GB2350330A

GB2350330A - Instrument panel with tear seam formed after moulding

Info

Publication number: GB2350330A
Application number: GB0010214A
Authority: GB
Inventors: Joseph J Davis; Jeffrey Leon Soncrant
Original assignee: Lear Automotive Dearborn Inc
Current assignee: Lear Automotive Dearborn Inc
Priority date: 1999-04-30
Filing date: 2000-04-27
Publication date: 2000-11-29
Also published as: GB0010214D0; DE10020997A1; SE0001585L; JP2000351162A; SE0001585D0

Abstract

A vehicle instrument panel 56 has a decorative forward face 25 and an underlying rear face 61 on the opposite side to the decorative face, with a tear seam 62 formed into the rear face of said panel after the panel has been moulded. The tear seam may be formed by a sonic welding tool 58 while the panel may be formed of a single layer of relatively rigid plastic or a dual layer of foam with a plastic skin (Fig 4). In a further embodiment of the invention a hinge member is attached to the rear face after the tear seam has been formed.

Description

2350330 docket #60,115-659 METHOD OF FORM TEAR SEAM INTO VEHICLE

INSTRUMENT PANEL

BACKGROUND OF THE INVENTION

This invention relates to a unique method for forming an airbag tear strip into a rear surface of an instrument panel.

Instrument panels have a decorative outer surface facing the vehicle cab and a rear surface facing away from the cab. Instrument panels are typically molded of either a single relatively rigid plastic layer, or a relatively thin soft skin over an underlying foam layer and an inner rigid skin. Recently, it has become common 0 practice to incorporate an air bag behind the instrument panel and in the vicinity of the passenger seat. The airbag is typically provided with a tear seam in the instrument panel such that when the airbag deploys the instrument panel tears to allow the airbag to move outwardly into the vehicle cab. Originally, the tear seam was formed in the outer decorative surface of the instrument panel. However, for aesthetic reasons, more recently the tear seam has been formed in the rear surface of the instrument panel, such that it would not be visible to the occupants of the vehicle.

Typically, molds for forming instrument panels have been formed with structure that forms the tear seam into the rear surface of the instrument panel.

I While this practice has been widely adopted, there are some deficiencies. First, the structure which forms the tear seam in the molded plastic part provides a restriction to flow of plastic through the mold. This has sometimes resulted in an undesirably high amount of scrap due to poor plastic flow within the mold.

docket #60,115-659 Moreover, the tear seams have sometimes formed localized wells in the outer surface of the instrument panel wherein the plastic has moved inwardly to create a void in the outer surface. This is undesirable, and also results in scrap.

It would be desirable to minimize the amount of scrap, and provide an improved method for forming a vehicle tear seam.

SUNMARY OF THE INVENTION In a disclosed embodiment of this invention, the instrument panel is initially molded without the tear seam. The tear seam is then formed into the rear surface of the instrument panel, preferably by a welding technique. Sonic welding is most preferably utilized. Most preferably, the instrument panel is molded, and can be a single layer of relatively rigid plastic, or a multiple layer of foam, plastic skins and a rigid plastic rear surface. Once the instrument panel has been molded, it may be removed from the mold, although removed is not necessary. The welding tool is then brought into contact with the rear surface of the instrument panel and the tear seam is welded into the rear surface. Since the instrument panel is molded in a mold without any restriction for the tear seam, there are fewer scrap parts.

Moreover, the localized depressions, etc. which were the result of prior art molded in tear seams are not created.

Once the tear seam has been formed into the instrument panel, a flap or hinge structure may be mounted to the rear surface, as known.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

docket #60,115-659 BRIEF DESCRIffION OF THE DRAWINGS Figure I is a schematic view of a vehicle instrument panel incorporating the present invention.

Figure 2 shows a prior art molding technique.

Figure 3a shows a first step in the inventive technique.

Figure 3b shows a subsequent step.

Figure 3c shows a final step.

Figure 4 shows an alternative embodiment.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

An instrument panel 20 according to the present invention is formed with a tear seam 22 on a rear surface, and preferably above the location of a glove compartment 24. A decorative outer surface 25 faces into the vehicle cab. As known, the instrument panel has an outer decorative surface 25. The tear seam 22 is formed in an the rear surface, which faces away from the vehicle cab.

