Abstract:
A method of reducing if not eliminating the possibility of tearing or ripping of a mesh screen of a filter during the manufacturing process includes the step of intentionally deforming the mesh screen. With this technique, as the plastic material that forms the frame of the filter begins to expand or change shape, as a result of the heating and squeezing steps involved with the molding process, the deformed mesh screen will be able to stretch or expand without the potential of tearing or ripping of the mesh screen. With the invention, numerous shapes and configurations of tools may be used to provide the intentional deformation of the mesh screen during the manufacturing process as well as to provide for control over the amount and degree of mesh screen deformation. Also, the resulting filter will have a mesh screen that has improved retention capabilities which will enhance the performance of the filter.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to the manufacture of filters for automotive applications and more specifically to deforming the mesh screen of the filter to allow for expansion of the filter frame and the mesh screen during the manufacture of the filter.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is known that in automatic transmissions of vehicles, for example, a transmission filter is used on the inlet side of the transmission hydraulic pump. The transmission filter, typically a fine mesh screen or similar filtering media, prevents harmful contaminants from entering the hydraulic system where they can increase wear and cause scoring and sticking of hydraulic control valves. If a major part fails inside the transmission, the transmission filter may prevent pieces of that part from contributing to a more catastrophic transmission failure. Normally, transmission filters trap metal chips from parts such as gears and bushings and the normal fine material that results from wear of the hydraulic clutch facings and bands.  
         [0003]     The known transmission filters are typically made of a plastic material formed as a frame around a mesh screen—the plastic frame molded into the desired configuration and onto the mesh screen. A rubber seal may be added to or molded with the frame. The rubber seal is used to seal the filter onto the inlet side of the hydraulic pump.  
         [0004]     The known transmission filters, however, are currently manufactured using techniques that have certain drawbacks. For example, the molded plastic frame that forms the perimeter or outer edge of the filter also forms individual, smaller sections or windows within the frame. The mesh screen extends across some or all of the smaller sections or windows, creating individual filter sections. Depending on the application, a filter may have one or more individual sections or windows within the filter, with each section having a unique shape and configuration. As a result, the filter must be molded to form each of these individual sections or windows. During the molding process, the plastic material that forms the frame of the filter is typically injection molded in the desired configuration and molded at an elevated temperature over the screen sections. At this elevated temperature, the plastic material that forms the frame and individual sections may change shape and consequently may stretch the mesh screen material that extends across the individual section, sometimes to the point of tearing or ripping of the mesh screen material. In other applications, where a rubber seal is added to the filter, a liquid injection molding process is used where the rubber seal is pressed or squeezed onto the filter frame at an elevated temperature. In these applications, the elevated temperature and the pressing of the rubber seal causes the plastic material that forms the frame to expand or change shape resulting in the stretching of the mesh screen, again sometimes to the point of tearing or ripping of the mesh screen.  
         [0005]     The present invention is directed at overcoming the known problem of tearing or ripping of the mesh screen as well as other known drawbacks with respect to the manufacture of filters and more broadly the application of molded plastic onto a mesh screen material.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention is directed to a technique for reducing, if not eliminating, the possibility of tearing or ripping of the mesh screen of a filter during the manufacturing process. With the teachings of the invention, the mesh screen is intentionally deformed to provide the mesh screen with an “oil canned” effect. With this configuration, as the plastic material that forms the frame of the filter begins to expand or change shape, as a result of the heating and squeezing steps involved with the manufacturing process, the deformed mesh screen will also be able to stretch without the potential of tearing or ripping of the mesh screen. The invention contemplates numerous shapes and configurations of tools that will provide the desired “oil canned” effect or intentional deformation of the mesh screen during the manufacturing process. The invention provides for control over the amount and degree of mesh screen deformation, as well as improving the retention forces on the mesh screen which improves the performance of the filter. The invention may be used with the manufacture of numerous types of filters and is also applicable to the manufacture of any part that requires the molding of a mesh screen material to a plastic material.  
         [0007]     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a plan view of an exemplary embodiment of a filter manufactured according to the teachings of the present invention.  
         [0009]      FIG. 2  is a partial cross-section view of a typical tool used to hold the mesh screen during the manufacture of the filter.  
         [0010]      FIG. 3  is a partial cross-section view of the filter made by the tool of  FIG. 2 .  
         [0011]      FIG. 4  is a partial cross-section view of a tool used to hold the mesh screen during the manufacture of the filter according to the present invention.  
         [0012]      FIG. 5  is a partial cross-section view of the filter made by the tool of  FIG. 4 .  
         [0013]      FIG. 6  is a partial cross-section view of another tool used to hold the mesh screen during the manufacture of the filter according to the present invention.  
