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Title:
METHOD AND DEVICE FOR INJECTION MOLDING
Document Type and Number:
WIPO Patent Application WO/1996/009155
Kind Code:
A1
Abstract:
The present invention contemplates an apparatus and method for molding an article that has a film bonded to a body portion of the finished article wherein the film is transported from a supply roll to a take-up roll so that the film covers the female mold cavity and the adjoining area of the female mold that is the non-molding area or portion of the female molding portion. The film is pre-heated to permit preforming of the sheet to the contour of the female mold cavity. As the female mold and the male mold are brought into abutting contact, the film is most preferably retained between certain portions of the mold to allow the movement of the film inwardly towards the mold cavity as thermoplastic material is injected into the mold cavity for bonding with the film as the article is formed in the mold cavity.

Inventors:
KAZMER BRYAN MICHAEL
STELLER ROGER ALAN
TOYODA PAUL S
WOODS CHRISTOPHER WILLIAM
URIG DAVID JOSEPH
Application Number:
PCT/US1995/011983
Publication Date:
March 28, 1996
Filing Date:
September 19, 1995
Export Citation:
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Assignee:
GEON CO (US)
International Classes:
B29C45/14; (IPC1-7): B29C45/14
Foreign References:
DE4033297A11991-05-02
EP0186015A21986-07-02
EP0186016A21986-07-02
EP0531977A11993-03-17
FR2459116A11981-01-09
Other References:
PATENT ABSTRACTS OF JAPAN vol. 8, no. 280 (M - 347)<1717> 21 December 1984 (1984-12-21)
PATENT ABSTRACTS OF JAPAN vol. 12, no. 424 (M - 761) 10 November 1988 (1988-11-10)
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Claims:
WHAT IS CLAIMED IS:
1. In a method for fabricating a shaped article having a film integrally formed on a portion of the surface of said article by means of an injection molding machine including a mold formed of one mold half and another mold half wherein each said mold half has at least one molding portion and a peripheral nonmolding portion, one of said mold sections having a molding surface in said molding portion connected to at least one nozzle for injecting thermoplastic material, said method including the following steps: positioning a film between said mold halves with the peripheral portion of the film extending outwardly of the molding portion thereof and overlying said peripheral nonmolding portions, said nonmolding portions contain a clamping region and a nonclamping gap, moving the one mold half towards the other mold half while kissing the peripheral portions of such film between the peripheral nonmolding portions of such mold halves, forming that portion of such film between said molding portions into a contour, injecting thermoplastic material into the space between said film movably positioned within said centrally disposed molding portions and the molding surface of said other mold section to form said article, and thence cooling said article with the film integral therewith.
2. The method as set forth in claim 1 wherein there is a feeding of said peripheral portions of said film into said molding portions while injecting said thermoplastic material into said molding portions to form such article without substantially reducing the film thickness.
3. The method as set forth in claim 2 further comprising the step of preheating said film with pressurized warm air and preshaping prior to injecting said thermoplastic material into said space between such mold sections.
4. The method as set forth in claim 3 wherein said film is preheated by directing pressurized air from said other mold section toward said film and against said one mold section.
5. The method as set forth in claim 1 wherein said film is movably held in a bend circumferentially around the periphery of said molding portion.
6. A method of molding an article by injection molding in a cavity containing a film, said film thereby bonded to at least a portion of one surface of said article, the method comprising the steps of positioning a film between female and male mold sections wherein the peripheral portion of said film extends outwardly of the molding area; clamping a male mold against said female mold at the peripheral portions of said molds beyond the area of said film, wherein said film lies in a predetermined gap within and outside of the molding area and said film is not under compression; injecting thermoplastic material into the cavity space between said film and the male mold said cavity space bounded by a parting line; and thence cooling said injected synthetic material in the shape defined by said cavity.
7. A method of molding an article as set forth in claim 6 where there is a directing of hot pressurized air into said molding cavity against said film prior to said injecting of said thermoplastic material.
8. A method of molding an article as set forth in claim 7 wherein said directing of hot pressurized air is from said male mold section towards said female mold section thereby causing said film to at least begin conforming to contour of said female mold prior to said injecting of thermoplastic material .
9. A method of molding an article as set forth in claim 6 wherein said film passes through a curvilinear gap located just outside of said paring line.
10. The method of molding as set forth in claim 6 wherein said film is deflected in a radiused bend just outside of said parting line.
