MOULD METHOD AND APPARATUS FOR PLASTIC SHELLS

Abstract: Apparatus and a process for manufacturing thin walled hollow plastic shells for parts such as automobile door panels, controls and instrument panels from dry thermoplastic pow­ ders includes a plurality of powder boxes and an open-ended heated mold. Each charge box is carried by an indexable car­ ousel which has a drive motor controlled by a programmable controller to position the carousel to off-load a given color to a powder casting mold carrier which is associated with means for sequentially and continuously 1) preheating a mold; 2) dumping powder from an off-loaded color box into a hea­ ted mold; 3) curing the cast powder in the mold; 4) cooling the mold; and 5) stripping the part from the mold.

Description: MOLD METHOD AND APPARATUS FOR PLASTIC SHELLS TECHNICAL FIELD This invention pertains to a method and apparatus for making hollow plastic articles especially suitable for use in automobile trim components such as interior door panels and more particularly to methods and apparatus for processing plastic powder to form articles of different color or the same color on a continuous programmable basis. BACKGROUND ART The automotive industry has turned to the use of interior trim components such as door panels comprising a polyvinyl chloride shell. See, for example, the trim components disclosed in U.S. Patent No. 3,123,403. The acceptance of such components has been because inter alia this type of construction permits a wide latitude in styling and color, and grain effects which are most desired particularly in the interior design of automobiles. The current state of the art includes a pre-formned grained vinyl shell made from dry thermoplastic powder particles which are applied to a heated shell<'>mold from a powder box to form a continuous monochromatic one-piece shell or to form a shell which includes two separate plastic shell sections formed from different colored plastic joined at a connection joint. The use of multi-color plastic is also known in the manufacture of colored filaments. Such manufacture includes use of a compartmented spinning head for making two-colored yarn as disclosed in USPN 3,049,397 issued August 14, 1962 for Process of Making Space-Dyed Yarn Apparatus and method for multiple colored thermoplastic floor materials are set forth in USPN 3,383,442 issued May 14, 1968. Neither of the aforesaid methods and apparatus for manufacture or resultant manufacture is directed to a process or apparatus for manufacturing a single piece shell from powder material suitable for use as an interior panel component of an automobile on a continuous basis, programmed to produce articles of a different monochro atic color or the same monochromatic color or alternatively to produce such articles having two-tone color segments. STATEMENT OF INVENTION AND ADVANTAGES In accordance with the present invention a process and apparatus for loading an open-ended heated mold with powder plastisol material includes the process of releasing a pre-charge of one monochromatic color from a single compartment or two or more colors of thermoplastic powder from separate compartments in a powder box for gravity flow into a preheated mold with means configured to produce either a one-piece shell with one monochromatic color or such a shell with two or more color tones to enhance the decor of the interior of an automobile and to do so by provision of a color carousel with plural powder boxes that are indexed on a programmable basis to be selectively associated with the preheated mold. A preloaded open-ended powder box is filled with a predetermined quantity of different color powder. The loaded open-ended powder box is carried by an indexable carrier that off-loads the box from the carrier to a mold carrier and frame assembly. The powder box is clamped to an open-ended mold on the carrier to form a closed system. The closed system is rotated so that the charge box releases the powder from the powder box compartments to flow evenly across the open end of the mold by gravity to produce a uniform thin shell across heated casting surfaces of the mold. Joint seals can be provided in association with two-color compartments to produce distinct strips of colors in a single-piece article with an integral joint formed