Abstract:
An injection molding apparatus includes a fixed injection molding machine having a housing, a first injection molding unit and a die associated therewith. A portable framework is removably attached to the molding machine housing and has at least a second injection machine molding unit operably aligned with the molding machine die and cooperable with the first injection molding unit.

Description:
FIELD OF THE INVENTION 
     This invention relates broadly to thermoplastic injection molding apparatus and, more particularly, pertains to the enhancement of a commercially available injection molding machine to increase production capability. 
     BACKGROUND OF THE INVENTION 
     Changes in plastics manufacturing strategies, particularly the growing emphasis on reducing in-process time and inventories, make multi-shot molding more viable and cost justifiable than single shot molding for a broader range of manufacturers. The multi-shot process allows multiple colors or materials to be sequentially injected in a single, continuous process to speed throughput, minimize production and assembly operations, improve part quality and create innovative part features. In most cases, a single injection molding machine with multiple injection units will generally cost less than an equivalent number of machines with single injection units. Likewise, a single two-color mold will usually cost less than two one-color molds. Because only a single machine operator is required for a multi-step process, there is a labor savings realized which can have major impact on payback calculations and life cycle costs. Floor space, electricity, and other utility costs are also reduced by consolidating operations on one machine. Faster inventory turns for savings on in-process inventory can be a critical factor in the decision matrix as well. 
     Despite their advantages, multi-shot injection molding machines are not readily available from the inventory from large press manufacturers and must often be custom built which results in several months of delay before the desired production can commence. Once the multi-shot machine is delivered and installed, the customer is locked into the particular design and location of the multiple injection units on a particular manufacturer&#39;s machine. There is no adjustability of the injection unit along the x and y axis, nor is there any interchangeability with another press manufacturer&#39;s machine or parts thereof. 
     Accordingly, it is desirable to provide an arrangement for removably mounting an injection molding unit on a commercially available injection molding machine in a manner which will produce all the advantages of a multi-shot machine without any of its drawbacks. It is also desirable to provide a universally applicable framework for marrying at least one molding unit into the existing die of a standard injection molding machine. 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to transform a known single shot molding machine into a multi-shot molding machine. 
     It is one object of the present invention to provide a portable injection molding unit for expanding the flexibility of a standard injection molding machine. 
     It is another object of the present invention to efficiently provide a rail mounted injection molding unit which is adjustable along three axes of movement relative to a fixed injection molding machine. 
     It is a further object of the present invention to provide an injection molding conversion arrangement which can be adapted for use on variously manufactured injection molding machines. 
     It is an additional object of the present invention to provide alternative multi-shot molding without requiring a custom built injection molding machine. 
     In one aspect of the invention, an injection molding machine having a die is improved such that an injection molding arrangement is removably mounted to the injection molding machine and cooperates with the die thereof to increase the molding capability of the machine. The injection molding arrangement includes an injection barrel which is adjustable along three axes relative to the injection molding machine. The injection molding arrangement is transferable from the injection molding machine to another injection molding machine. The injection molding arrangement includes rail structure engageable with bearing structure enabling movement of the injection molding unit longitudinally and laterally of the injection molding machine. The injection molding arrangement is comprised of at least one injection molding unit removably mounted to the injection molding machine. 
     In another aspect of the invention, an injection molding apparatus includes a fixed, injection molding machine having a housing, a first injection molding unit and a die associated therewith. A portable framework is removably mounted to the molding machine housing and has at least a second injection molding unit operably aligned with the molding machine die and cooperable with the first injection molding unit. The framework includes a base plate fixed to the molding machine housing, and a pair of parallel side panels slidably mounted on the base plate and interconnected by cross member structure. The second injection molding unit is slidably mounted on the cross member structure. A first adjustment device is disposed between one of the side panels and the base plate for enabling sliding movement of the side panels, cross member structure and second injection molding unit relative to the base plate. A second adjustment device is disposed between the side panels for providing sliding movement of the second injection molding unit relative to the side panels and base plate. One of the adjustment devices provides movement longitudinally of the molding machine housing and the other of the adjustment devices provides movement laterally of the molding machine housing. A first set of linear bearings is interposed between the side panels and the base plate. A second set of linear bearings is interposed between the cross member structure and a mounting block structure of the second injection molding unit. The side panels have bottom rails defining a longitudinal set of rails. The cross member structure has top portions defining a latitudinal set of rails. The mounting block structure includes a pair of mounting blocks interconnected by a tie bar. The first adjustment device includes a longitudinal lead screw, and the second adjustment device includes a latitudinal lead screw. The second injection molding unit has an injector barrel which is adjustable along three different axes of movement relative to the molding machine housing. 
