Abstract:
An in-machine assembly technique uses revolving mold sections that rotate perpendicularly to the clamping axis of the injection-molding machine to increase usable mold area and to provide improved access to molded parts before and after assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to injection molding machines and methods and, in particular, to an injection molding system that allows for the assembly of molded parts as a stage of the molding process.  
           [0002]    Injection molding is a manufacturing process in which heated thermoplastic is forced under pressure into a mold. After the thermoplastic cools, the mold is separated along a part line and a molded thermoplastic part is ejected. With the proper mold, complex parts can be manufactured in extremely high volumes and low per piece costs.  
           [0003]    Many products that cannot be manufactured by injection molding in a single mold can be assembled from one or more separately molded parts. The step of assembling these parts can significantly increase the cost of the product and in certain cases decrease part volumes otherwise obtainable.  
           [0004]    For this reason, there is considerable interest in so-called “in-mold” assembly techniques. In one such technique termed “two shot” molding, a mold having replaceable portions allows different features to be added into one changing mold cavity over several sequential steps of plastic injection. The resulting product may be a single, fused structure or, by making the two shots of plastics that resist adhesion to each other, the resulting product may be an assembled collection of movable parts.  
           [0005]    More complex products can be created by a different technique in which separately molded parts are partially retained by a portion of the mold which is then moved within the injection molding machine to a different position for assembly with other molded parts made simultaneously in a different portion of the same machine.  
           [0006]    In one published method using this technique henceforth referred to as “in-machine” assembly, a product is manufactured using a four-part mold having two outer sections attached to the molding machine platens, and two center sections between these outer sections and which may rotate about two offset axes both parallel to the mold clamp direction. During a first step, parts are molded in mold cavities formed by the joining of corresponding portions of pairs of the outer sections and center sections. The molded parts are then retained on the center sections which rotate to move the molded parts into opposition for assembly. The mold sections are again closed and the molded parts are assembled.  
           [0007]    The parts may be held together by adhesive, molded-in-place rivets or other techniques applied immediately before or during the mold closure. This technique for in-mold assembly may be suitable, for example, for manufacturing products having cavities loosely holding a non-molded material.  
           [0008]    The in-machine molding technique described above requires a shaft to be extended through each platen of the injection molding machine for rotating the revolving mold section sections such as may require substantial modification of the injection molding machine. Further the full area of the platen cannot be exploited for molding because of the need to reserve room for assembly of cooled parts. This limits the molding throughput. Finally, insertion of other parts or application of glue to the parts prior to assembly is difficult because the parts are always in-between the platens and the molds limit access to those parts.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    The present invention provides an in-machine assembly technique for injection-molded parts in which the revolving mold sections rotate perpendicularly to the clamping axis of the molds. This rotation direction allows the full area of the platen to be used for molding, the assembly of parts being conducted on opposed faces of revolving mold sections after they have been rotated.  
           [0010]    When a 90° rotational increment of each mold is adopted, the molded parts are exposed at the side of the machine for easy access when gluing or adding parts or inserts prior to assembly.  
           [0011]    A third plastic injector at the interface between the revolving mold sections can be used in the assembly process.  
           [0012]    Specifically, the present invention provides a molding system for in-machine assembly of product, the molding system usable on an injection-molding machine having opposed platens movable along a clamping axis. The system uses a first mold clamp plate having a mold face defining a first cavity portion for a first part, a first revolving mold section having at least two mold faces each defining a second cavity portion for the first part, the first revolving mold section rotatable about an axis perpendicular to the clamping axis to successively bring the mold faces of the first revolving mold section into opposition with the mold face of the first mold clamp plate.  
           [0013]    The system also provides a second mold clamp plate having a mold face defining a first cavity portion for a second part interfitting with the first part and a second revolving mold section having at least two mold faces each defining a second cavity portion for the second part, the second revolving mold section rotatable about an axis perpendicular to the clamping axis to successively bring one mold face of the second revolving mold section into opposition with the mold face of the second mold clamp plate and a second mold face of the second revolving mold section into opposition with a mold face of the first revolving mold section. Molded parts may be assembled at the interface of the first and second revolving mold section faces.  
