 be leaked. Further, an increased mass of the liquid base foaming material
 being cured presses the extension means against an inner side of the trim
 cover assembly to thereby positively close the opening against leakage of
 the liquid base foaming material therethrough.
 In one aspect of the present invention, the trim cover assembly and
 extension means are formed from a material having an elastic property, and
 a through-hole be formed in the extension means, thus having an elastic
 property for allowing its elastic deformation and recovery to its original
 diameter. In that instance, both injection nozzle means and catching means
 can be inserted through that through-hole while elastically deforming the
 same, at the step of inserting the injection nozzle means, and also
 removed via the through-hole from the trim cover assembly at the step of
 removing the injection nozzle means therefrom.
 In another aspect of the present invention, the extension means may
 comprise first and second extensions which are resiliently biased to
 contact with each other to normally close the opening, wherein the first
 extension is greater in length than the second extension, with a projected
 part defined continuously from the first extension. In that instance, at
 the step of drawing further the injection nozzle means in the second
 direction, the projected part of the first extension is bent toward the
 free end of second extension, thereby causing a tight contact of such
 projected part with the end of second extension, so that the opening is
 positively closed by the first and second extensions. Further, the
 projected part of first extension is folded about the end of said second
 extension by a pressure applied from an increased mass of said liquid base
 foaming material being cured, rendering more positive the closing of the
 opening to insure preventing the liquid base foaming material from the
 opening;
 Other various features and advantages of the present invention will become
 apparent from reading of the descriptions hereinafter with reference to
 the annexed drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
 Referring to FIGS. 1 through 8, there are illustrated preferred modes of
 method for forming a headrest (HD), by way of example, in accordance with
 the present invention.
 FIGS. 1 and 7 show a trim cover assembly (C) to be used in the method,
 which is of the three-dimensional bag-shaped type having a predetermined
 outer configuration of headrest. The trim cover assembly (C) itself is
 preformed into the illustrated three-dimensional shape by sewing together
 required separate cover sections, as known in the art. In accordance with
 the present invention, the construction of trim cover assembly (C) is
 based on a three-layer lamination structure composed of a top cover layer
 (a), a foam padding layer (b) and a back cover layer (C) in this order,
 wherein the foam padding layer (b) is made of a slab urethane foam
 material. A slot-like elongated opening (A) is defined in the bottom wall
 of trim cover assembly (C). The top cover layer (a) is preferably formed
 form a textile fabric material, a gigged or raised cloth material and the
 like. Thus, in addition to being of a rough texture with a friction
 effect, the trim cover assembly (C) is provided with an elastic property
 for a purpose to be set forth.
 According to the shown embodiment, a pair of first and second extensions
 (40) (30) are provided within the trim cover assembly (C) in a manner
 depending from the opening (A). The first and second extensions (40) (30)
 serve to prevent leakage of a liquid base foaming material (P1) via the
 opening (A) to the outside during a foaming process to be described later.
 This particular leakage-preventive structure is, however, known from the
 U.S. Pat. No. 5,855,831 assigned to the assignee of the present invention,
 and a detailed information in this particular regard may be obtained from
 that patent. Hence, within the gist of the present invention, those first
 and second extensions (40) (30) are just a part of required elements in
 the method described herein on one hand, and they should not always be
 formed in the trim cover assembly (C), on the other hand, depending on a
 particular design or structural simplicity of the trim cover assembly (C),
 as will be apparent later.
 As far as the embodiment shown in FIGS. 1 and 7 is concerned, the trim
 cover assembly (C) is generally composed of a generally bag-shaped body
 (C3), a first half wall section (C1), a second half wall section (C2), and
 a slot-like elongated opening (A) defined between the first and second
 half wall sections (C1) (C2). Of course, those three sections (C3, C1,C2)
 are each of the three-layer lamination structure as can be seen in FIG. 3,
 and sewn with one another to form a predetermined three-dimensional shape
 of headrest body shown in FIG. 7. In particular, as viewed from FIGS. 1
 and 3, the first and second half wall sections (C1) (C2) face with each
 other to define the elongated opening (A) which extends transversely of
 and in the width-wise direction of trim cover assembly (C).