11. A method for molding an article by injection molding of thermoplastic while simultaneously integrally joining a film onto one surface of such injection molded thermoplastic wherein the film is presoftened by pressing said film under air pressure against the contoured surface of a female mold and wherein the molten thermoplastic plastic material is injected from a male mold into the cavity defined by the film as abutting such cavity and the molding surface of a male mold, said method comprising the steps of transporting a film to cover the surface of the female mold with tne peripheral portion of such film extending outwardly of said cavity, preforming such film into the cavity surface of said female mold, injecting thermoplastic material into the cavity while drawing peripheral portions of such film into such cavity to integrally join such film to such thermoplastic material into an article, and cooling the integrally formed article.
12. A mold having a pair of mold sections, each mold section having a molding portion and an adjacent peripheral nonmolding portion, drive means operative to selectively move said mold sections into and out of molding engagement to provide in one instance a cooperation between said mold sections to define a mold cavity, sprue means connected to one of said mold sections operative to deliver a molten thermoplastic material for molding into a shape in said mold cavity, and said peripheral nonmolding portions defining a film feed region that is operative during molding operations to permit free movement of portions of the periphery of a film into said mold cavity.
13. A mold as set forth in claim 12 wherein said film feed region includes a curvilinear channel maintaining a gap that is operative to guide such film.
14. A mold as set forth in claim 13 wherein said gap maintained in said curvilinear channel is dimensioned at least to the same dimensions as the thickness of the of the film.
15. A mold as set forth in claim 13 wherein that portion of said curvilinear channel adjacent to said mold cavity is contoured in substantially the same general direction as the adjacent mold cavity.
16. A mold as set forth in claim 15 wherein each of said peripheral nonmolding portions are separate replaceable inserts to provide for the selective thickness of the film used with said mold cavity.
17. A mold as set forth in claim 16 wherein said one mold section has a plurality of bores in said molding portion, and a pressurizing source connected to said bores operative to shape film against the surface the said molding portion of said other mold section.
18. A mold as set forth in claim 17 wherein said gap in said curvilinear channel has a dimension from approximately ten thousandths of an inch to 100 thousandths upon closing of said mold section for molding.
19. A mold as set forth in claim 12 wherein one of said mold sections has said molding portion as a female molding portion, the other one of said mold sections has said molding portion as a male molding portion, said female molding portion has a surface operative to receive and contour a film received therein, said film feed region includes a contoured channel that receives the peripheral portions of the film that is being shaped in said mold cavity, and said drive means that is operative to move said mold sections into molding engagement moves said peripheral nonmolding portions of said mold section into kissing engagement with such periphical portions of said film upon closing of said mold section together.
20. A mold as set forth in claim 19 wherein said film feed region is contoured to a curvilinear surface and with the portion of the curvilinear surface adjacent to said mold cavity being generally in the same direction as the adjacent surface of said female molding section.
21. A mold as set forth in claim 20 wherein each of said peripheral nonmolding portions are removable inserts to provide for the selective thickness of the film used with said mold sections.
22. A mold as set forth in claim 21 wherein said other mold section has a plurality of bores in said molding portion, and a pressurizing source connected to said bores operative to shape film against said surface of said female molding section.
23. An injection molding device comprising a pair of mold sections; each mold section having a mold portion, a nonmolding portion and an abutting clamping portion; said nonmolding portions being located between said clamping portions and said molding portions; said clamping portions operative upon the closing of said mold section to abut each other while said mold portions define a mold cavity, film feed means operative to feed film to a position between said mold portions and said nonmolding portions of said mold sections, motive drive means operative upon actuation to move said clamping portions into abutting contact to position said film against said nonmolding portions and into said mold cavity, and sprue means connected to one of said mold sections for delivering thermoplastic film into said mold cavity while said nonmolding portion is operative to guide film into said mold portions of said mold sections.
Description:
DESCRIPTION

Method And Device For Injection Molding

TECHNICAL FIELD

The invention is directed to the field of injection molding of thermoplastics and more particularly to film transfer injection molding for manufacture of shaped laminates and the method thereof .

