WO1999059794A1

WO1999059794A1 - Method and apparatus for manufacture of thin-wall article from plastic particles

Info

Publication number: WO1999059794A1
Application number: PCT/IB1999/000830
Authority: WO
Inventors: Douglas J. Mcnally
Original assignee: Konal Engineering And Equipment Inc.
Priority date: 1998-05-15
Filing date: 1999-05-07
Publication date: 1999-11-25

Abstract

A molding process and apparatus including a powder box containing plastic particles which is brought into engagement with a mold shell (13) heated to a desired temperature. The powder box (21) and mold shell (13) together define a closed chamber (14). The powder box (21) includes therein an agitating arrangement (27) which creates a dense dispersion of particles within the chamber (14) and displaces the particles upwardly toward the heated face of the mold shell (13). The particles as they contact the heated face become sticky and adhere thereto due to the transfer of heat to the particles from the heated face by conduction. This heat transfer effects melting of the particles and results in formation of a layer of plastic over the face of the mold shell. The agitation of the particles continues for a time period sufficient to create an article having the desired thickness.

Description

METHOD AND APPARATUS FOR MANUFACTURE OF THIN-WALL ARTICLE FROM PLASTIC PARTICLES

FIELD OF THE INVENTION This invention relates to a method and apparatus for forming a thin-wall article from particulate plastic and, more specifically, an improved method and apparatus for molding a thin thermoplastic molded article in a heated mold shell and including use of a powder box containing plastic particles which are agitated so as to contact the heated mold shell and create the molded article.

BACKGROUND OF THE INVENTION Thermoplastic powder or slurries, known as dry or liquid plastisols, are conventionally cast on the inner surface of a thin metal mold member heated to the fusion temperature of the deposited material to form a gel coat which is heated sufficiently to form a thin, solid thermoplastic molded article (i.e., a shell or skin). The thin metal mold member remains heated until a thin layer of thermoplastic material is built up on the inner surface to form a thin plastic shell product, such as a product suitable for use as an outer skin or shell covering on automotive interior or exterior products such as door panels, instrument panels, bumper moldings or the like.

The methods and apparatus for the production of molded skins or shells are well known, such methods often being referred to as "rotational" or "slush" molding. The mold cavity defined by the mold shell is filled with a flowable plastic material and, due to heating of the mold shell, a thin layer of plastic material adheres to the surface of the mold shell and the remaining plastic material can then be shaken or poured out of the mold, as by rotating the mold. When the mold shell is further heated, the skin or shell product clinging thereto gels out. The finished skin or shell product can then be removed after the mold has cooled down. The operation of introducing the plastic material, when in the form of a powder or granule, is typically effected by rotating the mold so that its mold cavity opens downwardly, and then fixing onto the mold a box containing the plastic particles. The overall assembly consisting of the mold and box is then rotated through about 180° so that the plastic particles drop into the mold. After the plastic skin or shell has set against the heated mold surface, the mold assembly is rotated back to its original position and the box and excess powder are removed, with further heating of the mold then effecting proper melting and gelling of all of the plastic material adhered to the mold surface. The mold is then cooled and the molded skin or shell product removed.

The molding apparatus briefly described above typically includes a generally hollow mold housing on which the metal mold shell is mounted, which housing and mold shell cooperate to define a hollow interior chamber to which heated air is typically supplied so as to effect heating of the mold shell from the back surface thereof. In the typical rotational molding apparatus of the aforementioned type, the rotational mounting of the mold housing and shell necessarily imposes structural and functional restraints on the overall apparatus which not only limit the size of the mold, but also impose restrictions on the ability to efficiently supply heat to the mold shell, particularly with respect to the desired degree of uniformity thereof through the mold shell to hence result in a molded article having the desired physical characteristics and properties. This necessity of rotatably moving the mold, combined with the required movement of the powder box and its attachment to and detachment from the mold, is also believed to further reduce the overall effectiveness and efficiency of the molding operation due to the structural and operational steps and complexities involved. The arrangement whereby a large quantity of plastic particles is dumped into the mold and left therein during the molding operation is also believed to impact the quality of the finished product, particularly with respect to the ability to achieve the desired uniformity of wall thickness of the molded product without incurring undesired thickening or bridging at various locations thereon.

More specifically, the large quantity of plastic particles (typically about 250 pounds) supplied to the mold, in combination with the complex rotational pattern utilized in conventional rotational molding processes can place significant stress on the mold shell or tool during rotational movements thereof, which can shorten the life of the mold shell. In addition, conventional rotational systems which utilize heavy heating mediums such as oil and sand present a problem upon rotation of the system for the purpose of dumping the plastic particles into the mold cavity. Further, some molding processes utilize multiple powders which are layered one upon the other in order to achieve a laminate shell product. Accordingly, these processes typically require the utilization of multiple powder boxes for the various powders used. The time required for the necessary rotation of the system added to the time required to interchange powder boxes in this type of process can significantly increase cycle time per part. This increased cycle time reduces the efficiency of the process, and can also cause undesirable burning of the part. In addition, rotational systems are limited with regard to the types of powders which may be utilized therewith.

It is an object of this invention to provide an improved process and apparatus for molding articles of the aforesaid type, which process and apparatus overcomes many of the disadvantages associated with prior arrangements as briefly discussed above.

