WO1995003927A1

WO1995003927A1 - Method and apparatus for making plastic mirrors and the mirrors made therefrom

Info

Publication number: WO1995003927A1
Application number: PCT/US1994/008764
Authority: WO
Inventors: Rick Carlson
Original assignee: Aotec, Inc.
Priority date: 1993-08-03
Filing date: 1994-08-02
Publication date: 1995-02-09

Abstract

A film feeder and take-up device feeds Mylar film (16) which has a pattern of thin reflective material films (18) adhered thereto to a press (10). The press includes a movable press mold plate (24) having mold protrusions (44) and a fixed mold plate (52) having cavities (72) which receive the mold protrusions (44) when the press is closed. The Mylar film (16) is positioned with the reflective films (18) over the mold protrusions (44), and a pair of hold down bars (42) hold the Mylar film (16) to the press mold plate (24). Plastic is injected into the mold cavities (72), forcing the reflective films (18) up against the mold protrusions (44) with the Mylar film (16) therebetween. The heat from the plastic causes the reflective films (18) to thermally bond to the plastic and the adhesive to release the reflective films (18) from the Mylar film (16), thereby forming mirrors (90).

Description

METHOD AND APPARATUS FOR MAKING PLASTIC MIRRORS AND THE MIRRORS MADE THEREFROM

Background of the Invention:

The present invention relates to mirrors. More specifically, the present invention relates to a method and apparatus for making plastic mirrors and the mirrors made therefrom. Mirrors are well known in the prior art and generally comprise a glass substrate with a reflective film (e.g., silver or aluminum film) coated on one surface thereof. Light passes through the glass substrate and is reflected off of the reflective film and back through the glass substrate. Mirrors have many known applications in for example, automotive, home/personal, medical and otherwise. Also, mirrors comprising a plastic base with a silver or aluminum film adhered to one side thereof using an adhesive are known. However, unlike the glass mirrors the light reflected does not pass through the substrate (i.e., the plastic base), the light is reflected directly off of the silver or aluminum film. The quality of reflectance from such mirrors typically does not compare to the glass substrate mirrors described above. Further, without the glass substrate before the reflective film, a prism affect can not be obtained as is commonly used in rear view mirrors of automobiles. Summary of the Invention:

The above-discussed and other problems and deficiencies of the prior art are overcome or alleviated by the method and apparatus for making plastic mirrors and the mirrors made therefrom of the present invention. In accordance with the present invention, a press has a plurality of press plates attached to a press platen which is driven by the ram of the press and a plurality of fixed plates attached to a fixed platen of the press. A film feeder and take-up device is mounted to the press for feeding a mylar film. The mylar film includes a pattern of thin reflective material films adhered to one surface of the mylar. The mylar film also includes a longitudinal strip for y-axis orientation and a series of squares for x-axis orientation. The press plates include a press mold plate having mold protrusions at a surface of the plate. A pair of hydraulically driven hold down bars or a bracket are used to hold down the mylar film. The fixed plates include a fixed mold plate having cavities which are receptive to the protrusions on the press mold plate when the press is closed. A plurality of hydraulically driven ejection pins are used to eject the mold. Also, injection means is provided in the fixed plates and comprises a channel with a plurality of branches connected to each mold cavity A film positioning system is a part of the film feeder and take-up device described hereinbefore. The press is set to a first or open position wherein the mylar film is positioned as described above, i.e., the reflective films on the mylar are properly positioned over the mold protrusions. After the mylar film has been properly positioned the hold down bars are activated, thereby holding the mylar film in position with the reflective films aligned over mold protrusions.

The press is then closed whereby the ram of the press is actuated causing the press plates to move towards the fixed plates. Both injection and ejection are performed on one side of the press (i.e., the fixed side) while the press (or moving) side is used to hold the mylar film. When the press is closed the mold protrusions fit into the mold cavities with the reflective films still on the mylar film and disposed within the mold cavities against the mold protrusions. In this closed position, plastic (melted plastic) is injected under heat and pressure through the injection channel and branches into the mold cavities. As the plastic fills the mold cavities it forces the reflective films up against the mold protrusions with the mylar film therebetween. The heat from the plastic causes the reflective films to thermally bond to the plastic and the adhesive to release the reflective film from the mylar film. While still in the closed position the plastic is at least partially cooled and allowed to harden. Once the plastic has sufficiently hardened the press is opened. The plastic mirrors having been formed as described above and are now ready to be stripped from the press. This ejector pins are activated to push the molded plastic mirrors at least partially out of the mold cavities and the plastic mirrors are removed from the press. The press is reset to its initial position and the mylar film advanced whereby more plastic mirrors can be formed as described above.