           [0014]    Thus it is one object of the invention to provide an improved in-machine assembly technique offering higher volumes of part molding by better using the platen area.  
           [0015]    It is another object of the invention to provide an improved in-machine assembly technique not requiring modification of the injection-molding machine to insert mold moving mechanisms behind the platens.  
           [0016]    The first and second revolving mold sections may rotate by 180 degrees in between each molding cycle.  
           [0017]    It is thus another object of the invention to provide a simple molding system usable with revolving mold sections that are not square in cross-section, but rectangular, and thus adaptable for use with injection molding machines having limited platen separation.  
           [0018]    The first and second revolving mold sections each have four mold faces and may rotate by 90 degrees in between each molding cycle.  
           [0019]    It is another object of the invention to provide improved access to the molded parts prior to assembly or after assembly as may be desired.  
           [0020]    It is another object of the invention to provide an ability to use a third injector for the purpose of assembly of the parts or the adding of additional part features.  
           [0021]    An insert loader may be placed proximate to a mold face of one of the first and second revolving mold sections when the mold face is rotated to be substantially parallel to the clamping axis to install an insert into one of the first and second parts.  
           [0022]    It is another object of the invention to allow insertion of parts into a product during in-machine assembly.  
           [0023]    An adhesive dispenser may be placed proximate to a mold face of one of the first and second revolving mold sections when the mold face is rotated to be substantially parallel to the clamping axis to dispense adhesive onto one of the first and second parts at an area of contact between the first and second parts when the first and second parts are assembled.  
           [0024]    It is another object of the invention to provide a method in-machine assembly employing the application of common adhesives.  
           [0025]    An injector for thermoplastic may be placed proximate to the interface between the first and second revolving mold sections.  
           [0026]    Thus, it is another object of the invention to provide an in-machine assembly system that may connect parts through in-place molded rivets or seams.  
           [0027]    These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    [0028]FIG. 1 is a simplified perspective view of an injection molding machine using the molding system of the present invention showing the mold clamp plates flanking revolving mold sections in unclamped position between platens and showing locations of a first, second and optional third injector unit;  
         [0029]    [0029]FIG. 2 is a side elevational view of the molding system of FIG. 1 showing positioning of insert and adhesive depositing mechanisms to the side of the molds;  
         [0030]    [0030]FIG. 3 is a cross-sectional view through a product assembled out of a cover and base molded part moldable using the molds of FIG. 2 and holding an insert and showing four methods of joining the parts, a seam, molded rivets, adhesive, and snap surfaces;  
         [0031]    [0031]FIG. 4 is a detailed cross-sectional view of the cavity for molding the base of FIG. 3 formed by the connection of the first mold clamp plate and first revolving mold section such as will provide a seam at which a part will be assembled;  
         [0032]    [0032]FIG. 5 is a view of the cavity formed by the interface between the first and second revolving mold sections showing the production of a channel through which a seam material may be injected to assemble the parts together;  
         [0033]    [0033]FIG. 6 is a figure similar to that of FIG. 4 showing an alternative mold configuration that provides an hourglass-shaped rivet pocket; and  
         [0034]    [0034]FIG. 7 is a figure similar to that of FIG. 5 showing filling of the hourglass-shaped rivet pocket to produce a rivet. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0035]    Referring now to FIG. 1, the mold system  10  of the present invention may work with an injection-molding machine having opposed platens  12  and  14  that may be moved together in a part along clamping axis  16  about molds  18 . Thermoplastic injectors  20  and  22  are positioned behind platens  12  and  14 , respectively, to provide molten plastic material to mold clamp plates  24  and  26  attached to platens  12  and  14 . Mold clamp plates  24  and  26  present mold faces at mold face positions  34   a  and  34   f , respectively.  
         [0036]    Positioned between mold clamp plates  24  and  26  are revolving mold sections  28  and  30 . In the preferred embodiment revolving mold sections  28  and  30  have square cross-sections taken along a vertical plane and may be rotated by actuators  32  so as to present one of four equal area mold faces  33  at corresponding mold face positions  34   b - 34   e  and  34   g - 34   j  where initially mold face position  34 b is vertical and opposed to mold face position  34   a  for mold clamp plate  24  with the lettering of subsequent mold face positions proceeding clockwise per rotation of the revolving mold section  28  and, mold face position  34   g  is vertical and opposed to mold face position  34   f  for mold clamp plate  26  with the lettering of subsequent mold face positions proceeding counterclockwise per rotation of the revolving mold section  30 . The rotation mechanism for revolving mold sections  28  and  30  may make use of a mechanism similar to that described in pending U.S. application Ser. No. 09/993,202 filed Nov. 16, 2001 and hereby incorporated by reference.  