More specifically, in the improved process and apparatus of this invention, the mold shell can be mounted on a housing which is generally maintained stationary during the molding operation and is oriented so that the outer face of the mold shell faces downwardly. A powder box is movably supported so as to be moved upwardly into engagement with the mold shell to effectively close off the downwardly-oriented outer face thereof. The mold shell can be heated in a conventional manner. The particles in the powder box are agitated so as to become airborne within the closed chamber defined between the mold shell and the powder box. In the illustrated and preferred arrangement, the powder box is provided with one or more agitators therein, for example rotatably driven bladed wheels such as bladed propellers. These bladed wheels agitate the particles and cause them to become airborne and to be propelled upwardly toward the heated face of the mold shell. The particles as they contact the heated face become sticky and adhere to the face. The mold shell transfers heat to the particles by conduction and hence effects melting thereof to form an initial thin layer over the face of the mold shell. As the agitation of the particles continues, additional particles continue to impact and stick to the layer which is formed on the mold shell causing the thickness of the layer to progressively increase as additional particles contact and stick to the layer and become heated so as to melt into and become an integral part of the layer. The agitation of the particles continues for a time period sufficient to create an article having the desired thickness. Throughout this forming time, the mold housing and the mold shell mounted thereon are preferably maintained with the mold shell facing downwardly, and the mold shell may be maintained stationary. The agitation of the particles in the mold box is then terminated, and the powder box is detached and moved away from the mold shell, thereby permitting access to the mold shell so as to allow removal of the molded article therefrom. With the improved arrangement of the invention as briefly summarized above, the housing mounting the mold shell can be maintained stationary, thereby eliminating the structural complexity thereof and at the same time eliminating any driving devices therefor. This also enables the overall mold and specifically the mold shell to be of larger size to permit molding of larger articles, and also greatly simplifies the providing of heat to the rear of the mold shell to permit performance of the desired molding operation. The overall arrangement is believed to possess highly increased simplicity, which simplicity also permits the molding process to be carried out with increased simplicity, thereby providing for significantly reduced cost and increased efficiency of operation. As discussed above, the improved arrangement of the invention is particularly suitable for use with stationary mold boxes. However, the improved arrangement of the invention may also be utilized with conventional rotational molding systems, without the need for rotation thereof (i.e. the mold box can remain stationary) .

Further, it may be desirable to utilize the invention with molding systems capable of at least limited rotation in certain situations, for example when a tool is utilized having a complex configuration. In this situation, oscillation or tilting of the mold box may be necessary in order to remove excess powder from the mold tool. In addition, the present invention may be utilized with a molding system which utilizes any conventional heating methods for heating the tool, such as hot air, hot liquid (such as oil) , hot sand, or electric heaters. The molding arrangement according to the invention is particularly useful for producing multi-layer products as discussed above, since the invention can greatly reduce cycle time by eliminating the need for rotation of the mold housing or box. In addition, the invention enables easy and quick attachment and detachment of the various powder boxes to the mold box, since a fixed attachment of the powder box thereto is unnecessary. The advantageous arrangement and method of the present invention, and the objects and purposes thereof, will be apparent to persons familiar with molding of this general type upon reading the following specification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view, in cross section, and diagrammatically illustrates the molding apparatus of the present invention;

Figure 2 is a sectional view taken generally along line 2-2 in Figure 1. Figure 3 is a view similar to Figure 2 but illustrates the powder box attached to the mold box for effectively closing off the mold shell;

Figure 4 is a view similar to Figure 3 but illustrates the agitation of the plastic particles within the powder box;

Figure 5 is a diagrammatical side elevational view, in cross section, which is similar to Figure 1 but illustrates a variation of the invention;

Figure 6 is a fragmentary plan view of a further variation of the invention having portions of the powder box broken away;

Figure 7 is an enlarged cross-sectional view taken generally along line 7-7 in Figure 6; and

Figure 8 is an enlarged cross-sectional view taken generally along line 8-8 in Figure 6. Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words "upwardly" and "downwardly", "rightwardly" and "leftwardly" will refer to directions in the drawings to which reference is made. The words "inwardly" and "outwardly" will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

DETAILED DESCRIPTION Referring to Figures 1 and 2, there is illustrated a molding system 11 according to the present invention. This system includes a mold frame or housing 12 which removably mounts thereon, in a conventional manner, a thin metal mold shell or tool 13. The mold housing 12 , in the illustrated arrangement, is formed of a box-like structure defining an interior chamber 14, and the mold shell 13 is mounted within an opening defined on one side of the mold housing 12 and effectively closes off the opening so that the inner or back surface 16 of the mold shell 13 effectively defines a boundary of the chamber 14. The mold shell 13 is mounted on the housing in such a manner that the front or molding face 17 thereof is oriented to face downwardly. The mold shell 13 is typically contoured to define the shape of the article to be molded, and is typically contoured so that it projects into the mold box 12, with the configuration of the front or mold face 17 thus defining a mold cavity 18 which opens downwardly.