 The first and second extensions (40) (30) are each formed integrally and
 continuously from the respective free edges of first and second half wall
 sections (C1) (C2). As can be seen from FIGS. 1 and 3, the two extensions
 (40) (30), by the reason that they have the aforesaid three-layer
 lamination structure, are resiliently biased to contact with each other at
 their respective top cover layers (a) due to an elastic linear recovery
 property of the foam wadding layer (b) in each extension. Briefly stated,
 this normally causes the elongated opening (A) to be resiliently closed
 between the two extensions (40) (30), thus serving to prevent a liquid
 base foaming material (see the designation (P1) in FIG. 5 (B)) from being
 leaked through the opening (A) during a foaming process.
 As shown, the first extension (40) includes a projected part (41) which
 extends continuously therefrom, having the aforementioned three-layer
 lamination structure, so that the total length of both first extension
 (40) and projected part (41) is greater than that of the second extension
 (30). Formed in the projected part (41) is a through-hole (41A) for
 allowing a nozzle portion (1) to be inserted therethrough. The
 through-hole (41A) is disposed near to a juncture point between the first
 extension (40) and projected part (41), whereupon a foldable region (41B)
 is defined in the area of projected part (41) opposite to that juncture
 point relative to the through-hole (41A). This foldable region (41B) is to
 be folded about the end (30E) of the second extension (30) to embracingly
 close the elongated opening (A) for leakage preventive purpose, as will be
 explained.
 In accordance with the present invention, there is provided an injection
 nozzle device (10) as best shown in FIG. 2, including an entrapping or
 catching means (2) defined at the nozzle portion (1) thereof, which is
 designed to entrap or catch a portion of the extensions (40) (30) in a
 generic aspect of the present invention during an introductory step in the
 method of the present invention to be described later. While not shown,
 the injection device (10) is connected to a pump device, so that a liquid
 base foaming material (see designation P1 in FIG. 4 (B)) may be supplied
 to the device (10) by operation of the pump device and injected from the
 nozzle portion (1). Designation (1a) denotes a bore of the nozzle portion
 (1) through which the liquid base foaming material is to be injected.
 In the illustrated mode, such entrapping or catching means (2) may be
 embodied by a pair of catcher pieces (2A) projecting integrally from the
 nozzle portion (1) diameter-wise in a direction opposite to each other.
 Alternatively, as indicated by the phantom line, a disc-like catcher piece
 (2B) may be employed as another mode of the entrapping or catching means
 (2), which is formed integrally about the circumstance of the nozzle
 portion (1), projecting radially therefrom relative to the central axis
 thereof. It is important to note here that the diameter of both modes of
 catching means (2A and 2B) should be set to a degree at which a tolerable
 elastic deformation or widening of the through-hole (41A) is attained in
 order for the catching means (2) to bodily pass therethrough. For, the
 through-hole (41A) is provided with an elastic property for normally
 maintaining its original diameter while being resiliently widen relative
 thereto, due to the aforementioned elastic nature of the three layer
 materials (a,b,c) used in both first extension (40) and projected part
 (41). In this regard, it is also noted that the diameter of the
 through-hole (41A) per se is equal to or slightly smaller than the
 diameter of nozzle portion (1), but may be resiliently deformed or widened
 to such a diameter that allows the two catcher pieces (2A) or disc-like
 catcher piece (2B), which has a relatively large diameter, to pass
 therethrough. This is important for the purpose of preventing a liquid
 foaming base material against leakage from the through-hole (41A) as will
 be noted. However, those two modes of catching means (i.e. 2A and 2B) are
 not limitative, and the catching means (2) itself may be embodied in any
 other suitable form insofar as it achieves the same effects as noted above
 and to be described later within the scopes of the present invention.
 Designation (1a) denotes an insertion end area which is so defined in the
 nozzle portion (1) as to be capable of smooth introduction and insertion
 into the through-hole (41A), thereby permitting for direct, precise
 guiding of the entrapping or catching means (2A or 2B) to that particular
 through-hole (41A).