between each color. Such two-tone pieces and tooling for manufacturing such pieces are set forth in co-pending United States Patent Application S.N. 614,004 filed May 25, 1984, and commonly assigned. Plastics molding apparatus of the invention has a gravity fill system for flow of powder material into a heated mold to form a thin walled single plastic part of a color determined by the programmed indexation of the powder box carrier and off-loading of a powder box to means for coupling the powder box to a preheated mold and by provision of means for operating the coupled powder box and mold to dispose the charge box with respect to the mold for gravity flow of powder from the powder box into the mold so that flow of powder into the mold covers uniformly heated separate surfaces of the mold with either the same or different colors of plastic connected at a joint region to form a single part with at least two color panels there across . The mold-frame and mold apparatus are carried by indexable apparatus with respect to a preheat oven; the casting station; a cure oven; a cooling station; and a stripping position. In one embodiment the mold-frame and mold are carried on a multiple station manufacturing unit or octopus with a rotatable carriage and individual robot arms that reciprocate and rotate to off-load the powder box while casting powder to a mold. In another embodiment the mold-frame and mold are carried by separate robot which has an extendable arm that will position the mold at separate processing stations including a casting station. Other advantages and a more complete understanding B1 the invention will be apparent to those skilled in the art from the succeeding detailed description of the invention and the accompanying drawings thereof. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a perspective view of a powder box carrier and associated molding apparatus of the present invention shown with associated controls for programming indexing of a particular color box onto the molding apparatus; Figure 2 is a diagrammatic view of another embodiment of molding apparatus of the inventive apparatus; Figure 3 is a diagrammatically shown view of the powder box carrier and associated molding apparatus of the invention in association with a regrind fill station; Figures 4-10 is a diagrammatically shown process sequence of one embodiment of the process of the present invention; and Figure 11 is a diagrammatically shown view of another embodiment of a powder box carrier and molding apparatus. DETAILED DESCRIPTION OF THE INVENTION The process and apparatus of the present invention will be with reference to the production of plastic thin-walled shells for a typical automotive part such as an interior door panel, consoles and instrument panels. However it has application in the manufacture of other parts which are desirably processed by pre-programming production of different runs to have the same or different color. Figure 1 shows a typical automobile door panel application for either monochromatic or multi-color, single-piece interior plastic shells. The shell, preferably made of polyvinyl chloride material, is backed Dy a layer of polyurethane foam bonded to the shell by a mold process such as in USPN 3,123,403, issued March 3, 1964 for Automobile Arm Rest. An interior reinforcing insert may be connected at an outer shell. The shell is a one-piece plastic part either of monochromatic color or with an integral first panel of a dryca[epsilon]t plastic having a first color an integral joint to a second panel having a second color contrasting or complementing the color of the first panel or other interior components. For example, the upper panel can be red, blue, yellow or beige to contrast with or complement the interior color of seats, headliner[epsilon], crashpad[epsilon] and the like. The lower panel can be colored a deeper complementary tone color of a character which has a low impact or scuff display character. Such two-tone structures and tooling for producing the casting of two colors is set forth in the aforementioned USSN 614,004. Referring to Figures 4-10, a powder molding process is schematically shown as including a selectively heated mold 10. The box 12 includes an open end 14. The box 12 is supplied from a reservoir 15 having a distribution