To effect heating of the mold shell 13, a heated fluid such as air is typically supplied to or generated within the chamber 14 so as to effect heating of the mold shell 13 through exposure of the back surface 16 of the mold shell to heat energy, either through contact with a heated fluid such as air, or through exposure to radiant heat, which heat can be provided by any suitable means. The mold arrangement 11 also includes a particulate material supply box 21, commonly known as a powder box, for use in association with the mold shell 13. The powder box 21 is typically of a boxlike configuration having a top opening 22, and defining therein an interior chamber 23 which contains a significant quantity of a particulate material, such as powdered or granular thermoplastic. The granular or powdered thermoplastic, as indicated at 24, typically fills only a part of the chamber 23, and such is depicted by the upper level of the quantity of plastic being indicated at 25. The powder box 21 is mounted on a suitable movement device as indicated diagrammatically at 26, which device enables the powder box to 21 be lifted upwardly into engagement with the bottom of the mold box 12 , as illustrated by Figure 3, so that the powder box 21 hence effectively surrounds and closes of the outer periphery of the mold shell 13. The interior of the powder box 21 and the mold cavity 18 thus cooperate to effectively define a closed agitation chamber when the powder box 21 is in a position of engagement with the mold box 12. The lifting device 26 for the powder box 21 may comprise any type of conventional lifting or moving mechanism, such as a scissor lift or the like. Such mechanisms are typically utilized for this purpose, and further description thereof is believed unnecessary. According to the present invention, the powder box 21 has an agitating arrangement associated therewith for effecting agitation of the plastic particles within the powder box 21, particularly when the latter is attached to the mold box 12. This agitating arrangement includes at least one, and more preferably a plurality of, agitating devices 27 which are associated with the interior of the powder box 21 to effect rapid agitation of the plastic particles so as to cause the particles to become airborne and to be effectively propelled upwardly from the powder box 21 into the mold cavity 18 for contact with the heated front face 17 of the mold shell 13.

Each agitating device 27, in the illustrated embodiment, includes a bladed agitating member 28 such as a bladed wheel, the radially projecting blades of which preferably are twisted so as to create an axial flow component when the bladed wheel is rotated. The bladed wheel 28 is positioned interiorly of the chamber 23 below the typical static level 25 of the plastic particles 24, and is secured to a rotatable drive shaft 29 which projects downwardly through the bottom of the powder box 21 and is associated with a suitable drive motor 19 such as an electric motor. When the drive motors 19 are energized, the rotation of the agitator wheels 28 causes the plastic particles 24 to be highly agitated so that they effectively become airborne and are propelled upwardly toward the mold face 17, with the particles 24 being propelled and moved about the entirety of the enclosed mold cavity. This latter condition is diagrammatically depicted in Figure 4 which illustrates the particles being distributed throughout the mold cavity during agitation of the powder by rotation of the agitator wheels 28.

The number of agitating devices utilized will of course be a function of the size of the powder box, the size and density of the plastic particles being used, the shape of the mold surface, the size and shape and configuration of the agitator wheels, and other factors which can obviously influence the overall operation. It is normally preferred, however, that several agitating devices be distributed throughout the powder box so as to increase the effectiveness of the agitation of the particles.

To further increase the effectiveness of the agitation and the uniformity thereof throughout the entire mold cavity, it is contemplated that the individual agitating devices 27 will be mounted so that the drive shafts will vertically pivot or gyrate to hence cause transverse displacement of the rotating agitating wheel and thus more effective agitation and dispersement of the plastic particles.

In operation, the mold arrangement will initially be in the open position illustrated by Figures 1 and 2. The mold shell 13 is mounted and maintained stationary on the housing 12 so that the mold face 17 faces downwardly, and a powder box 21 containing therein a desired quantity of plastic particles will be provided for association with the arrangement, the powder box typically being maintained in an open position. When the mold cycle is initiated, the mold shell 13 is heated in any conventional manner, such as by supplying or generating heated air within the chamber 14 to effect heating of the front face 17 of the mold shell. The powder box 21 is lifted upwardly for attachment to the mold box 12 to thus cooperate with the mold shell 13 to close off the mold cavity 18, as illustrated by Figure 3. Thereafter the agitating devices 27 are energized to cause agitation of the plastic particles in the mold box, which particles become airborne and are propelled upwardly toward the mold shell 13, with the agitated and hence airborne particles being effectively distributed throughout the entire mold cavity 18. As the agitation is maintained, the particles contact the heated mold surface 17 of the mold shell 13 and tend to become sticky and adhere thereto, whereupon conductive heat is transmitted to the particles and they effectively gel and create a thin layer which coats over the mold face 17. As the agitation of the plastic particles continue, additional particles contact and adhere to the gel layer, which continues to be heated through the shell and effects more complete melting of the adhered layer, so that additional particles thus buildup the thickness of the adhered layer, effectively a small layer at a time, with the additional particles progressively themselves melting and hence becoming an integral part of the molded article. During the agitation cycle, the excess particles always tend to resettle in the powder box 21, and hence do not collect in the mold cavity 18. The agitation of the plastic particles is continued for a determined time until the article of desired thickness has been formed by being molded against the mold face 17 of the shell 13. Thereafter, the agitating devices are deenergized or stopped, thereby allowing the plastic particles to resettle in the powder box 21, and then the powder box 21 is detached and moved downwardly away from the shell 13. With the powder box 21 detached, the molded article within the mold shell 13 is permitted to cool, and is thereafter removed from the mold shell 3 to permit a subsequent molding cycle to be initiated.

It will be recognized that the mold shell 13 does not have to be perfectly horizontally oriented in order for the mold face 17 to face downwardly, and that the mold face 17 can be inclined with respect to the horizontal so long as the mold face 17 is sufficiently downwardly oriented as to prevent accumulation of excess plastic particles within the mold cavity 18. It will be appreciated that the agitating devices illustrated and described herein represent only one example of a device capable of achieving the desired agitation of the plastic particles. Other devices such as blowers or possibly even an air suspension to effect fluidization of the particles are also considered as alternatives for effecting the desired suspension and agitation of the particles to effect the desired molding operation.