 As described in the U.S. Pat. No. 5,855,831, the trim cover assembly (C)
 per se is preformed in the illustrated three-dimensional fashion, and
 also, an incomplete headrest unit is assembled ,as can be seen from FIG.
 1, by inserting a generally U-shaped headrest frame (F) via the elongated
 opening (A) into the interior of trim cover assembly (C), while passing
 the two headrest stay portions (S) thereof (see FIG. 7) through the
 respective two holes (C10) to project outwardly from the trim cover
 assembly (C).
 Description will now be made of the steps in accordance with the present
 invention, hereinafter, with particular reference to FIGS. 4(A) to 6.
 At the first stage, as can be seen from FIG. 1, to the thus-assembled
 incomplete headrest unit, is mounted the injection nozzle device (10) by
 inserting its nozzle portion (1) through the elongated opening (A) into
 the inside of trim cover assembly (C), with a pair of catcher pieces (2A)
 (or disc-like catcher piece (2B)) passed through the through-hole (41A) of
 first extension (40), as shown in FIG. 5(A). Specifically stated, at
 first, the projected part (41) of first extension (40) are in the state of
 being inclined in a direction to the second extension (30), thereby
 substantially locating the through-hole (41A) at a point below the opening
 (A). Then, a worker should insert the nozzle portion (1) of injection
 nozzle device (10) through the opening (A) into the interior of trim cover
 assembly (C), and then manipulate the nozzle portion (1) so as to
 penetrate the insertion end area (1a) thereof into the through-hole (41A)
 of first extension projected part (41). Thus, such insertion end area (1a)
 is slidingly moved forwards through the through-hole (41A) so that the two
 catcher pieces (2A) (or disc-like catcher piece (2B)) are directly
 introduced to and abutted against a local area of the projected part (41)
 which adjacently circumscribes the through-hole (41A). At this moment, the
 worker should continue on inserting the nozzle portion (1) towards the
 interior of trim cover assembly (C), thereby driving such catcher pieces
 (2A or 2B) into the through-hole (41A). Hence, as shown in FIG. 4, by
 applying a force as indicated by the arrow 1 to the foregoing local area
 of projected part (41) via the nozzle portion (1), overcoming a resilient
 force inherit in the local area, the worker can forcibly deform and widen
 the through-hole (41A) with a relatively small force and can easily pass
 the catcher pieces (2A or 2B) wherethrough.
 Accordingly, as shown in FIG. 5(A), the nozzle portion (1a) is inserted
 through both opening (A) and through-hole (41A), with the two catcher
 pieces (2A) being situated below the projected part (41) of first
 extension (40) within the hollow interior of trim cover assembly (C).
 Next, as indicated by the arrow 2 in FIG. 5(A), by drawing the injection
 nozzle device (10) upwardly (i.e. in a direction opposite to the foregoing
 first direction 1), the nozzle portion (1) is simultaneously slid upwards
 through the hole (41A), with the two catcher pieces (2A) being brought to
 contact with the projected part (41) of first extension (40). At this
 moment, a worker feels a touch indicative of the catcher pieces (2A)
 entrapping or catching that projected part (41) and should continue to
 draw the nozzle portion (1) upwardly so that the projected part (41) is
 bent by the catcher pieces (2A) in the same direction at a point (TP) to
 contact the end (30E) of second extension (30) tight as indicated by the
 phantom line. It is noted here that the thus-bent projected part (41) is
 in the state of extending horizontally at a right angle with respect to a
 vertical line of both first and second extensions (40) (30). Thus, the
 worker feels a stop which is indicative of a positive contact between the
 base of projected part (41) and the second extension end (30E), whereupon
 the elongated opening (A) is closed positively thereby within the trim
 cover assembly (C) as can be seen in FIG. 5(B).