BACKGROUND ART

The present invention relates to a method and apparatus for injection molding in a single or multiple cavity mold and more particularly to the molding apparatus that has transferred to it initially a film that is shaped by the molding apparatus and thence has a molten plastic compound injected into the mold cavity to form the finished article (s) with the film laminated to a portion of the surface. The invention is also directed to the molding.

Film transfer injection molding of a finished laminated article by injection molding in a cavity containing a film raises a challenge to provide desired flow of the film and achieving proper film thickness throughout different regions and contours in the shaped laminate. Various techniques of film pre¬ forming have been used off-line, that is in a separate step apart from the injection molding cycle, in attempts to control film thickness and prevent excessive film stretch thinning. Presently, for in-mold pre-forming, the film is clamped when the mold halves are brought

together, and certain portions of the film are stretched on contact with the male mold in the first stages while the remaining portions of the film in the mold are out of contact with any mold surface. The prior art molds may clamp the film throughout the non-molding area beginning at the cavity edge, or there may be clamping force more remotely applied, but nevertheless as the film under goes tension, wrinkling occurs. This wrinkling has limited the use of the film insert molding technique. Means for eliminating film wrinkling are still needed.

The present invention employs a new technique which allows an overlying film to freely gather over a large area with less stretch thinning. In the most preferred embodiment there is no clamp point on the film and this reduces further the degree of film stretch thinning. The film is in a confined gap space, is not under a pinch, but is merely in kiss contact with the mold halves. Thus, the film can yield over the entire film area. The film can freely move inwardly from a lateral non-molding area to a molding area to thus enhance the uniformity of flow, insuring a more consistent thickness in the contours of the shaped article. This process allows for use of a predetermined film thickness since the overall flow is more consistent. The present invention also eliminates the problem of wrinkling especially at the corners of angular edge portions of the article formed, wherein the film is deflected in a smooth curving circumfrential bend which is out of the plane of the parting line. The preferred bending pattern is around a

semicircle. Forcing the film on a circumfrential bend provides a means for ironing wrinkles as the film is drawn therethrough. This is akin to pulling the tensioned film over a mandrel .

DISCLOSURE OF INVENTION

The present invention is directed to the molding of a laminate article by the use of a pair of mold dies having sections or halves wherein each mold section has a non-molding portion, a molding cavity portion within the parting line and a die clamping portion. A film is located between the mold halves and occupies the non-molding portions and the molding portion but preferably not the clamping portion of the mold. On clamping of the mold halves, when the film is not under a pinch but occupies a machined gap designed into the cooperating mold halves, there is free film gathering inward toward the mold cavity with a low extent of film stretch-thinning as the cavity is filled. On clamping of the mold halves and injection of thermoplastic material into the cavity between the mold halves, the thermoplastic material presses the film against one mold half (typically the female half) while allowing the movement of the film located in the non-molding portions of the mold halves to move into the cavity as the thermoplastic material fills the mold cavity. Immediately outward from the parting line the mold provides a bending path for the film by way of complimentary channel and convex portions which causes counter tension and relieves the tendency to wrinkle. On cooling, the formed laminate article is removed and the

edges trimmed. The film coverage is improved and for decorative trim pieces in a variety of industrial and commercial uses, the parting line is totally hidden from view.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an elevational view in semi-schematic form partly in sectional showing the general arrangement of the apparatus;

Fig. 2 is a front elevational view of the female half (mold cavity) taken on line 2-2 of Fig. 1;

Fig. 3 is a front elevational view of the male half (mold core) taken on line 3-3 of Fig. 1;

Fig. 4 is a cross-section side elevational view of the mold halves in their open position taken on line 4-4 of Fig. 1 showing the film location and feed side rails;

Fig. 5 is a cross-sectional view of the cooperative mold halves in their closed position before injection of thermoplastic into the cavity space.