Figure 5 illustrates a modification of the invention, which is similar to the embodiment depicted in Figures 1-4 and the same reference numbers are therefore utilized to depict the same or similar components. The molding system 11A shown in Figure 5 includes additional agitating devices 27A located within the chamber 23 of powder box 21. The agitating devices 27A are similar in construction to the agitating devices 27, and the components thereof have the same reference numbers with the addition of an "A" thereto. In the illustrated embodiment, the agitating devices 27A are arranged in an alternating fashion with agitating devices 27, however, other arrangements may be desirable.

The agitating devices 27A each include a bladed agitating member 28A such as a bladed wheel. The bladed wheels 28A are secured to respective rotatable drive shafts 29A of a greater length than the drive shafts 29 of the agitating devices 27, so that the bladed wheels 28A are positioned above the typical static level 25 of the plastic particles 24 within powder box 21.

The operation of the embodiment illustrated in Figure 5 is essentially the same as that of the embodiment shown in Figures 1-4, except that upon or a short time after the lower stage agitating devices 27 are energized and effectively lift the plastic particles in the powder box 21 upwardly, the upper stage agitating devices 27A are energized and operate to further lift and fling or displace the plastic particles about the agitation chamber and into contact with the front face 17 of the mold shell 13. This two-stage arrangement effectively creates a cloud of plastic particles within the agitation chamber and thus effectively distributes the particles throughout the entire mold cavity 18. It will be appreciated that the agitating devices 27 and 27A are operated at the minimum necessary velocity so as to minimize cooling of the front face 17 of the mold shell 13 due to the air flow generated by the bladed wheels 28, 28A. In this regard, the lower stage agitating devices 27 and the upper stage agitating devices 27A can be controlled by a suitable control arrangement (not shown) so that, for example, the upper stage agitating devices 27A can be deactivated during a mold cycle either individually or as a group in order to allow both the front face 17 of the mold shell 13 and the layer of plastic adhered thereto to remain or be heated back up to the desired temperature. In addition, the lower stage agitating devices 27 can be deactivated during a mold cycle while the upper stage agitating devices 27A remain energized so as to assist in removing excess particles from the mold cavity 18.

It will also be appreciated that the upper and lower stage agitating devices 27 and 27A can be arranged within powder box 21 in a manner which is optimal with regard to the particular configuration of the mold shell 13. For example, if the mold shell 13 has deep channels or pockets, it may be desirable to position an upper stage agitating device 27A closely adjacent the channel so as to ensure the distribution of powder thereinto. In addition, it may be desirable to mount second stage agitating devices 27A along the upright side walls of the powder box 21 instead of along the bottom wall thereof, so that the bladed wheels rotate about a generally horizontal axis within chamber 23.

In addition, it may also be desirable to mount the agitating devices 27 and 27A so that same are vertically pivotable, as mentioned above.

Further, the embodiments depicted in Figures 1-5 may additionally be utilized with conventional rotational molding systems, without the need for rotation thereof. Turning now to Figures 6-8, a further modification of a molding system 30 according to the invention is illustrated therein. This system 30 includes a mold housing 12 (Figures 7 and 8) essentially identical to the mold housing 12 illustrated in Figures 1-5. The mold housing 12 will therefore not be discussed in further detail here, and the same reference numbers are utilized in Figures 7 and 8 to depict the various components thereof. The molding system 30 includes a particulate material supply box or powder box 31 for use in association with the mold shell 13. Powder box 31 has a generally box-like configuration which in the illustrated embodiment is defined by a bottom wall 32 and four upright side walls 33. The upper edges of the respective side walls 33 together define a top opening 34. The bottom wall 32 and side walls 33 define an interior chamber 35 which contains particulate material as indicated at 36. This powdered material typically fills only part of the chamber 35, and the upper level of the plastic material is indicated at 37.

The molding system 30 includes a frame 40 embodied by generally horizontally oriented upper and lower frame bars 41 and 42 connected to one another via upright frame bars 43 each of which defines a respective corner of the frame 40. The frame 40 additionally includes cross members 44 which extend inwardly (Figure 6) from the upper frame bars 41 and serve to support the powder box 31 in a generally horizontal manner. The frame 40 discussed above is presented as only one type of frame which may be utilized in accordance with the invention, and other frame configurations may be utilized to support the powder box 31.

As shown in Figures 7 and 8, the frame 40 and powder box 31 are mounted on a suitable movement device 26, such as a conventional scissor lift or the like. The powder box 31 has an agitating arrangement associated therewith for effecting agitation of the plastic particles within the powder box 31 when the latter is engaged with the mold housing 12 as discussed below. The agitating arrangement includes a plurality of agitating assemblies 50 located within the powder box 31. The agitating assemblies 50 each include an upper and a lower bladed agitating member 51 and 52 secured to a common rotatable drive shaft 53 which projects downwardly through the bottom wall 32 of the powder box 31. The upper bladed agitating member 51 preferably has a larger diameter as compared to the diameter of the lower bladed agitating member 52. In addition, the upper and lower agitating members 51 and 52 in the illustrated embodiment include an equal number of blades. However, it may be desirable to provide an upper agitating member 51 having a larger number of blades as compared to the lower agitating member 52 to provide greater particle dispersal and further lifting of powder particles within the powder box 31.