plate 16 operated to cast powder through an opening to fill box 12. Clamp means, not shown, join and seal the powder box 12 to mold 10 when the box 12 is in the positions shown in Figures 7-9. As a result, the interior of box 12 and the interior of mold 10 form a closed system 18 having one or more powder char[sigma]e[epsilon] in the box 12. Z :. accordance with the process and apparatus of the present invention, the box 12 is one of many carried on a color carousel 20, best shown in Figures 1 and 3. The color carousel 20 has separate elevators 21 each carrying a re[epsilon][epsilon]rvoir box 15 with a charge of pla[epsilon]tic powder material of a different color. The color carousel 20 concurrently rotates the boxes 12 from a bull gear 22 driven by a motor 24 which is indexable in wo directions under the control of a color carousel controller 26. The controller 26 is a[epsilon][epsilon]ociated with a programmable logic controller 28 to e[epsilon]tabli[epsilon]h which one of the boxes 12 will be off-loaded to casting machine 30. The programmable controller 28 includes a master control station (MCS 32) with either a paper tape or cassette input. The MCS 32 further includes a CRT indicating the color programmed for aach arm of a casting machine 30. The casting machine 30 includes eight arms 34a-34h each supported on a rotatable carriage 36 which i[epsilon] driven by a motor 38 and transmission through a bull gear 40. Each arm 32a-32h of the casting machine 30 includes an operating shaft 42 which is coupled to a tran[epsilon]mi[epsilon]sion 44 which will rotate the shaft 42 about its longitudinal axis 42a. Each arm 34a-34h is secured to a mold frame 46 that has spaced parallel tracks 48,50 that will support side flanges 52,54 on each of the powder boxes 12 when the powder box 12 is off-loaded from the color carousel to one of the frames 46. Each frame 46 further includes upper tracks 56, 8 for supporting a mold 10 one of which i[epsilon] shown in dotted line at arm 34d [epsilon]hown at an operator station 60. A mold 10 i[epsilon] initially loaded at operator station 60. The casting machine will drive it sequentially with respect to a first oven station 62; a second oven station 64; a color molding [epsilon]tation 66; a third oven station 68; a filler molding [epsilon]tation 70; a fourth oven [epsilon]tation 72; and a cooling [epsilon]tation 74. When the mold 10 i[epsilon] aligned with the color molding station 66 a preselected color has been indexed to locate a powder box of a given color in an off-loading position. A supply reservoir 15 i[epsilon] filled with one cf the [epsilon]electable color[epsilon] i[epsilon] raised on elevator 21 to clear a precisely charged color box 12 which i[epsilon] then off-loaded by a conveyor 76 including a drive chain 78 and motor 80. The off-loaded powder box 12 is [epsilon]upported by frame 46. Box 12 and heated mold 10 are clamped at station 66, shown in Figure 7. Then the frame 46 is rotated to distribute powder into the mold as [epsilon]hown in Figure 8. The frame 46 i[epsilon] rotated to return exce[epsilon][epsilon] powder to the powder box 12 as shown in Figure 9. Thereafter the powder box 12 i[epsilon] returned to the carousel 20 to be realigned with the raised reservoir 15 as [epsilon]hown in Figure 10. The reservoir 76 and powder box 12 are then returned to their original color loading po[epsilon]ition [epsilon]hown in Figure 4. The distributor plate 16 i[epsilon] activated by a motor controlled by [epsilon]ignal[epsilon] from a refill command circuit 75. An air [epsilon]olenoid 77 i[epsilon] provided to control air [epsilon]weep[epsilon] or the like in the [epsilon]y[epsilon]tem. The programmable controller 28 is programmed so that each arm 34a-34h i[epsilon] programmed for rotation of the mold frame 46 to determine the proper mold attitude during operation of the casting machine 32. A po[epsilon]ition [epsilon]en[epsilon]or line 61 i[epsilon]<'>provided to receive signals from transducers that indicate po[epsilon]ition of the mold frame 46 to provide such information to controller 28. At oven [epsilon]tation 62 oven control[epsilon] 78 are provided to both indicate and [epsilon]et temperatures in the oven. The oven control[epsilon] 78 include a [epsilon]tart-up temperature [epsilon]ignal line 80 