Fig. 6 is a cross-sectional view of the cooperative mold halves similar to Fig. 5 but with dried, pressurized air acting against the film located against the contour of the female cavity in the mold.

Fig. 7 is a cross sectional view of the cooperative mold halves similar to Fig. 5 but with a thermoplastic resin injected into the mold cavity space forcing the film against the female mold contour;

Fig. 8 is a side elevational view in cross section of the cooperative mold halves taken on line 8-8 of Fig. 7 showing the film location and feed end caps;

Fig. 9 is a cross sectional view in schematic form illustrating the end trimming of the molded article;

Fig. 10 is a perspective view of the laminated article with a portion thereof in cross section,-

Fig. 11 is an enlarged partial cross section view of cooperative mold halves in their closed position before injection of thermoplastic in the area of the side rails which contain a back- cut for film edge wrapping;

Fig. 12 is an enlarged partial cross section of the same region as Fig. 11 after injection of thermoplastic showing film edge wrapping to the back side of the molded laminate;

Fig. 13 is a perspective view of the trimmed, laminated article with a portion thereof in section, showing edge wrapping of the film.

BEST MODE OF CARRYING OUT THE INVENTION

Referring now to the drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, there is shown in Figs. 10 and 13 exemplary portions of molded articles 10 and 10", respectively, depicted in the shape of a trim strip which includes a body 12 having a decorative film 14 bonded thereto. Figure 1 depicts a verticle mold portion. As a reference, the depicted mold cavity forms an elongated article. The terms "upper" and lower" refer to the ends of the article. The term

"side" refers to the lateral elongated edges. Body 12 is a thermoplastic material suitable for injection molding while film 14 is a film, for example, a clear or pigmented thermoplastic film suitable as an appearance layer, or a scuff layer and/or a weathering layer, and the like. The film 14 is bonded to the adjacent portion of body 12 and becomes integral therewith. Molded article 10 is made by a novel molding assembly 16 and by the method of the present invention as described thereinafter.

Reference Listing

10, 10 molded article 45 upper end cap

12 body 46 lower end cap

14 film 50 peripheral molding surface of

16 molding assembly end cap

18 female mold section (half) 50 peripheral molding surface of

20 male mold section (half) end cap

21 mold base (stationary) 51 part line on side rail

22 mold base (moving) 52 part line on end cap

23 hydraulic cylinder 53 cavity edge opposite part

24 injection nozzle lines

25 injection molding device 54 passageway (runner)

26 air passageways 57 female mold region (cavity)

28 supply roll 59 convex portion

29 take up roll 60 back cut on convex portion

30 heater roll 61 side rail

31 guide roll 62 radius lip in side rail

32 cutter 64 convex portion opposite upper

33 lower guide roll end cap

34 socket head cap screws 65 convex portion opposite lower

35 machined pocket of 22 end cap

36 machined pocket of 21 66 convex portion opposite side

37 machined pocket shoulder rail

37 side of machined pocket 36 69 convex portion opposite side

38 lateral clamp surface rail

39 lateral clamp surface 70 curvilinear channel in rails

42 machined pocket surfaces 71 curvilinear channel in caps

42 machined pocket surfaces 72 edge wrap

43 ' - iv designed corners 74 surface of mold base 22

44 side rail 75 mold cavity

44 ' side rail 77 tapered surface at ends

80 tapered portion

81 tapered portion

82 tapered portion

83 tapered portion

84 tapered portion

85 tapered portion

With reference to Fig. 1, the molding assembly has a pair of mold sections 18 and 20. Depicted in the several figures, mold section 18 is the female mold half and mold section 20 is the male mold half. Male mold section 20 is securely attached to the stationary platen or mold base 21 while female mold section 18 is securely attached to a moving platen or mold base 22, which plate 22 is movable toward or away from the male mold section 20 by any conveying means such as a hydraulic cylinder or ram 23. The male mold section 20 is supplied thermoplastic material from an injection molding device 25, old and well known in the art. Preheated pressurized air is preferably supplied via passageways 26 (figs. 3,4, and 5) through male mold section 20 in a manner well understood in the art to pre-shape film 14 prior to the injection of thermoplastic material into the cavity.