The lower end of drive shaft 53 mounts thereon a pulley 54 associated with a suitable drive motor 55 via a drive wheel 56 and a belt 67 (Figure 8) . When the drive motors 55 are energized, the rotation of the upper and lower bladed agitating members 51 and 52 agitate the plastic particles within the powder box 31 as discussed in further detail below.

Each of the drive shafts 53 is supported relative to the bottom wall 32 of the powder box 31 by a swivel-type support such as a conventional self-aligning, anti-friction, roller-type bearing 60 which permits limited tilting of the respective drive shaft 53 relative to the vertical as indicated in dotted lines and arrows in Figure 8. More specifically, bearing 60 allows limited angular or swiveling displacement of the drive shaft 53 in any direction with respect to the vertical position of the drive shaft 53 as shown in Figure 7, and also allows the upper end of shaft 53 and the respective bladed agitating members 51 and 52 to be continuously movable along or within an imaginary circular path. For example, the shafts 53 are tiltable relative to the vertical in a range of about 1° to about 10° for a purpose as discussed below. It should be noted that the degree of tilt of the respective drive shafts 53 is necessarily limited by the particular size and configuration of the powder box 21, and particularly the proximity of the side walls 33 thereof to the bladed wheels. Therefore, the drive shafts 53 and the respective bladed wheels may be angularly displaceable to a greater degree than that given above if the side walls 33 of powder box 21 are located further outwardly and away from the bladed wheels so as to avoid interference therewith.

The agitating assemblies 50 additionally include a pair of vertically aligned support brackets 61 mounting thereon conventional bearings through which the respective drive shaft 53 extends. The support brackets 61 are fixed to one end of a generally flat mounting plate 62, and the respective drive motor 55 is fixed to the opposite end of mounting plate 62. Each mounting plate 62 has an elongate and generally vertically oriented corner-shaped bracket 63 mounted so as to extend along an edge portion thereof adjacent support brackets 61. Corner bracket 63 extends downwardly past the lower edge of mounting plate 62. A generally vertically oriented rod-like connecting pin 64 is fixed to the lower end of each corner bracket 63 and projects downwardly past a lowermost edge thereof.

As best shown in Figures 6 and 7, the agitating assemblies 50 are linked to one another via a plurality of elongate connecting rods 65 which in the illustrated embodiment are arranged so as to form a parallelogram. The connecting rods 65, at each of their respective ends, are connected to a connecting pin 64 via a conventional universal type hinge 70 which permits limited three- dimensional movement of the respective connecting rods 65 with respect to one another. Some examples of universal type hinges or joints usable in accordance with the invention include a loose pin-and-slot arrangement, a ball and socket arrangement or a lost motion connection. With reference to Figure 6, the agitating arrangement additionally includes a plurality of actuators such as pneumatic cylinders which are supported on corresponding lower frame bars 42. More specifically, a plurality of double-acting pneumatic cylinders 71 are arranged along one longitudinal side of the frame 40. The remote ends of the cylinders 71 are connected to the lower frame bar 42 and the outer terminal end of the piston rods 72 of the respective cylinders 71 connect to a corresponding connecting pin 64 via a universal hinge 73 of the type discussed above (i.e. a hinge which permits limited three dimensional movement of the ends of the respective cylinders 71) .

A pair of single-acting cylinders 75 are provided at opposite ends of the frame 40, the remote ends of which are connected to a lower frame bar 42 and the piston rods 76 of which are connected via universal hinges 77 to intermediate portions of the connecting rods 65 which extend in a generally endwise direction of the frame 40 (Figure 6) .

The operation of the embodiment of Figures 6-8 will now be described to ensure a complete understanding of the invention. Initially, the molding arrangement 30 is in the open configuration wherein the powder box 31 is spaced downwardly from the mold housing 12 (Figures 7 and 8) . The mold shell 13 is maintained stationary on housing 12 in a generally downwardly facing orientation, and heat is supplied to the chamber 14 of housing 12 from a heat source (shown schematically in Figure 7) to effect heating of the front face 17 of the mold shell 13. Heat may be supplied to chamber 14 by any conventional method, such as by providing hot air via blowers into chamber 14 , or by supplying hot liquid such as oil into chamber 14. Once the mold housing 12 is heated to the desired temperature, the powder box 31 containing therein a desired quantity of plastic particles 36 is lifted upwardly by lift device 26 into engagement with mold housing 12 to close off the mold cavity 18 (not shown, but see Figure 3) . In this regard, since there is no need to rotate the molding arrangement 30 in order to dump the plastic particles into the mold cavity 18 in accordance with the invention, the powder box 31 need not be fixedly attached to housing 12, i.e. with brackets, fasteners, etc., and can simply be raised and pressed into engagement with housing 12. As such, it may be desirable to provide the upper free edge of the powder box 31 with a ring-like seal member. The agitating assemblies 50 are then energized so as to cause rotation of the upper and lower agitating members 51 and 52. The lower agitating members 51 which are initially essentially covered by the plastic particles serve to agitate and thus lift the particles upwardly toward the mold shell 13. The upper agitating members 51 then serve to further lift and fling the particles in the agitating chamber so as to effectively distribute the particles throughout the entire mold cavity 18 and create a dense dispersion of particles within the agitating chamber. The particles thus contact the heated front face 17 of the mold shell 13 and adhere thereto, as discussed above.