running from interface and logic circuits 82; a temperature-reached [epsilon]ignal line 84 from the control 78 to the interface and logic circuits 82 and an oven door open signal line 86 from the circuits 82. A like start-up temperature line 88; temperature reached [epsilon]ignal line 90; oven door open [epsilon]ignal line 92; and temperature-reached [epsilon]ignal line 94 i[epsilon] provided between circuit[epsilon] 82 and oven control[epsilon] 96 foi the [epsilon]econd oven 64. The fir[epsilon]t and [epsilon]econd oven[epsilon] preferably are two [epsilon]tation pre-heat oven[epsilon] which are ga[epsilon] fired or equivalently heated. In one working embodiment a two hundred fifty degree fahrenheit (250<C>F) mold temperature range i[epsilon] controlled. Oven [epsilon]tation 68 i[epsilon] a cure oven. It ha[epsilon] [epsilon]tart signal, ready signal, door opening and temperature setting signal line[epsilon] 98a-98d interacting between an oven controller 100 and the circuit[epsilon] 82. Station 70 i[epsilon] a filler molding station in which a second charge of reground material i[epsilon] transferred from a powder box top filled with reground material. In the illustrated arrangement, start, ready, move tray and air [epsilon]ignal line[epsilon] 102a-102d are provided to control a conveyor 104 to move a powder box 106 of reground material to the frame 46. The filler molding [epsilon]tation will be operated to ca[epsilon]t a [epsilon]econd charge of powder into a mold if desired for a particular part. Oven [epsilon]tation 72 i[epsilon] a second cure [epsilon]tation which ha[epsilon] an oven controller 106 with [epsilon]ignal line[epsilon] 106a-d which are connected to control circuit[epsilon] 82 to control [epsilon]tart up temperature; ready temperature; oven door; and temperature [epsilon]etting of the oven, respectively. Infrared sensors 108a-108c are provided at oven[epsilon] 62, 64, 66 and 72 to feed back oven temperature signals to the respective oven control[epsilon]. Cooling [epsilon]tation 74 ha[epsilon] an infrared sensor 108 that i[epsilon] connected through a signal conditioner circuit 110 to produce an actual temperature signal on line 112 to programmable controller 28 that is programmed to energize an air drive system 114; and air valve 116 and a cooling water valve 118 via control [epsilon]ignal line[epsilon] 118a-c to produce a selective cooling of the exterior [epsilon]urface of the mold. Following cooling the molded part i[epsilon] stripped from the mold at the unload/operators [epsilon]tation. The color carousel controller 26 converses with controller 28 via a po[epsilon]ition line 120 that [epsilon]end[epsilon] a [epsilon]ignal of correct carou[epsilon]el po[epsilon]ition a[epsilon] indicated by po[epsilon]ition [epsilon]en[epsilon]ory means 122. The programmable controller provide[epsilon] air; de[epsilon]ired color; move powder box and [epsilon]tart signals to color carou[epsilon]el controller via line[epsilon] 124a-124d, re[epsilon]pectively . The[epsilon]e [epsilon]ignal[epsilon] are utilized by color carou[epsilon]el controller 26 to produce a [epsilon]peed [epsilon]ignal and direction [epsilon]ignal on line 126,128 to motor 24 for controlling the [epsilon]peed and direction of rotation of the carou[epsilon]el. Speed and direction [epsilon]ignal[epsilon] on line[epsilon] 130,131 are directed to conveyor motor 80 at the color molding [epsilon]tation 66. If de[epsilon]ired, a vibrator 132 can be operate in re[epsilon]pon[epsilon]e to a [epsilon]ignal on line 134 to vibrate the powder box prior to the color molding operation. The primary control for advancing of the ca[epsilon]ting arms will be by mold temperature in the fir[epsilon]t cure oven 68. Thi[epsilon] oven will be temperature controlled at [epsilon]ome predetermined temperature within il*F. When the mold temperature ha[epsilon] reached a predetermined point, movement of the arms 32a-32h will be initiated. It ust be recognized that with different molds on each arm and with a varying ambient temperatures, the time required to reach proper mold temperature in the first cure oven 60 will not always be the same. Because of this, control of the pre-heat oven will be somewhat different. It is proposed that the pre-heat oven temperature be controlled such that the mold temperature