The film 14 as depicted in Fig. 1 is vertically transported between the female mold section 18 and male mold section 20 by suitably unrolling the film 14 from a supply roll 28 and a take up roll 29. This orientation is equally applied to horizontal transport. There can be manual or robotic means for film insertion. The figures are merely illustrative and not limitative. The molded article may be separated from the non-molded portion of the film by suitable cutters, leaving the lateral edges of the remaining film portion intact so as to enable subsequent advancement of the film for successive injection moldings. The movement of the film 14 between the supply roll 28 and take up roll 29 is controlled by suitable guide

rolls, means for controlling tension and means for indexing the film for repetitive moldings in a manner well known in the art . Suitable heater means 30 can be optionally located anywhere between the supply roll 28, guide roll 31 and the female mold section 18 and a lower guide roll 33 to separate the molded article from the film 14 above and below the molded article as well as the sides thereof to maintain the film integrity to be transported downwardly towards the take up roll 29.

In Fig. 4 male mold insert section 20 has its platen or mold base 21 with machined pocket 36 at its central portion and with contours following at the lateral portion with a shoulder 37 and a side 37' . As illustrated, machined pocket 36 is twice the depth of shoulder 37, although the difference in depth is not critical. Fig. 4 depicts the most preferred embodiment wherein machined male mold insert section 20 and overlying side rails 44 and 44' are separate elements of the mold assembly. Less preferredly, side rails 44 and 44 ' and/or end caps 45-46 can be integral with male mold insert section 20. The preferred embodiment is more versatile and allows for fabricating various side rails 44 - 44' and end caps 45 - 46 to secure the machined male mold section. In this manner it is more cost effective for modifying the width of the gap between clamped mold halves. This enables rapid switching to films of differing thickness without the need for changing the entire tool.

Mold base or platen 21 has longitudinally extending lateral clamp surfaces 38 and 39 that extend for the full length thereof. The end caps have curvilinear channels shown at 71. As shown in Fig. 4 the male mold insert section 20 is machined along its sides to accept side rails 44 and 44 ' . Side rails 44 and 44 ' are secured to the mold base 20 as by socket head cap screws 34 and retain the male mold insert section 20 within the machined pocket in mold base 21. As depicted in Fig. 3, an upper end cap 45 and a lower end cap 46 are located respectively in the upper and lower end portions of the machined pocket 36 and abut the male mold insert 20. The end caps 45 and 46 are secured to the platen or mold base 21 by socket head cap screws 34. The surface of stationary mold base 21 between the respective longitudinally extending clamping surfaces 38 and 39 and the outer side edges of side rails 44 and 44' as well as end caps 45-46 provides machined pocket surfaces 42 and 42' . Preferably, the pocket depth plus side rail thickness provide a resulting gap sufficient to allow feeding of film without pinching or locational holding and clamping when the female and male molds are clamped together in the molding process . The machined pocket surfaces 42 and 42' with the installed inserts provide a recess at least about equal and preferably up to about no more than 0.050 in. more than the thickness of the film selected for use. Such machined pocket surfaces 42 and 42' extend upwardly and downwardly on male mold base 21 and merge inwardly around the respective upper and lower caps 45-46 to accommodate the movement of film. The recessed surfaces 42 and 42' of mold base 21 are preferably coplanar with the top

surfaces of the side rail inserts 44 and 44 ' and end caps 45-46. In handling films of varying thickness, mold insert side rails and end caps continue the gap through the part line for the film and should not restrict film feeding toward the mold cavity. There may be machined pocket surfaces on both male and female halves, or on either half, however it is merely preferred that a machined pocket surface is on the male half, as at 42-42' .