In order to provide a more random and chaotic movement of the plastic particles 36 within the agitation chamber, and to enable more uniform distribution of the particles to all parts of the front face 17 of the mold shell 13, one or more of the cylinders 71 and 75 are actuated so as to exert a generally linearly directed force on the corresponding connecting pin 64 which causes the corresponding mounting plate 62 and thus the entire agitating assembly 50 to tilt relative to the vertical as shown in dotted lines in Figure 8. This tilting of the upper and lower agitating members 51 and 52 enables variation in the flow direction thereof to provide a more random distribution of particles within the agitating chamber, and to improve the distribution of particles within deep channels or pockets within mold shell 13.

More specifically, the single-acting cylinders 75 may be actuated in tandem with one another to thus cause a back-and-forth swivelling motion of each agitating assembly 50 as indicated by the arrows in Figure 7. That is, the drive shafts 53 tilt back and forth in a vertical plane generally parallel to the lengthwise direction of the frame 40 of powder box 31. Alternatively, the double-acting cylinders 71 may be simultaneously actuated to cause a similar type of back-and-forth tilting motion of the drive shafts 53, i.e. the drive shafts 53 tilt within a vertical plane generally parallel to the widthwise direction of the frame 40 (see the arrows in Figure 8) . In each case, the universal hinge connections provided on the individual cylinders 71 and 75, and on the connecting rods 65, permit limited three-dimensional movement of these components to allow swinging motion of the drive shafts 53.

An even greater random distribution of the plastic particles within the agitation chamber may be achieved by randomly actuating the cylinders 71 and 75 in a non- synchronized manner with respect to one another so as to exert random forces on the various connecting pins 64 of the parallelogram linkage interconnecting the agitating assemblies 50 with one another. This type of random activation of the cylinders 71 and 75 whereby multi- directional forces are exerted on the connecting pins 64 enables three-dimensional movement of each of the bladed wheels 51 and 52 (and particularly the upper bladed wheels 51) of the individual agitating assemblies 50 about or within an imaginary circular or doughnut-shaped path.

The agitation of the plastic particles within the agitation chamber as discussed above is continued until the article of desired thickness has been formed by being molded against the front face 17 of the mold shell 13.

Thereafter, the agitating assemblies 50 are deactivated, thus permitting the remaining plastic particles not adhered to front face 17 to resettle in the powder box 31. The powder box 31 is then moved downwardly away from the housing 12 , the molded part is permitted to cool and is thereafter removed from the mold shell 31.

It will be appreciated that the cylinders 75 provided adjacent the opposite ends of the frame 40 may instead have the piston rods 76 thereof connected to one of the adjacent connecting pins 64. Further, it will also be appreciated that the a single double-acting cylinder may be provided at one end of the frame 40 in place of the two double-acting cylinders 75. In addition, pairs of single acting-cylinders disposed on opposite longitudinal sides of the frame 40 may be substituted for the respective double-acting cylinders 71. In addition, actuation of the various cylinders 71 and 75 may be controlled by a conventional computerized control arrangement (not shown) . Such arrangements are well known and will therefore not be discussed in detail herein.

It will also be appreciated that other mechanisms may be utilized to enable the tilting of the agitating assemblies 50. For example, connecting pins 64 may be actuated by a suitable cam arrangement supported on frame 40 to provide the desired movement of the agitating assemblies 50.

Further, the interconnection of the various agitating assemblies 50 may instead be achieved, for example, by a pair of rectangular plate-like members arranged in a side-by-side manner with one another, which plates have universal type hinges at the four corners thereof each for connection to a corresponding connecting pin 64. The inner facing corners of the plates can then be connected to one another via a pair of connecting rods similar to rods 65 so as to allow the plates to move and transmit force to one another in the lengthwise direction of the frame 40, and to allow the plates to move relative to one another (i.e. back-and-forth with respect to one another) in the widthwise direction of the frame 40.

Still further, the upper and lower agitating members 51 and 52 may be provided with separate drive shafts, for example concentric drive shafts which are rotatable independently of one another and associated with separate motors to enable individual control of the members 51 and 52, for example, so that the agitating members 51 and 52 may be rotated at different speeds from one another and individually activatable and deactivatable with respect to one another. The agitating arrangement disclosed herein is only an example of one type of an arrangement capable of lifting the plastic particles within the powder box 31. For example, the bladed members 51 and 52 disclosed herein direct air in a generally axial manner. However, other types of bladed wheels may be utilized such as centrifugal fans which discharge air in a radial manner with respect to the respective fan axis. In addition, perforated rods which direct air outwardly therefrom may be utilized within the powder box 31 so as to create the dense particle dispersion discussed above. Further, rotary devices which rotate about horizontal axes and have relatively short and scoop-like blades may be provided adjacent the lower portion of the powder box 31 so that the blades thereof dip into the plastic particles and fling same upwardly into the mold cavity 18. The molding arrangement according to the invention is particularly advantageous for producing a multi-layer part, i.e. a laminated part created from different powders. In this regard, multi-powder casting steps can be quickly performed in a single part-forming cycle since rotation of the mold housing 12 and attachment of the powder box 31 to the housing 12 are unnecessary. For example, it may be desirable to provide the finished part (for example a dashboard panel for a vehicle) with a UV resistant constituent to prevent deterioration such as cracking, or to provide the part with a particular color. These types of UV resistant or colorized powders are typically expensive. However, the invention enables rapid formation of a thin outer layer including the UV resistant constituent or color pigment, and then the rapid formation of an additional layer or layers under the outer layer having other desired properties, such as resiliency. Thus, the minimum amount of the higher cost plastic can be utilized, and other desirable characteristics can be provided to the panel utilizing less expensive plastic, which can reduce the overall cost of the part.