 Then, with the opening (A) thus closed, as shown in FIG. 5(B), a
 predetermined amount of liquid base foaming material (P1) is injected from
 the nozzle (1) into the hollow interior of trim cover assembly (C),
 followed by a foaming step shown in FIG. 5(C), using a suitable foaming
 die (not shown), wherein the liquid material (P1) is cured to increase its
 mass in the trim cover assembly (C). It is appreciated here that the
 above-described positive closing of the opening (A) via the catcher pieces
 (2A) insures avoiding creation of any loosen point or clearance at the
 opening (A), through which the liquid base foaming material (P1) will
 invade or will be leaked. Further, It is observed that an increased mass
 of foaming material (P1) being cured presses the foldable region (41B)
 associated with the first extension (41) in the upward direction so as to
 cause that particular foldable region (41B) to fold about the second
 extension end (30E) and closely contact the outer surface of the second
 extension (30) as in FIG. 5(C). At the same time, both first and second
 extensions (40) (30) are contacted tight with each other due to a high
 pressure being applied to them from both sides by the increased mass of
 foaming material (P1). Accordingly, it is to be appreciated that a
 three-fold closing effect is attained in that manner, leading to a
 complete sealing of the opening (A) against the leakage of liquid base
 foaming material during the whole foaming processes.
 At the completion of the foaming process, a resulting foam padding (P) is
 created and resiliently filled in the trim cover assembly (C), as shown in
 FIG. 5(D), after which, the nozzle portion (1) is removed from the opening
 (A) in the upward arrow direction 3. It is noted here that the two catcher
 pieces (2A) can easily be escaped through the through-hole (41A), because
 all the materials surrounding the catcher pieces (2A), i.e. the foaming
 padding (P), first and second extensions (40) (30), projected part (41)
 and the through-hole (41A), are of an elastic deformable property as
 stated earlier, which allows for easy removal of such projected pieces
 (2A) therefrom by applying a certain drawing force thereto from a worker
 involved in operation of this final stage.
 After having removed the injection nozzle device (10) from the final
 product of headrest (of course, also after having removed the final
 product from a foaming die, through not shown, if any), there is produced
 a resulting headrest (HD) with two headrest stays (S) (S), which is
 depicted in FIGS. 7 and 8 as having a tight closed state of the opening
 (A).
 The foregoing descriptions are made only about the two catcher pieces (2A)
 in conjunction with the FIGS. 5(A) to 5(D), but another mode, i.e. the
 disc-like catcher piece (2B), may also be employed and used in the same
 manner as described above throughout the foaming steps.
 It is to be also appreciated that the method of the present invention is
 highly improved over that of the U.S. Pat. No. 5,855,831 in terms of using
 the catching means (2) for the positive closing of the opening (A) against
 leakage of liquid base foaming material therethrough.
 While having described the present invention thus far, it should be
 understood that the invention is not limited to the illustrated
 embodiments, but any other modifications, replacements and additions may
 be applied thereto structurally and methodologically without departing
 from the scopes of the appended claims. For example, as understandable
 from FIGS. 3 and 6, the long projected part (41) employed in the foregoing
 embodiment may be replaced by a short projected part (41') without the
 through-hole (41A) therein, even in which case, the entrapping or catching
 means (2) within the scopes of the present invention will be used to
 entrap or catch that short projected part (41'). In other words, the
 projection of the catching means (2), be it two projections (at 2A) or
 circular projection (at 2B), may be used to catch the short projected part
 (41') and bend the same towards the edge (3E) of second extension (3), so
 that a worker can manipulate the nozzle portion (1) and catching means (2)
 such as to forcibly bring the entirety of projected part (41') to a close
 contact with the entirety of second extension edge (3E) to completely
 close the opening (A). Further, instead of the two extesnions (30) (40),
 only one extension may be formed continuosly from one of the two cover
 sections (C1) (C2), extending via the opening (A) and projecting within
 the trim cover assembly (C). In this case, the nozzel portion (1a) may be
 so manipulated as to cause such one extension to be caught by the catching
 means (2) and then drawn upwardly to bend and press the extension against
 the inner wall of two cover sections (C1) (C2) adjacent the opening (A),
 thereby closing the whole of opening (A) tight. Still further, both two
 extensions (30) (40) may not be proivded in the trim cover assembly (C),
 and instead thereof, a suitable member may be used to close the opening
 (A) in cooperation with the catching means (2).