As an illustration of set up considerations, when one desires to mold a laminate article using a film of nominal thickness 0.020 inch, such clearance at 42 and 42 ' inward from the clamping region between the mold bases (at clamping) should provide a gap of a ^ least 0.020 inch and more preferably equal to the upper film manufacturing tolerance specifications corresponding to a nominal 0.020 inch thickness (gauge) . Accordingly, the gap can be pre-selected by exchanging the side rails, and top and bottom end caps which are machined to a thickness to provide exact film gap requirements when secured to shoulder 37.

Because the film completes the gap space at the parting line, a gap which is wider than the film thickness would likely cause some flashing of thermoplastic material at the (male) parting line. Using a gap of several thousandths wider than the nominal film thickness gives acceptable moldings in the case of semi-rigid a;.d flexible polyvinyl chloride .

The gap between mold halves at clamping, in the region directly over the side rails and end caps is more critical to properly control film

feeding, whereas the machined gap outside of these elements can be larger as at 42-42 ' . The area outward from side rails and end caps is typically a permanent machined pocket in mold base 21, and the gap here is sufficient to accommodate the thickest film potentially used. Any gap ranging from about 0.01 inch to about 0.100 inch or more can be selected in accordance with the thickness of the desired film.

As viewed in Fig. 3, the male mold insert 20 presents a male molding portion 43 with four designed corners 43' 43" 43 ' ' ' and 43 lv . An injection nozzle 24 of Fig. 8 is connected to a runner system 54, which contain the sprue means, ie. , passageways for thermoplastic material . The openings into the cavity are shown in Figs . 3 and 4, at 54. Figure 3 shows the preferred aspect for passageways 26, referred to commercially as air poppet valves, for distribution of dry air throughout male insert section 43 as a means for partial film pre- shaping.

Figure 4 illustrates the female mold section 18 which is secured in the machined pocket of platen or mold base 22 and has a female molding region 57 with designed contours throughout which terminate into a curvillinear portion 63 then to protruding convex portions 66 and 69. The convex portion extends along the circumference of female mold region 57 and orients the film lying in the gap at a tangent to the side plane of the molded article. The gap is maintained throughout the convex portions and the curvilinar channel 70. This orienting means allows the film to lie perpendicular to

the parting line plane. There is a smooth curvature with convex portions 66 and 69. Using surface 74 as a reference, the lateral plane of the film outward of convex portions is parallel to plane of surface 74 on the mold platen. In the preferred embodiment the convex portions provide deflection of the film first toward the male half, then in a semicircular arc at 64, 65, 66 and 69. A deflection pattern only toward the female half as in a smooth radiused bend, such as a 90 degree bend, is also suitable .

The channel in side rails 44 - 44 ' and end caps 45-46 extends continuously and circumferentially around the area just outside the parting line of the cavity formed of the male and female halves . In the embodiment illustrated in Figs. 2 and 3, the channel is preferably located on the male (core) molding section and the corresponding convex region is located on the female (cavity) molding portion. This configuration can be reversed, wherein the channel is located on the female portion with the convex region 66 located on the male portion, however this would require special routing of the injection melt so as to cross between mold halves and fill from the female side in the reverse from what is illustrated. In the preferred configuration the male- channel/female-convex portion arrangement provides the least tortuous path for the injection melt.

The inward edges of channel 70 and inward edge of convex portions 66 and 69 form a gapped parting line. The film, inserted there

between, essentially completes the closing of the cavity. Surface 74 on mold base 22 is a flat surface which extends to the machined pocket 35 in mold base 22. On closing the mold halves, surfaces 74 and surfaces 38-39 contact each other and provide clamp force area, while the inner peripheral surfaces 42-42' do not contact surface 74 of the female mold. As illustrated in Fig. 5, film 14 has width which does not exceed the width of machined pocket surfaces 42-42 ' , so the film is preferably never clamped. The film may be clamped at a suitable distance from the parting line and it is expected that passage of the film through the channel/convex portion will still eliminate wrinkling within the cavity.