An alternate embodiment of the means for holding down the mylar film after it has been positioned comprises applying a vacuum to further hold the mylar film in place and to stretch out the mylar film to eliminate any wrinkles in the film. This vacuum is to be maintained until the press is opened, as described above.

The above discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.

Brief Description of the Drawings:

Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:

FIGURE 1 is a cross sectional side elevation view of the press plates with the film carrying a reflective material, in a first position, for use in making a plastic mirror in accordance with the present invention; FIGURE 2 is a cross sectional top view of the press plates with the film carrying a reflective material of FIGURE 1 , in the first position;

FIGURE 3 is an elevational view taken in the direction of line 3-3 of FIGURE i; FIGURE 4 is a cross sectional side elevation view of the press plates with the film carrying a reflective material, in a second position;

FIGURE 5 is a cross sectional top view of the press plates with the film carrying a reflective material of FIGURE 4, in the second position; FIGURE 6 is a cross sectional side elevation view of the press plates with the film carrying a reflective material, in a third position;

FIGURE 7 is a cross sectional top view of the press plates with the film carrying a reflective material of FIGURE 6, in the third position;

FIGURE 8 is a cross sectional side elevation view of the press plates with the film carrying a reflective material, in a fourth position;

FIGURE 9 is a cross sectional top view of the press plates with the film carrying a reflective material of FIGURE 8, in the fourth position;

FIGURE 10 is an elevation view of the film hold down bar in accordance with the present invention; FIGURE 11 is a cross sectional view taken along the line 11-11 in FIGURE 10;

FIGURE 12 an elevation view of a film hold down bracket in accordance with an alternate embodiment of the present invention;

FIGURE 13 is a cross sectional view taken along the line 13-13 in FIGURE 10;

FIGURE 14 is a cross sectional side elevation view of the plastic mirror made in accordance with the method of the present invention;

FIGURE 15 is a cross sectional side elevation view of an alternate embodiment plastic mirror made in accordance with the method of the present invention;

FIGURE 16 is a front view of the plastic mirror of FIGURE 14 prior to removal of the edge gate and runner; FIGURE 17 is a front view of the plastic mirror of FIGURE 14 after removal of the edge gate and runner; and

FIGURE 18 is an elevational view taken in the same direction as that of FIGURE 3 showing an alternative embodiment employing a vacuum hold down in accordance the present invention. Description of the Preferred Embodiment:

Referring first to FIGURES 1-3, press plates for use in a hydraulic press (not shown), such as a Cincinnati two hundred ton press, is shown generally at 10 in a first position. Plates 12 are attached to a press platen (not shown) which is driven by the ram of the press as is well known. Plates 14 are attached to a stationary or fixed platen (not shown) of the press. A film feeder and take-up device (not shown), for example, part numbers MA 500, MA 250 and MA 400 from Kurz-Hastings, is mounted to the press for feeding a mylar film 16. Mylar film 16 includes a pattern of thin aluminum shaped films 18 adhered to one surface of the mylar. The shape and size of films 18 is determined by the particular application, in this example an automotive rear view mirror. Further, films 18 may be comprised of any other suitable reflective material, e.g., silver. Mylar film 16 also includes a longitudinal strip 20 (or series of strips) for y-axis orientation and a series of squares or rectangles 22 for x-axis orientation. Strip 20 and squares 22 are silk screened opaque ink markings on the mylar. Plates 12 comprise a mold plate 24 attached to a plate 26 by a plurality of bolts

28. Plate 26 is attached to a plate 30 by a plurality of bolts 32. It will be appreciated that the bolt heads are disposed in corresponding recesses, as is shown in the FIGURES. A pair of plates 34 and 36 are disposed in an opening 38 of plate 30. A plurality of pins 40 are attached to these plates 34, 36 which extend through openings in plates 24 and 26 and connect to film hold down bars 42. Plates 34 and 36 are hydraulically driven within opening 38 by a plurality of hydraulic cylinders 44. Cylinders 44 are secured to plate 26, whereby flanges of the cylinders are disposed within recesses in plate 26 and held therein by plate 24. The pistons of the cylinders are connect to plates 34 and 36 to drive the same, whereby bars 42 are driven via pins 40. Mold plate 24 includes mold protrusions 44 at a surface 46 of the plate 24. An optical sensor 48 is mounted to plate

24 at surface 46 for detecting mark 22 and an optical sensor 50 is mounted to plate 24 at surface 46 for detecting mark 20.