         [0037]    Referring to FIG. 2, mold clamp plate  24  presents a mold face at mold face position  34 ( a ), the mold face having one or more mold cavities  36  communicating with injector  20  through platen  12  and manifold channel  38  (only one mold cavity  36  is shown in solid lines for clarity). Revolving mold section  28  presents a corresponding mold face having one or mold cavities  36  at mold face position  34 ( b ). When the platens  12  and  14  move together along the clamping axis  16 , the mold clamp plate  24  and revolving mold section  28  join to form a part cavity that may be filled with thermoplastic material as is understood in the art to form a first molded part, in this case, a molded base  46 .  
         [0038]    Likewise, mold clamp plate  26  presents a mold face at mold face position  34 ( f ), the mold face having one or more mold cavities  36 ′ (only one shown for clarity) different from the mold cavity  36  of mold clamp plate  24 . The mold cavity  36 ′ on the mold clamp plate  26  communicating with injector  22  through platen  14  and manifold channel  40 . Revolving mold section  30  presents a corresponding mold face having cavities  36 ′ at mold face position  34 ( g ). When the platens  12  and  14  move together along the clamping axis  16 , the mold clamp plate  26  and revolving mold section  30  join to form a part cavity that may be filled with thermoplastic material to form a second molded part, in this case, a molded cover  48 .  
         [0039]    After a first molding operation, revolving mold sections  28  and  30  will rotate 90 degrees, clockwise and counterclockwise, respectively, the molded base  46  and molded cover  48  remaining with the revolving mold sections (enforced by the use of ejector pins on the mold clamp plates  24  and  25 ) to move to mold face positions  34 ( c ) and  34 ( h ), respectively. New mold faces will now oppose mold clamp plate  24  and mold clamp plate  26 . The platens  12  and  14  will again close along axis  16  and injectors  20  and  22  will supply thermoplastic to the mold cavities  36  formed by the interface of mold clamp plate  24  and revolving mold section  28  and mold clamp plate  26  and revolving mold section  30  so new molded base  46  and molded cover  48  can be molded. It will be understood that the particular directions of rotation as clockwise and counterclockwise are a matter of engineering choice and not necessarily a limitation of the invention.  
         [0040]    When platens  12  and  14  again separate, the revolving mold sections  28  and  30  again rotate bringing the original molded base  46  and molded cover  48  into opposition at mold face positions  34 ( d ) and  34 ( i ). When the platens  12  and  14  close again to mold new parts, revolving mold sections  28  and  30  are joined assembling the molded base  46  and molded cover  48  at their interface. New parts are also molded at the interface between mold clamp plate  24  and revolving mold section  28 , and mold clamp plate  26  and revolving mold section  30 . This process may be continued with new parts being molded and assembled at each turn on the revolving mold sections  28  and  30 .  
         [0041]    Referring now to FIG. 3, the part being molded may comprise a molded base  46  molded using revolving mold section  28 , and a molded cover  48  molded using revolving mold section  30  and fitting over molded base  46  to produce an enclosed volume  50 . The enclosed volume  50  may, for example, hold an insert  52  such as a paper filter or the like, that is separate from the plastic of the molded base  46  and molded cover  48 .  
         [0042]    As shown in this example, the molded base  46  fits within the molded cover  48  to meet at a seam  54 . This seam can be joined by the application of adhesive at the seam  54  by a gasket material  58  (not necessarily flexible) which may be applied across the seam  54 , and rivets  60  may be molded through the seam  54 , or alternatively or in addition, by the detent surfaces  63  formed in interengaging surfaces of the molded base  46  and molded cover  48  allowing the molded base  46  and molded cover  48  to snap together with slight deformation of the plastic material of each.  