When the female mold section 18 closes with the male mold section 20, they define mold cavity 75 which is the shape of the article to be formed. When the mold is clamped together just before melt injection, there are three essential portions: (1) the clamp area abutting portions which include the outer peripheral surfaces 38-39 of the mold base 21 against the abutting surface 74 on mold base 22; (2) the gap area inward from machined gap edges including: non-molding portions at 42-42', the peripheral surfaces of the side rails 44-44' and end caps 45-46 adjacent to groove 70 and inward where the side rails meet peripheral molding surfaces 50-50' at the part line, (Fig. 3) and the complimentary surfaces of convex portion 64, 65, 66 and 69; and (3) the molding portion of the mold sections 18 and 20 which defines cavity 75.

The cavity edges on the female side are at 53 in Fig. 2. Opposite these edges at the male half are the parting lines 51 and 52 in Fig. 4 on the side rails and endcaps (Fig. 3) . The film exiting from the parting generally will define where the respective article is trimmed, which thereby defines the periphery or perimeter of the molded article containing the integrally bonded film on at least a portion thereof. In the simplest shape having a front show side and back surface, the film completely covers all the show surfaces and is trimmed at the back plane. When the laminated article is placed on a flat surface, the film covers the entire part and no injection material or parting lines are seen. The molding surfaces 50 on the side rails and 50 ' on the end caps converge to the inner most edge of groove 70. The respective ends of the molded article taper toward the parting line as seen in Figs. 2 and 3 along a line joining 43'- 43" and 43 ' ' -43 iv , which tapered portions are designated as 80 through 85 in Fig. 2 on the female mold section 18.

When the female mold section 18 is closed onto the male mold section 20, the entire perimeter of the removable inserts containing groove 70 defines a gap that is predetermined by the depth of the inserts. The principal function of channel 70 is to provide an oriented passage of the film so that the film is oriented at the parting line in a pL.ane which is perpendicular to the plane of the peripheral film portion outward of the groove region thus, the film is on a curving bend at the region nearest the parting lines in the mold. The predetermined gap can be the same as the film

thickness or it can be greater than the film thickness, such as up to 0.050 inches wider than the film thickness. The gap is advantageously not so much wider than the film thickness so as to allow for residual film wrinkling of the lateral article portions, particularly at the corners. Such gap also permits the flow of air out of the cavity to prevent the trapping of air within the mold cavity. This feature is referred to as venting.

With the use of films having elasticity, there has been observed unexpected edge wrap of the film as the molded article is ejected from the mold. The edge wrap effect was observed using the mold sections depicted in Figs. 2-7. This aspect is particularly favored for example where the predetermined gap is set at 0.020 inches and a relatively elastic film of about 0.010 inches is used. The elastic recovery in the film in the typical temperature range occurring on ejection can cause wrapping and some permanent adhesion on the back side surface of the article.

The method of operation will now be described. Assuming that the female mold section is in the withdrawn portion, Fig. 1 illustrates the supply roll 28 and the take up roll 29 which can be activated to advance a predetermined length of film 14. Prior to movement of the film 14, and/or during movement of the film 14, an optional heater means 30 is employed to preheat the film. During the clamping of the female mold section 18 with the male mold section 20, pressurized hot air is preferably directed from a plurality of

passageways 26 in the male mold section 20 towards the film 14 to facilitate the conformance of the film to the curved female mold surfaces on closing of the mold sections. After such closing, the film 14 lies in the gap of the non-molding portions of the female mold and male mold sections which is a tangential touching or a mere kissing of the film to the mold parts which hereinafter is meant and defined as a gentle touching between the parts that would allow the film to slide on the surface of the non-molding portions of the mold sections. This is in sharp contrast to a film in a prior art mold which is compressed at the part line. Stretching occurs from there and the film is drawn from a smaller square area. This prior art clamping of film is unyielding and prevents gathering movement from a large area. By the film being immovable at the part line, this dictates that conformance to the cavity shape takes place strictly as a stretching of the film from that point, and this cm give rise to tearing, and variation of film thickness, especially in the deeper drawn areas of the mold cavity. In the practice of the present invention, laminate molded articles are provided with more constant film cross sectional thickness. There is less film stretch thinning at the extremes and the incidence of film crease marks is eliminated. In the most preferred embodiments, the orientation of the film at the part line is in the plane congruent to the cavity edge, the film outward from the part line having been bent through groove 70 and around the convex portions acting as a mandrel.