The molding arrangement according to the invention may be utilized with the molding arrangement disclosed in pending U.S. Patent Application Serial No. 09/267 567 filed on March 12, 1999 entitled "MOLDING APPARATUS AND PROCESS EMPLOYING HEATED FLUID", and pending U.S. Patent

Application Serial No. filed on April 28,

1999 which is a continuation-in-part of the '567 application and entitled "MOLDING APPARATUS AND PROCESS EMPLOYING HEATED FLUID". The above-referenced applications, both of which are incorporated by reference herein in their entirety, discloses a mold tank which mounts thereon a thin mold shell, which mold shell is heated by partially filling the mold tank with heated liquid such as oil. Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.

Claims

What is claimed is:

1. A mold arrangement for molding thermoplastic particles into a solid thin shell-like article, said mold arrangement comprising: a mold assembly including a housing mounting thereon a thin mold shell which defines a back face subjected to heating and a front face which defines a mold cavity, said shell when mounted on said housing being oriented so that said front face is oriented downwardly and defines a mold cavity which opens downwardly; a powder box which is separate from said mold assembly and is movable between an inoperative position wherein it is detached from the mold assembly and an operative position wherein it engagingly cooperates with the mold shell to close off the mold cavity; said powder box defining therein a storage chamber containing a quantity of plastic particles which normally fill at least a part of said storage chamber, said chamber having a top opening which cooperates with the mold cavity when the powder box is engaged with the mold assembly so that the storage chamber and mold cavity directly communicate and jointly define an agitation chamber; and an agitating device associated with said storage chamber and when energized effecting agitation of the particles within the storage chamber so that the particles become airborne and are propelled upwardly of the agitating chamber for contact with the front face of the mold shell to permit the particles to be molded into a thin article having the contour of the front face.

2. An arrangement according to Claim 1, wherein the agitating device includes a bladed wheel which is positioned within said storage chamber, and a driving device connected to said bladed wheel for effecting selected rotation thereof, whereby the bladed wheel when rotated agitates the particles and propels them upwardly toward the front face of the mold shell.

3. A method for molding a thin thermoplastic article having a generally nonplanar shape in a mold assembly having a mold housing mounting a thin metal mold shell thereon and having a contoured front mold face which defines a mold cavity, comprising the steps of: orienting the mold assembly such that the contoured mold face is oriented downwardly with the mold cavity being disposed thereunder; providing a material supply container which defines therein a compartment containing a quantity of plastic particles with said compartment being open at the top; moving said container into a position where it is disposed below said mold shell and is substantially engaged with the mold assembly so that the compartment and mold cavity define an agitation chamber; heating the mold shell; flinging the plastic particles in the compartment so that they become airborne and are propelled upwardly throughout the agitating chamber for contact with the heated face of the mold to permit adhering and melting of the particles on the mold face to form a thin-walled article; terminating the flinging of the particles and detaching said container from said mold assembly; and removing the formed thin wall article from the mold cavity.

4. A method according to Claim 3 , including the step of heating a back surface of the mold shell to effect heating of the front face thereof.

5. A method according to Claim 3 , wherein the flinging of the particles in the agitation chamber is effected by providing a rotating bladed agitating member within a bottom portion of the compartment, and selectively rotating said agitating member to effect upward agitation and propelling of the plastic particles when agitation of the particles is desired.

6. A method according to Claim 5 wherein the flinging of the particles in the agitation chamber is effected by providing an agitating member including a bladed wheel having a plurality of blades fixed to a generally upright and rotatable drive shaft which defines an imaginary vertical reference line, said step of flinging further including tilting the drive shaft and the respective bladed wheel with respect to the vertical reference line and propelling particles upwardly and at an angle relative to the vertical reference line.

7. A method according to Claim 6 wherein said step of flinging further includes tilting the drive shaft within any vertical plane intersecting the vertical reference line to move the respective bladed wheel along or within an imaginary circular path having a center point defined by the vertical reference line.

8. A method according to Claim 3 wherein the flinging of the particles in the agitation chamber is effected by providing a pair of bladed wheels within the compartment, one of the bladed wheels being positioned closely adjacent a bottom portion of the compartment so as to be substantially immersed in the plastic particles and the other bladed wheel being positioned at a greater elevation within the compartment than the one bladed wheel and above the upper level of the plastic particles, said step of flinging further comprising rotating the one bladed wheel to agitate and lift the particles upwardly toward the front face of the mold shell and rotating the other bladed wheel to further agitate, lift and fling the particles within the agitation chamber to create a random, chaotic dispersion of the particles within the agitation chamber.

9. A method according to Claim 8 wherein the flinging of the particles is effected by providing a plurality of rotatable bladed wheels each including a plurality of blade members which are fixed to and project outwardly from a generally upright drive shaft defining an imaginary vertical reference line, the drive shafts at lower ends thereof being operatively connected to one another via a plurality of connecting members, said step of flinging further including exerting a force on at least one of the connecting members to cause tilting movement of at least some of the drive shafts within a vertical plane intersecting the respective vertical reference line.

10. A method according to Claim 9 wherein said step of flinging further includes exerting multi-directional forces on the connecting members to enable random tilting movement of at least some of the drive shafts and the respective bladed wheels to create a random chaotic dispersion of the particles within the agitation chamber.

