Abstract:
The present invention relates to a method and apparatus for molding plastic articles. More specifically, the present invention is directed to a staged sequentially separated apparatus for injection molding of plastic panels having a flap or tab molded therewith in a single molding and forming step. The present invention provides, among other things, a method and an apparatus for forming an injection molded part with an undercut, the undercut lying generally in a plane of a major portion of the part, the undercut having an open elongate opening and being positioned between an elongate integrally molded tongue and panel. The apparatus comprising a first mold half with a first mold cavity defining surface, a second mold half with a second mold cavity defining surface, a tongue member carried by the second mold half and projecting into a mold cavity. The tongue member having generally opposing facing surfaces spaced from the first and second mold cavity surfaces for forming opposite face of a molded part undercut. The apparatus also comprising means to selectively effect movement of the transverse mold insert relative to at least a portion of the remainder of the second mold half.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a method and apparatus for molding plastic articles. More specifically, the present invention is directed to a staged sequentially separated apparatus for injection molding of plastic panels having a flap or tab molded therewith in a single molding and forming step.  
         [0002]     Injection molding techniques of plastic materials is well known in the art. Molding techniques such as this are suitable for forming a wide variety of parts at relatively low costs. Injection molding is particularly advantageous for high speed forming large quantities of discrete parts from thermo-plastic resins/polymers. Certain features of a particular part sometimes utilize the application of some unique molding techniques. Ordinarily, an injection molding apparatus for manufacture of a molded part comprises a mold made of steel or other metallic substance. The molds usually have two mold halves which move relative to one another in generally opposite directions which limits molded part designs.  
         [0003]     The mold contains a mold cavity that is configured to match the part that is to be molded. The mold is typically characterized by a stationary molding half, and a movable molding half. The mold is openable or separable at a parting line so that the molded part can be removed from the mold cavity. A polymer based material such as polystyrene or the like is injected into the mold when the mold is closed. After the material has been cooled or set, the mold is opened and the molded part is ejected or removed from the mold. In some machines, both halves of the mold are moveable. The process is then repeated to form subsequent parts.  
         [0004]     One skilled in the art recognizes that the mold halves are clamped and tightly held together in order for the molded part to be properly formed.  
         [0005]     Certain types of molded parts have protrusions or edges, which are formed with an undercut in the part. Forming an undercut in a part generally requires that the molten material surrounds a tongue or other mold insert. As in all molding processes, the molded part with an undercut needs to be released from the mold for subsequent use. Any one of a variety of mechanisms may be employed for releasing the molded part from the mold parts forming such undercuts. Systems and techniques heretofore utilized are not suitable for molding parts having an undercut to form a relatively thin flap or tab.  
         [0006]     A simulated cedar shake siding panel, which utilizes a locking flap to interengage a locking lip located on a second panel, has been difficult to form utilizing traditional techniques because of the dimensional specifications of the tab and undercut. As such, a part like this is usually formed in a multi-step process. In other words a first process creates a first part, then an additional one or more processes, are employed, either locally or at a remote location, to add or form the tab to complete the part.  
         [0007]     A cedar shake siding panel  10  such as shown in  FIGS. 1 and 2  is traditionally formed in a multi-step manufacturing process. In its finished form the panel  10  has a nail hem  22 , a tab  24 , a top surface  26 , and laterally extending rows  27 A,  27 B of simulated wood or wood grain shingles  14 . A plurality of elongate slots  23  are provided in the nail hem  22 , for attaching the panel to a structure such as a wall.  
         [0008]     The first prior art manufacturing process is best described with reference to  FIG. 3A , in which a strip  20  is molded as part of the panel  10  having opposite ends  9 ,  11 . The strip  20  includes openings  28  and a row of bosses  30  located on the strip  20 , and a folding area  32  located therebetween. The strip  20  also includes a tab forming portion  23 . The tab forming portion  23 , strip  20 , openings  28 , bosses  30  and folding area  32  extend along the panel  10  between the opposite ends  9 ,  11 . Prior to the implementation of a second forming process or as a part thereof, the strip  20  is folded along the folding  32  in the direction shown A in  FIG. 3A . The location of the fold and the extent of the fold is such that the bosses  30  fit inside the openings  28 , and a tab  24  which extends downwardly is formed and spaced from the strip  20 , as shown in  FIG. 3B  forming an open sided groove  25  therebetween. Irrespective of when the fold is made, the second process involves joining the opposing surfaces of the strip  20 . As would be understood by one skilled in the art, such joining may be accomplished by heat, ultrasonic welding, mechanical interlude, adhesion or some other means. The result of the joint is an integrated structure with a tab  24  and groove  25  as shown in  FIG. 3B .  