Plates 16 comprise a mold plate 52 attached to a plate 54 by a plurality of bolts 56. Plate 54 is attached to a plate 58 by a plurality of bolts 60. It will be appreciated that the bolt heads are disposed in corresponding recesses, as is shown in the FIGURES. A pair of plates 62 and 64 are disposed in an opening 66 of plate 58. A plurality of ejection pins 68 are attached to these plates 62, 64 and extend through openings in plates 52 and 54. Plates 62 and 64 are hydraulically driven within opening 66 by a plurality of hydraulic cylinders 70. Cylinders 70 are secured to plate 54, whereby flanges of the cylinders are disposed within recesses in plate 54 and held therein by plate 52. The pistons of the cylinders are connect to plates 62 and 64 to drive the same, whereby ejection pins 68 are driven into mold cavities 72 within mold plate 52 at a surface 74 thereof. Cavities 72 are receptive to protrusions 44 when the press is closed. Cavities 76 are provided in plate 52 for receiving sensors 48 and 50 and cavities 78 are provided for receiving bars 42 when the press is closed. Also, injection means are provided which comprise a channel 80 which includes a plurality of branches 82 connected to each mold cavity 76. Channel 80 originates at an injection port 84 having a bushing 86 within plate 58. Channel 80 extends through openings in plates 64, 62, 58, 54 and 52. The film positioning system is a part of the film feeder and take-up device described hereinbefore. In accordance with such a system, the x sensor 48 is first used to position the film 16 relevant to an x-axis position. As the film 16 is advanced sensor 48 looks for marker 22. When marker 22 is detected (i.e., the light is blocked by the marker) advancement of film 16 is slowed down until light is again detected then advancement of film 16 is stopped. Next the y sensor 50 is used to position the film 16 relevant to the y-axis position. Film 16 is moved away (again by the feeder and take-up device) from the sensor 50 until light is detected, then film 16 is moved toward sensor 50 until no light is detected and the film 16 is stopped in this position. When film 16 has been positioned as described above, the reflective films 18 on the mylar are properly positioned over the protrusions 44 of plate 24.

Referring now to FIGURES 4 and 5, after film 16 has been properly positioned cylinders 44 are activated to push plates 34 and 36 away from plate 26. This causes bars 42 push against film 16 and surface 46 of plate 24, thereby holding film 16 in position with films 18 aligned over protrusions 44 on plate 24. The press is now ready to be closed. Referring to FIGURES 6 and 7, the press is closed whereby the ram of the press is actuated causing plates 12 to move towards plates 16. Plates 12 are often referred to as the "B" plates and are typically mounted to the fixed platen of the press, and plates 16 are often referred to as the "A" plates and are typically mounted on the press platen of the press. However, in the present invention the so called "A" plates are mounted on the fixed platen of the press, and the so called "B" plates are mounted on the press platen of the press. This allows both injection and ejection to be performed on one side of the press (i.e., the fixed platen side) while press platen side is used to hold the mylar film, as is more fully described below. When the press is closed the protrusions 44 fit into the cavities 72 with the reflective films 18 still on the mylar film 16 and disposed within cavities 72 against the protrusions 44. Sensors 48 and 50 are disposed in cavities 76, and bars 42 are disposed in cavities 78.

In this closed position, plastic (melted plastic) is injected under heat and pressure through channel 80 and branches 82 into cavities 72. As the plastic fills the cavities 72 it forces films 18 up against protrusions 44 with the mylar film 16 therebetween. The heat from the plastic causes the reflective films 18 to thermally bond to the plastic and the adhesive to release the film 18 from the film 16. While still in the closed position the plastic is at least partially cooled and allowed to harden. The mold is cooled by fluid (e.g., water) circulation or any other well known means. Once the plastic has sufficiently hardened the press is opened and returns the plates to the position shown in FIGURES 4 and 5.

Referring now to FIGURES 8 and 9, plastic mirrors have been formed as described above and are now ready to be stripped from the press. Cylinders 70 are activated to push plates 64 and 62 away from plate 54. These ejector pins 68 push molded plastic mirrors 90 at least partially out of cavities 72 whereby the plastic mirrors are removed from the press.

