Abstract:
A method of molding a second part onto a first part to form a molded product including placing a blank between a first mold half and a second mold half of a mold, where the first mold half includes at least one cavity, trimming the blank to form the first part, and injecting molten resin into the at least one cavity of the first mold half to mold the second part onto the first part.

Description:
TECHNICAL FIELD 
       [0001]    The present invention is related to molding processes, and more particularly to over-molding processes involving a trimming step. 
       BACKGROUND 
       [0002]    In molding operations, a base part on which another part is molded often needs to be trimmed to remove the base part from a blank or to simply change the size and/or shape of the base part. In the past, this has required a separate trimming operation, either prior to or after the actual molding step. For example, in the production of tympanic thermometer prove tip covers, structural elements may be overmolded onto a base of flexible polyethylene. A secondary trimming operation is required to remove the base from the web blank. This separate trimming step adds to the overall cost and reduces the yield of the molding process. 
         [0003]    Accordingly, there is a need for a molding process in which a part is molded onto a base element, where a trimming step for removing the base element from a blank, separate from the actual mold stroke cycle, is not required. 
       SUMMARY OF THE INVENTION 
       [0004]    A method of molding a second part onto a first part to form a molded product according to an exemplary embodiment of the present invention includes placing a blank between a first mold half and a second mold half of a mold, where the first mold half includes at least one cavity, trimming the blank to form the first part, and injecting molten resin into the at least one cavity of the first mold half to mold the second part onto the first part. 
         [0005]    In at least one embodiment, the blank is a flexible film, and the method further comprises a step of generating tension in the flexible film. 
         [0006]    In at least one embodiment, the molded product is a tympanic thermometer probe tip cover, and the trimming step comprises trimming the flexible film to form a disc-shaped base element of the probe tip cover as the first part. 
         [0007]    In at least one embodiment, the second part includes inner and outer rings of the probe tip cover. 
         [0008]    In at least one embodiment, the first mold half comprises two cavities that correspond to the inner and outer rings of the probe tip cover. 
         [0009]    In at least one embodiment, the flexible film is made of polyethylene. 
         [0010]    In at least one embodiment, the molten resin is high density polyethylene. 
         [0011]    In at least one embodiment, the molten resin includes polyesters, nylons, urethanes, silicone, polyvinyl chloride, neoprene, thermoplastic rubber, Tyvek® materials, polypropylene and/or polyethylene-terephthalate. 
         [0012]    A mold according to an exemplary embodiment of the present invention for molding a second part onto a first part to form a molded product during a molding operation includes a first mold half having at least one cavity that receives molten resin to form the second part, a second mold half, and a trimming element for trimming the first part during the molding operation. 
         [0013]    In at least one embodiment, the trimming element is disposed around the first mold half and is slidable relative to the first mold half to trim the first part. 
         [0014]    These and other features of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of this invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Various exemplary embodiments of this invention will be described in detail, with reference to the following figures, wherein: 
           [0016]      FIG. 1  is a plan view of a probe tip cover formed by the process according to an exemplary embodiment of the present invention; 
           [0017]      FIG. 2  is a cross-sectional view taken along the line  2 - 2  in  FIG. 1 ; 
           [0018]      FIG. 3  is a cross-sectional view of a mold used in a molding process according to an exemplary embodiment of the present invention; 
           [0019]      FIG. 4  is a representative drawing of a molding process line according to an exemplary embodiment of the present invention; 
           [0020]      FIG. 5  is a cross sectional view showing a molding process according to an exemplary embodiment of the present invention; and 
           [0021]      FIG. 6  is a partial plan view of a probe tip cover formed on a blank by the molding process according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    In the method according to various exemplary embodiments of the present invention, a first part is trimmed from a blank during a molding process in which a second part is overmolded onto the first part. According to the process, during a single stroke of the mold, the second part is overmolded while the first part is simultaneously trimmed. The simultaneous trimming and molding steps of the present invention provides improved alignment between the first and second parts, and offers a higher yield in the overall molding operation since less process steps are required. The present invention is described within the context of high density polyethylene (HDPE) overmolded onto a strip of flexible polyethylene, particularly to form a probe cover tip. However, it should be appreciated that the present invention is not intended to be limited to any particular materials or final product, and other materials, such as, for example, glass metal and ceramic raw materials, may be used in the process to form any other desired final or intermediate products. For example, the inventive process may be used to form a sterile barrier for any type of medical device, such as a flexible cover for an endoscope. Other flexible materials besides HDPE may be used, such as, for example, polyesters, nylons, urethanes, silicone, polyvinyl chloride, neoprene, thermoplastic rubber, Tyvek® materials, polypropylene and polyethylene-terephthalate, to name a few. Further, although the process shown and described herein is a horizontal molding operation, it should be appreciated that a vertical molding operating is also applicable. 