         [0009]     Generally and at best, the step in the manufacturing process for folding and joining the opposed surfaces of the strip  20  is performed in a post injection molding step and on a separate production line using additional equipment. More typically, the folding and the joining step in particular, occurs at a different facility, such as when the joining process involves ultrasonic welding of the part.  
         [0010]     In either case, and particularly in the situation where the parts are transported to a different facility, a number of issues that impact the cost and quality of the final product arise. For example, there are issues relating to handling, which can include movement or shipping of the parts, timing and frequency of such movements, and so on. The logistics involved in handling have an associated additional cost. Even further, there are the costs and other issues associated with the operations at the welding facility. Further still there are some duplicative efforts in the process as a whole such, such as in the packaging of the parts. Parts are packaged after the initial molding process for transportation to the welding facility and then again for final shipment of the completed panel  10 .  
         [0011]     There is therefore a need for a system and method that provides a simplified manufacturing process, wherein some cost savings, quality control and efficiencies can be achieved without adversely impacting the quality of the end product. Even further there is a need for a system and method that eliminates the need for the secondary and separate folding and welding operation described above while still meeting the specifications of the molded part. The present invention addresses this need and overcomes the limitations of the prior art.  
       SUMMARY OF THE INVENTION  
       [0012]     To address these and other concerns, the present invention provides, among other things, a  
         [0013]     method and an apparatus for forming in a single molding step in a mold, a part having an undercut, and at least one longitudinally extending groove in the general plane of the part, the undercut and groove presenting motion restricting surfaces. The apparatus comprising multiple moveable mold elements, the moveable mold elements adapted to fit together to define a cavity to form the part, the moveable mold elements adapted to be moved in a particular sequence to free the molded part. The apparatus also comprising means for releasing or ejecting the part from the mold. The multiple moveable mold elements comprise, a first mold half having a first mold cavity defining surface to match a portion of one side of the part, a slide having an overhang portion and a second mold half having a second mold cavity defining surface. Also included is an elongate transverse mold insert having a distal end that defines a portion of the mold cavity. The second mold half having a tongue with a top surface and a lower surface for forming the undercut in the molded part. The tongue protruding into the mold cavity. The mold cavity is at least partially defined by the first cavity defining surface of the first mold half, the overhang portion of the slide, along with the surface of mold insert, the second mold cavity defining surface and the surface of the tongue. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The present invention is further described with reference to the accompanying drawings, which show various constructions and implementations of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in constructions which are still within the spirit and scope of the present invention.  
         [0015]      FIG. 1  is a front elevation view of an exemplary plastic siding panel that may be formed by the system and method of the present invention;  
         [0016]      FIG. 2  is a left side view of the panel of  FIG. 1 ;  
         [0017]      FIG. 3A  is a fragmentary side view of the flap section of a siding panel prior to the folding and welding of the flap; (PRIOR ART)  
         [0018]      FIG. 3B  is a fragmentary side view of the flap section of a siding panel after the folding and welding of the flap; (PRIOR ART)  
         [0019]      FIG. 4  is an illustrative mold, for forming the panel of  FIG. 1  in accordance with the present invention, shown in the closed position;  
         [0020]      FIG. 5  is the mold of  FIG. 4  shown after a first mold opening step;  
         [0021]      FIG. 6  is the mold of  FIG. 5  shown with a partial second mold opening step and illustrating the flexing of the flap portion of the molded part;  
         [0022]      FIG. 7  is the mold of  FIG. 6  shown with a completed second mold opening step, wherein the second mold half is separated from the part; and  
         [0023]      FIG. 8  is the mold of  FIG. 7  illustrating a retracted slide and the ejected part. 
     
    
     DETAILED DESCRIPTION  
       [0024]     The present invention is directed to a tooling system and method for forming a molded plastic part having an undercut and exposing a flap or as in the embodiment described herein, an interlock feature or tab for a simulated wood shingle siding panel. The undercut is oriented such that it will lock the part to one or more components of the mold if the mold halves were to open in a simple unidirectional opening motion. More specifically, the present invention pertains to a mold or tooling construction and molding process that allows a tab or interlock feature, to be molded and formed concurrent with the molding of the part in a one step forming process using molding. The invention eliminates the requirement to perform secondary forming steps such as folding and ultrasonic welding, when creating parts of the type described.  
         [0025]     In an embodiment, the present invention utilizes aspects of formed part material properties and a retaining slide to mold an interlock tab in place. The slide insert is built into a mold construction and allows pulling force to be applied to wall members, to mold the interlock in place. The invention is hereinafter described with reference to the accompanying drawing Figures and one or more exemplary embodiments. It should be understood that the description herein is for illustrative purposes only and is in no way intended to limit or otherwise confine the invention to the specific embodiment or disclosed steps, procedures or components.  