11. An arrangement according to Claim 2 wherein said bladed wheel is a first bladed wheel and is disposed closely adjacent a bottom portion of said storage chamber, said arrangement further including a second bladed wheel positioned within said storage chamber and a driving device connected to said second bladed wheel for effecting rotation thereof, said second bladed wheel being positioned at a greater elevation within said storage chamber than said first bladed wheel.

12. An arrangement according to Claim 11 wherein said first bladed wheel is substantially covered by the particles prior to rotation thereof, whereby said first bladed wheel when rotated agitates and lifts the particles upwardly toward the front face of the mold shell, and said second bladed wheel when rotated further agitates and lifts the particles to uniformly distribute the particles within the mold cavity.

13. A material supply container assembly for use with a mold assembly mounting thereon a thin mold shell defining a back face subjected to heat and a front face defining a mold cavity which opens generally downwardly, said supply container assembly comprising: a powder box defining therein a storage chamber containing a quantity of plastic particles which partially fill said storage chamber, said storage chamber having an upper opening which directly communicates with the mold cavity of the mold assembly and therewith jointly defines a powder chamber upon said powder box being brought into engagement with the mold assembly; and an agitating arrangement disposed within said storage chamber to effect agitation of the particles therewithin, said agitating arrangement including a rotatable bladed wheel disposed to propel the particles upwardly toward the front face of the mold shell to permit the formation of a thin article having the contour of the front face.

14. A supply container assembly according to Claim 13 wherein said bladed wheel includes a plurality of blade members which are fixed to and project outwardly from a generally upright drive shaft defining an imaginary vertical reference line, said drive shaft being mounted for tilting movement with respect to the vertical reference line such that said blades when rotated propel particles upwardly and at an angle relative to the vertical reference line.

15. A supply container assembly according to Claim 14 wherein said drive shaft is mounted for tilting movement within any vertical plane intersecting the vertical reference line such that said bladed wheel is movable along or within an imaginary circular path having a center point defined by the vertical reference line.

16. A supply container assembly according to Claim 13 wherein said bladed wheel is a lower bladed wheel and said agitating arrangement includes an upper bladed wheel disposed above said lower bladed wheel.

17. A supply container assembly according to Claim 16 wherein said lower bladed wheel is positioned closely adjacent a bottom portion of said storage chamber and is substantially immersed in the plastic particles whereby said lower bladed wheel when rotated agitates and lifts the particles upwardly toward the front face of the mold shell, and said upper bladed wheel when rotated further agitates, lifts and flings the particles within the powder chamber to uniformly distribute the particles within the mold cavity.

18. A supply container assembly according to Claim 13 wherein said agitating arrangement includes a plurality of rotatable bladed wheels each including a plurality of blade members which are fixed to and project outwardly from a generally upright drive shaft defining an imaginary vertical reference line, each said drive shaft being mounted for tilting movement within any vertical plane intersecting the respective vertical reference line such that the respective bladed wheels are movable along respective imaginary circular paths each having a center point defined by the respective vertical reference line, said drive shafts being operatively connected to one another via a plurality of connecting members and said supply container assembly including at least one actuator disposed to exert a force on at least one of said connecting members to cause tilting movement of at least some of the respective drive shafts and bladed wheels.

19. A supply container assembly according to Claim 18 further including a plurality of said actuators disposed to exert multi-directional forces on said connecting members to enable random tilting movement of at least some of said drive shafts and the respective bladed wheels to cause random chaotic dispersion of the particles within said powder chamber.

20. A supply container assembly according to Claim 13 wherein said bladed wheel is a first bladed wheel and is positioned closely adjacent a bottom portion of said storage chamber, said first bladed wheel being connected to a driving device for effecting rotation thereof, and said agitating arrangement includes a second bladed wheel positioned within said storage chamber and a driving device for effecting selected rotation thereof independent of said first bladed wheel, said second bladed wheel being positioned at a greater elevation within said storage chamber than said first bladed wheel. AMENDED CLAIMS

[received by the International Bureau on 29 October 1999 (29.10.99); original claim 1 amended; remaining claims unchanged (1 page)]

1. A mold arrangement for molding thermoplastic particles into a solid thin shell-like article, said mold arrangement comprising: a mold assembly including a housing mounting thereon a thin mold shell which defines a back face subjected to heating and a front face which defines a mold cavity, said shell when mounted on said housing being oriented so that said front face is oriented downwardly and defines a mold cavity which opens downwardly; a powder box which is separate from said mold assembly and is movable between an inoperative position wherein it is detached from the mold assembly and an operative position wherein it engagingly cooperates with the mold shell to close off the mold cavity; said powder box defining therein a storage chamber containing a quantity of plastic particles which normally fill at least a part of said storage chamber, said chamber having a top opening which cooperates with the mold cavity when the powder box is engaged with the mold assembly so that the storage chamber and mold cavity directly communicate and jointly define an agitation chamber; and an agitating device associated with said storage chamber and when energized effecting agitation of the particles within the storage chamber so that the particles become airborne and are propelled upwardly of the agitating chamber for contact with the front face of the mold shell to permit the particles to be molded into a thin article which has the contour of the front face and is separable therefrom upon completion of a molding cycle.

2. An arrangement according to Claim 1, wherein the agitating device includes a bladed wheel which is positioned within said storage chamber, and a driving device connected to said bladed wheel for effecting