         [0023]      FIG. 1  is a plan view of a probe tip cover, generally designated by reference number  1 , formed using the process according to an exemplary embodiment of the present invention, and  FIG. 2  is a cross-sectional view taken along the line  2 - 2  in  FIG. 1  of the probe tip cover  1 . The probe tip cover  1  includes a generally disc-shaped base element  10 , an inner ring  20 , and a concentric outer ring  30 . The outer diameter edge  32  of the outer ring  30  is preferably aligned with the outer diameter edge  12  of the base element  10 . The inner ring  20  defines an inner portion  14  of the base element  10 , and the inner and outer rings  20 ,  30  define an outer portion  16  of the base element  10 . In use, the inner portion  14  of the base element  10  is disposed over the flat end of the probe tip of a tympanic thermometer, and the outer portion  16  of the base element  10  is disposed over the sides of the probe tip. 
         [0024]      FIG. 3  is a cross sectional view of a mold, generally designated by reference number  100 , used in the process according to an exemplary embodiment of the present invention. The mold  100  includes a lower mold half  110 , an upper mold half  120  and a cutting ring  130  disposed around and slidable vertically relative to the upper mold half  120 . The upper mold half  120  includes one or more cavities that receive molten mold material to form the final product. In the present embodiment, the upper mold half  120  includes an inner annular cavity  122  and a concentric outer annular cavity  124 , which receive molten material to form the inner and outer rings  20 ,  30 , respectively, of the probe tip cover  1 . The cutting ring  130  includes a downwardly extending annular flange  132  that functions as a cutting member during the molding operation. 
         [0025]    During the molding operation, the upper mold half  120  is moved downwardly over the lower mold half  110 , and the cutting ring  130  is slid downwards relative to the upper mold half  120  until the bottom surface of the annular flange  132  contacts the top surface of the lower mold half  110 . Thus, a portion of the inner diameter of the cutting ring  130  forms the outer wall of the second annular cavity  124  during the molding operation. Further, as explained in more detail below, the annular flange  132  trims a blank in the mold  100  to form the annular base member  10  of the probe cover  1 . Preferably, the upper mold half  120  is movable, while the lower mold half  110  is held stationary. 
         [0026]      FIG. 4  is a representative drawing of a molding process line, generally designated by reference number  200 , according to an exemplary embodiment of the present invention used to form the probe tip cover  1 . The process line  200  involves the use of a roll  202  of a flexible polyethylene strip  204  wound on a feed reel  206 . The strip  204  functions as the blank from which is formed the base element  10  of the probe tip cover  1 . 
         [0027]    The strip  204  is drawn off the feed reel  206  by film feed rolls  214 ,  206  located at the end portion of the process line  200 . The film feed rolls  214 ,  216  may be driven by a stepper motor (not shown) and timed with the opening of the mold  100 . An idler wheel  208  guides the strip  204  off the feed reel  206  towards a molding station  210 . A drag brake  212  may be used on the roll  202  to create desired tension on the strip  204  as it comes off the roll  202 . 
         [0028]    At the molding station  210 , the strip  204  passes over the stationary lower mold half  110 . At predetermined intervals, the drawing of the strip  204  from the feed reel  206  ceases and the upper mold half  120  and cutting ring  130  are moved into position over the lower mold half  110  with the strip  204  therebetween. As shown in  FIG. 5 , the continued downward movement of the upper mold half  120  and cutting ring  130  results in trimming of the strip  204  to form the annular base element  10  of the probe cover  1 . The annular flange  132  of the cutting ring  130  holds the base element  10  in position after the base element  10  is trimmed from the strip  204 . At the same time, molding resin, such as, for example, HDPE, is injected into the first and second annular cavities  122 ,  124  of the mold  100  through a runner (not shown), to thereby overmold the inner and outer rings  20 ,  30  onto the base element  10 . 
         [0029]      FIG. 6  is a partial plan view of the strip  204  after the inner and outer rings  20 , have been overmolded onto the base element  10  to form the probe tip cover  1 . The circular openings below the probe tip cover  1  show where base elements for previously formed probe tip covers were trimmed from the strip  204 . The unused portion of the strip  204  continues through the film feed rolls  214 ,  216  to scrap. 
         [0030]    Now that the preferred embodiments have been shown and described in detail, various modifications and improvements thereon will be readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is to be construed broadly and be limited only by the appended claims, and not by the foregoing specification.