Cylinders 70 and 44 are now actuated to return pins 68 and bars 42 respectively to their original positions, shown in FIGURES 1 and 2. Then the film 16 can be advanced and more plastic mirrors can be formed as described above. Referring to FIGURES 10 and 11 , one of the bars 42 is shown. Bar 42 is generally rectangularly shaped with rounded ends. Bar 42 has a longitudinal groove 92 therein wherein a rubber gasket 94 is secured. When the bars 42 are activated to hold the mylar film 16, as described above, the gasket 94 contacts the film 16 thereby avoiding damage to the film and avoiding any slippage of film 16 after it has been positioned.

Referring to FIGURES 12 and 13, an alternate embodiment of the means for holding down film 16 after it has been positioned is shown generally at 96. Hold down bracket 96 is closed rectangular or square loop. It will be appreciated that bracket 96 may be of any suitable shape dictated by the desired mirror's shape and size. Bracket

96 has a longitudinal groove 98 therein wherein a rubber gasket 100 is secured. When the bracket 96 is activated to hold the mylar film 16, as described above, the gasket 100 contacts the film 16 thereby avoiding damage to the film and avoiding any slippage of film 16 after it has been positioned. It is preferred that gasket 100 contact film 16 at all points thereabout when a vacuum is applied to further hold film 16 in place and to stretch out film 16 to eliminate ant wrinkles in the film. Such a vacuum could be applied through a channel 102 (FIGURE 18) which leads to a groove 104 in surface 46 of plate 24. Alternatively, a plurality of small openings could replace the groove 104. The vacuum would be applied after film 16 has been positioned but before bracket 96 is activated to hold down film 16. This vacuum is to be maintained until the press is opened, as described above.

Referring to FIGURE 14, a cross sectional view of the mirror 90 is shown. Mirror 90 comprises an optical grade transparent plastic layer 106, preferably an acrylic, with reflective film 18, preferably aluminum, thermally bonded thereto, by the injection molding process described above. Light passes through the plastic layer 106 and is reflected off of film 18 and back through plastic layer 106. This mirror is well suited for automotive use since it provides the same prism effect as does the prior art glass substrate mirrors. Further, mirror 90 fully complies with Department of Transportation specifications for automotive mirrors. Referring to FIGURE 15, a cross sectional view of an alternate embodiment mirror 108 is shown. Mirror 108 comprises a plastic layer 110 which is not required to be transparent, with reflective film 18, preferably aluminum, thermally bonded thereto, by the injection molding process described above. Light is reflected off of film 18 and does not pass through the plastic layer 110.

Referring to FIGURE 16, mirror 90 is shown with a edge gate 112 and a runner 114 extending therefrom as are commonly used in plastic injection molding. A large edge gate 112 is preferred as it eliminates imperfections in the mirror near the edge gate. The edge gate and runner are removed resulting in the mirror shown in FIGURE 17. The mirror may then be polished and finished as is well known in art of optical plastics.

While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.

What is claimed is:

Claims

Claims ;

CLAIM 1. An injection molding device for making plastic mirrors in a press having a fixed platen and a moving platen, the device comprising: a first mold plate connected to the moving platen, said first mold plate having first and second opposing surfaces, said first mold plate having a mold protrusion extending from said first surface thereof defining at least one surface of a mirror to be made; film means for carrying a reflective material, said film means being disposed near said mold protrusion of said first mold plate; positioning means for positioning said reflective material relative to said mold protrusion of said first mold plate; hold down means connected to said first mold plate, said hold down means for holding down said film means against said first surface of said first mold plate, whereby said reflective material is held relative to said mold protrusion of said first mold plate; a second plate connected to the fixed platen, said second plate having a mold cavity in a first surface thereof defining at least one other surface of a mirror to be made, said mold cavity for cooperating with said mold protrusion when the press is closed; injector means connected to said second mold plate and in communication with said cavity for injecting a plastic in said cavity when the press is closed; and ejector means connected to said second mold plate and for ejecting a molded plastic mirror from said cavity when the press is opened.

CLAIM 2. The device of claim 1 wherein said hold down means comprises: a plurality of spaced apart hold down bars; and means for actuating said hold down bars between release and hold down positions.

CLAIM 3. The device of claim 2 wherein said actuating means comprises: a third plate being displacable relative to said second surface of said first mold plate; a plurality of pins attached between said hold down bars and said third plate; and hydraulic cylinder means connected to said first mold plate for displacing said third plate relative to said first mold plate, whereby said hold down bars actuate between release and hold down positions in response to displacement of said third plate via said pins.