Thereafter, upon clamping, molten thermoplastic is injected through the injection nozzle 24 of the abutting portions of the mold sections as previously described, and through the passageways 54 in the male mold section 20 into the cavity 75, filling such cavity 75 and onto the back surface of film 14 firmly pressing it into the precise shape of the female mold surface. During this action and the pre-shaping action of the film 14, that portion of the film 14 that lies in the gap is free to move into the molding portions of the mold sections 18 and 20 as the film is pressed against the cavity surfaces by the advancing melt. The traversal in channel 70 is preferably a smooth directional movement of the film from the non-molding portion to the molding portion and stresses the film in such a way as to cancel the internal stresses that generate wrinkling. There may be some wrinkling up to the part line but none appears in the trimmed laminate. This smoothing function is not unlike an ironing means as it has been observed in experience with the mold of the invention, severe wrinkle patterns appear outward of the groove region, but in the groove region and within the molding section, the wrinkling is unexpectedly eliminated. In working with relatively large parts and viscous thermoplastic injection melts, the practitioner understands that balancing of melt flow is done to prevent film creasing at knit lines. This aspect is beyond the present disclosure.

Upon completion of the molding of the article, the female mold section 18 may be moved away from the male mold section 20 and the trim strip 10 moved away from the female mold

section 10 by tensioning the film strip between the guide rolls 31 and 33. Thereafter the film strip 10 is moved downwardly to a position where the formed trim strip is opposite the trimming device 32 where the trim strip is trimmed from the film along the parting line as defined herein above. Alternatively, air actuated steel ruled dies (clicker dies) can be incorporated in the conventional manner to cut the article away from the film.

Figure 11 illustrates a partial cross section showing mold halves in closed position prior to injection of thermoplastic material. Female mold section 18 contains convex portion 59 with an undercut (back cut) 60. Side rails 61 contains a radiused lip 62 which is at the male parting line. The parting line is thus rendered inward from the lateral most region of the cavity. This allows edge wrapping of the film. The back cut can run around the entire article edge or a portion thereof. In the illustrated figure, a back cut would also be included in the upper and lower end caps running the entire periphery of the cavity.

Figure 12 illustrates the effect of injection of thermoplastic material forming body 12. With the back cut on the convex portion mated to the lip 62 on the inner edge of the groove 70, the thermoplastic material forces film 14 out to the lateral edge while the film closes off the gap between mold halves. Part line 62 being inward, allows the film to wrap around the outer edge of the molded article.

Figure 13 illustrates the cross section showing the edge wrap of the film at 72.

The extent of back cut depth is limited to about 1/32 of an inch plus the film thickness without requiring moving parts in the mold. An edge wrap of about 0.030 inch is desirable and therefore an under cut plus film thickness totaling 0.030 should not render the molded part unextractable from the female mold half after mold parting. Extraction of the article can be accomplished while the hot modulus is low enough to deformation yield necessary to peel the part from the female mold. Trimming of an edge wrapped laminate would preferably be made at or just beyond the part line on the male side of the molding. The selection of thermoplastic material which will allow an undercut is within the skill and preference of the skilled practitioner and is beyond the scope of this disclosure.

In view of the above disclosure the invention can be applied to a mold having no moving parts as is illustrated, or the invention can be readily adapted to molds with slides, i.e., retracting means for removing under cuts. The use of flexible thermoplastic materials and small undercuts resulting in forced mold release is more preferred. Reference is made to Injection Molding Handbook. D. Rosato, et al . editors, Van Nostrand Reinhold, Inc. 1986, Chapter 3.

Thus, various other changes and modifications are contemplated and may obviously be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter defined by the attached claims.