be maintained with a 13<0>F range; adaptive control may be used that will compensate for changes in ambient temperature and, therefore, differences of mold temperature as it enters the oven 62. The control also i programmed to recognize which mold i in the pre-heat oven and also adju[epsilon]t for difference[epsilon] in mold types. Because the mold temperature exiting the pre-heat oven cannot be maintained within preci[epsilon]e limits, the ca[epsilon]ting time will be controlled a[epsilon] a function of temperature. The mold temperature will be sensed immediately prior to the ca[epsilon]ting, and thi temperature will determine the dwell time. The second cure oven 72 will control mold temperature through modulation of the oven temperature and will not affect the cycle in any way. A best shown in Figure 3, each oven ha[epsilon] an outer enclosure 62a, 64a, 68a and 72a with movable acce doors 62b, 64b, 68b and 72b which enable the rotating arms to clear the enclosure and which close to retain heat in the enclosure[epsilon]. In the embodiment of Figure 3 the color carousel 20 i in the form of a multiple arm robot 134 which has arms 136 each of which reciprocates to move a powder box 138 to the ca[epsilon]ting machine 30. The embodiment in Figure 2 i an embodiment in which a centrally located robot 140 Carries a mold frame 142. The with respect to a base 146. The arm 144 and frame are pivoted on base 146 to move the frame 142 into and out of a preheat oven 146; a cure oven 148 and a cooling station 150. In this embodiment, casting occurs at a solid color station mold [epsilon]tation 152 or two-tone molding station 153 on a rotary carou[epsilon]el 154. A solid color powder box 156 i connectable to a heated mold on frame 142 when it is off-loaded at station 152. The box 156 i[epsilon] rotated with the off-loaded mold to ca[epsilon]t powder at [epsilon]tation 152. A [epsilon]econd two-tone station 153 can be provided with a two-compartment box 158 to ca[epsilon]t two colors (as [epsilon]et forth in the aforementioned co-pending United State[epsilon] Application 614,004). Following casting at either station 152,153 the mold with powder ca[epsilon]t thereon i carried by robot 140 to the cure oven 148 and cooling [epsilon]tation 150. Yet another embodiment of the invention i set -forth i Figure 11 wherein a said color carousel 160 i associated with a continuous belt ccnveyor/casting apparatus 170. The carousel 160 ha four individual [epsilon]olid color powder boxes 162. The boxes are advanced by side loader line (either robot or conveyors) to alignment with a heated mold 164 at a color molding station 165. The box and mold 146 are joined and rotated on axis 166 to cast powder. The mold 164 is preheated at a preheat oven 168 (shown in outline) . After casting, the powder box l returned to the carou[epsilon]el and the mold with ca[epsilon]t material i[epsilon] advanced to a cure oven 170; a second fill station 172; and a [epsilon]econd cure station 174. The return line includes a cooling [epsilon]tation (not [epsilon]hown) . A two-tone color carousel 176 with four boxes with two color distribution can be provided at the color molding station 165. In the aforesaid embodiment the mold frames (carriers) contain the locking units and move along the chain or track apparatus . Arms or mechanisms of the molds are operated outside the oven as much as poss ibl e so as not to over-expo[epsilon]e the hardware to exce ssive heat. Cu[epsilon]tomer color change[epsilon] are made by container changes. For example, changes from a Ford red to a GM red can be acco pli[epsilon]hed without any lost production merely by changing containers on the carou[epsilon]el[epsilon]. Color boxe[epsilon] on the carousels can be moved to the color loading area, released and held to the color carou[epsilon]el platform. The platform or components thereon can then move in alignment with the mold and in interlocking relationship, at which point the casting cycle would begin. Each concept i[epsilon] adaptable for two-fill (Drysol shell with foam backing) operation. Thi[epsilon] manufacturing concept lends itself to a one on one foaming line and enables a manufacturer to adopt the " just-in-time" supply concepts because of the scheduling flexibility that is inherent in the apparatus and process .