         [0014]      FIG. 7  is a partial cross-section view of the filter made by the tool of  FIG. 6 . 
     
    
       [0015]     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof.  
       DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0016]     Referring to  FIG. 1 , an exemplary embodiment of a filter  10  made according to the teachings and principles of the present invention is depicted. The filter  10  is exemplary of a transmission filter and is exemplary of the numerous shapes and configurations of the possible filters that may be made according to the teachings of the invention. The filter  10  includes a filter frame  12  that forms or defines numerous frame sections  14 . As illustrated, each section  14  may define numerous possible shapes and configurations depending on the desired application. The frame  12  may be made of numerous materials, including a nylon material, such as 33% glass filled nylon 6/6.  
         [0017]     The frame  12  may include a track or channel  16  in which a silicone or rubber material may be added during a liquid injection molding process. The silicone or rubber material forms a seal around each of the sections  14 . As illustrated, the track  16  containing the silicone or rubber material forms a continuous track that extends around each of the sections  14  and the silicone or rubber material prevents any leaking around each of these sections. The frame  12  may also include one or more mounting holes  18  that serve to mount the filter  10  at the desired location, such as to the inlet side of a transmission pump.  
         [0018]     A mesh screen  20  is formed with the frame  12  using a plastic molding process, as described below. The mesh screen  20  may be made of numerous materials, including a polyester or nylon material, as well as stainless steel, or other suitable material. The mesh screen  20  is configured to extend across the sections  14  and serves as a filtering media to filter contaminants from a fluid or liquid, such as transmission fluid, as the fluid or liquid passes through the mesh screen  20 .  
         [0019]     Referring to  FIG. 2 , a cross-section of a known tool  30  that is used to hold the mesh screen in position during the plastic molding process includes tool halves  32 ,  34  each having planar, opposing surfaces  36 ,  38 . As known, the surfaces  36 ,  38  hold the mesh screen during the molding process while the injected plastic material flows through cavities  40 ,  42  to form the frame  12 . The frame  12  and accompanying mesh screen  20  are then placed in a mold for the liquid injection molding process during which the silicone or rubber material that forms the seal is added to the track  16 , and the frame  12  is squeezed in the mold to define the final configuration of the filter  10 .  
         [0020]      FIG. 3  shows a cross-section of the molded frame  12  with the mesh screen  20  extending between the frame  12  as formed by the known tool  30  of  FIG. 2 . As illustrated, the mesh screen  20  is planar or flat to match the shape of the opposing surfaces  36 ,  38 , and is held in position by the frame  12 . With the use of the type of tool  30  depicted in  FIG. 2 , as the plastic material that forms the frame  12  begins to expand or change shape, as a result of the plastic material being heated to approximately 300 degrees Fahrenheit during the liquid injection molding process and squeezed, the mesh screen  20 , because it is flat or planar, will have a tendency to be stretched between the frame  12  sections, sometimes to the point of tearing or ripping of the mesh screen. More specifically and by way of example, if the frame material consists of a nylon material having a coefficient of thermal expansion ranging from 1.0×10(−5) in./in./° F. to 5.0×10(−5) in./in./° F., when this material is exposed to a temperature of approximately 300 degrees Fahrenheit, the material may expand linearly approximately 0.0003 to 0.015 inches. This degree of linear expansion may result in the tearing or ripping of the mesh screen that is molded with the frame  12 .  
         [0021]     Referring to  FIG. 4 , a cross-section of a tool  50  that may be used with the teachings of the invention is depicted and includes tool halves  52 ,  54 . The half  52  defines a recess surface  56 , and the half  54  defines a boss surface  58 . The recess surface  56  may define angled wall surfaces  59  that join with a flat bottom wall surface  61 . The boss surface  58  may define angled wall surfaces  63  that join with a flat top wall surface  65 . The recess surface  56  and boss surface  58  are mating in that the surfaces  63  and  65  of the boss surface  58  will seat within the surfaces  59  and  61  of the recess surface  56 , as illustrated by  FIG. 4 . The recess and boss surfaces are used to hold the mesh screen  20  in position during the molding process. Importantly, the recess and boss surfaces also intentionally deform the mesh screen  20  to form a dome shaped profile, as illustrated by  FIG. 5 , thus creating an “oil-canned” effect. As discussed below, the “oil-canned” effect permits the mesh screen  20  to stretch or expand during the molding process, thereby reducing, if not eliminating the possibility of tearing or ripping of the mesh screen  20  as the plastic frame material expands.  