         [0043]    When the platens  12  and  14  are closed, the molded base  46  and molded cover  48  are supported on the upper face of revolving mold section  28  and  30 , respectively, and are readily accessible. A side-mounted adhesive gun  44  may be positioned near this side of the revolving mold section  28  to apply adhesive to the seam  54  of the molded base  46  when it is in this position.  
         [0044]    Likewise, when the molded cover  48  is correspondingly exposed at the top of revolving mold section  30 , the insert  52  may be placed in the molded cover  48  by a manipulator  62  or similar mechanism.  
         [0045]    Both the adhesive gun  44  and manipulator  62  are free from interference with the platens  12  and  14  and molds  24 ,  28 ,  30 , and  26  and thus may be easily positioned, and may operate with a simple linear motion different from that which would be required to insert parts within the gap between, for example, the mold clamp plate  26  and revolving mold section  30 .  
         [0046]    As mentioned, prior to assembly of each part, revolving mold sections  28  and  30  rotate in a clockwise and counter-clockwise direction, respectively, to bring molded base  46  and molded cover  48  into opposition at mold face positions  34 ( d ) and  34 ( j ) in FIG. 2. When the molds and platens  12  and  14  are closed again, molded base  46  held on revolving mold section  28  is inserted into molded cover  48  held on revolving mold section  30  and assembled. At this time, a third injector  64  positioned at the interface of revolving mold sections  28  and  30  when platens  12  and  14  are closed may be used to apply additional thermoplastic material to join the parts (as will be described) or to add additional structure or overmolding. Again, the injector  64  has good accessibility from the side of the injection molding machine.  
         [0047]    When the platens  12  and  14  open again, the assembled part may be ejected by internal ejector pins as is understood in the art to drop between the revolving mold section  28  and  30  into a receiving bin. Alternatively, the parts may be ejected from one of the revolving mold sections  28  and  30  after an additional rotation.  
         [0048]    Note alternatively, the lower surface of revolving mold section  28  and  30  may be used to place inserts into the mold cavities  36  and  36 ′ before injection of the parts using insertion arms  66  as will be understood in the art.  
         [0049]    It will be understood that although the horizontal axis of rotation of revolving mold sections  28  and  30  is shown in FIG. 1, a vertical axis perpendicular to axis  16  may also be employed. In addition, it will be understood that the rotation of revolving mold section  28  and  30  may be by increments of 180° per mold cycle rather than the 90 degrees described. In this case, revolving mold section  28  and  30  need not have square but may have rectangularcross-sections reducing the amount of separation required in the platens  14  and  16 . It will be further understood that additional revolving mold sections  28  and  30  (for example, three or more in a row) may in fact be used to provide for either additional molding or assembly operations.  
         [0050]    Referring now to FIG. 4, use of injected plastic from injector  64  may be used to join the molded base  46  and molded cover  48  by means of a channel  70  formed in revolving mold section  28  along the part line  72  between mold clamp plates  12  and revolving mold section  28 . The channel may extend toward the seam  54  on the molded base  46  but be blocked by an extension  74  of mold clamp plate  24 , which will provide a gasket space at a later step shown in FIG. 5. A corresponding channel  70 ′ leading to the seam.  54  may be provided by revolving mold section  30  and blocking extension  74  by mold clamp plate  26  (not shown).  
         [0051]    When revolving mold sections  28  and  30  are rotated and mated, the extension  74  is gone creating a pocket  76  which will receive a gasket material  58  injected through abutting channels  70  and  70 ′. The gasket material  58  covers the seam  54  holding the molded base  46  and molded cover  48  together.  
         [0052]    In an alternative embodiment shown in FIG. 6, wedge-tipped pins  80  may extend from revolving mold section  28  to the seam  54  of molded base  46  when the molded base  46  is molded. Channel  70  provides an access to the cavity formed by the wedge-tipped pins  80  when it is removed. Corresponding wedge-tipped pins  80  may extend from revolving mold section  30  to the seam  54  of molded cover  48  when the molded cover  48  is molded (not shown).  
         [0053]    Referring to FIG. 7, the channel made up of channel  70 ′ and  70  allows access to the cavities formed by wedge-tipped pins  80  to create an hourglass-shaped rivet  60  across seam  54  holding molded base  46  and molded cover  48  together.  
         [0054]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.