     In yet another aspect of the invention, there is contemplated a method of providing multi-shot molding capability in the production of plastic-based components. The method includes the steps of providing a fixed injection molding machine having a housing, a first injection molding unit and a die associated therewith; disposing a portable framework having at least a second injection molding unit upon the molding machine housing such that the second injection molding unit is operably aligned with the die in cooperation with the first injection molding unit; and removably fastening the framework to the molding machine housing. 
     Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become better understood by reference to the following detailed description of the preferred exemplary embodiment when read in conjunction with the appended drawing, wherein like numerals denote like elements and: 
     FIG. 1 is an elevational view of a portable injection molding arrangement removably mounted to an injection molding machine in accordance with the invention; 
     FIG. 2A is a left side perspective view of a portable injection molding arrangement removably mounted to a standard injection molding machine in accordance with the invention; 
     FIG. 2B is a right side perspective view of the arrangement shown in FIG. 1; 
     FIG. 3 is a left side perspective view of the framework in the arrangement with various components removed for clarity; 
     FIG. 4 is a right side perspective view of the framework shown in FIG. 3; 
     FIG. 5 is a view of a portable injection molding arrangement having two injection molding units mounted to the upper housing of the injection molding machine; and 
     FIG. 6 is a view of a portable injection molding arrangement having an injection molding unit removably mounted to the side housing of the injection molding machine. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIGS. 1-4, the reference numeral  10  generally designates a portable injection molding arrangement which is removably mounted on an upper housing portion  12  of a fixed, standard or commercially available injection molding machine  14 . As is well known, machine  14  includes at least one injection molding unit  16  which cooperates with a die  18  and injects heated pellets into a mold to produce plastic products of a desired structure. Such machines equipped with one injection molding unit  16  are referred to as single shot molding machines. As explained in the Background of the Invention, single shot molding machines are limited in their production capability and are being upstaged by multi-shot machines which are usually custom built by large press manufacturers. 
     The present invention converts or transforms the standard molding machine  14  into a two-shot or multi-shot machine, by means of a unique mounting arrangement, in a shorter period of time and without the enormous cost and long wait of a specially manufactured machine. 
     The portable arrangement  10  is characterized by a framework  20  for adjustably supporting at least one commonly-purchased injection molding unit  22  and an enclosure  24  for housing the various electrical controls therefor. As seen in FIGS. 3 and 4, framework  20  includes a pair of parallel side panels  26 , 28  interconnected by a front cross member  30 , an intermediate cross member  32  and a transverse support wall  34 . The bottom portions of the side panels  26 , 28  define respective longitudinal rails  36 , 38  which are slidably mounted in a set of four longitudinal linear bearings  40 , 42 , 44 , 46  anchored to a rectangular base plate  48 . Extending vertically upward from the side panels  26 , 28  immediately adjacent the support wall  34  is a pair of parallel uprights  50 , 52 . A cross piece  54  joins the uprights  50 , 52  at their upper ends and supports a pair of hydraulic manifolds  56 , 58  associated with the injection molding unit  22 . The electrical enclosure  24  is seated on the rear portions and top edges of the side panels  26 , 28  and behind the uprights  50 , 52 . It should be noted that the entire arrangement  10  is conveniently adapted to the standard molding machine  14  by removably securing the base plate  48 , such as by fasteners  60 , to the upper housing portion  12 . It should also be appreciated that base plate  48  spans the width of the framework  20 , and extends beyond the side panels  26 , 28  in order to provide stability to the add-on equipment. 
     The top portions of the front cross member  30  and intermediate cross member  32  form respective latitudinal rails  62 , 64  upon which a pair of respective latitudinal linear bearings  66 , 68  are slidably mounted. The bearings  66 , 68  underlie the injection molding unit  22  which includes a pair of hydraulic cylinder mounting blocks  70 , 72  coupled together by a tie bar  74  for a purpose to be more appreciated hereafter. The mounting blocks  70 , 72  support a main casting  76  movable upwardly and downwardly along respective cylinder rods  78 , 80  of a pair of carriage cylinders  82 , 84 . The casting  76  includes a hydraulic motor  86  for driving an injection screw  88  used to deliver thermoplastic pellets through a hopper feed throat  90  to the heater bands  92  of an injection barrel  94 . Heated flowable plastic is periodically injected or “shot” by means of an injection cylinder  96  from a nozzle tip  98  which is directed to the die  18  in the molding machine  14 . This additional “shot” supplied by arrangement  10  cooperates with the shot provided by the standard machine  14  to create a multi-shot machine having multi-color/material molding capability with more features, better quality and less cost than when using separate single shot machines. 