CLAIM 4. The device of claim 1 wherein said hold down means comprises: a hold down bracket; and means for actuating said hold down bracket between release and hold down positions.

CLAIM 5. The device of claim 4 wherein said actuating means comprises: a third plate being displacable relative to said second surface of said first mold plate; a plurality of pins attached between said hold down bracket and said third plate; and hydraulic cylinder means connected to said first mold plate for displacing said third plate relative to said first mold plate, whereby said hold down bracket actuates between release and hold down positions in response to displacement of said third plate via said pins.

CLAIM 6. The device of claim 1 further comprising: vacuum means in said first mold plate at said first surface thereof for holding down and stretching said film means.

CLAIM 7. The device of claim 4 wherein said hold down bracket further comprises: a gasket disposed at one surface of said hold down bracket for contacting said film means when said hold down bar is in the hold down position.

CLAIM 8. The device of claim 2 wherein each of said hold down bars further comprises: a gasket disposed at one surface of said hold down bar for contacting said film means when said hold down bar is in the hold down position.

CLAIM 9. The device of claim 1 wherein said reflective material comprises a thin film of aluminum or silver.

CLAIM 10. The device of claim 1 wherein said plastic comprises a transparent optical grade plastic.

CLAIM 11. The device of claim 10 wherein said plastic comprises an acrylic.

CLAIM 12. A method for making a plastic mirror using a press having a fixed platen and a moving platen, the method comprising the steps of: positioning a film carrying a reflective material relative to a mold protrusion extending from a first mold plate connected to the moving platen, said first mold plate having first and second opposing surfaces, said mold protrusion defining at least one surface of the plastic mirror being made holding down said positioned film against said first surface of said first mold plate, whereby said reflective material is held relative to said mold protrusion of said first mold plate; closing the press whereby said mold protrusion closes a mold cavity in a first surface of a second plate connected to the fixed platen, said mold cavity defming at least one other surface of the plastic mirror being made, said film with said reflective material being disposed within said mold cavity against said mold protrusion injecting a plastic through said second mold plate into said cavity under heat and pressure whereby said reflective material separates from said film and thermally bonds to the plastic; opening the press wherein said film is removed from said reflective material and the plastic; and ejecting a molded plastic mirror from said cavity.

CLAIM 13. The method of claim 12 further comprising the step of: finishing said molded plastic mirror.

CLAIM 14. The method of claim 12 wherein said step of holding down comprises: actuating a plurality of spaced apart hold down bars between release and hold down positions.

CLAIM 15. The method of claim 14 wherein said step of actuating comprises: hydraulically displacing a third plate relative to said first mold plate, whereby said hold down bars actuate between release and hold down positions in response to displacement of said third plate via a plurality of pins attached between said hold down bars and said third plate.

CLAIM 16. The method of claim 12 wherein said step of holding down comprises: actuating a hold down bracket between release and hold down positions.

CLAIM 17. The method of claim 16 wherein said step of actuating comprises: hydraulically displacing a third plate relative to said first mold plate, whereby said hold down bracket actuates between release and hold down positions in response to displacement of said third plate via a plurality of pins attached between said hold down bracket and said third plate.

CLAIM 18. The method of claim 12 further comprising the step of: holding down and stretching said film using vacuum means in said first mold plate at said first surface thereof.

CLAIM 19. The method of claim 16 wherein said hold down bracket further comprises: a gasket disposed at one surface of said hold down bracket for contacting said film when said hold down bracket is in the hold down position.

CLAIM 20. The method of claim 14 wherein each of said hold down bars further comprises: a gasket disposed at one surface of said hold down bar for contacting said film when said hold down bar is in the hold down position.

CLAIM 21. The method of claim 12 wherein said reflective material comprises a thin film of aluminum or silver.

CLAIM 22. The method of claim 12 wherein said plastic comprises a transparent optical grade plastic.

CLAIM 23. The method of claim 22 wherein said plastic comprises an aci lic.

CLAIM 24. A plastic mirror made by the method of claim 12.

CLAIM 25. A plastic mirror comprising: a transparent plastic substrate; and a thin film of reflective material disposed on one surface of said plastic substrate.

CLAIM 26. The mirror of claim 25 wherein said reflective material comprises a thin film of aluminum or silver.

CLAIM 27. The mirror of claim 25 wherein said plastic comprises a transparent optical grade plastic.

CLAIM 28. The mirror of claim 27 wherein said plastic comprises an acrylic.