As shown in Figure 2, in the prior art a mold 30 incorporated mold parts 32 and 34. A tear seam rim 36 was formed on one of the mold parts and restricted the cavity 38 to have localized reduced thickness areas 40. Those reduced thickness areas resulted in the tear seam once the instrument panel was molded. Also, cavities are formed in part 32 to result in mount structure 37, which will mount the air bag module. The restricted areas have sometimes resulted in insufficient plastic flowing into the area between the tear seams ribs 36. This problem is made more challenging by structure 37. Moreover, the existence of the molded-in tear seam docket #60,115-659 has sometimes resulted in an undesirable "shadow" or other depression in the decorative surface 25 at an area associated with the tear seam.

The present invention addresses this problem by a unique method, such as shown schematically in Figure 3a-3c. As shown in Figure 3a, a mold 50 incorporates mold portions 52 and 54 which together define a cavity 56 for forming a preform. The preform 56 does not include the tear seam.

The preform 56 is molded and then may be removed from the mold for the step of Figure 3B. Notably, the Figure 3B step could occur while the preform is still in one of the mold parts, although preferably the preform is first removed.

A welding tool 58, shown schematically, has structure 60 which contains the preferred cross-section for the tear seam. Structure 60 is brought into contact with the rear surface 61 of the preform 56. As shown, the tear seam 62 is then burned or welded into the rear surface 61. In this way, the tear seam can be carefully positioned, carefully dimensioned, and will not result in undesirable quality problems with the remaining areas of the instrument panel.

As shown in Figure 3c, once the tear seam 62 is formed, flap structure 70 having a hinge 72 may be attached to the rear surface 61. An air bag module 74 can be attached to mount structure 37. The structures 70, 72 and 74 are as known in the art, and does not itself form a portion of this invention.

The instrument panel 20 such as shown in Figures 3a, 3b and 3c is formed of a single rigid plastic layer. Figure 4 shows an alternative embodiment where an instrument panel 80 has its tear seam 82 formed in a method similar to that shown in Figures 3a-3c. However, the instrument panel 80 has an underlying foam layer docket #60,115-659 84 with a soft plastic skin 86 providing the decorative layer. The tear seam extends into a rear rigid skin 88, and may, or may not, extend into layer 84. The instrument panel is still formed in a method similar to the above method, although a somewhat different molding technique may be utilized to form the layers 84, 86 and 88. A preform is still initially formed, and the tear seam 82 is then forin6d after the formation of the preform.

Preferred embodiments of this invention have been disclosed; however, a worker of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

docket #60,115-659

Claims

WHAT IS CLAIMED IS:

1. A method of forming a vehicle instrument panel comprising the steps of:

(1) molding an instrument panel preform, said instrument panel having a decorative forward face, and an underlying rear face on an oppos&d side of said decorative face; and (2) then forming a tear seam into said rear face of said preform.

2. A method as recited in Claim 1, wherein said tear seam defines a generally enclosed shape.

3. A method as recited in Claim 2, wherein said tear seam is formed by a welding tool.

4. A method as recited in Claim 3, wherein said welding tool is a sonic welding tool.

5. A method as recited in Claim 4, wherein a flap is attached to said rear face around at least a portion of said tear seam after step (2).

6. A method as recited in Claim 1, wherein said tear seam is formed by a welding tool.

7. A method as recited in Claim 6, wherein said welding tool is a sonic welding tool.

8. A method as recited in Claim 1, wherein said preform is formed of a single layer of relatively rigid plastic.

9. A method as recited in Claim 1, wherein said preform is formed of a dual layer of foam and a plastic skin.

dmkcE #60,115-659

10. A vehicle instrument panel comprising:

a generally planar surface, said generally plana surface having a forward decorative face and a rear face, a tear seam formed into said rear face, said tear seam being formed after said planar surface is molded; and a hinge member attached to said rear face.

11. A method of forming a vehicle instrument panel substantially as herein described with reference to the accompanying drawings.

12. A vehicle instrument panel substantially as herein described with reference to the accompanying drawings.