     A salient feature of the present invention resides in the adjustability of the injection barrel  94  along three (x, y and z) axes relative to the molding machine  14 . As described above, movement of the injection barrel  94  along a vertical or z-axis is provided by means of the carriage cylinders  82 , 84 . To enable adjustment along an x-axis or longitudinally of the machine  14 , a longitudinal lead screw  100  having a nut  102  fixed thereto is threadedly received in a pair of pillow block bearings  104 , 106  joined to the side panel  26 . The nut  102  is captured in a support block  108  which is connected to the side panel  26  and slides on the linear bearings  40 , 42 . Because the side panels  26 , 28  are joined together, turning a handle  110  on lead screw  100  will move the side panels  26 , 28  and the remainder of framework  20  supporting injection barrel  94  forwardly and rearwardly in a horizontal plane parallel to the upper housing portion  12 . To enable adjustment along a y-axis or laterally of the machine  14 , a latitudinal lead screw  112  having a nut  114  fixed thereon is threadedly received in a pair of pillow block bearings  116 , 118  mounted on the top edges of side panels  26 , 28 . The nut  114  is joined directly with the mounting block  72  which is slidably mounted on rail  64 . Because the mounting blocks  70 , 72  are linked together by tie bar  74 , turning of a handle  120  on lead screw  112  will cause the mounting blocks  70 , 72  and the injection molding unit  22  including the injection barrel  74  to traverse from side-to-side in a horizontal plane parallel to its upper housing portion  12 . 
     When it is desired to enhance the molding capability of an existing molding machine  14 , a crane is used to lift the portable injection molding arrangement  10  to a flat plane of the upper housing portion  12 , and dispose the injection barrel  94  over the die  18  of the machine  14 . The entire framework  20  is lowered so that the base plate  48  lies flush on the upper housing portion  12 , after which fasteners  60  are used to secure the base plate  48  to the housing of the machine  14 . At this point, the various electrical, hydraulic and plastic lines are connected to the injection molding unit  22  and the enclosure  24 . If necessary, the handles  110 , 120  are manipulated to locate the proper x and y coordinates for the injector barrel  94 . Then, the cylinders  82 , 84  are employed to lower the barrel  94  to the proper injection location relative to the die of the machine  14 . 
     Another attractive feature of the present invention is the ability of the arrangement  10  to be used on other brands of molding machine  14 . By simply removing the fasteners  60  from the base plate  48 , a crane can be employed to transfer the arrangement  20  from one machine  14  to another. 
     It should be understood that the portable injection molding arrangement  10  can be readily supplied to the owner of a standard injection molding machine  14  to increase the versatility of the machine  14 . The present invention has a universal or modular design which permits the arrangement  10  to be easily installed on any machine  14  regardless of its particular manufacture. As a result, mold changeover is made remarkably convenient and enables the molder to meet the changing demands of customers with superior quality and high production volumes. The present invention creates valuable multi-shot capabilities which can be used to sequence molding and thus overmold an array of plastic components with various colors, materials and properties for greater appearance and perceived value. In addition to consolidating several molding operations on one machine, multi-shot molding can be employed to eliminate assembly operations. For example, a rigid automotive housing can be molded with a soft gasket eliminating secondary handling and assembly. 
     While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations, and omissions may be made without departing from the spirit thereof. For example, it should be understood that the invention further contemplates that a second injection molding unit  22 ′ (FIG. 5) may be removably mounted to the upper housing portion  12  of the machine  14 . In addition, an injection molding unit  22 ″ can be removably mounted to another housing portion such as a side portion  13  of the machine  14 , as shown in FIG.  6 . In each adaptation, the additional injection molding unit is arranged to cooperate with the die  18  of the machine  14  to increase the productivity thereof. Accordingly, the foregoing description is meant to be exemplary only, and should not be deemed limitative on the scope of the invention set forth with the following claims.