         [0022]     It should be understood that the recess surface  56  and boss surface  58  may have other shapes and configurations, including spherical, angular, flat or curvilinear surfaces, or a combination of these surfaces, that still provide the desired “oil canned” effect or intentional deformation of the mesh screen. It is also contemplated that the tool  50  may be used with all the sections  14  ( FIG. 1 ) to intentionally deform the mesh screen  20  within each of these sections.  
         [0023]     Referring to  FIG. 4 , the tool  50  also defines cavities  60 ,  62  through which flows the plastic material to form the frame  12  during the plastic molding process. The frame  12  and accompanying mesh screen  20  is then placed in a mold for the liquid injection molding process during which the rubber or silicone material is added to the track  16  of the frame  12  and then squeezed in the mold to define the final configuration of the filter  10 .  
         [0024]     Referring to  FIG. 5 , there is shown a cross-section of the frame  12  with the deformed mesh screen  20  extending between the frame  12 . The mesh screen  20  is intentionally deformed at  70  by the tool  50  to provide the mesh screen with a dome-shaped profile and thus the “oil canned” effect. With this configuration, as the plastic material that forms the frame  12  and sections  14  begins to expand or change shape, as a result of the heating and squeezing of the plastic material as described above, the dome-shaped, deformed mesh screen  20 , due to the additional mesh screen material as well as its non-planar shape, will be able to stretch or be put in tension, thereby reducing if not eliminating the potential for tearing or ripping of the mesh screen. It should be understood that the invention is not limited to the particular mesh screen deformation depicted at  70 , which shows a generally dome-shaped deformation. Rather, the invention contemplates any deformation of the mesh screen  20  that still permits the expansion of the mesh screen. Indeed, any non-planar or non-linear deformation of the mesh screen is contemplated with the invention to achieve the benefits of the invention.  
         [0025]     Referring to  FIG. 6  there is depicted a cross-section of another exemplary tool that may be used with the teachings of the invention. Tool  71  includes tool halves  72 ,  74  that in use define a cavity  75  formed by raised surface walls  76  and  77  and planar surface wall  81  of the tool half  72 , and raised surface walls  78  and  79  and planar surface wall  83  of the tool half  74 . With this embodiment, the mesh screen  20  is deformed or squeezed between opposing surface walls  77  and  78  and also between opposing surface walls  76  and  79  during the molding process. The squeezing of the mesh screen is performed adjacent to the frame  12  and for a distance of approximately 1 to 2 millimeters from the frame  12 . The intentional deformation of the mesh screen  20  at this location causes the mesh screen to displace toward the center or middle of the mesh screen to create the “oil-canned” effect, as illustrated by  FIG. 7 . Similar to the above embodiment, the “oil-canned” effect permits the mesh screen  20  to stretch or expand during the molding process, thereby reducing, if not eliminating the possibility of tearing or ripping of the mesh screen  20  as the plastic frame material expands or changes shape.  
         [0026]     Similar to the above embodiment, the tool  71  further defines cavities  80 ,  82  through which flows the plastic material to form the frame  12  during the plastic molding process. As described above, the frame  12  and accompanying mesh screen  20  are then placed in a mold for the liquid injection molding process during which the rubber material is added to the track  16  of the frame  12  and squeezed in the mold to form the final configuration of the filter  10 .  
         [0027]     Referring to  FIG. 7 , there is shown a cross-section of the frame  12  with the deformed mesh screen  20  extending between the frame  12 . With the use of the tool  71 , the mesh screen  20  is intentionally deformed or squeezed at mesh portions  84  and  86  by the surface walls  76 ,  77 ,  78  and  79  of the tool halves  72 ,  74 . As indicated above, the mesh screen  20  material will be pushed or displaced toward a middle portion  88  that will have a relatively thicker cross-section then the portions  84  and  86 . With this configuration, as the plastic material that forms the frame  12  and sections  14  begins to expand or change shape, as a result of the heating and squeezing of the plastic material as described above, the deformed mesh screen  20  will be able to stretch, thereby reducing if not eliminating the potential for tearing or ripping of the mesh screen.  
         [0028]     With the principles and teachings of the invention, the amount and degree of mesh screen deformation can be controlled. Also, the invention provides that the “oil canned” effect will be present, thereby reducing if not eliminating the likelihood of the mesh screen ripping or tearing when the plastic material that forms the frame expands or changes shape. In addition, the retention forces on the mesh screen of the final configuration of the filter are improved, thereby permitting more fluid force against the mesh screen during use of the filter without ripping or tearing of the mesh screen.  
         [0029]     Variations and modifications of the foregoing are within the scope of the present invention. It should be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.  
         [0030]     Various features of the invention are set forth in the following claims.