         [0026]     Referring to the drawings, there is shown in  FIG. 1 , a plastic (polymeric) panel  10  for use in covering a portion of a building exterior e.g. a sidewall. A plurality of such panels  10  are typically used to cover an appropriate portion of the building exterior. The plurality of panels  10  are designed to fit, or otherwise work, together. As such, the panels  10  are designed with a means to inter-engage one another and means to facilitate attachment to the building. The panels may also be designed to meet other aesthetic and functional needs. For example, the panel  10  may include laterally extending and substantially parallel rows of patterns/embossed designs formed to mimic the appearance of wood shingles or shakes  14 . The panel  10  may also be designed to attach to, or be attachable by a second and similar panel  12 . The means for inter-engaging the panels  10 ,  12  is best described with reference to the side view of the panel  10 , illustrated in  FIG. 2 .  
         [0027]     As shown in  FIG. 2 , panel  10  includes among other things, an upper row  27 A and lower row  27 B of simulated shingles  14  a tab  24  and a flange  38 . Multiple panels  10  are usually utilized to cover the exterior of a building. So, for example, when a first panel  10  is installed, a second panel  12  is installed above it and the sequence is repeated until the building exterior is covered. The panel  10  may have a continuous tab  24  and groove  25  extending the length of the panel between opposite ends  9 ,  11 . Alternatively, there could be multiple tabs  24  and groove  25  spaced along length of the panel  10 . At least one tab  24  of the first panel  10  is engaged by at least one flange  38  of the second panel  12 , such as illustrated in  FIG. 3B . Returning to  FIG. 2 , as would be understood by one skilled in the art there are a variety of surface contour(s)  16  that may be present on the tab  24  with opposing contour(s)  17  on the flange  38  such as to arrest or restrict relative vertical motion of the panels  10 , 12 .  
         [0028]     The molding of an article having an undercut such as panel  10  described herein as having a tab  24 , nail hem  22  and other features, is the subject of the system and method of the present invention. The described embodiment of the present invention is directed to the making of panel  10  in an injection molding process. As with any other plastic articles formed by a method of injection molding, the present invention also includes a mold. The mold of the present invention enables the molding of a panel  10  with the tab  24  in a single forming process. Even further, the present invention facilitates the end result without the need for a secondary folding and joining step to form the tab  24 . It should be understood that the present invention contemplates the elimination of the need for secondary processes, which may be employed to create a tab, or other such undercut forming member in the molding of any articles.  
         [0029]     The mold assembly of the present invention is best described with reference to  FIG. 4 .  FIG. 4  illustrates a mold assembly  40  for an injection mold apparatus that facilitates forming a panel  10  with a tab  24 . The mold assembly  40  is depicted in the closed position in  FIG. 4 .  
         [0030]     In an embodiment of the present invention, the mold assembly  40  includes a mold cavity  52 , for receiving flowable or pressure formable material to form the panel  10 , and ejectors  62  to eject the panel  10  from the cavity  52 . The mold cavity  52  is partially defined by a first mold half  46 , and a second mold half  44 . A transverse mold insert  50  is part of the second mold half  44 . The transverse mold insert  50  moves transverse to the parting line of the mold  40  and plane of the panel  10 . A portion of the mold insert  50  in conjunction with a slide  48  and the first mold half  46 , further define the mold cavity  52 . The surfaces defining the mold cavity  52  define the particular configuration of the panel  10 . For example, the second mold half  44  has contours and recesses that define one side of the panel  10 . The surface of the mold cavity  52  can include various surface portions.  
         [0031]     In the current embodiment, the slide  48  is designed with a wall  53 , an overhang portion  54 , having a sloped frontal surface  55 . The overhang portion  54 , is adjacent to and abuts the mold insert  50 , and also further defines at least a portion of the cavity  52  in conjunction with the surface of the first mold half  46 . The slide  48  is retained in a specific position over the cavity  52  by the second half mold  44  when the mold is closed. The second mold half  44  is fabricated with a tongue  56  having a first surface  58  and a second surface  60 . The first surface  58  is shaped to form the desired contour(s)  16  of one side of the tab  24  and groove  25 . The second surface  60  is shaped to form the opposing side of the groove  25 . The mold insert  50  may have a beveled first surface  51  that co-acts and is adjacent to the sloped frontal surface  55  of the slide  48 . The mold insert  50  may further have a molding surface constrained to and including a substantially planar surface  57  adjacent the beveled surface  51 , and a second surface  49  adjacent the generally planar surface  57 . The substantially planar surface  57  and the second shaped surface  49  are located on opposite sides of a distal end of the mold insert  50 . The second surface  49  of the insert  50  opposes and overlies a tongue  56  of the second mold half  44 . The second surface  49  defines the exterior or exposed portion of the tab  24 . The second shaped surface  49  of insert  50  and the first surface  58  of the tapered tongue  56  define a region in the cavity  52  for the tab  24  to be formed.  