Claims: 1. In a process for molding a single-piece plastic shell the steps comprising: (1) selectively positioning a carousel with a plurality of powder boxe[epsilon] at a molding station preheating an open-ended mold to a temperature near the fusing temperature of a powder ther oplastic material; (2) off-loading either a mold or one of the plurality of color boxes and connecting said powder box to the mold to form a closed system; (3) thereafter rotating the charge box means and mold in a powder ca sting sequence for releasing powder charges onto ca sting surfaces of the mold to build up a shell of de[epsilon]ired shape and size; (4) and thereafter returning the color box to the carousel. 2. In the process of claim 1, the flow control step 5 including distributing powder charges of different colors from the powder box against casting surfaces of the preheat powder box. 3. In the process of claim 1, providing a separately controlled source of powder for each box and selectively refilling the box when it is located on the box during indexing of another of the boxes to the color molding station. 4. In the process of claim 1, preprogramming the color box to be selected for off-loading at the molding station; and varying the [epsilon]peed and direction of drive of the color carousel to position the pre-programmed box selection at the color molding station. 5. Apparatu for molding a thin-walled plastic shell in a heated open-ended mold from a charge of thermoplastic powder material in open-ended charge box means comprising: carou[epsilon]el means having a plurality of separate powder boxe[epsilon] thereon; means for off-loading a powder box from [epsilon]aid carousel; a heated mold, means for joining said heated mold to [epsilon]aid off-loaded powder box in open-ended relationship; a rotatable mold indexing means including a rotatable arm to control the attitude of said joined box and mold to distribute a charge against the casting surfaces of the mold; preheat and cure oven ; and means for rotating said arm to carry said mold with respect to [epsilon]aid preheat and cure ovens prior to and s ubsequent to off-loading from and return of said box to said carousel. 6. In the apparatu of claim 5 said charge box means including a pair of side flange[epsilon] and a compartment having a predetermined charge of plastic powder, ; said mean for engaging [epsilon]aid mold with [epsilon]aid frame for receiving powder from the box compartment when the box and mold are joined and rotated. 7. In the apparatu[epsilon] of claim 5 said mold indexing means including a plurality of arms, a mold frame on each of [epsilon]aid arms, means for coupling a heated mold to each of [epsilon]aid frames, means for separately rotating each of said arms and mean[epsilon] [epsilon]electively progr ming each of [epsilon]aid arms to be rotated at a color molding [epsilon]tation to control the attitude of said frame for casting mold material onto the mold only at said molding station; said carou[epsilon]el being indexed to provide a color box of a desired shade at said molding station so as to program a production of color molded parts while continuously operating said mold indexing mean[epsilon] with re[epsilon]pect to [epsilon]aid molding [epsilon]tation. 8. In the combination of claim 5, said carou[epsilon]el mean[epsilon] including a plurality of powder supply re[epsilon]ervoir mean[epsilon]?mean[epsilon] for selectively filling one or more of the powder boxe[epsilon] from said reservoir mean[epsilon] on [epsilon]aid carou[epsilon]el mean[epsilon]; and mean[epsilon] including a conveyor to off-load a powder box following fill from said re[epsilon]ervoir means to [epsilon]aid mold indexing mean for transferring powder from the box to a preheated mold. 9. In the combination of claim 8, elevator mean[epsilon] on [epsilon]aid carousel for positioning said r eservoir in raised and lowered position with respect to one of [epsilon]aid powder boxes, said color box being off-loaded from said carou[epsilon]el only when said re[epsilon]ervoir i in it raised position. 10. In the combination of claim 5, a preheat oven, a cure oven and a cooling station, said rotatable arm mean being se lectively indexed with respect to said oven and enclosures for said oven[epsilon] and cooling station, cooling station, each of said oven[epsilon] ha acce doors thereto and mean for programming [epsilon]aid acce door[epsilon] to open and clo[epsilon]e upon indexing of [epsilon]aid mold index mean[epsilon] with re[epsilon]pect thereto. 1. A pr o c for moulding a plastic shell cor rising the steps of [epsilon]electively positioning a plurality of powder boxes at a moulding [epsilon]tation; preheating a mould, connecting a powder box to the mould to form a closed system; and rotating the connected po der box and mould in a powder casting sequence for releasing powder onto casting surfaces of the mould to form a shell of desired shape an size.

Inventors: GRAY, JOHN D.
Applicants: DAVIDSON TEXTRON INC.
Application year: 1986
Main classification: B29C41
IPC codes: B29C41, B29L31, B29C33, B29L22