         [0032]     Also illustrated in  FIG. 4 , are ejector pins  62  in a retracted or molding position, wherein the exposed ends of the ejector pins  62  form part of the mold cavity surface of the first mold half  46 . In many installations it may be preferable to have the ends of the ejector pins  62  slightly recessed or slightly projecting with respect to the surface of the cavity  52 . As would be recognized by those skilled in the art, any suitable number of mold elements or cores may be positioned to effect the desired mold form and the ejection of the part therein.  
         [0033]     In the molding process, the cavity  52  is filled with material under pressure with the mold in the closed position as illustrated in  FIG. 4  to form the panel  10 . The elements used for feeding material into the cavity  52 , as well as any elements required for heating the material etc., are not illustrated or described, in order to simplify the description. After a period of time sufficient for the formed panel  10  to cool and set as needed, the mold  40  is ready to be separated and the panel  10  ejected from the mold cavity  52 . As would be understood by one skilled in the art, the forces exerted on the part during the mold separation process are controlled to avoid potential damage to the part. The present invention utilizes a multiple stage mold separation process to achieve this end.  
         [0034]     In the first stage of the separation, mold insert  50  is removed from the second mold half  44  in a direction that is lateral to the opening and closing direction of the mold. The mold insert  50 , extends into a recess  45  of the second mold half  44 , and defines the outer surface of the tab  24 . The second mold half  44  and the slide  48  remain in place over the rest of the cavity  52 . Keeping the slide  48  and second mold half  44  in place during the initial mold opening causes the tab  24  to pull away from the stationary side of the mold, i.e. the first mold half  46 . The completion of the first stage of separation is illustrated in  FIG. 5 . As is readily seen, the mold insert  50  is fully withdrawn.  
         [0035]     The second stage of separation is commenced by the movement of the second mold half  44  away from the first mold half  46 . During the second stage, the tongue  56 , which extends underneath the tab  24 , simultaneously begins to flex the tab  24 . In accordance with known methods in the art, the tab  24  is formed to have memory, thus enabling it to flex and return to a desired position. The tab  24  is flexed in a direction that is consistent with the movement of the second mold half  44  and towards the slide  48 . The partial completion of the second stage of separation is illustrated in  FIG. 6 . As is readily seen, the flexed tab  24  provides a clearance that effects the separation of the second mold half  44  and the tongue  56 , without appreciable deformation to the tab  24 . The movement of the second mold half  44  continues until the tongue  56  clears the tab  24 .  
         [0036]     The completion of the second stage of separation is illustrated in  FIG. 7 . As is readily seen, the second mold half  44  is completely separated from the first mold half  46 , and the tongue  56  has cleared the tab  24 , thus allowing the tab  24  to return to a desired molded position. This allows the beginning of the final stage of mold and part separation.  
         [0037]     The final stage of separation is illustrated in  FIG. 8 . In the final stage of separation the slide  48  is moved transverse to direction of mold separation, in a relative lateral direction away from the cavity  52  and the newly molded panel  10 . The panel  10  having the interlock tab  24  can then be ejected and removed from the mold assembly  40 .  
         [0038]     In another embodiment of the present invention, immediately following part ejection, a robot is utilized to clamp down the tab  24 . The clamping of the tab  24  repositions the tab  24  to compensate for deformation that may result from the flexing of the tab  24  during retraction of the second mold half  44 .  
         [0039]     In yet another embodiment, the molded panel  10  is further controlled by utilizing the robot and also reheating the panel  10 . The panel  10  is placed on a conveyor and is exposed to a heated conveyor oven to initiate secondary crystallization. By raising the temperature of the panel  10  to the crystallization point or temperature, the tab  24  will be formed to the final described shape.  
         [0040]     The present invention provides an advantageous apparatus and method, comprising multiple mold elements and a sequential separation of the mold elements, in a molding technique that forms in place, extracts and prevents damage to a tab, on a newly molded part.  
         [0041]     Another advantage of the present invention is the elimination of a manufacturing step, in which a folding and welding of a newly molded part was required. A further advantage is in the cost savings, and efficiencies that are achieved without impacting the quality or specifications of the end product.  
         [0042]     The constructions described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the claims.  
         [0043]     From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the method and apparatus. It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and sub combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments of the invention may be made without departing from the scope thereof, it is also to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not limiting.  
         [0044]     The constructions described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. As used herein, the terms “having” and/or “including” and other terms of inclusion are terms indicative of inclusion rather than requirement.